Sample records for abrupt tropical climate

  1. Abrupt tropical climate change: past and present.

    PubMed

    Thompson, Lonnie G; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith

    2006-07-11

    Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions.

  2. Response of the tropical Pacific to abrupt climate change 8,200 years ago

    NASA Astrophysics Data System (ADS)

    Atwood, A. R.; Battisti, D.; Bitz, C. M.; Sachs, J. P.

    2017-12-01

    The relatively stable climate of the Holocene epoch was punctuated by a period of large and abrupt climate change ca. 8,200 yr BP, when an outburst of glacial meltwater into the Labrador Sea drove large and abrupt climate changes across the globe. However, little is known about the response of the tropical Pacific to this event. We present the first evidence for large perturbations to the eastern tropical Pacific climate, based on sedimentary biomarker and hydrogen isotopic records from a freshwater lake in the Galápagos Islands. We inform these reconstructions with freshwater forcing simulations performed with the Community Climate System Model version 4. Together, the biomarker records and model simulations provide evidence for a mechanistic link between (1) a southward shift of the Intertropical Convergence Zone in the eastern equatorial Pacific and (2) decreased frequency and/or intensity of Eastern Pacific El Niño events during the 8,200 BP event. While climate theory and modeling studies support a southward shift of the ITCZ in response to a weakened AMOC, the dynamical drivers for the observed change in ENSO variability are less well developed. To explore these linkages, we perform simulations with an intermediate complexity model of the tropical Pacific. These results provide valuable insight into the controls of tropical Pacific climate variability and the mechanisms behind the global response to abrupt climate change.

  3. Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics.

    PubMed

    Partin, J W; Quinn, T M; Shen, C-C; Okumura, Y; Cardenas, M B; Siringan, F P; Banner, J L; Lin, K; Hu, H-M; Taylor, F W

    2015-09-02

    Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10-100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland.

  4. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.

    PubMed

    Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L

    2012-09-04

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition.

  5. Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures

    PubMed Central

    Schmidt, Matthew W.; Chang, Ping; Hertzberg, Jennifer E.; Them, Theodore R.; Ji, Link; Otto-Bliesner, Bette L.

    2012-01-01

    Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256

  6. Climate Stability: Pathway to understand abrupt glacial climate shifts

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Knorr, G.; Barker, S.; Lohmann, G.

    2017-12-01

    Glacial climate is marked by abrupt, millennial-scale climate changes known as Dansgaard-Oeschger (DO) cycles that have been linked to variations in the Atlantic meridional overturning circulation (AMOC). The most pronounced stadial coolings, Heinrich Stadials (HSs), are associated with massive iceberg discharges to the North Atlantic. This motivates scientists to consider that the North Atlantic freshwater perturbations is a common trigger of the associated abrupt transitions between weak and strong AMOC states. However, recent studies suggest that the Heinrich ice-surging events are triggered by ocean subsurface warming associated with an AMOC slow-down. Furthermore, the duration of ice-rafting events does not systematically coincide with the beginning and end of the pronounced cold conditions during HSs. In this context, we show that both, changes in atmospheric CO2 and ice sheet configuration can provide important control on the stability of the AMOC, using a coupled atmosphere-ocean model. Our simulations reveal that gradual changes in Northern Hemisphere ice sheet height and atmospheric CO2 can act as a trigger of abrupt glacial/deglacial climate changes. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rain belts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence. We further find that under a delicate configuration of atmospheric CO2 and ice sheet height the AMOC can be characterized by a self-oscillation (resonance) feature (Hopf Bifucation) with a 1000-year cycle that is comparable with observed small DO events during the MIS 3. This provides an alternative explanation for millennial-scale DO variability during glacial periods.

  7. Abrupt climate change and extinction events

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  8. Abrupt climate change: can society cope?

    PubMed

    Hulme, Mike

    2003-09-15

    Consideration of abrupt climate change has generally been incorporated neither in analyses of climate-change impacts nor in the design of climate adaptation strategies. Yet the possibility of abrupt climate change triggered by human perturbation of the climate system is used to support the position of both those who urge stronger and earlier mitigative action than is currently being contemplated and those who argue that the unknowns in the Earth system are too large to justify such early action. This paper explores the question of abrupt climate change in terms of its potential implications for society, focusing on the UK and northwest Europe in particular. The nature of abrupt climate change and the different ways in which it has been defined and perceived are examined. Using the example of the collapse of the thermohaline circulation (THC), the suggested implications for society of abrupt climate change are reviewed; previous work has been largely speculative and has generally considered the implications only from economic and ecological perspectives. Some observations about the implications from a more social and behavioural science perspective are made. If abrupt climate change simply implies changes in the occurrence or intensity of extreme weather events, or an accelerated unidirectional change in climate, the design of adaptation to climate change can proceed within the existing paradigm, with appropriate adjustments. Limits to adaptation in some sectors or regions may be reached, and the costs of appropriate adaptive behaviour may be large, but strategy can develop on the basis of a predicted long-term unidirectional change in climate. It would be more challenging, however, if abrupt climate change implied a directional change in climate, as, for example, may well occur in northwest Europe following a collapse of the THC. There are two fundamental problems for society associated with such an outcome: first, the future changes in climate currently being

  9. The tropical climate and vegetation response to Heinrich Event 1

    NASA Astrophysics Data System (ADS)

    Handiani, D. N.; Paul, A.; Prange, M.; Merkel, U.; Dupont, L. M.; Zhang, X.

    2013-12-01

    Past abrupt climate change associated with Heinrich Event 1 (HE1, ca. 17.5 ka BP) is thought to be connected to a slowdown of the Atlantic Meridional Overturning Circulation (AMOC). The accompanying abrupt climate changes affect not only the ocean, but also the continents. Furthermore, a strong impact on vegetation patterns during this event is registered both at high latitudes of the Northern Hemisphere and in the tropics. Pollen data from the tropical regions around the Atlantic Ocean (in our study from Angola and Brazil) suggest an effect on tropical vegetation through a southward shift of the rainbelt. However, the response appears to be very different in eastern South America and western Africa. To understand the different climate and vegetation pattern responses in the terrestrial tropics and to gain deeper insight into high-low-latitude climate interactions, we studied the climate and vegetation changes during the HE1 by using two different global climate models: the University of Victoria Earth System-Climate Model (UVic ESCM) and the Community Climate System Model version 3 (CCSM3). In both models, we simulated a similar HE1-like climate state. To facilitate the comparison between the model results and the available pollen records, we generated a distribution of biomes from the simulated plant functional type (PFT) coverage and climate parameters in the models. The UVic ESCM and the CCSM3 showed a slowdown of the AMOC accompanied by a seesaw temperature pattern between the Northern and Southern Hemispheres, as well as a southward shift of the tropical rainbelt. The response of the tropical vegetation pattern around the Atlantic Ocean was more pronounced in the CCSM3 than in the UVic ESCM simulation. In tropical South America, opposite changes in tree and grass cover were found only in CCSM3. In tropical Africa, the tree cover decreased and grass cover increased around 15°N in the UVic ESCM and around 10°N in CCSM3. Changes in tree and grass cover in

  10. Continuous methane record of abrupt climate change 10-68 ka: sighting Heinrich events in the ice core record

    NASA Astrophysics Data System (ADS)

    Rhodes, Rachael; Brook, Edward; Chiang, John; Blunier, Thomas; Cheng, Hai; Edwards, R. Lawrence; Maselli, Olivia; McConnell, Joseph; Romanini, Daniele; Severinghaus, Jeffrey; Sowers, Todd; Stowasser, Christopher

    2014-05-01

    The Last Glacial period was punctuated by millennial scale abrupt climate changes - Dansgaard-Oeschger (D-O) cycles and Heinrich events. Controls on the magnitude and frequency of these climate perturbations, and how they may be inter-related, remain unclear. Specific problems include the difficulty of dating Heinrich sediment layers and local bias of key paleoclimate archives. We present a highly detailed and precise record of ice core methane (CH4), a globally integrated signal, which resolves climatic features in unprecedented resolution. Abrupt CH4 increases are resolved in Heinrich Stadials (HS) 1, 2, 4 and 5 where, in contrast to all D-O cycles, there are no concurrent abrupt changes in Greenland temperature. Using modern-day tropical rainfall variability as an analog, we propose that strong cooling in the North Atlantic severely restricted the northerly range of the Intertropical Convergence Zone (ITCZ), leading to an enhanced wet season over Southern Hemisphere tropical land areas, and consequently driving production of excess CH4 in tropical wetlands. Our findings place four Heinrich events firmly within ice core chronologies and suggest maximum durations of 778 to 1606 yr. CH4 anomalies are only associated with Heinrich events of Hudson Strait provenance, indicating that the tropical impacts of Heinrich events were not uniform.

  11. Abrupt Impacts of Climate Change: Anticipating Surprises

    NASA Astrophysics Data System (ADS)

    White, James W. C.; Alley, Richard B.; Archer, David E.; Barnosky, Anthony D.; Dunlea, Edward; Foley, Jonathan; Fu, Rong; Holland, Marika M.; Lozier, M. Susan; Schmitt, Johanna; Smith, Laurence C.; Sugihara, George; Thompson, David W. J.; Weaver, Andrew J.; Wofsy, Steven C.

    2014-05-01

    Levels of carbon dioxide and other greenhouse gases in Earth's atmosphere are exceeding levels recorded in the past millions of years, and thus climate is being forced beyond the range of the recent geological era. Lacking concerted action by the world's nations, it is clear that the future climate will be warmer, sea levels will rise, global rainfall patterns will change, and ecosystems will be altered. However, there is still uncertainty about how we will arrive at that future climate state. Although many projections of future climatic conditions have predicted steadily changing conditions giving the impression that communities have time to gradually adapt, the scientific community has been paying increasing attention to the possibility that at least some changes will be abrupt, perhaps crossing a threshold or "tipping point" to change so quickly that there will be little time to react. This presentation will synopsize the new US National Research Council Report, Abrupt Impacts of Climate Change: Anticipating Surprises, highlighting areas of increased and decreased concern, as well as areas of new concern. Emphasis is placed on not only abrupt change in physical climate, but on abrupt changes in human and natural systems that can occur as a result of a slowly changing climate. The report calls for action now on an abrupt change early warning system (ACEWS) if societies are to be resilient to climate change.

  12. The economics of abrupt climate change.

    PubMed

    Perrings, Charles

    2003-09-15

    The US National Research Council defines abrupt climate change as a change of state that is sufficiently rapid and sufficiently widespread in its effects that economies are unprepared or incapable of adapting. This may be too restrictive a definition, but abrupt climate change does have implications for the choice between the main response options: mitigation (which reduces the risks of climate change) and adaptation (which reduces the costs of climate change). The paper argues that by (i) increasing the costs of change and the potential growth of consumption, and (ii) reducing the time to change, abrupt climate change favours mitigation over adaptation. Furthermore, because the implications of change are fundamentally uncertain and potentially very high, it favours a precautionary approach in which mitigation buys time for learning. Adaptation-oriented decision tools, such as scenario planning, are inappropriate in these circumstances. Hence learning implies the use of probabilistic models that include socioeconomic feedbacks.

  13. Terrestrial Plant Biomarkers Preserved in Cariaco Basin Sediments: Records of Abrupt Tropical Vegetation Response to Rapid Climate Changes

    NASA Astrophysics Data System (ADS)

    Hughen, K. A.; Eglinton, T. I.; Makou, M.; Xu, L.; Sylva, S.

    2004-12-01

    versus δ 13C for Cariaco Basin and NW African leaf waxes indicate that biomarkers reflect real changes in local South American vegetation and not contamination from long-distance transport during cold windy climates. The precise temporal relationship between tropical vegetation shifts and climate changes is measured by direct comparison of terrestrial vegetation and climate proxies from the same core. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades.

  14. CO2 and fire influence tropical ecosystem stability in response to climate change.

    PubMed

    Shanahan, Timothy M; Hughen, Konrad A; McKay, Nicholas P; Overpeck, Jonathan T; Scholz, Christopher A; Gosling, William D; Miller, Charlotte S; Peck, John A; King, John W; Heil, Clifford W

    2016-07-18

    Interactions between climate, fire and CO2 are believed to play a crucial role in controlling the distributions of tropical woodlands and savannas, but our understanding of these processes is limited by the paucity of data from undisturbed tropical ecosystems. Here we use a 28,000-year integrated record of vegetation, climate and fire from West Africa to examine the role of these interactions on tropical ecosystem stability. We find that increased aridity between 28-15 kyr B.P. led to the widespread expansion of tropical grasslands, but that frequent fires and low CO2 played a crucial role in stabilizing these ecosystems, even as humidity changed. This resulted in an unstable ecosystem state, which transitioned abruptly from grassland to woodlands as gradual changes in CO2 and fire shifted the balance in favor of woody plants. Since then, high atmospheric CO2 has stabilized tropical forests by promoting woody plant growth, despite increased aridity. Our results indicate that the interactions between climate, CO2 and fire can make tropical ecosystems more resilient to change, but that these systems are dynamically unstable and potentially susceptible to abrupt shifts between woodland and grassland dominated states in the future.

  15. CO2 and fire influence tropical ecosystem stability in response to climate change

    NASA Astrophysics Data System (ADS)

    Shanahan, Timothy M.; Hughen, Konrad A.; McKay, Nicholas P.; Overpeck, Jonathan T.; Scholz, Christopher A.; Gosling, William D.; Miller, Charlotte S.; Peck, John A.; King, John W.; Heil, Clifford W.

    2016-07-01

    Interactions between climate, fire and CO2 are believed to play a crucial role in controlling the distributions of tropical woodlands and savannas, but our understanding of these processes is limited by the paucity of data from undisturbed tropical ecosystems. Here we use a 28,000-year integrated record of vegetation, climate and fire from West Africa to examine the role of these interactions on tropical ecosystem stability. We find that increased aridity between 28-15 kyr B.P. led to the widespread expansion of tropical grasslands, but that frequent fires and low CO2 played a crucial role in stabilizing these ecosystems, even as humidity changed. This resulted in an unstable ecosystem state, which transitioned abruptly from grassland to woodlands as gradual changes in CO2 and fire shifted the balance in favor of woody plants. Since then, high atmospheric CO2 has stabilized tropical forests by promoting woody plant growth, despite increased aridity. Our results indicate that the interactions between climate, CO2 and fire can make tropical ecosystems more resilient to change, but that these systems are dynamically unstable and potentially susceptible to abrupt shifts between woodland and grassland dominated states in the future.

  16. Abrupt glacial climate shifts controlled by ice sheet changes.

    PubMed

    Zhang, Xu; Lohmann, Gerrit; Knorr, Gregor; Purcell, Conor

    2014-08-21

    During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard-Oeschger (DO) events. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (BP) in the ice core record, and has drawn broad attention within the science and policy-making communities alike. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified. Here we show, by using a comprehensive fully coupled model, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere-ocean system and cause rapid glacial climate shifts closely resembling DO events. The simulated global climate responses--including abrupt warming in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw--are generally consistent with empirical evidence. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere-ocean-sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and abrupt climate changes in the coupled atmosphere-ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.

  17. Orbital Forcing driving climate variability on Tropical South Atlantic

    NASA Astrophysics Data System (ADS)

    Oliveira, A. S.; Baker, P. A.; Silva, C. G.; Dwyer, G. S.; Chiessi, C. M.; Rigsby, C. A.; Ferreira, F.

    2017-12-01

    Past research on climate response to orbital forcing in tropical South America has emphasized on high precession cycles influencing low latitude hydrologic cycles, and driving the meridional migration of Intertropical Convergence Zone (ITCZ).However, marine proxy records from the tropical Pacific Ocean showed a strong 41-ka periodicities in Pleistocene seawater temperature and productivity related to fluctuations in Earth's obliquity. It Indicates that the western Pacific ITCZ migration was influenced by combined precession and obliquity changes. To reconstruct different climate regimes over the continent and understand the orbital cycle forcing over Tropical South America climate, hydrological reconstruction have been undertaken on sediment cores located on the Brazilian continental slope, representing the past 1.6 million years. Core CDH 79 site is located on a 2345 m deep seamount on the northern Brazilian continental slope (00° 39.6853' N, 44° 20.7723' W), 320 km from modern coastline of the Maranhão Gulf. High-resolution XRF analyses of Fe, Ti, K and Ca are used to define the changes in precipitation and sedimentary input history of Tropical South America. The response of the hydrology cycle to orbital forcing was studied using spectral analysis.The 1600 ka records of dry/wet conditions presented here indicates that orbital time-scale climate change has been a dominant feature of tropical climate. We conclude that the observed oscillation reflects variability in the ITCZ activity associated with the Earth's tilt. The prevalence of the eccentricity and obliquity signals in continental hydrology proxies (Ti/Ca and Fe/K) as implicated in our precipitation records, highlights that these orbital forcings play an important role in tropics hydrologic cycles. Throughout the Quaternary abrupt shifts of tropical variability are temporally correlated with abrupt climate changes and atmospheric reorganization during Mid-Pleistocene Transition and Mid-Brunhes Events

  18. Synchronous interhemispheric Holocene climate trends in the tropical Andes

    PubMed Central

    Polissar, Pratigya J.; Abbott, Mark B.; Wolfe, Alexander P.; Vuille, Mathias; Bezada, Maximiliano

    2013-01-01

    Holocene variations of tropical moisture balance have been ascribed to orbitally forced changes in solar insolation. If this model is correct, millennial-scale climate evolution should be antiphased between the northern and southern hemispheres, producing humid intervals in one hemisphere matched to aridity in the other. Here we show that Holocene climate trends were largely synchronous and in the same direction in the northern and southern hemisphere outer-tropical Andes, providing little support for the dominant role of insolation forcing in these regions. Today, sea-surface temperatures in the equatorial Pacific Ocean modulate rainfall variability in the outer tropical Andes of both hemispheres, and we suggest that this mechanism was pervasive throughout the Holocene. Our findings imply that oceanic forcing plays a larger role in regional South American climate than previously suspected, and that Pacific sea-surface temperatures have the capacity to induce abrupt and sustained shifts in Andean climate. PMID:23959896

  19. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  20. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    NASA Astrophysics Data System (ADS)

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  1. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    PubMed Central

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-01-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change. PMID:26460042

  2. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models.

    PubMed

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-27

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  3. Final Scientific Report for "The Interhemispheric Pattern in 20th Century and Future Abrupt Change in Regional Tropical Rainfall"

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chiang, John C. H.; Wehner, Michael F.

    2012-10-29

    This is the final scientific report for grant DOE-FG02-08ER64588, "The Interhemispheric Pattern in 20th Century and Future Abrupt Change in Regional Tropical Rainfall."The project investigates the role of the interhemispheric pattern in surface temperature – i.e. the contrast between the northern and southern temperature changes – in driving rapid changes to tropical rainfall changes over the 20th century and future climates. Previous observational and modeling studies have shown that the tropical rainband – the Intertropical Convergence Zone (ITCZ) over marine regions, and the summer monsoonal rainfall over land – are sensitive to the interhemispheric thermal contrast; but that the linkmore » between the two has not been applied to interpreting long-term tropical rainfall changes over the 20th century and future.The specific goals of the project were to i) develop dynamical mechanisms to explain the link between the interhemispheric pattern to abrupt changes of West African and Asian monsoonal rainfall; ii) Undertake a formal detection and attribution study on the interhemispheric pattern in 20th century climate; and iii) assess the likelihood of changes to this pattern in the future. In line with these goals, our project has produced the following significant results: 1.We have developed a case that suggests that the well-known abrupt weakening of the West African monsoon in the late 1960s was part of a wider co-ordinated weakening of the West African and Asian monsoons, and driven from an abrupt cooling in the high latitude North Atlantic sea surface temperature at the same time. Our modeling work suggests that the high-latitude North Atlantic cooling is effective in driving monsoonal weakening, through driving a cooling of the Northern hemisphere that is amplified by positive radiative feedbacks. 2.We have shown that anthropogenic sulfate aerosols may have partially contributed to driving a progressively southward displacement of the Atlantic

  4. North Atlantic forcing of tropical Indian Ocean climate.

    PubMed

    Mohtadi, Mahyar; Prange, Matthias; Oppo, Delia W; De Pol-Holz, Ricardo; Merkel, Ute; Zhang, Xiao; Steinke, Stephan; Lückge, Andreas

    2014-05-01

    The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.

  5. The role of the Asian winter monsoon in the rapid propagation of abrupt climate changes during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Chu, Guoqiang; Sun, Qing; Zhu, Qingzeng; Shan, Yabing; Shang, Wenyu; Ling, Yuan; Su, Youliang; Xie, Manman; Wang, Xishen; Liu, Jiaqi

    2017-12-01

    High-resolution temperature records spanning the last deglaciation from low latitudes are scarce; however, they are important for understanding the rapid propagation of abrupt climate events throughout the Northern Hemisphere and the tropics. Here, we present a branched GDGTs-based temperature reconstruction from the sediments of Maar Lake Huguangyan in tropical China. The record reveals that the mean temperature during the Oldest Dryas was 17.8 °C, which was followed by a two-step increase of 2-3 °C to the Bølling-Allerød, a decrease to 19.8 °C during the Younger Dryas, and a rapid warming at the onset of the Holocene. The Oldest Dryas was about 2 °C warmer than the Younger Dryas. The reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column, greatly promoting biological productivity. In addition, the winter-biased temperature changes observed in the study are more distinctive than the summer-biased temperature records from extra-tropical regions of East Asia. This implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon. Within the limits of the dating uncertainties, the broadly similar pattern of winter-weighted temperature change observed in both tropical Lake Huguangyan and in Greenland ice cores indicates the occurrence of tightly-coupled interactions between high latitude ice sheets and land areas in the tropics. We suggest that the winter monsoon (especially cold surges) could play an important role in the rapid transmission of the temperature signal from the Arctic to the tropics.

  6. The resilience of postglacial hunter-gatherers to abrupt climate change.

    PubMed

    Blockley, Simon; Candy, Ian; Matthews, Ian; Langdon, Pete; Langdon, Cath; Palmer, Adrian; Lincoln, Paul; Abrook, Ashley; Taylor, Barry; Conneller, Chantal; Bayliss, Alex; MacLeod, Alison; Deeprose, Laura; Darvill, Chris; Kearney, Rebecca; Beavan, Nancy; Staff, Richard; Bamforth, Michael; Taylor, Maisie; Milner, Nicky

    2018-05-01

    Understanding the resilience of early societies to climate change is an essential part of exploring the environmental sensitivity of human populations. There is significant interest in the role of abrupt climate events as a driver of early Holocene human activity, but there are very few well-dated records directly compared with local climate archives. Here, we present evidence from the internationally important Mesolithic site of Star Carr showing occupation during the early Holocene, which is directly compared with a high-resolution palaeoclimate record from neighbouring lake beds. We show that-once established-there was intensive human activity at the site for several hundred years when the community was subject to multiple, severe, abrupt climate events that impacted air temperatures, the landscape and the ecosystem of the region. However, these results show that occupation and activity at the site persisted regardless of the environmental stresses experienced by this society. The Star Carr population displayed a high level of resilience to climate change, suggesting that postglacial populations were not necessarily held hostage to the flickering switch of climate change. Instead, we show that local, intrinsic changes in the wetland environment were more significant in determining human activity than the large-scale abrupt early Holocene climate events.

  7. Mid-Holocene to Present Climate Transition in Tropical South America

    NASA Astrophysics Data System (ADS)

    Turcq, B.; Cordeiro, R.; Sifeddine, A.; Braconnot, P.; Dias, P. S.; Costa, R.; Jorgetti, T.

    2008-12-01

    The classical illustration of Holocene climate changes in tropical South America is the huge rising of Titicaca lake level from 4400 to 4000 cal BP. Because the Amazon basin is the source of Andean rainfalls we have explored Amazonian data of climate changes during the Holocene to better understand the cause of this abrupt transition. Amazonian data confirm the existence of mid-Holocene dryness: (1) lacustrine level studies show a lower precipitation/evaporation budget than present, with the lowest lake levels between 8500 and 6800 cal BP; (2) although the dominant Holocene vegetation has always been the rainforest in the heart of Amazonia, this forest expanded towards the northwestern and southwestern regions from 6800 to 1550 cal BP, moreover, pioneer elements of the rainforest developed during the mid-Holocene and the best example is those of Cecropia, between 9000 and 5000 cal BP. (3) soil d13C indicates a forest expansion over savannas areas in Roraima (north), Mato Grosso and Rondonia (southwest), during the Holocene. (4) the mid-Holocene (8000- 4000 cal BP) is characterized by repeated occurrences of forest fires, marked by the presence of charcoals in soils and lacustrine sediments. However these different records are not characterized by abrupt transitions at the end of the Middle Holocene in Amazonia. In the Andean records there is a clear north-south shift in the timing of the transition. Analysis of coupled Ocean Atmosphere Model simulations suggest that convection in Amazon basin is directly controlled by insolation leading to an almost linear response of local climate to the global forcing. Differently, in the eastern and south-western regions where the rain is brought by the South American Monsoon, the climate transition appears more abrupt. It may be because the involved climate mechanisms are more complex and depend on Ocean/Atmosphere/Vegetation coupled process (ITCZ position, ZCAS formation, etc.). Tectonic movements or threshold links to

  8. Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Deser, Clara; Sun, Lantao; Tomas, Robert A.

    2018-05-01

    The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

  9. Tropical climate and vegetation changes during Heinrich Event 1: comparing climate model output to pollen-based vegetation reconstructions with emphasis on the region around the tropical Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Handiani, D.; Paul, A.; Dupont, L.

    2011-06-01

    Abrupt climate changes associated with Heinrich Event 1 (HE1) about 18 to 15 thousand years before present (ka BP) strongly affected climate and vegetation patterns not only in the Northern Hemisphere, but also in tropical regions in the South Atlantic Ocean. We used the University of Victoria (UVic) Earth System-Climate Model (ESCM) with dynamical vegetation and land surface components to simulate four scenarios of climate-vegetation interaction: the pre-industrial era (PI), the Last Glacial Maximum (LGM), and a Heinrich-like event with two different climate backgrounds (interglacial and glacial). The HE1-like simulation with a glacial climate background produced sea surface temperature patterns and enhanced interhemispheric thermal gradients in accordance with the "bipolar seesaw" hypothesis. It allowed us to investigate the vegetation changes that result from a transition to a drier climate as predicted for northern tropical Africa due to a southward shift of the Intertropical Convergence Zone (ITCZ). We found that a cooling of the Northern Hemisphere caused a southward shift of those plant-functional types (PFTs) in Northern Tropical Africa that are indicative of an increased desertification, and a retreat of broadleaf forests in Western Africa and Northern South America. We used the PFTs generated by the model to calculate mega-biomes to allow for a direct comparison between paleodata and palynological vegetation reconstructions. Our calculated mega-biomes for the pre-industrial period and the LGM corresponded well to the modern and LGM sites of the BIOME6000 (v.4.2) reconstruction, except that our present-day simulation predicted the dominance of grassland in Southern Europe and our LGM simulation simulated more forest cover in tropical and sub-tropical South America. The mega-biomes from the HE1 simulation with glacial background climate were in agreement with paleovegetation data from land and ocean proxies in West, Central, and Northern Tropical Africa as

  10. Response of seafloor ecosystems to abrupt global climate change

    PubMed Central

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-01-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L−1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems. PMID:25825727

  11. Response of seafloor ecosystems to abrupt global climate change

    NASA Astrophysics Data System (ADS)

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-04-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mLṡL-1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.

  12. Abrupt Climate Change: the View from the Past, the Present and the Future

    NASA Astrophysics Data System (ADS)

    White, J. W. C.

    2014-12-01

    Climate is changing as humans put more and more greenhouse gases into the atmosphere. With CO2 levels today around 400ppm, we are clearly committed to far more climate change, both in the near term, and well beyond our children's future. A key question is how that change will occur. Abrupt climate changes are those that exceed our expectations, preparedness, and ability to adapt. Such changes challenge us economically, physically, and socially. This talk will draw upon results from ice core research over the past twenty years, as well as a new NRC report on abrupt climate change in order to address abrupt change, as seen in the past in ice cores, as seen today in key environmental systems upon which humans depend, and what is may be coming in the future.

  13. Slowing down as an early warning signal for abrupt climate change.

    PubMed

    Dakos, Vasilis; Scheffer, Marten; van Nes, Egbert H; Brovkin, Victor; Petoukhov, Vladimir; Held, Hermann

    2008-09-23

    In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective.

  14. Slowing down as an early warning signal for abrupt climate change

    PubMed Central

    Dakos, Vasilis; Scheffer, Marten; van Nes, Egbert H.; Brovkin, Victor; Petoukhov, Vladimir; Held, Hermann

    2008-01-01

    In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective. PMID:18787119

  15. Abrupt climate warming in East Antarctica during the early Holocene

    NASA Astrophysics Data System (ADS)

    Cremer, Holger; Heiri, Oliver; Wagner, Bernd; Wagner-Cremer, Friederike

    2007-08-01

    We report a centennial-scale warming event between 8600 and 8400 cal BP from Amery Oasis, East Antarctica, that is documented by the geochemical record in a lacustrine sediment sequence. The organic carbon content, the C/S ratio, and the sedimentation rate in this core have distinctly elevated values around 8500 y ago reflecting relatively warm and ice-free conditions that led to well-ventilated conditions in the lake and considerable sedimentation of both autochthonous and allochthonous organic matter on the lake bottom. This abrupt warming event occurred concurrently with reported warm climatic conditions in the Southern Ocean while the climate in central East Antarctic remained cold. The comparison of the spatial and temporal variability of warm climatic periods documented in various terrestrial, marine, and glacial archives from East Antarctica elucidates the uniqueness of the centennial-scale warming event in the Amery Oasis. We also discuss a possible correlation of the Amery warming event with the abrupt climatic deterioration around 8200 cal BP on the Northern Hemisphere.

  16. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change.

    PubMed

    Lynch-Stieglitz, Jean

    2017-01-03

    Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

  17. Abrupt Climate Change Caused by Global Fires from a Large Meteor Impact

    NASA Astrophysics Data System (ADS)

    Bardeen, C.; Toon, O. B.; Garcia, R. R.; Otto-Bliesner, B. L.; Wolf, E. T.

    2015-12-01

    Global or near-global fires like those that are thought to have occurred after the Chicxulub asteroid impact are associated with abrupt climate change and the K-Pg mass extinction event. Using the Community Earth System Model (CESM), a three-dimensional coupled climate model with interactive chemistry, we have simulated the climate response to global fires assuming a burden of 70,000 Tg, as estimated from the K-Pg layer sediments by Wolbach et al. (1988). Soot aerosols are lofted by solar heating and remain in the atmosphere for about 6 years, warming the stratosphere by more than 240 K and suppressing completely solar radiation at the surface for 2 years. Global average land surface temperatures cool by -28 K after 3 years and ocean temperatures by -11 K after 4 years. Precipitation is reduced by 80 % for 5 years, and the ozone column is reduced by 80 % for 4 years. The tropical tropopause cold point disappears for a few years, leading to water vapor mixing ratios of > 1000 ppmv in the stratosphere. There is a rapid recovery around year 6, when the soot is removed by wet deposition as stratospheric water condenses and precipitates, but this is followed by a peak in the UV Index in the tropics of over 40 before stratospheric ozone recovers. Ocean temperature cools by more than -2 K to a depth of 300 m, and sea ice develops in the Black Sea, Caspian Sea, and Baltic Sea. Global fires, two years of darkness, extreme surface cooling, significant ocean cooling, increases in sea ice extent and a large short-term increase in UV Index would have been catastrophic for many life forms. This work is the first step in an effort to simulate the climatic effects of all of the aerosols and gases that may have been generated by the Chicxulub impact in a model that has been configured for late-Cretaceous conditions to help assess the role of the Chicxulub impact in the K-Pg extinction.

  18. Abrupt climate change and transient climates during the Paleogene: a marine perspective.

    PubMed

    Zachos, J C; Lohmann, K C; Walker, J C; Wise, S W

    1993-03-01

    Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

  19. Abrupt climate change and transient climates during the Paleogene: a marine perspective

    NASA Technical Reports Server (NTRS)

    Zachos, J. C.; Lohmann, K. C.; Walker, J. C.; Wise, S. W.

    1993-01-01

    Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

  20. The Arctic Grand Challenge: Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Wilkniss, P. E.

    2003-12-01

    Trouble in polar paradise (Science, 08/30/02), significant changes in the Arctic environment are scientifically documented (R.E. Moritz et al. ibid.). More trouble, lots more, "abrupt climate change," (R. B. Alley, et al. Science 03/28/03). R. Corell, Arctic Climate Impact Assessment team (ACIA), "If you want to see what will happen in the rest of the world 25 years from now just look what's happening in the Arctic," (Arctic Council meeting, Iceland, 08/03). What to do? Make abrupt Arctic climate change a grand challenge for the IPY-4 and beyond! Scientifically:Describe the "state" of the Arctic climate system as succinctly as possible and accept it as the point of departure.Develop a hypothesis and criteria what constitutes "abrupt climate change," in the Arctic that can be tested with observations. Observations: Bring to bear existing observations and coordinate new investments in observations through an IPY-4 scientific management committee. Make the new Barrow, Alaska, Global Climate Change Research Facility a major U.S. contribution and focal point for the IPY-4 in the U.S Arctic. Arctic populations, Native peoples: The people of the North are living already, daily, with wrenching change, encroaching on their habitats and cultures. For them "the earth is faster now," (I. Krupnik and D. Jolly, ARCUS, 2002). From a political, economic, social and entirely realistic perspective, an Arctic grand challenge without the total integration of the Native peoples in this effort cannot succeed. Therefore: Communications must be established, and the respective Native entities must be approached with the determination to create well founded, well functioning, enduring partnerships. In the U.S. Arctic, Barrow with its long history of involvement and active support of science and with the new global climate change research facility should be the focal point of choice Private industry: Resource extraction in the Arctic followed by oil and gas consumption, return the combustion

  1. Atmospheric CO2 and abrupt climate change on submillennial timescales

    NASA Astrophysics Data System (ADS)

    Ahn, Jinho; Brook, Edward

    2010-05-01

    How atmospheric CO2 varies and is controlled on various time scales and under various boundary conditions is important for understanding how the carbon cycle and climate change are linked. Ancient air preserved in ice cores provides important information on past variations in atmospheric CO2. In particular, concentration records for intervals of abrupt climate change may improve understanding of mechanisms that govern atmospheric CO2. We present new multi-decadal CO2 records that cover Greenland stadial 9 (between Dansgaard-Oeschger (DO) events 8 and 9) and the abrupt cooling event at 8.2 ka. The CO2 records come from Antarctic ice cores but are well synchronized with Greenland ice core records using new high-resolution CH4 records,precisely defining the timing of CO2 change with respect to abrupt climate events in Greenland. Previous work showed that during stadial 9 (40~38 ka), CO2 rose by about 15~20 ppm over around 2,000 years, and at the same time temperatures in Antarctica increased. Dust proxies indicate a decrease in dust flux over the same period. With more detailed data and better age controls we now find that approximately half of the CO2 increase during stadial 9 occurred abruptly, over the course of decades to a century at ~39.6 ka. The step increase of CO2 is synchronous with a similar step increase of Antarctic isotopic temperature and a small abrupt change in CH4, and lags after the onset of decrease in dust flux by ~400 years. New atmospheric CO2 records at the well-known ~8.2 ka cooling event were obtained from Siple Dome ice core, Antarctica. Our preliminary CO2 data span 900 years and include 19 data points within the 8.2 ka cooling event, which persisted for ~160 years (Thomas et al., Quarternary Sci. Rev., 2007). We find that CO2 increased by 2~4 ppm during that cooling event. Further analyses will improve the resolution and better constrain the CO2 variability during other times in the early Holocene to determine if the variations observed

  2. Precise interpolar phasing of abrupt climate change during the last ice age.

    PubMed

    2015-04-30

    The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.

  3. Extensive wildfires, climate change, and an abrupt state change in subalpine ribbon forests, Colorado.

    PubMed

    Calder, W John; Shuman, Bryan

    2017-10-01

    Ecosystems may shift abruptly when the effects of climate change and disturbance interact, and landscapes with regularly patterned vegetation may be especially vulnerable to abrupt shifts. Here we use a fossil pollen record from a regularly patterned ribbon forest (alternating bands of forests and meadows) in Colorado to examine whether past changes in wildfire and climate produced abrupt vegetation shifts. Comparing the percentages of conifer pollen with sedimentary δ 18 O data (interpreted as an indicator of temperature or snow accumulation) indicates a first-order linear relationship between vegetation composition and climate change with no detectable lags over the past 2,500 yr (r = 0.55, P < 0.001). Additionally, however, we find that the vegetation changed abruptly within a century of extensive wildfires, which were recognized in a previous study to have burned approximately 80% of the surrounding 1,000 km 2 landscape 1,000 yr ago when temperatures rose ~0.5°C. The vegetation change was larger than expected from the effects of climate change alone. Pollen assemblages changed from a composition associated with closed subalpine forests to one similar to modern ribbon forests. Fossil pollen assemblages then remained like those from modern ribbon forests for the following ~1,000 yr, providing a clear example of how extensive disturbances can trigger persistent new vegetation states and alter how vegetation responds to climate. © 2017 by the Ecological Society of America.

  4. Abrupt climate change and collapse of deep-sea ecosystems

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.

    2008-01-01

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

  5. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-03

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.

  6. Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

    PubMed Central

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie

    2013-01-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  7. Precise interpolar phasing of abrupt climate change during the last ice age

    USGS Publications Warehouse

    ,; Buizert, Christo; Adrian, Betty M.; Ahn, Jinho; Albert, Mary; Alley, Richard B.; Baggenstos, Daniel; Bauska, Thomas K.; Bay, Ryan C.; Bencivengo, Brian B.; Bentley, Charles R.; Brook, Edward J.; Chellman, Nathan J.; Clow, Gary D.; Cole-Dai, Jihong; Conway, Howard; Cravens, Eric; Cuffey, Kurt M.; Dunbar, Nelia W.; Edwards, Jon S.; Fegyveresi, John M.; Ferris, Dave G.; Fitzpatrick, Joan J.; Fudge, T. J.; Gibson, Chris J.; Gkinis, Vasileios; Goetz, Joshua J.; Gregory, Stephanie; Hargreaves, Geoffrey Mill; Iverson, Nels; Johnson, Jay A.; Jones, Tyler R.; Kalk, Michael L.; Kippenhan, Matthew J.; Koffman, Bess G.; Kreutz, Karl; Kuhl, Tanner W.; Lebar, Donald A.; Lee, James E.; Marcott, Shaun A.; Markle, Bradley R.; Maselli, Olivia J.; McConnell, Joseph R.; McGwire, Kenneth C.; Mitchell, Logan E.; Mortensen, Nicolai B.; Neff, Peter D.; Nishiizumi, Kunihiko; Nunn, Richard M.; Orsi, Anais J.; Pasteris, Daniel R.; Pedro, Joel B.; Pettit, Erin C.; Price, P. Buford; Priscu, John C.; Rhodes, Rachael H.; Rosen, Julia L.; Schauer, Andrew J.; Schoenemann, Spruce W.; Sendelbach, Paul J.; Severinghaus, Jeffrey P.; Shturmakov, Alexander J.; Sigl, Michael; Slawny, Kristina R.; Souney, Joseph M.; Sowers, Todd A.; Spencer, Matthew K.; Steig, Eric J.; Taylor, Kendrick C.; Twickler, Mark S.; Vaughn, Bruce H.; Voigt, Donald E.; Waddington, Edwin D.; Welten, Kees C.; Wendricks, Anthony W.; White, James W. C.; Winstrup, Mai; Wong, Gifford J.; Woodruff, Thomas E.

    2015-01-01

    The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives1. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa2, 3, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw4, 5, 6. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events7, 8, 9. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision2, 3,10. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.

  8. Abrupt Atmospheric Methane Increases Associated With Hudson Strait Heinrich Events

    NASA Astrophysics Data System (ADS)

    Rhodes, R.; Brook, E.; Chiang, J. C. H.; Blunier, T.; Maselli, O. J.; McConnell, J. R.; Romanini, D.; Severinghaus, J. P.

    2015-12-01

    The drivers of abrupt climate change during the Last Glacial Period are not well understood. While Dansgaard-Oeschger (DO) cycles are thought to be linked to variations in the strength of the Atlantic Meridional Ocean Circulation (AMOC), it is not clear how or if Heinrich Events—extensive influxes of icebergs into the North Atlantic Ocean that impacted global climate and biogeochemistry—are related. An enduring problem is the difficultly in dating iceberg rafted debris deposits that typically lack foraminifera. Here we present an ultra-high resolution record of methane from the West Antarctic Ice Sheet Divide ice core at unprecedented, continuous temporal resolution from 67.2-9.8 ka BP, which we propose constrains the timing of Heinrich events. Our methane record essentially mirrors Greenland ice core stable isotope variability across D-O events, except during Heinrich stadials 1, 2, 4 and 5. Partway through these stadials only, methane increases abruptly and rapidly, as at the onset of a D-O event but Greenland temperature exhibits no equivalent response. Speleothem records exhibit signatures of drought in the Northern extra-tropics and intensified monsoonal activity over South America at these times. We use a simple heuristic model to propose that cold air temperatures and extensive sea ice in the North, resulting from Heinrich events, caused extreme reorganization of tropical hydroclimate. This involved curtailment of the seasonal northerly migration of tropical rain belts, leading to intensification of rainfall over Southern Hemisphere tropical wetlands, thus allowing production of excess methane relative to a 'normal' Greenland stadial. We note that this mechanism can operate if AMOC is already in a slowed state when a Heinrich event occurs, as paleo-evidence suggests it was. Heinrich events and associated sea ice cover would therefore act to prolong the duration of this AMOC state. Our findings place the big four Heinrich events of Hudson Strait origin

  9. Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon

    NASA Astrophysics Data System (ADS)

    Chang, Ping; Zhang, Rong; Hazeleger, Wilco; Wen, Caihong; Wan, Xiuquan; Ji, Link; Haarsma, Reindert J.; Breugem, Wim-Paul; Seidel, Howard

    2008-07-01

    Abrupt changes in the African monsoon can have pronounced socioeconomic impacts on many West African countries. Evidence for both prolonged humid periods and monsoon failures have been identified throughout the late Pleistocene and early Holocene epochs. In particular, drought conditions in West Africa have occurred during periods of reduced North Atlantic thermohaline circulation, such as the Younger Dryas cold event. Here, we use an ocean-atmosphere general circulation model to examine the link between oceanographic changes in the North Atlantic Ocean and changes in the strength of the African monsoon. Our simulations show that when North Atlantic thermohaline circulation is substantially weakened, the flow of the subsurface North Brazil Current reverses. This leads to decreased upper tropical ocean stratification and warmer sea surface temperatures in the equatorial South Atlantic Ocean, and consequently reduces African summer monsoonal winds and rainfall over West Africa. This mechanism is in agreement with reconstructions of past climate. We therefore suggest that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the tropical Atlantic Ocean contributes to the rapidity of African monsoon transitions during abrupt climate change events.

  10. Tropical Atlantic climate response to different freshwater input in high latitudes with an ocean-only general circulation model

    NASA Astrophysics Data System (ADS)

    Men, Guang; Wan, Xiuquan; Liu, Zedong

    2016-10-01

    Tropical Atlantic climate change is relevant to the variation of Atlantic meridional overturning circulation (AMOC) through different physical processes. Previous coupled climate model simulation suggested a dipole-like SST structure cooling over the North Atlantic and warming over the South Tropical Atlantic in response to the slowdown of the AMOC. Using an ocean-only global ocean model here, an attempt was made to separate the total influence of various AMOC change scenarios into an oceanic-induced component and an atmospheric-induced component. In contrast with previous freshwater-hosing experiments with coupled climate models, the ocean-only modeling presented here shows a surface warming in the whole tropical Atlantic region and the oceanic-induced processes may play an important role in the SST change in the equatorial south Atlantic. Our result shows that the warming is partly governed by oceanic process through the mechanism of oceanic gateway change, which operates in the regime where freshwater forcing is strong, exceeding 0.3 Sv. Strong AMOC change is required for the gateway mechanism to work in our model because only when the AMOC is sufficiently weak, the North Brazil Undercurrent can flow equatorward, carrying warm and salty north Atlantic subtropical gyre water into the equatorial zone. This threshold is likely to be model-dependent. An improved understanding of these issues may have help with abrupt climate change prediction later.

  11. Early Holocene hydroclimate of Baffin Bay: Understanding the interplay between abrupt climate change events and ice sheet fluctuations

    NASA Astrophysics Data System (ADS)

    Corcoran, M. C.; Thomas, E. K.; Castañeda, I. S.; Briner, J. P.

    2017-12-01

    Understanding the causes of ice sheet fluctuations resulting in sea level rise is essential in today's warming climate. In high-latitude ice-sheet-proximal environments such as Baffin Bay, studying both the cause and the rate of ice sheet variability during past abrupt climate change events aids in predictions. Past climate reconstructions are used to understand ice sheet responses to changes in temperature and precipitation. The 9,300 and 8,200 yr BP events are examples of abrupt climate change events in the Baffin Bay region during which there were multiple re-advances of the Greenland and Laurentide ice sheets. High-resolution (decadal-scale) hydroclimate variability near the ice sheet margins during these abrupt climate change events is still unknown. We will generate a decadal-scale record of early Holocene temperature and precipitation using leaf wax hydrogen isotopes, δ2Hwax, from a lake sediment archive on Baffin Island, western Baffin Bay, to better understand abrupt climate change in this region. Shifts in temperature and moisture source result in changes in environmental water δ2H, which in turn is reflected in δ2Hwax, allowing for past hydroclimate to be determined from these compound-specific isotopes. The combination of terrestrial and aquatic δ2Hwax is used to determine soil evaporation and is ultimately used to reconstruct moisture variability. We will compare our results with a previous analysis of δ2Hwax and branched glycerol dialkyl glycerol tetraethers, a temperature and pH proxy, in lake sediment from western Greenland, eastern Baffin Bay, which indicates that cool and dry climate occurred in response to freshwater forcing events in the Labrador Sea. Reconstructing and comparing records on both the western and eastern sides of Baffin Bay during the early Holocene will allow for a spatial understanding of temperature and moisture balance changes during abrupt climate events, aiding in ice sheet modeling and predictions of future sea level

  12. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic

    2008-11-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.

  13. Constraining the sources of CH4 emissions during past abrupt climate change using CH4 triple isotopes mass balance from the ice core records

    NASA Astrophysics Data System (ADS)

    Dyonisius, M.; Petrenko, V. V.; Smith, A. W.; Hmiel, B.; Beck, J.; Seth, B.; Bock, M.; Hua, Q.; Yang, B.; Harth, C. M.; Beaudette, R.; Lee, J.; Erhardt, T.; Schmitt, J.; Brook, E.; Weiss, R. F.; Fischer, H.; Severinghaus, J. P.

    2017-12-01

    Methane (CH4) is the third most important greenhouse gas in the atmosphere after water vapor and CO2. Understanding how the natural CH4 budget has changed in response to changing climate in the past can provide insights on the sensitivity of the natural CH4 emissions to the current anthropogenic warming. CH4 isotopes (Δ14CH4, δ13C-CH4, and δD-CH4) from ice cores can be used to fingerprint the sources of CH4 increases in the past. We have successfully extracted 6 large volume (>1000kg) ice core samples from Taylor Glacier, Antarctica spanning the Oldest Dryas-Bølling transition ( 14.7ka) - the first abrupt warming and CH4 rise since the Last Glacial Maximum. Among the CH4 isotopes, our Δ 14CH4 data are unique in their ability to unambiguously distinguish between "old" CH4 sources (e.g. marine clathrate, geologic sources, old permafrost) and "modern" CH4 sources (e.g. tropical and boreal wetlands). Our Δ14CH4 data unambiguously rule out marine clathrate and old permafrost as the sources of the abrupt CH4 rise. Preliminary CH4 stable isotopes box modeling combined with interpolar CH4 concentration gradient from existing ice core records suggest that tropical wetlands were the dominant driver for the Oldest Dryas-Bølling CH4 rise.

  14. Postglacial Human resilience and susceptibility to abrupt climate change new insights from Star Carr

    NASA Astrophysics Data System (ADS)

    Blockley, Simon; Abrook, Ashley; Bayliss, Alex; Candy, Ian; Conneller, Chantal; Darvill, Chris; Deeprose, Laura; Kearney, Rebecca; Langdon, Pete; Langdon Langdon, Cath; Lincoln, Paul; Macleod, Alison; Matthews, Ian; Palmer, Adrian; Schreve, Danielle; Taylor, Barry; Milner, Nicky

    2017-04-01

    We know little about the lives of the early humans who lived during the early Postglacial period (the Lateglacial and Early Holocene), a time characterised by abrupt climate change after 16,000, which includes a series of abrupt climatic transitions linked to the reorganisation of the global environment after the glacial maximum and the last major global warming event at the onset of the Holocene. The hunter-gatherers who lived during the early Postglacial have been characterised as highly mobile, dispersed and living within small groups, and there is much debate as to how they adapted to climatic and environmental change: did they move in response to climatic transitions (and if so what was the climatic threshold), or instead adapt their lifeways to the new environmental conditions? A key area for examining these ideas is the British Isles as it sits on the Atlantic fringe of Northwest Europe with a climate that is highly responsive to the wider climate forcing experienced in the northern Hemisphere. Furthermore, in this period, Britain is directly linked to continental Europe due to lowered global sea levels allowing for the ease of human migration in and out of this region. In general the British record has been seen as being dominated by abandonment and reoccupation in the Postglacial during periods of climatic transition with hunter-gatherer mobility being closely linked to the prevailing environment. Recent discoveries at the Early Mesolithic site of Star Carr and surrounding area, linked to local and regional climate records, based on isotopic, chironomid and pollen proxy data and dated at high chronological resolution, offer a new picture. Postglacial human occupation of the area commences at the Pleistocene/Holocene transition but is short lived and appears to end close to the Pre-Boreal Oscillation, However, this is followed by a period where hunter-gatherers occupy Star Carr and settle and invest time and effort into building huts and large scale wooden

  15. The effect of abrupt climate changes and climate background conditions in Southern Europe during the last glacial

    NASA Astrophysics Data System (ADS)

    Knorr, Gregor; Martin-Puertas, Celia; Brauer, Achim; Lohmann, Gerrit

    2015-04-01

    The last glacial period is characterized by abrupt and large temperature shifts in Greenland and the North Atlantic realm. Pollen and sediment data from Lago Grande di Monticchio (MON) have demonstrated a clear imprint of these fluctuations operating at millennial time-scales. Interestingly, basic mean environmental condition changes with respect to temperature and precipitation occurred during MIS4, separating warm and dry conditions during MIS5 from relatively cold and humid conditions within MIS3. This general climate background shift is superposed by distinct millennial-scale variability at MON. Using a fully coupled atmosphere-ocean general circulation model applying boundary conditions at 32 ka BP and pre-industrial conditions as a surrogate for MIS3 and MIS5, we have simulated and analysed characteristic changes in Southern Europe during the last glacial. We find that changes in the mean state at MON are mainly related to a partial shift of the North Atlantic deep water (NADW) convection sites from the Nordic Seas to South of Iceland, the presence of the Fennoscandian ice sheet and lower greenhouse gas concentrations. These background characteristics provide the basis for enhanced zonal moisture transport from the eastern North Atlantic to Middle and Southern Europe. Furthermore, simulations of abrupt climate change scenarios show that a deactivation of the convection sites South of Iceland during MIS3 leads to cooler and dryer conditions at MON. Such temperature and precipitation changes are thought to provide a counter-acting effect on woody vegetation and associated pollen signals at MON. This is in contrast to the impact of abrupt climate perturbation scenarios during MIS5, where no significant precipitation changes are detected. Hence, the simulated changes and underlying mechanisms are largely consistent with the recorded proxy evidence with respect to both, mean state and millennial-scale changes.

  16. Phenology of temperate trees in tropical climates

    NASA Astrophysics Data System (ADS)

    Borchert, Rolf; Robertson, Kevin; Schwartz, Mark D.; Williams-Linera, Guadalupe

    2005-09-01

    Several North American broad-leaved tree species range from the northern United States at ˜47°N to moist tropical montane forests in Mexico and Central America at 15-20°N. Along this gradient the average minimum temperatures of the coldest month (T Jan), which characterize annual variation in temperature, increase from -10 to 12°C and tree phenology changes from deciduous to leaf-exchanging or evergreen in the southern range with a year-long growing season. Between 30 and 45°N, the time of bud break is highly correlated with T Jan and bud break can be reliably predicted for the week in which mean minimum temperature rises to 7°C. Temperature-dependent deciduous phenology—and hence the validity of temperature-driven phenology models—terminates in southern North America near 30°N, where T Jan>7°C enables growth of tropical trees and cultivation of frost-sensitive citrus fruits. In tropical climates most temperate broad-leaved species exchange old for new leaves within a few weeks in January-February, i.e., their phenology becomes similar to that of tropical leaf-exchanging species. Leaf buds of the southern ecotypes of these temperate species are therefore not winter-dormant and have no chilling requirement. As in many tropical trees, bud break of Celtis, Quercus and Fagus growing in warm climates is induced in early spring by increasing daylength. In tropical climates vegetative phenology is determined mainly by leaf longevity, seasonal variation in water stress and day length. As water stress during the dry season varies widely with soil water storage, climate-driven models cannot predict tree phenology in the tropics and tropical tree phenology does not constitute a useful indicator of global warming.

  17. Environment and Passive Climate Control Chiefly in Tropical Climates.

    ERIC Educational Resources Information Center

    Dean, John F.

    This paper focuses on some of the effects of climate on library and archives collections in tropical climates, and discusses some prudent alternatives to the mechanical and chemical approaches commonly used to control climate and its immediate effects. One of the most important factors affecting the longevity of library and archival materials is…

  18. Dynamic response of desert wetlands to abrupt climate change

    PubMed Central

    Springer, Kathleen B.; Manker, Craig R.; Pigati, Jeffrey S.

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming. PMID:26554007

  19. Dynamic response of desert wetlands to abrupt climate change

    USGS Publications Warehouse

    Springer, Kathleen; Manker, Craig; Pigati, Jeffrey S.

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming.

  20. Influence of external forcings on abrupt millennial-scale climate changes: a statistical modelling study

    NASA Astrophysics Data System (ADS)

    Mitsui, Takahito; Crucifix, Michel

    2017-04-01

    The last glacial period was punctuated by a series of abrupt climate shifts, the so-called Dansgaard-Oeschger (DO) events. The frequency of DO events varied in time, supposedly because of changes in background climate conditions. Here, the influence of external forcings on DO events is investigated with statistical modelling. We assume two types of simple stochastic dynamical systems models (double-well potential-type and oscillator-type), forced by the northern hemisphere summer insolation change and/or the global ice volume change. The model parameters are estimated by using the maximum likelihood method with the NGRIP Ca^{2+} record. The stochastic oscillator model with at least the ice volume forcing reproduces well the sample autocorrelation function of the record and the frequency changes of warming transitions in the last glacial period across MISs 2, 3, and 4. The model performance is improved with the additional insolation forcing. The BIC scores also suggest that the ice volume forcing is relatively more important than the insolation forcing, though the strength of evidence depends on the model assumption. Finally, we simulate the average number of warming transitions in the past four glacial periods, assuming the model can be extended beyond the last glacial, and compare the result with an Iberian margin sea-surface temperature (SST) record (Martrat et al. in Science 317(5837): 502-507, 2007). The simulation result supports the previous observation that abrupt millennial-scale climate changes in the penultimate glacial (MIS 6) are less frequent than in the last glacial (MISs 2-4). On the other hand, it suggests that the number of abrupt millennial-scale climate changes in older glacial periods (MISs 6, 8, and 10) might be larger than inferred from the SST record.

  1. An Abrupt Centennial-Scale Drought Event and Mid-Holocene Climate Change Patterns in Monsoon Marginal Zones of East Asia

    PubMed Central

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0–7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different

  2. An abrupt centennial-scale drought event and mid-holocene climate change patterns in monsoon marginal zones of East Asia.

    PubMed

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical

  3. Shifts on reproductive phenology of tropical cerrado savanna trees and climate changes

    NASA Astrophysics Data System (ADS)

    Morellato, Patricia

    2010-05-01

    Phenology is the study of cyclic biological events and its relationship to abiotic factors. Timing of flowering, fruiting and leafing is highly correlated to environmental factors such as temperature, precipitation, irradiance and isolation. Accordingly, any change in these factors may have a direct effect on the initiation, intensity and duration of different phenophases. Tropical phenology has not contributed much for climatic change research since historical data sets are scarce and the absence of sharp seasons and distinct factors driving phenology makes difficult the detection of changes over time. One way to have insights on climate driven phenology shifts on tropical plants is through the comparison of plant phenology under different environmental conditions. Fragmentation of natural landscape has exposed plants to edge effects - the interaction between two adjacent ecosystems, when the two are separated by an abrupt transition - the edge, including both abiotic and biological changes on environmental conditions that likely affect plant phenology. The microclimatic conditions along edges have important direct biological effects on the reproductive phenology and fitness of plant species. One can expected that the abiotic edge effects on plant phenology may be similar to some extent to certain effects induced by climate change on plant phenology since both involve shifts on environmental conditions. Due to the threatened status and rich biodiversity of Brazilian Neotropical savanna, or the Brazilian Cerrado, the present study aimed to understand edge effects on cerrado savanna species. We compared micro environmental factors and phenology of several species on the edge and in the interior of cerrado savanna. Our first results indicated that shifts on the micro environmental condition may have driven changes in time, duration and intensity of species phenology and may give us insights on savanna responses to climate changes.

  4. Holocene dynamics of the Florida Everglades with respect to climate, dustfall, and tropical storms

    USGS Publications Warehouse

    Glaser, Paul H.; Hansen, Barbara C. S.; Donovan, Joseph J.; Givnish, Thomas J.; Stricker, Craig A.; Volin, John C.

    2013-01-01

    Aeolian dust is rarely considered an important source for nutrients in large peatlands, which generally develop in moist regions far from the major centers of dust production. As a result, past studies assumed that the Everglades provides a classic example of an originally oligotrophic, P-limited wetland that was subsequently degraded by anthropogenic activities. However, a multiproxy sedimentary record indicates that changes in atmospheric circulation patterns produced an abrupt shift in the hydrology and dust deposition in the Everglades over the past 4,600 y. A wet climatic period with high loadings of aeolian dust prevailed before 2800 cal BP (calibrated years before present) when vegetation typical of a deep slough dominated the principal drainage outlet of the Everglades. This dust was apparently transported from distant source areas, such as the Sahara Desert, by tropical storms according to its elemental chemistry and mineralogy. A drier climatic regime with a steep decline in dustfall persisted after 2800 cal BP maintaining sawgrass vegetation at the coring site as tree islands developed nearby (and pine forests covered adjacent uplands). The marked decline in dustfall was related to corresponding declines in sedimentary phosphorus, organic nitrogen, and organic carbon, suggesting that a close relationship existed between dustfall, primary production, and possibly, vegetation patterning before the 20th century. The climatic change after 2800 cal BP was probably produced by a shift in the Bermuda High to the southeast, shunting tropical storms to the south of Florida into the Gulf of Mexico.

  5. Holocene dynamics of the Florida Everglades with respect to climate, dustfall, and tropical storms.

    PubMed

    Glaser, Paul H; Hansen, Barbara C S; Donovan, Joe J; Givnish, Thomas J; Stricker, Craig A; Volin, John C

    2013-10-22

    Aeolian dust is rarely considered an important source for nutrients in large peatlands, which generally develop in moist regions far from the major centers of dust production. As a result, past studies assumed that the Everglades provides a classic example of an originally oligotrophic, P-limited wetland that was subsequently degraded by anthropogenic activities. However, a multiproxy sedimentary record indicates that changes in atmospheric circulation patterns produced an abrupt shift in the hydrology and dust deposition in the Everglades over the past 4,600 y. A wet climatic period with high loadings of aeolian dust prevailed before 2800 cal BP (calibrated years before present) when vegetation typical of a deep slough dominated the principal drainage outlet of the Everglades. This dust was apparently transported from distant source areas, such as the Sahara Desert, by tropical storms according to its elemental chemistry and mineralogy. A drier climatic regime with a steep decline in dustfall persisted after 2800 cal BP maintaining sawgrass vegetation at the coring site as tree islands developed nearby (and pine forests covered adjacent uplands). The marked decline in dustfall was related to corresponding declines in sedimentary phosphorus, organic nitrogen, and organic carbon, suggesting that a close relationship existed between dustfall, primary production, and possibly, vegetation patterning before the 20th century. The climatic change after 2800 cal BP was probably produced by a shift in the Bermuda High to the southeast, shunting tropical storms to the south of Florida into the Gulf of Mexico.

  6. Abrupt cooling over the North Atlantic in modern climate models

    PubMed Central

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-01-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy. PMID:28198383

  7. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. Copyright © 2016, American Association for the Advancement of Science.

  8. Abrupt climate changes during Termination III in Southern Europe

    PubMed Central

    Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R. Lawrence

    2017-01-01

    The Late Quaternary glacial–interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium–thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I). PMID:28874530

  9. Abrupt climate changes during Termination III in Southern Europe.

    PubMed

    Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R Lawrence

    2017-09-19

    The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ 13 C, δ 18 O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).

  10. Abrupt climate changes during Termination III in Southern Europe

    NASA Astrophysics Data System (ADS)

    Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R. Lawrence

    2017-09-01

    The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).

  11. Tropical African Glacier Fluctuations During Termination 1

    NASA Astrophysics Data System (ADS)

    Jackson, M. S.; Kelly, M. A.; Russell, J. M.; Doughty, A. M.; Howley, J. A.; Zimmerman, S. R. H.

    2017-12-01

    As the primary source of latent heat and water vapor to the atmosphere, the tropics are a key element of Earth's climate system. However, the potential role of the tropics in past climate change, and particularly abrupt climate changes, is uncertain. A first step to assessing the role of the low latitudes in both past and future climate is to determine the timing and spatial variability of past climate change in the tropics. Termination 1, the time of most rapid global warming of the last glacial cycle, is an ideal period on which to focus. We present a 10Be chronology of glaciation from the Rwenzori Mountains, Uganda, which elucidates the timing and magnitude of deglacial warming in the African tropics through the Termination, from the Last Glacial Maximum (LGM) to the Holocene. Ice retreated from its maximum LGM extent by 20.7 ka. In the Bujuku valley, a series of nested moraines deposited between 15-14 ka attest to late-glacial ice extent. In both the Bujuku and Nyamugasani valleys, moraine sequences and erratic boulders indicate glacier retreat following the Younger Dryas (YD) and during the early Holocene. The preliminary chronology from these moraines suggests that glaciers were more extensive during the Antarctic Cold Reversal (ACR) than during the YD. This chronology is similar to that observed in the South American tropics, where expanded glaciers during the ACR are recognized across the high Andes. This suggests that glaciers across the tropics responded to a common forcing during Termination 1, likely temperature. Possible mechanisms to induce such temperature change include global climate boundary conditions, and greenhouse gas forcing in particular, as well as tropical ocean variability.

  12. Climate change and tropical biodiversity: a new focus.

    PubMed

    Brodie, Jedediah; Post, Eric; Laurance, William F

    2012-03-01

    Considerable efforts are focused on the consequences of climate change for tropical rainforests. However, potentially the greatest threats to tropical biodiversity (synergistic interactions between climatic changes and human land use) remain understudied. Key concerns are that aridification could increase the accessibility of previously non-arable or remote lands, elevate fire impacts and exacerbate ecological effects of habitat disturbance. The growing climatic change literature often fails to appreciate that, in coming decades, climate-land use interactions might be at least as important as abiotic changes per se for the fate of tropical biodiversity. In this review, we argue that protected area expansion along key ecological gradients, regulation of human-lit fires, strategic forest-carbon financing and re-evaluations of agricultural and biofuel subsidies could ameliorate some of these synergistic threats. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. Western Tropical Atlantic Hydrologic change during the last 130,000 years

    NASA Astrophysics Data System (ADS)

    McGrath, S. M.; Lavoie, N.; Oppo, D.

    2016-12-01

    Abrupt climate changes in the North Atlantic during the last 130,000 years are associated with hydrologic changes in the western tropical Atlantic Ocean. Previous studies on marine sediment cores from between 4°S and the equator have documented pulses of terrigenous sediment recording increased precipitation and weathering on the Brazilian Nordeste associated with Heinrich events. We worked on cores KNR197-3-11CDH (7°40'N, 53°49'W, water depth 550 m) and KNR 197-3-46CDH (7°50.1621'N, 53°39.8051'W, 947m water depth) located farther north along the South American continental slope, where sediment derives from the Amazon river basin and is transported by the North Brazilian Current. Preliminary stratigraphy based on magnetic susceptibility shows a possible correlation with the Greenland ice core δ18O stratigraphy. We use sediment elemental composition, determined by x-ray fluorescence (XRF) to evaluate variations in terrigenous sediment runoff and δ18O of the planktonic foraminifers Globierinoides ruber to evaluate variations in western tropical North Atlantic surface hydrography across North Atlantic abrupt climate events. Similarities and differences among our records and the records from the more southerly cores will help understand the mechanisms of hydrologic changes in the regions on abrupt climate time scales.

  14. Holocene dynamics of the Florida Everglades with respect to climate, dustfall, and tropical storms

    PubMed Central

    Glaser, Paul H.; Hansen, Barbara C. S.; Donovan, Joe J.; Givnish, Thomas J.; Stricker, Craig A.; Volin, John C.

    2013-01-01

    Aeolian dust is rarely considered an important source for nutrients in large peatlands, which generally develop in moist regions far from the major centers of dust production. As a result, past studies assumed that the Everglades provides a classic example of an originally oligotrophic, P-limited wetland that was subsequently degraded by anthropogenic activities. However, a multiproxy sedimentary record indicates that changes in atmospheric circulation patterns produced an abrupt shift in the hydrology and dust deposition in the Everglades over the past 4,600 y. A wet climatic period with high loadings of aeolian dust prevailed before 2800 cal BP (calibrated years before present) when vegetation typical of a deep slough dominated the principal drainage outlet of the Everglades. This dust was apparently transported from distant source areas, such as the Sahara Desert, by tropical storms according to its elemental chemistry and mineralogy. A drier climatic regime with a steep decline in dustfall persisted after 2800 cal BP maintaining sawgrass vegetation at the coring site as tree islands developed nearby (and pine forests covered adjacent uplands). The marked decline in dustfall was related to corresponding declines in sedimentary phosphorus, organic nitrogen, and organic carbon, suggesting that a close relationship existed between dustfall, primary production, and possibly, vegetation patterning before the 20th century. The climatic change after 2800 cal BP was probably produced by a shift in the Bermuda High to the southeast, shunting tropical storms to the south of Florida into the Gulf of Mexico. PMID:24101489

  15. High resolution water stable isotope profiles of abrupt climate transitions in Greenland ice with new observations from NEEM

    NASA Astrophysics Data System (ADS)

    Popp, T. J.; White, J. W. C.; Gkinis, V.; Vinther, B. M.; Johnsen, S. J.

    2012-04-01

    In 1989 Willi Dansgaard and others, using the DYE3 ice core, showed that the abrupt termination of the Younger Dryas expressed in water stable isotope ratios and deuterium excess was completed in less than 50 years. A few years later, using the GISP2 ice core, Richard Alley and others proposed that snow accumulation at the site doubled in as little as 1-3 years across the same climate transition at the end of the Younger Dryas. Over the next two decades, in large part due to such observations from Greenland ice cores, a paradigm of linked, abrupt changes in the North Atlantic region has been developed around North Atlantic deep water formation, North Atlantic sea ice extent, and widespread atmospheric circulation changes occurring repeatedly during the last glacial period in response to changing freshwater fluxes to the region, or perhaps other causes. More recently, with the NGRIP ice core, using a suite of high resolution proxy data, and in particular deuterium excess, it was observed again that certain features in the climate system can switch modes from one year to the next, while other proxies can take from decades to centuries to completely switch modes. Thus, an event seen in the proxy records such as the abrupt end of the Younger Dryas (or other interstadial events) may comprise multiple climatic or oceanic responses with different relative timing and duration which potentially follow a predictable sequence of events, in some cases separated by only a few years. Today, the search continues for these emerging patterns through isotopic and other highly resolvable proxy data series from ice cores. With the recent completion of the drilling at NEEM, many abrupt transitions have now been measured in detail over a geographic transect with drilling sites spanning from DYE3 in Southern Greenland, GISP2 in the central summit region, and up to NGRIP and NEEM in the far north. The anatomy of abrupt climate transitions can therefore be examined both spatially and

  16. Skilful multi-year predictions of tropical trans-basin climate variability

    PubMed Central

    Chikamoto, Yoshimitsu; Timmermann, Axel; Luo, Jing-Jia; Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Ishii, Masayoshi; Xie, Shang-Ping; Jin, Fei-Fei

    2015-01-01

    Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. The predictability of the corresponding atmospheric signals is typically limited to less than 1 year lead time. Here we present observational and modelling evidence for multi-year predictability of coherent trans-basin climate variations that are characterized by a zonal seesaw in tropical sea surface temperature and sea-level pressure between the Pacific and the other two ocean basins. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Niño Southern Oscillation flavours, can be predicted up to 3 years ahead, thus exceeding the predictive skill of current tropical climate forecasts for natural variability. This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation. PMID:25897996

  17. Skilful multi-year predictions of tropical trans-basin climate variability.

    PubMed

    Chikamoto, Yoshimitsu; Timmermann, Axel; Luo, Jing-Jia; Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Ishii, Masayoshi; Xie, Shang-Ping; Jin, Fei-Fei

    2015-04-21

    Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. The predictability of the corresponding atmospheric signals is typically limited to less than 1 year lead time. Here we present observational and modelling evidence for multi-year predictability of coherent trans-basin climate variations that are characterized by a zonal seesaw in tropical sea surface temperature and sea-level pressure between the Pacific and the other two ocean basins. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Niño Southern Oscillation flavours, can be predicted up to 3 years ahead, thus exceeding the predictive skill of current tropical climate forecasts for natural variability. This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation.

  18. The nature of abrupt climate change during the last glacial period from detailed isotopic records from the NGRIP ice core

    NASA Astrophysics Data System (ADS)

    Popp, T. J.; Svensson, A.; Steffensen, J. P.; Johnsen, S. J.; White, J. W. C.

    2009-04-01

    Isotopic and chemical impurity records from Greenland ice cores with sub-annual resolution across three fast climate transitions of the last deglacial termination reveal complex patterns of environmental change for the onset of Greenland Interstadial 1 (GI-1 or Bølling), the onset of Greenland Stadial 1 (GS-1 or Younger Dryas), and the onset of the Holocene. In the NGRIP ice core each of these transitions is initiated by a 1-3 year mode shift in deuterium excess, which is a proxy for the Greenland precipitation moisture source. These mode shifts in deuterium excess are decoupled in time from the isotopic (deuterium and oxygen-18) transitions from which they are derived. In general the abrupt isotopic transitions follow the corresponding deuterium excess shifts and span decades rather than years. Similar data from GISP2 confirms the clear deuterium excess mode shifts for transitions from cold states to warm states; however the abrupt deuterium excess transition at the onset of GS-1 is not expressed in a similar way at GISP2. Ironically, it appears that this cooling at the beginning of the Younger Dryas, for which we have theories of the triggering event, is less clearly recorded than warming events, the triggering of which is still poorly understood. Along with other available paleo-data, these results indicate that the sum of an abrupt climate change is composed of multiple responses from different parts of the climate system. These responses can be separated by as little as a single year to a few decades and the collection of these responses result in a variety of abrupt transitions giving each a unique anatomy. Here we expand this type of analysis with new isotope, deuterium excess, and accumulation rate time series from NGRIP across the abrupt transitions associated with several interstadial events of the Last Glacial period (Dansgaard-Oeschger events). Indeed the temporal phasing of deuterium excess and the isotopic content of the ice can vary from one event

  19. Tropical Pacific climate during the Medieval Climate Anomaly: progress and pitfalls

    NASA Astrophysics Data System (ADS)

    Cobb, K. M.; Westphal, N.; Charles, C.; Sayani, H. R.; Edwards, R. L.; Cheng, H.; Grothe, P. R.; Chen, T.; Hitt, N. T.; O'Connor, G.; Atwood, A. R.

    2016-12-01

    A vast trove of paleoclimate records indicates that the Medieval Climate Anomaly (MCA; 900-1200AD) was characterized by relative warmth throughout the Northern Hemisphere and significant hydroclimate anomalies - particularly well-resolved over North America - that posed a challenge to human populations. The global-scale nature of the climate anomalies has driven speculation that the tropical Pacific, with its rich spectrum of natural variability and far-reaching impact, may have undergone a prolonged reorganization during the MCA. While some key records from across the tropical Pacific document significant changes in temperature and/or hydrology, a dynamically-consistent picture of the MCA tropical Pacific climate state has proven elusive. In particular, there are few if any robust paleoclimate constraints from the central Pacific, where even modest changes in ocean temperature translate into distinct patterns of global atmospheric teleconnections. Here, we present a new collection of fossil coral multi-proxy records from Christmas Island (2N, 157W) that provide robust constraints on both temperature and hydrological changes during the MCA. We employ both modern coral data, instrumental climate data, and climate model output in developing a framework for quantifying the uncertainties associated with the new fossil coral data. In doing so, we illustrate the clear benefits of modern environmental monitoring campaigns that inform the generation of paleoclimate pseudo-proxies.

  20. Abrupt climate shift in the Western Mediterranean Sea.

    PubMed

    Schroeder, K; Chiggiato, J; Bryden, H L; Borghini, M; Ben Ismail, S

    2016-03-11

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.

  1. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions.

    PubMed

    Molina, Mario; Zaelke, Durwood; Sarma, K Madhava; Andersen, Stephen O; Ramanathan, Veerabhadran; Kaniaru, Donald

    2009-12-08

    Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of "dangerous anthropogenic interference" (DAI). Scientific and policy literature refers to the need for "early," "urgent," "rapid," and "fast-action" mitigation to help avoid DAI and abrupt climate changes. We define "fast-action" to include regulatory measures that can begin within 2-3 years, be substantially implemented in 5-10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO(2) GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO(2) emissions.

  2. Pan-Tropical Analysis of Climate Effects on Seasonal Tree Growth

    PubMed Central

    Wagner, Fabien; Rossi, Vivien; Aubry-Kientz, Mélaine; Bonal, Damien; Dalitz, Helmut; Gliniars, Robert; Stahl, Clément; Trabucco, Antonio; Hérault, Bruno

    2014-01-01

    Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO2. Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO2, water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intra-annual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent. PMID:24670981

  3. Pan-tropical analysis of climate effects on seasonal tree growth.

    PubMed

    Wagner, Fabien; Rossi, Vivien; Aubry-Kientz, Mélaine; Bonal, Damien; Dalitz, Helmut; Gliniars, Robert; Stahl, Clément; Trabucco, Antonio; Hérault, Bruno

    2014-01-01

    Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO2. Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO2, water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intra-annual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent.

  4. Tropical rainforest response to marine sky brightening climate engineering

    NASA Astrophysics Data System (ADS)

    Muri, Helene; Niemeier, Ulrike; Kristjánsson, Jón Egill

    2015-04-01

    Tropical forests represent a major atmospheric carbon dioxide sink. Here the gross primary productivity (GPP) response of tropical rainforests to climate engineering via marine sky brightening under a future scenario is investigated in three Earth system models. The model response is diverse, and in two of the three models, the tropical GPP shows a decrease from the marine sky brightening climate engineering. Partial correlation analysis indicates precipitation to be important in one of those models, while precipitation and temperature are limiting factors in the other. One model experiences a reversal of its Amazon dieback under marine sky brightening. There, the strongest partial correlation of GPP is to temperature and incoming solar radiation at the surface. Carbon fertilization provides a higher future tropical rainforest GPP overall, both with and without climate engineering. Salt damage to plants and soils could be an important aspect of marine sky brightening.

  5. The contrasting climate response to tropical and extratropical energy perturbations

    NASA Astrophysics Data System (ADS)

    Hawcroft, Matt; Haywood, Jim M.; Collins, Mat; Jones, Andy

    2018-01-01

    The link between cross-equatorial energy transport, the double-intertropical convergence zone (DI) problem and biases in tropical and extratropical albedo and energy budgets in climate models have been investigated in multiple studies, though DI biases persist in many models. Here, a coupled climate model, HadGEM2-ES, is used to investigate the response to idealised energy perturbations in the tropics and extratropics, in both the northern and southern hemispheres, through the imposition of stratospheric aerosols that reflect incoming radiation. The impact on the tropical climate of high and low latitude forcing strongly contrasts, with large changes in tropical precipitation and modulation of the DI bias when the tropics are cooled as precipitation moves away from the cooled hemisphere. These responses are muted when the extratropics are cooled, as the meridional energy transport anomalies that are excited by these energy budget anomalies are partitioned between the atmosphere and ocean. The results here highlight the persistence of the DI bias in HadGEM2-ES, indicating why little progress has been made in rectifying these problems through many generations of climate models. A highly linear relationship between cross-equatorial atmospheric energy transport, tropical precipitation asymmetry and tropical sea surface temperature biases is also demonstrated, giving some suggestion as to where improvements in these large scale, persistent biases may be achieved.

  6. Forest-climate interactions in fragmented tropical landscapes.

    PubMed

    Laurance, William F

    2004-03-29

    In the tropics, habitat fragmentation alters forest-climate interactions in diverse ways. On a local scale (less than 1 km), elevated desiccation and wind disturbance near fragment margins lead to sharply increased tree mortality, thus altering canopy-gap dynamics, plant community composition, biomass dynamics and carbon storage. Fragmented forests are also highly vulnerable to edge-related fires, especially in regions with periodic droughts or strong dry seasons. At landscape to regional scales (10-1000 km), habitat fragmentation may have complex effects on forest-climate interactions, with important consequences for atmospheric circulation, water cycling and precipitation. Positive feedbacks among deforestation, regional climate change and fire could pose a serious threat for some tropical forests, but the details of such interactions are poorly understood.

  7. Abrupt Holocene climate change as an important factor for human migration in West Greenland

    PubMed Central

    D’Andrea, William J.; Huang, Yongsong; Fritz, Sherilyn C.; Anderson, N. John

    2011-01-01

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation. PMID:21628586

  8. Abrupt climate shift in the Western Mediterranean Sea

    PubMed Central

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  9. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions

    PubMed Central

    Molina, Mario; Zaelke, Durwood; Sarma, K. Madhava; Andersen, Stephen O.; Ramanathan, Veerabhadran; Kaniaru, Donald

    2009-01-01

    Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of “dangerous anthropogenic interference” (DAI). Scientific and policy literature refers to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to help avoid DAI and abrupt climate changes. We define “fast-action” to include regulatory measures that can begin within 2–3 years, be substantially implemented in 5–10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO2 GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO2 emissions. PMID:19822751

  10. Climate Science: Tropical Expansion by Ocean Swing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lu, Jian

    The tropical belt has become wider over the past decades, but climate models fall short of capturing the full rate of the expansion. The latest analysis of the climate simulations suggests that a long-term swing of the Pacific Decadal Oscillation is the main missing cause.

  11. Nature and causes of Quaternary climate variation of tropical South America

    NASA Astrophysics Data System (ADS)

    Baker, Paul A.; Fritz, Sherilyn C.

    2015-09-01

    This selective review of the Quaternary paleoclimate of the South American summer monsoon (SASM) domain presents viewpoints regarding a range of key issues in the field, many of which are unresolved and some of which are controversial. (1) El Niño-Southern Oscillation variability, while the most important global-scale mode of interannual climate variation, is insufficient to explain most of the variation of tropical South American climate observed in both the instrumental and the paleoclimate records. (2) Significant climate variation in tropical South America occurs on seasonal to orbital (i.e. multi-millennial) time scales as a result of sea-surface temperature (SST) variation and ocean-atmosphere interactions of the tropical Atlantic. (3) Decadal-scale climate variability, linked with this tropical Atlantic variability, has been a persistent characteristic of climate in tropical South America for at least the past half millennium, and likely, far beyond. (4) Centennial-to-millennial climate events in tropical South America were of longer duration and, perhaps, larger amplitude than any observed in the instrumental period, which is little more than a century long in tropical South America. These were superimposed upon both precession-paced insolation changes that caused significant variation in SASM precipitation and eccentricity-paced global glacial boundary conditions that caused significant changes in the tropical South American moisture balance. As a result, river sediment and water discharge increased and decreased across tropical South America, lake levels rose and fell, paleolakes arose and disappeared on the Altiplano, glaciers waxed and waned in the tropical Andes, and the tropical rainforest underwent significant changes in composition and extent. To further evaluate climate forcing over the last glacial cycle (˜125 ka), we developed a climate forcing model that combines summer insolation forcing and a proxy for North Atlantic SST forcing to

  12. Climatic and Societal Causes for Abrupt Environmental Change in the Mediterranean During the Common Era

    NASA Astrophysics Data System (ADS)

    Mensing, S. A.; Tunno, I.; Sagnotti, L.; Florindo, F.; Noble, P. J.; Archer, C.; Zimmerman, S. R. H.; Pavón-Carrasco, F. J.; Cifnani, G.; Passigli, S.; Piovesan, G.

    2015-12-01

    We compare climatic and societal causes for abrupt environmental change for the last 2000 years in the Rieti Basin, central Italy using high-resolution sedimentary paleoenvironmental proxies, historical documents, and annually resolved independent climate reconstructions of temperature and precipitation. Pollen zones, identified from temporally constrained cluster analysis, coincide with historic periods developed from well-established ceramic sequences corresponding to the Roman Imperial through Late Antique (1 to 600 CE) Early Medieval (600 to 875 CE), Medieval through Late Medieval (875 to 1400 CE), Renaissance and Modern (1400 to 1725 CE), and Contemporary periods (1725 CE to present). Non-metric dimensional scaling (NMDS) ordination showed that each temporal period occupied a unique ecologic space suggesting that a new landscape was created during each successive historic period. During Roman time, between 1 and 500 CE, a modest decline in forest coincides with a positive phase of the North Atlantic Oscillation (NAO) and drier climate; however mesophyllous forest is preserved. Steep decline in forest cover between 850 and 950 CE coincides with positive temperature anomalies in Europe and a positive NAO. Although this would seem to suggest climate as a cause, temperature and precipitation changes are modest and the magnitude and rapidity of the vegetation change suggests climate played a small role. Archaeological evidence from across Europe identifies socioeconomic factors that produced forest clearing. In contrast, cooler temperatures and a negative NAO (increased ppt) appears to have been a catalyst for land abandonment and forest recovery in the 13th to 14th centuries. The NAO produces opposite effects on societies in the eastern and western Mediterranean with the negative phase in 1400 CE leading to cool wet climate and land abandonment in central Italy but an abrupt shift to drier conditions and change from sedentary village life to nomadism in Syria.

  13. Sensitivity of tropical carbon to climate change constrained by carbon dioxide variability.

    PubMed

    Cox, Peter M; Pearson, David; Booth, Ben B; Friedlingstein, Pierre; Huntingford, Chris; Jones, Chris D; Luke, Catherine M

    2013-02-21

    The release of carbon from tropical forests may exacerbate future climate change, but the magnitude of the effect in climate models remains uncertain. Coupled climate-carbon-cycle models generally agree that carbon storage on land will increase as a result of the simultaneous enhancement of plant photosynthesis and water use efficiency under higher atmospheric CO(2) concentrations, but will decrease owing to higher soil and plant respiration rates associated with warming temperatures. At present, the balance between these effects varies markedly among coupled climate-carbon-cycle models, leading to a range of 330 gigatonnes in the projected change in the amount of carbon stored on tropical land by 2100. Explanations for this large uncertainty include differences in the predicted change in rainfall in Amazonia and variations in the responses of alternative vegetation models to warming. Here we identify an emergent linear relationship, across an ensemble of models, between the sensitivity of tropical land carbon storage to warming and the sensitivity of the annual growth rate of atmospheric CO(2) to tropical temperature anomalies. Combined with contemporary observations of atmospheric CO(2) concentration and tropical temperature, this relationship provides a tight constraint on the sensitivity of tropical land carbon to climate change. We estimate that over tropical land from latitude 30° north to 30° south, warming alone will release 53 ± 17 gigatonnes of carbon per kelvin. Compared with the unconstrained ensemble of climate-carbon-cycle projections, this indicates a much lower risk of Amazon forest dieback under CO(2)-induced climate change if CO(2) fertilization effects are as large as suggested by current models. Our study, however, also implies greater certainty that carbon will be lost from tropical land if warming arises from reductions in aerosols or increases in other greenhouse gases.

  14. Coherent Sea Ice Variations in the Nordic Seas and Abrupt Greenland Climate Changes over Dansgaard-Oeschger Cycles

    NASA Astrophysics Data System (ADS)

    Sadatzki, H.; Berben, S.; Dokken, T.; Stein, R.; Fahl, K.; Jansen, E.

    2016-12-01

    Rapid changes in sea ice extent in the Nordic Seas may have played a crucial role in controlling the abruptness of ocean circulation and climate changes associated with Dansgaard-Oeschger (D-O) cycles during the last glacial (Li et al., 2010; Dokken et al., 2013). To investigate the role of sea ice for abrupt climate changes, we produced a sea ice record from the Norwegian Sea Core MD99-2284 at a temporal resolution approaching that of ice core records, covering four D-O cycles at ca. 32-41 ka. This record is based on the sea ice diatom biomarker IP25, open-water phytoplankton biomarker dinosterol and semi-quantitative phytoplankton-IP25 (PIP25) estimates. A detailed tephrochronology of MD99-2284 corroborates the tuning-based age model and independently constrains the GS9/GIS8 transition, allowing for direct comparison between our sediment and ice core records. For cold stadials we find extremely low fluxes of total organic carbon, dinosterol and IP25, which points to a general absence of open-water phytoplankton and ice algae production under a near-permanent sea ice cover. For the interstadials, in turn, all biomarker fluxes are strongly enhanced, reflecting a highly productive sea ice edge situation and implying largely open ocean conditions for the eastern Nordic Seas. As constrained by three tephra layers, we observe that the stadial-interstadial sea ice decline was rapid and may have induced a coeval abrupt northward shift in the Greenland precipitation moisture source as recorded in ice cores. The sea ice retreat also facilitated a massive heat release through deep convection in the previously stratified Nordic Seas, generating atmospheric warming of the D-O events. We thus conclude that rapid changes in sea ice extent in the Nordic Seas amplified oceanic reorganizations and were a key factor in controlling abrupt Greenland climate changes over D-O cycles. Dokken, T.M. et al., 2013. Paleoceanography 28, 491-502 Li, C. et al., 2010. Journ. Clim. 23, 5457-5475

  15. Climate mitigation and the future of tropical landscapes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thomson, Allison M.; Calvin, Katherine V.; Chini, Louise Parsons

    2010-11-16

    Land use change to meet 21st Century demands for food, fuel, and fiber will occur in the context of both a changing climate as well as societal efforts to mitigate climate change. This changing natural and human environment will have large consequences for forest resources, terrestrial carbon storage and emissions, and food and energy crop production over the next century. Any climate change mitigation policies enacted will change the environment under which land-use decisions are made and alter global land use change patterns. Here we use the GCAM integrated assessment model to explore how climate mitigation policies that achieve amore » climate stabilization at 4.5 W m-2 radiative forcing in 2100 and value carbon in terrestrial ecosystems interact with future agricultural productivity and food and energy demands to influence land use in the tropics. The regional land use results are downscaled from GCAM regions to produce gridded maps of tropical land use change. We find that tropical forests are preserved only in cases where a climate mitigation policy that values terrestrial carbon is in place, and crop productivity growth continues throughout the century. Crop productivity growth is also necessary to avoid large scale deforestation globally and enable the production of bioenergy crops. The terrestrial carbon pricing assumptions in GCAM are effective at avoiding deforestation even when cropland must expand to meet future food demand.« less

  16. Vegetation responses to abrupt climatic changes during the Last Interglacial Complex (Marine Isotope Stage 5) at Tenaghi Philippon, NE Greece

    NASA Astrophysics Data System (ADS)

    Milner, A. M.; Roucoux, K. H.; Collier, R. E. L.; Müller, U. C.; Pross, J.; Tzedakis, P. C.

    2016-12-01

    The discovery that climate variability during the Last Glacial shifted rapidly between climate states has intensified efforts to understand the distribution, timing and impact of abrupt climate change under a wide range of boundary conditions. In contribution to this, we investigate the nature of abrupt environmental changes in terrestrial settings of the Mediterranean region during the Last Interglacial Complex (Marine Isotope Stage [MIS] 5) and explore the relationships of these changes to high-latitude climate events. We present a new, temporally highly resolved (mean: 170 years) pollen record for the Last Interglacial Complex from Tenaghi Philippon, north-east Greece. The new pollen record, which spans the interval from 130,000 to 65,000 years ago, forms part of an exceptionally long polleniferous sediment archive covering the last 1.35 million years. The pollen data reveal an interglacial followed by alternating forest and steppe phases representing the interstadials and stadials of the Early Glacial. Superimposed on these millennial-scale changes is evidence of persistent sub-millennial-scale variability. We identify ten high-amplitude abrupt events in the pollen record, characterised by rapid contractions of closed forest to open steppe environment and interpreted to indicate major changes in moisture availability and temperature. The contractions in forest cover on millennial timescales appear associated with cooling events in the Mediterranean Sea, North Atlantic and Greenland regions, linked to the Dansgaard-Oeschger (DO) cycles of the Early Glacial. On sub-millennial timescales, the pattern of changes in forest cover at Tenaghi Philippon display a structure similar to the pattern of short-lived precursor and rebound-type events detected in the Greenland ice-core record. Our findings indicate that persistent, high-amplitude environmental variability occurred throughout the Early Glacial, on both millennial and submillennial timescales. Furthermore, the

  17. Climate change and tropical marine agriculture.

    PubMed

    Crabbe, M James C

    2009-01-01

    The coral reef ecosystem forms part of a 'seascape' that includes land-based ecosystems such as mangroves and forests, and ideally should form a complete system for conservation and management. Aquaculture, including artisanal fishing for fish and invertebrates, shrimp farming, and seaweed farming, is a major part of the farming and gleaning practices of many tropical communities, particularly on small islands, and depends upon the integrity of the reefs. Climate change is making major impacts on these communities, not least through global warming and high CO(2) concentrations. Corals grow within very narrow limits of temperature, provide livelihoods for millions of people in tropical areas, and are under serious threat from a variety of environmental and climate extremes. Corals survive and grow through a symbiotic relationship with photosynthetic algae: zooxanthellae. Such systems apply highly co-operative regulation to minimize the fluctuation of metabolite concentration profiles in the face of transient perturbations. This review will discuss research on how climate influences reef ecosystems, and how science can lead to conservation actions, with benefits for the human populations reliant on the reefs for their survival.

  18. Collaborative Project: Development of an Isotope-Enabled CESM for Testing Abrupt Climate Changes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Zhengyu

    One of the most important validations for a state-of-art Earth System Model (ESM) with respect to climate changes is the simulation of the climate evolution and abrupt climate change events in the Earth’s history of the last 21,000 years. However, one great challenge for model validation is that ESMs usually do not directly simulate geochemical variables that can be compared directly with past proxy records. In this proposal, we have met this challenge by developing the simulation capability of major isotopes in a state-of-art ESM, the Community Earth System Model (CESM), enabling us to make direct model-data comparison by comparingmore » the model directly against proxy climate records. Our isotope-enabled ESM incorporates the capability of simulating key isotopes and geotracers, notably δ 18O, δD, δ 14C, and δ 13C, Nd and Pa/Th. The isotope-enabled ESM have been used to perform some simulations for the last 21000 years. The direct comparison of these simulations with proxy records has shed light on the mechanisms of important climate change events.« less

  19. Tropical and Extratropical Cyclone Damages under Climate Change

    NASA Astrophysics Data System (ADS)

    Ranson, M.; Kousky, C.; Ruth, M.; Jantarasami, L.; Crimmins, A.; Tarquinio, L.

    2014-12-01

    This paper provides the first quantitative synthesis of the rapidly growing literature on future tropical and extratropical cyclone losses under climate change. We estimate a probability distribution for the predicted impact of changes in global surface air temperatures on future storm damages, using an ensemble of 296 estimates of the temperature-damage relationship from twenty studies. Our analysis produces three main empirical results. First, we find strong but not conclusive support for the hypothesis that climate change will cause damages from tropical cyclones and wind storms to increase, with most models (84 and 92 percent, respectively) predicting higher future storm damages due to climate change. Second, there is substantial variation in projected changes in losses across regions. Potential changes in damages are greatest in the North Atlantic basin, where the multi-model average predicts that a 2.5°C increase in global surface air temperature would cause hurricane damages to increase by 62 percent. The ensemble predictions for Western North Pacific tropical cyclones and European wind storms (extratropical cyclones) are approximately one third of that magnitude. Finally, our analysis shows that existing models of storm damages under climate change generate a wide range of predictions, ranging from moderate decreases to very large increases in losses.

  20. Extreme waves from tropical cyclones and climate change in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Appendini, Christian M.; Pedrozo-Acuña, Adrian; Meza-Padilla, Rafael; Torres-Freyermuth, Alec; Cerezo-Mota, Ruth; López-González, José

    2017-04-01

    Tropical cyclones generate extreme waves that represent a risk to infrastructure and maritime activities. The projection of the tropical cyclones derived wave climate are challenged by the short historical record of tropical cyclones, their low occurrence, and the poor wind field resolution in General Circulation Models. In this study we use synthetic tropical cyclones to overcome such limitations and be able to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. Synthetic events derived from the NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to force a third generation wave model to characterize the present and future wave climate under RCP 4.5 and 8.5 escenarios. An increase in wave activity is projected for the future climate, particularly for the GFDL model that shows less bias in the present climate, although some areas are expected to decrease the wave energy. The practical implications of determining the future wave climate is exemplified by means of the 100-year design wave, where the use of the present climate may result in under/over design of structures, since the lifespan of a structure includes the future wave climate period.

  1. Divergent trajectories in tropical rainforest carbon-climate relationships: results from a new tropical forest carbon inventory database

    NASA Astrophysics Data System (ADS)

    Taylor, P.; Wieder, W.; Townsend, A.; Asner, G. P.; Cleveland, C.; Loarie, S.

    2010-12-01

    Intact tropical rainforests play a disproportionate role in the terrestrial carbon (C) cycle because they exchange more CO2 with the atmosphere than any other biome. As with any ecosystem, climate controls rates of C uptake and storage; however, the specific nature of climate-carbon relationships in the tropics remains poorly understood and oft-debated. Consequently, there are major uncertainties in how human-driven climate change may alter tropical C storage. One way to investigate climate - forest C interactions is via meta-analyses that examine shifts in forest C dynamics along climatic gradients. Past such analyses for the role of precipitation suggest tropical aboveground net primary production (ANPP) peaks near 2500 mm/yr, and then sharply declines in wetter regions. However, the downturn in ANPP is driven by a bias in early databases toward montane forests, which may exhibit temperature-driven biogeochemical feedbacks not present in wet lowland forests. To address this possibility, we assembled a tropical forest carbon dynamics database that includes nearly 900 different sites. We found substantial divergence in montane versus lowland forest ANPP responses to shifts in rainfall. As previous analyses imply, montane forest ANPP shows a distinct “hump-shaped” pattern, with a downturn in wetter sites. However, in contrast to prevailing assumptions, we find that lowland forest ANPP and biomass remain steady or increase with increasing rainfall. The data suggest that temperature plays a key role in determining the shape of rainfall - forest C interactions by regulating plant-soil nutrient feedbacks that underlie trends in ANPP. In montane systems, lower temperatures under wet conditions allow the development of organic horizons and the persistence of low redox conditions that reduce fertility, but in lowland systems, higher temperatures prevent organic matter accumulation, and high precipitation appears to drive rapid exchanges of nutrients between litter and

  2. Climate Change and Tropical Total Lightning

    NASA Technical Reports Server (NTRS)

    Albrecht, R.; Petersen, W.; Buechler, D.; Goodman, S.; Blakeslee, R.; Christian, H.

    2009-01-01

    While global warming is regarded as a fact by many in the scientific community, its future impact remains a challenge to be determined and measured. The International Panel on Climate Change (IPCC) assessment report (IPCC, 2007) shows inconclusive answers on global rainfall trends and general agreement on a future drier climate with increased global warming. The relationship between temperature, humidity and convection is not linear and is strongly dependent on regional scale features, such as topography and land cover. Furthermore, the relationship between convective lightning production (thunderstorms) and temperature is even more complicated, being subjected to the cloud dynamics and microphysics. Total lightning (intracloud and cloud-to-ground) monitoring is a relatively new field of observation. Global and tropical total lightning began to be more extensively measured by satellites in the mid 90s. In this scope, the Lightning Imaging Sensor (LIS) onboard of the Tropical Rainfall Measurement Mission (TRMM) has been operational for over 11 years. Here we address total lightning trends observed by LIS from 1998 to 2008 in different temporal (annual and seasonal) and spatial (large and regional) scales. The observed 11-year trends are then associate to different predicted/hypothesized climate change scenarios.

  3. "What Controls the Structure and Stability of the Ocean Meridional Overturning Circulation: Implications for Abrupt Climate Change?"

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fedorov, Alexey

    2013-11-23

    The central goal of this research project is to understand the properties of the ocean meridional overturning circulation (MOC) – a topic critical for understanding climate variability and stability on a variety of timescales (from decadal to centennial and longer). Specifically, we have explored various factors that control the MOC stability and decadal variability in the Atlantic and the ocean thermal structure in general, including the possibility abrupt climate change. We have also continued efforts on improving the performance of coupled ocean-atmosphere GCMs.

  4. Abrupt Change in Ecological Systems: Inference and Diagnosis.

    PubMed

    Ratajczak, Zak; Carpenter, Stephen R; Ives, Anthony R; Kucharik, Christopher J; Ramiadantsoa, Tanjona; Stegner, M Allison; Williams, John W; Zhang, Jien; Turner, Monica G

    2018-05-18

    Abrupt ecological changes are, by definition, those that occur over short periods of time relative to typical rates of change for a given ecosystem. The potential for such changes is growing due to anthropogenic pressures, which challenges the resilience of societies and ecosystems. Abrupt ecological changes are difficult to diagnose because they can arise from a variety of circumstances, including rapid changes in external drivers (e.g., climate, or resource extraction), nonlinear responses to gradual changes in drivers, and interactions among multiple drivers and disturbances. We synthesize strategies for identifying causes of abrupt ecological change and highlight instances where abrupt changes are likely. Diagnosing abrupt changes and inferring causation are increasingly important as society seek to adapt to rapid, multifaceted environmental changes. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Diverging Responses of Tropical Andean Biomes under Future Climate Conditions

    PubMed Central

    Tovar, Carolina; Arnillas, Carlos Alberto; Cuesta, Francisco; Buytaert, Wouter

    2013-01-01

    Observations and projections for mountain regions show a strong tendency towards upslope displacement of their biomes under future climate conditions. Because of their climatic and topographic heterogeneity, a more complex response is expected for biodiversity hotspots such as tropical mountain regions. This study analyzes potential changes in the distribution of biomes in the Tropical Andes and identifies target areas for conservation. Biome distribution models were developed using logistic regressions. These models were then coupled to an ensemble of 8 global climate models to project future distribution of the Andean biomes and their uncertainties. We analysed projected changes in extent and elevational range and identified regions most prone to change. Our results show a heterogeneous response to climate change. Although the wetter biomes exhibit an upslope displacement of both the upper and the lower boundaries as expected, most dry biomes tend to show downslope expansion. Despite important losses being projected for several biomes, projections suggest that between 74.8% and 83.1% of the current total Tropical Andes will remain stable, depending on the emission scenario and time horizon. Between 3.3% and 7.6% of the study area is projected to change, mostly towards an increase in vertical structure. For the remaining area (13.1%–17.4%), there is no agreement between model projections. These results challenge the common believe that climate change will lead to an upslope displacement of biome boundaries in mountain regions. Instead, our models project diverging responses, including downslope expansion and large areas projected to remain stable. Lastly, a significant part of the area expected to change is already affected by land use changes, which has important implications for management. This, and the inclusion of a comprehensive uncertainty analysis, will help to inform conservation strategies in the Tropical Andes, and to guide similar assessments for

  6. Impacts of abrupt climate changes in the Levant from Last Glacial Dead Sea levels

    NASA Astrophysics Data System (ADS)

    Torfstein, Adi; Goldstein, Steven L.; Stein, Mordechai; Enzel, Yehouda

    2013-06-01

    A new, detailed lake level curve for Lake Lisan (the Last Glacial Dead Sea) reveals a high frequency of abrupt fluctuations during Marine Isotope Stage 3 (MIS3) compared to the relatively high stand characterizing MIS2, and the significantly lower Holocene lake. The lake level fluctuations reflect the hydrological conditions in the large watershed of the lake, which in turn reflects the hydro-climatic conditions in the central Levant region. The new curve shows that the fluctuations coincide on millennial timescales with temperature variations recorded in Greenland. Four patterns of correlation are observed through the last ice age: (1) maximum lake elevations were reached during MIS2, the coldest interval; (2) abrupt lake level drops to the lowest elevations coincided with the occurrence of Heinrich (H) events; (3) the lake returned to higher-stand conditions along with warming in Greenland that followed H-events; (4) significant lake level fluctuations coincided with virtually every Greenland stadial-interstadial cycle. Over glacial-interglacial time-scales, Northern Hemisphere glacial cooling induces extreme wetness in the Levant, with high lake levels reaching ˜160 m below mean sea level (mbmsl), approximately 240 m above typical Holocene levels of ˜400 mbmsl. These orbital time-scale shifts are driven by expansions of the European ice sheet, which deflect westerly storm tracks southward to the Eastern Mediterranean, resulting in increased sea-air temperature gradients that invoke increased cyclogenesis, and enhanced moisture delivery to the Levant. The millennial-scale lake level drops associated with Greenland stadials are most extreme during Heinrich stadials and reflect abrupt cooling of the Eastern Mediterranean atmosphere and sea-surface, which weaken the cyclogenic rain engine and cause extreme Levant droughts. During the recovery from the effect of Heinrich stadials, the regional climate configuration resumed typical glacial conditions, with enhanced

  7. Tropical Atlantic Impacts on the Decadal Climate Variability of the Tropical Ocean and Atmosphere.

    NASA Astrophysics Data System (ADS)

    Li, X.; Xie, S. P.; Gille, S. T.; Yoo, C.

    2015-12-01

    Previous studies revealed atmospheric bridges between the tropical Pacific, Atlantic, and Indian Ocean. In particular, several recent works indicate that the Atlantic sea surface temperature (SST) may contribute to the climate variability over the equatorial Pacific. Inspired by these studies, our work aims at investigating the impact of the tropical Atlantic on the entire tropical climate system, and uncovering the physical dynamics under these tropical teleconnections. We first performed a 'pacemaker' simulation by restoring the satellite era tropical Atlantic SST changes in a fully coupled model - the CESM1. Results reveal that the Atlantic warming heats the Indo-Western Pacific and cools the Eastern Pacific, enhances the Walker circulation and drives the subsurface Pacific to a La Niña mode, contributing to 60-70% of the above tropical changes in the past 30 years. The same pan-tropical teleconnections have been validated by the statistics of observations and 106 CMIP5 control simulations. We then used a hierarchy of atmospheric and oceanic models with different complexities, to single out the roles of atmospheric dynamics, atmosphere-ocean fluxes, and oceanic dynamics in these teleconnections. With these simulations we established a two-step mechanism as shown in the schematic figure: 1) Atlantic warming generates an atmospheric deep convection and induces easterly wind anomalies over the Indo-Western Pacific in the form of Kelvin waves, and westerly wind anomalies over the eastern equatorial Pacific as Rossby waves, in line with Gill's solution. This circulation changes warms the Indo-Western Pacific and cools the Eastern Pacific with the wind-evaporation-SST effect, forming a temperature gradient over the Indo-Pacific basins. 2) The temperature gradient further generates a secondary atmospheric deep convection, which reinforces the easterly wind anomalies over the equatorial Pacific and enhances the Walker circulation, triggering the Pacific to a La Ni

  8. Tropical Convection and Climate Processes in a Cumulus Ensemble Model

    NASA Technical Reports Server (NTRS)

    Sui, Chung-Hsiung

    1999-01-01

    Local convective-radiative equilibrium states of the tropical atmosphere are determined by the following external forcing: 1) Insolation, 2) Surface heat and moisture exchanges (primarily radiation and evaporation), 3) Heating and moistening induced by large-scale circulation. Understanding the equilibrium states of the tropical atmosphere in different external forcing conditions is of vital importance for studying cumulus parameterization, climate feedbacks, and climate changes. We extend our previous study using the Goddard Cumulus Ensemble (GCE) Model which resolves convective-radiative processes more explicitly than global climate models do. Several experiments are carried out under fixed insolation and sea surface temperature. The prescribed SST consists of a uniform warm pool (29C) surrounded by uniform cold SST (26C). The model produces "Walker"-type circulation with the ascending branch of the model atmosphere more humid than the descending part, but the vertically integrated temperature does not show a horizontal gradient. The results are compared with satellite measured moisture by SSM/I (Special Sensor Microwave/Imager) and temperature by MSU in the ascending and descending tropical atmosphere. The vertically integrated temperature and humidity in the two model regimes are comparable to the observed values in the tropics.

  9. Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

    DOE PAGES

    Wagner, Fabien H.; Hérault, Bruno; Bonal, Damien; ...

    2016-04-28

    Here, the seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positivelymore » to precipitation when rainfall is < 2000 mm yr -1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr -1.« less

  10. Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wagner, Fabien H.; Hérault, Bruno; Bonal, Damien

    Here, the seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positivelymore » to precipitation when rainfall is < 2000 mm yr -1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr -1.« less

  11. Sensitivity of tropical forest aboveground productivity to climate anomalies in SW Costa Rica

    NASA Astrophysics Data System (ADS)

    Hofhansl, Florian; Kobler, Johannes; Ofner, Joachim; Drage, Sigrid; Pölz, Eva-Maria; Wanek, Wolfgang

    2014-12-01

    The productivity of tropical forests is driven by climate (precipitation, temperature, and light) and soil fertility (geology and topography). While large-scale drivers of tropical productivity are well established, knowledge on the sensitivity of tropical lowland net primary production to climate anomalies remains scarce. We here analyze seven consecutive years of monthly recorded tropical forest aboveground net primary production (ANPP) in response to a recent El Niño-Southern Oscillation (ENSO) anomaly. The ENSO transition period resulted in increased temperatures and decreased precipitation during the El Niño dry period, causing a decrease in ANPP. However, the subsequent La Niña wet period caused strong increases in ANPP such that drought-induced reductions were overcompensated. Most strikingly, the climatic controls differed between canopy production (CP) and wood production (WP). Whereas CP showed strong seasonal variation but was not affected by ENSO, WP decreased significantly in response to a 3°C increase in annual maximum temperatures during the El Niño period but subsequently recovered to above predrought levels during the La Niña period. Moreover, the climate sensitivity of tropical forest ANPP components was affected by local topography (water availability) and disturbance history (species composition). Our results suggest that projected increases in temperature and dry season length could impact tropical carbon sequestration by shifting ANPP partitioning toward decreased WP, thus decreasing the carbon storage of highly productive lowland forests. We conclude that the impact of climate anomalies on tropical forest productivity is strongly related to local site characteristics and will therefore likely prevent uniform responses of tropical lowland forests to projected global changes.

  12. Glacier monitoring and glacier-climate interactions in the tropical Andes: A review

    NASA Astrophysics Data System (ADS)

    Veettil, Bijeesh Kozhikkodan; Wang, Shanshan; Florêncio de Souza, Sergio; Bremer, Ulisses Franz; Simões, Jefferson Cardia

    2017-08-01

    In this review, we summarized the evolution of glacier monitoring in the tropical Andes during the last few decades, particularly after the development of remote sensing and photogrammetry. Advantages and limitations of glacier mapping, applied so far, in Venezuela, Colombia, Ecuador, Peru and Bolivia are discussed in detail. Glacier parameters such as the equilibrium line altitude, snowline and mass balance were given special attention in understanding the complex cryosphere-climate interactions, particularly using remote sensing techniques. Glaciers in the inner and the outer tropics were considered separately based on the precipitation and temperature conditions within a new framework. The applicability of various methods to use glacier records to understand and reconstruct the tropical Andean climate between the Last Glacial Maximum (11,700 years ago) and the present is also explored in this paper. Results from various studies published recently were analyzed and we tried to understand the differences in the magnitudes of glacier responses towards the climatic perturbations in the inner tropics and the outer tropics. Inner tropical glaciers, particularly those in Venezuela and Colombia near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increase in temperature. Surface energy balance experiments show that outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. We also analyzed the gradients in glacier response to climate change from the Pacific coast towards the Amazon Basin as well as with the elevation. Based on the current trends synthesised from recent studies, it is hypothesized that the glaciers in the inner tropics and the southern wet outer tropics will disappear first as a response to global warming whereas glaciers in the northern wet outer tropics and dry outer tropics show resistance to warming trends due to

  13. Why tropical forest lizards are vulnerable to climate warming.

    PubMed

    Huey, Raymond B; Deutsch, Curtis A; Tewksbury, Joshua J; Vitt, Laurie J; Hertz, Paul E; Alvarez Pérez, Héctor J; Garland, Theodore

    2009-06-07

    Biological impacts of climate warming are predicted to increase with latitude, paralleling increases in warming. However, the magnitude of impacts depends not only on the degree of warming but also on the number of species at risk, their physiological sensitivity to warming and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of warming because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are warm all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of warm temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that warming will not only further depress their physiological performance in summer, but will also enable warm-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key components of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate warming, even though rates of tropical warming may be relatively low.

  14. Why tropical forest lizards are vulnerable to climate warming

    PubMed Central

    Huey, Raymond B.; Deutsch, Curtis A.; Tewksbury, Joshua J.; Vitt, Laurie J.; Hertz, Paul E.; Álvarez Pérez, Héctor J.; Garland, Theodore

    2009-01-01

    Biological impacts of climate warming are predicted to increase with latitude, paralleling increases in warming. However, the magnitude of impacts depends not only on the degree of warming but also on the number of species at risk, their physiological sensitivity to warming and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of warming because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are warm all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of warm temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that warming will not only further depress their physiological performance in summer, but will also enable warm-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key components of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate warming, even though rates of tropical warming may be relatively low. PMID:19324762

  15. Improving predictions of tropical forest response to climate change through integration of field studies and ecosystem modeling

    Treesearch

    Xiaohui Feng; María Uriarte; Grizelle González; Sasha Reed; Jill Thompson; Jess K. Zimmerman; Lora Murphy

    2018-01-01

    Tropical forests play a critical role in carbon and water cycles at a global scale. Rapid climate change is anticipated in tropical regions over the coming decades and, under a warmer and drier climate, tropical forests are likely to be net sources of carbon rather than sinks. However, our understanding of tropical forest response and feedback to climate change is very...

  16. Tropical forest soil microbes and climate warming: An Andean-Amazon gradient and `SWELTR'

    NASA Astrophysics Data System (ADS)

    Nottingham, A.; Turner, B. L.; Fierer, N.; Whitaker, J.; Ostle, N. J.; McNamara, N. P.; Bardgett, R.; Silman, M.; Bååth, E.; Salinas, N.; Meir, P.

    2017-12-01

    Climate warming predicted for the tropics in the coming century will result in average temperatures under which no closed canopy forest exists today. There is, therefore, great uncertainty associated with the direction and magnitude of feedbacks between tropical forests and our future climate - especially relating to the response of soil microbes and the third of global soil carbon contained in tropical forests. While warming experiments are yet to be performed in tropical forests, natural temperature gradients are powerful tools to investigate temperature effects on soil microbes. Here we draw on studies from a 3.5 km elevation gradient - and 20oC mean annual temperature gradient - in Peruvian tropical forest, to investigate how temperature affects the structure of microbial communities, microbial metabolism, enzymatic activity and soil organic matter cycling. With decreased elevation, soil microbial diversity increased and community composition shifted, from taxa associated with oligotrophic towards copiotrophic traits. A key role for temperature in shaping these patterns was demonstrated by a soil translocation experiment, where temperature-manipulation altered the relative abundance of specific taxa. Functional implications of these community composition shifts were indicated by changes in enzyme activities, the temperature sensitivity of bacterial and fungal growth rates, and the presence of temperature-adapted iso-enzymes at different elevations. Studies from a Peruvian elevation transect indicated that soil microbial communities are adapted to long-term (differences with elevation) and short-term (translocation responses) temperature changes. These findings indicate the potential for adaptation of soil microbes in tropical soils to future climate warming. However, in order to evaluate the sensitivity of these processes to climate warming in lowland forests, in situ experimentation is required. Finally, we describe SWELTR (Soil Warming Experiment in Lowland

  17. Reconstructing Eastern Tropical Pacific productivity across Marine Isotope Stage 3 using foraminifera faunal counts

    NASA Astrophysics Data System (ADS)

    McCourty, M.; Schmidt, M. W.; Glaubke, R.; Hertzberg, J. E.; Marcantonio, F.; Bianchi, T. S.

    2017-12-01

    The El Niño-Southern Oscillation is one of Earth's largest sources of interannual climate variability that has many global environmental impacts. Furthermore, the mean state of the tropical Pacific has the potential to change in the near future due to anthropogenic warming of the planet. In order to provide an analogue for future climate states, there is a critical need to understand how the tropical Pacific evolved across abrupt warming events in Earth's recent past. While most studies have focused on the evolution of ENSO across Marine Isotope Stages (MIS) 1 and 2, the dynamics of the tropical Pacific across the abrupt climate events of MIS 3 are still highly contentious. To develop a record of past changes in upwelling intensity in the EEP, a parameter critically linked to the tropical Pacific mean state, we quantify the faunal abundances of 6 planktonic foraminifera species from piston core MV1014-02-17JC (00° 10.83'S, 85° 52.00'W; 2846 m depth) on the Carnegie Ridge from 35 - 59 kyr. The relative abundance of Globigerina bulloides, a species associated with upwelling conditions, and 5 other planktonic foraminifera suggest an increase in water column productivity during Heinrich Event 4 and across several Dansgaard-Oeschger stadial intervals. Initial results suggest that stadials in the North Atlantic are associated with more permanent La Niña-like conditions in the EEP. However, multiple lines of evidence suggest that depth intervals in our core between 43.7 - 55.7 kyr were impacted by intense dissolution due to changes in bottom water chemistry, impacting the fidelity of our faunal count records across this interval. Future work includes extending our faunal record back to 100 kyr to include Heinrich Events 6 - 8.

  18. Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change.

    PubMed

    Boulton, Chris A; Lenton, Timothy M

    2015-09-15

    Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency--i.e., "redder"--variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900-present), as indicated by a robust increase in autocorrelation. This "reddening" of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent "regime shifts." Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems.

  19. Relationships among net primary productivity, nutrients and climate in tropical rain forest: A pan-tropical analysis

    USGS Publications Warehouse

    Cleveland, Cory C.; Townsend, Alan R.; Taylor, Philip; Alvarez-Clare, Silvia; Bustamante, Mercedes M.C.; Chuyong, George; Dobrowski, Solomon Z.; Grierson, Pauline; Harms, Kyle E.; Houlton, Benjamin Z.; Marklein, Alison; Parton, William; Porder, Stephen; Reed, Sasha C.; Sierra, Carlos A.; Silver, Whendee L.; Tanner, Edmund V.J.; Wieder, William R.

    2011-01-01

    Tropical rain forests play a dominant role in global biosphere-atmosphere CO2 exchange. Although climate and nutrient availability regulate net primary production (NPP) and decomposition in all terrestrial ecosystems, the nature and extent of such controls in tropical forests remain poorly resolved. We conducted a meta-analysis of carbon-nutrient-climate relationships in 113 sites across the tropical forest biome. Our analyses showed that mean annual temperature was the strongest predictor of aboveground NPP (ANPP) across all tropical forests, but this relationship was driven by distinct temperature differences between upland and lowland forests. Within lowland forests (< 1000 m), a regression tree analysis revealed that foliar and soil-based measurements of phosphorus (P) were the only variables that explained a significant proportion of the variation in ANPP, although the relationships were weak. However, foliar P, foliar nitrogen (N), litter decomposition rate (k), soil N and soil respiration were all directly related with total surface (0–10 cm) soil P concentrations. Our analysis provides some evidence that P availability regulates NPP and other ecosystem processes in lowland tropical forests, but more importantly, underscores the need for a series of large-scale nutrient manipulations – especially in lowland forests – to elucidate the most important nutrient interactions and controls.

  20. A Generalized Stability Analysis of the AMOC in Earth System Models: Implication for Decadal Variability and Abrupt Climate Change

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fedorov, Alexey V.

    2015-01-14

    The central goal of this research project was to understand the mechanisms of decadal and multi-decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) as related to climate variability and abrupt climate change within a hierarchy of climate models ranging from realistic ocean models to comprehensive Earth system models. Generalized Stability Analysis, a method that quantifies the transient and asymptotic growth of perturbations in the system, is one of the main approaches used throughout this project. The topics we have explored range from physical mechanisms that control AMOC variability to the factors that determine AMOC predictability in the Earth systemmore » models, to the stability and variability of the AMOC in past climates.« less

  1. Improving predictions of tropical forest response to climate change through integration of field studies and ecosystem modeling.

    PubMed

    Feng, Xiaohui; Uriarte, María; González, Grizelle; Reed, Sasha; Thompson, Jill; Zimmerman, Jess K; Murphy, Lora

    2018-01-01

    Tropical forests play a critical role in carbon and water cycles at a global scale. Rapid climate change is anticipated in tropical regions over the coming decades and, under a warmer and drier climate, tropical forests are likely to be net sources of carbon rather than sinks. However, our understanding of tropical forest response and feedback to climate change is very limited. Efforts to model climate change impacts on carbon fluxes in tropical forests have not reached a consensus. Here, we use the Ecosystem Demography model (ED2) to predict carbon fluxes of a Puerto Rican tropical forest under realistic climate change scenarios. We parameterized ED2 with species-specific tree physiological data using the Predictive Ecosystem Analyzer workflow and projected the fate of this ecosystem under five future climate scenarios. The model successfully captured interannual variability in the dynamics of this tropical forest. Model predictions closely followed observed values across a wide range of metrics including aboveground biomass, tree diameter growth, tree size class distributions, and leaf area index. Under a future warming and drying climate scenario, the model predicted reductions in carbon storage and tree growth, together with large shifts in forest community composition and structure. Such rapid changes in climate led the forest to transition from a sink to a source of carbon. Growth respiration and root allocation parameters were responsible for the highest fraction of predictive uncertainty in modeled biomass, highlighting the need to target these processes in future data collection. Our study is the first effort to rely on Bayesian model calibration and synthesis to elucidate the key physiological parameters that drive uncertainty in tropical forests responses to climatic change. We propose a new path forward for model-data synthesis that can substantially reduce uncertainty in our ability to model tropical forest responses to future climate. © 2017 John

  2. Improving predictions of tropical forest response to climate change through integration of field studies and ecosystem modeling

    USGS Publications Warehouse

    Feng, Xiaohui; Uriarte, María; González, Grizelle; Reed, Sasha C.; Thompson, Jill; Zimmerman, Jess K.; Murphy, Lora

    2018-01-01

    Tropical forests play a critical role in carbon and water cycles at a global scale. Rapid climate change is anticipated in tropical regions over the coming decades and, under a warmer and drier climate, tropical forests are likely to be net sources of carbon rather than sinks. However, our understanding of tropical forest response and feedback to climate change is very limited. Efforts to model climate change impacts on carbon fluxes in tropical forests have not reached a consensus. Here we use the Ecosystem Demography model (ED2) to predict carbon fluxes of a Puerto Rican tropical forest under realistic climate change scenarios. We parameterized ED2 with species-specific tree physiological data using the Predictive Ecosystem Analyzer workflow and projected the fate of this ecosystem under five future climate scenarios. The model successfully captured inter-annual variability in the dynamics of this tropical forest. Model predictions closely followed observed values across a wide range of metrics including above-ground biomass, tree diameter growth, tree size class distributions, and leaf area index. Under a future warming and drying climate scenario, the model predicted reductions in carbon storage and tree growth, together with large shifts in forest community composition and structure. Such rapid changes in climate led the forest to transition from a sink to a source of carbon. Growth respiration and root allocation parameters were responsible for the highest fraction of predictive uncertainty in modeled biomass, highlighting the need to target these processes in future data collection. Our study is the first effort to rely on Bayesian model calibration and synthesis to elucidate the key physiological parameters that drive uncertainty in tropical forests responses to climatic change. We propose a new path forward for model-data synthesis that can substantially reduce uncertainty in our ability to model tropical forest responses to future climate.

  3. Geochemical and Sedimentological Records of Late Quaternary Climate Change, Lake Tanganyika, Tropical East Africa

    NASA Astrophysics Data System (ADS)

    Felton, A. A.; Russell, J. M.; Cohen, A. S.; Baker, M. E.; McGlue, M. M.; Lezzar, K. E.

    2005-12-01

    We have analyzed piston core records from Lake Tanganyika (western Tanzania, East African Rift Valley) to investigate possible signals of tropical paleoclimate change during the Late Quaternary. Long paleoclimate records from East Africa are of importance for understanding climatic processes such as the role of solar variability in regulating tropical climates at Milankovitch time scales, and the relationship between abrupt climate changes, migration of Intertropical Convergence Zone, and regional climate variability (Nicholson, 2000). However, records of pre-Holocene climate variability from tropical African lakes (>25ka) are still quite rare. Long records from Lake Tanganyika are of particular interest given the lake's antiquity and its demonstrated potential for producing high resolution (frequently annually laminated) sedimentary records (Cohen et al., 1993). We analyzed physical properties, grain size, total organic carbon, major, minor and trace element variability, and biogenic silica data for a 7.75 m core from the Kalya slope and horst region of central Lake Tanganyika at 640m water depth. Nine 14C dates provide an age model for the core, which spans ~62 cal kyr. Elemental concentrations preserved in Lake Tanganyika sediments record variability in deposition and runoff into the lake basin. Under conditions of rapid erosion, exposure and rapid weathering of bedrock has been shown to generate high concentrations of original silicate minerals enriched in soluble cations such as sodium and potassium, elements that are also biologically conservative. Prior to 40ka cal yr. core sediments are characterized by high magnetic susceptibility, intermediate levels of organic carbon, low to intermediate levels of biogenic silica, and fine grain size, indicative of relatively high precipitation. There is a profound decrease in magnetic susceptibility, a decrease in organic carbon and an increase in grain size at 40ka cal yr, which persists until ~16ka cal yr. Seismic

  4. Climatic Teleconnections Recorded By Tropical Mountain Glaciers

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Permana, D.; Mosley-Thompson, E.; Davis, M. E.

    2014-12-01

    Information from ice cores from the world's highest mountains in the Tropics demonstrates both local climate variability and a high degree of teleconnectivity across the Pacific basin. Here we examine recently recovered ice core records from glaciers near Puncak Jaya in Papua, Indonesia, which lie on the highest peak between the Himalayas and the South American Andes. These glaciers are located on the western side of the Tropical Pacific warm pool, which is the "center of action" for interannual climate variability dominated by El Niño-Southern Oscillation (ENSO). ENSO either directly or indirectly affects most regions of Earth and their populations. In 2010, two ice cores measuring 32.13 m and 31.25 m were recovered to bedrock from the East Northwall Firn ice field. Both have been analyzed in high resolution (~3 cm sample length, 1156 and 1606 samples, respectively) for stable isotopes, dust, major ions and tritium concentrations. To better understand the controls on the oxygen isotopic (δ18 O) signal for this region, daily rainfall samples were collected between January 2013 and February 2014 at five weather stations over a distance of ~90 km ranging from 9 meters above sea level (masl) on the southern coast up to 3945 masl. The calculated isotopic lapse rate for this region is 0.24 ‰/100m. Papua, Indonesian ice core records are compared to ice core records from Dasuopu Glacier in the central Himalayas and from Quelccaya, Huascarán, Hualcán and Coropuna ice fields in the tropical Andes of Peru on the eastern side of the Pacific Ocean. The composite of the annual isotopic time series from these cores is significantly (R2 =0.53) related to tropical Pacific sea surface temperatures (SSTs), reflecting the strong linkage between tropical Pacific SSTs associated with ENSO and tropospheric temperatures in the low latitudes. New data on the already well-documented concomitant loss of ice on Quelccaya, Kilimanjaro in eastern Africa and the ice fields near Puncak

  5. Tropical cyclogenesis in warm climates simulated by a cloud-system resolving model

    NASA Astrophysics Data System (ADS)

    Fedorov, Alexey V.; Muir, Les; Boos, William R.; Studholme, Joshua

    2018-03-01

    Here we investigate tropical cyclogenesis in warm climates, focusing on the effect of reduced equator-to-pole temperature gradient relevant to past equable climates and, potentially, to future climate change. Using a cloud-system resolving model that explicitly represents moist convection, we conduct idealized experiments on a zonally periodic equatorial β-plane stretching from nearly pole-to-pole and covering roughly one-fifth of Earth's circumference. To improve the representation of tropical cyclogenesis and mean climate at a horizontal resolution that would otherwise be too coarse for a cloud-system resolving model (15 km), we use the hypohydrostatic rescaling of the equations of motion, also called reduced acceleration in the vertical. The simulations simultaneously represent the Hadley circulation and the intertropical convergence zone, baroclinic waves in mid-latitudes, and a realistic distribution of tropical cyclones (TCs), all without use of a convective parameterization. Using this model, we study the dependence of TCs on the meridional sea surface temperature gradient. When this gradient is significantly reduced, we find a substantial increase in the number of TCs, including a several-fold increase in the strongest storms of Saffir-Simpson categories 4 and 5. This increase occurs as the mid-latitudes become a new active region of TC formation and growth. When the climate warms we also see convergence between the physical properties and genesis locations of tropical and warm-core extra-tropical cyclones. While end-members of these types of storms remain very distinct, a large distribution of cyclones forming in the subtropics and mid-latitudes share properties of the two.

  6. Influence of tropical atmospheric variability on Weddell Sea deep water convection

    NASA Astrophysics Data System (ADS)

    Kleppin, H.

    2016-02-01

    Climate reconstructions from ice core records in Greenland and Antarctica have revealed a series of abrupt climate transitions, showing a distinct relationship between northern and southern hemisphere climate during the last glacial period. The recent ice core records from West Antarctica (WAIS) point towards an atmospheric teleconnection as a possible trigger for the interhemispheric climate variability (Markle et al., 2015). An unforced simulation of the Community Climate System Model, version 4 (CCSM4) reveals Greenland warming and cooling events, caused by stochastic atmospheric forcing, that resemble Dansgaard-Oeschger cycles in pattern and magnitude (Kleppin et al., 2015). Anti-phased temperature changes in the Southern Hemisphere are small in magnitude and have a spatially varying pattern. We argue that both north and south high latitude climate variability is triggered by changes in tropical atmospheric deep convection in the western tropical Pacific. The atmospheric wave guide provides a fast communication pathway connecting the deep tropics and the polar regions. In the Southern Hemisphere this is manifested as a distinct pressure pattern over West Antarctica. These altered atmospheric surface conditions over the convective region can lead to destabilization of the water column and thus to convective overturning in the Weddell Sea. However, opposed to what is seen in the Northern Hemisphere no centennial scale variability can establish, due to the absence of a strong feedback mechanism between ocean, atmosphere and sea ice. Kleppin, H., Jochum, M., Otto-Bliesner, B., Shields, C. A., & Yeager, S. (2015). Stochastic Atmospheric Forcing as a Cause of Greenland Climate Transitions. Journal of Climate, (2015). Markle, B. and Coauthors (2015, April). Atmospheric teleconnections between the tropics and high southern latitudes during millennial climate change. In EGU General Assembly Conference Abstracts (Vol. 17, p. 2569).

  7. Staying cool: preadaptation to temperate climates required for colonising tropical alpine-like environments.

    PubMed

    Gehrke, Berit

    2018-01-01

    Plant species tend to retain their ancestral ecology, responding to temporal, geographic and climatic changes by tracking suitable habitats rather than adapting to novel conditions. Nevertheless, transitions into different environments or biomes still seem to be common. Especially intriguing are the tropical alpine-like areas found on only the highest mountainous regions surrounded by tropical environments. Tropical mountains are hotspots of biodiversity, often with striking degrees of endemism at higher elevations. On these mountains, steep environmental gradients and high habitat heterogeneity within small spaces coincide with astounding species diversity of great conservation value. The analysis presented here shows that the importance of in situ speciation in tropical alpine-like areas has been underestimated. Additionally and contrary to widely held opinion, the impact of dispersal from other regions with alpine-like environments is relatively minor compared to that of immigration from other biomes with a temperate (but not alpine-like) climate. This suggests that establishment in tropical alpine-like regions is favoured by preadaptation to a temperate, especially aseasonal, freezing regime such as the cool temperate climate regions in the Tropics. Furthermore, emigration out of an alpine-like environment is generally rare, suggesting that alpine-like environments - at least tropical ones - are species sinks.

  8. Staying cool: preadaptation to temperate climates required for colonising tropical alpine-like environments

    PubMed Central

    Gehrke, Berit

    2018-01-01

    Abstract Plant species tend to retain their ancestral ecology, responding to temporal, geographic and climatic changes by tracking suitable habitats rather than adapting to novel conditions. Nevertheless, transitions into different environments or biomes still seem to be common. Especially intriguing are the tropical alpine-like areas found on only the highest mountainous regions surrounded by tropical environments. Tropical mountains are hotspots of biodiversity, often with striking degrees of endemism at higher elevations. On these mountains, steep environmental gradients and high habitat heterogeneity within small spaces coincide with astounding species diversity of great conservation value. The analysis presented here shows that the importance of in situ speciation in tropical alpine-like areas has been underestimated. Additionally and contrary to widely held opinion, the impact of dispersal from other regions with alpine-like environments is relatively minor compared to that of immigration from other biomes with a temperate (but not alpine-like) climate. This suggests that establishment in tropical alpine-like regions is favoured by preadaptation to a temperate, especially aseasonal, freezing regime such as the cool temperate climate regions in the Tropics. Furthermore, emigration out of an alpine-like environment is generally rare, suggesting that alpine-like environments – at least tropical ones – are species sinks. PMID:29706788

  9. Detecting Climate Variability in Tropical Rainfall

    NASA Astrophysics Data System (ADS)

    Berg, W.

    2004-05-01

    A number of satellite and merged satellite/in-situ rainfall products have been developed extending as far back as 1979. While the availability of global rainfall data covering over two decades and encompassing two major El Niño events is a valuable resource for a variety of climate studies, significant differences exist between many of these products. Unfortunately, issues such as availability often determine the use of a product for a given application instead of an understanding of the strengths and weaknesses of the various products. Significant efforts have been made to address the impact of sparse sampling by satellite sensors of variable rainfall processes by merging various satellite and in-situ rainfall products. These combine high spatial and temporal frequency satellite infrared data with higher quality passive microwave observations and rain gauge observations. Combining such an approach with spatial and temporal averaging of the data can reduce the large random errors inherent in satellite rainfall estimates to very small levels. Unfortunately, systematic biases can and do result in artificial climate signals due to the underconstrained nature of the rainfall retrieval problem. Because all satellite retrieval algorithms make assumptions regarding the cloud structure and microphysical properties, systematic changes in these assumed parameters between regions and/or times results in regional and/or temporal biases in the rainfall estimates. These biases tend to be relatively small compared to random errors in the retrieval, however, when random errors are reduced through spatial and temporal averaging for climate applications, they become the dominant source of error. Whether or not such biases impact the results for climate studies is very much dependent on the application. For example, all of the existing satellite rainfall products capture the increased rainfall in the east Pacific associated with El Niño, however, the resulting tropical response to

  10. Abrupt drying events in the Caribbean related to large Laurentide meltwater pulses during the glacial-to-Holocene transition

    NASA Astrophysics Data System (ADS)

    Vieten, Rolf; Warken, Sophie; Winter, Amos; Scholz, Denis; Black, David; Zanchettin, Davide; Miller, Thomas E.

    2017-04-01

    At the end of the last deglaciation North Atlantic meltwater pulses from the retreating Laurentide ice sheet triggered a chain of oceanic and atmospheric responses including temporary slow-down of the thermohaline circulation and hemispheric-scale alterations of the atmospheric circulation. The 8.2 ka event (occurring about 8.2 ka BP) is the most pronounced meltwater pulse during the Holocene and serves as an analogue to understand how North Atlantic fresh water influxes can affect the ocean-atmosphere coupled system on a basin, hemispheric or global scale. This event left strong regional climate imprints, such as abrupt cooling reconstructed over the North Atlantic and Europe lasting 100 to 150 years and drying in the northern hemispheric tropics. However, there is a lack of high resolution proxies to learn about the event's temporal structure especially in the tropics. We present geochemical evidence from a stalagmite indicating sudden climate fluctuations towards drier conditions in the northeastern Caribbean possibly related to rapid cooling in the high northern latitudes and a southward shift of the Inter-Tropical Convergence Zone (ITCZ). Stalagmite PR-PA-1 was collected in Palco cave, Puerto Rico, and it is a remarkable record of the 8.2 ka event because 15 MC-ICPMS 230Th/U-dates produce a precise chronology of its Holocene period growing solely between 9.0 ka BP to 7.5 ka BP. Based on 240 trace element and stable isotope ratio measurement we reconstructed hydrological changes with sub-decadal resolution. Our proxy data show large and rapid climate variations before 8.0 ka. Pronounced peaks in the Mg/Ca and δ13C records indicate three major events of abrupt drying. These fluctuations towards drier conditions took place in less than 10 years and the climate remained drier than the natural range for 10 to 20 years, before it returned to pre-fluctuation conditions again. Our observations confirm previous studies suggesting that repeated meltwater pulses

  11. Atlantic-induced pan-tropical climate change over the past three decades

    NASA Astrophysics Data System (ADS)

    Li, Xichen; Xie, Shang-Ping; Gille, Sarah T.; Yoo, Changhyun

    2016-03-01

    During the past three decades, tropical sea surface temperature (SST) has shown dipole-like trends, with warming over the tropical Atlantic and Indo-western Pacific but cooling over the eastern Pacific. Competing hypotheses relate this cooling, identified as a driver of the global warming hiatus, to the warming trends in either the Atlantic or Indian Ocean. However, the mechanisms, the relative importance and the interactions between these teleconnections remain unclear. Using a state-of-the-art climate model, we show that the Atlantic plays a key role in initiating the tropical-wide teleconnection, and the Atlantic-induced anomalies contribute ~55-75% of the tropical SST and circulation changes during the satellite era. The Atlantic warming drives easterly wind anomalies over the Indo-western Pacific as Kelvin waves and westerly anomalies over the eastern Pacific as Rossby waves. The wind changes induce an Indo-western Pacific warming through the wind-evaporation-SST effect, and this warming intensifies the La Niña-type response in the tropical Pacific by enhancing the easterly trade winds and through the Bjerknes ocean dynamical processes. The teleconnection develops into a tropical-wide SST dipole pattern. This mechanism, supported by observations and a hierarchy of climate models, reveals that the tropical ocean basins are more tightly connected than previously thought.

  12. Climate change, allergy and asthma, and the role of tropical forests.

    PubMed

    D'Amato, Gennaro; Vitale, Carolina; Rosario, Nelson; Neto, Herberto Josè Chong; Chong-Silva, Deborah Carla; Mendonça, Francisco; Perini, Josè; Landgraf, Loraine; Solé, Dirceu; Sánchez-Borges, Mario; Ansotegui, Ignacio; D'Amato, Maria

    2017-01-01

    Tropical forests cover less than 10 per cent of all land area (1.8 × 107 km 2 ) and over half of the tropical-forest area (1.1 × 107 Km 2 ) is represented by humid tropical forests (also called tropical rainforests). The Amazon basin contains the largest rainforest on Earth, almost 5.8 million km 2 , and occupies about 40% of South America; more than 60% of the basin is located in Brazil and the rest in Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname and Venezuela. Over the past decade the positive role of tropical rainforests in capturing large amounts of atmospheric carbon dioxide (CO 2 ) has been demonstrated. In response to the increase in atmospheric CO 2 concentration, tropical forests act as a global carbon sink. Accumulation of carbon in the tropical terrestrial biosphere strongly contributes to slowing the rate of increase of CO 2 into the atmosphere, thus resulting in the reduction of greenhouse gas effect. Tropical rainforests have been estimated to account for 32-36% of terrestrial Net Primary Productivity (NPP) that is the difference between total forest photosynthesis and plant respiration. Tropical rainforests have been acting as a strong carbon sink in this way for decades. However, over the past years, increased concentrations of greenhouse gases, and especially CO 2 , in the atmosphere have significantly affected the net carbon balance of tropical rainforests, and have warmed the planet substantially driving climate changes through more severe and prolonged heat waves, variability in temperature, increased air pollution, forest fires, droughts, and floods. The role of tropical forests in mitigating climate change is therefore critical. Over the past 30 years almost 600,000 km 2 have been deforested in Brazil alone due to the rapid development of Amazonia, this is the reason why currently the region is one of the 'hotspots' of global environmental change on the planet. Deforestation represents the second largest

  13. Moist Thermodynamics of Tropical Cyclone Formation and Intensification in High-Resolution Climate Models

    NASA Astrophysics Data System (ADS)

    Wing, A. A.; Camargo, S. J.; Sobel, A. H.; Kim, D.; Moon, Y.; Bosilovich, M. G.; Murakami, H.; Reed, K. A.; Vecchi, G. A.; Wehner, M. F.; Zarzycki, C. M.; Zhao, M.

    2017-12-01

    In recent years, climate models have improved such that high-resolution simulations are able to reproduce the climatology of tropical cyclone activity with some fidelity and show some skill in seasonal forecasting. However, biases remain in many models, motivating a better understanding of what factors control the representation of tropical cyclone activity in climate models. We explore tropical cyclogenesis and intensification processes in six high-resolution climate models from NOAA/GFDL, NCAR, and NASA, including both coupled and uncoupled configurations. Our analysis framework focuses on how convection, moisture, clouds and related processes are coupled and employs budgets of column moist static energy and the spatial variance of column moist static energy. The latter allows us to quantify the different feedback processes responsible for the amplification of moist static energy anomalies associated with the organization of convection and cyclogenesis, including surface flux feedbacks and cloud-radiative feedbacks. We track the formation and evolution of tropical cyclones in the climate model simulations and apply our analysis along the individual tracks and composited over many tropical cyclones. We use two methods of compositing: a composite over all TC track points in a given intensity range, and a composite relative to the time of lifetime maximum intensity for each storm (at the same stage in the TC life cycle).

  14. Finding Intervals of Abrupt Change in Earth Science Data

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Shekhar, S.; Liess, S.

    2011-12-01

    In earth science data (e.g., climate data), it is often observed that a persistently abrupt change in value occurs in a certain time-period or spatial interval. For example, abrupt climate change is defined as an unusually large shift of precipitation, temperature, etc, that occurs during a relatively short time period. A similar pattern can also be found in geographical space, representing a sharp transition of the environment (e.g., vegetation between different ecological zones). Identifying such intervals of change from earth science datasets is a crucial step for understanding and attributing the underlying phenomenon. However, inconsistencies in these noisy datasets can obstruct the major change trend, and more importantly can complicate the search of the beginning and end points of the interval of change. Also, the large volume of data makes it challenging to process the dataset reasonably fast. In earth science data (e.g., climate data), it is often observed that a persistently abrupt change in value occurs in a certain time-period or spatial interval. For example, abrupt climate change is defined as an unusually large shift of precipitation, temperature, etc, that occurs during a relatively short time period. A similar change pattern can also be found in geographical space, representing a sharp transition of the environment (e.g., vegetation between different ecological zones). Identifying such intervals of change from earth science datasets is a crucial step for understanding and attributing the underlying phenomenon. However, inconsistencies in these noisy datasets can obstruct the major change trend, and more importantly can complicate the search of the beginning and end points of the interval of change. Also, the large volume of data makes it challenging to process the dataset fast. In this work, we analyze earth science data using a novel, automated data mining approach to identify spatial/temporal intervals of persistent, abrupt change. We first

  15. Sulfate Aerosol Control of Tropical Atlantic Climate over the Twentieth Century

    NASA Technical Reports Server (NTRS)

    Chang, C.-Y.; Chiang, J. C. H.; Wehner, M. F.; Friedman, A. R.; Ruedy, R.

    2011-01-01

    The tropical Atlantic interhemispheric gradient in sea surface temperature significantly influences the rainfall climate of the tropical Atlantic sector, including droughts over West Africa and Northeast Brazil. This gradient exhibits a secular trend from the beginning of the twentieth century until the 1980s, with stronger warming in the south relative to the north. This trend behavior is on top of a multi-decadal variation associated with the Atlantic multi-decadal oscillation. A similar long-term forced trend is found in a multimodel ensemble of forced twentieth-century climate simulations. Through examining the distribution of the trend slopes in the multimodel twentieth-century and preindustrial models, the authors conclude that the observed trend in the gradient is unlikely to arise purely from natural variations; this study suggests that at least half the observed trend is a forced response to twentieth-century climate forcings. Further analysis using twentieth-century single-forcing runs indicates that sulfate aerosol forcing is the predominant cause of the multimodel trend. The authors conclude that anthropogenic sulfate aerosol emissions, originating predominantly from the Northern Hemisphere, may have significantly altered the tropical Atlantic rainfall climate over the twentieth century

  16. Spatial patterns and recent trends in the climate of tropical rainforest regions.

    PubMed

    Malhi, Yadvinder; Wright, James

    2004-03-29

    We present an analysis of the mean climate and climatic trends of tropical rainforest regions over the period 1960-1998, with the aid of explicit maps of forest cover and climatological databases. Until the mid-1970s most regions showed little trend in temperature, and the western Amazon experienced a net cooling probably associated with an interdecadal oscillation. Since the mid-1970s, all tropical rainforest regions have experienced a strong warming at a mean rate of 0.26 +/- 0.05 degrees C per decade, in synchrony with a global rise in temperature that has been attributed to the anthropogenic greenhouse effect. Over the study period, precipitation appears to have declined in tropical rainforest regions at a rate of 1.0 +/- 0.8% per decade (p < 5%), declining sharply in northern tropical Africa (at 3-4% per decade), declining marginally in tropical Asia and showing no significant trend in Amazonia. There is no evidence so far of a decline in precipitation in eastern Amazonia, a region thought vulnerable to climate-change-induced drying. The strong drying trend in Africa suggests that this should be a priority study region for understanding the impact of drought on tropical rainforests. We develop and use a dry-season index to study variations in the length and intensity of the dry season. Only African and Indian tropical rainforests appear to have seen a significant increase in dry-season intensity. In terms of interannual variability, the El Niño-Southern Oscillation (ENSO) is the primary driver of temperature variations across the tropics and of precipitation fluctuations for large areas of the Americas and southeast Asia. The relation between ENSO and tropical African precipitation appears less direct.

  17. Abrupt warming of the Red Sea

    NASA Astrophysics Data System (ADS)

    Raitsos, D. E.; Hoteit, I.; Prihartato, P. K.; Chronis, T.; Triantafyllou, G.; Abualnaja, Y.

    2011-07-01

    Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

  18. Tropical Climate Dynamics and Civilizations

    NASA Astrophysics Data System (ADS)

    Haug, G. H.; Yancheva, G.; Peterson, L. C.

    2005-12-01

    Dr. James P. Kennett has been a leader in the area of rapid climate change. Jim and his son Douglas J. Kennett, a scientific archeologist, were among the first to make a serious effort to combine high-quality climate data with archeological information to study the impact of climate on societies. They argued about the 'strong relationship between climatically induced changes in environmental conditions and social, political, and economic responses' in coastal California during the past 2 millennia. One tropical climate archive with an appropriate memory for the most relevant sub-centennial to sub-decadal scale climate swings is the anoxic Cariaco Basin off northern Venezuela. Millimeter to micrometer-scale geochemical data in the laminated sediments of the Cariaco Basin have been interpreted to reflect variations in the hydrological cycle and the mean annual position of the Intertropical Convergence Zone (ITCZ) over tropical South America during the past millennia. These data with decadal to (sub)annual resolution show that the Terminal Collapse of the Classic Maya civilization occurred during an extended dry period. In detail, the Cariaco record reveals evidence for three separate droughts during the period of Maya downfall, each lasting a decade or less. These data suggest that climate change was potentially one immediate cause of the demise of Mayan civilization, with a century-scale decline in rainfall putting a general strain on resources and several multi-year events of more intense drought pushing Mayan society over the edge. Here, we present a new data set of comparable quality and resolution from Southern China. In the sediments of lake Huguang Maar in coastal southeast China, the titanium content and redox-sensitive magnetic properties record the strength of winter monsoon winds at subdecadal resolution over the last 16 thousand years. The record indicates a stronger winter monsoon prior to the Boelling-Alleroed warming, during the Younger Dryas, and

  19. Predicting pan-tropical climate change induced forest stock gains and losses—implications for REDD

    NASA Astrophysics Data System (ADS)

    Gumpenberger, Marlies; Vohland, Katrin; Heyder, Ursula; Poulter, Benjamin; Macey, Kirsten; Rammig, Anja; Popp, Alexander; Cramer, Wolfgang

    2010-01-01

    Deforestation is a major threat to tropical forests worldwide, contributing up to one-fifth of global carbon emissions into the atmosphere. Despite protection efforts, deforestation of tropical forests has continued in recent years. Providing incentives to reducing deforestation has been proposed in the United Nations Framework Convention on Climate Change (UNFCCC) Bali negotiations in 2007 to decelerate emissions from deforestation (REDD—reduced emissions from deforestation and forest degradation). A number of methodological issues such as ensuring permanence, establishing reference emissions levels that do not reward business-as-usual and having a measuring, reporting and verification system in place are essential elements in implementing successful REDD schemes. To assess the combined impacts of climate and land-use change on tropical forest carbon stocks in the 21st century, we use a dynamic global vegetation model (LPJ DGVM) driven by five different climate change projections under a given greenhouse gas emission scenario (SRES A2) and two contrasting land-use change scenarios. We find that even under a complete stop of deforestation after the period of the Kyoto Protocol (post-2012) some countries may continue to lose carbon stocks due to climate change. Especially at risk is tropical Latin America, although the presence and magnitude of the risk depends on the climate change scenario. By contrast, strong protection of forests could increase carbon uptake in many tropical countries, due to CO2 fertilization effects, even under altered climate regimes.

  20. Northern tropical Atlantic climate since late Medieval times from Northern Caribbean coral geochemistry

    NASA Astrophysics Data System (ADS)

    Kilbourne, K. H.; Xu, Y.

    2015-12-01

    Paleoclimate reconstructions of different global climate modes over the last 1000 years provide the basis for testing the relative roles of forced and unforced variability climate system, which can help us improve projections of future climate change. The Medieval Climate Anomaly (MCA) has been characterized by a combination of persistent La Niña-like conditions, a positive North Atlantic Oscillation (+NAO), and increased Atlantic Meridional Overturning Circulation (AMOC). The northern tropical Atlantic is sensitive to each of these climate patterns, but not all of them have the same regional fingerprint in the modern northern tropical Atlantic. The relative influence of different processes related to these climate patterns can help us better understand regional responses to climate change. The regional response of the northern tropical Atlantic is important because the tropical Atlantic Ocean is a large source of heat and moisture to the global climate system that can feedback onto global climate patterns. This study presents new coral Sr/Ca and δ18O data from the northern tropical Atlantic (Anegada, British Virgin Islands). Comparison of the sub-fossil corals that grew during the 13th and 14th Centuries with modern coral geochemical data from this site indicates relatively cooler mean conditions with a decrease in the oxygen isotopic composition of the water consistent with lower salinities. Similar average annual cycles between modern and sub-fossil Sr/Ca indicate no change in seasonal temperature range, but a difference in the relative phasing of the δ18O seasonal cycles indicates that the fresher mean conditions may be due to a more northerly position of the regional salinity front. This localized response is consistent with some, but not all of the expected regional responses to a La Niña-like state, a +NAO state, and increased AMOC. Understanding these differences can provide insight into the relative importance of advection versus surface fluxes for

  1. Climate and Edaphic Controls on Humid Tropical Forest Tree Height

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Saatchi, S. S.; Xu, L.

    2014-12-01

    Uncertainty in the magnitude and spatial variations of forest carbon density in tropical regions is due to under sampling of forest structure from inventory plots and the lack of regional allometry to estimate the carbon density from structure. Here we quantify the variation of tropical forest structure by using more than 2.5 million measurements of canopy height from systematic sampling of Geoscience Laser Altimeter System (GLAS) satellite observations between 2004 to 2008 and examine the climate and edaphic variables influencing the variations. We used top canopy height of GLAS footprints (~ 0.25 ha) to grid the statistical mean and 90 percentile of samples at 0.5 degrees to capture the regional variability of large trees in tropics. GLAS heights were also aggregated based on a stratification of tropical regions using soil, elevation, and forest types. Both approaches provided consistent patterns of statistically dominant large trees and the least heterogeneity, both as strong drivers of distribution of high biomass forests. Statistical models accounting for spatial autocorrelation suggest that climate, soil and spatial features together can explain more than 60% of the variations in observed tree height information, while climate-only variables explains about one third of the first-order changes in tree height. Soil basics, including physical compositions such as clay and sand contents, chemical properties such as PH values and cation-exchange capacity, as well as biological variables such as organic matters, all present independent but statistically significant relationships to tree height variations. The results confirm other landscape and regional studies that soil fertility, geology and climate may jointly control a majority of the regional variations of forest structure in pan-tropics and influencing both biomass stocks and dynamics. Consequently, other factors such as biotic and disturbance regimes, not included in this study, may have less influence on

  2. Connecting tropical climate change with Southern Ocean heat uptake

    NASA Astrophysics Data System (ADS)

    Hwang, Yen-Ting; Xie, Shang-Ping; Deser, Clara; Kang, Sarah M.

    2017-09-01

    Under increasing greenhouse gas forcing, climate models project tropical warming that is greater in the Northern than the Southern Hemisphere, accompanied by a reduction in the northeast trade winds and a strengthening of the southeast trades. While the ocean-atmosphere coupling indicates a positive feedback, what triggers the coupled asymmetry and favors greater warming in the northern tropics remains unclear. Far away from the tropics, the Southern Ocean (SO) has been identified as the major region of ocean heat uptake. Beyond its local effect on the magnitude of sea surface warming, we show by idealized modeling experiments in a coupled slab ocean configuration that enhanced SO heat uptake has a profound global impact. This SO-to-tropics connection is consistent with southward atmospheric energy transport across the equator. Enhanced SO heat uptake results in a zonally asymmetric La-Nina-like pattern of sea surface temperature change that not only affects tropical precipitation but also has influences on the Asian and North American monsoons.

  3. The Genetic Architecture of Climatic Adaptation of Tropical Cattle

    PubMed Central

    Porto-Neto, Laercio R.; Reverter, Antonio; Prayaga, Kishore C.; Chan, Eva K. F.; Johnston, David J.; Hawken, Rachel J.; Fordyce, Geoffry; Garcia, Jose Fernando; Sonstegard, Tad S.; Bolormaa, Sunduimijid; Goddard, Michael E.; Burrow, Heather M.; Henshall, John M.; Lehnert, Sigrid A.; Barendse, William

    2014-01-01

    Adaptation of global food systems to climate change is essential to feed the world. Tropical cattle production, a mainstay of profitability for farmers in the developing world, is dominated by heat, lack of water, poor quality feedstuffs, parasites, and tropical diseases. In these systems European cattle suffer significant stock loss, and the cross breeding of taurine x indicine cattle is unpredictable due to the dilution of adaptation to heat and tropical diseases. We explored the genetic architecture of ten traits of tropical cattle production using genome wide association studies of 4,662 animals varying from 0% to 100% indicine. We show that nine of the ten have genetic architectures that include genes of major effect, and in one case, a single location that accounted for more than 71% of the genetic variation. One genetic region in particular had effects on parasite resistance, yearling weight, body condition score, coat colour and penile sheath score. This region, extending 20 Mb on BTA5, appeared to be under genetic selection possibly through maintenance of haplotypes by breeders. We found that the amount of genetic variation and the genetic correlations between traits did not depend upon the degree of indicine content in the animals. Climate change is expected to expand some conditions of the tropics to more temperate environments, which may impact negatively on global livestock health and production. Our results point to several important genes that have large effects on adaptation that could be introduced into more temperate cattle without detrimental effects on productivity. PMID:25419663

  4. Intraseasonal Variations in Tropical Energy Balance: Relevance to Climate Sensitivity?

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Ramey, Holly S.; Roberts, Jason B.

    2011-01-01

    Intraseasonal variability of deep convection represents a fundamental mode of organization for tropical convection. While most studies of intraseasonal oscillations (ISOs) have focused on the spatial propagation and dynamics of convectively coupled circulations, here we examine the projection of ISOs on the tropically-averaged heat and moisture budget. One unresolved question concerns the degree to which observable variations in the "fast" processes (e.g. convection, radiative / turbulent fluxes) can inform our understanding of feedback mechanisms operable in the context of climate change. Our analysis use daily data from satellite observations, the Modern Era analysis for Research and Applications (MERRA), and other model integrations to address these questions: (i) How are tropospheric temperature variations related to that tropical deep convection and the associated ice cloud fractional amount (ICF), ice water path (IWP), and properties of warmer liquid clouds? (ii) What role does moisture transport play vis-a-vis ocean latent heat flux in enabling the evolution of deep convection to mediate PBL - free atmospheric temperature equilibration? (iii) What affect do convectively generated upper-tropospheric clouds have on the TOA radiation budget? Our methodology is similar to that of Spencer et al., (2007 GRL ) whereby a composite time series of various quantities over 60+ ISO events is built using tropical mean tropospheric temperature signal as a reference to which the variables are related at various lag times (from -30 to +30 days). The area of interest encompasses the global oceans between 20oN/S. The increase of convective precipitation cannot be sustained by evaporation within the domain, implying strong moisture transports into the tropical ocean area. The decrease in net TOA radiation that develops after the peak in deep convective rainfall, is part of the response that constitutes a "discharge" / "recharge" mechanism that facilitates tropical heat balance

  5. Climate change in Australian tropical rainforests: an impending environmental catastrophe.

    PubMed

    Williams, Stephen E; Bolitho, Elizabeth E; Fox, Samantha

    2003-09-22

    It is now widely accepted that global climate change is affecting many ecosystems around the globe and that its impact is increasing rapidly. Many studies predict that impacts will consist largely of shifts in latitudinal and altitudinal distributions. However, we demonstrate that the impacts of global climate change in the tropical rainforests of northeastern Australia have the potential to result in many extinctions. We develop bioclimatic models of spatial distribution for the regionally endemic rainforest vertebrates and use these models to predict the effects of climate warming on species distributions. Increasing temperature is predicted to result in significant reduction or complete loss of the core environment of all regionally endemic vertebrates. Extinction rates caused by the complete loss of core environments are likely to be severe, nonlinear, with losses increasing rapidly beyond an increase of 2 degrees C, and compounded by other climate-related impacts. Mountain ecosystems around the world, such as the Australian Wet Tropics bioregion, are very diverse, often with high levels of restricted endemism, and are therefore important areas of biodiversity. The results presented here suggest that these systems are severely threatened by climate change.

  6. Climate change in Australian tropical rainforests: an impending environmental catastrophe.

    PubMed Central

    Williams, Stephen E; Bolitho, Elizabeth E; Fox, Samantha

    2003-01-01

    It is now widely accepted that global climate change is affecting many ecosystems around the globe and that its impact is increasing rapidly. Many studies predict that impacts will consist largely of shifts in latitudinal and altitudinal distributions. However, we demonstrate that the impacts of global climate change in the tropical rainforests of northeastern Australia have the potential to result in many extinctions. We develop bioclimatic models of spatial distribution for the regionally endemic rainforest vertebrates and use these models to predict the effects of climate warming on species distributions. Increasing temperature is predicted to result in significant reduction or complete loss of the core environment of all regionally endemic vertebrates. Extinction rates caused by the complete loss of core environments are likely to be severe, nonlinear, with losses increasing rapidly beyond an increase of 2 degrees C, and compounded by other climate-related impacts. Mountain ecosystems around the world, such as the Australian Wet Tropics bioregion, are very diverse, often with high levels of restricted endemism, and are therefore important areas of biodiversity. The results presented here suggest that these systems are severely threatened by climate change. PMID:14561301

  7. Atlantic Induced Pan-tropical Climate Variability in the Upper-ocean and Atmosphere

    NASA Astrophysics Data System (ADS)

    Li, X.; Xie, S. P.; Gille, S. T.; Yoo, C.

    2016-02-01

    During the last three decades, tropical sea surface temperature (SST) exhibited dipole-like trends, with warming over the tropical Atlantic and Indo-Western Pacific but cooling over the Eastern Pacific. The Eastern Pacific cooling has recently been identified as a driver of the global warming hiatus. Previous studies revealed atmospheric bridges between the tropical Pacific, Atlantic, and Indian Ocean, which could potentially contribute to this zonally asymmetric SST pattern. However, the mechanisms and the interactions between these teleconnections remain unclear. To investigate these questions, we performed a `pacemaker' simulation by restoring the tropical Atlantic SST changes in a state-of-the-art climate model - the CESM1. Results show that the Atlantic plays a key role in initiating the tropical-wide teleconnections, and the Atlantic-induced anomalies contribute 55%-75% of the total tropical SST and circulation changes during the satellite era. A hierarchy of oceanic and atmospheric models are then used to investigate the physical mechanisms of these teleconnections: the Atlantic warming enhances atmospheric deep convection, drives easterly wind anomalies over the Indo-Western Pacific through the Kelvin wave, and westerly anomalies over the eastern Pacific as Rossby waves, in line with Gill's solution (Fig1a). These wind changes induce an Indo-Western Pacific warming via the wind-evaporation-SST effect, and this warming intensifies the La Niña-type response in the upper Pacific Ocean by enhancing the easterly trade winds and through the Bjerknes ocean-dynamical processes (Fig1b). The teleconnection finally develops into a tropical-wide SST dipole pattern with an enhanced trade wind and Walker circulation, similar as the observed changes during the satellite era. This mechanism reveals that the tropical ocean basins are more tightly connected than previously thought, and the Atlantic plays a key role in the tropical climate pattern formation and further the

  8. Reducing The Risk Of Abrupt Climate Change: Emission Corridors Preserving The Thermohaline Circulation

    NASA Astrophysics Data System (ADS)

    Zickfeld, K.

    Paleo-reconstructions have shown that large and abrupt climate changes have occurred throughout the last ice-age cycles. This evidence, supplemented by insights into the complex and nonlinear nature of the climate system, gives raise to the concern that anthropogenic forcing may trigger such events in the future. A prominent example for such a potential climatic shift is the collapse of the North Atlantic thermohaline circu- lation (THC), which would cause a major cooling of the northern North Atlantic and north-western Europe and considerable regional sea level rise, with possibly severe consequences on, e.g., fisheries, agriculture and ecosystems. In this paper we present emission corridors for the 21st century preserving the THC. Emission corridors embrace the range of future emissions beyond which either the THC collapses or the mitigation burden becomes intolerable. They are calculated along the conceptual and methodological lines of the tolerable windows approach. We investigate the sensitivity of the emission corridors to the main uncertain parame- ters (climate and North Atlantic hydrological sensitivities as well as emissions of non CO_2 greenhouse gases). Results show a high dependence of the size of the emis- sion corridors on hydrological and climate sensitivities. For the best-guess values of both parameters we find that the emission corridors are wider than the range spanned by the SRES emissions scenarios. Thus, no immediate mitigation seems necessary in order to preserve the THC. For high but still realistic values of the sensitivities, however, even the low SRES emissions scenarios transgress the corridor boundaries. These findings imply that under 'business as usual' a non-negligible risk of either a THC collapse or an intolerable mitigation burden exists.

  9. Climate-mediated nitrogen and carbon dynamics in a tropical watershed

    NASA Astrophysics Data System (ADS)

    Ballantyne, A. P.; Baker, P. A.; Fritz, S. C.; Poulter, B.

    2011-06-01

    Climate variability affects the capacity of the biosphere to assimilate and store important elements, such as nitrogen and carbon. Here we present biogeochemical evidence from the sediments of tropical Lake Titicaca indicating that large hydrologic changes in response to global glacial cycles during the Quaternary were accompanied by major shifts in ecosystem state. During prolonged glacial intervals, lake level was high and the lake was in a stable nitrogen-limited state. In contrast, during warm dry interglacials lake level fell and rates of nitrogen concentrations increased by a factor of 4-12, resulting in a fivefold to 24-fold increase in organic carbon concentrations in the sediments due to increased primary productivity. Observed periods of increased primary productivity were also associated with an apparent increase in denitrification. However, the net accumulation of nitrogen during interglacial intervals indicates that increased nitrogen supply exceeded nitrogen losses due to denitrification, thereby causing increases in primary productivity. Although primary productivity in tropical ecosystems, especially freshwater ecosystems, tends to be nitrogen limited, our results indicate that climate variability may lead to changes in nitrogen availability and thus changes in primary productivity. Therefore some tropical ecosystems may shift between a stable state of nitrogen limitation and a stable state of nitrogen saturation in response to varying climatic conditions.

  10. Wet tropical climate in SE Tibet during the Late Eocene.

    PubMed

    Sorrel, Philippe; Eymard, Ines; Leloup, Philippe-Herve; Maheo, Gweltaz; Olivier, Nicolas; Sterb, Mary; Gourbet, Loraine; Wang, Guocan; Jing, Wu; Lu, Haijian; Li, Haibing; Yadong, Xu; Zhang, Kexin; Cao, Kai; Chevalier, Marie-Luce; Replumaz, Anne

    2017-08-10

    Cenozoic climate cooling at the advent of the Eocene-Oligocene transition (EOT), ~33.7 Ma ago, was stamped in the ocean by a series of climatic events albeit the impact of this global climatic transition on terrestrial environments is still fragmentary. Yet archival constraints on Late Eocene atmospheric circulation are scarce in (tropical) monsoonal Asia, and the paucity of terrestrial records hampers a meaningful comparison of the long-term climatic trends between oceanic and continental realms. Here we report new sedimentological data from the Jianchuan basin (SE Tibet) arguing for wetter climatic conditions in monsoonal Asia at ~35.5 Ma almost coevally to the aridification recognized northwards in the Xining basin. We show that the occurrence of flash-flood events in semi-arid to sub-humid palustrine-sublacustrine settings preceded the development of coal-bearing deposits in swampy-like environments, thus paving the way to a more humid climate in SE Tibet ahead from the EOT. We suggest that this moisture redistribution possibly reflects more northern and intensified ITCZ-induced tropical rainfall in monsoonal Asia around 35.5 Ma, in accordance with recent sea-surface temperature reconstructions from equatorial oceanic records. Our findings thus highlight an important period of climatic upheaval in terrestrial Asian environments ~2-4 millions years prior to the EOT.

  11. Downscaling CMIP5 climate models shows increased tropical cyclone activity over the 21st century

    PubMed Central

    Emanuel, Kerry A.

    2013-01-01

    A recently developed technique for simulating large [O(104)] numbers of tropical cyclones in climate states described by global gridded data is applied to simulations of historical and future climate states simulated by six Coupled Model Intercomparison Project 5 (CMIP5) global climate models. Tropical cyclones downscaled from the climate of the period 1950–2005 are compared with those of the 21st century in simulations that stipulate that the radiative forcing from greenhouse gases increases by over preindustrial values. In contrast to storms that appear explicitly in most global models, the frequency of downscaled tropical cyclones increases during the 21st century in most locations. The intensity of such storms, as measured by their maximum wind speeds, also increases, in agreement with previous results. Increases in tropical cyclone activity are most prominent in the western North Pacific, but are evident in other regions except for the southwestern Pacific. The increased frequency of events is consistent with increases in a genesis potential index based on monthly mean global model output. These results are compared and contrasted with other inferences concerning the effect of global warming on tropical cyclones. PMID:23836646

  12. Climate mitigation and the future of tropical landscapes.

    PubMed

    Thomson, Allison M; Calvin, Katherine V; Chini, Louise P; Hurtt, George; Edmonds, James A; Bond-Lamberty, Ben; Frolking, Steve; Wise, Marshall A; Janetos, Anthony C

    2010-11-16

    Land-use change to meet 21st-century demands for food, fuel, and fiber will depend on many interactive factors, including global policies limiting anthropogenic climate change and realized improvements in agricultural productivity. Climate-change mitigation policies will alter the decision-making environment for land management, and changes in agricultural productivity will influence cultivated land expansion. We explore to what extent future increases in agricultural productivity might offset conversion of tropical forest lands to crop lands under a climate mitigation policy and a contrasting no-policy scenario in a global integrated assessment model. The Global Change Assessment Model is applied here to simulate a mitigation policy that stabilizes radiative forcing at 4.5 W m(-2) (approximately 526 ppm CO(2)) in the year 2100 by introducing a price for all greenhouse gas emissions, including those from land use. These scenarios are simulated with several cases of future agricultural productivity growth rates and the results downscaled to produce gridded maps of potential land-use change. We find that tropical forests are preserved near their present-day extent, and bioenergy crops emerge as an effective mitigation option, only in cases in which a climate mitigation policy that includes an economic price for land-use emissions is in place, and in which agricultural productivity growth continues throughout the century. We find that idealized land-use emissions price assumptions are most effective at limiting deforestation, even when cropland area must increase to meet future food demand. These findings emphasize the importance of accounting for feedbacks from land-use change emissions in global climate change mitigation strategies.

  13. A glacial record of the last termination in the southern tropical Andes

    NASA Astrophysics Data System (ADS)

    Bromley, G. R.; Schaefer, J. M.; Winckler, G.; Hall, B. L.; Todd, C. E.; Rademaker, K.

    2012-12-01

    The last glacial termination represents the highest-magnitude climate change of the last hundred thousand years. Accurate resolution of events during the termination is vital to our understanding of how - and why - the global climate system transitions from a full glacial to interglacial state, as well as the causes of abrupt climate change during the late-glacial period. Palaeoclimate data from low latitudes, though relatively sparse, are particularly valuable, since the tropical ocean and atmosphere likely play a crucial role in Quaternary climate variability on all timescales. We present a detailed glacier record from the Andes of southern Peru (15°S), resolved with 3He surface-exposure dating and spanning the last glacial maximum and termination. Our dataset reveals that glaciers in this part of the Southern Hemisphere maintained their Late Pleistocene maxima for several millennia and that the onset of the termination may have occurred relatively late. Deglaciation was punctuated by two major advances during the late-glacial period. Following the glacial-interglacial transition, our preliminary chronologic and morphologic data suggest that, in contrast to the Northern Hemisphere, glaciers in the southern tropical Andes have experienced overall shrinkage during the Holocene.

  14. Reversal of Increasing Tropical Ocean Hypoxia Trends With Sustained Climate Warming

    NASA Astrophysics Data System (ADS)

    Fu, Weiwei; Primeau, Francois; Keith Moore, J.; Lindsay, Keith; Randerson, James T.

    2018-04-01

    Dissolved oxygen (O2) is essential for the survival of marine animals. Climate change impacts on future oxygen distributions could modify species biogeography, trophic interactions, biodiversity, and biogeochemistry. The Coupled Model Intercomparison Project Phase 5 models predict a decreasing trend in marine O2 over the 21st century. Here we show that this increasing hypoxia trend reverses in the tropics after 2100 in the Community Earth System Model forced by atmospheric CO2 from the Representative Concentration Pathway 8.5 and Extended Concentration Pathway 8.5. In tropical intermediate waters between 200 and 1,000 m, the model predicts a steady decline of O2 and an expansion of oxygen minimum zones (OMZs) during the 21st century. By 2150, however, the trend reverses with oxygen concentration increasing and OMZ volume shrinking through 2300. A novel five-box model approach in conjunction with output from the full Earth system model is used to separate the contributions of biological and physical processes to the trends in tropical oxygen. The tropical O2 recovery is caused mainly by reductions in tropical biological export, coupled with a modest increase in ventilation after 2200. The time-evolving oxygen distribution impacts marine nitrogen cycling, with potentially important climate feedbacks.

  15. Holocene constraints on simulated tropical Pacific climate

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Cobb, K. M.; Carre, M.; Braconnot, P.; Leloup, J.; Zhou, Y.; Harrison, S. P.; Correge, T.; Mcgregor, H. V.; Collins, M.; Driscoll, R.; Elliot, M.; Schneider, B.; Tudhope, A. W.

    2015-12-01

    The El Niño-Southern Oscillation (ENSO) influences climate and weather worldwide, so uncertainties in its response to external forcings contribute to the spread in global climate projections. Theoretical and modeling studies have argued that such forcings may affect ENSO either via the seasonal cycle, the mean state, or extratropical influences, but these mechanisms are poorly constrained by the short instrumental record. Here we synthesize a pan-Pacific network of high-resolution marine biocarbonates spanning discrete snapshots of the Holocene (past 10, 000 years of Earth's history), which we use to constrain a set of global climate model (GCM) simulations via a forward model and a consistent treatment of uncertainty. Observations suggest important reductions in ENSO variability throughout the interval, most consistently during 3-5 kyBP, when approximately 2/3 reductions are inferred. The magnitude and timing of these ENSO variance reductions bear little resemblance to those sim- ulated by GCMs, or to equatorial insolation. The central Pacific witnessed a mid-Holocene increase in seasonality, at odds with the reductions simulated by GCMs. Finally, while GCM aggregate behavior shows a clear inverse relationship between seasonal amplitude and ENSO-band variance in sea-surface temperature, in agreement with many previous studies, such a relationship is not borne out by these observations. Our synthesis suggests that tropical Pacific climate is highly variable, but exhibited millennia-long periods of reduced ENSO variability whose origins, whether forced or unforced, contradict existing explanations. It also points to deficiencies in the ability of current GCMs to simulate forced changes in the tropical Pacific seasonal cycle and its interaction with ENSO, highlighting a key area of growth for future modeling efforts.

  16. Do Quercus ilex Woodlands Undergo Abrupt Non-linear Changes in their Functional Dynamics in Response to Human Disturbance and Climatic Variation?

    NASA Astrophysics Data System (ADS)

    Bochet, E.; García-Fayos, P.; Molina, M. J.; Moreno de las Heras, M.; Espigares, T.; Nicolau, J. M.; Monleon, V. J.

    2017-12-01

    Theoretical models predict that drylands are particularly prone to suffer critical transitions with abrupt non-linear changes in their structure and functions as a result of the existing complex interactions between climatic fluctuations and human disturbances. How drylands undergo functional change has become an important issue in ecology which needs empirical data to validate theoretical models. We aim at determining the response of Mediterranean holm oak woodlands to human disturbance in three different climatic areas from Eastern Spain, under the hypothesis that semiarid and dry-transition landscapes are more prone to suffer abrupt functional changes than sub-humid ones. We used (a) remote-sensing estimations of precipitation-use-efficiency (PUE) from enhanced vegetation index (EVI) observations performed in 231 x 231 m plots of the Moderate Resolution Imaging Spectroradiometer (MODIS); (b) soil parameter (enzyme activity, organic matter) and (c) vegetation parameter (functional groups) determinations from soil sampling and vegetation surveys, respectively, performed in the same plots. We analyzed and compared the shape of the functional change (in terms of PUE, soil and vegetation parameters) in response to human disturbance intensity for our holm oak sites in the three climatic areas. Although no threshold of abrupt change is observed, important differences in the functional response of holm oak woodlands to disturbance exist between climatic conditions. Overall, semiarid and dry-transition woodlands suffer a non-linear functional decrease in terms of PUE, soil organic matter and enzyme activity with disturbance intensity. Differently, sub-humid woodlands experience a linear decrease of PUE with disturbance intensity and an increase of both soil parameters at high disturbance intensities after an important decrease at low disturbance intensities. The structural change from woody- to herbaceous-dominated landscapes in sub-humid areas explains the recovery of

  17. Tropical specialist vs. climate generalist: Diversification and demographic history of sister species of Carlia skinks from northwestern Australia.

    PubMed

    Afonso Silva, Ana C; Bragg, Jason G; Potter, Sally; Fernandes, Carlos; Coelho, Maria Manuela; Moritz, Craig

    2017-08-01

    Species endemic to the tropical regions are expected to be vulnerable to future climate change due in part to their relatively narrow climatic niches. In addition, these species are more likely to have responded strongly to past climatic change, and this can be explored through phylogeographic analyses. To test the hypothesis that tropical specialists are more sensitive to climate change than climate generalists, we generated and analyse sequence data from mtDNA and ~2500 exons to compare scales of historical persistence and population fluctuation in two sister species of Australian rainbow skinks: the tropical specialist Carlia johnstonei and the climate generalist C. triacantha. We expect the tropical specialist species to have deeper and finer-scale phylogeographic structure and stronger demographic fluctuations relative to the closely related climate generalist species, which should have had more stable populations through periods of harsh climate in the late Quaternary. Within C. johnstonei, we find that some populations from the northern Kimberley islands are highly divergent from mainland populations. In C. triacantha, one major clade occurs across the deserts and into the mesic Top End, and another occurs primarily in the Kimberley with scattered records eastwards. Where their ranges overlap in the Kimberley, both mitochondrial DNA and nuclear DNA suggest stronger phylogeographic structure and range expansion within the tropical specialist, whereas the climate generalist has minimal structuring and no evidence of recent past range expansion. These results are consistent with the hypothesis that tropical specialists are more sensitive to past climatic change. © 2017 John Wiley & Sons Ltd.

  18. The potential impacts of climate change induced changes to tropical leaf albedo and its feedback on global climate

    NASA Astrophysics Data System (ADS)

    Doughty, C.; Shenkin, A.; Bentley, L. P.; Malhi, Y.

    2017-12-01

    Tropical forest leaf albedo plays a critical role in global climate by determining how much radiation the planet absorbs near the equator. However, little is known about how tropical leaf albedo could be affected by climate change and how any such changes in albedo could, in turn, impact global climate. Here we measure sunlit leaf albedo along two elevation temperature gradients (a 3000-meter gradient in Peru (10 plots) and a 1500 m gradient in Australia (10 plots) and along two wet to dry transects (a 2000 mm yr-1 gradient in Ghana (10 plots) and a 2000 mm yr-1 gradient in Brazil (10 plots). We found a highly significant increase in visible leaf albedo with wetness at both wet to dry gradients. We also found a marginally significant trend of increased albedo with warmer temperatures along one of the elevation gradients. Leaf albedo can also be impacted by changes in species composition, variations in interspecific variation, and changes in leaf chlorophyll concentrations. We removed the dominant two species from the basal area weighting for each plots but found no significant change, a directional change of interspecific variation could change albedo by 0.01 in the NIR, and changes in chlorophyll could decrease visible albedo by 0.005. We then simulated changes in tropical leaf albedo with a climate model and show that such changes could act as a small negative feedback on climate, but most likely will not have a large impact on future climate.

  19. Climate-driven shifts in continental net primary production implicated as a driver of a recent abrupt increase in the land carbon sink

    NASA Astrophysics Data System (ADS)

    Buermann, Wolfgang; Beaulieu, Claudie; Parida, Bikash; Medvigy, David; Collatz, George J.; Sheffield, Justin; Sarmiento, Jorge L.

    2016-03-01

    The world's ocean and land ecosystems act as sinks for anthropogenic CO2, and over the last half century their combined sink strength grew steadily with increasing CO2 emissions. Recent analyses of the global carbon budget, however, have uncovered an abrupt, substantial ( ˜ 1 PgC yr-1) and sustained increase in the land sink in the late 1980s whose origin remains unclear. In the absence of this prominent shift in the land sink, increases in atmospheric CO2 concentrations since the late 1980s would have been ˜ 30 % larger than observed (or ˜ 12 ppm above current levels). Global data analyses are limited in regards to attributing causes to changes in the land sink because different regions are likely responding to different drivers. Here, we address this challenge by using terrestrial biosphere models constrained by observations to determine if there is independent evidence for the abrupt strengthening of the land sink. We find that net primary production significantly increased in the late 1980s (more so than heterotrophic respiration), consistent with the inferred increase in the global land sink, and that large-scale climate anomalies are responsible for this shift. We identify two key regions in which climatic constraints on plant growth have eased: northern Eurasia experienced warming, and northern Africa received increased precipitation. Whether these changes in continental climates are connected is uncertain, but North Atlantic climate variability is important. Our findings suggest that improved understanding of climate variability in the North Atlantic may be essential for more credible projections of the land sink under climate change.

  20. Quantifying Tropical Glacier Mass Balance Sensitivity to Climate Change Through Regional-Scale Modeling and The Randolph Glacier Inventory

    NASA Astrophysics Data System (ADS)

    Malone, A.

    2017-12-01

    Quantifying mass balance sensitivity to climate change is essential for forecasting glacier evolution and deciphering climate signals embedded in archives of past glacier changes. Ideally, these quantifications result from decades of field measurement, remote sensing, and a hierarchy modeling approach, but in data-sparse regions, such as the Himalayas and tropical Andes, regional-scale modeling rooted in first principles provides a first-order picture. Previous regional-scaling modeling studies have applied a surface energy and mass balance approach in order to quantify equilibrium line altitude sensitivity to climate change. In this study, an expanded regional-scale surface energy and mass balance model is implemented to quantify glacier-wide mass balance sensitivity to climate change for tropical Andean glaciers. Data from the Randolph Glacier Inventory are incorporated, and additional physical processes are included, such as a dynamic albedo and cloud-dependent atmospheric emissivity. The model output agrees well with the limited mass balance records for tropical Andean glaciers. The dominant climate variables driving interannual mass balance variability differ depending on the climate setting. For wet tropical glaciers (annual precipitation >0.75 m y-1), temperature is the dominant climate variable. Different hypotheses for the processes linking wet tropical glacier mass balance variability to temperature are evaluated. The results support the hypothesis that glacier-wide mass balance on wet tropical glaciers is largely dominated by processes at the lowest elevation where temperature plays a leading role in energy exchanges. This research also highlights the transient nature of wet tropical glaciers - the vast majority of tropical glaciers and a vital regional water resource - in an anthropogenic warming world.

  1. Improving predictions of carbon fluxes in the tropics undre climatic changes using ED2

    NASA Astrophysics Data System (ADS)

    Feng, X.; Uriarte, M.

    2016-12-01

    Tropical forests play a critical role in the exchange of carbon between land and atmosphere, highlighting the urgency of understanding the effects of climate change on these ecosystems. The most optimistic predictions of climate models indicate that global mean temperatures will increase by up to 2 0C with some tropical regions experiencing extreme heat. Drought and heat-induced tree mortality will accelerate the release of carbon to the atmosphere creating a positive feedback that greatly exacerbates global warming. Thus, under a warmer and drier climate, tropical forests may become net sources, rather than sinks, of carbon. Earth system models have not reached a consensus on the magnitude and direction of climate change impacts on tropical forests, calling into question the reliability of their predictions. Thus, there is an immediate need to improve the representation of tropical forests in earth system models to make robust predictions. The goal of our study is to quantify the responses of tropical forests to climate variability and improve the predictive capacity of terrestrial ecosystem models. We have collected species-specific physiological and functional trait data from 144 tree species in a Puerto Rican rainforest to parameterize the Ecosystem Demography model (ED2). The large amount of data generated by this research will lead to better validation and lowering the uncertainty in future model predictions. To best represent the forest landscape in ED2, all the trees have been assigned to three plant functional types (PFTs): early, mid, and late successional species. Trait data for each PFT were synthesized in a Bayesian meta-analytical model and posterior distributions of traits were used to parameterize the ED2 model. Model predictions show that biomass production of late successional PFT (118.89 ton/ha) was consistently higher than mid (71.33 ton/ha) and early (13.21 ton/ha) PFTs. However, mid successional PFT had the highest contributions to NPP for the

  2. Climate change impacts on tropical cyclones and extreme sea levels in the South Pacific — A regional assessment

    NASA Astrophysics Data System (ADS)

    Walsh, Kevin J. E.; McInnes, Kathleen L.; McBride, John L.

    2012-01-01

    This paper reviews the current understanding of the effect of climate change on extreme sea levels in the South Pacific region. This region contains many locations that are vulnerable to extreme sea levels in the current climate, and projections indicate that this vulnerability will increase in the future. The recent publication of authoritative statements on the relationship between global warming and global sea level rise, tropical cyclones and the El Niño-Southern Oscillation phenomenon has motivated this review. Confident predictions of global mean sea level rise are modified by regional differences in the steric (density-related) component of sea level rise and changing gravitational interactions between the ocean and the ice sheets which affect the regional distribution of the eustatic (mass-related) contribution to sea level rise. The most extreme sea levels in this region are generated by tropical cyclones. The intensity of the strongest tropical cyclones is likely to increase, but many climate models project a substantial decrease in tropical cyclone numbers in this region, which may lead to an overall decrease in the total number of intense tropical cyclones. This projection, however, needs to be better quantified using improved high-resolution climate model simulations of tropical cyclones. Future changes in ENSO may lead to large regional variations in tropical cyclone incidence and sea level rise, but these impacts are also not well constrained. While storm surges from tropical cyclones give the largest sea level extremes in the parts of this region where they occur, other more frequent high sea level events can arise from swell generated by distant storms. Changes in wave climate are projected for the tropical Pacific due to anthropogenically-forced changes in atmospheric circulation. Future changes in sea level extremes will be caused by a combination of changes in mean sea level, regional sea level trends, tropical cyclone incidence and wave

  3. Collaborative Project: Understanding Climate Model Biases in Tropical Atlantic and Their Impact on Simulations of Extreme Climate Events

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chang, Ping

    Recent studies have revealed that among all the tropical oceans, the tropical Atlantic has experienced the most pronounced warming trend over the 20th century. Many extreme climate events affecting the U.S., such as hurricanes, severe precipitation and drought events, are influenced by conditions in the Gulf of Mexico and the Atlantic Ocean. It is therefore imperative to have accurate simulations of the climatic mean and variability in the Atlantic region to be able to make credible projections of future climate change affecting the U.S. and other countries adjoining the Atlantic Ocean. Unfortunately, almost all global climate models exhibit large biasesmore » in their simulations of tropical Atlantic climate. The atmospheric convection simulation errors in the Amazon region and the associated errors in the trade wind simulations are hypothesized to be a leading cause of the tropical Atlantic biases in climate models. As global climate models have resolutions that are too coarse to resolve some of the atmospheric and oceanic processes responsible for the model biases, we propose to use a high-resolution coupled regional climate model (CRCM) framework to address the tropical bias issue. We propose to combine the expertise in tropical coupled atmosphere-ocean modeling at Texas A&M University (TAMU) and the coupled land-atmosphere modeling expertise at Pacific Northwest National Laboratory (PNNL) to develop a comprehensive CRCM for the Atlantic sector within a general and flexible modeling framework. The atmospheric component of the CRCM will be the NCAR WRF model and the oceanic component will be the Rutgers/UCLA ROMS. For the land component, we will use CLM modified at PNNL to include more detailed representations of vegetation and soil hydrology processes. The combined TAMU-PNNL CRCM model will be used to simulate the Atlantic climate, and the associated land-atmosphere-ocean interactions at a horizontal resolution of 9 km or finer. A particular focus of the

  4. Abrupt climate change: Past, present and the search for precursors as an aid to predicting events in the future (Hans Oeschger Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Mayewski, Paul Andrew

    2016-04-01

    The demonstration using Greenland ice cores that abrupt shifts in climate, Dansgaard-Oeschger (D-O) events, existed during the last glacial period has had a transformational impact on our understanding of climate change in the naturally forced world. The demonstration that D-O events are globally distributed and that they operated during previous glacial periods has led to extensive research into the relative hemispheric timing and causes of these events. The emergence of civilization during our current interglacial, the Holocene, has been attributed to the "relative climate quiescence" of this period relative to the massive, abrupt shifts in climate that characterized glacial periods in the form of D-O events. But, everything is relative and climate change is no exception. The demise of past civilizations, (eg., Mesopatamian, Mayan and Norse) is integrally tied to abrupt climate change (ACC) events operating at regional scales. Regionally to globally distributed ACC events have punctuated the Holocene and extreme events have always posed significant challenges to humans and ecosystems. Current warming of the Arctic, in terms of length of the summer season, is as abrupt and massive, albeit not as extensive, as the transition from the last major D-O event, the Younger Dryas into the Holocene (Mayewski et al., 2013). Tropospheric source greenhouse gas rise and ozone depletion in the stratosphere over Antarctica are triggers for the modern advent of human emission instigated ACCs. Arctic warming and Antarctic ozone depletion have resulted in significance changes to the atmospheric circulation systems that transport heat, moisture, and pollutants in both hemispheres. Climate models offer a critical tool for assessing trends, but they cannot as yet predict ACC events, as evidenced by the inability of these models to predict the rapid onset of Arctic warming and resulting changes in atmospheric circulation; and in the model vs past analog differences in projections for

  5. Energy and Cost Associated with Ventilating Office Buildings in a Tropical Climate

    PubMed Central

    Rim, Donghyun; Schiavon, Stefano; Nazaroff, William W.

    2015-01-01

    Providing sufficient amounts of outdoor air to occupants is a critical building function for supporting occupant health, well-being and productivity. In tropical climates, high ventilation rates require substantial amounts of energy to cool and dehumidify supply air. This study evaluates the energy consumption and associated cost for thermally conditioning outdoor air provided for building ventilation in tropical climates, considering Singapore as an example locale. We investigated the influence on energy consumption and cost of the following factors: outdoor air temperature and humidity, ventilation rate (L/s per person), indoor air temperature and humidity, air conditioning system coefficient of performance (COP), and cost of electricity. Results show that dehumidification of outdoor air accounts for more than 80% of the energy needed for building ventilation in Singapore’s tropical climate. Improved system performance and/or a small increase in the indoor temperature set point would permit relatively large ventilation rates (such as 25 L/s per person) at modest or no cost increment. Overall, even in a thermally demanding tropical climate, the energy cost associated with increasing ventilation rate up to 25 L/s per person is less than 1% of the wages of an office worker in an advanced economy like Singapore’s. This result implies that the benefits of increasing outdoor air ventilation rate up to 25 L/s per person — which is suggested to provide for productivity increases, lower sick building syndrome symptom prevalence, and reduced sick leave — can be much larger than the incremental cost of ventilation. PMID:25822504

  6. Energy and cost associated with ventilating office buildings in a tropical climate.

    PubMed

    Rim, Donghyun; Schiavon, Stefano; Nazaroff, William W

    2015-01-01

    Providing sufficient amounts of outdoor air to occupants is a critical building function for supporting occupant health, well-being and productivity. In tropical climates, high ventilation rates require substantial amounts of energy to cool and dehumidify supply air. This study evaluates the energy consumption and associated cost for thermally conditioning outdoor air provided for building ventilation in tropical climates, considering Singapore as an example locale. We investigated the influence on energy consumption and cost of the following factors: outdoor air temperature and humidity, ventilation rate (L/s per person), indoor air temperature and humidity, air conditioning system coefficient of performance (COP), and cost of electricity. Results show that dehumidification of outdoor air accounts for more than 80% of the energy needed for building ventilation in Singapore's tropical climate. Improved system performance and/or a small increase in the indoor temperature set point would permit relatively large ventilation rates (such as 25 L/s per person) at modest or no cost increment. Overall, even in a thermally demanding tropical climate, the energy cost associated with increasing ventilation rate up to 25 L/s per person is less than 1% of the wages of an office worker in an advanced economy like Singapore's. This result implies that the benefits of increasing outdoor air ventilation rate up to 25 L/s per person--which is suggested to provide for productivity increases, lower sick building syndrome symptom prevalence, and reduced sick leave--can be much larger than the incremental cost of ventilation.

  7. Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

    Treesearch

    Fabien H. Wagner; Bruno Herault; Damien Bonal; Clement Stahl; Liana O. Anderson; Timothy R. Baker; Gabriel Sebastian Becker; Hans Beeckman; Danilo Boanerges Souza; Paulo Cesar Botosso; David M. J. S. Bowman; Achim Brauning; Benjamin Brede; Foster Irving Brown; Jesus Julio Camarero; Plinio Barbosa Camargo; Fernanda C. G. Cardoso; Fabricio Alvim Carvalho; Wendeson Castro; Rubens Koloski Chagas; Jerome Chave; Emmanuel N. Chidumayo; Deborah A. Clark; Flavia Regina Capellotto Costa; Camille Couralet; Paulo Henrique da Silva Mauricio; Helmut Dalitz; Vinicius Resende de Castro; Jacanan Eloisa de Freitas Milani; Edilson Consuelo de Oliveira; Luciano de Souza Arruda; Jean-Louis Devineau; David M. Drew; Oliver Dunisch; Giselda Durigan; Elisha Elifuraha; Marcio Fedele; Ligia Ferreira Fedele; Afonso Figueiredo Filho; Cesar Augusto Guimaraes Finger; Augusto Cesar Franco; Joao Lima Freitas Junior; Franklin Galvao; Aster Gebrekirstos; Robert Gliniars; Paulo Mauricio Lima de Alencastro Graca; Anthony D. Griffiths; James Grogan; Kaiyu Guan; Jurgen Homeier; Maria Raquel Kanieski; Lip Khoon Kho; Jennifer Koenig; Sintia Valerio Kohler; Julia Krepkowski; Jose Pires Lemos-Filho; Diana Lieberman; Milton Eugene Lieberman; Claudio Sergio Lisi; Tomaz Longhi Santos; Jose Luis Lopez Ayala; Eduardo Eijji Maeda; Yadvinder Malhi; Vivian R. B. Maria; Marcia C. M. Marques; Renato Marques; Hector Maza Chamba; Lawrence Mbwambo; Karina Liana Lisboa Melgaco; Hooz Angela Mendivelso; Brett P. Murphy; Joseph O' Brien; Steven F. Oberbauer; Naoki Okada; Raphael Pelissier; Lynda D. Prior; Fidel Alejandro Roig; Michael Ross; Davi Rodrigo Rossatto; Vivien Rossi; Lucy Rowland; Ervan Rutishauser; Hellen Santana; Mark Schulze; Diogo Selhorst; Williamar Rodrigues Silva; Marcos Silveira; Susanne Spannl; Michael D. Swaine; Jose Julio Toledo; Marcos Miranda Toledo; Marisol Toledo; Takeshi Toma; Mario Tomazello Filho; Juan Ignacio Valdez Hernandez; Jan Verbesselt; Simone Aparecida Vieira; Gregoire Vincent; Carolina Volkmer de Castilho; Franziska Volland; Martin Worbes; Magda Lea Bolzan Zanon; Luiz E. O. C. Aragao

    2016-01-01

    The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter...

  8. Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes.

    PubMed

    Kaniewski, D; Paulissen, E; Van Campo, E; Al-Maqdissi, M; Bretschneider, J; Van Lerberghe, K

    2008-09-16

    The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to climatic changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP abrupt climate changes (ACCs), two large-scale shifts to a more arid climate have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100-800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome ca. 2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at ca. 1190 to 1185 B.C.

  9. Connecting the records: exploiting tephra deposits to help understand abrupt climate change

    NASA Astrophysics Data System (ADS)

    Davies, S. M.; Abbott, P. M.; Bourne, A. J.; Chapman, M.; Pearce, N. J. G.; Griggs, A. J.; Cook, E.

    2016-12-01

    The causal mechanism of abrupt climate change during the last glacial period remains a key challenge. Although these events are well-documented in a wide range of proxy records, the triggers and drivers remain poorly understood, largely due to the dating uncertainties that prevent the integration of different archives. Unravelling the lead/lag responses (hence cause and effect) between the Earth's climate components is limited by the challenges of synchronising palaeoclimate records on a common timescale. Here we present the potential and the challenges of optimising the use of cryptotephra deposits to precisely correlate the Greenland ice-cores with North Atlantic marine records. A series of new cryptotephra deposits have been identified in Greenland, increasing the scope of identifying coeval isochrons in the marine environment. This new framework, however, brings new challenges in the search for unique and robust geochemical fingerprints for unequivocal tephra correlations. As such, some tephra deposits are proposed to be more valuable than others and underpin key snapshots in time during the last glacial period. The North Atlantic Ash Zone II, for instance, represents the most widespread isochron and constrains the cooling of GI-15. Some tephra deposits in the ice-core record originate from ultra-distal sources beyond the North Atlantic region and we also explore the potential for establishing North Pacific linkages.

  10. Ocean waves from tropical cyclones in the Gulf of Mexico and the effect of climate change

    NASA Astrophysics Data System (ADS)

    Appendini, C. M.; Pedrozo-Acuña, A.; Meza-Padilla, R.; Torres-Freyermuth, A.; Cerezo-Mota, R.; López-González, J.

    2016-12-01

    To generate projections of wave climate associated to tropical cyclones is a challenge due to their short historical record of events, their low occurrence, and the poor wind field resolution in General Circulation Models. Synthetic tropical cyclones provide an alternative to overcome such limitations, improving robust statistics under present and future climates. We use synthetic events to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. The NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to derive present and future wave climate under RCPs 4.5 and 8.5. The results suggest an increase in wave activity for the future climate, particularly for the GFDL model that shows less bias in the present climate, although some areas are expected to decrease the wave energy. The practical implications of determining the future wave climate is exemplified by means of the 100-year design wave, where the use of the present climate may result in under/over design of structures, since the lifespan of a structure includes the future wave climate period.

  11. Coral Records of 20th Century Central Tropical Pacific SST and Salinity: Signatures of Natural and Anthropogenic Climate Change

    NASA Astrophysics Data System (ADS)

    Nurhati, I. S.; Cobb, K.; Di Lorenzo, E.

    2011-12-01

    Accurate forecasts of regional climate changes in many regions of the world largely depend on quantifying anthropogenic trends in tropical Pacific climate against its rich background of interannual to decadal-scale climate variability. However, the strong natural climate variability combined with limited instrumental climate datasets have obscured potential anthropogenic climate signals in the region. Here, we present coral-based sea-surface temperature (SST) and salinity proxy records over the 20th century (1898-1998) from the central tropical Pacific - a region sensitive to El Niño-Southern Oscillation (ENSO) whose variability strongly impacts the global climate. The SST and salinity proxy records are reconstructed via coral Sr/Ca and the oxygen isotopic composition of seawater (δ18Osw), respectively. On interannual (2-7yr) timescales, the SST proxy record tracks both eastern- and central-Pacific flavors of ENSO variability (R=0.65 and R=0.67, respectively). Interannual-scale salinity variability in our coral record highlights profound differences in precipitation and ocean advections during the two flavors of ENSO. On decadal (8yr-lowpassed) timescales, the central tropical Pacific SST and salinity proxy records are controlled by different sets of dynamics linked to the leading climate modes of North Pacific climate variability. Decadal-scale central tropical Pacific SST is highly correlated to the recently discovered North Pacific Gyre Oscillation (NPGO; R=-0.85), reflecting strong dynamical links between the central Pacific warming mode and extratropical decadal climate variability. Whereas decadal-scale salinity variations in the central tropical Pacific are significantly correlated with the Pacific Decadal Oscillation (PDO; R=0.54), providing a better understanding on low-frequency salinity variability in the region. Having characterized natural climate variability in this region, the coral record shows a +0.5°C warming trend throughout the last century

  12. Climate impacts on soil carbon processes along an elevation gradient in the tropical Luquillo Experimental Forest

    Treesearch

    Dingfang Chen; Mei Yu; Grizelle González; Xiaoming Zou; Qiong Gao

    2017-01-01

    Tropical forests play an important role in regulating the global climate and the carbon cycle. With the changing temperature and moisture along the elevation gradient, the Luquillo Experimental Forest in Northeastern Puerto Rico provides a natural approach to understand tropical forest ecosystems under climate change. In this study, we conducted a soil translocation...

  13. Climate Change and the Neglected Tropical Diseases.

    PubMed

    Booth, Mark

    2018-01-01

    Climate change is expected to impact across every domain of society, including health. The majority of the world's population is susceptible to pathological, infectious disease whose life cycles are sensitive to environmental factors across different physical phases including air, water and soil. Nearly all so-called neglected tropical diseases (NTDs) fall into this category, meaning that future geographic patterns of transmission of dozens of infections are likely to be affected by climate change over the short (seasonal), medium (annual) and long (decadal) term. This review offers an introduction into the terms and processes deployed in modelling climate change and reviews the state of the art in terms of research into how climate change may affect future transmission of NTDs. The 34 infections included in this chapter are drawn from the WHO NTD list and the WHO blueprint list of priority diseases. For the majority of infections, some evidence is available of which environmental factors contribute to the population biology of parasites, vectors and zoonotic hosts. There is a general paucity of published research on the potential effects of decadal climate change, with some exceptions, mainly in vector-borne diseases. © 2018 Elsevier Ltd All rights reserved.

  14. Integrated regional changes in arctic climate feedbacks: Implications for the global climate system

    USGS Publications Warehouse

    McGuire, A.D.; Chapin, F. S.; Walsh, J.E.; Wirth, C.; ,

    2006-01-01

    The Arctic is a key part of the global climate system because the net positive energy input to the tropics must ultimately be resolved through substantial energy losses in high-latitude regions. The Arctic influences the global climate system through both positive and negative feedbacks that involve physical, ecological, and human systems of the Arctic. The balance of evidence suggests that positive feedbacks to global warming will likely dominate in the Arctic during the next 50 to 100 years. However, the negative feedbacks associated with changing the freshwater balance of the Arctic Ocean might abruptly launch the planet into another glacial period on longer timescales. In light of uncertainties and the vulnerabilities of the climate system to responses in the Arctic, it is important that we improve our understanding of how integrated regional changes in the Arctic will likely influence the evolution of the global climate system. Copyright ?? 2006 by Annual Reviews. All rights reserved.

  15. The abrupt onset of the modern South Asian Monsoon winds.

    PubMed

    Betzler, Christian; Eberli, Gregor P; Kroon, Dick; Wright, James D; Swart, Peter K; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A; Alonso-García, Montserrat; Bialik, Or M; Blättler, Clara L; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M; Pratiwi, Santi D; Reijmer, John J G; Reolid, Jesús; Slagle, Angela L; Sloss, Craig R; Su, Xiang; Yao, Zhengquan; Young, Jeremy R

    2016-07-20

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  16. Role of internal variability in recent decadal to multidecadal tropical Pacific climate changes

    NASA Astrophysics Data System (ADS)

    Bordbar, Mohammad Hadi; Martin, Thomas; Latif, Mojib; Park, Wonsun

    2017-05-01

    While the Earth's surface has considerably warmed over the past two decades, the tropical Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds, the surface component of the Pacific Walker Circulation (PWC). Previous studies show that this decadal trend in the trade winds is generally beyond the range of decadal trends simulated by climate models when forced by historical radiative forcing. There is still a debate on the origin of and the potential role that internal variability may have played in the recent decadal surface wind trend. Using a number of long control (unforced) integrations of global climate models and several observational data sets, we address the question as to whether the recent decadal to multidecadal trends are robustly classified as an unusual event or the persistent response to external forcing. The observed trends in the tropical Pacific surface climate are still within the range of the long-term internal variability spanned by the models but represent an extreme realization of this variability. Thus, the recent observed decadal trends in the tropical Pacific, though highly unusual, could be of natural origin. We note that the long-term trends in the selected PWC indices exhibit a large observational uncertainty, even hindering definitive statements about the sign of the trends.Plain Language SummaryWhile the Earth's surface has considerably warmed over the past two decades, the <span class="hlt">tropical</span> Pacific has featured a cooling of sea surface temperatures in its eastern and central parts, which went along with an unprecedented strengthening of the equatorial trade winds. Here we show that <span class="hlt">climate</span> models simulate a high level of internal variability, so that the recent changes in the <span class="hlt">tropical</span> Pacific could still be due to natural processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950046311&hterms=climate+change+rainfall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dclimate%2Bchange%2Brainfall','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950046311&hterms=climate+change+rainfall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dclimate%2Bchange%2Brainfall"><span>The influence of <span class="hlt">tropical</span> heating displacements on the extratropical <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hou, Arthur Y.</p> <p>1993-01-01</p> <p>The hypothesis is advanced that a latitudinal shift in the <span class="hlt">tropical</span> convective heating pattern can significantly alter temperatures in the extratropics. Results of a simplified general circulation model (GCM) show that the shift of a prescribed <span class="hlt">tropical</span> heating toward the summer pole, on time scales longer than a few weeks, leads to a more intense cross-equatorial 'winter' Hadley circulation, enhanced upper-level <span class="hlt">tropical</span> easterlies, and a slightly stronger subtropical winter jet, accompanied by warming at the winter middle and high latitudes as a result of increased dynamical heating. The indications are that there is a robust connection between the net dynamic heating in the extratropics and the implied changes in the subtropical wind shear resulting from adjustments in the Hadley circulation associated with convective heating displacements in the <span class="hlt">tropics</span>. The implications are that (1) the low-frequency temporal variability in the Hadley circulation may play an important role in modulating wave transport in the winter extratropics, (2) the global <span class="hlt">climate</span> may be sensitive to those processes that control deep cumulus convection in the <span class="hlt">tropics</span>, and (3) systematic temperature biases in GCMs may be reduced by improving the <span class="hlt">tropical</span> rainfall simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2544558','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2544558"><span>Middle East coastal ecosystem response to middle-to-late Holocene <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kaniewski, D.; Paulissen, E.; Van Campo, E.; Al-Maqdissi, M.; Bretschneider, J.; Van Lerberghe, K.</p> <p>2008-01-01</p> <p>The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to <span class="hlt">climatic</span> changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes (ACCs), two large-scale shifts to a more arid <span class="hlt">climate</span> have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100–800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome ca. 2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at ca. 1190 to 1185 B.C. PMID:18772385</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......347M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......347M"><span>Investigations of the <span class="hlt">Climate</span> System Response to <span class="hlt">Climate</span> Engineering in a Hierarchy of Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McCusker, Kelly E.</p> <p></p> <p>Global warming due to anthropogenic emissions of greenhouse gases is causing negative impacts on diverse ecological and human systems around the globe, and these impacts are projected to worsen as <span class="hlt">climate</span> continues to warm. In the absence of meaningful greenhouse gas emissions reductions, new strategies have been proposed to engineer the <span class="hlt">climate</span>, with the aim of preventing further warming and avoiding associated <span class="hlt">climate</span> impacts. We investigate one such strategy here, falling under the umbrella of `solar radiation management', in which sulfate aerosols are injected into the stratosphere. We use a global <span class="hlt">climate</span> model with a coupled mixed-layer depth ocean and with a fully-coupled ocean general circulation model to simulate the stabilization of <span class="hlt">climate</span> by balancing increasing carbon dioxide with increasing stratospheric sulfate concentrations. We evaluate whether or not severe <span class="hlt">climate</span> impacts, such as melting Arctic sea ice, <span class="hlt">tropical</span> crop failure, or destabilization of the West Antarctic ice sheet, could be avoided. We find that while <span class="hlt">tropical</span> <span class="hlt">climate</span> emergencies might be avoided by use of stratospheric aerosol injections, avoiding polar emergencies cannot be guaranteed due to large residual <span class="hlt">climate</span> changes in those regions, which are in part due to residual atmospheric circulation anomalies. We also find that the inclusion of a fully-coupled ocean is important for determining the regional <span class="hlt">climate</span> response because of its dynamical feedbacks. The efficacy of stratospheric sulfate aerosol injections, and solar radiation management more generally, depends on its ability to be maintained indefinitely, without interruption from a variety of possible sources, such as technological failure, a breakdown in global cooperation, lack of funding, or negative unintended consequences. We next consider the scenario in which stratospheric sulfate injections are <span class="hlt">abruptly</span> terminated after a multi- decadal period of implementation while greenhouse gas emissions have continued unabated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4811574','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4811574"><span>Disaggregating <span class="hlt">Tropical</span> Disease Prevalence by <span class="hlt">Climatic</span> and Vegetative Zones within <span class="hlt">Tropical</span> West Africa</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Beckley, Carl S.; Shaban, Salisu; Palmer, Guy H.; Hudak, Andrew T.; Noh, Susan M.; Futse, James E.</p> <p>2016-01-01</p> <p><span class="hlt">Tropical</span> infectious disease prevalence is dependent on many socio-cultural determinants. However, rainfall and temperature frequently underlie overall prevalence, particularly for vector-borne diseases. As a result these diseases have increased prevalence in <span class="hlt">tropical</span> as compared to temperate regions. Specific to <span class="hlt">tropical</span> Africa, the tendency to incorrectly infer that <span class="hlt">tropical</span> diseases are uniformly prevalent has been partially overcome with solid epidemiologic data. This finer resolution data is important in multiple contexts, including understanding risk, predictive value in disease diagnosis, and population immunity. We hypothesized that within the context of a <span class="hlt">tropical</span> <span class="hlt">climate</span>, vector-borne pathogen prevalence would significantly differ according to zonal differences in rainfall, temperature, relative humidity and vegetation condition. We then determined if these environmental data were predictive of pathogen prevalence. First we determined the prevalence of three major pathogens of cattle, Anaplasma marginale, Babesia bigemina and Theileria spp, in the three vegetation zones where cattle are predominantly raised in Ghana: Guinea savannah, semi-deciduous forest, and coastal savannah. The prevalence of A. marginale was 63%, 26% for Theileria spp and 2% for B. bigemina. A. marginale and Theileria spp. were significantly more prevalent in the coastal savannah as compared to either the Guinea savanna or the semi-deciduous forest, supporting acceptance of the first hypothesis. To test the predictive power of environmental variables, the data over a three year period were considered in best subsets multiple linear regression models predicting prevalence of each pathogen. Corrected Akaike Information Criteria (AICc) were assigned to the alternative models to compare their utility. Competitive models for each response were averaged using AICc weights. Rainfall was most predictive of pathogen prevalence, and EVI also contributed to A. marginale and B. bigemina prevalence</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27022740','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27022740"><span>Disaggregating <span class="hlt">Tropical</span> Disease Prevalence by <span class="hlt">Climatic</span> and Vegetative Zones within <span class="hlt">Tropical</span> West Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Beckley, Carl S; Shaban, Salisu; Palmer, Guy H; Hudak, Andrew T; Noh, Susan M; Futse, James E</p> <p>2016-01-01</p> <p><span class="hlt">Tropical</span> infectious disease prevalence is dependent on many socio-cultural determinants. However, rainfall and temperature frequently underlie overall prevalence, particularly for vector-borne diseases. As a result these diseases have increased prevalence in <span class="hlt">tropical</span> as compared to temperate regions. Specific to <span class="hlt">tropical</span> Africa, the tendency to incorrectly infer that <span class="hlt">tropical</span> diseases are uniformly prevalent has been partially overcome with solid epidemiologic data. This finer resolution data is important in multiple contexts, including understanding risk, predictive value in disease diagnosis, and population immunity. We hypothesized that within the context of a <span class="hlt">tropical</span> <span class="hlt">climate</span>, vector-borne pathogen prevalence would significantly differ according to zonal differences in rainfall, temperature, relative humidity and vegetation condition. We then determined if these environmental data were predictive of pathogen prevalence. First we determined the prevalence of three major pathogens of cattle, Anaplasma marginale, Babesia bigemina and Theileria spp, in the three vegetation zones where cattle are predominantly raised in Ghana: Guinea savannah, semi-deciduous forest, and coastal savannah. The prevalence of A. marginale was 63%, 26% for Theileria spp and 2% for B. bigemina. A. marginale and Theileria spp. were significantly more prevalent in the coastal savannah as compared to either the Guinea savanna or the semi-deciduous forest, supporting acceptance of the first hypothesis. To test the predictive power of environmental variables, the data over a three year period were considered in best subsets multiple linear regression models predicting prevalence of each pathogen. Corrected Akaike Information Criteria (AICc) were assigned to the alternative models to compare their utility. Competitive models for each response were averaged using AICc weights. Rainfall was most predictive of pathogen prevalence, and EVI also contributed to A. marginale and B. bigemina prevalence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18.4657S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18.4657S"><span><span class="hlt">Tropical</span> convection regimes in <span class="hlt">climate</span> models: evaluation with satellite observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steiner, Andrea K.; Lackner, Bettina C.; Ringer, Mark A.</p> <p>2018-04-01</p> <p>High-quality observations are powerful tools for the evaluation of <span class="hlt">climate</span> models towards improvement and reduction of uncertainty. Particularly at low latitudes, the most uncertain aspect lies in the representation of moist convection and interaction with dynamics, where rising motion is tied to deep convection and sinking motion to dry regimes. Since humidity is closely coupled with temperature feedbacks in the <span class="hlt">tropical</span> troposphere, a proper representation of this region is essential. Here we demonstrate the evaluation of atmospheric <span class="hlt">climate</span> models with satellite-based observations from Global Positioning System (GPS) radio occultation (RO), which feature high vertical resolution and accuracy in the troposphere to lower stratosphere. We focus on the representation of the vertical atmospheric structure in <span class="hlt">tropical</span> convection regimes, defined by high updraft velocity over warm surfaces, and investigate atmospheric temperature and humidity profiles. Results reveal that some models do not fully capture convection regions, particularly over land, and only partly represent strong vertical wind classes. Models show large biases in <span class="hlt">tropical</span> mean temperature of more than 4 K in the tropopause region and the lower stratosphere. Reasonable agreement with observations is given in mean specific humidity in the lower to mid-troposphere. In moist convection regions, models tend to underestimate moisture by 10 to 40 % over oceans, whereas in dry downdraft regions they overestimate moisture by 100 %. Our findings provide evidence that RO observations are a unique source of information, with a range of further atmospheric variables to be exploited, for the evaluation and advancement of next-generation <span class="hlt">climate</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatCC...4..138J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatCC...4..138J"><span>Carbon stock corridors to mitigate <span class="hlt">climate</span> change and promote biodiversity in the <span class="hlt">tropics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jantz, Patrick; Goetz, Scott; Laporte, Nadine</p> <p>2014-02-01</p> <p>A key issue in global conservation is how biodiversity co-benefits can be incorporated into land use and <span class="hlt">climate</span> change mitigation activities, particularly those being negotiated under the United Nations to reduce emissions from <span class="hlt">tropical</span> deforestation and forest degradation. Protected areas have been the dominant strategy for <span class="hlt">tropical</span> forest conservation and they have increased substantially in recent decades. Avoiding deforestation by preserving carbon stored in vegetation between protected areas provides an opportunity to mitigate the effects of land use and <span class="hlt">climate</span> change on biodiversity by maintaining habitat connectivity across landscapes. Here we use a high-resolution data set of vegetation carbon stock to map corridors traversing areas of highest biomass between protected areas in the <span class="hlt">tropics</span>. The derived corridors contain 15% of the total unprotected aboveground carbon in the <span class="hlt">tropical</span> region. A large number of corridors have carbon densities that approach or exceed those of the protected areas they connect, suggesting these are suitable areas for achieving both habitat connectivity and <span class="hlt">climate</span> change mitigation benefits. To further illustrate how economic and biological information can be used for corridor prioritization on a regional scale, we conducted a multicriteria analysis of corridors in the Legal Amazon, identifying corridors with high carbon, high species richness and endemism, and low economic opportunity costs. We also assessed the vulnerability of corridors to future deforestation threat.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120008825','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120008825"><span>High Resolution Global <span class="hlt">Climate</span> Modeling with GEOS-5: Intense Precipitation, Convection and <span class="hlt">Tropical</span> Cyclones on Seasonal Time-Scales.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Putnam, WilliamM.</p> <p>2011-01-01</p> <p>In 2008 the World Modeling Summit for <span class="hlt">Climate</span> Prediction concluded that "<span class="hlt">climate</span> modeling will need-and is ready-to move to fundamentally new high-resolution approaches to capitalize on the seamlessness of the weather-<span class="hlt">climate</span> continuum." Following from this, experimentation with very high-resolution global <span class="hlt">climate</span> modeling has gained enhanced priority within many modeling groups and agencies. The NASA Goddard Earth Observing System model (GEOS-5) has been enhanced to provide a capability for the execution at the finest horizontal resolutions POS,SIOle with a global <span class="hlt">climate</span> model today. Using this high-resolution, non-hydrostatic version of GEOS-5, we have developed a unique capability to explore the intersection of weather and <span class="hlt">climate</span> within a seamless prediction system. Week-long weather experiments, to mUltiyear <span class="hlt">climate</span> simulations at global resolutions ranging from 3.5- to 14-km have demonstrated the predictability of extreme events including severe storms along frontal systems, extra-<span class="hlt">tropical</span> storms, and <span class="hlt">tropical</span> cyclones. The primary benefits of high resolution global models will likely be in the <span class="hlt">tropics</span>, with better predictions of the genesis stages of <span class="hlt">tropical</span> cyclones and of the internal structure of their mature stages. Using satellite data we assess the accuracy of GEOS-5 in representing extreme weather phenomena, and their interaction within the global <span class="hlt">climate</span> on seasonal time-scales. The impacts of convective parameterization and the frequency of coupling between the moist physics and dynamics are explored in terms of precipitation intensity and the representation of deep convection. We will also describe the seasonal variability of global <span class="hlt">tropical</span> cyclone activity within a global <span class="hlt">climate</span> model capable of representing the most intense category 5 hurricanes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29194879','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29194879"><span>Environmental heterogeneity and biotic interactions mediate <span class="hlt">climate</span> impacts on <span class="hlt">tropical</span> forest regeneration.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Uriarte, María; Muscarella, Robert; Zimmerman, Jess K</p> <p>2018-02-01</p> <p>Predicting the fate of <span class="hlt">tropical</span> forests under a changing <span class="hlt">climate</span> requires understanding species responses to <span class="hlt">climatic</span> variability and extremes. Seedlings may be particularly vulnerable to <span class="hlt">climatic</span> stress given low stored resources and undeveloped roots; they also portend the potential effects of <span class="hlt">climate</span> change on future forest composition. Here we use data for ca. 50,000 <span class="hlt">tropical</span> seedlings representing 25 woody species to assess (i) the effects of interannual variation in rainfall and solar radiation between 2007 and 2016 on seedling survival over 9 years in a subtropical forest; and (ii) how spatial heterogeneity in three environmental factors-soil moisture, understory light, and conspecific neighborhood density-modulate these responses. Community-wide seedling survival was not sensitive to interannual rainfall variability but interspecific variation in these responses was large, overwhelming the average community response. In contrast, community-wide responses to solar radiation were predominantly positive. Spatial heterogeneity in soil moisture and conspecific density were the predominant and most consistent drivers of seedling survival, with the majority of species exhibiting greater survival at low conspecific densities and positive or nonlinear responses to soil moisture. This environmental heterogeneity modulated impacts of rainfall and solar radiation. Negative conspecific effects were amplified during rainy years and at dry sites, whereas the positive effects of radiation on survival were more pronounced for seedlings existing at high understory light levels. These results demonstrate that environmental heterogeneity is not only the main driver of seedling survival in this forest but also plays a central role in buffering or exacerbating impacts of <span class="hlt">climate</span> fluctuations on forest regeneration. Since seedlings represent a key bottleneck in the demographic cycle of trees, efforts to predict the long-term effects of a changing <span class="hlt">climate</span> on <span class="hlt">tropical</span> forests must</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711040E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711040E"><span>Revisiting Lake Hämelsee: reconstructing <span class="hlt">abrupt</span> Lateglacial <span class="hlt">climate</span> transitions using state- of-the-art palaeoclimatological proxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Engels, Stefan; Hoek, Wim; Lane, Christine; Sachse, Dirk; Wagner-Cremer, Friederike</p> <p>2015-04-01</p> <p>Lake Hämelsee (Germany) is one of the northernmost sites in NW Europe that has varved sediments throughout large parts of its Lateglacial and Early Holocene sediment sequence. Previous research on this site has shown its potential, in terms of chronological resolution and palaeoecological reconstructions, for reconstructing the <span class="hlt">abrupt</span> transitions into and out of the Younger Dryas, the last cold period of the last glacial. The site was revisited during a 1-week summer school for Early Stage Researchers (2013), within the INTIMATE Example training and research project, supported by EU Cost Action ES0907. Two overlapping sediment sequences were retrieved from the centre of the lake during the summer school. These sediments have since formed the basis for follow-up research projects, which have sparked the collaboration of around 30 researchers in 12 laboratories across Europe. A chronological framework for the core has been composed from a combination of varve counting, radiocarbon dating and tephrochronology. Tephrostratigraphic correlations allow direct correlation and precise comparison of the record to marine and ice core records from the North Atlantic region, and other terrestrial European archives. Furthermore, the core is has been subjected to multiple sedimentological (e.g. XRF, loss-on-ignition), geochemical (e.g. lipid biomarkers, GDGTs) and palaeoecological (e.g. pollen, chironomids) proxy-based reconstructions of past environmental and <span class="hlt">climatic</span> conditions. The results provide important insights into the nature of the <span class="hlt">abrupt</span> <span class="hlt">climate</span> transitions of the Lateglacial and Early Holocene, both locally and on a continental scale. The INTIMATE Example participants: Illaria Baneschi, Achim Brauer, Christopher Bronk Ramsey, Renee de Bruijn, Siwan Davies, Aritina Haliuc, Katalin Hubay, Gwydion Jones, Meike Müller, Johanna Menges, Josef Merkt, Tom Peters, Francien Peterse, Anneke ter Schure, Kathrin Schuetrumpf, Richard Staff, Falko Turner, Valerie van den Bos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911207W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911207W"><span>Comparison of <span class="hlt">tropical</span> cyclogenesis processes in <span class="hlt">climate</span> model and cloud-resolving model simulations using moist static energy budget analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wing, Allison; Camargo, Suzana; Sobel, Adam; Kim, Daehyun; Murakami, Hiroyuki; Reed, Kevin; Vecchi, Gabriel; Wehner, Michael; Zarzycki, Colin; Zhao, Ming</p> <p>2017-04-01</p> <p>In recent years, <span class="hlt">climate</span> models have improved such that high-resolution simulations are able to reproduce the climatology of <span class="hlt">tropical</span> cyclone activity with some fidelity and show some skill in seasonal forecasting. However biases remain in many models, motivating a better understanding of what factors control the representation of <span class="hlt">tropical</span> cyclone activity in <span class="hlt">climate</span> models. We explore the <span class="hlt">tropical</span> cyclogenesis processes in five high-resolution <span class="hlt">climate</span> models, including both coupled and uncoupled configurations. Our analysis framework focuses on how convection, moisture, clouds and related processes are coupled and employs budgets of column moist static energy and the spatial variance of column moist static energy. The latter was originally developed to study the mechanisms of <span class="hlt">tropical</span> convective organization in idealized cloud-resolving models, and allows us to quantify the different feedback processes responsible for the amplification of moist static energy anomalies associated with the organization of convection and cyclogenesis. We track the formation and evolution of <span class="hlt">tropical</span> cyclones in the <span class="hlt">climate</span> model simulations and apply our analysis both along the individual tracks and composited over many <span class="hlt">tropical</span> cyclones. We then compare the genesis processes; in particular, the role of cloud-radiation interactions, to those of spontaneous <span class="hlt">tropical</span> cyclogenesis in idealized cloud-resolving model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMPP43A1210K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMPP43A1210K"><span>Holocene East Asian Monsoon Variability: Links to Solar and <span class="hlt">Tropical</span> Pacific Forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kandasamy, S.; Chen, C. A.; Lou, J.</p> <p>2006-12-01</p> <p>Sedimentary geochemical records from subalpine Retreat Lake, subtropical Taiwan, document the unstable East Asian Monsoon (EAM) <span class="hlt">climate</span> for the last ~10250 calendar years before the present (cal yr B.P.). The proxy records demonstrate cool, glacial conditions with weak EAM between ~10250 and 8640 cal yr B.P., the strongest EAM during the "Holocene optimum" (8640-4500 cal yr B.P.) with an <span class="hlt">abrupt</span>, decadal onset of postglacial EAM (8640-8600 cal yr B.P.), and relatively dry conditions since 4500 cal yr B.P. Although after 8600 cal yr B.P., EAM strength reduces gradually in response to the Northern Hemisphere summer insolation, heat and moisture transport and the development of late Holocene El-Niño-Southern Oscillation in the <span class="hlt">tropical</span> Pacific appear to corroborate the periods of <span class="hlt">abrupt</span> monsoon changes. Our proxy records reveal several weak monsoon intervals that correlate to low sea surface temperatures in the western <span class="hlt">tropical</span> Pacific and cold events in the North Atlantic, suggesting a mechanistic link. Among those, four weak EAM events at 8170, 5400, 4500-2100 and 2000-1600 cal yr B.P. are in phase with the timings of low concentrations of atmospheric methane and periods of reduced North Atlantic Deep Water production as well as the `8.2 ka cold spell' and widespread event of low-latitude cultural collapse. Our EAM records exhibit strong correlations with high- and low-latitude <span class="hlt">climate</span> and monsoon records; thus, provide robust evidences that the centennial-millennial scale monsoon variability during the Holocene are globally-mediated via sun- ocean-monsoon-North Atlantic linkages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26739003','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26739003"><span>Life in the clouds: are <span class="hlt">tropical</span> montane cloud forests responding to changes in <span class="hlt">climate</span>?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hu, Jia; Riveros-Iregui, Diego A</p> <p>2016-04-01</p> <p>The humid <span class="hlt">tropics</span> represent only one example of the many places worldwide where anthropogenic disturbance and <span class="hlt">climate</span> change are quickly affecting the feedbacks between water and trees. In this article, we address the need for a more long-term perspective on the effects of <span class="hlt">climate</span> change on <span class="hlt">tropical</span> montane cloud forests (TMCF) in order to fully assess the combined vulnerability and long-term response of <span class="hlt">tropical</span> trees to changes in precipitation regimes, including cloud immersion. We first review the ecophysiological benefits that cloud water interception offers to trees in TMCF and then examine current climatological evidence that suggests changes in cloud base height and impending changes in cloud immersion for TMCF. Finally, we propose an experimental approach to examine the long-term dynamics of <span class="hlt">tropical</span> trees in TMCF in response to environmental conditions on decade-to-century time scales. This information is important to assess the vulnerability and long-term response of TMCF to changes in cloud cover and fog frequency and duration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AREPS..46..549M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AREPS..46..549M"><span>Responses of the <span class="hlt">Tropical</span> Atmospheric Circulation to <span class="hlt">Climate</span> Change and Connection to the Hydrological Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Jian; Chadwick, Robin; Seo, Kyong-Hwan; Dong, Changming; Huang, Gang; Foltz, Gregory R.; Jiang, Jonathan H.</p> <p>2018-05-01</p> <p>This review describes the <span class="hlt">climate</span> change–induced responses of the <span class="hlt">tropical</span> atmospheric circulation and their impacts on the hydrological cycle. We depict the theoretically predicted changes and diagnose physical mechanisms for observational and model-projected trends in large-scale and regional <span class="hlt">climate</span>. The <span class="hlt">tropical</span> circulation slows down with moisture and stratification changes, connecting to a poleward expansion of the Hadley cells and a shift of the intertropical convergence zone. Redistributions of regional precipitation consist of thermodynamic and dynamical components, including a strong offset between moisture increase and circulation weakening throughout the <span class="hlt">tropics</span>. This allows other dynamical processes to dominate local circulation changes, such as a surface warming pattern effect over oceans and multiple mechanisms over land. To improve reliability in <span class="hlt">climate</span> projections, more fundamental understandings of pattern formation, circulation change, and the balance of various processes redistributing land rainfall are suggested to be important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4470684','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4470684"><span>Independent Demographic Responses to <span class="hlt">Climate</span> Change among Temperate and <span class="hlt">Tropical</span> Milksnakes (Colubridae: Genus Lampropeltis)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ruane, Sara; Torres-Carvajal, Omar; Burbrink, Frank T.</p> <p>2015-01-01</p> <p>The effects of Late Quaternary <span class="hlt">climate</span> change have been examined for many temperate New World taxa, but the impact of Pleistocene glacial cycles on Neotropical taxa is less well understood, specifically with respect to changes in population demography. Here, we examine historical demographic trends for six species of milksnake with representatives in both the temperate and <span class="hlt">tropical</span> Americas to determine if species share responses to <span class="hlt">climate</span> change as a taxon or by area (i.e., temperate versus <span class="hlt">tropical</span> environments). Using a multilocus dataset, we test for the demographic signature of population expansion and decline using non-genealogical summary statistics, as well as coalescent-based methods. In addition, we determine whether range sizes are correlated with effective population sizes for milksnakes. Results indicate that there are no identifiable trends with respect to demographic response based on location, and that species responded to changing <span class="hlt">climates</span> independently, with <span class="hlt">tropical</span> taxa showing greater instability. There is also no correlation between range size and effective population size, with the largest population size belonging to the species with the smallest geographic distribution. Our study highlights the importance of not generalizing the demographic histories of taxa by region and further illustrates that the New World <span class="hlt">tropics</span> may not have been a stable refuge during the Pleistocene. PMID:26083467</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26083467','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26083467"><span>Independent Demographic Responses to <span class="hlt">Climate</span> Change among Temperate and <span class="hlt">Tropical</span> Milksnakes (Colubridae: Genus Lampropeltis).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruane, Sara; Torres-Carvajal, Omar; Burbrink, Frank T</p> <p>2015-01-01</p> <p>The effects of Late Quaternary <span class="hlt">climate</span> change have been examined for many temperate New World taxa, but the impact of Pleistocene glacial cycles on Neotropical taxa is less well understood, specifically with respect to changes in population demography. Here, we examine historical demographic trends for six species of milksnake with representatives in both the temperate and <span class="hlt">tropical</span> Americas to determine if species share responses to <span class="hlt">climate</span> change as a taxon or by area (i.e., temperate versus <span class="hlt">tropical</span> environments). Using a multilocus dataset, we test for the demographic signature of population expansion and decline using non-genealogical summary statistics, as well as coalescent-based methods. In addition, we determine whether range sizes are correlated with effective population sizes for milksnakes. Results indicate that there are no identifiable trends with respect to demographic response based on location, and that species responded to changing <span class="hlt">climates</span> independently, with <span class="hlt">tropical</span> taxa showing greater instability. There is also no correlation between range size and effective population size, with the largest population size belonging to the species with the smallest geographic distribution. Our study highlights the importance of not generalizing the demographic histories of taxa by region and further illustrates that the New World <span class="hlt">tropics</span> may not have been a stable refuge during the Pleistocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C53A0830M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C53A0830M"><span>Flowline Modeling of the Quelccaya Icecap to Constrain <span class="hlt">Tropical</span> <span class="hlt">Climate</span> Fluctuations During the Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malone, A.; Pierrehumbert, R.; Insel, N.; Lowell, T. V.; Kelly, M. A.</p> <p>2012-12-01</p> <p>The response of the <span class="hlt">tropics</span> to <span class="hlt">climate</span> forcing mechanisms is poorly understood, and there is limited data regarding past <span class="hlt">tropical</span> <span class="hlt">climate</span> fluctuations. Past <span class="hlt">climate</span> fluctuations often leave a detectable record of glacial response in the location of moraines. Computer reconstructions of glacial length variations can thus help constrain past <span class="hlt">climate</span> fluctuations. Chronology and position data for Holocene moraines are available for the Quelccaya Ice Cap in the Peruvian Andes. The Quelccaya Ice Cap is the equatorial region's largest glaciated area, and given its size and the available data, it is an ideal location at which to use a computer glacier model to reconstruct past glacial extents and constrain past <span class="hlt">tropical</span> <span class="hlt">climate</span> fluctuations. We can reproduce the current length and shape of the glacier in the Huancane Valley of the Quelccaya Ice Cap using a 1-D mountain glacier flowline model with an orographic precipitation scheme, an energy balance model for the ablation scheme, and reasonable modern <span class="hlt">climate</span> conditions. We conduct two experiments. First, we determine the amount of cooling necessary to reproduce the observed Holocene moraine locations by holding the precipitation profile constant and varying the mean sea surface temperature (SST) values. Second, we determine the amount of precipitation increase necessary to reproduce the observed moraine locations by holding the mean SST value constant and varying the maximum precipitation values. We find that the glacier's length is highly sensitive to changes in temperature while only weakly sensitive to changes in precipitation. In the constant precipitation experiment, a decrease in the mean SST of only 0.35 °C can reproduce the nearest Holocene moraine downslope from the current glacier terminus and a decrease in the mean SST of only 1.43 °C can reproduce the furthest Holocene moraine downslope from the current terminus. In the experiment with constant SST, the necessary increase in maximum precipitation is much</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.438..122H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.438..122H"><span>Deglacial diatom production in the <span class="hlt">tropical</span> North Atlantic driven by enhanced silicic acid supply</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hendry, Katharine R.; Gong, Xun; Knorr, Gregor; Pike, Jennifer; Hall, Ian R.</p> <p>2016-03-01</p> <p>Major shifts in ocean circulation are thought to be responsible for <span class="hlt">abrupt</span> changes in temperature and atmospheric CO2 during the last deglaciation, linked to variability in meridional heat transport and deep ocean carbon storage. There is also widespread evidence for shifts in biological production during these times of deglacial CO2 rise, including enhanced diatom production in regions such as the <span class="hlt">tropical</span> Atlantic. However, it remains unclear as to whether this diatom production was driven by enhanced wind-driven upwelling or density-driven vertical mixing, or by elevated thermocline concentrations of silicic acid supplied to the surface at a constant rate. Here, we demonstrate that silicic acid supply at depth in the NE Atlantic was enhanced during the <span class="hlt">abrupt</span> <span class="hlt">climate</span> events of the deglaciation. We use marine sediment archives to show that an increase in diatom production during <span class="hlt">abrupt</span> <span class="hlt">climate</span> shifts could only occur in regions of the NE Atlantic where the deep supply of silicic acid could reach the surface. The associated changes are indicative of enhanced regional wind-driven upwelling and/or weakened stratification due to circulation changes during phases of weakened Atlantic meridional overturning. Globally near-synchronous pulses of diatom production and enhanced thermocline concentrations of silicic acid suggest that widespread deglacial surface-driven breakdown of stratification, linked to changes in atmospheric circulation, had major consequences for biological productivity and carbon cycling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B42A..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B42A..03W"><span><span class="hlt">Climatic</span> and biotic drivers of <span class="hlt">tropical</span> evergreen forest photosynthesis: integrating field, eddy flux, remote sensing and modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, J.; Serbin, S.; Xu, X.; Guan, K.; Albert, L.; Hayek, M.; Restrepo-Coupe, N.; Lopes, A. P.; Wiedemann, K. T.; Christoffersen, B. O.; Meng, R.; De Araujo, A. C.; Oliveira Junior, R. C.; Camargo, P. B. D.; Silva, R. D.; Nelson, B. W.; Huete, A. R.; Rogers, A.; Saleska, S. R.</p> <p>2016-12-01</p> <p><span class="hlt">Tropical</span> evergreen forest photosynthetic metabolism is an important driver of large-scale carbon, water, and energy cycles, generating various <span class="hlt">climate</span> feedbacks. However, considerable uncertainties remain regarding how best to represent evergreen forest photosynthesis in current terrestrial biosphere models (TBMs), especially its sensitivity to <span class="hlt">climatic</span> vs. biotic variation. Here, we develop a new approach to partition <span class="hlt">climatic</span> and biotic controls on <span class="hlt">tropical</span> forest photosynthesis from hourly to inter-annual timescales. Our results show that <span class="hlt">climatic</span> factors dominate photosynthesis dynamics at shorter-time scale (i.e. hourly), while biotic factors dominate longer-timescale (i.e. monthly and longer) photosynthetic dynamics. Focusing on seasonal timescales, we combine camera and ecosystem carbon flux observations of forests across a rainfall gradient in Amazonia to show that high dry season leaf turnover shifts canopy composition towards younger more efficient leaves. This seasonal variation in leaf quality (per-area leaf photosynthetic capacity) thus can explain the high photosynthetic seasonality observed in the <span class="hlt">tropics</span>. Finally, we evaluated the performance of models with different phenological schemes (i.e. leaf quantity versus leaf quality; with and without leaf phenological variation alone the vertical canopy profile). We found that models which represented the phenology of leaf quality and its within-canopy variation performed best in simulating photosynthetic seasonality in <span class="hlt">tropical</span> evergreen forests. This work highlights the importance of incorporating improved understanding of <span class="hlt">climatic</span> and biotic controls in next generation TBMs to project future carbon and water cycles in the <span class="hlt">tropics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Nonli..26R...1K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Nonli..26R...1K"><span><span class="hlt">Climate</span> science in the <span class="hlt">tropics</span>: waves, vortices and PDEs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khouider, Boualem; Majda, Andrew J.; Stechmann, Samuel N.</p> <p>2013-01-01</p> <p>Clouds in the <span class="hlt">tropics</span> can organize the circulation on planetary scales and profoundly impact long range seasonal forecasting and <span class="hlt">climate</span> on the entire globe, yet contemporary operational computer models are often deficient in representing these phenomena. On the other hand, contemporary observations reveal remarkably complex coherent waves and vortices in the <span class="hlt">tropics</span> interacting across a bewildering range of scales from kilometers to ten thousand kilometers. This paper reviews the interdisciplinary contributions over the last decade through the modus operandi of applied mathematics to these important scientific problems. Novel physical phenomena, new multiscale equations, novel PDEs, and numerical algorithms are presented here with the goal of attracting mathematicians and physicists to this exciting research area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23558172','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23558172"><span>Annually resolved ice core records of <span class="hlt">tropical</span> <span class="hlt">climate</span> variability over the past ~1800 years.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N</p> <p>2013-05-24</p> <p>Ice cores from low latitudes can provide a wealth of unique information about past <span class="hlt">climate</span> in the <span class="hlt">tropics</span>, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of <span class="hlt">climate</span> variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the <span class="hlt">tropical</span> eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the <span class="hlt">tropical</span> Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53D2289Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53D2289Y"><span>North <span class="hlt">Tropical</span> Atlantic <span class="hlt">Climate</span> Variability and Model Biases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Y.</p> <p>2017-12-01</p> <p>Remote forcing from El Niño-Southern Oscillation (ENSO) and local ocean-atmosphere feedback are important for <span class="hlt">climate</span> variability over the North <span class="hlt">Tropical</span> Atlantic. These two factors are extracted by the ensemble mean and inter-member difference of a 10-member Pacific Ocean-Global Atmosphere (POGA) experiment, in which sea surface temperatures (SSTs) are restored to the observed anomalies over the <span class="hlt">tropical</span> Pacific but fully coupled to the atmosphere elsewhere. POGA reasonably captures main features of observed North <span class="hlt">Tropical</span> Atlantic variability. ENSO forced and local North <span class="hlt">Tropical</span> Atlantic modes (NTAMs) develop with wind-evaporation-SST feedback, explaining one third and two thirds of total variance respectively. Notable biases, however, exist. The seasonality of the simulated NTAM is delayed by one month, due to the late development of the North Atlantic Oscillation (NAO) in the model. A spurious band of enhanced sea surface temperature (SST) variance (SBEV) is identified over the northern equatorial Atlantic in POGA and 14 out of 23 CMIP5 models. The SBEV is especially pronounced in boreal spring and due to the combined effect of both anomalous atmospheric thermal forcing and oceanic vertical upwelling. While the <span class="hlt">tropical</span> North Atlantic variability is only weakly correlated with the Atlantic Zonal Mode (AZM) in observations, the SBEV in CMIP5 produces conditions that drive and intensify the AZM variability via triggering the Bjerknes feedback. This partially explains why AZM is strong in some CMIP5 models even though the equatorial cold tongue and easterly trades are biased low.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911341V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911341V"><span>Centennial-to-millennial scale <span class="hlt">climate</span> change during the last 100,000 years: a Southern Hemisphere perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van den Bos, Valerie; Rees, Andrew; Newnham, Rewi; Augustinus, Paul</p> <p>2017-04-01</p> <p>The response of past terrestrial ecosystems to <span class="hlt">abrupt</span> <span class="hlt">climate</span> change is central to the debate surrounding the consequences of future <span class="hlt">climate</span> change. Many centennial-to-millennial scale episodes of rapid change over the past 117,000 years have been reported, notably the Dansgaard-Oeschger events of Greenland and the North Atlantic and Antarctic Isotope Maxima. Best expressed in past <span class="hlt">climate</span> records from the polar and <span class="hlt">tropical</span> regions, the timing, amplitude and duration of these changes are variable on a global scale, and it is unclear how the events are generated and transmitted to cause such asynchronous patterns. The southern mid-latitudes form a poorly understood piece of the puzzle. Our Marsden-funded project aims to increase understanding of the New Zealand <span class="hlt">climate</span> system in relation to global patterns over the last 100 kyr by developing high-resolution <span class="hlt">climate</span> records from the lake sediments contained within Auckland's maars. These crater lakes are unique, because their sediments are laminated throughout and the sedimentation rate is very high. Additionally, the numerous (>50) volcanic ash layers contained within the sediments act as anchor points in our chronologies. We have adopted a multiproxy approach that combines data from biotic, molecular biomarker isotope and geochemical analyses. The remit of my doctorate is to produce two independent, but complementary, temperature reconstructions from chironomid remains (mean summer temperatures) and pollen (mean annual temperatures) from Lake Pupuke sediments. This approach will eventually help us to address whether <span class="hlt">abrupt</span> <span class="hlt">climate</span> change events or changes in seasonality influenced <span class="hlt">climate</span> and biota over the past 100,000 years in northern New Zealand, and whether these changes were driven by triggers from the North Atlantic, Antarctica or the <span class="hlt">tropics</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25165769','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25165769"><span>From global change to a butterfly flapping: biophysics and behaviour affect <span class="hlt">tropical</span> <span class="hlt">climate</span> change impacts.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonebrake, Timothy C; Boggs, Carol L; Stamberger, Jeannie A; Deutsch, Curtis A; Ehrlich, Paul R</p> <p>2014-10-22</p> <p>Difficulty in characterizing the relationship between <span class="hlt">climatic</span> variability and <span class="hlt">climate</span> change vulnerability arises when we consider the multiple scales at which this variation occurs, be it temporal (from minute to annual) or spatial (from centimetres to kilometres). We studied populations of a single widely distributed butterfly species, Chlosyne lacinia, to examine the physiological, morphological, thermoregulatory and biophysical underpinnings of adaptation to <span class="hlt">tropical</span> and temperate <span class="hlt">climates</span>. Microclimatic and morphological data along with a biophysical model documented the importance of solar radiation in predicting butterfly body temperature. We also integrated the biophysics with a physiologically based insect fitness model to quantify the influence of solar radiation, morphology and behaviour on warming impact projections. While warming is projected to have some detrimental impacts on <span class="hlt">tropical</span> ectotherms, fitness impacts in this study are not as negative as models that assume body and air temperature equivalence would suggest. We additionally show that behavioural thermoregulation can diminish direct warming impacts, though indirect thermoregulatory consequences could further complicate predictions. With these results, at multiple spatial and temporal scales, we show the importance of biophysics and behaviour for studying biodiversity consequences of global <span class="hlt">climate</span> change, and stress that <span class="hlt">tropical</span> <span class="hlt">climate</span> change impacts are likely to be context-dependent. © 2014 The Author(s) Published by the Royal Society. All rights reserved.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4173678','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4173678"><span>From global change to a butterfly flapping: biophysics and behaviour affect <span class="hlt">tropical</span> <span class="hlt">climate</span> change impacts</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bonebrake, Timothy C.; Boggs, Carol L.; Stamberger, Jeannie A.; Deutsch, Curtis A.; Ehrlich, Paul R.</p> <p>2014-01-01</p> <p>Difficulty in characterizing the relationship between <span class="hlt">climatic</span> variability and <span class="hlt">climate</span> change vulnerability arises when we consider the multiple scales at which this variation occurs, be it temporal (from minute to annual) or spatial (from centimetres to kilometres). We studied populations of a single widely distributed butterfly species, Chlosyne lacinia, to examine the physiological, morphological, thermoregulatory and biophysical underpinnings of adaptation to <span class="hlt">tropical</span> and temperate <span class="hlt">climates</span>. Microclimatic and morphological data along with a biophysical model documented the importance of solar radiation in predicting butterfly body temperature. We also integrated the biophysics with a physiologically based insect fitness model to quantify the influence of solar radiation, morphology and behaviour on warming impact projections. While warming is projected to have some detrimental impacts on <span class="hlt">tropical</span> ectotherms, fitness impacts in this study are not as negative as models that assume body and air temperature equivalence would suggest. We additionally show that behavioural thermoregulation can diminish direct warming impacts, though indirect thermoregulatory consequences could further complicate predictions. With these results, at multiple spatial and temporal scales, we show the importance of biophysics and behaviour for studying biodiversity consequences of global <span class="hlt">climate</span> change, and stress that <span class="hlt">tropical</span> <span class="hlt">climate</span> change impacts are likely to be context-dependent. PMID:25165769</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JASS...34..207L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JASS...34..207L"><span><span class="hlt">Climate</span> Events and Cycles During the Last Glacial-Interglacial Transition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Eun Hee; Lee, Dae-Young; Park, Mi-Young</p> <p>2017-09-01</p> <p>During the last glacial-interglacial transition, there were multiple intense <span class="hlt">climatic</span> events such as the Bølling-Allerød warming and Younger Dryas cooling. These events show <span class="hlt">abrupt</span> and rapid <span class="hlt">climatic</span> changes. In this study, the <span class="hlt">climate</span> events and cycles during this interval are examined through wavelet analysis of Arctic and Antarctic ice-core 18O and <span class="hlt">tropical</span> marine 14C records. The results show that periods of 1383-1402, 1029-1043, 726-736, 441-497 and 202-247 years are dominant in the Arctic region, whereas periods of 1480, 765, 518, 311, and 207 years are prominent in the Antarctic TALDICE. In addition, cycles of 1019, 515, and 209 years are distinct in the <span class="hlt">tropical</span> region. Among these variations, the de Vries cycle of 202-209 years, correlated with variations in solar activity, was detected globally. In particular, this cycle shows a strong signal in the Antarctic between about 13,000 and 10,500 yr before present (BP). In contrast, the Eddy cycle of 1019-1043 years was prominent in Greenland and the <span class="hlt">tropical</span> region, but was not detected in the Antarctic TALDICE records. Instead, these records showed that the Heinrich cycle of 1480 year was very strong and significant throughout the last glacial-interglacial interval.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC23E0679J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC23E0679J"><span>Can Treeline Shift in <span class="hlt">Tropical</span> Africa be Used As Proxy to Study <span class="hlt">Climate</span> Change?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jacob, M.; Frankl, A.; De Ridder, M.; Guyassa, E.; Beeckman, H.; Nyssen, J.</p> <p>2014-12-01</p> <p>The important ecosystem services of the vulnerable high altitude forests of the <span class="hlt">tropical</span> African highlands are under increasing environmental and human pressure. The afro-alpine treeline forms an apparent and temperature-responsive vegetation boundary and is therefore potentially valuable as a proxy of <span class="hlt">climate</span> change in the <span class="hlt">tropics</span>. However, a review of the current literature about treeline dynamics in <span class="hlt">tropical</span> Africa indicates that <span class="hlt">climate</span> change did not cause rising treelines, due to high human pressure and growing human population densities. On average the treeline is depressed below its <span class="hlt">climatic</span> limit by 400 ± 300 meter, but regional differences are high and there are still many uncertainties. A multidisciplinary study of treeline dynamics is conducted in the north Ethiopian highlands. The Erica arborea L. treeline is studied over a century, using satellite imagery, aerial photographs, repeat photography and dendroclimatology. Repeat photography is proven a unique tool for the identification of treeline dynamics on the long-term. Results in the Simen Mts. indicate a treeline rise of more than 100 meters since the early 20th century. In contrast, historical satellite and aerial imagery indicate that there has been strong deforestation since the last 30 years and a significant (p<0.05) but small rise of the treeline elevation of 11 ± 4 vertical meters in Lib Amba Mt. Dendroclimatological results indicate a weak but significant (p<0.05) correlation between tree ring width and interannual precipitation patterns. However, since treelines in the African <span class="hlt">tropical</span> mountains are strongly disturbed by human and livestock pressure, they cannot directly be used as a proxy for <span class="hlt">climate</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24497954','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24497954"><span>Small changes in <span class="hlt">climate</span> can profoundly alter the dynamics and ecosystem services of <span class="hlt">tropical</span> crater lakes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saulnier-Talbot, Émilie; Gregory-Eaves, Irene; Simpson, Kyle G; Efitre, Jackson; Nowlan, Tobias E; Taranu, Zofia E; Chapman, Lauren J</p> <p>2014-01-01</p> <p>African <span class="hlt">tropical</span> lakes provide vital ecosystem services including food and water to some of the fastest growing human populations, yet they are among the most understudied ecosystems in the world. The consequences of <span class="hlt">climate</span> change and other stressors on the <span class="hlt">tropical</span> lakes of Africa have been informed by long-term analyses, but these studies have largely focused on the massive Great Rift Valley lakes. Our objective was to evaluate how recent <span class="hlt">climate</span> change has altered the functioning and services of smaller <span class="hlt">tropical</span> lakes, which are far more abundant on the landscape. Based on a paired analysis of 20 years of high-resolution water column data and a paleolimnological record from a small crater lake in western Uganda, we present evidence that even a modest warming of the air (∼0.9°C increase over 20 years) and changes in the timing and intensity of rainfall can have significant consequences on the dynamics of this common <span class="hlt">tropical</span> lake type. For example, we observed a significant nonlinear increase (R(2) adj  = 0.23, e.d.f. = 7, p<0.0001) in thermal stability over the past 20 years. This resulted in the expansion of anoxic waters and consequent deterioration of fish habitat and appears to have abated primary production; processes that may impair ecosystem services for a vulnerable human population. This study on a system representative of small <span class="hlt">tropical</span> crater lakes highlights the far-reaching effects of global <span class="hlt">climatic</span> change on <span class="hlt">tropical</span> waters. Increased research efforts into <span class="hlt">tropical</span> aquatic ecosystem health and the development of sound management practices are necessary in order to strengthen adaptive capabilities in <span class="hlt">tropical</span> regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP23D..07R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP23D..07R"><span>Central <span class="hlt">Tropical</span> Pacific Variability And ENSO Response To Changing <span class="hlt">Climate</span> Boundary Conditions: Evidence From Individual Line Island Foraminifera</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rustic, G. T.; Polissar, P. J.; Ravelo, A. C.; White, S. M.</p> <p>2017-12-01</p> <p>The El Niño Southern Oscillation (ENSO) plays a dominant role in Earth's <span class="hlt">climate</span> variability. Paleoceanographic evidence suggests that ENSO has changed in the past, and these changes have been linked to large-scale <span class="hlt">climatic</span> shifts. While a close relationship between ENSO evolution and <span class="hlt">climate</span> boundary conditions has been predicted, testing these predictions remains challenging. These <span class="hlt">climate</span> boundary conditions, including insolation, the mean surface temperature gradient of the <span class="hlt">tropical</span> Pacific, global ice volume, and <span class="hlt">tropical</span> thermocline depth, often co-vary and may work together to suppress or enhance the ocean-atmosphere feedbacks that drive ENSO variability. Furthermore, suitable paleo-archives spanning multiple <span class="hlt">climate</span> states are sparse. We have aimed to test ENSO response to changing <span class="hlt">climate</span> boundary conditions by generating new reconstructions of mixed-layer variability from sedimentary archives spanning the last three glacial-interglacial cycles from the Central <span class="hlt">Tropical</span> Pacific Line Islands, where El Niño is strongly expressed. We analyzed Mg/Ca ratios from individual foraminifera to reconstruct mixed-layer variability at discrete time intervals representing combinations of <span class="hlt">climatic</span> boundary conditions from the middle Holocene to Marine Isotope Stage (MIS) 8. We observe changes in the mixed-layer temperature variability during MIS 5 and during the previous interglacial (MIS 7) showing significant reductions in ENSO amplitude. Differences in variability during glacial and interglacial intervals are also observed. Additionally, we reconstructed mixed-layer and thermocline conditions using multi-species Mg/Ca and stable isotope measurements to more fully characterize the state of the Central <span class="hlt">Tropical</span> Pacific during these intervals. These reconstructions provide us with a unique view of Central <span class="hlt">Tropical</span> Pacific variability and water-column structure at discrete intervals under varying boundary <span class="hlt">climate</span> conditions with which to assess factors that shape ENSO</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MsT.........45S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MsT.........45S"><span>Assessing the influence of <span class="hlt">climate</span> change on flooding hazards following <span class="hlt">tropical</span> cyclone events in the Southeast United States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stone, Monica Helen</p> <p></p> <p>Recent <span class="hlt">tropical</span> cyclones, like Hurricane Katrina, have been some of the worst the United States has experienced. <span class="hlt">Tropical</span> cyclones are expected to intensify, bringing about 20% more precipitation, in the near future in response to global <span class="hlt">climate</span> warming. Further, global <span class="hlt">climate</span> warming may extend the hurricane season. This study focuses on four major river basins (Neches, Pearl, Mobile, and Roanoke) in the Southeast United States that are frequently impacted by <span class="hlt">tropical</span> cyclones. The Soil and Water Assessment Tool (SWAT) was used to model flow along these rivers from 1998-2014 with 20% more precipitation during <span class="hlt">tropical</span> cyclones. The results of this study show that an increase in <span class="hlt">tropical</span> cyclone precipitation due to future <span class="hlt">climate</span> change may increase peak flows at the mouths of these Southeast rivers by ˜7-18%. Most <span class="hlt">tropical</span> cyclones that impact these river basins occur during the low discharge season, and thus rarely produce flooding conditions at their mouths. An extension of the current hurricane season of June-November, due to global <span class="hlt">climate</span> warming, could encroach upon the wet season in these basins and lead to increased flooding. On average, this analysis shows that an extension of the hurricane season to May-December increased flooding susceptibility by 63% for the rivers analyzed in this study. That is, 4-6 more days per year likely would have been above bankfull discharge if an average <span class="hlt">tropical</span> cyclone had occurred any day (based on 1998-2014 data) in the months May-December than in the current hurricane season months of June-November. More research is needed on the mechanisms and processes involved in the water balance of the four rivers analyzed in this study, and others in the Southeast United States, and how this is likely to change in the near future with global <span class="hlt">climate</span> warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JAESc.155...58S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JAESc.155...58S"><span><span class="hlt">Abrupt</span> <span class="hlt">climatic</span> events recorded by the Ili loess during the last glaciation in Central Asia: Evidence from grain-size and minerals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Yougui; Zeng, Mengxiu; Chen, Xiuling; Li, Yue; Chang, Hong; An, Zhisheng; Guo, Xiaohua</p> <p>2018-04-01</p> <p>The loess record of Central Asia provides an important archive of regional <span class="hlt">climate</span> and environmental changes. In contrast to the widely investigated loess deposits in the Chinese Loess Plateau, Central Asian loess-paleosol sequences remain poorly understood. Here, we present an aeolian loess section in the southern Ili Basin. Based on granularity and mineralogical analyses, we reconstruct <span class="hlt">climatic</span> changes during the last glaciation. The results indicated that most of the <span class="hlt">abrupt</span> <span class="hlt">climatic</span> events (such as Dansgaard-Oeschger events and Heinrich events) were imprinted in this loess section, although their amplitudes and ages showed some differences. Compared with the millennial oscillations recoded in loess and stalagmites in East Asia, the arid Central Asia responded more sensitively to the warming events than to the cooling events. The shifting trajectory of westerlies across Central Asia played an important role in dust deposition during the stadials. The North Atlantic <span class="hlt">climatic</span> signals may have been transmitted from Central Asia to the East Asian monsoon regions via the westerlies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14...79K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14...79K"><span><span class="hlt">Climate</span> extremes in the Pacific: improving seasonal prediction of <span class="hlt">tropical</span> cyclones and extreme ocean temperatures to improve resilience</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuleshov, Y.; Jones, D.; Spillman, C. M.</p> <p>2012-04-01</p> <p><span class="hlt">Climate</span> change and <span class="hlt">climate</span> extremes have a major impact on Australia and Pacific Island countries. Of particular concern are <span class="hlt">tropical</span> cyclones and extreme ocean temperatures, the first being the most destructive events for terrestrial systems, while the latter has the potential to devastate ocean ecosystems through coral bleaching. As a practical response to <span class="hlt">climate</span> change, under the Pacific-Australia <span class="hlt">Climate</span> Change Science and Adaptation Planning program (PACCSAP), we are developing enhanced web-based information tools for providing seasonal forecasts for <span class="hlt">climatic</span> extremes in the Western Pacific. <span class="hlt">Tropical</span> cyclones are the most destructive weather systems that impact on coastal areas. Interannual variability in the intensity and distribution of <span class="hlt">tropical</span> cyclones is large, and presently greater than any trends that are ascribable to <span class="hlt">climate</span> change. In the warming environment, predicting <span class="hlt">tropical</span> cyclone occurrence based on historical relationships, with predictors such as sea surface temperatures (SSTs) now frequently lying outside of the range of past variability meaning that it is not possible to find historical analogues for the seasonal conditions often faced by Pacific countries. Elevated SSTs are the primary trigger for mass coral bleaching events, which can lead to widespread damage and mortality on reef systems. Degraded coral reefs present many problems, including long-term loss of tourism and potential loss or degradation of fisheries. The monitoring and prediction of thermal stress events enables the support of a range of adaptive and management activities that could improve reef resilience to extreme conditions. Using the <span class="hlt">climate</span> model POAMA (Predictive Ocean-Atmosphere Model for Australia), we aim to improve accuracy of seasonal forecasts of <span class="hlt">tropical</span> cyclone activity and extreme SSTs for the regions of Western Pacific. Improved knowledge of extreme <span class="hlt">climatic</span> events, with the assistance of tailored forecast tools, will help enhance the resilience and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........71P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........71P"><span>Sources and Impacts of Modeled and Observed Low-Frequency <span class="hlt">Climate</span> Variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parsons, Luke Alexander</p> <p></p> <p>Here we analyze <span class="hlt">climate</span> variability using instrumental, paleoclimate (proxy), and the latest <span class="hlt">climate</span> model data to understand more about the sources and impacts of low-frequency <span class="hlt">climate</span> variability. Understanding the drivers of <span class="hlt">climate</span> variability at interannual to century timescales is important for studies of <span class="hlt">climate</span> change, including analyses of detection and attribution of <span class="hlt">climate</span> change impacts. Additionally, correctly modeling the sources and impacts of variability is key to the simulation of <span class="hlt">abrupt</span> change (Alley et al., 2003) and extended drought (Seager et al., 2005; Pelletier and Turcotte, 1997; Ault et al., 2014). In Appendix A, we employ an Earth system model (GFDL-ESM2M) simulation to study the impacts of a weakening of the Atlantic meridional overturning circulation (AMOC) on the <span class="hlt">climate</span> of the American <span class="hlt">Tropics</span>. The AMOC drives some degree of local and global internal low-frequency <span class="hlt">climate</span> variability (Manabe and Stouffer, 1995; Thornalley et al., 2009) and helps control the position of the <span class="hlt">tropical</span> rainfall belt (Zhang and Delworth, 2005). We find that a major weakening of the AMOC can cause large-scale temperature, precipitation, and carbon storage changes in Central and South America. Our results suggest that possible future changes in AMOC strength alone will not be sufficient to drive a large-scale dieback of the Amazonian forest, but this key natural ecosystem is sensitive to dry-season length and timing of rainfall (Parsons et al., 2014). In Appendix B, we compare a paleoclimate record of precipitation variability in the Peruvian Amazon to <span class="hlt">climate</span> model precipitation variability. The paleoclimate (Lake Limon) record indicates that precipitation variability in western Amazonia is 'red' (i.e., increasing variability with timescale). By contrast, most state-of-the-art <span class="hlt">climate</span> models indicate precipitation variability in this region is nearly 'white' (i.e., equally variability across timescales). This paleo-model disagreement in the overall</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GBioC..23.3003L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GBioC..23.3003L"><span>Exploring the range of <span class="hlt">climate</span> biome projections for <span class="hlt">tropical</span> South America: The role of CO2 fertilization and seasonality</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lapola, David M.; Oyama, Marcos D.; Nobre, Carlos A.</p> <p>2009-09-01</p> <p><span class="hlt">Tropical</span> South America vegetation cover projections for the end of the century differ considerably depending on <span class="hlt">climate</span> scenario and also on how physiological processes are considered in vegetation models. In this paper we use a potential vegetation model (CPTEC-PVM2) to analyze biome distribution in <span class="hlt">tropical</span> South America under a range of <span class="hlt">climate</span> projections and a range of estimates about the effects of increased atmospheric CO2. We show that if the CO2 "fertilization effect" indeed takes place and is maintained in the long term in <span class="hlt">tropical</span> forests, then it will avoid biome shifts in Amazonia in most of the <span class="hlt">climate</span> scenarios, even if the effect of CO2 fertilization is halved. However, if CO2 fertilization does not play any important role on <span class="hlt">tropical</span> forests in the future or if dry season is longer than 4 months (projected by 2/14 GCMs), then there is replacement of large portions of Amazonia by <span class="hlt">tropical</span> savanna.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12721773','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12721773"><span>Drug formulations intended for the global market should be tested for stability under <span class="hlt">tropical</span> <span class="hlt">climatic</span> conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Risha, P G; Vervaet, C; Vergote, G; Bortel, L Van; Remon, J P</p> <p>2003-06-01</p> <p>The quality of drugs imported into developing countries having a <span class="hlt">tropical</span> <span class="hlt">climate</span> may be adversely affected if their formulations have not been optimized for stability under these conditions. The present study investigated the influence of <span class="hlt">tropical</span> <span class="hlt">climate</span> conditions (class IV: 40 degrees C, 75% relative humidity) on the drug content, in vitro dissolution and oral bioavailability of different formulations of two essential drugs marketed in Tanzania: diclofenac sodium and ciprofloxacin tablets. Before and after 3 and 6 months storage under class IV conditions the drug content and in vitro dissolution were evaluated using United States Pharmacopoeia (USP) 24 methods. Following a randomized four-period cross-over study, the pharmacokinetic parameters of drug formulations stored for 3 months under class IV conditions were compared with those stored at ambient conditions. Drug content and drug release from all tested ciprofloxacin formulations were within USP-24 requirements and remained stable during storage at simulated <span class="hlt">tropical</span> conditions. Oral bioavailability was also not influenced by <span class="hlt">tropical</span> conditions. The dissolution rate of two diclofenac formulations (Diclo 50 manufactured by Camden and Dicloflame 50 manufactured by Intas) reduced significantly during storage under class IV conditions. After oral administration Camden tablets stored for 3 months under class IV conditions showed a reduction in C(max) (90% CI of C(max) ratio: 0.59 - 0.76). This reduction was smaller than expected based on the in vitro tests. Some drug formulations imported into Tanzania are not optimized for stability in a <span class="hlt">tropical</span> <span class="hlt">climate</span>. Manufacturers and regulatory authorities should pay more attention to the WHO recommendations for testing the stability of drugs under <span class="hlt">tropical</span> <span class="hlt">climate</span> conditions. Efforts should be made to improve the in vitro tests to better predict the bioavailability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27283832','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27283832"><span>The <span class="hlt">abrupt</span> <span class="hlt">climate</span> change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming</p> <p>2016-06-10</p> <p>Extreme <span class="hlt">climatic</span> events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct <span class="hlt">climatic</span> variability during the Dawenkou (5,050-4,400 yr BP) and Longshan (4,400-4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, <span class="hlt">abrupt</span> changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local <span class="hlt">climate</span> changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This <span class="hlt">climatic</span> shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between <span class="hlt">climate</span> change and prehistoric cultural transitions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4901284','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4901284"><span>The <span class="hlt">abrupt</span> <span class="hlt">climate</span> change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming</p> <p>2016-01-01</p> <p>Extreme <span class="hlt">climatic</span> events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct <span class="hlt">climatic</span> variability during the Dawenkou (5,050–4,400 yr BP) and Longshan (4,400–4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, <span class="hlt">abrupt</span> changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local <span class="hlt">climate</span> changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This <span class="hlt">climatic</span> shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between <span class="hlt">climate</span> change and prehistoric cultural transitions. PMID:27283832</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CliPD..11.1407M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CliPD..11.1407M"><span>Millennial-scale precipitation variability over Easter Island (South Pacific) during MIS 3: inter-hemispheric teleconnections with North Atlantic <span class="hlt">abrupt</span> cold events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Margalef, O.; Cacho, I.; Pla-Rabes, S.; Cañellas-Boltà, N.; Pueyo, J. J.; Sáez, A.; Pena, L. D.; Valero-Garcés, B. L.; Rull, V.; Giralt, S.</p> <p>2015-04-01</p> <p>Marine Isotope Stage 3 (MIS 3, 59.4-27.8 kyr BP) is characterized by the occurrence of rapid millennial-scale <span class="hlt">climate</span> oscillations known as Dansgaard-Oeschger cycles (DO) and by <span class="hlt">abrupt</span> cooling events in the North Atlantic known as Heinrich events. Although both the timing and dynamics of these events have been broadly explored in North Atlantic records, the response of the <span class="hlt">tropical</span> and subtropical latitudes to these rapid <span class="hlt">climatic</span> excursions, particularly in the Southern Hemisphere, still remains unclear. The Rano Aroi peat record (Easter Island, 27° S) provides a unique opportunity to understand atmospheric and oceanic changes in the South Pacific during these DO cycles because of its singular location, which is influenced by the South Pacific Anticyclone (SPA), the Southern Westerlies (SW), and the Intertropical Convergence Zone (ITCZ) linked to the South Pacific Convergence Zone (SPCZ). The Rano Aroi sequence records 6 major events of enhanced precipitation between 38 and 65 kyr BP. These events are compared with other hydrological records from the <span class="hlt">tropical</span> and subtropical band supporting a coherent regional picture, with the dominance of humid conditions in Southern Hemisphere <span class="hlt">tropical</span> band during Heinrich Stadials (HS) 5, 5a and 6 and other Stadials while dry conditions prevailed in the Northern <span class="hlt">tropics</span>. This antiphased hydrological pattern between hemispheres has been attributed to ITCZ migration, which in turn might be associated with an eastward expansion of the SPCZ storm track, leading to an increased intensity of cyclogenic storms reaching Easter Island. Low Pacific Sea Surface Temperature (SST) gradients across the Equator were coincident with the here-defined Rano Aroi humid events and consistent with a reorganization of Southern Pacific atmospheric and oceanic circulation also at higher latitudes during Heinrich and Dansgaard-Oeschger stadials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/52705','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/52705"><span>Impacts of land use, restoration, and <span class="hlt">climate</span> change on <span class="hlt">tropical</span> peat carbon stocks in the twenty-first century: implications for <span class="hlt">climate</span> mitigation</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Matthew W. Warren; Steve Frolking; Zhaohua Dai; Sofyan Kurnianto</p> <p>2016-01-01</p> <p>The <span class="hlt">climate</span> mitigation potential of <span class="hlt">tropical</span> peatlands has gained increased attention as Southeast Asian peatlands are being deforested, drained and burned at very high rates, causing globally significant carbon dioxide (CO2) emissions to the atmosphere. We used a process-based dynamic <span class="hlt">tropical</span> peatland model to explore peat carbon (C) dynamics...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B11H0542F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B11H0542F"><span><span class="hlt">Tropical</span> peatland carbon dynamics simulated for scenarios of disturbance and restoration and <span class="hlt">climate</span> change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frolking, S. E.; Warren, M.; Dai, Z.; Kurnianto, S.; Hagen, S. C.</p> <p>2015-12-01</p> <p><span class="hlt">Tropical</span> peatlands contain a globally significant carbon pool. Southeast Asian peatlands are being deforested, drained and burned at very high rates, mostly for conversion to industrial oil palm or pulp and paper plantations. The <span class="hlt">climate</span> mitigation potential of <span class="hlt">tropical</span> peatlands has gained increasing attention in recent years as persistent greenhouse gas emissions can be avoided or decreased if peatlands remain intact or are rehabilitated. In addition, peatland conservation or rehabilitation for <span class="hlt">climate</span> mitigation also includes multiple co-benefits such as maintenance of ecosystem services, biodiversity, and air quality from reduced fire occurrence. Inventory guidelines and methodologies have only recently become available, and are based on few data from a limited number of sites. Few heuristic tools are available to evaluate the impact of management practices on carbon dynamics in <span class="hlt">tropical</span> peatlands, and the potential <span class="hlt">climate</span> mitigation benefits of peatland restoration. We used a process based dynamic <span class="hlt">tropical</span> peatland model to explore the C dynamics of several peatland management trajectories represented by hypothetical scenarios, within the context of simulated 21st century <span class="hlt">climate</span> change. All scenarios with land use, including those with optimal restoration, simulate C loss over the 21st century, with C losses ranging from 10% to essentially 100% of pre-disturbance values. Fire, either prescribed as part of a crop rotation cycle, or stochastic occurrences in sub-optimally managed degraded land can be the dominant C-loss pathway, particularly in the drier <span class="hlt">climate</span> scenario we tested. A single 25-year oil palm rotation, with a prescribed initial burn, lost 40-50 kg C/m2, equivalent to accumulation during the previous 500 years, 10-30% of which was restored in 75 years of optimal restoration. Our results indicate that even under the most optimistic scenario of hydrological and forest restoration and the wettest <span class="hlt">climate</span> regime, only about one-third of the carbon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23132618','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23132618"><span>Palynological composition of a Lower Cretaceous South American <span class="hlt">tropical</span> sequence: <span class="hlt">climatic</span> implications and diversity comparisons with other latitudes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mejia-Velasquez, Paula J; Dilcher, David L; Jaramillo, Carlos A; Fortini, Lucas B; Manchester, Steven R</p> <p>2012-11-01</p> <p>Reconstruction of floristic patterns during the early diversification of angiosperms is impeded by the scarce fossil record, especially in <span class="hlt">tropical</span> latitudes. Here we collected quantitative palynological data from a stratigraphic sequence in <span class="hlt">tropical</span> South America to provide floristic and <span class="hlt">climatic</span> insights into such <span class="hlt">tropical</span> environments during the Early Cretaceous. We reconstructed the floristic composition of an Aptian-Albian <span class="hlt">tropical</span> sequence from central Colombia using quantitative palynology (rarefied species richness and abundance) and used it to infer its predominant <span class="hlt">climatic</span> conditions. Additionally, we compared our results with available quantitative data from three other sequences encompassing 70 floristic assemblages to determine latitudinal diversity patterns. Abundance of humidity indicators was higher than that of aridity indicators (61% vs. 10%). Additionally, we found an angiosperm latitudinal diversity gradient (LDG) for the Aptian, but not for the Albian, and an inverted LDG of the overall diversity for the Albian. Angiosperm species turnover during the Albian, however, was higher in humid <span class="hlt">tropics</span>. There were humid <span class="hlt">climates</span> in northwestern South America during the Aptian-Albian interval contrary to the widespread aridity expected for the <span class="hlt">tropical</span> belt. The Albian inverted overall LDG is produced by a faster increase in per-sample angiosperm and pteridophyte diversity in temperate latitudes. However, humid <span class="hlt">tropical</span> sequences had higher rates of floristic turnover suggesting a higher degree of morphological variation than in temperate regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70041597','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70041597"><span>Palynological composition of a Lower Cretaceous South American <span class="hlt">tropical</span> sequence: <span class="hlt">Climatic</span> implications and diversity comparisons with other latitudes.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Mejia-Velasquez, Paula J.; Dilcher, David L.; Jaramillo, Carlos A.; Fortini, Lucas B.; Manchester, Steven R.</p> <p>2012-01-01</p> <p>Premise of the study: Reconstruction of floristic patterns during the early diversification of angiosperms is impeded by the scarce fossil record, especially in <span class="hlt">tropical</span> latitudes. Here we collected quantitative palynological data from a stratigraphic sequence in <span class="hlt">tropical</span> South America to provide floristic and <span class="hlt">climatic</span> insights into such <span class="hlt">tropical</span> environments during the Early Cretaceous. Methods: We reconstructed the floristic composition of an Aptian-Albian <span class="hlt">tropical</span> sequence from central Colombia using quantitative palynology (rarefied species richness and abundance) and used it to infer its predominant <span class="hlt">climatic</span> conditions. Additionally, we compared our results with available quantitative data from three other sequences encompassing 70 floristic assemblages to determine latitudinal diversity patterns. Key results: Abundance of humidity indicators was higher than that of aridity indicators (61% vs. 10%). Additionally, we found an angiosperm latitudinal diversity gradient (LDG) for the Aptian, but not for the Albian, and an inverted LDG of the overall diversity for the Albian. Angiosperm species turnover during the Albian, however, was higher in humid <span class="hlt">tropics</span>. Conclusions: There were humid <span class="hlt">climates</span> in northwestern South America during the Aptian-Albian interval contrary to the widespread aridity expected for the <span class="hlt">tropical</span> belt. The Albian inverted overall LDG is produced by a faster increase in per-sample angiosperm and pteridophyte diversity in temperate latitudes. However, humid <span class="hlt">tropical</span> sequences had higher rates of floristic turnover suggesting a higher degree of morphological variation than in temperate regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1177297-modeling-high-impact-weather-climate-lessons-from-tropical-cyclone-perspective','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1177297-modeling-high-impact-weather-climate-lessons-from-tropical-cyclone-perspective"><span>Modeling High-Impact Weather and <span class="hlt">Climate</span>: Lessons From a <span class="hlt">Tropical</span> Cyclone Perspective</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Done, James; Holland, Greg; Bruyere, Cindy</p> <p>2013-10-19</p> <p>Although the societal impact of a weather event increases with the rarity of the event, our current ability to assess extreme events and their impacts is limited by not only rarity but also by current model fidelity and a lack of understanding of the underlying physical processes. This challenge is driving fresh approaches to assess high-impact weather and <span class="hlt">climate</span>. Recent lessons learned in modeling high-impact weather and <span class="hlt">climate</span> are presented using the case of <span class="hlt">tropical</span> cyclones as an illustrative example. Through examples using the Nested Regional <span class="hlt">Climate</span> Model to dynamically downscale large-scale <span class="hlt">climate</span> data the need to treat bias inmore » the driving data is illustrated. Domain size, location, and resolution are also shown to be critical and should be guided by the need to: include relevant regional <span class="hlt">climate</span> physical processes; resolve key impact parameters; and to accurately simulate the response to changes in external forcing. The notion of sufficient model resolution is introduced together with the added value in combining dynamical and statistical assessments to fill out the parent distribution of high-impact parameters. Finally, through the example of a <span class="hlt">tropical</span> cyclone damage index, direct impact assessments are resented as powerful tools that distill complex datasets into concise statements on likely impact, and as highly effective communication devices.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11217855','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11217855"><span><span class="hlt">Tropical</span> <span class="hlt">climate</span> changes at millennial and orbital timescales on the Bolivian Altiplano.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baker, P A; Rigsby, C A; Seltzer, G O; Fritz, S C; Lowenstein, T K; Bacher, N P; Veliz, C</p> <p>2001-02-08</p> <p><span class="hlt">Tropical</span> South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation). Although this area plays a key role in global <span class="hlt">climate</span> cycles, little is known about South American <span class="hlt">climate</span> history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the <span class="hlt">tropical</span> Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum--marked in the drill core by continuous deposition of lacustrine sediments--appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in <span class="hlt">tropical</span> South America, suggesting a common forcing.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29316349','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29316349"><span>Adjusting to <span class="hlt">climate</span>: acclimation, adaptation, and developmental plasticity in physiological traits of a <span class="hlt">tropical</span> rainforest lizard.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Llewelyn, John; Macdonald, Stewart L; Moritz, Craig; Martins, Felipe; Hatcher, Amberlee; Phillips, Ben L</p> <p>2018-01-09</p> <p>The impact of <span class="hlt">climate</span> change may be felt most keenly by <span class="hlt">tropical</span> ectotherms. In these taxa, it is argued, thermal specialisation means a given shift in temperature will have a larger effect on fitness. For species with limited dispersal ability, the impact of <span class="hlt">climate</span> change depends on the capacity for their <span class="hlt">climate</span>-relevant traits to shift. Such shifts can occur through genetic adaptation, various forms of plasticity, or a combination of these processes. Here we assess the extent and causes of shifts in seven physiological traits in a <span class="hlt">tropical</span> lizard, the rainforest sunskink (Lampropholis coggeri). Two populations were sampled that differ from each other in both <span class="hlt">climate</span> and physiological traits. We compared trait values in each animal soon after field collection versus following acclimation to laboratory conditions. We also compared trait values between populations in: (1) recently field-collected animals, (2) the same animals following laboratory acclimation, and (3) the laboratory-reared offspring of these animals. Our results reveal high trait lability, driven primarily by acclimation and local adaptation. By contrast, developmental plasticity, resulting from incubation temperature, had little-to-no effect on most traits. These results suggest that, while specialised, <span class="hlt">tropical</span> ectotherms may be capable of rapid shifts in <span class="hlt">climate</span>-relevant traits. This article is protected by copyright. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/52636','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/52636"><span><span class="hlt">Climate</span> change and water resources in a <span class="hlt">tropical</span> island system: propagation of uncertainty from statistically downscaled <span class="hlt">climate</span> models to hydrologic models</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Ashley E. Van Beusekom; William A. Gould; Adam J. Terando; Jaime A. Collazo</p> <p>2015-01-01</p> <p>Many <span class="hlt">tropical</span> islands have limited water resources with historically increasing demand, all potentially affected by a changing <span class="hlt">climate</span>. The effects of <span class="hlt">climate</span> change on island hydrology are difficult to model due to steep local precipitation gradients and sparse data. Thiswork uses 10 statistically downscaled general circulationmodels (GCMs) under two greenhouse gas...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25156258','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25156258"><span>A major advance of <span class="hlt">tropical</span> Andean glaciers during the Antarctic cold reversal.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jomelli, V; Favier, V; Vuille, M; Braucher, R; Martin, L; Blard, P-H; Colose, C; Brunstein, D; He, F; Khodri, M; Bourlès, D L; Leanni, L; Rinterknecht, V; Grancher, D; Francou, B; Ceballos, J L; Fonseca, H; Liu, Z; Otto-Bliesner, B L</p> <p>2014-09-11</p> <p>The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the <span class="hlt">tropical</span> Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic (10)Be and (3)He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to <span class="hlt">climate</span> variability. Here we present a new (10)Be moraine chronology in Colombia showing that glaciers in the northern <span class="hlt">tropical</span> Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all (10)Be and (3)He moraine ages across the <span class="hlt">tropical</span> Andes, we show that this behaviour was common to the northern and southern <span class="hlt">tropical</span> Andes. Transient simulations with a coupled global <span class="hlt">climate</span> model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern <span class="hlt">tropical</span> Andes glaciers retreated owing to <span class="hlt">abrupt</span> regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern <span class="hlt">tropical</span> Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010QSRv...29.1017F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010QSRv...29.1017F"><span>Millennial-scale <span class="hlt">climate</span> variability during the Last Glacial period in the <span class="hlt">tropical</span> Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fritz, S. C.; Baker, P. A.; Ekdahl, E.; Seltzer, G. O.; Stevens, L. R.</p> <p>2010-04-01</p> <p>Millennial-scale <span class="hlt">climate</span> variation during the Last Glacial period is evident in many locations worldwide, but it is unclear if such variation occurred in the interior of <span class="hlt">tropical</span> South America, and, if so, how the low-latitude variation was related to its high-latitude counterpart. A high-resolution record, derived from the deep drilling of sediments on the floor of Lake Titicaca in the southern <span class="hlt">tropical</span> Andes, is presented that shows clear evidence of millennial-scale <span class="hlt">climate</span> variation between ˜60 and 20 ka BP. This variation is manifested by alternations of two interbedded sedimentary units. The two units have distinctive sedimentary, geochemical, and paleobiotic properties that are controlled by the relative abundance of terrigenous or nearshore components versus pelagic components. The sediments of more terrigenous or nearshore nature likely were deposited during regionally wetter <span class="hlt">climates</span> when river transport of water and sediment was higher, whereas the sediments of more pelagic character were deposited during somewhat drier <span class="hlt">climates</span> regionally. The majority of the wet periods inferred from the Lake Titicaca sediment record are correlated with the cold events in the Greenland ice cores and North Atlantic sediment cores, indicating that increased intensity of the South American summer monsoon was part of near-global scale <span class="hlt">climate</span> excursions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JHyd..560..451X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JHyd..560..451X"><span>Evaluation of the significance of <span class="hlt">abrupt</span> changes in precipitation and runoff process in China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, Ping; Wu, Ziyi; Sang, Yan-Fang; Gu, Haiting; Zhao, Yuxi; Singh, Vijay P.</p> <p>2018-05-01</p> <p><span class="hlt">Abrupt</span> changes are an important manifestation of hydrological variability. How to accurately detect the <span class="hlt">abrupt</span> changes in hydrological time series and evaluate their significance is an important issue, but methods for dealing with them effectively are lacking. In this study, we propose an approach to evaluate the significance of <span class="hlt">abrupt</span> changes in time series at five levels: no, weak, moderate, strong, and dramatic. The approach was based on an index of correlation coefficient calculated for the original time series and its <span class="hlt">abrupt</span> change component. A bigger value of correlation coefficient reflects a higher significance level of <span class="hlt">abrupt</span> change. Results of Monte-Carlo experiments verified the reliability of the proposed approach, and also indicated the great influence of statistical characteristics of time series on the significance level of <span class="hlt">abrupt</span> change. The approach was derived from the relationship between correlation coefficient index and <span class="hlt">abrupt</span> change, and can estimate and grade the significance levels of <span class="hlt">abrupt</span> changes in hydrological time series. Application of the proposed approach to ten major watersheds in China showed that <span class="hlt">abrupt</span> changes mainly occurred in five watersheds in northern China, which have arid or semi-arid <span class="hlt">climate</span> and severe shortages of water resources. Runoff processes in northern China were more sensitive to precipitation change than those in southern China. Although annual precipitation and surface water resources amount (SWRA) exhibited a harmonious relationship in most watersheds, <span class="hlt">abrupt</span> changes in the latter were more significant. Compared with <span class="hlt">abrupt</span> changes in annual precipitation, human activities contributed much more to the <span class="hlt">abrupt</span> changes in the corresponding SWRA, except for the Northwest Inland River watershed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Natur.554..351J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Natur.554..351J"><span>Southern Hemisphere <span class="hlt">climate</span> variability forced by Northern Hemisphere ice-sheet topography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, T. R.; Roberts, W. H. G.; Steig, E. J.; Cuffey, K. M.; Markle, B. R.; White, J. W. C.</p> <p>2018-02-01</p> <p>The presence of large Northern Hemisphere ice sheets and reduced greenhouse gas concentrations during the Last Glacial Maximum fundamentally altered global ocean-atmosphere <span class="hlt">climate</span> dynamics. Model simulations and palaeoclimate records suggest that glacial boundary conditions affected the El Niño-Southern Oscillation, a dominant source of short-term global <span class="hlt">climate</span> variability. Yet little is known about changes in short-term <span class="hlt">climate</span> variability at mid- to high latitudes. Here we use a high-resolution water isotope record from West Antarctica to demonstrate that interannual to decadal <span class="hlt">climate</span> variability at high southern latitudes was almost twice as large at the Last Glacial Maximum as during the ensuing Holocene epoch (the past 11,700 years). <span class="hlt">Climate</span> model simulations indicate that this increased variability reflects an increase in the teleconnection strength between the <span class="hlt">tropical</span> Pacific and West Antarctica, owing to a shift in the mean location of <span class="hlt">tropical</span> convection. This shift, in turn, can be attributed to the influence of topography and albedo of the North American ice sheets on atmospheric circulation. As the planet deglaciated, the largest and most <span class="hlt">abrupt</span> decline in teleconnection strength occurred between approximately 16,000 years and 15,000 years ago, followed by a slower decline into the early Holocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3591336','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3591336"><span>Environmental Predictors of Seasonal Influenza Epidemics across Temperate and <span class="hlt">Tropical</span> <span class="hlt">Climates</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tamerius, James D.; Shaman, Jeffrey; Alonso, Wladmir J.; Bloom-Feshbach, Kimberly; Uejio, Christopher K.; Comrie, Andrew; Viboud, Cécile</p> <p>2013-01-01</p> <p>Human influenza infections exhibit a strong seasonal cycle in temperate regions. Recent laboratory and epidemiological evidence suggests that low specific humidity conditions facilitate the airborne survival and transmission of the influenza virus in temperate regions, resulting in annual winter epidemics. However, this relationship is unlikely to account for the epidemiology of influenza in <span class="hlt">tropical</span> and subtropical regions where epidemics often occur during the rainy season or transmit year-round without a well-defined season. We assessed the role of specific humidity and other local <span class="hlt">climatic</span> variables on influenza virus seasonality by modeling epidemiological and <span class="hlt">climatic</span> information from 78 study sites sampled globally. We substantiated that there are two types of environmental conditions associated with seasonal influenza epidemics: “cold-dry” and “humid-rainy”. For sites where monthly average specific humidity or temperature decreases below thresholds of approximately 11–12 g/kg and 18–21°C during the year, influenza activity peaks during the cold-dry season (i.e., winter) when specific humidity and temperature are at minimal levels. For sites where specific humidity and temperature do not decrease below these thresholds, seasonal influenza activity is more likely to peak in months when average precipitation totals are maximal and greater than 150 mm per month. These findings provide a simple <span class="hlt">climate</span>-based model rooted in empirical data that accounts for the diversity of seasonal influenza patterns observed across temperate, subtropical and <span class="hlt">tropical</span> <span class="hlt">climates</span>. PMID:23505366</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130010098','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130010098"><span><span class="hlt">Tropical</span> Ocean Surface Energy Balance Variability: Linking Weather to <span class="hlt">Climate</span> Scales</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roberts, J. Brent; Clayson, Carol Anne</p> <p>2013-01-01</p> <p>Radiative and turbulent surface exchanges of heat and moisture across the atmosphere-ocean interface are fundamental components of the Earth s energy and water balance. Characterizing the spatiotemporal variability of these exchanges of heat and moisture is critical to understanding the global water and energy cycle variations, quantifying atmosphere-ocean feedbacks, and improving model predictability. These fluxes are integral components to <span class="hlt">tropical</span> ocean-atmosphere variability; they can drive ocean mixed layer variations and modify the atmospheric boundary layer properties including moist static stability, thereby influencing larger-scale <span class="hlt">tropical</span> dynamics. Non-parametric cluster-based classification of atmospheric and ocean surface properties has shown an ability to identify coherent weather regimes, each typically associated with similar properties and processes. Using satellite-based observational radiative and turbulent energy flux products, this study investigates the relationship between these weather states and surface energy processes within the context of <span class="hlt">tropical</span> <span class="hlt">climate</span> variability. Investigations of surface energy variations accompanying intraseasonal and interannual <span class="hlt">tropical</span> variability often use composite-based analyses of the mean quantities of interest. Here, a similar compositing technique is employed, but the focus is on the distribution of the heat and moisture fluxes within their weather regimes. Are the observed changes in surface energy components dominated by changes in the frequency of the weather regimes or through changes in the associated fluxes within those regimes? It is this question that the presented work intends to address. The distribution of the surface heat and moisture fluxes is evaluated for both normal and non-normal states. By examining both phases of the <span class="hlt">climatic</span> oscillations, the symmetry of energy and water cycle responses are considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18566247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18566247"><span>High-resolution Greenland ice core data show <span class="hlt">abrupt</span> <span class="hlt">climate</span> change happens in few years.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Steffensen, Jørgen Peder; Andersen, Katrine K; Bigler, Matthias; Clausen, Henrik B; Dahl-Jensen, Dorthe; Fischer, Hubertus; Goto-Azuma, Kumiko; Hansson, Margareta; Johnsen, Sigfús J; Jouzel, Jean; Masson-Delmotte, Valérie; Popp, Trevor; Rasmussen, Sune O; Röthlisberger, Regine; Ruth, Urs; Stauffer, Bernhard; Siggaard-Andersen, Marie-Louise; Sveinbjörnsdóttir, Arny E; Svensson, Anders; White, James W C</p> <p>2008-08-01</p> <p>The last two <span class="hlt">abrupt</span> warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both <span class="hlt">abrupt</span> Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these <span class="hlt">abrupt</span> shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7949D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7949D"><span>Are <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes predictable?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ditlevsen, Peter</p> <p>2013-04-01</p> <p>It is taken for granted that the limited predictability in the initial value problem, the weather prediction, and the predictability of the statistics are two distinct problems. Lorenz (1975) dubbed this predictability of the first and the second kind respectively. Predictability of the first kind in a chaotic dynamical system is limited due to the well-known critical dependence on initial conditions. Predictability of the second kind is possible in an ergodic system, where either the dynamics is known and the phase space attractor can be characterized by simulation or the system can be observed for such long times that the statistics can be obtained from temporal averaging, assuming that the attractor does not change in time. For the <span class="hlt">climate</span> system the distinction between predictability of the first and the second kind is fuzzy. This difficulty in distinction between predictability of the first and of the second kind is related to the lack of scale separation between fast and slow components of the <span class="hlt">climate</span> system. The non-linear nature of the problem furthermore opens the possibility of multiple attractors, or multiple quasi-steady states. As the ice-core records show, the <span class="hlt">climate</span> has been jumping between different quasi-stationary <span class="hlt">climates</span>, stadials and interstadials through the Dansgaard-Oechger events. Such a jump happens very fast when a critical tipping point has been reached. The question is: Can such a tipping point be predicted? This is a new kind of predictability: the third kind. If the tipping point is reached through a bifurcation, where the stability of the system is governed by some control parameter, changing in a predictable way to a critical value, the tipping is predictable. If the sudden jump occurs because internal chaotic fluctuations, noise, push the system across a barrier, the tipping is as unpredictable as the triggering noise. In order to hint at an answer to this question, a careful analysis of the high temporal resolution NGRIP isotope</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2489T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2489T"><span>Understanding the geographic distribution of <span class="hlt">tropical</span> cyclone formation for applications in <span class="hlt">climate</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tory, Kevin J.; Ye, H.; Dare, R. A.</p> <p>2018-04-01</p> <p>Projections of <span class="hlt">Tropical</span> cyclone (TC) formation under future <span class="hlt">climate</span> scenarios are dependent on <span class="hlt">climate</span> model simulations. However, many models produce unrealistic geographical distributions of TC formation, especially in the north and south Atlantic and eastern south Pacific TC basins. In order to improve confidence in projections it is important to understand the reasons behind these model errors. However, considerable effort is required to analyse the many models used in projection studies. To address this problem, a novel diagnostic is developed that provides compelling insight into why TCs form where they do, using a few summary diagrams. The diagnostic is developed after identifying a relationship between seasonal climatologies of atmospheric variables in 34 years of ECMWF reanalysis data, and TC detection distributions in the same data. Geographic boundaries of TC formation are constructed from four threshold quantities. TCs form where Emanuel's Maximum Potential Intensity, V_{{PI}}, exceeds 40 {ms}^{{ - 1}}, 700 hPa relative humidity, RH_{{700}}, exceeds 40%, and the magnitude of the difference in vector winds between 850 and 200 hPa, V_{{sh}}, is less than 20 {ms}^{{ - 1}}. The equatorial boundary is best defined by a composite quantity containing the ratio of absolute vorticity (η ) to the meridional gradient of absolute vorticity (β ^{*}), rather than η alone. {β ^*} is also identified as a potentially important ingredient for TC genesis indices. A comparison of detected <span class="hlt">Tropical</span> Depression (TD) and <span class="hlt">Tropical</span> Storm (TS) climatologies revealed TDs more readily intensify further to TS where {V_{PI}} is elevated and {V_{sh}} is relatively weak. The distributions of each threshold quantity identify the factors that favour and suppress TC formation throughout the <span class="hlt">tropics</span> in the real world. This information can be used to understand why TC formation is poorly represented in some <span class="hlt">climate</span> models, and shows potential for understanding anomalous TC formation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNH13D1973P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNH13D1973P"><span><span class="hlt">Climate</span> Risk Management Strategy in the <span class="hlt">Tropical</span> Low to Medium Income Countries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parhi, P.; Giannini, A.; Lall, U.</p> <p>2015-12-01</p> <p>The market penetration of index insurance sector, posed as an innovative weather risk management and <span class="hlt">climate</span> change adaptation tool, is growing in the <span class="hlt">tropical</span> low to medium income countries. Usually the underwriters such as regional, national or international organizations, banks or (re)insurance companies hold these risk portfolios. The micro-level insurance contracts when aggregated at state, country or regional level, could potentially pose significant systemic risk due to tail dependency, micro-correlation and fat-tail nature of the damage, threatening the survival of this micro-financial risk management sector, ultimately impeding the sustainable development goals. Analyzing the observed inter-annual variability of the <span class="hlt">tropical</span> <span class="hlt">climate</span> system, this paper identifies the physical mechanisms for heterogeneous <span class="hlt">climatic</span> response and suggests that diversification opportunity exists across different regions and seasons. Taking two case studies from <span class="hlt">tropical</span> Africa, an empirical analysis is done to highlight that El Niño modulates the number of wet days in an opposite way across the two regions and seasons, suggesting the possibility of diversification of the index insurance portfolios across regions and seasons. Specifically, El Niño is associated with drier condition over Sahel, while it is associated with wetter condition over <span class="hlt">Tropical</span> Eastern Africa (TEA), during their respective Jul-Aug-Sep and Oct-Nov-Dec rainy seasons. Such contrasting modulation in the number of wet days can be understood by the phase relationship between the local rainy season and El Niño evolution stage. The transient phase of El Niño, which is in phase with the rainy season (Jul-Sep) over Sahel, is characterized by tropospheric stability induced by tropospheric warming without regional North Atlantic sea surface temperature (SST) adjustment. In contrast, the mature phase of El Niño is in phase with the short rainy season (Oct-Dec) over TEA, and is characterized by adjusted warmer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AdAtS..21..291W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AdAtS..21..291W"><span><span class="hlt">Abrupt</span> <span class="hlt">climate</span> change around 4 ka BP: Role of the Thermohaline circulation as indicated by a GCM experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Shaowu; Zhou, Tianjun; Cai, Jingning; Zhu, Jinhong; Xie, Zhihui; Gong, Daoyi</p> <p>2004-04-01</p> <p>A great deal of palaeoenvironmental and palaeoclimatic evidence suggests that a predominant temperature drop and an aridification occurred at ca. 4.0 ka BP. Palaeoclimate studies in China support this dedution. The collapse of ancient civilizations at ca. 4.0 ka BP in the Nile Valley and Mesopotamia has been attributed to <span class="hlt">climate</span>-induced aridification. A widespread alternation of the ancient cultures was also found in China at ca. 4.0 ka BP in concert with the collapse of the civilizations in the Old World. Palaeoclimatic studies indicate that the <span class="hlt">abrupt</span> <span class="hlt">climate</span> change at 4.0 ka BP is one of the realizations of the cold phase in millennial scale <span class="hlt">climate</span> oscillations, which may be related to the modulation of the Thermohaline Circulation (THC) over the Atlantic Ocean. Therefore, this study conducts a numerical experiment of a GCM with SST forcing to simulate the impact of the weakening of the THC. Results show a drop in temperature from North Europe, the northern middle East Asia, and northern East Asia and a significant reduction of precipitation in East Africa, the Middle East, the Indian Peninsula, and the Yellow River Valley. This seems to support the idea that coldness and aridification at ca. 4.0 ka BP was caused by the weakening of the THC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A13C2084E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A13C2084E"><span>The Strength of Cloud Feedbacks and the Structure of <span class="hlt">Tropical</span> <span class="hlt">Climate</span> Change - A CESM Sensitivity Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erfani, E.; Burls, N.</p> <p>2017-12-01</p> <p>The nature of local coupled ocean-atmosphere interactions within the <span class="hlt">tropics</span> is determined by background conditions such as the depth of the equatorial thermocline, the water vapor content of the <span class="hlt">tropical</span> atmosphere, and the radiative forcing of <span class="hlt">tropical</span> clouds. These factors are set not only by the coupled <span class="hlt">tropical</span> variability itself but also by extra-<span class="hlt">tropical</span> conditions. For example, the strength of the cold tongue is ultimately controlled by the temperature of waters subducted in the extra-<span class="hlt">tropics</span> and transported to the equator by the ocean subtropical cells (STCs). Similarly, inter-hemispheric asymmetries in extra-<span class="hlt">tropical</span> atmospheric heating are communicated to the <span class="hlt">tropics</span> affecting cross-equatorial heat transport and ITCZ position. Acknowledging from a fully coupled perspective the influence of both <span class="hlt">tropical</span> and extra-<span class="hlt">tropical</span> conditions, we are performing a suite of CESM experiments across which we systematically alter the strength of convective and stratus cloud feedbacks. By systematically exploring the sensitivity of the <span class="hlt">tropical</span> coupled system to imposed changes in the strength of <span class="hlt">tropical</span> and extra-<span class="hlt">tropical</span> cloud feedbacks to CO2-induced warming this work aims to formalize our understanding of cloud controls on <span class="hlt">tropical</span> <span class="hlt">climate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26811764','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26811764"><span>Thermal tolerance and <span class="hlt">climate</span> warming sensitivity in <span class="hlt">tropical</span> snails.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marshall, David J; Rezende, Enrico L; Baharuddin, Nursalwa; Choi, Francis; Helmuth, Brian</p> <p>2015-12-01</p> <p><span class="hlt">Tropical</span> ectotherms are predicted to be especially vulnerable to <span class="hlt">climate</span> change because their thermal tolerance limits generally lie close to current maximum air temperatures. This prediction derives primarily from studies on insects and lizards and remains untested for other taxa with contrasting ecologies. We studied the HCT (heat coma temperatures) and ULT (upper lethal temperatures) of 40 species of <span class="hlt">tropical</span> eulittoral snails (Littorinidae and Neritidae) inhabiting exposed rocky shores and shaded mangrove forests in Oceania, Africa, Asia and North America. We also estimated extremes in animal body temperature at each site using a simple heat budget model and historical (20 years) air temperature and solar radiation data. Phylogenetic analyses suggest that HCT and ULT exhibit limited adaptive variation across habitats (mangroves vs. rocky shores) or geographic locations despite their contrasting thermal regimes. Instead, the elevated heat tolerance of these species (HCT = 44.5 ± 1.8°C and ULT = 52.1 ± 2.2°C) seems to reflect the extreme temperature variability of intertidal systems. Sensitivity to <span class="hlt">climate</span> warming, which was quantified as the difference between HCT or ULT and maximum body temperature, differed greatly between snails from sunny (rocky shore; Thermal Safety Margin, TSM = -14.8 ± 3.3°C and -6.2 ± 4.4°C for HCT and ULT, respectively) and shaded (mangrove) habitats (TSM = 5.1 ± 3.6°C and 12.5 ± 3.6°C). Negative TSMs in rocky shore animals suggest that mortality is likely ameliorated during extreme <span class="hlt">climatic</span> events by behavioral thermoregulation. Given the low variability in heat tolerance across species, habitat and geographic location account for most of the variation in TSM and may adequately predict the vulnerability to <span class="hlt">climate</span> change. These findings caution against generalizations on the impact of global warming across ectothermic taxa and highlight how the consideration of nonmodel animals, ecological transitions</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010E%26ES....9a2003G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010E%26ES....9a2003G"><span><span class="hlt">Tropical</span> vegetation evidence for rapid sea level changes associated with Heinrich Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>González, Catalina; Dupont, Lydie M.</p> <p>2010-03-01</p> <p>A Cariaco Basin pollen record shows the development of <span class="hlt">tropical</span> salt marshes during marine isotope stage 3. Rapid and <span class="hlt">abrupt</span> expansions of salt marsh vegetation in <span class="hlt">tropical</span> South America are associated with north Atlantic Heinrich Events stadials (HE-stadials). Intervals of salt marsh expansion have an internal structure, which consists of a recurrent alternation of species that starts with pollen increments of Chenopodiaceae, that are followed by increments of grasses, and subsequently by increments of Cyperaceae. This pattern suggests a successional process that is determined by the close relationship between sea-level and plant community dynamics. The salt tolerant Chenopodiaceae, indicate hypersaline intertidal environments, which were most likely promoted by extremely dry atmospheric conditions. Rapid sea-level rise characterizes the onset of HE-stadials, causing the continued recruitment of pioneer species, which are the only ones tolerating rapid rates of disturbance. Once sea-level rise decelerates, marsh plants are able to trap and stabilize sediments, favouring the establishment of more competitive species. These results add to the scarce knowledge on the dynamics of <span class="hlt">tropical</span> salt marsh ecosystems, and provide independent paleoclimatic evidence on sea-level changes following Antarctic <span class="hlt">climate</span> variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=analysis+AND+climatic&pg=3&id=ED301218','ERIC'); return false;" href="https://eric.ed.gov/?q=analysis+AND+climatic&pg=3&id=ED301218"><span>Prevention and Treatment of Mold in Library Collections with an Emphasis on <span class="hlt">Tropical</span> <span class="hlt">Climates</span>: A Ramp Study.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Wood Lee, Mary</p> <p></p> <p>This study focuses on the prevention and basic treatment of recurring mold growth in <span class="hlt">tropical</span> <span class="hlt">climates</span> where library-wide environmental control is not always possible. The introduction discusses major <span class="hlt">climatic</span> groups; the effects of <span class="hlt">climate</span> on specific materials found in library resources; and the range of options for modifying the environment.…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRG..118..783C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRG..118..783C"><span>Field-quantified responses of <span class="hlt">tropical</span> rainforest aboveground productivity to increasing CO2 and <span class="hlt">climatic</span> stress, 1997-2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clark, Deborah A.; Clark, David B.; Oberbauer, Steven F.</p> <p>2013-06-01</p> <p>A directional change in <span class="hlt">tropical</span>-forest productivity, a large component in the global carbon budget, would affect the rate of increase in atmospheric carbon dioxide ([CO2]). One current hypothesis is that "CO2 fertilization" has been increasing <span class="hlt">tropical</span> forest productivity. Some lines of evidence instead suggest <span class="hlt">climate</span>-driven productivity declines. Relevant direct field observations remain extremely limited for this biome. Using a unique long-term record of annual field measurements, we assessed annual aboveground net primary productivity (ANPP) and its relation to <span class="hlt">climatic</span> factors and [CO2] in a neotropical rainforest through 1997-2009. Over this 12 year period, annual productivity did not increase, as would be expected with a dominant CO2 fertilization effect. Instead, the negative responses of ANPP components to <span class="hlt">climatic</span> stress far exceeded the small positive responses associated with increasing [CO2]. Annual aboveground biomass production was well explained (73%) by the independent negative effects of increasing minimum temperatures and greater dry-season water stress. The long-term records enable a first field-based estimate of the [CO2] response of <span class="hlt">tropical</span> forest ANPP: 5.24 g m-2 yr-1 yr-1 (the summed [CO2]-associated increases in two of the four production components; the largest component, leaf litterfall, showed no [CO2] association). If confirmed by longer data series, such a small response from a fertile <span class="hlt">tropical</span> rainforest would indicate that current global models overestimate the benefits from CO2 fertilization for this biome, where most forests' poorer nutrient status more strongly constrains productivity responses to increasing [CO2]. Given the rapidly intensifying warming across <span class="hlt">tropical</span> regions, <span class="hlt">tropical</span> forest productivity could sharply decline through coming decades.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFMPP22C..01W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFMPP22C..01W"><span>Work More? The 8.2 kaBP <span class="hlt">Abrupt</span> <span class="hlt">Climate</span> Change Event and the Origins of Irrigation Agriculture and Surplus Agro-Production in Mesopotamia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weiss, H.</p> <p>2003-12-01</p> <p>The West Asian archaeological record is of sufficient transparency and resolution to permit observation of the social responses to the major Holocene <span class="hlt">abrupt</span> <span class="hlt">climate</span> change events at 8.2, 5.2 and 4.2 kaBP. The 8.2kaBP <span class="hlt">abrupt</span> <span class="hlt">climate</span> change event in West Asia was a three hundred year aridification and cooling episode. During this period rain-fed agriculture, established for over a millennium in northern Mesopotamia, suddenly collapsed. Irrigation agriculture, pastoral nomadism, or migration were the only subsistence alternatives for populations previously supported by cereal dry-farming. Irrigation agriculture was not, however, possible along the northern alluvial plains of the Tigris and Euphrates Rivers, where incised riverbeds were several meters below plain level. Exploitable plain-level levees were only accessible in southern-most alluvial plain, at the head of the present-day Persian Gulf. The archaeological data from this region documents the first irrigation agriculture settlement of the plain during the 8.2 kaBP event. Irrigation agriculture provides about twice the yield of dry-farming in Mesopotamia, but at considerable labor costs relative to dry-farming. With irrigation agriculture surplus production was now available for deployment. But why work more? The 8.2 kaBP event provided the natural force for Mesopotamian irrigation agriculture and surplus production that were essential for the earliest class-formation and urban life.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A11G..01K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A11G..01K"><span>Sensitivity of South American <span class="hlt">tropical</span> <span class="hlt">climate</span> to Last Glacial Maximum boundary conditions: focus on teleconnections with <span class="hlt">tropics</span> and extratropics (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khodri, M.; Kageyama, M.; Roche, D. M.</p> <p>2009-12-01</p> <p> dynamical equilibrium due to both reduced GHG and land ice sheets. We also show that the overall <span class="hlt">tropical</span> Pacific circulation response to land ice albedo alone consists in a substantial thermo-dynamical stabilisation of the equatorial atmosphere. The upper troposphere warming spreading out from South East Central Pacific, analogous to the atmosphere response to El-Niño conditions, results in enhanced rainfall over Nordeste and Southeastern Brazil. Such <span class="hlt">tropics-tropics</span> teleconnection is essential to explain the moistening of the southern <span class="hlt">tropics</span>, amplifying thereby the influence of the extratropical atmosphere on the LGM <span class="hlt">tropical</span> <span class="hlt">climate</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29549991','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29549991"><span>Extinction risks forced by <span class="hlt">climatic</span> change and intraspecific variation in the thermal physiology of a <span class="hlt">tropical</span> lizard.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pontes-da-Silva, Emerson; Magnusson, William E; Sinervo, Barry; Caetano, Gabriel H; Miles, Donald B; Colli, Guarino R; Diele-Viegas, Luisa M; Fenker, Jessica; Santos, Juan C; Werneck, Fernanda P</p> <p>2018-04-01</p> <p>Temperature increases can impact biodiversity and predicting their effects is one of the main challenges facing global <span class="hlt">climate</span>-change research. Ectotherms are sensitive to temperature change and, although predictions indicate that <span class="hlt">tropical</span> species are highly vulnerable to global warming, they remain one of the least studied groups with respect to the extent of physiological variation and local extinction risks. We model the extinction risks for a <span class="hlt">tropical</span> heliothermic teiid lizard (Kentropyx calcarata) integrating previously obtained information on intraspecific phylogeographic structure, eco-physiological traits and contemporary species distributions in the Amazon rainforest and its ecotone to the Cerrado savannah. We also investigated how thermal-biology traits vary throughout the species' geographic range and the consequences of such variation for lineage vulnerability. We show substantial variation in thermal tolerance of individuals among thermally distinct sites. Thermal critical limits were highly correlated with operative environmental temperatures. Our physiological/<span class="hlt">climatic</span> model predicted relative extinction risks for local populations within clades of K. calcarata for 2050 ranging between 26.1% and 70.8%, while for 2070, extinction risks ranged from 52.8% to 92.8%. Our results support the hypothesis that <span class="hlt">tropical</span>-lizard taxa are at high risk of local extinction caused by increasing temperatures. However, the thermo-physiological differences found across the species' distribution suggest that local adaptation may allow persistence of this <span class="hlt">tropical</span> ectotherm in global warming scenarios. These results will serve as basis to further research to investigate the strength of local adaptation to <span class="hlt">climate</span> change. Persistence of Kentropyx calcarata also depends on forest preservation, but the Amazon rainforest is currently under high deforestation rates. We argue that higher conservation priority is necessary so the Amazon rainforest can fulfill its capacity to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040171266&hterms=ocean+climate+changes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Docean%2Bclimate%2Bchanges','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040171266&hterms=ocean+climate+changes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Docean%2Bclimate%2Bchanges"><span>Warm Rain Processes Over the <span class="hlt">Tropical</span> Oceans and Implications on <span class="hlt">Climate</span> Change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K. M.; Wu, H. T.</p> <p>2004-01-01</p> <p>In this talk, we will first show results from TRMM regarding the characteristics of warm rains over the <span class="hlt">tropical</span> oceans, and the dependence of rate of warm rain production on sea surface temperature. Results lead to the hypothesis that warm rain production efficiency, i.e., autoconversion, may be increased in a warm <span class="hlt">climate</span>. We use the GEOS-II GCM to test this hypothesis. Our modeling results show that in a <span class="hlt">climate</span> with increased rate of autoconversion, the total rain amount is increased, with warm rain contributing to a larger portion of the increase. The abundant rainout of warm precipitation at middle to low levels causes a reduction of high cloud cover due to the depletion of water available for ice-phase rain production. As a result, more isolated, but more intense penetrative convection develops. Results also show that increased autoconversion reduces the convective adjustment time scale tends, implying a faster recycling of atmospheric water. Most interestingly, the increased low level heating associated with warm rain leads to more energetic Madden and Julian oscillations in the <span class="hlt">tropics</span>, with well-defined eastward propagation. While reducing the autoconversion leads to an abundant mix of westward and eastward <span class="hlt">tropical</span> disturbance on daily to weekly time scales. The causes of the sensitivity of the dynamical regimes to the microphysics parameterization in the GCM will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27254115','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27254115"><span><span class="hlt">Tropical</span> amphibians in shifting thermal landscapes under land-use and <span class="hlt">climate</span> change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nowakowski, A Justin; Watling, James I; Whitfield, Steven M; Todd, Brian D; Kurz, David J; Donnelly, Maureen A</p> <p>2017-02-01</p> <p>Land-cover and <span class="hlt">climate</span> change are both expected to alter species distributions and contribute to future biodiversity loss. However, the combined effects of land-cover and <span class="hlt">climate</span> change on assemblages, especially at the landscape scale, remain understudied. Lowland <span class="hlt">tropical</span> amphibians may be particularly susceptible to changes in land cover and <span class="hlt">climate</span> warming because many species have narrow thermal safety margins resulting from air and body temperatures that are close to their critical thermal maxima (CT max ). We examined how changing thermal landscapes may alter the area of thermally suitable habitat (TSH) for <span class="hlt">tropical</span> amphibians. We measured microclimates in 6 land-cover types and CT max of 16 frog species in lowland northeastern Costa Rica. We used a biophysical model to estimate core body temperatures of frogs exposed to habitat-specific microclimates while accounting for evaporative cooling and behavior. Thermally suitable habitat area was estimated as the portion of the landscape where species CT max exceeded their habitat-specific maximum body temperatures. We projected changes in TSH area 80 years into the future as a function of land-cover change only, <span class="hlt">climate</span> change only, and combinations of land-cover and <span class="hlt">climate</span>-change scenarios representing low and moderate rates of change. Projected decreases in TSH area ranged from 16% under low emissions and reduced forest loss to 30% under moderate emissions and business-as-usual land-cover change. Under a moderate emissions scenario (A1B), <span class="hlt">climate</span> change alone contributed to 1.7- to 4.5-fold greater losses in TSH area than land-cover change only, suggesting that future decreases in TSH from <span class="hlt">climate</span> change may outpace structural habitat loss. Forest-restricted species had lower mean CT max than species that occurred in altered habitats, indicating that thermal tolerances will likely shape assemblages in changing thermal landscapes. In the face of ongoing land-cover and <span class="hlt">climate</span> change, it will be critical to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSMPP31A..01B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSMPP31A..01B"><span>Vegetation and <span class="hlt">climate</span> variability in <span class="hlt">tropical</span> and subtropical South America during the late Quaternary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Behling, H.</p> <p>2013-05-01</p> <p>Detailed palynological studies from different ecosystems in <span class="hlt">tropical</span> and subtropical South America reflect interesting vegetation and <span class="hlt">climate</span> dynamics, in particular during glacial and late glacial times. Records from ecosystems such as the Amazon rainforest, savanna, Caatinga, Atlantic rainforest, Araucaria forest and grasslands provide interesting insight of past <span class="hlt">climate</span> variability. The influence of events such as Dansgaard-Oeschger, Heinnrich stadials, changes in the thermohaline circulation (THC) will be discussed. In particular the Younger Dryas (YD) period shows at different places distinct vegetational changes, revealing unexpected past <span class="hlt">climatic</span> conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3399193','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3399193"><span>Projected changes in distributions of Australian <span class="hlt">tropical</span> savanna birds under <span class="hlt">climate</span> change using three dispersal scenarios</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Reside, April E; VanDerWal, Jeremy; Kutt, Alex S</p> <p>2012-01-01</p> <p>Identifying the species most vulnerable to extinction as a result of <span class="hlt">climate</span> change is a necessary first step in mitigating biodiversity decline. Species distribution modeling (SDM) is a commonly used tool to assess potential <span class="hlt">climate</span> change impacts on distributions of species. We use SDMs to predict geographic ranges for 243 birds of Australian <span class="hlt">tropical</span> savannas, and to project changes in species richness and ranges under a future <span class="hlt">climate</span> scenario between 1990 and 2080. Realistic predictions require recognition of the variability in species capacity to track <span class="hlt">climatically</span> suitable environments. Here we assess the effect of dispersal on model results by using three approaches: full dispersal, no dispersal and a partial-dispersal scenario permitting species to track <span class="hlt">climate</span> change at a rate of 30 km per decade. As expected, the projected distributions and richness patterns are highly sensitive to the dispersal scenario. Projected future range sizes decreased for 66% of species if full dispersal was assumed, but for 89% of species when no dispersal was assumed. However, realistic future predictions should not assume a single dispersal scenario for all species and as such, we assigned each species to the most appropriate dispersal category based on individual mobility and habitat specificity; this permitted the best estimates of where species will be in the future. Under this “realistic” dispersal scenario, projected ranges sizes decreased for 67% of species but showed that migratory and <span class="hlt">tropical</span>-endemic birds are predicted to benefit from <span class="hlt">climate</span> change with increasing distributional area. Richness hotspots of <span class="hlt">tropical</span> savanna birds are expected to move, increasing in southern savannas and southward along the east coast of Australia, but decreasing in the arid zone. Understanding the complexity of effects of <span class="hlt">climate</span> change on species’ range sizes by incorporating dispersal capacities is a crucial step toward developing adaptation policies for the conservation of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6338793-how-ice-age-climate-got-shakes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6338793-how-ice-age-climate-got-shakes"><span>How ice age <span class="hlt">climate</span> got the shakes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kerr, R.A.</p> <p>1993-05-14</p> <p>Records in Greenland ice, ocean mud, and ancient corals are revealing <span class="hlt">abrupt</span> <span class="hlt">climate</span> shifts during the last ice age. The <span class="hlt">climate</span> at the end of the last ice age apparently jumped from cold to warmer conditions, jumped back to cold, and then jumped into the present warm weather conditions. The mechanism for this erratic behavior is unknown, but appears to be an interaction of North Atlantic ocean currents and the ice sheets themselves. Warm water from the <span class="hlt">tropics</span> would evaporate and become more saline and dense as it moved north. The colder, denser water would then sink and flow backmore » to the <span class="hlt">tropics</span>. The melting of ice caused by the warm water would decrease the salinity of the North Atlantic current, the water would not sink, the return current would be shut down, and the waters surrounding the ice sheets would become colder, slowing melting of the sheets. The cycle could be started again by collapse of the ice sheets from their internal heat. There may be other switches that could cause sudden <span class="hlt">climate</span> change, as may be evidenced by links between changes in the Pacific and a decade of erratic weather in North America. Researcher would like to identify these switches to prevent them from being activated by human activity.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EnMan..60..422D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EnMan..60..422D"><span><span class="hlt">Climatic</span>-Induced Shifts in the Distribution of Teak ( Tectona grandis) in <span class="hlt">Tropical</span> Asia: Implications for Forest Management and Planning</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deb, Jiban Chandra; Phinn, Stuart; Butt, Nathalie; McAlpine, Clive A.</p> <p>2017-09-01</p> <p>Modelling the future suitable <span class="hlt">climate</span> space for tree species has become a widely used tool for forest management planning under global <span class="hlt">climate</span> change. Teak ( Tectona grandis) is one of the most valuable <span class="hlt">tropical</span> hardwood species in the international timber market, and natural teak forests are distributed from India through Myanmar, Laos and Thailand. The extents of teak forests are shrinking due to deforestation and the local impacts of global <span class="hlt">climate</span> change. However, the direct impacts of <span class="hlt">climate</span> changes on the continental-scale distributions of native and non-native teak have not been examined. In this study, we developed a species distribution model for teak across its entire native distribution in <span class="hlt">tropical</span> Asia, and its non-native distribution in Bangladesh. We used presence-only records of trees and twelve environmental variables that were most representative for current teak distributions in South and Southeast Asia. MaxEnt (maximum entropy) models were used to model the distributions of teak under current and future <span class="hlt">climate</span> scenarios. We found that land use/land cover change and elevation were the two most important variables explaining the current and future distributions of native and non-native teak in <span class="hlt">tropical</span> Asia. Changes in annual precipitation, precipitation seasonality and annual mean actual evapotranspiration may result in shifts in the distributions of teak across <span class="hlt">tropical</span> Asia. We discuss the implications for the conservation of critical teak habitats, forest management planning, and risks of biological invasion that may occur due to its cultivation in non-native ranges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.5533H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.5533H"><span>How well do simulated last glacial maximum <span class="hlt">tropical</span> temperatures constrain equilibrium <span class="hlt">climate</span> sensitivity?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hopcroft, Peter O.; Valdes, Paul J.</p> <p>2015-07-01</p> <p>Previous work demonstrated a significant correlation between <span class="hlt">tropical</span> surface air temperature and equilibrium <span class="hlt">climate</span> sensitivity (ECS) in PMIP (Paleoclimate Modelling Intercomparison Project) phase 2 model simulations of the last glacial maximum (LGM). This implies that reconstructed LGM cooling in this region could provide information about the <span class="hlt">climate</span> system ECS value. We analyze results from new simulations of the LGM performed as part of Coupled Model Intercomparison Project (CMIP5) and PMIP phase 3. These results show no consistent relationship between the LGM <span class="hlt">tropical</span> cooling and ECS. A radiative forcing and feedback analysis shows that a number of factors are responsible for this decoupling, some of which are related to vegetation and aerosol feedbacks. While several of the processes identified are LGM specific and do not impact on elevated CO2 simulations, this analysis demonstrates one area where the newer CMIP5 models behave in a qualitatively different manner compared with the older ensemble. The results imply that so-called Earth System components such as vegetation and aerosols can have a significant impact on the <span class="hlt">climate</span> response in LGM simulations, and this should be taken into account in future analyses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9544M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9544M"><span>Extrapolating carbon dynamics of <span class="hlt">tropical</span> dry forests into future <span class="hlt">climates</span>: improving simulation models with empirical observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Medvigy, David; Waring, Bonnie; Vargas, German; Xu, Xiangtao; Smith, Christina; Becknell, Justin; Trierweiler, Annette; Brodribb, Timothy; Powers, Jennifer</p> <p>2017-04-01</p> <p><span class="hlt">Tropical</span> dry forests occur in areas with warm temperatures and a pronounced dry season with little to no rainfall that lasts 3 to 7 months. The potential area covered by this biome is vast: globally, 47% of all forest occurs in <span class="hlt">tropical</span> and subtropical latitudes, and of all <span class="hlt">tropical</span> forests approximately 42% are classified as dry forests. Throughout the last several centuries, the area covered by <span class="hlt">tropical</span> dry forests has been dramatically reduced through conversion to grazing and croplands, and they are now considered the most threatened <span class="hlt">tropical</span> biome. However, in many regions, <span class="hlt">tropical</span> dry forests are now growing back. There is growing concern that this recovery process will be strongly impacted by <span class="hlt">climate</span> variability and change. Observations show that <span class="hlt">climate</span> is changing in the seasonal <span class="hlt">tropics</span>, and <span class="hlt">climate</span> models forecast that neotropical dry forests will receive significantly less rainfall in the 21st century than in the 20th century. Rates of nitrogen deposition are also changing rapidly in this sector, and the fertility of some soils may still be recovering from past land use. We are engaged in several efforts to understand how water and nutrients limit the productivity of these forests, including manipulative experiments, modeling, and investigation of responses to natural <span class="hlt">climate</span> variability. In 2015, at a well-characterized site in Guanacaste, Costa Rica, we established a full-factorial fertilization experiment with N and P in diverse mature forest stands. Initial responses highlight stronger ecosystem sensitivity to P addition than to N addition. Intriguingly, pre-experiment numerical simulations with a mechanistic ecosystem model had indicated the reverse. Work is ongoing to use field observations to better represent critical processes in the model, and ultimately to improve the model's sensitivity to nutrients and water. In addition, in 2016, we established a full factorial nutrient addition and drought experiment in plantations. Thus far, soil</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28958434','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28958434"><span>Field study of thermal comfort in non-air-conditioned buildings in a <span class="hlt">tropical</span> island <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lu, Shilei; Pang, Bo; Qi, Yunfang; Fang, Kun</p> <p>2018-01-01</p> <p>The unique geographical location of Hainan makes its <span class="hlt">climate</span> characteristics different from inland areas in China. The thermal comfort of Hainan also owes its uniqueness to its <span class="hlt">tropical</span> island <span class="hlt">climate</span>. In the past decades, there have been very few studies on thermal comfort of the residents in <span class="hlt">tropical</span> island areas in China. A thermal environment test for different types of buildings in Hainan and a thermal comfort field investigation of 1944 subjects were conducted over a period of about two months. The results of the survey data show that a high humidity environment did not have a significant impact on human comfort. The neutral temperature for the residents in <span class="hlt">tropical</span> island areas was 26.1 °C, and the acceptable temperature range of thermal comfort was from 23.1 °C to 29.1 °C. Residents living in <span class="hlt">tropical</span> island areas showed higher heat resistance capacity, but lower cold tolerance than predicted. The neutral temperature for females (26.3 °C) was higher than for males (25.8 °C). Additionally, females were more sensitive to air temperature than males. The research conclusions can play a guiding role in the thermal environment design of green buildings in Hainan Province. Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29898426','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29898426"><span>Resilience and reliability of compact vertical-flow treatment wetlands designed for <span class="hlt">tropical</span> <span class="hlt">climates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lombard-Latune, R; Pelus, L; Fina, N; L'Etang, F; Le Guennec, B; Molle, P</p> <p>2018-06-10</p> <p>Most of the <span class="hlt">tropical</span> areas have sanitation problems to contend with. The French system of vertical-flow treatment wetlands (FS-VFTW) fed with raw wastewater could be a good water and sludge management solution. The purpose-adapted <span class="hlt">tropical</span> design can reduce area requirement to below 1 m 2 /population equivalents (p.e.). The Taupinière FS-VFTW on Martinique Island was built according to this design, with one stage but with a saturated layer at the bottom of the filter and a simplified trickling filter (TF) added for further treatment to meet the high performances targeted. Unsaturated/saturated vertical-flow filters (US/S FS-VFTW) have shown improved performances on total nitrogen, carbon and suspended solids removal in temperate <span class="hlt">climates</span>, but the performances in <span class="hlt">tropical</span> conditions remain unknown. Here, we report on real-world-operation in the French Overseas Territories (FOT), the reliability and performances of this VFCW <span class="hlt">tropical</span>-design. The system experienced loading conditions ranging from 30% to 165% of nominal carbonaceous biological oxygen demand (BOD 5 ), as well as <span class="hlt">tropical</span> rainstorms that brought over 7 times the nominal hydraulic load. Over a period of 3 years, 29 campaigns collected 24-h flow-proportional samples at each treatment stage (raw wastewater, FS-VFTW outlet, TF outlet). When applied loads were close to nominal values, the US/S FS-VFTW itself guarantees 85/90/60/50% removal and 125/25/40/50 mg/L at the outlet for chemical oxygen demand (COD)/total suspended solids (TSS)/total Kjeldahl nitrogen (TKN)/total nitrogen (TN), respectively. By comparison with US/S systems in mainland France, it appears that the warmer <span class="hlt">tropical-climate</span> temperatures facilitate both nitrification and denitrification kinetics. Performances in overload conditions confirm that the US/S FS-VFTW remains robust and reliable although COD and TKN removal are impacted, especially after strong <span class="hlt">tropical</span> rain events. By adding a simple compact trickling filter to a US/S FS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP23D..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP23D..01H"><span><span class="hlt">Abrupt</span> <span class="hlt">Climate</span> Change in the Southern Great Plains during the Last Glacial Interval</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Housson, A. L.; Maupin, C. R.; Roark, B.; Shen, C. C.; Baykara, O.; White, K.; Kampen-Lewis, S. V.; McChesney, C. L.</p> <p>2016-12-01</p> <p>Understanding how the <span class="hlt">climate</span> of the North American Great Plains may change in the future is of tremendous socioeconomic importance, yet the regional response to previous <span class="hlt">abrupt</span> global <span class="hlt">climate</span> events, such as the Dansgaard-Oeschger (DO) cycles of the last glacial interval, are poorly known. Here we present two absolutely dated (U/Th), partially replicated oxygen isotope (δ18O) records from calcite speleothems in central Texas (30° N, 98° W) that grew during marine isotope stage 3 (MIS 3) (31 to 49 ky BP). The study site experiences boreal spring and fall maxima in precipitation with rainfall moisture sourced almost exclusively from the Gulf of Mexico. The two samples exhibit reproducible δ18O means and variability during overlapping growth intervals. Weak correlations between paired oxygen and carbon isotopic values coupled with reproducible δ18O strongly suggest that dripwater δ18O and calcite formation temperatures are the primary drivers of speleothem δ18O variations through time. We interpret more depleted (enriched) δ18O values to reconstruct warmer and wetter (cooler and drier) conditions based on observations of modern rainfall stable isotope variations at the study site. We find that warmer and wetter conditions in the Southern Plains are contemporaneous with MIS 3 DO interstadials, while cooler and more arid conditions prevail during stadials and Heinrich Events 4 and 5. Our results show a response opposite that of hydrologic reconstructions from the American Southwest, where wetter conditions occur with stadial conditions. Future work includes exploration of paleoclimate model results to examine potential mechanisms responsible for this opposite phasing. Our speleothem data indicate that further intensification of rainy seasons in the Southern Plains should not be ruled out as a response to anthropogenic global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15212097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15212097"><span>Sources or sinks? The responses of <span class="hlt">tropical</span> forests to current and future <span class="hlt">climate</span> and atmospheric composition.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Clark, Deborah A</p> <p>2004-03-29</p> <p>How <span class="hlt">tropical</span> rainforests are responding to the ongoing global changes in atmospheric composition and <span class="hlt">climate</span> is little studied and poorly understood. Although rising atmospheric carbon dioxide (CO2) could enhance forest productivity, increased temperatures and drought are likely to diminish it. The limited field data have produced conflicting views of the net impacts of these changes so far. One set of studies has seemed to point to enhanced carbon uptake; however, questions have arisen about these findings, and recent experiments with <span class="hlt">tropical</span> forest trees indicate carbon saturation of canopy leaves and no biomass increase under enhanced CO2. Other field observations indicate decreased forest productivity and increased tree mortality in recent years of peak temperatures and drought (strong El Niño episodes). To determine current <span class="hlt">climatic</span> responses of forests around the world <span class="hlt">tropics</span> will require careful annual monitoring of ecosystem performance in representative forests. To develop the necessary process-level understanding of these responses will require intensified experimentation at the whole-tree and stand levels. Finally, a more complete understanding of <span class="hlt">tropical</span> rainforest carbon cycling is needed for determining whether these ecosystems are carbon sinks or sources now, and how this status might change during the next century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.3011C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.3011C"><span>Timeslice experiments for understanding regional <span class="hlt">climate</span> projections: applications to the <span class="hlt">tropical</span> hydrological cycle and European winter circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chadwick, Robin; Douville, Hervé; Skinner, Christopher B.</p> <p>2017-11-01</p> <p>A set of atmosphere-only timeslice experiments are described, designed to examine the processes that cause regional <span class="hlt">climate</span> change and inter-model uncertainty in coupled <span class="hlt">climate</span> model responses to CO_2 forcing. The timeslice experiments are able to reproduce the pattern of regional <span class="hlt">climate</span> change in the coupled models, and are applied here to two cases where inter-model uncertainty in future projections is large: the <span class="hlt">tropical</span> hydrological cycle, and European winter circulation. In <span class="hlt">tropical</span> forest regions, the plant physiological effect is the largest cause of hydrological cycle change in the two models that represent this process. This suggests that the CMIP5 ensemble mean may be underestimating the magnitude of water cycle change in these regions, due to the inclusion of models without the plant effect. SST pattern change is the dominant cause of precipitation and circulation change over the <span class="hlt">tropical</span> oceans, and also appears to contribute to inter-model uncertainty in precipitation change over <span class="hlt">tropical</span> land regions. Over Europe and the North Atlantic, uniform SST increases drive a poleward shift of the storm-track. However this does not consistently translate into an overall polewards storm-track shift, due to large circulation responses to SST pattern change, which varies across the models. Coupled model SST biases influence regional rainfall projections in regions such as the Maritime Continent, and so projections in these regions should be treated with caution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22919908','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22919908"><span>Extrinsic regime shifts drive <span class="hlt">abrupt</span> changes in regeneration dynamics at upper treeline in the Rocky Mountains, U.S.A.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Elliott, Grant P</p> <p>2012-07-01</p> <p>Given the widespread and often dramatic influence of <span class="hlt">climate</span> change on terrestrial ecosystems, it is increasingly common for <span class="hlt">abrupt</span> threshold changes to occur, yet explicitly testing for <span class="hlt">climate</span> and ecological regime shifts is lacking in <span class="hlt">climatically</span> sensitive upper treeline ecotones. In this study, quantitative evidence based on empirical data is provided to support the key role of extrinsic, <span class="hlt">climate</span>-induced thresholds in governing the spatial and temporal patterns of tree establishment in these high-elevation environments. Dendroecological techniques were used to reconstruct a 420-year history of regeneration dynamics within upper treeline ecotones along a latitudinal gradient (approximately 44-35 degrees N) in the Rocky Mountains. Correlation analysis was used to assess the possible influence of minimum and maximum temperature indices and cool-season (November-April) precipitation on regional age-structure data. Regime-shift analysis was used to detect thresholds in tree establishment during the entire period of record (1580-2000), temperature variables significantly Correlated with establishment during the 20th century, and cool-season precipitation. Tree establishment was significantly correlated with minimum temperature during the spring (March-May) and cool season. Regime-shift analysis identified an <span class="hlt">abrupt</span> increase in regional tree establishment in 1950 (1950-1954 age class). Coincident with this period was a shift toward reduced cool-season precipitation. The alignment of these <span class="hlt">climate</span> conditions apparently triggered an <span class="hlt">abrupt</span> increase in establishment that was unprecedented during the period of record. Two main findings emerge from this research that underscore the critical role of <span class="hlt">climate</span> in governing regeneration dynamics within upper treeline ecotones. (1) Regional <span class="hlt">climate</span> variability is capable of exceeding bioclimatic thresholds, thereby initiating synchronous and <span class="hlt">abrupt</span> changes in the spatial and temporal patterns of tree establishment at broad</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008218','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008218"><span><span class="hlt">Tropical</span> Cyclones, Hurricanes, and <span class="hlt">Climate</span>: NASA's Global Cloud-Scale Simulations and New Observations that Characterize the Lifecycle of Hurricanes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Putman, William M.</p> <p>2010-01-01</p> <p>One of the primary interests of Global Change research is the impact of <span class="hlt">climate</span> changes and <span class="hlt">climate</span> variability on extreme weather events, such as intense <span class="hlt">tropical</span> storms and hurricanes. Atmospheric <span class="hlt">climate</span> models run at resolutions of global weather models have been used to study the impact of <span class="hlt">climate</span> variability, as seen in sea surface temperatures, on the frequency and intensity of <span class="hlt">tropical</span> cyclones. NASA's Goddard Earth Observing System Model, version 5 (GEOS-5) in ensembles run at 50 km resolution has been able to reproduce the interannual variations of <span class="hlt">tropical</span> cyclone frequency seen in nature. This, and other global models, have found it much more difficult to reproduce the interannual changes in intensity, a result that reflects the inability of the models to simulate the intensities of the most extreme storms. Better representation of the structures of cyclones requires much higher resolution models. Such improved representation is also fundamental to making best use of satellite observations. In collaboration with NOAA's Geophysical Fluid Dynamics Laboratory, GEOS-5 now has the capability of running at much higher resolution to better represent cloud-scale resolutions. Global simulations at cloud-permitting resolutions (10- to 3.5-km) allows for the development of realistic <span class="hlt">tropical</span> cyclones from <span class="hlt">tropical</span> storm 119 km/hr winds) to category 5 (>249km1hr winds) intensities. GEOS-5 has produced realistic rain-band and eye-wall structures in <span class="hlt">tropical</span> cyclones that can be directly analyzed against satellite observations. For the first time a global <span class="hlt">climate</span> model is capable of representing realistic intensity and track variability on a seasonal scale across basins. GEOS-5 is also used in assimilation mode to test the impact of NASA's observations on <span class="hlt">tropical</span> cyclone forecasts. One such test, for <span class="hlt">tropical</span> cyclone Nargis in the Indian Ocean in May 2008, showed that observations from Atmospheric Infrared Sounder (AIRS) and the Advanced Microwave Sounding Unit</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...29P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...29P"><span>The response of land-falling <span class="hlt">tropical</span> cyclone characteristics to projected <span class="hlt">climate</span> change in northeast Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, Chelsea L.; Bruyère, Cindy L.; Mooney, Priscilla A.; Lynch, Amanda H.</p> <p>2018-01-01</p> <p>Land-falling <span class="hlt">tropical</span> cyclones along the Queensland coastline can result in serious and widespread damage. However, the effects of <span class="hlt">climate</span> change on cyclone characteristics such as intensity, trajectory, rainfall, and especially translation speed and size are not well-understood. This study explores the relative change in the characteristics of three case studies by comparing the simulated <span class="hlt">tropical</span> cyclones under current <span class="hlt">climate</span> conditions with simulations of the same systems under future <span class="hlt">climate</span> conditions. Simulations are performed with the Weather Research and Forecasting Model and environmental conditions for the future <span class="hlt">climate</span> are obtained from the Community Earth System Model using a pseudo global warming technique. Results demonstrate a consistent response of increasing intensity through reduced central pressure (by up to 11 hPa), increased wind speeds (by 5-10% on average), and increased rainfall (by up to 27% for average hourly rainfall rates). The responses of other characteristics were variable and governed by either the location and trajectory of the current <span class="hlt">climate</span> cyclone or the change in the steering flow. The cyclone that traveled furthest poleward encountered a larger <span class="hlt">climate</span> perturbation, resulting in a larger proportional increase in size, rainfall rate, and wind speeds. The projected monthly average change in the 500 mb winds with <span class="hlt">climate</span> change governed the alteration in the both the trajectory and translation speed for each case. The simulated changes have serious implications for damage to coastal settlements, infrastructure, and ecosystems through increased wind speeds, storm surge, rainfall, and potentially increased size of some systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/000275.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/000275.htm"><span><span class="hlt">Tropical</span> sprue</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... than avoiding living in or traveling to <span class="hlt">tropical</span> <span class="hlt">climates</span>, there is no known prevention for <span class="hlt">tropical</span> sprue. ... Clinical Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP41E..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP41E..02B"><span>The <span class="hlt">Abrupt</span> Onset of the Modern South Asian Monsoon Winds (iodp Exp. 359)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Betzler, C.; Eberli, G. P.; Kroon, D.; Wright, J. D.; Swart, P. K.; Nath, B. N.; Reijmer, J.; Alvarez Zarikian, C. A.</p> <p>2016-12-01</p> <p>The South Asian Monson (SAM) is one of the most extreme features in Earth's <span class="hlt">climate</span> system, yet its initiation and variations are not well established. The SAM is a seasonal reversal of winds accompanied by changes in precipitation with heavy rain during the summer monsoon. It is one of the most intense annually recurring <span class="hlt">climatic</span> elements and of immense importance in supplying moisture to the Indian subcontinent thus affecting human population and vegetation, as well as marine biota in the surrounding seas. The seasonal precipitation change is one of the SAM elements most noticed on land, whereas the reversal of the wind regime is the dominating driver of circulation in the central and northern Indian Ocean realm. New data acquired during International Ocean Discovery Program Expedition 359 from the Inner Sea of the Maldives provide a previously unread archive that reveals an <span class="hlt">abrupt</span> onset of the SAM-linked ocean circulation pattern and its relationship to the long term Neogene <span class="hlt">climate</span> cooling. In particular it registers ocean current fluctuations and changes of intermediate water mass properties for the last 25 myrs that are directly related to the monsoon. Dating the deposits of SAM wind-driven currents yields an age of 12.9 Ma indicating an <span class="hlt">abrupt</span> SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of sedimentary organic matter. A weaker `proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. <span class="hlt">Abrupt</span> SAM initiation favors a strong influence of <span class="hlt">climate</span> in addition to the tectonic control, and we propose that the post Miocene <span class="hlt">Climate</span> Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMED41A0695B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMED41A0695B"><span>The Relationship Between <span class="hlt">Tropical</span> Cyclone Frequency and '<span class="hlt">Climate</span> Change'</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bolton, M.; Mogil, M.</p> <p>2013-12-01</p> <p>Please note: there have been minor updates to this work since the main author, Matt Bolton, graduated high school, but the majority of the research was compiled by him while he was a high school junior in 2011. Abstract: In recent years, there has been a growing trend by many, in the meteorological community (media and scientist) to predict expected seasonal <span class="hlt">tropical</span> cyclone frequency in the Atlantic and Pacific Basins. Typically, the numbers are related to seasonal averages. However, these predictions often show a large positive bias (i.e., there are more years in which the expected number of storms exceeds or far exceeds average). Further, observed numbers often come close to bearing out the forecasts (actually a good thing). From a public perspective (and based on extrapolations performed by media and some scientific groups), this peaking of Atlantic <span class="hlt">tropical</span> cyclone activity is observed globally. In an attempt to determine if such a global trend exists, we set out to collect data from weather agencies around the world and present it in a way that was as unbiased as possible. While there were inconsistencies across the various datasets, especially in regard to wind data, we were still able to construct a realistic global cyclone database. We have concluded that high activity levels in one basin are often balanced by areas of low activity in others. The Atlantic - Eastern Pacific couplet is one such example. This paper will serve as an update to our previous 2011 paper, which introduced our efforts. At that time, we found, on average, 70 named <span class="hlt">tropical</span> cyclones worldwide. In both this and our original study, we did not address the issue of naming short-lived <span class="hlt">tropical</span> systems, which was found to be inconsistent across worldwide ocean basins. Our results suggest, that from a global <span class="hlt">climate</span> change perspective, a growing NUMBER of <span class="hlt">tropical</span> cyclones is NOT being observed. In the current iteration of our study, we are examining, at least preliminarily, global</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PalOc..32.1291M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PalOc..32.1291M"><span>The Role of African Dust in Atlantic <span class="hlt">Climate</span> During Heinrich Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murphy, L. N.; Goes, M.; Clement, A. C.</p> <p>2017-11-01</p> <p>Increased ice discharge in the North Atlantic is thought to cause a weakening, or collapse, of the Atlantic meridional overturning circulation (AMOC) during Heinrich events. Paleoclimate records indicate that these periods were marked by severe <span class="hlt">tropical</span> aridity and dustiness. Although the driver of these events is still under debate, large freshwater input is necessary for <span class="hlt">climate</span> models to simulate the magnitude, geographical extent, and <span class="hlt">abruptness</span> of these events, indicating that they may be missing feedbacks. We hypothesize that the dust-<span class="hlt">climate</span> feedback is one such feedback that has not been previously considered. Here we analyze the role of dust-<span class="hlt">climate</span> feedbacks on the AMOC by parameterizing the dust radiative effects in an intermediate complexity model and consider uncertainties due to wind stress forcing and the magnitude of both atmospheric dust loading and freshwater hosing. We simulate both stable and unstable AMOC regimes by changing the prescribed wind stress forcing. In the unstable regime, additional dust loading during Heinrich events cools and freshens the North Atlantic and <span class="hlt">abruptly</span> reduces the AMOC by 20% relative to a control simulation. In the stable regime, however, additional dust forcing alone does not alter the AMOC strength. Including both freshwater and dust forcing results in a cooling of the subtropical North Atlantic more comparable to proxy records than with freshwater forcing alone. We conclude that dust-<span class="hlt">climate</span> feedbacks may provide amplification to Heinrich cooling by further weakening AMOC and increasing North Atlantic sea ice coverage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24464954','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24464954"><span>Synchronous fire activity in the <span class="hlt">tropical</span> high Andes: an indication of regional <span class="hlt">climate</span> forcing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Román-Cuesta, R M; Carmona-Moreno, C; Lizcano, G; New, M; Silman, M; Knoke, T; Malhi, Y; Oliveras, I; Asbjornsen, H; Vuille, M</p> <p>2014-06-01</p> <p>Global <span class="hlt">climate</span> models suggest enhanced warming of the <span class="hlt">tropical</span> mid and upper troposphere, with larger temperature rise rates at higher elevations. Changes in fire activity are amongst the most significant ecological consequences of rising temperatures and changing hydrological properties in mountainous ecosystems, and there is a global evidence of increased fire activity with elevation. Whilst fire research has become popular in the <span class="hlt">tropical</span> lowlands, much less is known of the <span class="hlt">tropical</span> high Andean region (>2000 masl, from Colombia to Bolivia). This study examines fire trends in the high Andes for three ecosystems, the Puna, the Paramo and the Yungas, for the period 1982-2006. We pose three questions: (i) is there an increased fire response with elevation? (ii) does the El Niño- Southern Oscillation control fire activity in this region? (iii) are the observed fire trends human driven (e.g., human practices and their effects on fuel build-up) or <span class="hlt">climate</span> driven? We did not find evidence of increased fire activity with elevation but, instead, a quasicyclic and synchronous fire response in Ecuador, Peru and Bolivia, suggesting the influence of high-frequency <span class="hlt">climate</span> forcing on fire responses on a subcontinental scale, in the high Andes. ENSO variability did not show a significant relation to fire activity for these three countries, partly because ENSO variability did not significantly relate to precipitation extremes, although it strongly did to temperature extremes. Whilst ENSO did not individually lead the observed regional fire trends, our results suggest a <span class="hlt">climate</span> influence on fire activity, mainly through a sawtooth pattern of precipitation (increased rainfall before fire-peak seasons (t-1) followed by drought spells and unusual low temperatures (t0), which is particularly common where fire is carried by low fuel loads (e.g., grasslands and fine fuel). This <span class="hlt">climatic</span> sawtooth appeared as the main driver of fire trends, above local human influences and fuel build</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000072439','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000072439"><span>Significant Features Found in Simulated <span class="hlt">Tropical</span> <span class="hlt">Climates</span> Using a Cloud Resolving Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shie, C.-L.; Tao, W.-K.; Simpson, J.; Sui, C.-H.</p> <p>2000-01-01</p> <p>Cloud resolving model (CRM) has widely been used in recent years for simulations involving studies of radiative-convective systems and their role in determining the <span class="hlt">tropical</span> regional <span class="hlt">climate</span>. The growing popularity of CRMs usage can be credited for their inclusion of crucial and realistic features such like explicit cloud-scale dynamics, sophisticated microphysical processes, and explicit radiative-convective interaction. For example, by using a two-dimensional cloud model with radiative-convective interaction process, found a QBO-like (quasibiennial oscillation) oscillation of mean zonal wind that affected the convective system. Accordingly, the model-generated rain band corresponding to convective activity propagated in the direction of the low-level zonal mean winds; however, the precipitation became "localized" (limited within a small portion of the domain) as zonal mean winds were removed. Two other CRM simulations by S94 and Grabowski et al. (1996, hereafter G96), respectively that produced distinctive quasi-equilibrium ("<span class="hlt">climate</span>") states on both <span class="hlt">tropical</span> water and energy, i.e., a cold/dry state in S94 and a warm/wet state in G96, have later been investigated by T99. They found that the pattern of the imposed large-scale horizontal wind and the magnitude of the imposed surface fluxes were the two crucial mechanisms in determining the <span class="hlt">tropical</span> <span class="hlt">climate</span> states. The warm/wet <span class="hlt">climate</span> was found associated with prescribed strong surface winds, or with maintained strong vertical wind shears that well-organized convective systems prevailed. On the other hand, the cold/dry <span class="hlt">climate</span> was produced due to imposed weak surface winds and weak wind shears throughout a vertically mixing process by convection. In this study, considered as a sequel of T99, the model simulations to be presented are generally similar to those of T99 (where a detailed model setup can be found), except for a more detailed discussion along with few more simulated experiments. There are twelve major</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1916878P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1916878P"><span><span class="hlt">Climate</span> change projections for winter precipitation over <span class="hlt">Tropical</span> America using statistical downscaling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palomino-Lemus, Reiner; Córdoba-Machado, Samir; Quishpe-Vásquez, César; García-Valdecasas-Ojeda, Matilde; Raquel Gámiz-Fortis, Sonia; Castro-Díez, Yolanda; Jesús Esteban-Parra, María</p> <p>2017-04-01</p> <p>In this study the Principal Component Regression (PCR) method has been used as statistical downscaling technique for simulating boreal winter precipitation in <span class="hlt">Tropical</span> America during the period 1950-2010, and then for generating <span class="hlt">climate</span> change projections for 2071-2100 period. The study uses the Global Precipitation Climatology Centre (GPCC, version 6) data set over the <span class="hlt">Tropical</span> America region [30°N-30°S, 120°W-30°W] as predictand variable in the downscaling model. The mean monthly sea level pressure (SLP) from the National Center for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR reanalysis project), has been used as predictor variable, covering a more extended area [30°N-30°S, 180°W-30°W]. Also, the SLP outputs from 20 GCMs, taken from the Coupled Model Intercomparison Project (CMIP5) have been used. The model data include simulations with historical atmospheric concentrations and future projections for the representative concentration pathways RCP2.6, RCP4.5, and RCP8.5. The ability of the different GCMs to simulate the winter precipitation in the study area for present <span class="hlt">climate</span> (1971-2000) was analyzed by calculating the differences between the simulated and observed precipitation values. Additionally, the statistical significance at 95% confidence level of these differences has been estimated by means of the bilateral rank sum test of Wilcoxon-Mann-Whitney. Finally, to project winter precipitation in the area for the period 2071-2100, the downscaling model, recalibrated for the total period 1950-2010, was applied to the SLP outputs of the GCMs under the RCP2.6, RCP4.5, and RCP8.5 scenarios. The results show that, generally, for present <span class="hlt">climate</span> the statistical downscaling shows a high ability to faithfully reproduce the precipitation field, while the simulations performed directly by using not downscaled outputs of GCMs strongly distort the precipitation field. For future <span class="hlt">climate</span>, the projected predictions under the RCP4</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24457919','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24457919"><span>Are <span class="hlt">tropical</span> small mammals physiologically vulnerable to Arrhenius effects and <span class="hlt">climate</span> change?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lovegrove, Barry G; Canale, Cindy; Levesque, Danielle; Fluch, Gerhard; Reháková-Petrů, Milada; Ruf, Thomas</p> <p>2014-01-01</p> <p>There is some urgency in the necessity to incorporate physiological data into mechanistic, trait-based, demographic <span class="hlt">climate</span> change models. Physiological responses at the individual level provide the mechanistic link between environmental changes and individual performances and hence population dynamics. Here we consider the causal relationship between ambient temperature (Ta) and metabolic rate (MR), namely, the Arrhenius effect, which is directly affected by global warming through increases in average global air temperatures and the increase in the frequency and intensity of extreme <span class="hlt">climate</span> events. We measured and collated data for several small, free-ranging <span class="hlt">tropical</span> arboreal mammals and evaluated their vulnerability to Arrhenius effects and putative heat stress associated with <span class="hlt">climate</span> change. Skin temperatures (Tskin) were obtained from free-ranging tarsiers (Tarsius syrichta) on Bohol Island, Philippines. Core body temperature (Tb) was obtained from the greater hedgehog tenrec (Setifer setosus) and the gray brown mouse lemur (Microcebus ravelobensis) from Ankarafantsika, Madagascar. Tskin for another mouse lemur, Microcebus griseorufus, was obtained from the literature. All four species showed evidence of hyperthermia during the daytime rest phase in the form of either Tskin or Tb that was higher than the normothermic Tb during the nighttime active phase. Potentially, <span class="hlt">tropical</span> arboreal mammals with the lowest MRs and Tb, such as tarsiers, are the most vulnerable to sustained heat stress because their Tb is already close to Ta. <span class="hlt">Climate</span> change may involve increases in MRs due to Arrhenius effects, especially during the rest phase or during torpor and hibernation. The most likely outcome of increased Arrhenius effects with <span class="hlt">climate</span> change will be an increase in energy expenditure at the expense of other critical functions such as reproduction or growth and will thus affect fitness. However, we propose that these hypothetical Arrhenius costs can be, and in some</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4100510','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4100510"><span>The <span class="hlt">tropicalization</span> of temperate marine ecosystems: <span class="hlt">climate</span>-mediated changes in herbivory and community phase shifts</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vergés, Adriana; Steinberg, Peter D.; Hay, Mark E.; Poore, Alistair G. B.; Campbell, Alexandra H.; Ballesteros, Enric; Heck, Kenneth L.; Booth, David J.; Coleman, Melinda A.; Feary, David A.; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M.; Mizerek, Toni; Mumby, Peter J.; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A.; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K.</p> <p>2014-01-01</p> <p><span class="hlt">Climate</span>-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when <span class="hlt">tropical</span> fish herbivory decreases, and from algal forests to ‘barrens’ when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by <span class="hlt">tropical</span> herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of <span class="hlt">tropical</span> species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by <span class="hlt">tropical</span> herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of <span class="hlt">tropical</span> fishes on temperate reefs. PMID:25009065</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.5709H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.5709H"><span>Dynamic vegetation modeling of <span class="hlt">tropical</span> biomes during Heinrich events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Handiani, Dian Noor; Paul, André; Dupont, Lydie M.</p> <p>2010-05-01</p> <p>Heinrich events are thought to be associated with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC), which in turn would lead to a cooling of the North Atlantic Ocean and a warming of the South Atlantic Ocean (the "bipolar seesaw" hypothesis). The accompanying <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes occurred not only in the ocean but also on the continents. Changes were strongest in the Northern Hemisphere but were registered in the <span class="hlt">tropics</span> as well. Pollen data from Angola and Brazil showed that <span class="hlt">climate</span> changes during Heinrich events affected vegetation patterns very differently in eastern South America and western Africa. To understand the differential response in the terrestrial <span class="hlt">tropics</span>, we studied the vegetation changes during Heinrich events by using a dynamic global vegetation model (TRIFFID) as part of the University of Victoria (UVic) Earth System-<span class="hlt">Climate</span> Model (ESCM). The model results show a bipolar seesaw pattern in temperature and precipitation during a near-collapse of the AMOC. The succession in plant-functional types (PFTs) showed changes from forest to shrubs to desert, including spreading desert in northwest Africa, retreating broadleaf trees in West Africa and northern South America, but advancing broadleaf trees in Brazil. The pattern is explained by a southward shift of the <span class="hlt">tropical</span> rainbelt resulting in a strong decrease in precipitation over northwest and West Africa as well as in northern South America, but an increase in precipitation in eastern Brazil. To facilitate the comparison between modeled vegetation results with pollen data, we diagnosed the distribution of biomes from the PFT coverage and the simulated model <span class="hlt">climate</span>. The biome distribution was computed for Heinrich event 1 and the Last Glacial Maximum as well as for pre-industrial conditions. We used a classification of biomes in terms of "mega-biomes", which were defined following a scheme originally proposed by BIOME 6000 (v 4.2). The biome distribution of the Sahel region</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20180002900&hterms=ECS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DECS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20180002900&hterms=ECS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DECS"><span>Internal Variability and Disequilibrium Confound Estimates of <span class="hlt">Climate</span> Sensitivity from Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marvel, Kate; Pincus, Robert; Schmidt, Gavin A.; Miller, Ron L.</p> <p>2018-01-01</p> <p>An emerging literature suggests that estimates of equilibrium <span class="hlt">climate</span> sensitivity (ECS) derived from recent observations and energy balance models are biased low because models project more positive <span class="hlt">climate</span> feedback in the far future. Here we use simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to show that across models, ECS inferred from the recent historical period (1979-2005) is indeed almost uniformly lower than that inferred from simulations subject to <span class="hlt">abrupt</span> increases in CO2-radiative forcing. However, ECS inferred from simulations in which sea surface temperatures are prescribed according to observations is lower still. ECS inferred from simulations with prescribed sea surface temperatures is strongly linked to changes to <span class="hlt">tropical</span> marine low clouds. However, feedbacks from these clouds are a weak constraint on long-term model ECS. One interpretation is that observations of recent <span class="hlt">climate</span> changes constitute a poor direct proxy for long-term sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1595M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1595M"><span>Internal Variability and Disequilibrium Confound Estimates of <span class="hlt">Climate</span> Sensitivity From Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marvel, Kate; Pincus, Robert; Schmidt, Gavin A.; Miller, Ron L.</p> <p>2018-02-01</p> <p>An emerging literature suggests that estimates of equilibrium <span class="hlt">climate</span> sensitivity (ECS) derived from recent observations and energy balance models are biased low because models project more positive <span class="hlt">climate</span> feedback in the far future. Here we use simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to show that across models, ECS inferred from the recent historical period (1979-2005) is indeed almost uniformly lower than that inferred from simulations subject to <span class="hlt">abrupt</span> increases in CO2 radiative forcing. However, ECS inferred from simulations in which sea surface temperatures are prescribed according to observations is lower still. ECS inferred from simulations with prescribed sea surface temperatures is strongly linked to changes to <span class="hlt">tropical</span> marine low clouds. However, feedbacks from these clouds are a weak constraint on long-term model ECS. One interpretation is that observations of recent <span class="hlt">climate</span> changes constitute a poor direct proxy for long-term sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23966269','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23966269"><span>Consistent response of vegetation dynamics to recent <span class="hlt">climate</span> change in <span class="hlt">tropical</span> mountain regions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krishnaswamy, Jagdish; John, Robert; Joseph, Shijo</p> <p>2014-01-01</p> <p>Global <span class="hlt">climate</span> change has emerged as a major driver of ecosystem change. Here, we present evidence for globally consistent responses in vegetation dynamics to recent <span class="hlt">climate</span> change in the world's mountain ecosystems located in the pan-<span class="hlt">tropical</span> belt (30°N-30°S). We analyzed decadal-scale trends and seasonal cycles of vegetation greenness using monthly time series of satellite greenness (Normalized Difference Vegetation Index) and <span class="hlt">climate</span> data for the period 1982-2006 for 47 mountain protected areas in five biodiversity hotspots. The time series of annual maximum NDVI for each of five continental regions shows mild greening trends followed by reversal to stronger browning trends around the mid-1990s. During the same period we found increasing trends in temperature but only marginal change in precipitation. The amplitude of the annual greenness cycle increased with time, and was strongly associated with the observed increase in temperature amplitude. We applied dynamic models with time-dependent regression parameters to study the time evolution of NDVI-<span class="hlt">climate</span> relationships. We found that the relationship between vegetation greenness and temperature weakened over time or was negative. Such loss of positive temperature sensitivity has been documented in other regions as a response to temperature-induced moisture stress. We also used dynamic models to extract the trends in vegetation greenness that remain after accounting for the effects of temperature and precipitation. We found residual browning and greening trends in all regions, which indicate that factors other than temperature and precipitation also influence vegetation dynamics. Browning rates became progressively weaker with increase in elevation as indicated by quantile regression models. <span class="hlt">Tropical</span> mountain vegetation is considered sensitive to <span class="hlt">climatic</span> changes, so these consistent vegetation responses across widespread regions indicate persistent global-scale effects of <span class="hlt">climate</span> warming and associated moisture</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ESD.....9..285T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ESD.....9..285T"><span>Sensitivity of the <span class="hlt">tropical</span> <span class="hlt">climate</span> to an interhemispheric thermal gradient: the role of <span class="hlt">tropical</span> ocean dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talento, Stefanie; Barreiro, Marcelo</p> <p>2018-03-01</p> <p>This study aims to determine the role of the <span class="hlt">tropical</span> ocean dynamics in the response of the <span class="hlt">climate</span> to extratropical thermal forcing. We analyse and compare the outcomes of coupling an atmospheric general circulation model (AGCM) with two ocean models of different complexity. In the first configuration the AGCM is coupled with a slab ocean model while in the second a reduced gravity ocean (RGO) model is additionally coupled in the <span class="hlt">tropical</span> region. We find that the imposition of extratropical thermal forcing (warming in the Northern Hemisphere and cooling in the Southern Hemisphere with zero global mean) produces, in terms of annual means, a weaker response when the RGO is coupled, thus indicating that the <span class="hlt">tropical</span> ocean dynamics oppose the incoming remote signal. On the other hand, while the slab ocean coupling does not produce significant changes to the equatorial Pacific sea surface temperature (SST) seasonal cycle, the RGO configuration generates strong warming in the central-eastern basin from April to August balanced by cooling during the rest of the year, strengthening the seasonal cycle in the eastern portion of the basin. We hypothesize that such changes are possible via the dynamical effect that zonal wind stress has on the thermocline depth. We also find that the imposed extratropical pattern affects El Niño-Southern Oscillation, weakening its amplitude and low-frequency behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/54123','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/54123"><span>Modeled effects of <span class="hlt">climate</span> change and plant invasion on watershed function across a steep <span class="hlt">tropical</span> rainfall gradient</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Ayron M. Strauch; Christian P. Giardina; Richard A. MacKenzie; Chris Heider; Tom W. Giambelluca; Ed Salminen; Gregory L. Bruland</p> <p>2017-01-01</p> <p><span class="hlt">Climate</span> change is anticipated to affect freshwater resources, but baseline data on the functioning of <span class="hlt">tropical</span> watersheds is lacking, limiting efforts that seek to predict how watershed processes, water supply, and streamflow respond to anticipated changes in <span class="hlt">climate</span> and vegetation change, and to management. To address this data gap, we applied the distributed...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GPC....72..390B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GPC....72..390B"><span>Cenozoic vegetation, <span class="hlt">climate</span> changes and hominid evolution in <span class="hlt">tropical</span> Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonnefille, Raymonde</p> <p>2010-07-01</p> <p> Ma in East Africa, 3 Ma earlier than in West Africa where it is documented at 7 Ma. At large geographical scale, this first increase in grass pollen simultaneously to forest increase in the marine records is interpreting as reflecting wetter conditions over the continent. Indeed, under global humid conditions, savanna could spread over the desert areas in the Northern and Eastern directions. A forest phase is well documented in West Africa between 7.5 and 7 Ma, but has not been shown in East Africa, mainly because of low resolution analysis of the DSDP East African record which needs further investigation for that period. A strong vegetation change took place between 6.3 and 6 Ma. It was marked by a trend of important decrease tree cover of the vegetation, simultaneous in West and East Africa. At that time, very arid conditions shown by scarce tree cover occurred over the whole <span class="hlt">tropical</span> region. This happened before (or at) the early beginning of the Messinian crisis. Generally arid conditions coincide with the accepted timing for the Chimpanzee/hominid split, and record of Sahelanthropus tchadensis in Chad and Orrorin tugenensis in Kenya, although these fossils were found under locally wooded environment. The period from 6 to 4 Ma saw the appearance of Ardipithecus and diversification of Australopithecines occurring during a progressive increased tree cover in the broad-scale vegetation that culminated at 3.9 Ma, during A. anamensis time and before the first appearance of Australopithecus afarensis. Important variations in the vegetation occurred between 4 and 3 Ma, and many plant ecosystems were available to A.afarensis, a hominid which had a wide geographical distribution and persisted at Hadar under temporal <span class="hlt">climatic</span> and environmental variability. The strongest and <span class="hlt">abrupt</span> decline of forest pollen accompanied by an increase in the grass pollen was found at 2.7 Ma, more pronounced in the West than in East Africa. It was accompanied by a significant increase in C 4</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25009065','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25009065"><span>The <span class="hlt">tropicalization</span> of temperate marine ecosystems: <span class="hlt">climate</span>-mediated changes in herbivory and community phase shifts.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vergés, Adriana; Steinberg, Peter D; Hay, Mark E; Poore, Alistair G B; Campbell, Alexandra H; Ballesteros, Enric; Heck, Kenneth L; Booth, David J; Coleman, Melinda A; Feary, David A; Figueira, Will; Langlois, Tim; Marzinelli, Ezequiel M; Mizerek, Toni; Mumby, Peter J; Nakamura, Yohei; Roughan, Moninya; van Sebille, Erik; Gupta, Alex Sen; Smale, Dan A; Tomas, Fiona; Wernberg, Thomas; Wilson, Shaun K</p> <p>2014-08-22</p> <p><span class="hlt">Climate</span>-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when <span class="hlt">tropical</span> fish herbivory decreases, and from algal forests to 'barrens' when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by <span class="hlt">tropical</span> herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of <span class="hlt">tropical</span> species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by <span class="hlt">tropical</span> herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of <span class="hlt">tropical</span> fishes on temperate reefs. © 2014 The Author(s) Published by the Royal Society. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP31B1630S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP31B1630S"><span>New insights into deglacial <span class="hlt">climate</span> variability in <span class="hlt">tropical</span> South America from molecular fossil and isotopic indicators in Lake Titicaca</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shanahan, T. M.; Hughen, K. A.; Fornace, K.; Baker, P. A.; Fritz, S. C.</p> <p>2010-12-01</p> <p>As one of the main centers of <span class="hlt">tropical</span> convection, the South American Altiplano plays a crucial role in the long-term <span class="hlt">climate</span> variability of South America. However, both the timing and the drivers of <span class="hlt">climate</span> variability on orbital to millennial timescales remain poorly understood for this region. New data from molecular fossil (e.g., TEX86) and compound specific hydrogen isotope (D/H) analyses provide new insights into the <span class="hlt">climate</span> evolution of this region over the last ~50 kyr. TEX86 temperature reconstructions suggest that the Altiplano warmed as early as 19- 21 kyr ago and proceeded rapidly, consistent with published evidence for an early retreat of LGM glaciers at this time at some locations. The early warming signal observed at Lake Titicaca also appears to be synchronous with continental temperature reconstructions at some sites in <span class="hlt">tropical</span> Africa, but leads <span class="hlt">tropical</span> SST changes by several thousands of years. Although the initiation of warming coincided with the peak in southern hemisphere summer insolation, subsequent temperature increases were accompanied by decreases in southern hemisphere insolation, suggesting a northern hemisphere driver for temperature changes in <span class="hlt">tropical</span> South America. Preliminary D/H ratios from leaf waxes appear to support existing data suggesting that wet conditions prevailed until the late glacial/early Holocene and are broadly consistent with local southern hemisphere summer insolation forcing of the summer monsoon. These data suggest that temperature and precipitation changes during the last deglaciation were decoupled and that both local and extratropical drivers are important for controlling <span class="hlt">climate</span> change in this region on orbital timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP21A1885P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP21A1885P"><span><span class="hlt">Tropical</span> North Atlantic subsurface temperature anomalies: evidence for AMOC variability across Dansgaard-Oscheger events?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, A. O.; Schmidt, M. W.; Chang, P.</p> <p>2013-12-01</p> <p>A common mechanism often proposed to explain the <span class="hlt">abrupt</span> <span class="hlt">climate</span> events of Marine Isotope Stage 3 (MIS 3), known as Dansgaard-Oscheger (D-O) cycles, invokes variability in the strength of the Atlantic Meridional Overturning Circulation (AMOC). Although proxy evidence shows that D-O cycles resulted in large-scale changes in atmospheric circulation patterns around the planet, an understanding of how the AMOC varied across these events remains unclear. Coupled ocean-atmosphere models demonstrate that AMOC variability is linked to <span class="hlt">abrupt</span> change in the <span class="hlt">tropical</span> North Atlantic (TNA) through both oceanic and atmospheric processes. A reduction in AMOC causes a subsurface oceanic warming in the TNA as the western boundary current slows, allowing the warm salinity maximum waters to enter the deep <span class="hlt">tropics</span>. Recently, Schmidt et al. (2012) identified an <span class="hlt">abrupt</span> subsurface warming at the onset of AMOC slow down during both Heinrich 1 and the Younger Dryas, suggesting this signal may be a robust feature of AMOC variability in the TNA. In order to determine if AMOC variability was the driver of D-O cycles during MIS 3, we present new, high-resolution Mg/Ca and δ18O records from the near-surface dwelling planktonic foraminifera G. ruber and the lower-thermocline dwelling planktonic foraminifera G. crassaformis from 22 - 52 ka BP in southern Caribbean core VM12-107 (11.33oN, 66.63oW, 1079m depth). Sedimentation rates in VM12-107 average 24cm/kyr, providing high temporal resolution able to resolve millennial-scale events. The G. ruber δ18O record shows <span class="hlt">abrupt</span> oscillations up to 1‰ as well as Mg/Ca-based SST changes of 1.5 - 2oC that are synchronous with some D-O cycles recorded in the Greenland ice cores. Given our ability to resolve D-O cycles in the planktonic record, we find that Mg/Ca ratios from G. crassaformis were, on average, 0.13 × 0.04 mmol/mol higher during stadials. This equates to a temperature increase during stadials of up to 1.5oC. These results imply that AMOC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1366588-objective-tropical-cyclone-extratropical-transition-detection-high-resolution-reanalysis-climate-model-data','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1366588-objective-tropical-cyclone-extratropical-transition-detection-high-resolution-reanalysis-climate-model-data"><span>Objective <span class="hlt">tropical</span> cyclone extratropical transition detection in high-resolution reanalysis and <span class="hlt">climate</span> model data</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Zarzycki, Colin M.; Thatcher, Diana R.; Jablonowski, Christiane</p> <p>2017-01-22</p> <p>This paper describes an objective technique for detecting the extratropical transition (ET) of <span class="hlt">tropical</span> cyclones (TCs) in high-resolution gridded <span class="hlt">climate</span> data. The algorithm is based on previous observational studies using phase spaces to define the symmetry and vertical thermal structure of cyclones. Storm tracking is automated, allowing for direct analysis of <span class="hlt">climate</span> data. Tracker performance in the North Atlantic is assessed using 23 years of data from the variable-resolution Community Atmosphere Model (CAM) at two different resolutions (DX 55 km and 28 km), the <span class="hlt">Climate</span> Forecast System Reanalysis (CFSR, DX 38 km), and the ERA-Interim Reanalysis (ERA-I, DX 80 km).more » The mean spatiotemporal climatologies and seasonal cycles of objectively detected ET in the observationally constrained CFSR and ERA-I are well matched to previous observational studies, demonstrating the capability of the scheme to adequately find events. High resolution CAM reproduces TC and ET statistics that are in general agreement with reanalyses. One notable model bias, however, is significantly longer time between ET onset and ET completion in CAM, particularly for TCs that lose symmetry prior to developing a cold-core structure and becoming extratropical cyclones, demonstrating the capability of this method to expose model biases in simulated cyclones beyond the <span class="hlt">tropical</span> phase.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018IJBm..tmp...74R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018IJBm..tmp...74R"><span>Thermoregulatory responses and reproductive traits in composite beef bulls raised in a <span class="hlt">tropical</span> <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Romanello, Narian; de Brito Lourenço Junior, José; Barioni Junior, Waldomiro; Brandão, Felipe Zandonadi; Marcondes, Cintia Righetti; Pezzopane, José Ricardo Macedo; de Andrade Pantoja, Messy Hannear; Botta, Daniela; Giro, Alessandro; Moura, Ana Beatriz Bossois; do Nascimento Barreto, Andréa; Garcia, Alexandre Rossetto</p> <p>2018-05-01</p> <p>It is believed that increased livestock production is limited by <span class="hlt">tropical</span> <span class="hlt">climate</span>. Thermal imbalance in bulls can lead to hyperthermia and alter testicular metabolism, causing subfertility or infertility. Therefore, the thermoregulation of composite Canchim bulls (5/8 Charolais × 3/8 Zebu) raised in <span class="hlt">tropical</span> <span class="hlt">climate</span> as well as their consequences in the physiological, hematological, hormonal, and andrological parameters were evaluated monthly. The bulls (n = 18; 30.0 ± 1.5 months; 503.8 ± 23.0 kg) were kept on pasture, in a single group, from August 2015 to March 2016, comprising the winter, spring, and summer seasons. Biometeorological variables were continuously monitored, and the Temperature and Humidity Index (THI) was calculated. A greater thermal challenge occurred in spring and summer (THI ≥ 72.0). Nevertheless, the bulls exhibited normothermia (38.6 to 38.9 °C) in these seasons. The cortisol did not vary between seasons (7.0 vs. 8.7 vs. 6.8 ng/mL; P > 0.05) and remained within the physiological patterns. Independent of the seasons, stress leukogram was also not observed, refuting the incidence of acute or chronic thermal stress. It is noteworthy that T3 and testosterone increased (P < 0.0001, P < 0.05) in spring and summer, the time that coincides with the breeding season, when there is increased metabolic requirement from the bulls. The progressive thermal challenge increase did not affect the scrotal thermoregulatory capacity, and in general, scrotal temperature remained at 5.2 °C below the internal body temperature. In summer, there was a 5% reduction in the minor sperm defects (P < 0.05) and DNA fragmentation in 2.4% of spermatozoa, a compatible value for high fertility bulls. The results show that the studied composite bulls can be considered as <span class="hlt">climatically</span> adapted and constitute a viable alternative to be used in production systems in a <span class="hlt">tropical</span> <span class="hlt">climate</span>, even if the breeding seasons occur during the most critical thermal condition periods of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5095186','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5095186"><span>Extinction debt from <span class="hlt">climate</span> change for frogs in the wet <span class="hlt">tropics</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brook, Barry W.; Hoskin, Conrad J.; Pressey, Robert L.; VanDerWal, Jeremy; Williams, Stephen E.</p> <p>2016-01-01</p> <p>The effect of twenty-first-century <span class="hlt">climate</span> change on biodiversity is commonly forecast based on modelled shifts in species ranges, linked to habitat suitability. These projections have been coupled with species–area relationships (SAR) to infer extinction rates indirectly as a result of the loss of <span class="hlt">climatically</span> suitable areas and associated habitat. This approach does not model population dynamics explicitly, and so accepts that extinctions might occur after substantial (but unknown) delays—an extinction debt. Here we explicitly couple bioclimatic envelope models of <span class="hlt">climate</span> and habitat suitability with generic life-history models for 24 species of frogs found in the Australian Wet <span class="hlt">Tropics</span> (AWT). We show that (i) as many as four species of frogs face imminent extinction by 2080, due primarily to <span class="hlt">climate</span> change; (ii) three frogs face delayed extinctions; and (iii) this extinction debt will take at least a century to be realized in full. Furthermore, we find congruence between forecast rates of extinction using SARs, and demographic models with an extinction lag of 120 years. We conclude that SAR approaches can provide useful advice to conservation on <span class="hlt">climate</span> change impacts, provided there is a good understanding of the time lags over which delayed extinctions are likely to occur. PMID:27729484</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27729484','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27729484"><span>Extinction debt from <span class="hlt">climate</span> change for frogs in the wet <span class="hlt">tropics</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fordham, Damien A; Brook, Barry W; Hoskin, Conrad J; Pressey, Robert L; VanDerWal, Jeremy; Williams, Stephen E</p> <p>2016-10-01</p> <p>The effect of twenty-first-century <span class="hlt">climate</span> change on biodiversity is commonly forecast based on modelled shifts in species ranges, linked to habitat suitability. These projections have been coupled with species-area relationships (SAR) to infer extinction rates indirectly as a result of the loss of <span class="hlt">climatically</span> suitable areas and associated habitat. This approach does not model population dynamics explicitly, and so accepts that extinctions might occur after substantial (but unknown) delays-an extinction debt. Here we explicitly couple bioclimatic envelope models of <span class="hlt">climate</span> and habitat suitability with generic life-history models for 24 species of frogs found in the Australian Wet <span class="hlt">Tropics</span> (AWT). We show that (i) as many as four species of frogs face imminent extinction by 2080, due primarily to <span class="hlt">climate</span> change; (ii) three frogs face delayed extinctions; and (iii) this extinction debt will take at least a century to be realized in full. Furthermore, we find congruence between forecast rates of extinction using SARs, and demographic models with an extinction lag of 120 years. We conclude that SAR approaches can provide useful advice to conservation on <span class="hlt">climate</span> change impacts, provided there is a good understanding of the time lags over which delayed extinctions are likely to occur. © 2016 The Author(s).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010CliPD...6.2687H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010CliPD...6.2687H"><span>Modeling geologically <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes in the Miocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haupt, B. J.; Seidov, D.</p> <p>2010-12-01</p> <p>The gradual cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically <span class="hlt">abrupt</span> warming and cooling episodes - strong deviations from the cooling trend with time span of ten to hundred thousands of years. Our working hypothesis is that some of those warming episodes at least partially might have been caused by dynamics of the emerging Antarctic Ice Sheet, which, in turn, might have caused strong changes of sea surface salinity in the Miocene Southern Ocean. Feasibility of this hypothesis is explored in a series of coupled ocean-atmosphere computer experiments. The results suggest that relatively small and geologically short-lived changes in freshwater balance in the Southern Ocean could have significantly contributed to at least two prominent warming episodes in the Miocene. Importantly, the experiments also suggest that the Southern Ocean was more sensitive to the salinity changes in the Miocene than today, which can attributed to the opening of the Central American Isthmus as a major difference between the Miocene and the present-day ocean-sea geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23661358','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23661358"><span>The impact of <span class="hlt">climate</span> change measured at relevant spatial scales: new hope for <span class="hlt">tropical</span> lizards.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Logan, Michael L; Huynh, Ryan K; Precious, Rachel A; Calsbeek, Ryan G</p> <p>2013-10-01</p> <p>Much attention has been given to recent predictions that widespread extinctions of <span class="hlt">tropical</span> ectotherms, and <span class="hlt">tropical</span> forest lizards in particular, will result from anthropogenic <span class="hlt">climate</span> change. Most of these predictions, however, are based on environmental temperature data measured at a maximum resolution of 1 km(2), whereas individuals of most species experience thermal variation on a much finer scale. To address this disconnect, we combined thermal performance curves for five populations of Anolis lizard from the Bay Islands of Honduras with high-resolution temperature distributions generated from physical models. Previous research has suggested that open-habitat species are likely to invade forest habitat and drive forest species to extinction. We test this hypothesis, and compare the vulnerabilities of closely related, but allopatric, forest species. Our data suggest that the open-habitat populations we studied will not invade forest habitat and may actually benefit from predicted warming for many decades. Conversely, one of the forest species we studied should experience reduced activity time as a result of warming, while two others are unlikely to experience a significant decline in performance. Our results suggest that global-scale predictions generated using low-resolution temperature data may overestimate the vulnerability of many <span class="hlt">tropical</span> ectotherms to <span class="hlt">climate</span> change. © 2013 John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CliPD...8.2819H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CliPD...8.2819H"><span><span class="hlt">Climate</span> and vegetation changes around the Atlantic Ocean resulting from changes in the meridional overturning circulation during deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Handiani, D.; Paul, A.; Dupont, L.</p> <p>2012-07-01</p> <p>The Bølling-Allerød (BA, starting ~ 14.5 ka BP) is one of the most pronounced <span class="hlt">abrupt</span> warming periods recorded in ice and pollen proxies. The leading explanation of the cause of this warming is a sudden increase in the rate of deepwater formation in the North Atlantic Ocean and the resulting effect on the heat transport by the Atlantic Meridional Overturning Circulation (AMOC). In this study, we used the University of Victoria (UVic) Earth System-<span class="hlt">Climate</span> Model (ESCM) to run simulations, in which a freshwater perturbation initiated a BA-like warming period. We found that under present <span class="hlt">climate</span> conditions, the AMOC intensified when freshwater was added to the Southern Ocean. However, under Heinrich event 1 (HE1, ~ 16 ka BP) <span class="hlt">climate</span> conditions, the AMOC only intensified when freshwater was extracted from the North Atlantic Ocean, possibly corresponding to an increase in evaporation or a decrease in precipitation in this region. The intensified AMOC led to a warming in the North Atlantic Ocean and a cooling in the South Atlantic Ocean, resembling the bipolar seesaw pattern typical of the last glacial period. In addition to the physical response, we also studied the simulated vegetation response around the Atlantic Ocean region. Corresponding with the bipolar seesaw hypothesis, the rainbelt associated with the Intertropical Convergence Zone (ITCZ) shifted northward and affected the vegetation pattern in the <span class="hlt">tropics</span>. The most sensitive vegetation area was found in <span class="hlt">tropical</span> Africa, where grass cover increased and tree cover decreased under dry <span class="hlt">climate</span> conditions. An equal but opposite response to the collapse and recovery of the AMOC implied that the change in vegetation cover was transient and robust to an <span class="hlt">abrupt</span> <span class="hlt">climate</span> change such as during the BA period, which is also supported by paleovegetation data. The results are in agreement with paleovegetation records from Western <span class="hlt">tropical</span> Africa, which also show a reduction in forest cover during this time period. Further</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1092643-climate-model-response-from-geoengineering-model-intercomparison-project-geomip','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1092643-climate-model-response-from-geoengineering-model-intercomparison-project-geomip"><span><span class="hlt">Climate</span> Model Response from the Geoengineering Model Intercomparison Project (GeoMIP)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kravitz, Benjamin S.; Caldeira, Ken; Boucher, Olivier</p> <p>2013-08-09</p> <p>Solar geoengineering—deliberate reduction in the amount of solar radiation retained by the Earth—has been proposed as a means of counteracting some of the <span class="hlt">climatic</span> effects of anthropogenic greenhouse gas emissions. We present results from Experiment G1 of the Geoengineering Model Intercomparison Project, in which 12 <span class="hlt">climate</span> models have simulated the <span class="hlt">climate</span> response to an <span class="hlt">abrupt</span> quadrupling of CO2 from preindustrial concentrations brought into radiative balance via a globally uniform reduction in insolation. Models show this reduction largely offsets global mean surface temperature increases due to quadrupled CO2 concentrations and prevents 97% of the Arctic sea ice loss that would otherwisemore » occur under high CO2 levels but, compared to the preindustrial <span class="hlt">climate</span>, leaves the <span class="hlt">tropics</span> cooler (-0.3 K) and the poles warmer (+0.8 K). Annual mean precipitation minus evaporation anomalies for G1 are less than 0.2mmday-1 in magnitude over 92% of the globe, but some <span class="hlt">tropical</span> regions receive less precipitation, in part due to increased moist static stability and suppression of convection. Global average net primary productivity increases by 120% in G1 over simulated preindustrial levels, primarily from CO2 fertilization, but also in part due to reduced plant heat stress compared to a high CO2 world with no geoengineering. All models show that uniform solar geoengineering in G1 cannot simultaneously return regional and global temperature and hydrologic cycle intensity to preindustrial levels.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRD..118.8320K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRD..118.8320K"><span><span class="hlt">Climate</span> model response from the Geoengineering Model Intercomparison Project (GeoMIP)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kravitz, Ben; Caldeira, Ken; Boucher, Olivier; Robock, Alan; Rasch, Philip J.; Alterskjær, Kari; Karam, Diana Bou; Cole, Jason N. S.; Curry, Charles L.; Haywood, James M.; Irvine, Peter J.; Ji, Duoying; Jones, Andy; Kristjánsson, Jón Egill; Lunt, Daniel J.; Moore, John C.; Niemeier, Ulrike; Schmidt, Hauke; Schulz, Michael; Singh, Balwinder; Tilmes, Simone; Watanabe, Shingo; Yang, Shuting; Yoon, Jin-Ho</p> <p>2013-08-01</p> <p>geoengineering—deliberate reduction in the amount of solar radiation retained by the Earth—has been proposed as a means of counteracting some of the <span class="hlt">climatic</span> effects of anthropogenic greenhouse gas emissions. We present results from Experiment G1 of the Geoengineering Model Intercomparison Project, in which 12 <span class="hlt">climate</span> models have simulated the <span class="hlt">climate</span> response to an <span class="hlt">abrupt</span> quadrupling of CO2 from preindustrial concentrations brought into radiative balance via a globally uniform reduction in insolation. Models show this reduction largely offsets global mean surface temperature increases due to quadrupled CO2 concentrations and prevents 97% of the Arctic sea ice loss that would otherwise occur under high CO2 levels but, compared to the preindustrial <span class="hlt">climate</span>, leaves the <span class="hlt">tropics</span> cooler (-0.3 K) and the poles warmer (+0.8 K). Annual mean precipitation minus evaporation anomalies for G1 are less than 0.2 mm day-1 in magnitude over 92% of the globe, but some <span class="hlt">tropical</span> regions receive less precipitation, in part due to increased moist static stability and suppression of convection. Global average net primary productivity increases by 120% in G1 over simulated preindustrial levels, primarily from CO2 fertilization, but also in part due to reduced plant heat stress compared to a high CO2 world with no geoengineering. All models show that uniform solar geoengineering in G1 cannot simultaneously return regional and global temperature and hydrologic cycle intensity to preindustrial levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28070560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28070560"><span>Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang</p> <p>2017-01-01</p> <p>Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most <span class="hlt">climate</span> model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO 2 concentration is <span class="hlt">abruptly</span> doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different <span class="hlt">climate</span> responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the <span class="hlt">tropical</span> Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term <span class="hlt">climate</span> projection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5217057','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5217057"><span>Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Liu, Wei; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang</p> <p>2017-01-01</p> <p>Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most <span class="hlt">climate</span> model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is <span class="hlt">abruptly</span> doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different <span class="hlt">climate</span> responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the <span class="hlt">tropical</span> Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term <span class="hlt">climate</span> projection. PMID:28070560</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27211989','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27211989"><span>Elevational sensitivity in an Asian 'hotspot': moth diversity across elevational gradients in <span class="hlt">tropical</span>, sub-<span class="hlt">tropical</span> and sub-alpine China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ashton, L A; Nakamura, A; Burwell, C J; Tang, Y; Cao, M; Whitaker, T; Sun, Z; Huang, H; Kitching, R L</p> <p>2016-05-23</p> <p>South-western China is widely acknowledged as a biodiversity 'hotspot': there are high levels of diversity and endemism, and many environments are under significant anthropogenic threats not least <span class="hlt">climate</span> warming. Here, we explore diversity and compare response patterns of moth assemblages among three elevational gradients established within different <span class="hlt">climatic</span> bioregions - <span class="hlt">tropical</span> rain forest, sub-<span class="hlt">tropical</span> evergreen broad-leaved forest and sub-alpine coniferous forest in Yunnan Province, China. We hypothesised that <span class="hlt">tropical</span> assemblages would be more elevationally stratified than temperate assemblages, and <span class="hlt">tropical</span> species would be more elevationally restricted than those in the temperate zone. Contrary to our hypothesis, the moth fauna was more sensitive to elevational differences within the temperate transect, followed by sub-<span class="hlt">tropical</span> and <span class="hlt">tropical</span> transects. Moths in the cooler and more seasonal temperate sub-alpine gradient showed stronger elevation-decay beta diversity patterns, and more species were restricted to particular elevational ranges. Our study suggests that moth assemblages are under threat from future <span class="hlt">climate</span> change and sub-alpine rather than <span class="hlt">tropical</span> faunas may be the most sensitive to <span class="hlt">climate</span> change. These results improve our understanding of China's biodiversity and can be used to monitor future changes to herbivore assemblages in a 'hotspot' of biodiversity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatSR...4E3706Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatSR...4E3706Z"><span>Constant diurnal temperature regime alters the impact of simulated <span class="hlt">climate</span> warming on a <span class="hlt">tropical</span> pseudoscorpion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeh, Jeanne A.; Bonilla, Melvin M.; Su, Eleanor J.; Padua, Michael V.; Anderson, Rachel V.; Zeh, David W.</p> <p>2014-01-01</p> <p>Recent theory suggests that global warming may be catastrophic for <span class="hlt">tropical</span> ectotherms. Although most studies addressing temperature effects in ectotherms utilize constant temperatures, Jensen's inequality and thermal stress considerations predict that this approach will underestimate warming effects on species experiencing daily temperature fluctuations in nature. Here, we tested this prediction in a neotropical pseudoscorpion. Nymphs were reared in control and high-temperature treatments under a constant daily temperature regime, and results compared to a companion fluctuating-temperature study. At constant temperature, pseudoscorpions outperformed their fluctuating-temperature counterparts. Individuals were larger, developed faster, and males produced more sperm, and females more embryos. The greatest impact of temperature regime involved short-term, adult exposure, with constant temperature mitigating high-temperature effects on reproductive traits. Our findings demonstrate the importance of realistic temperature regimes in <span class="hlt">climate</span> warming studies, and suggest that exploitation of microhabitats that dampen temperature oscillations may be critical in avoiding extinction as <span class="hlt">tropical</span> <span class="hlt">climates</span> warm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..920L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..920L"><span>Impact of chlorophyll bias on the <span class="hlt">tropical</span> Pacific mean <span class="hlt">climate</span> in an earth system model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lim, Hyung-Gyu; Park, Jong-Yeon; Kug, Jong-Seong</p> <p>2017-12-01</p> <p><span class="hlt">Climate</span> modeling groups nowadays develop earth system models (ESMs) by incorporating biogeochemical processes in their <span class="hlt">climate</span> models. The ESMs, however, often show substantial bias in simulated marine biogeochemistry which can potentially introduce an undesirable bias in physical ocean fields through biogeophysical interactions. This study examines how and how much the chlorophyll bias in a state-of-the-art ESM affects the mean and seasonal cycle of <span class="hlt">tropical</span> Pacific sea-surface temperature (SST). The ESM used in the present study shows a sizeable positive bias in the simulated <span class="hlt">tropical</span> chlorophyll. We found that the correction of the chlorophyll bias can reduce the ESM's intrinsic cold SST mean bias in the equatorial Pacific. The biologically-induced cold SST bias is strongly affected by seasonally-dependent air-sea coupling strength. In addition, the correction of chlorophyll bias can improve the annual cycle of SST by up to 25%. This result suggests a possible modeling approach in understanding the two-way interactions between physical and chlorophyll biases by biogeophysical effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22270703','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22270703"><span>Arctic <span class="hlt">climate</span> tipping points.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lenton, Timothy M</p> <p>2012-02-01</p> <p>There is widespread concern that anthropogenic global warming will trigger Arctic <span class="hlt">climate</span> tipping points. The Arctic has a long history of natural, <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes, which together with current observations and model projections, can help us to identify which parts of the Arctic <span class="hlt">climate</span> system might pass future tipping points. Here the <span class="hlt">climate</span> tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic <span class="hlt">climate</span> tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic <span class="hlt">climate</span> tipping points.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC43L..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC43L..05S"><span>Coexistence of Trees and Grass: Importance of <span class="hlt">climate</span> and fire within the <span class="hlt">tropics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shuman, J. K.; Fisher, R.; Koven, C.; Knox, R. G.; Andre, B.; Kluzek, E. B.</p> <p>2017-12-01</p> <p><span class="hlt">Tropical</span> forests are characterized by transition zones where dominance shifts between trees and grasses with some areas exhibiting bistability of the two. The cause of this transition and bistability has been linked to the interacting effects of <span class="hlt">climate</span>, vegetation structure and fire behavior. Utilizing the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), a demographic vegetation model, and the CESM ESM, we explore the coexistence of trees and grass across the <span class="hlt">tropics</span> with an active fire regime. FATES has been updated to use a fire module based on Spitfire. FATES-Spitfire tracks fire ignition, spread and impact based on fuel state and combustion. Fire occurs within the model with variable intensity that kills trees according to the combined effects of cambial damage and crown scorch due to flame height and fire intensity. As a size-structured model, FATES allows for variable mortality based on the size of tree cohorts, where larger trees experience lower morality compared to small trees. Results for simulation scenarios where vegetation is represented by all trees, all grass, or a combination of competing trees and grass are compared to assess changes in biomass, fire regime and tree-grass coexistence. Within the forest-grass transition area there is a critical time during which grass fuels fire spread and prevents the establishment of trees. If trees are able to escape mortality a tree-grass bistable area is successful. The ability to simulate the bistability and transition of trees and grass throughout the <span class="hlt">tropics</span> is critical to representing vegetation dynamics in response to changing <span class="hlt">climate</span> and CO2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/47187','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/47187"><span><span class="hlt">Climate</span> change and land use drivers of fecal bacteria in <span class="hlt">tropical</span> Hawaiian rivers</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Ayron M. Strauch; Richard A. Mackenzie; Gregory L. Bruland; Ralph Tingley; Christian P. Giardina</p> <p>2014-01-01</p> <p>Potential shifts in rainfall driven by <span class="hlt">climate</span> change are anticipated to affect watershed processes (e.g., soil moisture, runoff, stream flow), yet few model systems exist in the <span class="hlt">tropics</span> to test hypotheses about how these processes may respond to these shifts. We used a sequence of nine watersheds on Hawaii Island spanning 3000 mm (7500–4500 mm) of mean annual rainfall...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B13L..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B13L..04D"><span>Revisiting drought impact on <span class="hlt">tropical</span> forest photosynthesis: a novel multi-scale integrated approach reveals new insights</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Detto, M.; Wu, J.; Xu, X.; Serbin, S.; Rogers, A.</p> <p>2017-12-01</p> <p>A fundamental unanswered question for global change ecology is to determine the vulnerability of <span class="hlt">tropical</span> forests to <span class="hlt">climate</span> change, particularly with increasing intensity and frequency of drought events. This question, despite its apparent simplicity, remains difficult for earth system models to answer, and is controversial in remote sensing literature. Here, we leverage unique multi-scale remote sensing measurements (from leaf to crown) in conjunction with four-continuous-year (2013-2017) eddy covariance measurements of ecosystem carbon fluxes in a <span class="hlt">tropical</span> forest in Panama to revisit this question. We hypothesize that drought impacts <span class="hlt">tropical</span> forest photosynthesis through variation in abiotic drivers (solar radiation, diffuse light fraction, and vapor pressure deficit) that interact with physiological traits that govern photosynthesis, and biotic variation in ecosystem photosynthetic capacity associated with changes in the traits themselves. Our study site, located in a seasonal <span class="hlt">tropical</span> forest on Barro Colorado Island (BCI), Panama, experienced a significant drought in 2015. Local eddy covariance derived photosynthesis shows an <span class="hlt">abrupt</span> increase during the drought year. Our specific goal here is to assess the relative impact of abiotic and biotic drivers of such photosynthesis response to interannual drought. To this goal, we derived abiotic drivers from eddy tower-based meteorological measurements. We will derive the biotic drivers using a recently developed leaf demography-ontogeny model, where ecosystem photosynthetic capacity can be described as the product of field measured, age-dependent leaf photosynthetic capacity and local tower-camera derived ecosystem-scale inter-annual variability in leaf age demography of the same time period (2013-2017). Lastly, we will use a process-based model to assess the separate and joint effects of abiotic and biotic drivers on eddy covariance derive photosynthetic interannual variability. Collectively, this novel multi</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Chaos..27l6704S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Chaos..27l6704S"><span>Role of atmosphere-ocean interactions in supermodeling the <span class="hlt">tropical</span> Pacific <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Mao-Lin; Keenlyside, Noel; Bhatt, Bhuwan C.; Duane, Gregory S.</p> <p>2017-12-01</p> <p>The supermodel strategy interactively combines several models to outperform the individual models comprising it. A key advantage of the approach is that nonlinear improvements can be achieved, in contrast to the linear weighted combination of individual unconnected models. This property is found in a <span class="hlt">climate</span> supermodel constructed by coupling two versions of an atmospheric model differing only in their convection scheme to a single ocean model. The ocean model receives a weighted combination of the momentum and heat fluxes. Optimal weights can produce a supermodel with a basic state similar to observations: a single Intertropical Convergence zone (ITCZ), with a western Pacific warm pool and an equatorial cold tongue. This is in stark contrast to the erroneous double ITCZ pattern simulated by both of the two stand-alone coupled models. By varying weights, we develop a conceptual scheme to explain how combining the momentum fluxes of the two different atmospheric models affects equatorial upwelling and surface wind feedback so as to give a realistic basic state in the <span class="hlt">tropical</span> Pacific. In particular, we propose a mechanism based on the competing influences of equatorial zonal wind and off-equatorial wind stress curl in driving equatorial upwelling in the coupled models. Our results show how nonlinear ocean-atmosphere interaction is essential in combining these two effects to build different sea surface temperature structures, some of which are realistic. They also provide some insight into observed and modelled <span class="hlt">tropical</span> Pacific <span class="hlt">climate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMPP71C..08H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMPP71C..08H"><span>a Marine Record of Holocene <span class="hlt">Climate</span> Events in <span class="hlt">Tropical</span> South America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haug, G. H.; Günther, D.; Hughen, K. A.; Peterson, L. C.; Röhl, U.</p> <p>2002-12-01</p> <p>Metal concentration data (Ti, Fe) from the anoxic Cariaco Basin off the Venezuelan coast record with subdecadal to seasonal resolution variations in the hydrological cycle over <span class="hlt">tropical</span> South America during the last 14 ka. Following a dry Younger Dryas, a period of increased precipitation and riverine discharge occurred during the Holocene `thermal maximum'. Since ~5.4 ka, a trend towards drier conditions is evident from the data, with high amplitude fluctuations and precipitation minima during the time interval 3.8 to 2.8 ka and during the `Little Ice Age'. O pronouced increase in precipitation coincides with the phase sometimes referred to as the `Medieval Warm Period'. These regional changes in precipitation are best explained by shifts in the mean latitude of the Atlantic Intertropical Convergence Zone (ITCZ), potentially driven by Pacific-based <span class="hlt">climate</span> variability. The variations recorded in Cariaco Basin sediments coincide with events in societal evolution that have been suggested previously to be motivated by environmental change. Regionally, the Cariaco record supports the notion that the collapse of this civilization between 800 and 1000 AD coincided with an extended period of drier conditions, implying that the rapid growth of Mayan culture from 600 to 800 AD may have resulted in a population operating at the fringes of the environment's carrying capacity. The Cariaco Basin record also hints at <span class="hlt">tropical</span> <span class="hlt">climate</span> events similar in timing to high latitude changes in the North Atlantic often invoked as pivotal to societal developments in Europe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29289039','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29289039"><span>Role of atmosphere-ocean interactions in supermodeling the <span class="hlt">tropical</span> Pacific <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Mao-Lin; Keenlyside, Noel; Bhatt, Bhuwan C; Duane, Gregory S</p> <p>2017-12-01</p> <p>The supermodel strategy interactively combines several models to outperform the individual models comprising it. A key advantage of the approach is that nonlinear improvements can be achieved, in contrast to the linear weighted combination of individual unconnected models. This property is found in a <span class="hlt">climate</span> supermodel constructed by coupling two versions of an atmospheric model differing only in their convection scheme to a single ocean model. The ocean model receives a weighted combination of the momentum and heat fluxes. Optimal weights can produce a supermodel with a basic state similar to observations: a single Intertropical Convergence zone (ITCZ), with a western Pacific warm pool and an equatorial cold tongue. This is in stark contrast to the erroneous double ITCZ pattern simulated by both of the two stand-alone coupled models. By varying weights, we develop a conceptual scheme to explain how combining the momentum fluxes of the two different atmospheric models affects equatorial upwelling and surface wind feedback so as to give a realistic basic state in the <span class="hlt">tropical</span> Pacific. In particular, we propose a mechanism based on the competing influences of equatorial zonal wind and off-equatorial wind stress curl in driving equatorial upwelling in the coupled models. Our results show how nonlinear ocean-atmosphere interaction is essential in combining these two effects to build different sea surface temperature structures, some of which are realistic. They also provide some insight into observed and modelled <span class="hlt">tropical</span> Pacific <span class="hlt">climate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1082972','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1082972"><span>High-Resolution Modeling to Assess <span class="hlt">Tropical</span> Cyclone Activity in Future <span class="hlt">Climate</span> Regimes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Lackmann, Gary</p> <p>2013-06-10</p> <p>Applied research is proposed with the following objectives: (i) to determine the most likely level of <span class="hlt">tropical</span> cyclone intensity and frequency in future <span class="hlt">climate</span> regimes, (ii) to provide a quantitative measure of uncertainty in these predictions, and (iii) to improve understanding of the linkage between <span class="hlt">tropical</span> cyclones and the planetary-scale circulation. Current mesoscale weather forecasting models, such as the Weather Research and Forecasting (WRF) model, are capable of simulating the full intensity of <span class="hlt">tropical</span> cyclones (TC) with realistic structures. However, in order to accurately represent both the primary and secondary circulations in these systems, model simulations must be configured withmore » sufficient resolution to explicitly represent convection (omitting the convective parameterization scheme). Most previous numerical studies of TC activity at seasonal and longer time scales have not utilized such explicit convection (EC) model runs. Here, we propose to employ the moving nest capability of WRF to optimally represent TC activity on a seasonal scale using a downscaling approach. The statistical results of a suite of these high-resolution TC simulations will yield a realistic representation of TC intensity on a seasonal basis, while at the same time allowing analysis of the feedback that TCs exert on the larger-scale <span class="hlt">climate</span> system. Experiments will be driven with analyzed lateral boundary conditions for several recent Atlantic seasons, spanning a range of activity levels and TC track patterns. Results of the ensemble of WRF simulations will then be compared to analyzed TC data in order to determine the extent to which this modeling setup can reproduce recent levels of TC activity. Next, the boundary conditions (sea-surface temperature, tropopause height, and thermal/moisture profiles) from the recent seasons will be altered in a manner consistent with various future GCM/RCM scenarios, but that preserves the large-scale shear and incipient disturbance</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5414686','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5414686"><span><span class="hlt">Climate</span> change mitigation: potential benefits and pitfalls of enhanced rock weathering in <span class="hlt">tropical</span> agriculture</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lim, Felix; James, Rachael H.; Pearce, Christopher R.; Scholes, Julie; Freckleton, Robert P.; Beerling, David J.</p> <p>2017-01-01</p> <p>Restricting future global temperature increase to 2°C or less requires the adoption of negative emissions technologies for carbon capture and storage. We review the potential for deployment of enhanced weathering (EW), via the application of crushed reactive silicate rocks (such as basalt), on over 680 million hectares of <span class="hlt">tropical</span> agricultural and tree plantations to offset fossil fuel CO2 emissions. Warm <span class="hlt">tropical</span> <span class="hlt">climates</span> and productive crops will substantially enhance weathering rates, with potential co-benefits including decreased soil acidification and increased phosphorus supply promoting higher crop yields sparing forest for conservation, and reduced cultural eutrophication. Potential pitfalls include the impacts of mining operations on deforestation, producing the energy to crush and transport silicates and the erosion of silicates into rivers and coral reefs that increases inorganic turbidity, sedimentation and pH, with unknown impacts for biodiversity. We identify nine priority research areas for untapping the potential of EW in the <span class="hlt">tropics</span>, including effectiveness of <span class="hlt">tropical</span> agriculture at EW for major crops in relation to particle sizes and soil types, impacts on human health, and effects on farmland, adjacent forest and stream-water biodiversity. PMID:28381631</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28381631','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28381631"><span><span class="hlt">Climate</span> change mitigation: potential benefits and pitfalls of enhanced rock weathering in <span class="hlt">tropical</span> agriculture.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Edwards, David P; Lim, Felix; James, Rachael H; Pearce, Christopher R; Scholes, Julie; Freckleton, Robert P; Beerling, David J</p> <p>2017-04-01</p> <p>Restricting future global temperature increase to 2°C or less requires the adoption of negative emissions technologies for carbon capture and storage. We review the potential for deployment of enhanced weathering (EW), via the application of crushed reactive silicate rocks (such as basalt), on over 680 million hectares of <span class="hlt">tropical</span> agricultural and tree plantations to offset fossil fuel CO 2 emissions. Warm <span class="hlt">tropical</span> <span class="hlt">climates</span> and productive crops will substantially enhance weathering rates, with potential co-benefits including decreased soil acidification and increased phosphorus supply promoting higher crop yields sparing forest for conservation, and reduced cultural eutrophication. Potential pitfalls include the impacts of mining operations on deforestation, producing the energy to crush and transport silicates and the erosion of silicates into rivers and coral reefs that increases inorganic turbidity, sedimentation and pH, with unknown impacts for biodiversity. We identify nine priority research areas for untapping the potential of EW in the <span class="hlt">tropics</span>, including effectiveness of <span class="hlt">tropical</span> agriculture at EW for major crops in relation to particle sizes and soil types, impacts on human health, and effects on farmland, adjacent forest and stream-water biodiversity. © 2017 The Author(s).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001ESRv...55...73F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001ESRv...55...73F"><span>The potential negative impacts of global <span class="hlt">climate</span> change on <span class="hlt">tropical</span> montane cloud forests</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Foster, Pru</p> <p>2001-10-01</p> <p>Nearly every aspect of the cloud forest is affected by regular cloud immersion, from the hydrological cycle to the species of plants and animals within the forest. Since the altitude band of cloud formation on <span class="hlt">tropical</span> mountains is limited, the <span class="hlt">tropical</span> montane cloud forest occurs in fragmented strips and has been likened to island archipelagoes. This isolation and uniqueness promotes explosive speciation, exceptionally high endemism, and a great sensitivity to <span class="hlt">climate</span>. Global <span class="hlt">climate</span> change threatens all ecosystems through temperature and rainfall changes, with a typical estimate for altitude shifts in the <span class="hlt">climatic</span> optimum for mountain ecotones of hundreds of meters by the time of CO 2 doubling. This alone suggests complete replacement of many of the narrow altitude range cloud forests by lower altitude ecosystems, as well as the expulsion of peak residing cloud forests into extinction. However, the cloud forest will also be affected by other <span class="hlt">climate</span> changes, in particular changes in cloud formation. A number of global <span class="hlt">climate</span> models suggest a reduction in low level cloudiness with the coming <span class="hlt">climate</span> changes, and one site in particular, Monteverde, Costa Rica, appears to already be experiencing a reduction in cloud immersion. The coming <span class="hlt">climate</span> changes appear very likely to upset the current dynamic equilibrium of the cloud forest. Results will include biodiversity loss, altitude shifts in species' ranges and subsequent community reshuffling, and possibly forest death. Difficulties for cloud forest species to survive in <span class="hlt">climate</span>-induced migrations include no remaining location with a suitable <span class="hlt">climate</span>, no pristine location to colonize, migration rates or establishment rates that cannot keep up with <span class="hlt">climate</span> change rates and new species interactions. We review previous cloud forest species redistributions in the paleo-record in light of the coming changes. The characteristic epiphytes of the cloud forest play an important role in the light, hydrological and nutrient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B11H0132H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B11H0132H"><span>Microbial Community Dynamics from Permafrost Across the Pleistocene-Holocene Boundary and Response to <span class="hlt">Abrupt</span> <span class="hlt">Climate</span> Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammad, A.; Mahony, M.; Froese, D. G.; Lanoil, B. D.</p> <p>2014-12-01</p> <p>Earth is currently undergoing rapid warming similar to that observed about 10,000 years ago at the end of the Pleistocene. We know a considerable amount about the adaptations and extinctions of mammals and plants at the Pleistocene/Holocene (P/H) boundary, but relatively little about changes at the microbial level. Due to permafrost soils' freezing anoxic conditions, they act as microbial diversity archives allowing us to determine how microbial communities adapted to the <span class="hlt">abrupt</span> warming at the end of P. Since microbial community composition only helps differentiate viable and extant microorganisms in frozen permafrost, microbial activity in thawing permafrost must be investigated to provide a clear understanding of microbial response to <span class="hlt">climate</span> change. Current increased temperatures will result in warming and potential thaw of permafrost and release of stored organic carbon, freeing it for microbial utilization; turning permafrost into a carbon source. Studying permafrost viable microbial communities' diversity and activity will provide a better understanding of how these microorganisms respond to soil edaphic variability due to <span class="hlt">climate</span> change across the P/H boundary, providing insight into the changes that the soil community is currently undergoing in this modern era of rapid <span class="hlt">climate</span> change. Modern soil, H and P permafrost cores were collected from Lucky Lady II site outside Dawson City, Yukon. 16S rRNA high throughput sequencing of permafrost DNA showed the same trends for total and viable community richness and diversity with both decreasing with permafrost depth and only the richness increasing in mid and early P. The modern, H and P soils had 50.9, 33.9, and 27.3% unique viable species and only 14% of the total number of viable species were shared by all soils. Gas flux measurements of thawed permafrost showed metabolic activity in modern and permafrost soils, aerobic CH­­4 consumption in modern, some H and P soils, and anaerobic CH­­4 production in one H</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.1404R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.1404R"><span>Stable "Waterbelt" <span class="hlt">climates</span> controlled by <span class="hlt">tropical</span> ocean heat transport: A nonlinear coupled <span class="hlt">climate</span> mechanism of relevance to Snowball Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rose, Brian E. J.</p> <p>2015-02-01</p> <p>Ongoing controversy about Neoproterozoic Snowball Earth events motivates a theoretical study of stability and hysteresis properties of very cold <span class="hlt">climates</span>. A coupled atmosphere-ocean-sea ice general circulation model (GCM) has four stable equilibria ranging from 0% to 100% ice cover, including a "Waterbelt" state with <span class="hlt">tropical</span> sea ice. All four states are found at present-day insolation and greenhouse gas levels and with two idealized ocean basin configurations. The Waterbelt is stabilized against albedo feedback by intense but narrow wind-driven ocean overturning cells that deliver roughly 100 W m-2 heating to the ice edges. This requires three-way feedback between winds, ocean circulation, and ice extent in which circulation is shifted equatorward, following the baroclinicity at the ice margins. The thermocline is much shallower and outcrops in the <span class="hlt">tropics</span>. Sea ice is snow-covered everywhere and has a minuscule seasonal cycle. The Waterbelt state spans a 46 W m-2 range in solar constant, has a significant hysteresis, and permits near-freezing equatorial surface temperatures. Additional context is provided by a slab ocean GCM and a diffusive energy balance model, both with prescribed ocean heat transport (OHT). Unlike the fully coupled model, these support no more than one stable ice margin, the position of which is slaved to regions of rapid poleward decrease in OHT convergence. Wide ranges of different <span class="hlt">climates</span> (including the stable Waterbelt) are found by varying the magnitude and spatial structure of OHT in both models. Some thermodynamic arguments for the sensitivity of <span class="hlt">climate</span>, and ice extent to OHT are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7233O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7233O"><span>Analysis agriculture's impact in a system of lakes on a karst environment with <span class="hlt">tropical</span> <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olea Olea, Selene; Escolero Fuentes, Oscar</p> <p>2015-04-01</p> <p>This paper has as main object to analyze the impact of agriculture in the water quality of the "Lagos de Montebello" area; which is located in the Southeast of Mexico. This area is prominent by its <span class="hlt">tropical</span> <span class="hlt">climate</span> and a karstic environment. The issue arises in a lake system affected by pollution in the later years, which has turned its former clear water into a highly sedimented muddy water in the topographically lower terrains while no polluted on the higher ones; therefore it is intended to determine if the rise in agricultural activity in the lower terrains has induced this phenomenon. The impact of agriculture has been historically studied in temperate <span class="hlt">climates</span> with karstic environments; nevertheless it has not been very well studied in <span class="hlt">tropical</span> <span class="hlt">climates</span>; which are the reason of this proposal to perform a study to analyze the impact of the intensive agriculture running in the area. To develop this project we studied the area regarding to the types of crops that has being established in the zone, being mostly tomato, corn, and bean; and the fertilizers and pesticides applied to them. A groundwater monitoring plan was designed with a variety of phases such as: piezometers building, measurement of groundwater levels, measurement of field parameters, with a two months intervals (Ph, temperature, electric conductivity, total dissolved solids), and water samplings for laboratory analysis (major ions, nutrients, total organic carbon, pesticides) at twice a year, once during rainy season and then on drought. The rates of pollution agents infiltration depends on the type of soil retention and volume of water. The materials found in the soil by the piezometers are clay, silt, sand and variations between them. We determined that the geochemical qualities of the groundwater vary from calcic bicarbonate to calcic sulfated. The results reached with this monitoring provides a preliminary diagnosis on the possible causes and other implications that intensive agriculture in a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1916367D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1916367D"><span>Evaluation of DGVMs in <span class="hlt">tropical</span> areas: linking patterns of vegetation cover, <span class="hlt">climate</span> and fire to ecological processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Onofrio, Donatella; von Hardenberg, Jost; Baudena, Mara</p> <p>2017-04-01</p> <p>Many current Dynamic Global Vegetation Models (DGVMs), including those incorporated into Earth System Models (ESMs), are able to realistically reproduce the distribution of the most worldwide biomes. However, they display high uncertainty in predicting the forest, savanna and grassland distributions and the transitions between them in <span class="hlt">tropical</span> areas. These biomes are the most productive terrestrial ecosystems, and owing to their different biogeophysical and biogeochemical characteristics, future changes in their distributions could have also impacts on <span class="hlt">climate</span> states. In particular, expected increasing temperature and CO2, modified precipitation regimes, as well as increasing land-use intensity could have large impacts on global biogeochemical cycles and precipitation, affecting the land-<span class="hlt">climate</span> interactions. The difficulty of the DGVMs in simulating <span class="hlt">tropical</span> vegetation, especially savanna structure and occurrence, has been associated with the way they represent the ecological processes and feedbacks between biotic and abiotic conditions. The inclusion of appropriate ecological mechanisms under present <span class="hlt">climatic</span> conditions is essential for obtaining reliable future projections of vegetation and <span class="hlt">climate</span> states. In this work we analyse observed relationships of tree and grass cover with <span class="hlt">climate</span> and fire, and the current ecological understanding of the mechanisms driving the forest-savanna-grassland transition in Africa to evaluate the outcomes of a current state-of-the-art DGVM and to assess which ecological processes need to be included or improved within the model. Specifically, we analyse patterns of woody and herbaceous cover and fire return times from MODIS satellite observations, rainfall annual average and seasonality from TRMM satellite measurements and tree phenology information from the ESA global land cover map, comparing them with the outcomes of the LPJ-GUESS DGVM, also used by the EC-Earth global <span class="hlt">climate</span> model. The comparison analysis with the LPJ</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26442494','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26442494"><span>French vertical-flow constructed wetland design: adaptations for <span class="hlt">tropical</span> <span class="hlt">climates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Molle, P; Latune, R Lombard; Riegel, C; Lacombe, G; Esser, D; Mangeot, L</p> <p>2015-01-01</p> <p>The French Outermost Regions are under <span class="hlt">tropical</span> <span class="hlt">climate</span> yet still have to comply with both French and EU regulations. French vertical-flow constructed wetland systems appear well adapted to the technical specifics of these regions but their adaptation to <span class="hlt">tropical</span> <span class="hlt">climate</span> requires new design guidelines to be defined (area needed, number of filters, type of plants, material to be used, etc.). A study was started in 2008, with backing from the national water authorities, to implement full-scale experimental sites and assess the impacts of local context on design and performances. This paper reports the monitoring results on three vertical-flow constructed wetlands fed directly with raw wastewater (known as the 'French system') in Mayotte and French Guiana. The plants, now in operation for between 1 and 6 years, range from 160 to 480 population equivalent (p.e.). Monitoring consisted of 28 daily composite flow samples in different seasons (dry season, rainy season) at the inlet and outlet of each filter. Performances are benchmarked against French mainland area standards from Irstea's database. Results show that performances are improved by warmer temperature for chemical oxygen demand (COD), suspended solids (SS) and total Kjeldahl nitrogen (TKN) and satisfy national quality objectives with a single stage of filters. Treatment plant footprint can thus be reduced as only two parallel filters are needed. Indeed, warm temperatures allow faster mineralization of the sludge deposit, making it possible to operate at similar rest and feeding period durations. Systems operated using one twin-filter stage can achieve over 90% COD, SS and TKN removal for a total surface of 0.8 m²/p.e.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhDT.......129P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT.......129P"><span>Application of advanced data assimilation techniques to the study of cloud and precipitation feedbacks in the <span class="hlt">tropical</span> <span class="hlt">climate</span> system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Posselt, Derek J.</p> <p></p> <p>The research documented in this study centers around two topics: evaluation of the response of precipitating cloud systems to changes in the <span class="hlt">tropical</span> <span class="hlt">climate</span> system, and assimilation of cloud and precipitation information from remote-sensing platforms. The motivation for this work proceeds from the following outstanding problems: (1) Use of models to study the response of clouds to perturbations in the <span class="hlt">climate</span> system is hampered by uncertainties in cloud microphysical parameterizations. (2) Though there is an ever-growing set of available observations, cloud and precipitation assimilation remains a difficult problem, particularly in the <span class="hlt">tropics</span>. (3) Though it is widely acknowledged that cloud and precipitation processes play a key role in regulating the Earth's response to surface warming, the response of the <span class="hlt">tropical</span> hydrologic cycle to <span class="hlt">climate</span> perturbations remains largely unknown. The above issues are addressed in the following manner. First, Markov chain Monte Carlo (MCMC) methods are used to quantify the sensitivity of the NASA Goddard Cumulus Ensemble (GCE) cloud resolving model (CRM) to changes in its cloud odcrnpbymiC8l parameters. TRMM retrievals of precipitation rate, cloud properties, and radiative fluxes and heating rates over the South China Sea are then assimilated into the GCE model to constrain cloud microphysical parameters to values characteristic of convection in the <span class="hlt">tropics</span>, and the resulting observation-constrained model is used to assess the response of the <span class="hlt">tropical</span> hydrologic cycle to surface warming. The major findings of this study are the following: (1) MCMC provides an effective tool with which to evaluate both model parameterizations and the assumption of Gaussian statistics used in optimal estimation procedures. (2) Statistics of the <span class="hlt">tropical</span> radiation budget and hydrologic cycle can be used to effectively constrain CRM cloud microphysical parameters. (3) For 2D CRM simulations run with and without shear, the precipitation efficiency of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1840R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1840R"><span>Nor<span class="hlt">Tropical</span> Warm Pool variability and its effects on the <span class="hlt">climate</span> of Colombia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ricaurte Villota, Constanza; Romero-Rodriguez, Deisy; Coca-Domínguez, Oswaldo</p> <p>2015-04-01</p> <p>Much has been said about the effects of El Niño Southern Oscillation (ENSO) on oceanographic and <span class="hlt">climatic</span> conditions in Colombia, but little is known about the influence of the Atlantic Warm Pool (AWP), which includes the gulf of Mexico, the Caribbean and the western <span class="hlt">tropical</span> North Atlantic. The AWP has been identified by some authors as an area that influences the Earth's <span class="hlt">climate</span>, associated with anomalous summer rainfall and hurricane activity in the Atlantic. The aim of this study was to understand the variation in the AWP and its effects on the <span class="hlt">climate</span> of Colombia. An annual average of sea surface temperature (SST) was obtained from the composition of monthly images of the Spectroradiometer Moderate Resolution Imaging Spectroradiometer (MODIS), with resolution of 4 km, for one area that comprises the marine territory of Colombia, Panama, Costa Rica both the Pacific and the Caribbean, and parts of the Caribbean coast of Nicaragua, for the period between 2007 and 2013. The results suggest that warm pool is not restricted to the Caribbean, but it also covers a strip Pacific bordering Central America and the northern part of the Colombian coast, so it should be called the Nor-<span class="hlt">Tropical</span> Warm pool (NTWP). Within the NTWP higher SST correspond to a marine area extending about 1 degree north and south of Central and out of the Colombian Caribbean coast. The NTWP also showed large interannual variability, with the years 2008 and 2009 with lower SST in average, while 2010, 2011 and 2013 years with warmer conditions, matching with greater precipitation. It was also noted that during warmer conditions (high amplitude NTWP) the cold tongue from the south Pacific has less penetration on Colombian coast. Finally, the results suggest a strong influence of NTWP in <span class="hlt">climatic</span> conditions in Colombia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9895B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9895B"><span>Bayesian comparison of conceptual models of <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes during the last glacial period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boers, Niklas; Ghil, Michael; Rousseau, Denis-Didier</p> <p>2017-04-01</p> <p>Records of oxygen isotope ratios and dust concentrations from the North Greenland Ice Core Project (NGRIP) provide accurate proxies for the evolution of Arctic temperature and atmospheric circulation during the last glacial period (12ka to 100ka b2k) [1]. The most distinctive feature of these records are sudden transitions, called Dansgaard-Oeschger (DO) events, during which Arctic temperatures increased by up to 10 K within a few decades. These warming events are consistently followed by more gradual cooling in Antarctica [2]. The physical mechanisms responsible for these transitions and their out-of-phase relationship between the northern and southern hemisphere remain unclear. Substantial evidence hints at variations of the Atlantic Meridional Overturning Circulation as a key mechanism [2,3], but also other mechanisms, such as variations of sea ice extent [4] or ice shelf coverage [5] may play an important role. Here, we intend to shed more light on the relevance of the different mechanisms suggested to explain the <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes and their inter-hemispheric coupling. For this purpose, several conceptual differential equation models are developed that represent the suggested physical mechanisms. Optimal parameters for each model candidate are then determined via maximum likelihood estimation with respect to the observed paleoclimatic data. Our approach is thus semi-empirical: While a model's general form is deduced from physical arguments about relevant <span class="hlt">climatic</span> mechanisms — oceanic and atmospheric — its specific parameters are obtained by training the model on observed data. The distinct model candidates are evaluated by comparing statistical properties of time series simulated with these models to the observed statistics. In particular, Bayesian model selection criteria like Maximum Likelihood Ratio tests are used to obtain a hierarchy of the different candidates in terms of their likelihood, given the observed oxygen isotope and dust time series</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ClDy...45.2033C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ClDy...45.2033C"><span>Intensified impact of <span class="hlt">tropical</span> Atlantic SST on the western North Pacific summer <span class="hlt">climate</span> under a weakened Atlantic thermohaline circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Wei; Lee, June-Yi; Lu, Riyu; Dong, Buwen; Ha, Kyung-Ja</p> <p>2015-10-01</p> <p>The <span class="hlt">tropical</span> North Atlantic (TNA) sea surface temperature (SST) has been identified as one of regulators on the boreal summer <span class="hlt">climate</span> over the western North Pacific (WNP), in addition to SSTs in the <span class="hlt">tropical</span> Pacific and Indian Oceans. The major physical process proposed is that the TNA warming induces a pair of cyclonic circulation anomaly over the eastern Pacific and negative precipitation anomalies over the eastern to central <span class="hlt">tropical</span> Pacific, which in turn lead to an anticyclonic circulation anomaly over the western to central North Pacific. This study further demonstrates that the modulation of the TNA warming to the WNP summer <span class="hlt">climate</span> anomaly tends to be intensified under background of the weakened Atlantic thermohaline circulation (THC) by using a water-hosing experiment. The results suggest that the weakened THC induces a decrease in thermocline depth over the TNA region, resulting in the enhanced sensitivity of SST variability to wind anomalies and thus intensification of the interannual variation of TNA SST. Under the weakened THC, the atmospheric responses to the TNA warming are westward shifted, enhancing the anticyclonic circulation and negative precipitation anomaly over the WNP. This study supports the recent finding that the negative phase of the Atlantic multidecadal oscillation after the late 1960s has been favourable for the strengthening of the connection between TNA SST variability and WNP summer <span class="hlt">climate</span> and has important implications for seasonal prediction and future projection of the WNP summer <span class="hlt">climate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26177097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26177097"><span>The Relative Impact of <span class="hlt">Climate</span> Change on the Extinction Risk of Tree Species in the Montane <span class="hlt">Tropical</span> Andes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tejedor Garavito, Natalia; Newton, Adrian C; Golicher, Duncan; Oldfield, Sara</p> <p>2015-01-01</p> <p>There are widespread concerns that anthropogenic <span class="hlt">climate</span> change will become a major cause of global biodiversity loss. However, the potential impact of <span class="hlt">climate</span> change on the extinction risk of species remains poorly understood, particularly in comparison to other current threats. The objective of this research was to examine the relative impact of <span class="hlt">climate</span> change on extinction risk of upper montane tree species in the <span class="hlt">tropical</span> Andes, an area of high biodiversity value that is particularly vulnerable to <span class="hlt">climate</span> change impacts. The extinction risk of 129 tree species endemic to the region was evaluated according to the IUCN Red List criteria, both with and without the potential impacts of <span class="hlt">climate</span> change. Evaluations were supported by development of species distribution models, using three methods (generalized additive models, recursive partitioning, and support vector machines), all of which produced similarly high AUC values when averaged across all species evaluated (0.82, 0.86, and 0.88, respectively). Inclusion of <span class="hlt">climate</span> change increased the risk of extinction of 18-20% of the tree species evaluated, depending on the <span class="hlt">climate</span> scenario. The relative impact of <span class="hlt">climate</span> change was further illustrated by calculating the Red List Index, an indicator that shows changes in the overall extinction risk of sets of species over time. A 15% decline in the Red List Index was obtained when <span class="hlt">climate</span> change was included in this evaluation. While these results suggest that <span class="hlt">climate</span> change represents a significant threat to tree species in the <span class="hlt">tropical</span> Andes, they contradict previous suggestions that <span class="hlt">climate</span> change will become the most important cause of biodiversity loss in coming decades. Conservation strategies should therefore focus on addressing the multiple threatening processes currently affecting biodiversity, rather than focusing primarily on potential <span class="hlt">climate</span> change impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4503679','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4503679"><span>The Relative Impact of <span class="hlt">Climate</span> Change on the Extinction Risk of Tree Species in the Montane <span class="hlt">Tropical</span> Andes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tejedor Garavito, Natalia; Newton, Adrian C.; Golicher, Duncan; Oldfield, Sara</p> <p>2015-01-01</p> <p>There are widespread concerns that anthropogenic <span class="hlt">climate</span> change will become a major cause of global biodiversity loss. However, the potential impact of <span class="hlt">climate</span> change on the extinction risk of species remains poorly understood, particularly in comparison to other current threats. The objective of this research was to examine the relative impact of <span class="hlt">climate</span> change on extinction risk of upper montane tree species in the <span class="hlt">tropical</span> Andes, an area of high biodiversity value that is particularly vulnerable to <span class="hlt">climate</span> change impacts. The extinction risk of 129 tree species endemic to the region was evaluated according to the IUCN Red List criteria, both with and without the potential impacts of <span class="hlt">climate</span> change. Evaluations were supported by development of species distribution models, using three methods (generalized additive models, recursive partitioning, and support vector machines), all of which produced similarly high AUC values when averaged across all species evaluated (0.82, 0.86, and 0.88, respectively). Inclusion of <span class="hlt">climate</span> change increased the risk of extinction of 18–20% of the tree species evaluated, depending on the <span class="hlt">climate</span> scenario. The relative impact of <span class="hlt">climate</span> change was further illustrated by calculating the Red List Index, an indicator that shows changes in the overall extinction risk of sets of species over time. A 15% decline in the Red List Index was obtained when <span class="hlt">climate</span> change was included in this evaluation. While these results suggest that <span class="hlt">climate</span> change represents a significant threat to tree species in the <span class="hlt">tropical</span> Andes, they contradict previous suggestions that <span class="hlt">climate</span> change will become the most important cause of biodiversity loss in coming decades. Conservation strategies should therefore focus on addressing the multiple threatening processes currently affecting biodiversity, rather than focusing primarily on potential <span class="hlt">climate</span> change impacts. PMID:26177097</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020080780&hterms=Shrink&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DShrink','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020080780&hterms=Shrink&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DShrink"><span>New Insights on Hydro-<span class="hlt">Climate</span> Feedback Processes over the <span class="hlt">Tropical</span> Ocean from TRMM</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K. M.; Wu, H. T.; Li, Xiaofan; Sui, C. H.</p> <p>2002-01-01</p> <p>In this paper, we study hydro-<span class="hlt">climate</span> feedback processes over the <span class="hlt">tropical</span> oceans, by examining the relationships among large scale circulation and <span class="hlt">Tropical</span> Rainfall Measuring Mission Microwave Imager-Sea Surface Temperature (TMI-SST), and a range of TRMM rain products including rain rate, cloud liquid water, precipitable water, cloud types and areal coverage, and precipitation efficiency. Results show that for a warm event (1998), the 28C threshold of convective precipitation is quite well defined over the <span class="hlt">tropical</span> oceans. However, for a cold event (1999), the SST threshold is less well defined, especially over the central and eastern Pacific cold tongue, where stratiform rain occurs at much lower than 28 C. Precipitation rates and cloud liquid water are found to be more closely related to the large scale vertical motion than to the underlying SST. While total columnar water vapor is more strongly dependent on SST. For a large domain, over the eastern Pacific, we find that the areal extent of the cloudy region tends to shrink as the SST increases. Examination of the relationship between cloud liquid water and rain rate suggests that the residence time of cloud liquid water tends to be shorter, associated with higher precipitation efficiency in a warmer <span class="hlt">climate</span>. It is hypothesized that the reduction in cloudy area may be influenced both by the shift in large scale cloud patterns in response to changes in large scale forcings, and possible increase in the cloud liquid water conversion to rain water in a warmer environment. Results of numerical experiments with the Goddard cloud resolving model to test the hypothesis will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP33A1318L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP33A1318L"><span><span class="hlt">Tropical</span> Hydroclimate Change during Heinrich Stadial 1: An Integrative Proxy-Model Synthesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lawman, A. E.; Sun, T.; Shanahan, T. M.; Di Nezio, P. N.; Gomez, K.; Piatrunia, N.; Sun, C.; Wu, X.; Kageyama, M.; Merkel, U.; Otto-Bliesner, B. L.; Abe-Ouchi, A.; Lohmann, G.; Singarayer, J. S.</p> <p>2017-12-01</p> <p>We explore the response of <span class="hlt">tropical</span> <span class="hlt">climate</span> to <span class="hlt">abrupt</span> cooling of the North Atlantic (NA) during Heinrich Stadial 1 (HS1) combining paleoclimate proxies with model simulations. A total of 146 published paleoclimate records from <span class="hlt">tropical</span> locations are used to categorize whether HS1 was wetter, drier, or unchanged relative to a deglacial baseline state. Only records with sufficient resolution to resolve HS1 and sufficient length to characterize the deglacial trend are considered. This synthesis reveals large-scale patterns of hydroclimate change relative to glacial conditions, confirming previously reported weaker Indian summer monsoon, a wetter southern Africa, and drying over the Caribbean. Our synthesis also reveals large-scale drying over the Maritime continent as well as wetter conditions in northern Australia and southern <span class="hlt">tropical</span> South America. Our reinterpretation of the available proxy data reveals far more complexity and uncertainties for equatorial East Africa, a region that appears to straddle a pattern of dryer conditions to the north and wetter conditions to the south. Overall, these patterns of hydroclimate change depart from a southward shift of the Inter <span class="hlt">Tropical</span> Convergence Zone (ITCZ), particularly outside the <span class="hlt">tropical</span> Atlantic. We explore mechanisms driving these changes using a multi-model ensemble of "hosing" simulations performed relative to glacial conditions. The models show robust weakening of the Afro-Asian Monsoon, which we attribute to ventilation of colder mid-latitude air. Not all models simulate the remaining patterns inferred from the proxy data. The best-agreeing models indicate that cooling over the <span class="hlt">tropical</span> NA and the Caribbean may be essential to communicate the response to the global <span class="hlt">tropics</span>. This response can induce warming over the <span class="hlt">tropical</span> South Atlantic via the wind-evaporation-SST feedback, driving wetter conditions in South Africa and <span class="hlt">tropical</span> South America. Cooling over the Caribbean is communicated to the Pacific over the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC53A..10T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC53A..10T"><span><span class="hlt">Tropical</span> <span class="hlt">climate</span> trends inferred from coral δ18O: a comparison of CMIP5 forward-model results with paleoclimatic observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, D. M.; Evans, M. N.; Cole, J. E.; Ault, T. R.; Emile-Geay, J.</p> <p>2011-12-01</p> <p>The response of the <span class="hlt">tropical</span> Pacific Ocean to anthropogenic <span class="hlt">climate</span> change remains highly uncertain, in part because of the disagreement among 20th-century trends derived from observations and coupled general circulation models (CGCMs). We use a model of reef coral oxygen isotopic composition (δ18O) to compare the observational coral network with synthetic corals ('pseudocorals') modeled from CGCM sea-surface temperature (SST) and sea-surface salinity (SSS). When driven with historical data, we found that a linear temperature and salinity driven model for δ18Ocoral was able to capture the spatial and temporal pattern of ENSO and the linear trend observed in 23 Indo-Pacific coral records between 1958 and 1990. However, we found that none of the pseudocoral networks obtained from a subset of 20th-century AR4 CGCM runs reproduced the magnitude of the secular trend, the change in mean state, or the change in ENSO-related variance observed in the coral network from 1890 to 1990 (Thompson et al., 2011). We believe differences between corals and AR4 CGCM simulated pseudocorals arose from uncertainties in the observed coral network or linear bivariate coral model, undersensitivity of AR4 CGCMs to radiative forcing during the 20th century, and/or biases in the simulated AR4 CGCM SSS fields. Here we apply the same approach to an extended temperature and salinity reanalysis product (SODA v2.2.4, 1871-2008) and CMIP 5 historical simulations to further address 20th-century <span class="hlt">tropical</span> <span class="hlt">climate</span> trends and assess remaining uncertainties in both the proxies and models. We explore whether model improvements in the <span class="hlt">tropical</span> Pacific have led to a stronger agreement between simulated and observed <span class="hlt">tropical</span> <span class="hlt">climate</span> trends. [Thompson, D. M., T. R. Ault, M. N. Evans, J. E. Cole, and J. Emile-Geay (2011), Comparison of observed and simulated <span class="hlt">tropical</span> <span class="hlt">climate</span> trends using a forward model of coral δ18O, Geophys. Res. Lett., 38, L14706, doi:10.1029/2011GL048224.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP31A1835W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP31A1835W"><span>An 8700 Year Record of Holocene <span class="hlt">Climate</span> Variability from the Yucatan Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wahl, D.; Byrne, R.; Anderson, L.</p> <p>2013-12-01</p> <p>Our understanding of Holocene <span class="hlt">climate</span> change in the Maya lowlands of Central America has improved significantly during the last several decades thanks to the development of proxy <span class="hlt">climate</span> records from lake cores and speleothems. One important finding is that longer-term <span class="hlt">climate</span> changes (i.e., millennial scale) were driven primarily by precessional forcing; less clear, however, are the causes of <span class="hlt">abrupt</span> shifts and higher frequency (centennial to decadal) change recognized in many Holocene <span class="hlt">climate</span> reconstructions. The mechanisms driving <span class="hlt">climate</span> change on these time scales have been difficult to identify in the region, in part because the Yucatan peninsula is influenced by <span class="hlt">climatic</span> conditions linked to both the <span class="hlt">tropical</span> Atlantic and Pacific oceans. Additional complications arise from the development of dense human populations following the initial introduction of agriculture ~5000 cal yr BP, which had significant impact on the environment as a whole. Here we present the results of analyses (stable isotope, pollen, magnetic susceptibility, and physical properties) of a 7.25 m sediment core from Lago Puerto Arturo, a closed basin lake in the northern Peten, Guatemala. An age-depth model, based on 6 AMS radiocarbon determinations and created using CLAM, indicates the record extends to 8700 cal yr BP. Proxy data suggest that, similar to other low latitude sites, millennial scale <span class="hlt">climate</span> at Lago Puerto Arturo was driven by changes in insolation. Higher frequency variability is associated with El Niño/Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) dynamics, reflecting latitudinal shifts in the Intertropical Convergence Zone in both the <span class="hlt">tropical</span> North Atlantic and North Pacific. Solar forcing may also play a role in short-term <span class="hlt">climate</span> change. The pollen and isotope records show that the entire period of prehispanic settlement and agricultural activity, i.e. ~5000-1000 cal yr B.P., was characterized by relatively dry conditions compared to before or after.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/52132','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/52132"><span>Disaggregating <span class="hlt">tropical</span> disease prevalence by <span class="hlt">climatic</span> and vegetative zones within <span class="hlt">tropical</span> west Africa</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Carl S. Beckley; Salisu Shaban; Guy H. Palmer; Andrew T. Hudak; Susan M. Noh; James E. Futse</p> <p>2016-01-01</p> <p><span class="hlt">Tropical</span> infectious disease prevalence is dependent on many socio-cultural determinants. However, rainfall and temperature frequently underlie overall prevalence, particularly for vector-borne diseases. As a result these diseases have increased prevalence in <span class="hlt">tropical</span> as compared to temperate regions. Specific to <span class="hlt">tropical</span> Africa, the tendency to incorrectly...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28146325','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28146325"><span>Organismal responses to habitat change: herbivore performance, <span class="hlt">climate</span> and leaf traits in regenerating <span class="hlt">tropical</span> dry forests.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Agosta, Salvatore J; Hulshof, Catherine M; Staats, Ethan G</p> <p>2017-05-01</p> <p>The ecological effects of large-scale <span class="hlt">climate</span> change have received much attention, but the effects of the more acute form of <span class="hlt">climate</span> change that results from local habitat alteration have been less explored. When forest is fragmented, cut, thinned, cleared or otherwise altered in structure, local <span class="hlt">climates</span> and microclimates change. Such changes can affect herbivores both directly (e.g. through changes in body temperature) and indirectly (e.g. through changes in host plant traits). We advance an eco-physiological framework to understand the effects of changing forests on herbivorous insects. We hypothesize that if <span class="hlt">tropical</span> forest caterpillars are <span class="hlt">climate</span> and resource specialists, then they should have reduced performance outside of mature forest conditions. We tested this hypothesis with a field experiment contrasting the performance of Rothschildia lebeau (Saturniidae) caterpillars feeding on the host plant Casearia nitida (Salicaceae) in two different aged and structured <span class="hlt">tropical</span> dry forests in Area de Conservación Guanacaste, Costa Rica. Compared to more mature closed-canopy forest, in younger secondary forest we found that: (1) ambient conditions were hotter, drier and more variable; (2) caterpillar growth and development were reduced; and (3) leaves were tougher, thicker and drier. Furthermore, caterpillar growth and survival were negatively correlated with these leaf traits, suggesting indirect host-mediated effects of <span class="hlt">climate</span> on herbivores. Based on the available evidence, and relative to mature forest, we conclude that reduced herbivore performance in young secondary forest could have been driven by changes in <span class="hlt">climate</span>, leaf traits (which were likely <span class="hlt">climate</span> induced) or both. However, additional studies will be needed to provide more direct evidence of cause-and-effect and to disentangle the relative influence of these factors on herbivore performance in this system. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140012059','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140012059"><span>Characteristics of <span class="hlt">Tropical</span> Cyclones in High-Resolution Models of the Present <span class="hlt">Climate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shaevitz, Daniel A.; Camargo, Suzana J.; Sobel, Adam H.; Jonas, Jeffery A.; Kim, Daeyhun; Kumar, Arun; LaRow, Timothy E.; Lim, Young-Kwon; Murakami, Hiroyuki; Roberts, Malcolm J.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140012059'); toggleEditAbsImage('author_20140012059_show'); toggleEditAbsImage('author_20140012059_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140012059_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140012059_hide"></p> <p>2014-01-01</p> <p>The global characteristics of <span class="hlt">tropical</span> cyclones (TCs) simulated by several <span class="hlt">climate</span> models are analyzed and compared with observations. The global <span class="hlt">climate</span> models were forced by the same sea surface temperature (SST) in two types of experiments, using a climatological SST and interannually varying SST. TC tracks and intensities are derived from each model's output fields by the group who ran that model, using their own preferred tracking scheme; the study considers the combination of model and tracking scheme as a single modeling system, and compares the properties derived from the different systems. Overall, the observed geographic distribution of global TC frequency was reasonably well reproduced. As expected, with the exception of one model, intensities of the simulated TC were lower than in observations, to a degree that varies considerably across models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000770','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000770"><span>Characteristics of <span class="hlt">Tropical</span> Cyclones in High-resolution Models in the Present <span class="hlt">Climate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shaevitz, Daniel A.; Camargo, Suzana J.; Sobel, Adam H.; Jonas, Jeffrey A.; Kim, Daehyun; Kumar, Arun; LaRow, Timothy E.; Lim, Young-Kwon; Murakami, Hiroyuki; Reed, Kevin; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20150000770'); toggleEditAbsImage('author_20150000770_show'); toggleEditAbsImage('author_20150000770_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20150000770_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20150000770_hide"></p> <p>2014-01-01</p> <p>The global characteristics of <span class="hlt">tropical</span> cyclones (TCs) simulated by several <span class="hlt">climate</span> models are analyzed and compared with observations. The global <span class="hlt">climate</span> models were forced by the same sea surface temperature (SST) fields in two types of experiments, using climatological SST and interannually varying SST. TC tracks and intensities are derived from each model's output fields by the group who ran that model, using their own preferred tracking scheme; the study considers the combination of model and tracking scheme as a single modeling system, and compares the properties derived from the different systems. Overall, the observed geographic distribution of global TC frequency was reasonably well reproduced. As expected, with the exception of one model, intensities of the simulated TC were lower than in observations, to a degree that varies considerably across models.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1029794','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1029794"><span>Ensemble Prediction of <span class="hlt">Tropical</span> Cyclone Genesis</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2017-02-23</p> <p>future changes in <span class="hlt">tropical</span> cyclone (TC) activity around the Hawaiian Islands are investigated using the state-of-the-art <span class="hlt">climate</span> models1–3. We find that...future warmer <span class="hlt">climate</span> . This is in contrast to the NA, where BDI increases for all dynamic variables investigated while it shows little change for...Li, and A. Kitoh, 2013: Projected future increase in <span class="hlt">tropical</span> cyclones near Hawaii. Nature <span class="hlt">Climate</span> Change , 3, 749-754, doi:10.1038/nclimate1890</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24128847','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24128847"><span>An imperative need for global change research in <span class="hlt">tropical</span> forests.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Xuhui; Fu, Yuling; Zhou, Lingyan; Li, Bo; Luo, Yiqi</p> <p>2013-09-01</p> <p><span class="hlt">Tropical</span> forests play a crucial role in regulating regional and global <span class="hlt">climate</span> dynamics, and model projections suggest that rapid <span class="hlt">climate</span> change may result in forest dieback or savannization. However, these predictions are largely based on results from leaf-level studies. How <span class="hlt">tropical</span> forests respond and feedback to <span class="hlt">climate</span> change is largely unknown at the ecosystem level. Several complementary approaches have been used to evaluate the effects of <span class="hlt">climate</span> change on <span class="hlt">tropical</span> forests, but the results are conflicting, largely due to confounding effects of multiple factors. Although altered precipitation and nitrogen deposition experiments have been conducted in <span class="hlt">tropical</span> forests, large-scale warming and elevated carbon dioxide (CO2) manipulations are completely lacking, leaving many hypotheses and model predictions untested. Ecosystem-scale experiments to manipulate temperature and CO2 concentration individually or in combination are thus urgently needed to examine their main and interactive effects on <span class="hlt">tropical</span> forests. Such experiments will provide indispensable data and help gain essential knowledge on biogeochemical, hydrological and biophysical responses and feedbacks of <span class="hlt">tropical</span> forests to <span class="hlt">climate</span> change. These datasets can also inform regional and global models for predicting future states of <span class="hlt">tropical</span> forests and <span class="hlt">climate</span> systems. The success of such large-scale experiments in natural <span class="hlt">tropical</span> forests will require an international framework to coordinate collaboration so as to meet the challenges in cost, technological infrastructure and scientific endeavor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4876391','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4876391"><span>Elevational sensitivity in an Asian ‘hotspot’: moth diversity across elevational gradients in <span class="hlt">tropical</span>, sub-<span class="hlt">tropical</span> and sub-alpine China</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ashton, L. A.; Nakamura, A.; Burwell, C. J.; Tang, Y.; Cao, M.; Whitaker, T.; Sun, Z.; Huang, H.; Kitching, R. L.</p> <p>2016-01-01</p> <p>South-western China is widely acknowledged as a biodiversity ‘hotspot’: there are high levels of diversity and endemism, and many environments are under significant anthropogenic threats not least <span class="hlt">climate</span> warming. Here, we explore diversity and compare response patterns of moth assemblages among three elevational gradients established within different <span class="hlt">climatic</span> bioregions - <span class="hlt">tropical</span> rain forest, sub-<span class="hlt">tropical</span> evergreen broad-leaved forest and sub-alpine coniferous forest in Yunnan Province, China. We hypothesised that <span class="hlt">tropical</span> assemblages would be more elevationally stratified than temperate assemblages, and <span class="hlt">tropical</span> species would be more elevationally restricted than those in the temperate zone. Contrary to our hypothesis, the moth fauna was more sensitive to elevational differences within the temperate transect, followed by sub-<span class="hlt">tropical</span> and <span class="hlt">tropical</span> transects. Moths in the cooler and more seasonal temperate sub-alpine gradient showed stronger elevation-decay beta diversity patterns, and more species were restricted to particular elevational ranges. Our study suggests that moth assemblages are under threat from future <span class="hlt">climate</span> change and sub-alpine rather than <span class="hlt">tropical</span> faunas may be the most sensitive to <span class="hlt">climate</span> change. These results improve our understanding of China’s biodiversity and can be used to monitor future changes to herbivore assemblages in a ‘hotspot’ of biodiversity. PMID:27211989</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...626513A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...626513A"><span>Elevational sensitivity in an Asian ‘hotspot’: moth diversity across elevational gradients in <span class="hlt">tropical</span>, sub-<span class="hlt">tropical</span> and sub-alpine China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ashton, L. A.; Nakamura, A.; Burwell, C. J.; Tang, Y.; Cao, M.; Whitaker, T.; Sun, Z.; Huang, H.; Kitching, R. L.</p> <p>2016-05-01</p> <p>South-western China is widely acknowledged as a biodiversity ‘hotspot’: there are high levels of diversity and endemism, and many environments are under significant anthropogenic threats not least <span class="hlt">climate</span> warming. Here, we explore diversity and compare response patterns of moth assemblages among three elevational gradients established within different <span class="hlt">climatic</span> bioregions - <span class="hlt">tropical</span> rain forest, sub-<span class="hlt">tropical</span> evergreen broad-leaved forest and sub-alpine coniferous forest in Yunnan Province, China. We hypothesised that <span class="hlt">tropical</span> assemblages would be more elevationally stratified than temperate assemblages, and <span class="hlt">tropical</span> species would be more elevationally restricted than those in the temperate zone. Contrary to our hypothesis, the moth fauna was more sensitive to elevational differences within the temperate transect, followed by sub-<span class="hlt">tropical</span> and <span class="hlt">tropical</span> transects. Moths in the cooler and more seasonal temperate sub-alpine gradient showed stronger elevation-decay beta diversity patterns, and more species were restricted to particular elevational ranges. Our study suggests that moth assemblages are under threat from future <span class="hlt">climate</span> change and sub-alpine rather than <span class="hlt">tropical</span> faunas may be the most sensitive to <span class="hlt">climate</span> change. These results improve our understanding of China’s biodiversity and can be used to monitor future changes to herbivore assemblages in a ‘hotspot’ of biodiversity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP13D1109M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP13D1109M"><span>Isotopic composition of ice core air reveals <span class="hlt">abrupt</span> Antarctic warming during and after Heinrich Event 1a</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morgan, J. D.; Bereiter, B.; Baggenstos, D.; Kawamura, K.; Shackleton, S. A.; Severinghaus, J. P.</p> <p>2017-12-01</p> <p>Antarctic temperature variations during Heinrich events, as recorded by δ18O­ice­, generally show more gradual changes than the <span class="hlt">abrupt</span> warmings seen in Greenland ice. However, quantitative temperature interpretation of the water isotope temperature proxy is difficult as the relationship between δ18Oice and temperature is not constant through time. Fortunately, ice cores offer a second temperature proxy based on trapped gases. During times of surface warming, thermal fractionation of gases in the column of unconsolidated snow (firn) on top of the ice sheet results in isotopically heavier nitrogen (N2) and argon (Ar) being trapped in the ice core bubbles. During times of surface cooling, isotopically lighter gases are trapped. Measurements of δ15N and δ40Ar can therefore be used, in combination with a model for the height of the column of firn, to quantitatively reconstruct surface temperatures. In the WAIS Divide Ice Core, the two temperature proxies show a brief disagreement during Heinrich Stadial 1. Despite δ18Oice recording relatively constant temperature, the nitrogen and argon isotopes imply an <span class="hlt">abrupt</span> warming between 16 and 15.8 kyr BP, manifest as an <span class="hlt">abrupt</span> 1.25oC increase in the firn temperature gradient. To our knowledge, this would be the first evidence that such <span class="hlt">abrupt</span> <span class="hlt">climate</span> change has been recorded in an Antarctic <span class="hlt">climate</span> proxy. If confirmed by more detailed studies, this event may represent warming due to an extreme southward shift of the Earth's thermal equator (and the southern hemisphere westerly wind belt), caused by the 16.1 ka Heinrich Event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1394474-advancing-model-validated-statistical-method-decomposing-key-oceanic-drivers-regional-climate-focus-northern-tropical-african-climate-variability-community-earth-system-model-cesm','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1394474-advancing-model-validated-statistical-method-decomposing-key-oceanic-drivers-regional-climate-focus-northern-tropical-african-climate-variability-community-earth-system-model-cesm"><span>Advancing a Model-Validated Statistical Method for Decomposing the Key Oceanic Drivers of Regional <span class="hlt">Climate</span>: Focus on Northern and <span class="hlt">Tropical</span> African <span class="hlt">Climate</span> Variability in the Community Earth System Model (CESM)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wang, Fuyao; Yu, Yan; Notaro, Michael</p> <p></p> <p>This study advances the practicality and stability of the traditional multivariate statistical method, generalized equilibrium feedback assessment (GEFA), for decomposing the key oceanic drivers of regional atmospheric variability, especially when available data records are short. An advanced stepwise GEFA methodology is introduced, in which unimportant forcings within the forcing matrix are eliminated through stepwise selection. Method validation of stepwise GEFA is performed using the CESM, with a focused application to northern and <span class="hlt">tropical</span> Africa (NTA). First, a statistical assessment of the atmospheric response to each primary oceanic forcing is carried out by applying stepwise GEFA to a fully coupled controlmore » run. Then, a dynamical assessment of the atmospheric response to individual oceanic forcings is performed through ensemble experiments by imposing sea surface temperature anomalies over focal ocean basins. Finally, to quantify the reliability of stepwise GEFA, the statistical assessment is evaluated against the dynamical assessment in terms of four metrics: the percentage of grid cells with consistent response sign, the spatial correlation of atmospheric response patterns, the area-averaged seasonal cycle of response magnitude, and consistency in associated mechanisms between assessments. In CESM, <span class="hlt">tropical</span> modes, namely El Niño–Southern Oscillation and the <span class="hlt">tropical</span> Indian Ocean Basin, <span class="hlt">tropical</span> Indian Ocean dipole, and <span class="hlt">tropical</span> Atlantic Niño modes, are the dominant oceanic controls of NTA <span class="hlt">climate</span>. In complementary studies, stepwise GEFA is validated in terms of isolating terrestrial forcings on the atmosphere, and observed oceanic and terrestrial drivers of NTA <span class="hlt">climate</span> are extracted to establish an observational benchmark for subsequent coupled model evaluation and development of process-based weights for regional <span class="hlt">climate</span> projections.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1394474-advancing-model-validated-statistical-method-decomposing-key-oceanic-drivers-regional-climate-focus-northern-tropical-african-climate-variability-community-earth-system-model-cesm','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1394474-advancing-model-validated-statistical-method-decomposing-key-oceanic-drivers-regional-climate-focus-northern-tropical-african-climate-variability-community-earth-system-model-cesm"><span>Advancing a Model-Validated Statistical Method for Decomposing the Key Oceanic Drivers of Regional <span class="hlt">Climate</span>: Focus on Northern and <span class="hlt">Tropical</span> African <span class="hlt">Climate</span> Variability in the Community Earth System Model (CESM)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wang, Fuyao; Yu, Yan; Notaro, Michael; ...</p> <p>2017-09-27</p> <p>This study advances the practicality and stability of the traditional multivariate statistical method, generalized equilibrium feedback assessment (GEFA), for decomposing the key oceanic drivers of regional atmospheric variability, especially when available data records are short. An advanced stepwise GEFA methodology is introduced, in which unimportant forcings within the forcing matrix are eliminated through stepwise selection. Method validation of stepwise GEFA is performed using the CESM, with a focused application to northern and <span class="hlt">tropical</span> Africa (NTA). First, a statistical assessment of the atmospheric response to each primary oceanic forcing is carried out by applying stepwise GEFA to a fully coupled controlmore » run. Then, a dynamical assessment of the atmospheric response to individual oceanic forcings is performed through ensemble experiments by imposing sea surface temperature anomalies over focal ocean basins. Finally, to quantify the reliability of stepwise GEFA, the statistical assessment is evaluated against the dynamical assessment in terms of four metrics: the percentage of grid cells with consistent response sign, the spatial correlation of atmospheric response patterns, the area-averaged seasonal cycle of response magnitude, and consistency in associated mechanisms between assessments. In CESM, <span class="hlt">tropical</span> modes, namely El Niño–Southern Oscillation and the <span class="hlt">tropical</span> Indian Ocean Basin, <span class="hlt">tropical</span> Indian Ocean dipole, and <span class="hlt">tropical</span> Atlantic Niño modes, are the dominant oceanic controls of NTA <span class="hlt">climate</span>. In complementary studies, stepwise GEFA is validated in terms of isolating terrestrial forcings on the atmosphere, and observed oceanic and terrestrial drivers of NTA <span class="hlt">climate</span> are extracted to establish an observational benchmark for subsequent coupled model evaluation and development of process-based weights for regional <span class="hlt">climate</span> projections.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.8950H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.8950H"><span>Multi-decadal carbon and water relations of African <span class="hlt">tropical</span> humid forests: a tree-ring stable isotope analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hufkens, Koen; Helle, Gerd; Beeckman, Hans; de Haulleville, Thales; Kearsley, Elizabeth; Boeckx, Pascal</p> <p>2013-04-01</p> <p>Little is known about the temporal dynamics of the carbon sequestering capacity and dynamics of African <span class="hlt">tropical</span> humid forest ecosystems in response to various environmental drivers. This lack of knowledge is mainly due to the absence of ecosystem scale flux measurements of gas exchange. However, tree growth often displays itself as alternating pattern of visible rings due to the seasonally varying growth speed of the vascular cambium. Consequently, analysis of tree growth through tree-ring analysis provides us with insights into past responses of the carbon sequestering capacity of key species to <span class="hlt">abrupt</span> ecosystem disturbances and, while slower, a changing <span class="hlt">climate</span>. Not only does the width and density of growth rings reflect annual growth but their isotopic composition of 13C/12C and 18O/16O isotopes also reveal the environmental conditions in which the trees were growing. In particular, stable isotope ratios in tree-rings of carbon are influenced by fractionation through carboxylation during photosynthesis and changes in leaf stomatal conductance. Similarly, fractionation of oxygen isotopes of soil water occurs at the leaf level through evapo-transipiration. As a consequence, 18O/16O (δ18O) values in wood cores will reflect both the signal of the source water as well as that of for example summer humidity. Therefore, both C and O stable isotopes might not only be valuable as proxy data for past <span class="hlt">climatic</span> conditions but they also serve as an important tool in understanding carbon and water relations within a <span class="hlt">tropical</span> forest ecosystems. To this end we correlate long term <span class="hlt">climate</span> records (1961 - present) with tree ring measurement of incremental growth and high resolution analysis of tree-core stable isotope composition(δ13C , δ18O) at a <span class="hlt">tropical</span> humid forests in the DR Congo. The Yangambi Man And Biosphere (MAB) reserve is located in the north-eastern part of DR Congo, with a distinct <span class="hlt">tropical</span> rainforest <span class="hlt">climate</span>. In addition to the tree-core data records and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160013621&hterms=trees&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtrees','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160013621&hterms=trees&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtrees"><span><span class="hlt">Abrupt</span> Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20160013621'); toggleEditAbsImage('author_20160013621_show'); toggleEditAbsImage('author_20160013621_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20160013621_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20160013621_hide"></p> <p>2014-01-01</p> <p>Interactions between <span class="hlt">climate</span> and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, longterm experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW x m(exp -1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with less than 1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to <span class="hlt">climate</span> change across drier portions of the Amazon require more than simulation of global <span class="hlt">climate</span> forcing alone and must also include interactions of extreme weather events, fire, and land-use change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24733937','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24733937"><span><span class="hlt">Abrupt</span> increases in Amazonian tree mortality due to drought-fire interactions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K; Nepstad, Daniel C; Morton, Douglas C; Putz, Francis E; Coe, Michael T; Silvério, Divino; Macedo, Marcia N; Davidson, Eric A; Nóbrega, Caroline C; Alencar, Ane; Soares-Filho, Britaldo S</p> <p>2014-04-29</p> <p>Interactions between <span class="hlt">climate</span> and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to <span class="hlt">climate</span> change across drier portions of the Amazon require more than simulation of global <span class="hlt">climate</span> forcing alone and must also include interactions of extreme weather events, fire, and land-use change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4035969','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4035969"><span><span class="hlt">Abrupt</span> increases in Amazonian tree mortality due to drought–fire interactions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silvério, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nóbrega, Caroline C.; Alencar, Ane; Soares-Filho, Britaldo S.</p> <p>2014-01-01</p> <p>Interactions between <span class="hlt">climate</span> and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by <span class="hlt">abruptly</span> increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found <span class="hlt">abrupt</span> increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW⋅m−1). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to <span class="hlt">climate</span> change across drier portions of the Amazon require more than simulation of global <span class="hlt">climate</span> forcing alone and must also include interactions of extreme weather events, fire, and land-use change. PMID:24733937</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090014193&hterms=water+vapor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dwater%2Bvapor','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090014193&hterms=water+vapor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dwater%2Bvapor"><span>Water Vapor Feedback and Links to Mechanisms of Recent <span class="hlt">Tropical</span> <span class="hlt">Climate</span> Variations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, F. R.; Miller, Tim L.</p> <p>2008-01-01</p> <p>Recent variations of <span class="hlt">tropical</span> <span class="hlt">climate</span> on interannual to near-decadal scales have provided a useful target for studying feedback processes. A strong warm/cold ENSO couplet (e.g. 1997-2000) along with several subsequent weaker events are prominent interannual signals that are part of an apparent longer term strengthening of the Walker circulation during the mid to late1990 s with some weakening thereafter. Decadal scale changes in <span class="hlt">tropical</span> SST structure during the 1990s are accompanied by focusing of precipitation over the Indo-Pacific warm pool and an increase in <span class="hlt">tropical</span> ocean evaporation of order 1.0 %/decade. Here we use a number of diverse satellite measurements to explore connections between upper-tropospheric humidity (UTH) variations on these time scales and changes in other water and energy fluxes. Precipitation (GPCP, TRMM), turbulent fluxes (OAFlux), and radiative fluxes (ERBE / CERES, SRB) are use to analyze vertically-integrated divergence of moist static energy, divMSE, and its dry and moist components. Strong signatures of MSE flux transport linking ascending and descending regions of <span class="hlt">tropical</span> circulations are found. Relative strengths of these transports compared to radiative flux changes are interpreted as a measure of efficiency in the overall process of heat rejection during episodes of warm or cold SST forcing. In conjunction with the diagnosed energy transports we explore frequency distributions of upper-tropospheric humidity as inferred from SSM/T-2 and AMSU-B passive microwave measurements. Relating these variations to SST changes suggests positive water vapor feedback, but at a level reduced from constant relative humidity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=316917','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=316917"><span><span class="hlt">Abrupt</span> shifts in phenology and vegetation productivity under <span class="hlt">climate</span> extremes</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>Amplification of the hydrologic cycle as a consequence of global warming is predicted to increase <span class="hlt">climate</span> variability and the frequency and severity of droughts. Predicting how ecosystems will be affected by <span class="hlt">climate</span> change requires not only reliable forecasts of future <span class="hlt">climate</span>, but also observationa...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26508809','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26508809"><span><span class="hlt">Climate</span> as a driver of <span class="hlt">tropical</span> insular diversity: comparative phylogeography of two ecologically distinctive frogs in Puerto Rico.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barker, Brittany S; Rodríguez-Robles, Javier A; Cook, Joseph A</p> <p>2015-08-01</p> <p>The effects of late Quaternary <span class="hlt">climate</span> on distributions and evolutionary dynamics of insular species are poorly understood in most <span class="hlt">tropical</span> archipelagoes. We used ecological niche models under past and current <span class="hlt">climate</span> to derive hypotheses regarding how stable <span class="hlt">climatic</span> conditions shaped genetic diversity in two ecologically distinctive frogs in Puerto Rico. Whereas the Mountain Coquí, Eleutherodactylus portoricensis , is restricted to montane forest in the Cayey and Luquillo Mountains, the Red-eyed Coquí, E. antillensis , is a habitat generalist distributed across the entire Puerto Rican Bank (Puerto Rico and the Virgin Islands, excluding St. Croix). To test our hypotheses, we conducted phylogeographic and population genetic analyses based on mitochondrial and nuclear loci of each species across their range in Puerto Rico. Patterns of population differentiation in E. portoricensis , but not in E. antillensis , supported our hypotheses. For E. portoricensis , these patterns include: individuals isolated by long-term unsuitable <span class="hlt">climate</span> in the Río Grande de Loíza Basin in eastern Puerto Rico belong to different genetic clusters; past and current <span class="hlt">climate</span> strongly predicted genetic differentiation; and Cayey and Luquillo Mountains populations split prior to the last interglacial. For E. antillensis , these patterns include: genetic clusters did not fully correspond to predicted long-term unsuitable <span class="hlt">climate</span>; and past and current <span class="hlt">climate</span> weakly predicted patterns of genetic differentiation. Genetic signatures in E. antillensis are consistent with a recent range expansion into western Puerto Rico, possibly resulting from <span class="hlt">climate</span> change and anthropogenic influences. As predicted, regions with a large area of long-term suitable <span class="hlt">climate</span> were associated with higher genetic diversity in both species, suggesting larger and more stable populations. Finally, we discussed the implications of our findings for developing evidence-based management decisions for E. portoricensis , a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008EOSTr..89..422M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008EOSTr..89..422M"><span>Fixing <span class="hlt">Climate</span>: What Past <span class="hlt">Climate</span> Changes Reveal About the Current Threat-And How to Counter It</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKinley, Galen A.</p> <p>2008-10-01</p> <p>The Earth's <span class="hlt">climate</span> is changing due to human activities. Recent polls suggest that the U.S. public generally recognizes this fact, and the efforts that led the Intergovernmental Panel on <span class="hlt">Climate</span> Change (IPCC) and former U.S. vice president Al Gore to win the 2007 Nobel Peace Prize have played no small role in bringing most of the public to realize what scientists have been discussing for years. Yet aside from distorted Hollywood movie accounts such as The Day After Tomorrow, the public knows little about the potential for <span class="hlt">abrupt</span> change in the <span class="hlt">climate</span> system. With support from <span class="hlt">climate</span> science philanthropist Gary Comer, <span class="hlt">climate</span> scientist Wally Broecker has teamed with science writer Robert Kunzig in this book to bring <span class="hlt">abrupt</span> <span class="hlt">climate</span> change into public view. They do this elegantly and convincingly, making the first 12 chapters quite enjoyable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20609116','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20609116"><span>The <span class="hlt">climatic</span> sensitivity of the forest, savanna and forest-savanna transition in <span class="hlt">tropical</span> South America.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hirota, Marina; Nobre, Carlos; Oyama, Marcos Daisuke; Bustamante, Mercedes M C</p> <p>2010-08-01</p> <p>*We used a <span class="hlt">climate</span>-vegetation-natural fire (CVNF) conceptual model to evaluate the sensitivity and vulnerability of forest, savanna, and the forest-savanna transition to environmental changes in <span class="hlt">tropical</span> South America. *Initially, under current environmental conditions, CVNF model results suggested that, in the absence of fires, <span class="hlt">tropical</span> forests would extend c. 200 km into the presently observed savanna domain. *Environmental changes were then imposed upon the model in temperature, precipitation and lightning strikes. These changes ranged from 2 to 6 degrees C warming, +10 to -20% precipitation change and 0 to 15% increase in lightning frequency, which, in aggregate form, represent expected future <span class="hlt">climatic</span> changes in response to global warming and deforestation. *The most critical vegetation changes are projected to take place over the easternmost portions of the basin, with a widening of the forest-savanna transition. The transition width would increase from 150 to c. 300 km, with tree cover losses ranging from 20 to 85%. This means that c. 6% of the areas currently covered by forests could potentially turn into grass-dominated savanna landscapes. The mechanism driving tree cover reduction consists of the combination of less favorable <span class="hlt">climate</span> conditions for trees and more fire activity. In addition, this sensitivity analysis predicts that the current dry shrubland vegetation of northeast Brazil could potentially turn into a bare soil landscape.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A41K..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A41K..04L"><span>Attribution of Extreme Rainfall from Landfalling <span class="hlt">Tropical</span> Cyclones to <span class="hlt">Climate</span> Change for the Eastern United States</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, M.; Yang, L.; Smith, J. A.; Vecchi, G. A.</p> <p>2017-12-01</p> <p>Extreme rainfall and flooding associated with landfalling <span class="hlt">tropical</span> cyclones (TC) is responsible for vast socioeconomic losses and fatalities. Landfalling <span class="hlt">tropical</span> cyclones are an important element of extreme rainfall and flood peak distributions in the eastern United States. Record floods for USGS stream gauging stations over the eastern US are closely tied to landfalling hurricanes. A small number of storms account for the largest record floods, most notably Hurricanes Diane (1955) and Agnes (1972). The question we address is: if the synoptic conditions accompanying those hurricanes were to be repeated in the future, how would the thermodynamic and dynamic storm properties and associated extreme rainfall differ in response to <span class="hlt">climate</span> change? We examine three hurricanes: Diane (1955), Agnes (1972) and Irene (2011), due to the contrasts in structure/evolution properties and their important roles in dictating the upper tail properties of extreme rainfall and flood frequency over eastern US. Extreme rainfall from Diane is more localized as the storm maintains <span class="hlt">tropical</span> characteristics, while synoptic-scale vertical motion associated with extratropical transition is a central feature for extreme rainfall induced by Agnes. Our analyses are based on ensemble simulations using the Weather Research and Forecasting (WRF) model, considering combinations of different physics options (i.e., microphysics, boundary layer schemes). The initial and boundary conditions of WRF simulations for the present-day <span class="hlt">climate</span> are using the Twentieth Century Reanalysis (20thCR). A sub-selection of GCMs is used, as part of phase 5 of the Coupled Model Intercomparison Project (CMIP5), to provide future <span class="hlt">climate</span> projections. For future simulations, changes in model fields (i.e., temperature, humidity, geopotential height) between present-day and future <span class="hlt">climate</span> are first derived and then added to the same 20thCR initial and boundary data used for the present-day simulations, and the ensemble is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28763150','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28763150"><span>Pneumonia in the <span class="hlt">tropics</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lim, Tow Keang; Siow, Wen Ting</p> <p>2018-01-01</p> <p>Pneumonia in the <span class="hlt">tropics</span> poses a heavy disease burden. The complex interplay of <span class="hlt">climate</span> change, human migration influences and socio-economic factors lead to changing patterns of respiratory infections in <span class="hlt">tropical</span> <span class="hlt">climate</span> but also increasingly in temperate countries. <span class="hlt">Tropical</span> and poorer countries, especially South East Asia, also bear the brunt of the global tuberculosis (TB) pandemic, accounting for almost one-third of the burden. But, as human migration patterns evolve, we expect to see more TB cases in higher income as well as temperate countries, and rise in infections like scrub typhus from ecotourism activities. Fuelled by the ease of air travel, novel zoonotic infections originating from the <span class="hlt">tropics</span> have led to global respiratory pandemics. As such, clinicians worldwide should be aware of these new conditions as well as classical <span class="hlt">tropical</span> bacterial pneumonias such as melioidosis. Rarer entities such as co-infections of leptospirosis and chikungunya or dengue will need careful consideration as well. In this review, we highlight aetiologies of pneumonia seen more commonly in the <span class="hlt">tropics</span> compared with temperate regions, their disease burden, variable clinical presentations as well as impact on healthcare delivery. © 2017 Asian Pacific Society of Respirology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010QuRes..74..207K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010QuRes..74..207K"><span>Late second-early first millennium BC <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes in coastal Syria and their possible significance for the history of the Eastern Mediterranean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaniewski, D.; Paulissen, E.; Van Campo, E.; Weiss, H.; Otto, T.; Bretschneider, J.; Van Lerberghe, K.</p> <p>2010-09-01</p> <p>The alluvial deposits near Gibala-Tell Tweini provide a unique record of environmental history and food availability estimates covering the Late Bronze Age and the Early Iron Age. The refined pollen-derived <span class="hlt">climatic</span> proxy suggests that drier <span class="hlt">climatic</span> conditions occurred in the Mediterranean belt of Syria from the late 13th/early 12th centuries BC to the 9th century BC. This period corresponds with the time frame of the Late Bronze Age collapse and the subsequent Dark Age. The <span class="hlt">abrupt</span> <span class="hlt">climate</span> change at the end of the Late Bronze Age caused region-wide crop failures, leading towards socio-economic crises and unsustainability, forcing regional habitat-tracking. Archaeological data show that the first conflagration of Gibala occurred simultaneously with the destruction of the capital city Ugarit currently dated between 1194 and 1175 BC. Gibala redeveloped shortly after this destruction, with large-scale urbanization visible in two main architectural phases during the Early Iron Age I. The later Iron Age I city was destroyed during a second conflagration, which is radiocarbon-dated at circa 2950 cal yr BP. The data from Gibala-Tell Tweini provide evidence in support of the drought hypothesis as a triggering factor behind the Late Bronze Age collapse in the Eastern Mediterranean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC51G1100M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC51G1100M"><span><span class="hlt">Climate</span> Mitigation Versus Agriculture in the <span class="hlt">Tropics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McAfee, K.</p> <p>2011-12-01</p> <p>Significant new drivers of land-use change in the <span class="hlt">tropics</span> are market-based strategies for <span class="hlt">climate</span>-change mitigation and biodiversity conservation. These strategies are based on the putative monetary values of new commodities: genetic resources and ecosystem services, especially carbon sequestration services by forests. Payments for Ecosystem Services projects are expanding in Latin America, Asia, and some parts of Africa, promising a 'triple-win' for nature, the private sector, and the poor. Analysis of Mexico's national PES program and review of a growing body of PES case studies, however, reveal a pattern of conflict between poverty alleviation and other social goals, on the one hand, and the market-efficiency criteria that frame many PES projects, on the other hand. This poses a warning for more ambitious, global schemes based on similar principles, such as Reduced Emissions from Deforestation and Degradation (REDD). Additionally, transnational trade in carbon offsets, seen as a source of finance for PES and for REDD, puts <span class="hlt">climate</span> policy on a collision course with agriculture, particularly given the context of closing land frontiers and international 'land-grabbing' claims on land for food-export plantations. Because market-based PES and REDD tend to target small- and medium-scale farmers, they are likely to constrain agriculture for domestic needs in regions where food security is already weak. Land-use governance based on conservation-by-commercialization can be compared to alternative approaches that link greening, food production, and social equity in a more integrated way, by combining scientific and local ecological and agroecological knowledge with strategies for rural revitalization and development.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040171277&hterms=ocean+climate+changes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Docean%2Bclimate%2Bchanges','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040171277&hterms=ocean+climate+changes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Docean%2Bclimate%2Bchanges"><span>Warm Rain Processes Over the <span class="hlt">Tropical</span> Oceans and Implications on <span class="hlt">Climate</span> Change: Results from TRMM and GOES GCM</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K. M.; Wu, H. T.</p> <p>2004-01-01</p> <p>In this talk, we will first show results from TRMM data regarding the characteristics of warm rains over the <span class="hlt">tropical</span> oceans, and the dependence of rate of warm rain production on sea surface temperature. Results lead to the hypothesis that warm rain production efficiency, i.e., autoconversion, may be increased in a warm <span class="hlt">climate</span>. We use the GEOS-II GCM to test this hypothesis. Our modeling results show that in a <span class="hlt">climate</span> with increased rate of autoconversion, the total rain amount is increased, with warm rain contributing to a larger portion of the increase. The abundant rainout of warm precipitation causes a reduction of low and middle cloud amount due to rainout, and reduced high clouds due to less water vapor available for ice-phase convection. However, clod radiation feedback caused by the increased rainfall efficiency, leads to differential vertical heating/cooling producing a more unstable atmosphere, allowing, more intense, but isolated penetrative convection, with contracted anvils to develop. Results also show that increased autoconversion reduces the convective adjustment time scale, resulting in faster recycling of atmospheric water. Most interestingly, the increased low level heating associated with warm rain leads to more energetic Madden and Julian oscillations in the <span class="hlt">tropics</span>, with well-defined eastward propagation. While reducing the autoconversion leads to an abundant mix of westward and eastward <span class="hlt">tropical</span> disturbances on daily to weekly time scales. The crucial link of precipitation microphysical processes to <span class="hlt">climate</span> change including the effects of aerosols will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040171579&hterms=ocean+climate+changes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Docean%2Bclimate%2Bchanges','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040171579&hterms=ocean+climate+changes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Docean%2Bclimate%2Bchanges"><span>Warm Rain Processes over the <span class="hlt">Tropical</span> Oceans and Implications on <span class="hlt">Climate</span> Change: Results from TRMM and GEOS GCM</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K. M.; Wu, H. T.</p> <p>2004-01-01</p> <p>In this talk, we will first show results from TRMM data regarding the characteristics of warm rains over the <span class="hlt">tropical</span> oceans, and the dependence of rate of warm rain production on sea surface temperature. Results lead to the hypothesis that warm rain production efficiency, i.e., autoconversion, may be increased in a warm <span class="hlt">climate</span>. We use the GEOS-II GCM to test this hypothesis. Our modeling results show that in a <span class="hlt">climate</span> with increased rate of autoconversion, the total rain amount is increased, with warm rain contributing to larger portion of the increase. The abundant rainout of warm precipitation causes a reduction of low and middle cloud amount due to rainout, and reduced high clouds due to less water vapor available for ice-phase convection. However, clod radiation feedback caused by the increased rainfall efficiency, leads to differential vertical heating/cooling producing a more unstable atmosphere, allowing, more intense, but isolated penetrative convection, with contracted anvils to develop. Results also show that increased autoconversion reduces the convective adjustment time scale, resulting in faster recycling of atmospheric water. Most interestingly, the increased low level heating associated with warm rain leads to more energetic Madden and Julian oscillations in the <span class="hlt">tropics</span>, with well-defined eastward propagation. While reducing the autoconversion leads to an abundant mix of westward and eastward <span class="hlt">tropical</span> disturbances on daily to weekly time scales. The crucial link of precipitation microphysical processes to <span class="hlt">climate</span> change including the effects of aerosols will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC53F..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC53F..08W"><span>Assessing the 100-Year <span class="hlt">Climate</span> Change Mitigation Potential of Large-Scale <span class="hlt">Tropical</span> Forest Restoration Under the Bonn Challenge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wheeler, C. E.; Mitchard, E. T.; Lewis, S. L.</p> <p>2017-12-01</p> <p>Restoring degraded and deforested <span class="hlt">tropical</span> lands to sequester carbon is widely considered to offer substantial <span class="hlt">climate</span> change mitigation opportunities, if conducted over large spatial scales. Despite this assertion, explicit estimates of how much carbon could be sequestered because of large-scale restoration are rare and have large uncertainties. This is principally due to the many different characteristics of land available for restoration, and different potential restoration activities, which together cause very different rates of carbon sequestration. For different restoration pathways: natural regeneration of degraded and secondary forest, timber plantations and agroforestry, we estimate carbon sequestration rates from the published literature. Then based on <span class="hlt">tropical</span> restoration commitments made under the Bonn challenge and using carbon density maps, these carbon sequestration rates were used to predict total pan-<span class="hlt">tropical</span> carbon sequestration to 2100. Restoration of degraded or secondary forest via natural regeneration offers the greatest carbon sequestration potential, considerably exceeding the carbon captured by either timber plantations or agroforestry. This is predominantly due to naturally regenerating forests representing a more permanent store of carbon in comparison to timber plantations and agroforestry land-use options, which, due to their rotational nature, result in the sequential return of carbon to the atmosphere. If the Bonn Challenge is to achieve its ambition of providing substantial <span class="hlt">climate</span> change mitigation from restoration it must incorporate large areas of natural regeneration back to an intact forest state, otherwise it stands to be a missed opportunity in helping meet the Paris <span class="hlt">climate</span> change goals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1237126-characteristics-tropical-cyclones-high-resolution-models-present-climate','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1237126-characteristics-tropical-cyclones-high-resolution-models-present-climate"><span>Characteristics of <span class="hlt">tropical</span> cyclones in high-resolution models in the present <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Shaevitz, Daniel A.; Camargo, Suzana J.; Sobel, Adam H.; ...</p> <p>2014-12-05</p> <p>The global characteristics of <span class="hlt">tropical</span> cyclones (TCs) simulated by several <span class="hlt">climate</span> models are analyzed and compared with observations. The global <span class="hlt">climate</span> models were forced by the same sea surface temperature (SST) fields in two types of experiments, using climatological SST and interannually varying SST. TC tracks and intensities are derived from each model's output fields by the group who ran that model, using their own preferred tracking scheme; the study considers the combination of model and tracking scheme as a single modeling system, and compares the properties derived from the different systems. Overall, the observed geographic distribution of global TCmore » frequency was reasonably well reproduced. As expected, with the exception of one model, intensities of the simulated TC were lower than in observations, to a degree that varies considerably across models.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMNH22A..04O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMNH22A..04O"><span>Ensemble <span class="hlt">tropical</span>-extratropical cyclone coastal flood hazard assessment with <span class="hlt">climate</span> change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orton, P. M.; Lin, N.; Colle, B.</p> <p>2016-12-01</p> <p>A challenge with quantifying future changes in coastal flooding for the U.S. East Coast is that <span class="hlt">climate</span> change has varying effects on different types of storms, in addition to raising mean sea levels. Moreover, future flood hazard uncertainties are large and come from many sources. Here, a new coastal flood hazard assessment approach is demonstrated that separately evaluates and then combines probabilities of storm tide generated from <span class="hlt">tropical</span> cyclones (TCs) and extratropical cyclones (ETCs). The separation enables us to incorporate <span class="hlt">climate</span> change impacts on both types of storms. The assessment accounts for epistemic storm tide uncertainty using an ensemble of different prior studies and methods of assessment, merged with uncertainty in <span class="hlt">climate</span> change effects on storm tides and sea levels. The assessment is applied for New York Harbor, under the auspices of the New York City Panel on <span class="hlt">Climate</span> Change (NPCC). In the New York Bight region and much of the U.S. East Coast, differing flood exceedance curve slopes for TCs and ETCs arise due to their differing physics. It is demonstrated how errors can arise for this region from mixing together storm types in an extreme value statistical analysis, a common practice when using observations. The effects of <span class="hlt">climate</span> change on TC and ETC flooding have recently been assessed for this region, for TCs using a Global <span class="hlt">Climate</span> Model (GCM) driven hurricane model with hydrodynamic modeling, and for ETCs using a GCM-driven multilinear regression-based storm surge model. The results of these prior studies are applied to our central estimates of the flood exceedance curve probabilities, transforming them for <span class="hlt">climate</span> change effects. The results are useful for decision-makers because they highlight the large uncertainty in present-day and future flood risk, and also for scientists because they identify the areas where further research is most needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2841931','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2841931"><span><span class="hlt">Tropical</span> cloud forest <span class="hlt">climate</span> variability and the demise of the Monteverde golden toad</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Anchukaitis, Kevin J.; Evans, Michael N.</p> <p>2010-01-01</p> <p>Widespread amphibian extinctions in the mountains of the American <span class="hlt">tropics</span> have been blamed on the interaction of anthropogenic <span class="hlt">climate</span> change and a lethal pathogen. However, limited meteorological records make it difficult to conclude whether current <span class="hlt">climate</span> conditions at these sites are actually exceptional in the context of natural variability. We use stable oxygen isotope measurements from trees without annual rings to reconstruct a century of hydroclimatology in the Monteverde Cloud Forest of Costa Rica. High-resolution measurements reveal coherent isotope cycles that provide annual chronological control and paleoclimate information. <span class="hlt">Climate</span> variability is dominated by interannual variance in dry season moisture associated with El Niño Southern Oscillation events. There is no evidence of a trend associated with global warming. Rather, the extinction of the Monteverde golden toad (Bufo periglenes) appears to have coincided with an exceptionally dry interval caused by the 1986–1987 El Niño event. PMID:20194772</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.473..104E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.473..104E"><span>Could gradual changes in Holocene Saharan landscape have caused the observed <span class="hlt">abrupt</span> shift in North Atlantic dust deposition?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja</p> <p>2017-09-01</p> <p>The <span class="hlt">abrupt</span> change in North Atlantic dust deposition found in sediment records has been associated with a rapid large scale transition of Holocene Saharan landscape. We hypothesize that gradual changes in the landscape may have caused this <span class="hlt">abrupt</span> shift in dust deposition either because of the non-linearity in dust activation or because of the heterogeneous distribution of major dust sources. To test this hypothesis, we investigate the response of North Atlantic dust deposition to a prescribed 1) gradual and spatially homogeneous decrease and 2) gradual southward retreat of North African vegetation and lakes during the Holocene using the aerosol-<span class="hlt">climate</span> model ECHAM-HAM. In our simulations, we do not find evidence of an <span class="hlt">abrupt</span> increase in dust deposition as observed in marine sediment records along the Northwest African margin. We conclude that such gradual changes in landscape are not sufficient to explain the observed <span class="hlt">abrupt</span> changes in dust accumulation in marine sediment records. Instead, our results point to a rapid large-scale retreat of vegetation and lakes in the area of significant dust sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999ClDy...15..451F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999ClDy...15..451F"><span>Coupled ocean-atmosphere surface variability and its <span class="hlt">climate</span> impacts in the <span class="hlt">tropical</span> Atlantic region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fontaine, B.; Janicot, Serge; Roucou, P.</p> <p></p> <p>This study examines time evolution and statistical relationships involving the two leading ocean-atmosphere coupled modes of variability in the <span class="hlt">tropical</span> Atlantic and some <span class="hlt">climate</span> anomalies over the <span class="hlt">tropical</span> 120°W-60°W region using selected historical files (75-y near global SSTs and precipitation over land), more recent observed data (30-y SST and pseudo wind stress in the <span class="hlt">tropical</span> Atlantic) and reanalyses from the US National Centers for Environmental Prediction (NCEP/NCAR) reanalysis System on the period 1968-1997: surface air temperature, sea level pressure, moist static energy content at 850 hPa, precipitable water and precipitation. The first coupled mode detected through singular value decomposition of the SST and pseudo wind-stress data over the <span class="hlt">tropical</span> Atlantic (30°N-20°S) expresses a modulation in the thermal transequatorial gradient of SST anomalies conducted by one month leading wind-stress anomalies mainly in the <span class="hlt">tropical</span> north Atlantic during northern winter and fall. It features a slight dipole structure in the meridional plane. Its time variability is dominated by a quasi-decadal signal well observed in the last 20-30 ys and, when projected over longer-term SST data, in the 1920s and 1930s but with shorter periods. The second coupled mode is more confined to the south-equatorial <span class="hlt">tropical</span> Atlantic in the northern summer and explains considerably less wind-stress/SST cross-covariance. Its time series features an interannual variability dominated by shorter frequencies with increased variance in the 1960s and 1970s before 1977. Correlations between these modes and the ENSO-like Nino3 index lead to decreasing amplitude of thermal anomalies in the <span class="hlt">tropical</span> Atlantic during warm episodes in the Pacific. This could explain the nonstationarity of meridional anomaly gradients on seasonal and interannual time scales. Overall the relationships between the oceanic component of the coupled modes and the <span class="hlt">climate</span> anomaly patterns denote thermodynamical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8750B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8750B"><span>Understanding the <span class="hlt">tropical</span> warm temperature bias simulated by <span class="hlt">climate</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brient, Florent; Schneider, Tapio</p> <p>2017-04-01</p> <p>The state-of-the-art coupled general circulation models have difficulties in representing the observed spatial pattern of surface tempertaure. A majority of them suffers a warm bias in the <span class="hlt">tropical</span> subsiding regions located over the eastern parts of oceans. These regions are usually covered by low-level clouds scattered from stratus along the coasts to more vertically developed shallow cumulus farther from them. Models usually fail to represent accurately this transition. Here we investigate physical drivers of this warm bias in CMIP5 models through a near-surface energy budget perspective. We show that overestimated solar insolation due to a lack of stratocumulus mostly explains the warm bias. This bias also arises partly from inter-model differences in surface fluxes that could be traced to differences in near-surface relative humidity and air-sea temperature gradient. We investigate the role of the atmosphere in driving surface biases by comparing historical and atmopsheric (AMIP) experiments. We show that some differences in boundary-layer characteristics, mostly those related to cloud fraction and relative humidity, are already present in AMIP experiments and may be the drivers of coupled biases. This gives insights in how models can be improved for better simulations of the <span class="hlt">tropical</span> <span class="hlt">climate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B23C0442S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B23C0442S"><span>Response of <span class="hlt">Tropical</span> Forests to Intense <span class="hlt">Climate</span> Variability and Rainfall Anomaly of Last Decade</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saatchi, S. S.; Asefi Najafabady, S.</p> <p>2011-12-01</p> <p>During the last decade, strong precipitation anomalies resulted from increased sea surface temperature in the <span class="hlt">tropical</span> Atlantic, have caused extensive drying trends in rainforests of western Amazonia, exerting water stress, tree mortality, biomass loss, and large-scale fire disturbance. In contrast, there have been no reports on large-scale disturbance in rainforests of west and central Africa, though being exposed to similar intensity of <span class="hlt">climate</span> variability. Using data from <span class="hlt">Tropical</span> Rainfall Mapping Mission (TRMM) (1999-2010), and time series of rainfall observations from meteorological stations (1971-2000), we show that both Amazonian and African rainforest experienced strong precipitation anomalies from 2005-2010. We monitored the response of forest to the <span class="hlt">climate</span> variability by analyzing the canopy water content observed by SeaWinds Ku-band Scatterometer (QSCAT) (1999-2009) and found that more than 70 million ha of forests in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy backscatter that persisted until the next major drought in 2010. This decline in backscatter has been attributed to loss of canopy water content and large-scale tree mortality corroborated by ground and airborne observations. However, no strong impacts was observed on <span class="hlt">tropical</span> forests of Africa, suggesting that the African rainforest may have more resilience to droughts. We tested this hypothesis by examining the seasonal rainfall patterns, maximum water deficit, and the surface temperature variations. Results show that there is a complex pattern of low annual rainfall, moderate seasonality, and lower surface temperature in Central Africa compared to Amazonia, indicating potentially a lower evapotranspiration circumventing strong water deficits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP41F..06K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP41F..06K"><span>Reconstructing medieval <span class="hlt">climate</span> in the <span class="hlt">tropical</span> North Atlantic with corals from Anegada, British Virgin Islands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kilbourne, K. H.; Xu, Y. Y.</p> <p>2014-12-01</p> <p>Resolving the patterns of <span class="hlt">climate</span> variability during the Medieval <span class="hlt">Climate</span> Anomaly (MCA) is key for exploring forced versus unforced variability during the last 1000 years. <span class="hlt">Tropical</span> Atlantic <span class="hlt">climate</span> is currently not well resolved during the MCA despite it being an important source of heat and moisture to the <span class="hlt">climate</span> system today. To fill this data gap, we collected cores from Diploria strigosa corals brought onto the low-lying island of Anegada, British Virgin Islands (18.7˚N, 64.3˚S) during an overwash event and use paired analysis of Sr/Ca and δ18O in the skeletal aragonite to explore <span class="hlt">climate</span> in the <span class="hlt">tropical</span> Atlantic at the end of the MCA. The three sub-fossil corals used in this analysis overlap temporally and together span the years 1256-1372 C.E. An assessment of three modern corals from the study site indicates that the most robust features of <span class="hlt">climate</span> reconstructions using Sr/Ca and δ18O in this species are the seasonal cycle and inter-annual variability. The modern seasonal temperature range is 2.8 degrees Celsius and the similarity between the modern and sub-fossil coral Sr/Ca indicates a similar range during the MCA. Today seasonal salinity changes locally are driven in large part by the migration of a regional salinity front. The modern corals capture the related large seasonal seawater δ18O change, but the sub-fossil corals indicate stable seawater δ18O throughout the year, supporting the idea that this site remained on one side of the salinity front continuously throughout the year. Inter-annual variability in the region is influenced by the cross-equatorial SST gradient, the North Atlantic Oscillation and ENSO. Gridded instrumental SST from the area surrounding Anegada and coral geochemical records from nearby Puerto Rico demonstrate concentrations of variance in specific frequency bands associated with these phenomena. The sub-fossil coral shows no concentration of variance in the modern ENSO frequency band, consistent with reduced ENSO</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3729957','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3729957"><span>Current Analogues of Future <span class="hlt">Climate</span> Indicate the Likely Response of a Sensitive Montane <span class="hlt">Tropical</span> Avifauna to a Warming World</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Anderson, Alexander S.; Storlie, Collin J.; Shoo, Luke P.; Pearson, Richard G.; Williams, Stephen E.</p> <p>2013-01-01</p> <p>Among birds, <span class="hlt">tropical</span> montane species are likely to be among the most vulnerable to <span class="hlt">climate</span> change, yet little is known about how <span class="hlt">climate</span> drives their distributions, nor how to predict their likely responses to temperature increases. Correlative models of species’ environmental niches have been widely used to predict changes in distribution, but direct tests of the relationship between key variables, such as temperature, and species’ actual distributions are few. In the absence of historical data with which to compare observations and detect shifts, space-for-time substitutions, where warmer locations are used as analogues of future conditions, offer an opportunity to test for species’ responses to <span class="hlt">climate</span>. We collected density data for rainforest birds across elevational gradients in northern and southern subregions within the Australian Wet <span class="hlt">Tropics</span> (AWT). Using environmental optima calculated from elevational density profiles, we detected a significant elevational difference between the two regions in ten of 26 species. More species showed a positive (19 spp.) than negative (7 spp.) displacement, with a median difference of ∼80.6 m across the species analysed that is concordant with that expected due to latitudinal temperature differences (∼75.5 m). Models of temperature gradients derived from broad-scale <span class="hlt">climate</span> surfaces showed comparable performance to those based on in-situ measurements, suggesting the former is sufficient for modeling impacts. These findings not only confirm temperature as an important factor driving elevational distributions of these species, but also suggest species will shift upslope to track their preferred environmental conditions. Our approach uses optima calculated from elevational density profiles, offering a data-efficient alternative to distribution limits for gauging <span class="hlt">climate</span> constraints, and is sensitive enough to detect distribution shifts in this avifauna in response to temperature changes of as little as 0.4 degrees</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23936005','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23936005"><span>Current analogues of future <span class="hlt">climate</span> indicate the likely response of a sensitive montane <span class="hlt">tropical</span> avifauna to a warming world.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Anderson, Alexander S; Storlie, Collin J; Shoo, Luke P; Pearson, Richard G; Williams, Stephen E</p> <p>2013-01-01</p> <p>Among birds, <span class="hlt">tropical</span> montane species are likely to be among the most vulnerable to <span class="hlt">climate</span> change, yet little is known about how <span class="hlt">climate</span> drives their distributions, nor how to predict their likely responses to temperature increases. Correlative models of species' environmental niches have been widely used to predict changes in distribution, but direct tests of the relationship between key variables, such as temperature, and species' actual distributions are few. In the absence of historical data with which to compare observations and detect shifts, space-for-time substitutions, where warmer locations are used as analogues of future conditions, offer an opportunity to test for species' responses to <span class="hlt">climate</span>. We collected density data for rainforest birds across elevational gradients in northern and southern subregions within the Australian Wet <span class="hlt">Tropics</span> (AWT). Using environmental optima calculated from elevational density profiles, we detected a significant elevational difference between the two regions in ten of 26 species. More species showed a positive (19 spp.) than negative (7 spp.) displacement, with a median difference of ∼80.6 m across the species analysed that is concordant with that expected due to latitudinal temperature differences (∼75.5 m). Models of temperature gradients derived from broad-scale <span class="hlt">climate</span> surfaces showed comparable performance to those based on in-situ measurements, suggesting the former is sufficient for modeling impacts. These findings not only confirm temperature as an important factor driving elevational distributions of these species, but also suggest species will shift upslope to track their preferred environmental conditions. Our approach uses optima calculated from elevational density profiles, offering a data-efficient alternative to distribution limits for gauging <span class="hlt">climate</span> constraints, and is sensitive enough to detect distribution shifts in this avifauna in response to temperature changes of as little as 0.4 degrees. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/31820','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/31820"><span><span class="hlt">Climate</span> change; Confronting the global experiment</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Constance I. Millar</p> <p>2006-01-01</p> <p>Earth’s natural <span class="hlt">climate</span> system is characterized by continually changing <span class="hlt">climates</span>, with <span class="hlt">climate</span> regimes that oscillate quasi-cyclically at multiple and nested scales from annual to multi-millennial, and commonly change <span class="hlt">abruptly</span>. Under naturally changing <span class="hlt">climates</span>, plant species track changes at all scales in individualistic manner, with plant communities...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23569264','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23569264"><span><span class="hlt">Abrupt</span> drainage cycles of the Fennoscandian Ice Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard</p> <p>2013-04-23</p> <p>Continental ice sheets are a key component of the Earth's <span class="hlt">climate</span> system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the <span class="hlt">climate</span>-lake-FIS system, linked to changes in the availability of subglacial water, led to <span class="hlt">abrupt</span> drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ∼100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014QSRv...97...58H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014QSRv...97...58H"><span><span class="hlt">Abrupt</span> variations of Indian and East Asian summer monsoons during the last deglacial stadial and interstadial</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hong, Bing; Hong, Yetang; Uchida, Masao; Shibata, Yasuyuki; Cai, Cheng; Peng, Haijun; Zhu, Yongxuan; Wang, Yu; Yuan, Linggui</p> <p>2014-08-01</p> <p>The phase relationship between the Indian summer monsoon (ISM) and the East Asian summer monsoon (EASM) during the last deglaciation remains controversial. Here, we reconstruct a 15,000-year plant cellulose δ13C proxy record for the ISM from the Yuexi peat bog in southwestern China. The record shows that the ISM <span class="hlt">abruptly</span> decreases during the Younger Dryas (YD) stadial and <span class="hlt">abruptly</span> increases during the Bølling-Allerød (BA) interstadial. A comparison of the Yuexi record with other related proxy <span class="hlt">climate</span> records reveals two types of phenomena. First, the strengths of the two Asian monsoons are inversely related during the YD stadial, i.e., the ISM strength decreases and the EASM increases. During this period, the southern Chinese mainland consisted of a wide arid zone while the northern Chinese mainland was much wetter. The arid zone in southern China resulted from two different types of monsoon processes: the abnormal northward extension of the EASM rain belt, leading to less rainfall in southeast China, or an illusion that the EASM weakened. The other process is a real weakening of the ISM. Second, during the BA interstadial, the strengths of both the ISM and EASM clearly increased. However, the maximum strengths appear to have occurred in the Allerød period. During this period, the entire Chinese mainland, both northern and southern, experienced wet conditions. The abnormal <span class="hlt">climate</span> pattern of wet in the north and dry in the south during the YD stadial occurs because of the combined effects of the strengthened EASM, intensified westerlies, and weakened ISM, which could be attributed to the response to the <span class="hlt">abrupt</span> cooling in the high northern latitudes and to the El Niño-like activity in the equatorial Pacific. The widespread wet <span class="hlt">climate</span> during the BA interstadial may be related to an <span class="hlt">abrupt</span> increase in the greenhouse gases (GHGs) concentrations in the atmosphere and to the La Niña-like activity in the equatorial Pacific. These results contribute to a better</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A51C0070C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A51C0070C"><span>Rectification of the Diurnal Cycle and the Impact of Islands on the <span class="hlt">Tropical</span> <span class="hlt">Climate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cronin, T. W.; Emanuel, K.</p> <p>2012-12-01</p> <p><span class="hlt">Tropical</span> islands are observed to be rainier than nearby ocean areas, and rainfall over the islands of the Maritime Continent plays an important role in the atmospheric general circulation. Convective heating over <span class="hlt">tropical</span> islands is also strongly modulated by the diurnal cycle of solar insolation and surface enthalpy fluxes, and convective parameterizations in general circulation models are known to reproduce the phase and amplitude of the observed diurnal cycle of convection rather poorly. Connecting these ideas suggests that poor representation of the diurnal cycle of convection and precipitation over <span class="hlt">tropical</span> islands in <span class="hlt">climate</span> models may be a significant source of model biases. Here, we explore how a highly idealized island, which differs only in heat capacity from the surrounding ocean, could rectify the diurnal cycle and impact the <span class="hlt">tropical</span> <span class="hlt">climate</span>, especially the spatial distribution of rainfall. We perform simulations of radiative-convective equilibrium with the System for Atmospheric Modeling cloud-system-resolving model, with interactive surface temperature and a varied surface heat capacity. For the case of relatively small-scale simulations, where a shallow (~5 cm) slab-ocean "swamp island" surface is embedded in a deeper (~1 m) slab-ocean domain, the precipitation rate over the island is more than double the domain average value, with island rainfall occurring primarily in a strong regular convective event each afternoon. In addition to this island precipitation enhancement, the upper troposphere also warms with the inclusion of a low- heat capacity island. We discuss two radiative mechanisms that contribute to both island precipitation enhancement and free tropospheric warming, by producing a top-of-atmosphere radiative surplus over the island. The first radiative mechanism is a clear-sky effect, related to nonlinearities in the surface energy budget, and differences in how surface energy balance is achieved over surfaces of different heat capacities</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.1393T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.1393T"><span>Impact of <span class="hlt">tropical</span> cyclones on modeled extreme wind-wave <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Timmermans, Ben; Stone, Dáithí; Wehner, Michael; Krishnan, Harinarayan</p> <p>2017-02-01</p> <p>The effect of forcing wind resolution on the extremes of global wind-wave <span class="hlt">climate</span> are investigated in numerical simulations. Forcing winds from the Community Atmosphere Model at horizontal resolutions of ˜1.0° and ˜0.25° are used to drive Wavewatch III. Differences in extreme wave height are found to manifest most strongly in <span class="hlt">tropical</span> cyclone (TC) regions, emphasizing the need for high-resolution forcing in those areas. Comparison with observations typically show improvement in performance with increased forcing resolution, with a strong influence in the tail of the distribution, although simulated extremes can exceed observations. A simulation for the end of the 21st century under a RCP 8.5 type emission scenario suggests further increases in extreme wave height in TC regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSME24E0760S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSME24E0760S"><span>Impact of Hypoxia on Startle Response (C-start) of Fish in a <span class="hlt">Tropical</span> Urban Estuary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sánchez-García, M.; Zottoli, S. J.; Roberson, L.</p> <p>2016-02-01</p> <p>Hypoxic zones have become more prevalent in marine ecosystems as a result of physical changes to the coastal zone, pollution and eutrophication, and are expected to increase in prevalence with <span class="hlt">climate</span> change. While some studies have examined the behavioral effects of hypoxia on coastal fishes in temperate and sub-<span class="hlt">tropical</span> zones, none have focused on <span class="hlt">tropical</span> coastal zones. Behavioral changes may affect fish survival, predator-prey interactions and ultimately ecosystem structure. Through behavioral endpoints we evaluated the effects of non-lethal levels of hypoxia on estuarine fish collected from the <span class="hlt">tropical</span> Condado Lagoon, San Juan P.R, in a laboratory setting. Two groups of 10 fishes were placed individually in a sound test chamber and oxygen concentrations were modulated from a pre-treatment at 100% oxygen to increasing levels of hypoxia (80, 70, & 60%), followed by a reversal treatment (100%) to test for recovery of pretreatment behavior. An <span class="hlt">abrupt</span> sound stimulus was used to elicit a startle response, a quantifiable biological endpoint, while recording with a high speed camera. This approach can lend valuable insight into changes in the central nervous system and effects of anthropogenic inputs on <span class="hlt">tropical</span> ecosystems at the individual- and population-level. We found that hypoxic conditions significantly decrease fish responsiveness; fish startled only half the time at 80% O2 and dropped as much as 61% at 60% O2. Additionally, responsiveness in reversal tests were significantly lower than under pre-treatment conditions. These results indicate that hypoxia may have long-term or possibly permanent effects, even under relatively mild hypoxia conditions common to <span class="hlt">tropical</span> estuaries. Future work will aim to understand if the startle response can be regained after a hypoxic event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP53C2376A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP53C2376A"><span>Paleoecology, Biostratigraphy, and Response of Calcareous Nannoplankton Communities to <span class="hlt">Climate</span> Fluctuations during the Late Oligocene in the <span class="hlt">Tropics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aljahdali, M. H.; Wise, S. W.</p> <p>2015-12-01</p> <p>The earliest Oligocene is considered the time that the Cenozoic icehouse world was initiated when the Antarctic continental ice sheet first reached sea level. Subsequently during the Oligocene, <span class="hlt">climate</span> then fluctuated between glacial (Oi) and warming events as recorded by stable isotopes. Relatively little is known about the paleoecological response of calcareous nannoplankton at low latitudes during these <span class="hlt">climate</span> deteriorations. Here we investigate the biotic response along with the stable-isotope (δ18O and δ13C) record and multivariate analyses from four ODP and IODP sites cored in three oceans along the <span class="hlt">tropical</span> belt through strata 24-30 Ma in age. Within this time frame, two major <span class="hlt">climatic</span> shifts occurred, the Oi-2b glacial event and the Late Oligocene Warming Event (LOWE). During the Oi-events (26.5-30 Ma) temperate-water taxa associated with eutrophic taxa dominated the overall assemblage, suggesting that relatively cooler water rich in nutrients invaded the <span class="hlt">tropical</span> region. In contrast, during the LOWE (24-26.5 Ma), a major turnover between temperate-water taxa and warm-water taxa occurred when the surface waters became warm and oligotrophic in nature. Additionally, several increases in both abundance and size were recorded through the upper Oligocene including increased abundance in Sphenolithus predistentus, a major biostratigraphic marker in the upper Oligocene, and increased size in S. moriformis. Moreover, a new additional major biostratigraphic event in the upper Oligocene was recorded; Crassidiscus backmanii shows a very short range at low latitudes. These paleoecological responses can be utilized to construct a detailed global late Oligocene biostratigraphy throughout the <span class="hlt">tropics</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5314898','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5314898"><span><span class="hlt">Tropical</span> cyclones in a year of rising global temperatures and a strengthening El Niño</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shultz, James M; Shepherd, J Marshall; Bagrodia, Rohini; Espinel, Zelde</p> <p>2014-01-01</p> <p>The year 2015 is notable for the coincidence of several strong <span class="hlt">climate</span> indicators that having bearing on the occurrence and intensity of <span class="hlt">tropical</span> cyclones worldwide. This year, 2015, is clearly on track to become the warmest on record in terms of global temperatures. During the latter half of 2015, a very strong El Niño has formed and is predicted to build impressively, perhaps rivaling the memorable El Niño of 1997/1998. Warm Pacific Ocean temperatures, coupled with a strengthening El Niño, have supported the proliferation of Western North Pacific basin typhoons and Eastern/Central North Pacific Hurricanes. Most notable among these, Hurricane Patricia formed on October 20, 2015 and experienced extremely rapid intensification to become the strongest hurricane in the history of the Western Hemisphere and then weakened just as <span class="hlt">abruptly</span> before dissipating on October 24, 2015. Rather than an aberration, these <span class="hlt">climate</span> patterns of 2015 represent an ongoing trend with implications for the disaster health of coastal populations worldwide. PMID:28229010</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15271474','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15271474"><span>The use of hormonal treatments to improve reproductive performance of anestrous beef cattle in <span class="hlt">tropical</span> <span class="hlt">climates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baruselli, P S; Reis, E L; Marques, M O; Nasser, L F; Bó, G A</p> <p>2004-07-01</p> <p>Most of the world's bovine herd is found in <span class="hlt">tropical</span> regions. Bos indicus predominates, due to their adaptation to the <span class="hlt">climate</span> and management conditions. Anestrous is the main factor that negatively affects reproductive performance of animals bred in these regions of the globe. Several factors affect postpartum anestrous, including suckling and maternal-offspring bond, and pre- and postpartum nutritional status. The short duration of estrus and the tendency to show estrus during the night, greatly affect the efficiency of artificial insemination (AI) programs in B. indicus cattle managed in <span class="hlt">tropical</span> areas. Several restricted suckling or weaning procedures (temporary or permanent), and hormonal treatments have been used to induce ovulation and cyclicity in postpartum cows. Most hormonal treatments are based on progesterone/progestogen (P4) releasing devices associated with estradiol benzoate (EB), or a combination of GnRH/PGF(2alpha)/GnRH (Ovsynch). Treatments with GnRH/PGF(2alpha)/GnRH has presented inconsistent results, probably due to the variable number of cows in anestrous. Treatments using P4 devices and EB have resulted in apparently more consistent results than Ovsynch programs in B. indicus cattle; however, pregnancy rates are low in herds presenting high anestrous rates and moderate to low body condition. The addition of an eCG treatment at the time of device removal, which increased plasma progesterone concentrations and pregnancy rates in anestrous postpartum suckled B. indicus cows, may be useful to improve reproductive performance of beef cattle in <span class="hlt">tropical</span> <span class="hlt">climates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26455783','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26455783"><span>The emerging threats of <span class="hlt">climate</span> change on <span class="hlt">tropical</span> coastal ecosystem services, public health, local economies and livelihood sustainability of small islands: Cumulative impacts and synergies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hernández-Delgado, E A</p> <p>2015-12-15</p> <p><span class="hlt">Climate</span> change has significantly impacted <span class="hlt">tropical</span> ecosystems critical for sustaining local economies and community livelihoods at global scales. Coastal ecosystems have largely declined, threatening the principal source of protein, building materials, tourism-based revenue, and the first line of defense against storm swells and sea level rise (SLR) for small <span class="hlt">tropical</span> islands. <span class="hlt">Climate</span> change has also impacted public health (i.e., altered distribution and increased prevalence of allergies, water-borne, and vector-borne diseases). Rapid human population growth has exacerbated pressure over coupled social-ecological systems, with concomitant non-sustainable impacts on natural resources, water availability, food security and sovereignty, public health, and quality of life, which should increase vulnerability and erode adaptation and mitigation capacity. This paper examines cumulative and synergistic impacts of <span class="hlt">climate</span> change in the challenging context of highly vulnerable small <span class="hlt">tropical</span> islands. Multiple adaptive strategies of coupled social-ecological ecosystems are discussed. Multi-level, multi-sectorial responses are necessary for adaptation to be successful. Copyright © 2015 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26ES..129a2030K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26ES..129a2030K"><span>The Dutch colonial architecture of buildings in Manado’s Old City: A response to the coastal <span class="hlt">tropical</span> <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumurur, V. A.; Tampi, D. M.</p> <p>2018-03-01</p> <p>The late 19th and early 20th centuries was an era when the phenomenon of global warming began, as did the development of cities in Indonesia. In that era, cities in Indonesia functioned as colonial cities. The city of Manado is one of the coastal cities, written in the Dutch Royal Act of 1814 as the territory of Dutch sovereignty, was amended in 1848, 1872 and 1922. Dutch colonial art and architecture in Indonesia are not only influenced by culture but also the <span class="hlt">climate</span>. For the purpose of physical comfort in the <span class="hlt">tropical</span> environments, architects began to use local building materials, since the early 19th century, and the building began to be replaced by a customizing architecture. Descriptive analysis was employed as the method in this study. The result found that the Dutch Colonial Architecture emphasized the physical aspects, the royal style adapted to local conditions, and the local building emphasis on function. The <span class="hlt">tropical</span> <span class="hlt">climate</span> of Manado City influences the shape of the building with Dutch colonial architectural style in this area. As <span class="hlt">climate</span> change is shown by rising temperatures, further observations on the design of colonial architecture will be important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29265499','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29265499"><span>Long-term increases in <span class="hlt">tropical</span> flowering activity across growth forms in response to rising CO2 and <span class="hlt">climate</span> change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pau, Stephanie; Okamoto, Daniel K; Calderón, Osvaldo; Wright, S Joseph</p> <p>2018-05-01</p> <p>Mounting evidence suggests that anthropogenic global change is altering plant species composition in <span class="hlt">tropical</span> forests. Fewer studies, however, have focused on long-term trends in reproductive activity, in part because of the lack of data from <span class="hlt">tropical</span> sites. Here, we analyze a 28-year record of <span class="hlt">tropical</span> flower phenology in response to anthropogenic <span class="hlt">climate</span> and atmospheric change. We show that a multidecadal increase in flower activity is most strongly associated with rising atmospheric CO 2 concentrations using yearly aggregated data. Compared to significant <span class="hlt">climatic</span> factors, CO 2 had on average an approximately three-, four-, or fivefold stronger effect than rainfall, solar radiation, and the Multivariate ENSO Index, respectively. Peaks in flower activity were associated with greater solar radiation and lower rainfall during El Niño years. The effect of atmospheric CO 2 on flowering has diminished over the most recent decade for lianas and canopy trees, whereas flowering of midstory trees and shrub species continued to increase with rising CO 2 . Increases in flowering were accompanied by a lengthening of flowering duration for canopy and midstory trees. Understory treelets did not show increases in flowering but did show increases in duration. Given that atmospheric CO 2 will likely continue to climb over the next century, a long-term increase in flowering activity may persist in some growth forms until checked by nutrient limitation or by <span class="hlt">climate</span> change through rising temperatures, increasing drought frequency and/or increasing cloudiness and reduced insolation. © 2017 John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006EOSTr..87..205H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006EOSTr..87..205H"><span>Santa Barbara Basin Study Extends Global <span class="hlt">Climate</span> Record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hopkins, Sarah; Kennett, James; Nicholson, Craig; Pak, Dorothy; Sorlien, Christopher; Behl, Richard; Normark, William; Sliter, Ray; Hill, Tessa; Schimmelmann, Arndt; Cannariato, Kevin</p> <p>2006-05-01</p> <p>A fundamental goal of Earth science is to understand the remarkable instability of late Quarternary global <span class="hlt">climate</span> prior to the beginning of the Holocene, about 11,000 years ago. This unusual <span class="hlt">climate</span> behavior was characterized by millennial-scale <span class="hlt">climate</span> oscillations on suborbital timescales, and a distinctive `Sawtooth' pattern of very <span class="hlt">abrupt</span> glacial and stadial terminations (within decades) followed by more gradual global cooling [e.g., Dansgaard et al., 1993; Hendy and Kennett, 1999]. The fact that both major (glacial) and minor (stadial) cooling periods in Earth's <span class="hlt">climate</span> were terminated by similar <span class="hlt">abrupt</span> warming episodes suggests a common mechanism driving such rapid changes in global <span class="hlt">climate</span>. Understanding the causes of this instability is crucial given developing concerns about global warming, yet knowledge about this <span class="hlt">climate</span> behavior has been essentially confined to the last 150,000 years or so, owing to the absence of available sequences of sufficient age and chronological resolution. The high-resolution paleoclimate record from the Greenland ice cores is limited to about 110 thousand years ago (ka), and although Antarctic ice cores now extend back to more than 740 ka [European Project for Ice Coring in Antarctica, 2004], these latter cores primarily provide information about high-latitude conditions at much lower resolution than is required to address <span class="hlt">abrupt</span> <span class="hlt">climate</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26465729','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26465729"><span><span class="hlt">Climate</span> change effects on the geographic distribution of specialist tree species of the Brazilian <span class="hlt">tropical</span> dry forests.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rodrigues, P M S; Silva, J O; Eisenlohr, P V; Schaefer, C E G R</p> <p>2015-08-01</p> <p>The aim of this study was to evaluate the ecological niche models (ENMs) for three specialist trees (Anadenanthera colubrina, Aspidosperma pyrifolium and Myracrodruon urundeuva) in seasonally dry <span class="hlt">tropical</span> forests (SDTFs) in Brazil, considering present and future pessimist scenarios (2080) of <span class="hlt">climate</span> change. These three species exhibit typical deciduousness and are widely distributed by SDTF in South America, being important in studies of the historical and evolutionary processes experienced by this ecosystem. The modeling of the potential geographic distribution of species was done by the method of maximum entropy (Maxent).We verified a general expansion of suitable areas for occurrence of the three species in future (c.a., 18%), although there was reduction of areas with high environmental suitability in Caatinga region. Precipitation of wettest quarter and temperature seasonality were the predictor variables that most contributed to our models. <span class="hlt">Climatic</span> changes can provide more severe and longer dry season with increasing temperature and tree mortality in <span class="hlt">tropics</span>. On this scenario, areas currently occupied by rainforest and savannas could become more suitable for occurrence of the SDTF specialist trees, whereas regions occupied by Caatinga could not support the future level of unsustainable (e.g., aridity). Long-term multidisciplinary studies are necessary to make reliable predictions of the plant's adaptation strategies and responses to <span class="hlt">climate</span> changes in dry forest at community level. Based on the high deforestation rate, endemism and threat, public policies to minimize the effects of <span class="hlt">climate</span> change on the biodiversity found within SDTFs must be undertaken rapidly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4620057','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4620057"><span><span class="hlt">Climate</span> as a driver of <span class="hlt">tropical</span> insular diversity: comparative phylogeography of two ecologically distinctive frogs in Puerto Rico</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Barker, Brittany S.; Rodríguez-Robles, Javier A.; Cook, Joseph A.</p> <p>2014-01-01</p> <p>The effects of late Quaternary <span class="hlt">climate</span> on distributions and evolutionary dynamics of insular species are poorly understood in most <span class="hlt">tropical</span> archipelagoes. We used ecological niche models under past and current <span class="hlt">climate</span> to derive hypotheses regarding how stable <span class="hlt">climatic</span> conditions shaped genetic diversity in two ecologically distinctive frogs in Puerto Rico. Whereas the Mountain Coquí, Eleutherodactylus portoricensis, is restricted to montane forest in the Cayey and Luquillo Mountains, the Red-eyed Coquí, E. antillensis, is a habitat generalist distributed across the entire Puerto Rican Bank (Puerto Rico and the Virgin Islands, excluding St. Croix). To test our hypotheses, we conducted phylogeographic and population genetic analyses based on mitochondrial and nuclear loci of each species across their range in Puerto Rico. Patterns of population differentiation in E. portoricensis, but not in E. antillensis, supported our hypotheses. For E. portoricensis, these patterns include: individuals isolated by long-term unsuitable <span class="hlt">climate</span> in the Río Grande de Loíza Basin in eastern Puerto Rico belong to different genetic clusters; past and current <span class="hlt">climate</span> strongly predicted genetic differentiation; and Cayey and Luquillo Mountains populations split prior to the last interglacial. For E. antillensis, these patterns include: genetic clusters did not fully correspond to predicted long-term unsuitable <span class="hlt">climate</span>; and past and current <span class="hlt">climate</span> weakly predicted patterns of genetic differentiation. Genetic signatures in E. antillensis are consistent with a recent range expansion into western Puerto Rico, possibly resulting from <span class="hlt">climate</span> change and anthropogenic influences. As predicted, regions with a large area of long-term suitable <span class="hlt">climate</span> were associated with higher genetic diversity in both species, suggesting larger and more stable populations. Finally, we discussed the implications of our findings for developing evidence-based management decisions for E. portoricensis, a taxon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A21I2265W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A21I2265W"><span>The Seasonal cycle of the <span class="hlt">Tropical</span> Lower Stratospheric Water Vapor in Chemistry-<span class="hlt">Climate</span> Models in Comparison with Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, X.; Dessler, A. E.</p> <p>2017-12-01</p> <p>The seasonal cycle is one of the key features of the <span class="hlt">tropical</span> lower stratospheric water vapor, so it is important that the <span class="hlt">climate</span> models reproduce it. In this analysis, we evaluate how well the Goddard Earth Observing System Chemistry <span class="hlt">Climate</span> Model (GEOSCCM) and the Whole Atmosphere Community <span class="hlt">Climate</span> Model (WACCM) reproduce the seasonal cycle of <span class="hlt">tropical</span> lower stratospheric water vapor. We do this by comparing the models to observations from the Microwave Limb Sounder (MLS) and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim (ERAi). We also evaluate if the chemistry-<span class="hlt">climate</span> models (CCMs) reproduce the key transport and dehydration processes that regulate the seasonal cycle using a forward, domain filling, diabatic trajectory model. Finally, we explore the changes of the seasonal cycle during the 21st century in the two CCMs. Our results show general agreement in the seasonal cycles from the MLS, the ERAi, and the CCMs. Despite this agreement, there are some clear disagreements between the models and the observations on the details of transport and dehydration in the TTL. Finally, both the CCMs predict a moister seasonal cycle by the end of the 21st century. But they disagree on the changes of the seasonal amplitude, which is predicted to increase in the GEOSCCM and decrease in the WACCM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=319964','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=319964"><span>Disaggregating <span class="hlt">tropical</span> disease prevalence by <span class="hlt">climatic</span> and vegetative zones within <span class="hlt">tropical</span> West Africa</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p><span class="hlt">Tropical</span> infectious disease prevalence is dependent on many socio-cultural determinants. However, rainfall and temperature frequently underlie overall prevalence, particularly for vector-borne diseases. As a result these diseases have increased prevalence in <span class="hlt">tropical</span> as compared to temperate regions...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3206942','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3206942"><span>The Influence of <span class="hlt">Climatic</span> Seasonality on the Diversity of Different <span class="hlt">Tropical</span> Pollinator Groups</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Abrahamczyk, Stefan; Kluge, Jürgen; Gareca, Yuvinka; Reichle, Steffen; Kessler, Michael</p> <p>2011-01-01</p> <p><span class="hlt">Tropical</span> South America is rich in different groups of pollinators, but the biotic and abiotic factors determining the geographical distribution of their species richness are poorly understood. We analyzed the species richness of three groups of pollinators (bees and wasps, butterflies, hummingbirds) in six <span class="hlt">tropical</span> forests in the Bolivian lowlands along a gradient of <span class="hlt">climatic</span> seasonality and precipitation ranging from 410 mm to 6250 mm. At each site, we sampled the three pollinator groups and their food plants twice for 16 days in both the dry and rainy seasons. The richness of the pollinator groups was related to <span class="hlt">climatic</span> factors by linear regressions. Differences in species numbers between pollinator groups were analyzed by Wilcoxon tests for matched pairs and the proportion in species numbers between pollinator groups by correlation analyses. Species richness of hummingbirds was most closely correlated to the continuous availability of food, that of bees and wasps to the number of food plant species and flowers, and that of butterflies to air temperature. Only the species number of butterflies differed significantly between seasons. We were not able to find shifts in the proportion of species numbers of the different groups of pollinators along the study gradient. Thus, we conclude that the diversity of pollinator guilds is determined by group-specific factors and that the constant proportions in species numbers of the different pollinator groups constitute a general pattern. PMID:22073268</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70178643','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70178643"><span>Vulnerability of island <span class="hlt">tropical</span> montane cloud forests to <span class="hlt">climate</span> change, with special reference to East Maui, Hawaii</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Loope, Lloyd L.; Giambelluca, Thomas W.</p> <p>1998-01-01</p> <p>Island <span class="hlt">tropical</span> montane cloud forests may be among the most sensitive of the world's ecosystems to global <span class="hlt">climate</span> change. Measurements in and above a montane cloud forest on East Maui, Hawaii, document steep microclimatic gradients. Relatively small <span class="hlt">climate</span>-driven shifts in patterns of atmospheric circulation are likely to trigger major local changes in rainfall, cloud cover, and humidity. Increased interannual variability in precipitation and hurricane incidence would provide additional stresses on island biota that are highly vulnerable to disturbance-related invasion of non-native species. Because of the exceptional sensitivity of these microclimates and forests to change, they may provide valuable ‘listening posts’ for detecting the onset of human-induced global <span class="hlt">climate</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141652&hterms=pollen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dpollen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141652&hterms=pollen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dpollen"><span>Sensitivity and rapidity of vegetational response to <span class="hlt">abrupt</span> <span class="hlt">climate</span> change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Peteet, D.</p> <p>2000-01-01</p> <p>Rapid <span class="hlt">climate</span> change characterizes numerous terrestrial sediment records during and since the last glaciation. Vegetational response is best expressed in terrestrial records near ecotones, where sensitivity to <span class="hlt">climate</span> change is greatest, and response times are as short as decades.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7493G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7493G"><span><span class="hlt">Abrupt</span> transitions to a cold North Atlantic in the late Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Geirsdóttir, Áslaug; Miller, Gifford; Larsen, Darren; Florian, Christopher; Pendleton, Simon</p> <p>2015-04-01</p> <p>The Holocene provides a time interval with boundary conditions similar to present, except for greenhouse gas concentrations. Recent high-resolution Northern Hemisphere records show general cooling related to orbital terms through the late Holocene, but also highly non-linear <span class="hlt">abrupt</span> departures of centennial scale summer cold periods. These <span class="hlt">abrupt</span> departures are evident within the last two millennia (the transitions between the Roman Warm Period (RWP, ~2,000 yr BP), the Dark Ages Cold Period (DACP, ~500-900 years AD), the Medieval Warm Period (MWP, 1000-1200 years AD) and the Little Ice Age (LIA, ~1300-1900 AD). A series of new, high-resolution and securely dated lake records from Iceland also show <span class="hlt">abrupt</span> <span class="hlt">climate</span> departures over the past 2 ka, characterized by shifts to persistent cold summers and an expanded cryosphere. Despite substantial differences in catchment-specific processes that dominate the lake records, the multi-proxy reconstructions are remarkably similar. After nearly a millennium with little evidence of significant <span class="hlt">climate</span> shifts, the beginning of the first millennium AD is characterized by renewed summer cooling that leads to an expanding cryosphere. Slow summer cooling over the first five centuries is succeeded by widespread substantial cooling, with evidence for substantial expansion of glaciers and ice caps throughout our field areas between 530 and 900 AD, and an accompanying reduction in vegetation cover across much of Iceland that led to widespread landscape instability. These data suggest that the North Atlantic system began a transition into a new cold state early in the first millennium AD, which was amplified after 500 AD, until it was interrupted by warmer Medieval times between ~1000 and 1250 AD. Although severe soil erosion in Iceland is frequently associated with human settlement dated to 871 ±2 AD our reconstructions indicate that soil erosion began several centuries before settlement, during the DACP, whereas for several centuries</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160009339&hterms=influence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dinfluence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160009339&hterms=influence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dinfluence"><span>Human Influence on <span class="hlt">Tropical</span> Cyclone Intensity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sobel, Adam H.; Camargo, Suzana J.; Hall, Timothy M.; Lee, Chia-Ying; Tippett, Michael K.; Wing, Allison A.</p> <p>2016-01-01</p> <p>Recent assessments agree that <span class="hlt">tropical</span> cyclone intensity should increase as the <span class="hlt">climate</span> warms. Less agreement exists on the detection of recent historical trends in <span class="hlt">tropical</span> cyclone intensity.We interpret future and recent historical trends by using the theory of potential intensity, which predicts the maximum intensity achievable by a <span class="hlt">tropical</span> cyclone in a given local environment. Although greenhouse gas-driven warming increases potential intensity, <span class="hlt">climate</span> model simulations suggest that aerosol cooling has largely canceled that effect over the historical record. Large natural variability complicates analysis of trends, as do poleward shifts in the latitude of maximum intensity. In the absence of strong reductions in greenhouse gas emissions, future greenhouse gas forcing of potential intensity will increasingly dominate over aerosol forcing, leading to substantially larger increases in <span class="hlt">tropical</span> cyclone intensities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22802959','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22802959"><span>Will temperature effects or phenotypic plasticity determine the thermal response of a heterothermic <span class="hlt">tropical</span> bat to <span class="hlt">climate</span> change?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stawski, Clare; Geiser, Fritz</p> <p>2012-01-01</p> <p>The proportion of organisms exposed to warm conditions is predicted to increase during global warming. To better understand how bats might respond to <span class="hlt">climate</span> change, we aimed to obtain the first data on how use of torpor, a crucial survival strategy of small bats, is affected by temperature in the <span class="hlt">tropics</span>. Over two mild winters, <span class="hlt">tropical</span> free-ranging bats (Nyctophilus bifax, 10 g, n = 13) used torpor on 95% of study days and were torpid for 33.5±18.8% of 113 days measured. Torpor duration was temperature-dependent and an increase in ambient temperature by the predicted 2°C for the 21(st) century would decrease the time in torpor to 21.8%. However, comparisons among Nyctophilus populations show that regional phenotypic plasticity attenuates temperature effects on torpor patterns. Our data suggest that heterothermy is important for energy budgeting of bats even under warm conditions and that flexible torpor use will enhance bats' chance of survival during <span class="hlt">climate</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A31E2244L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A31E2244L"><span>Investigation of <span class="hlt">tropical</span> diurnal convection biases in a <span class="hlt">climate</span> model using TWP-ICE observations and convection-permitting simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, W.; Xie, S.; Jackson, R. C.; Endo, S.; Vogelmann, A. M.; Collis, S. M.; Golaz, J. C.</p> <p>2017-12-01</p> <p><span class="hlt">Climate</span> models are known to have difficulty in simulating <span class="hlt">tropical</span> diurnal convections that exhibit distinct characteristics over land and open ocean. While the causes are rooted in deficiencies in convective parameterization in general, lack of representations of mesoscale dynamics in terms of land-sea breeze, convective organization, and propagation of convection-induced gravity waves also play critical roles. In this study, the problem is investigated at the process-level with the U.S. Department of Energy Accelerated <span class="hlt">Climate</span> Modeling for Energy (ACME) model in short-term hindcast mode using the Cloud Associated Parameterization Testbed (CAPT) framework. Convective-scale radar retrievals and observation-driven convection-permitting simulations for the <span class="hlt">Tropical</span> Warm Pool-International Cloud Experiment (TWP-ICE) cases are used to guide the analysis of the underlying processes. The emphasis will be on linking deficiencies in representation of detailed process elements to the model biases in diurnal convective properties and their contrast among inland, coastal and open ocean conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040171212&hterms=Influence+clouds+climate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DInfluence%2Bclouds%2Bclimate','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040171212&hterms=Influence+clouds+climate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DInfluence%2Bclouds%2Bclimate"><span>NASA GEOS-3/TRMM Re-analysis: Capturing Observed <span class="hlt">Tropical</span> Rainfall Variability in Global Analysis for <span class="hlt">Climate</span> Research</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hou, Arthur Y.</p> <p>2004-01-01</p> <p>Understanding <span class="hlt">climate</span> variability over a wide range of space-time scales requires a comprehensive description of the earth system. Global analyses produced by a fixed assimilation system (i.e., re-analyses) - as their quality continues to improve - have the potential of providing a vital tool for meeting this challenge. But at the present time, the usefulness of re-analyses is limited by uncertainties in such basic fields as clouds, precipitation, and evaporation - especially in the <span class="hlt">tropics</span>, where observations are relatively sparse. Analyses of the <span class="hlt">tropics</span> have long been shown to be sensitive to. the treatment of cloud precipitation processes, which remains a major source of uncertainty in current models. Yet, for many <span class="hlt">climate</span> studies it is crucial that analyses can accurately reproduce the observed rainfall intensity and variability since a small error of 1 mm/d in surface rain translates into an error of approx. 30 W/sq m in energy (latent heat) flux. Currently, discrepancies between the observed and analyzed monthly-mean rain rates averaged to 100 km x 100 km resolution can exceed 4 mm/d (or 120 W/sq m ), compared to uncertainties in surface radiative fluxes of approx. 10-20 W/sq m . Improving precipitation in analyses would reduce a major source of uncertainty in the global energy budget. Uncertainties in <span class="hlt">tropical</span> precipitation have also been a major impediment in understanding how the <span class="hlt">tropics</span> interact with other regions, including the remote response to El Nino/Southern Oscillation (ENSO) variability on interannual time scales, the influence of Madden-Julian Oscillation (MJO) and monsoons on intraseasonal time scales. A global analysis that can replicate the observed precipitation variability together with physically consistent estimates of other atmospheric variables provides the key to breaking this roadblock. NASA Goddard Space Flight Center has been exploring the use of satellite-based microwave rainfall measurements in improving global analyses and has</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1413778S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1413778S"><span>Response of <span class="hlt">Tropical</span> Forests to Intense <span class="hlt">Climate</span> Variability and Rainfall Anomaly over the Last Decade</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saatchi, S.; Asefi, S.</p> <p>2012-04-01</p> <p>During the last decade, strong precipitation anomalies resulted from increased sea surface temperature in the <span class="hlt">tropical</span> Atlantic, have caused extensive drying trends in rainforests of western Amazonia, exerting water stress, tree mortality, biomass loss, and large-scale fire disturbance. In contrast, there have been no reports on large-scale disturbance in rainforests of west and central Africa, though being exposed to similar intensity of <span class="hlt">climate</span> variability. Using data from <span class="hlt">Tropical</span> Rainfall Mapping Mission (TRMM) (1999-2010), and time series of rainfall observations from meteorological stations (1971-2000), we show that both Amazonian and African rainforest experienced strong precipitation anomalies from 2005-2010. We monitored the response of forest to the <span class="hlt">climate</span> variability by analyzing the canopy water content observed by SeaWinds Ku-band Scatterometer (QSCAT) (1999-2009) and found that more than 70 million ha of forests in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy backscatter that persisted until the next major drought in 2010. This decline in backscatter has been attributed to loss of canopy water content and large-scale tree mortality corroborated by ground and airborne observations. However, no strong impacts was observed on <span class="hlt">tropical</span> forests of Africa, suggesting that the African rainforest may have more resilience to droughts. We tested this hypothesis by examining the seasonal rainfall patterns, maximum water deficit, and the surface temperature variations. Results show that there is a complex pattern of low annual rainfall, moderate seasonality, and lower surface temperature in Central Africa compared to Amazonia, indicating potentially a lower evapotranspiration circumventing strong water deficits</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1436150-impact-tropical-cyclones-modeled-extreme-wind-wave-climate','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1436150-impact-tropical-cyclones-modeled-extreme-wind-wave-climate"><span>Impact of <span class="hlt">tropical</span> cyclones on modeled extreme wind-wave <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Timmermans, Ben; Stone, Daithi; Wehner, Michael; ...</p> <p>2017-02-16</p> <p>Here, the effect of forcing wind resolution on the extremes of global wind-wave <span class="hlt">climate</span> are investigated in numerical simulations. Forcing winds from the Community Atmosphere Model at horizontal resolutions of ~1.0° and ~0.25° are used to drive Wavewatch III. Differences in extreme wave height are found to manifest most strongly in <span class="hlt">tropical</span> cyclone (TC) regions, emphasizing the need for high-resolution forcing in those areas. Comparison with observations typically show improvement in performance with increased forcing resolution, with a strong influence in the tail of the distribution, although simulated extremes can exceed observations. A simulation for the end of the 21stmore » century under a RCP 8.5 type emission scenario suggests further increases in extreme wave height in TC regions.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/569258-interaction-between-enso-asian-monsoon-coral-record-tropical-climate','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/569258-interaction-between-enso-asian-monsoon-coral-record-tropical-climate"><span>Interaction between the ENSO and the Asian monsoon in a coral record of <span class="hlt">tropical</span> <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Charles, C.D.; Hunter, D.E.; Fairbanks, R.G.</p> <p>1997-08-15</p> <p>The oxygen isotopic composition of a banded coral from the western equatorial Indian Ocean provides a 150-year-long history of the relation between the El Nino-Southern Oscillation (ENSO) phenomenon and the Asian monsoon. Interannual cycles in the coral time series were found to correlate with Pacific coral and instrumental <span class="hlt">climate</span> records, suggesting a consistent linkage across ocean basins, despite the changing frequency and amplitude of the ENSO. However, decadal variability that is characteristic of the monsoon system also dominates the coral record, which implies important interactions between <span class="hlt">tropical</span> and midlatitude <span class="hlt">climate</span> variability. One prominent manifestation of this interaction is the strongmore » amplitude modulation of the quasi-biennial cycle. 26 refs., 4 figs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B34C..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B34C..06R"><span><span class="hlt">Tropical</span> rain forest biogeochemistry in a warmer world: initial results from a novel warming experiment in a Puerto Rico <span class="hlt">tropical</span> forest</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reed, S.; Cavaleri, M. A.; Alonso-Rodríguez, A. M.; Kimball, B. A.; Wood, T. E.</p> <p>2016-12-01</p> <p><span class="hlt">Tropical</span> forests represent one of the planet's most active biogeochemical engines. They account for the dominant proportion of Earth's live terrestrial plant biomass, nearly one-third of all soil carbon, and exchange more CO2 with the atmosphere than any other biome. In the coming decades, the <span class="hlt">tropics</span> will experience extraordinary changes in temperature, and our understanding of how this warming will affect biogeochemical cycling remains notably poor. Given the large amounts of carbon <span class="hlt">tropical</span> forests store and cycle, it is no surprise that our limited ability to characterize <span class="hlt">tropical</span> forest responses to <span class="hlt">climate</span> change may represent the largest hurdle in accurately predicting Earth's future <span class="hlt">climate</span>. Here we describe initial results from the world's first <span class="hlt">tropical</span> forest field warming experiment, where forest understory plants and soils are being warmed 4 °C above ambient temperatures. This <span class="hlt">Tropical</span> Responses to Altered <span class="hlt">Climate</span> Experiment (TRACE) was established in a rain forest in Puerto Rico to investigate the effects of increased temperature on key biological processes that control <span class="hlt">tropical</span> forest carbon cycling, and to establish the steps that need to be taken to resolve the uncertainties surrounding <span class="hlt">tropical</span> forest responses to warming. In this talk we will describe the experimental design, as well as the wide range of measurements being conducted. We will also present results from the initial phase of warming, including data on how increased temperatures from infrared lamp warming affected soil moisture, soil respiration rates, a suite of carbon pools, soil microbial biomass, nutrient availability, and the exchange of elements between leaf litter and soil. These data represent a first look into <span class="hlt">tropical</span> rain forest responses to an experimentally-warmed <span class="hlt">climate</span> in the field, and provide exciting insight into the non-linear ways <span class="hlt">tropical</span> biogeochemical cycles respond to change. Overall, we strive to improve Earth System Model parameterization of the pools and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=272539','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=272539"><span>Analysis of <span class="hlt">abrupt</span> transitions in ecological systems</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The occurrence and causes of <span class="hlt">abrupt</span> transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of <span class="hlt">abrupt</span> transitions has been advanced by theory, but hindered by the l...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29210686','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29210686"><span>A modelling study of the event-based retention performance of green roof under the hot-humid <span class="hlt">tropical</span> <span class="hlt">climate</span> in Kuching.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chai, C T; Putuhena, F J; Selaman, O S</p> <p>2017-12-01</p> <p>The influences of <span class="hlt">climate</span> on the retention capability of green roof have been widely discussed in existing literature. However, knowledge on how the retention capability of green roof is affected by the <span class="hlt">tropical</span> <span class="hlt">climate</span> is limited. This paper highlights the retention performance of the green roof situated in Kuching under hot-humid <span class="hlt">tropical</span> <span class="hlt">climatic</span> conditions. Using the green roof water balance modelling approach, this study simulated the hourly runoff generated from a virtual green roof from November 2012 to October 2013 based on past meteorological data. The result showed that the overall retention performance was satisfactory with a mean retention rate of 72.5% from 380 analysed rainfall events but reduced to 12.0% only for the events that potentially trigger the occurrence of flash flood. By performing the Spearman rank's correlation analysis, it was found that the rainfall depth and mean rainfall intensity, individually, had a strong negative correlation with event retention rate, suggesting that the retention rate increases with decreased rainfall depth. The expected direct relationship between retention rate and antecedent dry weather period was found to be event size dependent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP33B1324H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP33B1324H"><span><span class="hlt">Tropical</span> Pacific Mean State and ENSO Variability across Marine Isotope Stage 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hertzberg, J. E.; Schmidt, M. W.; Marcantonio, F.; Bianchi, T. S.</p> <p>2017-12-01</p> <p>The El Niño/Southern Oscillation (ENSO) phenomenon is the largest natural interannual signal in the Earth's <span class="hlt">climate</span> system and has widespread effects on global <span class="hlt">climate</span> that impact millions of people worldwide. A series of recent research studies predict an increase in the frequency of extreme El Niño and La Niña events as Earth's <span class="hlt">climate</span> continues to warm. In order for <span class="hlt">climate</span> scientists to forecast how ENSO will evolve in response to global warming, it is necessary to have accurate, comprehensive records of how the system has naturally changed in the past, especially across past <span class="hlt">abrupt</span> warming events. Nevertheless, there remains significant uncertainty about past changes in <span class="hlt">tropical</span> Pacific <span class="hlt">climate</span> and how ENSO variability relates to the millennial-scale warming events of the last ice age. This study aims to reconstruct changes in the <span class="hlt">tropical</span> Pacific mean state and ENSO variability across Marine Isotope Stage 3 from a sediment core recovered from the Eastern Equatorial Pacific cold tongue (MV1014-02-17JC, 0°10.8' S, 85°52.0' W, 2846 m water depth). In this region, thermocline temperatures are significantly correlated to ENSO variability - thus, we analyzed Mg/Ca ratios in the thermocline dwelling foraminifera Neogloboquadrina dutertrei as a proxy for thermocline temperatures in the past. Bulk ( 50 tests/sample) foraminifera Mg/Ca temperatures are used to reconstruct long-term variability in the mean state, while single shell ( 1 test/sample, 60 samples) Mg/Ca analyses are used to assess thermocline temperature variance. Based on our refined age model, we find that thermocline temperature increases of up to 3.5°C occur in-step with interstadial warming events recorded in Greenland ice cores. Cooler thermocline temperatures prevail during stadial intervals and Heinrich Events. This suggests that interstadials were more El-Niño like, while stadials and Heinrich Events were more La-Niña like. These temperature changes are compared to new records of dust flux</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29863798','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29863798"><span>No association between month of birth and biliary atresia in a country with <span class="hlt">tropical</span> <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tanpowpong, Pornthep; Lertudomphonwanit, Chatmanee; Phuapradit, Pornpimol; Treepongkaruna, Suporn</p> <p>2018-06-04</p> <p>Children with biliary atresia (BA) born in countries with temperate <span class="hlt">climate</span> showed month-of-birth (MoB) predilection during cooler months. To date, no study on the MoB-BA association has been performed in a <span class="hlt">tropical</span> country. Our aim was to define MoB variation in children with BA in a <span class="hlt">tropical</span> country. We studied 150 children diagnosed with BA between January 1996 and April 2015 at a teaching hospital. MoB was defined by two categories based on the precipitation: rain and dry, and three categories based on the air temperature: high, average and low. We applied the country's population data on the number of births in each period as the expected proportions of birth. A slightly higher proportion of BA children was born in the rainy months (52.7%); however, the difference was not significant compared to the general population's birth (P = 0.87). For the MoB based on the air temperature, no statistically significant difference was noted. Males with BA seemed to have a greater MoB variation compared to females, but this did not reach statistical significance. We could not find an association between MoB and BA in a <span class="hlt">tropical</span> country. Multinational studies may aid in understanding the MoB-BA association in the <span class="hlt">tropical</span> countries. © 2018 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP51A2098H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP51A2098H"><span>Multi-proxy Reconstructions of Deglacial Variability of Antarctic Intermediate Water Circulation in the Western <span class="hlt">Tropical</span> Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, K.; Oppo, D.; Curry, W. B.</p> <p>2012-12-01</p> <p>Reconstruction of changes in Antarctic Intermediate Water (AAIW) circulation across the last deglaciation is critical in constraining the links between AAIW and Atlantic Meridional Overturning Circulation (AMOC) and understanding how AAIW influences oceanic heat transport and carbon budget across <span class="hlt">abrupt</span> <span class="hlt">climate</span> events. Here we systematically establish in situ calibrations for carbonate saturation state (B/Ca), nutrient (Cd/Ca and δ13C) and watermass proxies (ɛNd) in foraminifera using multicore tops and ambient seawater samples collected from the Demerara Rise, western <span class="hlt">tropical</span> Atlantic. Through the multi-proxy reconstructions, deglacial variability of intermediate water circulation in the western <span class="hlt">tropical</span> Atlantic can be further constrained. The reconstructed seawater Cd record from the Demerara Rise sediment core (KNR197-3-46CDH, at 947 m water depth) over the last 21 kyrs suggests reduced presence of AAIW during the cold intervals (LGM, H1 and YD) when AMOC was reduced. Down-core B/Ca record shows elevated intermediate water Δ[CO32-] during these cold intervals, further indicating a weaker influence of AAIW in the western <span class="hlt">tropical</span> Atlantic. The δ13C record exhibits a pronounced deglacial minimum and a clear decoupling between δ13C and Cd/Ca after the AMOC completely recovered at around 8 kyr BP. This could be due to the carbonate ion effect on benthic Cd/Ca or the influence of organic matter remineralization on benthic δ13C. A new ɛNd record for the last deglaciation will be provided to evaluate the relative proportions of southern and northern waters at this intermediate site in the western <span class="hlt">tropical</span> Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRG..119.1432Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRG..119.1432Z"><span>Environmental determinants of <span class="hlt">tropical</span> forest and savanna distribution: A quantitative model evaluation and its implication</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeng, Zhenzhong; Chen, Anping; Piao, Shilong; Rabin, Sam; Shen, Zehao</p> <p>2014-07-01</p> <p>The distributions of <span class="hlt">tropical</span> ecosystems are rapidly being altered by <span class="hlt">climate</span> change and anthropogenic activities. One possible trend—the loss of <span class="hlt">tropical</span> forests and replacement by savannas—could result in significant shifts in ecosystem services and biodiversity loss. However, the influence and the relative importance of environmental factors in regulating the distribution of <span class="hlt">tropical</span> forest and savanna biomes are still poorly understood, which makes it difficult to predict future <span class="hlt">tropical</span> forest and savanna distributions in the context of <span class="hlt">climate</span> change. Here we use boosted regression trees to quantitatively evaluate the importance of environmental predictors—mainly <span class="hlt">climatic</span>, edaphic, and fire factors—for the <span class="hlt">tropical</span> forest-savanna distribution at a mesoscale across the <span class="hlt">tropics</span> (between 15°N and 35°S). Our results demonstrate that <span class="hlt">climate</span> alone can explain most of the distribution of <span class="hlt">tropical</span> forest and savanna at the scale considered; dry season average precipitation is the single most important determinant across <span class="hlt">tropical</span> Asia-Australia, Africa, and South America. Given the strong tendency of increased seasonality and decreased dry season precipitation predicted by global <span class="hlt">climate</span> models, we estimate that about 28% of what is now <span class="hlt">tropical</span> forest would likely be lost to savanna by the late 21st century under the future scenario considered. This study highlights the importance of <span class="hlt">climate</span> seasonality and interannual variability in predicting the distribution of <span class="hlt">tropical</span> forest and savanna, supporting the <span class="hlt">climate</span> as the primary driver in the savanna biogeography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/30118','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/30118"><span>Variations in Belowground Carbon Storage and Soil CO2 Flux Rates along a Wet <span class="hlt">Tropical</span> <span class="hlt">Climate</span> Gradient</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Megan McGroddy; Whendee L. Silver</p> <p>2000-01-01</p> <p>We used a humid <span class="hlt">tropical</span> elevation gradient to examine the relationships among <span class="hlt">climate</span>, edaphic conditions, belowground carbon storage, and soil respiration rates. We also compared open and closed canopy sites to increase the range of microclimate conditions sampled along the gradient, and determine the effects of canopy openings on C and P storage, and C dynamics....</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/50694','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/50694"><span><span class="hlt">Climate</span> Change Implications for <span class="hlt">Tropical</span> Islands: Interpolating and Interpreting Statistically Downscaled GCM Projections for Management and Planning</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Azad Henareh Khalyani; William A. Gould; Eric Harmsen; Adam Terando; Maya Quinones; Jaime A. Collazo</p> <p>2016-01-01</p> <p><The potential ecological and economic effects of <span class="hlt">climate</span> change for <span class="hlt">tropical</span> islands were studied using output from 12 statistically downscaled general circulation models (GCMs) taking Puerto Rico as a test case. Two model selection/model averaging strategies were used: the average of all available GCMs and the av-erage of the models that are able to...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5724848','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5724848"><span>Two decades of <span class="hlt">climate</span> driving the dynamics of functional and taxonomic diversity of a <span class="hlt">tropical</span> small mammal community in western Mexico</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2017-01-01</p> <p>Understanding the effects of global <span class="hlt">climate</span> disruption on biodiversity is important to future conservation efforts. While taxonomic diversity is widely studied, functional diversity of plants, and recently animals, is receiving increasing attention. Most studies of mammals are short-term, focus on temperate habitats, and rely on traits described in the literature rather than generating traits from observations. Unlike previous studies, this long-term field study assessed the factors driving the functional and taxonomic diversity of small-mammal assemblages in dry <span class="hlt">tropical</span> forests using both traits recorded from literature and a demographic database. We assessed the drivers (abundance and biomass, temperature and rainfall) of taxonomic richness and functional diversity for two rain-driven seasons in two adjacent but distinct forests—upland and lowland (arroyo or riparian) forests. Our analysis found that rainfall, both seasonal and atypical, was the primary factor driving functional and taxonomic diversity of small-mammal assemblages. Functional responses differed between the two types of forests, however, with effects being stronger in the harsher conditions of the upland forests than in the less severe conditions prevailing in the arroyo (riparian) forest. The latter also supports a richer, more diverse, and more stable small-mammal assemblage. These findings highlight the importance of <span class="hlt">climate</span> to <span class="hlt">tropical</span> biological diversity, as extreme <span class="hlt">climate</span> events (hurricanes, droughts and floods) and disruption of rainfall patterns were shown to decrease biodiversity. They also support the need to preserve these habitats, as their high taxonomic diversity and functional redundancy makes them resilient against global <span class="hlt">climate</span> disruption and local extreme events. <span class="hlt">Tropical</span> dry forests constitute a potential reservoir for biodiversity and the ecosystem services they provide. Unfortunately, these forests are among the most endangered terrestrial ecosystems because of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29228017','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29228017"><span>Two decades of <span class="hlt">climate</span> driving the dynamics of functional and taxonomic diversity of a <span class="hlt">tropical</span> small mammal community in western Mexico.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mason-Romo, Edgard David; Farías, Ariel A; Ceballos, Gerardo</p> <p>2017-01-01</p> <p>Understanding the effects of global <span class="hlt">climate</span> disruption on biodiversity is important to future conservation efforts. While taxonomic diversity is widely studied, functional diversity of plants, and recently animals, is receiving increasing attention. Most studies of mammals are short-term, focus on temperate habitats, and rely on traits described in the literature rather than generating traits from observations. Unlike previous studies, this long-term field study assessed the factors driving the functional and taxonomic diversity of small-mammal assemblages in dry <span class="hlt">tropical</span> forests using both traits recorded from literature and a demographic database. We assessed the drivers (abundance and biomass, temperature and rainfall) of taxonomic richness and functional diversity for two rain-driven seasons in two adjacent but distinct forests-upland and lowland (arroyo or riparian) forests. Our analysis found that rainfall, both seasonal and atypical, was the primary factor driving functional and taxonomic diversity of small-mammal assemblages. Functional responses differed between the two types of forests, however, with effects being stronger in the harsher conditions of the upland forests than in the less severe conditions prevailing in the arroyo (riparian) forest. The latter also supports a richer, more diverse, and more stable small-mammal assemblage. These findings highlight the importance of <span class="hlt">climate</span> to <span class="hlt">tropical</span> biological diversity, as extreme <span class="hlt">climate</span> events (hurricanes, droughts and floods) and disruption of rainfall patterns were shown to decrease biodiversity. They also support the need to preserve these habitats, as their high taxonomic diversity and functional redundancy makes them resilient against global <span class="hlt">climate</span> disruption and local extreme events. <span class="hlt">Tropical</span> dry forests constitute a potential reservoir for biodiversity and the ecosystem services they provide. Unfortunately, these forests are among the most endangered terrestrial ecosystems because of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004EOSTr..85Q.186S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004EOSTr..85Q.186S"><span><span class="hlt">Climate</span> Change, Salmon in the NOAA Budget Spotlight</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Showstack, Randy</p> <p>2004-05-01</p> <p>A U.S. Senate hearing on 29 April about the administration's proposed budget for the National Oceanic and Atmospheric Administration fiscal year 2005 turned testy when senators pressed for specific information about the agency's programs on <span class="hlt">abrupt</span> <span class="hlt">climate</span> change and protecting wild salmon. Sen. Olympia Snowe (R-Maine), chair of the Senate Commerce, Science, and Transportation's Subcommittee on Oceans, Fisheries, and Coast Guard, expressed concern that funding for the agency's program on <span class="hlt">abrupt</span> <span class="hlt">climate</span> change appears to be eliminated in the proposed budget.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B43B0594M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B43B0594M"><span>Phenology of seed and leaves rain in response to periodic <span class="hlt">climatic</span> variability in a seasonal wet <span class="hlt">tropical</span> forest</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matteo, D.; Wright, S. J.; Davies, S. J.; Muller-Landau, H. C.; Wolfe, B.; Detto, M.</p> <p>2016-12-01</p> <p>Phenology, by controlling the rhythms of plants, plays a fundamental role in regulating access to resources, ecosystem processes, competition among species, interactions with consumers and feedbacks to the <span class="hlt">climate</span>. In high biodiverse <span class="hlt">tropical</span> forests, where phenology of flowering and leafing are complex, an adequate representation of phenology must take into account a given set of <span class="hlt">climatic</span>, edaphic and biotic factors. <span class="hlt">Climatic</span> factors are particularly important because plants may use them as cues for timing different phenological phases and be influenced by their intensity. <span class="hlt">Climatic</span> variability can be periodic, if events occur with regular frequency, or aperiodic. One prominent periodic large-scale pattern that causes unusual weather is ENSO event. In general, Central America tends to be dry and warm during a mature phase of an ENSO event, which usually peaks between October and January with a frequency of 2-3 events per decade. Because in many <span class="hlt">tropical</span> areas the effect of ENSO is highly prominent, it is plausible that plants have adapted their growth and reproduction mechanisms to synchronize ENSO phases, in a similar way that plants do during the seasonal cycle. We used a long dataset (30+ years) of fruits and leaves rains of <span class="hlt">tropical</span> trees and lianas to determine ecosystem response and species specific response of these phenological events to local <span class="hlt">climate</span> variability corresponding to the modes of ENSO. Specifically, we tested the hypothesis that phenological responses to ENSO are similar to response to seasonal cycles, i.e., higher litterfall before a warm-dry phase and higher fruiting after such phase, with strong correlation between seeds and leaves. At sub-community level, we evaluated whether evergreen and deciduous, biotic and abiotic dispersers and free and climbing life forms, have the same response to ENSO in terms of leaves and seeds rain. At species level we tested the hypothesis that species with low photosynthetic capacity leaves are more responsive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27418502','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27418502"><span>Human influence on <span class="hlt">tropical</span> cyclone intensity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sobel, Adam H; Camargo, Suzana J; Hall, Timothy M; Lee, Chia-Ying; Tippett, Michael K; Wing, Allison A</p> <p>2016-07-15</p> <p>Recent assessments agree that <span class="hlt">tropical</span> cyclone intensity should increase as the <span class="hlt">climate</span> warms. Less agreement exists on the detection of recent historical trends in <span class="hlt">tropical</span> cyclone intensity. We interpret future and recent historical trends by using the theory of potential intensity, which predicts the maximum intensity achievable by a <span class="hlt">tropical</span> cyclone in a given local environment. Although greenhouse gas-driven warming increases potential intensity, <span class="hlt">climate</span> model simulations suggest that aerosol cooling has largely canceled that effect over the historical record. Large natural variability complicates analysis of trends, as do poleward shifts in the latitude of maximum intensity. In the absence of strong reductions in greenhouse gas emissions, future greenhouse gas forcing of potential intensity will increasingly dominate over aerosol forcing, leading to substantially larger increases in <span class="hlt">tropical</span> cyclone intensities. Copyright © 2016, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912714B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912714B"><span>Do Quercus ilex woodlands undergo <span class="hlt">abrupt</span> non-linear functional changes in response to human disturbance along a <span class="hlt">climatic</span> gradient?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bochet, Esther; García-Fayos, Patricio; José Molina, Maria; Moreno de las Heras, Mariano; Espigares, Tíscar; Nicolau, Jose Manuel; Monleon, Vicente</p> <p>2017-04-01</p> <p>Theoretical models predict that drylands are particularly prone to suffer critical transitions with <span class="hlt">abrupt</span> non-linear changes in their structure and functions as a result of the existing complex interactions between <span class="hlt">climatic</span> fluctuations and human disturbances. However, so far, few studies provide empirical data to validate these models. We aim at determining how holm oak (Quercus ilex) woodlands undergo changes in their functions in response to human disturbance along an aridity gradient (from semi-arid to sub-humid conditions), in eastern Spain. For that purpose, we used (a) remote-sensing estimations of precipitation-use-efficiency (PUE) from enhanced vegetation index (EVI) observations performed in 231x231 m plots of the Moderate Resolution Imaging Spectroradiometer (MODIS); (b) biological and chemical soil parameter determinations (extracellular soil enzyme activity, soil respiration, nutrient cycling processes) from soil sampled in the same plots; (c) vegetation parameter determinations (ratio of functional groups) from vegetation surveys performed in the same plots. We analyzed and compared the shape of the functional change (in terms of PUE and soil and vegetation parameters) in response to human disturbance intensity for our holm oak sites along the aridity gradient. Overall, our results evidenced important differences in the shape of the functional change in response to human disturbance between <span class="hlt">climatic</span> conditions. Semi-arid areas experienced a more accelerated non-linear decrease with an increasing disturbance intensity than sub-humid ones. The proportion of functional groups (herbaceous vs. woody cover) played a relevant role in the shape of the functional response of the holm oak sites to human disturbance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B31G0550L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B31G0550L"><span>Separating the Effects of <span class="hlt">Tropical</span> Atlantic and Pacific SST-driven <span class="hlt">Climate</span> Variability on Amazon Carbon Exchange</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liptak, J.; Keppel-Aleks, G.</p> <p>2016-12-01</p> <p>Amazon forests store an estimated 25% percent of global terrestrial carbon per year1, 2, but the responses of Amazon carbon uptake to <span class="hlt">climate</span> change is highly uncertain. One source of this uncertainty is <span class="hlt">tropical</span> sea surface temperature variability driven by teleconnections. El Nino-Southern Oscillation (ENSO) is a key driver of year-to-year Amazon carbon exchange, with associated temperature and precipitation changes favoring net carbon storage in La Nina years, and net carbon release during El Nino years3. To determine how Amazon <span class="hlt">climate</span> and terrestrial carbon fluxes react to ENSO alone and in concert with other SST-driven teleconnections such as the Atlantic Multidecadal Oscillation (AMO), we force the atmosphere (CAM5) and land (CLM4) components of the CESM(BGC) with prescribed monthly SSTs over the period 1950—2014 in a Historical control simulation. We then run an experiment (PAC) with time-varying SSTs applied only to the <span class="hlt">tropical</span> equatorial Pacific Ocean, and repeating SST seasonal cycle climatologies elsewhere. Limiting SST variability to the equatorial Pacific indicates that other processes enhance ENSO-driven Amazon <span class="hlt">climate</span> anomalies. Compared to the Historical control simulation, warming, drying and terrestrial carbon loss over the Amazon during El Nino periods are lower in the PAC simulation, especially prior to 1990 during the cool phase of the AMO. Cooling, moistening, and net carbon uptake during La Nina periods are also reduced in the PAC simulation, but differences are greater after 1990 during the warm phase of the AMO. By quantifying the relationships among <span class="hlt">climate</span> drivers and carbon fluxes in the Historical and PAC simulations, we both assess the sensitivity of these relationships to the magnitude of ENSO forcing and quantify how other teleconnections affect ENSO-driven Amazon <span class="hlt">climate</span> feedbacks. We expect that these results will help us improve hypotheses for how Atlantic and Pacific <span class="hlt">climate</span> trends will affect future Amazon carbon carbon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMEP52A..06V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMEP52A..06V"><span>Controls on the <span class="hlt">abruptness</span> of gravel-sand transitions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Venditti, J. G.; Church, M. A.; Lamb, M. P.; Domarad, N.; Rennie, C. D.</p> <p>2014-12-01</p> <p>As gravel-bedded rivers fine downstream, they characteristically exhibit an <span class="hlt">abrupt</span> transition from gravel- to sand-bed. This is the only <span class="hlt">abrupt</span> transition in grain-size that occurs in the fluvial system and has attracted considerable attention. A number of competing theories have been proposed to account for the <span class="hlt">abruptness</span> of the transition, including base-level control, attrition of ~10mm gravel to produce sand, and sediment sorting processes. The prevailing theory for the emergence of <span class="hlt">abrupt</span> transitions is size selective sorting of bimodal sediment wherein gravel deposits due to downstream declining shear stress, fining the bedload until a sand-bed emerges. We explored this hypothesis by examining grain-size, shear stress, gravel mobility and sand suspension thresholds through the gravel-sand transition (GST) of the Fraser River, British Columbia. The Fraser GST is an arrested gravel wedge with patches of gravel downstream of the wedge forming a diffuse extension. There is an <span class="hlt">abrupt</span> change in bed slope through the transition that leads to an <span class="hlt">abrupt</span> change in shear stress. The GST, bed-slope change and backwater caused by the ocean are all coincident spatially, which enhances the sharpness of the GST. Interestingly, the bimodal reach of the river occurs downstream of the GST and exhibits no downstream gradients in shear stress, suspended sediment flux, gravel mobility or sand suspension thresholds. This calls into question the prevailing theory for the emergence of an <span class="hlt">abrupt</span> GST by size selective sorting. We provide evidence, both empirical and theoretical, that suggests the emergence of an <span class="hlt">abrupt</span> GST is caused by rapid deposition of sand when fine gravel deposits. We argue that the emergence of gravel-sand transitions is a consequence of gravel-bedded rivers adopting a steeper slope than sand-bedded rivers. The <span class="hlt">abruptness</span> arises because the bed slope required to convey the gravel load fixes the distal location of a terminal gravel wedge, and once the river has</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020049829&hterms=climate+change+anthropogenic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dclimate%2Bchange%2Banthropogenic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020049829&hterms=climate+change+anthropogenic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dclimate%2Bchange%2Banthropogenic"><span>Sensitivity of the <span class="hlt">Tropical</span> Atmospheric Energy Balance to ENSO-Related SST Changes: Comparison of <span class="hlt">Climate</span> Model Simulations to Observed Responses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, Franklin R.; Fitzjarrald, Dan; Marshall, Susan; Oglesby, Robert; Roads, John; Arnold, James E. (Technical Monitor)</p> <p>2001-01-01</p> <p>This paper focuses on how fresh water and radiative fluxes over the <span class="hlt">tropical</span> oceans change during ENSO warm and cold events and how these changes affect the <span class="hlt">tropical</span> energy balance. At present, ENSO remains the most prominent known mode of natural variability at interannual time scales. While this natural perturbation to <span class="hlt">climate</span> is quite distinct from possible anthropogenic changes in <span class="hlt">climate</span>, adjustments in the <span class="hlt">tropical</span> water and energy budgets during ENSO may give insight into feedback processes involving water vapor and cloud feedbacks. Although great advances have been made in understanding this phenomenon and realizing prediction skill over the past decade, our ability to document the coupled water and energy changes observationally and to represent them in <span class="hlt">climate</span> models seems far from settled (Soden, 2000 J <span class="hlt">Climate</span>). In a companion paper we have presented observational analyses, based principally on space-based measurements which document systematic changes in rainfall, evaporation, and surface and top-of-atmosphere (TOA) radiative fluxes. Here we analyze several contemporary <span class="hlt">climate</span> models run with observed SSTs over recent decades and compare SST-induced changes in radiation, precipitation, evaporation, and energy transport to observational results. Among these are the NASA / NCAR Finite Volume Model, the NCAR Community <span class="hlt">Climate</span> Model, the NCEP Global Spectral Model, and the NASA NSIPP Model. Key disagreements between model and observational results noted in the recent literature are shown to be due predominantly to observational shortcomings. A reexamination of the Langley 8-Year Surface Radiation Budget data reveals errors in the SST surface longwave emission due to biased SSTs. Subsequent correction allows use of this data set along with ERBE TOA fluxes to infer net atmospheric radiative heating. Further analysis of recent rainfall algorithms provides new estimates for precipitation variability in line with interannual evaporation changes inferred from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESSD....9..679S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESSD....9..679S"><span>The ACER pollen and charcoal database: a global resource to document vegetation and fire response to <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes during the last glacial period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sánchez Goñi, María Fernanda; Desprat, Stéphanie; Daniau, Anne-Laure; Bassinot, Frank C.; Polanco-Martínez, Josué M.; Harrison, Sandy P.; Allen, Judy R. M.; Anderson, R. Scott; Behling, Hermann; Bonnefille, Raymonde; Burjachs, Francesc; Carrión, José S.; Cheddadi, Rachid; Clark, James S.; Combourieu-Nebout, Nathalie; Mustaphi, Colin. J. Courtney; Debusk, Georg H.; Dupont, Lydie M.; Finch, Jemma M.; Fletcher, William J.; Giardini, Marco; González, Catalina; Gosling, William D.; Grigg, Laurie D.; Grimm, Eric C.; Hayashi, Ryoma; Helmens, Karin; Heusser, Linda E.; Hill, Trevor; Hope, Geoffrey; Huntley, Brian; Igarashi, Yaeko; Irino, Tomohisa; Jacobs, Bonnie; Jiménez-Moreno, Gonzalo; Kawai, Sayuri; Kershaw, A. Peter; Kumon, Fujio; Lawson, Ian T.; Ledru, Marie-Pierre; Lézine, Anne-Marie; Liew, Ping Mei; Magri, Donatella; Marchant, Robert; Margari, Vasiliki; Mayle, Francis E.; Merna McKenzie, G.; Moss, Patrick; Müller, Stefanie; Müller, Ulrich C.; Naughton, Filipa; Newnham, Rewi M.; Oba, Tadamichi; Pérez-Obiol, Ramón; Pini, Roberta; Ravazzi, Cesare; Roucoux, Katy H.; Rucina, Stephen M.; Scott, Louis; Takahara, Hikaru; Tzedakis, Polichronis C.; Urrego, Dunia H.; van Geel, Bas; Valencia, B. Guido; Vandergoes, Marcus J.; Vincens, Annie; Whitlock, Cathy L.; Willard, Debra A.; Yamamoto, Masanobu</p> <p>2017-09-01</p> <p>Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past <span class="hlt">climate</span> changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid <span class="hlt">climate</span> change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on <span class="hlt">climate</span>. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (<span class="hlt">Abrupt</span> <span class="hlt">Climate</span> Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73-15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U/230Th, optically stimulated luminescence (OSL), 40Ar/39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in <span style="" class="text">Microsoft AccessTM at <a href="https://doi.org/10.1594/PANGAEA.870867" target="_blank">https://doi.org/10.1594/PANGAEA.870867</a>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813962K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813962K"><span>Modelling trends in <span class="hlt">tropical</span> column ozone with the UKCA chemistry-<span class="hlt">climate</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keeble, James; Bednarz, Ewa; Banerjee, Antara; Abraham, Luke; Harris, Neil; Maycock, Amanda; Pyle, John</p> <p>2016-04-01</p> <p>Trends in <span class="hlt">tropical</span> column ozone under a number of different emissions scenarios are explored with the UM-UKCA coupled chemistry <span class="hlt">climate</span> model. A transient 1960-2100 simulation was run following the RCP6 scenario. <span class="hlt">Tropical</span> averaged (10S-10N) total column ozone values decrease from the 1970s, reaching a minimum around 2000, and return to their 1980 values around 2040, consistent with the use and emission of ozone depleting substances, and their later controls under the Montreal Protocol. However, when the total column is subdivided into three partial columns, extending from the surface to the tropopause, the tropopause to 30km, and 30km to 50km, significant differences to the total column trend are seen. Modelled tropospheric column values increase from 1960-2000 before remaining steady throughout the 21st Century. Lower stratospheric column values decrease rapidly from 1960-2000, remain steady until 2050 before slowly decreasing to 2100, never recovering to their 1980s values. Upper stratospheric values decrease from 1960-2000, before rapidly increasing throughout the 21st Century, recovering to 1980s values by ~2020 and are significantly increased above the 1980s values by 2100. Using a series of idealised model simulations with varying concentrations of greenhouse gases and ozone depleting substances, we assess the physical processes driving the partial column response in the troposphere, lower stratosphere and upper stratosphere, and assess how these processes change under different emissions scenarios. Finally, we present a simple, linearised model for predicting <span class="hlt">tropical</span> column ozone values based on greenhouse gas and ozone depleting substance scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA620426','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA620426"><span><span class="hlt">Tropical</span> Cyclone Reconnaissance with the Global Hawk: Operational Thresholds and Characteristics of Convective Systems Over the <span class="hlt">Tropical</span> Western North Pacific</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-12-01</p> <p><span class="hlt">Tropical</span> cyclone research is an intense ongoing science that has acquired even greater importance in this era of global <span class="hlt">climate</span> change . Increased study of...RECONNAISSANCE WITH THE GLOBAL HAWK: OPERATIONAL THRESHOLDS AND CHARACTERISTICS OF CONVECTIVE SYSTEMS OVER THE <span class="hlt">TROPICAL</span> WESTERN NORTH PACIFIC by...<span class="hlt">TROPICAL</span> CYCLONE RECONNAISSANCE WITH THE GLOBAL HAWK: OPERATIONAL THRESHOLDS AND CHARACTERISTICS OF CONVECTIVE SYSTEMS OVER THE <span class="hlt">TROPICAL</span> WESTERN</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A33B0206L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A33B0206L"><span>Reconstruction of Last Glacial <span class="hlt">Tropical</span> SST Anomalies from Mg/Ca and UK37' to Constrain <span class="hlt">Climate</span> Sensitivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lea, D. W.; de Garidel-Thoron, T.; Bard, E. G.; Kienast, M.</p> <p>2016-12-01</p> <p>Proxy paleoclimate data provides an important constrain on <span class="hlt">climate</span> sensitivity. The <span class="hlt">tropics</span> have been identified as a region which primarily responds to greenhouse gas forcing (GHF). The SENSETROP (Sensitivity of the <span class="hlt">Tropics</span>) group has identified the LGM, HS1 and HS2 as key time windows to test the hypothesis that SST anomalies recorded by two geochemical paleothermometers, Mg/Ca and UK37', can be used to establish <span class="hlt">tropical</span> <span class="hlt">climate</span> response and, via the magnitude and spatial pattern of these anomalies, provide robust comparisons to the output of general circulation models. This work is a logical extension of prior efforts such as CLIMAP and MARGO, which largely relied on faunal SST proxies that are affected by other factors such as productivity or water column structure. With this goal in mind we have developed the SENSETROP database of published and unpublished Mg/Ca and UK37' data from low latitude (30° N to 30° S) marine cores spanning the last glacial cycle. The database contains 78 Mg/Ca records and 40 UK37' records, distributed between the <span class="hlt">tropical</span> ocean basins: 49 in the Pacific Ocean, 32 in the Indian Ocean, and 27 in the Atlantic Ocean. Most of the cores are confined to the ocean margins. All of the data come from well dated records that include radiocarbon. As a test of the database, we determined the average SST anomaly during the LGM, 19,000-23,000 yr BP, relative to the late Holocene, 0-4,000 yr BP, from select records that contain at least 4 SST points in each time window for which the SDs < 0.75 °C. For G. ruber (all morphotypes) Mg/Ca, the recorded anomaly from 23 cores is -2.6 ± 0.6 °C, based on >1100 individual determinations. For UK37', the recorded anomaly for 14 cores is -2.4 ± 0.9 °C, based on >400 individual determinations. Agreement between these two independent proxies increases confidence in the LGM cooling level. The new results from the SENSETROP database show a strong level of homogeneity throughout the <span class="hlt">tropics</span>, with slightly ( 0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP42A..08L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP42A..08L"><span>Reconstructing <span class="hlt">Tropical</span> Southwest Pacific <span class="hlt">Climate</span> Variability and Mean State Changes at Vanuatu during the Medieval <span class="hlt">Climate</span> Anomaly using Geochemical Proxies from Corals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lawman, A. E.; Quinn, T. M.; Partin, J. W.; Taylor, F. W.; Thirumalai, K.; WU, C. C.; Shen, C. C.</p> <p>2017-12-01</p> <p>The Medieval <span class="hlt">Climate</span> Anomaly (MCA: 950-1250 CE) is identified as a period during the last 2 millennia with Northern Hemisphere surface temperatures similar to the present. However, our understanding of <span class="hlt">tropical</span> <span class="hlt">climate</span> variability during the MCA is poorly constrained due to a lack of sub-annually resolved proxy records. We investigate seasonal and interannual variability during the MCA using geochemical records developed from two well preserved Porites lutea fossilized corals from the <span class="hlt">tropical</span> southwest Pacific (Tasmaloum, Vanuatu; 15.6°S, 166.9°E). Absolute U/Th dates of 1127.1 ± 2.7 CE and 1105.1 ± 3.0 CE indicate that the selected fossil corals lived during the MCA. We use paired coral Sr/Ca and δ18O measurements to reconstruct sea surface temperature (SST) and the δ18O of seawater (a proxy for salinity). To provide context for the fossil coral records and test whether the mean state and <span class="hlt">climate</span> variability at Vanuatu during the MCA is similar to the modern <span class="hlt">climate</span>, our analysis also incorporates two modern coral records from Sabine Bank (15.9°S, 166.0°E) and Malo Channel (15.7°S, 167.2°E), Vanuatu for comparison. We quantify the uncertainty in our modern and fossil coral SST estimates via replication with multiple, overlapping coral records. Both the modern and fossil corals reproduce their respective mean SST value over their common period of overlap, which is 25 years in both cases. Based on over 100 years of monthly Sr/Ca data from each time period, we find that SSTs at Vanuatu during the MCA are 1.3 ± 0.7°C cooler relative to the modern. We also find that the median amplitude of the annual cycle is 0.8 ± 0.3°C larger during the MCA relative to the modern. Multiple data analysis techniques, including the standard deviation and the difference between the 95th and 5th percentiles of the annual SST cycle estimates, also show that the MCA has greater annual SST variability relative to the modern. Stable isotope data acquisition is ongoing, and when</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B51D0466C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B51D0466C"><span>Seasonal and Inter-annual Variation in Wood Production in <span class="hlt">Tropical</span> Trees on Barro Colorado Island, Panama, is Related to Local <span class="hlt">Climate</span> and Species Functional Traits</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cushman, K.; Muller-Landau, H. C.; Kellner, J. R.; Wright, S. J.; Condit, R.; Detto, M.; Tribble, C. M.</p> <p>2015-12-01</p> <p><span class="hlt">Tropical</span> forest carbon budgets play a major role in global carbon dynamics, but the responses of <span class="hlt">tropical</span> forests to current and future inter-annual <span class="hlt">climatic</span> variation remains highly uncertain. Better predictions of future <span class="hlt">tropical</span> forest carbon fluxes require an improved understanding of how different species of <span class="hlt">tropical</span> trees respond to changes in <span class="hlt">climate</span> at seasonal and inter-annual temporal scales. We installed dendrometer bands on a size-stratified sample of 2000 trees in old growth forest on Barro Colorado Island, Panama, a moist lowland forest that experiences an annual dry season of approximately four months. Tree diameters were measured at the beginning and end of the rainy season since 2008. Additionally, we recorded the canopy illumination level, canopy intactness, and liana coverage of all trees during each census. We used linear mixed-effects models to evaluate how tree growth was related to seasonal and interannual variation in local <span class="hlt">climate</span>, tree condition, and species identity, and how species identity effects related to tree functional traits. <span class="hlt">Climatic</span> variables considered included precipitation, solar radiation, soil moisture, and climatological water deficit, and were all calculated from high-quality on-site measurements. Functional traits considered included wood density, maximum adult stature, deciduousness, and drought tolerance. We found that annual wood production was positively related to water availability, with higher growth in wetter years. Species varied in their response to seasonal water availability, with some species showing more pronounced reduction of growth during the dry season when water availability is limited. Interspecific variation in seasonal and interannual growth patterns was related to life-history strategies and species functional traits. The finding of higher growth in wetter years is consistent with previous tree ring studies conducted on a small subset of species with reliable annual rings. Together with previous</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED432438.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED432438.pdf"><span><span class="hlt">Tropical</span> Rainforest Education. ERIC Digest.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Rillero, Peter</p> <p></p> <p>This digest provides four guideposts for <span class="hlt">tropical</span> rainforest education: (1) structure; (2) location and <span class="hlt">climate</span>; (3) importance; and (4) conservation of resources. Research is cited and background information provided about the layers of life and the adaptations of life within the <span class="hlt">tropical</span> rain forest. Aspects of life within and near rain forests…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1114032S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1114032S"><span>From <span class="hlt">Abrupt</span> Change to the Future (Hans Oeschger Medal Lecture)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stocker, T.</p> <p>2009-04-01</p> <p>The award of the Oeschger Medal 2009 is a particular honor and pleasure for me as I was given the chance to take over from Hans Oeschger the lead of a wonderful Institute at the University of Bern in 1993. Very apprehensive first, in front of the huge expectations and challenges, I quickly found dear colleagues, close collaborators and extremely supportive staff who all dedicated their time and creativity to work for the common goal of better understanding the Earth System, its variations in the past and its sensitivity to perturbations that man is inflicting on it today. Although met with innate skepticism first by the experimental physicists, our efforts in modelling, particularly the approach of using <span class="hlt">climate</span> models of reduced complexity, quickly paid off and provided added value to the hard won data and measurements from polar ice cores. It is clear that modelling in such a diverse environment is so much more stimulating and enriching than working on a sophisticated parameterisation in a big modelling centre. Simple models have suggested that the Earth System may have limited stability and that rather fundamental changes could be triggered by the increase of greenhouse gases. However, it is the unique results from polar ice cores, particularly from Greenland that showed that, indeed, the Earth System has limited stability and can react in extremely <span class="hlt">abrupt</span> ways to changes in forcing. Likewise, the Antarctic ice cores have provided one of the corner stones of our knowledge about <span class="hlt">climate</span> change: Concentrations of CO2 are today 29% higher than ever during the last 800,000 years. These two fundamental insights from the paleoclimatic archive call for accelerated research into the sensitivity of the <span class="hlt">climate</span> system and its components to perturbations, as well as the investigation of feedback mechanisms in the biogeochemical cycles that are disturbed by the input of CO2 into the atmosphere by burning fossil fuels and land use change. Our research has only scratched the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170003432','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170003432"><span>Positive Low Cloud and Dust Feedbacks Amplify <span class="hlt">Tropical</span> North Atlantic Multidecadal Variability</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yuan, Tianle; Oraiopoulos, Lazaros; Zelinka, Mark; Yu, Hongbin; Norris, Joel R.; Chin, Mian; Platnick, Steven; Meyer, Kerry</p> <p>2016-01-01</p> <p>The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of <span class="hlt">climatic</span> impacts. While the <span class="hlt">tropical</span> arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many <span class="hlt">climate</span> model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the <span class="hlt">tropical</span> arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened <span class="hlt">tropical</span> trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the <span class="hlt">tropical</span> Atlantic, which warms the <span class="hlt">tropical</span> North Atlantic SST. Together they contribute to appearance of the <span class="hlt">tropical</span> arm of AMO. Most current <span class="hlt">climate</span> models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many <span class="hlt">climatic</span> studies related to the AMO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3223651','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3223651"><span>Latitude, elevational <span class="hlt">climatic</span> zonation and speciation in New World vertebrates</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cadena, Carlos Daniel; Kozak, Kenneth H.; Gómez, Juan Pablo; Parra, Juan Luis; McCain, Christy M.; Bowie, Rauri C. K.; Carnaval, Ana C.; Moritz, Craig; Rahbek, Carsten; Roberts, Trina E.; Sanders, Nathan J.; Schneider, Christopher J.; VanDerWal, Jeremy; Zamudio, Kelly R.; Graham, Catherine H.</p> <p>2012-01-01</p> <p>Many biodiversity hotspots are located in montane regions, especially in the <span class="hlt">tropics</span>. A possible explanation for this pattern is that the narrow thermal tolerances of <span class="hlt">tropical</span> species and greater <span class="hlt">climatic</span> stratification of <span class="hlt">tropical</span> mountains create more opportunities for <span class="hlt">climate</span>-associated parapatric or allopatric speciation in the <span class="hlt">tropics</span> relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, <span class="hlt">climatic</span> zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of <span class="hlt">climate</span> in speciation in <span class="hlt">tropical</span> versus temperate areas. Here, we quantify overlap in the <span class="hlt">climatic</span> distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World <span class="hlt">tropics</span> or to the Northern temperate zone. We show that elevational ranges of <span class="hlt">tropical</span>- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the <span class="hlt">tropics</span>. Moreover, <span class="hlt">tropical</span> sister species tend to exhibit greater similarity in their <span class="hlt">climatic</span> distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of <span class="hlt">tropical</span> taxa, coupled with the greater thermal zonation of <span class="hlt">tropical</span> mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in <span class="hlt">tropical</span> montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global <span class="hlt">climatic</span> variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of <span class="hlt">tropical</span> montane regions. PMID:21632626</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5952327','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5952327"><span>Application of CRISPR/Cas9 Genome Editing Technology for the Improvement of Crops Cultivated in <span class="hlt">Tropical</span> <span class="hlt">Climates</span>: Recent Progress, Prospects, and Challenges</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Haque, Effi; Taniguchi, Hiroaki; Hassan, Md. Mahmudul; Bhowmik, Pankaj; Karim, M. Rezaul; Śmiech, Magdalena; Zhao, Kaijun; Rahman, Mahfuzur; Islam, Tofazzal</p> <p>2018-01-01</p> <p>The world population is expected to increase from 7.3 to 9.7 billion by 2050. Pest outbreak and increased abiotic stresses due to <span class="hlt">climate</span> change pose a high risk to <span class="hlt">tropical</span> crop production. Although conventional breeding techniques have significantly increased crop production and yield, new approaches are required to further improve crop production in order to meet the global growing demand for food. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 (CRISPR-associated protein9) genome editing technology has shown great promise for quickly addressing emerging challenges in agriculture. It can be used to precisely modify genome sequence of any organism including plants to achieve the desired trait. Compared to other genome editing tools such as zinc finger nucleases (ZFNs) and transcriptional activator-like effector nucleases (TALENs), CRISPR/Cas9 is faster, cheaper, precise and highly efficient in editing genomes even at the multiplex level. Application of CRISPR/Cas9 technology in editing the plant genome is emerging rapidly. The CRISPR/Cas9 is becoming a user-friendly tool for development of non-transgenic genome edited crop plants to counteract harmful effects from <span class="hlt">climate</span> change and ensure future food security of increasing population in <span class="hlt">tropical</span> countries. This review updates current knowledge and potentials of CRISPR/Cas9 for improvement of crops cultivated in <span class="hlt">tropical</span> <span class="hlt">climates</span> to gain resiliency against emerging pests and abiotic stresses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29868073','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29868073"><span>Application of CRISPR/Cas9 Genome Editing Technology for the Improvement of Crops Cultivated in <span class="hlt">Tropical</span> <span class="hlt">Climates</span>: Recent Progress, Prospects, and Challenges.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Haque, Effi; Taniguchi, Hiroaki; Hassan, Md Mahmudul; Bhowmik, Pankaj; Karim, M Rezaul; Śmiech, Magdalena; Zhao, Kaijun; Rahman, Mahfuzur; Islam, Tofazzal</p> <p>2018-01-01</p> <p>The world population is expected to increase from 7.3 to 9.7 billion by 2050. Pest outbreak and increased abiotic stresses due to <span class="hlt">climate</span> change pose a high risk to <span class="hlt">tropical</span> crop production. Although conventional breeding techniques have significantly increased crop production and yield, new approaches are required to further improve crop production in order to meet the global growing demand for food. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 (CRISPR-associated protein9) genome editing technology has shown great promise for quickly addressing emerging challenges in agriculture. It can be used to precisely modify genome sequence of any organism including plants to achieve the desired trait. Compared to other genome editing tools such as zinc finger nucleases (ZFNs) and transcriptional activator-like effector nucleases (TALENs), CRISPR/Cas9 is faster, cheaper, precise and highly efficient in editing genomes even at the multiplex level. Application of CRISPR/Cas9 technology in editing the plant genome is emerging rapidly. The CRISPR/Cas9 is becoming a user-friendly tool for development of non-transgenic genome edited crop plants to counteract harmful effects from <span class="hlt">climate</span> change and ensure future food security of increasing population in <span class="hlt">tropical</span> countries. This review updates current knowledge and potentials of CRISPR/Cas9 for improvement of crops cultivated in <span class="hlt">tropical</span> <span class="hlt">climates</span> to gain resiliency against emerging pests and abiotic stresses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015QSRv..123..215S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015QSRv..123..215S"><span><span class="hlt">Abrupt</span> <span class="hlt">climate</span> variability since the last deglaciation based on a high-resolution, multi-proxy peat record from NW Iran: The hand that rocked the Cradle of Civilization?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharifi, Arash; Pourmand, Ali; Canuel, Elizabeth A.; Ferer-Tyler, Erin; Peterson, Larry C.; Aichner, Bernhard; Feakins, Sarah J.; Daryaee, Touraj; Djamali, Morteza; Beni, Abdolmajid Naderi; Lahijani, Hamid A. K.; Swart, Peter K.</p> <p>2015-09-01</p> <p>We present a high-resolution (sub-decadal to centennial), multi-proxy reconstruction of aeolian input and changes in palaeohydrological conditions based on a 13000 Yr record from Neor Lake's peripheral peat in NW Iran. Variations in relative abundances of refractory (Al, Zr, Ti, and Si), redox sensitive (Fe) and mobile (K and Rb) elements, total organic carbon (TOC), δ13CTOC, compound-specific leaf wax hydrogen isotopes (δD), carbon accumulation rates and dust fluxes presented here fill a large gap in the existing terrestrial paleoclimate records from the interior of West Asia. Our results suggest that a transition occurred from dry and dusty conditions during the Younger Dryas (YD) to a relatively wetter period with higher carbon accumulation rates and low aeolian input during the early Holocene (9000-6000 Yr BP). This period was followed by relatively drier and dustier conditions during middle to late Holocene, which is consistent with orbital changes in insolation that affected much of the northern hemisphere. Numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the middle to late Holocene. Wavelet analysis of variations in Ti abundances as a proxy for aeolian input revealed notable periodicities at 230, 320, and 470 years with significant periodicities centered around 820, 1550, and 3110 years over the last 13000 years. Comparison with palaeoclimate archives from West Asia, the North Atlantic and African lakes point to a teleconnection between North Atlantic <span class="hlt">climate</span> and the interior of West Asia during the last glacial termination and the Holocene epoch. We further assess the potential role of <span class="hlt">abrupt</span> <span class="hlt">climate</span> change on early human societies by comparing our record of palaeoclimate variability with historical, geological and archaeological archives from this region. The terrestrial record from this study confirms previous evidence from marine sediments of the Arabian Sea that suggested <span class="hlt">climate</span> change influenced the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028212','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028212"><span>Globally synchronous ice core volcanic tracers and <span class="hlt">abrupt</span> cooling during the last glacial period</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.</p> <p>2006-01-01</p> <p>We perform a Monte Carlo pattern recognition analysis of the coincidence between three regional volcanic histories from ice coring of Greenland and Antarctica over the period 2 to 45 ka, using SO4 anomalies in Greenland and East Antarctica determined by continuous core chemistry, together with West Antarctic volcanic ash layers determined by remote optical borehole logging and core assays. We find that the Antarctic record of volcanism correlates with Glacial <span class="hlt">abrupt</span> <span class="hlt">climate</span> change at a 95% to >99.8% (???3??) significance level and that volcanic depositions at the three locations match at levels exceeding 3??, likely indicating that many common horizons represent single eruptive events which dispersed material world wide. These globally coincident volcanics were associated with <span class="hlt">abrupt</span> cooling, often simultaneous with onsets or sudden intensifications of millennial cold periods. The striking agreement between sites implies that the consistency of current timescales obtained by isotopic and glaciological dating methods is better than estimated. Copyright 2006 by the American Geogphysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/54329','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/54329"><span>Analyzing cloud base at local and regional scales to understand <span class="hlt">tropical</span> montane cloud forest vulnerability to <span class="hlt">climate</span> change</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Ashley E. Van Beusekom; Grizelle Gonzalez; Martha A. Scholl</p> <p>2017-01-01</p> <p>The degree to which cloud immersion provides water in addition to rainfall, suppresses transpiration, and sustains <span class="hlt">tropical</span> montane cloud forests (TMCFs) during rainless periods is not well understood. <span class="hlt">Climate</span> and land use changes represent a threat to these forests if cloud base altitude rises as a result of regional warming or deforestation. To establish a baseline...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006Natur.441...73V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006Natur.441...73V"><span>Weakening of <span class="hlt">tropical</span> Pacific atmospheric circulation due to anthropogenic forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vecchi, Gabriel A.; Soden, Brian J.; Wittenberg, Andrew T.; Held, Isaac M.; Leetmaa, Ants; Harrison, Matthew J.</p> <p>2006-05-01</p> <p>Since the mid-nineteenth century the Earth's surface has warmed, and models indicate that human activities have caused part of the warming by altering the radiative balance of the atmosphere. Simple theories suggest that global warming will reduce the strength of the mean <span class="hlt">tropical</span> atmospheric circulation. An important aspect of this <span class="hlt">tropical</span> circulation is a large-scale zonal (east-west) overturning of air across the equatorial Pacific Ocean-driven by convection to the west and subsidence to the east-known as the Walker circulation. Here we explore changes in <span class="hlt">tropical</span> Pacific circulation since the mid-nineteenth century using observations and a suite of global <span class="hlt">climate</span> model experiments. Observed Indo-Pacific sea level pressure reveals a weakening of the Walker circulation. The size of this trend is consistent with theoretical predictions, is accurately reproduced by <span class="hlt">climate</span> model simulations and, within the <span class="hlt">climate</span> models, is largely due to anthropogenic forcing. The <span class="hlt">climate</span> model indicates that the weakened surface winds have altered the thermal structure and circulation of the <span class="hlt">tropical</span> Pacific Ocean. These results support model projections of further weakening of <span class="hlt">tropical</span> atmospheric circulation during the twenty-first century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25145694','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25145694"><span>Extreme temperatures, foundation species, and <span class="hlt">abrupt</span> ecosystem change: an example from an iconic seagrass ecosystem.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomson, Jordan A; Burkholder, Derek A; Heithaus, Michael R; Fourqurean, James W; Fraser, Matthew W; Statton, John; Kendrick, Gary A</p> <p>2015-04-01</p> <p>Extreme <span class="hlt">climatic</span> events can trigger <span class="hlt">abrupt</span> and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under <span class="hlt">climate</span> change, the impact of these events on many foundation species and the ecosystems they support remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia--a relatively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit--as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing <span class="hlt">climate</span>. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the event compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Chelonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the event. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized framework for assessing the vulnerability of ecosystems to <span class="hlt">abrupt</span> change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing <span class="hlt">climate</span>. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contribution to this framework. © 2014 John Wiley</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.1629E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.1629E"><span>The potential effects of <span class="hlt">climate</span> change on malaria in <span class="hlt">tropical</span> Africa using regionalised <span class="hlt">climate</span> projections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ermert, V.; Fink, A. H.; Paeth, H.; Morse, A. P.</p> <p>2012-04-01</p> <p>The projected <span class="hlt">climate</span> change will probably alter the range and transmission potential of malaria in Africa. The potential impacts of <span class="hlt">climate</span> change on the malaria distribution is assessed for <span class="hlt">tropical</span> Africa. Bias-corrected regional <span class="hlt">climate</span> projections with a horizontal resolution of 0.5° are used from the Regional Model (REMO), which include land use and land cover changes. The malaria models employed are the 2010 version of the Liverpool Malaria Model (LMM2010), the Garki model, the Plasmodium falciparum infection model from Smith et al. (2005) (S2005), and the Malaria Seasonality Model (MSM) from the Mapping Malaria Risk in Africa project. The results of the models are compared with data from the Malaria Atlas Project (MAP) and novel validation procedures for the LMM2010 and MSM lend more credence to their results. For <span class="hlt">climate</span> scenarios A1B and B1 and for 2001-2050, REMO projects an overall drying and warming trend in the African malaria belt, that is largely imposed by the man-made degradation of vegetation. As a result, the malaria projections show a decreased malaria spread in West Africa. The northern Sahel is no more suitable for malaria in the projections. More unstable malaria transmission and shorter malaria seasons are expected for various areas farther south. An increase in the malaria epidemic risk is found for more densely populated areas in the southern part of the Sahel. In East Africa, higher temperatures and nearly unchanged precipitation patterns lead to longer transmission seasons and an increase in the area of highland malaria. For altitudes up to 2000 m the malaria transmission stabilises and the epidemic risk is reduced but for higher altitudes the risk of malaria epidemics is increased. The results of the more complex and simple malaria models are similar to each other. However, a different response to the warming of highlands is found for the LMM2010 and MSM. This shows the requirement of a multi model uncertainty analysis for the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25526660','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25526660"><span>Gross mismatch between thermal tolerances and environmental temperatures in a <span class="hlt">tropical</span> freshwater snail: <span class="hlt">climate</span> warming and evolutionary implications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Polgar, Gianluca; Khang, Tsung Fei; Chua, Teddy; Marshall, David J</p> <p>2015-01-01</p> <p>The relationship between acute thermal tolerance and habitat temperature in ectotherm animals informs about their thermal adaptation and is used to assess thermal safety margins and sensitivity to <span class="hlt">climate</span> warming. We studied this relationship in an equatorial freshwater snail (Clea nigricans), belonging to a predominantly marine gastropod lineage (Neogastropoda, Buccinidae). We found that tolerance of heating and cooling exceeded average daily maximum and minimum temperatures, by roughly 20°C in each case. Because habitat temperature is generally assumed to be the main selective factor acting on the fundamental thermal niche, the discordance between thermal tolerance and environmental temperature implies trait conservation following 'in situ' environmental change, or following novel colonisation of a thermally less-variable habitat. Whereas heat tolerance could relate to an historical association with the thermally variable and extreme marine intertidal fringe zone, cold tolerance could associate with either an ancestral life at higher latitudes, or represent adaptation to cooler, higher-altitudinal, <span class="hlt">tropical</span> lotic systems. The broad upper thermal safety margin (difference between heat tolerance and maximum environmental temperature) observed in this snail is grossly incompatible with the very narrow safety margins typically found in most terrestrial <span class="hlt">tropical</span> ectotherms (insects and lizards), and hence with the emerging prediction that <span class="hlt">tropical</span> ectotherms, are especially vulnerable to environmental warming. A more comprehensive understanding of <span class="hlt">climatic</span> vulnerability of animal ectotherms thus requires greater consideration of taxonomic diversity, ecological transition and evolutionary history. Copyright © 2014 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020022509&hterms=climate+change+evidence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dclimate%2Bchange%2Bevidence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020022509&hterms=climate+change+evidence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dclimate%2Bchange%2Bevidence"><span>Evidence for Large Decadal Variability in the <span class="hlt">Tropical</span> Mean Radiative Energy Budget</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wielicki, Bruce A.; Wong, Takmeng; Allan, Richard; Slingo, Anthony; Kiehl, Jeffrey T.; Soden, Brian J.; Gordon, C. T.; Miller, Alvin J.; Yang, Shi-Keng; Randall, David R.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20020022509'); toggleEditAbsImage('author_20020022509_show'); toggleEditAbsImage('author_20020022509_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20020022509_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20020022509_hide"></p> <p>2001-01-01</p> <p>It is widely assumed that variations in the radiative energy budget at large time and space scales are very small. We present new evidence from a compilation of over two decades of accurate satellite data that the top-of-atmosphere (TOA) <span class="hlt">tropical</span> radiative energy budget is much more dynamic and variable than previously thought. We demonstrate that the radiation budget changes are caused by changes In <span class="hlt">tropical</span> mean cloudiness. The results of several current <span class="hlt">climate</span> model simulations fall to predict this large observed variation In <span class="hlt">tropical</span> energy budget. The missing variability in the models highlights the critical need to Improve cloud modeling in the <span class="hlt">tropics</span> to support Improved prediction of <span class="hlt">tropical</span> <span class="hlt">climate</span> on Inter-annual and decadal time scales. We believe that these data are the first rigorous demonstration of decadal time scale changes In the Earth's <span class="hlt">tropical</span> cloudiness, and that they represent a new and necessary test of <span class="hlt">climate</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..3324706S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..3324706S"><span>Solar and anthropogenic forcing of <span class="hlt">tropical</span> hydrology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shindell, Drew T.; Faluvegi, Greg; Miller, Ron L.; Schmidt, Gavin A.; Hansen, James E.; Sun, Shan</p> <p>2006-12-01</p> <p>Holocene <span class="hlt">climate</span> proxies suggest substantial correlations between <span class="hlt">tropical</span> meteorology and solar variations, but these have thus far not been explained. Using a coupled ocean-atmosphere-composition model forced by sustained multi-decadal irradiance increases, we show that greater <span class="hlt">tropical</span> temperatures alter the hydrologic cycle, enhancing the climatological precipitation maxima in the <span class="hlt">tropics</span> while drying the subtropical subsidence regions. The shift is enhanced by tropopause region ozone increases, and the model captures the pattern inferred from paleoclimate records. The physical process we describe likely affected past civilizations, including the Maya, Moche, and Ancestral Puebloans who experienced drought coincident with increased irradiance during the late medieval (~900-1250). Similarly, decreased irradiance may have affected cultures via a weakened monsoon during the Little Ice Age (~1400-1750). Projections of 21st-century <span class="hlt">climate</span> change yield hydrologic cycle changes via similar processes, suggesting a strong likelihood of increased subtropical drought as <span class="hlt">climate</span> warms.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP31C1155S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP31C1155S"><span>Diatoms as Proxies for <span class="hlt">Abrupt</span> Events in the Hudson River Estuary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skorski, W.; Abbott, D. H.; Recasens, C.; Breger, D. L.</p> <p>2014-12-01</p> <p>The Hudson River estuary has been subject to many <span class="hlt">abrupt</span> events throughout its history including hurricanes, droughts and pluvials. Hurricanes in particular are rare, discrete events that if fingerprinted can be used to develop better age models for Hudson River sediments. Proxies use observed physical characteristics or biological assemblages (e.g. diatom and foraminiferal assemblages) as tools to reconstruct past conditions prior to the modern instrumental record. Using a sediment core taken from the Hudson River (CDO2-29A), in New York City, drought and pluvial layers were selected based on Cs-137 dating while hurricane layers were determined from occurrences of <span class="hlt">tropical</span> to subtropical foraminifera. Contrary to previous studies (Weaver, 1970, Weiss et al, 1978), more than sixty different diatom species have been identified using a scanning electron microscope (SEM). Cosmopolitan, hurricane and drought assemblages have begun to be identified after observing multiple layers (Table 1). <span class="hlt">Tropical</span> foraminifera dominated by Globigerinoides ruber pink were also found in a hurricane layer that we infer was deposited during Hurricane Belle in 1976. More diatom abundance analyses and cataloged SEM pictures will provide further insight into these proxies. Table 1 Diatom Genera and Species Environment Clarification Cyclotella caspia Planktonic, marine-brackish Cosmopolitan Karayevia clevei Freshwater Cosmopolitan Melosira sp Planktonic, marine Cosmopolitan Thalassiosira sp Marine, brackish Cosmopolitan Staurosirella leptostauron Benthic, freshwater Cosmopolitan Actinoptychus senarius Planktonic or benthic, freshwater to brackish Hurricane and pluvial layers Amphora aff. sp Benthic, marine or freshwater Hurricane layers only Nitzschia sp Benthic, marine or freshwater Hurricane layers only Gomphonema sp Freshwater Hurricane layers only Surirella sp Marine-brackish Drought layer only Triceratium sp Marine Drought layer only Other Genera and species Environment Clarification</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A13H2212M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A13H2212M"><span>Process-Oriented Diagnostics of <span class="hlt">Tropical</span> Cyclones in Global <span class="hlt">Climate</span> Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moon, Y.; Kim, D.; Camargo, S. J.; Wing, A. A.; Sobel, A. H.; Bosilovich, M. G.; Murakami, H.; Reed, K. A.; Vecchi, G. A.; Wehner, M. F.; Zarzycki, C. M.; Zhao, M.</p> <p>2017-12-01</p> <p>Simulating <span class="hlt">tropical</span> cyclone (TC) activity with global <span class="hlt">climate</span> models (GCMs) remains a challenging problem. While some GCMs are able to simulate TC activity that is in good agreement with the observations, many other models exhibit strong biases. Decreasing horizontal grid spacing of the GCM simulations tends to improve the characteristics of simulated TCs, but this enhancement alone does not necessarily lead to greater skill in simulating TC activity. This study uses process-based diagnostics to identify model characteristics that could explain why some GCM simulations are able to produce more realistic TC activity than others. The diagnostics examine how convection, moisture, clouds and related processes are coupled at individual grid points, which yields useful information into how convective parameterizations interact with resolved model dynamics. These diagnostics share similarities with those originally developed to examine the Madden-Julian Oscillations in <span class="hlt">climate</span> models. This study will examine TCs in eight different GCM simulations performed at NOAA/GFDL, NCAR and NASA that have different horizontal resolutions and ocean coupling. Preliminary results suggest that stronger TCs are closely associated with greater rainfall - thus greater diabatic heating - in the inner-core regions of the storms, which is consistent with previous theoretical studies. Other storm characteristics that can be used to infer why GCM simulations with comparable horizontal grid spacings produce different TC activity will be examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.9721N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.9721N"><span>Western North Pacific <span class="hlt">Tropical</span> Cyclone Model Tracks in Present and Future <span class="hlt">Climates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Jennifer; Camargo, Suzana J.; Sobel, Adam H.; Henderson, Naomi; Emanuel, Kerry A.; Kumar, Arun; LaRow, Timothy E.; Murakami, Hiroyuki; Roberts, Malcolm J.; Scoccimarro, Enrico; Vidale, Pier Luigi; Wang, Hui; Wehner, Michael F.; Zhao, Ming</p> <p>2017-09-01</p> <p>Western North Pacific <span class="hlt">tropical</span> cyclone (TC) model tracks are analyzed in two large multimodel ensembles, spanning a large variety of models and multiple future <span class="hlt">climate</span> scenarios. Two methodologies are used to synthesize the properties of TC tracks in this large data set: cluster analysis and mass moment ellipses. First, the models' TC tracks are compared to observed TC tracks' characteristics, and a subset of the models is chosen for analysis, based on the tracks' similarity to observations and sample size. Potential changes in track types in a warming <span class="hlt">climate</span> are identified by comparing the kernel smoothed probability distributions of various track variables in historical and future scenarios using a Kolmogorov-Smirnov significance test. Two track changes are identified. The first is a statistically significant increase in the north-south expansion, which can also be viewed as a poleward shift, as TC tracks are prevented from expanding equatorward due to the weak Coriolis force near the equator. The second change is an eastward shift in the storm tracks that occur near the central Pacific in one of the multimodel ensembles, indicating a possible increase in the occurrence of storms near Hawaii in a warming <span class="hlt">climate</span>. The dependence of the results on which model and future scenario are considered emphasizes the necessity of including multiple models and scenarios when considering future changes in TC characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B21H0164W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B21H0164W"><span><span class="hlt">Climatic</span> controls on the isotopic composition and availability of soil nitrogen in mountainous <span class="hlt">tropical</span> forests</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weintraub, S. R.; Cole, R. J.; Schmitt, C. G.; All, J.</p> <p>2014-12-01</p> <p><span class="hlt">Tropical</span> forests in mountainous regions are often assumed to be nitrogen (N) limited, yet N dynamics across rugged terrain can be complex due to gradients in <span class="hlt">climate</span> and topography. Elucidating patterns of N availability and loss across such gradients is necessary to predict and manage <span class="hlt">tropical</span> forest response to environmental changes such as increasing N deposition and rising temperatures. However, such data is currently lacking, particularly in remote locations that are of high conservation value. To address this gap, a research expedition organized by the American Climber Science Program recently made a coast-to-coast journey across a remote region of Costa Rica, travelling over the Cordillera Talamanca and through La Amistad International Park. Numerous biological, chemical and hydrologic measurements were made en-route across montane to premontane wet <span class="hlt">tropical</span> forests, spanning nearly 2,000 m in elevation and 200 km. Surface soil samples collected at regular intervals along this transect illuminate environmental drivers of N dynamics across the region. The dataset reveals strong links between soil natural abundance N isotopic composition (δ15N) and elevation and temperature parameters, and weaker links to precipitation and topography. This is in general agreement with global scale observations, but divergence from some previously published works is apparent and will be discussed. δ15N mass balance models suggest that N isotope patterns reflect differences in forms of N loss and the relative importance of fractionating and non-fractionating pathways. When combined with data on several other edaphic properties, especially C:N stoichiometry, the results points toward notable variation in soil N availability and N constraints across the transect. This study illustrates large, but predictable, variation in key N cycle traits across the premontane to montane wet <span class="hlt">tropical</span> forest transition. These findings have management-relevant implications for <span class="hlt">tropical</span> regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC51A0953M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC51A0953M"><span>Implications of global warming for regional <span class="hlt">climate</span> and water resources of <span class="hlt">tropical</span> islands: Case studies over Sri Lanka and Puerto Rico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mawalagedara, R.; Kumar, D.; Oglesby, R. J.; Ganguly, A. R.</p> <p>2013-12-01</p> <p>The IPCC AR4 identifies small islands as particularly vulnerable to <span class="hlt">climate</span> change. Here we consider the cases of two <span class="hlt">tropical</span> islands: Sri Lanka in the Indian Ocean and Puerto Rico in the Caribbean. The islands share a predominantly <span class="hlt">tropical</span> <span class="hlt">climate</span> with diverse topography and hence significant spatial variability of regional <span class="hlt">climate</span>. Seasonal variability in temperatures is relatively small, but spatial variations can be large owing to topography. Precipitation mechanisms and patterns over the two islands are different however. Sri Lanka receives a majority of the annual rainfall from the summer and winter monsoons, with convective rainfall dominating in the inter-monsoon period. Rainfall generating mechanisms over Puerto Rico can range from orographic lifting, disturbances embedded in Easterly waves and synoptic frontal systems. Here we compare the projected changes in the regional and seasonal means and extremes of temperature and precipitation over the two islands during the middle of this century with the present conditions. Two 5-year regional <span class="hlt">climate</span> model runs for each region, representing the present (2006-2010) and future (2056-2060) conditions, are performed using the Weather Research and Forecasting model with the lateral boundary conditions provided using the output from CCSM4 RCP8.5 greenhouse gas emissions pathway simulation from the CMIP5 ensemble. The consequences of global warming for water resources and the overall economy are examined. While both economies have substantial contributions from tourism, there are major differences: The agricultural sector is much more important over Sri Lanka compared to Puerto Rico, while the latter exhibits no recent growth in population or in urbanization trends unlike the former. Policy implications for water sustainability and security are discussed, which highlight how despite the differences, certain lessons learned may generalize across the two relatively small <span class="hlt">tropical</span> islands, which in turn have diverse</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4382685','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4382685"><span><span class="hlt">Tropical</span> cyclone rainfall area controlled by relative sea surface temperature</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lin, Yanluan; Zhao, Ming; Zhang, Minghua</p> <p>2015-01-01</p> <p><span class="hlt">Tropical</span> cyclone rainfall rates have been projected to increase in a warmer <span class="hlt">climate</span>. The area coverage of <span class="hlt">tropical</span> cyclones influences their impact on human lives, yet little is known about how <span class="hlt">tropical</span> cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that <span class="hlt">tropical</span> cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the <span class="hlt">tropical</span> mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between <span class="hlt">tropical</span> cyclone size and mid-tropospheric relative humidity. Global statistics of <span class="hlt">tropical</span> cyclone rainfall area are not expected to change markedly under a warmer <span class="hlt">climate</span> provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3435174','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3435174"><span><span class="hlt">Climate</span>-driven regime shifts in Arctic marine benthos</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank; Renaud, Paul E.; Rodrigues, João; Lønne, Ole Jørgen; Gulliksen, Bjørn</p> <p>2012-01-01</p> <p><span class="hlt">Climate</span> warming can trigger <span class="hlt">abrupt</span> ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid <span class="hlt">climate</span> warming in the Arctic, few long time series exist that allow addressing these research goals. During a 30-y period (1980–2010) of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an <span class="hlt">abrupt</span> fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The <span class="hlt">abrupt</span>, substantial, and persistent nature of the changes observed is indicative of a <span class="hlt">climate</span>-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years. PMID:22891319</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.3627W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.3627W"><span>Variability of <span class="hlt">tropical</span> cyclone rapid intensification in the North Atlantic and its relationship with <span class="hlt">climate</span> variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Chunzai; Wang, Xidong; Weisberg, Robert H.; Black, Michael L.</p> <p>2017-12-01</p> <p>The paper uses observational data from 1950 to 2014 to investigate rapid intensification (RI) variability of <span class="hlt">tropical</span> cyclones (TCs) in the North Atlantic and its relationships with large-scale <span class="hlt">climate</span> variations. RI is defined as a TC intensity increase of at least 15.4 m/s (30 knots) in 24 h. The seasonal RI distribution follows the seasonal TC distribution, with the highest number in September. Although an RI event can occur anywhere over the <span class="hlt">tropical</span> North Atlantic (TNA), there are three regions of maximum RI occurrence: (1) the western TNA of 12°N-18°N and 60°W-45°W, (2) the Gulf of Mexico and the western Caribbean Sea, and (3) the open ocean southeast and east of Florida. RI events also show a minimum value in the eastern Caribbean Sea north of South America—a place called a hurricane graveyard due to atmospheric divergence and subsidence. On longer time scales, RI displays both interannual and multidecadal variability, but RI does not show a long-term trend due to global warming. The top three <span class="hlt">climate</span> indices showing high correlations with RI are the June-November ENSO and Atlantic warm pool indices, and the January-March North Atlantic oscillation index. It is found that variabilities of vertical wind shear and TC heat potential are important for TC RI in the hurricane main development region, whereas relative humidity at 500 hPa is the main factor responsible for TC RI in the eastern TNA. However, the large-scale oceanic and atmospheric variables analyzed in this study do not show an important role in TC RI in the Gulf of Mexico and the open ocean southeast and east of Florida. This suggests that other factors such as small-scale changes of oceanic and atmospheric variables or TC internal processes may be responsible for TC RI in these two regions. Additionally, the analyses indicate that large-scale atmospheric and oceanic variables are not critical to TC genesis and formation; however, once a <span class="hlt">tropical</span> depression forms, large-scale <span class="hlt">climate</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP21C1347P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP21C1347P"><span>Mid- to Late Holocene <span class="hlt">Climate</span> Shift in the Southern Gulf of California and <span class="hlt">Tropical</span> Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perez-Cruz, L. L.; Fucugauchi, J. U.; Velasco, V.; Rodriguez, A.; Choumiline, K.</p> <p>2014-12-01</p> <p>A multiproxy record has been acquired from a gravity core (DIPAL-I K47) taken in La Paz Basin, an area which is situated in the southwestern sector of the Gulf of California at the junction to the <span class="hlt">Tropical</span> Pacific Ocean. The high-resolution data sets, from XRF, TOC, magnetic susceptibility and hysteresis measurements, were used to track <span class="hlt">climatic</span> changes in the <span class="hlt">tropical</span> <span class="hlt">climate</span> system at sub-centennial time scales over the past 7.3 cal kyr BP. The paleoprecipitation record shows variation trends, with a shift during the mid- to late Holocene, characterized by changes from high to low humidity. Pluvial, biogenic and eolian input, marked by variations in Ti, Si, Fe, K, Ca, Zr/Ti, Ca/Ti and magnetic susceptibility, shows trend changes between 7-5 cal kyr, 5-4.5 cal kyr, 4.5-3.5 cal kyr and 2.15-1.4 kyr. Drought events are recognized from 3.7 to 3.4, 2.8 to 1.8 cal kyr BP, and between 1.4 and 1.2 cal kyr BP. The southern Gulf is well suited for documenting the <span class="hlt">climatic</span> and precipitation changes in the <span class="hlt">tropical</span> Pacific Ocean associated with ITCZ latitudinal migration, PDO, ENSO events and the North American monsoon. Analysis of sourcing, transport and deposition of sediments is used for reconstructing the changing ocean-atmosphere circulation patterns, particularly sensitive to paleoprecipitation. The Bay receives sediments mainly from the surrounding volcanic ranges of the peninsular Baja California. There are no rivers in the peninsula and sediments are related to pluvial input trough ephemeral creeks along the steep cliff ranges and narrow shelf. Biogenic sediments are associated with productivity and oceanographic conditions through upwellings and mesoscale gyres. Eolian sediments are transported into the basin from the peninsula and continent, including transport of fine dust from the northern desert of Sonora-Mojave and arid terrains in the peninsula. It is important to highlight that a common 1800 yr solar variation spectral periodicity has been captured</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999Natur.398..611P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999Natur.398..611P"><span>Biological response to <span class="hlt">climate</span> change on a <span class="hlt">tropical</span> mountain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pounds, J. Alan; Fogden, Michael P. L.; Campbell, John H.</p> <p>1999-04-01</p> <p>Recent warming has caused changes in species distribution and abundance, but the extent of the effects is unclear. Here we investigate whether such changes in highland forests at Monteverde, Costa Rica, are related to the increase in air temperatures that followed a step-like warming of <span class="hlt">tropical</span> oceans in 1976 (refs4, 5). Twenty of 50 species of anurans (frogs and toads) in a 30-km2 study area, including the locally endemic golden toad (Bufo periglenes), disappeared following synchronous population crashes in 1987 (refs 6-8). Our results indicate that these crashes probably belong to a constellation of demographic changes that have altered communities of birds, reptiles and amphibians in the area and are linked to recent warming. The changes are all associated with patterns of dry-season mist frequency, which is negatively correlated with sea surface temperatures in the equatorial Pacific and has declined dramatically since the mid-1970s. The biological and <span class="hlt">climatic</span> patterns suggest that atmospheric warming has raised the average altitude at the base of the orographic cloud bank, as predicted by the lifting-cloud-base hypothesis,.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoRL..3923706N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoRL..3923706N"><span>Multidecadal <span class="hlt">climate</span> variability in Brazil's Nordeste during the last 3000 years based on speleothem isotope records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Novello, Valdir F.; Cruz, Francisco W.; Karmann, Ivo; Burns, Stephen J.; Stríkis, Nicolás M.; Vuille, Mathias; Cheng, Hai; Lawrence Edwards, R.; Santos, Roberto V.; Frigo, Everton; Barreto, Eline A. S.</p> <p>2012-12-01</p> <p>We present the first high resolution, approximately ∼4 years sample spacing, precipitation record from northeastern Brazil (hereafter referred to as ‘Nordeste’) covering the last ∼3000 yrs from 230Th-dated stalagmites oxygen isotope records. Our record shows <span class="hlt">abrupt</span> fluctuations in rainfall tied to variations in the intensity of the South American summer monsoon (SASM), including the periods corresponding to the Little Ice Age (LIA), the Medieval <span class="hlt">Climate</span> Anomaly (MCA) and an event around 2800 yr B.P. Unlike other monsoon records in southern <span class="hlt">tropical</span> South America, dry conditions prevailed during the LIA in the Nordeste. Our record suggests that the region is currently undergoing drought conditions that are unprecedented over the past 3 millennia, rivaled only by the LIA period. Using spectral, wavelet and cross-wavelet analyses we show that changes in SASM activity in the region are mainly associated with variations of the Atlantic Multidecadal Oscillation (AMO) and to a lesser degree caused by fluctuations in <span class="hlt">tropical</span> Pacific SST. Our record also shows a distinct periodicity around 210 years, which has been linked to solar variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP53D..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP53D..06P"><span>Subtropical <span class="hlt">Climate</span> Variability since the Last Glacial Maximum from Speleothem Precipitation Reconstructions in Florida</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polk, J.; van Beynen, P.; DeLong, K. L.; Asmerom, Y.; Polyak, V. J.</p> <p>2017-12-01</p> <p>Teleconnections between the <span class="hlt">tropical</span>-subtropical regions of the Americas since the Last Glacial Maximum (LGM), particularly the Mid- to Late-Holocene, and high-resolution proxy records refining <span class="hlt">climate</span> variability over this period continue to receive increasing attention. Here, we present a high-resolution, precisely dated speleothem record spanning multiple periods of time since the LGM ( 30 ka) for the Florida peninsula. The data indicate that the amount effect plays a significant role in determining the isotopic signal of the speleothem calcite. Collectively, the records indicate distinct differences in <span class="hlt">climate</span> in the region between the LGM, Mid-Holocene, and Late Holocene, including a progressive shift in ocean composition and precipitation isotopic values through the period, suggesting Florida's sensitivity to regional and global <span class="hlt">climatic</span> shifts. Comparisons between speleothem δ18O values and Gulf of Mexico marine records reveal a strong connection between the Gulf region and the terrestrial subtropical <span class="hlt">climate</span> in the Late Holocene, while the North Atlantic's influence is clear in the earlier portions of the record. Warmer sea surface temperatures correspond to enhanced evaporation, leading to more intense atmospheric convection in Florida, and thereby modulating the isotopic composition of rainfall above the cave. These regional signals in <span class="hlt">climate</span> extend from the subtropics to the <span class="hlt">tropics</span>, with a clear covariance between the speleothem signal and other proxy records from around the region, as well as global agreement during the LGM period with other records. These latter connections appear to be driven by changes in the mean position of the Intertropical Convergence Zone and time series analysis of the δ18O values reveals significant multidecadal periodicities in the record, which are evidenced by agreement with the AMV and other multidecadal influences (NAO and PDO) likely having varying influence throughout the period of record. The <span class="hlt">climate</span> variability</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26347558','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26347558"><span><span class="hlt">Tropical</span> flatback turtle (Natator depressus) embryos are resilient to the heat of <span class="hlt">climate</span> change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Howard, Robert; Bell, Ian; Pike, David A</p> <p>2015-10-01</p> <p><span class="hlt">Climate</span> change is threatening reproduction of many ectotherms by increasing nest temperatures, potentially making it more difficult for females to locate nest sites that provide suitable incubation regimes during embryonic development. Elevated nest temperatures could increase the incidence of embryonic mortality and/or maladaptive phenotypes. We investigated whether elevated nest temperatures reduce hatching success in <span class="hlt">tropical</span> flatback turtles (Natator depressus) nesting in the Gulf of Carpentaria, Australia. Egg incubation treatments began at 29.5°C and progressively increased in temperature throughout incubation, up to maxima of 31, 32, 33, 34 and 35°C. Elevated nest temperatures did not reduce hatching success or hatchling body size relative to control temperatures (29.5°C), but did speed up embryonic development. A combination of sudden exposure to high temperatures during the first 2 weeks of incubation (>36°C for 48 h) and prolonged warming throughout incubation (from 29.5-35°C) did not reduce hatching success. We also recorded an unusually high pivotal sex-determining temperature in this flatback turtle population relative to other sea turtle populations: an equal ratio of male and female hatchlings is produced at ∼30.4°C. This adaptation may allow some flatback turtle populations to continue producing large numbers of hatchlings of both sexes under the most extreme <span class="hlt">climate</span> change scenarios. Some <span class="hlt">tropical</span> populations of nesting flatbacks may possess important adaptations to high-temperature incubation environments, which are not found in more southerly temperate populations. © 2015. Published by The Company of Biologists Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70155916','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70155916"><span>Urgent need for warming experiments in <span class="hlt">tropical</span> forests</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Calaveri, Molly A.; Reed, Sasha C.; Smith, W. Kolby; Wood, Tana E.</p> <p>2015-01-01</p> <p>Although <span class="hlt">tropical</span> forests account for only a fraction of the planet's terrestrial surface, they exchange more carbon dioxide with the atmosphere than any other biome on Earth, and thus play a disproportionate role in the global <span class="hlt">climate</span>. In the next 20 years, the <span class="hlt">tropics</span> will experience unprecedented warming, yet there is exceedingly high uncertainty about their potential responses to this imminent <span class="hlt">climatic</span> change. Here, we prioritize research approaches given both funding and logistical constraints in order to resolve major uncertainties about how <span class="hlt">tropical</span> forests function and also to improve predictive capacity of earth system models. We investigate overall model uncertainty of <span class="hlt">tropical</span> latitudes and explore the scientific benefits and inevitable trade-offs inherent in large-scale manipulative field experiments. With a Coupled Model Intercomparison Project Phase 5 analysis, we found that model variability in projected net ecosystem production was nearly 3 times greater in the <span class="hlt">tropics</span> than for any other latitude. Through a review of the most current literature, we concluded that manipulative warming experiments are vital to accurately predict future <span class="hlt">tropical</span> forest carbon balance, and we further recommend the establishment of a network of comparable studies spanning gradients of precipitation, edaphic qualities, plant types, and/or land use change. We provide arguments for long-term, single-factor warming experiments that incorporate warming of the most biogeochemically active ecosystem components (i.e. leaves, roots, soil microbes). Hypothesis testing of underlying mechanisms should be a priority, along with improving model parameterization and constraints. No single <span class="hlt">tropical</span> forest is representative of all <span class="hlt">tropical</span> forests; therefore logistical feasibility should be the most important consideration for locating large-scale manipulative experiments. Above all, we advocate for multi-faceted research programs, and we offer arguments for what we consider the most</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25641092','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25641092"><span>Urgent need for warming experiments in <span class="hlt">tropical</span> forests.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cavaleri, Molly A; Reed, Sasha C; Smith, W Kolby; Wood, Tana E</p> <p>2015-06-01</p> <p>Although <span class="hlt">tropical</span> forests account for only a fraction of the planet's terrestrial surface, they exchange more carbon dioxide with the atmosphere than any other biome on Earth, and thus play a disproportionate role in the global <span class="hlt">climate</span>. In the next 20 years, the <span class="hlt">tropics</span> will experience unprecedented warming, yet there is exceedingly high uncertainty about their potential responses to this imminent <span class="hlt">climatic</span> change. Here, we prioritize research approaches given both funding and logistical constraints in order to resolve major uncertainties about how <span class="hlt">tropical</span> forests function and also to improve predictive capacity of earth system models. We investigate overall model uncertainty of <span class="hlt">tropical</span> latitudes and explore the scientific benefits and inevitable trade-offs inherent in large-scale manipulative field experiments. With a Coupled Model Intercomparison Project Phase 5 analysis, we found that model variability in projected net ecosystem production was nearly 3 times greater in the <span class="hlt">tropics</span> than for any other latitude. Through a review of the most current literature, we concluded that manipulative warming experiments are vital to accurately predict future <span class="hlt">tropical</span> forest carbon balance, and we further recommend the establishment of a network of comparable studies spanning gradients of precipitation, edaphic qualities, plant types, and/or land use change. We provide arguments for long-term, single-factor warming experiments that incorporate warming of the most biogeochemically active ecosystem components (i.e. leaves, roots, soil microbes). Hypothesis testing of underlying mechanisms should be a priority, along with improving model parameterization and constraints. No single <span class="hlt">tropical</span> forest is representative of all <span class="hlt">tropical</span> forests; therefore logistical feasibility should be the most important consideration for locating large-scale manipulative experiments. Above all, we advocate for multi-faceted research programs, and we offer arguments for what we consider the most</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMGC12A..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMGC12A..04A"><span>Changes of cloudiness over <span class="hlt">tropical</span> land during the past few decades and its link to global <span class="hlt">climate</span> change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arias, P.; Fu, R.; Li, W.</p> <p>2007-12-01</p> <p><span class="hlt">Tropical</span> forests play a key role in determining the global carbon-<span class="hlt">climate</span> feedback in the 21st century. Changes in rainforest growth and mortality rates, especially in the deep and least perturbed forest areas, have been consistently observed across global <span class="hlt">tropics</span> in recent years. Understanding the underlying causes of these changes, especially their links to the global <span class="hlt">climate</span> change, is especially important in determining the future of the <span class="hlt">tropical</span> rainforests in the 21st century. Previous studies have mostly focus on the potential influences from elevated atmospheric CO2 and increasing surface temperature. Because the rainforests in wet <span class="hlt">tropical</span> region is often light limited, we explore whether cloudiness have changed, if so, whether it is consistent with that expected from changes in forest growth rate. We will report our observational analysis examining the trends in annual average shortwave (SW) downwelling radiation, total cloud cover, and cumulus cover over the <span class="hlt">tropical</span> land regions and to link them with trends in convective available potencial energy (CAPE). ISCCP data and radiosonde records available from the Department of Atmospheric Sciences of the University of Wyoming (http://www.weather.uwyo.edu/upperair/sounding.html) are used to study the trends. The period for the trend analysis is 1984-2004 for the ISCCP data and 1980-2006 for the radiosondes. The results for the Amazon rainforest region suggest a decreasing trend in total cloud and convective cloud covers, which results in an increase in downwelling SW radiation at the surface. These changes of total and convective clouds are consistent with a trend of decreasing CAPE and an elevated Level of Free Convection (LFC) height, as obtained from the radiosondes. All the above mentioned trends are statistically significant based on the Mann-Kendall test with 95% of confidence. These results consistently suggest the downward surface solar radiation has been increasing since 1984, result from a decrease</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14558897','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14558897"><span>Palaeoclimatic insights into future <span class="hlt">climate</span> challenges.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alley, Richard B</p> <p>2003-09-15</p> <p>Palaeoclimatic data document a sensitive <span class="hlt">climate</span> system subject to large and perhaps difficult-to-predict <span class="hlt">abrupt</span> changes. These data suggest that neither the sensitivity nor the variability of the <span class="hlt">climate</span> are fully captured in some <span class="hlt">climate</span>-change projections, such as the Intergovernmental Panel on <span class="hlt">Climate</span> Change (IPCC) Summary for Policymakers. Because larger, faster and less-expected <span class="hlt">climate</span> changes can cause more problems for economies and ecosystems, the palaeoclimatic data suggest the hypothesis that the future may be more challenging than anticipated in ongoing policy making. Large changes have occurred repeatedly with little net forcing. Increasing carbon dioxide concentration appears to have globalized deglacial warming, with <span class="hlt">climate</span> sensitivity near the upper end of values from general circulation models (GCMs) used to project human-enhanced greenhouse warming; data from the warm Cretaceous period suggest a similarly high <span class="hlt">climate</span> sensitivity to CO(2). <span class="hlt">Abrupt</span> <span class="hlt">climate</span> changes of the most recent glacial-interglacial cycle occurred during warm as well as cold times, linked especially to changing North Atlantic freshwater fluxes. GCMs typically project greenhouse-gas-induced North Atlantic freshening and circulation changes with notable but not extreme consequences; however, such models often underestimate the magnitude, speed or extent of past changes. Targeted research to assess model uncertainties would help to test these hypotheses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24463514','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24463514"><span>A two-fold increase of carbon cycle sensitivity to <span class="hlt">tropical</span> temperature variations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Xuhui; Piao, Shilong; Ciais, Philippe; Friedlingstein, Pierre; Myneni, Ranga B; Cox, Peter; Heimann, Martin; Miller, John; Peng, Shushi; Wang, Tao; Yang, Hui; Chen, Anping</p> <p>2014-02-13</p> <p>Earth system models project that the <span class="hlt">tropical</span> land carbon sink will decrease in size in response to an increase in warming and drought during this century, probably causing a positive <span class="hlt">climate</span> feedback. But available data are too limited at present to test the predicted changes in the <span class="hlt">tropical</span> carbon balance in response to <span class="hlt">climate</span> change. Long-term atmospheric carbon dioxide data provide a global record that integrates the interannual variability of the global carbon balance. Multiple lines of evidence demonstrate that most of this variability originates in the terrestrial biosphere. In particular, the year-to-year variations in the atmospheric carbon dioxide growth rate (CGR) are thought to be the result of fluctuations in the carbon fluxes of <span class="hlt">tropical</span> land areas. Recently, the response of CGR to <span class="hlt">tropical</span> <span class="hlt">climate</span> interannual variability was used to put a constraint on the sensitivity of <span class="hlt">tropical</span> land carbon to <span class="hlt">climate</span> change. Here we use the long-term CGR record from Mauna Loa and the South Pole to show that the sensitivity of CGR to <span class="hlt">tropical</span> temperature interannual variability has increased by a factor of 1.9 ± 0.3 in the past five decades. We find that this sensitivity was greater when <span class="hlt">tropical</span> land regions experienced drier conditions. This suggests that the sensitivity of CGR to interannual temperature variations is regulated by moisture conditions, even though the direct correlation between CGR and <span class="hlt">tropical</span> precipitation is weak. We also find that present terrestrial carbon cycle models do not capture the observed enhancement in CGR sensitivity in the past five decades. More realistic model predictions of future carbon cycle and <span class="hlt">climate</span> feedbacks require a better understanding of the processes driving the response of <span class="hlt">tropical</span> ecosystems to drought and warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5349522','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5349522"><span><span class="hlt">Abrupt</span> response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bastian, Luc; Revel, Marie; Bayon, Germain; Dufour, Aurélie; Vigier, Nathalie</p> <p>2017-01-01</p> <p>Chemical weathering of silicate rocks on continents acts as a major sink for atmospheric carbon dioxide and has played an important role in the evolution of the Earth’s <span class="hlt">climate</span>. However, the magnitude and the nature of the links between weathering and <span class="hlt">climate</span> are still under debate. In particular, the timescale over which chemical weathering may respond to <span class="hlt">climate</span> change is yet to be constrained at the continental scale. Here we reconstruct the relationships between rainfall and chemical weathering in northeast Africa for the last 32,000 years. Using lithium isotopes and other geochemical proxies in the clay-size fraction of a marine sediment core from the Eastern Mediterranean Sea, we show that chemical weathering in the Nile Basin fluctuated in parallel with the monsoon-related <span class="hlt">climatic</span> evolution of northeast Africa. We also evidence strongly reduced mineral alteration during centennial-scale regional drought episodes. Our findings indicate that silicate weathering may respond as quickly as physical erosion to <span class="hlt">abrupt</span> hydroclimate reorganization on continents. Consequently, we anticipate that the forthcoming hydrological disturbances predicted for northeast Africa may have a major impact on chemical weathering patterns and soil resources in this region. PMID:28290474</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28290474','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28290474"><span><span class="hlt">Abrupt</span> response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bastian, Luc; Revel, Marie; Bayon, Germain; Dufour, Aurélie; Vigier, Nathalie</p> <p>2017-03-14</p> <p>Chemical weathering of silicate rocks on continents acts as a major sink for atmospheric carbon dioxide and has played an important role in the evolution of the Earth's <span class="hlt">climate</span>. However, the magnitude and the nature of the links between weathering and <span class="hlt">climate</span> are still under debate. In particular, the timescale over which chemical weathering may respond to <span class="hlt">climate</span> change is yet to be constrained at the continental scale. Here we reconstruct the relationships between rainfall and chemical weathering in northeast Africa for the last 32,000 years. Using lithium isotopes and other geochemical proxies in the clay-size fraction of a marine sediment core from the Eastern Mediterranean Sea, we show that chemical weathering in the Nile Basin fluctuated in parallel with the monsoon-related <span class="hlt">climatic</span> evolution of northeast Africa. We also evidence strongly reduced mineral alteration during centennial-scale regional drought episodes. Our findings indicate that silicate weathering may respond as quickly as physical erosion to <span class="hlt">abrupt</span> hydroclimate reorganization on continents. Consequently, we anticipate that the forthcoming hydrological disturbances predicted for northeast Africa may have a major impact on chemical weathering patterns and soil resources in this region.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8684H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8684H"><span>Ecosystem resilience to <span class="hlt">abrupt</span> late Quaternary change in continental southern Siberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harding, Poppy; Mackay, Anson; Bezrukova, Elena; Shchetnikov, Alexander</p> <p>2017-04-01</p> <p>Quaternary <span class="hlt">climate</span> variability is dominated by long term orbital forcing along with <span class="hlt">abrupt</span> sub-Milankovitch events on the scales of millennia to centuries, driven by internal feedback mechanisms, volcanic forcing and fluctuating solar activity. Although these are well documented in the North Atlantic region, their expression is poorly understood in Siberia, particularly in relation to <span class="hlt">abrupt</span> <span class="hlt">climatic</span> events. Siberia has the world's highest level of continentality offering an opportunity to study changes remote from oceanic influences and improving understanding of interactions between the Siberian High and other atmospheric systems including the Aleutian Low, Arctic oscillation and Icelandic Low1 and ENSO2. Understanding of palaeoenvironmental change in Siberia is essential due to the region's high sensitivity to <span class="hlt">climatic</span> change, with warming rates considerably higher than the global average over the past 50 years3, triggering significant environmental changes, including permafrost degradation, shifts in the forest-steppe biome, increases in forest fires and warming of seasonally ice-covered lakes. Additionally, the region provides essential palaeoenvironmental context for early hominins, for example at globally important sites such as Denisova cave4, and megafauna extinctions5. This presentation outlines ongoing work at Lake Baunt, SE Siberia including: key quaternary <span class="hlt">climate</span> forcings, the site and its regional context, the key methods and preliminary results. These include a dated record back to ˜30ka BP (based on multiple 14C dates and Bayesian age modelling), multiproxy indicators of palaeoproductivity (e.g. biogenic silica and diatom analyses) and lake mixing regimes (inferred from diatom analyses). Together these highlight several key Quaternary fluctuations potentially correlated to events recorded in Greenland Ice Cores (GS2, GS2.1, GI1, GS1), and these are considered against key Quaternary records including those from nearby Lake Baikal and Hulu Cave in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890010418','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890010418"><span>TRMM (<span class="hlt">Tropical</span> Rainfall Measuring Mission): A satellite mission to measure <span class="hlt">tropical</span> rainfall</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simpson, Joanne (Editor)</p> <p>1988-01-01</p> <p>The <span class="hlt">Tropical</span> Rainfall Measuring Mission (TRMM) is presented. TRMM is a satellite program being studied jointly by the United States and Japan which would carry out the systematic study of <span class="hlt">tropical</span> rainfall required for major strides in weather and <span class="hlt">climate</span> research. The scientific justification for TRMM is discussed. The implementation process for the scientific community, NASA management, and the other decision-makers and advisory personnel who are expected to evaluate the priority of the project is outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1249953-positive-low-cloud-dust-feedbacks-amplify-tropical-north-atlantic-multidecadal-oscillation','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1249953-positive-low-cloud-dust-feedbacks-amplify-tropical-north-atlantic-multidecadal-oscillation"><span>Positive low cloud and dust feedbacks amplify <span class="hlt">tropical</span> North Atlantic Multidecadal Oscillation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Yuan, Tianle; Oreopoulos, Lazaros; Zelinka, Mark; ...</p> <p>2016-02-04</p> <p>The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of <span class="hlt">climatic</span> impacts. While the <span class="hlt">tropical</span> arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many <span class="hlt">climate</span> model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the <span class="hlt">tropical</span> arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropicalmore » trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the <span class="hlt">tropical</span> Atlantic, which warms the <span class="hlt">tropical</span> North Atlantic SST. Together they contribute to the appearance of the <span class="hlt">tropical</span> arm of AMO. Most current <span class="hlt">climate</span> models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many <span class="hlt">climatic</span> studies related to the AMO.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211165L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211165L"><span>Sahara and Sahel vulnerability to <span class="hlt">climate</span> changes, lessons from the past</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lezine, Anne-Marie; Hély, Christelle; Grenier, Christophe; Braconnot, Pascale</p> <p>2010-05-01</p> <p>Since the Sahelian drought in the 1970s, <span class="hlt">climate</span> variability in north <span class="hlt">tropical</span> Africa has been the subject of intensive research focusing on the functioning of the Atlantic monsoon system as well as on past variations in rainfall from historical and natural archives. An "<span class="hlt">abrupt</span>" <span class="hlt">climate</span> change has been recorded off the Mauritanian coast at the end of the African Humid Period (AHP) 5500 years ago illustrating the onset of the modern <span class="hlt">climate</span> regime [deMenocal et al., 2000]. At lake Yoa in NE Chad, [Kroepelin et al., 2008] report a "gradual" environmental change. Was this change <span class="hlt">abrupt</span> or gradual, and amplified or not through vegetation change and feedbacks to the atmosphere is still the subject of debate. Here, we compile paleohydrological and palynological data between 10 and 28°N in the Sahara and Sahel with the purpose of understanding the response of the hydrological system and the vegetation cover to rainfall fluctuations from the onset of the AHP. Our data set is extracted from published studies. It is composed of 1651 dated samples from about 420 localities in the present day Sahara and Sahel. The occurrence of high and intermediate lake levels, fluvial terraces and wetlands as well as of dune edification are analysed with a 1000 yr period from 16 000 yrs BP to present. Clear trends are observed in the evolution of paleohydrological indicators versus time and latitude showing the progression of the centre of the distribution of humidity from south to north during the humid period and to the south after the AHP. The humidity maximum is observed with some temporal delay as compared to the June solar radiation maximum at 30°N. The reasons are investigated along the line of pure <span class="hlt">climate</span> based processes and/or hydrological impacts. Further, the overall coherence among these signals is examined. Using <span class="hlt">climate</span> simulations for different key periods in the Holocene, we investigate the relative impact of the insolation forcing, of the remnant ice sheet in the early</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B51I0122M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B51I0122M"><span>Remote Detection and Modeling of <span class="hlt">Abrupt</span> and Gradual Tree Mortality in the Southwestern USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muss, J. D.; Xu, C.; McDowell, N. G.</p> <p>2014-12-01</p> <p>Current <span class="hlt">climate</span> models predict a warming and drying trend that has a high probability of increasing the frequency and spatial extent of tree mortality events. Field surveys can be used to identify, date, and attribute a cause of mortality to specific trees, but monetary and time constraints prevent broad-scale surveys, which are necessary to establish regional or global trends in tree mortality. This is significant because widespread forest mortality will likely lead to radical changes in evapotranspiration and surface albedo, which could compound <span class="hlt">climate</span> change. While understanding the causes and mechanisms of tree mortality events is crucial, it is equally important to be able to detect and monitor mortality and subsequent changes to the ecosystem at broad spatial- and temporal-scales. Over the past five years our ability to remotely detect <span class="hlt">abrupt</span> forest mortality events has improved greatly, but gradual events—such as those caused by drought or certain types of insects—are still difficult to identify. Moreover, it is virtually impossible to quantify the amount of mortality that has occurred within a mixed pixel. We have developed a system that fuses <span class="hlt">climate</span> and satellite-derived spectral data to identify both the date and the agent of forest mortality events. This system has been used with Landsat time series data to detect both <span class="hlt">abrupt</span> and general trends in tree loss that have occurred during the past quarter-century in northern New Mexico. It has also been used with MODIS data to identify pixels with a high likelihood of drought-caused tree mortality in the Southwestern US. These candidate pixels were then fed to ED-FRT, a coupled forest dynamics-radiative transfer model, to generate estimates of drought-induced. We demonstrate a multi-scale approach that can produce results that will be instrumental in advancing our understanding of tree mortality-<span class="hlt">climate</span> feedbacks, and improve our ability to predict what forests could look like in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2362W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2362W"><span>Potential regulation on the <span class="hlt">climatic</span> effect of Tibetan Plateau heating by <span class="hlt">tropical</span> air-sea coupling in regional models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Ziqian; Duan, Anmin; Yang, Song</p> <p>2018-05-01</p> <p>Based on the conventional weather research and forecasting (WRF) model and the air-sea coupled mode WRF-OMLM, we investigate the potential regulation on the <span class="hlt">climatic</span> effect of Tibetan Plateau (TP) heating by the air-sea coupling over the <span class="hlt">tropical</span> Indian Ocean and western Pacific. Results indicate that the TP heating significantly enhances the southwesterly monsoon circulation over the northern Indian Ocean and the South Asia subcontinent. The intensified southwesterly wind cools the sea surface mainly through the wind-evaporation-SST (sea surface temperature) feedback. Cold SST anomaly then weakens monsoon convective activity, especially that over the Bay of Bengal, and less water vapor is thus transported into the TP along its southern slope from the <span class="hlt">tropical</span> oceans. As a result, summer precipitation decreases over the TP, which further weakens the TP local heat source. Finally, the changed TP heating continues to influence the summer monsoon precipitation and atmospheric circulation. To a certain extent, the air-sea coupling over the adjacent oceans may weaken the effect of TP heating on the mean <span class="hlt">climate</span> in summer. It is also implied that considerations of air-sea interaction are necessary in future simulation studies of the TP heating effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21247001','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21247001"><span>The effect of <span class="hlt">climate</span> and soil conditions on tree species turnover in a <span class="hlt">Tropical</span> Montane Cloud Forest in Costa Rica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Häger, Achim</p> <p>2010-12-01</p> <p>On a global level, <span class="hlt">Tropical</span> Montane Cloud Forests constitute important centers of vascular plant diversity. Tree species turnover along environmental gradients plays an important role in larger scale diversity patterns in <span class="hlt">tropical</span> mountains. This study aims to estimate the magnitude of beta diversity across the Tilardn mountain range in North-Western Costa Rica, and to elucidate the impact of <span class="hlt">climate</span> and soil conditions on tree species turnover at a local scale. Seven <span class="hlt">climate</span> stations measuring rainfall, horizontal precipitation (clouds and wind-driven rain) and temperatures were installed along a 2.5km transect ranging from 1200 m.a.s.l. on the Atlantic to 1200 m.a.s.l. on the Pacific slope. The ridge top <span class="hlt">climate</span> station was located at 1500 m.a.s.l. <span class="hlt">Climate</span> data were recorded from March through December 2003. Additionally, seven 0.05 ha plots were established. On all plots soil moisture was monitored for one year, furthermore soil type and soil chemistry were assessed. Woody plants with a diameter at breast height (dbh) > or = 5 cm were identified to species. Species' distributions were explored by feeding pairwise Serensen measures between plots into a Principal Component Analysis. Relationships between floristic similarity and environmental variables were analyzed using Mantel tests. Pronounced gradients in horizontal precipitation, temperatures and soil conditions were found across the transect. In total, 483 woody plants were identified, belonging to 132 species. Environmental gradients were paralleled by tree species turnover; the plots could be divided in three distinctive floristic units which reflected different topographic positions on the transect (lower slopes, mid slopes and ridge). Most notably there was a complete species turnover between the ridge and the lower Pacific slope. Floristic similarity was negatively correlated with differences in elevation, horizontal precipitation, temperatures and soil conditions between plots. It is suggested that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.U24B..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.U24B..01L"><span>Assessing Extratropical Influence on <span class="hlt">Tropical</span> Climatology and Variability with Regional Coupled Data Assimilation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, F.; Liu, Z.; Liu, Y.; Zhang, S.; Jacob, R. L.</p> <p>2017-12-01</p> <p>The Regional Coupled Data Assimilation (RCDA) method is introduced as a tool to study coupled <span class="hlt">climate</span> dynamics and teleconnections. The RCDA method is built on an ensemble-based coupled data assimilation (CDA) system in a coupled general circulation model (CGCM). The RCDA method limits the data assimilation to the desired model components (e.g. atmosphere) and regions (e.g. the extratropics), and studies the ensemble-mean model response (e.g. <span class="hlt">tropical</span> response to "observed" extratropical atmospheric variability). When applied to the extratropical influence on <span class="hlt">tropical</span> <span class="hlt">climate</span>, the RCDA method has shown some unique advantages, namely the combination of a fully coupled model, real-world observations and an ensemble approach. <span class="hlt">Tropical</span> variability (e.g. El Niño-Southern Oscillation or ENSO) and climatology (e.g. asymmetric Inter-<span class="hlt">Tropical</span> Convergence Zone or ITCZ) were initially thought to be determined mostly by local forcing and ocean-atmosphere interaction in the <span class="hlt">tropics</span>. Since late 20th century, numerous studies have showed that extratropical forcing could affect, or even largely determine some aspects of the <span class="hlt">tropical</span> <span class="hlt">climate</span>. Due to the coupled nature of the <span class="hlt">climate</span> system, however, the challenge of determining and further quantifying the causality of extratropical forcing on the <span class="hlt">tropical</span> <span class="hlt">climate</span> remains. Using the RCDA method, we have demonstrated significant control of extratropical atmospheric forcing on ENSO variability in a CGCM, both with model-generated and real-world observation datasets. The RCDA method has also shown robust extratropical impact on the <span class="hlt">tropical</span> double-ITCZ bias in a CGCM. The RCDA method has provided the first systematic and quantitative assessment of extratropical influence on <span class="hlt">tropical</span> climatology and variability by incorporating real world observations in a CGCM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP11D1051S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP11D1051S"><span>Compound-Specific Hydrogen Isotopic Records of Holocene <span class="hlt">Climate</span> Dynamics in the Northeastern U.S.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stefanescu, I.; Shuman, B. N.</p> <p>2017-12-01</p> <p>The northeastern United States, located between the location of Laurentide ice sheet and the dynamic North Atlantic Ocean, is an ideal region for studying paleoclimate changes on centennial to multi-millennial time scales because the region experienced multiple <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes and variations over the past 14 ka. Over the Holocene, the region's long-term <span class="hlt">climate</span> trend was influenced by isolation changes, the retreat of the Laurentide Ice Sheet (LIS), changes in atmospheric composition and changes in the North Atlantic Meridional Overturning Circulation (AMOC). Hydrological and pollen records show that multiple <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes punctuate the long-term trends, even after the widely recognized events associated with the LIS and AMOC, but the mechanisms behind the <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes observed are not well understood. To understand the mechanisms behind <span class="hlt">abrupt</span> <span class="hlt">climate</span> shifts, their impact on hydrology, ecosystems, regional and local <span class="hlt">climates</span>, additional insights are needed. Compound-specific hydrogen isotope (D/H) ratios derived from terrestrial and aquatic leaf waxes and preserved in lake sediments, have been shown to record D/H ratios of environmental water and we use such data to further investigate the regional <span class="hlt">climate</span> history. Here we present hydrogen isotope records of precipitation using compound specific hydrogen isotope of leaf wax n-alkanes derived from aquatic and terrestrial leaf waxes from three lakes: Twin Ponds, Vermont; Blanding Pond, Pennsylvania; and Crooked Pond, Massachusetts. We use the results to evaluate common <span class="hlt">climate</span> trends across the region from an isotopic perspective and to assess changes in the spatial isotopic gradients across the northeastern US during the Holocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912409F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912409F"><span>Transitions between multiple equilibria of paleo <span class="hlt">climate</span>: a glimpse in to the dynamics of <span class="hlt">abrupt</span> <span class="hlt">climate</span> change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferreira, David; Marshall, John; Ito, Takamitsu; McGee, David; Moreno-Chamarro, Eduardo</p> <p>2017-04-01</p> <p>The dynamics regulating large <span class="hlt">climatic</span> transitions such as glacial-interglacial cycles or DO events remains a puzzle. Forcings behind these transitions are not robustly identified and potential candidates (e.g. Milankovitch cycles, freshwater perturbations) often appear too weak to explain such dramatic transitions. A potential solution to this long-standing puzzle is that Earth's <span class="hlt">climate</span> is endowed with multiple equilibrium states of global extent. Such states are commonly found in low-order or conceptual <span class="hlt">climate</span> models, but it is unclear whether a system as complex as Earth's <span class="hlt">climate</span> can sustain multiple equilibrium states. Here we report that multiple equilibrium states of the <span class="hlt">climate</span> system are also possible in a complex, fully dynamical coupled ocean-atmosphere-sea ice GCM with idealized Earth-like geometry, resolved weather systems and a hydrological cycle. In our model, two equilibrium states coexist for the same parameters and external forcings: a Warm <span class="hlt">climate</span> with a small Northern hemisphere sea ice cap and a large southern one and a Cold <span class="hlt">climate</span> with large ice caps at both poles. The dynamical states of the Warm and Cold solutions exhibit striking similarities with our present-day <span class="hlt">climate</span> and the <span class="hlt">climate</span> of the Last Glacial Maximum, respectively. A carbon cycle model driven by the two dynamical states produces an atmospheric pCO2 draw-down of about 110 pm between the Warm and Cold states, close to Glacial-Interglacial differences found in ice cores. Mechanism controlling the existence of the multiple states and changes in the atmospheric CO2 will be briefly presented. Finally we willdescribe transition experiments from the Cold to the Warm state, focusing on the lead-lags in the system, notably between the Northern and Southern Hemispheres <span class="hlt">climates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1407302-hurricanes-climate-clivar-working-group-hurricanes','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1407302-hurricanes-climate-clivar-working-group-hurricanes"><span>Hurricanes and <span class="hlt">Climate</span>: The U.S. CLIVAR Working Group on Hurricanes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Walsh, Kevin J. E.; Camargo, Suzana J.; Vecchi, Gabriel A.; ...</p> <p>2015-06-01</p> <p>While a quantitative <span class="hlt">climate</span> theory of <span class="hlt">tropical</span> cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate <span class="hlt">tropical</span> cyclone climatologies and to understand the relationship between <span class="hlt">climate</span> and <span class="hlt">tropical</span> cyclone formation. <span class="hlt">Climate</span> models are now able to simulate a realistic rate of global <span class="hlt">tropical</span> cyclone formation, although simulation of the Atlantic <span class="hlt">tropical</span> cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. This article summarizes published research from the idealized experiments of the Hurricane Working Group of U.S. <span class="hlt">Climate</span> and Ocean: Variability, Predictability and Change (CLIVAR). This work, combined with results frommore » other model simulations, has strengthened relationships between <span class="hlt">tropical</span> cyclone formation rates and <span class="hlt">climate</span> variables such as midtropospheric vertical velocity, with decreased climatological vertical velocities leading to decreased <span class="hlt">tropical</span> cyclone formation. Systematic differences are shown between experiments in which only sea surface temperature is increased compared with experiments where only atmospheric carbon dioxide is increased. Experiments where only carbon dioxide is increased are more likely to demonstrate a decrease in <span class="hlt">tropical</span> cyclone numbers, similar to the decreases simulated by many <span class="hlt">climate</span> models for a future, warmer <span class="hlt">climate</span>. Experiments where the two effects are combined also show decreases in numbers, but these tend to be less for models that demonstrate a strong <span class="hlt">tropical</span> cyclone response to increased sea surface temperatures. Lastly, further experiments are proposed that may improve our understanding of the relationship between <span class="hlt">climate</span> and <span class="hlt">tropical</span> cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1407302','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1407302"><span>Hurricanes and <span class="hlt">Climate</span>: The U.S. CLIVAR Working Group on Hurricanes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Walsh, Kevin J. E.; Camargo, Suzana J.; Vecchi, Gabriel A.</p> <p></p> <p>While a quantitative <span class="hlt">climate</span> theory of <span class="hlt">tropical</span> cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate <span class="hlt">tropical</span> cyclone climatologies and to understand the relationship between <span class="hlt">climate</span> and <span class="hlt">tropical</span> cyclone formation. <span class="hlt">Climate</span> models are now able to simulate a realistic rate of global <span class="hlt">tropical</span> cyclone formation, although simulation of the Atlantic <span class="hlt">tropical</span> cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. This article summarizes published research from the idealized experiments of the Hurricane Working Group of U.S. <span class="hlt">Climate</span> and Ocean: Variability, Predictability and Change (CLIVAR). This work, combined with results frommore » other model simulations, has strengthened relationships between <span class="hlt">tropical</span> cyclone formation rates and <span class="hlt">climate</span> variables such as midtropospheric vertical velocity, with decreased climatological vertical velocities leading to decreased <span class="hlt">tropical</span> cyclone formation. Systematic differences are shown between experiments in which only sea surface temperature is increased compared with experiments where only atmospheric carbon dioxide is increased. Experiments where only carbon dioxide is increased are more likely to demonstrate a decrease in <span class="hlt">tropical</span> cyclone numbers, similar to the decreases simulated by many <span class="hlt">climate</span> models for a future, warmer <span class="hlt">climate</span>. Experiments where the two effects are combined also show decreases in numbers, but these tend to be less for models that demonstrate a strong <span class="hlt">tropical</span> cyclone response to increased sea surface temperatures. Lastly, further experiments are proposed that may improve our understanding of the relationship between <span class="hlt">climate</span> and <span class="hlt">tropical</span> cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC14B..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC14B..03P"><span>Heterogeneous Sensitivity of <span class="hlt">Tropical</span> Precipitation Extremes during Growth and Mature Phases of Atmospheric Warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parhi, P.; Giannini, A.; Lall, U.; Gentine, P.</p> <p>2016-12-01</p> <p>Assessing and managing risks posed by <span class="hlt">climate</span> variability and change is challenging in the <span class="hlt">tropics</span>, from both a socio-economic and a scientific perspective. Most of the vulnerable countries with a limited <span class="hlt">climate</span> adaptation capability are in the <span class="hlt">tropics</span>. However, <span class="hlt">climate</span> projections, particularly of extreme precipitation, are highly uncertain there. The CMIP5 (Coupled Model Inter- comparison Project - Phase 5) inter-model range of extreme precipitation sensitivity to the global temperature under <span class="hlt">climate</span> change is much larger in the <span class="hlt">tropics</span> as compared to the extra-<span class="hlt">tropics</span>. It ranges from nearly 0% to greater than 30% across models (O'Gorman 2012). The uncertainty is also large in historical gauge or satellite based observational records. These large uncertainties in the sensitivity of <span class="hlt">tropical</span> precipitation extremes highlight the need to better understand how <span class="hlt">tropical</span> precipitation extremes respond to warming. We hypothesize that one of the factors explaining the large uncertainty is due to differing sensitivities during different phases of warming. We consider the `growth' and `mature' phases of warming under <span class="hlt">climate</span> variability case- typically associated with an El Niño event. In the remote <span class="hlt">tropics</span> (away from <span class="hlt">tropical</span> Pacific Ocean), the response of the precipitation extremes during the two phases can be through different pathways: i) a direct and fast changing radiative forcing in an atmospheric column, acting top-down due to the tropospheric warming, and/or ii) an indirect effect via changes in surface temperatures, acting bottom-up through surface water and energy fluxes. We also speculate that the insights gained here might be useful in interpreting the large sensitivity under <span class="hlt">climate</span> change scenarios, since the physical mechanisms during the two warming phases under <span class="hlt">climate</span> variability case, have some correspondence with an increasing and stabilized green house gas emission scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP11C1370H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP11C1370H"><span>Thermocline Temperature Variability Reveals Shifts in the <span class="hlt">Tropical</span> Pacific Mean State across Marine Isotope Stage 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hertzberg, J. E.; Schmidt, M. W.</p> <p>2014-12-01</p> <p>The eastern equatorial Pacific (EEP) is one of the most dynamic oceanographic regions, making it a critical area for understanding past <span class="hlt">climate</span> change. Despite this, there remains uncertainty on the <span class="hlt">climatic</span> evolution of the EEP through the last glacial period. According to the ocean dynamical thermostat theory, warming (cooling) of the <span class="hlt">tropical</span> Pacific Ocean may lead to a more La Niña (El Niño)-like mean state due to zonally asymmetric heating and subsequent easterly (westerly) wind anomalies at the equator (Clement and Cane, 1999). Attempts to understand these feedbacks on millennial timescales across Marine Isotope Stage 3 (MIS 3) have proven to be fruitful in the western equatorial Pacific (WEP) (Stott et al., 2002), yet complimentary, high-resolution records from the EEP are lacking. To provide a more complete understanding of the feedback mechanisms of the dynamical thermostat across periods of <span class="hlt">abrupt</span> <span class="hlt">climate</span> change, we reconstruct thermocline temperature variability across MIS 3 from a sediment core located in the EEP, directly within the equatorial cold tongue upwelling region (core MV1014-02-17JC). Temperature anomalies in thermocline waters of the EEP are integrally linked to the ENSO system, with large positive and negative anomalies recorded during El Niño and La Niña events, respectively. Mg/Ca ratios in the thermocline-dwelling planktonic foraminifera Neogloboquadrina dutertrei were measured at 2 cm intervals, resulting in a temporal resolution of <200 years. Preliminary results across Interstadials 5-7 reveal warmer thermocline temperatures (an increase in Mg/Ca of .25 ± .02 mmol/mol) during periods of cooling following peak Interstadial warmth over Greenland, as seen from the NGRIP δ18O record. Thus, periods of cooling over Greenland appear to correspond to an El Niño-like mean state in the <span class="hlt">tropical</span> Pacific, in line with predictions of an ocean dynamical thermostat. Interestingly, Heinrich Event 3 corresponds to cooler thermocline</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP13B1430Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP13B1430Y"><span>Heat waves connect <span class="hlt">abrupt</span> polar <span class="hlt">climate</span> changes during the past 67ka: evidence from sediment core GeoB3912-1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, X.; Rial, J. A.</p> <p>2014-12-01</p> <p>According to the hypothesis of polar synchronization, <span class="hlt">climate</span> variations of Earth's poles are connected with a persistent phase lock of π/2 throughout the last glacial period. However, it is not clear yet how the Earth's two poles communicate with each other, the Thermohaline circulation (THC) being a possible candidate for signal carrier. Here we present a possible way of <span class="hlt">climate</span> variation propagation through the Atlantic Ocean - likely in the form of heat or thermal wave (Cattaneo's solution) - based on lagged correlation between an organic carbon <span class="hlt">climate</span> proxy record from the <span class="hlt">tropical</span> Atlantic and the south-north polar temperature gradient. We further demonstrate that the speed of such propagation is frequency dependent, of which the wave of the longest period travels the fastest at the speed of ~32 km/year consistent with the estimated speed of the THC. The observed speed - frequency relationship can be successfully modeled as resulting from a propagating dispersive thermal wave initiated by the polar temperature gradient maximum. We show that such heat wave propagation is a potential mechanism to couple and synchronize the polar <span class="hlt">climates</span> during the last glacial period and to force the occurrence of Heinrich events. To summarize, the polar temperature gradient anomalies are consequence of the π/2 phase lock between the polar <span class="hlt">climates</span>, which is caused by polar synchronization maintained by the coupling, which is, as the data suggest, in the form of thermal waves. The spikes in organic carbon and the Fe/Ca ratio records in the core GeoB3912-1 can be thought of as snapshots of the passage of strong meteorological wavefronts through the equatorial region. The results strongly suggest that each peak in the organic carbon recorded a half-hemisphere-delayed passage of a wave-like disturbance through the equator carrying the south-north temperature gradient maxima. And each of these occurs within timing error of the Heinrich events H0-H6.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950033018&hterms=temperature+variability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dtemperature%2Bvariability','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950033018&hterms=temperature+variability&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dtemperature%2Bvariability"><span><span class="hlt">Tropical</span> cloud feedbacks and natural variability of <span class="hlt">climate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, R. L.; Del Genio, A. D.</p> <p>1994-01-01</p> <p>Simulations of natural variability by two general circulation models (GCMs) are examined. One GCM is a sector model, allowing relatively rapid integration without simplification of the model physics, which would potentially exclude mechanisms of variability. Two mechanisms are found in which <span class="hlt">tropical</span> surface temperature and sea surface temperature (SST) vary on interannual and longer timescales. Both are related to changes in cloud cover that modulate SST through the surface radiative flux. Over the equatorial ocean, SST and surface temperature vary on an interannual timescale, which is determined by the magnitude of the associated cloud cover anomalies. Over the subtropical ocean, variations in low cloud cover drive SST variations. In the sector model, the variability has no preferred timescale, but instead is characterized by a 'red' spectrum with increasing power at longer periods. In the terrestrial GCM, SST variability associated with low cloud anomalies has a decadal timescale and is the dominant form of global temperature variability. Both GCMs are coupled to a mixed layer ocean model, where dynamical heat transports are prescribed, thus filtering out El Nino-Southern Oscillation (ENSO) and thermohaline circulation variability. The occurrence of variability in the absence of dynamical ocean feedbacks suggests that <span class="hlt">climatic</span> variability on long timescales can arise from atmospheric processes alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001E%26PSL.184..505M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001E%26PSL.184..505M"><span><span class="hlt">Abrupt</span> intensification of the SW Indian Ocean monsoon during the last deglaciation: constraints from Th, Pa, and He isotopes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marcantonio, Franco; Anderson, Robert F.; Higgins, Sean; Fleisher, Martin Q.; Stute, Martin; Schlosser, Peter</p> <p>2001-01-01</p> <p>Sediments from western Arabian Sea core 74KL representing the last 23 ka were analyzed for helium, thorium, and protactinium isotopes. Assuming global average fluxes of extraterrestrial 3He and 230Th, the average 3He-derived sediment mass accumulation rate (MAR) is a factor of 1.8 higher than the average 230Th-derived MAR. 3He- and 230Th-derived MARs converge, however, during the Younger Dryas (YD) and during the peak of the early Holocene humid interval. These features, not seen anywhere else in the world, probably reflect a combination of <span class="hlt">climate</span>-driven changes in the flux of 230Th and 3He. Ratios of xs 231Pa/xs 230Th, proxies of paleoproductivity, are lowest during the last glacial maximum (LGM), and increase <span class="hlt">abruptly</span> during the Bolling-Allerod. Later, following a sudden decrease to near-LGM values during the YD, they rise <span class="hlt">abruptly</span> to maximum values for the entire record in the early Holocene. We hypothesize that low xs 231Pa/xs 230Th ratios reflect low productivity due to the decreased intensity of the SW monsoon, whereas the opposite is true for high ratios. The correlation between Arabian Sea productivity and monsoonal upwelling, on the one hand, and North Atlantic <span class="hlt">climate</span> variability, on the other, suggests a linkage between high- and low-latitude <span class="hlt">climates</span> caused by changing patterns of atmospheric circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950034655&hterms=climate+change+rainfall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dclimate%2Bchange%2Brainfall','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950034655&hterms=climate+change+rainfall&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dclimate%2Bchange%2Brainfall"><span>Albedo as a modulator of <span class="hlt">climate</span> response to <span class="hlt">tropical</span> deforestation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dirmeyer, Paul A.; Shukla, J.</p> <p>1994-01-01</p> <p>An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local <span class="hlt">climate</span> due to <span class="hlt">tropical</span> deforestation for the Amazon basin. One control and three anomaly integrations of 4 years' duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in <span class="hlt">climate</span>, particularly rainfall, is strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/45763-albedo-modulator-climate-response-tropical-deforestation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/45763-albedo-modulator-climate-response-tropical-deforestation"><span>Albedo as a modulator of <span class="hlt">climate</span> response to <span class="hlt">tropical</span> deforestation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Dirmeyer, P.A.; Shukla, J.</p> <p>1994-10-01</p> <p>An atmospheric general circulation model with land surface properties represented by the simplified Simple Biosphere model is used to investigate the effects on local <span class="hlt">climate</span> due to <span class="hlt">tropical</span> deforestation for the Amazon basin. One control and three anomaly integrations of 4 years` duration are performed. In the anomaly integrations, rain forest in South America is replaced by degraded grassland. The anomaly integrations differ only in the optical properties of the grassland vegetation, with net surface albedos ranging from the same as to 0.09 lighter than that of rain forest. It is found that the change in <span class="hlt">climate</span>, particularly rainfall, ismore » strongly dependent on the change in surface albedo that accompanies deforestation. Replacement of forest by grass causes a reduction in transpiration and reduces frictional convergence by decreasing surface roughness. However, precipitation averaged over the deforested area is not necessarily reduced. Average precipitation decreases when the increase in albedo is greater than 0.03. If surface albedo is not increased appreciably as a result of deforestation, moisture flux convergence driven by the increase in surface temperature can offset the other effects, and average precipitation increases. As albedo is increased, surface temperature does not change, but surface latent and sensible heat flux decreases due to reduced radiational energy absorbed at the surface, resulting in a reduction in convection and precipitation. A change in the distribution of precipitation due to deforestation that appears to be independent of the albedo is observed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/50752','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/50752"><span><span class="hlt">Tropical</span> wetlands, <span class="hlt">climate</span>, and land-use change: adaptation and mitigation opportunities</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Randy Kolka; D. Murdiyarso; J. B. Kauffman; Richard Birdsey</p> <p>2016-01-01</p> <p><span class="hlt">Tropical</span> wetland ecosystems, especially mangroves and peatlands, are carbon (C) rich ecosystems. Globally, <span class="hlt">tropical</span> mangroves store about 20 PgC, however, deforestation has contributed 10 % of the total global emissions from <span class="hlt">tropical</span> deforestation, even though mangroves account for only about 0.7 % of the world’s <span class="hlt">tropical</span> forest area (Donato et al. 2011). Meanwhile,...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24907712','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24907712"><span>The effects of season and meteorology on human mortality in <span class="hlt">tropical</span> <span class="hlt">climates</span>: a systematic review.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burkart, Katrin; Khan, Md Mobarak Hossain; Schneider, Alexandra; Breitner, Susanne; Langner, Marcel; Krämer, Alexander; Endlicher, Wilfried</p> <p>2014-07-01</p> <p>Research in the field of atmospheric science and epidemiology has long recognized the health effects of seasonal and meteorological conditions. However, little scientific knowledge exists to date about the impacts of atmospheric parameters on human mortality in <span class="hlt">tropical</span> regions. Working within the scope of this systematic review, this investigation conducted a literature search using different databases; original research articles were chosen according to pre-defined inclusion and exclusion criteria. Both seasonal and meteorological effects were considered. The findings suggest that high amounts of rainfall and increasing temperatures cause a seasonal excess in infectious disease mortality and are therefore relevant in regions and populations in which such diseases are prevalent. On the contrary, moderately low and very high temperatures exercise an adverse effect on cardio-respiratory mortality and shape the mortality pattern in areas and sub-groups in which these diseases are dominant. Atmospheric effects were subject to population-specific factors such as age and socio-economic status and differed between urban and rural areas. The consequences of <span class="hlt">climate</span> change as well as environmental, epidemiological and social change (e.g., emerging non-communicable diseases, ageing of the population, urbanization) suggest a growing relevance of heat-related excess mortality in <span class="hlt">tropical</span> regions. © The Author 2014. Published by Oxford University Press on behalf of Royal Society of <span class="hlt">Tropical</span> Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007ERL.....2d5021G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007ERL.....2d5021G"><span>EDITORIAL: <span class="hlt">Tropical</span> deforestation and greenhouse gas emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gibbs, Holly K.; Herold, Martin</p> <p>2007-10-01</p> <p>Carbon emissions from <span class="hlt">tropical</span> deforestation have long been recognized as a key component of the global carbon budget, and more recently of our global <span class="hlt">climate</span> system. <span class="hlt">Tropical</span> forest clearing accounts for roughly 20% of anthropogenic carbon emissions and destroys globally significant carbon sinks (IPCC 2007). Global <span class="hlt">climate</span> policy initiatives are now being proposed to address these emissions and to more actively include developing countries in greenhouse gas mitigation (e.g. Santilli et al 2005, Gullison et al 2007). In 2005, at the Conference of the Parties (COP) in Montreal, the United Nations Framework Convention on <span class="hlt">Climate</span> Change (UNFCCC) launched a new initiative to assess the scientific and technical methods and issues for developing policy approaches and incentives to reduce emissions from deforestation and degradation (REDD) in developing countries (Gullison et al 2007). Over the last two years the methods and tools needed to estimate reductions in greenhouse gas emissions from deforestation have quickly evolved, as the scientific community responded to the UNFCCC policy needs. This focus issue highlights those advancements, covering some of the most important technical issues for measuring and monitoring emissions from deforestation and forest degradation and emphasizing immediately available methods and data, as well as future challenges. Elements for effective long-term implementation of a REDD mechanism related to both environmental and political concerns are discussed in Mollicone et al. Herold and Johns synthesize viewpoints of national parties to the UNFCCC on REDD and expand upon key issues for linking policy requirements and forest monitoring capabilities. In response to these expressed policy needs, they discuss a remote-sensing-based observation framework to start REDD implementation activities and build historical deforestation databases on the national level. Achard et al offer an assessment of remote sensing measurements across the world</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=world+AND+forests&pg=6&id=ED297979','ERIC'); return false;" href="https://eric.ed.gov/?q=world+AND+forests&pg=6&id=ED297979"><span><span class="hlt">Tropical</span> Forests. Global Issues Education Packet.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Holm, Amy E.</p> <p></p> <p><span class="hlt">Tropical</span> forests provide the world with many products and an incredible diversity of plant and animal life. These forests also provide watershed areas, soil control, <span class="hlt">climate</span> regulation, and winter homes for migrating birds from North America. It is believed that about 40% of <span class="hlt">tropical</span> forests have already been destroyed in the last 20-30 years,…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29358022','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29358022"><span>Innovative dual-step management of semi-aerobic landfill in a <span class="hlt">tropical</span> <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lavagnolo, Maria Cristina; Grossule, Valentina; Raga, Roberto</p> <p>2018-04-01</p> <p>Despite concerted efforts to innovate the solid waste management (SWM) system, land disposal continues to represent the most widely used technology in the treatment of urban solid waste worldwide. On the other hand, landfilling is an unavoidable step in closing the material cycle, since final residues, although minimized, need to be safely disposed of and confined. In recent years, the implementation of more sustainable landfilling aims to achieve the Final Storage Quality conditions as fast as possible. In particular, semi-aerobic landfill appears to represent an effective solution for use in the poorest economies due to lower management costs and shorter aftercare resulting from aerobic stabilisation of the waste. Nevertheless, the implementation of a semi-aerobic landfill in a <span class="hlt">tropical</span> <span class="hlt">climate</span> may affect the correct functioning of the plant: a lack of moisture during the dry season and heavy rainfalls during the wet season could negatively affect performance of both the degradation process, and of leachate and biogas management. This paper illustrates the results obtained through the experimentation of a potential dual-step management of semi-aerobic landfilling in a <span class="hlt">tropical</span> <span class="hlt">climate</span> in which composting process was reproduced during the dry season and subsequently flushing (high rainfall rate) during the wet period. Eight bioreactors specifically designed: four operated under anaerobic conditions and four under semi-aerobic conditions; half of the reactors were filled with high organic content waste, half with residual waste obtained following enhanced source segregation. The synergic effect of the subsequent phases (composting and flushing) in the semi-aerobic landfill was evaluated on the basis of both types of waste. Biogas production, leachate composition and waste stabilization were analysed during the trial and at the end of each step, and compared in view of the performance of anaerobic reactors. The results obtained underlined the effectiveness of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000052590','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000052590"><span>The <span class="hlt">Tropical</span> Rainfall Measuring Mission (TRMM)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simpson, Joanne; Kummerow, Christian D.; Meneghini, Robert; Hou, Arthur; Adler, Robert F.; Huffman, George; Barkstrom, Bruce; Wielicki, Bruce; Goodman, Steven J.; Christian, Hugh; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20000052590'); toggleEditAbsImage('author_20000052590_show'); toggleEditAbsImage('author_20000052590_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20000052590_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20000052590_hide"></p> <p>1999-01-01</p> <p>Recognizing the importance of rain in the <span class="hlt">tropics</span> and the accompanying latent heat release, NASA for the U.S. and NASDA for Japan have partnered in the design, construction and flight of an Earth Probe satellite to measure <span class="hlt">tropical</span> rainfall and calculate the associated heating. Primary mission goals are: 1) the understanding of crucial links in <span class="hlt">climate</span> variability by the hydrological cycle, 2) improvement in the large-scale models of weather and <span class="hlt">climate</span>, and 3) improvement in understanding cloud ensembles and their impacts on larger scale circulations. The linkage with the <span class="hlt">tropical</span> oceans and landmasses are also emphasized. The <span class="hlt">Tropical</span> Rainfall Measuring Mission (TRMM) satellite was launched in November 1997 with fuel enough to obtain a four to five year data set of rainfall over the global <span class="hlt">tropics</span> from 37 deg N to 37 deg S. This paper reports progress from launch date through the spring of 1999. The data system and its products and their access is described, as are the algorithms used to obtain the data. Some exciting early results from TRMM are described. Some important algorithm improvements are shown. These will be used in the first total data reprocessing, scheduled to be complete in early 2000. The reader is given information on how to access and use the data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMPP71A0379H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMPP71A0379H"><span>Decadal- to Orbital-Scale Links Between <span class="hlt">Climate</span>, Productivity and Denitrification on the Peru Margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Higginson, M. J.; Altabet, M. A.; Herbert, T. D.</p> <p>2002-12-01</p> <p>Denitrification is the predominant global loss term for combined nitrogen and can exert a major control on its oceanic inventory, global productivity and atmospheric CO2. Our prior work demonstrates that proxy records for changing denitrification, oxygenation and productivity in the recent geological past in the Arabian Sea exhibit unprecedented similarity with <span class="hlt">abrupt</span> <span class="hlt">climate</span> fluctuations recorded in high-latitude ice-cores. Since the Peru Margin and Arabian Sea together constitute almost two-thirds of global marine water-column denitrification, changes in concert in these two regions could potentially have effected rapid global <span class="hlt">climate</span> changes through an oceanic mechanism. The Peru Margin is intimately coupled to the Equatorial Pacific, source of El Ni&ño-La Niña SST, productivity and precipitation anomalies. Here, biogeochemical cycles are especially sensitive to <span class="hlt">abrupt</span> <span class="hlt">climatic</span> changes on decadal time-scales by virtue of this ENSO coupling. The purpose of our research is to investigate whether longer changes in <span class="hlt">tropical</span> Pacific oceanography represent a 'scaling up' of anomalous ENSO conditions, modulated by both internal (e.g. nutrient inventory or WPWP heat budget) and external (e.g. orbital) forcing throughout the last glacial/inter-glacial cycle. Here we present first results of a detailed investigation of recently-recovered sediments from ODP Site 1228 on the Peru margin upper continental slope, in an attempt to capture some of the essential aspects of ENSO-like variability. Despite the existing availability of high quality sediment cores from this margin, little detailed paleoclimatic information currently exists because of poor sedimentary carbonate preservation (exacerbated post-recovery) which has limited generation of essential chronostratigraphic controls. Instead, we rely on the development and novel application of compound-specific AMS dating verified and supplemented by intermittent foraminiferal and bulk-carbon AMS dates, a magnetic paleo</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70122660','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70122660"><span>Influence of <span class="hlt">climate</span> on deep-water clastic sedimentation: application of a modern model, Peru-Chile Trough, to an ancient system, Ouachita Trough</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Edgar, N. Terence; Cecil, C. Blaine</p> <p>2003-01-01</p> <p>Traditionally, an <span class="hlt">abrupt</span> and massive influx of siliciclastic sediments into an area of deposition has been attributed to tectonic uplift without consideration of the influence of <span class="hlt">climate</span> or <span class="hlt">climatic</span> change on rates of weathering, erosion, transportation, and deposition. With few exceptions, fluvial sediment transport is minimal in both extremely arid <span class="hlt">climates</span> and in perhumid (everwet) <span class="hlt">climates</span>. Maximum sediment transport occurs in <span class="hlt">climates</span> characterized by strongly seasonal rainfall, where the effect of vegetation on erosion is minimal. The Peru–Chile trench and Andes Mountain system (P–CT/AMS) of the eastern Pacific Ocean clearly illustrates the effects of <span class="hlt">climate</span> on rates of weathering, erosion, transport, and deep-sea sedimentation. Terrigenous sediment is virtually absent in the arid belt north of lat. 30° S in the P–CT, but in the belt of seasonal rainfall south of lat. 30° S terrigenous sediment is abundant. Spatial variations in the amount and seasonality of annual precipitation are now generally accepted as the cause for this difference. The spatial variation in sediment supply to the P–CT appears to be an excellent modern analogue for the temporal variation in sediment supply to certain ancient systems, such as the Ouachita Trough in the southern United States. By comparison, during the Ordovician through the early Mississippian, sediment was deposited at very slow rates as the Ouachita Trough moved northward through the southern hemisphere dry belt (lat. 10° S to lat. 30° S). The deposystem approached the <span class="hlt">tropical</span> humid zone during the Mississippian, coincident with increased coarse clastic sedimentation. By the Middle Pennsylvanian (Atokan), the provenance area and the deposystem moved well into the <span class="hlt">tropical</span> humid zone, and as much as 8,500 m of mineralogically mature (but texturally immature) quartz sand was introduced and deposited. This increase in clastic sediment deposition traditionally has been attributed solely to tectonic activity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4424453','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4424453"><span>Hydration and Thermoregulation During a Half-Ironman Performed in <span class="hlt">Tropical</span> <span class="hlt">Climate</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Baillot, Michelle; Hue, Olivier</p> <p>2015-01-01</p> <p>The aim of this study was to compare the core temperature (TC) and markers of hydration status in athletes performing a half Ironman triathlon race in hot and humid conditions (27.2 ± 0.5°C, relative humidity was 80 ± 2%). Before and immediately after the 2012 Guadeloupe half Ironman triathlon, body mass and urine osmolarity (mean ± SD) were measured in 19 well-trained male triathletes. TC was measured before and after the race, and at each transition during the event, using an ingestible pill telemetry system. Ambient temperature and heart rate (HR) were measured throughout the race. Mean ± SD performance time was 331 ± 36 minutes and HR was 147 ± 16 beats·min-1. Wet bulb globe temperature (WBGT) averaged 25.4 ± 1.0°C and ocean temperature was 29.5°C. The average TC at the beginning of the race (TC1) was 37.1 ± 0.7°C; it was 37.8 ± 0.9°C after swimming (TC2), 37.8 ± 1.0°C after cycling (TC3), and (TC4) 38.4 ± 0.7°C after running. Body mass significantly declined during the race by 3.7 ± 1.9 kg (4.8 ± 2.4%; p < 0.05), whereas urine osmolarity significantly increased from 491.6 ± 300.6 to 557.9 ± 207.9 mosm·L-1 (p < 0.05). Changes in body mass were not related to finishing TC or urine osmolarity. Ad libitum fluid intake appears applicable to athletes acclimatized to <span class="hlt">tropical</span> <span class="hlt">climate</span>, when performing a half Ironman triathlon in a warm and humid environment. Key points Ad libitum fluid intake appears applicable to athletes acclimatized to <span class="hlt">tropical</span> <span class="hlt">climate</span> when performing a half Ironman triathlon in a warm and humid environment. The final core temperature average was 38.8 ± 0.7ºC after the event in these triathletes and the athletes showed no evidence of heat illness while competing in a warm and humid environment. Core temperature was dependent on both activity and anthropometry. PMID:25983573</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMGC43C0761H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMGC43C0761H"><span>The Amazon rainforest, <span class="hlt">climate</span> change, and drought: How will what is below the surface affect the <span class="hlt">climate</span> of <span class="hlt">tropical</span> South America?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harper, A.; Denning, A. S.; Baker, I.; Randall, D.; Dazlich, D.</p> <p>2008-12-01</p> <p>Several <span class="hlt">climate</span> models have predicted an increase in long-term droughts in <span class="hlt">tropical</span> South America due to increased greenhouse gases in the atmosphere. Although the Amazon rainforest is resilient to seasonal drought, multi-year droughts pose a definite problem for the ecosystem's health. Furthermore, drought- stressed vegetation participates in feedbacks with the atmosphere that can exacerbate drought. Namely, reduced evapotranspiration further dries out the atmosphere and affects the regional <span class="hlt">climate</span>. Trees in the rainforest survive seasonal drought by using deep roots to access adequate stores of soil moisture. We investigate the <span class="hlt">climatic</span> impacts of deep roots and soil moisture by coupling the Simple Biosphere (SiB3) model to Colorado State University's general circulation model (BUGS5). We compare two versions of SiB3 in the GCM during years with anomalously low rainfall. The first has strong vegetative stress due to soil moisture limitations. The second experiences less stress and has more realistic representations of surface biophysics. In the model, basin-wide reductions in soil moisture stress result in increased evapotranspiration, precipitation, and moisture recycling in the Amazon basin. In the savannah region of southeastern Brazil, the unstressed version of SiB3 produces decreased precipitation and weaker moisture flux, which is more in-line with observations. The improved simulation of precipitation and evaporation also produces a more realistic Bolivian high and Nordeste low. These changes highlight the importance of subsurface biophysics for the Amazonian <span class="hlt">climate</span>. The presence of deep roots and soil moisture will become even more important if <span class="hlt">climate</span> change brings more frequent droughts to this region in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4707C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4707C"><span>Indo-Pacific <span class="hlt">climate</span> during the decaying phase of the 2015/16 El Niño: role of southeast <span class="hlt">tropical</span> Indian Ocean warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Zesheng; Du, Yan; Wen, Zhiping; Wu, Renguang; Wang, Chunzai</p> <p>2018-06-01</p> <p>This study investigates the influence of southeast <span class="hlt">tropical</span> Indian Ocean (SETIO) sea surface temperature (SST) warming on Indo-Pacific <span class="hlt">climate</span> during the decaying phase of the 2015/16 El Niño by using observations and model experiments. The results show that the SETIO SST warming in spring 2016 enhanced local convection and forced a "C-shape" wind anomaly pattern in the lower troposphere. The "C-shape" wind anomaly pattern over the eastern <span class="hlt">tropical</span> Indian Ocean consists of anomalous westerly flow south of the equator and anomalous easterly flow north of the equator. The anomalous easterly flow then extended eastward into the western North Pacific (WNP) and facilitates the development or the maintenance of an anomalous anticyclone over the South China Sea (SCS). Correspondingly, the eastern part of the Bay of Bengal, the SCS and the WNP suffered less rainfall. Such precipitation features and the associated "C-shape" wind anomaly pattern shifted northward about five latitudes in summer 2016. Additionally, the SETIO warming can induce local meridional circulation anomalies, which directly affect Indo-Pacific <span class="hlt">climate</span>. Numerical model experiments further confirm that the SETIO SST warming plays an important role in modulating Indo-Pacific <span class="hlt">climate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28414883','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28414883"><span>Temperature and rainfall interact to control carbon cycling in <span class="hlt">tropical</span> forests.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Taylor, Philip G; Cleveland, Cory C; Wieder, William R; Sullivan, Benjamin W; Doughty, Christopher E; Dobrowski, Solomon Z; Townsend, Alan R</p> <p>2017-06-01</p> <p><span class="hlt">Tropical</span> forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short-term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer-term <span class="hlt">climate</span> variability on <span class="hlt">tropical</span> forest carbon dynamics are still not well understood. We synthesised field data from more than 150 <span class="hlt">tropical</span> forest sites to explore how <span class="hlt">climate</span> regulates <span class="hlt">tropical</span> forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore <span class="hlt">climate</span> - C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (< 20 °C), high rainfall slowed rates of C cycling, but in warm <span class="hlt">tropical</span> forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of <span class="hlt">climate</span> - C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth. © 2017 John Wiley & Sons Ltd/CNRS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29146008','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29146008"><span>Heat and pregnancy-related emergencies: Risk of placental <span class="hlt">abruption</span> during hot weather.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>He, Siyi; Kosatsky, Tom; Smargiassi, Audrey; Bilodeau-Bertrand, Marianne; Auger, Nathalie</p> <p>2018-02-01</p> <p>Outdoor heat increases the risk of preterm birth and stillbirth, but the association with placental <span class="hlt">abruption</span> has not been studied. Placental <span class="hlt">abruption</span> is a medical emergency associated with major morbidity and mortality in pregnancy. We determined the relationship between ambient temperature and risk of placental <span class="hlt">abruption</span> in warm seasons. We performed a case-crossover analysis of 17,172 women whose pregnancies were complicated by placental <span class="hlt">abruption</span> in Quebec, Canada from May to October 1989-2012. The main exposure measure was the maximum temperature reached during the week before <span class="hlt">abruption</span>. We computed odds ratios (OR) and 95% confidence intervals (CI) for the association of temperature with placental <span class="hlt">abruption</span>, adjusted for humidity and public holidays. We assessed whether associations were stronger preterm or at term, or varied with maternal age, parity, comorbidity and socioeconomic status. Compared with 15°C, a maximum weekly temperature of 30°C was associated with 1.07 times the odds of <span class="hlt">abruption</span> (95% CI 0.99-1.16). When the timing of <span class="hlt">abruption</span> was examined, the associations were significantly stronger at term (OR 1.12, 95% CI 1.02-1.24) than preterm (OR 0.96, 95% CI 0.83-1.10). Relationships were more prominent at term for women who were younger than 35years old, nulliparous or socioeconomically disadvantaged, but did not vary with comorbidity. Associations were stronger within 1 and 5days of <span class="hlt">abruption</span>. Temperature was not associated with preterm <span class="hlt">abruption</span> regardless of maternal characteristics. Elevated temperatures in warm seasons may increase the risk of <span class="hlt">abruption</span> in women whose pregnancies are near or at term. Pregnant women may be more sensitive to heat and should consider preventive measures such as air conditioning and hydration during hot weather. Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70000125','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70000125"><span>Anomalous cold in the Pangaean <span class="hlt">tropics</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Soreghan, G.S.; Soreghan, M.J.; Poulsen, C.J.; Young, R.A.; Eble, C.F.; Sweet, D.E.; Davogustto, O.C.</p> <p>2008-01-01</p> <p>The late Paleozoic archives the greatest glaciation of the Phanerozoic. Whereas high-latitude Gondwanan strata preserve widespread evidence for continental ice, the Permo-Carboniferous <span class="hlt">tropics</span> have long been considered analogous to today's: warm and shielded from the highlatitude cold. Here, we report on glacial and periglacial indicators that record episodes of freezing continental temperatures in western equatorial Pangaea. An exhumed glacial valley and associated deposits record direct evidence for glaciation that extended to low paleoelevations in the ancestral Rocky Mountains. Furthermore, the Permo-Carboniferous archives the only known occurrence of widespread <span class="hlt">tropical</span> loess in Earth's history; the volume, chemistry, and provenance of this loess(ite) is most consistent with glacial derivation. Together with emerging indicators for cold elsewhere in low-latitude Pangaea, these results suggest that <span class="hlt">tropical</span> <span class="hlt">climate</span> was not buffered from the high latitudes and may record glacial-interglacial <span class="hlt">climate</span> shifts of very large magnitude. Coupled <span class="hlt">climate</span>-ice sheet model simulations demonstrate that low atmospheric CO2 and solar luminosity alone cannot account for such cold, and that other factors must be considered in attempting to explain this 'best-known' analogue to our present Earth. ?? 2008 The Geological Society of America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22493225','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22493225"><span>Role of the Bering Strait on the hysteresis of the ocean conveyor belt circulation and glacial <span class="hlt">climate</span> stability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hu, Aixue; Meehl, Gerald A; Han, Weiqing; Timmermann, Axel; Otto-Bliesner, Bette; Liu, Zhengyu; Washington, Warren M; Large, William; Abe-Ouchi, Ayako; Kimoto, Masahide; Lambeck, Kurt; Wu, Bingyi</p> <p>2012-04-24</p> <p><span class="hlt">Abrupt</span> <span class="hlt">climate</span> transitions, known as Dansgaard-Oeschger and Heinrich events, occurred frequently during the last glacial period, specifically from 80-11 thousand years before present, but were nearly absent during interglacial periods and the early stages of glacial periods, when major ice-sheets were still forming. Here we show, with a fully coupled state-of-the-art <span class="hlt">climate</span> model, that closing the Bering Strait and preventing its throughflow between the Pacific and Arctic Oceans during the glacial period can lead to the emergence of stronger hysteresis behavior of the ocean conveyor belt circulation to create conditions that are conducive to triggering <span class="hlt">abrupt</span> <span class="hlt">climate</span> transitions. Hence, it is argued that even for greenhouse warming, <span class="hlt">abrupt</span> <span class="hlt">climate</span> transitions similar to those in the last glacial time are unlikely to occur as the Bering Strait remains open.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8790M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8790M"><span>Lateglacial <span class="hlt">climate</span> reconstruction on the Bolivian Altiplano inferred from paleoglaciers and paleolakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, Léo; Blard, Pierre-Henri; Lavé, Jérôme; Prémaillon, Mélody; Jomelli, Vincent; Brunstein, Daniel; Lupker, Maarten; Charreau, Julien; Mariotti, Véronique; Condom, Thomas; Bourles, Didier</p> <p>2016-04-01</p> <p>Recent insights shed light on the global mechanisms involved in the <span class="hlt">abrupt</span> oscillations of the Earth <span class="hlt">climate</span> for the Late Glacial Maximum (LGM) to Holocene period (Zhang et al., 2014; Banderas et al., 2015). Yet the concomitant patterns of regional <span class="hlt">climate</span> reorganization on continental areas are for now poorly documented. Particularly, few attempts have been made to propose temporal reconstructions of the regional <span class="hlt">climate</span> variables in the High <span class="hlt">Tropical</span> Andes, a region under the influence of multiple global <span class="hlt">climate</span> forcings (Jomelli et al., 2014). We present new glacial chronologies from four sites of the Bolivian Altiplano: the Wara-Wara valley (17.3°S - 66.1°W), the Zongo valley (16.3°S - 68.1°W), the Cerro Tunupa (19.8°S - 67.6°W) and the Nevado Sajama (18.1°S 68.9°W). These chronologies are based on Cosmic Ray Exposure dating (CRE) from an exceptional suite of recessive moraines. These new data permitted to refine existing chronologies of Smith et al., 2005; Zech et al., 2010 and Blard et al., 2009. In both sites, glaciers recorded stillstand episodes synchronous with cold events such as the Henrich 1 event, the Younger Dryas and the Antarctic Cold Reversal. Since the nearby Altiplano basin registered lake level variations over the same period, we were able to apply a joint modelling of glaciers Equilibrium Line Altitude (ELA) and lake budget. This method permits to derive a temporal evolution of temperature and precipitation for the four sites. These new reconstructions show for all sites that glaciers of the <span class="hlt">Tropical</span> Andes were influenced by the major <span class="hlt">climatic</span> events of the Northern and Southern Hemispheres. Furthermore, the temperature variability observed at high latitudes results in these <span class="hlt">tropical</span> latitudes in major precipitation variability whereas the lateglacial temperature patterns remain globally monotonic. This conversion of global temperature variability into regional precipitation variability support the idea that North Hemisphere cold</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1892g0006L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1892g0006L"><span>Supercritical flow characteristics at <span class="hlt">abrupt</span> expansion structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lim, Jia Jun; Puay, How Tion; Zakaria, Nor Azazi</p> <p>2017-10-01</p> <p>When dealing with the design of a hydraulic structure, lateral expansion is often necessary for flow emerging at high velocity served as a cross-sectional transition. If the <span class="hlt">abrupt</span> expansion structure is made to diverge rapidly, it will cause the major part of the flow fail to follow the boundaries. If the transition is too gradual, it will result in a waste of structural material. A preliminary study on the flow structure near the expansion and its relationship with flow parameter is carried out in this study. A two-dimensional depth-averaged model is developed to simulate the supercritical flow at the <span class="hlt">abrupt</span> expansion structure. Constrained Interpolation Profile (CIP) scheme (which is of third order accuracy) is adopted in the numerical model. Results show that the flow structure and flow characteristics at the <span class="hlt">abrupt</span> expansion can be reproduced numerically. The validation of numerical result is done against analytical studies. The result from numerical simulation showed good agreement with the analytical solution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009QuRes..71..142A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009QuRes..71..142A"><span>Paleoecological evidence for <span class="hlt">abrupt</span> cold reversals during peak Holocene warmth on Baffin Island, Arctic Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Axford, Yarrow; Briner, Jason P.; Miller, Gifford H.; Francis, Donna R.</p> <p>2009-03-01</p> <p>A continuous record of insect (Chironomidae) remains preserved in lake sediments is used to infer temperature changes at a small lake in Arctic Canada through the Holocene. Early Holocene summers at the study site were characterized by more thermophilous assemblages and warmer inferred temperatures than today, presumably in response to the positive anomaly in Northern Hemisphere summer insolation. Peak early Holocene warmth was interrupted by two cold reversals between 9.5 and 8 cal ka BP, during which multiple cold-stenothermous chironomid taxa appeared in the lake. The earlier reversal appears to correlate with widespread <span class="hlt">climate</span> anomalies around 9.2 cal ka BP; the age of the younger reversal is equivocal but it may correlate with the 8.2 cal ka BP cold event documented elsewhere. Widespread, <span class="hlt">abrupt</span> <span class="hlt">climate</span> shifts in the early Holocene illustrate the susceptibility of the <span class="hlt">climate</span> system to perturbations, even during periods of enhanced warmth in the Northern Hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4811H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4811H"><span><span class="hlt">Abrupt</span> decadal-to-centennial hydroclimate changes in the Mediterranean region since the mid-Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Hsun-Ming; Shen, Chuan-Chou; Jiang, Xiuyang; Wang, Yongjin; Mii, Horng-Sheng; Michel, Véronique</p> <p>2016-04-01</p> <p>A series of severe drought events in the Mediterranean region over the past two decades has posed a threat on both human society and biosystem. Holocene hydrological dynamics can offer valuable clues for understanding future <span class="hlt">climate</span> and making proper adaption strategy. Here, we present a decadal-resolved stalagmite record documenting various hydroclimatic fluctuations in the north central Mediterranean region since the middle Holocene. The stalagmite δ18O sequence shows dramatic instability, characterized by <span class="hlt">abrupt</span> shifts between dry and wet conditions <50 years. The timing of regional culture demises, such as the Hittite Kingdom, Mycenaean Greece, Akkadian Empire, Egyptian Old Kingdom, and Uruk, occurred during the drought events, suggesting an important role of <span class="hlt">climate</span> impact on human civilization. The unstable hydroclimate evolution is related to transferred North Atlantic Oscillation states. Rate of rapid transfer of precipitation patterns, which can be pin-pointed by our good chronology, improves the prediction to future <span class="hlt">climate</span> changes in North Atlantic region. We also found that a strong correlation between this stalagmite δ18O and sea surface temperatures especially in Pacific Ocean. This agreement suggests a distant interregional <span class="hlt">climate</span> teleconnection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1076751','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1076751"><span>Quantifying <span class="hlt">Climate</span> Feedbacks from <span class="hlt">Abrupt</span> Changes in High-Latitude Trace-Gas Emissions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Schlosser, Courtney Adam; Walter-Anthony, Katey; Zhuang, Qianlai</p> <p>2013-04-26</p> <p>Our overall goal was to quantify the potential for threshold changes in natural emission rates of trace gases, particularly methane and carbon dioxide, from pan-arctic terrestrial systems under the spectrum of anthropogenically forced <span class="hlt">climate</span> warming, and the extent to which these emissions provide a strong feedback mechanism to global <span class="hlt">climate</span> warming. This goal is motivated under the premise that polar amplification of global <span class="hlt">climate</span> warming will induce widespread thaw and degradation of the permafrost, and would thus cause substantial changes in the extent of wetlands and lakes, especially thermokarst (thaw) lakes, over the Arctic. Through a coordinated effort of fieldmore » measurements, model development, and numerical experimentation with an integrated assessment model framework, we have investigated the following hypothesis: There exists a <span class="hlt">climate</span>-warming threshold beyond which permafrost degradation becomes widespread and thus instigates strong and/or sharp increases in methane emissions (via thermokarst lakes and wetland expansion). These would outweigh any increased uptake of carbon (e.g. from peatlands) and would result in a strong, positive feedback to global <span class="hlt">climate</span> warming.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24352845','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24352845"><span>Temperature and rainfall strongly drive temporal growth variation in Asian <span class="hlt">tropical</span> forest trees.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vlam, Mart; Baker, Patrick J; Bunyavejchewin, Sarayudh; Zuidema, Pieter A</p> <p>2014-04-01</p> <p><span class="hlt">Climate</span> change effects on growth rates of <span class="hlt">tropical</span> trees may lead to alterations in carbon cycling of carbon-rich <span class="hlt">tropical</span> forests. However, <span class="hlt">climate</span> sensitivity of broad-leaved lowland <span class="hlt">tropical</span> trees is poorly understood. Dendrochronology (tree-ring analysis) provides a powerful tool to study the relationship between <span class="hlt">tropical</span> tree growth and annual <span class="hlt">climate</span> variability. We aimed to establish <span class="hlt">climate</span>-growth relationships for five annual-ring forming tree species, using ring-width data from 459 canopy and understory trees from a seasonal <span class="hlt">tropical</span> forest in western Thailand. Based on 183/459 trees, chronologies with total lengths between 29 and 62 years were produced for four out of five species. Bootstrapped correlation analysis revealed that <span class="hlt">climate</span>-growth responses were similar among these four species. Growth was significantly negatively correlated with current-year maximum and minimum temperatures, and positively correlated with dry-season precipitation levels. Negative correlations between growth and temperature may be attributed to a positive relationship between temperature and autotrophic respiration rates. The positive relationship between growth and dry-season precipitation levels likely reflects the strong water demand during leaf flush. Mixed-effect models yielded results that were consistent across species: a negative effect of current wet-season maximum temperatures on growth, but also additive positive effects of, for example, prior dry-season maximum temperatures. Our analyses showed that annual growth variability in <span class="hlt">tropical</span> trees is determined by a combination of both temperature and precipitation variability. With rising temperature, the predominantly negative relationship between temperature and growth may imply decreasing growth rates of <span class="hlt">tropical</span> trees as a result of global warming.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC53A0865W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC53A0865W"><span><span class="hlt">Tropical</span> cyclones in a stabilized 1.5 and 2 degree warmer world.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wehner, M. F.; Stone, D. A.; Loring, B.; Krishnan, H.</p> <p>2017-12-01</p> <p>We present an ensemble of very high resolution global <span class="hlt">climate</span> model simulations of a stabilized 1.5oC and 2oC warmer <span class="hlt">climate</span> as envisioned by the Paris COP21 agreement. The resolution of this global <span class="hlt">climate</span> model (25km) permits simulated <span class="hlt">tropical</span> cyclones up to Category Five on the Saffir-Simpson scale Projected changes in <span class="hlt">tropical</span> cyclones are significant. <span class="hlt">Tropical</span> cyclones in the two stabilization scenarios are less frequent but more intense than in simulations of the present. Output data from these simulations is freely available to all interested parties and should prove a useful resource to those interested in studying the impacts of stabilized global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP31C2262M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP31C2262M"><span>Lateglacial temperature reconstruction in the Eastern <span class="hlt">Tropical</span> Andes (Bolivia) inferred from paleoglaciers and paleolakes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martin, L.; Blard, P. H.; Lave, J.; Prémaillon, M.; Jomelli, V.; Brunstein, D.; Lupker, M.; Charreau, J.; Mariotti, V.; Condom, T.; Bourles, D. L.</p> <p>2015-12-01</p> <p>Recent insights shed light on the global mechanisms involved in the <span class="hlt">abrupt</span> oscillations of the Earth <span class="hlt">climate</span> for the Late Glacial Maximum (LGM) to Holocene period (Zhang et al., 2014; Banderas et al., 2015). Yet the concomitant patterns of regional <span class="hlt">climate</span> reorganization on continental areas are for now poorly documented. Particularly, few attempts have been made to propose temporal reconstructions of the regional <span class="hlt">climate</span> variables in the High <span class="hlt">Tropical</span> Andes, a region under the direct influence of the upper part of the troposphere. We present new glacial chronologies from the Zongo (16.3°S - 68.1°W, Bolivia) and Wara-Wara (17.3°S - 66.1°W, Bolivia) valleys based on Cosmic Ray Exposure dating (CRE) from an exceptional suite of recessive moraines. These new data permitted to refine existing chronologies (Smith et al., 2005 ; Zech et al., 2010): the Zongo valley is characterized by an older local last glacial maximum than the Wara Wara valley. Both sites however exhibit similar glacier behaviours, with a progressive regression between 18 ka and the Holocene. In both sites, glaciers recorded stillstand episodes synchronous with the cold events of the Norther Hemisphere (Henrich 1 event, Younger Dryas). Since the nearby Altiplano basin registered lake level variations over the same period, we were able to apply a joint modelling of glaciers Equilibrium Line Altitude (ELA) and lake budget. This permits to derive a temporal evolution of temperature and precipitation for both sites. These new reconstructions show for both sites that glaciers of the Eastern <span class="hlt">Tropical</span> Andes were both influenced by the major <span class="hlt">climatic</span> events of the Northern and Southern Hemispheres. However, precipitation variability is more influenced by the Northern Atlantic events. This observation is in good agreement with the theories suggesting that North Hemisphere cold events are coeval with an important southward deflexion of the Intertropical Convergence Zone (ITCZ) due to the inter</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24679966','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24679966"><span>Thermal comfort of various building layouts with a proposed discomfort index range for <span class="hlt">tropical</span> <span class="hlt">climate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Md Din, Mohd Fadhil; Lee, Yee Yong; Ponraj, Mohanadoss; Ossen, Dilshan Remaz; Iwao, Kenzo; Chelliapan, Shreeshivadasan</p> <p>2014-04-01</p> <p>Recent years have seen issues related to thermal comfort gaining more momentum in <span class="hlt">tropical</span> countries. The thermal adaptation and thermal comfort index play a significant role in evaluating the outdoor thermal comfort. In this study, the aim is to capture the thermal sensation of respondents at outdoor environment through questionnaire survey and to determine the discomfort index (DI) to measure the thermal discomfort level. The results indicated that most respondents had thermally accepted the existing environment conditions although they felt slightly warm and hot. A strong correlation between thermal sensation and measured DI was also identified. As a result, a new discomfort index range had been proposed in association with local <span class="hlt">climate</span> and thermal sensation of occupants to evaluate thermal comfort. The results had proved that the respondents can adapt to a wider range of thermal conditions.Validation of the questionnaire data at Putrajaya was done to prove that the thermal sensation in both Putrajaya and UTM was almost similar since they are located in the same <span class="hlt">tropical</span> <span class="hlt">climate</span> region. Hence, a quantitative field study on building layouts was done to facilitate the outdoor human discomfort level based on newly proposed discomfort index range. The results showed that slightly shaded building layouts of type- A and B exhibited higher temperature and discomfort index. The resultant adaptive thermal comfort theory was incorporated into the field studies as well. Finally, the study also showed that the DI values were highly dependent on ambient temperature and relative humidity but had fewer effects for solar radiation intensity. Copyright © 2014 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESD.....8..495S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESD.....8..495S"><span>Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schewe, Jacob; Levermann, Anders</p> <p>2017-07-01</p> <p>Projections of the response of Sahel rainfall to future global warming diverge significantly. Meanwhile, paleoclimatic records suggest that Sahel rainfall is capable of <span class="hlt">abrupt</span> transitions in response to gradual forcing. Here we present <span class="hlt">climate</span> modeling evidence for the possibility of an <span class="hlt">abrupt</span> intensification of Sahel rainfall under future <span class="hlt">climate</span> change. Analyzing 30 coupled global <span class="hlt">climate</span> model simulations, we identify seven models where central Sahel rainfall increases by 40 to 300 % over the 21st century, owing to a northward expansion of the West African monsoon domain. Rainfall in these models is non-linearly related to sea surface temperature (SST) in the <span class="hlt">tropical</span> Atlantic and Mediterranean moisture source regions, intensifying <span class="hlt">abruptly</span> beyond a certain SST warming level. We argue that this behavior is consistent with a self-amplifying dynamic-thermodynamical feedback, implying that the gradual increase in oceanic moisture availability under warming could trigger a sudden intensification of monsoon rainfall far inland of today's core monsoon region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/7065692-climate-collapse-civilization','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/7065692-climate-collapse-civilization"><span><span class="hlt">Climate</span> and the collapse of civilization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Abate, T.</p> <p>1994-09-01</p> <p>This article looks at the archaeological debate over two important questions: whether <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes caused or contributed to the collapse of ancient civilizations and, if the archaeological and paleoclimatological record yields evidence to that effect, what would it mean in a world that today debates whether industrial civilization is altering Earth's <span class="hlt">climate</span> with uncertain consequences. Areas discussed include the following: <span class="hlt">climate</span> hints from archaeological sites; hesitations about whether <span class="hlt">climate</span> change caused civilizations to collapse; and the interdisciplinary checks on each side.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17479295','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17479295"><span>Sea turtle species vary in their susceptibility to <span class="hlt">tropical</span> cyclones.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pike, David A; Stiner, John C</p> <p>2007-08-01</p> <p>Severe <span class="hlt">climatic</span> events affect all species, but there is little quantitative knowledge of how sympatric species react to such situations. We compared the reproductive seasonality of sea turtles that nest sympatrically with their vulnerability to <span class="hlt">tropical</span> cyclones (in this study, "<span class="hlt">tropical</span> cyclone" refers to <span class="hlt">tropical</span> storms and hurricanes), which are increasing in severity due to changes in global <span class="hlt">climate</span>. Storm surges significantly decreased reproductive output by lowering the number of nests that hatched and the number of hatchlings that emerged from nests, but the severity of this effect varied by species. Leatherback turtles (Dermochelys coriacea) began nesting earliest and most offspring hatched before the <span class="hlt">tropical</span> cyclone season arrived, resulting in little negative effect. Loggerhead turtles (Caretta caretta) nested intermediately, and only nests laid late in the season were inundated with seawater during storm surges. Green turtles (Chelonia mydas) nested last, and their entire nesting season occurred during the <span class="hlt">tropical</span> cyclone season; this resulted in a majority (79%) of green turtle nests incubating in September, when <span class="hlt">tropical</span> cyclones are most likely to occur. Since this timing overlaps considerably with the <span class="hlt">tropical</span> cyclone season, the developing eggs and nests are extremely vulnerable to storm surges. Increases in the severity of <span class="hlt">tropical</span> cyclones may cause green turtle nesting success to worsen in the future. However, published literature suggests that loggerhead turtles are nesting earlier in the season and shortening their nesting seasons in response to increasing sea surface temperatures caused by global <span class="hlt">climate</span> change. This may cause loggerhead reproductive success to improve in the future because more nests will hatch before the onset of <span class="hlt">tropical</span> cyclones. Our data clearly indicate that sympatric species using the same resources are affected differently by <span class="hlt">tropical</span> cyclones due to slight variations in the seasonal timing of nesting, a key life</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMIN11A0027F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMIN11A0027F"><span>Towards a Statistical Model of <span class="hlt">Tropical</span> Cyclone Genesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernandez, A.; Kashinath, K.; McAuliffe, J.; Prabhat, M.; Stark, P. B.; Wehner, M. F.</p> <p>2017-12-01</p> <p><span class="hlt">Tropical</span> Cyclones (TCs) are important extreme weather phenomena that have a strong impact on humans. TC forecasts are largely based on global numerical models that produce TC-like features. Aspects of <span class="hlt">Tropical</span> Cyclones such as their formation/genesis, evolution, intensification and dissipation over land are important and challenging problems in <span class="hlt">climate</span> science. This study investigates the environmental conditions associated with <span class="hlt">Tropical</span> Cyclone Genesis (TCG) by testing how accurately a statistical model can predict TCG in the CAM5.1 <span class="hlt">climate</span> model. TCG events are defined using TECA software @inproceedings{Prabhat2015teca, title={TECA: Petascale Pattern Recognition for <span class="hlt">Climate</span> Science}, author={Prabhat and Byna, Surendra and Vishwanath, Venkatram and Dart, Eli and Wehner, Michael and Collins, William D}, booktitle={Computer Analysis of Images and Patterns}, pages={426-436}, year={2015}, organization={Springer}} to extract TC trajectories from CAM5.1. L1-regularized logistic regression (L1LR) is applied to the CAM5.1 output. The predictions have nearly perfect accuracy for data not associated with TC tracks and high accuracy differentiating between high vorticity and low vorticity systems. The model's active variables largely correspond to current hypotheses about important factors for TCG, such as wind field patterns and local pressure minima, and suggests new routes for investigation. Furthermore, our model's predictions of TC activity are competitive with the output of an instantaneous version of Emanuel and Nolan's Genesis Potential Index (GPI) @inproceedings{eman04, title = "<span class="hlt">Tropical</span> cyclone activity and the global <span class="hlt">climate</span> system", author = "Kerry Emanuel and Nolan, {David S.}", year = "2004", pages = "240-241", booktitle = "26th Conference on Hurricanes and <span class="hlt">Tropical</span> Meteorology"}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP51A1591G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP51A1591G"><span>50,000 years of Environmental Change in West <span class="hlt">Tropical</span> Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gosling, W. D.; Miller, C. S.</p> <p>2010-12-01</p> <p><span class="hlt">Tropical</span> forests provide three vital ‘ecosystem services’ to the Earth, they: i) contain c. 40% of the terrestrial carbon stock, ii) store c. 50% of global biodiversity, and iii) feedback into global <span class="hlt">climate</span> and carbon cycles. In addition, <span class="hlt">tropical</span> forests are thought to have been actively absorbing atmospheric carbon dioxide over recent decades and consequently may be mitigating the impact of ongoing human induced global <span class="hlt">climate</span> change. The services provided by <span class="hlt">tropical</span> ecosystems are now threatened by human land use practices and projected future <span class="hlt">climate</span> change. However, due to the complex nature of <span class="hlt">tropical</span> ecosystems it is unclear how vegetation will respond to changes in global <span class="hlt">climate</span> conditions. To provide an empirical insight into the response of <span class="hlt">tropical</span> vegetation to global <span class="hlt">climate</span> change it is necessary to learn lessons from the past by exploring the fossil record. Lake sediments are the ideal source for fossils to provide evidence of terrestrial vegetation response to past global <span class="hlt">climate</span> change. The identification of fossil pollen grains trapped within lake sediments is a tried and tested way of establishing past terrestrial vegetation change. Determining the types of plant represented in the fossil pollen record at any particular point in time provides a good indication of the vegetation that surrounded that lake during sediment deposition. In this paper we present a new c. 50,000 year fossil pollen record from Lake Bosumtwi (Ghana; 06o 30’N, 01o 25’ W; c. 100 m above sea level). Lake Bosumtwi is today located within the Guineo-Congolian rainforest close to the ecotone. The seasonal migration of the Inter <span class="hlt">Tropical</span> Convergence Zone (ITCZ) passes over Bosumtwi and consequently vegetation is likely to be sensitive to any changes in the ITCZ position and the associated monsoon. Sediments recovered from Lake Bosumtwi in 2004 by the Intercontinental Drilling Program provide an opportunity to investigate <span class="hlt">tropical</span> vegetation response to <span class="hlt">climate</span> change</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....14829S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....14829S"><span><span class="hlt">Climatic</span> Variability In <span class="hlt">Tropical</span> Countries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seneviratne, L. W.</p> <p>2003-04-01</p> <p> atmospheric condition and hence reduces rainfall for about 1.5 years in <span class="hlt">tropical</span> countries. This was proved in 2001. This forecast was presented as a paper in 1998 Stockholm Water Symposium. The results were true for Brazil as well. The danger is now over when the episode is relaxed. Second half of 2002 was heavily wet and all the tanks in Sri Lanka except Kirindioya complex in Hambanthoa area got filled. This condition was seen in 1997 where all tanks got filled. El Nino analysts declared 1997 as a drought year as the previous year had experienced warming in Pacific Ocean. Southern Oscillation events are now dissociating to conformity. Discussion Hambanthoa District remained in the dry zone of Sri Lanka for 2000 years as the soil forms expressed as reddish brown earths. Original kingdoms had its base in Anuradhapura in Northcentral Province and Magama in Hambanthota district. Tools used by contemporary farmers were not powerful to use enormous water resources in wet zone. A system of diversion dams and use of run of the river irrigation has proved as the main criteria of that era. Diversion dams and canal projects were in existence. The diversion dams with special shape was mistaken by british surveyors and marked as broken dams in plans. DLOMendis later identified these as effective deflecting dams. The purpose was to wet the area to do cultivation. This system of wetting the land was suitable for dry <span class="hlt">climates</span> with low rainfall. High technology was introduced by Irrigation Department to construct several reservoirs in Hambanthota. This was planned after the insufficient water use of Ellagala anicut from Kirindi Oya. Next step was to plan a reservoir project at Lunugamvehera dam site. Precipitation data available for 50 years were studied and a reservoir was designed for 20 000acres of paddy. It was planned to cultivate rice for Maha season and other field crops for Yala season. Cultivation commenced in 1985 and the farmers had enough water for 20000acres including</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.cpc.ncep.noaa.gov/products/outreach/CDPW41/CDPW41.php','SCIGOVWS'); return false;" href="http://www.cpc.ncep.noaa.gov/products/outreach/CDPW41/CDPW41.php"><span><span class="hlt">Climate</span> Prediction Center - Outreach: 41st Annual <span class="hlt">Climate</span> Diagnostics &</span></a></p> <p><a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a></p> <p></p> <p></p> <p>the University of Maine <em><span class="hlt">Climate</span></em> <em>Change</em> Institute and School of Earth and <em><span class="hlt">Climate</span></em> Sciences and is co (drought, heat waves, severe weather, <span class="hlt">tropical</span> cyclones) in the framework of <em><span class="hlt">climate</span></em> variability and <em>change</em> and including the use of paleoclimate data. Arctic <em><span class="hlt">climate</span></em> variability and <em>change</em>, and linkages to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000769','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000769"><span>Hurricanes and <span class="hlt">Climate</span>: the U.S. CLIVAR Working Group on Hurricanes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Walsh, Kevin; Camargo, Suzana J.; Vecchi, Gabriel A.; Daloz, Anne Sophie; Elsner, James; Emanuel, Kerry; Horn, Michael; Lim, Young-Kwon; Roberts, Malcolm; Patricola, Christina; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20150000769'); toggleEditAbsImage('author_20150000769_show'); toggleEditAbsImage('author_20150000769_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20150000769_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20150000769_hide"></p> <p>2015-01-01</p> <p>While a quantitative <span class="hlt">climate</span> theory of <span class="hlt">tropical</span> cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate <span class="hlt">tropical</span> cyclone climatologies and understand the relationship between <span class="hlt">climate</span> and <span class="hlt">tropical</span> cyclone formation. <span class="hlt">Climate</span> models are now able to simulate a realistic rate of global <span class="hlt">tropical</span> cyclone formation, although simulation of the Atlantic <span class="hlt">tropical</span> cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. The idealized experiments of the Hurricane Working Group of U.S. CLIVAR, combined with results from other model simulations, have suggested relationships between <span class="hlt">tropical</span> cyclone formation rates and <span class="hlt">climate</span> variables such as mid-tropospheric vertical velocity. Systematic differences are shown between experiments in which only sea surface temperature is increases versus experiments where only atmospheric carbon dioxide is increased, with the carbon dioxide experiments more likely to demonstrate a decrease in numbers. Further experiments are proposed that may improve our understanding of the relationship between <span class="hlt">climate</span> and <span class="hlt">tropical</span> cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4777015','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4777015"><span><span class="hlt">Climate</span> Warming and Soil Carbon in <span class="hlt">Tropical</span> Forests: Insights from an Elevation Gradient in the Peruvian Andes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nottingham, Andrew T.; Whitaker, Jeanette; Turner, Benjamin L.; Salinas, Norma; Zimmermann, Michael; Malhi, Yadvinder; Meir, Patrick</p> <p>2015-01-01</p> <p>The temperature sensitivity of soil organic matter (SOM) decomposition in <span class="hlt">tropical</span> forests will influence future <span class="hlt">climate</span>. Studies of a 3.5-kilometer elevation gradient in the Peruvian Andes, including short-term translocation experiments and the examination of the long-term adaptation of biota to local thermal and edaphic conditions, have revealed several factors that may regulate this sensitivity. Collectively this work suggests that, in the absence of a moisture constraint, the temperature sensitivity of decomposition is regulated by the chemical composition of plant debris (litter) and both the physical and chemical composition of preexisting SOM: higher temperature sensitivities are found in litter or SOM that is more chemically complex and in SOM that is less occluded within aggregates. In addition, the temperature sensitivity of SOM in <span class="hlt">tropical</span> montane forests may be larger than previously recognized because of the presence of “cold-adapted” and nitrogen-limited microbial decomposers and the possible future alterations in plant and microbial communities associated with warming. Studies along elevation transects, such as those reviewed here, can reveal factors that will regulate the temperature sensitivity of SOM. They can also complement and guide in situ soil-warming experiments, which will be needed to understand how this vulnerability to temperature may be mediated by altered plant productivity under future <span class="hlt">climatic</span> change. PMID:26955086</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24771544','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24771544"><span>Ocean cleaning stations under a changing <span class="hlt">climate</span>: biological responses of <span class="hlt">tropical</span> and temperate fish-cleaner shrimp to global warming.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rosa, Rui; Lopes, Ana Rita; Pimentel, Marta; Faleiro, Filipa; Baptista, Miguel; Trübenbach, Katja; Narciso, Luis; Dionísio, Gisela; Pegado, Maria Rita; Repolho, Tiago; Calado, Ricardo; Diniz, Mário</p> <p>2014-10-01</p> <p>Cleaning symbioses play an important role in the health of certain coastal marine communities. These interspecific associations often occur at specific sites (cleaning stations) where a cleaner organism (commonly a fish or shrimp) removes ectoparasites/damaged tissue from a 'client' (a larger cooperating fish). At present, the potential impact of <span class="hlt">climate</span> change on the fitness of cleaner organisms remains unknown. This study investigated the physiological and biochemical responses of <span class="hlt">tropical</span> (Lysmata amboinensis) and temperate (L. seticaudata) cleaner shrimp to global warming. Specifically, thermal limits (CTMax), metabolic rates, thermal sensitivity, heat shock response (HSR), lipid peroxidation [malondialdehyde (MDA) concentration], lactate levels, antioxidant (GST, SOD and catalase) and digestive enzyme activities (trypsin and alkaline phosphatase) at current and warming (+3 °C) temperature conditions. In contrast to the temperate species, CTMax values decreased significantly from current (24-27 °C) to warming temperature conditions (30 °C) for the <span class="hlt">tropical</span> shrimp, where metabolic thermal sensitivity was affected and the HSR was significantly reduced. MDA levels in <span class="hlt">tropical</span> shrimp increased dramatically, indicating extreme cellular lipid peroxidation, which was not observed in the temperate shrimp. Lactate levels, GST and SOD activities were significantly enhanced within the muscle tissue of the <span class="hlt">tropical</span> species. Digestive enzyme activities in the hepatopancreas of both species were significantly decreased by warmer temperatures. Our data suggest that the <span class="hlt">tropical</span> cleaner shrimp will be more vulnerable to global warming than the temperate Lysmata seticaudata; the latter evolved in a relatively unstable environment with seasonal thermal variations that may have conferred greater adaptive plasticity. Thus, <span class="hlt">tropical</span> cleaning symbioses may be challenged at a greater degree by warming-related anthropogenic forcing, with potential cascading effects on the health</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811375S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811375S"><span>Mechanisms that triggered hydrological changes in the <span class="hlt">tropical</span> lowlands of northern Central America during the past 85 ka</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sylvestre, Florence; Perez, Liseth; Paillès, Christine; Schwalb, Antje; Kutterolf, Steffen; Brenner, Mark; Curtis, Jason; Ariztegui, Daniel; Anselmetti, Flavio; Hodell, David</p> <p>2016-04-01</p> <p>). Moreover, between 80 and 61 ka, fresher sea surface waters are inferred from the adjacent oceans, associated with globally warmer temperatures, implying moister conditions for the Yucatán Peninsula (Leduc et al., 2007). Our results highlight shifts through time in the major forcing mechanisms that triggered water-level changes in Lake Petén Itzá. These new paleoenvironmental proxy data will be useful for selecting parameters to be included in future modelling experiments that test forcing of <span class="hlt">tropical</span> <span class="hlt">climatic</span> changes during the late Quaternary. Hodell, D.A., Anselmetti, F.S., Ariztegui, D., Brenner, M., Curtis, J.H., Gilli, A., Grzesik, D.A., Guilderson, T.J., Muller, A.D., Bush, M.B., Correa-Metrio, Y.A., Escobar, J., and Kutterolf, S., 2008. An 85-ka Record of <span class="hlt">Climate</span> Change in Lowland Central America, Quaternary Science Reviews, 27, 1152- 1165. Leduc, G., Vidal, L., Tachikawa, K., Rostek, F., Sonzogni, C., Beaufort, L., Bard, E., 2007. Moisture transport across Central America as a positive feedback on <span class="hlt">abrupt</span> <span class="hlt">climatic</span> changes. Nature, 445, 908-911.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.cpc.ncep.noaa.gov/products/CDB','SCIGOVWS'); return false;" href="http://www.cpc.ncep.noaa.gov/products/CDB"><span><span class="hlt">Climate</span> Prediction Center - Outlooks</span></a></p> <p><a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a></p> <p></p> <p></p> <p>Weather Service NWS logo - Click to go to the NWS home page <em><span class="hlt">Climate</span></em> Prediction Center Home Site Map News Web resources and services. HOME > Outreach > Publications > <em><span class="hlt">Climate</span></em> Diagnostics Bulletin <em><span class="hlt">Climate</span></em> Diagnostics Bulletin - <span class="hlt">Tropics</span> <em><span class="hlt">Climate</span></em> Diagnostics Bulletin - Forecast <em><span class="hlt">Climate</span></em> Diagnostics</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18556546','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18556546"><span>Forests and <span class="hlt">climate</span> change: forcings, feedbacks, and the <span class="hlt">climate</span> benefits of forests.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonan, Gordon B</p> <p>2008-06-13</p> <p>The world's forests influence <span class="hlt">climate</span> through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. These complex and nonlinear forest-atmosphere interactions can dampen or amplify anthropogenic <span class="hlt">climate</span> change. <span class="hlt">Tropical</span>, temperate, and boreal reforestation and afforestation attenuate global warming through carbon sequestration. Biogeophysical feedbacks can enhance or diminish this negative <span class="hlt">climate</span> forcing. <span class="hlt">Tropical</span> forests mitigate warming through evaporative cooling, but the low albedo of boreal forests is a positive <span class="hlt">climate</span> forcing. The evaporative effect of temperate forests is unclear. The net <span class="hlt">climate</span> forcing from these and other processes is not known. Forests are under tremendous pressure from global change. Interdisciplinary science that integrates knowledge of the many interacting <span class="hlt">climate</span> services of forests with the impacts of global change is necessary to identify and understand as yet unexplored feedbacks in the Earth system and the potential of forests to mitigate <span class="hlt">climate</span> change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21900078','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21900078"><span>The impact of regional <span class="hlt">climate</span> change on malaria risk due to greenhouse forcing and land-use changes in <span class="hlt">tropical</span> Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ermert, Volker; Fink, Andreas H; Morse, Andrew P; Paeth, Heiko</p> <p>2012-01-01</p> <p><span class="hlt">Climate</span> change will probably alter the spread and transmission intensity of malaria in Africa. In this study, we assessed potential changes in the malaria transmission via an integrated weather-disease model. We simulated mosquito biting rates using the Liverpool Malaria Model (LMM). The input data for the LMM were bias-corrected temperature and precipitation data from the regional model (REMO) on a 0.5° latitude-longitude grid. A Plasmodium falciparum infection model expands the LMM simulations to incorporate information on the infection rate among children. Malaria projections were carried out with this integrated weather-disease model for 2001 to 2050 according to two <span class="hlt">climate</span> scenarios that include the effect of anthropogenic land-use and land-cover changes on <span class="hlt">climate</span>. Model-based estimates for the present <span class="hlt">climate</span> (1960 to 2000) are consistent with observed data for the spread of malaria in Africa. In the model domain, the regions where malaria is epidemic are located in the Sahel as well as in various highland territories. A decreased spread of malaria over most parts of <span class="hlt">tropical</span> Africa is projected because of simulated increased surface temperatures and a significant reduction in annual rainfall. However, the likelihood of malaria epidemics is projected to increase in the southern part of the Sahel. In most of East Africa, the intensity of malaria transmission is expected to increase. Projections indicate that highland areas that were formerly unsuitable for malaria will become epidemic, whereas in the lower-altitude regions of the East African highlands, epidemic risk will decrease. We project that <span class="hlt">climate</span> changes driven by greenhouse-gas and land-use changes will significantly affect the spread of malaria in <span class="hlt">tropical</span> Africa well before 2050. The geographic distribution of areas where malaria is epidemic might have to be significantly altered in the coming decades.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP31E..01M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP31E..01M"><span>Varying Influence of Different Forcings on the Indo-Pacific Warm Pool <span class="hlt">Climate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohtadi, M.; Huang, E.; Hollstein, M.; Chen, Y.; Schefuß, E.; Rosenthal, Y.; Prange, M.; Oppo, D.; Liu, J.; Steinke, S.; Martinez-Mendez, G.; Tian, J.; Moffa-Sanchez, P.; Lückge, A.</p> <p>2017-12-01</p> <p>Proxy records of rainfall in marine archives from the eastern and western parts of the Indo-Pacific Warm Pool (IPWP) vary at precessional band and suggest a dominant role of orbital forcing by modulating monsoon rainfall and the position of the Inter <span class="hlt">Tropical</span> Convergence Zone. Rainfall changes recorded in marine archives from the northern South China Sea reveal a more complex history. They are largely consistent with those recorded in the Chinese cave speleothems during glacial periods, but show opposite changes during interglacial peaks that coincide with strong Northern Hemisphere summer insolation maxima. During glacial periods, the establishment of massive Northern Hemisphere ice sheets and the exposure of broad continental shelves in East and Southeast Asia alter the large-scale routes and amounts of water vapor transport onto land relative to interglacials. Precipitation over China during glacials varies at precessional band and is dominated by water vapor transport from the nearby <span class="hlt">tropical</span> and northwest Pacific, resulting in consistent changes in precipitation over large areas. In the absence of ice forcing during peak interglacials with a strong summer insolation, the low-level southerly monsoonal winds mainly of the Indian Ocean origin penetrate further landward and rainout along their path over China. Subsurface temperatures from the IPWP lack changes on glacial-interglacial timescales but follow the obliquity cycle, and suggest that obliquity-paced <span class="hlt">climate</span> variations at mid-latitudes remotely control subsurface temperatures in the IPWP. Temperature and rainfall in the IPWP respond primarily to <span class="hlt">abrupt</span> <span class="hlt">climate</span> changes in the North Atlantic on millennial timescales, and to ENSO and solar forcing on interannual to decadal timescales. In summary, results from marine records reveal that the IPWP <span class="hlt">climate</span> is sensitive to changes in spatial and temporal distribution of heat by many types of forcing, the influence of which seems to vary in time and space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21553594','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21553594"><span>Understanding global <span class="hlt">climate</span> change: paleoclimate perspective from the world's highest mountains.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thompson, Lonnie G</p> <p>2010-06-01</p> <p>Glaciers are among the world's best recorders of, and first responders to, natural and anthropogenic <span class="hlt">climate</span> change and provide a time perspective for current <span class="hlt">climatic</span> and environmental variations. Over the last 50 years such records have been recovered from the polar regions as well as low-latitude, high-elevation ice fields. Analyses of these ice cores and of the glaciers from which they have been drilled have yielded three lines of evidence for past and present <span class="hlt">abrupt</span> <span class="hlt">climate</span> change: (1) the temperature and precipitation histories recorded in the glaciers as revealed by the <span class="hlt">climate</span> records extracted from the ice cores; (2) the accelerating loss of the glaciers themselves; and (3) the uncovering of ancient fauna and flora from the margins of the glaciers as a result of their recent melting, thus illustrating the significance of the current ice loss. The current melting of high-altitude, low-latitude ice fields is consistent with model predictions for a vertical amplification of temperature in the <span class="hlt">tropics</span>. The ongoing rapid retreat of the world's mountain glaciers, as well as the margins of the Greenland and Antarctic ice sheets, is not only contributing to global sea level rise, but also threatening fresh-water supplies in many of the most populous regions. More recently, strong evidence has appeared for the acceleration of the rate of ice loss in the <span class="hlt">tropics</span>, which especially presents a clear and present danger to water supplies for at-risk populations in South America and Asia. The human response to this issue, however, is not so clear, for although the evidence from both data and models becomes more compelling, the rate of global CO2 emissions continues to accelerate. Climatologically, we are in unfamiliar territory, and the world's ice cover is responding dramatically. The loss of glaciers, which can be viewed as the world's water towers, threatens water resources that are essential for hydroelectric power, crop irrigation, municipal water supplies, and even</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC21B1073F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC21B1073F"><span>Long-Term <span class="hlt">Climate</span> Implications of Persistent Loss of <span class="hlt">Tropical</span> Peat Carbon Following Land Use Conversion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frolking, S. E.; Dommain, R.; Glaser, P. H.; Joos, F.; Jeltsch-Thommes, A.</p> <p>2016-12-01</p> <p>The <span class="hlt">climate</span> mitigation potential of <span class="hlt">tropical</span> peatlands has gained increased attention as Southeast Asian <span class="hlt">tropical</span> peat swamp forests are being deforested, drained and burned at very high rates, causing globally significant carbon dioxide (CO2) emissions to the atmosphere. We used a simple force-restore model to represent the perturbation to the atmospheric CO2 and CH4 burdens, and net radiative forcing, resulting from long-term conversion of <span class="hlt">tropical</span> peat swamp forests to oil palm or acacia plantations. Drainage ditches are installed in land-use conversion to both oil palm and acacia, leading to a persistent change in the system greenhouse gas balance with the atmosphere. Drainage causes the net CO2 exchange to switch from a weak sink (removal from the atmosphere) in the accumulating peat of a swamp forest to a relatively strong source as the peat is oxidized. CH4 emissions increase due to relatively high emissions from the ditches themselves. For these systems, persistent CO2 fluxes have a much stronger impact on atmospheric radiative forcing than do the CH4 fluxes. Prior to conversion, slow peat accumulation (net CO2 uptake) over millennia establishes a slowly increasing net radiative cooling perturbation to the atmosphere. Upon conversion, CO2 loss rates are 16-32 times higher than pre-conversion CO2 uptake rates. Rapid loss rates cause the net radiative forcing perturbation to quickly (decades) become a net warming, which can persist for many centuries after the peat has all been oxidized.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. Their policies may differ from this site.</div> </div><!-- container --> <footer><a id="backToTop" href="#top"> </a><nav><a id="backToTop" href="#top"> </a><ul class="links"><a id="backToTop" href="#top"> </a><li><a id="backToTop" href="#top"></a><a href="/sitemap.html">Site Map</a></li> <li><a href="/members/index.html">Members Only</a></li> <li><a href="/website-policies.html">Website Policies</a></li> <li><a href="https://doe.responsibledisclosure.com/hc/en-us" target="_blank">Vulnerability Disclosure Program</a></li> <li><a href="/contact.html">Contact Us</a></li> </ul> <div class="small">Science.gov is maintained by the U.S. Department of Energy's <a href="https://www.osti.gov/" target="_blank">Office of Scientific and Technical Information</a>, in partnership with <a href="https://www.cendi.gov/" target="_blank">CENDI</a>.</div> </nav> </footer> <script type="text/javascript"><!-- // var lastDiv = ""; function showDiv(divName) { // hide last div if (lastDiv) { document.getElementById(lastDiv).className = "hiddenDiv"; } //if value of the box is not nothing and an object with that name exists, then change the class if (divName && document.getElementById(divName)) { document.getElementById(divName).className = "visibleDiv"; lastDiv = divName; } } //--> </script> <script> /** * Function that tracks a click on an outbound link in Google Analytics. * This function takes a valid URL string as an argument, and uses that URL string * as the event label. */ var trackOutboundLink = function(url,collectionCode) { try { h = window.open(url); setTimeout(function() { ga('send', 'event', 'topic-page-click-through', collectionCode, url); }, 1000); } catch(err){} }; </script> <!-- Google Analytics --> <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-1122789-34', 'auto'); ga('send', 'pageview'); </script> <!-- End Google Analytics --> <script> showDiv('page_1') </script> </body> </html>