Sample records for abrupt climatic events

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Abrupt climatic events recorded by the Ili loess during the last glaciation in Central Asia: Evidence from grain-size and minerals

    NASA Astrophysics Data System (ADS)

    Song, Yougui; Zeng, Mengxiu; Chen, Xiuling; Li, Yue; Chang, Hong; An, Zhisheng; Guo, Xiaohua

    2018-04-01

    The loess record of Central Asia provides an important archive of regional climate 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 climatic changes during the last glaciation. The results indicated that most of the abrupt climatic 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 climatic signals may have been transmitted from Central Asia to the East Asian monsoon regions via the westerlies.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Work More? The 8.2 kaBP Abrupt Climate Change Event and the Origins of Irrigation Agriculture and Surplus Agro-Production in Mesopotamia

    NASA Astrophysics Data System (ADS)

    Weiss, H.

    2003-12-01

    The West Asian archaeological record is of sufficient transparency and resolution to permit observation of the social responses to the major Holocene abrupt climate change events at 8.2, 5.2 and 4.2 kaBP. The 8.2kaBP abrupt climate 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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).

  1. 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).

  2. Heinrich Events as an integral part of glacial-interglacial climate dynamics

    NASA Astrophysics Data System (ADS)

    Barker, S.; Knorr, G.; Zhang, X.; Gong, X.; Lohmann, G.; Bazin, L.

    2017-12-01

    Since their discovery in the 1980s Heinrich Events have provided a playground for climate scientists trying to understand the interactions between ice sheets and the ocean. Subsequently it has become clear that these interactions extend to almost all parts of the global climate system, from temperature, winds and rainfall to deep ocean currents and atmospheric CO2. Furthermore it remains unclear as to whether these dramatic events are a cause or consequence (or both) of regional to global perturbations in a range of parameters, including meridional overturning circulation within the Atlantic. Here we will discuss some of these aspects to highlight ongoing and future research related to Heinrich events and abrupt change more generally. We will discuss some of the possible triggers for H-events, including abrupt versus more gradual forcing mechanisms and conversely the potential influence of such events on the wider climate system, including deglacial climate change.

  3. Isotopic composition of ice core air reveals abrupt Antarctic warming during and after Heinrich Event 1a

    NASA Astrophysics Data System (ADS)

    Morgan, J. D.; Bereiter, B.; Baggenstos, D.; Kawamura, K.; Shackleton, S. A.; Severinghaus, J. P.

    2017-12-01

    Antarctic temperature variations during Heinrich events, as recorded by δ18O­ice­, generally show more gradual changes than the abrupt 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 abrupt warming between 16 and 15.8 kyr BP, manifest as an abrupt 1.25oC increase in the firn temperature gradient. To our knowledge, this would be the first evidence that such abrupt climate change has been recorded in an Antarctic climate 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.

  4. 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

  5. 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

  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. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. Percolation Features on Climate Network under Attacks of El Niño Events

    NASA Astrophysics Data System (ADS)

    Lu, Z.

    2015-12-01

    Percolation theory under different attacks is one of the main research areas in complex networks but never be applied to investigate climate network. In this study, for the first time we construct a climate network of surface air temperature field to analyze its percolation features. Here, we regard El Niño event as a kind of naturally attacks generated from Pacific Ocean to attack its upper climate network. We find that El Niño event leads an abrupt percolation phase transition to the climate network which makes it splitting and unstable suddenly. Comparing the results of the climate network under three different forms of attacks, including most connected attack (MA), localized attack (LA) and random attack (RA) respectively, it is found that both MA and LA lead first-order transition and RA leads second-order transition to the climate network. Furthermore, we find that most real attacks consist of all these three forms of attacks. With El Niño event emerging, the ratios of LA and MA increase and dominate the style of attack while RA decreasing. It means the percolation phase transition due to El Niño events is close to first-order transition mostly affected by LA and MA. Our research may help us further understand two questions from perspective of percolation on network: (1) Why not all warming in Pacific Ocean but El Niño events could affect the climate. (2) Why the climate affected by El Niño events changes abruptly.

  15. 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

  16. 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.

  17. The Role of African Dust in Atlantic Climate During Heinrich Events

    NASA Astrophysics Data System (ADS)

    Murphy, L. N.; Goes, M.; Clement, A. C.

    2017-11-01

    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 tropical aridity and dustiness. Although the driver of these events is still under debate, large freshwater input is necessary for climate models to simulate the magnitude, geographical extent, and abruptness of these events, indicating that they may be missing feedbacks. We hypothesize that the dust-climate feedback is one such feedback that has not been previously considered. Here we analyze the role of dust-climate 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 abruptly 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-climate feedbacks may provide amplification to Heinrich cooling by further weakening AMOC and increasing North Atlantic sea ice coverage.

  18. Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation.

    PubMed

    Chen, Tianyu; Robinson, Laura F; Burke, Andrea; Southon, John; Spooner, Peter; Morris, Paul J; Ng, Hong Chin

    2015-09-25

    Antarctic ice-core data reveal that the atmosphere experienced abrupt centennial increases in CO2 concentration during the last deglaciation (~18 thousand to 11 thousand years ago). Establishing the role of ocean circulation in these changes requires high-resolution, accurately dated marine records. Here, we report radiocarbon data from uranium-thorium-dated deep-sea corals in the Equatorial Atlantic and Drake Passage over the past 25,000 years. Two major deglacial radiocarbon shifts occurred in phase with centennial atmospheric CO2 rises at 14.8 thousand and 11.7 thousand years ago. We interpret these radiocarbon-enriched signals to represent two short-lived (less than 500 years) "overshoot" events, with Atlantic meridional overturning stronger than that of the modern era. These results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation. Copyright © 2015, American Association for the Advancement of Science.

  19. 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

  20. Lead-Lag relationships? Asynchrounous and Abrupt Shifts in Atmospheric Circulation, Temperature, and Vegetation during the 8.2 ka Event in the Eastern Mediterranean at Tenaghi Philippon, Greece

    NASA Astrophysics Data System (ADS)

    Niedermeyer, E. M.; Mulch, A.; Pross, J.

    2017-12-01

    The "8.2 ka event" has been an abrupt and prominent climate perturbation during the Holocene, and is characterized by an episode of generally colder and dryer conditions in the Northern Hemisphere realm. However, evidence to what extent this event has had an impact on climate in the Mediterranean region is ambiguous, in particular with respect to rainfall, temperature and vegetation change on land. Here we present a new, high-resolution record (ø 15 years during the event) of paleotemperatures from the Tenaghi Philippon peat deposit, Eastern Macedonia, Greece, using the MBT'/CBT index based on brGDGTs (branched Glycerol-Dialkyl-Glycerol-Tetraethers). Our data show fairly stable temperatures before the event, which is initiated at 8.1 ka by an abrupt and continuous cooling during the first 35 years of the event. After a short, 10-year episode of minimum temperatures, the event is ended by a similarly abrupt and continuous warming within 38 years. Comparison of our record with a previous study of the stable hydrogen isotopic composition of higher-plant waxes (δDwax) on the same core1 shows that changes in temperature occurred simultaneously with shifts in atmospherics moisture sources (Mediterranean vs Atlantic). Interestingly, further comparison of our data with a previous palynological study of the same core2 reveals that changes in vegetation associated with the 8.2 ka event precede shifts in hydrology and temperature by 100 years. This suggests either pronounced changes in seasonality of temperature and rainfall after the onset of the 8.2 ka event, i.e. at the peak of the event, or that changes in local atmospheric circulation (moisture sources) and temperature where not the initial trigger of changes in vegetation. References: Pross, J., Kotthoff, U., Müller, U.C., Peyron, O., Dormoy, I., Schmiedl, G., Kalaitzidis, S. and Smith, A.M. (2009): Massive perturbation in terrestrial ecosystems of the Eastern Mediterranean region associated with the 8.2 kyr B

  1. 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

  2. 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

  3. 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

  4. Modelling extreme climatic events in Guadalquivir Estuary ( Spain)

    NASA Astrophysics Data System (ADS)

    Delgado, Juan; Moreno-Navas, Juan; Pulido, Antoine; García-Lafuente, Juan; Calero Quesada, Maria C.; García, Rodrigo

    2017-04-01

    Extreme climatic events, such as heat waves and severe storms are predicted to increase in frequency and magnitude as a consequence of global warming but their socio-ecological effects are poorly understood, particularly in estuarine ecosystems. The Guadalquivir Estuary has been anthropologically modified several times, the original salt marshes have been transformed to grow rice and cotton and approximately one-fourth of the total surface of the estuary is now part of two protected areas, one of them is a UNESCO, MAB Biosphere Reserve. The climatic events are most likely to affect Europe in forthcoming decades and a further understanding how these climatic disturbances drive abrupt changes in the Guadalquivir estuary is needed. A barotropic model has been developed to study how severe storm events affects the estuary by conducting paired control and climate-events simulations. The changes in the local wind and atmospheric pressure conditions in the estuary have been studied in detail and several scenarios are obtained by running the model under control and real storm conditions. The model output has been validated with in situ water elevation and good agreement between modelled and real measurements have been obtained. Our preliminary results show that the model demonstrated the capability describe of the tide-surge levels in the estuary, opening the possibility to study the interaction between climatic events and the port operations and food production activities. The barotropic hydrodynamic model provide spatially explicit information on the key variables governing the tide dynamics of estuarine areas under severe climatic scenarios . The numerical model will be a powerful tool in future climate change mitigation and adaptation programs in a complex socio-ecological system.

  5. Did Heinrich Events Impact Climate in the Southwest Pacific? - Evidence From New Zealand Speleothems

    NASA Astrophysics Data System (ADS)

    Whittaker, T. E.; Hendy, C. H.; Hellstrom, J.

    2008-12-01

    Speleothems, layered calcium-carbonate cave deposits such as stalagmites, stalactites and flowstones, have been shown to offer much potential as paleoclimate archives. We present a new, high-resolution, independently-dated, paleoclimate record from a stalagmite which formed in Hollywood Cave (42.0°S, 171.5°E) on South Island, New Zealand. Over 700 stable oxygen and carbon isotope measurement pairs are supported by a chronology from 18 sequential 230Th dates. The stalagmite grew between 73 and 11 kyr B.P. Growth rates varied from ~1-54 mm/kyr and data resolution yields one sample per 10- 320 years. Weak covariance between δ13C and δ18O in the speleothem calcite suggests that recorded climate signals are primarily driven by mean annual precipitation amount and source. Both stable isotope proxies indicate relatively cold and dry conditions prevailed for much of the period 73-11 kyr B.P. However, abrupt-onset, millennial-scale shifts to wet and cool climate interrupt the dry conditions at 67.7-61, 56-55, 50.5-47.5, 40-39, 30.5-29, 25.5-24.3, 16.1-15, and 12.2-11.8 kyr B.P. Significantly, these eight abrupt climate changes occur synchronously with widely accepted ages for Heinrich events H6-H0 (including H5a). Many of these abrupt events can also be matched to known periods of glacier advance in the Southern Alps, New Zealand, which, arguably, were driven by increased mean annual precipitation and reduced potential for summer melting. In addition, preliminary stable isotope data (> 550 δ13C and δ18O pairs) from two North Island, New Zealand (~38°S), stalagmites will be shown that also displays abrupt shifts from relatively dry to wet climate during the period 60-6 kyr B.P. In combination, these results argue stongly for coeval climate changes in antipodean locations, and therefore provide compelling evidence for globally synchronous climate variability during the last glacial period.

  6. A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy

    NASA Astrophysics Data System (ADS)

    Rasmussen, Sune O.; Bigler, Matthias; Blockley, Simon P.; Blunier, Thomas; Buchardt, Susanne L.; Clausen, Henrik B.; Cvijanovic, Ivana; Dahl-Jensen, Dorthe; Johnsen, Sigfus J.; Fischer, Hubertus; Gkinis, Vasileios; Guillevic, Myriam; Hoek, Wim Z.; Lowe, J. John; Pedro, Joel B.; Popp, Trevor; Seierstad, Inger K.; Steffensen, Jørgen Peder; Svensson, Anders M.; Vallelonga, Paul; Vinther, Bo M.; Walker, Mike J. C.; Wheatley, Joe J.; Winstrup, Mai

    2014-12-01

    Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial-Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. North Pacific deglacial hypoxic events linked to abrupt ocean warming

    USGS Publications Warehouse

    Praetorius, Summer K; Mix, Alan C.; Davies, Maureen H.; Wolhowe, Matthew D; Addison, Jason A.; Prahl, Frederick G

    2015-01-01

    Marine sediments from the North Pacific document two episodes of expansion and strengthening of the subsurface oxygen minimum zone (OMZ) accompanied by seafloor hypoxia during the last deglacial transition1, 2, 3, 4. The mechanisms driving this hypoxia remain under debate1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. We present a new high-resolution alkenone palaeotemperature reconstruction from the Gulf of Alaska that reveals two abrupt warming events of 4–5 degrees Celsius at the onset of the Bølling and Holocene intervals that coincide with sudden shifts to hypoxia at intermediate depths. The presence of diatomaceous laminations and hypoxia-tolerant benthic foraminiferal species, peaks in redox-sensitive trace metals12, 13, and enhanced 15N/14N ratio of organic matter13, collectively suggest association with high export production. A decrease in 18O/16O values of benthic foraminifera accompanying the most severe deoxygenation event indicates subsurface warming of up to about 2 degrees Celsius. We infer that abrupt warming triggered expansion of the North Pacific OMZ through reduced oxygen solubility and increased marine productivity via physiological effects; following initiation of hypoxia, remobilization of iron from hypoxic sediments could have provided a positive feedback on ocean deoxygenation through increased nutrient utilization and carbon export. Such a biogeochemical amplification process implies high sensitivity of OMZ expansion to warming.

  13. Evidence of resilience to past climate change in Southwest Asia: Early farming communities and the 9.2 and 8.2 ka events

    NASA Astrophysics Data System (ADS)

    Flohr, Pascal; Fleitmann, Dominik; Matthews, Roger; Matthews, Wendy; Black, Stuart

    2016-03-01

    Climate change is often cited as a major factor in social change. The so-called 8.2 ka event was one of the most pronounced and abrupt Holocene cold and arid events. The 9.2 ka event was similar, albeit of a smaller magnitude. Both events affected the Northern Hemisphere climate and caused cooling and aridification in Southwest Asia. Yet, the impacts of the 8.2 and 9.2 ka events on early farming communities in this region are not well understood. Current hypotheses for an effect of the 8.2 ka event vary from large-scale site abandonment and migration (including the Neolithisation of Europe) to continuation of occupation and local adaptation, while impacts of the 9.2 ka have not previously been systematically studied. In this paper, we present a thorough assessment of available, quality-checked radiocarbon (14C) dates for sites from Southwest Asia covering the time interval between 9500 and 7500 cal BP, which we interpret in combination with archaeological evidence. In this way, the synchronicity between changes observed in the archaeological record and the rapid climate events is tested. It is shown that there is no evidence for a simultaneous and widespread collapse, large-scale site abandonment, or migration at the time of the events. However, there are indications for local adaptation. We conclude that early farming communities were resilient to the abrupt, severe climate changes at 9250 and 8200 cal BP.

  14. Climate Events and Cycles During the Last Glacial-Interglacial Transition

    NASA Astrophysics Data System (ADS)

    Lee, Eun Hee; Lee, Dae-Young; Park, Mi-Young

    2017-09-01

    During the last glacial-interglacial transition, there were multiple intense climatic events such as the Bølling-Allerød warming and Younger Dryas cooling. These events show abrupt and rapid climatic changes. In this study, the climate events and cycles during this interval are examined through wavelet analysis of Arctic and Antarctic ice-core 18O and tropical 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 tropical 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 tropical 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.

  15. Not Just the 8.2 event: Dynamic Early Holocene Climate in Arctic Canada

    NASA Astrophysics Data System (ADS)

    Axford, Y.; Briner, J. P.; Miller, G. H.; Francis, D. R.

    2006-12-01

    Temperature reconstructions from a lake in the eastern Canadian Arctic indicate that peak warmth in the early Holocene was interrupted by two abrupt, short-lived temperature reversals at ~9.l and ~8.5 ka. Summer temperatures at Lake CF8, Baffin Island (~500 km west of Greenland) are inferred from subfossil midge (Chironomidae) assemblages. Our results indicate that the site, like others on Baffin Island, experienced exceptionally warm summers (almost 5°C warmer than present) through much of the early Holocene, presumably in response to enhanced summer insolation. After 1000 years of very warm, stable climate, warmth was interrupted by two discrete cold reversals at ~9.1 and ~8.5 ka, during which multiple cold-stenothermous midge taxa appeared in the lake and summer temperatures dropped more than 3°C. These two clearly-defined reversals, well beyond the range of background variability, were of similar amplitude and duration, and were separated by several centuries of near-peak warmth. The only Holocene events of comparable amplitude at this site are the rapid onset of Holocene warmth, and the more gradual Neoglacial cooling after 8 ka. Abrupt cooling events over the Baffin region are consistent with model simulations of the impacts of freshwater outbursts into the Labrador Sea, such as the Lake Agassiz outburst flood that occurred ~8.4 ka. That there are two discrete events recorded at this site indicates that the "8.2 event" was not uniquely significant in this region; rather, the period between approximately ~9.2 and 8 ka was characterized by repeated climate fluctuations forced by multiple outburst floods or other mechanisms. Thus global correlations among paleoclimate records need not assume that climate perturbations during this time period necessarily correlate with the draining of Lake Agassiz or the 8.2 ka cooling in central Greenland.

  16. 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.

  17. Prehistoric land use and Neolithisation in Europe in the context of regional climate events

    NASA Astrophysics Data System (ADS)

    Lemmen, C.; Wirtz, K. W.; Gronenborn, D.

    2009-04-01

    We present a simple, adaptation-driven, spatially explicit model of pre-Bronze age socio-technological change, called the Global Land Use and Technological Evolution Simulator (GLUES). The socio-technological realm is described by three characteristic traits: available technology, subsistence style ratio, and economic diversity. Human population and culture develop in the context of global paleoclimate and regional paleoclimate events. Global paleoclimate is derived from CLIMBER-2 Earth System Model anomalies superimposed on the IIASA temperature and precipitation database. Regional a forcing is provided by abrupt climate deteriorations from a compilation of 138 long-term high-resolution climate proxy time series from mostly terrestrial and near-shore archives. The GLUES simulator provides for a novel way to explore the interplay between climate, climate change, and cultural evolution both on the Holocene timescale as well as for short-term extreme event periods. We sucessfully simulate the migration of people and the diffusion of Neolithic technology from the Near East into Europe in the period 12000-4000 a BP. We find good agreement with recent archeological compilations of Western Eurasian Neolithic sites. No causal relationship between climate events and cultural evolution could be identified, but the speed of cultural development is found to be modulated by the frequency of climate events. From the demographic evolution and regional ressource consumption, we estimate regional land use change and prehistoric greenhouse gas emissions.

  18. Rapid sea level rise and ice sheet response to 8,200-year climate event

    USGS Publications Warehouse

    Cronin, T. M.; Vogt, P.R.; Willard, D.A.; Thunell, R.; Halka, J.; Berke, M.; Pohlman, J.

    2007-01-01

    The largest abrupt climatic reversal of the Holocene interglacial, the cooling event 8.6–8.2 thousand years ago (ka), was probably caused by catastrophic release of glacial Lake Agassiz-Ojibway, which slowed Atlantic meridional overturning circulation (AMOC) and cooled global climate. Geophysical surveys and sediment cores from Chesapeake Bay reveal the pattern of sea level rise during this event. Sea level rose ∼14 m between 9.5 to 7.5 ka, a pattern consistent with coral records and the ICE-5G glacio-isostatic adjustment model. There were two distinct periods at ∼8.9–8.8 and ∼8.2–7.6 ka when Chesapeake marshes were drown as sea level rose rapidly at least ∼12 mm yr−1. The latter event occurred after the 8.6–8.2 ka cooling event, coincided with extreme warming and vigorous AMOC centered on 7.9 ka, and may have been due to Antarctic Ice Sheet decay.

  19. High-resolution Greenland ice core data show abrupt climate change happens in few years.

    PubMed

    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

    2008-08-01

    The last two abrupt 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 abrupt 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 abrupt 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.

  20. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage.

    PubMed

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-06-10

    Extreme climatic 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 climatic 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, abrupt 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 climate 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 climatic 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 climate change and prehistoric cultural transitions.

  1. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage

    PubMed Central

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-01-01

    Extreme climatic 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 climatic 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, abrupt 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 climate 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 climatic 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 climate change and prehistoric cultural transitions. PMID:27283832

  2. Abrupt Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions

    NASA Technical Reports Server (NTRS)

    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.; hide

    2014-01-01

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly 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 abrupt 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 climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

  3. Abrupt increases in Amazonian tree mortality due to drought-fire interactions.

    PubMed

    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

    2014-04-29

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly 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 abrupt 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 climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

  4. Abrupt increases in Amazonian tree mortality due to drought–fire interactions

    PubMed Central

    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.

    2014-01-01

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly 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 abrupt 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 climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change. PMID:24733937

  5. 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.

  6. Abrupt Climate Change in the Southern Great Plains during the Last Glacial Interval

    NASA Astrophysics Data System (ADS)

    Housson, A. L.; Maupin, C. R.; Roark, B.; Shen, C. C.; Baykara, O.; White, K.; Kampen-Lewis, S. V.; McChesney, C. L.

    2016-12-01

    Understanding how the climate of the North American Great Plains may change in the future is of tremendous socioeconomic importance, yet the regional response to previous abrupt global climate 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.

  7. 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.

  8. 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

  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. 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.

  11. Extreme temperatures, foundation species, and abrupt ecosystem change: an example from an iconic seagrass ecosystem.

    PubMed

    Thomson, Jordan A; Burkholder, Derek A; Heithaus, Michael R; Fourqurean, James W; Fraser, Matthew W; Statton, John; Kendrick, Gary A

    2015-04-01

    Extreme climatic events can trigger abrupt 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 climate 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 climate. 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 abrupt change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. 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

  12. Altered cropping pattern and cultural continuation with declined prosperity following abrupt and extreme arid event at ~4,200 yrs BP: Evidence from an Indus archaeological site Khirsara, Gujarat, western India.

    PubMed

    Pokharia, Anil K; Agnihotri, Rajesh; Sharma, Shalini; Bajpai, Sunil; Nath, Jitendra; Kumaran, R N; Negi, Bipin Chandra

    2017-01-01

    Archaeological sites hold important clues to complex climate-human relationships of the past. Human settlements in the peripheral zone of Indus culture (Gujarat, western India) are of considerable importance in the assessment of past monsoon-human-subsistence-culture relationships and their survival thresholds against climatic stress exerted by abrupt changes. During the mature phase of Harappan culture between ~4,600-3,900yrsBP, the ~4,100±100yrsBP time slice is widely recognized as one of the major, abrupt arid-events imprinted innumerous well-dated palaeo records. However, the veracity of this dry event has not been established from any archaeological site representing the Indus (Harappan) culture, and issues concerning timing, changes in subsistence pattern, and the likely causes of eventual abandonment (collapse) continue to be debated. Here we show a significant change in crop-pattern (from barley-wheat based agriculture to 'drought-resistant' millet-based crops) at ~4,200 yrs BP, based on abundant macrobotanical remains and C isotopes of soil organic matter (δ13CSOM) in an archaeological site at Khirsara, in the Gujarat state of western India. The crop-change appears to be intentional and was likely used as an adaptation measure in response to deteriorated monsoonal conditions. The ceramic and architectural remains of the site indicate that habitation survived and continued after the ~4,200yrsBP dry climatic phase, but with declined economic prosperity. Switching to millet-based crops initially helped inhabitants to avoid immediate collapse due to climatic stresses, but continued aridity and altered cropping pattern led to a decline in prosperity levels of inhabitants and eventual abandonment of the site at the end of the mature Harappan phase.

  13. 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.

  14. Millennial-scale precipitation variability over Easter Island (South Pacific) during MIS 3: inter-hemispheric teleconnections with North Atlantic abrupt cold events

    NASA Astrophysics Data System (ADS)

    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.

    2015-04-01

    Marine Isotope Stage 3 (MIS 3, 59.4-27.8 kyr BP) is characterized by the occurrence of rapid millennial-scale climate oscillations known as Dansgaard-Oeschger cycles (DO) and by abrupt 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 tropical and subtropical latitudes to these rapid climatic 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 tropical and subtropical band supporting a coherent regional picture, with the dominance of humid conditions in Southern Hemisphere tropical band during Heinrich Stadials (HS) 5, 5a and 6 and other Stadials while dry conditions prevailed in the Northern tropics. 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.

  15. "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.

  16. Altered cropping pattern and cultural continuation with declined prosperity following abrupt and extreme arid event at ~4,200 yrs BP: Evidence from an Indus archaeological site Khirsara, Gujarat, western India

    PubMed Central

    Pokharia, Anil K.; Sharma, Shalini; Bajpai, Sunil; Nath, Jitendra; Kumaran, R. N.; Negi, Bipin Chandra

    2017-01-01

    Archaeological sites hold important clues to complex climate-human relationships of the past. Human settlements in the peripheral zone of Indus culture (Gujarat, western India) are of considerable importance in the assessment of past monsoon-human-subsistence-culture relationships and their survival thresholds against climatic stress exerted by abrupt changes. During the mature phase of Harappan culture between ~4,600–3,900yrsBP, the ~4,100±100yrsBP time slice is widely recognized as one of the major, abrupt arid-events imprinted innumerous well-dated palaeo records. However, the veracity of this dry event has not been established from any archaeological site representing the Indus (Harappan) culture, and issues concerning timing, changes in subsistence pattern, and the likely causes of eventual abandonment (collapse) continue to be debated. Here we show a significant change in crop-pattern (from barley-wheat based agriculture to ‘drought-resistant’ millet-based crops) at ~4,200 yrs BP, based on abundant macrobotanical remains and C isotopes of soil organic matter (δ13CSOM) in an archaeological site at Khirsara, in the Gujarat state of western India. The crop-change appears to be intentional and was likely used as an adaptation measure in response to deteriorated monsoonal conditions. The ceramic and architectural remains of the site indicate that habitation survived and continued after the ~4,200yrsBP dry climatic phase, but with declined economic prosperity. Switching to millet-based crops initially helped inhabitants to avoid immediate collapse due to climatic stresses, but continued aridity and altered cropping pattern led to a decline in prosperity levels of inhabitants and eventual abandonment of the site at the end of the mature Harappan phase. PMID:28985232

  17. 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.

  18. 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.

  19. Are abrupt climate changes predictable?

    NASA Astrophysics Data System (ADS)

    Ditlevsen, Peter

    2013-04-01

    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 climate 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 climate 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 climate has been jumping between different quasi-stationary climates, 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

  20. Bayesian comparison of conceptual models of abrupt climate changes during the last glacial period

    NASA Astrophysics Data System (ADS)

    Boers, Niklas; Ghil, Michael; Rousseau, Denis-Didier

    2017-04-01

    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 abrupt climate 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 climatic 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

  1. Remote Detection and Modeling of Abrupt and Gradual Tree Mortality in the Southwestern USA

    NASA Astrophysics Data System (ADS)

    Muss, J. D.; Xu, C.; McDowell, N. G.

    2014-12-01

    Current climate 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 climate 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 abrupt 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 climate 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 abrupt 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-climate feedbacks, and improve our ability to predict what forests could look like in the future.

  2. 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.

  3. 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

  4. 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

  5. A role for land surface forcing of North Atlantic climate and isotope signals during the 8.2kyr event?

    NASA Astrophysics Data System (ADS)

    Hopcroft, Peter; Valdes, Paul

    2014-05-01

    An important example of abrupt climate change occurred 8200 years ago in the North Atlantic and is generally known as the 8.2kyr event. This abrupt ~160 year cooling appears to coincide with the final drainage of the ice-dammed Lakes Agassiz and Ojibway. The resultant influx of meltwater to the North Atlantic is assumed to have perturbed the Atlantic Meridional Overturning circulation, reducing northward heat transport and causing widespread cooling. Numerous lines of evidence support this theory, with reconstructions showing changes in deep water formation, reductions in salinity and evidence of sea-level rise. Coupled general circulation model (GCM) simulations driven with realistic estimates of the meltwater flux show a regional cooling but fail to replicate the duration or the magnitude of this event in comparison with proxy archives. Meltwater injection was not the only rapid climate forcing in operation at this time. Drainage of the pro-glacial lakes would have had a profound effect on the boundary layer heat fluxes over North America, with potential teleconnections further afield. In this work we use an isotope-enabled version of the coupled GCM HadCM3 with boundary conditions appropriate for the time period of 9kyr (including ice sheets, greenhouse gases and orbital parameters). This model tracks oxygen isotopes throughout the hydrological cycle allowing more robust comparison with proxy archives. We analyse the impact of the removal of a lake area corresponding to Lakes Agassiz and Ojibway at this time and present sensitivity tests designed to analyse the contributions from lake removal, orographic change and the assumed isotopic content of the pro-glacial lakes. The results show a distinct pattern of cooling across North America (in the annual mean) with an apparent teleconnection to the Barents Sea, where there is warming associated with sea-ice reduction. The isotopic implications depend on the initial isotopic content of the pro-glacial lake. Assuming

  6. 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

  7. 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.

  8. The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period

    NASA Astrophysics Data System (ADS)

    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

    2017-09-01

    Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate 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 climate. 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 (Abrupt Climate 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 Microsoft AccessTM at https://doi.org/10.1594/PANGAEA.870867.

  9. The Legacy of Episodic Climatic Events in Shaping Temperate, Broadleaf Forests

    NASA Technical Reports Server (NTRS)

    Pederson, Neil; Dyer, James M.; McEwan, Ryan W.; Hessl, Amy E.; Mock, Cary J.; Orwig, David A.; Rieder, Harald E.; Cook, Benjamin I.

    2015-01-01

    subcontinental scale during the late-1600s suggesting that this event was severe enough to open large canopy gaps. These disturbances and their climatic drivers support the hypothesis that punctuated, episodic, climatic events impart a legacy in broadleaf-dominated forests centuries after their occurrence. Given projections of future drought, these results also reveal the potential for abrupt, meso- to large-scale forest change in broadleaf-dominated forests over future decades.

  10. Holocene climate and cultural evolution in late prehistoric-early historic West Asia

    NASA Astrophysics Data System (ADS)

    Staubwasser, Michael; Weiss, Harvey

    2006-11-01

    The precipitation climatology and the underlying climate mechanisms of the eastern Mediterranean, West Asia, and the Indian subcontinent are reviewed, with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation. Holocene climate change of the region is summarized from proxy records. The Indian monsoon weakened during the Holocene over its northernmost region, the Ganges and Indus catchments and the western Arabian Sea. Southern regions, the Indian Peninsula, do not show a reduction, but an increase of summer monsoon rain across the Holocene. The long-term trend towards drier conditions in the eastern Mediterranean can be linked to a regionally complex monsoon evolution. Abrupt climate change events, such as the widespread droughts around 8200, 5200 and 4200 cal yr BP, are suggested to be the result of altered subtropical upper-level flow over the eastern Mediterranean and Asia. The abrupt climate change events of the Holocene radically altered precipitation, fundamental for cereal agriculture, across the expanse of late prehistoric-early historic cultures known from the archaeological record in these regions. Social adaptations to reduced agro-production, in both dry-farming and irrigation agriculture regions, are visible in the archaeological record during each abrupt climate change event in West Asia. Chronological refinement, in both the paleoclimate and archaeological records, and transfer functions for both precipitation and agro-production are needed to understand precisely the evident causal linkages.

  11. Abrupt decadal-to-centennial hydroclimate changes in the Mediterranean region since the mid-Holocene

    NASA Astrophysics Data System (ADS)

    Hu, Hsun-Ming; Shen, Chuan-Chou; Jiang, Xiuyang; Wang, Yongjin; Mii, Horng-Sheng; Michel, Véronique

    2016-04-01

    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 climate 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 abrupt 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 climate 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 climate 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 climate teleconnection.

  12. Ecosystem resilience to abrupt late Quaternary change in continental southern Siberia

    NASA Astrophysics Data System (ADS)

    Harding, Poppy; Mackay, Anson; Bezrukova, Elena; Shchetnikov, Alexander

    2017-04-01

    Quaternary climate variability is dominated by long term orbital forcing along with abrupt 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 abrupt climatic 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 climatic 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 climate 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

  13. 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

  14. 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.

  15. Will extreme climatic events facilitate biological invasions?

    USDA-ARS?s Scientific Manuscript database

    Extreme climatic events, such as intense heat waves, hurricanes, floods and droughts, can dramatically affect ecological and evolutionary processes, and more extreme events are projected with ongoing climate change. However, the implications of these events for biological invasions, which themselves...

  16. 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.

  17. Abrupt and unexpected stressful life events are followed with increased disease activity in spondyloarthritis: a two years web-based cohort study.

    PubMed

    Luo, Guanguan; Boelle, Pierre Yves; Turbelin, Clément; Costantino, Félicie; Kerneis, Solen; Nahal, Roula Said; Breban, Maxime; Hanslik, Thomas

    2018-06-05

    The contribution of environmental factors to spondyloarthritis (SpA) course remains poorly characterized. We previously reported a possible triggering of disease flares by stressful life events and vaccination. The objective of the present study was to specify the types of vaccine and life event that may influence disease activity. A prospective cohort of adult SpA was followed for two years. Patients logged on to a secured website every month to complete a standardized auto-questionnaire. They reported whether they had been exposed to stressful life events, vaccinations or other environmental factors. Patients were asked to rate the distress resulting from exposure to life events on a numerical rating scale (NRS: 0-10). Primary outcome variable was the variation of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) measured on two consecutive connections. Months where an event occurred were compared to months without events. The cutoff value of 1 is defined as the minimal clinically important variation for the BASDAI. The 272 enrolled SpA patients returned 3,388 questionnaires. Months where an abrupt and unexpected traumatic event occurred were associated with a significant increase of BASDAI of 0.57 [95%CI: 0.29; 0.85] (p<0.001). The higher the rating of distress, the larger the impact on BASDAI, reaching a clinically meaningful increase of 0.99 [0.17; 1.82] for a VNS ≥9. The effect of stressful events on BASDAI persisted during a median of 3 months. No other environmental factor was significantly associated with BASDAI variations. Among stressful life events, abrupt and unexpected events were associated with transient worsening of disease activity in SpA, which reached a clinically meaningful increase for the highest rating of distress. Association between vaccines and disease flare was not confirmed. Copyright © 2018. Published by Elsevier Masson SAS.

  18. Globally synchronous ice core volcanic tracers and abrupt cooling during the last glacial period

    USGS Publications Warehouse

    Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.

    2006-01-01

    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 abrupt climate 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 abrupt 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.

  19. Palaeoclimate: ocean tides and Heinrich events.

    PubMed

    Arbic, Brian K; Macayeal, Douglas R; Mitrovica, Jerry X; Milne, Glenn A

    2004-11-25

    Climate varied enormously over the most recent ice age--for example, large pulses of ice-rafted debris, originating mainly from the Labrador Sea, were deposited into the North Atlantic at roughly 7,000-year intervals, with global climatic implications. Here we show that ocean tides within the Labrador Sea were exceptionally large over the period spanning these huge, abrupt ice movements, which are known as Heinrich events. We propose that tides played a catalytic role in liberating iceberg armadas during that time.

  20. 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.

  1. To what extent can global warming events influence scaling properties of climatic fluctuations in glacial periods?

    NASA Astrophysics Data System (ADS)

    Alberti, Tommaso; Lepreti, Fabio; Vecchio, Antonio; Carbone, Vincenzo

    2017-04-01

    The Earth's climate is an extremely unstable complex system consisting of nonlinear and still rather unknown interactions among atmosphere, land surface, ice and oceans. The system is mainly driven by solar irradiance, even if internal components as volcanic eruptions and human activities affect the atmospheric composition thus acting as a driver for climate changes. Since the extreme climate variability is the result of a set of phenomena operating from daily to multi-millennial timescales, with different correlation times, a study of the scaling properties of the system can evidence non-trivial persistent structures, internal or external physical processes. Recently, the scaling properties of the paleoclimate changes have been analyzed by distinguish between interglacial and glacial climates [Shao and Ditlevsen, 2016]. The results show that the last glacial record (20-120 kyr BP) presents some elements of multifractality, while the last interglacial period (0-10 kyr BP), say the Holocene period, seems to be characterized by a mono-fractal structure. This is associated to the absence of Dansgaard-Oeschger (DO) events in the interglacial climate that could be the cause for the absence of multifractality. This hypothesis is supported by the analysis of the period between 18 and 27 kyr BP, i.e. during the Last Glacial Period, in which a single DO event have been registred. Through the Empirical Mode Decomposition (EMD) we were able to detect a timescale separation within the Last Glacial Period (20-120 kyr BP) in two main components: a high-frequency component, related to the occurrence of DO events, and a low-frequency one, associated to the cooling/warming phase switch [Alberti et al., 2014]. Here, we investigate the scaling properties of the climate fluctuations within the Last Glacial Period, where abrupt climate changes, characterized by fast increase of temperature usually called Dansgaard-Oeschger (DO) events, have been particularly pronounced. By using the

  2. Investigating the Influence of Climate Changes on Rodent Communities at a Regional-Scale (MIS 1-3, Southwestern France)

    PubMed Central

    Royer, Aurélien; Montuire, Sophie; Legendre, Serge; Discamps, Emmanuel; Jeannet, Marcel; Lécuyer, Christophe

    2016-01-01

    Terrestrial ecosystems have continuously evolved throughout the Late Pleistocene and the Holocene, deeply affected by both progressive environmental and climatic modifications, as well as by abrupt and large climatic changes such as the Heinrich or Dansgaard-Oeschger events. Yet, the impacts of these different events on terrestrial mammalian communities are poorly known, as is the role played by potential refugia on geographical species distributions. This study examines community changes in rodents of southwestern France between 50 and 10 ky BP by integrating 94 dated faunal assemblages coming from 37 archaeological sites. This work reveals that faunal distributions were modified in response to abrupt and brief climatic events, such as Heinrich events, without actually modifying the rodent community on a regional scale. However, the succession of events which operated between the Late Pleistocene and the Holocene gradually led to establishing a new rodent community at the regional scale, with intermediate communities occurring between the Bølling and the Allerød. PMID:26789523

  3. Public perceptions of climate change and extreme weather events

    NASA Astrophysics Data System (ADS)

    Bruine de Bruin, W.; Dessai, S.; Morgan, G.; Taylor, A.; Wong-Parodi, G.

    2013-12-01

    Climate experts face a serious communication challenge. Public debate about climate change continues, even though at the same time people seem to complain about extreme weather events becoming increasingly common. As compared to the abstract concept of ';climate change,' (changes in) extreme weather events are indeed easier to perceive, more vivid, and personally relevant. Public perception research in different countries has suggested that people commonly expect that climate change will lead to increases in temperature, and that unseasonably warm weather is likely to be interpreted as evidence of climate change. However, relatively little is known about whether public concerns about climate change may also be driven by changes in other types of extreme weather events, such as exceptional amounts of precipitation or flooding. We therefore examined how perceptions of and personal experiences with changes in these specific weather events are related to public concerns about climate change. In this presentation, we will discuss findings from two large public perception surveys conducted in flood-prone Pittsburgh, Pennsylvania (US) and with a national sample in the UK, where extreme flooding has recently occurred across the country. Participants completed questions about their perceptions of and experiences with specific extreme weather events, and their beliefs about climate change. We then conducted linear regressions to predict individual differences in climate-change beliefs, using perceptions of and experiences with specific extreme weather events as predictors, while controlling for demographic characteristics. The US study found that people (a) perceive flood chances to be increasing over the decades, (b) believe climate change to play a role in increases in future flood chances, and (c) would interpret future increases in flooding as evidence for climate change. The UK study found that (a) UK residents are more likely to perceive increases in ';wet' events such

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

    PubMed Central

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

    2008-01-01

    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. PMID:18772385

  5. Abrupt Climatic Change during the Latest Maastrichtian: Establishing Robust Temporal Links with the Onset of Deccan Volcanism and K/Pg Mass Extinction

    NASA Astrophysics Data System (ADS)

    Barnet, J.; Littler, K.; Kroon, D.; Leng, M. J.; Westerhold, T.; Roehl, U.; Zachos, J. C.

    2017-12-01

    A transient period of climate change, characterized by a global warming of 2.5-5°C followed by a cooling to pre-excursion conditions, occurred during the last 300 kyr of the Maastrichtian ( 66.34-66.02 Ma). This instability may have played a role in destabilizing marine and terrestrial ecosystems, priming the system for abrupt extinction at the K-Pg boundary, likely triggered by a large bolide impact. This pre-K-Pg warming event has often been linked to the main phase of Deccan Trap volcanism, however large uncertainties associated with radio-isotopic dating methods of basalts, along with low sedimentation rates and hiatuses in many studied sedimentary sequences, have long hampered a definitive correlation. To complement recent advances in dating of the traps, we have generated the first complete and highest resolution (2.5-4 kyr) benthic stable δ13C and δ18O record for the final million years of the Maastrichtian using the epifaunal foraminifera species Nuttallides truempyi from ODP Site 1262, Walvis Ridge, South Atlantic, calibrated to an updated orbitally-tuned age model. We then compare our data to other previously published geochemical data from other sites in the high, middle, and low latitudes. Our data confirms that the onset of the warming event coincides with the onset of the main phase of Deccan volcanism, strongly suggesting a causal link. Furthermore, spectral analysis of our extended late Maastrichtian-Early Eocene record suggests that the onset of the warming event corresponds to a 405-kyr eccentricity minima, in contrast to many transient warming events (hyperthermals) of the Paleogene, suggesting a control by orbital forcing alone is unlikely. A peculiar feature of the event, compared to other hyperthermals, is a muted carbon cycle response during warming, which may be related to the comparatively heavier δ13C signature of volcanogenic CO2 (-7‰), compared to other sources of light carbon invoked to explain Paleogene hyperthermals. The warming

  6. Role of the Bering Strait on the hysteresis of the ocean conveyor belt circulation and glacial climate stability.

    PubMed

    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

    2012-04-24

    Abrupt climate 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 climate 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 abrupt climate transitions. Hence, it is argued that even for greenhouse warming, abrupt climate transitions similar to those in the last glacial time are unlikely to occur as the Bering Strait remains open.

  7. Revisiting Lake Hämelsee: reconstructing abrupt Lateglacial climate transitions using state- of-the-art palaeoclimatological proxies

    NASA Astrophysics Data System (ADS)

    Engels, Stefan; Hoek, Wim; Lane, Christine; Sachse, Dirk; Wagner-Cremer, Friederike

    2015-04-01

    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 abrupt 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 climatic conditions. The results provide important insights into the nature of the abrupt climate 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.

  8. Future climate risk from compound events

    NASA Astrophysics Data System (ADS)

    Zscheischler, Jakob; Westra, Seth; van den Hurk, Bart J. J. M.; Seneviratne, Sonia I.; Ward, Philip J.; Pitman, Andy; AghaKouchak, Amir; Bresch, David N.; Leonard, Michael; Wahl, Thomas; Zhang, Xuebin

    2018-06-01

    Floods, wildfires, heatwaves and droughts often result from a combination of interacting physical processes across multiple spatial and temporal scales. The combination of processes (climate drivers and hazards) leading to a significant impact is referred to as a `compound event'. Traditional risk assessment methods typically only consider one driver and/or hazard at a time, potentially leading to underestimation of risk, as the processes that cause extreme events often interact and are spatially and/or temporally dependent. Here we show how a better understanding of compound events may improve projections of potential high-impact events, and can provide a bridge between climate scientists, engineers, social scientists, impact modellers and decision-makers, who need to work closely together to understand these complex events.

  9. Paleoecological evidence for abrupt cold reversals during peak Holocene warmth on Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Axford, Yarrow; Briner, Jason P.; Miller, Gifford H.; Francis, Donna R.

    2009-03-01

    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 climate 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, abrupt climate shifts in the early Holocene illustrate the susceptibility of the climate system to perturbations, even during periods of enhanced warmth in the Northern Hemisphere.

  10. Quantifying the effect of trend, fluctuation, and extreme event of climate change on ecosystem productivity.

    PubMed

    Liu, Yupeng; Yu, Deyong; Su, Yun; Hao, Ruifang

    2014-12-01

    Climate change comprises three fractions of trend, fluctuation, and extreme event. Assessing the effect of climate change on terrestrial ecosystem requires an understanding of the action mechanism of these fractions, respectively. This study examined 11 years of remotely sensed-derived net primary productivity (NPP) to identify the impacts of the trend and fluctuation of climate change as well as extremely low temperatures caused by a freezing disaster on ecosystem productivity in Hunan province, China. The partial least squares regression model was used to evaluate the contributions of temperature, precipitation, and photosynthetically active radiation (PAR) to NPP variation. A climatic signal decomposition and contribution assessment model was proposed to decompose climate factors into trend and fluctuation components. Then, we quantitatively evaluated the contributions of each component of climatic factors to NPP variation. The results indicated that the total contribution of the temperature, precipitation, and PAR to NPP variation from 2001 to 2011 in Hunan province is 85 %, and individual contributions of the temperature, precipitation, and PAR to NPP variation are 44 % (including 34 % trend contribution and 10 % fluctuation contribution), 5 % (including 4 % trend contribution and 1 % fluctuation contribution), and 36 % (including 30 % trend contribution and 6 % fluctuation contribution), respectively. The contributions of temperature fluctuation-driven NPP were higher in the north and lower in the south, and the contributions of precipitation trend-driven NPP and PAR fluctuation-driven NPP are higher in the west and lower in the east. As an instance of occasionally triggered disturbance in 2008, extremely low temperatures and a freezing disaster produced an abrupt decrease of NPP in forest and grass ecosystems. These results prove that the climatic trend change brought about great impacts on ecosystem productivity and that climatic fluctuations and

  11. Attribution of extreme weather and climate-related events.

    PubMed

    Stott, Peter A; Christidis, Nikolaos; Otto, Friederike E L; Sun, Ying; Vanderlinden, Jean-Paul; van Oldenborgh, Geert Jan; Vautard, Robert; von Storch, Hans; Walton, Peter; Yiou, Pascal; Zwiers, Francis W

    2016-01-01

    Extreme weather and climate-related events occur in a particular place, by definition, infrequently. It is therefore challenging to detect systematic changes in their occurrence given the relative shortness of observational records. However, there is a clear interest from outside the climate science community in the extent to which recent damaging extreme events can be linked to human-induced climate change or natural climate variability. Event attribution studies seek to determine to what extent anthropogenic climate change has altered the probability or magnitude of particular events. They have shown clear evidence for human influence having increased the probability of many extremely warm seasonal temperatures and reduced the probability of extremely cold seasonal temperatures in many parts of the world. The evidence for human influence on the probability of extreme precipitation events, droughts, and storms is more mixed. Although the science of event attribution has developed rapidly in recent years, geographical coverage of events remains patchy and based on the interests and capabilities of individual research groups. The development of operational event attribution would allow a more timely and methodical production of attribution assessments than currently obtained on an ad hoc basis. For event attribution assessments to be most useful, remaining scientific uncertainties need to be robustly assessed and the results clearly communicated. This requires the continuing development of methodologies to assess the reliability of event attribution results and further work to understand the potential utility of event attribution for stakeholder groups and decision makers. WIREs Clim Change 2016, 7:23-41. doi: 10.1002/wcc.380 For further resources related to this article, please visit the WIREs website.

  12. Patterns of human occupation during the early Holocene in the Central Ebro Basin (NE Spain) in response to the 8.2 ka climatic event

    NASA Astrophysics Data System (ADS)

    González-Sampériz, P.; Utrilla, P.; Mazo, C.; Valero-Garcés, B.; Sopena, MC.; Morellón, M.; Sebastián, M.; Moreno, A.; Martínez-Bea, M.

    2009-03-01

    The Central Ebro River Basin (NE Spain) is the most northern area of truly semi-arid Mediterranean climate in Europe and prehistoric human occupation there has been strongly influenced by this extreme environmental condition. Modern climate conditions single out this region due to the harsh environment, characterised by the highest absolute summer temperatures of the Ebro River Basin. The Bajo Aragón region (SE Ebro River Basin) was intensively populated during the Early Holocene (9400-8200 cal yr BP) but the settlements were abandoned abruptly at around 8200 cal yr BP. We propose that this "archaeological silence" was caused by the regional impact of the global abrupt 8.2 ka cold event. Available regional paleoclimate archives demonstrate the existence of an aridity crisis then that interrupted the humid Early Holocene. That environmental crisis would have forced hunter-gatherer groups from the Bajo Aragón to migrate to regions with more favourable conditions (i.e. more humid mountainous areas) and only return in the Neolithic. Coherently, archaeological sites persist during this crisis in the nearby Iberian Range (Maestrazgo) and the North Ebro River area (Pre-Pyrenean mountains and along the northwestern Ebro Basin).

  13. Extreme Weather Events and Climate Change Attribution

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

    Thomas, Katherine

    A report from the National Academies of Sciences, Engineering, and Medicine concludes it is now possible to estimate the influence of climate change on some types of extreme events. The science of extreme event attribution has advanced rapidly in recent years, giving new insight to the ways that human-caused climate change can influence the magnitude or frequency of some extreme weather events. This report examines the current state of science of extreme weather attribution, and identifies ways to move the science forward to improve attribution capabilities. Confidence is strongest in attributing types of extreme events that are influenced by climatemore » change through a well-understood physical mechanism, such as, the more frequent heat waves that are closely connected to human-caused global temperature increases, the report finds. Confidence is lower for other types of events, such as hurricanes, whose relationship to climate change is more complex and less understood at present. For any extreme event, the results of attribution studies hinge on how questions about the event's causes are posed, and on the data, modeling approaches, and statistical tools chosen for the analysis.« less

  14. Financial market response to extreme events indicating climatic change

    NASA Astrophysics Data System (ADS)

    Anttila-Hughes, J. K.

    2016-05-01

    A variety of recent extreme climatic events are considered to be strong evidence that the climate is warming, but these incremental advances in certainty often seem ignored by non-scientists. I identify two unusual types of events that are considered to be evidence of climate change, announcements by NASA that the global annual average temperature has set a new record, and the sudden collapse of major polar ice shelves, and then conduct an event study to test whether news of these events changes investors' valuation of energy companies, a subset of firms whose future performance is closely tied to climate change. I find evidence that both classes of events have influenced energy stock prices since the 1990s, with record temperature announcements on average associated with negative returns and ice shelf collapses associated with positive returns. I identify a variety of plausible mechanisms that may be driving these differential responses, discuss implications for energy markets' views on long-term regulatory risk, and conclude that investors not only pay attention to scientifically significant climate events, but discriminate between signals carrying different information about the nature of climatic change.

  15. Diatoms as Proxies for Abrupt Events in the Hudson River Estuary

    NASA Astrophysics Data System (ADS)

    Skorski, W.; Abbott, D. H.; Recasens, C.; Breger, D. L.

    2014-12-01

    The Hudson River estuary has been subject to many abrupt 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 tropical 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). Tropical 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

  16. Relative sea-level data from southwest Scotland constrain meltwater-driven sea-level jumps prior to the 8.2 kyr BP event

    NASA Astrophysics Data System (ADS)

    Lawrence, Thomas; Long, Antony J.; Gehrels, W. Roland; Jackson, Luke P.; Smith, David E.

    2016-11-01

    The most significant climate cooling of the Holocene is centred on 8.2 kyr BP (the '8.2 event'). Its cause is widely attributed to an abrupt slowdown of the Atlantic Meridional Overturning Circulation (AMOC) associated with the sudden drainage of Laurentide proglacial Lakes Agassiz and Ojibway, but model simulations have difficulty reproducing the event with a single-pulse scenario of freshwater input. Several lines of evidence point to multiple episodes of freshwater release from the decaying Laurentide Ice Sheet (LIS) between ∼8900 and ∼8200 cal yr BP, yet the precise number, timing and magnitude of these events - critical constraints for AMOC simulations - are far from resolved. Here we present a high-resolution relative sea level (RSL) record for the period 8800 to 7800 cal yr BP developed from estuarine and salt-marsh deposits in SW Scotland. We find that RSL rose abruptly in three steps by 0.35 m, 0.7 m and 0.4 m (mean) at 8760-8640, 8595-8465, 8323-8218 cal yr BP respectively. The timing of these RSL steps correlate closely with short-lived events expressed in North Atlantic proxy climate and oceanographic records, providing evidence of at least three distinct episodes of enhanced meltwater discharge from the decaying LIS prior to the 8.2 event. Our observations can be used to test the fidelity of both climate and ice-sheet models in simulating abrupt change during the early Holocene.

  17. NASA Climate Days: Promoting Climate Literacy One Ambassador and One Event at a Time

    NASA Astrophysics Data System (ADS)

    Weir, H. M.; Lewis, P. M.; Chambers, L. H.; Millham, R. A.; Richardson, A.

    2012-12-01

    With so many informal outreach and education venues across the world, leveraging them for climate education allows vast amounts of information to be translated to the public in a familiar setting through trusted local sources. One of the challenges is the development of an effective process for training informal educators and providing them with adequate support materials. The 'NASA Climate Day Kit', and its related training strategy for Earth Ambassadors, is designed to address some of these issues. The purpose of the NASA Climate Day project is to collect existing NASA climate education materials, assemble a cadre of informal educators, and provide professional development on the subject of climate change. This training is accomplished through a series of exercises, games, science talks and place-based training. After their training and immersion in climate-related content, participants develop and implement a climate event at their local informal education venue. Throughout their training the Earth Ambassadors are exposed to a wide array of climate related exercises and background content. Some of these include one-on-one science content talks with NASA scientists who study climate on a daily basis. This allows the Ambassador to have direct access to new cutting edge data and information. To complement the science talks, participants explore activities and games that can engage all ages at their climate event. During their training, they also explore the 'Climate Day Kit'. This Kit is an assemblage of climate-related materials created by various NASA groups. Key components of this Kit include data visualizations, articles, electronic reference material, science talks, NASA Education and Public Outreach (E/PO) climate materials, and examples of Climate Day events that have been conducted in the past. As an on-going resource and to use for their own climate event, each group of Earth Ambassadors has access to a dynamic website that hosts all of the science

  18. Compound-Specific Hydrogen Isotopic Records of Holocene Climate Dynamics in the Northeastern U.S.

    NASA Astrophysics Data System (ADS)

    Stefanescu, I.; Shuman, B. N.

    2017-12-01

    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 abrupt climate changes and variations over the past 14 ka. Over the Holocene, the region's long-term climate 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 abrupt climate changes punctuate the long-term trends, even after the widely recognized events associated with the LIS and AMOC, but the mechanisms behind the abrupt climate changes observed are not well understood. To understand the mechanisms behind abrupt climate shifts, their impact on hydrology, ecosystems, regional and local climates, 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 climate 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 climate trends across the region from an isotopic perspective and to assess changes in the spatial isotopic gradients across the northeastern US during the Holocene.

  19. Evaluation of the significance of abrupt changes in precipitation and runoff process in China

    NASA Astrophysics Data System (ADS)

    Xie, Ping; Wu, Ziyi; Sang, Yan-Fang; Gu, Haiting; Zhao, Yuxi; Singh, Vijay P.

    2018-05-01

    Abrupt changes are an important manifestation of hydrological variability. How to accurately detect the abrupt 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 abrupt 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 abrupt change component. A bigger value of correlation coefficient reflects a higher significance level of abrupt 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 abrupt change. The approach was derived from the relationship between correlation coefficient index and abrupt change, and can estimate and grade the significance levels of abrupt changes in hydrological time series. Application of the proposed approach to ten major watersheds in China showed that abrupt changes mainly occurred in five watersheds in northern China, which have arid or semi-arid climate 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, abrupt changes in the latter were more significant. Compared with abrupt changes in annual precipitation, human activities contributed much more to the abrupt changes in the corresponding SWRA, except for the Northwest Inland River watershed.

  20. Extreme weather and climate events with ecological relevance: a review.

    PubMed

    Ummenhofer, Caroline C; Meehl, Gerald A

    2017-06-19

    Robust evidence exists that certain extreme weather and climate events, especially daily temperature and precipitation extremes, have changed in regard to intensity and frequency over recent decades. These changes have been linked to human-induced climate change, while the degree to which climate change impacts an individual extreme climate event (ECE) is more difficult to quantify. Rapid progress in event attribution has recently been made through improved understanding of observed and simulated climate variability, methods for event attribution and advances in numerical modelling. Attribution for extreme temperature events is stronger compared with other event types, notably those related to the hydrological cycle. Recent advances in the understanding of ECEs, both in observations and their representation in state-of-the-art climate models, open new opportunities for assessing their effect on human and natural systems. Improved spatial resolution in global climate models and advances in statistical and dynamical downscaling now provide climatic information at appropriate spatial and temporal scales. Together with the continued development of Earth System Models that simulate biogeochemical cycles and interactions with the biosphere at increasing complexity, these make it possible to develop a mechanistic understanding of how ECEs affect biological processes, ecosystem functioning and adaptation capabilities. Limitations in the observational network, both for physical climate system parameters and even more so for long-term ecological monitoring, have hampered progress in understanding bio-physical interactions across a range of scales. New opportunities for assessing how ECEs modulate ecosystem structure and functioning arise from better scientific understanding of ECEs coupled with technological advances in observing systems and instrumentation.This article is part of the themed issue 'Behavioural, ecological and evolutionary responses to extreme climatic events

  1. Transitions between multiple equilibria of paleo climate: a glimpse in to the dynamics of abrupt climate change

    NASA Astrophysics Data System (ADS)

    Ferreira, David; Marshall, John; Ito, Takamitsu; McGee, David; Moreno-Chamarro, Eduardo

    2017-04-01

    The dynamics regulating large climatic 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 climate is endowed with multiple equilibrium states of global extent. Such states are commonly found in low-order or conceptual climate models, but it is unclear whether a system as complex as Earth's climate can sustain multiple equilibrium states. Here we report that multiple equilibrium states of the climate 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 climate with a small Northern hemisphere sea ice cap and a large southern one and a Cold climate with large ice caps at both poles. The dynamical states of the Warm and Cold solutions exhibit striking similarities with our present-day climate and the climate 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 climates.

  2. Extreme weather and climate events with ecological relevance: a review

    PubMed Central

    Meehl, Gerald A.

    2017-01-01

    Robust evidence exists that certain extreme weather and climate events, especially daily temperature and precipitation extremes, have changed in regard to intensity and frequency over recent decades. These changes have been linked to human-induced climate change, while the degree to which climate change impacts an individual extreme climate event (ECE) is more difficult to quantify. Rapid progress in event attribution has recently been made through improved understanding of observed and simulated climate variability, methods for event attribution and advances in numerical modelling. Attribution for extreme temperature events is stronger compared with other event types, notably those related to the hydrological cycle. Recent advances in the understanding of ECEs, both in observations and their representation in state-of-the-art climate models, open new opportunities for assessing their effect on human and natural systems. Improved spatial resolution in global climate models and advances in statistical and dynamical downscaling now provide climatic information at appropriate spatial and temporal scales. Together with the continued development of Earth System Models that simulate biogeochemical cycles and interactions with the biosphere at increasing complexity, these make it possible to develop a mechanistic understanding of how ECEs affect biological processes, ecosystem functioning and adaptation capabilities. Limitations in the observational network, both for physical climate system parameters and even more so for long-term ecological monitoring, have hampered progress in understanding bio-physical interactions across a range of scales. New opportunities for assessing how ECEs modulate ecosystem structure and functioning arise from better scientific understanding of ECEs coupled with technological advances in observing systems and instrumentation. This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic

  3. Abrupt climate change around 4 ka BP: Role of the Thermohaline circulation as indicated by a GCM experiment

    NASA Astrophysics Data System (ADS)

    Wang, Shaowu; Zhou, Tianjun; Cai, Jingning; Zhu, Jinhong; Xie, Zhihui; Gong, Daoyi

    2004-04-01

    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 climate-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 abrupt climate change at 4.0 ka BP is one of the realizations of the cold phase in millennial scale climate 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.

  4. Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event.

    PubMed

    Petrenko, Vasilii V; Smith, Andrew M; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F; Severinghaus, Jeffrey P

    2017-08-23

    Methane (CH 4 ) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane ( 14 CH 4 ) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt warming event that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today's natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal event was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.

  5. Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt warming event

    NASA Astrophysics Data System (ADS)

    Petrenko, Vasilii V.; Smith, Andrew M.; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F.; Severinghaus, Jeffrey P.

    2017-08-01

    Methane (CH4) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane (14CH4) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt warming event that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today’s natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal event was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal warming are comparable to those of the current anthropogenic warming, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.

  6. 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

  7. Genetic and life-history consequences of extreme climate events

    PubMed Central

    Mangel, Marc; Jesensek, Dusan; Garza, John Carlos; Crivelli, Alain J.

    2017-01-01

    Climate change is predicted to increase the frequency and intensity of extreme climate events. Tests on empirical data of theory-based predictions on the consequences of extreme climate events are thus necessary to understand the adaptive potential of species and the overarching risks associated with all aspects of climate change. We tested predictions on the genetic and life-history consequences of extreme climate events in two populations of marble trout Salmo marmoratus that have experienced severe demographic bottlenecks due to flash floods. We combined long-term field and genotyping data with pedigree reconstruction in a theory-based framework. Our results show that after flash floods, reproduction occurred at a younger age in one population. In both populations, we found the highest reproductive variance in the first cohort born after the floods due to a combination of fewer parents and higher early survival of offspring. A small number of parents allowed for demographic recovery after the floods, but the genetic bottleneck further reduced genetic diversity in both populations. Our results also elucidate some of the mechanisms responsible for a greater prevalence of faster life histories after the extreme event. PMID:28148745

  8. Genetic and life-history consequences of extreme climate events.

    PubMed

    Vincenzi, Simone; Mangel, Marc; Jesensek, Dusan; Garza, John Carlos; Crivelli, Alain J

    2017-02-08

    Climate change is predicted to increase the frequency and intensity of extreme climate events. Tests on empirical data of theory-based predictions on the consequences of extreme climate events are thus necessary to understand the adaptive potential of species and the overarching risks associated with all aspects of climate change. We tested predictions on the genetic and life-history consequences of extreme climate events in two populations of marble trout Salmo marmoratus that have experienced severe demographic bottlenecks due to flash floods. We combined long-term field and genotyping data with pedigree reconstruction in a theory-based framework. Our results show that after flash floods, reproduction occurred at a younger age in one population. In both populations, we found the highest reproductive variance in the first cohort born after the floods due to a combination of fewer parents and higher early survival of offspring. A small number of parents allowed for demographic recovery after the floods, but the genetic bottleneck further reduced genetic diversity in both populations. Our results also elucidate some of the mechanisms responsible for a greater prevalence of faster life histories after the extreme event. © 2017 The Author(s).

  9. Recent advances on reconstruction of climate and extreme events in China for the past 2000 year

    NASA Astrophysics Data System (ADS)

    Zheng, Jingyun; Hao, Zhixin; Ge, Quansheng; Liu, Yang

    2016-04-01

    The study of regional climate changes for past 2000 year could present spatial pattern of climate variation and various historical analogues for the sensitivity and operation of the climate system (e.g., the modulations of internal variability, feedbacks and teleconnections, abrupt changes and regional extreme events, etc.) from inter-annual to centennial scales and provide the knowledge to predict and project climate in the near future. China is distinguished by a prominent monsoon climate in east, continental arid climate in northwest and high land cold climate in Qinghai-Tibetan Plateau located at southwest. The long history of civilization and the variety of climate in China provides an abundant and well-dated documentary records and a wide range of natural archives (e.g., tree-ring, ice core, stalagmite, varved lake sediment, etc.) for high-resolution paleoclimate reconstruction. This paper presented a review of recent advances on reconstruction of climate and extreme events in China for the past 2000 years. In recent 10 years, there were many new high-resolution paleoclimatic reconstructions reported in China, e.g., the annual and decadal resolution series of temperature and precipitation in eastern China derived from historical documents, in western China derived from tree-ring and other natural archives. These new reconstructions provided more proxies and better spatial coverage to understand the characteristics of climate change over China and the uncertainty of regional reconstructions, as well as to reconstruct the high-resolution temperature series and the spatial pattern of precipitation change for whole China in the past millenniums by synthesizing the multi-proxy together. The updated results show that, in China, the warm intervals for the past 2000 years were in AD 1-200, AD 551-760, AD 951-1320, and after AD 1921; as well as the cold intervals were in AD 201-350, AD 441-530, AD 781-950, and AD 1321-1920. The extreme cold winters occurred in periods

  10. Climate Change Extreme Events: Meeting the Information Needs of Water Resource Managers

    NASA Astrophysics Data System (ADS)

    Quay, R.; Garfin, G. M.; Dominguez, F.; Hirschboeck, K. K.; Woodhouse, C. A.; Guido, Z.; White, D. D.

    2013-12-01

    Information about climate has long been used by water managers to develop short term and long term plans and strategies for regional and local water resources. Inherent within longer term forecasts is an element of uncertainty, which is particularly evident in Global Climate model results for precipitation. For example in the southwest estimates in the flow of the Colorado River based on GCM results indicate changes from 120% or current flow to 60%. Many water resource managers are now using global climate model down scaled estimates results as indications of potential climate change as part of that planning. They are addressing the uncertainty within these estimates by using an anticipatory planning approach looking at a range of possible futures. One aspect of climate that is important for such planning are estimates of future extreme storm (short term) and drought (long term) events. However, the climate science of future possible changes in extreme events is less mature than general climate change science. At a recent workshop among climate scientists and water managers in the southwest, it was concluded the science of climate change extreme events is at least a decade away from being robust enough to be useful for water managers in their water resource management activities. However, it was proposed that there are existing estimates and records of past flooding and drought events that could be combined with general climate change science to create possible future events. These derived events could be of sufficient detail to be used by water resource managers until such time that the science of extreme events is able to provide more detailed estimates. Based on the results of this workshop and other work being done by the Decision Center for a Desert City at Arizona State University and the Climate Assessment for the Southwest center at University of Arizona., this article will 1) review what are the extreme event data needs of Water Resource Managers in the

  11. Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

    PubMed

    Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

    2012-11-01

    Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

  12. Abrupt shift in the observed runoff from the southwestern Greenland ice sheet

    PubMed Central

    Ahlstrøm, Andreas P.; Petersen, Dorthe; Langen, Peter L.; Citterio, Michele; Box, Jason E.

    2017-01-01

    The recent decades of accelerating mass loss of the Greenland ice sheet have arisen from an increase in both surface meltwater runoff and ice flow discharge from tidewater glaciers. Despite the role of the Greenland ice sheet as the dominant individual cryospheric contributor to sea level rise in recent decades, no observational record of its mass loss spans the 30-year period needed to assess its climatological state. We present for the first time a 40-year (1975–2014) time series of observed meltwater discharge from a >6500-km2 catchment of the southwestern Greenland ice sheet. We find that an abrupt 80% increase in runoff occurring between the 1976–2002 and 2003–2014 periods is due to a shift in atmospheric circulation, with meridional exchange events occurring more frequently over Greenland, establishing the first observation-based connection between ice sheet runoff and climate change. PMID:29242827

  13. Extrinsic regime shifts drive abrupt changes in regeneration dynamics at upper treeline in the Rocky Mountains, U.S.A.

    PubMed

    Elliott, Grant P

    2012-07-01

    Given the widespread and often dramatic influence of climate change on terrestrial ecosystems, it is increasingly common for abrupt threshold changes to occur, yet explicitly testing for climate and ecological regime shifts is lacking in climatically sensitive upper treeline ecotones. In this study, quantitative evidence based on empirical data is provided to support the key role of extrinsic, climate-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 abrupt 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 climate conditions apparently triggered an abrupt increase in establishment that was unprecedented during the period of record. Two main findings emerge from this research that underscore the critical role of climate in governing regeneration dynamics within upper treeline ecotones. (1) Regional climate variability is capable of exceeding bioclimatic thresholds, thereby initiating synchronous and abrupt changes in the spatial and temporal patterns of tree establishment at broad

  14. Changes in the Perceived Risk of Climate Change: Evidence from Sudden Climatic Events

    NASA Astrophysics Data System (ADS)

    Anttila-Hughes, J. K.

    2009-12-01

    In the course of the past two decades the threat of anthropogenic climate change has moved from a scientific concern of relative obscurity to become one of the largest environmental and public goods problems in history. During this period public understanding of the risk of climate change has shifted from negligible to quite large. In this paper I propose a means of quantifying this change by examining how sudden events supporting the theory of anthropogenic climate change have affected carbon intensive companies' stock prices. Using CAPM event study methodology for companies in several carbon-intensive industries, I find strong evidence that markets have been reacting to changes in the scientific evidence for climate change for some time. Specifically, the change in magnitude of response over time seems to indicate that investors believed climate change was a potentially serious risk to corporate profits as early as the mid 1990s. Moreover, market reaction dependence on event type indicates that investors are differentiating between different advances in the scientific knowledge. Announcements by NASA GISS that the previous year was a “record hot year” for the globe are associated with negative excess returns, while news of ice shelf collapses are associated with strong positive excess returns. These results imply that investors are aware of how different aspects of climate change will affect carbon intensive companies, specifically in terms of the link between warming in general and polar ice cover. This implies that policy choices based on observable public opinion have lagged actual private concern over climate change's potential threat.

  15. Climate change, extreme weather events, and us health impacts: what can we say?

    PubMed

    Mills, David M

    2009-01-01

    Address how climate change impacts on a group of extreme weather events could affect US public health. A literature review summarizes arguments for, and evidence of, a climate change signal in select extreme weather event categories, projections for future events, and potential trends in adaptive capacity and vulnerability in the United States. Western US wildfires already exhibit a climate change signal. The variability within hurricane and extreme precipitation/flood data complicates identifying a similar climate change signal. Health impacts of extreme events are not equally distributed and are very sensitive to a subset of exceptional extreme events. Cumulative uncertainty in forecasting climate change driven characteristics of extreme events and adaptation prevents confidently projecting the future health impacts from hurricanes, wildfires, and extreme precipitation/floods in the United States attributable to climate change.

  16. The Abrupt Onset of the Modern South Asian Monsoon Winds (iodp Exp. 359)

    NASA Astrophysics Data System (ADS)

    Betzler, C.; Eberli, G. P.; Kroon, D.; Wright, J. D.; Swart, P. K.; Nath, B. N.; Reijmer, J.; Alvarez Zarikian, C. A.

    2016-12-01

    The South Asian Monson (SAM) is one of the most extreme features in Earth's climate 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 climatic 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 abrupt onset of the SAM-linked ocean circulation pattern and its relationship to the long term Neogene climate 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 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 sedimentary 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.

  17. Changes in the Perceived Risk of Climate Change: Evidence from Sudden Climatic Events

    NASA Astrophysics Data System (ADS)

    Anttila-Hughes, J. K.

    2009-12-01

    In the course of the past two decades the threat of anthropogenic climate change has moved from a scientific concern of relative obscurity to become one of the largest environmental and public goods problems in history. During this period public understanding of the risk of climate change has shifted from negligible to quite large. In this paper I propose a means of quantifying this change by examining how sudden events supporting the theory of anthropogenic climate change have affected carbon intensive companies' stock prices. Using CAPM event study methodology for companies in several carbon-intensive industries, I find strong evidence that markets have been reacting to changes in the scientific evidence for climate change for some time. Specifically, the change in magnitude of response over time seems to indicate that investors believed climate change was a potentially serious risk to corporate profits as early as the mid 1990s. Moreover, market reaction dependence on event type indicates that investors are differentiating between different advances in the scientific knowledge. Announcements by NASA GISS that the previous year was a “record hot year” for the globe are associated with negative excess returns, while news of ice shelf collapses are associated with strong positive excess returns. These results imply that investors are aware of how different aspects of climate change will affect carbon intensive companies, specifically in terms of the link between warming in general and polar ice cover.

  18. The impacts of climate change on the risk of natural disasters.

    PubMed

    van Aalst, Maarten K

    2006-03-01

    Human emissions of greenhouse gases are already changing our climate. This paper provides an overview of the relation between climate change and weather extremes, and examines three specific cases where recent acute events have stimulated debate on the potential role of climate change: the European heatwave of 2003; the risk of inland flooding, such as recently in Central Europe and Great Britain; and the harsh Atlantic hurricane seasons of 2004 and 2005. Furthermore, it briefly assesses the relation between climate change and El Niño, and the potential of abrupt climate change. Several trends in weather extremes are sufficiently clear to inform risk reduction efforts. In many instances, however, the potential increases in extreme events due to climate change come on top of alarming rises in vulnerability. Hence, the additional risks due to climate change should not be analysed or treated in isolation, but instead integrated into broader efforts to reduce the risk of natural disasters.

  19. Constructing regional climate networks in the Amazonia during recent drought events.

    PubMed

    Guo, Heng; Ramos, Antônio M T; Macau, Elbert E N; Zou, Yong; Guan, Shuguang

    2017-01-01

    Climate networks are powerful approaches to disclose tele-connections in climate systems and to predict severe climate events. Here we construct regional climate networks from precipitation data in the Amazonian region and focus on network properties under the recent drought events in 2005 and 2010. Both the networks of the entire Amazon region and the extreme networks resulted from locations severely affected by drought events suggest that network characteristics show slight difference between the two drought events. Based on network degrees of extreme drought events and that without drought conditions, we identify regions of interest that are correlated to longer expected drought period length. Moreover, we show that the spatial correlation length to the regions of interest decayed much faster in 2010 than in 2005, which is because of the dual roles played by both the Pacific and Atlantic oceans. The results suggest that hub nodes in the regional climate network of Amazonia have fewer long-range connections when more severe drought conditions appeared in 2010 than that in 2005.

  20. Extreme climate events counteract the effects of climate and land-use changes in Alpine treelines

    PubMed Central

    Barros, Ceres; Guéguen, Maya; Douzet, Rolland; Carboni, Marta; Boulangeat, Isabelle; Zimmermann, Niklaus E.; Münkemüller, Tamara; Thuiller, Wilfried

    2017-01-01

    Summary 1. Climate change and extreme events, such as drought, threaten ecosystems worldwide and in particular mountain ecosystems, where species often live at their environmental tolerance limits. In the European Alps, plant communities are also influenced by land-use abandonment leading to woody encroachment of subalpine and alpine grasslands. 2. In this study, we explored how the forest–grassland ecotone of Alpine treelines will respond to gradual climate warming, drought events and land-use change in terms of forest expansion rates, taxonomic diversity and functional composition. We used a previously validated dynamic vegetation model, FATE-HD, parameterised for plant communities in the Ecrins National Park in the French Alps. 3. Our results showed that intense drought counteracted the forest expansion at higher elevations driven by land-use abandonment and climate change, especially when combined with high drought frequency (occurring every 2 or less than 2 years). 4. Furthermore, intense and frequent drought accelerated the rates of taxonomic change and resulted in overall higher taxonomic spatial heterogeneity of the ecotone than would be expected under gradual climate and land-use changes only. 5. Synthesis and applications. The results from our model show that intense and frequent drought counteracts forest expansion driven by climate and land-use changes in the forest–grassland ecotone of Alpine treelines. We argue that land-use planning must consider the effects of extreme events, such as drought, as well as climate and land-use changes, since extreme events might interfere with trends predicted under gradual climate warming and agricultural abandonment. PMID:28670002

  1. Abrupt termination of Marine Isotope Stage 16 (Termination VII) at 631.5 ka in Santa Barbara Basin, Californi

    USGS Publications Warehouse

    Dean, Walter E.; Kennett, James P.; Behl, Richard J.; Nicholson, Craig; Sorlien, Christopher C.

    2015-01-01

    The Marine Isotope Stage 16–15 boundary (Termination VII) is the first deglacial warming step of the late Quaternary following the mid-Pleistocene transition (MPT), when 41 kyr climatic cycles shifted to strong 100 kyr cycles. The detailed structure of this important climatic event has remained unknown until now. Core MV0508-19JPC from Santa Barbara Basin, California, contains a decadal-scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (<700 years), in a progression of three abrupt warming steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably abrupt with 4–5°C sea surface warming in ~50 years. The deglacial sequence contains the well-dated Lava Creek tephra (631.3 ± 4 ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5 ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal-scale negative excursions in δ13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level. A warm interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox-sensitive elements indicating sulfidic, oxygen-deficient bottom and pore-waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean-atmosphere system following the MPT.

  2. Are Madrean ecosystems approaching tipping points? Anticipating interactions of landscape disturbance and climate change

    Treesearch

    Donald A. Falk

    2013-01-01

    Contemporary climate change is driving transitions in many Madrean ecosystems, but the time scale of these changes is accelerated greatly by severe landscape disturbances such as wildfires and insect outbreaks. Landscape-scale disturbance events such as wildfires interact with prior disturbance patterns and landscape structure to catalyze abrupt transitions to novel...

  3. Climate modelling of mass-extinction events: a review

    NASA Astrophysics Data System (ADS)

    Feulner, Georg

    2009-07-01

    Despite tremendous interest in the topic and decades of research, the origins of the major losses of biodiversity in the history of life on Earth remain elusive. A variety of possible causes for these mass-extinction events have been investigated, including impacts of asteroids or comets, large-scale volcanic eruptions, effects from changes in the distribution of continents caused by plate tectonics, and biological factors, to name but a few. Many of these suggested drivers involve or indeed require changes of Earth's climate, which then affect the biosphere of our planet, causing a global reduction in the diversity of biological species. It can be argued, therefore, that a detailed understanding of these climatic variations and their effects on ecosystems are prerequisites for a solution to the enigma of biological extinctions. Apart from investigations of the paleoclimate data of the time periods of mass extinctions, climate-modelling experiments should be able to shed some light on these dramatic events. Somewhat surprisingly, however, only a few comprehensive modelling studies of the climate changes associated with extinction events have been undertaken. These studies will be reviewed in this paper. Furthermore, the role of modelling in extinction research in general and suggestions for future research are discussed.

  4. The 9.2 ka event in Asian summer monsoon area: the strongest millennial scale collapse of the monsoon during the Holocene

    NASA Astrophysics Data System (ADS)

    Zhang, Wenchao; Yan, Hong; Dodson, John; Cheng, Peng; Liu, Chengcheng; Li, Jianyong; Lu, Fengyan; Zhou, Weijian; An, Zhisheng

    2018-04-01

    Numerous Holocene paleo-proxy records exhibit a series of centennial-millennial scale rapid climatic events. Unlike the widely acknowledged 8.2 ka climate anomaly, the likelihood of a significant climate excursion at around 9.2 cal ka BP, which has been notably recognized in some studies, remains to be fully clarified in terms of its magnitude and intensity, as well as its characteristics and spatial distributions in a range of paleoclimatic records. In this study, a peat sediment profile from the Dajiuhu Basin in central China was collected with several geochemical proxies and a pollen analysis carried out to help improve understanding of the climate changes around 9.2 cal ka BP. The results show that the peat development was interrupted abruptly at around 9.2 cal ka BP, when the chemical weathering strength decreased and the tree-pollen declined. This suggests that a strong drier regional climatic event occurred at around 9.2 cal ka BP in central China, which was, in turn, probably connected to the rapid 9.2 ka climate event co-developing worldwide. In addition, based on the synthesis of our peat records and the other Holocene hydrological records from Asian summer monsoon (ASM) region, we further found that the 9.2 ka event probably constituted the strongest abrupt collapse of the Asian monsoon system during the full Holocene interval. The correlations between ASM and the atmospheric 14C production rate, the North Atlantic drift ice records and Greenland temperature indicated that the weakened ASM event at around 9.2 cal ka BP could be interpreted by the co-influence of external and internal factors, related to the changes of the solar activity and the Atlantic Meridional Overturning Circulation (AMOC).

  5. Ocean circulation and climate during the past 120,000 years

    NASA Astrophysics Data System (ADS)

    Rahmstorf, Stefan

    2002-09-01

    Oceans cover more than two-thirds of our blue planet. The waters move in a global circulation system, driven by subtle density differences and transporting huge amounts of heat. Ocean circulation is thus an active and highly nonlinear player in the global climate game. Increasingly clear evidence implicates ocean circulation in abrupt and dramatic climate shifts, such as sudden temperature changes in Greenland on the order of 5-10 °C and massive surges of icebergs into the North Atlantic Ocean - events that have occurred repeatedly during the last glacial cycle.

  6. Centennial-to-millennial scale climate change during the last 100,000 years: a Southern Hemisphere perspective

    NASA Astrophysics Data System (ADS)

    van den Bos, Valerie; Rees, Andrew; Newnham, Rewi; Augustinus, Paul

    2017-04-01

    The response of past terrestrial ecosystems to abrupt climate change is central to the debate surrounding the consequences of future climate 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 climate records from the polar and tropical 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 climate system in relation to global patterns over the last 100 kyr by developing high-resolution climate 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 abrupt climate change events or changes in seasonality influenced climate 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 tropics.

  7. Climate forcing due to the 8200 cal yr BP event observed at Early Neolithic sites in the eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Weninger, Bernhard; Alram-Stern, Eva; Bauer, Eva; Clare, Lee; Danzeglocke, Uwe; Jöris, Olaf; Kubatzki, Claudia; Rollefson, Gary; Todorova, Henrieta; van Andel, Tjeerd

    2006-11-01

    We explore the hypothesis that the abrupt drainage of Laurentide lakes and associated rapid switch of the North Atlantic thermohaline circulation 8200 yr ago had a catastrophic influence on Neolithic civilisation in large parts of southeastern Europe, Anatolia, Cyprus, and the Near East. The event at 8200 cal yr BP is observed in a large number of high-resolution climate proxies in the Northern Hemisphere, and in many cases corresponds to markedly cold and arid conditions. We identify the relevant archaeological levels of major Neolithic settlements in Central Anatolia, Cyprus, Greece and Bulgaria, and examine published stratigraphic, architectural, cultural and geoarchaeological studies for these sites. The specific archaeological events and processes we observe at a number of these sites during the study interval 8400-8000 cal yr BP lead us to refine some previously established Neolithisation models. The introduction of farming to South-East Europe occurs in all study regions (Thrace, Macedonia, Thessaly, Bulgaria) near 8200 cal yr BP. We observe major disruptions of Neolithic cultures in the Levant, North Syria, South-East Anatolia, Central Anatolia and Cyprus, at the same time. We conclude that the 8200 cal yr BP aridity event triggered the spread of early farmers, by different routes, out of West Asia and the Near East into Greece and Bulgaria.

  8. Observation and analysis of abrupt changes in the interplanetary plasma velocity and magnetic field.

    NASA Technical Reports Server (NTRS)

    Martin, R. N.; Belcher, J. W.; Lazarus, A. J.

    1973-01-01

    This paper presents a limited study of the physical nature of abrupt changes in the interplanetary plasma velocity and magnetic field based on 19 day's data from the Pioneer 6 spacecraft. The period was chosen to include a high-velocity solar wind stream and low-velocity wind. Abrupt events were accepted for study if the sum of the energy density in the magnetic field and velocity changes was above a specified minimum. A statistical analysis of the events in the high-velocity solar wind stream shows that Alfvenic changes predominate. This conclusion is independent of whether steady state requirements are imposed on conditions before and after the event. Alfvenic changes do not dominate in the lower-speed wind. This study extends the plasma field evidence for outwardly propagating Alfvenic changes to time scales as small as 1 min (scale lengths on the order of 20,000 km).

  9. Modeling geologically abrupt climate changes in the Miocene

    NASA Astrophysics Data System (ADS)

    Haupt, B. J.; Seidov, D.

    2010-12-01

    The gradual cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically abrupt 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.

  10. Conceptualizing Holistic Community Resilience to Climate Events: Foundation for a Climate Resilience Screening Index

    EPA Science Inventory

    The concept of resilience has been evolving over the past decade as a way to address the current and future challenges nations, states, and cities face from a changing climate. Understanding how the environment (natural and built), climate event risk, societal interactions, and g...

  11. Simultaneous abrupt shifts in hydrology and fish assemblage structure in a floodplain lake in the central Amazon

    PubMed Central

    Röpke, Cristhiana P.; Amadio, Sidinéia; Zuanon, Jansen; Ferreira, Efrem J. G.; Deus, Cláudia Pereira de; Pires, Tiago H. S.; Winemiller, Kirk O.

    2017-01-01

    Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon. PMID:28071701

  12. Simultaneous abrupt shifts in hydrology and fish assemblage structure in a floodplain lake in the central Amazon.

    PubMed

    Röpke, Cristhiana P; Amadio, Sidinéia; Zuanon, Jansen; Ferreira, Efrem J G; Deus, Cláudia Pereira de; Pires, Tiago H S; Winemiller, Kirk O

    2017-01-10

    Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon.

  13. Impact of an extreme climatic event on community assembly.

    PubMed

    Thibault, Katherine M; Brown, James H

    2008-03-04

    Extreme climatic events are predicted to increase in frequency and magnitude, but their ecological impacts are poorly understood. Such events are large, infrequent, stochastic perturbations that can change the outcome of entrained ecological processes. Here we show how an extreme flood event affected a desert rodent community that has been monitored for 30 years. The flood (i) caused catastrophic, species-specific mortality; (ii) eliminated the incumbency advantage of previously dominant species; (iii) reset long-term population and community trends; (iv) interacted with competitive and metapopulation dynamics; and (v) resulted in rapid, wholesale reorganization of the community. This and a previous extreme rainfall event were punctuational perturbations-they caused large, rapid population- and community-level changes that were superimposed on a background of more gradual trends driven by climate and vegetation change. Captured by chance through long-term monitoring, the impacts of such large, infrequent events provide unique insights into the processes that structure ecological communities.

  14. Arctic climate tipping points.

    PubMed

    Lenton, Timothy M

    2012-02-01

    There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate 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 climate 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 climate tipping points.

  15. Abrupt change of Antarctic moisture origin at the end of Termination II

    PubMed Central

    Masson-Delmotte, V.; Stenni, B.; Blunier, T.; Cattani, O.; Chappellaz, J.; Cheng, H.; Dreyfus, G.; Edwards, R. L.; Falourd, S.; Govin, A.; Kawamura, K.; Johnsen, S. J.; Jouzel, J.; Landais, A.; Lemieux-Dudon, B.; Lourantou, A.; Marshall, G.; Minster, B.; Mudelsee, M.; Pol, K.; Röthlisberger, R.; Selmo, E.; Waelbroeck, C.

    2010-01-01

    The deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin. New data obtained from the European Project for Ice Coring in Antarctica Dome C East Antarctic ice core provide new insights on the sequence of events involved in Termination II, the transition between the penultimate glacial and interglacial periods. This termination is marked by a north–south seesaw behavior, with first a slow methane concentration rise associated with a strong Antarctic temperature warming and a slow deuterium excess rise. This first step is followed by an abrupt north Atlantic warming, an abrupt resumption of the East Asian summer monsoon, a sharp methane rise, and a CO2 overshoot, which coincide within dating uncertainties with the end of Antarctic optimum. Here, we show that this second phase is marked by a very sharp Dome C centennial deuterium excess rise, revealing abrupt reorganization of atmospheric circulation in the southern Indian Ocean sector. PMID:20566887

  16. Imminent onset and abrupt increase in duration of low aragonite and calcite saturation state events in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Friedrich, T.; Hauri, C.; Timmermann, A.

    2015-12-01

    Rapid progression of ocean acidification is a threat to key organisms of the Southern Ocean ecosystem. While the severity of ocean acidification impacts is mainly determined by the duration, intensity, and spatial extent of low aragonite or calcite saturation state events, little is known about the nature of these events, their evolving attributes, and the timing of their onset. Using output of historical and RCP 8.5 simulations from ten Earth System Models from CMIP5, we found that aragonite undersaturation, which decreases the calcification rate of pteropods and causes dissolution of their aragonitic shell, will spread rapidly after 2035, covering 70 % of the Southern Ocean surface waters by 2095. Surface aragonite undersaturation events will last for about 5 months in areas south of 60°S by 2055, and for more than 8 months by the end of the century. Overall, the duration of these events increases from 1 month to more than 6 months within fewer than 20 years in >75 % of the affected area. This abrupt change in exposure duration to unfavorable conditions may be too fast for pteropods to adapt, as these chemical changes will occur within just a few generations. As a result of two month-long calcite undersaturation events projected for the end of this century, even organisms built of the more stable calcium carbonate mineral calcite will face prolonged chemical dissolution. The threat of ocean acidification to the Southern Ocean ecosystem may be more imminent than previously thought, and may spread quickly to the southern tips of New Zealand, South America, and South Africa, with potentially far-reaching consequences to fisheries, local economies, and livelihoods.

  17. Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960 2000: Evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate-induced variations

    NASA Astrophysics Data System (ADS)

    Oguz, Temel; Gilbert, Denis

    2007-02-01

    Functioning of the Black Sea ecosystem has profoundly changed since the early 1970s under cumulative effects of excessive nutrient enrichment, strong cooling/warming, over-exploitation of pelagic fish stocks, and population outbreak of gelatinous carnivores. Applying a set of criteria to the long-term (1960-2000) ecological time-series data, the present study demonstrates that the Black Sea ecosystem was reorganised during this transition phase in different forms of top-down controlled food web structure through successive regime-shifts of distinct ecological properties. The Secchi disc depth, oxic-anoxic interface zone, dissolved oxygen and hydrogen sulphide concentrations also exhibit abrupt transition between their alternate regimes, and indicate tight coupling between the lower trophic food web structure and the biogeochemical pump in terms of regime-shift events. The first shift, in 1973-1974, marks a switch from large predatory fish to small planktivore fish-controlled system, which persisted until 1989 in the form of increasing small pelagic and phytoplankton biomass and decreasing zooplankton biomass. The increase in phytoplankton biomass is further supported by a bottom-up contribution due to the cumulative response to high anthropogenic nutrient load and the concurrent shift of the physical system to the "cold climate regime" following its ˜20-year persistence in the "warm climate regime". The end of the 1980s signifies the depletion of small planktivores and the transition to a gelatinous carnivore-controlled system. By the end of the 1990s, small planktivore populations take over control of the system again. Concomitantly, their top-down pressure when combined with diminishing anthropogenic nutrient load and more limited nutrient supply into the surface waters due to stabilizing effects of relatively warm winter conditions switched the "high production" regime of phytoplankton to its background "low production" regime. The Black Sea regime

  18. Towards Greenland Glaciation: cumulative or abrupt transition?

    NASA Astrophysics Data System (ADS)

    Ramstein, Gilles; Tan, Ning; Ladant, Jean-baptiste; Dumas, Christophe; Contoux, Camille

    2017-04-01

    During the mid-Pliocene warming period (3-3.3 Ma BP), the global annual mean temperatures inferred by data and model studies were 2-3° warmer than pre-industrial values. Accordingly, Greenland ice sheet volume is supposed to reach at the most, only half of that of present-day [Haywood et al. 2010]. Around 2.7-2.6 Ma BP, just ˜ 500 kyr after the warming peak of mid-Pliocene, the Greenland ice sheet has reached its full size [Lunt et al. 2008]. A crucial question concerns the evolution of the Greenland ice sheet from half to full size during the 3 - 2.5 Ma period. Data show a decreasing trend of atmospheric CO2 concentration from 3 Ma to 2.5 Ma [Seki et al.2010; Bartoli et al. 2011; Martinez et al. 2015]. However, a recent study [Contoux et al. 2015] suggests that a lowering of CO2 is not sufficient to initiate a perennial glaciation on Greenland and must be combined with low summer insolation to preserve the ice sheet during insolation maxima. This suggests rather a cumulative process than an abrupt event. In order to diagnose the evolution of the ice sheet build-up, we carry on, for the first time, a transient simulation of climate and ice sheet evolutions from 3 Ma to 2.5 Ma. This strategy enables us to investigate the waxing and waning of the ice sheet during several orbital cycles. We use a tri-dimensional interpolation method designed by Ladant et al. (2014), which allows the evolution of CO2 concentration and of orbital parameters, and the evolution of the Greenland ice sheet size to be taken into account. By interpolating climatic snapshot simulations ran with various possible combinations of CO2, orbits and ice sheet sizes, we can build a continuous climatic forcing that is then used to provide 500 kyrs-long ice sheet simulations. With such a tool, we may offer a physically based answer to different CO2 reconstructions scenarios and analyse which one is the most consistent with Greenland ice sheet buildup.

  19. 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.

  20. Microbial Community Dynamics from Permafrost Across the Pleistocene-Holocene Boundary and Response to Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Hammad, A.; Mahony, M.; Froese, D. G.; Lanoil, B. D.

    2014-12-01

    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 abrupt 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 climate 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 climate change across the P/H boundary, providing insight into the changes that the soil community is currently undergoing in this modern era of rapid climate 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

  1. Effect of the Bering Strait on the AMOC hysteresis and glacial climate stability (Invited)

    NASA Astrophysics Data System (ADS)

    Hu, A.; Meehl, G. A.; Han, W.; Timmermann, A.; Otto-Bliesner, B. L.; Liu, Z.; Abe-Ouchi, A.

    2013-12-01

    Abrupt climate transitions, such as Dansgaard-Oeschger and Heinrich events, occurred frequently during the last glacial period, especially from 80 - 11 thousand years before present, but were nearly absent during Holocene and the early stages of last glacial period. Here we show, with a fully coupled climate 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 Atlantic meridional overturning circulation (AMOC) to create conditions that are conducive to triggering abrupt climate transitions. Hence, it is argued that even for greenhouse warming, abrupt climate transitions similar to those in the last glacial time are unlikely to occur as the Bering Strait remains open. Qualitatively the same result is arrived in new simulations by employing the glacial background conditions using the same climate model. Theoretical and simulated AMOC hysteresis curves (a, b) and the associated changes of Greenland surface temperature and meridional heat transport at 65°N in the Atlantic (c, d). In panel a), 'S' is the bifurcation point beyond which AMOC collapses and the '+/-F' values indicate the freshwater forcing strength. In panels b), c), and d), the black/red (blue/green) lines are for the closed (open) BS simulation. The black/blue (red/green) lines represent the phase of freshwater forcing increase (decrease) in these simulations. Note that a change of the freshwater forcing by 0.1 Sv (Sv≡106m3s-1) in this figure takes place over 500 model years.

  2. Framework for Detection and Localization of Extreme Climate Event with Pixel Recursive Super Resolution

    NASA Astrophysics Data System (ADS)

    Kim, S. K.; Lee, J.; Zhang, C.; Ames, S.; Williams, D. N.

    2017-12-01

    Deep learning techniques have been successfully applied to solve many problems in climate and geoscience using massive-scaled observed and modeled data. For extreme climate event detections, several models based on deep neural networks have been recently proposed and attend superior performance that overshadows all previous handcrafted expert based method. The issue arising, though, is that accurate localization of events requires high quality of climate data. In this work, we propose framework capable of detecting and localizing extreme climate events in very coarse climate data. Our framework is based on two models using deep neural networks, (1) Convolutional Neural Networks (CNNs) to detect and localize extreme climate events, and (2) Pixel recursive recursive super resolution model to reconstruct high resolution climate data from low resolution climate data. Based on our preliminary work, we have presented two CNNs in our framework for different purposes, detection and localization. Our results using CNNs for extreme climate events detection shows that simple neural nets can capture the pattern of extreme climate events with high accuracy from very coarse reanalysis data. However, localization accuracy is relatively low due to the coarse resolution. To resolve this issue, the pixel recursive super resolution model reconstructs the resolution of input of localization CNNs. We present a best networks using pixel recursive super resolution model that synthesizes details of tropical cyclone in ground truth data while enhancing their resolution. Therefore, this approach not only dramat- ically reduces the human effort, but also suggests possibility to reduce computing cost required for downscaling process to increase resolution of data.

  3. Changes in the probability of co-occurring extreme climate events

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.

    2017-12-01

    Extreme climate events such as floods, droughts, heatwaves, and severe storms exert acute stresses on natural and human systems. When multiple extreme events co-occur, either in space or time, the impacts can be substantially compounded. A diverse set of human interests - including supply chains, agricultural commodities markets, reinsurance, and deployment of humanitarian aid - have historically relied on the rarity of extreme events to provide a geographic hedge against the compounded impacts of co-occuring extremes. However, changes in the frequency of extreme events in recent decades imply that the probability of co-occuring extremes is also changing, and is likely to continue to change in the future in response to additional global warming. This presentation will review the evidence for historical changes in extreme climate events and the response of extreme events to continued global warming, and will provide some perspective on methods for quantifying changes in the probability of co-occurring extremes in the past and future.

  4. Managing the Risks of Extreme Events and Disasters in a Changing Climate: Lessons for Adaptation to Climate Change (Invited)

    NASA Astrophysics Data System (ADS)

    Mastrandrea, M.; Field, C. B.; Mach, K. J.; Barros, V.

    2013-12-01

    The IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, published in 2012, integrates expertise in climate science, disaster risk reduction, and adaptation to inform discussions on how to reduce and manage the risks of extreme events and disasters in a changing climate. Impacts and the risks of disasters are determined by the interaction of the physical characteristics of weather and climate events with the vulnerability of exposed human society and ecosystems. The Special Report evaluates the factors that make people and infrastructure vulnerable to extreme events, trends in disaster losses, recent and future changes in the relationship between climate change and extremes, and experience with a wide range of options used by institutions, organizations, and communities to reduce exposure and vulnerability, and improve resilience, to climate extremes. Actions ranging from incremental improvements in governance and technology to more transformational changes are assessed. The Special Report provides a knowledge base that is also relevant to the broader context of managing the risks of climate change through mitigation, adaptation, and other responses, assessed in the IPCC's Fifth Assessment Report (AR5), to be completed in 2014. These themes include managing risks through an iterative process involving learning about risks and the effectiveness of responses, employing a portfolio of actions tailored to local circumstances but with links from local to global scales, and considering additional benefits of actions such as improving livelihoods and well-being. The Working Group II contribution to the AR5 also examines the ways that extreme events and their impacts contribute to understanding of vulnerabilities and adaptation deficits in the context of climate change, the extent to which impacts of climate change are experienced through changes in the frequency and severity of extremes as opposed to mean changes

  5. [Temporal and spatial variations of extreme climatic events in Songnen Grassland, Northeast China during 1960-2014].

    PubMed

    Ma, Qi Yun; Zhang, Ji Quan; Lai, Quan; Zhang, Feng; Dong, Zhen Hua; A, Lu Si

    2017-06-18

    Fourteen extreme climatic indices related with main regional meteorological disasters and vegetation growth were calculated based on daily data from 13 meteorological stations during 1960-2014 in Songnen Grassland, Northeast China. Then, the variation trend and the spatial and temporal patterns of climatic extreme events were analyzed by using regression analysis, break trend analy-sis, Mann-Kendall test, Sen's slope estimator and moving t-test method. The results indicated that summer days (SU25), warm days (TX90P), warm nights (TN90P) and warm spell duration (WSDI) representing extremely high temperatures showed significant increasing trends (P<0.05). Meanwhile, frost days (FD0), cold days (TX10P), cold nights (TN10P) and cold spell duration indicator (CSDI) representing extremely low temperatures showed obviously decreasing trends. The magnitudes of changes in cold indices (FD0, TX10P, TN10P and CSDI) were clearly greater than those of warm indices (SU25, TX90P, TN90P and WSDI), and that changes in night indices were larger than those of day indices. Regional climate warming trend was obvious from 1970 to 2009, and the most occurrences of the abrupt changes in these indices were identified in this period. The extreme precipitation indices did not show obvious trend, in general, SDII and CDD experienced a slightly decreasing trend while RX5D, R95P, PRCPTOT and CWD witnessed a mildly increasing trend. It may be concluded that regional climate changed towards warming and slightly wetting in Songnen Grassland. The most sensitive region for extreme temperature was distributed in the south and north region. Additionally, the extreme temperature indices showed clearly spatial difference between the south and the north. As for the spatial variations of extreme precipitation indices, the climate could be characterized by becoming wetter in northern region, and getting drier in southern region, especially in southwestern region with a high drought risk.

  6. Managing the risks of extreme events and disasters to advance climate change adaptation. Special report of the Intergovernmental Panel on Climate Change (IPCC)

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

    Field, C.B.; Barros, V.; Stocker, T.F.

    2012-07-01

    This Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) has been jointly coordinated by Working Groups I (WGI) and II (WGII) of the Intergovernmental Panel on Climate Change (IPCC). The report focuses on the relationship between climate change and extreme weather and climate events, the impacts of such events, and the strategies to manage the associated risks. This Special Report, in particular, contributes to frame the challenge of dealing with extreme weather and climate events as an issue in decision making under uncertainty, analyzing response in the context of risk management.more » The report consists of nine chapters, covering risk management; observed and projected changes in extreme weather and climate events; exposure and vulnerability to as well as losses resulting from such events; adaptation options from the local to the international scale; the role of sustainable development in modulating risks; and insights from specific case studies. (LN)« less

  7. Cyclones and extreme windstorm events over Europe under climate change: Global and regional climate model diagnostics

    NASA Astrophysics Data System (ADS)

    Leckebusch, G. C.; Ulbrich, U.

    2003-04-01

    More than any changes of the climate system mean state conditions, the development of extreme events may influence social, economic and legal aspects of our society. This linkage results from the impact of extreme climate events (natural hazards) on environmental systems which again are directly linked to human activities. Prominent examples from the recent past are the record breaking rainfall amounts of August 2002 in central Europe which produced widespread floodings or the wind storm Lothar of December 1999. Within the MICE (Modelling the Impact of Climate Extremes) project framework an assessment of the impact of changes in extremes will be done. The investigation is carried out for several different impact categories as agriculture, energy use and property damage. Focus is laid on the diagnostics of GCM and RCM simulations under different climate change scenarios. In this study we concentrate on extreme windstorms and their relationship to cyclone activity in the global HADCM3 as well as in the regional HADRM3 model under two climate change scenarios (SRESA2a, B2a). In order to identify cyclones we used an objective algorithm from Murry and Simmonds which was widely tested under several different conditions. A slight increase in the occurrence of systems is identified above northern parts of central Europe for both scenarios. For more severe systems (core pressure < 990 hPa) we find an increase for western Europe. Strong wind events can be defined via different percentile values of the windspeed (e.g. above the 95 percentile). By this means the relationship between strong wind events and cyclones is also investigated. For several regions (e.g. Germany, France, Spain) a shift to more deep cyclones connected with an increasing number of strong wind events is found.

  8. Convection-Resolving Climate Change Simulations: Intensification of Heavy Hourly Precipitation Events

    NASA Astrophysics Data System (ADS)

    Ban, N.; Schmidli, J.; Schar, C.

    2014-12-01

    Reliable climate-change projections of extreme precipitation events are of great interest to decision makers, due to potentially important hydrological impacts such as floods, land slides and debris flows. Low-resolution climate models generally project increases of heavy precipitation events with climate change, but there are large uncertainties related to the limited spatial resolution and the parameterized representation of atmospheric convection. Here we employ a convection-resolving version of the COSMO model across an extended region (1100 km x 1100 km) covering the European Alps to investigate the differences between parameterized and explicit convection in climate-change scenarios. We conduct 10-year long integrations at resolutions of 12 and 2km. Validation using ERA-Interim driven simulations reveals major improvements with the 2km resolution, in particular regarding the diurnal cycle of mean precipitation and the representation of hourly extremes. In addition, 2km simulations replicate the observed super-adiabatic scaling at precipitation stations, i.e. peak hourly events increase faster with temperature than the Clausius-Clapeyron scaling of 7%/K (see Ban et al. 2014). Convection-resolving climate change scenarios are conducted using control (1991-2000) and scenario (2081-2090) simulations driven by a CMIP5 GCM (i.e. the MPI-ESM-LR) under the IPCC RCP8.5 scenario. Comparison between 12 and 2km resolutions with parameterized and explicit convection, respectively, reveals close agreement in terms of mean summer precipitation amounts (decrease by 30%), and regarding slight increases of heavy day-long events (amounting to 15% for 90th-percentile for wet-day precipitation). However, the different resolutions yield large differences regarding extreme hourly precipitation, with the 2km version projecting substantially faster increases of heavy hourly precipitation events (about 30% increases for 90th-percentile hourly events). Ban, N., J. Schmidli and C. Sch

  9. Eocene Hyperthermal Event Offers Insight Into Greenhouse Warming

    NASA Astrophysics Data System (ADS)

    Bowen, Gabriel J.; Bralower, Timothy J.; Delaney, Margaret L.; Dickens, Gerald R.; Kelly, Daniel C.; Koch, Paul L.; Kump, Lee R.; Meng, Jin; Sloan, Lisa C.; Thomas, Ellen; Wing, Scott L.; Zachos, James C.

    2006-04-01

    What happens to the Earth's climate, environment, and biota when thousands of gigatons of greenhouse gases are rapidly added to the atmosphere? Modern anthropogenic forcing of atmospheric chemistry promises to provide an experiment in such change that has not been matched since the early Paleogene, more than 50 million years ago (Ma),when catastrophic release of carbon to the atmosphere drove abrupt, transient, hyperthermal events. Research on the Paleocene-Eocene Thermal Maximum (PETM)-the best documented of these events, which occurred about 55 Ma-has advanced significantly since its discovery 15 years ago. During the PETM, carbon addition to the oceans and atmosphere was of a magnitude similar to that which is anticipated through the 21st century. This event initiated global warming, biotic extinction and migration, and fundamental changes in the carbon and hydrological cycles that transformed the early Paleogene world.

  10. Transformation of soil organics under extreme climate events: a project description

    NASA Astrophysics Data System (ADS)

    Blagodatskaya, Evgenia

    2017-04-01

    Recent climate scenarios predict not only continued global warming but also an increased frequency and intensity of extreme climatic events such as strong changes in temperature and precipitation with unusual regional dynamics. Weather anomalies at European territory of Russia are currently revealed as long-term drought and strong showers in summer and as an increased frequency of soil freezing-thawing cycles. Climate extremes totally change biogeochemical processes and elements cycling both at the ecosystem level and at the level of soil profile mainly affecting soil biota. Misbalance in these processes can cause a reduction of soil carbon stock and an increase of greenhouse gases emission. Our project aims to reveal the transformation mechanisms of soil organic matter caused by extreme weather events taking into consideration the role of biotic-abiotic interactions in regulation of formation, maintenance and turnover of soil carbon stock. Our research strategy is based on the novel concept considering extreme climatic events (showers after long-term droughts, soil flooding, freezing-thawing) as abiotic factors initiating a microbial succession. Study on stoichiometric flexibility of plants under climate extremes as well as on resulting response of soil heterotrophs on stoichiometric changes in substrate will be used for experimental prove and further development of the theory of ecological stoichiometry. The results enable us to reveal the mechanisms of biotic - abiotic interactions responsible for the balance between mobilization and stabilization of soil organic matter. Identified mechanisms will form the basis of an ecosystem model enabled to predict the effects of extreme climatic events on biogenic carbon cycle in the biosphere.

  11. Climate Extreme Events over Northern Eurasia in Changing Climate

    NASA Astrophysics Data System (ADS)

    Bulygina, O.; Korshunova, N. N.; Razuvaev, V. N.; Groisman, P. Y.

    2014-12-01

    During the period of widespread instrumental observations in Northern Eurasia, the annual surface air temperature has increased by 1.5°C. Close to the north in the Arctic Ocean, the late summer sea ice extent has decreased by 40% providing a near-infinite source of water vapor for the dry Arctic atmosphere in the early cold season months. The contemporary sea ice changes are especially visible in the Eastern Hemisphere All these factors affect the change extreme events. Daily and sub-daily data of 940 stations to analyze variations in the space time distribution of extreme temperatures, precipitation, and wind over Russia were used. Changing in number of days with thaw over Russia was described. The total seasonal numbers of days, when daily surface air temperatures (wind, precipitation) were found to be above (below) selected thresholds, were used as indices of climate extremes. Changing in difference between maximum and minimum temperature (DTR) may produce a variety of effects on biological systems. All values falling within the intervals ranged from the lowest percentile to the 5th percentile and from the 95th percentile to the highest percentile for the time period of interest were considered as daily extremes. The number of days, N, when daily temperatures (wind, precipitation, DTR) were within the above mentioned intervals, was determined for the seasons of each year. Linear trends in the number of days were calculated for each station and for quasi-homogeneous climatic regions. Regional analysis of extreme events was carried out using quasi-homogeneous climatic regions. Maps (climatology, trends) are presented mostly for visualization purposes. Differences in regional characteristics of extreme events are accounted for over a large extent of the Russian territory and variety of its physical and geographical conditions. The number of days with maximum temperatures higher than the 95% percentile has increased in most of Russia and decreased in Siberia in

  12. Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes.

    PubMed

    McManus, J F; Francois, R; Gherardi, J-M; Keigwin, L D; Brown-Leger, S

    2004-04-22

    The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.

  13. An abrupt weakening of the subpolar gyre as trigger of Little Ice Age-type episodes

    NASA Astrophysics Data System (ADS)

    Moreno-Chamarro, Eduardo; Zanchettin, Davide; Lohmann, Katja; Jungclaus, Johann H.

    2017-02-01

    We investigate the mechanism of a decadal-scale weakening shift in the strength of the subpolar gyre (SPG) that is found in one among three last millennium simulations with a state-of-the-art Earth system model. The SPG shift triggers multicentennial anomalies in the North Atlantic climate driven by long-lasting internal feedbacks relating anomalous oceanic and atmospheric circulation, sea ice extent, and upper-ocean salinity in the Labrador Sea. Yet changes throughout or after the shift are not associated with a persistent weakening of the Atlantic Meridional Overturning Circulation or shifts in the North Atlantic Oscillation. The anomalous climate state of the North Atlantic simulated after the shift agrees well with climate reconstructions from within the area, which describe a transition between a stronger and weaker SPG during the relatively warm medieval climate and the cold Little Ice Age respectively. However, model and data differ in the timing of the onset. The simulated SPG shift is caused by a rapid increase in the freshwater export from the Arctic and associated freshening in the upper Labrador Sea. Such freshwater anomaly relates to prominent thickening of the Arctic sea ice, following the cluster of relatively small-magnitude volcanic eruptions by 1600 CE. Sensitivity experiments without volcanic forcing can nonetheless produce similar abrupt events; a necessary causal link between the volcanic cluster and the SPG shift can therefore be excluded. Instead, preconditioning by internal variability explains discrepancies in the timing between the simulated SPG shift and the reconstructed estimates for the Little Ice Age onset.

  14. Climate change impacts on extreme events in the United States: an uncertainty analysis

    EPA Science Inventory

    Extreme weather and climate events, such as heat waves, droughts and severe precipitation events, have substantial impacts on ecosystems and the economy. However, future climate simulations display large uncertainty in mean changes. As a result, the uncertainty in future changes ...

  15. Abrupt shifts in phenology and vegetation productivity under climate extremes

    USDA-ARS?s Scientific Manuscript database

    Amplification of the hydrologic cycle as a consequence of global warming is predicted to increase climate variability and the frequency and severity of droughts. Predicting how ecosystems will be affected by climate change requires not only reliable forecasts of future climate, but also observationa...

  16. Abrupt sand-dune accumulation at the northeastern margin of the Tibetan Plateau challenges the wet MIS3a inferred from numerous lake-highstands

    PubMed Central

    Long, Hao; Fuchs, Markus; Yang, Linhai; Cheng, Hongyi

    2016-01-01

    Over the Tibetan Plateau and adjacent regions, numerous 14C-based lake records revealed a ubiquitous wet climatic period during 40–25 ka (late MIS 3), which is in contradiction with the global pattern of generally cold and dry climates. This paper focuses on OSL dating results of a large set of sand dunes and alluvial sediments (50 OSL ages) from the Qinwangchuan (QWC) Basin at the northeast edge of the Tibetan Plateau, with the aim to test the validity of the anomalous wet condition for the late MIS 3 interval, evidenced by numerous lake highstands. The abrupt sand dune accumulation as indication of increased aridity in the study area was OSL dated to ~40–13 ka. This dry climatic inference of the sand dune system from QWC apparently shows no wet MIS 3a event. Thus, the anomalous wet conditions revealed by high lake levels for the late MIS 3 phase may not be a universal phenomena across entire western China. PMID:27172907

  17. Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present

    PubMed Central

    Hoff, Ulrike; Rasmussen, Tine L.; Stein, Ruediger; Ezat, Mohamed M.; Fahl, Kirsten

    2016-01-01

    In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland–Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean. PMID:27456826

  18. Sea ice and millennial-scale climate variability in the Nordic seas 90 kyr ago to present.

    PubMed

    Hoff, Ulrike; Rasmussen, Tine L; Stein, Ruediger; Ezat, Mohamed M; Fahl, Kirsten

    2016-07-26

    In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial-scale climatic events (Dansgaard/Oeschger events) using the sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the southeast Norwegian Sea. We demonstrate that expansion and retreat of sea ice varies consistently in pace with the rapid climate changes 90 kyr ago to present. Sea ice retreats abruptly at the start of warm interstadials, but spreads rapidly during cooling phases of the interstadials and becomes near perennial and perennial during cold stadials and Heinrich events, respectively. Low-salinity surface water and the sea ice edge spreads to the Greenland-Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean.

  19. Semi-supervised tracking of extreme weather events in global spatio-temporal climate datasets

    NASA Astrophysics Data System (ADS)

    Kim, S. K.; Prabhat, M.; Williams, D. N.

    2017-12-01

    Deep neural networks have been successfully applied to solve problem to detect extreme weather events in large scale climate datasets and attend superior performance that overshadows all previous hand-crafted methods. Recent work has shown that multichannel spatiotemporal encoder-decoder CNN architecture is able to localize events in semi-supervised bounding box. Motivated by this work, we propose new learning metric based on Variational Auto-Encoders (VAE) and Long-Short-Term-Memory (LSTM) to track extreme weather events in spatio-temporal dataset. We consider spatio-temporal object tracking problems as learning probabilistic distribution of continuous latent features of auto-encoder using stochastic variational inference. For this, we assume that our datasets are i.i.d and latent features is able to be modeled by Gaussian distribution. In proposed metric, we first train VAE to generate approximate posterior given multichannel climate input with an extreme climate event at fixed time. Then, we predict bounding box, location and class of extreme climate events using convolutional layers given input concatenating three features including embedding, sampled mean and standard deviation. Lastly, we train LSTM with concatenated input to learn timely information of dataset by recurrently feeding output back to next time-step's input of VAE. Our contribution is two-fold. First, we show the first semi-supervised end-to-end architecture based on VAE to track extreme weather events which can apply to massive scaled unlabeled climate datasets. Second, the information of timely movement of events is considered for bounding box prediction using LSTM which can improve accuracy of localization. To our knowledge, this technique has not been explored neither in climate community or in Machine Learning community.

  20. Fixing Climate: What Past Climate Changes Reveal About the Current Threat-And How to Counter It

    NASA Astrophysics Data System (ADS)

    McKinley, Galen A.

    2008-10-01

    The Earth's climate 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 Climate 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 abrupt change in the climate system. With support from climate science philanthropist Gary Comer, climate scientist Wally Broecker has teamed with science writer Robert Kunzig in this book to bring abrupt climate change into public view. They do this elegantly and convincingly, making the first 12 chapters quite enjoyable.

  1. Deglacial climate variability in central Florida, USA

    USGS Publications Warehouse

    Willard, D.A.; Bernhardt, C.E.; Brooks, G.R.; Cronin, T. M.; Edgar, T.; Larson, R.

    2007-01-01

    Pollen and ostracode evidence from lacustrine sediments underlying modern Tampa Bay, Florida, document frequent and abrupt climatic and hydrological events superimposed on deglacial warming in the subtropics. Radiocarbon chronology on well-preserved mollusk shells and pollen residue from core MD02-2579 documents continuous sedimentation in a variety of non-marine habitats in a karst-controlled basin from 20 ka to 11.5 ka. During the last glacial maximum (LGM), much drier and cooler-than-modern conditions are indicated by pollen assemblages enriched in Chenopodiaceae and Carya, with rare Pinus (Pinus pollen increased to 20–40% during the warming of the initial deglaciation (∼ 17.2 ka), reaching near modern abundance (60–80%) during warmer, moister climates of the Bølling/Allerød interval (14.7–12.9 ka). Within the Bølling/Allerød, centennial-scale dry events corresponding to the Older Dryas and Intra-Allerød Cold Period indicate rapid vegetation response (

  2. Late second-early first millennium BC abrupt climate changes in coastal Syria and their possible significance for the history of the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Kaniewski, D.; Paulissen, E.; Van Campo, E.; Weiss, H.; Otto, T.; Bretschneider, J.; Van Lerberghe, K.

    2010-09-01

    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 climatic proxy suggests that drier climatic 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 abrupt climate 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.

  3. Late Quaternary Climate and Vegetation of the Sudanian Zone of Northeast Nigeria

    NASA Astrophysics Data System (ADS)

    Salzmann, Ulrich; Hoelzmann, Philipp; Morczinek, Irena

    2002-07-01

    The Lake Tilla crater lake in northeastern Nigeria (10°23'N, 12°08'E) provides a ca. 17,000 14C yr multiproxy record of the environmental history of a Sudanian savanna in West Africa. Evaluation of pollen, diatoms, and sedimentary geochemistry from cores suggests that dry climatic conditions prevailed throughout the late Pleistocene. Before the onset of the Holocene, the slow rise in lake levels was interrupted by a distinct dry event between ca. 10,900 and 10,500 14C yr B.P., which may coincide with the Younger Dryas episode. The onset of the Holocene is marked by an abrupt increase in lake levels and a subsequent spread of Guinean and Sudanian tree taxa into the open grass savanna that predominated throughout the Late Pleistocene. The dominance of the mountain olive Olea hochstetteri suggests cool climatic conditions prior to ca. 8600 14C yr B.P. The early to mid-Holocene humid period culminated between ca. 8500 and 7000 14C yr B.P. with the establishment of a dense Guinean savanna during high lake levels. Frequent fires were important in promoting the open character of the vegetation. The palynological and palaeolimnological data demonstrate that the humid period terminated after ca. 7000 14C yr B.P. in a gradual decline of the precipitation/evaporation ratio and was not interrupted by abrupt climatic events. The aridification trend intensified after ca. 3800 14C yr B.P. and continued until the present.

  4. Developing research about extreme events and impacts to support international climate policy

    NASA Astrophysics Data System (ADS)

    Otto, Friederike; James, Rachel; Parker, Hannah; Boyd, Emily; Jones, Richard; Allen, Myles; Mitchell, Daniel; Cornforth, Rosalind

    2015-04-01

    Climate change is expected to have some of its most significant impacts through changes in the frequency and severity of extreme events. There is a pressing need for policy to support adaptation to changing climate risks, and to deal with residual loss and damage from climate change. In 2013, the Warsaw International Mechanism was established by the United Nations Framework Convention on Climate Change (UNFCCC) to address loss and damage in developing countries. Strategies to help vulnerable regions cope with losses from extreme events will presumably require information about the influence of anthropogenic forcing on extreme weather. But what kind of scientific evidence will be most useful for the Warsaw Mechanism? And how can the scientific communities working on extreme events and impacts develop their research to support the advance of this important policy? As climate scientists conducting probabilistic event attribution studies, we have been working with social scientists to investigate these questions. Our own research seeks to examine the role of external drivers, including greenhouse gas emissions, on the risk of extreme weather events such as heatwaves, flooding, and drought. We use large ensembles of climate models to compute the probability of occurrence of extreme events under current conditions and in a world which might have been without anthropogenic interference. In cases where the models are able to simulate extreme weather, the analysis allows for conclusions about the extent to which climate change may have increased, decreased, or made no change to the risk of the event occurring. These results could thus have relevance for the UNFCCC negotiations on loss and damage, and we have been communicating with policymakers and observers to the policy process to better understand how we can develop our research to support their work; by attending policy meetings, conducting interviews, and using a participatory game developed with the Red Cross

  5. A Glacial Perspective on the Impact of Heinrich Stadials on North Atlantic Climate

    NASA Astrophysics Data System (ADS)

    Bromley, G. R.; Putnam, A. E.; Rademaker, K. M.; Balter, A.; Hall, B. L.

    2017-12-01

    The British Isles contain a rich geologic record of Late Pleistocene ice sheet behaviour in the NE North Atlantic basin. We are using cosmogenic 10Be surface-exposure dating, in conjunction with detailed glacial-geomorphic mapping, to reconstruct the timing and nature of cryospheric change - and thus climate variability - in northern Scotland since the Last Glacial Maximum. Our specific focus is Heinrich Stadial 1 (18,300-14,700 years ago), arguably the most significant abrupt climate event of the last glacial cycle and a major feature in global palaeoclimate records. Such constraint is needed because of currently conflicting models of how these events impact terrestrial environments and a recent hypothesis attributing this disparity to enhanced seasonality in the North Atlantic basin. To date, we have measured 10Be in > 30 samples from glacial erratics located on moraines deposited by the British Ice Sheet as it retreated from the continental shelf to its highland source regions. Our preliminary results indicate that the stadial was characterised by widespread deglaciation driven by atmospheric warming, a pattern that is suggestive of pronounced seasonality. Additionally, we report new exposure ages from moraines deposited during a subsequent phase of alpine glaciation (known locally as the Loch Lomond Readvance) that has long been attributed to the Younger Dryas stadial. With the growing focus on the full expression of stadials, and the inherent vulnerability of Europe to shifts in North Atlantic climate, developing the extant record of terrestrial glaciation and comparing these data to marine records is a critical step towards understanding the drivers of abrupt climate change.

  6. Did accelerated North American ice sheet melt contribute to the 8.2 ka cooling event ?

    NASA Astrophysics Data System (ADS)

    Matero, Ilkka S. O.; Gregoire, Lauren J.; Ivanović, Ruža F.; Tindall, Julia C.; Haywood, Alan M.

    2016-04-01

    The 8.2 ka event was an abrupt cooling of the Northern Hemisphere 8,200 years ago. It is an almost ideal case study to benchmark the sensitivity of climate models to freshening of the North Atlantic by ice sheet melt (Schmidt and LeGrande, 2005). The event is attributed to the outburst of North American proglacial lakes into the Labrador Sea, causing a slow-down in Atlantic overturning circulation and cooling of 1-2.5 °C around the N. Atlantic (Alley and Ágústsdóttir,2005). Climate models fail to simulate the ~150 year duration of the event when forced with a sudden (0.5 to 5 years) drainage of the lakes (Morrill et al., 2013a). This could be because of missing forcings. For example, the separation of ice sheet domes around the Hudson Bay is thought to have produced a pronounced acceleration in ice sheet melt through a saddle collapse mechanism around the time of the event (Gregoire et al., 2012). Here we investigate whether this century scale acceleration of melt contributed to the observed climatic perturbation, using the coupled Ocean-Atmosphere climate model HadCM3. We designed and ran a set of simulations with temporally variable ice melt scenarios based on a model of the North American ice sheet. The simulated magnitude and duration of the cold period is controlled by the duration and amount of freshwater introduced to the ocean. With a 100-200 year-long acceleration of ice melt up to a maximum of 0.61 Sv, we simulate 1-3 °C cooling in the North Atlantic and ~0.5-1 °C cooling in Continental Europe; which are similar in magnitude to the ~1-2 °C cooling estimated from records for these areas (Morrill et al., 2013b). Some of the observed features are however not reproduced in our experiments, such as the most pronounced cooling of ~6 °C observed in central Greenland (Alley and Ágústsdóttir, 2005). The results suggest that the ~150 year North Atlantic and European cooling could be caused by ~200 years of accelerated North American ice sheet melt. This

  7. Using a Family Science Day Event to Engage Youth in Climate Change Issues

    NASA Astrophysics Data System (ADS)

    Brevik, C.; Brevik, E. C.

    2015-12-01

    Each fall, Dickinson State University organizes four Family Science Day events for elementary-aged children to increase their engagement in the sciences. Offered on Saturday afternoons, each event focuses on a different science-related theme. Families can attend these events free of charge, and the kids participate in a large variety of hands-on activities which center around the event's theme. This year, the November event focused on climate change and the roles soil plays in the climate system. The timing of this topic was carefully chosen. 2015 has been declared the International Year of Soil by the United Nations, and the Soil Science Society of America theme for the month of November was Soils and Climate. This public outreach event was an amazing opportunity to help the youth in our community learn about climate change and soil in a fun, interactive environment. The activities also helped the children learn how science is a process of discovery that allows them to better understand the world they live in. In addition to the hands-on activities, a planetarium show focusing on climate change was also offered during the event. The fully immersive, 360-degree show allowed the kids and their parents to personally observe phenomena that are otherwise difficult to visualize. All of the activities at the Family Science Day event were staffed by university students, and this proved to be a very valuable experience for them as well. Some of the students who helped are majoring in a science field, and for them, the experience taught public communication. They learned to break complicated concepts down into simpler terms that young kids can understand. Education majors who participated practiced communicating science concepts to children, and students in other majors who helped with this event gained experiences that reinforced various concepts they had learned in their general education science courses.

  8. Could gradual changes in Holocene Saharan landscape have caused the observed abrupt shift in North Atlantic dust deposition?

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2017-09-01

    The abrupt 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 abrupt 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-climate model ECHAM-HAM. In our simulations, we do not find evidence of an abrupt 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 abrupt 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.

  9. Food Security Under Shifting Economic, Demographic, and Climatic Conditions (Invited)

    NASA Astrophysics Data System (ADS)

    Naylor, R. L.

    2013-12-01

    Global demand for food, feed, and fuel will continue to rise in a more populous and affluent world. Meeting this demand in the future will become increasingly challenging with global climate change; when production shocks stemming from climate variability are added to the new mean climate state, food markets could become more volatile. This talk will focus on the interacting market effects of demand and supply for major food commodities, with an eye on climate-related supply trends and shocks. Lessons from historical patterns of climate variability (e.g., ENSO and its global teleconnections) will be used to infer potential food security outcomes in the event of abrupt changes in the mean climate state. Domestic food and trade policy responses to crop output and price volatility in key producing and consuming nations, such as export bans and import tariffs, will be discussed as a potentially major destabilizing force, underscoring the important influence of uncertainty in achieving--or failing to achieve--food security.

  10. Developmental phenotypic plasticity helps bridge stochastic weather events associated with climate change.

    PubMed

    Burggren, Warren

    2018-05-10

    The slow, inexorable rise in annual average global temperatures and acidification of the oceans are often advanced as consequences of global change. However, many environmental changes, especially those involving weather (as opposed to climate), are often stochastic, variable and extreme, particularly in temperate terrestrial or freshwater habitats. Moreover, few studies of animal and plant phenotypic plasticity employ realistic (i.e. short-term, stochastic) environmental change in their protocols. Here, I posit that the frequently abrupt environmental changes (days, weeks, months) accompanying much longer-term general climate change (e.g. global warming over decades or centuries) require consideration of the true nature of environmental change (as opposed to statistical means) coupled with an expansion of focus to consider developmental phenotypic plasticity. Such plasticity can be in multiple forms - obligatory/facultative, beneficial/deleterious - depending upon the degree and rate of environmental variability at specific points in organismal development. Essentially, adult phenotypic plasticity, as important as it is, will be irrelevant if developing offspring lack sufficient plasticity to create modified phenotypes necessary for survival. © 2018. Published by The Company of Biologists Ltd.

  11. Climate change; Confronting the global experiment

    Treesearch

    Constance I. Millar

    2006-01-01

    Earth’s natural climate system is characterized by continually changing climates, with climate regimes that oscillate quasi-cyclically at multiple and nested scales from annual to multi-millennial, and commonly change abruptly. Under naturally changing climates, plant species track changes at all scales in individualistic manner, with plant communities...

  12. Abrupt drainage cycles of the Fennoscandian Ice Sheet.

    PubMed

    Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard

    2013-04-23

    Continental ice sheets are a key component of the Earth's climate 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 climate-lake-FIS system, linked to changes in the availability of subglacial water, led to abrupt 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.

  13. Abrupt variations of Indian and East Asian summer monsoons during the last deglacial stadial and interstadial

    NASA Astrophysics Data System (ADS)

    Hong, Bing; Hong, Yetang; Uchida, Masao; Shibata, Yasuyuki; Cai, Cheng; Peng, Haijun; Zhu, Yongxuan; Wang, Yu; Yuan, Linggui

    2014-08-01

    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 abruptly decreases during the Younger Dryas (YD) stadial and abruptly increases during the Bølling-Allerød (BA) interstadial. A comparison of the Yuexi record with other related proxy climate 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 climate 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 abrupt cooling in the high northern latitudes and to the El Niño-like activity in the equatorial Pacific. The widespread wet climate during the BA interstadial may be related to an abrupt 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

  14. Extreme Weather Events and Interconnected Infrastructures: Toward More Comprehensive Climate Change Planning [Meeting challenges in understanding impacts of extreme weather events on connected infrastructures

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

    Wilbanks, Thomas J.; Fernandez, Steven J.; Allen, Melissa R.

    The President s Climate Change Action Plan calls for the development of better science, data, and tools for climate preparedness. Many of the current questions about preparedness for extreme weather events in coming decades are, however, difficult to answer with assets that have been developed by climate science to answer longer-term questions about climate change. Capacities for projecting exposures to climate-related extreme events, along with their implications for interconnected infrastructures, are now emerging.

  15. Extreme Weather Events and Interconnected Infrastructures: Toward More Comprehensive Climate Change Planning [Meeting challenges in understanding impacts of extreme weather events on connected infrastructures

    DOE PAGES

    Wilbanks, Thomas J.; Fernandez, Steven J.; Allen, Melissa R.

    2015-06-23

    The President s Climate Change Action Plan calls for the development of better science, data, and tools for climate preparedness. Many of the current questions about preparedness for extreme weather events in coming decades are, however, difficult to answer with assets that have been developed by climate science to answer longer-term questions about climate change. Capacities for projecting exposures to climate-related extreme events, along with their implications for interconnected infrastructures, are now emerging.

  16. Revealing Abrupt and Spontaneous Ruptures of Protein Native Structure under picoNewton Compressive Force Manipulation.

    PubMed

    Chowdhury, S Roy; Cao, Jin; He, Yufan; Lu, H Peter

    2018-03-27

    Manipulating protein conformations for exploring protein structure-function relationship has shown great promise. Although protein conformational changes under pulling force manipulation have been extensively studied, protein conformation changes under a compressive force have not been explored quantitatively. The latter is even more biologically significant and relevant in revealing protein functions in living cells associated with protein crowdedness, distribution fluctuations, and cell osmotic stress. Here we report our experimental observations on abrupt ruptures of protein native structures under compressive force, demonstrated and studied by single-molecule AFM-FRET spectroscopic nanoscopy. Our results show that the protein ruptures are abrupt and spontaneous events occurred when the compressive force reaches a threshold of 12-75 pN, a force amplitude accessible from thermal fluctuations in a living cell. The abrupt ruptures are sensitive to local environment, likely a general and important pathway of protein unfolding in living cells.

  17. Conclusive evidence of abrupt coagulation inside the void during cyclic nanoparticle formation in reactive plasma

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

    Wetering, F. M. J. H. van de; Nijdam, S.; Beckers, J.

    2016-07-25

    In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an abrupt coagulation event as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon–acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, abrupt contraction, and continued expansion. The abrupt contraction was termed “hiccup” and was related to collective coagulation of a new generation of nanoparticles growing in the void using relativelymore » indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.« less

  18. Precise dating of Dansgaard-Oeschger climate oscillations in western Europe from stalagmite data.

    PubMed

    Genty, D; Blamart, D; Ouahdi, R; Gilmour, M; Baker, A; Jouzel, J; Van-Exter, Sandra

    2003-02-20

    The signature of Dansgaard-Oeschger events--millennial-scale abrupt climate oscillations during the last glacial period--is well established in ice cores and marine records. But the effects of such events in continental settings are not as clear, and their absolute chronology is uncertain beyond the limit of (14)C dating and annual layer counting for marine records and ice cores, respectively. Here we present carbon and oxygen isotope records from a stalagmite collected in southwest France which have been precisely dated using 234U/230Th ratios. We find rapid climate oscillations coincident with the established Dansgaard-Oeschger events between 83,000 and 32,000 years ago in both isotope records. The oxygen isotope signature is similar to a record from Soreq cave, Israel, and deep-sea records, indicating the large spatial scale of the climate oscillations. The signal in the carbon isotopes gives evidence of drastic and rapid vegetation changes in western Europe, an important site in human cultural evolution. We also find evidence for a long phase of extremely cold climate in southwest France between 61.2 +/- 0.6 and 67.4 +/- 0.9 kyr ago.

  19. Nearly synchronous climate change in the Northern Hemisphere during the last glacial termination

    USGS Publications Warehouse

    Benson, L.; Burdett, J.; Lund, S.; Kashgarian, Michaele; Mensing, S.

    1997-01-01

    The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17.711.5 kyr ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bolling/Older Dryas/Allerod/Younger Dryas vegetational sequence, has been found in Greenland ice cores. The geographical extent of many of these oscillations is not well known, but the last major cold event (the Younger Dryas) seems to have been global in extent. Here we present evidence of four major oscillations in the hydrological balance of the Owens basin, California, that occurred during the last glacial termination. Dry events in western North America occurred at approximately the same time as cold events recorded in Greenland ice, with transitions between climate regimes in the two regions taking place within a few hundred years of each other. Our observations thus support recent climate simulations which indicate that cooling of the North Atlantic Ocean results in cooling of the North Pacific Ocean which, in turn, leads to a drier climate in western North America.

  20. The 8.2 ka cooling event caused by Laurentide ice saddle collapse

    NASA Astrophysics Data System (ADS)

    Matero, I. S. O.; Gregoire, L. J.; Ivanovic, R. F.; Tindall, J. C.; Haywood, A. M.

    2017-09-01

    The 8.2 ka event was a period of abrupt cooling of 1-3 °C across large parts of the Northern Hemisphere, which lasted for about 160 yr. The original hypothesis for the cause of this event has been the outburst of the proglacial Lakes Agassiz and Ojibway. These drained into the Labrador Sea in ∼0.5-5 yr and slowed the Atlantic Meridional Overturning Circulation, thus cooling the North Atlantic region. However, climate models have not been able to reproduce the duration and magnitude of the cooling with this forcing without including additional centennial-length freshwater forcings, such as rerouting of continental runoff and ice sheet melt in combination with the lake release. Here, we show that instead of being caused by the lake outburst, the event could have been caused by accelerated melt from the collapsing ice saddle that linked domes over Hudson Bay in North America. We forced a General Circulation Model with time varying meltwater pulses (100-300 yr) that match observed sea level change, designed to represent the Hudson Bay ice saddle collapse. A 100 yr long pulse with a peak of 0.6 Sv produces a cooling in central Greenland that matches the 160 yr duration and 3 °C amplitude of the event recorded in ice cores. The simulation also reproduces the cooling pattern, amplitude and duration recorded in European Lake and North Atlantic sediment records. Such abrupt acceleration in ice melt would have been caused by surface melt feedbacks and marine ice sheet instability. These new realistic forcing scenarios provide a means to reconcile longstanding mismatches between proxy data and models, allowing for a better understanding of both the sensitivity of the climate models and processes and feedbacks in motion during the disintegration of continental ice sheets.

  1. Using Dynamically Downscaled Climate Model Outputs to Inform Projections of Extreme Precipitation Events

    NASA Technical Reports Server (NTRS)

    Wobus, Cameron; Reynolds, Lara; Jones, Russell; Horton, Radley; Smith, Joel; Fries, J. Stephen; Tryby, Michael; Spero, Tanya; Nolte, Chris

    2015-01-01

    Many of the storms that generate damaging floods are caused by locally intense, sub-daily precipitation, yet the spatial and temporal resolution of the most widely available climate model outputs are both too coarse to simulate these events. Thus there is often a disconnect between the nature of the events that cause damaging floods and the models used to project how climate change might influence their magnitude. This could be a particular problem when developing scenarios to inform future storm water management options under future climate scenarios. In this study we sought to close this gap, using sub-daily outputs from the Weather Research and Forecasting model (WRF) from each of the nine climate regions in the United States. Specifically, we asked 1) whether WRF outputs projected consistent patterns of change for sub-daily and daily precipitation extremes; and 2) whether this dynamically downscaled model projected different magnitudes of change for 3-hourly vs 24-hourly extreme events. We extracted annual maximum values for 3-hour through 24-hour precipitation totals from an 11-year time series of hindcast (1995-2005) and mid-century (2045-2055) climate, and calculated the direction and magnitude of change for 3-hour and 24-hour extreme events over this timeframe. The model results project that the magnitude of both 3-hour and 24-hour events will increase over most regions of the United States, but there was no clear or consistent difference in the relative magnitudes of change for sub-daily vs daily events.

  2. Terrestrial Vegetation Dynamics, Global Climate Controls, and Extreme Events

    NASA Astrophysics Data System (ADS)

    Klooster, S.; Potter, C.; Boriah, S.; Steinbach, M.; Kumar, V.

    2006-12-01

    Monthly greenness data from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to reconstruct vegetation dynamics in response to climate patterns over the period 2000-2005. Results suggest that plant growth over extensive land areas of southern Africa and Central Asia were the most closely coupled of any major land area to El Niño-Southern Oscillation (ENSO) effects on regional climate. Others land areas strongly tied to recent ENSO climate effects were in northern Canada, Alaska, western United States, northern Mexico, northern Argentina, and Australia. Localized variations in precipitation were the most common controllers of monthly values for the fraction absorbed of photosynthetically active radiation (FPAR) over these regions. In addition to the areas cited above, seasonal FPAR values were closely coupled to rainfall patterns in grassland and cropland areas of the northern and central United States. Historical associations between global vegetation FPAR and atmospheric carbon dioxide anomalies suggest that the terrestrial biosphere can contribute major fluxes of carbon dioxide during major drought events, such as those triggered by the 1997-98 El Niño event.

  3. State survey of medical boards regarding abrupt loss of a prescriber of controlled substances.

    PubMed

    Sera, Leah; Brown, Micke; McPherson, Mary Lynn; Walker, Kathryn A; Klein-Schwartz, Wendy

    The purpose of the study was to evaluate states' experiences with abrupt changes in controlled substances (CS) prescribing, to determine whether states have action plans in place to manage such situations, and describe the components of any such plans. A survey of executive directors of 51 medical boards was conducted to evaluate states' experiences with abrupt changes in CS prescribing, the extent of consumer complaints attributed to these events, and the types of plans in place to manage these situations. Forty-six executive directors of medical boards responded. Twenty boards (43.5 percent) confirmed that their state had experienced abrupt loss of CS providers and 11 (55 percent) of these executive directors indicated that the loss resulted in increased consumer complaints. The majority of executive directors (86 percent) had no action plan. Six executive directors reported some type of action plan or process consisting of regulatory action, patient-provider connection, professional education, patient education, or public notice. Most states do not have operational plans in place. However, a few have key strategies that may be useful in addressing potential problems following abrupt loss of a CS prescriber. State medical boards can play a significant role in the development of comprehensive preparedness plans to mitigate damage from the loss of CS prescribers in the community.

  4. Santa Barbara Basin Study Extends Global Climate Record

    NASA Astrophysics Data System (ADS)

    Hopkins, Sarah; Kennett, James; Nicholson, Craig; Pak, Dorothy; Sorlien, Christopher; Behl, Richard; Normark, William; Sliter, Ray; Hill, Tessa; Schimmelmann, Arndt; Cannariato, Kevin

    2006-05-01

    A fundamental goal of Earth science is to understand the remarkable instability of late Quarternary global climate prior to the beginning of the Holocene, about 11,000 years ago. This unusual climate behavior was characterized by millennial-scale climate oscillations on suborbital timescales, and a distinctive `Sawtooth' pattern of very abrupt 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 climate were terminated by similar abrupt warming episodes suggests a common mechanism driving such rapid changes in global climate. Understanding the causes of this instability is crucial given developing concerns about global warming, yet knowledge about this climate 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 abrupt climate change.

  5. Consequences of past climate change for species engaged in obligatory interactions

    NASA Astrophysics Data System (ADS)

    Blatrix, Rumsaïs; McKey, Doyle; Born, Céline

    2013-07-01

    Obligatory interactions between species are fundamental to ecosystem functioning and are expected to be particularly sensitive to climate change. Although the effect of past and current climate changes on individual species has been thoroughly investigated, their effect on obligatory interactions has been overlooked. In this review, we present predictions about the effects of climate change on obligatory interactions and illustrate these predictions with examples from the literature. We focus on abrupt past climate change, especially during the Quaternary, because knowing past responses is useful for understanding and predicting the response of organisms and ecosystems to the current climate change. We also pinpoint the need for better time calibration of demographic events from genetic data, and for more studies focused on particularly suitable biological models. We hope that this review will stimulate interaction between the earth sciences and the life sciences on this timely topic.

  6. An observational and modeling study of the August 2017 Florida climate extreme event.

    NASA Astrophysics Data System (ADS)

    Konduru, R.; Singh, V.; Routray, A.

    2017-12-01

    A special report on the climate extremes by the Intergovernmental Panel on Climate Change (IPCC) elucidates that the sole cause of disasters is due to the exposure and vulnerability of the human and natural system to the climate extremes. The cause of such a climate extreme could be anthropogenic or non-anthropogenic. Therefore, it is challenging to discern the critical factor of influence for a particular climate extreme. Such kind of perceptive study with reasonable confidence on climate extreme events is possible only if there exist any past case studies. A similar rarest climate extreme problem encountered in the case of Houston floods and extreme rainfall over Florida in August 2017. A continuum of hurricanes like Harvey and Irma targeted the Florida region and caused catastrophe. Due to the rarity of August 2017 Florida climate extreme event, it requires the in-depth study on this case. To understand the multi-faceted nature of the event, a study on the development of the Harvey hurricane and its progression and dynamics is significant. Current article focus on the observational and modeling study on the Harvey hurricane. A global model named as NCUM (The global UK Met office Unified Model (UM) operational at National Center for Medium Range Weather Forecasting, India, was utilized to simulate the Harvey hurricane. The simulated rainfall and wind fields were compared with the observational datasets like Tropical Rainfall Measuring Mission rainfall datasets and Era-Interim wind fields. The National Centre for Environmental Prediction (NCEP) automated tracking system was utilized to track the Harvey hurricane, and the tracks were analyzed statistically for different forecasts concerning the Harvey hurricane track of Joint Typhon Warning Centre. Further, the current study will be continued to investigate the atmospheric processes involved in the August 2017 Florida climate extreme event.

  7. Climate Central World Weather Attribution (WWA) project: Real-time extreme weather event attribution analysis

    NASA Astrophysics Data System (ADS)

    Haustein, Karsten; Otto, Friederike; Uhe, Peter; Allen, Myles; Cullen, Heidi

    2015-04-01

    Extreme weather detection and attribution analysis has emerged as a core theme in climate science over the last decade or so. By using a combination of observational data and climate models it is possible to identify the role of climate change in certain types of extreme weather events such as sea level rise and its contribution to storm surges, extreme heat events and droughts or heavy rainfall and flood events. These analyses are usually carried out after an extreme event has occurred when reanalysis and observational data become available. The Climate Central WWA project will exploit the increasing forecast skill of seasonal forecast prediction systems such as the UK MetOffice GloSea5 (Global seasonal forecasting system) ensemble forecasting method. This way, the current weather can be fed into climate models to simulate large ensembles of possible weather scenarios before an event has fully emerged yet. This effort runs along parallel and intersecting tracks of science and communications that involve research, message development and testing, staged socialization of attribution science with key audiences, and dissemination. The method we employ uses a very large ensemble of simulations of regional climate models to run two different analyses: one to represent the current climate as it was observed, and one to represent the same events in the world that might have been without human-induced climate change. For the weather "as observed" experiment, the atmospheric model uses observed sea surface temperature (SST) data from GloSea5 (currently) and present-day atmospheric gas concentrations to simulate weather events that are possible given the observed climate conditions. The weather in the "world that might have been" experiments is obtained by removing the anthropogenic forcing from the observed SSTs, thereby simulating a counterfactual world without human activity. The anthropogenic forcing is obtained by comparing the CMIP5 historical and natural simulations

  8. Atmospheric Rivers and floods in Southern California: Climate forcing of extreme weather events.

    NASA Astrophysics Data System (ADS)

    Hendy, I. L.; Heusser, L. E.; Napier, T.; Pak, D. K.

    2016-12-01

    Southern California has a Mediterranean type climate characterized by warm dry summers associated with the North Pacific High pressure system and cool, wet winters primarily associated in low pressure systems originating in the high latitude North Pacific. Extreme precipitation, however, is connected to strong zonal flow that brings warm, moist tropical across the Pacific (AKA atmospheric river). Here we present a revised record of flood events in Santa Barbara Basin that have been linked to atmospheric rivers focusing on events associated with transitions between known climate events using new radiocarbon chronology and detailed sediment composition. Flood events identified by homogenous grey layers are present throughout the Holocene with a recurrence every 110 years, but are particularly common (85 year recurrence) between 4,200 and 2,000 years BP. Interval between 6,500 and 4,500 commonly associated with dry conditions in California was associated with fewer flood events (recurrence interval increased to 176 years). Intervals of high lake levels in California associated with pluvials appear to be associated with more frequent extreme precipitation events. The longest recurrence interval (535 years) is associated with the Medieval Climate Anomaly. The season in which the atmospheric river occurs was estimated using the relative abundance of pollen within the flood deposit. The 735 and 1270 C.E. flood events are associated with May-June flowering vegetation, while the most recent events (1861-2 and 1761 C.E.) were associated with November to March flowering vegetation. This agrees with the December-January rainfall records of the historic 1861-62. We conclude the frequency of extreme precipitation events appears to increase as climate cools (e.g. the Little Ice Age).

  9. Paradox of the peak-PCIM (Paleocene Carbon Isotope Maxima; ~57.8Ma) and Abrupt Global Warming

    NASA Astrophysics Data System (ADS)

    Harper, D. T.; Hoenisch, B.; Zachos, J. C.

    2015-12-01

    The Paleocene Carbon Isotope Maxima (PCIM; ~57.8Ma) represents a major transition in global δ13C during the late Paleocene, when the long-term positive trend in δ13C reversed from positive to negative. The peak-PCIM (~57.7Ma) has been tightly resolved in new high-resolution, astronomically-tuned benthic isotope records from IODP Sites 1209 (Pacific) and 1262 (Atlantic), which show the final phase of δ13C enrichment as abrupt (~1‰ in <100kyrs) and coinciding with a 0.5‰ decline in benthic δ18O indicative of 2-3ºC of bottom water warming, effectively marking the onset of a gradual 8Myr long warming trend [Littler et al., EPSL 2014]. Typically, during the Paleogene on orbital time scales, warming is observed during intervals of δ13C depletion, consistent with release of isotopically light carbon to the atmosphere. This event, which has the appearance of a bifurcation in the long-term coupling of climate system and the carbon cycle, poses an interesting paradox as any rapid carbon release to the atmosphere should, in theory, create a negative excursion because all of the major carbon sources are isotopically light, whether volcanic outgassing, weathering/oxidation of organic carbon, or methane release [Dunkley-Jones et al., Phil. Trans. R. Soc. A 2010]. If global, there are several testable mechanisms that may explain the shift including increase in burial flux of light carbon, a reduction in heavy carbon burial flux, or a large-scale circulation change perhaps associated with the transition of a major oceanic gateway. Using trace metal (B/Ca and Mg/Ca) and stable isotope (δ11B, δ18O, and δ13C) geochemistry, here we establish the nature of the peak-PCIM at sites from 3 different ocean basins (IODP Sites 690, 1209, and 1262) and begin to test several of the possible mechanisms for change. Mg/Ca in mixed-layer planktonic foraminifera show 2-3°C of sea surface warming coinciding with, and abrupt as, the benthic carbon isotope enrichment at all sites. Bottom

  10. 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.

  11. Helpful and Hindering Multicultural Events in Group Supervision: Climate and Multicultural Competence

    ERIC Educational Resources Information Center

    Kaduvettoor, Anju; O'Shaughnessy, Tiffany; Mori, Yoko; Beverly, Clyde, III; Weatherford, Ryan D.; Ladany, Nicholas

    2009-01-01

    This study examines the relationship between multicultural events in group supervision, group climate, and supervisee multicultural competence using a mixed qualitative/quantitative design. The discovery-oriented approach yielded 196 helpful and hindering multicultural events among 136 participants. The most common events included multicultural…

  12. Analysis of the Impact of Climate Change on Extreme Hydrological Events in California

    NASA Astrophysics Data System (ADS)

    Ashraf Vaghefi, Saeid; Abbaspour, Karim C.

    2016-04-01

    Estimating magnitude and occurrence frequency of extreme hydrological events is required for taking preventive remedial actions against the impact of climate change on the management of water resources. Examples include: characterization of extreme rainfall events to predict urban runoff, determination of river flows, and the likely severity of drought events during the design life of a water project. In recent years California has experienced its most severe drought in recorded history, causing water stress, economic loss, and an increase in wildfires. In this paper we describe development of a Climate Change Toolkit (CCT) and demonstrate its use in the analysis of dry and wet periods in California for the years 2020-2050 and compare the results with the historic period 1975-2005. CCT provides four modules to: i) manage big databases such as those of Global Climate Models (GCMs), ii) make bias correction using observed local climate data , iii) interpolate gridded climate data to finer resolution, and iv) calculate continuous dry- and wet-day periods based on rainfall, temperature, and soil moisture for analysis of drought and flooding risks. We used bias-corrected meteorological data of five GCMs for extreme CO2 emission scenario rcp8.5 for California to analyze the trend of extreme hydrological events. The findings indicate that frequency of dry period will increase in center and southern parts of California. The assessment of the number of wet days and the frequency of wet periods suggests an increased risk of flooding in north and north-western part of California, especially in the coastal strip. Keywords: Climate Change Toolkit (CCT), Extreme Hydrological Events, California

  13. Sensitivity and rapidity of vegetational response to abrupt climate change

    NASA Technical Reports Server (NTRS)

    Peteet, D.

    2000-01-01

    Rapid climate 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 climate change is greatest, and response times are as short as decades.

  14. Abrupt transitions to a cold North Atlantic in the late Holocene

    NASA Astrophysics Data System (ADS)

    Geirsdóttir, Áslaug; Miller, Gifford; Larsen, Darren; Florian, Christopher; Pendleton, Simon

    2015-04-01

    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 abrupt departures of centennial scale summer cold periods. These abrupt 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 abrupt climate 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 climate 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

  15. Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

    PubMed

    Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

    2014-07-03

    Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the

  16. Hydrological studies of the historical and palaeoflood events on the middle Yihe River, China

    NASA Astrophysics Data System (ADS)

    Hu, Guiming; Huang, Chun Chang; Zhou, Yali; Pang, Jiangli; Zha, Xiaochun; Guo, Yongqiang; Zhang, Yuzhu; Zhao, Xueru

    2016-12-01

    Palaeo-hydrological and sedimentary investigations were carried out in the Longmenxia Gorge of the middle Yihe River. Five bedsets of flood slackwater deposits (SWD) were found interbedded into Holocene aeolian loess-soil profiles in the river bank at the Longmenxia site. They were identified as the deposits of the suspended sediment load during the extreme flood events of the Holocene. The minimum flood peak discharges were estimated to be 12, 300-15, 300 m3/s using the slope-area method. These are about twice the largest gauged record (7180 m3/s) that has occurred since 1937. These flood events occurred at 3100-3000 a B.P., 1800-1700 a B.P., 700-550 a B.P. and 350-250 a B.P., as dated by optically stimulated luminescence (OSL) in combination with stratigraphic correlation, to which may be added the recorded events of the 223 and 1761 CE floods. These were associated with Holocene monsoonal shifts and abrupt climatic events. This research not only provides palaeoflood discharge estimates on the middle Yihe River, but also provides important data for understanding interactions between regional hydro-climatic systems and global climate change in humid and semi-humid monsoonal regions, such as China.

  17. Variability of extreme climate events in the territory and water area of Russia

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Kostianoy, Andrey

    2016-04-01

    The Fourth (2007) and Fifth (2014) Assessment Reports on Climate Change of the Intergovernmental Panel on Climate Change (IPCC) state that in the XXI century, climate change will be accompanied by an increase in the frequency, intensity and duration of extreme nature events such as: extreme precipitation and extreme high and low air temperatures. All these will lead to floods, droughts, fires, shallowing of rivers, lakes and water reservoirs, desertification, dust storms, melting of glaciers and permafrost, algal bloom events in the seas, lakes and water reservoirs. In its turn, these events will lead to chemical and biological contamination of water, land and air. These events will result in a deterioration of quality of life, significant financial loss due to damage to the houses, businesses, roads, agriculture, forestry, tourism, and in many cases they end in loss of life. These predictions are confirmed by the results of the studies presented in the RosHydromet First (2008) and Second (2014) Assessment Reports on Climate Change and its Consequences in Russian Federation. Scientists predictions have been repeatedly confirmed in the last 15 years - floods in Novorossiysk (2002), Krymsk and Gelendzhik (2012), the Far East (2013), heat waves in 2010, unusually cold winter (February) of 2012 and unusually warm winter of 2013/2014 in the European territory of Russia. In this regard, analysis and forecasting of extreme climate events associated with climate change in the territory of Russia are an extremely important task. This task is complicated by the fact that modern atmospheric models used by IPCC and RosHydromet badly reproduce and predict the intensity of precipitation. We are analyzing meteorological reanalysis data (NCEP/NCAR, 20th Century Reanalysis, ERA-20C, JRA-55) and satellite data (NASA and AVISO) on air, water and land temperature, rainfall, wind speed and cloud cover, water levels in seas and lakes, index of vegetation over the past 30-60 years

  18. [Extreme Climatic Events in the Altai Republic According to Dendrochronological Data].

    PubMed

    Barinov, V V; Myglan, V S; Nazarov, A N; Vaganov, E A; Agatova, A R; Nepop, R K

    2016-01-01

    The results of dating of extreme climatic events by damage to the anatomical structure and missing tree rings of the Siberian larch in the upper forest boundary of the Altai Republic are given. An analysis of the spatial distribution of the revealed dates over seven plots (Kokcy, Chind, Ak-ha, Jelo, Tute, Tara, and Sukor) allowed us to distinguish the extreme events on interregional (1700, 1783, 1788, 1812, 1814, 1884), regional (1724, 1775, 1784, 1835, 1840, 1847, 1850, 1852, 1854, 1869, 1871, 1910, 1917, 1927, 1938, 1958, 1961), and local (1702, 1736, 1751, 1785, 1842, 1843,1874, 1885, 1886, 1919, 2007, and 2009) scales. It was shown that the events of an interregional scale correspond with the dates of major volcanic eruptions (Grimsvotn, Lakagigar, Etna, Awu, Tambora, Soufriere St. Vinsent, Mayon, and Krakatau volcanos) and extreme climatic events, crop failures, lean years, etc., registered in historical sources.

  19. Assessing, Modeling, and Monitoring the Impacts of Extreme Climate Events

    NASA Astrophysics Data System (ADS)

    Murnane, Richard J.; Diaz, Henry F.

    2006-01-01

    Extreme weather and climate events provide dramatic content for the news media, and the past few years have supplied plenty of material. The 2004 and 2005 Atlantic hurricane seasons were very active; the United States was struck repeatedly by landfalling major hurricanes. A five-year drought in the southwestern United States was punctuated in 2003 by wildfires in southern California that caused billions of dollars in losses. Ten cyclones of at least tropical storm strength struck Japan in 2004, easily breaking the 1990 and 1993 records of six cyclones each year. Hurricane Catarina was the first recorded hurricane in the South Atlantic. Europe's summer of 2003 saw record-breaking heat that caused tens of thousands of deaths. These events have all been widely publicized, and they naturally raise several questions: Is climate changing, and if so, why? What can we expect in the future? How can we better respond to climate variability regardless of its source?

  20. Continuous and discrete extreme climatic events affecting the dynamics of a high-arctic reindeer population.

    PubMed

    Chan, Kung-Sik; Mysterud, Atle; Øritsland, Nils Are; Severinsen, Torbjørn; Stenseth, Nils Chr

    2005-10-01

    Climate at northern latitudes are currently changing both with regard to the mean and the temporal variability at any given site, increasing the frequency of extreme events such as cold and warm spells. Here we use a conceptually new modelling approach with two different dynamic terms of the climatic effects on a Svalbard reindeer population (the Brøggerhalvøya population) which underwent an extreme icing event ("locked pastures") with 80% reduction in population size during one winter (1993/94). One term captures the continuous and linear effect depending upon the Arctic Oscillation and another the discrete (rare) "event" process. The introduction of an "event" parameter describing the discrete extreme winter resulted in a more parsimonious model. Such an approach may be useful in strongly age-structured ungulate populations, with young and very old individuals being particularly prone to mortality factors during adverse conditions (resulting in a population structure that differs before and after extreme climatic events). A simulation study demonstrates that our approach is able to properly detect the ecological effects of such extreme climate events.

  1. [Smoking abstinence rate and its associated factors between abrupt and gradual smoking cessation].

    PubMed

    Hao, R; Zhou, J P; Ni, L; Li, Q Y; Shi, G C

    2017-12-12

    Objective: To analyze and compare the abstinence rate of smoking quitting methods and its associated factors between abrupt and gradual smoking cessation in smokers with drug-based therapy. Methods: A prospective clinical study was conducted in patients undergoing quitting smoking intervention in Ruijin Hospital smoking cessation clinic between June 2013 and May 2016. All the subjects were randomized in a 1∶1 ratio into the abrupt smoking cessation group (smoking as usual over 3 weeks before a planned quit day, and then stopping smoking abruptly) and the gradual smoking cessation group (gradually reducing tobacco use over 3 weeks before a planned quit day, and then stopping smoking totally). The primary outcome was the complete abstinence rate, and the secondary outcomes included 1-month, 3-month and 6 month 7-day point prevalence of abstinence rates and 3 month sustained abstinence rates. Changes of body weight and drug adverse events were also compared. Results: A total of 314 moderate to severe nicotine-dependent patients were admitted in the study, including 157 patients in the abrupt smoking cessation and 157 patients in the gradual smoking cessation group. Fourteen patients fell off during the follow-up. For the complete abstinence rate, the gradual smoking cessation group was higher than the abrupt smoking cessation group(55.0% vs . 36.9%, χ(2)=9.841, P =0.002) .For 7-d smoking abstinence rate in the 1st, 3rd, 6th month, there was no significant difference between the 2 groups (all P >0.05). As for the 3-month sustained abstinence rate, a higher smoking quitting rate was seen in the gradual smoking cessation group compared to the abrupt smoking cessation group in the 6-month follow-up (17.9% vs .8.7%, χ(2)=5.441, P =0.020). The adverse drug reaction incidence was higher in the abrupt smoking cessation group than the gradual smoking cessation group (Gastrointestinal discomfort: 39.2% vs . 17.7%, χ(2)=12.336, P =0.000; Dreaminess: 40.2% vs . 13.3%, χ(2

  2. Relationships between northern Adriatic Sea mucilage events and climate variability.

    PubMed

    Deserti, Marco; Cacciamani, Carlo; Chiggiato, Jacopo; Rinaldi, Attilio; Ferrari, Carla R

    2005-12-15

    A long term analysis (1865-2002) of meteorological data collected in the Po Valley and Northern Adriatic Basin have been analysed to find possible links between variability in the climatic parameters and the phenomenon of mucilage. Seasonal anomalies of temperature, calculated as spatial mean over the Po Valley area, and anomalies of North Atlantic Oscillation were compared with the historical record of mucilage episodes. Both climatic indices were found to be positively correlated with mucilage events, suggesting a possible relationship between climatic variability and the increased appearance of mucilage aggregates.

  3. Analysis of abrupt transitions in ecological systems

    USDA-ARS?s Scientific Manuscript database

    The occurrence and causes of abrupt 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 abrupt transitions has been advanced by theory, but hindered by the l...

  4. Gap formation following climatic events in spatially structured plant communities

    PubMed Central

    Liao, Jinbao; De Boeck, Hans J.; Li, Zhenqing; Nijs, Ivan

    2015-01-01

    Gaps play a crucial role in maintaining species diversity, yet how community structure and composition influence gap formation is still poorly understood. We apply a spatially structured community model to predict how species diversity and intraspecific aggregation shape gap patterns emerging after climatic events, based on species-specific mortality responses. In multispecies communities, average gap size and gap-size diversity increased rapidly with increasing mean mortality once a mortality threshold was exceeded, greatly promoting gap recolonization opportunity. This result was observed at all levels of species richness. Increasing interspecific difference likewise enhanced these metrics, which may promote not only diversity maintenance but also community invasibility, since more diverse niches for both local and exotic species are provided. The richness effects on gap size and gap-size diversity were positive, but only expressed when species were sufficiently different. Surprisingly, while intraspecific clumping strongly promoted gap-size diversity, it hardly influenced average gap size. Species evenness generally reduced gap metrics induced by climatic events, so the typical assumption of maximum evenness in many experiments and models may underestimate community diversity and invasibility. Overall, understanding the factors driving gap formation in spatially structured assemblages can help predict community secondary succession after climatic events. PMID:26114803

  5. Subsurface warming in the subpolar North Atlantic during rapid climate events in the Early and Mid-Pleistocene

    NASA Astrophysics Data System (ADS)

    Hernández-Almeida, Iván; Sierro, Francisco; Cacho, Isabel; Abel Flores, José

    2014-05-01

    A new high-resolution reconstruction of the temperature and salinity of the subsurface waters using paired Mg/Ca-δ18O measurements on the planktonic foraminifera Neogloboquadrina pachyderma sinistrorsa (sin.) was conducted on a deep-sea sediment core in the subpolar North Atlantic (Site U1314). This study aims to reconstruct millennial-scale subsurface hydrography variations during the Early and Mid-Pleistocene (MIS 31-19). These rapid climate events are characterized by abrupt shifts between warm/cold conditions, and ice-sheet oscillations, as evidenced by major ice rafting events recorded in the North Atlantic sediments (Hernández-Almeida et al., 2012), similar to those found during the Last Glacial period (Marcott et al, 2011). The Mg/Ca derived paleotemperature and salinity oscillations prior and during IRD discharges at Site U1314 are related to changes in intermediate circulation. The increases in Mg/Ca paleotemperatures and salinities during the IRD event are preceded by short episodes of cooling and freshening of subsurface waters. The response of the AMOC to this perturbation is an increased of warm and salty water coming from the south, transported to high latitudes in the North Atlantic beneath the thermocline. This process is accompanied by a southward shift in the convection cell from the Nordic Seas to the subpolar North Atlantic and better ventilation of the North Atlantic at mid-depths. Poleward transport of warm and salty subsurface subtropical waters causes intense basal melting and thinning of marine ice-shelves, that culminates in large-scale instability of the ice sheets, retreat of the grounding line and iceberg discharge. The mechanism proposed involves the coupling of the AMOC with ice-sheet dynamics, and would explain the presence of these fluctuations before the establishment of high-amplitude 100-kyr glacial cycles. Hernández-Almeida, I., Sierro, F.J., Cacho, I., Flores, J.A., 2012. Impact of suborbital climate changes in the North

  6. Science-based risk assessments for rare events in a changing climate

    NASA Astrophysics Data System (ADS)

    Sobel, A. H.; Tippett, M. K.; Camargo, S. J.; Lee, C. Y.; Allen, J. T.

    2014-12-01

    History shows that substantial investments in protection against any specific type of natural disaster usually occur only after (usually shortly after) that specific type of disaster has happened in a given place. This is true even when it was well known before the event that there was a significant risk that it could occur. Presumably what psychologists Kahneman and Tversky have called "availability bias" is responsible, at least in part, for these failures to act on known but out-of-sample risks. While understandable, this human tendency prepares us poorly for events which are very rare (on the time scales of human lives) and even more poorly for a changing climate, as historical records become a poorer guide. A more forward-thinking and rational approach would require scientific risk assessments that can place meaningful probabilities on events that are rare enough to be absent from the historical record, and that can account for the influences of both anthropogenic climate change and low-frequency natural climate variability. The set of tools available for doing such risk assessments is still quite limited, particularly for some of the most extreme events such as tropical cyclones and tornadoes. We will briefly assess the state of the art for these events in particular, and describe some of our ongoing research to develop new tools for quantitative risk assessment using hybrids of statistical methods and physical understanding of the hazards.

  7. Climate change and health in Israel: adaptation policies for extreme weather events.

    PubMed

    Green, Manfred S; Pri-Or, Noemie Groag; Capeluto, Guedi; Epstein, Yoram; Paz, Shlomit

    2013-06-27

    Climatic changes have increased the world-wide frequency of extreme weather events such as heat waves, cold spells, floods, storms and droughts. These extreme events potentially affect the health status of millions of people, increasing disease and death. Since mitigation of climate change is a long and complex process, emphasis has recently been placed on the measures required for adaptation. Although the principles underlying these measures are universal, preparedness plans and policies need to be tailored to local conditions. In this paper, we conducted a review of the literature on the possible health consequences of extreme weather events in Israel, where the conditions are characteristic of the Mediterranean region. Strong evidence indicates that the frequency and duration of several types of extreme weather events are increasing in the Mediterranean Basin, including Israel. We examined the public health policy implications for adaptation to climate change in the region, and proposed public health adaptation policy options. Preparedness for the public health impact of increased extreme weather events is still relatively limited and clear public health policies are urgently needed. These include improved early warning and monitoring systems, preparedness of the health system, educational programs and the living environment. Regional collaboration should be a priority.

  8. Climate change and health in Israel: adaptation policies for extreme weather events

    PubMed Central

    2013-01-01

    Climatic changes have increased the world-wide frequency of extreme weather events such as heat waves, cold spells, floods, storms and droughts. These extreme events potentially affect the health status of millions of people, increasing disease and death. Since mitigation of climate change is a long and complex process, emphasis has recently been placed on the measures required for adaptation. Although the principles underlying these measures are universal, preparedness plans and policies need to be tailored to local conditions. In this paper, we conducted a review of the literature on the possible health consequences of extreme weather events in Israel, where the conditions are characteristic of the Mediterranean region. Strong evidence indicates that the frequency and duration of several types of extreme weather events are increasing in the Mediterranean Basin, including Israel. We examined the public health policy implications for adaptation to climate change in the region, and proposed public health adaptation policy options. Preparedness for the public health impact of increased extreme weather events is still relatively limited and clear public health policies are urgently needed. These include improved early warning and monitoring systems, preparedness of the health system, educational programs and the living environment. Regional collaboration should be a priority. PMID:23805950

  9. What are the Best Practices of Using to Twitter in Climate Change Communication?: A Case Study of Two Climate Related Events

    NASA Astrophysics Data System (ADS)

    McNeal, K.; Luginbuhl, S.; Ngo, A. M.

    2017-12-01

    Climate change is a major environmental issue that is often discussed throughout the world using social media outlets. One major social media site that is commonly utilized by the public is Twitter, with over 300 million active users. Using a Twitter account and Ncapture we were able to collect tens of thousands of tweets around the COP21 event, a United Nations climate change conference held on Dec. 7-8, 2015 in Paris, and the 2015 Encyclical Release by the Pope, using the hashtags @climate, pope, and COP21. This research aimed to follow and collect tweets about what and who the major influencers on Twitter are concerning these events, and subsequently climate change in general, and what content was most persistent. Specifically, we examined Twitter users with high numbers of followers (>10,000), the number of re-tweets, the frequency of tweets, and the content of the tweet. We have tabulated the top 10 most influential Tweeters among each of the months (August, September, October, November and December) of 2015 leading up to and following the COP21 event, which included an array of Twitter users from NGOs, Politicians, Celebrities, Religious Leaders, Governmental Organizations, among others. We also examined tweets about climate change as they relate to the two events and interpret why these tweets may have persisted in the twitter space. From our observations, we have established some best practices in how to create climate messages that have high reach and longevity. We hope our results assist climate change communicators in understanding the role Twitter plays in regard to climate change discourse and how to most efficiently utilize it for reaching broad audiences and engaging them in the climate conversation.

  10. The INTIMATE event stratigraphy of the last glacial period

    NASA Astrophysics Data System (ADS)

    Olander Rasmussen, Sune; Svensson, Anders

    2015-04-01

    The North Atlantic INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) group has previously recommended an Event Stratigraphy approach for the synchronisation of records of the Last Termination using the Greenland ice core records as the regional stratotypes. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. In addition to presenting the updated event stratigraphy, we make a series of recommendations on how to refer to these periods in a way that promotes unambiguous comparison and correlation between different proxy records, providing a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is a part of a newly published paper in an INTIMATE special issue of Quaternary Science Reviews: Rasmussen et al., 'A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event

  11. Climate Change, Salmon in the NOAA Budget Spotlight

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2004-05-01

    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 abrupt climate 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 abrupt climate change appears to be eliminated in the proposed budget.

  12. Climate network analysis of regional precipitation extremes: The true story told by event synchronization

    NASA Astrophysics Data System (ADS)

    Odenweller, Adrian; Donner, Reik V.

    2017-04-01

    Over the last decade, complex network methods have been frequently used for characterizing spatio-temporal patterns of climate variability from a complex systems perspective, yielding new insights into time-dependent teleconnectivity patterns and couplings between different components of the Earth climate. Among the foremost results reported, network analyses of the synchronicity of extreme events as captured by the so-called event synchronization have been proposed to be powerful tools for disentangling the spatio-temporal organization of particularly extreme rainfall events and anticipating the timing of monsoon onsets or extreme floodings. Rooted in the analysis of spike train synchrony analysis in the neurosciences, event synchronization has the great advantage of automatically classifying pairs of events arising at two distinct spatial locations as temporally close (and, thus, possibly statistically - or even dynamically - interrelated) or not without the necessity of selecting an additional parameter in terms of a maximally tolerable delay between these events. This consideration is conceptually justified in case of the original application to spike trains in electroencephalogram (EEG) recordings, where the inter-spike intervals show relatively narrow distributions at high temporal sampling rates. However, in case of climate studies, precipitation extremes defined by daily precipitation sums exceeding a certain empirical percentile of their local distribution exhibit a distinctively different type of distribution of waiting times between subsequent events. This raises conceptual concerns if event synchronization is still appropriate for detecting interlinkages between spatially distributed precipitation extremes. In order to study this problem in more detail, we employ event synchronization together with an alternative similarity measure for event sequences, event coincidence rates, which requires a manual setting of the tolerable maximum delay between two

  13. Do Quercus ilex woodlands undergo abrupt non-linear functional changes in response to human disturbance along a climatic gradient?

    NASA Astrophysics Data System (ADS)

    Bochet, Esther; García-Fayos, Patricio; José Molina, Maria; Moreno de las Heras, Mariano; Espigares, Tíscar; Nicolau, Jose Manuel; Monleon, Vicente

    2017-04-01

    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. 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 climatic 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.

  14. Controls on the abruptness of gravel-sand transitions

    NASA Astrophysics Data System (ADS)

    Venditti, J. G.; Church, M. A.; Lamb, M. P.; Domarad, N.; Rennie, C. D.

    2014-12-01

    As gravel-bedded rivers fine downstream, they characteristically exhibit an abrupt transition from gravel- to sand-bed. This is the only abrupt 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 abruptness 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 abrupt 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 abrupt change in bed slope through the transition that leads to an abrupt 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 abrupt GST by size selective sorting. We provide evidence, both empirical and theoretical, that suggests the emergence of an abrupt 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 abruptness 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

  15. Widespread, Very Heavy Precipitation Events in Contemporary and Scenario Summer Climates from NARCCAP Simulations

    NASA Astrophysics Data System (ADS)

    Kawazoe, S.; Gutowski, W. J., Jr.

    2015-12-01

    We analyze the ability of regional climate models (RCMs) to simulate very heavy daily precipitation and supporting processes for both contemporary and future-scenario simulations during summer (JJA). RCM output comes from North American Regional Climate Change Assessment Program (NARCCAP) simulations, which are all run at a spatial resolution of 50 km. Analysis focuses on the upper Mississippi basin for summer, between 1982-1998 for the contemporary climate, and 2052-2068 during the scenario climate. We also compare simulated precipitation and supporting processes with those obtained from observed precipitation and reanalysis atmospheric states. Precipitation observations are from the University of Washington (UW) and the Climate Prediction Center (CPC) gridded dataset. Utilizing two observational datasets helps determine if any uncertainties arise from differences in precipitation gridding schemes. Reanalysis fields come from the North American Regional Reanalysis. The NARCCAP models generally reproduce well the precipitation-vs.-intensity spectrum seen in observations, while producing overly strong precipitation at high intensity thresholds. In the future-scenario climate, there is a decrease in frequency for light to moderate precipitation intensities, while an increase in frequency is seen for the higher intensity events. Further analysis focuses on precipitation events exceeding the 99.5 percentile that occur simultaneously at several points in the region, yielding so-called "widespread events". For widespread events, we analyze local and large scale environmental parameters, such as 2-m temperature and specific humidity, 500-hPa geopotential heights, Convective Available Potential Energy (CAPE), vertically integrated moisture flux convergence, among others, to compare atmospheric states and processes leading to such events in the models and observations. The results suggest that an analysis of atmospheric states supporting very heavy precipitation events is a

  16. Response of the auroral electrojet indices to abrupt southward IMF turnings

    NASA Astrophysics Data System (ADS)

    Gjerloev, J. W.; Hoffman, R. A.; Ohtani, S.; Weygand, J.; Barnes, R.

    2010-05-01

    We present results from a study of the behavior of the auroral electrojet indices following abrupt southward turnings of the IMF Bz. The auroral electrojet indices are calculated from observations made by more than 100 ground based stations provided by the SuperMAG collaborators. Based on three simple criteria we selected 73 events. In each event the interval of analysis started at the time of the IMF Bz southward turning and ended 45 minutes later or at the onset of any abrupt energy unloading event in the magnetosphere, regardless of size. We refer to this period as the "pre-unloading phase". To isolate the dependence of the auroral electrojets on the solar induced ionospheric conductivity during this phase we separated the standard AU/AL indices into two new sets of indices defined by the upper and lower envelope of the north-south component for all sunlit stations (AUs/ALs) and for all stations in darkness (AUd/ALd). Based on events and statistical analyses we can conclude that following a southward turning of the IMF Bz the AUd/ALd indices show no measurable response while the AUs/ALs indices clearly intensify. The intensifications of AUs/ALs are dependent on the intensity of the solar wind driver (as measured by IMF Bz or the Akasofu ɛ parameter). The lack of AUd/ALd response does not depend on the intensity of any subsequent substorm. We find that during these isolated events the ionospheric current system is primarily confined to the sunlit ionosphere. This truncated version of the classical global DP-2 current system suggests that auroral electrojet continuity is not maintained across the terminator. Because of its conductivity dependence on the solar zenith angle, this truncated global current pattern is expected to be highly dependent on UT and season and thus can be asymmetric between hemispheres. Thus we argue that the global two-cell DP-2 current system is not a consequence only of a southward turning of the IMF but requires also the reduction of the

  17. Linking the 8.2 ka Event and its Freshwater Forcing in the Labrador Sea

    NASA Technical Reports Server (NTRS)

    Hoffman, Jeremy S.; Carlson, Anders E.; Winsor, Kelsey; Klinkhammer, Gary P.; LeGrande, Allegra N.; Andrews, John T.; Strasser, C.

    2012-01-01

    The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in (delta)18O of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we demonstrate that approx. 3 C of near-surface ocean cooling masked an 1.0 % decrease in western Labrador Sea (delta)18O of seawater concurrent with Lake Agassiz drainage. Comparison with North Atlantic (delta)18O of seawater records shows that the freshwater discharge was transported to regions of deep-water formation where it could perturb AMOC and force the 8.2 ka event.

  18. Exposure to Unethical Career Events: Effects on Decision-Making, Climate, and Socialization

    PubMed Central

    Mumford, Michael D.; Waples, Ethan P.; Antes, Alison L.; Murphy, Stephen T.; Connelly, Shane; Brown, Ryan P.; Devenport, Lynn D.

    2009-01-01

    An implicit goal of many interventions intended to enhance integrity is to minimize peoples’ exposure to unethical events. The intent of the present effort was to examine if exposure to unethical practices in the course of one’s work is related to ethical decision-making. Accordingly, 248 doctoral students in the biological, health, and social sciences were asked to complete a field appropriate measure of ethical decision-making. In addition, they were asked to complete measures examining the perceived acceptability of unethical events and a measure examining perceptions of ethical climate. When these criterion measures were correlated with a measure examining the frequency with which they had been exposed to unethical events in their day-to-day work, it was found that event exposure was strongly related to ethical decision-making, but less strongly related to climate perceptions and perceptions of event acceptability. However, these relationships were moderated by level of experience. The implications of these findings for practices intended to improve ethics are discussed. PMID:19936323

  19. Exposure to Unethical Career Events: Effects on Decision-Making, Climate, and Socialization.

    PubMed

    Mumford, Michael D; Waples, Ethan P; Antes, Alison L; Murphy, Stephen T; Connelly, Shane; Brown, Ryan P; Devenport, Lynn D

    2009-09-01

    An implicit goal of many interventions intended to enhance integrity is to minimize peoples' exposure to unethical events. The intent of the present effort was to examine if exposure to unethical practices in the course of one's work is related to ethical decision-making. Accordingly, 248 doctoral students in the biological, health, and social sciences were asked to complete a field appropriate measure of ethical decision-making. In addition, they were asked to complete measures examining the perceived acceptability of unethical events and a measure examining perceptions of ethical climate. When these criterion measures were correlated with a measure examining the frequency with which they had been exposed to unethical events in their day-to-day work, it was found that event exposure was strongly related to ethical decision-making, but less strongly related to climate perceptions and perceptions of event acceptability. However, these relationships were moderated by level of experience. The implications of these findings for practices intended to improve ethics are discussed.

  20. From Abrupt Change to the Future (Hans Oeschger Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Stocker, T.

    2009-04-01

    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 climate 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 abrupt ways to changes in forcing. Likewise, the Antarctic ice cores have provided one of the corner stones of our knowledge about climate 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 climate 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

  1. Ecology and the ratchet of events: climate variability, niche dimensions, and species distributions

    USGS Publications Warehouse

    Jackson, Stephen T.; Betancourt, Julio L.; Booth, Robert K.; Gray, Stephen T.

    2009-01-01

    Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics.

  2. Ecology and the ratchet of events: Climate variability, niche dimensions, and species distributions

    USGS Publications Warehouse

    Jackson, S.T.; Betancourt, J.L.; Booth, R.K.; Gray, S.T.

    2009-01-01

    Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and morefundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics.

  3. Ecology and the ratchet of events: Climate variability, niche dimensions, and species distributions

    PubMed Central

    Jackson, Stephen T.; Betancourt, Julio L.; Booth, Robert K.; Gray, Stephen T.

    2009-01-01

    Climate change in the coming centuries will be characterized by interannual, decadal, and multidecadal fluctuations superimposed on anthropogenic trends. Predicting ecological and biogeographic responses to these changes constitutes an immense challenge for ecologists. Perspectives from climatic and ecological history indicate that responses will be laden with contingencies, resulting from episodic climatic events interacting with demographic and colonization events. This effect is compounded by the dependency of environmental sensitivity upon life-stage for many species. Climate variables often used in empirical niche models may become decoupled from the proximal variables that directly influence individuals and populations. Greater predictive capacity, and more-fundamental ecological and biogeographic understanding, will come from integration of correlational niche modeling with mechanistic niche modeling, dynamic ecological modeling, targeted experiments, and systematic observations of past and present patterns and dynamics. PMID:19805104

  4. Vulnerability of global food production to extreme climatic events.

    PubMed

    Yeni, F; Alpas, H

    2017-06-01

    It is known that the frequency, intensity or duration of the extreme climatic events have been changing substantially. The ultimate goal of this study was to identify current vulnerabilities of global primary food production against extreme climatic events, and to discuss potential entry points for adaptation planning by means of an explorative vulnerability analysis. Outcomes of this analysis were demonstrated as a composite index where 118 country performances in maintaining safety of food production were compared and ranked against climate change. In order to better interpret the results, cluster analysis technique was used as a tool to group the countries based on their vulnerability index (VI) scores. Results suggested that one sixth of the countries analyzed were subject to high level of exposure (0.45-1), one third to high to very high level of sensitivity (0.41-1) and low to moderate level of adaptive capacity (0-0.59). Proper adaptation strategies for reducing the microbial and chemical contamination of food products, soil and waters on the field were proposed. Finally, availability of data on food safety management systems and occurrence of foodborne outbreaks with global coverage were proposed as key factors for improving the robustness of future vulnerability assessments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Quantifying the influence of global warming on unprecedented extreme climate events

    PubMed Central

    Singh, Deepti; Horton, Daniel E.; Swain, Daniel L.; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala

    2017-01-01

    Efforts to understand the influence of historical global warming on individual extreme climate events have increased over the past decade. However, despite substantial progress, events that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global warming on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical warming has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry events, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent. PMID:28439005

  6. Quantifying the influence of global warming on unprecedented extreme climate events.

    PubMed

    Diffenbaugh, Noah S; Singh, Deepti; Mankin, Justin S; Horton, Daniel E; Swain, Daniel L; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala

    2017-05-09

    Efforts to understand the influence of historical global warming on individual extreme climate events have increased over the past decade. However, despite substantial progress, events that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global warming on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical warming has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry events, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.

  7. Quantifying the Influence of Global Warming on Unprecedented Extreme Climate Events

    NASA Technical Reports Server (NTRS)

    Diffenbaugh, Noah S.; Singh, Deepti; Mankin, Justin S.; Horton, Daniel E.; Swain, Daniel L.; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; hide

    2017-01-01

    Efforts to understand the influence of historical global warming on individual extreme climate events have increased over the past decade. However, despite substantial progress, events that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global warming on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical warming has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry events, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.

  8. Preface: Impacts of extreme climate events and disturbances on carbon dynamics

    USGS Publications Warehouse

    Xiao, Jingfeng; Liu, Shuguang; Stoy, Paul C.

    2016-01-01

    The impacts of extreme climate events and disturbances (ECE&D) on the carbon cycle have received growing attention in recent years. This special issue showcases a collection of recent advances in understanding the impacts of ECE&D on carbon cycling. Notable advances include quantifying how harvesting activities impact forest structure, carbon pool dynamics, and recovery processes; observed drastic increases of the concentrations of dissolved organic carbon and dissolved methane in thermokarst lakes in western Siberia during a summer warming event; disentangling the roles of herbivores and fire on forest carbon dioxide flux; direct and indirect impacts of fire on the global carbon balance; and improved atmospheric inversion of regional carbon sources and sinks by incorporating disturbances. Combined, studies herein indicate several major research needs. First, disturbances and extreme events can interact with one another, and it is important to understand their overall impacts and also disentangle their effects on the carbon cycle. Second, current ecosystem models are not skillful enough to correctly simulate the underlying processes and impacts of ECE&D (e.g., tree mortality and carbon consequences). Third, benchmark data characterizing the timing, location, type, and magnitude of disturbances must be systematically created to improve our ability to quantify carbon dynamics over large areas. Finally, improving the representation of ECE&D in regional climate/earth system models and accounting for the resulting feedbacks to climate are essential for understanding the interactions between climate and ecosystem dynamics.

  9. Abrupt climate 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?

    NASA Astrophysics Data System (ADS)

    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.

    2015-09-01

    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 climate and the interior of West Asia during the last glacial termination and the Holocene epoch. We further assess the potential role of abrupt climate 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 climate change influenced the

  10. Late glacial and Early Holocene climatic conditions along the margin of the Greenland Ice Sheet, registered by glacial extents in Milne Land, east Greenland

    NASA Astrophysics Data System (ADS)

    Levy, L.; Kelly, M. A.; Lowell, T. V.

    2010-12-01

    Determining the mechanisms that caused past abrupt climate changes is important for understanding today’s rapidly warming climate and, in particular, whether we may be faced with abrupt climate change in the future. Scientists, policy makers and the public are concerned about ongoing warming because it is sending our climate into unprecedented territory at a rapid pace. The Younger Dryas cold event (~12,850-11,650 cal yr B.P.) was an abrupt climate event that occurred during the last transition from glacial to interglacial conditions. Due to its abrupt nature and the magnitude of temperature change that occurred, the Younger Dryas has been the focus of extensive research, however, the mechanisms that caused this cold event are still not well understood. Wide belts (up to 5 km) of moraines, known as the Milne Land stade moraines, are present in the Scoresby Sund region of central east Greenland. Previous work in the region using a combination of equilibrium line altitudes, surface exposure dating of moraines, and relative sea level changes indicates that mountain glacier advances during Younger Dryas time represent only moderate summer temperature cooling (~3-4C colder than at present). In contrast, Greenland ice cores, which register mean annual temperatures, indicate that Younger Dryas temperatures over the ice sheet were ~15C colder than at present. This mismatch between the two nearby paleoclimate records is interpreted to result from strong seasonality (very cold winters and only moderately cold summers) during Younger Dryas time. We are examining seasonality during Younger Dryas time by developing records of summer temperatures from local glaciers in Milne Land (71.0°N, 25.6°W). These mountain glaciers are located adjacent to the Greenland Ice Sheet, less than 50 km from the location of Renland Ice core and only ~250 km from the locations of the GISP2 and GRIP cores. We present new 10Be ages of local glacial extents in Milne Land. Ages range from 11,880 yr

  11. Climate variations of Central Asia on orbital to millennial timescales.

    PubMed

    Cheng, Hai; Spötl, Christoph; Breitenbach, Sebastian F M; Sinha, Ashish; Wassenburg, Jasper A; Jochum, Klaus Peter; Scholz, Denis; Li, Xianglei; Yi, Liang; Peng, Youbing; Lv, Yanbin; Zhang, Pingzhong; Votintseva, Antonina; Loginov, Vadim; Ning, Youfeng; Kathayat, Gayatri; Edwards, R Lawrence

    2016-11-11

    The extent to which climate variability in Central Asia is causally linked to large-scale changes in the Asian monsoon on varying timescales remains a longstanding question. Here we present precisely dated high-resolution speleothem oxygen-carbon isotope and trace element records of Central Asia's hydroclimate variability from Tonnel'naya cave, Uzbekistan, and Kesang cave, western China. On orbital timescales, the supra-regional climate variance, inferred from our oxygen isotope records, exhibits a precessional rhythm, punctuated by millennial-scale abrupt climate events, suggesting a close coupling with the Asian monsoon. However, the local hydroclimatic variability at both cave sites, inferred from carbon isotope and trace element records, shows climate variations that are distinctly different from their supra-regional modes. Particularly, hydroclimatic changes in both Tonnel'naya and Kesang areas during the Holocene lag behind the supra-regional climate variability by several thousand years. These observations may reconcile the apparent out-of-phase hydroclimatic variability, inferred from the Holocene lake proxy records, between Westerly Central Asia and Monsoon Asia.

  12. Climate variations of Central Asia on orbital to millennial timescales

    PubMed Central

    Cheng, Hai; Spötl, Christoph; Breitenbach, Sebastian F. M.; Sinha, Ashish; Wassenburg, Jasper A.; Jochum, Klaus Peter; Scholz, Denis; Li, Xianglei; Yi, Liang; Peng, Youbing; Lv, Yanbin; Zhang, Pingzhong; Votintseva, Antonina; Loginov, Vadim; Ning, Youfeng; Kathayat, Gayatri; Edwards, R. Lawrence

    2016-01-01

    The extent to which climate variability in Central Asia is causally linked to large-scale changes in the Asian monsoon on varying timescales remains a longstanding question. Here we present precisely dated high-resolution speleothem oxygen-carbon isotope and trace element records of Central Asia’s hydroclimate variability from Tonnel’naya cave, Uzbekistan, and Kesang cave, western China. On orbital timescales, the supra-regional climate variance, inferred from our oxygen isotope records, exhibits a precessional rhythm, punctuated by millennial-scale abrupt climate events, suggesting a close coupling with the Asian monsoon. However, the local hydroclimatic variability at both cave sites, inferred from carbon isotope and trace element records, shows climate variations that are distinctly different from their supra-regional modes. Particularly, hydroclimatic changes in both Tonnel’naya and Kesang areas during the Holocene lag behind the supra-regional climate variability by several thousand years. These observations may reconcile the apparent out-of-phase hydroclimatic variability, inferred from the Holocene lake proxy records, between Westerly Central Asia and Monsoon Asia. PMID:27833133

  13. Using Atmospheric Circulation Patterns to Detect and Attribute Changes in the Risk of Extreme Climate Events

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.; Horton, D. E.; Singh, D.; Swain, D. L.; Touma, D. E.; Mankin, J. S.

    2015-12-01

    Because of the high cost of extreme events and the growing evidence that global warming is likely to alter the statistical distribution of climate variables, detection and attribution of changes in the probability of extreme climate events has become a pressing topic for the scientific community, elected officials, and the public. While most of the emphasis has thus far focused on analyzing the climate variable of interest (most often temperature or precipitation, but also flooding and drought), there is an emerging emphasis on applying detection and attribution analysis techniques to the underlying physical causes of individual extreme events. This approach is promising in part because the underlying physical causes (such as atmospheric circulation patterns) can in some cases be more accurately represented in climate models than the more proximal climate variable (such as precipitation). In addition, and more scientifically critical, is the fact that the most extreme events result from a rare combination of interacting causes, often referred to as "ingredients". Rare events will therefore always have a strong influence of "natural" variability. Analyzing the underlying physical mechanisms can therefore help to test whether there have been changes in the probability of the constituent conditions of an individual event, or whether the co-occurrence of causal conditions cannot be distinguished from random chance. This presentation will review approaches to applying detection/attribution analysis to the underlying physical causes of extreme events (including both "thermodynamic" and "dynamic" causes), and provide a number of case studies, including the role of frequency of atmospheric circulation patterns in the probability of hot, cold, wet and dry events.

  14. Deciphering landscape complexity to predict (non)linear responses to extreme climatic events

    USDA-ARS?s Scientific Manuscript database

    Extreme events are increasing in frequency and magnitude for many landscapes globally. Ecologically, most of the focus on extreme climatic events has been on effects of either short-term pulses (floods, freezes) or long-term drought. Multi-year increases in precipitation are also occurring with litt...

  15. Climate-driven regime shifts in Arctic marine benthos

    PubMed Central

    Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank; Renaud, Paul E.; Rodrigues, João; Lønne, Ole Jørgen; Gulliksen, Bjørn

    2012-01-01

    Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate 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 abrupt 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 abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-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

  16. Extreme temperature events on Greenland in observations and the MAR regional climate model

    NASA Astrophysics Data System (ADS)

    Leeson, Amber A.; Eastoe, Emma; Fettweis, Xavier

    2018-03-01

    Meltwater from the Greenland Ice Sheet contributed 1.7-6.12 mm to global sea level between 1993 and 2010 and is expected to contribute 20-110 mm to future sea level rise by 2100. These estimates were produced by regional climate models (RCMs) which are known to be robust at the ice sheet scale but occasionally miss regional- and local-scale climate variability (e.g. Leeson et al., 2017; Medley et al., 2013). To date, the fidelity of these models in the context of short-period variability in time (i.e. intra-seasonal) has not been fully assessed, for example their ability to simulate extreme temperature events. We use an event identification algorithm commonly used in extreme value analysis, together with observations from the Greenland Climate Network (GC-Net), to assess the ability of the MAR (Modèle Atmosphérique Régional) RCM to reproduce observed extreme positive-temperature events at 14 sites around Greenland. We find that MAR is able to accurately simulate the frequency and duration of these events but underestimates their magnitude by more than half a degree Celsius/kelvin, although this bias is much smaller than that exhibited by coarse-scale Era-Interim reanalysis data. As a result, melt energy in MAR output is underestimated by between 16 and 41 % depending on global forcing applied. Further work is needed to precisely determine the drivers of extreme temperature events, and why the model underperforms in this area, but our findings suggest that biases are passed into MAR from boundary forcing data. This is important because these forcings are common between RCMs and their range of predictions of past and future ice sheet melting. We propose that examining extreme events should become a routine part of global and regional climate model evaluation and that addressing shortcomings in this area should be a priority for model development.

  17. Focusing Events and Constrains on Policy Addressing Long-Term Climate Change Risks

    NASA Astrophysics Data System (ADS)

    O'Donovan, K.

    2014-12-01

    When policy makers are aware of immediate and long-term risks to communities, what do they do to plan for and mitigate the effects of climate change? This paper addresses that question in two ways. First, as an organizing framework it presents an overview of the empirical evidence on focusing events. Focusing events are defined as sudden, rare events that reveal harm or the potential for future harm that the general public and policy makers become aware of simultaneously. These large-scale events are typically natural and disasters, crisis, or technological accidents. This paper considers the empirical evidence of the relationship between focusing events, the harm revealed by the event and policy change aimed at reducing future risk of harm. Second, this paper reviews the case of flood mitigation policy in the United States from 1968 to 2008. It considers the ways in which policy makers have and have not integrated future flood risks into mitigation policy and planning, particularly after large-scale floods. It analyzes the political, intergovernmental, demographic and geographic factors that have promoted and constrained long-term flood mitigation policy. This paper concludes with a discussion of the meaning and implications of potential focusing events and constrains on policy for long-term climate change concerns.

  18. Palaeoclimatic insights into future climate challenges.

    PubMed

    Alley, Richard B

    2003-09-15

    Palaeoclimatic data document a sensitive climate system subject to large and perhaps difficult-to-predict abrupt changes. These data suggest that neither the sensitivity nor the variability of the climate are fully captured in some climate-change projections, such as the Intergovernmental Panel on Climate Change (IPCC) Summary for Policymakers. Because larger, faster and less-expected climate 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 climate 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 climate sensitivity to CO(2). Abrupt climate 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.

  19. Communicating Climate Uncertainties: Challenges and Opportunities Related to Spatial Scales, Extreme Events, and the Warming 'Hiatus'

    NASA Astrophysics Data System (ADS)

    Casola, J. H.; Huber, D.

    2013-12-01

    Many media, academic, government, and advocacy organizations have achieved sophistication in developing effective messages based on scientific information, and can quickly translate salient aspects of emerging climate research and evolving observations. However, there are several ways in which valid messages can be misconstrued by decision makers, leading them to inaccurate conclusions about the risks associated with climate impacts. Three cases will be discussed: 1) Issues of spatial scale in interpreting climate observations: Local climate observations may contradict summary statements about the effects of climate change on larger regional or global spatial scales. Effectively addressing these differences often requires communicators to understand local and regional climate drivers, and the distinction between a 'signal' associated with climate change and local climate 'noise.' Hydrological statistics in Missouri and California are shown to illustrate this case. 2) Issues of complexity related to extreme events: Climate change is typically invoked following a wide range of damaging meteorological events (e.g., heat waves, landfalling hurricanes, tornadoes), regardless of the strength of the relationship between anthropogenic climate change and the frequency or severity of that type of event. Examples are drawn from media coverage of several recent events, contrasting useful and potentially confusing word choices and frames. 3) Issues revolving around climate sensitivity: The so-called 'pause' or 'hiatus' in global warming has reverberated strongly through political and business discussions of climate change. Addressing the recent slowdown in warming yields an important opportunity to raise climate literacy in these communities. Attempts to use recent observations as a wedge between climate 'believers' and 'deniers' is likely to be counterproductive. Examples are drawn from Congressional testimony and media stories. All three cases illustrate ways that decision

  20. The Extreme Climate Index: a novel and multi-hazard index for extreme weather events.

    NASA Astrophysics Data System (ADS)

    Cucchi, Marco; Petitta, Marcello; Calmanti, Sandro

    2017-04-01

    In this presentation we introduce the Extreme Climate Index (ECI): an objective, multi-hazard index capable of tracking changes in the frequency or magnitude of extreme weather events in African countries, thus indicating that a shift to a new climate regime is underway in a particular area. This index has been developed in the context of XCF (eXtreme Climate Facilities) project lead by ARC (African Risk Capacity, specialised agency of the African Union), and will be used in the payouts triggering mechanism of an insurance programme against risks related to the increase of frequency and magnitude of extreme weather events due to climate regimes' changes. The main hazards covered by ECI will be extreme dry, wet and heat events, with the possibility of adding region-specific risk events such as tropical cyclones for the most vulnerable areas. It will be based on data coming from consistent, sufficiently long, high quality historical records and will be standardized across broad geographical regions, so that extreme events occurring under different climatic regimes in Africa can be comparable. The first step to construct such an index is to define single hazard indicators. In this first study we focused on extreme dry/wet and heat events, using for their description respectively the well-known SPI (Standardized Precipitation Index) and an index developed by us, called SHI (Standardized Heat-waves Index). The second step consists in the development of a computational strategy to combine these, and possibly other indices, so that the ECI can describe, by means of a single indicator, different types of climatic extremes. According to the methodology proposed in this paper, the ECI is defined by two statistical components: the ECI intensity, which indicates whether an event is extreme or not; the angular component, which represent the contribution of each hazard to the overall intensity of the index. The ECI can thus be used to identify "extremes" after defining a

  1. Abrupt response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa

    PubMed Central

    Bastian, Luc; Revel, Marie; Bayon, Germain; Dufour, Aurélie; Vigier, Nathalie

    2017-01-01

    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 climate. However, the magnitude and the nature of the links between weathering and climate are still under debate. In particular, the timescale over which chemical weathering may respond to climate 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 climatic 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 abrupt 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

  2. Abrupt response of chemical weathering to Late Quaternary hydroclimate changes in northeast Africa.

    PubMed

    Bastian, Luc; Revel, Marie; Bayon, Germain; Dufour, Aurélie; Vigier, Nathalie

    2017-03-14

    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 climate. However, the magnitude and the nature of the links between weathering and climate are still under debate. In particular, the timescale over which chemical weathering may respond to climate 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 climatic 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 abrupt 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.

  3. Separating out the influence of climatic trend, fluctuations, and extreme events on crop yield: a case study in Hunan Province, China

    NASA Astrophysics Data System (ADS)

    Wang, Zhu; Shi, Peijun; Zhang, Zhao; Meng, Yongchang; Luan, Yibo; Wang, Jiwei

    2017-09-01

    Separating out the influence of climatic trend, fluctuations and extreme events on crop yield is of paramount importance to climate change adaptation, resilience, and mitigation. Previous studies lack systematic and explicit assessment of these three fundamental aspects of climate change on crop yield. This research attempts to separate out the impacts on rice yields of climatic trend (linear trend change related to mean value), fluctuations (variability surpassing the "fluctuation threshold" which defined as one standard deviation (1 SD) of the residual between the original data series and the linear trend value for each climatic variable), and extreme events (identified by absolute criterion for each kind of extreme events related to crop yield). The main idea of the research method was to construct climate scenarios combined with crop system simulation model. Comparable climate scenarios were designed to express the impact of each climate change component and, were input to the crop system model (CERES-Rice), which calculated the related simulated yield gap to quantify the percentage impacts of climatic trend, fluctuations, and extreme events. Six Agro-Meteorological Stations (AMS) in Hunan province were selected to study the quantitatively impact of climatic trend, fluctuations and extreme events involving climatic variables (air temperature, precipitation, and sunshine duration) on early rice yield during 1981-2012. The results showed that extreme events were found to have the greatest impact on early rice yield (-2.59 to -15.89%). Followed by climatic fluctuations with a range of -2.60 to -4.46%, and then the climatic trend (4.91-2.12%). Furthermore, the influence of climatic trend on early rice yield presented "trade-offs" among various climate variables and AMS. Climatic trend and extreme events associated with air temperature showed larger effects on early rice yield than other climatic variables, particularly for high-temperature events (-2.11 to -12

  4. Reducing uncertainty in Climate Response Time Scale by Bayesian Analysis of the 8.2 ka event

    NASA Astrophysics Data System (ADS)

    Lorenz, A.; Held, H.; Bauer, E.; Schneider von Deimling, T.

    2009-04-01

    We analyze the possibility of uncertainty reduction in Climate Response Time Scale by utilizing Greenland ice-core data that contain the 8.2 ka event within a Bayesian model-data intercomparison with the Earth system model of intermediate complexity, CLIMBER-2.3. Within a stochastic version of the model it has been possible to mimic the 8.2 ka event within a plausible experimental setting and with relatively good accuracy considering the timing of the event in comparison to other modeling exercises [1]. The simulation of the centennial cold event is effectively determined by the oceanic cooling rate which depends largely on the ocean diffusivity described by diffusion coefficients of relatively wide uncertainty ranges. The idea now is to discriminate between the different values of diffusivities according to their likelihood to rightly represent the duration of the 8.2 ka event and thus to exploit the paleo data to constrain uncertainty in model parameters in analogue to [2]. Implementing this inverse Bayesian Analysis with this model the technical difficulty arises to establish the related likelihood numerically in addition to the uncertain model parameters: While mainstream uncertainty analyses can assume a quasi-Gaussian shape of likelihood, with weather fluctuating around a long term mean, the 8.2 ka event as a highly nonlinear effect precludes such an a priori assumption. As a result of this study [3] the Bayesian Analysis showed a reduction of uncertainty in vertical ocean diffusivity parameters of factor 2 compared to prior knowledge. This learning effect on the model parameters is propagated to other model outputs of interest; e.g. the inverse ocean heat capacity, which is important for the dominant time scale of climate response to anthropogenic forcing which, in combination with climate sensitivity, strongly influences the climate systems reaction for the near- and medium-term future. 1 References [1] E. Bauer, A. Ganopolski, M. Montoya: Simulation of the

  5. Impacts and environmental catastrophes: A study of the effects of impact events on the climate system

    NASA Technical Reports Server (NTRS)

    Pierazzo, E.

    2005-01-01

    The goal of this work is to investigate the perturbation of the climate system due to large impact events. Impacts are among the most important mechanisms for the evolution, distribution, and destruction of life in the universe. However, the possible climatic effects of an impact were not seriously considered until 1980, when Louis and Walter Alvarez suggested that the profound end-Cretaceous extinction might have been caused by the impact of an asteroid or comet about 10 km in diameter. Since then, the climatic change associated with the end-Cretaceous impact has become one of the most interesting and still unresolved questions in linking the well-known Chicxulub impact event and the end- Cretaceous mass extinction. While the end-Cretaceous impact offers the best-documented case of an impact affecting the Earth's climate and biota, even smaller (and more frequent in time) impacts could introduce significant perturbations of the climate comparable, if not larger, to the largest known volcanic perturbations. We propose to study the mechanical and thermal state of the atmosphere following an impact event. This will be done by using both one-dimensional and three-dimensional climate models. When necessary, modifications of the state-of-the-art general circulation models will b e carried out. We want to use the end-Cretaceous impact event as a case study. This allows us to take advantage of the extensive modeling of this impact event that has already been carried out through a previous Exobiology grant. Furthermore, a large experimental dataset, that can be used to constrain and test our models, is associated with the end-Cretaceous mass extinction (one of the largest of the Phanerozoic) and impact event.

  6. Climate Resiliency Planning: Making Extreme Event Science Useful for Managers and Planners in Northern Nevada

    NASA Astrophysics Data System (ADS)

    McCarthy, M.; Kenneston, A.; Wall, T. U.; Brown, T. J.; Redmond, K. T.

    2014-12-01

    Effective climate resiliency planning at the regional level requires extensive interactive dialogue among climate scientists, emergency managers, public health officials, urban planners, social scientists, and policy makers. Engaging federal, tribal, state, local governments and private sector business and infrastructure owners/operators in defining, assessing and characterizing the impacts of extreme events allows communities to understand how different events "break the system" forcing local communities to seek support and resources from state/federal governments and/or the private sector and what actions can be taken proactively to mitigate consequences and accelerate recovery. The Washoe County Regional Resiliency Study was prepared in response to potential climate variability related impacts specific to the Northern Nevada Region. The last several decades have seen dramatic growth in the region, coupled with increased resource demands that have forced local governments to consider how those impacts will affect the region and may, in turn, impact the region's ability to provide essential services. The Western Regional Climate Center of the Desert Research Institute provided a synthesis of climate studies with predictions regarding plausible changes in the local climate of Northern California and Nevada for the next 50 years. In general, these predictions indicate that the region's climate is undergoing a gradual shift, which will primarily affect the frequency, amount, and form of precipitation in the Sierra Nevada and Great Basin. Changes in water availability and other extreme events may have serious and long lasting effects in the Northern Nevada Region, and create a variety of social, environmental and economic concerns. A range of extreme events were considered including Adverse Air Quality, Droughts, Floods, Heat Waves, High Wind, Structure Fires, Wildland Fires, and Major Winter Storms. Due to the complexity of our climate systems, and the difficulty in

  7. Bipolar correlation of volcanism with millennial climate change

    PubMed Central

    Bay, Ryan C.; Bramall, Nathan; Price, P. Buford

    2004-01-01

    Analyzing data from our optical dust logger, we find that volcanic ash layers from the Siple Dome (Antarctica) borehole are simultaneous (with >99% rejection of the null hypothesis) with the onset of millennium-timescale cooling recorded at Greenland Ice Sheet Project 2 (GISP2; Greenland). These data are the best evidence yet for a causal connection between volcanism and millennial climate change and lead to possibilities of a direct causal relationship. Evidence has been accumulating for decades that volcanic eruptions can perturb climate and possibly affect it on long timescales and that volcanism may respond to climate change. If rapid climate change can induce volcanism, this result could be further evidence of a southern-lead North–South climate asynchrony. Alternatively, a volcanic-forcing viewpoint is of particular interest because of the high correlation and relative timing of the events, and it may involve a scenario in which volcanic ash and sulfate abruptly increase the soluble iron in large surface areas of the nutrient-limited Southern Ocean, stimulate growth of phytoplankton, which enhance volcanic effects on planetary albedo and the global carbon cycle, and trigger northern millennial cooling. Large global temperature swings could be limited by feedback within the volcano–climate system. PMID:15096586

  8. Abrupt shifts in ecosystem function and intensification of global biogeochemical cycle driven by hydroclimatic extremes

    NASA Astrophysics Data System (ADS)

    Ma, Xuanlong; Huete, Alfredo; Ponce-Campos, Guillermo; Zhang, Yongguang; Xie, Zunyi; Giovannini, Leandro; Cleverly, James; Eamus, Derek

    2016-04-01

    Amplification of the hydrologic cycle as a consequence of global warming is increasing the frequency, intensity, and spatial extent of extreme climate events globally. The potential influences resulting from amplification of the hydro-climatic cycle, coupled with an accelerating warming trend, pose great concerns on the sustainability of terrestrial ecosystems to sequester carbon, maintain biodiversity, provide ecosystem services, food security, and support human livelihood. Despite the great implications, the magnitude, direction, and carry-over effect of these extreme climate events on ecosystem function, remain largely uncertain. To address these pressing issues, we conducted an observational, interdisciplinary study using satellite retrievals of atmospheric CO2 and photosynthesis (chlorophyll fluorescence), and in-situ flux tower measures of ecosystem-atmosphere carbon exchange, to reveal the shifts in ecosystem function across extreme drought and wet periods. We further determine the factors that govern ecosystem sensitivity to hydroclimatic extremes. We focus on Australia but extended our analyses to other global dryland regions due to their significant role in global biogeochemical cycles. Our results revealed dramatic impacts of drought and wet hydroclimatic extremes on ecosystem function, with abrupt changes in vegetation productivity, carbon uptake, and water-use-efficiency between years. Drought resulted in widespread reductions or collapse in the normal patterns of vegetation growth seasonality such that in many cases there was no detectable phenological cycle during extreme drought years. We further identified a significant increasing trend (p < 0.001) in extreme wet year precipitation amounts over Australia and many other global regions, resulting in an increasing trend in magnitude of the episodic carbon sink pulses coupled to each La Niña-induced wet years. This finding is of global biogeochemical significance, with the consequence of amplifying

  9. Rainfall-triggered shallow landslides at catchment scale: Threshold mechanics-based modeling for abruptness and localization

    NASA Astrophysics Data System (ADS)

    von Ruette, J.; Lehmann, P.; Or, D.

    2013-10-01

    Rainfall-induced shallow landslides may occur abruptly without distinct precursors and could span a wide range of soil mass released during a triggering event. We present a rainfall-induced landslide-triggering model for steep catchments with surfaces represented as an assembly of hydrologically and mechanically interconnected soil columns. The abruptness of failure was captured by defining local strength thresholds for mechanical bonds linking soil and bedrock and adjacent columns, whereby a failure of a single bond may initiate a chain reaction of subsequent failures, culminating in local mass release (a landslide). The catchment-scale hydromechanical landslide-triggering model (CHLT) was applied to results from two event-based landslide inventories triggered by two rainfall events in 2002 and 2005 in two nearby catchments located in the Prealps in Switzerland. Rainfall radar data, surface elevation and vegetation maps, and a soil production model for soil depth distribution were used for hydromechanical modeling of failure patterns for the two rainfall events at spatial and temporal resolutions of 2.5 m and 0.02 h, respectively. The CHLT model enabled systematic evaluation of the effects of soil type, mechanical reinforcement (soil cohesion and lateral root strength), and initial soil water content on landslide characteristics. We compared various landslide metrics and spatial distribution of simulated landslides in subcatchments with observed inventory data. Model parameters were optimized for the short but intense rainfall event in 2002, and the calibrated model was then applied for the 2005 rainfall, yielding reasonable predictions of landslide events and volumes and statistically reproducing localized landslide patterns similar to inventory data. The model provides a means for identifying local hot spots and offers insights into the dynamics of locally resolved landslide hazards in mountainous regions.

  10. Rain-on-snow events, floods and climate change in the Alps: Events may increase with warming up to 4°C and decrease thereafter.

    PubMed

    Beniston, Martin; Stoffel, Markus

    2016-11-15

    This paper focuses on the influence of mountain rain-on-snow (ROS) events that can on occasion trigger major floods in alpine catchments. In order to assess the evolution of these events in a recent past, and the potential changes that could be experienced in a changing climate over coming decades, we have focused on a small catchment in north-eastern Switzerland, the Sitter, well-endowed with both climate and hydrological data. Observations show that there has been an increase in the number of rain-on-snow events since the early 1960s related to the rise in atmospheric temperatures. Results from a simple temperature-based snow model show that the number of ROS events could increase by close to 50% with temperatures 2-4°C warmer than today, before declining when temperatures go beyond 4°C. The likelihood of more ROS events suggests that the risks of flooding in a future climate may indeed get worse before they improve. Copyright © 2016. Published by Elsevier B.V.

  11. Abrupt intensification of the SW Indian Ocean monsoon during the last deglaciation: constraints from Th, Pa, and He isotopes

    NASA Astrophysics Data System (ADS)

    Marcantonio, Franco; Anderson, Robert F.; Higgins, Sean; Fleisher, Martin Q.; Stute, Martin; Schlosser, Peter

    2001-01-01

    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 climate-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 abruptly during the Bolling-Allerod. Later, following a sudden decrease to near-LGM values during the YD, they rise abruptly 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 climate variability, on the other, suggests a linkage between high- and low-latitude climates caused by changing patterns of atmospheric circulation.

  12. Climate Products and Services to Meet the Challenges of Extreme Events

    NASA Astrophysics Data System (ADS)

    McCalla, M. R.

    2008-12-01

    The 2002 Office of the Federal Coordinator for Meteorological Services and Supporting Research (OFCM1)-sponsored report, Weather Information for Surface Transportation: National Needs Assessment Report, addressed meteorological needs for six core modes of surface transportation: roadway, railway, transit, marine transportation/operations, pipeline, and airport ground operations. The report's goal was to articulate the weather information needs and attendant surface transportation weather products and services for those entities that use, operate, and manage America's surface transportation infrastructure. The report documented weather thresholds and associated impacts which are critical for decision-making in surface transportation. More recently, the 2008 Climate Change Science Program's (CCSP) Synthesis and Assessment Product (SAP) 4.7 entitled, Impacts of Climate Change and Variability on Transportation Systems and Infrastructure: Gulf Coast Study, Phase I, included many of the impacts from the OFCM- sponsored report in Table 1.1 of this SAP.2 The Intergovernmental Panel on Climate Change (IPCC) reported that since 1950, there has been an increase in the number of heat waves, heavy precipitation events, and areas of drought. Moreover, the IPCC indicated that greater wind speeds could accompany more severe tropical cyclones.3 Taken together, the OFCM, CCSP, and IPCC reports indicate not only the significance of extreme events, but also the potential increasing significance of many of the weather thresholds and associated impacts which are critical for decision-making in surface transportation. Accordingly, there is a real and urgent need to understand what climate products and services are available now to address the weather thresholds within the surface transportation arena. It is equally urgent to understand what new climate products and services are needed to address these weather thresholds, and articulate what can be done to fill the gap between the

  13. Reconstructing Past Climate Using Speleothems from Cueva de las Perlas, Northern Spain.

    NASA Astrophysics Data System (ADS)

    Deeprose, Laura; Wynn, Peter; Barker, Philip; Leng, Melanie; Noble, Stephen; Sahy, Diana

    2017-04-01

    Abrupt and severe oscillations in climate, termed Heinrich events, are documented in North Atlantic Ocean sediments between 85,000 - 30,000 years ago [1]. This time period also encapsulates the Neanderthal demise, a key transition in human evolution which is proposed to be driven at least in part by changing climate. The Iberian Peninsula represents the last known refuge of the Neanderthals. However, due to a scarcity of palaeoclimate archives from Iberia during this time period, the expression of these cooling events in the terrestrial realm remains poorly understood. As the extinction of the Neanderthal population seems to broadly coincide with the timing of Heinrich event 4, it is therefore critical to understand the terrestrial expression of these changes in ocean circulation. Speleothems from Cueva de las Perlas, northern Spain are being used to reconstruct past climatic and environmental change spanning this period of Neanderthal demise. U-Th dating has identified three suitable speleothems, allowing a precise chronology to be established. Through contemporary monitoring, the oxygen isotope composition of speleothem carbonate has been interpreted to carry a primary environmental signal of rainfall amount. The oxygen isotope values indicate a drying climate across the period of the Neanderthal population demise. Additionally, the carbon isotope record, interpreted to represent shifts in vegetation dynamics, indicates an overall drying during the studied time period. A high degree of climatic instability is superimposed on the overall drying trend, suggesting the prevailing climatic conditions could have been adding environmental pressure to an already marginalised hominin population. Further U-Th dating and high-resolution stable isotope analysis aims to constrain the magnitude and timing of these events. [1] Bond, G., Broecker, W., Johnsen, S.J., McManus, J., Labeyrie, L., Jouzel, J., Bonani, G., 1993. Correlations between North Atlantic sediments and

  14. Abrupt global-ocean anoxia during the Late Ordovician-early Silurian detected using uranium isotopes of marine carbonates.

    PubMed

    Bartlett, Rick; Elrick, Maya; Wheeley, James R; Polyak, Victor; Desrochers, André; Asmerom, Yemane

    2018-05-21

    Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ 238 U values of marine limestones as a global seawater redox proxy. The δ 238 U trends at Anticosti Island, Canada, document an abrupt late Hirnantian ∼0.3‰ negative shift continuing through the early Silurian indicating more reducing seawater conditions. The lack of observed anoxic facies and no covariance among δ 238 U values and other local redox proxies suggests that the δ 238 U trends represent a global-ocean redox record. The Hirnantian ocean anoxic event (HOAE) onset is coincident with the extinction pulse indicating its importance in triggering it. Anoxia initiated during high sea levels before peak Hirnantian glaciation, and continued into the subsequent lowstand and early Silurian deglacial eustatic rise, implying that major climatic and eustatic changes had little effect on global-ocean redox conditions. The HOAE occurred during a global δ 13 C positive excursion, but lasted longer indicating that controls on the C budget were partially decoupled from global-ocean redox trends. U cycle modeling suggests that there was a ∼15% increase in anoxic seafloor area and ∼80% of seawater U was sequestered into anoxic sediments during the HOAE. Unlike other ocean anoxic events (OAE), the HOAE occurred during peak and waning icehouse conditions rather than during greenhouse climates. We interpret that anoxia was driven by global cooling, which reorganized thermohaline circulation, decreased deep-ocean ventilation, enhanced nutrient fluxes, stimulated productivity, which lead to expanded oxygen minimum zones. Copyright © 2018 the Author(s). Published by PNAS.

  15. Abrupt lake-level changes in the Rocky Mountains and surrounding regions since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Shuman, B. N.; Serravezza, M.

    2016-12-01

    The paleohydrologic record of western North America since the last glacial maximum reveals a wide range of hydroclimatic variability and distinctive patterns associated with abrupt climate changes. To evaluate the sequence of abrupt hydroclimatic shifts and centennial-to-millennial hydrologic variability in western North America over the past 17 ka, we reconstruct lake-level histories from two high-elevation lakes in the Beartooth and Bighorn Mountains. The lakes represent the headwaters of the Missouri River drainage in northern Wyoming, but also have the potential to capture regional hydroclimate variability that links the northern Rocky Mountains to the mid-continent, Pacific Northwest, and the Great Basin. We first discuss the stratigraphic record of lake-level changes in small mid-latitude lakes and then use ground-penetrating radar (GPR) and sediment cores to track the elevations of shoreline sediments within the lakes through time. We compare the stratigraphies to the records from four other lakes in Wyoming and Colorado, and find widespread evidence for a Terminal Pleistocene Drought from 15-11 ka, an early Holocene humid period from 11-8 ka, and a period of severe mid-Holocene aridity from 8-5.7 ka. The northern Wyoming lakes also provide evidence of high levels before ca. 15 ka, including rapid hydroclimatic changes at ca. 16.8 ka during Heinrich Event 1. We place the changes in a broad context by summarizing and mapping water-level changes from 107 additional, previously studied lakes. Important patterns include 1) extensive drying across the western U.S. after 15 ka; 2) coherent sub-regional differences during the Younger Dryas and Pleistocene-Holocene transition; 3) a north-south contrast from 9-6 ka consistent with a northward shift in storm tracks as the influence of the Laurentide Ice Sheet diminished; and 4) rapid increases in effective moisture across much of western North America from 6-4 ka.

  16. When a drought event unfolds the question comes "Is this climate change?"

    NASA Astrophysics Data System (ADS)

    Stahl, Kerstin

    2017-04-01

    Is this what climate change looks like? This was the first question from most journalists who interviewed me during the drought of 2015 in Germany, once impacts started to hit hard. Likely, the same question is asked during other extreme events. I'll provide some examples of how the conversations and articles during the drought event developed. Then, let's discuss how to communicate what one particular event can mean in the context of long-term changes.

  17. Climate Change and Hydrological Extreme Events - Risks and Perspectives for Water Management in Bavaria and Québec

    NASA Astrophysics Data System (ADS)

    Ludwig, R.

    2017-12-01

    There is as yet no confirmed knowledge whether and how climate change contributes to the magnitude and frequency of hydrological extreme events and how regional water management could adapt to the corresponding risks. The ClimEx project (2015-2019) investigates the effects of climate change on the meteorological and hydrological extreme events and their implications for water management in Bavaria and Québec. High Performance Computing is employed to enable the complex simulations in a hydro-climatological model processing chain, resulting in a unique high-resolution and transient (1950-2100) dataset of climatological and meteorological forcing and hydrological response: (1) The climate module has developed a large ensemble of high resolution data (12km) of the CRCM5 RCM for Central Europe and North-Eastern North America, downscaled from 50 members of the CanESM2 GCM. The dataset is complemented by all available data from the Euro-CORDEX project to account for the assessment of both natural climate variability and climate change. The large ensemble with several thousand model years provides the potential to catch rare extreme events and thus improves the process understanding of extreme events with return periods of 1000+ years. (2) The hydrology module comprises process-based and spatially explicit model setups (e.g. WaSiM) for all major catchments in Bavaria and Southern Québec in high temporal (3h) and spatial (500m) resolution. The simulations form the basis for in depth analysis of hydrological extreme events based on the inputs from the large climate model dataset. The specific data situation enables to establish a new method for `virtual perfect prediction', which assesses climate change impacts on flood risk and water resources management by identifying patterns in the data which reveal preferential triggers of hydrological extreme events. The presentation will highlight first results from the analysis of the large scale ClimEx model ensemble, showing the

  18. Heat and pregnancy-related emergencies: Risk of placental abruption during hot weather.

    PubMed

    He, Siyi; Kosatsky, Tom; Smargiassi, Audrey; Bilodeau-Bertrand, Marianne; Auger, Nathalie

    2018-02-01

    Outdoor heat increases the risk of preterm birth and stillbirth, but the association with placental abruption has not been studied. Placental abruption is a medical emergency associated with major morbidity and mortality in pregnancy. We determined the relationship between ambient temperature and risk of placental abruption in warm seasons. We performed a case-crossover analysis of 17,172 women whose pregnancies were complicated by placental abruption in Quebec, Canada from May to October 1989-2012. The main exposure measure was the maximum temperature reached during the week before abruption. We computed odds ratios (OR) and 95% confidence intervals (CI) for the association of temperature with placental abruption, 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 abruption (95% CI 0.99-1.16). When the timing of abruption 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 abruption. Temperature was not associated with preterm abruption regardless of maternal characteristics. Elevated temperatures in warm seasons may increase the risk of abruption 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.

  19. Two Extreme Climate Events of the Last 1000 Years Recorded in Himalayan and Andean Ice Cores: Impacts on Humans

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.; Kenny, D. V.; Lin, P.

    2013-12-01

    In the last few decades numerous studies have linked pandemic influenza, cholera, malaria, and viral pneumonia, as well as droughts, famines and global crises, to the El Niño-Southern Oscillation (ENSO). Two annually resolved ice core records, one from Dasuopu Glacier in the Himalaya and one from the Quelccaya Ice Cap in the tropical Peruvian Andes provide an opportunity to investigate these relationships on opposite sides of the Pacific Basin for the last 1000 years. The Dasuopu record provides an annual history from 1440 to 1997 CE and a decadally resolved record from 1000 to 1440 CE while the Quelccaya ice core provides annual resolution over the last 1000 years. Major ENSO events are often recorded in the oxygen isotope, insoluble dust, and chemical records from these cores. Here we investigate outbreaks of diseases, famines and global crises during two of the largest events recorded in the chemistry of these cores, particularly large peaks in the concentrations of chloride (Cl-) and fluoride (Fl-). One event is centered on 1789 to 1800 CE and the second begins abruptly in 1345 and tapers off after 1360 CE. These Cl- and F- peaks represent major droughts and reflect the abundance of continental atmospheric dust, derived in part from dried lake beds in drought stricken regions upwind of the core sites. For Dasuopu the likely sources are in India while for Quelccaya the sources would be the Andean Altiplano. Both regions are subject to drought conditions during the El Niño phase of the ENSO cycle. These two events persist longer (10 to 15 years) than today's typical ENSO events in the Pacific Ocean Basin. The 1789 to 1800 CE event was associated with a very strong El Niño event and was coincidental with the Boji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive droughts are documented in Central and South America. Likewise, the 1345 to 1360 CE event, although poorly documented

  20. Bottom-up perspectives of extreme event and climate change threats to water quality: Drinking water utilities in California

    NASA Astrophysics Data System (ADS)

    Ekstrom, J.; Klasic, M.; Fencl, A.; Lubell, M.; Bedsworth, L. W.; Baker, E.

    2016-12-01

    Extreme events impact water quality, which pose serious challenges for drinking water systems. Such extreme events, including wildfire, storm surge, and other weather-related extremes, are projected to increase under a changing climate. It remains unclear what climate change information can support water managers in preparing for more extreme events. Exploring this topic requires understanding the larger question: What is the role of scientific information in adapting to climate change? We present two parts of a three-year study geared to understand whether, where, why and in what way climate information (or the lack of) is used or needed to support long term water quality planning for extreme events. In 2015 we surveyed California drinking water utilities and found a wide range of extreme event/water quality issues, perspectives on the severity of climate change threats, drought impacts and trusted information sources relating to water quality concerns. Approximately 70% of 259 respondents had recently experienced extreme weather-related events that worsen or trigger water quality. Survey results informed development of a case study analysis to gain a more in-depth understanding of what type of - or when - extreme events information could support climate adaptation. Projections of extreme events are often not in a form that is useable for water quality planning. Relative to supply-related projections, water quality has received much less scientific attention, leaving it an assumed scientific information gap and need for management. The question remains whether filling this gap would help adaptation, whom it would help, and in what way. Based on interviews with water systems in Summer 2016, our case study analyses reinforce that extreme events threaten water quality in many ways; largely as secondary impacts of climate change. Secondary impacts involve disinfection byproducts, increasing salinity in the Delta, and the use of lower quality sources. The most common

  1. Sensitivity of Water Scarcity Events to ENSO-Driven Climate Variability at the Global Scale

    NASA Technical Reports Server (NTRS)

    Veldkamp, T. I. E.; Eisner, S.; Wada, Y.; Aerts, J. C. J. H.; Ward, P. J.

    2015-01-01

    Globally, freshwater shortage is one of the most dangerous risks for society. Changing hydro-climatic and socioeconomic conditions have aggravated water scarcity over the past decades. A wide range of studies show that water scarcity will intensify in the future, as a result of both increased consumptive water use and, in some regions, climate change. Although it is well-known that El Niño- Southern Oscillation (ENSO) affects patterns of precipitation and drought at global and regional scales, little attention has yet been paid to the impacts of climate variability on water scarcity conditions, despite its importance for adaptation planning. Therefore, we present the first global-scale sensitivity assessment of water scarcity to ENSO, the most dominant signal of climate variability. We show that over the time period 1961-2010, both water availability and water scarcity conditions are significantly correlated with ENSO-driven climate variability over a large proportion of the global land area (> 28.1 %); an area inhabited by more than 31.4% of the global population. We also found, however, that climate variability alone is often not enough to trigger the actual incidence of water scarcity events. The sensitivity of a region to water scarcity events, expressed in terms of land area or population exposed, is determined by both hydro-climatic and socioeconomic conditions. Currently, the population actually impacted by water scarcity events consists of 39.6% (CTA: consumption-to-availability ratio) and 41.1% (WCI: water crowding index) of the global population, whilst only 11.4% (CTA) and 15.9% (WCI) of the global population is at the same time living in areas sensitive to ENSO-driven climate variability. These results are contrasted, however, by differences in growth rates found under changing socioeconomic conditions, which are relatively high in regions exposed to water scarcity events. Given the correlations found between ENSO and water availability and scarcity

  2. Supercritical flow characteristics at abrupt expansion structure

    NASA Astrophysics Data System (ADS)

    Lim, Jia Jun; Puay, How Tion; Zakaria, Nor Azazi

    2017-10-01

    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 abrupt 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 abrupt 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 abrupt 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.

  3. Detection and Attribution of Simulated Climatic Extreme Events and Impacts: High Sensitivity to Bias Correction

    NASA Astrophysics Data System (ADS)

    Sippel, S.; Otto, F. E. L.; Forkel, M.; Allen, M. R.; Guillod, B. P.; Heimann, M.; Reichstein, M.; Seneviratne, S. I.; Kirsten, T.; Mahecha, M. D.

    2015-12-01

    Understanding, quantifying and attributing the impacts of climatic extreme events and variability is crucial for societal adaptation in a changing climate. However, climate model simulations generated for this purpose typically exhibit pronounced biases in their output that hinders any straightforward assessment of impacts. To overcome this issue, various bias correction strategies are routinely used to alleviate climate model deficiencies most of which have been criticized for physical inconsistency and the non-preservation of the multivariate correlation structure. We assess how biases and their correction affect the quantification and attribution of simulated extremes and variability in i) climatological variables and ii) impacts on ecosystem functioning as simulated by a terrestrial biosphere model. Our study demonstrates that assessments of simulated climatic extreme events and impacts in the terrestrial biosphere are highly sensitive to bias correction schemes with major implications for the detection and attribution of these events. We introduce a novel ensemble-based resampling scheme based on a large regional climate model ensemble generated by the distributed weather@home setup[1], which fully preserves the physical consistency and multivariate correlation structure of the model output. We use extreme value statistics to show that this procedure considerably improves the representation of climatic extremes and variability. Subsequently, biosphere-atmosphere carbon fluxes are simulated using a terrestrial ecosystem model (LPJ-GSI) to further demonstrate the sensitivity of ecosystem impacts to the methodology of bias correcting climate model output. We find that uncertainties arising from bias correction schemes are comparable in magnitude to model structural and parameter uncertainties. The present study consists of a first attempt to alleviate climate model biases in a physically consistent way and demonstrates that this yields improved simulations of

  4. Detection of photosynthetic responses of cool-temperate forests following extreme climate events using Bayesian inversion

    NASA Astrophysics Data System (ADS)

    Toda, M.; Knohl, A.; Herbst, M.; Keenan, T. F.; Yokozawa, M.

    2016-12-01

    The increase in extreme climate events associated with ongoing global warming may create severe damage to terrestrial ecosystems, changing plant structure and the eco-physiological functions that regulate ecosystem carbon exchange. However, most damage is usually due to moderate, rather than catastrophic, disturbances. The nature of plant functional responses to such disturbances, and the resulting effects on the terrestrial carbon cycle, remain poorly understood. To unravel the scientific question, tower-based eddy covariance data in the cool-temperate forests were used to constrain plant eco-physiological parameters in a persimoneous ecosystem model that may have affected carbon dynamics following extreme climate events using the statistic Bayesian inversion approach. In the present study, we raised two types of extreme events relevant for cool-temperate regions, i.e. a typhoon with mechanistic foliage destraction and a heat wave with severe drought. With appropriate evaluation of parameter and predictive uncertainties, the inversion analysis shows annual trajectory of activated photosynthetic responses following climate extremes compared the pre-disturbance state in each forest. We address that forests with moderate disturbance show substantial and rapid photosynthetic recovery, enhanced productivity, and, thus, ecosystem carbon exchange, although the effect of extreme climatic events varies depending on the stand successional phase and the type, intensity, timing and legacy of the disturbance.

  5. Quantifying Climate Feedbacks from Abrupt Changes in High-Latitude Trace-Gas Emissions

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

    Schlosser, Courtney Adam; Walter-Anthony, Katey; Zhuang, Qianlai

    2013-04-26

    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 climate warming, and the extent to which these emissions provide a strong feedback mechanism to global climate warming. This goal is motivated under the premise that polar amplification of global climate 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 climate-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 climate warming.« less

  6. Remote Sensing Techniques for Rapid Assessment of Forest Damage Caused by Catastrophic Climatic Events, NA-TP-01-01

    Treesearch

    William Ciesla; William Frament; Margaret Miller-Weeks

    2001-01-01

    Catastrophic climatic events such as hurricanes, tornadoes, and ice storms can cause billions of dollars in damage to infrastructure and personal property, loss of lives, and damage to natural resources. Forests are especially susceptible to these events. The following is a list of recent climatic events in North America that have had devastating effects on forest...

  7. Heat waves connect abrupt polar climate changes during the past 67ka: evidence from sediment core GeoB3912-1

    NASA Astrophysics Data System (ADS)

    Yang, X.; Rial, J. A.

    2014-12-01

    According to the hypothesis of polar synchronization, climate 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 climate 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 climate proxy record from the tropical 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 climates 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 climates, 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.

  8. Autochthonous Chikungunya Transmission and Extreme Climate Events in Southern France.

    PubMed

    Roiz, David; Boussès, Philippe; Simard, Frédéric; Paupy, Christophe; Fontenille, Didier

    2015-06-01

    Extreme precipitation events are increasing as a result of ongoing global warming, but controversy surrounds the relationship between flooding and mosquito-borne diseases. A common view among the scientific community and public health officers is that heavy rainfalls have a flushing effect on breeding sites, which negatively affects vector populations, thereby diminishing disease transmission. During 2014 in Montpellier, France, there were at least 11 autochthonous cases of chikungunya caused by the invasive tiger mosquito Aedes albopictus in the vicinity of an imported case. We show that an extreme rainfall event increased and extended the abundance of the disease vector Ae. albopictus, hence the period of autochthonous transmission of chikungunya. We report results from close monitoring of the adult and egg population of the chikungunya vector Ae. albopictus through weekly sampling over the entire mosquito breeding season, which revealed an unexpected pattern. Statistical analysis of the seasonal dynamics of female abundance in relation to climatic factors showed that these relationships changed after the heavy rainfall event. Before the inundations, accumulated temperatures are the most important variable predicting Ae. albopictus seasonal dynamics. However, after the inundations, accumulated rainfall over the 4 weeks prior to capture predicts the seasonal dynamics of this species and extension of the transmission period. Our empirical data suggests that heavy rainfall events did increase the risk of arbovirus transmission in Southern France in 2014 by favouring a rapid rise in abundance of vector mosquitoes. Further studies should now confirm these results in different ecological contexts, so that the impact of global change and extreme climatic events on mosquito population dynamics and the risk of disease transmission can be adequately understood.

  9. Climate and the collapse of civilization

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

    Abate, T.

    1994-09-01

    This article looks at the archaeological debate over two important questions: whether abrupt climate 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 climate with uncertain consequences. Areas discussed include the following: climate hints from archaeological sites; hesitations about whether climate change caused civilizations to collapse; and the interdisciplinary checks on each side.

  10. Climate Change, Extreme Weather Events, and Human Health Implications in the Asia Pacific Region.

    PubMed

    Hashim, Jamal Hisham; Hashim, Zailina

    2016-03-01

    The Asia Pacific region is regarded as the most disaster-prone area of the world. Since 2000, 1.2 billion people have been exposed to hydrometeorological hazards alone through 1215 disaster events. The impacts of climate change on meteorological phenomena and environmental consequences are well documented. However, the impacts on health are more elusive. Nevertheless, climate change is believed to alter weather patterns on the regional scale, giving rise to extreme weather events. The impacts from extreme weather events are definitely more acute and traumatic in nature, leading to deaths and injuries, as well as debilitating and fatal communicable diseases. Extreme weather events include heat waves, cold waves, floods, droughts, hurricanes, tropical cyclones, heavy rain, and snowfalls. Globally, within the 20-year period from 1993 to 2012, more than 530 000 people died as a direct result of almost 15 000 extreme weather events, with losses of more than US$2.5 trillion in purchasing power parity. © 2015 APJPH.

  11. Late Pleistocene climate drivers of early human migration.

    PubMed

    Timmermann, Axel; Friedrich, Tobias

    2016-10-06

    On the basis of fossil and archaeological data it has been hypothesized that the exodus of Homo sapiens out of Africa and into Eurasia between ~50-120 thousand years ago occurred in several orbitally paced migration episodes. Crossing vegetated pluvial corridors from northeastern Africa into the Arabian Peninsula and the Levant and expanding further into Eurasia, Australia and the Americas, early H. sapiens experienced massive time-varying climate and sea level conditions on a variety of timescales. Hitherto it has remained difficult to quantify the effect of glacial- and millennial-scale climate variability on early human dispersal and evolution. Here we present results from a numerical human dispersal model, which is forced by spatiotemporal estimates of climate and sea level changes over the past 125 thousand years. The model simulates the overall dispersal of H. sapiens in close agreement with archaeological and fossil data and features prominent glacial migration waves across the Arabian Peninsula and the Levant region around 106-94, 89-73, 59-47 and 45-29 thousand years ago. The findings document that orbital-scale global climate swings played a key role in shaping Late Pleistocene global population distributions, whereas millennial-scale abrupt climate changes, associated with Dansgaard-Oeschger events, had a more limited regional effect.

  12. Late Pleistocene climate drivers of early human migration

    NASA Astrophysics Data System (ADS)

    Timmermann, Axel; Friedrich, Tobias

    2016-10-01

    On the basis of fossil and archaeological data it has been hypothesized that the exodus of Homo sapiens out of Africa and into Eurasia between ~50-120 thousand years ago occurred in several orbitally paced migration episodes. Crossing vegetated pluvial corridors from northeastern Africa into the Arabian Peninsula and the Levant and expanding further into Eurasia, Australia and the Americas, early H. sapiens experienced massive time-varying climate and sea level conditions on a variety of timescales. Hitherto it has remained difficult to quantify the effect of glacial- and millennial-scale climate variability on early human dispersal and evolution. Here we present results from a numerical human dispersal model, which is forced by spatiotemporal estimates of climate and sea level changes over the past 125 thousand years. The model simulates the overall dispersal of H. sapiens in close agreement with archaeological and fossil data and features prominent glacial migration waves across the Arabian Peninsula and the Levant region around 106-94, 89-73, 59-47 and 45-29 thousand years ago. The findings document that orbital-scale global climate swings played a key role in shaping Late Pleistocene global population distributions, whereas millennial-scale abrupt climate changes, associated with Dansgaard-Oeschger events, had a more limited regional effect.

  13. Identifying evidence of climate change impact on extreme events in permeable chalk catchments

    NASA Astrophysics Data System (ADS)

    Butler, A. P.; Nubert, S.

    2009-12-01

    The permeable chalk catchments of southern England are vital for the economy and well being of the UK. Not only important as a water resource, their freely draining soils support intensive agricultural production, and the rolling downs and chalk streams provide important habitants for many protected plant and animal species. Consequently, there are concerns about the potential impact of climate change on such catchments, particularly in relation to groundwater recharge. Of major concern are possible changes in extreme events, such as groundwater floods and droughts, as any increase in the frequency and/or severity of these has important consequences for water resources, ecological systems and local infrastructure. Studies of climate change impact on extreme events for such catchments have indicated that, under medium and high emissions scenarios, droughts are likely to become more severe whilst floods less so. However, given the uncertainties in such predictions and the inherent variability in historic data, producing definitive evidence of changes in flood/drought frequency/severity poses a significant challenge. Thus, there is a need for specific extreme event statistics that can be used as indicators of actual climate change in streamflow and groundwater level observations. Identifying such indicators that are sufficiently robust requires catchments with long historic time series data. One such catchment is the River Lavant, an intermittent chalk stream in West Sussex, UK. Located within this catchment is Chilgrove House, the site of the UK’s longest groundwater monitoring well (with a continuous record of water level observations of varying frequency dating back to 1836). Using a variety of meteorological datasets, the behaviour of the catchment has been modelled, from 1855 to present, using a 'leaky aquifer' conceptual model. Model calibration was based on observed daily streamflow, at a gauging station just outside the town of Chichester, from 1970. Long

  14. 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

  15. Tropical North Atlantic subsurface temperature anomalies: evidence for AMOC variability across Dansgaard-Oscheger events?

    NASA Astrophysics Data System (ADS)

    Parker, A. O.; Schmidt, M. W.; Chang, P.

    2013-12-01

    A common mechanism often proposed to explain the abrupt climate 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 abrupt change in the tropical 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 tropics. Recently, Schmidt et al. (2012) identified an abrupt 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 abrupt 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

  16. Interpreting the Climatic Effects on Xylem Functional Traits in Two Mediterranean Oak Species: The Role of Extreme Climatic Events.

    PubMed

    Rita, Angelo; Borghetti, Marco; Todaro, Luigi; Saracino, Antonio

    2016-01-01

    In the Mediterranean region, the widely predicted rise in temperature, change in the precipitation pattern, and increase in the frequency of extreme climatic events are expected to alter the shape of ecological communities and to affect plant physiological processes that regulate ecosystem functioning. Although change in the mean values are important, there is increasing evidence that plant distribution, survival, and productivity respond to extremes rather than to the average climatic condition. The present study aims to assess the effects of both mean and extreme climatic conditions on radial growth and functional anatomical traits using long-term tree-ring time series of two co-existing Quercus spp. from a drought-prone site in Southern Italy. In particular, this is the first attempt to apply the Generalized Additive Model for Location, Scale, and Shape (GAMLSS) technique and Bayesian modeling procedures to xylem traits data set, with the aim of (i) detecting non-linear long-term responses to climate and (ii) exploring relationships between climate extreme and xylem traits variability in terms of probability of occurrence. This study demonstrates the usefulness of long-term xylem trait chronologies as records of environmental conditions at annual resolution. Statistical analyses revealed that most of the variability in tree-ring width and specific hydraulic conductivity might be explained by cambial age. Additionally, results highlighted appreciable relationships between xylem traits and climate variability more than tree-ring width, supporting also the evidence that the plant hydraulic traits are closely linked to local climate extremes rather than average climatic conditions. We reported that the probability of extreme departure in specific hydraulic conductivity (Ks) rises at extreme values of Standardized Precipitation Index (SPI). Therefore, changing frequency or intensity of extreme events might overcome the adaptive limits of vascular transport, resulting

  17. Interpreting the Climatic Effects on Xylem Functional Traits in Two Mediterranean Oak Species: The Role of Extreme Climatic Events

    PubMed Central

    Rita, Angelo; Borghetti, Marco; Todaro, Luigi; Saracino, Antonio

    2016-01-01

    In the Mediterranean region, the widely predicted rise in temperature, change in the precipitation pattern, and increase in the frequency of extreme climatic events are expected to alter the shape of ecological communities and to affect plant physiological processes that regulate ecosystem functioning. Although change in the mean values are important, there is increasing evidence that plant distribution, survival, and productivity respond to extremes rather than to the average climatic condition. The present study aims to assess the effects of both mean and extreme climatic conditions on radial growth and functional anatomical traits using long-term tree-ring time series of two co-existing Quercus spp. from a drought-prone site in Southern Italy. In particular, this is the first attempt to apply the Generalized Additive Model for Location, Scale, and Shape (GAMLSS) technique and Bayesian modeling procedures to xylem traits data set, with the aim of (i) detecting non-linear long-term responses to climate and (ii) exploring relationships between climate extreme and xylem traits variability in terms of probability of occurrence. This study demonstrates the usefulness of long-term xylem trait chronologies as records of environmental conditions at annual resolution. Statistical analyses revealed that most of the variability in tree-ring width and specific hydraulic conductivity might be explained by cambial age. Additionally, results highlighted appreciable relationships between xylem traits and climate variability more than tree-ring width, supporting also the evidence that the plant hydraulic traits are closely linked to local climate extremes rather than average climatic conditions. We reported that the probability of extreme departure in specific hydraulic conductivity (Ks) rises at extreme values of Standardized Precipitation Index (SPI). Therefore, changing frequency or intensity of extreme events might overcome the adaptive limits of vascular transport, resulting

  18. Impacts of Climate Change On The Occurrence of Extreme Events: The Mice Project

    NASA Astrophysics Data System (ADS)

    Palutikof, J. P.; Mice Team

    It is widely accepted that climate change due to global warming will have substan- tial impacts on the natural environment, and on human activities. Furthermore, it is increasingly recognized that changes in the severity and frequency of extreme events, such as windstorm and flood, are likely to be more important than changes in the average climate. The EU-funded project MICE (Modelling the Impacts of Climate Extremes) commenced in January 2002. It seeks to identify the likely changes in the occurrence of extremes of rainfall, temperature and windstorm due to global warm- ing, using information from climate models as a basis, and to study the impacts of these changes in selected European environments. The objectives are: a) to evaluate, by comparison with gridded and station observations, the ability of climate models to successfully reproduce the occurrence of extremes at the required spatial and temporal scales. b) to analyse model output with respect to future changes in the occurrence of extremes. Statistical analyses will determine changes in (i) the return periods of ex- tremes, (ii) the joint probability of extremes (combinations of damaging events such as windstorm followed by heavy rain), (iii) the sequential behaviour of extremes (whether events are well-separated or clustered) and (iv) the spatial patterns of extreme event occurrence across Europe. The range of uncertainty in model predictions will be ex- plored by analysing changes in model experiments with different spatial resolutions and forcing scenarios. c) to determine the impacts of the predicted changes in extremes occurrence on selected activity sectors: agriculture (Mediterranean drought), commer- cial forestry and natural forest ecosystems (windstorm and flood in northern Europe, fire in the Mediterranean), energy use (temperature extremes), tourism (heat stress and Mediterranean beach holidays, changes in the snow pack and winter sports ) and civil protection/insurance (windstorm and flood

  19. Astronomical constraints on global carbon-cycle perturbation during Oceanic Anoxic Event 2 (OAE2)

    NASA Astrophysics Data System (ADS)

    Li, Yong-Xiang; Montañez, Isabel P.; Liu, Zhonghui; Ma, Lifeng

    2017-03-01

    Oceanic Anoxic Event 2 (OAE2) was a major disturbance in global carbon cycling and transient climate disruption, triggered by a pulse of volcanic CO2. Although this well-studied perturbation to the ocean-atmosphere system offers a unique opportunity to better understand abrupt climate change in response to CO2-forcing, the origin, evolution and duration of the event are still debated due in large part to the temporal resolution of existing OAE2 records and uncertainty over the duration of the overall perturbation and C cycle shifts within it. Here we report coupled magnetic susceptibility (MS) and carbon-isotope time-series of ∼2.5 to 5 ± 0.5kyr resolution from an expanded OAE2 interval from southern Tibet, China. MS cyclicity indicates short eccentricity modulation, permitting the construction of a high-precision orbital timescale which, when integrated with the high resolution δ13Ccarb record, fully constrains the timing and nature of onset through recovery of OAE2, revealing finer-scale structure than previously recognized. Abrupt coupled shifts in δ13Ccarb and MS, and changing phase relationships in-step with transitions between high and low long eccentricity, indicate orbitally linked changes in marine carbon cycling and monsoon dynamics superimposed on repeated wholesale oceanographic changes. In particular, the high-resolution Tibetan record reveals dynamic shifts in the phasing relationship of MS and δ13 C, which suggests that the initiation of ocean anoxia was probably not orbitally forced. This finding is in sharp contrast with the paradigm of orbitally forced ocean anoxia. Conversely, the new record suggests that termination of anoxia was likely orbitally forced and superimposed on a dramatic oceanographic change.

  20. Mitigation of Disasters Due to Severe Climate Events: from Policy to Practice,the West African Coastal Region Experience

    NASA Astrophysics Data System (ADS)

    Ediang, Okuku

    2016-07-01

    The distributive pattern of disaster due to severe climate events over the coast of West Africa especially Nigeria was examined using yearly mean disaster due to severe climatic events for the period of 30 years (1981-2010) from the marine stations in the coastal region of Nigeria. Graphical and isohyetal analyses were used to look into the patter of severe weather events over the area considered and to see if the severe weather events is increasing or not in the coast of West Africa especially the Nigerian coast and how to mitigate ,were policy relating to severe weather events are discussed. The paper conclude that due to the nature of coast of West Africa and Nigeria in particular, it enjoys longer severe weather events season than dry during the wet season, it is common to observe periods of enhanced or suppressed convective activity to persist over the wide areas for somedays. This paper also contributes to the wealth of knowledge already existing on Indigenous people play major roles in preserving the ecosystem especially during severe weather events . This has resulted in the recent calls for the integration of indigenous knowledge systems into global knowledge system strategies. Until now, integrating local knowledge systems into severe weather events and climate change concerns is not a completely new idea. A comprehensive review of literature using electronic and non-electronic databases formed the methodology. The paper conclude also by drawing the attention that by targeting Promoting indigenous people's participation in severe weather events and climate change issues is an important initiative towards adaptation and sustainable development in Africa and around the world. It is increasingly realized that the global knowledge system has dominated research, policies and programmes that address current severe weather events and climate change's challenges,mitigation and adaptation strategies.

  1. Quantifying population exposure to airborne particulate matter during extreme events in California due to climate change

    NASA Astrophysics Data System (ADS)

    Mahmud, A.; Hixson, M.; Kleeman, M. J.

    2012-02-01

    The effect of climate change on population-weighted concentrations of particulate matter (PM) during extreme events was studied using the Parallel Climate Model (PCM), the Weather Research and Forecasting (WRF) model and the UCD/CIT 3-D photochemical air quality model. A "business as usual" (B06.44) global emissions scenario was dynamically downscaled for the entire state of California between the years 2000-2006 and 2047-2053. Air quality simulations were carried out for 1008 days in each of the present-day and future climate conditions using year-2000 emissions. Population-weighted concentrations of PM0.1, PM2.5, and PM10 total mass, components species, and primary source contributions were calculated for California and three air basins: the Sacramento Valley air basin (SV), the San Joaquin Valley air basin (SJV) and the South Coast Air Basin (SoCAB). Results over annual-average periods were contrasted with extreme events. Climate change between 2000 vs. 2050 did not cause a statistically significant change in annual-average population-weighted PM2.5 mass concentrations within any major sub-region of California in the current study. Climate change did alter the annual-average composition of the airborne particles in the SoCAB, with notable reductions of elemental carbon (EC; -3%) and organic carbon (OC; -3%) due to increased annual-average wind speeds that diluted primary concentrations from gasoline combustion (-3%) and food cooking (-4%). In contrast, climate change caused significant increases in population-weighted PM2.5 mass concentrations in central California during extreme events. The maximum 24-h average PM2.5 concentration experienced by an average person during a ten-year period in the SJV increased by 21% due to enhanced production of secondary particulate matter (manifested as NH4NO3). In general, climate change caused increased stagnation during future extreme pollution events, leading to higher exposure to diesel engines particles (+32%) and wood

  2. Oasis deposits in the southern margin of the Taklimakan Desert and abrupt environmental changes during the last 30 ka

    NASA Astrophysics Data System (ADS)

    Shu, P.; Li, B.; Wang, H.; Cheng, P.; An, Z.; Zhou, W.; Zhang, D. D.

    2017-12-01

    Taklimakan Desert, the largest arid landform in the Eurasia, is one of the most important dust sources in the world. Growing evidences shows that millennial-scale abrupt climate changes during the last glacial period in the region. However, records on millennial-scale climate and environmental changes remain poorly understood because dating eolian, lacustrine, and fluvial sediments and establishing the reliable environmental proxies from these records are always challenging. Here, we present 32 AMS 14C dates of bulk sediments, grain size, and Rb/Sr ratio parameters from the oasis sequence and dates of bulk loess and charcoal from the upstream source regions to examine the significance of oasis sediments on millennial-scale environmental changes in the Taklimakan Desert. We found that substantial reversal of radiocarbon dates on total organic carbon (TOC) was controlled by source region organic carbon input. Loess hills, alpine meadow north of the study region provided fluvial deposits along drainage system and deflation in the river valleys further provide eolain materials. We argue that early oasis deposits experienced deflation and re-deposition less severe than the younger oasis deposits. After refining radiocarbon age-depth relationships for an age model by Bacon package, proxy records show substantial abrupt fluctuations in climate and environments during the last glacial period, among which three wet intervals, two dry periods are identified. The wetter and warmer conditions during the Holocene facilitated human to occupy the oasis.

  3. A conditional approach to determining the effect of anthropogenic climate change on very rare events.

    NASA Astrophysics Data System (ADS)

    Wehner, Michael; Pall, Pardeep; Zarzycki, Colin; Stone, Daithi

    2016-04-01

    Probabilistic extreme event attribution is especially difficult for weather events that are caused by extremely rare large-scale meteorological patterns. Traditional modeling techniques have involved using ensembles of climate models, either fully coupled or with prescribed ocean and sea ice. Ensemble sizes for the latter case ranges from several 100 to tens of thousand. However, even if the simulations are constrained by the observed ocean state, the requisite large-scale meteorological pattern may not occur frequently enough or even at all in free running climate model simulations. We present a method to ensure that simulated events similar to the observed event are modeled with enough fidelity that robust statistics can be determined given the large scale meteorological conditions. By initializing suitably constrained short term ensemble hindcasts of both the actual weather system and a counterfactual weather system where the human interference in the climate system is removed, the human contribution to the magnitude of the event can be determined. However, the change (if any) in the probability of an event of the observed magnitude is conditional not only on the state of the ocean/sea ice system but also on the prescribed initial conditions determined by the causal large scale meteorological pattern. We will discuss the implications of this technique through two examples; the 2013 Colorado flood and the 2014 Typhoon Haiyan.

  4. Going, Going, Gone: Localizing Abrupt Offsets of Moving Objects

    ERIC Educational Resources Information Center

    Maus, Gerrit W.; Nijhawan, Romi

    2009-01-01

    When a moving object abruptly disappears, this profoundly influences its localization by the visual system. In Experiment 1, 2 aligned objects moved across the screen, and 1 of them abruptly disappeared. Observers reported seeing the objects misaligned at the time of the offset, with the continuing object leading. Experiment 2 showed that the…

  5. Public interest in climate change over the past decade and the effects of the ‘climategate’ media event

    NASA Astrophysics Data System (ADS)

    Anderegg, William R. L.; Goldsmith, Gregory R.

    2014-05-01

    Despite overwhelming scientific consensus concerning anthropogenic climate change, many in the non-expert public perceive climate change as debated and contentious. There is concern that two recent high-profile media events—the hacking of the University of East Anglia emails and the Himalayan glacier melt rate presented in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change—may have altered public opinion of climate change. While survey data is valuable for tracking public perception and opinion over time, including in response to climate-related media events, emerging methods that facilitate rapid assessment of spatial and temporal patterns in public interest and opinion could be exceptionally valuable for understanding and responding to these events’ effects. We use a novel, freely-available dataset of worldwide web search term volumes to assess temporal patterns of interest in climate change over the past ten years, with a particular focus on looking at indicators of climate change skepticism around the high-profile media events. We find that both around the world and in the US, the public searches for the issue as ‘global warming,’ rather than ‘climate change,’ and that search volumes have been declining since a 2007 peak. We observe high, but transient spikes of search terms indicating skepticism around the two media events, but find no evidence of effects lasting more than a few months. Our results indicate that while such media events are visible in the short-term, they have little effect on salience of skeptical climate search terms on longer time-scales.

  6. Thyroperoxidase and thyroglobulin antibodies in early pregnancy and placental abruption.

    PubMed

    Haddow, James E; McClain, Monica R; Palomaki, Glenn E; Neveux, Louis M; Lambert-Messerlian, Geralyn; Canick, Jacob A; Malone, Fergal D; Porter, T Flint; Nyberg, David A; Bernstein, Peter S; D'Alton, Mary E

    2011-02-01

    To estimate the relationship between thyroid antibodies and placental abruption. This cohort study assesses thyroperoxidase and thyroglobulin antibodies in relation to placental abruption among 10,062 women with singleton viable pregnancies (from the First and Second Trimester Risk of Aneuploidy [FaSTER] trial). A thyroperoxidase antibody cutoff of 50 international units/mL is used for comparison with published data from another cohort. Women with elevated thyroperoxidase antibody levels in the first and second trimesters have a higher rate of placental abruption than antibody-negative women. This relationship is less strong in the first trimester (1.51% compared with 0.83%; odds ratio [OR], 1.83; 95% confidence interval [CI], 0.99-3.37) than in the second trimester (1.78% compared with 0.82%; OR, 2.20; 95% CI, 1.21-3.99). A similar, but weaker, relationship is present for thyroglobulin antibodies. Sixty-four of 782 thyroperoxidase antibody-positive pregnancies without abruption become negative by the second trimester; one pregnancy with abruption becomes antibody-positive. Odds ratios for pregnancies with both thyroperoxidase and thyroglobulin antibody elevations are also higher (first trimester: OR, 2.10; 95% CI, 0.91-4.86; second trimester: OR, 2.73; 95% CI, 1.17-6.33). The present data confirm an association between thyroid antibody elevations and placental abruption described in a recent report. These findings, however, do not provide support for recommending routine testing for thyroid antibodies during pregnancy. II.

  7. An extreme climatic event alters marine ecosystem structure in a global biodiversity hotspot

    NASA Astrophysics Data System (ADS)

    Wernberg, Thomas; Smale, Dan A.; Tuya, Fernando; Thomsen, Mads S.; Langlois, Timothy J.; de Bettignies, Thibaut; Bennett, Scott; Rousseaux, Cecile S.

    2013-01-01

    Extreme climatic events, such as heat waves, are predicted to increase in frequency and magnitude as a consequence of global warming but their ecological effects are poorly understood, particularly in marine ecosystems. In early 2011, the marine ecosystems along the west coast of Australia--a global hotspot of biodiversity and endemism--experienced the highest-magnitude warming event on record. Sea temperatures soared to unprecedented levels and warming anomalies of 2-4°C persisted for more than ten weeks along >2,000km of coastline. We show that biodiversity patterns of temperate seaweeds, sessile invertebrates and demersal fish were significantly different after the warming event, which led to a reduction in the abundance of habitat-forming seaweeds and a subsequent shift in community structure towards a depauperate state and a tropicalization of fish communities. We conclude that extreme climatic events are key drivers of biodiversity patterns and that the frequency and intensity of such episodes have major implications for predictive models of species distribution and ecosystem structure, which are largely based on gradual warming trends.

  8. Do climate extreme events foster violent civil conflicts? A coincidence analysis

    NASA Astrophysics Data System (ADS)

    Schleussner, Carl-Friedrich; Donges, Jonathan F.; Donner, Reik V.

    2014-05-01

    Civil conflicts promoted by adverse environmental conditions represent one of the most important potential feedbacks in the global socio-environmental nexus. While the role of climate extremes as a triggering factor is often discussed, no consensus is yet reached about the cause-and-effect relation in the observed data record. Here we present results of a rigorous statistical coincidence analysis based on the Munich Re Inc. extreme events database and the Uppsala conflict data program. We report evidence for statistically significant synchronicity between climate extremes with high economic impact and violent conflicts for various regions, although no coherent global signal emerges from our analysis. Our results indicate the importance of regional vulnerability and might aid to identify hot-spot regions for potential climate-triggered violent social conflicts.

  9. Estimating the impact of extreme climatic events on riverine sediment transport: new tools and methods

    NASA Astrophysics Data System (ADS)

    Lajeunesse, E.; Delacourt, C.; Allemand, P.; Limare, A.; Dessert, C.; Ammann, J.; Grandjean, P.

    2010-12-01

    A series of recent works have underlined that the flux of material exported outside of a watershed is dramatically increased during extreme climatic events, such as storms, tropical cyclones and hurricanes [Dadson et al., 2003 and 2004; Hilton et al., 2008]. Indeed the exceptionally high rainfall rates reached during these events trigger runoff and landsliding which destabilize slopes and accumulate a significant amount of sediments in flooded rivers. This observation raises the question of the control that extreme climatic events might exert on the denudation rate and the morphology of watersheds. Addressing this questions requires to measure sediment transport in flooded rivers. However most conventional sediment monitoring technics rely on manned operated measurements which cannot be performed during extreme climatic events. Monitoring riverine sediment transport during extreme climatic events remains therefore a challenging issue because of the lack of instruments and methodologies adapted to such extreme conditions. In this paper, we present a new methodology aimed at estimating the impact of extreme events on sediment transport in rivers. Our approach relies on the development of two instruments. The first one is an in-situ optical instrument, based on a LISST-25X sensor, capable of measuring both the water level and the concentration of suspended matter in rivers with a time step going from one measurement every hour at low flow to one measurement every 2 minutes during a flood. The second instrument is a remote controlled drone helicopter used to acquire high resolution stereophotogrammetric images of river beds used to compute DEMs and to estimate how flash floods impact the granulometry and the morphology of the river. These two instruments were developed and tested during a 1.5 years field survey performed from june 2007 to january 2009 on the Capesterre river located on Basse-Terre island (Guadeloupe archipelago, Lesser Antilles Arc).

  10. Mid-late Holocene climate, demography, and cultural dynamics in Iberia: A multi-proxy approach

    NASA Astrophysics Data System (ADS)

    Lillios, Katina T.; Blanco-González, Antonio; Drake, Brandon Lee; López-Sáez, José Antonio

    2016-03-01

    Despite increasing interest in the relationship between culture transformation and abrupt climate change, their complexities are poorly understood. The local impact of global environmental fluctuations depends on multiple factors, and their effects on societal collapse are often assumed rather than demonstrated. One of the major changes in west European later prehistory was the Copper to Bronze Age transition, contemporaneous with the 4.2 ky cal. BP event. This article offers a multi-dimensional insight into this historical process in the Iberian Peninsula from a multi-proxy and comparative perspective. Three study areas, representative of diverse ecological settings and historical trajectories, are compared. Using radiocarbon dates, 13C discrimination (Δ13C) values on C3 plants, and high-resolution palynological records as palaeoclimatic and palaeodemographic proxies, this study tracks the uneven signals of Holocene climate. The wettest Northwest region features the most stable trend lines, whereas the Southwest exhibits an abrupt decrease in its demographic signals c. 4500 cal. BP, which is then followed by a subsequent rise in the neighbouring Southeast. These lines of evidence suggest the possibility, never previously noted, of demic migration from the Southwest to the Southeast in the Early Bronze Age as a contributing factor to the cultural dynamics of southern Iberia.

  11. The association between maternal smoking and placenta abruption: a meta-analysis.

    PubMed

    Shobeiri, Fatemeh; Masoumi, Seyedeh Zahra; Jenabi, Ensiyeh

    2017-08-01

    Several epidemiological studies have determined that maternal smoking can increase the risk of placenta abruption. To date, only a meta-analysis has been performed for assessing the relationship between smoking and placenta abruption. This meta-analysis was conducted to estimate the association between smoking and the risk of placenta abruption. A literature search was conducted in major databases such as PubMed, Web of Science, and Scopus from the earliest possible year to April 2016. The heterogeneity across studies was explored by Q-test and I 2 statistic. The publication bias was assessed using Begg's and Egger's tests. The results were reported using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random effects model. The literature search yielded 1167 publications until April 2016 with 4 309 610 participants. Based on OR estimates obtained from case-control and cohort studies, there was a significant association between smoking and placenta abruption (1.80; 95% CI: 1.75, 1.85). Based on the results of cohort studies, smoking and placenta abruption had a significant association (relative risk ratio: 1.65; 95% CI: 1.51, 1.80). Based on reports in epidemiological studies, we showed that smoking is a risk factor for placenta abruption.

  12. Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise: North American MWP1a Contribution

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

    Gregoire, Lauren J.; Otto-Bliesner, Bette; Valdes, Paul J.

    Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions ofmore » 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.« less

  13. Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise: North American MWP1a Contribution

    DOE PAGES

    Gregoire, Lauren J.; Otto-Bliesner, Bette; Valdes, Paul J.; ...

    2016-08-23

    Elucidating the source(s) of Meltwater Pulse 1a, the largest rapid sea level rise caused by ice melt (14-18 m in less than 340 years, 14,600 years ago), is important for understanding mechanisms of rapid ice melt and the links with abrupt climate change. Here we quantify how much and by what mechanisms the North American ice sheet could have contributed to Meltwater Pulse 1a, by driving an ice sheet model with two transient climate simulations of the last 21,000 years. Ice sheet perturbed physics ensembles were run to account for model uncertainties, constraining ice extent and volume with reconstructions ofmore » 21,000 years ago to present. We determine that the North American ice sheet produced 3-4 m global mean sea level rise in 340 years due to the abrupt Bølling warming, but this response is amplified to 5-6 m when it triggers the ice sheet saddle collapse.« less

  14. The Nonlinear Response of the Equatorial Pacific Ocean-Atmosphere System to Periodic Variations in Insolation and its Association with the Abrupt Climate Transitions during the Quaternary.

    NASA Astrophysics Data System (ADS)

    Lopes, P. G.

    2015-12-01

    The evidences of climate changes during the Quaternary are abundant but the physical mechanisms behind the climate transitions are controversial. The theory of Milankovitch takes into account the periodic orbital variations and the solar radiation received by the Earth as the main explanation for the glacial-interglacial cycles. However, some gaps in the theory still remain. In this study, we propose elucidating some of these gaps by approaching the Equatorial Pacific Ocean as a large oscillator, capable of triggering climate changes in different temporal scales. A mathematical model representing El Ninõ-like phenomena, based on Duffing equation and modulated by the astronomical cycle of 100 ka, was used to simulate the variability of the equatorial Pacific climate system over the last 2 Ma. The physical configuration of the Pacific Ocean, expressed in the equation, explains the temporal limit of the glacial-interglacial cycles. According to the simulation results, consistent with paleoclimate records, the amplification of the effects of the gradual variation of the Earth's orbit eccentricity - another unclear question - is due to the feedback mechanism of the Pacific ocean-atmosphere system, which responds non-linearly to small variations in insolation forcing and determines the ENSO-like phase (warm or cold) at different time scales and different intensities. The approach proposed here takes into account that the abrupt transitions between the ENSO-like phases, and the consequent changes in the sea surface temperature (SST) along the Equatorial Pacific Ocean, produce reactions that act as secondary causes of the temperature fluctuations that result in a glaciation (or deglaciation) - as the drastic change on the rate of evaporation/precipitation around the globe, and the increase (or decrease) of the atmospheric CO2 absorption by the phytoplankton. The transitional behavior between the warm and the cold phases, according to the presented model, is enhanced as

  15. Abrupt Changes at the Permian/Triassic Boundary: Tempo of Events from High-Resolution Cyclostratigraphy

    NASA Technical Reports Server (NTRS)

    Rampino, M. R.; Prokoph, A.; Adler, A. C.

    2000-01-01

    The Permian/Triassic (P/Tr) boundary (251.4 +/- 3 Myr) is marked by the most severe mass extinction in the geologic record. Recently, precise absolute dating has bracketed the marine extinctions and associated carbon-isotope anomaly within less than 1 Myr. We improve this resolution through high-resolution stratigraphy across the P/Tr boundary in the 331-m Gartnerkofel-1 core and nearby Reppwand outcrop section (Carnic Alps, Austria) utilizing FFT and wavelet timeseries analyses of cyclic components in down-hole core logs of density and natural gamma-ray intensity, and carbon-isotopic ratios of bulk samples. The wavelet analysis indicates continuity of deposition across the P/Tr boundary interval, and the timeseries analyses show evidence for persistent cycles in the ratio of approximately 40: 10: 4.7: 2.3 meters, correlated with Milankovitch-band orbital cycles of approximately 412: 100: 40: 20 kyr (eccentricity 1 and 2, obliquity, and precession), and giving a consistent average sedimentation rate of approximately 10 cm/1,000 yr. Milankovitch periods in delta C-13 and density in these shallow-water carbonates were most likely the result of climatically induced oscillations of sea level and climate, coupled with changes in ocean circulation and productivity, that affected sedimentation. Fluctuations in gamma radiation reflect varying input of clay minerals and the presence of shaly interbeds. Throughout the P/Tr boundary interval in the core, the 100,000-year eccentricity cycle seems to be dominant. Weaker obliquity and precession cycles are in line with the location of the Austrian section in the latest Permian, close to the Equator in the western bight of the Tethys, where obliquity and precessional effects on seasonal contrast might be subdued. Using the improved resolution provided by cycle analysis in the GK-1 core, we find that the dramatic change in the faunal record that marks the P/Tr boundary takes place over less than 6m, or less than 60,000 years. In

  16. Abrupt drainage cycles of the Fennoscandian Ice Sheet

    PubMed Central

    Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard

    2013-01-01

    Continental ice sheets are a key component of the Earth’s climate 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 climate–lake–FIS system, linked to changes in the availability of subglacial water, led to abrupt 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. PMID:23569264

  17. Quantifying the probability of record-setting heat events in the historical record and at different levels of climate forcing

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.

    2017-12-01

    Severe heat provides one of the most direct, acute, and rapidly changing impacts of climate on people and ecostystems. Theory, historical observations, and climate model simulations all suggest that global warming should increase the probability of hot events that fall outside of our historical experience. Given the acutre impacts of extreme heat, quantifying the probability of historically unprecedented hot events at different levels of climate forcing is critical for climate adaptation and mitigation decisions. However, in practice that quantification presents a number of methodological challenges. This presentation will review those methodological challenges, including the limitations of the observational record and of climate model fidelity. The presentation will detail a comprehensive approach to addressing these challenges. It will then demonstrate the application of that approach to quantifying uncertainty in the probability of record-setting hot events in the current climate, as well as periods with lower and higher greenhouse gas concentrations than the present.

  18. A Comparative Analysis of Climate-Risk and Extreme Event-Related Impacts on Well-Being and Health: Policy Implications

    PubMed Central

    Al-Amin, Abul Quasem; Wiesböck, Laura; Mugabe, Paschal; Aparicio-Effen, Marilyn; Fudjumdjum, Hubert; Chiappetta Jabbour, Charbel Jose

    2018-01-01

    There are various climate risks that are caused or influenced by climate change. They are known to have a wide range of physical, economic, environmental and social impacts. Apart from damages to the physical environment, many climate risks (climate variability, extreme events and climate-related hazards) are associated with a variety of impacts on human well-being, health, and life-supporting systems. These vary from boosting the proliferation of vectors of diseases (e.g., mosquitos), to mental problems triggered by damage to properties and infrastructure. There is a great variety of literature about the strong links between climate change and health, while there is relatively less literature that specifically examines the health impacts of climate risks and extreme events. This paper is an attempt to address this knowledge gap, by compiling eight examples from a set of industrialised and developing countries, where such interactions are described. The policy implications of these phenomena and the lessons learned from the examples provided are summarised. Some suggestions as to how to avert the potential and real health impacts of climate risks are made, hence assisting efforts to adapt to a problem whose impacts affect millions of people around the world. All the examples studied show some degree of vulnerability to climate risks regardless of their socioeconomic status and need to increase resilience against extreme events. PMID:29438345

  19. A Comparative Analysis of Climate-Risk and Extreme Event-Related Impacts on Well-Being and Health: Policy Implications.

    PubMed

    Filho, Walter Leal; Al-Amin, Abul Quasem; Nagy, Gustavo J; Azeiteiro, Ulisses M; Wiesböck, Laura; Ayal, Desalegn Y; Morgan, Edward A; Mugabe, Paschal; Aparicio-Effen, Marilyn; Fudjumdjum, Hubert; Chiappetta Jabbour, Charbel Jose

    2018-02-13

    There are various climate risks that are caused or influenced by climate change. They are known to have a wide range of physical, economic, environmental and social impacts. Apart from damages to the physical environment, many climate risks (climate variability, extreme events and climate-related hazards) are associated with a variety of impacts on human well-being, health, and life-supporting systems. These vary from boosting the proliferation of vectors of diseases (e.g., mosquitos), to mental problems triggered by damage to properties and infrastructure. There is a great variety of literature about the strong links between climate change and health, while there is relatively less literature that specifically examines the health impacts of climate risks and extreme events. This paper is an attempt to address this knowledge gap, by compiling eight examples from a set of industrialised and developing countries, where such interactions are described. The policy implications of these phenomena and the lessons learned from the examples provided are summarised. Some suggestions as to how to avert the potential and real health impacts of climate risks are made, hence assisting efforts to adapt to a problem whose impacts affect millions of people around the world. All the examples studied show some degree of vulnerability to climate risks regardless of their socioeconomic status and need to increase resilience against extreme events.

  20. Quantifying population exposure to airborne particulate matter during extreme events in California due to climate change

    NASA Astrophysics Data System (ADS)

    Mahmud, A.; Hixson, M.; Kleeman, M. J.

    2012-08-01

    The effect of climate change on population-weighted concentrations of particulate matter (PM) during extreme pollution events was studied using the Parallel Climate Model (PCM), the Weather Research and Forecasting (WRF) model and the UCD/CIT 3-D photochemical air quality model. A "business as usual" (B06.44) global emissions scenario was dynamically downscaled for the entire state of California between the years 2000-2006 and 2047-2053. Air quality simulations were carried out for 1008 days in each of the present-day and future climate conditions using year-2000 emissions. Population-weighted concentrations of PM0.1, PM2.5, and PM10 total mass, components species, and primary source contributions were calculated for California and three air basins: the Sacramento Valley air basin (SV), the San Joaquin Valley air basin (SJV) and the South Coast Air Basin (SoCAB). Results over annual-average periods were contrasted with extreme events. The current study found that the change in annual-average population-weighted PM2.5 mass concentrations due to climate change between 2000 vs. 2050 within any major sub-region in California was not statistically significant. However, climate change did alter the annual-average composition of the airborne particles in the SoCAB, with notable reductions of elemental carbon (EC; -3%) and organic carbon (OC; -3%) due to increased annual-average wind speeds that diluted primary concentrations from gasoline combustion (-3%) and food cooking (-4%). In contrast, climate change caused significant increases in population-weighted PM2.5 mass concentrations in central California during extreme events. The maximum 24-h average PM2.5 concentration experienced by an average person during a ten-yr period in the SJV increased by 21% due to enhanced production of secondary particulate matter (manifested as NH4NO3). In general, climate change caused increased stagnation during future extreme pollution events, leading to higher exposure to diesel engines

  1. The association between uterine leiomyoma and placenta abruption: A meta-analysis.

    PubMed

    Jenabi, Ensiyeh; Ebrahimzadeh Zagami, Samira

    2017-11-01

    Some epidemiological studies have found that uterine leiomyoma can increase the risk of placenta abruption. To date, the meta-analysis has not been performed for assessing the relationship between uterine leiomyoma and placenta abruption. This meta-analysis was conducted to estimate the association between uterine leiomyoma and the risk of placenta abruption. A literature search was conducted out in major databases PubMed, Web of Science, and Scopus from the earliest possible year to October 2016. The heterogeneity across studies was explored by Q-test and I 2 statistic. The publication bias was assessed by Begg's and Egger's tests. The results were showed using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random-effects model. The literature search included 953 articles until October 2016 with 232,024 participants. Based on OR estimates obtained from case-control and cohort studies, there was significant association between uterine leiomyoma and placenta abruption (2.63; 95% CI: 1.38, 3.88). We showed based on reports in observational studies that uterine leiomyoma is a risk factor for placenta abruption.

  2. An international contrast of rates of placental abruption: an age-period-cohort analysis.

    PubMed

    Ananth, Cande V; Keyes, Katherine M; Hamilton, Ava; Gissler, Mika; Wu, Chunsen; Liu, Shiliang; Luque-Fernandez, Miguel Angel; Skjærven, Rolv; Williams, Michelle A; Tikkanen, Minna; Cnattingius, Sven

    2015-01-01

    Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries. Women that delivered in the US (n = 863,879; 1979-10), Canada (4 provinces, n = 5,407,463; 1982-11), Sweden (n = 3,266,742; 1978-10), Denmark (n = 1,773,895; 1978-08), Norway (n = 1,780,271, 1978-09), Finland (n = 1,411,867; 1987-10), and Spain (n = 6,151,508; 1999-12) were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries. Abruption rates varied across the seven countries (3-10 per 1000), Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01) and Sweden (P<0.01). There is a strong maternal age effect on abruption. While the abruption rate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.

  3. A stratigraphic framework for naming and robust correlation of abrupt climatic changes during the last glacial period based on three synchronized Greenland ice core records

    NASA Astrophysics Data System (ADS)

    Rasmussen, Sune O.

    2014-05-01

    Due to their outstanding resolution and well-constrained chronologies, Greenland ice core records have long been used as a master record of past climatic changes during the last interglacial-glacial cycle in the North Atlantic region. As part of the INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. This is based on a combination of isotope ratios (δ18O, reflecting mainly local temperature) and calcium concentrations (reflecting mainly atmospheric dust loading). In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. This is a key step aimed at promoting unambiguous comparison and correlation between different proxy records, as well as a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is under review for publication in Quaternary Science Reviews. Author team: S

  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. Phase Memory Preserving Harmonics from Abruptly Autofocusing Beams.

    PubMed

    Koulouklidis, Anastasios D; Papazoglou, Dimitris G; Fedorov, Vladimir Yu; Tzortzakis, Stelios

    2017-12-01

    We demonstrate both theoretically and experimentally that the harmonics from abruptly autofocusing ring-Airy beams present a surprising property: They preserve the phase distribution of the fundamental beam. Consequently, this "phase memory" imparts to the harmonics the abrupt autofocusing behavior, while, under certain conditions, their foci coincide in space with the one of the fundamental. Experiments agree well with our theoretical estimates and detailed numerical calculations. Our findings open the way for the use of such beams and their harmonics in strong field science.

  6. Investigations of the Climate System Response to Climate Engineering in a Hierarchy of Models

    NASA Astrophysics Data System (ADS)

    McCusker, Kelly E.

    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 climate continues to warm. In the absence of meaningful greenhouse gas emissions reductions, new strategies have been proposed to engineer the climate, with the aim of preventing further warming and avoiding associated climate 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 climate model with a coupled mixed-layer depth ocean and with a fully-coupled ocean general circulation model to simulate the stabilization of climate by balancing increasing carbon dioxide with increasing stratospheric sulfate concentrations. We evaluate whether or not severe climate impacts, such as melting Arctic sea ice, tropical crop failure, or destabilization of the West Antarctic ice sheet, could be avoided. We find that while tropical climate emergencies might be avoided by use of stratospheric aerosol injections, avoiding polar emergencies cannot be guaranteed due to large residual climate 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 climate 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 abruptly terminated after a multi- decadal period of implementation while greenhouse gas emissions have continued unabated

  7. Slow Onsets, Abrupt Changes, and Fast Reflexes: Learning from Climate Hazards in a Changing World

    NASA Astrophysics Data System (ADS)

    Pulwarty, R. S.

    2016-12-01

    Adaptation is higher than ever before on the global agenda. Awareness of risks across the weather-climate continuum has increased pressure for information to support planning under changing rates and emergence of multiple hazards (e.g. drought, heat waves, floods). In recognition of this demand, the global community is developing a Global Framework for Climate Services, implementing the Sendai Framework on disaster risk reduction, and formulating climate-sensitive development and research initiatives aimed at nations and communities. The gap between conceptual feasibility and practical implementation remains immense. One of Gilbert White's many important contributions was in developing a framework for structuring adjustment decisions in the context of longer-term risks. The physical environment at a given stage of technology sets the theoretical range of choice while the practical range of choice is set by culture, capacity and institutions. These factors facilitate or impede efficient and equitable responses, with the latter being key in the underestimation of the complexities of adaptation. This presentation will focus on the scientific research, monitoring and information needed to address challenges in (1) Understanding thresholds in the relationship between physical and social changes, including those in connected systems such as water, food and energy, (2) Designing and diffusion of decision support tools and smart practices, and (3) Understanding the links between capacity-building and implementation, including the need to focus researchers and institutions on improving decision quality (not just meeting "user needs"). The author will engage the audience in a discussion of the drivers of social transitions and transformations, drawing on cases from around the world. Key questions, include "What leads to proactive collaboration and action?"; "How often should we revise our assumptions about the direction and magnitude of changes as events unfold?"; and "What

  8. From drought to flooding: understanding the abrupt 2010-11 hydrological annual cycle in the Amazonas River and tributaries

    NASA Astrophysics Data System (ADS)

    Carlo Espinoza, Jhan; Ronchail, Josyane; Loup Guyot, Jean; Junquas, Clementine; Drapeau, Guillaume; Martinez, Jean Michel; Santini, William; Vauchel, Philippe; Lavado, Waldo; Ordoñez, Julio; Espinoza, Raúl

    2012-06-01

    In this work we document and analyze the hydrological annual cycles characterized by a rapid transition between low and high flows in the Amazonas River (Peruvian Amazon) and we show how these events, which may impact vulnerable riverside residents, are related to regional climate variability. Our analysis is based on comprehensive discharge, rainfall and average suspended sediment data sets. Particular attention is paid to the 2010-11 hydrological year, when an unprecedented abrupt transition from the extreme September 2010 drought (8300 m3 s-1) to one of the four highest discharges in April 2011 (49 500 m3 s-1) was recorded at Tamshiyacu (Amazonas River). This unusual transition is also observed in average suspended sediments. Years with a rapid increase in discharge are characterized by negative sea surface temperature anomalies in the central equatorial Pacific during austral summer, corresponding to a La Niña-like mode. It originates a geopotential height wave train over the subtropical South Pacific and southeastern South America, with a negative anomaly along the southern Amazon and the southeastern South Atlantic convergence zone region. As a consequence, the monsoon flux is retained over the Amazon and a strong convergence of humidity occurs in the Peruvian Amazon basin, favoring high rainfall and discharge. These features are also reported during the 2010-11 austral summer, when an intense La Niña event characterized the equatorial Pacific.

  9. The Response of Different Audiences to Place-based Communication about the Role of Climate Change in Extreme Weather Events

    NASA Astrophysics Data System (ADS)

    Halperin, A.; Walton, P.

    2015-12-01

    As the science of extreme event attribution grows, there is an increasing need to understand how the public responds to this type of climate change communication. Extreme event attribution has the unprecedented potential to locate the effects of climate change in the here and now, but there is little information about how different facets of the public might respond to these local framings of climate change. Drawing on theories of place attachment and psychological distance, this paper explores how people with different beliefs and values shift their willingness to mitigate and adapt to climate change in response to local or global communication of climate change impacts. Results will be presented from a recent survey of over 600 Californians who were each presented with one of three experimental conditions: 1) a local framing of the role of climate change in the California drought 2) a global framing of climate change and droughts worldwide, or 3) a control condition of no text. Participants were categorized into groups based on their prior beliefs about climate change according to the Six Americas classification scheme (Leiserowitz et al., 2011). The results from the survey in conjunction with qualitative results from follow-up interviews shed insight into the importance of place in communicating climate change for people in each of the Six Americas. Additional results examine the role of gender and political affiliation in mediating responses to climate change communication. Despite research that advocates unequivocally for local framing of climate change, this study offers a more nuanced perspective of under which circumstances extreme event attribution might be an effective tool for changing behaviors. These results could be useful for scientists who wish to gain a better understanding of how their event attribution research is perceived or for educators who want to target their message to audiences where it could have the most impact.

  10. 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

  11. Decision-support tools for Extreme Weather and Climate Events in the Northeast United States

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Lowery, M.; Whelchel, A.

    2013-12-01

    Decision-support tools were assessed for the 2013 National Climate Assessment technical input document, "Climate Change in the Northeast, A Sourcebook". The assessment included tools designed to generate and deliver actionable information to assist states and highly populated urban and other communities in assessment of climate change vulnerability and risk, quantification of effects, and identification of adaptive strategies in the context of adaptation planning across inter-annual, seasonal and multi-decadal time scales. State-level adaptation planning in the Northeast has generally relied on qualitative vulnerability assessments by expert panels and stakeholders, although some states have undertaken initiatives to develop statewide databases to support vulnerability assessments by urban and local governments, and state agencies. The devastation caused by Superstorm Sandy in October 2012 has raised awareness of the potential for extreme weather events to unprecedented levels and created urgency for action, especially in coastal urban and suburban communities that experienced pronounced impacts - especially in New Jersey, New York and Connecticut. Planning approaches vary, but any adaptation and resiliency planning process must include the following: - Knowledge of the probable change in a climate variable (e.g., precipitation, temperature, sea-level rise) over time or that the climate variable will attain a certain threshold deemed to be significant; - Knowledge of intensity and frequency of climate hazards (past, current or future events or conditions with potential to cause harm) and their relationship with climate variables; - Assessment of climate vulnerabilities (sensitive resources, infrastructure or populations exposed to climate-related hazards); - Assessment of relative risks to vulnerable resources; - Identification and prioritization of adaptive strategies to address risks. Many organizations are developing decision-support tools to assist in the urban

  12. Extreme climatic events change the dynamics and invasibility of semi-arid annual plant communities.

    PubMed

    Jiménez, Milagros A; Jaksic, Fabian M; Armesto, Juan J; Gaxiola, Aurora; Meserve, Peter L; Kelt, Douglas A; Gutiérrez, Julio R

    2011-12-01

    Extreme climatic events represent disturbances that change the availability of resources. We studied their effects on annual plant assemblages in a semi-arid ecosystem in north-central Chile. We analysed 130 years of precipitation data using generalised extreme-value distribution to determine extreme events, and multivariate techniques to analyse 20 years of plant cover data of 34 native and 11 exotic species. Extreme drought resets the dynamics of the system and renders it susceptible to invasion. On the other hand, by favouring native annuals, moderately wet events change species composition and allow the community to be resilient to extreme drought. The probability of extreme drought has doubled over the last 50 years. Therefore, investigations on the interaction of climate change and biological invasions are relevant to determine the potential for future effects on the dynamics of semi-arid annual plant communities. 2011 Blackwell Publishing Ltd/CNRS.

  13. Can dynamically downscaled climate model outputs improve pojections of extreme precipitation events?

    EPA Science Inventory

    Many of the storms that generate damaging floods are caused by locally intense, sub-daily precipitation, yet the spatial and temporal resolution of the most widely available climate model outputs are both too coarse to simulate these events. Thus there is often a disconnect betwe...

  14. Abrupt release of terrigenous organic carbon to the Laptev Sea at termination of the Younger Dryas

    NASA Astrophysics Data System (ADS)

    Tesi, T.; Muschitiello, F.; Smittenberg, R.; Jakobsson, M.; Vonk, J.; Hill, P.; Dudarev, O.; Semiletov, I. P.; Kirchner, N.; Noormets, R.; Andersson, A.; Gustafsson, O.

    2015-12-01

    Based on analysis of a piston core collected in 2014 from the Lena River paleo delta, now Laptev Sea, we show that rapid and massive organic carbon (OC) deposition took place into the marine system at the termination of the Younger Dryas when the Arctic region experienced a large and extremely fast climate change. The highly laminated strata with absence of bioturbation further confirm the rapid event-driven emplacement of this deposit which was largely dominated by terrigenous OC as indicated by depleted δ13C values and high concentrations of terrestrial fossil biomarkers (lignin phenols and cutin-derived products). Moreover, the hydrogen isotopic composition (δ2H) of HMW n-alkanes indicates that this terrestrially-derived translocated OC was produced in the watershed during a relatively cold period. The OC appears to be a few thousand years old at time of deposition (ca. 4-5000 radiocarbon years; reservoir age corrected), consistent with the radiocarbon age of pre-aged OC currently supplied by the Lena river. Altogether our results indicate that fast climate warming exerts first-order control on large-scale carbon redistribution. Because the Younger Dryas-Preboreal transition occurred within a few decades, we infer that the abrupt and large release of terrigenous OC was essentially driven by rapid changes in the permafrost stability (i.e., thermal collapse/thawing) and increase in precipitation over the Siberian watershed. Interestingly, only surface and sub-surface carbon pools (i.e., active layer) were remobilized while deep and old sources (radiocarbon dead) did not seem to have substantially contributed to the total land-to-ocean flux during the Younger Dryas-Preboreal transition.

  15. Climatic Impacts of a Volcanic Double Event: 536/540 CE

    NASA Astrophysics Data System (ADS)

    Toohey, M.; Krüger, K.; Sigl, M.; Stordal, F.; Svensen, H.

    2015-12-01

    Volcanic activity in and around the year 536 CE led to the coldest decade of the Common Era, and has been speculatively linked to large-scale societal crises around the world. Using a coupled aerosol-climate model, with eruption parameters constrained by recently re-dated ice core records and historical observations of the aerosol cloud, we reconstruct the radiative forcing resulting from a sequence of two major volcanic eruptions in 536 and 540 CE. Comparing with a reconstruction of volcanic forcing over the past 1200 years, we estimate that the decadal-scale Northern Hemisphere (NH) extra-tropical radiative forcing from this volcanic "double event" was larger than that of any known period. Earth system model simulations including the volcanic forcing are used to explore the temperature and precipitation anomalies associated with the eruptions, and compared to available proxy records, including maximum latewood density (MXD) temperature reconstructions. Special attention is placed on the decadal persistence of the cooling signal in tree rings, and whether the climate model simulations reproduce such long-term climate anomalies. Finally, the climate model results will be used to explore the probability of socioeconomic crisis resulting directly from the volcanic radiative forcing in different regions of the world.

  16. An ecohydrological model to quantify the risk of drought-induced forest mortality events across climate regimes

    NASA Astrophysics Data System (ADS)

    Parolari, A.; Katul, G. G.; Porporato, A. M.

    2013-12-01

    Regional scale drought-induced forest mortality events are projected to become more frequent under future climates due to changes in rainfall patterns. However, the ability to predict the conditions under which such events occur is currently lacking. To quantify and understand the underlying causes of drought-induced forest mortality, we propose a stochastic ecohydrological model that explicitly couples tree water and carbon use strategies with climate characteristics, such as the frequency and severity of drought. Using the model and results from a controlled drought experiment, we identify the soil, vegetation, and climate factors that underlie tree water and carbon deficits and, ultimately, the risk of drought-induced forest mortality. This mortality risk is then compared across the spectrum of anisohydric-isohydric stomatal control strategies and a range of rainfall regimes. These results suggest certain soil-plant combinations may maximize the survivable drought length in a given climate. Finally, we discuss how this approach can be expanded to estimate the effect of anticipated climate change on drought-induced forest mortality and associated consequences for forest water and carbon balances.

  17. Persistent millennial-scale shifts in moisture regimes in western Canada during the past six millennia

    PubMed Central

    Cumming, Brian F.; Laird, Kathleen R.; Bennett, Joseph R.; Smol, John P.; Salomon, Anne K.

    2002-01-01

    Inferences of past climatic conditions from a sedimentary record from Big Lake, British Columbia, Canada, over the past 5,500 years show strong millennial-scale patterns, which oscillate between periods of wet and drier climatic conditions. Higher frequency decadal- to centennial-scale fluctuations also occur within the dominant millennial-scale patterns. These changes in climatic conditions are based on estimates of changes in lake depth and salinity inferred from diatom assemblages in a well dated sediment core. After periods of relative stability, abrupt shifts in diatom assemblages and inferred climatic conditions occur approximately every 1,220 years. The correspondence of these shifts to millennial-scale variations in records of glacial expansion/recession and ice-rafting events in the Atlantic suggest that abrupt millennial-scale shifts are important to understanding climatic variability in North America during the mid- to late Holocene. Unfortunately, the spatial patterns and mechanisms behind these large and abrupt swings are poorly understood. Similar abrupt and prolonged changes in climatic conditions today could pose major societal challenges for many regions. PMID:12461174

  18. Persistent millennial-scale shifts in moisture regimes in western Canada during the past six millennia.

    PubMed

    Cumming, Brian F; Laird, Kathleen R; Bennett, Joseph R; Smol, John P; Salomon, Anne K

    2002-12-10

    Inferences of past climatic conditions from a sedimentary record from Big Lake, British Columbia, Canada, over the past 5,500 years show strong millennial-scale patterns, which oscillate between periods of wet and drier climatic conditions. Higher frequency decadal- to centennial-scale fluctuations also occur within the dominant millennial-scale patterns. These changes in climatic conditions are based on estimates of changes in lake depth and salinity inferred from diatom assemblages in a well dated sediment core. After periods of relative stability, abrupt shifts in diatom assemblages and inferred climatic conditions occur approximately every 1,220 years. The correspondence of these shifts to millennial-scale variations in records of glacial expansionrecession and ice-rafting events in the Atlantic suggest that abrupt millennial-scale shifts are important to understanding climatic variability in North America during the mid- to late Holocene. Unfortunately, the spatial patterns and mechanisms behind these large and abrupt swings are poorly understood. Similar abrupt and prolonged changes in climatic conditions today could pose major societal challenges for many regions.

  19. Neanderthal and Anatomically Modern Human interaction with Abrupt Late Pleistocene Environments - the data is finally good enough to talk about climate change!

    NASA Astrophysics Data System (ADS)

    Blockley, Simon; Schreve, Danielle

    2015-04-01

    The timing and nature of the appearance of Anatomically Modern Humans (AMH) in Europe, their interaction with, and eventual morphological replacement of Neanderthals (despite some shared genetic heritage) has been a matter of intense debate within archaeology for a generation. This period, often termed the Middle to Upper Palaeolithic transition occurs in the latter part of Marine Isotope Stage Three and in recent decades archaeological interest has been complemented by the input of palaeoclimate scientists, over the role of abrupt climate change in this process. This was due to the recognition from ice core and marine proxy archives, in particular, of periods if intense cooling, correlated to the marine record of Heinrich ice rafted debris layers from the Atlantic. As a result of these collaborations between the archaeological and palaeoenvironmental communities various drivers have been proposed for the Middle to Upper Palaeolithic Transition that include: (1) resource competition between two species occupying similar niches; (2) the impact of repeated cycles of Heinrich event cooling, leading to the decline and eventual disappearance of the Neanderthal populations, leaving a new region open for AMH exploitation; and (3) catastrophic impacts of large volcanic eruptions on Neanderthal populations. Attempts to address the above hypotheses have been dogged by the chronological precision available for a number of key archives. The accuracy of many of the radiocarbon ages that underpin the chronology for both Neanderthal and AMH archaeological sites has been questioned1. This has been exacerbated by uncertainties over the influence of variability in the radiocarbon marine reservoir effect on marine palaeoclimate records and a marine dominated radiocarbon calibration curve. Additionally, the counting uncertainties of the master Greenland palaeoclimate archives are also large by this time, meaning palaeoclimate interpretation can be equivocal. However, several research

  20. ClimEx - Climate change and hydrological extreme events - risks and perspectives for water management in Bavaria and Québec

    NASA Astrophysics Data System (ADS)

    Ludwig, Ralf; Baese, Frank; Braun, Marco; Brietzke, Gilbert; Brissette, Francois; Frigon, Anne; Giguère, Michel; Komischke, Holger; Kranzlmueller, Dieter; Leduc, Martin; Martel, Jean-Luc; Ricard, Simon; Schmid, Josef; von Trentini, Fabian; Turcotte, Richard; Weismueller, Jens; Willkofer, Florian; Wood, Raul

    2017-04-01

    The recent accumulation of extreme hydrological events in Bavaria and Québec has stimulated scientific and also societal interest. In addition to the challenges of an improved prediction of such situations and the implications for the associated risk management, there is, as yet, no confirmed knowledge whether and how climate change contributes to the magnitude and frequency of hydrological extreme events and how regional water management could adapt to the corresponding risks. The ClimEx project (2015-2019) investigates the effects of climate change on the meteorological and hydrological extreme events and their implications for water management in Bavaria and Québec. High Performance Computing is employed to enable the complex simulations in a hydro-climatological model processing chain, resulting in a unique high-resolution and transient (1950-2100) dataset of climatological and meteorological forcing and hydrological response: (1) The climate module has developed a large ensemble of high resolution data (12km) of the CRCM5 RCM for Central Europe and North-Eastern North America, downscaled from 50 members of the CanESM2 GCM. The dataset is complemented by all available data from the Euro-CORDEX project to account for the assessment of both natural climate variability and climate change. The large ensemble with several thousand model years provides the potential to catch rare extreme events and thus improves the process understanding of extreme events with return periods of 1000+ years. (2) The hydrology module comprises process-based and spatially explicit model setups (e.g. WaSiM) for all major catchments in Bavaria and Southern Québec in high temporal (3h) and spatial (500m) resolution. The simulations form the basis for in depth analysis of hydrological extreme events based on the inputs from the large climate model dataset. The specific data situation enables to establish a new method for 'virtual perfect prediction', which assesses climate change impacts

  1. Impacts of different climate change regimes and extreme climatic events on an alpine meadow community

    PubMed Central

    Alatalo, Juha M.; Jägerbrand, Annika K.; Molau, Ulf

    2016-01-01

    Climate variability is expected to increase in future but there exist very few experimental studies that apply different warming regimes on plant communities over several years. We studied an alpine meadow community under three warming regimes over three years. Treatments consisted of (a) a constant level of warming with open-top chambers (ca. 1.9 °C above ambient), (b) yearly stepwise increases in warming (increases of ca. 1.0, 1.9 and 3.5 °C), and (c) pulse warming, a single first-year pulse event of warming (increase of ca. 3.5 °C). Pulse warming and stepwise warming was hypothesised to cause distinct first-year and third-year effects, respectively. We found support for both hypotheses; however, the responses varied among measurement levels (whole community, canopy, bottom layer, and plant functional groups), treatments, and time. Our study revealed complex responses of the alpine plant community to the different experimentally imposed climate warming regimes. Plant cover, height and biomass frequently responded distinctly to the constant level of warming, the stepwise increase in warming and the extreme pulse-warming event. Notably, we found that stepwise warming had an accumulating effect on biomass, the responses to the different warming regimes varied among functional groups, and the short-term perturbations had negative effect on species richness and diversity PMID:26888225

  2. Modeling the Effects of Drought Events on Forest Ecosystem Functioning Historically and Under Scenarios of Climate Change

    NASA Astrophysics Data System (ADS)

    Ren, J.; Hanan, E. J.; Kolden, C.; Abatzoglou, J. T.; Tague, C.; Liu, M.; Adam, J. C.

    2017-12-01

    Drought events have been increasing across the western United States in recent years. Many studies have shown that, in the context of climate change, droughts will continue to be stronger, more frequent, and prolonged in the future. However, the response of forest ecosystems to droughts, particularly multi-year droughts, is not well understood. The objectives of this study are to examine how drought events of varying characteristics (e.g. intensity, duration, frequency, etc.) have affected the functioning of forest ecosystems historically, and how changing drought characteristics (including multi-year droughts) may affect forest functioning in a future climate. We utilize the Regional Hydro-Ecological Simulation System (RHESSys) to simulate impacts of both historical droughts and scenarios of future droughts on forest ecosystems. RHESSys is a spatially-distributed and process-based model that captures the interactions between coupled biogeochemical and hydrologic cycles at catchment scales. Here our case study is the Trail Creek catchment of the Big Wood River basin in Idaho, the Northwestern USA. For historical simulations, we use the gridded meteorological data of 1979 to 2016; for future climate scenarios, we utilize downscaled data from GCMs that have been demonstrated to capture drought events in the Northwest of the USA. From these climate projections, we identify various types of drought in intensity and duration, including multi-year drought events. We evaluate the following responses of ecosystems to these events: 1) evapotranspiration and streamflow; 2) gross primary productivity; 3) the post-drought recovery of plant biomass; and 4) the forest functioning and recovery after multi-year droughts. This research is part of an integration project to examine the roles of drought, insect outbreak, and forest management activities on wildfire activity and its impacts. This project will provide improved information for forest managers and communities in the wild

  3. Deglacial climate modulated by the storage and release of Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Condron, A.; Coletti, A. J.; Bradley, R. S.

    2017-12-01

    Periods of abrupt climate cooling during the last deglaciation (20 - 8 kyr ago) are often attributed to glacial outburst floods slowing the Atlantic meridional overturning circulation (AMOC). Here, we present results from a series of climate model simulations showing that the episodic break-up and mobilization of thick, perennial, Arctic sea ice during this time would have released considerable volumes of freshwater directly to the Nordic Seas, where processes regulating large-scale climate occur. Massive sea ice export events to the North Atlantic are generated whenever the transport of sea ice is enhanced, either by changes in atmospheric circulation, rising sea level submerging the Bering land bridge, or glacial outburst floods draining into the Arctic Ocean from the Mackenzie River. We find that the volumes of freshwater released to the Nordic Seas are similar to, or larger than, those estimated to have come from terrestrial outburst floods, including the discharge at the onset of the Younger Dryas. Our results provide the first evidence that the storage and release of Arctic sea ice helped drive deglacial climate change by modulating the strength of the AMOC.

  4. Extreme Flood Events Over the Past 300 Years Recorded in the Sediments of a Mountain Lake in the Altay Mountains, Northwestern China

    NASA Astrophysics Data System (ADS)

    Wu, J.; Zhou, J.; Shen, B.; Zeng, H.

    2017-12-01

    Global climate change has the potential to accelerate the hydrological cycle, which may further enhance the temporal frequency of regional extreme floods. Climatic models predict that intra-annual rainfall variability will intensify, which will shift current rainfall regimes towards more extreme systems with lower precipitation frequencies, longer dry periods, and larger individual precipitation events worldwide. Understanding the temporal variations of extreme floods that occur in response to climate change is essential to anticipate the trends in flood magnitude and frequency in the context of global warming. However, currently available instrumental data are not long enough for capturing the most extreme events, thus the acquisition of long duration datasets for historical floods that extend beyond available instrumental records is clearly an important step in discerning trends in flood frequency and magnitude with respect to climate change. In this study, a reconstruction of paleofloods over the past 300 years was conducted through an analysis of grain sizes from the sediments of Kanas Lake in the Altay Mountains of northwestern China. Grain parameters and frequency distributions both demonstrate that two abrupt environment changes exist within the lake sedimentary sequence. Based on canonical discriminant analysis (CDA) and C-M pattern analysis, two flood events corresponding to ca. 1760 AD and ca. 1890 AD were identified, both of which occurred during warmer and wetter climate conditions according to tree-ring records. These two flood events are also evidenced by lake sedimentary records in the Altay and Tianshan areas. Furthermore, through a comparison with other records, the flood event in ca. 1760 AD seems to have occurred in both the arid central Asia and the Alps in Europe, and thus may have been associated with changes in the North Atlantic Oscillation (NAO) index.

  5. IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation

    NASA Astrophysics Data System (ADS)

    Field, C. B.; Stocker, T. F.; Barros, V. R.; Qin, D.; Ebi, K. L.; Midgley, P. M.

    2011-12-01

    The Summary for Policy Makers of the IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation will be approved by the world governments in November 2011. The focus of the Special Report is on climate change and its role in altering the frequency, severity, and impact of extreme events or disasters, and on the costs of both impacts and the actions taken to prepare for, respond to, and recover from extreme events and disasters. The emphasis is on understanding the factors that make people and infrastructure vulnerable to extreme events, on recent and future changes in the relationship between climate change and extremes, and on managing the risks of disasters over a wide range of spatial and temporal scales. The assessment considers a broad suite of adaptations and explores the limits to adaptation. The assessment was designed to build durable links and foundations for partnerships between the stakeholder communities focused on climate change and those focused on disaster risk reduction. The Special Report begins with material that frames the issues, followed by an assessment of the reasons that communities are vulnerable. Two chapters assess the role of past and future climate change in altering extremes and the impact of these on the physical environment and human systems. Three chapters assess available knowledge on impacts and adaptation, with separate chapters considering the literature, stakeholder relationships, and potential policy tools relevant to the local, national, and international scales. Longer-term components of adaptation to weather and climate extremes and disasters are assessed in the context of moving toward sustainability. The final chapter provides case studies that integrate themes across several chapters or are so unique that they need to be considered separately.

  6. Education and Climate Change: Living and Learning in Interesting Times

    ERIC Educational Resources Information Center

    Kagawa, Fumiyo, Ed.; Selby, David, Ed.

    2009-01-01

    There is widespread consensus in the international scientific community that climate change is happening and that abrupt and irreversible impacts are already set in motion. What part does education have to play in helping alleviate rampant climate change and in mitigating its worst effects? In this volume, contributors review and reflect upon…

  7. The "New Climate" New Atmospheric Events and "New Climate Risks": The case of Morocco

    NASA Astrophysics Data System (ADS)

    Karrouk, M. S.

    2015-12-01

    Since the end of last century, qualified meteorological events of "exceptional" causing floods have ceased to occur in Morocco and elsewhere, with a recurrence increasingly high, prompting to wonder about the "new" mode of climate's hydrothermal functioning inducing torrential rains, as well as its effect on the environment and societies.The latest event is the disaster of November 2014 flooding in southern Morocco, which is due especially to the non usual rains return.Weather conditions were marked by enhanced Meridian Atmospheric Circulation (MAC), characterized by persistent high temperatures during the autumn period in Morocco, mainly south of the Atlas, combined by the intrusion of a cold drop in the beginning of the event on 11.17.2014, and straightforward installation of a planetary valley across the Moroccan coast on 11.24.2014, which has evolved into storm (Xandra) in which depression has reached the surprising value of 975 hPa on 11.28.2014.Human and material damage caused by this flood are impressive: people died, roads, bridges and crops have been destroyed, overwhelmed dams. It has been a catastrophe.This event and others like it (Mohammedia 2002, Tangier 2008, Gharb 2009-2010, Casablanca 2010), must be considered as references for the simulation of future situations, and integration into development plans on future.This communication aims to identify the processes and conditions that have generated these events causing floods, the "exceptional" characteristics of recorded rainfall, the spatial and temporal distribution of events. Those floods affect the whole country, especially low areas, foothills and the mouths of rivers. There are the most vulnerable locations mainly on the autumn which is the most exposed to torrential rainfall season !! ... Etc.

  8. Estimating least-developed countries' vulnerability to climate-related extreme events over the next 50 years.

    PubMed

    Patt, Anthony G; Tadross, Mark; Nussbaumer, Patrick; Asante, Kwabena; Metzger, Marc; Rafael, Jose; Goujon, Anne; Brundrit, Geoff

    2010-01-26

    When will least developed countries be most vulnerable to climate change, given the influence of projected socio-economic development? The question is important, not least because current levels of international assistance to support adaptation lag more than an order of magnitude below what analysts estimate to be needed, and scaling up support could take many years. In this paper, we examine this question using an empirically derived model of human losses to climate-related extreme events, as an indicator of vulnerability and the need for adaptation assistance. We develop a set of 50-year scenarios for these losses in one country, Mozambique, using high-resolution climate projections, and then extend the results to a sample of 23 least-developed countries. Our approach takes into account both potential changes in countries' exposure to climatic extreme events, and socio-economic development trends that influence countries' own adaptive capacities. Our results suggest that the effects of socio-economic development trends may begin to offset rising climate exposure in the second quarter of the century, and that it is in the period between now and then that vulnerability will rise most quickly. This implies an urgency to the need for international assistance to finance adaptation.

  9. Estimating least-developed countries’ vulnerability to climate-related extreme events over the next 50 years

    PubMed Central

    Patt, Anthony G.; Tadross, Mark; Nussbaumer, Patrick; Asante, Kwabena; Metzger, Marc; Rafael, Jose; Goujon, Anne; Brundrit, Geoff

    2010-01-01

    When will least developed countries be most vulnerable to climate change, given the influence of projected socio-economic development? The question is important, not least because current levels of international assistance to support adaptation lag more than an order of magnitude below what analysts estimate to be needed, and scaling up support could take many years. In this paper, we examine this question using an empirically derived model of human losses to climate-related extreme events, as an indicator of vulnerability and the need for adaptation assistance. We develop a set of 50-year scenarios for these losses in one country, Mozambique, using high-resolution climate projections, and then extend the results to a sample of 23 least-developed countries. Our approach takes into account both potential changes in countries’ exposure to climatic extreme events, and socio-economic development trends that influence countries’ own adaptive capacities. Our results suggest that the effects of socio-economic development trends may begin to offset rising climate exposure in the second quarter of the century, and that it is in the period between now and then that vulnerability will rise most quickly. This implies an urgency to the need for international assistance to finance adaptation. PMID:20080585

  10. Extreme weather events in Iran under a changing climate

    NASA Astrophysics Data System (ADS)

    Alizadeh-Choobari, Omid; Najafi, M. S.

    2018-01-01

    Observations unequivocally show that Iran has been rapidly warming over recent decades, which in sequence has triggered a wide range of climatic impacts. Meteorological records of several ground stations across Iran with daily temporal resolution for the period 1951-2013 were analyzed to investigate the climate change and its impact on some weather extremes. Iran has warmed by nearly 1.3 °C during the period 1951-2013 (+0.2 °C per decade), with an increase of the minimum temperature at a rate two times that of the maximum. Consequently, an increase in the frequency of heat extremes and a decrease in the frequency of cold extremes have been observed. The annual precipitation has decreased by 8 mm per decade, causing an expansion of Iran's dry zones. Previous studies have pointed out that warming is generally associated with more frequent heavy precipitation because a warmer air can hold more moisture. Nevertheless, warming in Iran has been associated with more frequent light precipitation, but less frequent moderate, heavy and extremely heavy precipitation. This is because in the subtropical dry zones, a longer time is required to recharge the atmosphere with water vapour in a warmer climate, causing more water vapour to be transported from the subtropics to high latitudes before precipitations forms. In addition, the altitude of the condensation level increases in a warmer climate in subtropical regions, causing an overall decrease of precipitation. We argue that changing in the frequency of heavy precipitation in response to warming varies depending on the geographical location. Warming over the dry subtropical regions is associated with a decrease in the frequency of heavy precipitation, while an increase is expected over both subpolar and tropical regions. The warmer climate has also led to the increase in the frequency of both thunderstorms (driven by convective heating) and dust events over Iran.

  11. Late Holocene to present climatic and anthropogenic drivers affecting wetland plant communities, Florida Everglades, USA

    NASA Astrophysics Data System (ADS)

    Bernhardt, C. E.; Willard, D. A.

    2011-12-01

    We synthesize the paleoecological results of dozens of sediment cores to evaluate the complex interactions of regional climate variability and anthropogenic modifications during the late Holocene affecting the development, stability, and resilience of the Florida Everglades wetlands. The Everglades is a mosaic of wetland types whose distributions are controlled by water depth, hydroperiod, fire, and substrate. External stressors could trigger shifts in the vegetation composition and change the community structure. Episodic severe periods of aridity during the late Holocene caused regional shifts in vegetation including the initiation and development of tree islands and sawgrass ridges, which became established during abrupt drought events. While the timing varies site to site, most droughts occurred during well-documented global climate events like the Medieval Climate Anomaly and the Little Ice Age. However, slough vegetation is more resilient to climate variability and quickly returns to its original composition after droughts. Twentieth century modification to the natural Everglades hydrology saw the distribution wetlands severely altered. The response was not homogeneous. Some communities were drowned by prolonged hydroperiods whereas other communities, such as marl prairies became drier. However, slough vegetation in the ridge and slough landscape did not respond to 20th century land use but instead has been sensitive to changes in precipitation associated with the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation.

  12. Self-reported smoking habits and serum cotinine levels in women with placental abruption.

    PubMed

    Tikkanen, Minna; Surcel, Heljä-Marja; Bloigu, Aini; Nuutila, Mika; Ylikorkala, Olavi; Hiilesmaa, Vilho; Paavonen, Jorma

    2010-12-01

    smoking is an important risk factor for placental abruption with strong dose-dependency. Pregnant smokers often underreport tobacco use which can be objectively assessed by measuring serum cotinine levels. We examined the accuracy between self-reported smoking habits and early pregnancy serum cotinine levels in women with or without placental abruption. retrospective case-control study. university Hospital. a total of 175 women with placental abruption and 370 control women. serum samples collected during the first trimester were analyzed for serum cotinine levels. Cotinine concentration over 15 ng/ml was considered as the cutoff indicating active smoking. Smoking habits of the women and their partners were recorded at the same visit. placental abruption. of the cases of women with placental abruption, 27.4% reported smoking compared with 14.3% of the controls (p < 0.001). Based on serum cotinine levels, 30.3% of the case women and 17.6% of the control women were considered smokers (p = 0.003). Serum cotinine levels among smokers were higher in the abruption group than in the control group (median 229.5 ng/ml (interquartile range 169.8-418.1) vs. 153.5 ng/ml (56.6-241.4), p = 0.002). Self-reported number of cigarettes smoked daily correlated well with the cotinine levels (r = 0.68, p < 0.001). Of the women reporting as nonsmokers, approximately 7% were considered smokers based on cotinine testing. pregnant women with subsequent placental abruption are heavier smokers than pregnant control women. Self-reported smoking habits correlate well with serum cotinine levels in Finland. Therefore, self-reported smoking can be considered as a risk marker for placental abruption.

  13. Geologic events coupled with Pleistocene climatic oscillations drove genetic variation of Omei treefrog (Rhacophorus omeimontis) in southern China.

    PubMed

    Li, Jun; Zhao, Mian; Wei, Shichao; Luo, Zhenhua; Wu, Hua

    2015-12-21

    Pleistocene climatic oscillations and historical geological events may both influence current patterns of genetic variation, and the species in southern China that faced unique climatic and topographical events have complex evolutionary histories. However, the relative contributions of climatic oscillations and geographical events to the genetic variation of these species remain undetermined. To investigate patterns of genetic variation and to test the hypotheses about the factors that shaped the distribution of this genetic variation in species of southern China, mitochondrial genes (cytochrome b and NADH dehydrogenase subunit 2) and nine microsatellite loci of the Omei tree frog (Rhacophorus omeimontis) were amplified in this study. The genetic diversity in the populations of R. omeimontis was high. The phylogenetic trees reconstructed from the mitochondrial DNA (mtDNA) haplotypes and the Bayesian genetic clustering analysis based on microsatellite data both revealed that all populations were divided into three lineages (SC, HG and YN). The two most recent splitting events among the lineages coincided with recent geological events (including the intense uplift of the Qinghai-Tibet Plateau, QTP and the subsequent movements of the Yun-Gui Plateau, YGP) and the Pleistocene glaciations. Significant expansion signals were not detected in mismatch analyses or neutrality tests. And the effective population size of each lineage was stable during the Pleistocene. Based on the results of this study, complex geological events (the recent dramatic uplift of the QTP and the subsequent movements of the YGP) and the Pleistocene glaciations were apparent drivers of the rapid divergence of the R. omeimontis lineages. Each diverged lineages survived in situ with limited gene exchanges, and the stable demographics of lineages indicate that the Pleistocene climatic oscillations were inconsequential for this species. The analysis of genetic variation in populations of R. omeimontis

  14. Dynamic vegetation modeling of tropical biomes during Heinrich events

    NASA Astrophysics Data System (ADS)

    Handiani, Dian Noor; Paul, André; Dupont, Lydie M.

    2010-05-01

    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 abrupt climate changes occurred not only in the ocean but also on the continents. Changes were strongest in the Northern Hemisphere but were registered in the tropics as well. Pollen data from Angola and Brazil showed that climate changes during Heinrich events affected vegetation patterns very differently in eastern South America and western Africa. To understand the differential response in the terrestrial tropics, 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-Climate 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 tropical 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 climate. 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

  15. Northern Hemisphere glaciation and the evolution of Plio-Pleistocene climate noise

    NASA Astrophysics Data System (ADS)

    Meyers, Stephen R.; Hinnov, Linda A.

    2010-08-01

    Deterministic orbital controls on climate variability are commonly inferred to dominate across timescales of 104-106 years, although some studies have suggested that stochastic processes may be of equal or greater importance. Here we explicitly quantify changes in deterministic orbital processes (forcing and/or pacing) versus stochastic climate processes during the Plio-Pleistocene, via time-frequency analysis of two prominent foraminifera oxygen isotopic stacks. Our results indicate that development of the Northern Hemisphere ice sheet is paralleled by an overall amplification of both deterministic and stochastic climate energy, but their relative dominance is variable. The progression from a more stochastic early Pliocene to a strongly deterministic late Pleistocene is primarily accommodated during two transitory phases of Northern Hemisphere ice sheet growth. This long-term trend is punctuated by “stochastic events,” which we interpret as evidence for abrupt reorganization of the climate system at the initiation and termination of the mid-Pleistocene transition and at the onset of Northern Hemisphere glaciation. In addition to highlighting a complex interplay between deterministic and stochastic climate change during the Plio-Pleistocene, our results support an early onset for Northern Hemisphere glaciation (between 3.5 and 3.7 Ma) and reveal some new characteristics of the orbital signal response, such as the puzzling emergence of 100 ka and 400 ka cyclic climate variability during theoretical eccentricity nodes.

  16. Carbonaceous Aerosol Removal During Precipitation Events: Climate Implications

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Bridges, G. L.; Marchany-Rivera, A.; Begum, M.

    2009-12-01

    Atmospheric aerosols and their links to clouds are one of the main focus areas of the Department of Energy’s Atmospheric Systems Research, due to the fact that aerosols and clouds constitute the major uncertainties in radiative forcing that need to be reduced for more accurate modeling of climate, particularly regional climate. The impact of absorbing aerosols on radiative balance of the atmosphere will depend on their atmospheric lifetimes as well as their UV-visible absorption profiles. Aerosol lifetimes depend on the aerosols ability to take up water and grow to sufficient size to be either removed by gravitational settling or to act as cloud condensation nuclei and be removed by precipitation scavenging. The investigation of uv-visible absorbing aerosols is underway using a seven-channel aethalometer to evaluate the change in aerosol optical absorption during precipitation events. Angstrom absorption exponents (AAEs) are determined before, during, and after rain events to examine the impact on the aerosol absorption profiles anticipated by removal of the water soluble short-wave absorbing species (i.e. HULIS) that can be produced by photochemical oxidation of biogenic emissions (isoprene, monoterpenes, sesquiterpenes). Aerosol absorption data are presented from observations made at the University of Arkansas at Little Rock and other sites, which clearly show that a significant amount of absorbing carbon is not removed during rain events, and that the organic matter removed is likely secondary organics produced from biogenic precursors. The dissolved organic carbon measured in precipitation samples along with determinations of natural radionuclide tracers are also used to help examine the extent of carbonaceous aerosol removal by precipitation. The data are discussed in terms of the potential impacts of anthropogenic enhancement of aerosol absorption by secondary organic aerosols adding to atmospheric heating and changes in atmospheric dynamics. The potential

  17. Antarctic climate change: extreme events disrupt plastic phenotypic response in Adélie penguins.

    PubMed

    Lescroël, Amélie; Ballard, Grant; Grémillet, David; Authier, Matthieu; Ainley, David G

    2014-01-01

    In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A 'natural experiment' brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The 'natural experiment' uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise.

  18. Antarctic Climate Change: Extreme Events Disrupt Plastic Phenotypic Response in Adélie Penguins

    PubMed Central

    Lescroël, Amélie; Ballard, Grant; Grémillet, David; Authier, Matthieu; Ainley, David G.

    2014-01-01

    In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A ‘natural experiment’ brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The ‘natural experiment’ uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise. PMID:24489657

  19. Threshold effects in the vegetation response to Holocene climate changes in central Asia

    NASA Astrophysics Data System (ADS)

    Zhao, Y.

    2015-12-01

    Understanding the response of ecosystems to past climate is critical for evaluating the impacts of future climate changes. A relatively abrupt vegetation shift in response to the late Holocene gradual climate changes has been well documented for the Sahara-Sahel ecosystem. However, whether such threshold shift is of universal significance remains to be further addressed. Here, we examine the vegetation-climate relationships in central Asia based on four newly recovered Holocene pollen records and a synthesis on previously published pollen data. The results show that the orbital-induced gradual climate trend during the Holocene led to two major abrupt vegetation shifts, and that the timings of these shifts are highly dependent of the local rainfall conditions. Instead, the mid-Holocene vegetation remained rather stable despite of the changing climate. These new findings demonstrate generally significant threshold and truncation effects of climate changes on vegetation, as are strongly supported by surface pollen data and LPJ-GUESS modeling. The results also imply that using pollen data to reconstruct past climate changes is not always straightforward. Our findings have important implication for understanding the potential effects of global warming on dryland ecosystem change.

  20. Abrupt changes in Antarctic Intermediate Water strength lead Atlantic Meridional Overturning Circulation changes during the last deglacial

    NASA Astrophysics Data System (ADS)

    Xie, R.; Marcantonio, F.; Schmidt, M. W.

    2011-12-01

    depth that is greater than that of modern AAIW flow, may actually be recording shoaling of the southern-sourced mid-depth circulation instead of variations of AAIW. At the beginning of the YD, Bølling-Allerød, and H1 in the Florida Straits, changing ɛNd values lead benthic foraminiferal δ18O changes in 26JPC and 31JPC,which have previously been interpreted as reflecting AMOC variability [3]. This suggests that variations in the strength of AAIW lead significant changes in AMOC across abrupt climate events across the deglacial, providing evidence that the trigger for abrupt climate change may reside in the Southern Hemisphere. Additional high-resolution ɛNd results from VM12-107 will be presented in an effort to better constrain the role of intermediate waters during the last deglaction. [1] Came et al. (2008) Paleoceanography 23, PA1217 [2] Pahnke et al. (2008) Nature Geoscience 1, 870-874 [3] Lynch-Stieglitz et al. (2011) Paleoceanography 26, PA1205

  1. Generating extreme weather event sets from very large ensembles of regional climate models

    NASA Astrophysics Data System (ADS)

    Massey, Neil; Guillod, Benoit; Otto, Friederike; Allen, Myles; Jones, Richard; Hall, Jim

    2015-04-01

    Generating extreme weather event sets from very large ensembles of regional climate models Neil Massey, Benoit P. Guillod, Friederike E. L. Otto, Myles R. Allen, Richard Jones, Jim W. Hall Environmental Change Institute, University of Oxford, Oxford, UK Extreme events can have large impacts on societies and are therefore being increasingly studied. In particular, climate change is expected to impact the frequency and intensity of these events. However, a major limitation when investigating extreme weather events is that, by definition, only few events are present in observations. A way to overcome this issue it to use large ensembles of model simulations. Using the volunteer distributed computing (VDC) infrastructure of weather@home [1], we run a very large number (10'000s) of RCM simulations over the European domain at a resolution of 25km, with an improved land-surface scheme, nested within a free-running GCM. Using VDC allows many thousands of climate model runs to be computed. Using observations for the GCM boundary forcings we can run historical "hindcast" simulations over the past 100 to 150 years. This allows us, due to the chaotic variability of the atmosphere, to ascertain how likely an extreme event was, given the boundary forcings, and to derive synthetic event sets. The events in these sets did not actually occur in the observed record but could have occurred given the boundary forcings, with an associated probability. The event sets contain time-series of fields of meteorological variables that allow impact modellers to assess the loss the event would incur. Projections of events into the future are achieved by modelling projections of the sea-surface temperature (SST) and sea-ice boundary forcings, by combining the variability of the SST in the observed record with a range of warming signals derived from the varying responses of SSTs in the CMIP5 ensemble to elevated greenhouse gas (GHG) emissions in three RCP scenarios. Simulating the future with a

  2. To what extent has climate change contributed to the recent epidemiology of tick-borne diseases?

    PubMed

    Randolph, Sarah E

    2010-02-10

    There is no doubt that all vector-borne diseases are very sensitive to climatic conditions. Many such diseases have shown marked increases in both distribution and incidence during the past few decades, just as human-induced climate change is thought to have exceeded random fluctuations. This coincidence has led to the general perception that climate change has driven disease emergence, but climate change is the inevitable backdrop for all recent events, without implying causality. Coincidence and causality can be disentangled using tick-borne encephalitis (TBE) as a test case, based on the excellent long-term data for this medically significant European disease system. Detailed analysis of climate records since 1970 has revealed abrupt temperature increases just prior to the dramatic upsurge in TBE incidence in many parts of central and eastern Europe. Furthermore, the seasonal patterns of this temperature change are such as might have favoured the transmission of TBE virus between co-feeding ticks. Nevertheless, the pattern of climate change is too uniform to explain the marked heterogeneity in the timing and degree of TBE upsurge, for example in different counties within each of the Baltic countries. Recent decreases as well as increases in TBE incidence must also be taken into account. Instead of a single cause, a network of interacting factors, acting synergistically but with differential force in space and time, would generate this epidemiological heterogeneity. From analysis of past and present events, it appears that human behavioural factors have played a more significant role than purely biological enzootic factors, although there is an explicit causal linkage from one to the other. This includes a range of abiotic and biotic environmental factors, together with human behaviour determined by socio-economic conditions. Many of the abrupt changes followed from the shift from planned to market economies with the fall of Soviet rule. Comparisons between eight

  3. Holocene lowering of the Laurentide ice sheet affects North Atlantic gyre circulation and climate

    NASA Astrophysics Data System (ADS)

    Ivanovic, R. F.; Gregoire, L. J.; Maycock, A.; Valdes, P. J.

    2017-12-01

    The Laurentide ice sheet, which covered Canada during glacial periods, had a major influence on atmospheric circulation and surface climate, but its role in climate during the early Holocene (9-7 ka), when it was thinner and confined around Hudson Bay, is unclear. It has been suggested that the demise of the ice sheet played a role in the 8.2 ka event (an abrupt 1-3 °C Northern Hemisphere cooling lasting 160 years) through the influence of changing topography on atmospheric circulation. To test this hypothesis, and to investigate the broader implications of changing ice sheet topography for climate, we analyse a set of equilibrium climate simulations with ice sheet topographies taken at 500 year intervals from 9.5 ka to 8.0 ka. Between 9.5 and 8.0 ka, our simulations show a 2 °C cooling south of Iceland and a 1 °C warming between 40-50° N in the North Atlantic. These surface temperature changes are associated with a weakening of the subtropical and subpolar gyres caused by a decreasing wind stress curl over the mid-North Atlantic as the ice sheet lowers. The climate response is strongest during the period of peak ice volume change (9.5 ka - 8.5 ka), but becomes negligible after 8.5 ka. The climatic effects of the Laurentide ice sheet lowering are restricted to the North Atlantic sector. Thus, topographic forcing did not play a significant role in the 8.2 ka event and had only a small effect on Holocene climate change compared to the effects of changes in greenhouse gases, insolation and ice sheet meltwater.

  4. Holocene lowering of the Laurentide ice sheet affects North Atlantic gyre circulation and climate

    NASA Astrophysics Data System (ADS)

    Gregoire, Lauren J.; Ivanovic, Ruza F.; Maycock, Amanda C.; Valdes, Paul J.; Stevenson, Samantha

    2018-02-01

    The Laurentide ice sheet, which covered Canada during glacial periods, had a major influence on atmospheric circulation and surface climate, but its role in climate during the early Holocene (9-7 ka), when it was thinner and confined around Hudson Bay, is unclear. It has been suggested that the demise of the ice sheet played a role in the 8.2 ka event (an abrupt 1-3 °C Northern Hemisphere cooling lasting 160 years) through the influence of changing topography on atmospheric circulation. To test this hypothesis, and to investigate the broader implications of changing ice sheet topography for climate, we analyse a set of equilibrium climate simulations with ice sheet topographies taken at 500 year intervals from 9.5 to 8.0 ka. Between 9.5 and 8.0 ka, our simulations show a 2 °C cooling south of Iceland and a 1 °C warming between 40° and 50°N in the North Atlantic. These surface temperature changes are associated with a weakening of the subtropical and subpolar gyres caused by a decreasing wind stress curl over the mid-North Atlantic as the ice sheet lowers. The climate response is strongest during the period of peak ice volume change (9.5-8.5 ka), but becomes negligible after 8.5 ka. The climatic effects of the Laurentide ice sheet lowering during the Holocene are restricted to the North Atlantic sector. Thus, topographic forcing is unlikely to have played a major role in the 8.2 ka event and had only a small effect on Holocene climate change compared to the effects of changes in greenhouse gases, insolation and ice sheet meltwater.

  5. Extreme Events in China under Climate Change: Uncertainty and related impacts (CSSP-FOREX)

    NASA Astrophysics Data System (ADS)

    Leckebusch, Gregor C.; Befort, Daniel J.; Hodges, Kevin I.

    2016-04-01

    Suitable adaptation strategies or the timely initiation of related mitigation efforts in East Asia will strongly depend on robust and comprehensive information about future near-term as well as long-term potential changes in the climate system. Therefore, understanding the driving mechanisms associated with the East Asian climate is of major importance. The FOREX project (Fostering Regional Decision Making by the Assessment of Uncertainties of Future Regional Extremes and their Linkage to Global Climate System Variability for China and East Asia) focuses on the investigation of extreme wind and rainfall related events over Eastern Asia and their possible future changes. Here, analyses focus on the link between local extreme events and their driving weather systems. This includes the coupling between local rainfall extremes and tropical cyclones, the Meiyu frontal system, extra-tropical teleconnections and monsoonal activity. Furthermore, the relation between these driving weather systems and large-scale variability modes, e.g. NAO, PDO, ENSO is analysed. Thus, beside analysing future changes of local extreme events, the temporal variability of their driving weather systems and related large-scale variability modes will be assessed in current CMIP5 global model simulations to obtain more robust results. Beyond an overview of FOREX itself, first results regarding the link between local extremes and their steering weather systems based on observational and reanalysis data are shown. Special focus is laid on the contribution of monsoonal activity, tropical cyclones and the Meiyu frontal system on the inter-annual variability of the East Asian summer rainfall.

  6. Developing future precipitation events from historic events: An Amsterdam case study.

    NASA Astrophysics Data System (ADS)

    Manola, Iris; van den Hurk, Bart; de Moel, Hans; Aerts, Jeroen

    2016-04-01

    Due to climate change, the frequency and intensity of extreme precipitation events is expected to increase. It is therefore of high importance to develop climate change scenarios tailored towards the local and regional needs of policy makers in order to develop efficient adaptation strategies to reduce the risks from extreme weather events. Current approaches to tailor climate scenarios are often not well adopted in hazard management, since average changes in climate are not a main concern to policy makers, and tailoring climate scenarios to simulate future extremes can be complex. Therefore, a new concept has been introduced recently that uses known historic extreme events as a basis, and modifies the observed data for these events so that the outcome shows how the same event would occur in a warmer climate. This concept is introduced as 'Future Weather', and appeals to the experience of stakeholders and users. This research presents a novel method of projecting a future extreme precipitation event, based on a historic event. The selected precipitation event took place over the broader area of Amsterdam, the Netherlands in the summer of 2014, which resulted in blocked highways, disruption of air transportation, flooded buildings and public facilities. An analysis of rain monitoring stations showed that an event of such intensity has a 5 to 15 years return period. The method of projecting a future event follows a non-linear delta transformation that is applied directly on the observed event assuming a warmer climate to produce an "up-scaled" future precipitation event. The delta transformation is based on the observed behaviour of the precipitation intensity as a function of the dew point temperature during summers. The outcome is then compared to a benchmark method using the HARMONIE numerical weather prediction model, where the boundary conditions of the event from the Ensemble Prediction System of ECMWF (ENS) are perturbed to indicate a warmer climate. The two

  7. Water-Borne Diseases and Extreme Weather Events in Cambodia: Review of Impacts and Implications of Climate Change

    PubMed Central

    Davies, Grace I.; McIver, Lachlan; Kim, Yoonhee; Hashizume, Masahiro; Iddings, Steven; Chan, Vibol

    2014-01-01

    Cambodia is prone to extreme weather events, especially floods, droughts and typhoons. Climate change is predicted to increase the frequency and intensity of such events. The Cambodian population is highly vulnerable to the impacts of these events due to poverty; malnutrition; agricultural dependence; settlements in flood-prone areas, and public health, governance and technological limitations. Yet little is known about the health impacts of extreme weather events in Cambodia. Given the extremely low adaptive capacity of the population, this is a crucial knowledge gap. A literature review of the health impacts of floods, droughts and typhoons in Cambodia was conducted, with regional and global information reviewed where Cambodia-specific literature was lacking. Water-borne diseases are of particular concern in Cambodia, in the face of extreme weather events and climate change, due to, inter alia, a high pre-existing burden of diseases such as diarrhoeal illness and a lack of improved sanitation infrastructure in rural areas. A time-series analysis under quasi-Poisson distribution was used to evaluate the association between floods and diarrhoeal disease incidence in Cambodian children between 2001 and 2012 in 16 Cambodian provinces. Floods were significantly associated with increased diarrhoeal disease in two provinces, while the analysis conducted suggested a possible protective effect from toilets and piped water. Addressing the specific, local pre-existing vulnerabilities is vital to promoting population health resilience and strengthening adaptive capacity to extreme weather events and climate change in Cambodia. PMID:25546280

  8. Water-borne diseases and extreme weather events in Cambodia: review of impacts and implications of climate change.

    PubMed

    Davies, Grace I; McIver, Lachlan; Kim, Yoonhee; Hashizume, Masahiro; Iddings, Steven; Chan, Vibol

    2014-12-23

    Cambodia is prone to extreme weather events, especially floods, droughts and typhoons. Climate change is predicted to increase the frequency and intensity of such events. The Cambodian population is highly vulnerable to the impacts of these events due to poverty; malnutrition; agricultural dependence; settlements in flood-prone areas, and public health, governance and technological limitations. Yet little is known about the health impacts of extreme weather events in Cambodia. Given the extremely low adaptive capacity of the population, this is a crucial knowledge gap. A literature review of the health impacts of floods, droughts and typhoons in Cambodia was conducted, with regional and global information reviewed where Cambodia-specific literature was lacking. Water-borne diseases are of particular concern in Cambodia, in the face of extreme weather events and climate change, due to, inter alia, a high pre-existing burden of diseases such as diarrhoeal illness and a lack of improved sanitation infrastructure in rural areas. A time-series analysis under quasi-Poisson distribution was used to evaluate the association between floods and diarrhoeal disease incidence in Cambodian children between 2001 and 2012 in 16 Cambodian provinces. Floods were significantly associated with increased diarrhoeal disease in two provinces, while the analysis conducted suggested a possible protective effect from toilets and piped water. Addressing the specific, local pre-existing vulnerabilities is vital to promoting population health resilience and strengthening adaptive capacity to extreme weather events and climate change in Cambodia.

  9. Wildland fire emissions, carbon, and climate: Science overview and knowledge needs

    Treesearch

    William T. Sommers; Rachel A. Loehman; Colin C. Hardy

    2014-01-01

    Wildland fires have influenced the global carbon cycle for 420 million years of Earth history, interacting with climate to define vegetation characteristics and distributions, trigger abrupt ecosystem shifts, and move carbon among terrestrial and atmospheric pools. Carbon dioxide (CO2) is the dominant driver of ongoing climate change and the principal emissions...

  10. Extreme Rainfall Events Over Southern Africa: Assessment of a Climate Model to Reproduce Daily Extremes

    NASA Astrophysics Data System (ADS)

    Williams, C.; Kniveton, D.; Layberry, R.

    2007-12-01

    It is increasingly accepted that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The subcontinent is considered especially vulnerable extreme events, due to a number of factors including extensive poverty, disease and political instability. Rainfall variability and the identification of rainfall extremes is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. The majority of previous climate model verification studies have compared model output with observational data at monthly timescales. In this research, the assessment of a state-of-the-art climate model to simulate climate at daily timescales is carried out using satellite derived rainfall data from the Microwave Infra-Red Algorithm (MIRA). This dataset covers the period from 1993-2002 and the whole of southern Africa at a spatial resolution of 0.1 degree longitude/latitude. Once the model's ability to reproduce extremes has been assessed, idealised regions of SST anomalies are used to force the model, with the overall aim of investigating the ways in which SST anomalies influence rainfall extremes over southern Africa. In this paper, results from sensitivity testing of the UK Meteorological Office Hadley Centre's climate model's domain size are firstly presented. Then simulations of current climate from the model, operating in both regional and global mode, are compared to the MIRA dataset at daily timescales. Thirdly, the ability of the model to reproduce daily rainfall extremes will be assessed, again by a comparison with extremes from the MIRA dataset. Finally, the results from the idealised SST experiments are briefly presented, suggesting associations between rainfall extremes and both local and remote SST anomalies.

  11. Ultra-wideband horn antenna with abrupt radiator

    DOEpatents

    McEwan, Thomas E.

    1998-01-01

    An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna.

  12. Risk of fetal death associated with maternal drug dependence and placental abruption: a population-based study.

    PubMed

    McDonald, Sarah D; Vermeulen, Marian J; Ray, Joel G

    2007-07-01

    Substance use in pregnancy is associated with placental abruption, but the risk of fetal death independent of abruption remains undetermined. Our objective was to examine the effect of maternal drug dependence on placental abruption and on fetal death in association with abruption and independent of it. To examine placental abruption and fetal death, we performed a retrospective population-based study of 1 854 463 consecutive deliveries of liveborn and stillborn infants occurring between January 1, 1995 and March 31, 2001, using the Canadian Institute for Health Information Discharge Abstract Database. Maternal drug dependence was associated with a tripling of the risk of placental abruption in singleton pregnancies (adjusted odds ratio [OR] 3.1; 95% confidence intervals [CI] 2.6-3.7), but not in multiple gestations (adjusted OR 0.88; 95% CI 0.12-6.4). Maternal drug dependence was associated with an increased risk of fetal death independent of abruption (adjusted OR 1.6: 95% CI 1.1-2.2) in singleton pregnancies, but not in multiples. Risk of fetal death was increased with placental abruption in both singleton and multiple gestations, even after controlling for drug dependence (adjusted OR 11.4 in singleton pregnancy; 95% CI 10.6-12.2, and 3.4 in multiple pregnancy; 95% CI 2.4-4.9). Maternal drug use is associated with an increased risk of intrauterine fetal death independent of placental abruption. In singleton pregnancies, maternal drug dependence is associated with an increased risk of placental abruption.

  13. Interpreting the power spectrum of Dansgaard-Oeschger events via stochastic dynamical systems

    NASA Astrophysics Data System (ADS)

    Mitsui, Takahito; Lenoir, Guillaume; Crucifix, Michel

    2017-04-01

    Dansgaard-Oeschger (DO) events are abrupt climate shifts, which are particularly pronounced in the North Atlantic region during glacial periods [Dansgaard et al. 1993]. The signals are most clearly found in δ 18O or log [Ca2+] records of Greenland ice cores. The power spectrum S(f) of DO events has attracted attention over two decades with debates on the apparent 1.5-kyr periodicity [Grootes & Stuiver 1997; Schultz et al. 2002; Ditlevsen et al. 2007] and scaling property over several time scales [Schmitt, Lovejoy, & Schertzer 1995; Rypdal & Rypdal 2016]. The scaling property is written most simply as S(f)˜ f-β , β ≈ 1.4. However, physical as well as underlying dynamics of the periodicity and the scaling property are still not clear. Pioneering works for modelling the spectrum of DO events are done by Cessi (1994) and Ditlevsen (1999), but their model-data comparisons of the spectra are rather qualitative. Here, we show that simple stochastic dynamical systems can generate power spectra statistically consistent with the observed spectra over a wide range of frequency from orbital to the Nyquist frequency (=1/40 yr-1). We characterize the scaling property of the spectrum by defining a local scaling exponentβ _loc. For the NGRIP log [Ca2+] record, the local scaling exponent β _loc increases from ˜ 1 to ˜ 2 as the frequency increases from ˜ 1/5000 yr-1 to ˜ 1/500 yr-1, and β _loc decreases toward zero as the frequency increases from ˜ 1/500 yr-1 to the Nyquist frequency. For the δ 18O record, the local scaling exponent β _loc increases from ˜ 1 to ˜ 1.5 as the frequency increases from ˜ 1/5000 yr^{-1 to ˜ 1/1000 yr-1, and β _loc decreases toward zero as the frequency increases from ˜ 1/1000 yr-1 to the Nyquist frequency. This systematic breaking of a single scaling is reproduced by the simple stochastic models. Especially, the models suggest that the flattening of the spectra starting from multi-centennial scale and ending at the Nyquist frequency

  14. 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.

  15. Detecting mismatches in the phenology of cotton bollworm larvae and cotton flowering in response to climate change

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Hao, HongFei

    2018-05-01

    Current evidence suggests that climate change has directly affected the phenology of many invertebrate species associated with agriculture. Such changes in phenology have the potential to cause temporal mismatches between predators and prey and may lead to a disruption in natural pest control ecosystem. Understanding the synchrony between pest insects and host plant responses to climate change is a key step to improve integrated pest management strategies. Cotton bollworm larvae damage cotton, and thus, data from Magaiti County, China, collected during the period of 1990-2015 were analyzed to assess the effects of climate change on cotton bollworm larvae and cotton flowering. The results showed that a warming climate advanced the phenology of cotton bollworm larvae and cotton flowering. However, the phenological rate of change was faster in cotton bollworm larvae than that in cotton flowering, and the larval period was prolonged, resulting in a great increase of the larval population. The abrupt phenological changes in cotton bollworm larvae occurred earlier than that in cotton, and the abrupt phenological changes in cotton flowering occurred earlier than that in larval abundance. However, the timing of abrupt changes in larval abundance all occurred later than that in temperature. Thus, the abrupt changes that occurred in larvae, cotton flowering and climate were asynchronous. The interval days between the cotton flowering date (CFD) and the half-amount larvae date (HLD) expanded by 3.41 and 4.41 days with a 1 °C increase of T mean in May and June, respectively. The asynchrony between cotton bollworm larvae and cotton flowering will likely broaden as the climate changes. The effective temperature in March and April and the end date of larvae (ED) were the primary factors affecting asynchrony.

  16. Detecting mismatches in the phenology of cotton bollworm larvae and cotton flowering in response to climate change.

    PubMed

    Huang, Jian; Hao, HongFei

    2018-05-11

    Current evidence suggests that climate change has directly affected the phenology of many invertebrate species associated with agriculture. Such changes in phenology have the potential to cause temporal mismatches between predators and prey and may lead to a disruption in natural pest control ecosystem. Understanding the synchrony between pest insects and host plant responses to climate change is a key step to improve integrated pest management strategies. Cotton bollworm larvae damage cotton, and thus, data from Magaiti County, China, collected during the period of 1990-2015 were analyzed to assess the effects of climate change on cotton bollworm larvae and cotton flowering. The results showed that a warming climate advanced the phenology of cotton bollworm larvae and cotton flowering. However, the phenological rate of change was faster in cotton bollworm larvae than that in cotton flowering, and the larval period was prolonged, resulting in a great increase of the larval population. The abrupt phenological changes in cotton bollworm larvae occurred earlier than that in cotton, and the abrupt phenological changes in cotton flowering occurred earlier than that in larval abundance. However, the timing of abrupt changes in larval abundance all occurred later than that in temperature. Thus, the abrupt changes that occurred in larvae, cotton flowering and climate were asynchronous. The interval days between the cotton flowering date (CFD) and the half-amount larvae date (HLD) expanded by 3.41 and 4.41 days with a 1 °C increase of T mean in May and June, respectively. The asynchrony between cotton bollworm larvae and cotton flowering will likely broaden as the climate changes. The effective temperature in March and April and the end date of larvae (ED) were the primary factors affecting asynchrony.

  17. Six climate change-related events in the United States accounted for about $14 billion in lost lives and health costs.

    PubMed

    Knowlton, Kim; Rotkin-Ellman, Miriam; Geballe, Linda; Max, Wendy; Solomon, Gina M

    2011-11-01

    The future health costs associated with predicted climate change-related events such as hurricanes, heat waves, and floods are projected to be enormous. This article estimates the health costs associated with six climate change-related events that struck the United States between 2000 and 2009. The six case studies came from categories of climate change-related events projected to worsen with continued global warming-ozone pollution, heat waves, hurricanes, infectious disease outbreaks, river flooding, and wildfires. We estimate that the health costs exceeded $14 billion, with 95 percent due to the value of lives lost prematurely. Actual health care costs were an estimated $740 million. This reflects more than 760,000 encounters with the health care system. Our analysis provides scientists and policy makers with a methodology to use in estimating future health costs related to climate change and highlights the growing need for public health preparedness.

  18. Applying Customized Climate Advisory Information to Translate Extreme Rainfall Events into Farming Options in the Sudan-Sahel of West Africa

    NASA Astrophysics Data System (ADS)

    Salack, S.; Worou, N. O.; Sanfo, S.; Nikiema, M. P.; Boubacar, I.; Paturel, J. E.; Tondoh, E. J.

    2017-12-01

    In West Africa, the risk of food insecurity linked to the low productivity of small holder farming increases as a result of rainfall extremes. In its recent evolution, the rainy season in the Sudan-Sahel zone presents mixed patterns of extreme climatic events. In addition to intense rain events, the distribution of events is associated with pockets of intra-seasonal long dry spells. The negative consequences of these mixed patterns are obvious on the farm: soil water logging, erosion of arable land, dwartness and dessication of crops, and loss in production. The capacity of local farming communities to respond accordingly to rainfall extreme events is often constrained by lack of access to climate information and advisory on smart crop management practices that can help translate extreme rainfall events into farming options. The objective of this work is to expose the framework and the pre-liminary results of a scheme that customizes climate-advisory information package delivery to subsistence farmers in Bakel (Senegal), Ouahigouya & Dano (Burkina Faso) and Bolgatanga (Ghana) for sustainable family agriculture. The package is based on the provision of timely climate information (48-hours, dekadal & seasonal) embedded with smart crop management practices to explore and exploite the potential advantage of intense rainfall and extreme dry spells in millet, maize, sorghum and cowpea farming communities. It is sent via mobile phones and used on selected farms (i.e agro-climatic farm schools) on which some small on-farm infrastructure were built to alleviate negative impacts of weather. Results provide prominent insight on how co-production of weather/climate information, customized access and guidiance on its use can induce fast learning (capacity building of actors), motivation for adaptation, sustainability, potential changes in cropping system, yields and family income in the face of a rainfall extremes at local scales of Sudan-Sahel of West Africa. Keywords: Climate

  19. Anticipatory adjustments to abrupt changes of opposing forces.

    PubMed

    Rapp, Katrin; Heuer, Herbert

    2015-01-01

    Anticipatory adjustments to abrupt load changes are based on task-specific predictive information. The authors asked whether anticipatory adjustments to abrupt offsets of horizontal forces are related to expectancy. In two experiments participants held a position against an opposing force or moved against it. At force offset they had to stop rapidly. Duration of the opposing force or distance moved against it varied between blocks of trials and was constant within each block, or it varied from trial to trial. These two variations resulted in opposite changes of the expectancy of force offset with the passage of time or distance. With constant force durations or distances in each block of trials, anticipatory adjustments tended to be poorest with the longest duration or distance, but with variable force durations or distances they tended to be best with the longest duration or distance. Thus anticipatory adjustments were related to expectancy rather than time or distance per se. Anticipatory adjustments resulted in shorter peak amplitudes of the involuntary movements, accompanied by longer movement times in Experiment 1 and faster movement times in Experiment 2. Thus, for different states of the limb at abrupt dynamic changes anticipatory adjustments involve different mechanisms that modulate different mechanical characteristics.

  20. Rapid climate fluctuations over the past millennium: evidence from a lacustrine record of Basomtso Lake, southeastern Tibetan Plateau

    PubMed Central

    Li, Kai; Liu, Xingqi; Herzschuh, Ulrike; Wang, Yongbo

    2016-01-01

    Abrupt climate changes and fluctuations over short time scales are superimposed on long-term climate changes. Understanding rapid climate fluctuations at the decadal time scale over the past millennium will enhance our understanding of patterns of climate variability and aid in forecasting climate changes in the future. In this study, climate changes on the southeastern Tibetan Plateau over the past millennium were determined from a 4.82-m-long sediment core from Basomtso Lake. At the centennial time scale, the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Current Warm Period (CWP) are distinct in the Basomtso region. Rapid climate fluctuations inferred from five episodes with higher sediment input and likely warmer conditions, as well as seven episodes with lower sediment input and likely colder conditions, were well preserved in our record. These episodes with higher and lower sediment input are characterized by abrupt climate changes and short time durations. Spectral analysis indicates that the climate variations at the centennial scale on the southeastern Tibetan Plateau are influenced by solar activity during the past millennium. PMID:27091591

  1. The Imprint of Extreme Climate Events in Century-Long Time Series of Wood Anatomical Traits in High-Elevation Conifers

    PubMed Central

    Carrer, Marco; Brunetti, Michele; Castagneri, Daniele

    2016-01-01

    Extreme climate events are of key importance for forest ecosystems. However, both the inherent infrequency, stochasticity and multiplicity of extreme climate events, and the array of biological responses, challenges investigations. To cope with the long life cycle of trees and the paucity of the extreme events themselves, our inferences should be based on long-term observations. In this context, tree rings and the related xylem anatomical traits represent promising sources of information, due to the wide time perspective and quality of the information they can provide. Here we test, on two high-elevation conifers (Larix decidua and Picea abies sampled at 2100 m a.s.l. in the Eastern Alps), the associations among temperature extremes during the growing season and xylem anatomical traits, specifically the number of cells per ring (CN), cell wall thickness (CWT), and cell diameter (CD). To better track the effect of extreme events over the growing season, tree rings were partitioned in 10 sectors. Climate variability has been reconstructed, for 1800–2011 at monthly resolution and for 1926–2011 at daily resolution, by exploiting the excellent availability of very long and high quality instrumental records available for the surrounding area, and taking into account the relationship between meteorological variables and site topographical settings. Summer temperature influenced anatomical traits of both species, and tree-ring anatomical profiles resulted as being associated to temperature extremes. Most of the extreme values in anatomical traits occurred with warm (positive extremes) or cold (negative) conditions. However, 0–34% of occurrences did not match a temperature extreme event. Specifically, CWT and CN extremes were more clearly associated to climate than CD, which presented a bias to track cold extremes. Dendroanatomical analysis, coupled to high-quality daily-resolved climate records, seems a promising approach to study the effects of extreme events on

  2. Circum-Mediterranean fire activity and climate changes during the mid Holocene environmental transition (8500-2500 cal yr BP)

    NASA Astrophysics Data System (ADS)

    Vannière, Boris; Power, Mitch J.; Roberts, Neil; Tinner, Willy; Carrión, José; Magny, Michel; Bartlein, Patrick

    2010-05-01

    In this contribution I will present a synthesis of mid- to late-Holocene fire activity from the Mediterranean basin and explore the linkages among fire, climate variability and seasonality, and people through several climatic and ecological transitions. Regional fire histories were created from 36 radiocarbon-dated sedimentary charcoal records, available from the Global Charcoal Database. During the mid-Holocene "Thermal Maximum", charcoal records from the northern Mediterranean suggest the region was more fire prone while records from the southern Mediterranean indicate a decrease in fire activity associated with wetter-than-present summers. A North-South partition at 40-43°N is apparent in the central and western Mediterranean. In the context of orbitally-induced summer insolation decrease, South Mediterranean wet conditions could be linked to the Afro-Asian summer monsoon which weakened after ca. 8000-6000 cal yr BP. Relatively abrupt changes in fire regime observed at ca. 5500-5000 cal yr BP may be associated to a threshold in this weakening influence of the orbitally-driven Afro-Asian monsoon strength. Charcoal records of past fire activity appear sensitive to both orbitally-forced climate changes and shorter lived excursions which may be related to cold events apparent in the North Atlantic record of ice-rafted debris. These results contradict former notions of gradual aridification of the entire region due to climatic forcing and/or human activities. In contrast, they suggest: 1) Teleconnections between the Mediterranean area and other climatic regions, in particular the North Atlantic and the low-latitude monsoon areas, influenced past fire regimes; 2) Gradual forcing, such as changes in orbital parameters, may have triggered more abrupt shifts in fire regime, either directly or indirectly through these teleconnections.

  3. Global situational awareness and early warning of high-consequence climate change.

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

    Backus, George A.; Carr, Martin J.; Boslough, Mark Bruce Elrick

    2009-08-01

    Global monitoring systems that have high spatial and temporal resolution, with long observational baselines, are needed to provide situational awareness of the Earth's climate system. Continuous monitoring is required for early warning of high-consequence climate change and to help anticipate and minimize the threat. Global climate has changed abruptly in the past and will almost certainly do so again, even in the absence of anthropogenic interference. It is possible that the Earth's climate could change dramatically and suddenly within a few years. An unexpected loss of climate stability would be equivalent to the failure of an engineered system on amore » grand scale, and would affect billions of people by causing agricultural, economic, and environmental collapses that would cascade throughout the world. The probability of such an abrupt change happening in the near future may be small, but it is nonzero. Because the consequences would be catastrophic, we argue that the problem should be treated with science-informed engineering conservatism, which focuses on various ways a system can fail and emphasizes inspection and early detection. Such an approach will require high-fidelity continuous global monitoring, informed by scientific modeling.« less

  4. Development of a Climate Resilience Screening Index (CRSI): An Assessment of Resilience to Acute Meteorological Events and Selected Natural Hazards

    EPA Science Inventory

    We developed a conceptual model of climate resilience (CRSI – Climate Resilience Screening Index ) designed to be sensitive to changes in the natural environment, built environment, governance, and social structure and vulnerability or risk to climate events. CRSI has been used ...

  5. An Agenda for Climate Impacts Science

    NASA Astrophysics Data System (ADS)

    Kaye, J. A.

    2009-12-01

    The report Global Change Impacts in the United States released by the US Global Change Research Program in June 2009 identifies a number of areas in which inadequate information or understanding hampers our ability to estimate likely future climate change and its impacts. In this section of the report, the focus is on those areas of climate science that could contribute most towards advancing our knowledge of climate change impacts and those aspects of climate change responsible for these impacts in order to continue to guide decision making. The Report identifies the six most important gaps in knowledge and offers some thoughts on how to address those gaps: 1. Expand our understanding of climate change impacts. There is a clear need to increase understanding of how ecosystems, social and economic systems, human health, and the built environment will be affected by climate change in the context of other stresses. 2. Refine ability to project climate change, including extreme events, at local scales. While climate change is a global issue, it has a great deal of regional variability. There is an indisputable need to improve understanding of climate system effects at these smaller scales, because these are often the scales of decision-making in society. This includes advances in modeling capability and observations needed to address local scales and high-impact extreme events. 3. Expand capacity to provide decision makers and the public with relevant information on climate change and its impacts. Significant potential exists in the US to create more comprehensive measurement, archive, and data-access systems that could provide great benefit to society, which requires defining needed information, gathering it, expanding capacity to deliver it, and improving tools by which decision makers use it to best advantage. 4. Improve understanding of thresholds likely to lead to abrupt changes in climate or ecosystems. Potential areas of research include thresholds that could

  6. Extreme climatic events drive mammal irruptions: regression analysis of 100-year trends in desert rainfall and temperature

    PubMed Central

    Greenville, Aaron C; Wardle, Glenda M; Dickman, Chris R

    2012-01-01

    Extreme climatic events, such as flooding rains, extended decadal droughts and heat waves have been identified increasingly as important regulators of natural populations. Climate models predict that global warming will drive changes in rainfall and increase the frequency and severity of extreme events. Consequently, to anticipate how organisms will respond we need to document how changes in extremes of temperature and rainfall compare to trends in the mean values of these variables and over what spatial scales the patterns are consistent. Using the longest historical weather records available for central Australia – 100 years – and quantile regression methods, we investigate if extreme climate events have changed at similar rates to median events, if annual rainfall has increased in variability, and if the frequency of large rainfall events has increased over this period. Specifically, we compared local (individual weather stations) and regional (Simpson Desert) spatial scales, and quantified trends in median (50th quantile) and extreme weather values (5th, 10th, 90th, and 95th quantiles). We found that median and extreme annual minimum and maximum temperatures have increased at both spatial scales over the past century. Rainfall changes have been inconsistent across the Simpson Desert; individual weather stations showed increases in annual rainfall, increased frequency of large rainfall events or more prolonged droughts, depending on the location. In contrast to our prediction, we found no evidence that intra-annual rainfall had become more variable over time. Using long-term live-trapping records (22 years) of desert small mammals as a case study, we demonstrate that irruptive events are driven by extreme rainfalls (>95th quantile) and that increases in the magnitude and frequency of extreme rainfall events are likely to drive changes in the populations of these species through direct and indirect changes in predation pressure and wildfires. PMID:23170202

  7. Tackling extremes: challenges for ecological and evolutionary research on extreme climatic events.

    PubMed

    Bailey, Liam D; van de Pol, Martijn

    2016-01-01

    Extreme climatic events (ECEs) are predicted to become more frequent as the climate changes. A rapidly increasing number of studies - though few on animals - suggest that the biological consequences of ECEs can be severe. However, ecological research on the impacts of ECEs has been limited by a lack of cohesiveness and structure. ECEs are often poorly defined and have often been confusingly equated with climatic variability, making comparison between studies difficult. In addition, a focus on short-term studies has provided us with little information on the long-term implications of ECEs, and the descriptive and anecdotal nature of many studies has meant it is still unclear what the key research questions are. Synthesizing the current state of work is essential to identify ways to make progress. We conduct a synthesis of the literature and discuss conceptual and practical challenges faced by research on ECEs. We consider three steps to advance research. First, we discuss the importance of choosing an ECE definition and identify the pros and cons of 'climatological' and 'biological' definitions of ECEs. Secondly, we advocate research beyond short-term descriptive studies to address questions concerning the long-term implications of ECEs, focussing on selective pressures and phenotypically plastic responses and how they might differ from responses to a changing climatic mean. Finally, we encourage a greater focus on multi-event studies that help us understand the implications of changing patterns of ECEs, through the combined use of modelling, experimental and observational field studies. This study aims to open a discussion on the definitions, questions and methods currently used to study ECEs, which will lead to a more cohesive approach to future ECE research. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

  8. From products to processes: Academic events to foster interdisciplinary and iterative dialogue in a changing climate

    NASA Astrophysics Data System (ADS)

    Addor, Nans; Ewen, Tracy; Johnson, Leigh; Ćöltekin, Arzu; Derungs, Curdin; Muccione, Veruska

    2015-08-01

    In the context of climate change, both climate researchers and decision makers deal with uncertainties, but these uncertainties differ in fundamental ways. They stem from different sources, cover different temporal and spatial scales, might or might not be reducible or quantifiable, and are generally difficult to characterize and communicate. Hence, a mutual understanding between current and future climate researchers and decision makers must evolve for adaptation strategies and planning to progress. Iterative two-way dialogue can help to improve the decision making process by bridging current top-down and bottom-up approaches. One way to cultivate such interactions is by providing venues for these actors to interact and exchange on the uncertainties they face. We use a workshop-seminar series involving academic researchers, students, and decision makers as an opportunity to put this idea into practice and evaluate it. Seminars, case studies, and a round table allowed participants to reflect upon and experiment with uncertainties. An opinion survey conducted before and after the workshop-seminar series allowed us to qualitatively evaluate its influence on the participants. We find that the event stimulated new perspectives on research products and communication processes, and we suggest that similar events may ultimately contribute to the midterm goal of improving support for decision making in a changing climate. Therefore, we recommend integrating bridging events into university curriculum to foster interdisciplinary and iterative dialogue among researchers, decision makers, and students.

  9. Ultra-wideband horn antenna with abrupt radiator

    DOEpatents

    McEwan, T.E.

    1998-05-19

    An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna. 8 figs.

  10. Abruptness of Cascade Failures in Power Grids

    NASA Astrophysics Data System (ADS)

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into ``super-grids''.

  11. Abruptness of cascade failures in power grids.

    PubMed

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-15

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into "super-grids".

  12. 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

  13. Can animal habitat use patterns influence their vulnerability to extreme climate events? An estuarine sportfish case study.

    PubMed

    Boucek, Ross E; Heithaus, Michael R; Santos, Rolando; Stevens, Philip; Rehage, Jennifer S

    2017-10-01

    Global climate forecasts predict changes in the frequency and intensity of extreme climate events (ECEs). The capacity for specific habitat patches within a landscape to modulate stressors from extreme climate events, and animal distribution throughout habitat matrices during events, could influence the degree of population level effects following the passage of ECEs. Here, we ask (i) does the intensity of stressors of an ECE vary across a landscape? And (ii) Do habitat use patterns of a mobile species influence their vulnerability to ECEs? Specifically, we measured how extreme cold spells might interact with temporal variability in habitat use to affect populations of a tropical, estuarine-dependent large-bodied fish Common Snook, within Everglades National Park estuaries (FL US). We examined temperature variation across the estuary during cold disturbances with different degrees of severity, including an extreme cold spell. Second, we quantified Snook distribution patterns when the passage of ECEs is most likely to occur from 2012 to 2016 using passive acoustic tracking. Our results revealed spatial heterogeneity in the intensity of temperature declines during cold disturbances, with some habitats being consistently 3-5°C colder than others. Surprisingly, Snook distributions during periods of greatest risk to experience an extreme cold event varied among years. During the winters of 2013-2014 and 2014-2015 a greater proportion of Snook occurred in the colder habitats, while the winters of 2012-2013 and 2015-2016 featured more Snook observed in the warmest habitats. This study shows that Snook habitat use patterns could influence vulnerability to extreme cold events, however, whether Snook habitat use increases or decreases their vulnerability to disturbance depends on the year, creating temporally dynamic vulnerability. Faunal global change research should address the spatially explicit nature of extreme climate events and animal habitat use patterns to identify

  14. The Big Chills

    NASA Astrophysics Data System (ADS)

    Bond, G. C.; Dwyer, G. S.; Bauch, H. A.

    2002-12-01

    At the end of the last glacial, the Earth's climate system abruptly shifted into the Younger Dryas, a 1500-year long cold snap known in the popular media as the Big Chill. Following an abrupt warming ending the Younger Dryas about 11,600 years ago, the climate system has remained in an interglacial state, thought to have been relatively stable and devoid, with possibly one or two exceptions, of abrupt climate change. A growing amount of evidence suggests that this benign view of interglacial climate is incorrect. High resolution records of North Atlantic ice rafted sediment, now regarded as evidence of extreme multiyear sea ice drift, reveal abrupt shifts on centennial and millennial time scales. These have been traced from the end of the Younger Dryas to the present, revealing evidence of significant climate variability through all of the last two millennia. Correlatives of these events have been found in drift ice records from the Arctic's Laptev Sea, in the isotopic composition of North Grip ice, and in dissolved K from the GISP2 ice core, attesting to their regional extent and imprint in proxies of very different origins. Measurements of Mg/Ca ratios in planktic foraminifera over the last two millennia in the eastern North Atlantic demonstrate that increases in drifting multiyear sea ice were accompanied by abrupt decreases in sea surface temperatures, especially during the Little Ice Age. Estimated rates of temperature change are on the order of two degrees centigrade, more than thirty percent of the regional glacial to interglacial change, within a few decades. When compared at the same resolution, these interglacial variations are as abrupt as the last glacial's Dansgaard-Oeschger cycles. The interglacial abrupt changes are especially striking because they occurred within the core of the warm North Atlantic Current. The changes may have been triggered by variations in solar irradiance, but if so their large magnitude and regional extent requires amplifying

  15. Predictability of Extreme Climate Events via a Complex Network Approach

    NASA Astrophysics Data System (ADS)

    Muhkin, D.; Kurths, J.

    2017-12-01

    We analyse climate dynamics from a complex network approach. This leads to an inverse problem: Is there a backbone-like structure underlying the climate system? For this we propose a method to reconstruct and analyze a complex network from data generated by a spatio-temporal dynamical system. This approach enables us to uncover relations to global circulation patterns in oceans and atmosphere. This concept is then applied to Monsoon data; in particular, we develop a general framework to predict extreme events by combining a non-linear synchronization technique with complex networks. Applying this method, we uncover a new mechanism of extreme floods in the eastern Central Andes which could be used for operational forecasts. Moreover, we analyze the Indian Summer Monsoon (ISM) and identify two regions of high importance. By estimating an underlying critical point, this leads to an improved prediction of the onset of the ISM; this scheme was successful in 2016 and 2017.

  16. A climate-based multivariate extreme emulator of met-ocean-hydrological events for coastal flooding

    NASA Astrophysics Data System (ADS)

    Camus, Paula; Rueda, Ana; Mendez, Fernando J.; Tomas, Antonio; Del Jesus, Manuel; Losada, Iñigo J.

    2015-04-01

    Atmosphere-ocean general circulation models (AOGCMs) are useful to analyze large-scale climate variability (long-term historical periods, future climate projections). However, applications such as coastal flood modeling require climate information at finer scale. Besides, flooding events depend on multiple climate conditions: waves, surge levels from the open-ocean and river discharge caused by precipitation. Therefore, a multivariate statistical downscaling approach is adopted to reproduce relationships between variables and due to its low computational cost. The proposed method can be considered as a hybrid approach which combines a probabilistic weather type downscaling model with a stochastic weather generator component. Predictand distributions are reproduced modeling the relationship with AOGCM predictors based on a physical division in weather types (Camus et al., 2012). The multivariate dependence structure of the predictand (extreme events) is introduced linking the independent marginal distributions of the variables by a probabilistic copula regression (Ben Ayala et al., 2014). This hybrid approach is applied for the downscaling of AOGCM data to daily precipitation and maximum significant wave height and storm-surge in different locations along the Spanish coast. Reanalysis data is used to assess the proposed method. A commonly predictor for the three variables involved is classified using a regression-guided clustering algorithm. The most appropriate statistical model (general extreme value distribution, pareto distribution) for daily conditions is fitted. Stochastic simulation of the present climate is performed obtaining the set of hydraulic boundary conditions needed for high resolution coastal flood modeling. References: Camus, P., Menéndez, M., Méndez, F.J., Izaguirre, C., Espejo, A., Cánovas, V., Pérez, J., Rueda, A., Losada, I.J., Medina, R. (2014b). A weather-type statistical downscaling framework for ocean wave climate. Journal of

  17. Characterization of the Temporal Clustering of Flood Events across the Central United States in terms of Climate States

    NASA Astrophysics Data System (ADS)

    Mallakpour, Iman; Villarini, Gabriele; Jones, Michael; Smith, James

    2016-04-01

    The central United States is a region of the country that has been plagued by frequent catastrophic flooding (e.g., flood events of 1993, 2008, 2013, and 2014), with large economic and social repercussions (e.g., fatalities, agricultural losses, flood losses, water quality issues). The goal of this study is to examine whether it is possible to describe the occurrence of flood events at the sub-seasonal scale in terms of variations in the climate system. Daily streamflow time series from 774 USGS stream gage stations over the central United States (defined here to include North Dakota, South Dakota, Nebraska, Kansas, Missouri, Iowa, Minnesota, Wisconsin, Illinois, West Virginia, Kentucky, Ohio, Indiana, and Michigan) with a record of at least 50 years and ending no earlier than 2011 are used for this study. We use a peak-over-threshold (POT) approach to identify flood peaks so that we have, on average two events per year. We model the occurrence/non-occurrence of a flood event over time using regression models based on Cox processes. Cox processes are widely used in biostatistics and can be viewed as a generalization of Poisson processes. Rather than assuming that flood events occur independently of the occurrence of previous events (as in Poisson processes), Cox processes allow us to account for the potential presence of temporal clustering, which manifests itself in an alternation of quiet and active periods. Here we model the occurrence/non-occurrence of flood events using two climate indices as climate time-varying covariates: the North Atlantic Oscillation (NAO) and the Pacific-North American pattern (PNA). The results of this study show that NAO and/or PNA can explain the temporal clustering in flood occurrences in over 90% of the stream gage stations we considered. Analyses of the sensitivity of the results to different average numbers of flood events per year (from one to five) are also performed and lead to the same conclusions. The findings of this work

  18. Evolution of extreme temperature events in short term climate projection for Iberian Peninsula.

    NASA Astrophysics Data System (ADS)

    Rodriguez, Alfredo; Tarquis, Ana M.; Sanchez, Enrique; Dosio, Alessandro; Ruiz-Ramos, Margarita

    2014-05-01

    Extreme events of maximum and minimum temperatures are a main hazard for agricultural production in Iberian Peninsula. For this purpose, in this study we analyze projections of their evolution that could be valid for the next decade, represented in this study by the 30-year period 2004-2034 (target period). For this purpose two kinds of data were used in this study: 1) observations from the station network of AEMET (Spanish National Meteorological Agency) for five Spanish locations, and 2) simulated data at a resolution of 50 ×50 km horizontal grid derived from the outputs of twelve Regional Climate Models (RCMs) taken from project ENSEMBLES (van der Linden and Mitchell, 2009), with a bias correction (Dosio and Paruolo, 2011; Dosio et al., 2012) regarding the observational dataset Spain02 (Herrera et al., 2012). To validate the simulated climate, the available period of observations was compared to a baseline period (1964-1994) of simulated climate for all locations. Then, to analyze the changes for the present/very next future, probability of extreme temperature events for 2004-2034 were compared to that of the baseline period. Although only minor changes are expected, small variations in variability may have a significant impact in crop performance. The objective of the work is to evaluate the utility of these short term projections for potential users, as for instance insurance companies. References Dosio A. and Paruolo P., 2011. Bias correction of the ENSEMBLES high-resolution climate change projections for use by impact models: Evaluation on the present climate. Journal of Geophysical Research, VOL. 116,D16106, doi:10.1029/2011JD015934 Dosio A., Paruolo P. and Rojas R., 2012. Bias correction of the ENSEMBLES high resolution climate change projections for use by impact models: Analysis of the climate change signal. Journal of Geophysical Research,Volume 117, D17, doi: 0.1029/2012JD017968 Herrera et. al. (2012) Development and Analysis of a 50 year high

  19. Framing Extreme Event Attribution from the Bottom up - an Enquiry into the Social Representations of key stakeholders, of the Press and of Climate Scientists.

    NASA Astrophysics Data System (ADS)

    Vanderlinden, J. P.; Fellmer, M.; Capellini, N.; Meinke, I.; Remvikos, Y.; Bray, D.; Pacteau, C.; Von Storch, H.

    2014-12-01

    Attribution of extreme weather events has recently generated a lot of interest simultaneously within the general public, the scientific community, and stakeholders affected by meteorological extremes. This interest calls for the need to explore the potential convergence of the current atttribution science with the desire and needs of stakeholders. Such an euiry contributes to the development of climate services aiming at quantifying the human responsibility for particular events. Through interviews with climate scientists, through the analysis of the press coverage of extreme meteorological events, and through stakeholder (private sector, covernment services and local and regional government) focus groups, we analyze how social representations of the concepts associated with extreme event attribution are theorized. From the corpuses generated in the course of this enquiry, we build up a grounded, bottom-up, theorization of extreme weather event attribution. This bottom-up theorization allows for a framing of the potential climate services in a way that is attuned to the needs and expectations of the stakeholders. From apparently simple formulations: "what is an extreme event?", "what makes it extreme?", "what is meant by attribution of extreme weather events?", "what do we want to attribute?", "what is a climate service?", we demonstrate the polysemy of these terms and propose ways to address the challenges associated with the juxtaposition of four highly loaded concepts: extreme - event - attribution - climate services.

  20. Abrupt Change of the Transboundary Runoff and Its Influence on Water Security of Lanstang-Mekong River

    NASA Astrophysics Data System (ADS)

    Sang, Y. F.; Xie, P.; Ziyi, W.; Jiangyan, Z.; Qianjin, D.; Xu, L.

    2017-12-01

    As a significant manifestation of hydrological variability, abrupt change will obviously impact on the water security. To analyze what does the variation bring under changing environment, abrupt change detection should be a basic task, as well as variation level evaluation and hydrological frequency analysis. However, there lacks an effective method to reach those purposes systematically. Here we derived correlation coefficient between the original series and the jump-component series which is related to the difference degree of mean value before and after the abrupt change. Based on it, we proposed the moving-correlation-coefficient-based detection method and evaluated the significance of abrupt change as different levels related to the value of correlation coefficient. Then, with the obtained results, we calculated hydrological frequency in different situation (before and after the abrupt change). The approach above was employed to investigate the transboundary runoff of Lanstang-Mekong River at some kinds of time scale. We obtained the abrupt changes from runoff series of year, flood season and dry season which are almost the same. All the abrupt changes were significant which could reach to the moderate level. Compared with the past situation (before the abrupt change), the hydrological frequency in the current situation (after the abrupt change) indicated the water security of the water supply and flood control in the lower reaches of Lanstang-Mekong River could be guaranteed better, which is owed to the construction and operation of the water conservancy projects on the upper Lanstang-Mekong River.

  1. Model-based assessment of the role of human-induced climate change in the 2005 Caribbean coral bleaching event.

    PubMed

    Donner, Simon D; Knutson, Thomas R; Oppenheimer, Michael

    2007-03-27

    Episodes of mass coral bleaching around the world in recent decades have been attributed to periods of anomalously warm ocean temperatures. In 2005, the sea surface temperature (SST) anomaly in the tropical North Atlantic that may have contributed to the strong hurricane season caused widespread coral bleaching in the Eastern Caribbean. Here, we use two global climate models to evaluate the contribution of natural climate variability and anthropogenic forcing to the thermal stress that caused the 2005 coral bleaching event. Historical temperature data and simulations for the 1870-2000 period show that the observed warming in the region is unlikely to be due to unforced climate variability alone. Simulation of background climate variability suggests that anthropogenic warming may have increased the probability of occurrence of significant thermal stress events for corals in this region by an order of magnitude. Under scenarios of future greenhouse gas emissions, mass coral bleaching in the Eastern Caribbean may become a biannual event in 20-30 years. However, if corals and their symbionts can adapt by 1-1.5 degrees C, such mass bleaching events may not begin to recur at potentially harmful intervals until the latter half of the century. The delay could enable more time to alter the path of greenhouse gas emissions, although long-term "committed warming" even after stabilization of atmospheric CO(2) levels may still represent an additional long-term threat to corals.

  2. Climate change, variability and extreme events : risk assessment and management strategies in a Peach cultivated area in Italy.

    NASA Astrophysics Data System (ADS)

    Alfieri, Silvia Maria; De Lorenzi, Francesca; Basile, Angelo; Bonfante, Antonello; Missere, Daniele; Menenti, Massimo

    2014-05-01

    Climate change in Mediterranean area is likely to reduce precipitation amounts and to increase temperature thus affecting the timing of development stages and the productivity of crops. Further, extreme weather events are expected to increase in the future leading to significant increase in agricultural risk. Some strategies for effectively managing risks and adapting to climate change involve adjustments to irrigation management and use of different varieties. We quantified the risk on Peach production in an irrigated area of "Emilia Romagna" region ( Italy) taking into account the impact on crop yield due to climate change and variability and to extreme weather events as well as the ability of the agricultural system to modulate this impact (adaptive capacity) through changes in water and crop management. We have focused on climatic events causing insufficient water supply to crops, while taking into account the effect of climate on the duration and timing of phenological stages. Further, extreme maximum and minimum temperature events causing significant reduction of crop yield have been considered using phase-specific critical temperatures. In our study risk was assessed as the product of the probability of a damaging event (hazard), such as drought or extreme temperatures, and the estimated impact of such an event (vulnerability). To estimate vulnerability we took into account the possible options to reduce risk, by combining estimates of the sensitivity of the system (negative impact on crop yield) and its adaptive capacity. The latter was evaluated as the relative improvement due to alternate management options: the use of alternate varieties or the changes in irrigation management. Vulnerability was quantified using cultivar-specific thermal and hydrologic requirements of a set of cultivars determined by experimental data and from scientific literature. Critical temperatures determining a certain reduction of crop yield have been estimated and used to assess

  3. Hydrocode simulation of the Chicxulub impact event and the production of climatically active gases

    NASA Astrophysics Data System (ADS)

    Pierazzo, Elisabetta; Kring, David A.; Melosh, H. Jay

    1998-12-01

    We constructed a numerical model of the Chicxulub impact event using the Chart-D Squared (CSQ) code coupled with the ANalytic Equation Of State (ANEOS) package. In the simulations we utilized a target stratigraphy based on borehole data and employed newly developed equations of state for the materials that are believed to play a crucial role in the impact-related extinction hypothesis: carbonates (calcite) and evaporites (anhydrite). Simulations explored the effects of different projectile sizes (10 to 30 km in diameter) and porosity (0 to 50%). The effect of impact speed is addressed by doing simulations of asteroid impacts (vi=20km/s) and comet impacts (vi=50km/s). The masses of climatically important species injected into the upper atmosphere by the impact increase with the energy of the impact event, ranging from 350 to 3500 Gt for CO2, from 40 to 560 Gt for S, and from 200 to 1400 Gt for water vapor. While our results are in good agreement with those of Ivanov et al. [1996], our estimated CO2 production is 1 to 2 orders of magnitude lower than the results of Takata and Ahrens [1994], indicating that the impact event enhanced the end-Cretaceous atmospheric CO2 inventory by, at most, 40%. Consequently, sulfur may have been the most important climatically active gas injected into the stratosphere. The amount of S released by the impact is several orders of magnitude higher than any known volcanic eruption and, with H2O, is high enough to produce a sudden and significant perturbation of Earth's climate.

  4. Climatic history of the northeastern United States during the past 3000 years

    USGS Publications Warehouse

    Marlon, Jennifer R.; Pederson, Neil; Nolan, Connor; Goring, Simon; Shuman, Bryan; Robertson, Ann; Booth, Robert K.; Bartlein, Patrick J.; Berke, Melissa A.; Clifford, Michael; Cook, Edward; Dieffenbacher-Krall, Ann; Dietze, Michael C.; Hessl, Amy; Hubeny, J. Bradford; Jackson, Stephen T.; Marsicek, Jeremiah; McLachlan, Jason S.; Mock, Cary J.; Moore, David J. P.; Nichols, Jonathan M.; Peteet, Dorothy M.; Schaefer, Kevin; Trouet, Valerie; Umbanhowar, Charles; Williams, John W.; Yu, Zicheng

    2017-01-01

    Many ecosystem processes that influence Earth system feedbacks, including vegetation growth, water and nutrient cycling, and disturbance regimes, are strongly influenced by multi-decadal to millennial-scale variations in climate that cannot be captured by instrumental climate observations. Paleoclimate information is therefore essential for understanding contemporary ecosystems and their potential trajectories under a variety of future climate conditions. With the exception of fossil pollen records, there are a limited number of northeastern US (NE US) paleoclimate archives that can provide constraints on its temperature and hydroclimate history. Moreover, the records that do exist have not been considered together. Tree-ring data indicate that the 20th century was one of the wettest of the past 500 years in the eastern US (Pederson et al., 2014), and lake-level records suggest it was one of the wettest in the Holocene (Newby et al., 2014); how such results compare with other available data remains unclear, however. Here we conduct a systematic review, assessment, and comparison of paleotemperature and paleohydrological proxies from the NE US for the last 3000 years. Regional temperature reconstructions are consistent with the long-term cooling trend (1000 BCE–1700 CE) evident in hemispheric-scale reconstructions, but hydroclimate reconstructions reveal new information, including an abrupt transition from wet to dry conditions around 550–750 CE. NE US paleo data suggest that conditions during the Medieval Climate Anomaly were warmer and drier than during the Little Ice Age, and drier than today. There is some evidence for an acceleration over the past century of a longer-term wetting trend in the NE US, and coupled with the abrupt shift from a cooling trend to a warming trend from increased greenhouse gases, may have wide-ranging implications for species distributions, ecosystem dynamics, and extreme weather events. More work is needed to gather paleoclimate

  5. The Social Cost of Stochastic and Irreversible Climate Change

    NASA Astrophysics Data System (ADS)

    Cai, Y.; Judd, K. L.; Lontzek, T.

    2013-12-01

    Many scientists are worried about climate change triggering abrupt and irreversible events leading to significant and long-lasting damages. For example, a rapid release of methane from permafrost may lead to amplified global warming, and global warming may increase the frequency and severity of heavy rainfall or typhoon, destroying large cities and killing numerous people. Some elements of the climate system which might exhibit such a triggering effect are called tipping elements. There is great uncertainty about the impact of anthropogenic carbon and tipping elements on future economic wellbeing. Any rational policy choice must consider the great uncertainty about the magnitude and timing of global warming's impact on economic productivity. While the likelihood of tipping points may be a function of contemporaneous temperature, their effects are long lasting and might be independent of future temperatures. It is assumed that some of these tipping points might occur even in this century, but also that their duration and post-tipping impact are uncertain. A faithful representation of the possibility of tipping points for the calculation of social cost of carbon would require a fully stochastic formulation of irreversibility, and accounting for the deep layer of uncertainties regarding the duration of the tipping process and also its economic impact. We use DSICE, a DSGE extension of the DICE2007 model of William Nordhaus, which incorporates beliefs about the uncertain economic impact of possible climate tipping events and uses empirically plausible parameterizations of Epstein-Zin preferences to represent attitudes towards risk. We find that the uncertainty associated with anthropogenic climate change imply carbon taxes much higher than implied by deterministic models. This analysis indicates that the absence of uncertainty in DICE2007 and similar IAM models may result in substantial understatement of the potential benefits of policies to reduce GHG emissions.

  6. Abrupt climatic changes as triggering mechanisms of massive volcanic collapses: examples from Mexico (Invited)

    NASA Astrophysics Data System (ADS)

    Capra, L.

    2010-12-01

    Climate changes have been considered to be a triggering mechanism for large magmatic eruptions. However they can also trigger volcanic collapses, phenomena that cause the destruction of the entire sector of a volcano, including its summit. During the past 30 ka, major volcanic collapses occurred just after main glacial peaks that ended with a rapid deglaciation. Glacial debuttressing, load discharge and fluid circulation coupled with the post-glacial increase of humidity and heavy rains can activate the failure of unstable edifices. Looking at the synchronicity of the maximum glaciations during the late Pleistocene and Holocene in the northern and southern hemispheres it is evident that several volcanic collapses are absent during a glacial climax, but start immediately after it during a period of rapid retreat. Several examples can be detected around the world and Mexico is not an exception. The 28 ka Nevado de Toluca volcanic collapse occurred during an intraglacial stage, under humid conditions as evidenced by paleoclimatic studies on lacustrine sediments of the area. The debris avalanche deposit associated to this event clearly shows evidence of a large amount of water into the mass previous to the failure that enhanced its mobility. It also contains peculiar, plastically deformed, m-sized fragment of lacustrine sediments eroded from glacial berms. The 17 ka BP collapse of the Colima Volcano corresponds to the initial stage of glacial retreat in Mexico after the Last Glacial Maximum (22-17.5ka). Also in this case the depositional sequence reflects high humidity conditions with voluminous debris flow containing a large amount logs left by pine trees. The occurrence of cohesive debris flows originating from the failure of a volcanic edifice can also reflect the climatic conditions, indicating important hydrothermal alteration and fluid circulation from ice-melting at an ice-capped volcano, as observed for example at the Pico de Orizaba volcano for the Tetelzingo

  7. Abruptness of Cascade Failures in Power Grids

    PubMed Central

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into “super-grids”. PMID:24424239

  8. The potential impacts of climate variability and change on health impacts of extreme weather events in the United States.

    PubMed Central

    Greenough, G; McGeehin, M; Bernard, S M; Trtanj, J; Riad, J; Engelberg, D

    2001-01-01

    Extreme weather events such as precipitation extremes and severe storms cause hundreds of deaths and injuries annually in the United States. Climate change may alter the frequency, timing, intensity, and duration of these events. Increases in heavy precipitation have occurred over the past century. Future climate scenarios show likely increases in the frequency of extreme precipitation events, including precipitation during hurricanes, raising the risk of floods. Frequencies of tornadoes and hurricanes cannot reliably be projected. Injury and death are the direct health impacts most often associated with natural disasters. Secondary effects, mediated by changes in ecologic systems and public health infrastructure, also occur. The health impacts of extreme weather events hinge on the vulnerabilities and recovery capacities of the natural environment and the local population. Relevant variables include building codes, warning systems, disaster policies, evacuation plans, and relief efforts. There are many federal, state, and local government agencies and nongovernmental organizations involved in planning for and responding to natural disasters in the United States. Future research on health impacts of extreme weather events should focus on improving climate models to project any trends in regional extreme events and as a result improve public health preparedness and mitigation. Epidemiologic studies of health effects beyond the direct impacts of disaster will provide a more accurate measure of the full health impacts and will assist in planning and resource allocation. PMID:11359686

  9. The potential impacts of climate variability and change on health impacts of extreme weather events in the United States.

    PubMed

    Greenough, G; McGeehin, M; Bernard, S M; Trtanj, J; Riad, J; Engelberg, D

    2001-05-01

    Extreme weather events such as precipitation extremes and severe storms cause hundreds of deaths and injuries annually in the United States. Climate change may alter the frequency, timing, intensity, and duration of these events. Increases in heavy precipitation have occurred over the past century. Future climate scenarios show likely increases in the frequency of extreme precipitation events, including precipitation during hurricanes, raising the risk of floods. Frequencies of tornadoes and hurricanes cannot reliably be projected. Injury and death are the direct health impacts most often associated with natural disasters. Secondary effects, mediated by changes in ecologic systems and public health infrastructure, also occur. The health impacts of extreme weather events hinge on the vulnerabilities and recovery capacities of the natural environment and the local population. Relevant variables include building codes, warning systems, disaster policies, evacuation plans, and relief efforts. There are many federal, state, and local government agencies and nongovernmental organizations involved in planning for and responding to natural disasters in the United States. Future research on health impacts of extreme weather events should focus on improving climate models to project any trends in regional extreme events and as a result improve public health preparedness and mitigation. Epidemiologic studies of health effects beyond the direct impacts of disaster will provide a more accurate measure of the full health impacts and will assist in planning and resource allocation.

  10. The impact of economic austerity and prosperity events on suicide in Greece: a 30-year interrupted time-series analysis

    PubMed Central

    Branas, Charles C; Kastanaki, Anastasia E; Michalodimitrakis, Manolis; Tzougas, John; Kranioti, Elena F; Theodorakis, Pavlos N; Carr, Brendan G; Wiebe, Douglas J

    2015-01-01

    Objectives To complete a 30-year interrupted time-series analysis of the impact of austerity-related and prosperity-related events on the occurrence of suicide across Greece. Setting Greece from 1 January 1983 to 31 December 2012. Participants A total of 11 505 suicides, 9079 by men and 2426 by women, occurring in Greece over the study period. Primary and secondary outcomes National data from the Hellenic Statistical Authority assembled as 360 monthly counts of: all suicides, male suicides, female suicides and all suicides plus potentially misclassified suicides. Results In 30 years, the highest months of suicide in Greece occurred in 2012. The passage of new austerity measures in June 2011 marked the beginning of significant, abrupt and sustained increases in total suicides (+35.7%, p<0.001) and male suicides (+18.5%, p<0.01). Sensitivity analyses that figured in undercounting of suicides also found a significant, abrupt and sustained increase in June 2011 (+20.5%, p<0.001). Suicides by men in Greece also underwent a significant, abrupt and sustained increase in October 2008 when the Greek recession began (+13.1%, p<0.01), and an abrupt but temporary increase in April 2012 following a public suicide committed in response to austerity conditions (+29.7%, p<0.05). Suicides by women in Greece also underwent an abrupt and sustained increase in May 2011 following austerity-related events (+35.8%, p<0.05). One prosperity-related event, the January 2002 launch of the Euro in Greece, marked an abrupt but temporary decrease in male suicides (−27.1%, p<0.05). Conclusions This is the first multidecade, national analysis of suicide in Greece using monthly data. Select austerity-related events in Greece corresponded to statistically significant increases for suicides overall, as well as for suicides among men and women. The consideration of future austerity measures should give greater weight to the unintended mental health consequences that may follow and the public

  11. Behavioural, ecological and evolutionary responses to extreme climatic events: challenges and directions.

    PubMed

    van de Pol, Martijn; Jenouvrier, Stéphanie; Cornelissen, Johannes H C; Visser, Marcel E

    2017-06-19

    More extreme climatic events (ECEs) are among the most prominent consequences of climate change. Despite a long-standing recognition of the importance of ECEs by paleo-ecologists and macro-evolutionary biologists, ECEs have only recently received a strong interest in the wider ecological and evolutionary community. However, as with many rapidly expanding fields, it lacks structure and cohesiveness, which strongly limits scientific progress. Furthermore, due to the descriptive and anecdotal nature of many ECE studies it is still unclear what the most relevant questions and long-term consequences are of ECEs. To improve synthesis, we first discuss ways to define ECEs that facilitate comparison among studies. We then argue that biologists should adhere to more rigorous attribution and mechanistic methods to assess ECE impacts. Subsequently, we discuss conceptual and methodological links with climatology and disturbance-, tipping point- and paleo-ecology. These research fields have close linkages with ECE research, but differ in the identity and/or the relative severity of environmental factors. By summarizing the contributions to this theme issue we draw parallels between behavioural, ecological and evolutionary ECE studies, and suggest that an overarching challenge is that most empirical and theoretical evidence points towards responses being highly idiosyncratic, and thus predictability being low. Finally, we suggest a roadmap based on the proposition that an increased focus on the mechanisms behind the biological response function will be crucial for increased understanding and predictability of the impacts of ECE.This article is part of the themed issue 'Behavioural, ecological and evolutionary responses to extreme climatic events'. © 2017 The Author(s).

  12. Climate, ENSO and 'Black Swans' over the Last Millennium

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

    2014-12-01

    Tropical rainfall patterns influence the lives of billions of people both north and south of the Equator. Evidence of major ENSO events such as droughts is often recorded in the oxygen isotopic ratios and aerosol concentrations in tropical ice cores. Here we examine unusual events recorded in three ice cores, two (Quelccaya and Coropuna) in the Southern Hemisphere on the Peruvian Altiplano and the third (Dasuopu) located 22,000 km away on the southern edge of the Tibetan Plateau at the top of the Himalayas. These records suggest that the unique lower and middle tropospheric air flow over chloride (Cl-) and fluoride (F-) enriched areas upwind of the sites during ENSO events leads to enhanced deposition of these species on these glaciers. Linkages are demonstrated between ice-core chemistry and drought indicators, changes in lake levels, and ENSO and monsoon indices. Two unusual events, in the late 18th and mid-14th Centuries, are marked by abnormally high concentrations of F- and Cl- in at least two of the ice core records. All three records document a drought from 1789 to 1800 CE in which increases in these anionic concentrations reflect the abundance of continental atmospheric dust derived from arid regions upwind of the core sites. The earlier event, apparent only in the Quelccaya and Dasuopu ice cores, begins abruptly in 1343 and tapers off by 1375. The interaction between high frequency El Niños and low frequency shifts in the inter-tropical convergence zone may have resulted in these unusually severe and extended droughts. These "Black Swan" events correspond to historically documented, devastating population disruptions that were in part climate related. The 1789 to 1800 CE event was concurrent with the Doji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive climate disruptions are documented in Central and South America. The mid-14th Century drought is concomitant with major monsoon

  13. Maternal sleep duration and complaints of vital exhaustion during pregnancy is associated with placental abruption.

    PubMed

    Qiu, Chunfang; Sanchez, Sixto E; Gelaye, Bizu; Enquobahrie, Daniel A; Ananth, Cande V; Williams, Michelle A

    2015-02-01

    Sleep disorders are associated with cardiovascular complications and preterm delivery (PTD). Insufficient sleep results in metabolic alterations and increased inflammation, both known to contribute to placental abruption (abruption), a determinant of PTD. We examined associations of abruption with sleep duration and complaints of vital exhaustion. The study included 164 abruption cases and 160 controls in a multicenter study in Peru. Data on habitual sleep duration and vital exhaustion during the first 6 months of pregnancy were elicited during interviews conducted following delivery. Women were categorized according to short, normal and long sleep duration (≤6, 7-8 and ≥9 h); and frequency of feeling exhausted. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. Short and long sleep durations were associated with increased odds of abruption. The ORs of abruption in relation to short (≤6 h) and long (≥9 h) sleep duration were 2.0 (95% CI 1.1-3.7) and 2.1 (95% CI 1.1-4.1), compared with normal sleep duration (7-8 h). Complaints of vital exhaustion were also associated with abruption (OR = 2.37; 95% CI 1.46-3.85), and were independent of sleep duration. We extend the existing literature and support the thesis that maternal sleep habits and disorders should be assessed among pregnant women.

  14. Identification of unusual events in multi-channel bridge monitoring data

    NASA Astrophysics Data System (ADS)

    Omenzetter, Piotr; Brownjohn, James Mark William; Moyo, Pilate

    2004-03-01

    Continuously operating instrumented structural health monitoring (SHM) systems are becoming a practical alternative to replace visual inspection for assessment of condition and soundness of civil infrastructure such as bridges. However, converting large amounts of data from an SHM system into usable information is a great challenge to which special signal processing techniques must be applied. This study is devoted to identification of abrupt, anomalous and potentially onerous events in the time histories of static, hourly sampled strains recorded by a multi-sensor SHM system installed in a major bridge structure and operating continuously for a long time. Such events may result, among other causes, from sudden settlement of foundation, ground movement, excessive traffic load or failure of post-tensioning cables. A method of outlier detection in multivariate data has been applied to the problem of finding and localising sudden events in the strain data. For sharp discrimination of abrupt strain changes from slowly varying ones wavelet transform has been used. The proposed method has been successfully tested using known events recorded during construction of the bridge, and later effectively used for detection of anomalous post-construction events.

  15. Satellite-based characterization of climatic conditions before large-scale general flowering events in Peninsular Malaysia

    PubMed Central

    Azmy, Muna Maryam; Hashim, Mazlan; Numata, Shinya; Hosaka, Tetsuro; Noor, Nur Supardi Md.; Fletcher, Christine

    2016-01-01

    General flowering (GF) is a unique phenomenon wherein, at irregular intervals, taxonomically diverse trees in Southeast Asian dipterocarp forests synchronize their reproduction at the community level. Triggers of GF, including drought and low minimum temperatures a few months previously has been limitedly observed across large regional scales due to lack of meteorological stations. Here, we aim to identify the climatic conditions that trigger large-scale GF in Peninsular Malaysia using satellite sensors, Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS), to evaluate the climatic conditions of focal forests. We observed antecedent drought, low temperature and high photosynthetic radiation conditions before large-scale GF events, suggesting that large-scale GF events could be triggered by these factors. In contrast, we found higher-magnitude GF in forests where lower precipitation preceded large-scale GF events. GF magnitude was also negatively influenced by land surface temperature (LST) for a large-scale GF event. Therefore, we suggest that spatial extent of drought may be related to that of GF forests, and that the spatial pattern of LST may be related to that of GF occurrence. With significant new findings and other results that were consistent with previous research we clarified complicated environmental correlates with the GF phenomenon. PMID:27561887

  16. Satellite-based characterization of climatic conditions before large-scale general flowering events in Peninsular Malaysia.

    PubMed

    Azmy, Muna Maryam; Hashim, Mazlan; Numata, Shinya; Hosaka, Tetsuro; Noor, Nur Supardi Md; Fletcher, Christine

    2016-08-26

    General flowering (GF) is a unique phenomenon wherein, at irregular intervals, taxonomically diverse trees in Southeast Asian dipterocarp forests synchronize their reproduction at the community level. Triggers of GF, including drought and low minimum temperatures a few months previously has been limitedly observed across large regional scales due to lack of meteorological stations. Here, we aim to identify the climatic conditions that trigger large-scale GF in Peninsular Malaysia using satellite sensors, Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS), to evaluate the climatic conditions of focal forests. We observed antecedent drought, low temperature and high photosynthetic radiation conditions before large-scale GF events, suggesting that large-scale GF events could be triggered by these factors. In contrast, we found higher-magnitude GF in forests where lower precipitation preceded large-scale GF events. GF magnitude was also negatively influenced by land surface temperature (LST) for a large-scale GF event. Therefore, we suggest that spatial extent of drought may be related to that of GF forests, and that the spatial pattern of LST may be related to that of GF occurrence. With significant new findings and other results that were consistent with previous research we clarified complicated environmental correlates with the GF phenomenon.

  17. Using Critical Thresholds to Customize Climate Projections of Extreme Events to User Needs and Support Decisions

    NASA Astrophysics Data System (ADS)

    Garfin, G. M.; Petersen, A.; Shafer, M.; MacClune, K.; Hayhoe, K.; Riley, R.; Nasser, E.; Kos, L.; Allan, C.; Stults, M.; LeRoy, S. R.

    2016-12-01

    Many communities in the United States are already vulnerable to extreme events; many of these vulnerabilities are likely to increase with climate change. In order to promote the development of effective community responses to climate change, we tested a participatory process for developing usable climate science, in which our project team worked with decision-makers to identify extreme event parameters and critical thresholds associated with policy development and adaptation actions. Our hypothesis is that conveying climate science and data through user-defined parameters and thresholds will help develop capacity to streamline the use of climate projections in developing strategies and actions, and motivate participation by a variety of preparedness planners. Our team collaborated with urban decision-makers, in departments that included resilience, planning, public works, public health, emergency management, and others, in four cities in the semi-arid south-central plains and intermountain areas of Colorado, New Mexico, Oklahoma, and Texas. Through an iterative process, we homed in on both simple and hybrid indicators for which we could develop credible city-specific projections, to stimulate discussion about adaptation actions; throughout the process, we communicated information about confidence and uncertainty, in order to develop a blend of historic and projected climate data, as appropriate, depending on levels of uncertainty. Our collaborations have resulted in (a) the identification of more than 50 unique indicators and thresholds across the four communities, (b) the development of adaptation action strategies in each community, and (c) the implementation of actions, ranging from a climate leadership training program for city staff members, to a rainwater capture project to improve responses to expected increases in both stormwater runoff and water capture for drought episodes.

  18. [Reversible catatonia after the abrupt discontinuation of clozapine: Case report].

    PubMed

    Jaafari, M; Bout, A; Rammouz, I; Aalouane, R

    2016-12-01

    In this paper, we report the case of a patient, aged 26, with schizophrenia who was admitted to psychiatric emergencies for catatonia, one week after abrupt discontinuation of clozapine. An improvement was seen after only two days of the reintroduction of clozapine alone. This catatonia is reversible and it responds magnificently to the reintroduction of clozapine. And we conclude that patients and their caregivers need to be educated about the effects of abrupt cessation of clozapine administration. Copyright © 2016 L’Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.

  19. Ecosystem thresholds in Lake Kälksjön, Sweden, in response to rapid climate cooling 8200 years ago

    NASA Astrophysics Data System (ADS)

    Randsalu Wendrup, Linda; Conley, Daniel J.; Hammarlund, Dan; Snowball, Ian; Carstensen, Jacob; Fritz, Sherilyn C.

    2010-05-01

    Commonly, ecosystems are thought to show a smooth response in relation to gradually changing conditions, shifting over long periods of time from one state to another, thus reflecting the continuum of change along environmental gradients for each set of conditions. The theoretical concept that ecosystems can experience regime shifts and shift abruptly from one state to another, producing changes in dominance of organisms and overall ecosystem behaviour has, however, existed for more than 30 years. The theory has been further developed and it has been demonstrated, in a number of different terrestrial, freshwater and marine systems, that ecosystems stressed by human or climate perturbations can undergo drastic changes, first reaching an ecological threshold and then switching abruptly to an alternative state. The study of regime shifts in lakes as a result of climate change is complicated because lake biota and processes depend not only on regional climate changes but also on changes in the lake catchment and processes within the lake. Many factors in a lake will respond simultaneously and differently to the effects of climate change, resulting in complex synergy within the aquatic environment. Nevertheless we want to bring together concepts generated in contemporary ecological studies to study and test hypotheses regarding sudden mode shifts and ecological reorganisations in lakes using paleoecological methods, using diatom and numerical analyses as the main analytical tools. We are investigating how lakes respond to climate, during periods of both cooling and warming, identifying thresholds at which regime shifts occur and trying to develop numerical methods to test for regime shifts in paleoecological data. Here we present the preliminary results from a study of the ecosystem response to the "8.2 ka cold event" in Lake Kälksjön in west central Sweden. The lake is annually laminated (varved) and a series of nine radiocarbon measurements obtained at increments of

  20. The Challenges from Extreme Climate Events for Sustainable Development in Amazonia: the Acre State Experience

    NASA Astrophysics Data System (ADS)

    Araújo, M. D. N. M.

    2015-12-01

    In the past ten years Acre State, located in Brazil´s southwestern Amazonia, has confronted sequential and severe extreme events in the form of droughts and floods. In particular, the droughts and forest fires of 2005 and 2010, the 2012 flood within Acre, the 2014 flood of the Madeira River which isolated Acre for two months from southern Brazil, and the most severe flooding throughout the state in 2015 shook the resilience of Acrean society. The accumulated costs of these events since 2005 have exceeded 300 million dollars. For the last 17 years, successive state administrations have been implementing a socio-environmental model of development that strives to link sustainable economic production with environmental conservation, particularly for small communities. In this context, extreme climate events have interfered significantly with this model, increasing the risks of failure. The impacts caused by these events on development in the state have been exacerbated by: a) limitations in monitoring; b) extreme events outside of Acre territory (Madeira River Flood) affecting transportation systems; c) absence of reliable information for decision-making; and d) bureaucratic and judicial impediments. Our experience in these events have led to the following needs for scientific input to reduce the risk of disasters: 1) better monitoring and forecasting of deforestation, fires, and hydro-meteorological variables; 2) ways to increase risk perception in communities; 3) approaches to involve more effectively local and regional populations in the response to disasters; 4) more accurate measurements of the economic and social damages caused by these disasters. We must improve adaptation to and mitigation of current and future extreme climate events and implement a robust civil defense, adequate to these new challenges.

  1. Abrupt aridities in the Levant-Sahel linked with solar activities

    NASA Astrophysics Data System (ADS)

    Stein, M.; Kushnir, Y.

    2012-04-01

    Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan Sahel and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea and Sahelian lake levels and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the Sahel and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an antiphase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However, the records are punctuated by abrupt lake-level drops and extensive expansion of the desert belt at ~8.1, 5.7, 3.3 and 1.4 ka cal BP, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We link these cooling to solar activity variations that were identified in the North Atlantic IRD and cosmogenic isotopes records.

  2. Was millennial scale climate change during the Last Glacial triggered by explosive volcanism?

    PubMed Central

    Baldini, James U.L.; Brown, Richard J.; McElwaine, Jim N.

    2015-01-01

    The mechanisms responsible for millennial scale climate change within glacial time intervals are equivocal. Here we show that all eight known radiometrically-dated Tambora-sized or larger NH eruptions over the interval 30 to 80 ka BP are associated with abrupt Greenland cooling (>95% confidence). Additionally, previous research reported a strong statistical correlation between the timing of Southern Hemisphere volcanism and Dansgaard-Oeschger (DO) events (>99% confidence), but did not identify a causative mechanism. Volcanic aerosol-induced asymmetrical hemispheric cooling over the last few hundred years restructured atmospheric circulation in a similar fashion as that associated with Last Glacial millennial-scale shifts (albeit on a smaller scale). We hypothesise that following both recent and Last Glacial NH eruptions, volcanogenic sulphate injections into the stratosphere cooled the NH preferentially, inducing a hemispheric temperature asymmetry that shifted atmospheric circulation cells southward. This resulted in Greenland cooling, Antarctic warming, and a southward shifted ITCZ. However, during the Last Glacial, the initial eruption-induced climate response was prolonged by NH glacier and sea ice expansion, increased NH albedo, AMOC weakening, more NH cooling, and a consequent positive feedback. Conversely, preferential SH cooling following large SH eruptions shifted atmospheric circulation to the north, resulting in the characteristic features of DO events. PMID:26616338

  3. Was millennial scale climate change during the Last Glacial triggered by explosive volcanism?

    PubMed

    Baldini, James U L; Brown, Richard J; McElwaine, Jim N

    2015-11-30

    The mechanisms responsible for millennial scale climate change within glacial time intervals are equivocal. Here we show that all eight known radiometrically-dated Tambora-sized or larger NH eruptions over the interval 30 to 80 ka BP are associated with abrupt Greenland cooling (>95% confidence). Additionally, previous research reported a strong statistical correlation between the timing of Southern Hemisphere volcanism and Dansgaard-Oeschger (DO) events (>99% confidence), but did not identify a causative mechanism. Volcanic aerosol-induced asymmetrical hemispheric cooling over the last few hundred years restructured atmospheric circulation in a similar fashion as that associated with Last Glacial millennial-scale shifts (albeit on a smaller scale). We hypothesise that following both recent and Last Glacial NH eruptions, volcanogenic sulphate injections into the stratosphere cooled the NH preferentially, inducing a hemispheric temperature asymmetry that shifted atmospheric circulation cells southward. This resulted in Greenland cooling, Antarctic warming, and a southward shifted ITCZ. However, during the Last Glacial, the initial eruption-induced climate response was prolonged by NH glacier and sea ice expansion, increased NH albedo, AMOC weakening, more NH cooling, and a consequent positive feedback. Conversely, preferential SH cooling following large SH eruptions shifted atmospheric circulation to the north, resulting in the characteristic features of DO events.

  4. Cloud Formation and Water Transport on Mars after Major Outflow Events

    NASA Technical Reports Server (NTRS)

    Santiago, D. L.; Colaprete, A.; Kreslavsky, M.; Kahre, M. A.; Asphaug, E.

    2012-01-01

    The triggering of a robust water cycle on Mars might have been caused by the gigantic flooding events evidenced by outflow channels. We use the Ames Mars General Circulation Model (MGCM) to test this hypothesis, studying how these presumably abrupt eruptions of water might have affected the climate of Mars in the past. We model where the water ultimately went as part of a transient atmospheric water cycle, to answer questions including: (1) Can sudden introductions of large amounts of water on the Martian surface lead to a new equilibrated water cycle? (2) What are the roles of water vapor and water ice clouds to sudden changes in the water cycle on Mars? (3) How are radiative feedbacks involved with this? (4) What is the ultimate fate of the outflow water? (5) Can we tie certain geological features to outflow water redistributed by the atmosphere?

  5. Detrital Carbonate Events on the Labrador Shelf, a 13 to 7 kyr Template for Freshwater Forcing From the Laurentide Ice Sheet

    NASA Astrophysics Data System (ADS)

    Jennings, A. E.; Andrews, J. T.

    2008-12-01

    A complex sequence of abrupt glacial advances and retreats punctuate the late phases of Laurentide Ice Sheet deglaciation. These episodes have been reconstructed from interpretation and mapping of glacial deposits on land and in marine basins proximal to the former ice margins in Hudson Strait, Hudson Bay, and the SE Baffin Island shelf. As these events likely produced pulses of freshwater discharge into the North Altantic, which may be responsible for rapid climate change, their timing and magnitude need to be understood. The timing of these events is well constrained by radiocarbon ages, but the ocean reservoir age in ice proximal areas is subject to very large uncertainties, making it difficult to determine calibrated ages for the glacial events so that they can be compared to other climate records. We suggest that the sequence of high detrital carbonate peaks in Holocene and Late Glacial sediments in the Cartwright Saddle of the Labrador shelf provides a template of the abrupt glacial events of the NE margin of the Laurentide Ice Sheet, particularly events that issued from Hudson Strait and Hudson Bay, but possibly including events in Baffin Bay. Once the Labrador Shelf was deglaciated and the local ice had retreated inland, the Cartwright Saddle was a distal trap for sediments released from Hudson Strait and other ice sheet outlets farther north as their sediments and meltwater were carried southwards by surface currents. Core MD99-2236 contains a sediment record beginning c. 13.9 cal ka. We assume a marine reservoir age for the Cartwright Saddle of 450 yrs, which is reasonable given the ice distal and oceanic position of the site. Carbonate was measured on average at a 30 yr time resolution. Carbonate values are elevated between 11.7 and 7 cal kyr BP, with six spikes exceeding 30 percent. Each spike corresponds to a light isotope spike in foraminifers, suggesting that each major spike is associated with a pulse of glacial meltwater. Elevated IRD counts

  6. A modelling study of the event-based retention performance of green roof under the hot-humid tropical climate in Kuching.

    PubMed

    Chai, C T; Putuhena, F J; Selaman, O S

    2017-12-01

    The influences of climate 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 tropical climate is limited. This paper highlights the retention performance of the green roof situated in Kuching under hot-humid tropical climatic 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.

  7. End-of-century projections of North American atmospheric river events in CMIP5 climate models

    NASA Astrophysics Data System (ADS)

    Warner, M.; Mass, C.; Salathe, E. P., Jr.

    2013-12-01

    Most extreme precipitation events that occur along the North American west coast are associated with narrow plumes of above-average water vapor concentration that stretch from the tropics or subtropics to the West Coast. These events generally occur during the wet season (October-March) and are referred to as atmospheric rivers (AR). ARs can cause major river management problems, damage from flooding or landslides, and loss of life. It is expected that anthropogenic global warming could lead to changes in the general circulation of the atmosphere, such as Hadley Cell expansion and jet stream and storm track shifts. Since AR events are associated with cyclonic activity that originates near and propagates along the jet stream, the jet stream configuration influences the frequency and location of AR landfall along the North American west coast. Therefore, it is probable that any changes in the general circulation of the atmosphere will result in changes in the frequency, orientation, and location of AR landfalls. Generally, along the West Coast, CMIP5 models predict increases in integrated water vapor and precipitation, and little change in low-level wind associated with AR events. In this study, CMIP5 RCP 8.5 climate models and high resolution regional climate models are used to analyze predicted changes in frequency and location of AR events impacting the West Coast from the contemporary period (1970-1999) to the end of this century (2070-2099).

  8. Comparison of the timings between abrupt climate changes in Greenland, Antarctica, China and Japan based on robust correlation using Lake Suigetsu as a template.

    NASA Astrophysics Data System (ADS)

    Nakagawa, T.

    2014-12-01

    High-resolution pollen-derived climate records from Lake Suigetsu varved sediment core were compared with climate archives from other regions and revealed a particular spatio-temporal structure of the monsoon climate change during so-called D-O events. Leads and lags of the climate change between different regions hold the key to understand the climate system. However, robust assessment of the relative timing of the climate change is often very challenging because correlation of the climatic archives from different regions often has inevitable uncertainties. Greenland and Cariaco basin, for example, provide two of the most frequently sited palaeoclimatic proxy data representative of the high- and low-latitudinal Atlantic regions. However, robust correlation of the records from those regions is difficult because of the uncertainties in layer countings, lack of the radiocarbon age control from ice cores, marine reservoir age of the Cariaco sediments, and the absence of the tephra layers shared by both cites. Similarly, Speleothem and ice core records are not robustly correlated to each other, either for the dead carbon fraction in the speleothems and lack of reliable correlation markers. The generally accepted hypothesis of synchronous climate change between China and the Greenland is, therefore, essentially hypothetical. Lake Suigetsu provides solution to this problem. The lake Suigetsu chronology is supposed to be coherent to the speleothems' U-Th age scale. Suigetsu's semi-continuous radiocarbon dataset, which constitutes major component of the IntCal13 radiocarbon calibration model, also provides opportunity to correlate lake Suigetsu and the Greenland and Antarctic ice cores using cosmogenic isotopes as the correlation key. Results of the correlation and timing comparison, which cast new lights to the mechanism of the monsoon change, will be presented.

  9. Placental abruption possibly due to parvovirus B19 infection.

    PubMed

    Kawabe, Ayaka; Takai, Yasushi; Tamaru, Jun-Ichi; Samejima, Kouki; Seki, Hiroyuki

    2016-01-01

    There is concern about the development of anemia-associated fetal hydrops associated with maternal parvovirus B19 infection. Parvovirus B19 infection occurs via the globoside (P antigen) receptor, the main glycolipid of erythroid cells, which induces apoptosis. Similar findings have been reported for the P antigen of globoside-containing placental trophoblast cells. A 32-year-old woman was infected with human parvovirus B19 at week 32 of pregnancy, and had severe anemia at week 34. At week 37, an emergency cesarean section was performed because of sudden abdominal pain and fetal bradycardia; placental abruption was found. A live male infant was delivered with no sign of fetal hydrops or fetal infection. Placental tissue was positive for parvovirus B19 according to polymerase chain reaction. Immunohistochemical analysis using caspase-related M30 CytoDEATH monoclonal antibody revealed M30 staining of the placental villous trophoblasts. Placental trophoblasts and erythroid precursor cells have been reported to express globoside (P antigen), which is necessary for parvovirus B19 infectivity, and to show apoptotic activity as a result of infection. Placentas from three other pregnancies with documented abruption showed no M30 staining. The present case strongly suggests an association between placental abruption and apoptosis resulting from parvovirus B19 infection.

  10. Polar UVI observations of dayside auroral transient events

    NASA Astrophysics Data System (ADS)

    Vorobjev, V. G.; Yagodkina, O. I.; Sibeck, D. G.; Liou, K.; Meng, C.-I.

    2001-12-01

    We analyze Polar Ultraviolet Imager (UVI) observations of auroral transient events (ATEs) in the dayside Northern Hemisphere. During 5 winter months in 1996 and 1997, we found 31 prenoon ATEs but only 13 afternoon events. Prenoon and afternoon event characteristics differ. Prenoon ATEs generally appear as bright spots of auroral luminosity in the area from 0800 to 1000 magnetic local time (MLT) and 74.5° and 76.5° corrected geomagnetic latitude (CGL). Bright aurorae then quickly expand westward and poleward, accompanied by high-latitude magnetic impulsive events (MIE) and traveling convection vortices (TCV). Afternoon ATEs usually appear as a sudden intensification of aurorae in the area from 1400 to 1600 MLT and 75.5° to 78.5° CGL. Within 15-20 min the bright band of luminosity extends eastward to reach 2000-2100 MLT at 70°-72° CGL. Although midlatitude and low-latitude ground magnetograms in the evening sector record increases in the horizontal component of the magnetic field, no corresponding features occur at stations in the morning sector. Afternoon ATEs correspond to abrupt changes in the interplanetary magnetic field (IMF) orientation, but not to significant variations of the solar wind dynamic pressure, indicating that the auroral transient events occur as part of the magnetospheric response to abrupt changes in the foreshock geometry.

  11. Climate Informed Low Flow Frequency Analysis Using Nonstationary Modeling

    NASA Astrophysics Data System (ADS)

    Liu, D.; Guo, S.; Lian, Y.

    2014-12-01

    Stationarity is often assumed for frequency analysis of low flows in water resources management and planning. However, many studies have shown that flow characteristics, particularly the frequency spectrum of extreme hydrologic events,were modified by climate change and human activities and the conventional frequency analysis without considering the non-stationary characteristics may lead to costly design. The analysis presented in this paper was based on the more than 100 years of daily flow data from the Yichang gaging station 44 kilometers downstream of the Three Gorges Dam. The Mann-Kendall trend test under the scaling hypothesis showed that the annual low flows had significant monotonic trend, whereas an abrupt change point was identified in 1936 by the Pettitt test. The climate informed low flow frequency analysis and the divided and combined method are employed to account for the impacts from related climate variables and the nonstationarities in annual low flows. Without prior knowledge of the probability density function for the gaging station, six distribution functions including the Generalized Extreme Values (GEV), Pearson Type III, Gumbel, Gamma, Lognormal, and Weibull distributions have been tested to find the best fit, in which the local likelihood method is used to estimate the parameters. Analyses show that GEV had the best fit for the observed low flows. This study has also shown that the climate informed low flow frequency analysis is able to exploit the link between climate indices and low flows, which would account for the dynamic feature for reservoir management and provide more accurate and reliable designs for infrastructure and water supply.

  12. Annual proxy data from Lago Grande di Monticchio (southern Italy) contributing to chronological constraints and abrupt climatic oscillations between 76 and 112 ka

    NASA Astrophysics Data System (ADS)

    Martin-Puertas, C.; Brauer, A.; Wulf, S.; Ott, F.; Lauterbach, S.; Dulski, P.

    2014-06-01

    We present annual sedimentological proxies and sub-annual element scanner data from the Lago Grande di Monticchio (MON) sediment record for the sequence 76-112 ka, which, combined with the decadal to centennial resolved pollen assemblage, allow a comprehensive reconstruction of six major abrupt cold and relatively humid spells (MON 1-6) in the central Mediterranean during early phase of the last glaciation. These climatic oscillations are defined by intervals of thicker varves and high Ti-counts and coincide with episodes of forest depletion interpreted as cold and wet oscillations. Based on the independent and slightly revised MON-2014 varve chronology (76-112 ka), a detailed comparison with the Greenland ice-core δ18O record (NGRIP) and northern Alps speleothem δ18O data (NALPS) is presented. Based on visual inspection of major changes in the proxy data, MON 2-6 are suggested to correlate with GS 25-20. MON 1 (Woillard event), the first and shortest cooling spell in the Mediterranean after a long phase of stable interglacial conditions, has no counterpart in the Greenland ice core, but coincides with the lowest isotope values at the end of the gradual decrease in δ18O in NGRIP during the second half of the GI 25. MON 3 is the least pronounced cold spell and shows gradual transitions, whereas its NGRIP counterpart GS 24 is characterized by sharp changes in the isotope records. MON 2 and MON 4 are the longest most pronounced oscillations in the MON sediments in good agreement with their counterparts in the ice and spelethem records. The length of MON 4 (correlating with GS 22) support the duration of this stadial proposed by the NALPS timescales and suggests ca. 500 yr longer duration than calculated by GICC05 and AICC2012, which would confirm a~possible underestimation in the ice-core. Absolute dating of the cold spells occurring from 112 to 100 ka (MON 1-3) in the MON-2014 chronology is in good agreement with the GICC05 and NALPS timescales but the younger

  13. An Assessment of Direct and Indirect Economic Losses of Climatic Extreme Events

    NASA Astrophysics Data System (ADS)

    Otto, C.; Willner, S. N.; Wenz, L.; Levermann, A.

    2015-12-01

    Risk of extreme weather events like storms, heat extremes, and floods has already risen due to anthropogenic climate change and is likely to increase further under future global warming. Additionally, the structure of the global economy has changed importantly in the last decades. In the process of globalization, local economies have become more and more interwoven forming a complex network. Together with a trend towards lean production, this has resulted in a strong dependency of local manufacturers on global supply and value added chains, which may render the economic network more vulnerable to climatic extremes; outages of local manufacturers trigger indirect losses, which spread along supply chains and can even outstrip direct losses. Accordingly, in a comprehensive climate risk assessment these inter-linkages should be considered. Here, we present acclimate, an agent based dynamic damage propagation model. Its agents are production and consumption sites, which are interlinked by economic flows accounting for the complexity as well as the heterogeneity of the global supply network. Assessing the economic response on the timescale of the adverse event, the model permits to study temporal and spatial evolution of indirect production losses during the disaster and in the subsequent recovery phase of the economy. In this study, we focus on the dynamic economic resilience defined here as the ratio of direct to total losses. This implies that the resilience of the system under consideration is low if the high indirect losses are high. We find and assess a nonlinear dependence of the resilience on the disaster size. Further, we analyze the influence of the network structure upon resilience and discuss the potential of warehousing as an adaptation option.

  14. Evidence for Millennial-Scale Climate Variability in the Surface Waters Above ODP Site 980, NE Atlantic Ocean During the Last Glacial Interval (MIS 4-2)

    NASA Astrophysics Data System (ADS)

    Michaud, J. R.; Cullen, J. L.; McManus, J. F.; Oppo, D. W.

    2004-05-01

    Successful efforts to recover quality high sedimentation rate deep-sea sediment sections from the North Atlantic over the last decade have produced a number of studies demonstrating that climate instability at sub-orbital and even millennial time-scales is a pervasive component of Late Pleistocene North Atlantic climate. This is particularly true during Marine Isotope Stages (MIS) 4-2, i.e., the last glacial interval. One such high sedimentation rate section was recovered at ODP Site 980, Northeast Atlantic Ocean where sedimentation rates during MIS 4-2 exceed 15cm/kyr. Recently, we have begun to generate more detailed records from MIS 4-2 at Site 980 by reducing our sampling interval from 20 to around 2.5 cm, improving the resolution of our records an order of magnitude, from 1200-1300 to 100-200 years. 300 samples were used to generate high resolution records of changes in the input of ice-rafted detritus (IRD), along with limited data documenting changes in the relative abundance of the N. pachyderma, left coiling, which can be evaluated within the context of our previously generated lower resolution planktic and benthic oxygen isotope records used to generate our age model for this interval. Our previously published low resolution IRD record enabled us to identify Heinrich events 1-6 within the sediment interval deposited during the last glacial. Each event is characterized by IRD concentrations ranging from 500 to over 2500 lithic grains >150 microns per gram sediment. Superimposing our new high resolution IRD record reveals that Heinrich events 3,2,1 occurring at approximately 32, 23, and 17 kya, respectively, are each composed of a series of separate abrupt rapid increases in IRD concentrations approaching 1,000 grains per gram. An additional comparable event occurring at approximately 20 kya has also been identified. In the early part of the last glacial H6, H5, and H4 occurring at approximately 66, 47, and 38 kya, respectively, are recorded as much more

  15. Climate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica: An interdecadal (1993-2013) analysis

    NASA Astrophysics Data System (ADS)

    Kim, Hyewon; Doney, Scott C.; Iannuzzi, Richard A.; Meredith, Michael P.; Martinson, Douglas G.; Ducklow, Hugh W.

    2016-09-01

    We analyzed 20 years (1993-2013) of observations of dissolved inorganic macronutrients (nitrate, N; phosphate, P; and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large-scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low-frequency dynamics). The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December-March, which are correlated to Chl EOF1. Si EOF2 captures a drawdown event during November-December, which is correlated to Chl EOF2. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. N and P drawdown events during December-March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM-driven winter sea ice and spring wind dynamics. Si drawdown during November-December is influenced by early sea ice retreat, where ice breakup may induce abrupt water column stratification and a subsequent diatom bloom or release of diatom cells from within the sea ice. Our findings underscore that seasonal nutrient dynamics in the coastal WAP are coupled to large-scale climate forcing and related physics, understanding of which may enable improved projections of biogeochemical responses to climate change.

  16. Exploring the Human Ecology of the Younger Dryas Extraterrestrial Impact Event

    NASA Astrophysics Data System (ADS)

    Kennett, D. J.; Erlandson, J. M.; Braje, T. J.; Culleton, B. J.

    2007-05-01

    Several lines of evidence now exist for a major extraterrestrial impact event in North America at 12.9 ka (the YDB). This impact partially destabilized the Laurentide and Cordilleran ice sheets, triggered abrupt Younger Dryas cooling and extensive wildfires, and contributed to megafaunal extinction. This event also occurred soon after the well established colonization of the Americas by anatomically modern humans. Confirmation of this event would represent the first near-time extraterrestrial impact with significant effects on human populations. These likely included widespread, abrupt human mortality, population displacement, migration into less effected or newly established habitats, loss of cultural traditions, and resource diversification in the face of the massive megafaunal extinction and population reductions in surviving animal populations. Ultimately, these transformations established the context for the special character of plant and animal domestication and the emergence of agricultural economies in North America. We explore the Late Pleistocene archaeological record in North America within the context of documented major biotic changes associated with the YDB in North America and of the massive ecological affects hypothesized for this event.

  17. Abrupt global events in the Earth's history: a physics perspective

    NASA Astrophysics Data System (ADS)

    Ryskin, Gregory

    2010-12-01

    The timeline of the Earth's history reveals quasi-periodicity of the geological record over the last 542 Myr, on timescales close, in the order of magnitude, to 1 Myr. What is the origin of this quasi-periodicity? What is the nature of the global events that define the boundaries of the geological time scale? I propose that a single mechanism is responsible for all three types of such events: mass extinctions, geomagnetic polarity reversals, and sea-level fluctuations. The mechanism is fast, and involves a significant energy release. The mechanism is unlikely to have astronomical causes, both because of the energies involved and because it acts quasi-periodically. It must then be sought within the Earth itself. And it must be capable of reversing the Earth's magnetic field. The last requirement makes it incompatible with the consensus model of the origin of the geomagnetic field—the hydromagnetic dynamo operating in the Earth's fluid core. In the second part of the paper, I show that a vast amount of seemingly unconnected geophysical and geological data can be understood in a unified way if the source of the Earth's main magnetic field is a ~200 km thick lithosphere, repeatedly magnetized as a result of methane-driven oceanic eruptions, which produce ocean flow capable of dynamo action. The eruptions are driven by the interplay of buoyancy forces and exsolution of dissolved gas, which accumulates in the oceanic water masses prone to stagnation and anoxia. Polarity reversals, mass extinctions and sequence boundaries are consequences of these eruptions. Unlike the consensus model of geomagnetism, this scenario is consistent with the paleomagnetic data showing that 'directional changes during a reversal can be astonishingly fast, possibly occurring as a nearly instantaneous jump from one inclined dipolar state to another in the opposite hemisphere'.

  18. Abrupt hydroclimate disruption across the Australian arid zone 50 ka coincident with human colonization

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Fogel, M. L.; Magee, J. W.; Gagan, M. K.

    2016-12-01

    Although many studies focus on how climate change impacted ancient societies, in Australia a growing body of evidence indicates that activities of the earliest human colonizers in turn altered the Australian climate. We utilize the stable isotopes of carbon and oxygen preserved in near-continuous 100 ka time series of avian eggshell from five regions across the Australian arid zone to reconstruct ecosystem status (d13C) and effective moisture (d18O). Training sets of sub-modern samples provide the basis for the reconstructions. Together, d13C and d18O provide independent estimates of ecosystem status and climate over the past 100 ka from the same dated sample, reducing correlation uncertainties between proxies. Changes in eggshell d13C document a dramatic reduction of palatable summer-wet C4 grasses in all regions between 50 and 45 ka, that has persisted through to modern times. Continuous 100 ka records of effective moisture derived from eggshell d18O show moist conditions from 100 to 60 ka, with variable drying after 60 ka, but the strong shift toward greatest aridity is coincident with the onset of the last glacial maximum 30 ka ago, 15 ka after the observed ecosystem restructuring. Combining the d13C and d18O time-series shows that an abrupt and permanent restructuring of the moisture/ecosystem balance occurred between 50 and 45 ka. Additional studies show that most large monsoon-fed inland arid-zone lakes carried permanent water at least intermittently between 120 and 50 ka, but never experienced permanent deep-water status after 45 ka, despite a wide range of global climate states, including the early Holocene when most other monsoon systems were reinvigorated. The lack of exceptional climate shifts either locally or globally between 60 and 40 ka eliminates climate as the cause of the ecosystem restructuring and persistent lake desiccation. Collectively these data suggest the wave of human colonization across Australia in altered land surface characteristics

  19. A laboratory scale model of abrupt ice-shelf disintegration

    NASA Astrophysics Data System (ADS)

    Macayeal, D. R.; Boghosian, A.; Styron, D. D.; Burton, J. C.; Amundson, J. M.; Cathles, L. M.; Abbot, D. S.

    2010-12-01

    An important mode of Earth’s disappearing cryosphere is the abrupt disintegration of ice shelves along the Peninsula of Antarctica. This disintegration process may be triggered by climate change, however the work needed to produce the spectacular, explosive results witnessed with the Larsen B and Wilkins ice-shelf events of the last decade comes from the large potential energy release associated with iceberg capsize and fragmentation. To gain further insight into the underlying exchanges of energy involved in massed iceberg movements, we have constructed a laboratory-scale model designed to explore the physical and hydrodynamic interactions between icebergs in a confined channel of water. The experimental apparatus consists of a 2-meter water tank that is 30 cm wide. Within the tank, we introduce fresh water and approximately 20-100 rectangular plastic ‘icebergs’ having the appropriate density contrast with water to mimic ice. The blocks are initially deployed in a tight pack, with all blocks arranged in a manner to represent the initial state of an integrated ice shelf or ice tongue. The system is allowed to evolve through time under the driving forces associated with iceberg hydrodynamics. Digitized videography is used to quantify how the system of plastic icebergs evolves between states of quiescence to states of mobilization. Initial experiments show that, after a single ‘agitator’ iceberg begins to capsize, an ‘avalanche’ of capsizing icebergs ensues which drives horizontal expansion of the massed icebergs across the water surface, and which stimulates other icebergs to capsize. A surprise initially evident in the experiments is the fact that the kinetic energy of the expanding mass of icebergs is only a small fraction of the net potential energy released by the rearrangement of mass via capsize. Approximately 85 - 90 % of the energy released by the system goes into water motion modes, including a pervasive, easily observed seich mode of the tank

  20. Violent events, ward climate and ideas for violence prevention among nurses in psychiatric wards: a focus group study.

    PubMed

    Lantta, Tella; Anttila, Minna; Kontio, Raija; Adams, Clive E; Välimäki, Maritta

    2016-01-01

    Patient violence against nurses in their work environments is a widespread global concern, particularly in the field of mental health care. A high prevalence of violent events impacts the well-being of nurses and may also impair overall ward climate. However, it has been proposed that nurses' use limited techniques to prevent patient violence, and, therefore, more comprehensive methods for dealing with patient violence are needed. There is still restricted understanding of the ward climate during the occurrence of a violent event as well as how these incidents could be more effectively prevented. This study aimed to explore nurses' experiences of violent events in psychiatric wards, give insight into ward climates and examine suggestions for violence prevention. This study employed a descriptive, exploratory design including focus groups (n = 5) and open-ended questions. The participants were registered and enrolled nurses (n = 22) working on three closed psychiatric in-patient wards in one Finnish hospital district. Focus groups were tape-recorded, transcribed and analyzed with inductive content analysis. Nurses' experiences of violent events included a variety of warning signs and high-risk situations which helped them to predict forthcoming violence. Patient-instigated violent events were described as complicated situations involving both nurses and patients. When the wards were overloaded with work or emotions, or if nurses had become cynical from dealing with such events, well-being of nurses was impaired and nursing care was complicated. Suggestions for violence prevention were identified, and included, for example, more skilled interaction between nurses and patients and an increase in contact between nurses and patients on the ward. This study revealed the complexity of violent events on psychiatric wards as well as the implications of these events on clinical practice development and training, administration and policy. A routine process is needed

  1. Abrupt Climate Transition of Icy Worlds from Snowball to Moist or Runaway Greenhouse

    NASA Astrophysics Data System (ADS)

    Yang, J.; Ding, F.; Ramirez, R. M.; Peltier, W. R.; Hu, Y.; Liu, Y.

    2017-12-01

    Ongoing and future space missions aim to identify potentially habitable planets in our Solar System and beyond. Planetary habitability is determined not only by a planet's current stellar insolation and atmospheric properties, but also by the evolutionary history of its climate. It has been suggested that icy planets and moons become habitable after their initial ice shield melts as their host stars brighten. Here we show from global climate model simulations that a habitable state is not achieved in the climatic evolution of those icy planets and moons that possess an inactive carbonate-silicate cycle and low concentrations of greenhouse gases. Examples for such planetary bodies are the icy moons Europa and Enceladus, and certain icy exoplanets orbiting G and F stars. We find that the stellar fluxes that are required to overcome a planet's initial snowball state are so large that they lead to significant water loss and preclude a habitable planet. Specifically, they exceed the moist greenhouse limit, at which water vapour accumulates at high altitudes where it can readily escape, or the runaway greenhouse limit, at which the strength of the greenhouse increases until the oceans boil away. We suggest that some icy planetary bodies may transition directly to a moist or runaway greenhouse without passing through a habitable Earth-like state.

  2. Abrupt climate transition of icy worlds from snowball to moist or runaway greenhouse

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Ding, Feng; Ramirez, Ramses M.; Peltier, W. R.; Hu, Yongyun; Liu, Yonggang

    2017-08-01

    Ongoing and future space missions aim to identify potentially habitable planets in our Solar System and beyond. Planetary habitability is determined not only by a planet's current stellar insolation and atmospheric properties, but also by the evolutionary history of its climate. It has been suggested that icy planets and moons become habitable after their initial ice shield melts as their host stars brighten. Here we show from global climate model simulations that a habitable state is not achieved in the climatic evolution of those icy planets and moons that possess an inactive carbonate-silicate cycle and low concentrations of greenhouse gases. Examples for such planetary bodies are the icy moons Europa and Enceladus, and certain icy exoplanets orbiting G and F stars. We find that the stellar fluxes that are required to overcome a planet's initial snowball state are so large that they lead to significant water loss and preclude a habitable planet. Specifically, they exceed the moist greenhouse limit, at which water vapour accumulates at high altitudes where it can readily escape, or the runaway greenhouse limit, at which the strength of the greenhouse increases until the oceans boil away. We suggest that some icy planetary bodies may transition directly to a moist or runaway greenhouse without passing through a habitable Earth-like state.

  3. Towards Greenland Glaciation: Cumulative or Abrupt Transition?

    NASA Astrophysics Data System (ADS)

    Tan, N.; Ramstein, G.; Contoux, C.; Ladant, J. B.; Dumas, C.; Donnadieu, Y.

    2014-12-01

    The insolation evolution [Laskar 2004] from 4 to 2.5 Ma depicts a series of three summer solstice insolation minima between 2.7 and 2.6 Ma, but there are other more important summer solstice minima notably around 3.82 and 3.05 Ma. On such a time span of more than 1 Ma, data shows that there are variations in the evolution of atmospheric CO2 concentration with a local maximum around 3 Ma [Seki et al.2010; Bartoli et al. 2011], before a decrease between 3 and 2.6 Ma. The latter, suggesting an abrupt ice sheet inception around 2.7 Ma, has been shown to be a major culprit for the full Greenland Glaciation [Lunt et al. 2008]. However, a recent study [Contoux et al. 2014, in review] suggests that a lowering of CO2 is not sufficient to initiate a glaciation on Greenland and must be combined to low summer insolation, with surviving ice during insolation maximum, suggesting a cumulative process in the first place, which could further lead to full glaciation at 2.7 Ma. Through a new tri-dimensional interpolation method implemented within the asynchronous coupling between an atmosphere ocean general circulation model (IPSL-CM5A) and an ice sheet model (GRISLI), we investigate the transient evolution of Greenland ice sheet during the Pliocene to diagnose whether the ice sheet inception is an abrupt event or rather a cumulative process, involving waxing and waning of the ice sheet during several orbital cycles. ReferencesBartoli, G., Hönisch, B., & Zeebe, R. E. (2011). Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4). Contoux C, Dumas C, Ramstein G, Jost A, Dolan A. M. (2014) Modelling Greenland Ice sheet inception and sustainability during the late Pliocene. (in review for Earth and Planetary Science Letters.).Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428

  4. Identification of Extreme Events Under Climate Change Conditions Over Europe and The Northwest-atlantic Region: Spatial Patterns and Time Series Characteristics

    NASA Astrophysics Data System (ADS)

    Leckebusch, G.; Ulbrich, U.; Speth, P.

    In the context of climate change and the resulting possible impacts on socio-economic conditions for human activities it seems that due to a changed occurrence of extreme events more severe consequences have to be expected than from changes in the mean climate. These extreme events like floods, excessive heats and droughts or windstorms possess impacts on human social and economic life in different categories such as forestry, agriculture, energy use, tourism and the reinsurance business. Reinsurances are affected by nearly 70% of all insured damages over Europe in the case of wind- storms. Especially the December 1999 French windstorms caused damages about 10 billion. A new EU-founded project (MICE = Modelling the Impact of Climate Ex- tremes) will focus on these impacts caused by changed occurrences of extreme events over Europe. Based upon the output of general circulation models as well as regional climate models, investigations are carried out with regard to time series characteristics as well as the spatial patterns of extremes under climate changed conditions. After the definition of specific thresholds for climate extremes, in this talk we will focus on the results of the analysis for the different data sets (HadCM3 and CGCMII GCM's and RCM's, re-analyses, observations) with regard to windstorm events. At first the results of model outputs are validated against re-analyses and observations. Especially a comparison of the stormtrack (2.5 to 8 day bandpass filtered 500 hPa geopotential height), cyclone track, cyclone frequency and intensity is presented. Highly relevant to damages is the extreme wind near the ground level, so the 10 m wind speed will be investigated additionally. of special interest to possible impacts is the changed spatial occurrence of windspeed maxima under 2xCO2-induced climate change.

  5. a Marine Record of Holocene Climate Events in Tropical South America

    NASA Astrophysics Data System (ADS)

    Haug, G. H.; Günther, D.; Hughen, K. A.; Peterson, L. C.; Röhl, U.

    2002-12-01

    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 tropical 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 climate 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 tropical climate events similar in timing to high latitude changes in the North Atlantic often invoked as pivotal to societal developments in Europe.

  6. The nummulithoclast event within the Lower Eocene in the Southern Tethyan margin: Mechanisms involved, analogy with the filament event and climate implication (Kairouan, Central Tunisia)

    NASA Astrophysics Data System (ADS)

    Mardassi, Besma

    2017-10-01

    Early Eocene deposits in Tunisia are marked by clear variations in terms of facies and thickness. Each facies corresponds to an appropriate depositional environment. Shallow water deposits pass gradually offshore into deeper carbonates along a homoclinal ramp. In Central Tunisia, detailed investigation of carbonate facies under transmitted light shows a particular richness of the middle part of Early Eocene deposits in nummulithoclasts. These facies are often frequent within corrugated banks. They are overlaying Globigerina rich well-bedded limestones and overlain by nummulites and Discocyclina rich massively-bedded carbonates. Nummulithoclasts occurrence is recorded on field by an abrupt vertical change from autochthonous thinly-bedded limestones to massively-bedded fossiliferous carbonates. Change concerns structures, textures and limestones' composition. Nummulithoclasts are associated either to planktonic micro-organisms or to benthic fauna and phosphates grains. The middle and the upper parts of the Early Eocene deposits, particularly, fossilize hummocky cross-stratifications and megaripples. Their presence advocates the role of energetic currents in sweeping nummulites from lower circatidal to upper bathyal environments. The absence of a slope break helped the settling of reworked nummulites within deeper environments. The abrupt change, nummulithoclast associations and current structures arouse reflection and make them not reliable to characterize depositional environments. However, their preferential occurrence within the middle part of Early Eocene deposits and the tight linkage with storm activity lead them to be considered as event. The large scale hummocks recorded on field suggests that nummulite fragmentation was triggered by tropical cyclones rather than humble storms. The frequent occurrence of cyclones which correspond to low pressure atmospheric systems seems in relation with a global warming enhancing the sea surface temperature.

  7. Changes in CO2 during Ocean Anoxic Event 1d indicate similarities to other carbon cycle perturbations

    NASA Astrophysics Data System (ADS)

    Richey, Jon D.; Upchurch, Garland R.; Montañez, Isabel P.; Lomax, Barry H.; Suarez, Marina B.; Crout, Neil M. J.; Joeckel, R. M.; Ludvigson, Greg A.; Smith, Jon J.

    2018-06-01

    Past greenhouse intervals of the Mesozoic were repeatedly punctuated by Ocean Anoxic Events (OAEs), major perturbations to the global carbon cycle and abrupt climate changes that may serve as relevant analogs for Earth's greenhouse gas-forced climate future. The key to better understanding these transient climate disruptions and possible CO2-forced tipping-points resides in high-resolution, precise, and accurate estimates of atmospheric CO2 for individual OAEs. Here we present a high-temporal resolution, multi-proxy pCO2 reconstruction for the onset of mid-Cretaceous (Albian-Cenomanian Boundary) OAE1d. Coupling of pCO2 estimates with carbon isotopic compositions (δ13C) of charcoal, vitrain, and cuticle from the Rose Creek Pit (RCP), Nebraska, reveals complex phasing, including a lag between the well-documented negative δ13C excursion defining the onset of OAE1d and the CO2 increase. This lag indicates that increased CO2 or other C-based greenhouse gases may not have been the primary cause of the negative excursion. Our study reveals a pCO2 increase within the interval of the negative δ13C excursion, reaching a maximum of up to ∼840 ppm (95% confidence interval -307 ppm/+167 ppm) toward its end. The reconstructed magnitude of CO2 increase (∼357 ppm) is similar to that of Late Cretaceous OAE2 but of smaller magnitude than that of other major carbon cycle perturbations of the Mesozoic assessed via stomatal methods (e.g., the Toarcian OAE [TOAE], Triassic-Jurassic boundary event, Cretaceous-Paleogene Boundary event). Furthermore, our results indicate a possible shared causal or developmental mechanism with OAE1a and the TOAE.

  8. Detection of abrupt changes in dynamic systems

    NASA Technical Reports Server (NTRS)

    Willsky, A. S.

    1984-01-01

    Some of the basic ideas associated with the detection of abrupt changes in dynamic systems are presented. Multiple filter-based techniques and residual-based method and the multiple model and generalized likelihood ratio methods are considered. Issues such as the effect of unknown onset time on algorithm complexity and structure and robustness to model uncertainty are discussed.

  9. 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

  10. IMPACTS OF CLIMATE-INDUCED CHANGES IN EXTREME EVENTS ON OZONE AND PARTICULATE MATTER AIR QUALITY

    EPA Science Inventory

    Historical data records of air pollution meteorology from multiple datasets will be compiled and analyzed to identify possible trends in extreme events. Changes in climate and air quality between 2010 and 2050 will be simulated with a suite of models. The consequential effe...

  11. The European ruminants during the "Microbunodon Event" (MP28, Latest Oligocene): impact of climate changes and faunal event on the ruminant evolution.

    PubMed

    Mennecart, Bastien

    2015-01-01

    The Earth already experienced numerous episodes of global warming and cooling. One of the latest impressive events of temperature rising was the Late Oligocene Warming that occurred around 25 Mya. An increase of the marine temperature of 2 to 4°C has been observed in a short time interval. In Europe, this major climatic event can be correlated to the continental faunal turnover "Microbunodon Event". This event is marked by a huge faunal turnover (40% of the ungulate fauna during the first 500k years) and environmental changes. Drier conditions associated to the appearance of the seasonality lead to new environmental conditions dominated by wooded savannahs. This is correlated to a major arrival of Asiatic immigrants. Moreover, from a homogenous fauna during the main part of the Oligocene, local climatic variations between the European Western coast and the more central Europe could have provided faunal regionalism during the latest Oligocene and earliest Miocene. Considering the ruminants, this event is the major ever known for this group in Europe. A total renewal at the family level occurred. Thanks to a precise stratigraphic succession, major evolutionary elements are highlighted. Typical Oligocene species, mainly Tragulina, were adapted to wooded environments and were leaves/fruits eaters. They disappeared at the end of MP27 or the early MP28. This corresponds to the appearance of the Asiatic immigrants. The Tragulina (Lophiomerycidae, Bachitheriidae) and stem Pecora gave way to more derived stem and maybe crown Pecora (e.g. "Amphitragulus", Babameryx, Dremotherium). These newcomers were adapted to more open environments and mixed feeding. The disappearance of the Tragulina is probably linked to environmental and vegetation changes, and competition. They give way to more derived ruminants having a more efficient metabolism in drier conditions and a better assimilation of less energetic food.

  12. 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.

  13. Molybdenum accumulation in Cariaco basin sediment over the past 24 k.y.: A record of water-column anoxia and climate

    USGS Publications Warehouse

    Dean, W.E.; Piper, D.Z.; Peterson, L.C.

    1999-01-01

    Molybdenum (Mo) concentrations in a sediment core from the Cariaco basin on the Venezuelan continental shelf can be partitioned between a marine fraction and a terrigenous fraction. The accumulation rate of the marine fraction of Mo increased abruptly 15 000 calendar years ago (15 ka), from 4 ??g ?? cm-2 ?? yr-1, and then decreased abruptly at 9 ka. The accumulation rate remained high throughout this 6 k.y. period, but exhibited maxima at 15-14 and 12.5 ka, corresponding in time to meltwater pulse IA into the Gulf of Mexico and the onset of the Younger Dryas cold event, respectively. The marine fraction of Mo is interpreted in terms of redox conditions of bottom water, as dictated by both the flux of settling organic matter and bottom-water residence time. Correspondence between geochemical extremes in this core with changes in sea level and global climate demonstrates the high degree to which this ocean-margin basin has responded to the paleoceanographic regime throughout the past 24 k.y.

  14. Evaluation of cool season precipitation event characteristics over the Northeast US in a suite of downscaled climate model hindcasts

    NASA Astrophysics Data System (ADS)

    Loikith, Paul C.; Waliser, Duane E.; Kim, Jinwon; Ferraro, Robert

    2017-08-01

    Cool season precipitation event characteristics are evaluated across a suite of downscaled climate models over the northeastern US. Downscaled hindcast simulations are produced by dynamically downscaling the Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA2) using the National Aeronautics and Space Administration (NASA)-Unified Weather Research and Forecasting (WRF) regional climate model (RCM) and the Goddard Earth Observing System Model, Version 5 (GEOS-5) global climate model. NU-WRF RCM simulations are produced at 24, 12, and 4-km horizontal resolutions using a range of spectral nudging schemes while the MERRA2 global downscaled run is provided at 12.5-km. All model runs are evaluated using four metrics designed to capture key features of precipitation events: event frequency, event intensity, even total, and event duration. Overall, the downscaling approaches result in a reasonable representation of many of the key features of precipitation events over the region, however considerable biases exist in the magnitude of each metric. Based on this evaluation there is no clear indication that higher resolution simulations result in more realistic results in general, however many small-scale features such as orographic enhancement of precipitation are only captured at higher resolutions suggesting some added value over coarser resolution. While the differences between simulations produced using nudging and no nudging are small, there is some improvement in model fidelity when nudging is introduced, especially at a cutoff wavelength of 600 km compared to 2000 km. Based on the results of this evaluation, dynamical regional downscaling using NU-WRF results in a more realistic representation of precipitation event climatology than the global downscaling of MERRA2 using GEOS-5.

  15. Abrupt Changes in Bottom Water Benthic Foraminiferal Assemblages during Heinrich Events 1-4

    NASA Astrophysics Data System (ADS)

    Lazar, K.; Rashid, H.; Vermooten, M.; Mingqiu, D.

    2017-12-01

    The extent to which Heinrich iceberg-rafting events modify bottom water ecology resulting in changes in benthic foraminifera is poorly known. Here, we report centennial to millennial scale changes in the benthic foraminiferal assemblages from sediment core Pa96018-06 (47.75oN; 46.21oW). It was collected on the northern slope of the Flemish Pass of southern Labrador Sea and is bathed by Labrador Sea Water, one of the major components of the meridional overturning circulation of the Atlantic. Benthic foraminiferal assemblages were determined and numerous species identified. X-ray fluorescence (XRF) on the bulk sediments and iceberg-rafted detritus (IRD) in addition to oxygen isotopes on polar planktonic foraminiferal Neogloboquadrina pachyderma (sinistral) were used to identify the detrital carbonate-rich Heinrich iceberg-rafting events 1 to 4. Changes in the total numbers of Elphidium excavatum subsp. clavatum typically mirror changes in the total benthic population, yet the percentage of E. e. clavatum as part of the total sample increases through time. E. e. clavatum comprises approximately 60% of the benthic assemblage in H4, and steadily increases to 80% of the assemblage in H1 and H2. Total benthic foraminiferal numbers increase at the onset of each Heinrich event, with the two largest peaks in the entire record characterizing H2 and H3. In addition, the fine-scale feature in H1 suggests an initial decrease in the % E. e. clavatum (and total benthics) which then increased to 85% of the assemblage during the latter part of H1. Our data suggest that harsh living conditions prevailed during the initial phases of Heinrich events when the availability of meltwater and the deposition of fine-grained carbonate sediments were dominant. However, it appears that the ecology was favorable for E. e. clavatum during the latter phase of Heinrich events when the deposition of fine-grained sediments dissipated and the supply of meltwater was limited. These latter stages

  16. Sensitivity of the Atmospheric Response to Warm Pool El Nino Events to Modeled SSTs and Future Climate Forcings

    NASA Technical Reports Server (NTRS)

    Hurwitz, Margaret M.; Garfinkel, Chaim I.; Newman, Paul A.; Oman, Luke D.

    2013-01-01

    Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific. Under present-day climate conditions, WPEN events generate poleward propagating wavetrains and enhance midlatitude planetary wave activity, weakening the stratospheric polar vortices. The late 21st century extratropical atmospheric response to WPEN events is investigated using the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM), version 2. GEOSCCM simulations are forced by projected late 21st century concentrations of greenhouse gases (GHGs) and ozone-depleting substances (ODSs) and by SSTs and sea ice concentrations from an existing ocean-atmosphere simulation. Despite known ocean-atmosphere model biases, the prescribed SST fields represent a best estimate of the structure of late 21st century WPEN events. The future Arctic vortex response is qualitatively similar to that observed in recent decades but is weaker in late winter. This response reflects the weaker SST forcing in the Nino 3.4 region and subsequently weaker Northern Hemisphere tropospheric teleconnections. The Antarctic stratosphere does not respond to WPEN events in a future climate, reflecting a change in tropospheric teleconnections: The meridional wavetrain weakens while a more zonal wavetrain originates near Australia. Sensitivity simulations show that a strong poleward wavetrain response to WPEN requires a strengthening and southeastward extension of the South Pacific Convergence Zone; this feature is not captured by the late 21st century modeled SSTs. Expected future increases in GHGs and decreases in ODSs do not affect the polar stratospheric responses to WPEN.

  17. Release of Mercury Mine Tailings from Mine Impacted Watersheds by Extreme Events Resulting from Climate Change

    NASA Astrophysics Data System (ADS)

    Rytuba, J. J.

    2015-12-01

    An increase in intensity and frequency of extreme events resulting from climate change is expected to result in extreme precipitation events on both regional and local scales. Extreme precipitation events have the potential to mobilize large volumes of mercury (Hg) mine tailings in watersheds where tailings reside in the floodplain downstream from historic Hg mines. The California Hg mineral belt produced one third of the worlds Hg from over 100 mines from the 1850's to 1972. In the absence of environmental regulations, tailings were disposed of into streams adjacent to the mines in order to have them transported from the mine site during storm events. Thus most of the tailings no longer reside at the mine site. Addition of tailings to the streams resulted in stream aggradation, increased over-bank flow, and deposition of tailings in the floodplain for up to 25 kms downstream from the mines. After cessation of mining, the decrease in tailings entering the streams resulted in degradation, incision of the streams into the floodplain, and inability of the streams to access the floodplain. Thus Hg tailings have remained stored in the floodplain since cessation of mining. Hg phases in these tailings consist of cinnabar, metacinnabar and montroydite based on EXAFS analysis. Size analysis indicates that Hg phases are fine grained, less than 1 um. The last regional scale extreme precipitation events to effect the entire area of the California Hg mineral belt were the ARkStorm events of 1861-1862 that occurred prior to large scale Hg mining. Extreme regional ARkStorm precipitation events as well as local summer storms, such as the July 2006 flood in the Clear Creek Hg mining district, are expected to increase in frequency and have the potential to remobilize the large volume of tailings stored in floodplain deposits. Although Hg mine remediation has decreased Hg release from mine sites in a period of benign climate, no remediation efforts have addressed the large source of

  18. The impact of economic austerity and prosperity events on suicide in Greece: a 30-year interrupted time-series analysis.

    PubMed

    Branas, Charles C; Kastanaki, Anastasia E; Michalodimitrakis, Manolis; Tzougas, John; Kranioti, Elena F; Theodorakis, Pavlos N; Carr, Brendan G; Wiebe, Douglas J

    2015-02-02

    To complete a 30-year interrupted time-series analysis of the impact of austerity-related and prosperity-related events on the occurrence of suicide across Greece. Greece from 1 January 1983 to 31 December 2012. A total of 11 505 suicides, 9079 by men and 2426 by women, occurring in Greece over the study period. National data from the Hellenic Statistical Authority assembled as 360 monthly counts of: all suicides, male suicides, female suicides and all suicides plus potentially misclassified suicides. In 30 years, the highest months of suicide in Greece occurred in 2012. The passage of new austerity measures in June 2011 marked the beginning of significant, abrupt and sustained increases in total suicides (+35.7%, p<0.001) and male suicides (+18.5%, p<0.01). Sensitivity analyses that figured in undercounting of suicides also found a significant, abrupt and sustained increase in June 2011 (+20.5%, p<0.001). Suicides by men in Greece also underwent a significant, abrupt and sustained increase in October 2008 when the Greek recession began (+13.1%, p<0.01), and an abrupt but temporary increase in April 2012 following a public suicide committed in response to austerity conditions (+29.7%, p<0.05). Suicides by women in Greece also underwent an abrupt and sustained increase in May 2011 following austerity-related events (+35.8%, p<0.05). One prosperity-related event, the January 2002 launch of the Euro in Greece, marked an abrupt but temporary decrease in male suicides (-27.1%, p<0.05). This is the first multidecade, national analysis of suicide in Greece using monthly data. Select austerity-related events in Greece corresponded to statistically significant increases for suicides overall, as well as for suicides among men and women. The consideration of future austerity measures should give greater weight to the unintended mental health consequences that may follow and the public messaging of these policies and related events. Published by the BMJ Publishing Group

  19. Acute diabetes insipidus mediated by vasopressinase after placental abruption.

    PubMed

    Wallia, Amisha; Bizhanova, Aigerim; Huang, Wenyu; Goldsmith, Susan L; Gossett, Dana R; Kopp, Peter

    2013-03-01

    Postpartum, diabetes insipidus (DI) can be part of Sheehan's syndrome or lymphocytic hypophysitis in combination with anterior pituitary hormone deficiencies. In contrast, acute onset of isolated DI in the postpartum period is unusual. This patient presented at 33 weeks gestation with placental abruption, prompting a cesarean delivery of twins. Immediately after delivery, she developed severe DI. The DI could be controlled with the vasopressinase-resistant 1-deamino-8-D-arginine vasopressin (DDAVP), but not with arginine vasopressin (AVP), and it resolved within a few weeks. The aim of this study was to demonstrate that the postpartum DI in this patient was caused by the release of placental vasopressinase into the maternal bloodstream. Cells were transiently transfected with the AVP receptor 2 (AVPR2) and treated with either AVP or DDAVP in the presence of the patient's serum collected postpartum or 10 weeks after delivery. The response to the different treatments was evaluated by measuring the activity of a cAMP-responsive firefly luciferase reporter construct. The in vitro studies demonstrate that the patient's postpartum serum disrupts activation of the AVPR2 by AVP, but not by the vasopressinase-resistant DDAVP. Placental abruption can rarely be associated with acute postpartum DI caused by release of placental vasopressinase into the bloodstream. This clinical entity must be considered in patients with placental abruption and when evaluating patients presenting with DI after delivery.

  20. 3D modelling of the climatic impact of outflow channel formation events on early Mars

    NASA Astrophysics Data System (ADS)

    Turbet, Martin; Forget, Francois; Head, James W.; Wordsworth, Robin

    2017-05-01

    Mars was characterized by cataclysmic groundwater-sourced surface flooding that formed large outflow channels and that may have altered the climate for extensive periods during the Hesperian era. In particular, it has been speculated that such events could have induced significant rainfall and caused the formation of late-stage valley networks. We present the results of 3-D Global Climate Model simulations reproducing the short and long term climatic impact of a wide range of outflow channel formation events under cold ancient Mars conditions. We find that the most intense of these events (volumes of water up to 107 km3 and released at temperatures up to 320 K) cannot trigger long-term greenhouse global warming, regardless of how favorable are the external conditions (e.g. obliquity and seasons). Furthermore, the intensity of the response of the events is significantly affected by the atmospheric pressure, a parameter not well constrained for the Hesperian era. Thin atmospheres (P < 80 mbar) can be heated efficiently because of their low volumetric heat capacity, triggering the formation of a convective plume that is very efficient in transporting water vapor and ice at the global scale. Thick atmospheres (P > 0.5 bar) have difficulty in producing precipitation far from the water flow area, and are more efficient in generating snowmelt. In any case, outflow channel formation events at any atmospheric pressure are unable to produce rainfall or significant snowmelt at latitudes below 40°N. As an example, for an outflow channel event (under a 0.2 bar atmospheric pressure and 45° obliquity) releasing 106 km3 of water heated at 300 K and at a discharge rate of 109 m3 s-1 , the flow of water reaches the lowest point of the northern lowlands (around ∼70°N, 30°W) after ∼3 days and forms a 200 m deep lake of 4.2 × 106 km2 after ∼20 days; the lake becomes entirely covered by an ice layer after ∼500 days. Over the short term, such an event leaves 6.5 × 103 km3

  1. Staying cool in a changing climate: Reaching vulnerable populations during heat events

    PubMed Central

    Sampson, Natalie R.; Gronlund, Carina J.; Buxton, Miatta A.; Catalano, Linda; White-Newsome, Jalonne L.; Conlon, Kathryn C.; O’Neill, Marie S.; McCormick, Sabrina; Parker, Edith A.

    2017-01-01

    The frequency and intensity of hot weather events are expected to increase globally, threatening human health, especially among the elderly, poor, and chronically ill. Current literature indicates that emergency preparedness plans, heat health warning systems, and related interventions may not be reaching or supporting behavior change among those most vulnerable in heat events. Using a qualitative multiple case study design, we comprehensively examined practices of these populations to stay cool during hot weather (“cooling behaviors”) in four U.S. cities with documented racial/ethnic and socio-economic disparities and diverse heat preparedness strategies: Phoenix, Arizona; Detroit, Michigan; New York City, New York; and Philadelphia, Pennsylvania. Based on semi-structured in-depth interviews we conducted with 173 community members and organizational leaders during 2009–2010, we assessed why vulnerable populations do or do not participate in health-promoting behaviors at home or in their community during heat events, inquiring about perceptions of heat-related threats and vulnerability and the role of social support. While vulnerable populations often recognize heat’s potential health threats, many overlook or disassociate from risk factors or rely on experiences living in or visiting warmer climates as a protective factor. Many adopt basic cooling behaviors, but unknowingly harmful behaviors such as improper use of fans and heating and cooling systems are also adopted. Decision-making related to commonly promoted behaviors such as air conditioner use and cooling center attendance is complex, and these resources are often inaccessible financially, physically, or culturally. Interviewees expressed how interpersonal, intergenerational relationships are generally but not always protective, where peer relationships are a valuable mechanism for facilitating cooling behaviors among the elderly during heat events. To prevent disparities in heat morbidity and

  2. Climate change increases the probability of heavy rains in Northern England/Southern Scotland like those of storm Desmond—a real-time event attribution revisited

    NASA Astrophysics Data System (ADS)

    Otto, Friederike E. L.; van der Wiel, Karin; van Oldenborgh, Geert Jan; Philip, Sjoukje; Kew, Sarah F.; Uhe, Peter; Cullen, Heidi

    2018-02-01

    On 4-6 December 2015, storm Desmond caused very heavy rainfall in Northern England and Southern Scotland which led to widespread flooding. A week after the event we provided an initial assessment of the influence of anthropogenic climate change on the likelihood of one-day precipitation events averaged over an area encompassing Northern England and Southern Scotland using data and methods available immediately after the event occurred. The analysis was based on three independent methods of extreme event attribution: historical observed trends, coupled climate model simulations and a large ensemble of regional model simulations. All three methods agreed that the effect of climate change was positive, making precipitation events like this about 40% more likely, with a provisional 2.5%-97.5% confidence interval of 5%-80%. Here we revisit the assessment using more station data, an additional monthly event definition, a second global climate model and regional model simulations of winter 2015/16. The overall result of the analysis is similar to the real-time analysis with a best estimate of a 59% increase in event frequency, but a larger confidence interval that does include no change. It is important to highlight that the observational data in the additional monthly analysis does not only represent the rainfall associated with storm Desmond but also that of storms Eve and Frank occurring towards the end of the month.

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

    Hill, Christopher

    This project investigated possible mechanisms by which melt-water pulses can induce abrupt change in the Atlantic Meridional Overturning Circulation (AMOC) magnitude. AMOC magnitude is an important ingredient in present day climate. Previous studies have hypothesized abrupt reduction in AMOC magnitude in response to influxes of glacial melt water into the North Atlantic. Notable fresh-water influxes are associated with the terminus of the last ice age. During this period large volumes of melt water accumulated behind retreating ice sheets and subsequently drained rapidly when the ice weakened sufficiently. Rapid draining of glacial lakes into the North Atlantic is a possible originmore » of a number of paleo-record abrupt climate shifts. These include the Younger-Dryas cooling event and the 8,200 year cooling event. The studies undertaken focused on whether the mechanistic sequence by which glacial melt-water impacts AMOC, which then impacts Northern Hemisphere global mean surface temperature, is dynamically plausible. The work has implications for better understanding past climate stability. The work also has relevance for today’s environment, in which high-latitude ice melting in Greenland appears to be driving fresh water outflows at an accelerating pace.« less

  4. Correspondence between North Pacific Ocean ventilation, Cordilleran Ice Sheet variations, and North Atlantic Heinrich Events

    NASA Astrophysics Data System (ADS)

    Walczak, M. H.; Mix, A.; Fallon, S.; Praetorius, S. K.; Cowan, E. A.; Du, J.; Hobern, T.; Padman, J.; Fifield, L. K.; Stoner, J. S.; Haley, B. A.

    2017-12-01

    Much remains unresolved concerning the origin and global implications of the episodes of rapid glacial failure in the North Atlantic known as Heinrich Events. Thought to occur during or at the termination of the coldest of the abrupt stadial climate events known as Dansgaard-Oschger cycles, various trigger mechanisms have been theorized, including external forcing in the form of oceanic or atmospheric warming, internal dynamics of the large Laurentide ice sheet, or the episodic failure of another (presumably European) ice sheet. Heinrich events may also be associated with a decrease in North Atlantic deep-water formation. New results from Gulf of Alaska IODP Expedition 341 reveal events of Cordilleran Ice Sheet retreat (based on ice-rafted detritus and sedimentation rates) synchronous with reorganization of ocean circulation (based on benthic-planktic 14C pairs) spanning the past 45,000 years on an independent high-resolution radiocarbon-based chronology. We document the relationship between these Pacific records and the North Atlantic Heinrich events, and find the data show an early Pacific expression of ice sheet instability in the form of pulses of Cordilleran glacial discharge. The benthic radiocarbon anomalies in the Northeast Pacific contemporaneous with Cordilleran discharge events indicate a close coupling of ice-ocean dynamics throughout Marine Isotope Stage 2. These data are hard to reconcile with triggering in the North Atlantic or internal to the Laurentide ice sheet, requiring us to re-think both the mechanisms that generate Heinrich events and their far-field impacts.

  5. Diatoms (Class Bacillariophyceae) and geochemistry from annually laminated mid-Holocene sediments, west coast Canada: insights into abrupt climate change in the past

    NASA Astrophysics Data System (ADS)

    Chang, A.; Pedersen, T. F.

    2009-04-01

    A 115-year record of annually laminated sediments from Effingham Inlet, a small anoxic fjord on the west coast of Vancouver Island, British Columbia (49˚N, 125˚W), was analyzed for diatoms (species and abundances) and geochemistry (C and N isotopes, organic C and trace elements Ag, Cd, Re and Mo) from a piston core. The sediments were radiocarbon dated at approx. 4200-4400 years before present (yr BP) and show diatom enriched varves in the lower 70 years, with a sudden transition to diatom impoverished varves above. In the lower section, varves are thick (2-5 mm) and consist of well-defined Thalassiosira-Skeletonema-Chaetoceros spring bloom successions. Diatom concentrations average at 787 ± 733 million valves/g of dry sediment, del 15N at 7.0 ± 0.5 per mil, and organic C at 5.2 ± 0.5 wt. %. In the upper section, the varves are thinner (1-2 mm), do not clearly show the seasonal diatom succession, and contain increased terrigenous detritus. Diatom concentrations average at 388 ± 202 million valves/g with an increased relative abundance of benthic and freshwater taxa, del 15N at 7.3 ± 0.6 per mil and organic C at 5.7 ± 0.5 wt. %. Values of del 13C for both sections are similar, averaging at -24.0 ± 0.5 per mil. The trace element concentrations are quite variable throughout the section. However, several thin (<1 cm) nonlaminated intervals show decreased diatom abundances with concomitant increases in trace element concentrations, suggesting short-lived changes in surface productivity, upwelling and nutrient delivery, and/or anoxic conditions. The abrupt transition from diatom-rich to diatom-poor varves could reflect a shift in dominance of the North Pacific High and Aleutian Low atmospheric pressure systems over the northeast Pacific Ocean, not unlike the well-documented 1976/1977 climate regime shift which showed a change in upwelling and nutrient delivery. A transition between warm and sunny climates to cooler and wetter regimes at around 4000 yr BP has

  6. Assessment of future extreme climate events over the Porto wine Region

    NASA Astrophysics Data System (ADS)

    Viceto, Carolina; Cardoso, Susana; Marta-Almeida, Martinho; Gorodetskaya, Irina; Rocha, Alfredo

    2017-04-01

    to be produced (Porto and Douro wine), while climate variability affects the annual productivity and quality of the grape harvest. Our study investigates changes in the extreme climate events in the future model runs, through a set of climate change indicators defined by the WRCP's Expert Team in Climate Change Detection and Indices, which uses variables such as daily maximum and minimum temperatures and precipitation amounts. Furthermore, we explore heat waves and their properties (duration, intensity and recovery factor). The analysis shows an increase of the mean temperature in the DDR higher than 2°C by the mid-21st century and 4.5°C by the end of the century, relatively to the reference period. Moreover, we found a major predisposition towards higher values of minimum and maximum daily temperatures and a decrease in the total precipitation during both future periods. These preliminary results indicate increased climatic stress on the DDR wine production and increased vulnerability of the wine varieties in this region.

  7. (When and where) Do extreme climate events trigger extreme ecosystem responses? - Development and initial results of a holistic analysis framework

    NASA Astrophysics Data System (ADS)

    Hauber, Eva K.; Donner, Reik V.

    2015-04-01

    In the context of ongoing climate change, extremes are likely to increase in magnitude and frequency. One of the most important consequences of these changes is that the associated ecological risks and impacts are potentially rising as well. In order to better anticipate and understand these impacts, it therefore becomes more and more crucial to understand the general connection between climate extremes and the response and functionality of ecosystems. Among other region of the world, Europe presents an excellent test case for studies concerning the interaction between climate and biosphere, since it lies in the transition region between cold polar and warm tropical air masses and thus covers a great variety of different climatic zones and associated terrestrial ecosystems. The large temperature differences across the continent make this region particularly interesting for investigating the effects of climate change on biosphere-climate interactions. However, previously used methods for defining an extreme event typically disregard the necessity of taking seasonality as well as seasonal variance appropriately into account. Furthermore, most studies have focused on the impacts of individual extreme events instead of considering a whole inventory of extremes with their respective spatio-temporal extents. In order to overcome the aforementioned research gaps, this work introduces a new approach to studying climate-biosphere interactions associated with extreme events, which comprises three consecutive steps: (1) Since Europe exhibits climatic conditions characterized by marked seasonality, a novel method is developed to define extreme events taking into account the seasonality in all quantiles of the probability distribution of the respective variable of interest. This is achieved by considering kernel density estimates individually for each observation date during the year, including the properly weighted information from adjacent dates. By this procedure, we obtain

  8. Climate Signals: An On-Line Digital Platform for Mapping Climate Change Impacts in Real Time

    NASA Astrophysics Data System (ADS)

    Cutting, H.

    2016-12-01

    Climate Signals is an on-line digital platform for cataloging and mapping the impacts of climate change. The CS platform specifies and details the chains of connections between greenhouse gas emissions and individual climate events. Currently in open-beta release, the platform is designed to to engage and serve the general public, news media, and policy-makers, particularly in real-time during extreme climate events. Climate Signals consists of a curated relational database of events and their links to climate change, a mapping engine, and a gallery of climate change monitors offering real-time data. For each event in the database, an infographic engine provides a custom attribution "tree" that illustrates the connections to climate change. In addition, links to key contextual resources are aggregated and curated for each event. All event records are fully annotated with detailed source citations and corresponding hyper links. The system of attribution used to link events to climate change in real-time is detailed here. This open-beta release is offered for public user testing and engagement. Launched in May 2016, the operation of this platform offers lessons for public engagement in climate change impacts.

  9. Can Regional Climate Models be used in the assessment of vulnerability and risk caused by extreme events?

    NASA Astrophysics Data System (ADS)

    Nunes, Ana

    2015-04-01

    Extreme meteorological events played an important role in catastrophic occurrences observed in the past over densely populated areas in Brazil. This motived the proposal of an integrated system for analysis and assessment of vulnerability and risk caused by extreme events in urban areas that are particularly affected by complex topography. That requires a multi-scale approach, which is centered on a regional modeling system, consisting of a regional (spectral) climate model coupled to a land-surface scheme. This regional modeling system employs a boundary forcing method based on scale-selective bias correction and assimilation of satellite-based precipitation estimates. Scale-selective bias correction is a method similar to the spectral nudging technique for dynamical downscaling that allows internal modes to develop in agreement with the large-scale features, while the precipitation assimilation procedure improves the modeled deep-convection and drives the land-surface scheme variables. Here, the scale-selective bias correction acts only on the rotational part of the wind field, letting the precipitation assimilation procedure to correct moisture convergence, in order to reconstruct South American current climate within the South American Hydroclimate Reconstruction Project. The hydroclimate reconstruction outputs might eventually produce improved initial conditions for high-resolution numerical integrations in metropolitan regions, generating more reliable short-term precipitation predictions, and providing accurate hidrometeorological variables to higher resolution geomorphological models. Better representation of deep-convection from intermediate scales is relevant when the resolution of the regional modeling system is refined by any method to meet the scale of geomorphological dynamic models of stability and mass movement, assisting in the assessment of risk areas and estimation of terrain stability over complex topography. The reconstruction of past extreme

  10. Population age and initial density in a patchy environment affect the occurrence of abrupt transitions in a birth-and-death model of Taylor's law

    USGS Publications Warehouse

    Jiang, Jiang; DeAngelis, Donald L.; Zhang, B.; Cohen, J.E.

    2014-01-01

    Taylor's power law describes an empirical relationship between the mean and variance of population densities in field data, in which the variance varies as a power, b, of the mean. Most studies report values of b varying between 1 and 2. However, Cohen (2014a) showed recently that smooth changes in environmental conditions in a model can lead to an abrupt, infinite change in b. To understand what factors can influence the occurrence of an abrupt change in b, we used both mathematical analysis and Monte Carlo samples from a model in which populations of the same species settled on patches, and each population followed independently a stochastic linear birth-and-death process. We investigated how the power relationship responds to a smooth change of population growth rate, under different sampling strategies, initial population density, and population age. We showed analytically that, if the initial populations differ only in density, and samples are taken from all patches after the same time period following a major invasion event, Taylor's law holds with exponent b=1, regardless of the population growth rate. If samples are taken at different times from patches that have the same initial population densities, we calculate an abrupt shift of b, as predicted by Cohen (2014a). The loss of linearity between log variance and log mean is a leading indicator of the abrupt shift. If both initial population densities and population ages vary among patches, estimates of b lie between 1 and 2, as in most empirical studies. But the value of b declines to ~1 as the system approaches a critical point. Our results can inform empirical studies that might be designed to demonstrate an abrupt shift in Taylor's law.

  11. Mountain Rivers and Climate Change: Analysis of hazardous events in torrents of small alpine watersheds

    NASA Astrophysics Data System (ADS)

    Lutzmann, Silke; Sass, Oliver

    2016-04-01

    Torrential processes like flooding, heavy bedload transport or debris flows in steep mountain channels emerge during intense, highly localized rainfall events. They pose a serious risk on the densely populated Alpine region. Hydrogeomorphic hazards are profoundly nonlinear, threshold mediated phenomena frequently causing costly damage to infrastructure and people. Thus, in the context of climate change, there is an ever rising interest in whether sediment cascades of small alpine catchments react to changing precipitation patterns and how the climate signal is propagated through the fluvial system. We intend to answer the following research questions: (i) What are critical meteorological characteristics triggering torrential events in the Eastern Alps of Austria? (ii) The effect of external triggers is strongly mediated by the internal disposition of catchments to respond. Which factors control the internal susceptibility? (iii) Do torrential processes show an increase in magnitude and frequency or a shift in seasonality in the recent past? (iv) Which future changes can be expected under different climate scenarios? Quantifications of bedload transport in small alpine catchments are rare and often associated with high uncertainties. Detailed knowledge though exists for the Schöttlbach catchment, a 71 km2 study area in Styria in the Eastern Alps. The torrent is monitored since a heavy precipitation event resulted in a disastrous flood in July 2011. Sediment mobilisation from slopes as well as within-channel storage and fluxes are regularly measured by photogrammetric methods and sediment impact sensors (SIS). The associated hydro-meteorological conditions are known from a dense station network. Changing states of connectivity can thus be related to precipitation and internal dynamics (sediment availability, cut-and-fill cycles). The site-specific insights are then conceptualized for application to a broader scale. Therefore, a Styria wide database of torrential

  12. Identifying Typhoon Tracks based on Event Synchronization derived Spatially Embedded Climate Networks

    NASA Astrophysics Data System (ADS)

    Ozturk, Ugur; Marwan, Norbert; Kurths, Jürgen

    2017-04-01

    Complex networks are commonly used for investigating spatiotemporal dynamics of complex systems, e.g. extreme rainfall. Especially directed networks are very effective tools in identifying climatic patterns on spatially embedded networks. They can capture the network flux, so as the principal dynamics of spreading significant phenomena. Network measures, such as network divergence, bare the source-receptor relation of the directed networks. However, it is still a challenge how to catch fast evolving atmospheric events, i.e. typhoons. In this study, we propose a new technique, namely Radial Ranks, to detect the general pattern of typhoons forward direction based on the strength parameter of the event synchronization over Japan. We suggest to subset a circular zone of high correlation around the selected grid based on the strength parameter. Radial sums of the strength parameter along vectors within this zone, radial ranks are measured for potential directions, which allows us to trace the network flux over long distances. We employed also the delay parameter of event synchronization to identify and separate the frontal storms' and typhoons' individual behaviors.

  13. Recommended Experimental Procedures for Evaluation of Abrupt Wing Stall Characteristics

    NASA Technical Reports Server (NTRS)

    Capone, F. J.; Hall, R. M.; Owens, D. B.; Lamar, J. E.; McMillin, S. N.

    2003-01-01

    This paper presents a review of the experimental program under the Abrupt Wing Stall (AWS) Program. Candidate figures of merit from conventional static tunnel tests are summarized and correlated with data obtained in unique free-to-roll tests. Where possible, free-to-roll results are also correlated with flight data. Based on extensive studies of static experimental figures of merit in the Abrupt Wing Stall Program for four different aircraft configurations, no one specific figure of merit consistently flagged a warning of potential lateral activity when actual activity was seen to occur in the free-to-roll experiments. However, these studies pointed out the importance of measuring and recording the root mean square signals of the force balance.

  14. Decadal-scale Climate Variability on the Central Iranian Plateau Spanning the So-called 4.2 ka BP Drought Event

    NASA Astrophysics Data System (ADS)

    Carolin, S.; Walker, R. T.; Henderson, G. M.; Maxfield, L.; Ersek, V.; Sloan, A.; Talebian, M.; Fattahi, M.; Nezamdoust, J.

    2015-12-01

    The influence of climate on the growth and development of ancient civilizations throughout the Holocene remains a topic of heated debate. The 4.2 ka BP global-scale mid-to-low latitude aridification event (Walker et al., 2012) in particular has incited various correlation proposals. Some authors suggest that this event may have led to the collapse of the Akkadian empire in Mesopotamia, one of the first empires in human history, as well as to changes among other Early Bronze Age societies dependent on cereal agriculture (eg. Staubwasser and Weiss, 2006). Other authors remain doubtful of the impact of environmental factors on the collapse of past societies (eg. Middleton, 2012). While coincident timing of an environmental event with archeological evidence does not necessitate a causation, a comprehensive understanding of climate variability in the ancient Near East is nonetheless an essential component to resolving the full history of early human settlements. Paleoclimate data on the Central Iranian Plateau, a region rich with ancient history, is exceptionally sparse compared to other areas. Many karst locations are found throughout the region, however, setting the stage for the development of several high-resolution, accurate and precisely-dated climate proxy records if a correlation between the chemistry of semi-arid speleothem samples and climate is resolved. Here we present a 5.1-3.7 ka BP record of decadal-scale stalagmite stable isotope and trace metal variability. The stalagmite was collected in Gol-e zard cave (35.8oN, 52.0oE), ~100 km NE of Tehran on the southern flank of the Alborz mountain range (2530masl). The area currently receives ~270mm mean annual precipitation, with more than 90% of precipitation falling within the wet season (November-May). We use GNIP data from Tehran and local and regional meteorological data to resolve the large-scale mechanisms forcing isotopic variations in rainwater over Gol-e zard cave. We discuss possible transformation of

  15. Sensitivity of the Younger Dryas climate to changes in orbtial, greenhouse gas, and freshwater forcing in CESM1

    NASA Astrophysics Data System (ADS)

    Hughlett, T. M.; Winguth, A. M. E.; Rosenbloom, N. A.; He, F.

    2016-12-01

    The Younger Dryas cooling event ( 12,900 years before present) was the most recent abrupt climate change in the geologic record where climate for the Northern Hemisphere returned to a near-glacial state. The cause of this cooling event is widely controversial, and no consensus has been found as to why the onset of the cooling occurred. Of the several hypotheses proposed, the freshening of the North Atlantic Ocean due to meltwater discharge from the retreating Lake Agassiz and subsequent changes in Atlantic meridional oceanic circulation (AMOC) is the most widely accepted one. In this study, the Community Earth System Model version 1 was used to perform sensitivity experiments to test how the AMOC responds to a freshwater discharge into the Northern Atlantic Ocean over the course of 1,000 years. This study is the first fully coupled, moderate-resolution simulation that implements a 13.1ka ice sheet (ICE-5G) along with Younger Dryas boundary and initial conditions. With the addition of the 13.1ka ice sheet and a 0.3 Sverdrup (Sv) freshwater discharge into the Northern Atlantic Ocean, the AMOC reduces by approximately 20 Sv, coming to a substantially slowed-down state of approximately 5 Sv. This reduction of the AMOC causes a decrease in surface air temperature of approximately 15 °C, which is in agreement with surface air temperature reconstructions from the Greenland Ice Sheet Project 2. Overall, the simulation presented in this study accurately represents the climatic state of the Younger Dryas cooling event.

  16. Avifauna response to hurricanes: regional changes in community similarity

    Treesearch

    Chadwick D. Rittenhouse; Anna M. Pidgeon; Thomas P. Albright; Patrick D. Culbert; Murray K. Clayton; Curtis H. Flather; Chengquan Huang; Jeffrey G. Masek; Volker C. Radeloff

    2010-01-01

    Global climate models predict increases in the frequency and intensity of extreme climatic events such as hurricanes, which may abruptly alter ecological processes in forests and thus affect avian diversity. Developing appropriate conservation measures necessitates identifying patterns of avifauna response to hurricanes. We sought to answer two questions: (1) does...

  17. Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI

    DTIC Science & Technology

    2015-09-30

    Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI T. M. Shaun Johnston Scripps Institution of Oceanography...westward flow in the North Equatorial Current (NEC) encounters tall, steep, submarine topography and islands. During the Flow Encountering Abrupt... Topography (FLEAT) DRI, investigators will determine: • Whether appreciable energy/momentum is lost from the large-scale NEC flow to smaller scales and

  18. Past climate variability inferred from statistical processing of documentary data: a case study on extreme meteorological events in western central France from 1500 to 2000 AD

    NASA Astrophysics Data System (ADS)

    Poirier, Clément; Chaumillon, Eric; Audé, Jean-Luc

    2010-05-01

    Recent human-induced climate changes are expected to have an impact on extreme events including shifts in storm tracks, heavier precipitations and more severe droughts (Planton, 2008). Although climate models successfully describe the past mean climate variability, they often fail to correctly reproduce such extreme events, mainly because of a low spatial and temporal resolution (Sánchez et al., 2004). Reports of extreme meteorological events gathered from documentary archives are be useful to fill this gap, and would also provide insights into local climatic variations (Leijonhufvud et al., 2008; Rodrigo, 2008; Wheeler, 2006). In this study, a local text book published by Audé (2006) was used as a source of climatic data. It consists of a list of extreme meteorological events recorded in historical archives (diaries mainly) in western central France, along the Bay of Biscay. From the book, 284 extreme meteorological events that occurred between 1500 and 2000 were selected. A presence-absence matrix was built, the events being classified in 7 distinct categories by Audé. A preliminary multivariate analysis (Principal Component Analysis) was used to group these categories into 4 classes of events. First axis (22.3% of explained variance) discriminated the events related to temperature, with frosts and snowfalls on one side, versus gales and storms on the other side. Second axis (18.5% of explained variance) discriminated the events related to precipitation, with floods and rainfalls on one side (humid), versus droughts on the other (dry). For each class, a 29-year running mean was computed to convert binary qualitative data to semi-quantitative curves. A spectral analysis was also performed on the same binary data to detect potential climatic cycles. Despite the randomness of the historical records reported in this book, that much relies on the subjective perception of meteorological events by past witnesses, the results obtained are consistent with existing data

  19. Climate events synchronize the dynamics of a resident vertebrate community in the high Arctic.

    PubMed

    Hansen, Brage B; Grøtan, Vidar; Aanes, Ronny; Sæther, Bernt-Erik; Stien, Audun; Fuglei, Eva; Ims, Rolf A; Yoccoz, Nigel G; Pedersen, Ashild Ø

    2013-01-18

    Recently accumulated evidence has documented a climate impact on the demography and dynamics of single species, yet the impact at the community level is poorly understood. Here, we show that in Svalbard in the high Arctic, extreme weather events synchronize population fluctuations across an entire community of resident vertebrate herbivores and cause lagged correlations with the secondary consumer, the arctic fox. This synchronization is mainly driven by heavy rain on snow that encapsulates the vegetation in ice and blocks winter forage availability for herbivores. Thus, indirect and bottom-up climate forcing drives the population dynamics across all overwintering vertebrates. Icing is predicted to become more frequent in the circumpolar Arctic and may therefore strongly affect terrestrial ecosystem characteristics.

  20. Missing rings in Pinus halepensis – the missing link to relate the tree-ring record to extreme climatic events

    Treesearch

    Klemen Novak; Martin de Luis; Miguel A. Saz; Luis A. Longares; Roberto Serrano-Notivoli; Josep Raventos; Katarina Cufar; Jozica Gricar; Alfredo Di Filippo; Gianluca Piovesan; Cyrille B.K. Rathgeber; Andreas Papadopoulos; Kevin T. Smith

    2016-01-01

    Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of...