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1

Solar air conditioning applications for warm humid climate  

Microsoft Academic Search

Air conditioning in warm humid climates presents certain difficulties as well as advantages associated with the given climatic conditions. Humidity control by conventional cooling methods depends upon the use of coil temperatures low enough to achieve the proper dew point temperature for the conditioned air. The solar-driven absorption unit loses both capacity and performance when lower evaporation temperatures are required.

T. G. Olsen; R. K. Swartman

1976-01-01

2

Is the climate warming?  

Microsoft Academic Search

Summary form only given. The balance of evidence suggests that the climate is not warming. A US National Research Council report has highlighted, but not explained, the disparity between different data sets: while a variety of surface thermometers report a substantial warming trend, microwave sensing units (MSU) on weather satellites, and also radiosondes carried in weather balloons, show little if

S. F. Singer

2002-01-01

3

Computations on frost damage to Scots pine under climatic warming in boreal conditions  

SciTech Connect

To investigate the risk of frost damage to Scots pine (Pinus sylvestris L.) in northern regions under climatic warming, a submodel for such damage to trees was included in a forest ecosystem model of the gap type. An annual growth multiplier describing the effects of frost was calculated with the help of simulated daily frost hardiness and daily minimum temperature. The annual growth multiplier was used in the main ecosystem model when simulating the development of a tree stand using a time step of one year. Simulations of the growth and development of Scots pine stands in southern Finland (61{degrees} N) under an elevating temperature indicated that climatic warming could increase the risk of frost damage due to premature onset of growth during warm spells in the late winter and early spring. Risk of frost damage implies uncertainty in yield expectations from boreal forest ecosystems in the event of climatic warming. 38 refs., 9 figs., 4 tabs.

Kellomaeki, S.; Haenninen, H.; Kolstroem, M. [Univ. of Joensuu (Finland)

1995-02-01

4

Sea-ice and North Atlantic climate response to CO2-induced warming and cooling conditions  

NASA Astrophysics Data System (ADS)

Using a global climate model coupled with an ocean and a sea-ice model, we compare the effects of doubling CO2 and halving CO2 on sea-ice cover and connections with the atmosphere and ocean. An overall warming in the 2 × CO2 experiment causes reduction of sea-ice extent by 15%, with maximum decrease in summer and autumn, consistent with observed seasonal sea-ice changes. The intensification of the Northern Hemisphere circulation is reflected in the positive phase of the Arctic Oscillation (AO), associated with higher-than-normal surface pressure south of about 50° N and lower-than-normal surface pressure over the high northern latitudes. Strengthening the polar cell causes enhancement of westerlies around the Arctic perimeter during winter. Cooling, in the 0.5 × CO2 experiment, leads to thicker and more extensive sea ice. In the Southern Hemisphere, the increase in ice-covered area (28%) dominates the ice-thickness increase (5%) due to open ocean to the north. In the Northern Hemisphere, sea-ice cover increases by only 8% due to the enclosed land/sea configuration, but sea ice becomes much thicker (108%). Substantial weakening of the polar cell due to increase in sea-level pressure over polar latitudes leads to a negative trend of the winter AO index. The model reproduces large year-to-year variability under both cooling and warming conditions.

Nazarenko, Larissa; Tausnev, Nickolai; Hansen, James

5

Warm climate surprises  

SciTech Connect

Over the last decade, paleoclimatic data from ice cores and sediments have shown that the climate system is capable of switching between significantly different modes, suggesting that climatic surprises may lie ahead. Most attention in the growing area of abrupt climatic change research continues to be focused on large changes observed during glacial periods. The weight of paleoclimatic evidence now suggests that conforting conclusions of benign warm climate variability may be incorrect. The article goes on to discuss the evidence for this. 17 refs.

Overpeck, J.T. [National Geophysical Data Center, Boulder, CO (United States)

1996-03-29

6

Sea-ice and North Atlantic climate response to CO2-induced warming and cooling conditions  

Microsoft Academic Search

Using a global climate model coupled with an ocean and a sea-ice model, we compare the effects of doubling CO2 and halving CO2 on sea-ice cover and connections with the atmosphere and ocean. An overall warming in the 2 × CO2 experiment causes reduction of sea-ice extent by 15%, with maximum decrease in summer and autumn, consistent with observed seasonal

Larissa Nazarenko; Nickolai Tausnev; James Hansen

2006-01-01

7

Assessment of permafrost conditions under Northern Quebec's airports: an integrative approach for the development of adaptation strategies to climate warming  

NASA Astrophysics Data System (ADS)

Community airports in Nunavik were built between 1984 and 1992 and were designed by using a thick embankment of rock fill placed on undisturbed ground surface to prevent the thawing of the underlying permafrost. However, since around 2000, many of the runways show signs of permafrost disturbance as some localized differential settlements have begun to take place. With the anticipated rise of air temperature, the vulnerability of transportation infrastructures to permafrost degradation raises concerns. Several studies initiated by MTQ were undertaken by CEN to evaluate the permafrost conditions underneath airports. These studies provide valuable baseline information but also reveal the needs for a better understanding of the spatial variability of the surficial deposits, their geotechnical properties and permafrost conditions underneath embankments to assess its sensibility to thawing and to plan adaptation strategies in face of climate warming. A geomorphological and geotechnical investigation campaign, including surficial geology mapping using pre-construction air photographs and recovery of drilled frozen cores, was carried out in the summers 2008 and 2009 at eight airports. The impact of the runway embankments on surface drainage, snow drift accumulation and permafrost thawing was also determined. Stratigraphic information from drilling was used to reinterpret CCR and GPR surveys done in previous studies. High resolution cross-sections of the stratigraphy and permafrost conditions could then be drawn. Lab testing over undisturbed frozen samples was performed to determine the geotechnical properties of the different stratigraphic units encountered, particularly thaw consolidation ratios. Field measurements of ground temperatures and numerical modeling of the thermal regime of the embankment and subgrade were also performed to assess the potential impacts on permafrost stability alongside and beneath embankments under different climate change scenarios. Thermistor readings show that the active layer in the central part of the runways is in most case still contained in the embankment or within the prior-to-construction consolidated active layer. However, a residual thaw layer (talik) is now present at the toe of embankments where significant snow accumulations occurred. Thermal modeling indicates that water accumulation and seepage as well as snow accumulation along embankment shoulders are currently the dominant factors of permafrost degradation. In the future, centerlines of embankment built on ice rich permafrost will gradually settle as the climate warms up; therefore periodic reloading will be necessary. To counter permafrost degradation alongside runways and access roads, the proposed mitigation strategies focus on minimizing snow and water accumulation by making gentler slopes (1:6) and by improving the drainage system to avoid potential seepage through embankments.

L'Hérault, E.; Allard, M.; Doré, G.; Barrette, C.; Verreault, J.; Sarrazin, D.; Doyon, J.; Guimond, A.

2011-12-01

8

Surface thermohaline forcing conditions and the response of the present-day global ocean climate to global warming  

Microsoft Academic Search

I investigate the response of the present-day thermohaline circulation to a greenhouse gas induced global warming under different surface thermohaline conditions in a global Bryan\\/Cox [Bryan, 1969; Cox, 1989] ocean general circulation model with realistic bathymetry and geometry. Initially the model is spun up with surface temperature and salinity relaxed to Levitus [1982] climatologies. The forcing condition for salinity is

Wenju Cai

1996-01-01

9

Climate projection: Refining global warming projections  

NASA Astrophysics Data System (ADS)

Accurately determining the warming associated with scenarios of greenhouse gas emissions remains an overarching aim of climate modelling. Research now shows that contemporary measurements significantly reduce uncertainty bounds and indicate that some more extreme warming predictions may be less likely.

Huntingford, Chris

2013-08-01

10

Warming asymmetry in climate change simulations  

Microsoft Academic Search

Climate change simulations made with coupled global climate models typically show a marked hemispheric asymmetry with more warming in the northern high lati- tudes than in the south. This asymmetry is ascribed to heat uptake by the ocean at high southern latitudes. A re- cent version of the CCCma climate model exhibits a much more symmetric warming, compared to an

G. M. Flato; G. J. Boer

2001-01-01

11

Monitoring Global Climate Change: The Case of Greenhouse Warming  

Microsoft Academic Search

Recent record high temperatures and drought conditions in many regions of the United States have prompted heightened concern about whether these are early manifestations of the global green house warming projected by the major climate models. An improved global climate monitoring and reporting capability is urgently needed in order to ensure that interpretation of climate trends and comparison with model

Fred B. Wood

1990-01-01

12

The global climate for September-November 1992: Weak warm ENSO episode conditions linger in the tropical Pacific  

SciTech Connect

During the September-November (SON) 1992 transition season, the tropical Pacific initially featured a continuation of the normal conditions observed during July and August 1992 and then surprisingly late in the season, showed reemergence of weak warm El Nino-southern Oscillation (ENSO) eventlike conditions. The Tahiti-Darwin Southern Oscillation index, after having returned to zero in August and September, dropped to strong negative values during both October and November. During November, low-level equatorial easterliest remained anomalously weak throughout the tropical Pacific consistent with increased convective activity near the date line. Seasonal mean surface temperature over the northernmost latitudes of the Eurasian continent were much below normal in contrast to the positive anomalies generally experienced over the recent past summers. For the United States as a whole, during the SON 1992 season, the mean precipitation was near normal, however, there was considerable variability in the precipitation anomalies across the country.

Chelliah, M. [Climate Analysis Center, Washington, DC (United States)] [Climate Analysis Center, Washington, DC (United States)

1994-10-01

13

Effects of climate warming, North Atlantic Oscillation, and El Niño-Southern Oscillation on thermal conditions and plankton dynamics in northern hemispheric lakes.  

PubMed

Impacts of climate warming on freshwater ecosystems have been documented recently for a variety of sites around the globe. Here we provide a review of studies that report long-term (multidecadal) effects of warming trends on thermal properties and plankton dynamics in northern hemispheric lakes. We show that higher lake temperatures, shorter periods with ice cover, and shorter stagnation periods were common trends for lakes across the hemisphere in response to the warmer conditions. Only for shallow dimictic lakes was it observed that deep-water temperatures decreased. Moreover, it became evident that phytoplankton dynamics and primary productivity altered in conjunction with changes in lake physics. Algal spring blooms developed early and were more pronounced in several European lakes after mild winters with short ice cover periods, and primary productivity increased in North American lakes. Effects of elevated temperatures on zooplankton communities were seen in an early development of various species and groups, as is documented for cladocerans, copepods, and rotifers in European lakes. Furthermore, thermophile species reached higher abundance in warmer years. Obviously, the nature of responses is species specific, and depends on the detailed seasonal patterning of warming. Complex responses such as effects propagating across trophic levels are likely, indicating that observed climate-ecosystem relationships are not generally applicable. Nonetheless, the picture emerges that climate-driven changes in freshwater ecosystems may be synchronised to a certain extent among lakes even over great distances if climatic influences are not masked by anthropogenic impacts or differences in lake morphology. Macro-scale climatic fluctuations--such as the North Atlantic Oscillation or the El Niño-Southern Oscillation--were identified as the most important candidates responsible for such coherence, with the former predominating in Europe and the latter in North America. We emphasise, however, that the driving mechanisms and the future behaviour of these oscillations are rather uncertain, which complicates extrapolation of observed effects into the future. Thus, it is necessary to quantify the most important climate-ecosystem relationships in models of appropriate complexity. Such models will help elucidate the multiple pathways climate affects freshwater ecosystems, and will indicate possible adverse effects of a warmer future climate. PMID:12805986

Gerten, Dieter; Adrian, Rita

2002-03-01

14

Warming trends: Nonlinear climate change  

NASA Astrophysics Data System (ADS)

Most studies assume that temperature trends are linear. Now, research demonstrates that warming trends are nonlinear, that warming accelerated over most of the twentieth century and is much stronger since 1980 than calculated by linear methods.

Franzke, Christian L. E.

2014-06-01

15

Shifting suitability for malaria vectors across Africa with warming climates  

Microsoft Academic Search

BACKGROUND: Climates are changing rapidly, producing warm climate conditions globally not previously observed in modern history. Malaria is of great concern as a cause of human mortality and morbidity, particularly across Africa, thanks in large part to the presence there of a particularly competent suite of mosquito vector species. METHODS: I derive spatially explicit estimates of human populations living in

A Townsend Peterson

2009-01-01

16

State-dependent climate sensitivity in past warm climates and its implications for future climate projections.  

PubMed

Projections of future climate depend critically on refined estimates of climate sensitivity. Recent progress in temperature proxies dramatically increases the magnitude of warming reconstructed from early Paleogene greenhouse climates and demands a close examination of the forcing and feedback mechanisms that maintained this warmth and the broad dynamic range that these paleoclimate records attest to. Here, we show that several complementary resolutions to these questions are possible in the context of model simulations using modern and early Paleogene configurations. We find that (i) changes in boundary conditions representative of slow "Earth system" feedbacks play an important role in maintaining elevated early Paleogene temperatures, (ii) radiative forcing by carbon dioxide deviates significantly from pure logarithmic behavior at concentrations relevant for simulation of the early Paleogene, and (iii) fast or "Charney" climate sensitivity in this model increases sharply as the climate warms. Thus, increased forcing and increased slow and fast sensitivity can all play a substantial role in maintaining early Paleogene warmth. This poses an equifinality problem: The same climate can be maintained by a different mix of these ingredients; however, at present, the mix cannot be constrained directly from climate proxy data. The implications of strongly state-dependent fast sensitivity reach far beyond the early Paleogene. The study of past warm climates may not narrow uncertainty in future climate projections in coming centuries because fast climate sensitivity may itself be state-dependent, but proxies and models are both consistent with significant increases in fast sensitivity with increasing temperature. PMID:23918397

Caballero, Rodrigo; Huber, Matthew

2013-08-27

17

State-dependent climate sensitivity in past warm climates and its implications for future climate projections  

PubMed Central

Projections of future climate depend critically on refined estimates of climate sensitivity. Recent progress in temperature proxies dramatically increases the magnitude of warming reconstructed from early Paleogene greenhouse climates and demands a close examination of the forcing and feedback mechanisms that maintained this warmth and the broad dynamic range that these paleoclimate records attest to. Here, we show that several complementary resolutions to these questions are possible in the context of model simulations using modern and early Paleogene configurations. We find that (i) changes in boundary conditions representative of slow “Earth system” feedbacks play an important role in maintaining elevated early Paleogene temperatures, (ii) radiative forcing by carbon dioxide deviates significantly from pure logarithmic behavior at concentrations relevant for simulation of the early Paleogene, and (iii) fast or “Charney” climate sensitivity in this model increases sharply as the climate warms. Thus, increased forcing and increased slow and fast sensitivity can all play a substantial role in maintaining early Paleogene warmth. This poses an equifinality problem: The same climate can be maintained by a different mix of these ingredients; however, at present, the mix cannot be constrained directly from climate proxy data. The implications of strongly state-dependent fast sensitivity reach far beyond the early Paleogene. The study of past warm climates may not narrow uncertainty in future climate projections in coming centuries because fast climate sensitivity may itself be state-dependent, but proxies and models are both consistent with significant increases in fast sensitivity with increasing temperature.

Caballero, Rodrigo; Huber, Matthew

2013-01-01

18

Evaluating the dominant components of warming in Pliocene climate simulations  

NASA Astrophysics Data System (ADS)

The Pliocene Model Intercomparison Project is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 °C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean-atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with cloud albedo feedbacks enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere mid-latitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with cloud albedo feedbacks in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that high latitude albedo feedbacks provide the most significant enhancements to Pliocene greenhouse warming.

Hill, D. J.; Haywood, A. M.; Lunt, D. J.; Hunter, S. J.; Bragg, F. J.; Contoux, C.; Stepanek, C.; Sohl, L.; Rosenbloom, N. A.; Chan, W.-L.; Kamae, Y.; Zhang, Z.; Abe-Ouchi, A.; Chandler, M. A.; Jost, A.; Lohmann, G.; Otto-Bliesner, B. L.; Ramstein, G.; Ueda, H.

2013-03-01

19

Indian Ocean warming modulates Pacific climate change  

PubMed Central

It has been widely believed that the tropical Pacific trade winds weakened in the last century and would further decrease under a warmer climate in the 21st century. Recent high-quality observations, however, suggest that the tropical Pacific winds have actually strengthened in the past two decades. Precise causes of the recent Pacific climate shift are uncertain. Here we explore how the enhanced tropical Indian Ocean warming in recent decades favors stronger trade winds in the western Pacific via the atmosphere and hence is likely to have contributed to the La Niña-like state (with enhanced east–west Walker circulation) through the Pacific ocean–atmosphere interactions. Further analysis, based on 163 climate model simulations with centennial historical and projected external radiative forcing, suggests that the Indian Ocean warming relative to the Pacific’s could play an important role in modulating the Pacific climate changes in the 20th and 21st centuries.

Luo, Jing-Jia; Sasaki, Wataru; Masumoto, Yukio

2012-01-01

20

The global climate for June to August 1990: Drought returns to sub-Saharan West Africa and warm southern oscillation episode conditions develop in the central pacific  

SciTech Connect

Although the general monsoon circulation evolved relatively normally over most of the globe, dry conditions returned to sub-Saharan West Africa. The Northern Hemisphere summer surface temperature continued to be above normal over most land areas, but in general the anomolies were less extreme. The equatorial sea surface temperatures continued to move toward warm episode Southern Oscillation conditions in the central Pacific, but without an accompanying warming in the traditional eastern Pacific El Nino areas.

Ropelewski, C.F. (Climate Analysis Center, Washington, DC (United States)); Lamb, P.J.; Portis, D.H. (Univ. of Oklahoma, Norman, OK (United States))

1993-11-01

21

Evaluating the dominant components of warming in Pliocene climate simulations  

NASA Astrophysics Data System (ADS)

The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 °C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean-atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene.

Hill, D. J.; Haywood, A. M.; Lunt, D. J.; Hunter, S. J.; Bragg, F. J.; Contoux, C.; Stepanek, C.; Sohl, L.; Rosenbloom, N. A.; Chan, W.-L.; Kamae, Y.; Zhang, Z.; Abe-Ouchi, A.; Chandler, M. A.; Jost, A.; Lohmann, G.; Otto-Bliesner, B. L.; Ramstein, G.; Ueda, H.

2014-01-01

22

Divergence of reproductive phenology under climate warming  

PubMed Central

Because the flowering and fruiting phenology of plants is sensitive to environmental cues such as temperature and moisture, climate change is likely to alter community-level patterns of reproductive phenology. Here we report a previously unreported phenomenon: experimental warming advanced flowering and fruiting phenology for species that began to flower before the peak of summer heat but delayed reproduction in species that started flowering after the peak temperature in a tallgrass prairie in North America. The warming-induced divergence of flowering and fruiting toward the two ends of the growing season resulted in a gap in the staggered progression of flowering and fruiting in the community during the middle of the season. A double precipitation treatment did not significantly affect flowering and fruiting phenology. Variation among species in the direction and magnitude of their response to warming caused compression and expansion of the reproductive periods of different species, changed the amount of overlap between the reproductive phases, and created possibilities for an altered selective environment to reshape communities in a future warmed world.

Sherry, Rebecca A.; Zhou, Xuhui; Gu, Shiliang; Arnone, John A.; Schimel, David S.; Verburg, Paul S.; Wallace, Linda L.; Luo, Yiqi

2007-01-01

23

Bering Strait influences climate conditions  

NASA Astrophysics Data System (ADS)

The Atlantic meridional overturning circulation (AMOC) acts as a heat conveyer belt, bringing warm tropical water northward in the Atlantic Ocean and carrying cold dense water back southward. Some studies have suggested that changes in AMOC could result in seesaw-like climate changes between the North Atlantic and North Pacific, in which the North Pacific warms while the North Atlantic cools. In fact, paleoclimate studies have found that such a seesaw effect may have occurred during the Heinrich 1 (H1) event about 15-17.5 thousand years ago. However, global climate conditions are much warmer today than they were during the H1 event. Sea level was much lower during the H1 event, and the Bering Strait, which now connects the North Pacific Ocean to the Arctic Ocean, was closed. Some studies have suggested that AMOC could weaken or even collapse entirely as global climate warms because of anthropogenic influence. Would such AMOC changes lead to the seesaw effect seen during the H1 event?

Balcerak, Ernie

2012-03-01

24

Lagging adaptation to warming climate in Arabidopsis thaliana.  

PubMed

If climate change outpaces the rate of adaptive evolution within a site, populations previously well adapted to local conditions may decline or disappear, and banked seeds from those populations will be unsuitable for restoring them. However, if such adaptational lag has occurred, immigrants from historically warmer climates will outperform natives and may provide genetic potential for evolutionary rescue. We tested for lagging adaptation to warming climate using banked seeds of the annual weed Arabidopsis thaliana in common garden experiments in four sites across the species' native European range: Valencia, Spain; Norwich, United Kingdom; Halle, Germany; and Oulu, Finland. Genotypes originating from geographic regions near the planting site had high relative fitness in each site, direct evidence for broad-scale geographic adaptation in this model species. However, genotypes originating in sites historically warmer than the planting site had higher average relative fitness than local genotypes in every site, especially at the northern range limit in Finland. This result suggests that local adaptive optima have shifted rapidly with recent warming across the species' native range. Climatic optima also differed among seasonal germination cohorts within the Norwich site, suggesting that populations occurring where summer germination is common may have greater evolutionary potential to persist under future warming. If adaptational lag has occurred over just a few decades in banked seeds of an annual species, it may be an important consideration for managing longer-lived species, as well as for attempts to conserve threatened populations through ex situ preservation. PMID:24843140

Wilczek, Amity M; Cooper, Martha D; Korves, Tonia M; Schmitt, Johanna

2014-06-01

25

Lagging adaptation to warming climate in Arabidopsis thaliana  

PubMed Central

If climate change outpaces the rate of adaptive evolution within a site, populations previously well adapted to local conditions may decline or disappear, and banked seeds from those populations will be unsuitable for restoring them. However, if such adaptational lag has occurred, immigrants from historically warmer climates will outperform natives and may provide genetic potential for evolutionary rescue. We tested for lagging adaptation to warming climate using banked seeds of the annual weed Arabidopsis thaliana in common garden experiments in four sites across the species’ native European range: Valencia, Spain; Norwich, United Kingdom; Halle, Germany; and Oulu, Finland. Genotypes originating from geographic regions near the planting site had high relative fitness in each site, direct evidence for broad-scale geographic adaptation in this model species. However, genotypes originating in sites historically warmer than the planting site had higher average relative fitness than local genotypes in every site, especially at the northern range limit in Finland. This result suggests that local adaptive optima have shifted rapidly with recent warming across the species’ native range. Climatic optima also differed among seasonal germination cohorts within the Norwich site, suggesting that populations occurring where summer germination is common may have greater evolutionary potential to persist under future warming. If adaptational lag has occurred over just a few decades in banked seeds of an annual species, it may be an important consideration for managing longer-lived species, as well as for attempts to conserve threatened populations through ex situ preservation.

Wilczek, Amity M.; Cooper, Martha D.; Korves, Tonia M.; Schmitt, Johanna

2014-01-01

26

The response of Picea crassifolia forest to climate warming  

NASA Astrophysics Data System (ADS)

Picea crassifolia forest, an endemic genus mainly distributing in the Qilian Mountain of Northwest China, is very sensitive to climate warming. In the present study, the response of treeline, phenological period, and sap flow of P. crassifolia forest to climate warming were analyzed though a set of observations and experiments. The result showed: (1) During the past 50 years, the temperature had raised at a mean rate of 0.29° C per decade in this region, especially since 1980s (had increased by a total of more than 1.25° C), obviously higher than increment degree IPCC reported. This resulted in the increase of tree recruitment which was significantly positively correlated with the mean growing season temperature and with the mean minimum temperature in June and in winter. Treeline elevation shifted upward by 5.7 to 13.6 m from 1907 to 1957 and by 6.1 to 10.4 m after 1957. (2) By quantifying the canopy phenology events based on satellite-derived datasets (MODIS-NDVI) from 2001 to 2011, and investigating the correlation with climate factors, a conclusion had been drawn which revealed a 3.7 days/decade advance in the length of growing season. Our results suggested that temperature controlled treeline dynamics and phenological period more strongly than precipitation in the Qilian Mountains. (3) In the case of experimental warming (mean daily temperature was increased 0.83° C, mean daily maximum temperature was increased 4.7° C), the trend for the mass growth of P. crassifolia sapling presented a notable increase under conditions of warming, especially for tree height. The data of sap flow showed that warming facilitated the sap flow of sapling in the end of growing season, which indicated the temperature was a major restriction to sap flow rate, especially in the condition of lower temperature.

He, Zhibin; Du, Jun; Yang, Junjun; Chen, Longfei; Zhu, Xi

2014-05-01

27

The Medieval Warm Period, the Little Ice Age and simulated climatic variability  

Microsoft Academic Search

The CSIRO Mark 2 coupled global climatic model has been used to generate a 10,000-year simulation for ‘present’ climatic conditions. The model output has been analysed to identify sustained climatic fluctuations, such as those attributed to the Medieval Warm Period (MWP) and the Little Ice Age (LIA). Since no external forcing was permitted during the model run all such fluctuations

B. G. Hunt

2006-01-01

28

Early Eocene climate warming increased petroleum production  

NASA Astrophysics Data System (ADS)

From the late Paleocene, about 58 million years ago, to the early Eocene, about 51 million years ago, Earth's surface temperatures warmed by about 5°-10°C. Also in the early Eocene, there was an increase of carbon-13-depleted carbon in the oceans that cannot be accounted for by changes in carbon cycling at the surface. To better understand the source of that carbon, Kroeger and Funnell modeled the thermal evolution of four sedimentary basins in the southwestern Pacific Ocean. The authors show that the rising surface temperatures of the early Eocene eventually led to warming of the sedimentary beds deep beneath the surface. Petroleum can be produced at only a certain range of temperatures; rising temperatures at greater depths would bring more potential source rocks into temperature conditions under which oil and gas can be produced and released.

Balcerak, Ernie

2012-04-01

29

How to preserve the tundra in a warming climate?  

NASA Astrophysics Data System (ADS)

The warming climate of the polar regions may change much of the current arctic-alpine tundra to forest or dense scrubland. This modification requires adaptation by traditional livelihoods such as reindeer herding, which relies on diverse, seasonal pasturelands. Vegetation change may also trigger positive warming feedbacks, where more abundant forest-scrub vegetation will decrease the global albedo. NCoE Tundra team investigates the complex climate-animal-plant interaction of the tundra ecosystem and aim to unravel the capability of herbivorous mammals to control the expansion of woody vegetation. Our interdisciplinary approach involves several work packages, whose results will be summarised in the presentation. In the ecological WPs, we study the dynamics of the natural food chains involving small herbivorous and the impacts of reindeer on the vegetation and the population dynamics of those arctic-alpine plants, which are most likely to become threatened in a warmer climate. Our study demonstrates the potential of a relatively sparse reindeer stocks (2-5 heads per km2) together with natural populations of arvicoline rodents to prevent the expansion of erect woody plants at the arctic-alpine timberline. In the climatic WPs we study the impact of grazing-dependent vegetation differences on the fraction of solar energy converted to heat. In the socio-economic WPs, we study the conditions for maintaining the economic and cultural viability of reindeer herding while managing the land use so that the arctic-alpine biota would be preserved.

Käyhkö, Jukka

2014-05-01

30

Multiple vegetation states in a warm climate  

NASA Astrophysics Data System (ADS)

Using the Max Planck earth system model, multiple steady states in vegetation cover are evaluated for preindustrial and Early Eocene boundary conditions. By setting the soil albedo either to a value similar to vegetation albedo or to a value much higher than vegetation albedo, the hydrological and the albedo effect of vegetation on climate are separated. Considering only the hydrological effect, multiple solutions for the Early Eocene vegetation cover exist. In central Asia, a desert evolves. This desert is smaller when the simulation is started with trees on all continents instead of bare soil. Started with trees, the climate in central Asia is more humid than when started with bare soil. In the more humid climate, more vegetation grows. For the preindustrial climate, only one solution for vegetation exists. The atmospheric circulation prevents multiple solutions for vegetation in the Sahara. Strong subsidence prevails over the Sahara. Under strong subsidence the hydrological effect becomes ineffective. Considering the hydrological and the albedo effect of vegetation, only one solution for Early Eocene and preindustrial vegetation exists. Starting the simulations with trees, the Early Eocene central Asia and preindustrial Sahara start from a humid climate, but the initial climate is not humid enough to allow a dense vegetation cover. With shrinking vegetation cover, surface albedo increases. Increasing albedo amplifies aridification by inducing the Charney effect. The vegetation cover shrinks further until a dry desert state is reached. This study shows that the existence of multiple steady vegetation states depends on the boundary conditions, such as continent distribution. This result implies that the existence and the driving mechanisms of multiple stable vegetation states differ for present day, past, and probably future conditions.

Port, Ulrike; Claussen, Martin

2014-05-01

31

Ocean Biogeochemistry in the warm climate of the Late Paleocene  

NASA Astrophysics Data System (ADS)

The Late Paleocene is characterized by warm and stable climatic conditions which served as the background climate for the Paleocene-Eocene Thermal Maximum (PETM, ~55 million years ago). With respect to feedback processes in the carbon cycle, the ocean biogeochemical background state is of major importance for projecting the climatic response to a carbon perturbation related to the PETM. Therefore we use the Hamburg Ocean Carbon Cycle model HAMOCC, embedded into the ocean general circulation model of the Max Planck Institute for Meteorology, MPIOM, to constrain the ocean biogeochemistry of the Late Paleocene. We focus on the evaluation of modeled spatial and vertical distributions of the ocean carbon cycle parameters in a long-term warm steady-state ocean, based on a 560 ppm CO2 atmosphere. Model results are discussed in the context of available proxy data and simulations of pre-industrial conditions. Our results illustrate that ocean biogeochemistry is shaped by the warm and sluggish ocean state of the Late Paleocene, which affects the strength and spatial variation of the different carbon pumps. Primary production is only slightly reduced in comparison to present-day; it is intensified along the equator, especially in the Atlantic. This enhances remineralization of organic matter, resulting in strong oxygen minimum zones and CaCO3 dissolution in intermediate waters. We show that an equilibrium CO2 exchange without increasing total alkalinity concentrations above today's values is achieved. Yet, the surface ocean pH and the saturation state with respect to CaCO3 are lower than today. Our results indicate that under such conditions, the surface ocean carbonate chemistry is expected to be more sensitive to a carbon perturbation (i.e. the PETM) due to lower CO32- concentration, whereas the deep ocean calcite sediments would be less vulnerable to dissolution due to the sluggish ocean.

Heinze, M.; Ilyina, T.

2014-04-01

32

The case for a wet, warm climate on early Mars  

NASA Astrophysics Data System (ADS)

The conditions under which Mars could have had a warm wet climate during its early evolution are explored by means of numerical simulations, incorporating more accurate data on the opacity of gaseous CO2 and H2O in the solar and thermal spectral regions (McClatchey et al., 1971) into the one-dimensional radiative-convective greenhouse model of Kasting and Ackerman (1986). The results are presented in extensive graphs and characterized in detail, with consideration of atmospheric CO2 loss rates, sources of atmospheric CO2, CO2 partitioning between atmosphere and hydrosphere, the Mars volatile inventory, the CO2 geochemical cycle, climate evolution, and observational tests. It is concluded that greenhouse conditions (requiring atmospheric CO2 of 1-5 bar) could have existed for a period of about 1 Gyr if the total surficial inventory of CO2 was 2-10 bar.

Pollack, J. B.; Kasting, J. F.; Richardson, S. M.; Poliakoff, K.

1987-08-01

33

El Niño dynamics in the warm Pliocene climate  

NASA Astrophysics Data System (ADS)

A 'permanent' El Niño climate state has been suggested for the warm Pliocene interval, the most recent period similar to what is expected for the twenty-first century. Main piece of evidence of such conditions is the small east-west sea surface temperature (SST) difference that is found in proxy temperature records of the equatorial Pacific Ocean. Using a version of the Zebiak-Cane model for which the tropical Pacific background state is part of the solution, we study the sensitivity of the Pacific background climate and El Niño/Southern Oscillation (ENSO) variability to Pliocene climate changes. The parameters varied in this sensitivity study include changes in the trade wind strength due to a reduced equator-to-pole temperature gradient, higher global mean temperatures and an open Panama gateway. All these changes lead to a westward shift of the position of the cold tongue along the equator by up to 2000 km. This result is consistent with data from the PRISM3D Pliocene SST reconstruction. The associated changes in thermocline tilt across the equatorial Pacific are, however, not uniform and depend on the relative strength of the processes involved. Our model further suggests that ENSO variability is present and similar to today in the Pliocene climate. A background climate that would resemble a 'permanent' El Niño with weak to no east-west temperature difference along the equator is only found for a very weak equator-pole temperature gradient, which seems unrealistic for the Pliocene climate.

von der Heydt, A. S.; Dijkstra, H. A.

2012-04-01

34

Why tropical forest lizards are vulnerable to climate warming  

PubMed Central

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

Huey, Raymond B.; Deutsch, Curtis A.; Tewksbury, Joshua J.; Vitt, Laurie J.; Hertz, Paul E.; Alvarez Perez, Hector J.; Garland, Theodore

2009-01-01

35

The European climate under a 2?°C global warming  

NASA Astrophysics Data System (ADS)

A global warming of 2?°C relative to pre-industrial climate has been considered as a threshold which society should endeavor to remain below, in order to limit the dangerous effects of anthropogenic climate change. The possible changes in regional climate under this target level of global warming have so far not been investigated in detail. Using an ensemble of 15 regional climate simulations downscaling six transient global climate simulations, we identify the respective time periods corresponding to 2?°C global warming, describe the range of projected changes for the European climate for this level of global warming, and investigate the uncertainty across the multi-model ensemble. Robust changes in mean and extreme temperature, precipitation, winds and surface energy budgets are found based on the ensemble of simulations. The results indicate that most of Europe will experience higher warming than the global average. They also reveal strong distributional patterns across Europe, which will be important in subsequent impact assessments and adaptation responses in different countries and regions. For instance, a North-South (West-East) warming gradient is found for summer (winter) along with a general increase in heavy precipitation and summer extreme temperatures. Tying the ensemble analysis to time periods with a prescribed global temperature change rather than fixed time periods allows for the identification of more robust regional patterns of temperature changes due to removal of some of the uncertainty related to the global models’ climate sensitivity.

Vautard, Robert; Gobiet, Andreas; Sobolowski, Stefan; Kjellström, Erik; Stegehuis, Annemiek; Watkiss, Paul; Mendlik, Thomas; Landgren, Oskar; Nikulin, Grigory; Teichmann, Claas; Jacob, Daniela

2014-03-01

36

Estimating the Potential for Adaptation of Corals to Climate Warming  

Microsoft Academic Search

The persistence of tropical coral reefs is threatened by rapidly increasing climate warming, causing a functional breakdown of the obligate symbiosis between corals and their algal photosymbionts (Symbiodinium) through a process known as coral bleaching. Yet the potential of the coral-algal symbiosis to genetically adapt in an evolutionary sense to warming oceans is unknown. Using a quantitative genetics approach, we

Nikolaus B. M. Császár; Peter J. Ralph; Richard Frankham; Ray Berkelmans; Madeleine J. H. van Oppen; Robert Desalle

2010-01-01

37

Climate Warming and Disease Risks for Terrestrial and Marine Biota  

Microsoft Academic Search

Infectious diseases can cause rapid population declines or species extinctions. Many pathogens of terrestrial and marine taxa are sensitive to temperature, rainfall, and humidity, creating synergisms that could affect biodiversity. Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Although most host-parasite systems are predicted to experience more frequent or severe disease impacts with warming,

C. Drew Harvell; Charles E. Mitchell; Jessica R. Ward; Sonia Altizer; Andrew P. Dobson; Richard S. Ostfeld; Michael D. Samuel

2002-01-01

38

Microbial mediation of carbon-cycle feedbacks to climate warming  

NASA Astrophysics Data System (ADS)

Understanding the mechanisms of biospheric feedbacks to climate change is critical to project future climate warming. Although microorganisms catalyse most biosphere processes related to fluxes of greenhouse gases, little is known about the microbial role in regulating future climate change. Integrated metagenomic and functional analyses of a long-term warming experiment in a grassland ecosystem showed that microorganisms play crucial roles in regulating soil carbon dynamics through three primary feedback mechanisms: shifting microbial community composition, which most likely led to the reduced temperature sensitivity of heterotrophic soil respiration; differentially stimulating genes for degrading labile but not recalcitrant carbon so as to maintain long-term soil carbon stability and storage; and enhancing nutrient-cycling processes to promote plant nutrient-use efficiency and hence plant growth. Elucidating microbially mediated feedbacks is fundamental to understanding ecosystem responses to climate warming and provides a mechanistic basis for carbon-climate modelling.

Zhou, Jizhong; Xue, Kai; Xie, Jianping; Deng, Ye; Wu, Liyou; Cheng, Xiaoli; Fei, Shenfeng; Deng, Shiping; He, Zhili; van Nostrand, Joy D.; Luo, Yiqi

2012-02-01

39

Ocean climate and seal condition  

PubMed Central

Background The condition of many marine mammals varies with fluctuations in productivity and food supply in the ocean basin where they forage. Prey is impacted by physical environmental variables such as cyclic warming trends. The weaning weight of northern elephant seal pups, Mirounga angustirostris, being closely linked to maternal condition, indirectly reflects prey availability and foraging success of pregnant females in deep waters of the northeastern Pacific. The aim of this study was to examine the effect of ocean climate on foraging success in this deep-diving marine mammal over the course of three decades, using cohort weaning weight as the principal metric of successful resource accrual. Results The mean annual weaning weight of pups declined from 1975 to the late 1990s, a period characterized by a large-scale, basin-wide warm decadal regime that included multiple strong or long-duration El Niños; and increased with a return to a cool decadal regime from about 1999 to 2004. Increased foraging effort and decreased mass gain of adult females, indicative of reduced foraging success and nutritional stress, were associated with high ocean temperatures. Conclusion Despite ranging widely and foraging deeply in cold waters beyond coastal thermoclines in the northeastern Pacific, elephant seals are impacted significantly by ocean thermal dynamics. Ocean warming redistributes prey decreasing foraging success of females, which in turn leads to lower weaning mass of pups. Annual fluctuations in weaning mass, in turn, reflect the foraging success of females during the year prior to giving birth and signals changes in ocean temperature cycles.

Le Boeuf, Burney J; Crocker, Daniel E

2005-01-01

40

Climate warming and precipitation redistribution modify tree-grass interactions and tree species establishment in a warm-temperate savanna.  

PubMed

Savanna tree-grass interactions may be particularly sensitive to climate change. Establishment of two tree canopy dominants, post oak (Quercus stellata) and eastern redcedar (Juniperus virginiana), grown with the dominant C4 perennial grass (Schizachyrium scoparium) in southern oak savanna of the United States were evaluated under four climatic scenarios for 6 years. Tree-grass interactions were examined with and without warming (+1.5 °C) in combination with a long-term mean rainfall treatment and a modified rainfall regime that redistributed 40% of summer rainfall to spring and fall, intensifying summer drought. The aim was to determine: (1) the relative growth response of these species, (2) potential shifts in the balance of tree-grass interactions, and (3) the trajectory of juniper encroachment into savannas, under these anticipated climatic conditions. Precipitation redistribution reduced relative growth rate (RGR) of trees grown with grass. Warming increased growth of J. virginiana and strongly reduced Q. stellata survival. Tiller numbers of S. scoparium plants were unaffected by warming, but the number of reproductive tillers was increasingly suppressed by intensified drought each year. Growth rates of J. virginiana and Q. stellata were suppressed by grass presence early, but in subsequent years were higher when grown with grass. Quercus stellata had overall reduced RGR, but enhanced survival when grown with grass, while survival of J. virginiana remained near 100% in all treatments. Once trees surpassed a threshold height of 1.1 m, both tiller number and survival of S. scoparium plants were drastically reduced by the presence of J. virginiana, but not Q. stellata. Juniperus virginiana was the only savanna dominant in which neither survival nor final aboveground mass were adversely affected by the climate scenario of warming and intensified summer drought. These responses indicate that climate warming and altered precipitation patterns will further accelerate juniper encroachment and woody thickening in a warm-temperate oak savanna. PMID:23504841

Volder, Astrid; Briske, David D; Tjoelker, Mark G

2013-03-01

41

Robust increase in equilibrium climate sensitivity under global warming  

NASA Astrophysics Data System (ADS)

Equilibrium climate sensitivity (ECS) is a widely accepted measure of Earth's susceptibility to radiative forcing. While ECS is often assumed to be constant to a first order of approximation, recent studies suggested that ECS might depend on the climate state. Here it is shown that the latest generation of climate models consistently exhibits an increasing ECS in warmer climates due to a strengthening of the water-vapor feedback with increasing surface temperatures. The increasing ECS is replicated by a one-dimensional radiative-convective equilibrium model, which further shows that the enhanced water-vapor feedback follows from the rising of the tropopause in a warming climate. This mechanism is potentially important for understanding both warm climates of Earth's past and projections of future high-emission scenarios.

Meraner, Katharina; Mauritsen, Thorsten; Voigt, Aiko

2013-11-01

42

Seasonal Climate Extremes : Mechanism, Predictability and Responses to Global Warming  

NASA Astrophysics Data System (ADS)

Climate extremes are rarely occurring natural phenomena in the climate system. They often pose one of the greatest environmental threats to human and natural systems. Statistical methods are commonly used to investigate characteristics of climate extremes. The fitted statistical properties are often interpolated or extrapolated to give an indication of the likelihood of a certain event within a given period or interval. Under changing climatic conditions, the statistical properties of climate extremes are also changing. It is an important scientific goal to predict how the properties of extreme events change. To achieve this goal, observational and model studies aimed at revealing important features are a necessary prerequisite. Notable progress has been made in understanding mechanisms that influence climate variability and extremes in many parts of the globe including Europe. However, some of the recently observed unprecedented extremes cannot be fully explained from the already identified forcing factors. A better understanding of why these extreme events occur and their sensitivity to certain reinforcing and/or competing factors is useful. Understanding their basic form as well as their temporal variability is also vital and can contribute to global scientific efforts directed at advancing climate prediction capabilities, particularly making skilful forecasts and realistic projections of extremes. In this thesis temperature and precipitation extremes in Europe and Africa, respectively, are investigated. Emphasis is placed on the mechanisms underlying the occurrence of the extremes, their predictability and their likely response to global warming. The focus is on some selected seasons when extremes typically occur. An atmospheric energy budget analysis for the record-breaking European Autumn 2006 event has been carried out with the goal to identify the sources of energy for the extreme event. Net radiational heating is compared to surface turbulent fluxes of energy and dynamic horizontal advection of heat. There is clear evidence that the central North Atlantic Ocean was the major source of energy for the Autumn 2006 extreme event. Within Europe, anomalously high atmospheric water-vapor loading played a significant role through its strong greenhouse effect which resulted in an increase of downwelling infrared flux to the surface. Potential influences and connections between boreal snow cover during the melt season (February--April) and near-surface temperature in the spring season are established. Large amounts of snow act as a precursor to cold spring seasons by altering the coupling between the land and the overlying air through a modification of the surface energy and hydrological processes. In operational numerical models, a snow signal is found to provide some seasonal forecast skill for cold spring seasons in Europe. Changes in the intensity of droughts and floods in Africa in response to global warming are investigated and compared with changes in mean precipitation simulated by an ensemble of climate models selected from the Intergovernmental Panel on Climate Change (IPCC) fourth assessment report (AR4) set. The model simulations are objectively combined using a Bayesian weighting procedure. In southern Africa south of about 15° S, the most robust climate-change signal is a shortening of the main rainfall season. This arises from a delayed onset of seasonal rainfall associated with a reduction in lower-tropospheric moisture advection from the southwestern Indian Ocean. The semi-arid areas closer to the Kalahari desert are projected to become drier, while the wet areas are projected to become wetter. East Africa is projected to get wet in the future climate, much wetter than other regions within the same latitudinal belt. The zonal asymmetry in tropical precipitation increase is associated with a shift towards positive Indian Ocean Zonal Mode (IOZM)-like events via an alteration in the structure of the Eastern Hemisphere Walker circulation.

Shongwe, M. E.

2010-01-01

43

The case for a wet, warm climate on early Mars.  

PubMed

Theoretical arguments are presented in support of the idea that Mars possessed a dense CO2 atmosphere and a wet, warm climate early in its history. Calculations with a one-dimensional radiative-convective climate model indicate that CO2 pressures between 1 and 5 bars would have been required to keep the surface temperature above the freezing point of water early in the planet's history. The higher value corresponds to globally and orbitally averaged conditions and a 30% reduction in solar luminosity; the lower value corresponds to conditions at the equator during perihelion at times of high orbital eccentricity and the same reduced solar luminosity. The plausibility of such a CO2 greenhouse is tested by formulating a simple model of the CO2 geochemical cycle on early Mars. By appropriately scaling the rate of silicate weathering on present Earth, we estimate a weathering time constant of the order of several times 10(7) years for early Mars. Thus, a dense atmosphere could have persisted for a geologically significant time period (approximately 10(9) years) only if atmospheric CO2 was being continuously resupplied. The most likely mechanism by which this might have been accomplished is the thermal decomposition of carbonate rocks induced directly and indirectly (through burial) by intense, global-scale volcanism. For plausible values of the early heat flux, the recycling time constant is also of the order of several times 10(7) years. The amount of CO2 dissolved in standing bodies of water was probably small; thus, the total surficial CO2 inventory required to maintain these conditions was approximately 2 to 10 bars. The amount of CO2 in Mars' atmosphere would eventually have dwindled, and the climate cooled, as the planet's internal heat engine ran down. A test for this theory will be provided by spectroscopic searches for carbonates in Mars' crust. PMID:11539035

Pollack, J B; Kasting, J F; Richardson, S M; Poliakoff, K

1987-01-01

44

Climate change mitigation: Deposing global warming potentials  

NASA Astrophysics Data System (ADS)

Accounting for time-dependent mechanisms in greenhouse gas radiative forcing and evaluating the performance of mitigation technologies in the context of climate stabilization targets can better inform technology choices today and in the future.

Kendall, Alissa

2014-05-01

45

Hydrologic Response and Watershed Sensitivity to Climate Warming in California's Sierra Nevada  

PubMed Central

This study focuses on the differential hydrologic response of individual watersheds to climate warming within the Sierra Nevada mountain region of California. We describe climate warming models for 15 west-slope Sierra Nevada watersheds in California under unimpaired conditions using WEAP21, a weekly one-dimensional rainfall-runoff model. Incremental climate warming alternatives increase air temperature uniformly by 2°, 4°, and 6°C, but leave other climatic variables unchanged from observed values. Results are analyzed for changes in mean annual flow, peak runoff timing, and duration of low flow conditions to highlight which watersheds are most resilient to climate warming within a region, and how individual watersheds may be affected by changes to runoff quantity and timing. Results are compared with current water resources development and ecosystem services in each watershed to gain insight into how regional climate warming may affect water supply, hydropower generation, and montane ecosystems. Overall, watersheds in the northern Sierra Nevada are most vulnerable to decreased mean annual flow, southern-central watersheds are most susceptible to runoff timing changes, and the central portion of the range is most affected by longer periods with low flow conditions. Modeling results suggest the American and Mokelumne Rivers are most vulnerable to all three metrics, and the Kern River is the most resilient, in part from the high elevations of the watershed. Our research seeks to bridge information gaps between climate change modeling and regional management planning, helping to incorporate climate change into the development of regional adaptation strategies for Sierra Nevada watersheds.

Null, Sarah E.; Viers, Joshua H.; Mount, Jeffrey F.

2010-01-01

46

Climate and conflicts: the security risks of global warming  

Microsoft Academic Search

Since the publication of the fourth assessment report of the Intergovernmental Panel on Climate Change in 2007, the securitization\\u000a of global warming has reached a new level. Numerous public statements and a growing research literature have discussed the\\u000a potential security risks and conflicts associated with climate change. This article provides an overview of this debate and\\u000a introduces an assessment framework

Jürgen Scheffran; Antonella Battaglini

2011-01-01

47

Earth's Warming Climate: Are We Responsible?  

NSDL National Science Digital Library

This tutorial provides the evidence that the amount of CO² in the atmosphere has not been as high as it is currently for nearly half a million years and that this increase corresponds with data that human activity is responsible. Learners examine scientific data showing increases in both atmospheric becomes CO² and the Earth's average temperature and analyze changes in atmospheric concentration of CO² over time. They reflect on some of the barriers involved in teaching global climate change and how using data in the classroom may be used to overcome those barriers. Multimedia resources such as video clips, a data visualization exercise featuring digital resources on climate.nasa.gov, and an interview with NASA climate scientist, Dr. Gavin Schmidt, are included. This is the second of ten self-paced professional development modules providing opportunities for teachers to learn about climate change through first-hand data exploration. Lesson plans for middle and high school students, descriptions of data collection instruments, glossary links to vocabulary are included.

48

Climate warming and disease risks for terrestrial and marine biota  

USGS Publications Warehouse

Infectious diseases can cause rapid population declines or species extinctions. Many pathogens of terrestrial and marine taxa are sensitive to temperature, rainfall, and humidity, creating synergisms that could affect biodiversity. Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Although most host-parasite systems are predicted to experience more frequent or severe disease impacts with warming, a subset of pathogens might decline with warming, releasing hosts from disease. Recently, changes in El Niño–Southern Oscillation events have had a detectable influence on marine and terrestrial pathogens, including coral diseases, oyster pathogens, crop pathogens, Rift Valley fever, and human cholera. To improve our ability to predict epidemics in wild populations, it will be necessary to separate the independent and interactive effects of multiple climate drivers on disease impact.

Harvell, C. D.; Mitchell, C. E.; Ward, J. R.; Altizer, S.; Dobson, A. P.; Ostfeld, R. S.; Samuel, M. D.

2002-01-01

49

Seventh grade students' conceptions of global warming and climate change  

Microsoft Academic Search

The purpose of this study was to investigate seventh grade students' conceptions of global warming and climate change. The study was descriptive in nature and involved the collection of qualitative data from 91 seventh grade students from three different schools in the Midwest, USA. An open response and draw and explain assessment instrument was administered to students. These data were

Daniel P. Shepardson; Dev Niyogi; Soyoung Choi; Umarporn Charusombat

2009-01-01

50

Method of warming cold engines in cold climates  

SciTech Connect

This patent describes a method of warming cold engines in low temperature conditions comprising the steps of: (a) placing a flammable compound inside a nonflammable fabric bag; (b) placing the bag on an engine; and (c) igniting the flammable compound.

Forschirm, A.

1988-12-06

51

First tropical warm rain estimates could improve global climate models  

NSDL National Science Digital Library

This study breaks down the type of rainfall in the tropical zones. Microwave images and radar data from the Tropical Rainfall Measuring Mission were examined. It was found that approximately 72 percent of the total rain area and 31 percent of the total rain amount in the tropics comes from warm rain. The relationship between liquid water in a cloud and the rain rate was also measured. Results can be used in climate models to represent convection cycles and their role in global warming.

Lau, William; Wu, H. T.; Agu

52

Quantifying Contributions of Climate Feedbacks to Global Warming Pattern Formation  

NASA Astrophysics Data System (ADS)

The ';';climate feedback-response analysis method'' (CFRAM) was applied to the NCAR CCSM3.0 simulation to analyze the strength and spatial distribution of climate feedbacks and to quantify their contributions to global and regional surface temperature changes in response to a doubling of CO2. Instead of analyzing the climate sensitivity, the CFRAM directly attributes the temperature change to individual radiative and non-radiative feedbacks. The radiative feedback decomposition is based on hourly model output rather than monthly mean data that are commonly used in climate feedback analysis. This gives a more accurate quantification of the cloud and albedo feedbacks. The process-based decomposition of non-radiative feedback enables us to understand the roles of GCM physical and dynamic processes in climate change. The pattern correlation, the centered root-mean-square (RMS) difference and the ratio of variations (represented by standard deviations) between the partial surface temperature change due to each feedback process and the total surface temperature change in CCSM3.0 simulation are examined to quantify the roles of each feedback process in the global warming pattern formation. The contributions of climate feedbacks to the regional warming are also discussed.

Song, X.; Zhang, G. J.; Cai, M.

2013-12-01

53

Climate warming and Bergmann's rule through time: is there any evidence?  

PubMed Central

Climate change is expected to induce many ecological and evolutionary changes. Among these is the hypothesis that climate warming will cause a reduction in body size. This hypothesis stems from Bergmann's rule, a trend whereby species exhibit a smaller body size in warmer climates, and larger body size under colder conditions in endotherms. The mechanisms behind this rule are still debated, and it is not clear whether Bergmann's rule can be extended to predict the effects of climate change through time. We reviewed the primary literature for evidence (i) of a decrease in body size in response to climate warming, (ii) that changing body size is an adaptive response and (iii) that these responses are evolutionary or plastic. We found weak evidence for changes in body size through time as predicted by Bergmann's rule. Only three studies investigated the adaptive nature of these size decreases. Of these, none reported evidence of selection for smaller size or of a genetic basis for the size change, suggesting that size decreases could be due to nonadaptive plasticity in response to changing environmental conditions. More studies are needed before firm conclusions can be drawn about the underlying causes of these changes in body size in response to a warming climate.

Teplitsky, Celine; Millien, Virginie

2014-01-01

54

Cold Climate, Warm Climates: How Can We Tell Past Temperatures?  

NSDL National Science Digital Library

This brief NASA article provides general information about paleoclimatology (the study of past climate). Focusing on ice core data and foraminifera (shelled marine microorganisms) in deep sea sediments, the article provides a summary of how paleoclimate can be inferred.

Schmidt, Gavin; Studies, Nasa G.

55

Insects overshoot the expected upslope shift caused by climate warming.  

PubMed

Along elevational gradients, climate warming may lead to an upslope shift of the lower and upper range margin of organisms. A recent meta-analysis concluded that these shifts are species specific and considerably differ among taxonomic lineages. We used the opportunity to compare upper range margins of five lineages (plants, beetles, flies, hymenoptera, and birds) between 1902-1904 and 2006-2007 within one region (Bavarian Forest, Central Europe). Based on the increase in the regional mean annual temperature during this period and the regional lapse rate, the upslope shift is expected to be between 51 and 201 m. Averaged across species within lineages, the range margin of all animal lineages shifted upslope, but that of plants did not. For animals, the observed shifts were probably due to shifts in temperature and not to changes in habitat conditions. The range margin of plants is therefore apparently not constrained by temperature, a result contrasting recent findings. The mean shift of birds (165 m) was within the predicted range and consistent with a recent global meta-analysis. However, the upslope shift of the three insect lineages (>260 m) exceeded the expected shift even after considering several sources of uncertainty, which indicated a non-linear response to temperature. Our analysis demonstrated broad differences among lineages in their response to climate change even within one region. Furthermore, on the considered scale, the response of ectothermic animals was not consistent with expectations based on shifts in the mean annual temperature. Irrespective of the reasons for the overshooting of the response of the insects, these shifts lead to reorganizations in the composition of assemblages with consequences for ecosystem processes. PMID:23762439

Bässler, Claus; Hothorn, Torsten; Brandl, Roland; Müller, Jörg

2013-01-01

56

High Arctic wetting reduces permafrost carbon feedbacks to climate warming  

NASA Astrophysics Data System (ADS)

The carbon (C) balance of permafrost regions is predicted to be extremely sensitive to climatic changes. Major uncertainties exist in the rate of permafrost thaw and associated C emissions (33-508PgC or 0.04-1.69°C by 2100; refs , ) and plant C uptake. In the High Arctic, semi-deserts retain unique soil-plant-permafrost interactions and heterogeneous soil C pools (>12PgC ref. ). Owing to its coastal proximity, marked changes are expected for High Arctic tundra. With declining summer sea-ice cover, these systems are simultaneously exposed to rising temperatures, increases in precipitation and permafrost degradation. Here we show, using measurements of tundra-atmosphere C fluxes and soil C sources (14C) at a long-term climate change experiment in northwest Greenland, that warming decreased the summer CO2 sink strength of semi-deserts by up to 55%. In contrast, warming combined with wetting increased the CO2 sink strength by an order of magnitude. Further, wetting while relocating recently assimilated plant C into the deep soil decreased old C loss compared with the warming-only treatment. Consequently, the High Arctic has the potential to remain a strong C sink even as the rest of the permafrost region transitions to a net C source as a result of future global warming.

Lupascu, M.; Welker, J. M.; Seibt, U.; Maseyk, K.; Xu, X.; Czimczik, C. I.

2014-01-01

57

Bracketing the Warm Peak Phases of the Middle Pliocene Climate  

Microsoft Academic Search

Estimates of sea surface temperature (SST) from ocean cores reveal a warm phase of the Pliocene between about 3.3 and 3.0 Ma. Pollen records from land-based cores and sections, although not as well-dated, also show evidence for a warmer climate at about the same time. Increased greenhouse forcing and altered ocean heat transports are the leading candidates for the underlying

H. J. Dowsett; M. A. Chandler; G. S. Dwyer; T. M. Cronin

2004-01-01

58

Climate extremes and ecosystem productivity in global warming simulations  

NASA Astrophysics Data System (ADS)

Ecosystem responses to present-day droughts and heat-waves are often considered indicative of future global warming impacts on ecosystems, under the assumption that the temperature above which vegetation experiences heat and drought stress is invariant with changes in climate and carbon dioxide concentration. Understanding how the impacts of temperature extremes on ecosystems can change with climate change is essential for correctly evaluating and developing Earth System Models (ESMs). The Coupled Model Inter-comparison Project (CMIP5) historical and future (RCP8.5) climate predictions were analyzed in this study to illustrate non-stationarity of climate impacts on ecosystems, as evident by changes in the distribution of Gross Primary Production (GPP) as a function of temperature between future and historical climates. These changes consist of (1) a uniform shift in the GPP distribution toward warmer temperatures between future and historical climates, and (2) a proportional increase in GPP at all temperatures, consistent with CO2 fertilization. The temperature at which GPP has a local maximum within a given climate increases with global warming and closely tracks the change in mean temperature for each ecosystem. This maximum GPP temperature can be conceptualized as a stable equilibrium determined by the temperature at which an increase in plant water stress is compensated by a decrease in light stress (decreasing cloud cover) with increasing temperature. Temperature relative to the temperature of maximum GPP is proposed as an improved measure of climate extremes more relevant to ecosystem productivity than absolute temperature. The percentage change in GPP attributed to changes in relative temperature extremes is up to 3% per K (decrease in GPP), and reflects both an increase in the frequency of climate extremes in global warming scenarios and the change in temperature criteria for negative climate impacts on ecosystem productivity. Temperature at GPP maximum as a function of the growing season average temperature, for each ecosystem type. Lengths of crosshairs indicate the standard error of the CMIP5 ensemble average. Both future and historical averages are shown (the temperature of GPP maximum increases monotonically with growing season average temperature between future and historical simulations).

Williams, I. N.; Torn, M. S.; Riley, W. J.; Wehner, M. F.; Collins, W.

2013-12-01

59

Reductions in labour capacity from heat stress under climate warming  

NASA Astrophysics Data System (ADS)

A fundamental aspect of greenhouse-gas-induced warming is a global-scale increase in absolute humidity. Under continued warming, this response has been shown to pose increasingly severe limitations on human activity in tropical and mid-latitudes during peak months of heat stress. One heat-stress metric with broad occupational health applications is wet-bulb globe temperature. We combine wet-bulb globe temperatures from global climate historical reanalysis and Earth System Model (ESM2M) projections with industrial and military guidelines for an acclimated individual's occupational capacity to safely perform sustained labour under environmental heat stress (labour capacity)--here defined as a global population-weighted metric temporally fixed at the 2010 distribution. We estimate that environmental heat stress has reduced labour capacity to 90% in peak months over the past few decades. ESM2M projects labour capacity reduction to 80% in peak months by 2050. Under the highest scenario considered (Representative Concentration Pathway 8.5), ESM2M projects labour capacity reduction to less than 40% by 2200 in peak months, with most tropical and mid-latitudes experiencing extreme climatological heat stress. Uncertainties and caveats associated with these projections include climate sensitivity, climate warming patterns, CO2 emissions, future population distributions, and technological and societal change.

Dunne, John P.; Stouffer, Ronald J.; John, Jasmin G.

2013-06-01

60

The warming hole as an internal climate variability phenomenon  

NASA Astrophysics Data System (ADS)

A potentially outstanding manifestation of the effects of internal variability is the so-called warming hole that extends over the south-eastern United States. In this region no warming trend was detected during most of the 20th century and even a slight cooling was observed in the second half of the century. Although many mechanisms were proposed in the attempt to explain the presence of this peculiar feature (e.g. changes in land use and aerosol emissions), we demonstrate that the warming hole may have at least partly resulted from internal variability temporarily obscuring the warming signal in the region. The role of internal variability is tested using a 21-member ensemble generated by the fully coupled NCAR's Community Earth System Model (CESM) for the period 1950-2100 with slightly perturbed initial conditions. The possibility of simulating the warming hole in the reference period 1960-2004 is investigated by introducing a simple identification criterion based on near-surface temperature changes. Not unexpectedly, the warming hole does not appear in the simulated ensemble average temperature changes but is identified in 6 out of the 21 runs. In a perfect-model approach and assuming correct external forcing, this is suggestive of the fact that the warming hole may occur under particular circumstances due to internal variability. In a second step we explore what modes of variability account for the lack of warming in certain realisations of the model. To this end, a principal component analysis was performed on the set of the 21 simulated mean winter 500hPa geopotential height trend patterns over North America (10-90°N, 170°E-30°W) in the period 1960-2004. The first two EOFs collectively explain approximately 63% of the total variance and are recognised as representative of the time evolution of two different configurations of the Pacific/North American Pattern (PNA). Resorting to a regression method, the temperature trend contribution of this mode is then removed from individual runs, which results in the disappearance of the warming hole in filtered fields. Our experiment thus suggests that internal variability masking the warming signal may account for a large portion of the observed warming hole. In particular, the observed negative temperature trends in the south-eastern United States may have been produced by a long-term positive trend of the Pacific/North American Pattern, shifting towards a positive phase. Such a trend is indeed detectable in observations and is also evident in those model runs featuring a warming hole when looking at the time series of the principal component of the second EOF, associated with the warming hole structure.

Saffioti, Claudio; Fischer, Erich M.; Knutti, Reto

2014-05-01

61

Permafrost carbon-climate feedbacks accelerate global warming  

PubMed Central

Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH4 emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO2 by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO2 fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH4/y to 41–70 Tg CH4/y, with increases due to CO2 fertilization, permafrost thaw, and warming-induced increased CH4 flux densities partially offset by a reduction in wetland extent.

Koven, Charles D.; Ringeval, Bruno; Friedlingstein, Pierre; Ciais, Philippe; Cadule, Patricia; Khvorostyanov, Dmitry; Krinner, Gerhard; Tarnocai, Charles

2011-01-01

62

Foraging by forest ants under experimental climatic warming: a test at two sites  

PubMed Central

Climatic warming is altering the behavior of individuals and the composition of communities. However, recent studies have shown that the impact of warming on ectotherms varies geographically: species at warmer sites where environmental temperatures are closer to their upper critical thermal limits are more likely to be negatively impacted by warming than are species inhabiting relatively cooler sites. We used a large-scale experimental temperature manipulation to warm intact forest ant assemblages in the field and examine the impacts of chronic warming on foraging at a southern (North Carolina) and northern (Massachusetts) site in eastern North America. We examined the influence of temperature on the abundance and recruitment of foragers as well as the number of different species observed foraging. Finally, we examined the relationship between the mean temperature at which a species was found foraging and the critical thermal maximum temperature of that species, relating functional traits to behavior. We found that forager abundance and richness were related to the experimental increase in temperature at the southern site, but not the northern site. Additionally, individual species responded differently to temperature: some species foraged more under warmer conditions, whereas others foraged less. Importantly, these species-specific responses were related to functional traits of species (at least at the Duke Forest site). Species with higher critical thermal maxima had greater forager densities at higher temperatures than did species with lower critical thermal maxima. Our results indicate that while climatic warming may alter patterns of foraging activity in predictable ways, these shifts vary among species and between sites. More southerly sites and species with lower critical thermal maxima are likely to be at greater risk to ongoing climatic warming.

Stuble, Katharine L; Pelini, Shannon L; Diamond, Sarah E; Fowler, David A; Dunn, Robert R; Sanders, Nathan J

2013-01-01

63

Climatic Conditions in Classrooms.  

ERIC Educational Resources Information Center

Presents an overview of research on the ways in which classroom thermal environment, lighting conditions, ion state, and electromagnetic and air pollution affect learning and the performance of students and teachers. (SJL)

Kevan, Simon M.; Howes, John D.

1980-01-01

64

Midlatitude Ocean-Atmosphere Interactions in a Warming Climate  

NASA Astrophysics Data System (ADS)

Recent studies have shown that mid-latitude regions with strong SST gradients as they can be found in the Gulf Stream and it's extension are a key-region for midlatitude ocean-atmosphere interactions; SST variability on inter-annual to decadal timescales in this region has a distinct impact on the overlying atmosphere. Climate projections with coupled general circulation models show strong indications, that the strength and the shape of the ocean circulation might underly crucial changes in a warming climate. This work presents an analysis of the atmospheric part of a long-term (covering the period until 2300) RCP 8.5 scenario run of a coupled general circulation model (MPI-ESM-LR) with focus on the North Atlantic. The ocean component of the model shows a strong decrease in the meridional overturning circulation and a northward-shift of the boundary between the subpolar and the subtropical gyre. This leads to significant changes of the ocean surface conditions in the Gulf Stream and the Gulf Stream extension. The weakened MOC and the northward shift of the SST front leads to a weakening of the SST gradients in the historical Gulf Stream area and a strengthening of the gradients east of Newfoundland. We analysed the impact of the changes in the ocean on precipitation, a quantity which has been shown to be highly sensitive to the position of the SST front and the absolute value of SST in that region in previous studies. In winter the model shows a large region with strongly enhanced precipitation southeast off Newfoundland, likely related to a slight intensification of the North-Atlantic storm track present in the future projection. In summer the most prominent feature in terms of precipitation is a decrease in the region off the US east coast, where the historical control experiment had the strongest SST gradients, but shows weaker gradients in the future. A preliminary analysis of the hydrological cycle gives indications, that the precipitation changes are induced by a combination of (globally) warmer air temperatures enhancing the hydrological cycle and an effect due to shifted ocean surface patterns. Sensitivity experiments with the atmospheric component of the model are being performed to separate and quantify these two effects better.

Hand, Ralf; Keenlyside, Noel S.; Greatbatch, Richard J.; Omrani, Nour-Eddine

2014-05-01

65

The impact of global warming on the range distribution of different climatic groups of Aspidoscelis costata costata.  

PubMed

The ectothermic nature of reptiles makes them especially sensitive to global warming. Although climate change and its implications are a frequent topic of detailed studies, most of these studies are carried out without making a distinction between populations. Here we present the first study of an Aspidoscelis species that evaluates the effects of global warming on its distribution using ecological niche modeling. The aims of our study were (1) to understand whether predicted warmer climatic conditions affect the geographic potential distribution of different climatic groups of Aspidoscelis costata costata and (2) to identify potential altitudinal changes of these groups under global warming. We used the maximum entropy species distribution model (MaxEnt) to project the potential distributions expected for the years 2020, 2050, and 2080 under a single simulated climatic scenario. Our analysis suggests that some climatic groups of Aspidoscelis costata costata will exhibit reductions and in others expansions in their distribution, with potential upward shifts toward higher elevation in response to climate warming. Different climatic groups were revealed in our analysis that subsequently showed heterogeneous responses to climatic change illustrating the complex nature of species geographic responses to environmental change and the importance of modeling climatic or geographic groups and/or populations instead of the entire species' range treated as a homogeneous entity. PMID:23215975

Güizado-Rodríguez, Martha Anahí; Ballesteros-Barrera, Claudia; Casas-Andreu, Gustavo; Barradas-Miranda, Victor Luis; Téllez-Valdés, Oswaldo; Salgado-Ugarte, Isaías Hazarmabeth

2012-12-01

66

Projection of Global Warming using an Empirical Model of Climate  

NASA Astrophysics Data System (ADS)

An empirical model of climate based on multiple linear regression of the century-long global surface temperature record is used to quantify the rise in global average temperature in 2053, the time CO2 reaches 560 ppm (2x pre-industrial) in the RCP 8.5 scenario. This rise in temperature is inherently uncertain due to the cantilevering of aerosol radiative forcing and climate feedback, coupled with the projection that aerosol radiative forcing will diminish in the coming decades due to air quality concerns. We show that, considering this cantilevering, the rise in global temperature at the time CO2 doubles will likely be between 1 and 2 degrees Celsius (relative to a 1961 to 1990 baseline). This empirically driven estimate of future warming is considerably less than projected by CMIP5 models.

Canty, Tim; Hope, Austin; Mascioli, Nora; Salawitch, Ross

2014-05-01

67

The effect of slope aspect on the response of snowpack to climate warming in the Pyrenees  

NASA Astrophysics Data System (ADS)

The aim of this study was to analyse the effect of slope aspect on the response of snowpack to climate warming in the Pyrenees. For this purpose, data available from five automatic weather stations were used to simulate the energy and mass balance of snowpack, assuming different magnitudes of an idealized climate warming (upward shifting of 1, 2 and 3 °C the temperature series). Snow energy and mass balance were simulated using the Cold Regions Hydrological Modelling platform (CRHM). CRHM was used to create a model that enabled correction of the all-wave incoming radiation fluxes from the observation sites for various slope aspects (N, NE, E, SE, S, SW,W,NW and flat areas), which enabled assessment of the differential impact of climate warming on snow processes on mountain slopes. The results showed that slope aspect was responsible for substantial variability in snow accumulation and the duration of the snowpack. Simulated variability markedly increased with warmer temperature conditions. Annual maximum snow accumulation (MSA) and annual snowpack duration (ASD) showed marked sensitivity to a warming of 1 °C. Thus, the sensitivity of the MSA in flat areas ranged from 11 to 17 % per degree C amongst the weather stations, and the ASD ranged from 11 to 20 days per degree C. There was a clear increase in the sensitivity of the snowpack to climate warming on those slopes that received intense solar radiation (S, SE and SW slopes) compared with those slopes where the incident radiation was more limited (N, NE and NW slopes). The sensitivity of the MSA and the ASD increased as the temperature increased, particularly on the most irradiated slopes. Large interannual variability was also observed. Thus, with more snow accumulation and longer duration the sensitivity of the snowpack to temperature decreased, especially on south-facing slopes.

López-Moreno, J. I.; Revuelto, J.; Gilaberte, M.; Morán-Tejeda, E.; Pons, M.; Jover, E.; Esteban, P.; García, C.; Pomeroy, J. W.

2013-09-01

68

Estimated Impacts of Climate Warming on California Water Availability Under Twelve Future Climate Scenarios  

Microsoft Academic Search

Spatially disaggregated estimates of over 131 streamflow, ground water, and reservoir evaporation monthly time series in California have been created for 12 different climate warming scenarios for a 72-year period. Such disaggregated hydrologic estimates of multiple hydrologic cycle components are important for impact and adaptation studies of Californias water system. A statewide trend of increased winter and spring runoff and

Tingju Zhu; Marion W. Jenkins; Jay R. Lund

2005-01-01

69

Implications of global warming for the climate of African rainforests  

PubMed Central

African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions.

James, Rachel; Washington, Richard; Rowell, David P.

2013-01-01

70

Implications of global warming for the climate of African rainforests.  

PubMed

African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions. PMID:23878329

James, Rachel; Washington, Richard; Rowell, David P

2013-01-01

71

Estimating the Potential for Adaptation of Corals to Climate Warming  

PubMed Central

The persistence of tropical coral reefs is threatened by rapidly increasing climate warming, causing a functional breakdown of the obligate symbiosis between corals and their algal photosymbionts (Symbiodinium) through a process known as coral bleaching. Yet the potential of the coral-algal symbiosis to genetically adapt in an evolutionary sense to warming oceans is unknown. Using a quantitative genetics approach, we estimated the proportion of the variance in thermal tolerance traits that has a genetic basis (i.e. heritability) as a proxy for their adaptive potential in the widespread Indo-Pacific reef-building coral Acropora millepora. We chose two physiologically different populations that associate respectively with one thermo-tolerant (Symbiodinium clade D) and one less tolerant symbiont type (Symbiodinium C2). In both symbiont types, pulse amplitude modulated (PAM) fluorometry and high performance liquid chromatography (HPLC) analysis revealed significant heritabilities for traits related to both photosynthesis and photoprotective pigment profile. However, quantitative real-time polymerase chain reaction (qRT-PCR) assays showed a lack of heritability in both coral host populations for their own expression of fundamental stress genes. Coral colony growth, contributed to by both symbiotic partners, displayed heritability. High heritabilities for functional key traits of algal symbionts, along with their short clonal generation time and high population sizes allow for their rapid thermal adaptation. However, the low overall heritability of coral host traits, along with the corals' long generation time, raise concern about the timely adaptation of the coral-algal symbiosis in the face of continued rapid climate warming.

Csaszar, Nikolaus B. M.; Ralph, Peter J.; Frankham, Richard; Berkelmans, Ray; van Oppen, Madeleine J. H.

2010-01-01

72

Anticipated impacts of climate warming on ecosystems in Interior Alaska  

NASA Astrophysics Data System (ADS)

Future climate scenarios predict a roughly 5 degree increase in mean annual air temperatures for the Alaskan Interior over the next 80 years. This is expected to be enough to initiate permafrost degradation in Interior Alaska which could lead to widespread thermokarst and talik development and potentially a thicker seasonally thawed (active) layer. These changes could dramatically affect hydrology, ground surface topography and vegetation. Forecasting ecological responses to climate warming is complicated by many factors including variations in soil type, precipitation, surface and ground water hydrology, vegetation, slope, aspect, fire prevalence, and the thermal state of permafrost. We are making field measurements and time series repeat imagery at upland and lowland landscapes to determine where and what ecosystem processes may be most susceptible for rapid or unpredictable changes with climate warming or changing land use activities. By integrating existing cryospheric (permafrost and snow), hydrologic and vegetation succession modeling capabilities we hope to enhance our ability to predict how climate change and other stressors may affect ecosystem dynamics and fire susceptibility. We will include the effects of non-climate related anthropogenic stressors like changes in land use activities and infrastructure development. Numerous electrical resistivity geophysical measurements have been made across a variety of landscapes to investigate how vegetation, soils, and land use relates to permafrost distribution. Our project results will be synthesized into a spatially-explicit decision support system to assist with land use management decision-making for Interior Alaska. This Geographic Information Systems (GIS)-based tool is being developed through a combination of field work and modeling. We will identify challenges for management activities given the projected ecosystem response to anticipated climate change by the end-of-the century. This presentation will summarize the first year of research results from this multi-agency, multidisciplinary research project. The project team includes more than 20 researchers, collaborators, students and land users that are actively working on this research program. Results will include geophysical measurements of surface soils and permafrost, the first hydrologic measurements across the Tanana Flats lowlands and the glacier fed Jarvis Creek, repeat imagery of landscapes exhibiting change over time, vegetation mapping, and hydrologic and ecosystem simulations.

Douglas, T. A.; Liljedahl, A. K.; Astley, B. N.; Downer, C. W.; Jorgenson, T. T.; Bagley, C.; Burks-Copes, K.

2011-12-01

73

Typhoon and storm surge intensity changes under the warming climate around Korean Peninsula  

NASA Astrophysics Data System (ADS)

This study investigates the intensity change in typhoons and storm surges surrounding the Korean Peninsula under global warming conditions as obtained from the MPI_ECHAM5 climate model using the A1B series. The authors use the Cyclostationary Empirical Orthogonal Function to estimate future background fields for typhoon simulations from twenty-first-century prediction results. A series of numerical experiments applies WRF (Weather Research and Forecasting) and POM (Prinston Ocean Model) models to simulate two historical typhoons, Maemi (2003) and Rusa (2002), and associated storm surges under real historical and future warming conditions. Applying numerical experiments to two typhoons, this study found that their central pressure dropped about 19 and 17 hPa, respectively, when considering the future sea surface temperature (a warming of 3.9 K for 100 years) over the East China Sea (Exp. 1). The associated enhancement of storm surge height ranged from 16 to 67 cm along the southern coast of the Korean Peninsula. However, when the study considered global warming conditions for other atmospheric variables such as sea-level pressure, air temperature, relative humidity, geopotential height, and wind in the typhoon simulations (Exp. 2), the intensities of the two typhoons and their associated surge heights scarcely increased compared to the results of Exp. 1. Analyzing projected atmospheric variables, the authors found that air temperatures at the top of the storm around 200 hPa increased more than those at the surface in tropical and mid-latitudes. The reduced vertical temperature difference provided an unfavorable condition in the typhoon's development even under conditions of global warming. This suggests that global warming may not always correlate with a large increase in the number of intense cyclones and/or an increase in associated storm surges.

Oh, Sang Myeong; Moon, Il-Ju

2014-05-01

74

Elevated CO2 further lengthens growing season under warming conditions.  

PubMed

Observations of a longer growing season through earlier plant growth in temperate to polar regions have been thought to be a response to climate warming. However, data from experimental warming studies indicate that many species that initiate leaf growth and flowering earlier also reach seed maturation and senesce earlier, shortening their active and reproductive periods. A conceptual model to explain this apparent contradiction, and an analysis of the effect of elevated CO2--which can delay annual life cycle events--on changing season length, have not been tested. Here we show that experimental warming in a temperate grassland led to a longer growing season through earlier leaf emergence by the first species to leaf, often a grass, and constant or delayed senescence by other species that were the last to senesce, supporting the conceptual model. Elevated CO2 further extended growing, but not reproductive, season length in the warmed grassland by conserving water, which enabled most species to remain active longer. Our results suggest that a longer growing season, especially in years or biomes where water is a limiting factor, is not due to warming alone, but also to higher atmospheric CO2 concentrations that extend the active period of plant annual life cycles. PMID:24759322

Reyes-Fox, Melissa; Steltzer, Heidi; Trlica, M J; McMaster, Gregory S; Andales, Allan A; LeCain, Dan R; Morgan, Jack A

2014-06-12

75

Biogeochemical characteristics of Siberia's Kolyma River watershed in relation to climate warming and permafrost degradation  

NASA Astrophysics Data System (ADS)

The Kolyma River in northeast Siberia, one of the six largest rivers entering the Arctic Ocean, is draining a region experiencing significant climate warming and is expected to undergo ever further warming over the coming century. The Kolyma River watershed is underlain with vast deposits of Pleistocene-aged loess known as Yedoma, which is associated with ice-rich continuous permafrost and organic carbon-rich soils. When these Yedoma permafrost soils thaw under warming conditions, carbon can be released to the atmosphere as CH4 and CO2, but also to nearby lakes, streams, and rivers as dissolved organic carbon (DOC). In July 2008, we conducted a survey of the Kolyma watershed to describe biogeochemical characteristics of water in streams and rivers draining a diverse set of subwatersheds, as well as longitudinal patterns in the Kolyma mainstem itself. Forty-two water samples were analyzed for pH, conductivity, dissolved oxygen (DO), and UV light absorbance at 254 nm (UV-254; a proxy for DOC concentrations and characteristics). We focus here primarily on UV-254, as the processing and transport of DOC in streams and rivers under a warming climate in this region may have globally significant implications for carbon cycling. GIS analyses show that UV-254 is dependent upon watershed area and land cover type (e.g., tundra, forested upland, or wetland), where UV-254 (and thereby DOC concentration) is higher in smaller, wetland- dominated watersheds. Overall, we find clear spatial variation in UV-254 of waters throughout the Kolyma River watershed, indicating that variability in watershed characteristics and location in the landscape strongly impact DOC concentrations and characteristics. Establishing these relationships is critical for predicting how future climate warming may ultimately impact the flux of DOC to the Arctic Ocean. This study is the result of an undergraduate field experience called The Polaris Project (www.thepolarisproject.org), which will continue through the summers of 2009 and 2010.

Willis, K. S.; Abbott, K. R.; Bulygina, E.; Frey, K. E.; Holmes, R. M.; Schade, J. D.

2008-12-01

76

Modeling Multi-Reservoir Hydropower Systems in the Sierra Nevada with Environmental Requirements and Climate Warming  

NASA Astrophysics Data System (ADS)

Hydropower systems and other river regulation often harm instream ecosystems, partly by altering the natural flow and temperature regimes that ecosystems have historically depended on. These effects are compounded at regional scales. As hydropower and ecosystems are increasingly valued globally due to growing values for clean energy and native species as well as and new threats from climate warming, it is important to understand how climate warming might affect these systems, to identify tradeoffs between different water uses for different climate conditions, and to identify promising water management solutions. This research uses traditional simulation and optimization to explore these issues in California's upper west slope Sierra Nevada mountains. The Sierra Nevada provides most of the water for California's vast water supply system, supporting high-elevation hydropower generation, ecosystems, recreation, and some local municipal and agricultural water supply along the way. However, regional climate warming is expected to reduce snowmelt and shift runoff to earlier in the year, affecting all water uses. This dissertation begins by reviewing important literature related to the broader motivations of this study, including river regulation, freshwater conservation, and climate change. It then describes three substantial studies. First, a weekly time step water resources management model spanning the Feather River watershed in the north to the Kern River watershed in the south is developed. The model, which uses the Water Evaluation And Planning System (WEAP), includes reservoirs, run-of-river hydropower, variable head hydropower, water supply demand, and instream flow requirements. The model is applied with a runoff dataset that considers regional air temperature increases of 0, 2, 4 and 6 °C to represent historical, near-term, mid-term and far-term (end-of-century) warming. Most major hydropower turbine flows are simulated well. Reservoir storage is also generally well simulated, mostly limited by the accuracy of inflow hydrology. System-wide hydropower generation is reduced by 9% with 6 °C warming. Most reductions in hydropower generation occur in the highly productive watersheds in the northern Sierra Nevada. The central Sierra Nevada sees less reduction in annual runoff and can adapt better to changes in runoff timing. Generation in southern watersheds is expected to decrease. System-wide, reservoirs adapt to capture earlier runoff, but mostly decrease in mean reservoir storage with warming due to decreasing annual runoff. Second, a multi-reservoir optimization model is developed using linear programming that considers the minimum instream flows (MIFs) and weekly down ramp rates (DRRs) in the Upper Yuba River in the northern Sierra Nevada. Weekly DRR constraints are used to mimic spring snowmelt flows, which are particularly important for downstream ecosystems in the Sierra Nevada but are currently missing due to the influence of dams. Trade-offs between MIFs, DRRs and hydropower are explored with air temperature warming (+0, 2, 4 and 6 °C). Under base case operations, mean annual hydropower generation increases slightly with 2 °C warming and decreases slightly with 6 °C warming. With 6 °C warming, the most ecologically beneficial MIF and DRR reduce hydropower generation 5.5% compared to base case operations and a historical climate, which has important implications for re-licensing the hydropower project. Finally, reservoir management for downstream temperatures is explored using a linear programming model to optimally release water from a reservoir using selective withdrawal. The objective function is to minimize deviations from desired downstream temperatures, which are specified to mimic the natural temperature regime in the river. One objective of this study was to develop a method that can be readily integrated into a basin-scale multi-reservoir optimization model using a network representation of system features. The second objective was to explore the potential use of reservoirs to maintain an ideal str

Rheinheimer, David Emmanuel

77

The case for a wet, warm climate on early Mars  

NASA Technical Reports Server (NTRS)

Arguments are presented in support of the idea that Mars possessed a dense CO2 atmosphere and a wet, warm climate early in its history. The plausibility of a CO2 greenhouse is tested by formulating a simple model of the CO2 geochemical cycle on early Mars. By scaling the rate of silicate weathering on Earth, researchers estimated a weathering time constant of the order of several times 10 to the 7th power years for early Mars. Thus, a dense atmosphere could have existed for a geologically significant time period (approx. 10 to the 9th power years) only if atmospheric CO2 was being continuously resupplied. The most likely mechanism by which this could have been accomplished is the thermal decomposition of carbonate rocks induced directly or indirectly by intense, global scale volcanism.

Pollack, J. B.; Kasting, J. F.; Richardson, S. M.; Poliakoff, K.

1987-01-01

78

Unexpected response of high Alpine Lake waters to climate warming.  

PubMed

Over the past two decades, we have observed a substantial rise in solute concentration at two remote high mountain lakes in catchments of metamorphic rocks in the European Alps. At Rasass See, the electrical conductivity increased 18-fold. Unexpectedly high nickel concentrations at Rasass See, which exceeded the limit in drinking water by more than 1 order of magnitude, cannot be related to catchment geology. We attribute these changes in lake water quality to solute release from the ice of an active rock glacier in the catchment as a response to climate warming. Similar processes occurred at the higher elevation lake Schwarzsee ob Sölden, where electrical conductivity has risen 3-fold during the past two decades. PMID:18044521

Thies, Hansjörg; Nickus, Ulrike; Mair, Volkmar; Tessadri, Richard; Tait, Danilo; Thaler, Bertha; Psenner, Roland

2007-11-01

79

Climatic warming increases voltinism in European butterflies and moths  

PubMed Central

Climate change is altering geographical ranges, population dynamics and phenologies of many organisms. For ectotherms, increased ambient temperatures frequently have direct consequences for metabolic rates, activity patterns and developmental rates. Consequently, in many insect species both an earlier beginning and prolongation of seasonal duration occurred in parallel with recent global warming. However, from an ecological and evolutionary perspective, the number of generations (voltinism) and investment into each generation may be even more important than seasonality, since an additional generation per unit time may accelerate population growth or adaptation. Using a dataset extending back to the mid-nineteenth century, I report changes in the voltinism of butterfly and moth species of Central Europe. A significant proportion of 263 multi-voltine species showed augmented frequency of second and subsequent generations relative to the first generation in a warm period since 1980, and 44 species even increased the number of generations after 1980. Expected ecological consequences are diverse. Since multi-voltinism has been linked to insect outbreaks they include an increase in the abundance of herbivorous pests of agriculture and forestry. However, disruption of the developmental synchrony associated with multi-voltinism and host plant phenology may also reduce fitness, potentially having unexpected consequences for species of conservation concern. The ability of species to adapt evolutionarily to a changing environment may be facilitated by increased voltinism.

Altermatt, Florian

2010-01-01

80

Declining ocean anoxia in a warming climate (Invited)  

NASA Astrophysics Data System (ADS)

The warming of Earth's climate is expected to lead to a loss of oceanic dissolved oxygen, an important constraint on marine species habitat. The mechanisms underlying this so-called deoxygenation are that dissolved gases are less soluble in warmer waters, and the rate at which O2-rich surface water is circulated into the low-O2 interior ocean is also reduced due to increased thermal stratification. Here we show that a robust prediction of state-of-the-art Earth System Models is that in the oxygen minimum zone of the tropical thermocline, oxygen concentrations are relatively stable or even increasing in a warming climate. The tropical immunity to deoxygenation arises because the lower solubility of O2 is closely compensated by a reduced upwelling at the equator, which slows the rate of biological productivity at the surface and the bacterial oxygen demand in deeper waters. The reduction of nutrient supply to the surface ocean is driven not by stratification but by a weakening of the tropical trade winds. However it can also be viewed as a necessary consequence of the reduced ventilation in mid-latitudes, arising from the conservation of mass and the close coupling of nutrient and oxygen cycles. On centennial time scales, these dynamics are predicted to lead to a reduction of anoxia in the ocean, even while oxygen is steadily declining globally. Evidence from sediment cores along the North American margin suggest a gradual reduction in 20th century denitrification, and support the wind-driven mechanism predicted by Earth System Models.

Deutsch, C. A.; Ito, T.; van Geen, A.; Berelson, W.; Thunell, R.

2013-12-01

81

Rapid micro-evolution and loss of chromosomal diversity in Drosophila in response to climate warming  

Microsoft Academic Search

Concern regarding the ecological impact of rapid global warming has encouraged research on climate-induced changes in biological systems. Critical problems, still poorly understood, are the potential for rapid adaptive responses and their genetic costs to populations. The O chromosomal polymorphisms of Drosophila subobscura have been monitored at a southern Palearctic locality experiencing sustained climate warming since the mid-1970s. Observations suggest

Francisco Rodríguez-Trelles; Miguel A. Rodríguez

1998-01-01

82

Thermodynamical constraints on the meridional overturning circulation in warming climates  

NASA Astrophysics Data System (ADS)

In midlatitudes of present-day climate, the circulation averaged on moist isentropes is twice as strong as the circulation averaged on dry isentropes (Pauluis et al., 2010, J. Clim.). In the A1B climate scenario, Laliberte and Pauluis (2010, GRL) showed that the winter moist circulation strengthens with respect to the dry circulation, indicating that the latent heat component of the circulation increases at the expense of the sensible heat component. Climate modeling studies covering a wide range of surface temperatures support this observation and show that the overturning circulation attains a maximum and then weakens as surface temperatures rise (Caballero and Langen, 2005, GRL; Rose and Ferreira, 2012, J. Clim). The latent heat component of the circulation therefore cannot increase indefinitely with rising surface temperatures, indicating that a thermodynamical constraint might determine the maximum relative strength of the moist and dry circulations circulation attainable in warmer climates. Here, such a constraint is derived using a theoretical model describing the structure of the dry and moist isentropic circulations in the lower troposphere. The model decomposes the meridional flow in the troposphere into three contributions: a dry equatorward flow; a cold/moist equatorward flow; and a warm/moist poleward flow in the mixed layer. It is based on the joint distribution of meridional mass fluxes in potential temperature and equivalent potential temperature. It updates an existing model of the dry circulation by emphasizing the role of moisture in the mixed layer. The model is used to derive an expression for the ratio of moist to dry circulations strengths, which is used to assess the influence of surface thermodynamics on the circulations. This expression indicates that while an increase in the total heat fluxes occurs when surface temperature variability increases (via an increase in latent heat flux), it cannot increase indefinitely.

Laliberté, F. B.; Shaw, T. A.; Pauluis, O. M.; Kushner, P. J.

2012-12-01

83

Impacts of climate warming on vegetation in Qaidam Area from 1990 to 2003.  

PubMed

The observed warming trend in the Qaidam area, an arid basin surrounded by high mountains, has caused land surface dynamics that are detectable using remotely sensed data. In this paper, we detected land-cover changes in the Qaidam Area between 1990 and 2003 in attempt to depict its spatial variability. The land-cover changes were categorized into two trends: degradation and amelioration, and their spatial patterns were examined. Then we estimated the correlation coefficients between growing-season NDVI and several climatic factors with the consideration of duration and lagging effects. The results show that the inter-annual NDVI variations are positively correlated with May to July precipitations, but not significantly correlated with sunshine duration. We observed no obvious trend in precipitation or sunshine duration from 1990 to 2003. Thus, the authors suggest that their slight fluctuations may not be responsible to the decade-scaled land-cover changes. However, our results indicate a good positive relationship between the NDVI trend and climate warming in the ameliorated areas, but a negative one in the degraded areas. By statistical analyses, we found that degradations mainly occurred at the oasis boundaries and at lower elevations in the non-oasis regions where effective soil moisture might have been reduced by the warming-caused increase in evapotranspiration. At higher elevations where thermal condition acts as a major limiting factor, ameliorations were unequivocally detected, which is attributable to the direct facilitation by temperature increases. We suggest that the impacts of the observed climate warming on vegetation are spatially heterogeneous, depending on the combinations of thermal condition and moisture availability. PMID:17965943

Zeng, Biao; Yang, Tai-Bao

2008-09-01

84

Changes in ecologically critical terrestrial climate conditions.  

PubMed

Terrestrial ecosystems have encountered substantial warming over the past century, with temperatures increasing about twice as rapidly over land as over the oceans. Here, we review the likelihood of continued changes in terrestrial climate, including analyses of the Coupled Model Intercomparison Project global climate model ensemble. Inertia toward continued emissions creates potential 21st-century global warming that is comparable in magnitude to that of the largest global changes in the past 65 million years but is orders of magnitude more rapid. The rate of warming implies a velocity of climate change and required range shifts of up to several kilometers per year, raising the prospect of daunting challenges for ecosystems, especially in the context of extensive land use and degradation, changes in frequency and severity of extreme events, and interactions with other stresses. PMID:23908225

Diffenbaugh, Noah S; Field, Christopher B

2013-08-01

85

An explanation for the difference between twentieth and twenty-first century land-sea warming ratio in climate models  

NASA Astrophysics Data System (ADS)

A land-sea surface warming ratio (or ?) that exceeds unity is a robust feature of both observed and modelled climate change. Interestingly, though climate models have differing values for ?, it remains almost time-invariant for a wide range of twenty-first century climate transient warming scenarios, while varying in simulations of the twentieth century. Here, we present an explanation for time-invariant land-sea warming ratio that applies if three conditions on radiative forcing are met: first, spatial variations in the climate forcing must be sufficiently small that the lower free troposphere warms evenly over land and ocean; second, the temperature response must not be large enough to change the global circulation to zeroth order; third, the temperature response must not be large enough to modify the boundary layer amplification mechanisms that contribute to making ? exceed unity. Projected temperature changes over this century are too small to breach the latter two conditions. Hence, the mechanism appears to show why both twenty-first century and time-invariant CO2 forcing lead to similar values of ? in climate models despite the presence of transient ocean heat uptake, whereas twentieth century forcing—which has a significant spatially confined anthropogenic tropospheric aerosol component that breaches the first condition—leads to modelled values of ? that vary widely amongst models and in time. Our results suggest an explanation for the behaviour of ? when climate is forced by other regionally confined forcing scenarios such as geo-engineered changes to oceanic clouds. Our results show how land-sea contrasts in surface and boundary layer characteristics act in tandem to produce the land-sea surface warming contrast.

Joshi, M. M.; Lambert, F. H.; Webb, M. J.

2013-10-01

86

Greenland soil bacteria & biogeochemistry: a vegetation cover proxy for climate warming effects  

NASA Astrophysics Data System (ADS)

Climate warming in the high Arctic is expected to increase plant biomass, deepen thaw, and stimulate decomposition of soil organic matter. However, it remains unclear how warming, plant growth, and microbial processing will interact to drive Arctic carbon and nutrient cycling. For example, greater plant growth should increase carbon storage in the ecosystem; however, increasing plant C inputs and thawing permafrost carbon should stimulate microbial biomass, potentially causing soil respiration to outpace storage. Alternatively, greater plant cover may lower soil temperature through shading, potentially curtailing the predicted increase in microbial activity. To evaluate microbial responses to climate warming in the high Arctic, we characterized the soil bacterial community and related soil biogeochemical properties, including pH, temperature, moisture, bulk density, extractable nutrient pools, extractable organic carbon and nitrogen, and total microbial biomass along a vegetation cover gradient in northwest Greenland. Vegetation cover was classified using the Normalized Difference Vegetation Index (NDVI), and vegetation cover classes were used as a proxy for changes associated with warming. We found that soil moisture increased and soil temperature decreased significantly with vegetation cover; moisture and temperature were higher in organic than in mineral horizons. Extractable nutrients (NO3-, NH4+, PO43-) and extractable organic C and N generally increased with vegetation cover and are higher in organic than in mineral horizons within a given vegetation class, with the exception of NO3-, which was comparable between horizons. Despite increases in available carbon and nutrients, microbial biomass carbon in both horizons ultimately decreased with vegetation cover, as did microbial biomass nitrogen in the mineral horizon. Moreover, the relative proportion of microbial biomass carbon to extractable organic carbon decreased with vegetation cover, indicating that decomposers in more vegetated soils do not readily use available carbon. Our results suggest that despite an increase in available substrate in high vegetation cover soils, the insulating properties of vegetation ultimately limit decomposer activity. We hypothesize that as plant cover in the high Arctic increases with climate warming, nutrient mineralization - initially heightened by higher temperatures - will ultimately be curtailed by the insulating properties of vegetation, leading to decreased nutrient availability to plants and a decline in plant cover until soils warm and dry to reach conditions more optimal for microbial processing. Following oscillations between higher and lower vegetation cover, soils may ultimately return to a 'baseline' moderate vegetation cover.

Dowdy, K. L.; Sistla, S.; Buckeridge, K. M.; Schimel, J.; Schaeffer, S. M.

2013-12-01

87

Projection of Summer Climate on Tokyo Metropolitan Area using Pseudo Global Warming Method  

NASA Astrophysics Data System (ADS)

Recent surface air temperature observations in most of urban areas show the remarkable increasing trend affected by the global warming and the heat island effects. There are many populous areas in Japan. In such areas, the effects of land-use change and urbanization on the local climate are not negligible (Fujibe, 2010). The heat stress for citizen there is concerned to swell moreover in the future. Therefore, spatially detailed climate projection is required for making adaptation and mitigation plans. This study focuses on the Tokyo metropolitan area (TMA) in summer and aims to estimate the local climate change over the TMA in 2070s using a regional climate model. The Regional Atmospheric Modeling System (RAMS) was used for downscaling. A single layer urban canopy model (Kusaka et al., 2001) is built into RAMS as a parameterization expressing the features of urban surface. We performed two experiments for estimating present and future climate. In the present climate simulation, the initial and boundary conditions for RAMS are provided from the JRA-25/JCDAS. On the other hand, the Pseudo Global Warming (PGW) method (Sato et al., 2007) is applied to estimate the future climate, instead of the conventional dynamical downscaling method. The PGW method is expected to reduce the model biases in the future projection estimated by Atmosphere-Ocean General Circulation Models (AOGCM). The boundary conditions used in the PGW method is given by the PGW data, which are obtained by adding the climate monthly difference between 1990s and 2070s estimated by AOGCMs to the 6-hourly reanalysis data. In addition, the uncertainty in the regional climate projection depending on the AOGCM projections is estimated from additional downscaling experiments using the different PGW data obtained from five AOGCMs. Acknowledgment: This work was supported by the Global Environment Research Fund (S-5-3) of the Ministry of the Environment, Japan. References: 1. Fujibe, F., Int. J. Climatol., doi:10.1002/joc.2142 (2010). 2. Kusaka, H., H. Kondo, Y. Kikegawa, and F. Kimura, Bound.-Layer Meteor., 101, 329-358 (2001). 3. Sato, T., F. Kimura, and A. Kitoh, J. Hydrology, 144-154 (2007).

Adachi, S. A.; Kimura, F.; Kusaka, H.; Hara, M.

2010-12-01

88

Reconstruction of spatial patterns of climatic anomalies during the medieval warm period (AD 900-1300).  

National Technical Information Service (NTIS)

The workshop will focus on climatic variations during the Medieval Warm Period or Little Climatic Optimum. The nominal time interval assigned to this period is AD 900--1300, but climate information available during the century or two preceding and followi...

H. F. Diaz M. K. Hughes

1992-01-01

89

The acoustical performance of building facades designed for warm and humid climates  

NASA Astrophysics Data System (ADS)

The effects of noise on man are known to range from simple nuisances to illnesses and trauma. Studies of acoustic isolation provided by buildings in urban centers assume that external openings such as windows and doors remain closed. However, this paper presents results of a study of the acoustic isolation of airborne noise for different types of facade construction in the city of Belen, Brazil. The study recognizes that windows and doors are opened as a function of the local climatic conditions since the city is located in a warm and humid tropical area. The purpose of the investigation is to provide information to planners so that they can better control acoustic contamination of buildings located in these kinds of climates. It is concluded that acoustic isolation is affected by the facade construction and by openings in the facade.

Lobato de Moraes, Elcione Maria

2002-11-01

90

Total environmental warming impact (TEWI) calculations for alternative automative air-conditioning systems  

SciTech Connect

The Montreal Protocol phase-out of chlorofluorocarbons (CFCs) has required manufacturers to develop refrigeration and air-conditioning systems that use refrigerants that can not damage stratospheric ozone. Most refrigeration industries have adapted their designs to use hydrochlorofluorocarbon (HCFC) or hydrofluorocarbon (HFC) refrigerants; new automobile air- conditioning systems use HFC-134a. These industries are now being affected by scientific investigations of greenhouse warming and questions about the effects of refrigerants on global warming. Automobile air-conditioning has three separate impacts on global warming; (1) the effects of refrigerant inadvertently released to the atmosphere from accidents, servicing, and leakage; (2) the efficiency of the cooling equipment (due to the emission of C0{sub 2} from burning fuel to power the system); and (3) the emission of C0{sub 2} from burning fuel to transport the system. The Total Equivalent Warming Impact (TEWI) is an index that should be used to compare the global warming effects of alternative air-conditioning systems because it includes these contributions from the refrigerant, cooling efficiency, and weight. This paper compares the TEWI of current air-conditioning systems using HFC-134a with that of transcritical vapor compression system using carbon dioxide and systems using flammable refrigerants with secondary heat transfer loops. Results are found to depend on both climate and projected efficiency of C0{sub 2}systems. Performance data on manufacturing prototype systems are needed to verify the potential reductions in TEWI. Extensive field testing is also required to determine the performance, reliability, and ``serviceability`` of each alternative to HFC-134a to establish whether the potential reduction of TEWI can be achieved in a viable consumer product.

Sand, J.R.; Fischer, S.K.

1997-01-01

91

Effects Of Climate, Permafrost And Fire On Potential Vegetation Change In Siberia In A Warming Climate  

NASA Astrophysics Data System (ADS)

Observations and general circulation model projections suggest significant temperature increases in Siberia this century, which are expected to have profound effects on Siberian vegetation. Increased permafrost melt and forest fire directly affected by climate warming are predicted to additionally influence vegetation change. Our goal is to model potential vegetation change across Siberia (within the territory between the Urals and Yakutia and between the southern border of Russia and the Arctic ocean) using several Hadley Center climate change scenarios for 2020, 2050 and 2080, with explicit consideration of permafrost and fire activity. To predict vegetation change, we use SiBCliM, our Siberian BioClimatic Model, an envelope-type model that predicts a vegetation type from three climatic indices: growing degree days, base 5oC; negative degree days below 0oC; and annual moisture index (a ratio between growing degree days and annual precipitation). All vegetation predictions are corrected for the influence of climate on permafrost active layer depth. Potential fire danger is evaluated using a regression model that relates the annual number of high fire danger days (Nesterov index is 4000-10000) to annual moisture index. Shifts in the climate necessary to support current Siberian vegetation are notable by 2020. Biomes and major tree species are predicted to shift northwards as far as 600-1000 km by 2080. Forest-steppe and steppe ecosystems rather than forests are predicted to dominate over half of Siberia due to the dryer climate. Despite the large predicted increases in warming, permafrost is not predicted to thaw deep enough to sustain dark taiga. Over eastern Siberia, larch (Larix dahurica) taiga is predicted to continue to be the dominant zonobiome because of their ability to withstand continuous permafrost. Our model also predicts new temperate broadleaf and forest-steppe habitats by 2080. Fire danger is predicted to increase by 2080, especially in southern Siberia, where wildland fires would promote habitats for steppe and forest-steppe. Melting permafrost and fire are the principal mechanisms that facilitate vegetation change, which leads to a new equilibrium between vegetation and climate across Siberia.

Tchebakova, N. M.; Parfenova, E. I.; Soja, A. J.

2008-12-01

92

Warming experiments under-predict plant phenological responses to climate change  

NASA Astrophysics Data System (ADS)

Experimental warming studies in natural communities have become an increasingly common method to estimate plant responses to global climate change. Many of these efforts focus on plant species' phenology-a sensitive indicator of species responses to climate-and show advances in spring timing with increasing temperatures. To be useful, however, results from warming experiments should match responses to climate change observed in unmanipulated plant communities, including the responses due to anthropogenic warming that has already occurred. Here we present a comprehensive synthesis of phenological responses to climate change for both experiments and long-term monitoring of natural plant communities. By comparing 14 long-term monitoring datasets with 36 experimental warming studies spanning four continents and 1560 species, we estimate that warming experiments underpredict, by 8.2 and 4.6X (for flowering and leafing, respectively), plant responses to warming when compared to long-term observations. The warming experiments also failed to reproduce the greater temperature sensitivity observed in populations of wild species that flower early in the spring. Further, when considering species for which we had data from both study-types, experiments failed to predict both the magnitude and direction of phenological responses. Among these species, warming experiments predicted a delay of flowering, not the well-documented advance that has tracked recent warming in the observational records. This discrepancy appears unrelated to study length and degree of warming, Instead a number of known artifacts associated with warming experiments could lead to underestimated plant sensitivities. We recommend ways in which the design, documentation and analysis of future experimental and observational studies can be improved to estimate and to predict more accurately plant phenological responses to climate change.

Wolkovich, E. M.; Cook, B. I.; Allen, J.; Crimmins, T. M.; Travers, S.; Pau, S.; Cleland, E. E.

2011-12-01

93

Effect of a fibromyalgia rehabilitation programme in warm versus cold climate: A randomized controlled study.  

PubMed

Objective: To study the long-term effects on symptoms and physical function of a 4-week rehabilitation programme for patients with fibromyalgia, and to determine whether there are any differences if this programme is applied in a warm or cold climate. Methods: A total of 132 patients with fibromyalgia were randomized to a rehabilitation programme in a warm or cold climate, or to a control group without intervention. Assessments were performed before and after intervention, and after 3 and 12 months. The main outcome measures were pain, measured by tender point count (TPC), and physical function, measured with the 6-min walk test (6MWT). Results: There was no difference in any outcome variables at baseline. Persistent reduction in pain measured by TPC occurred only in the warm climatic setting. Mean difference (95% confidence interval (CI)) in TPC between warm and cold climate groups 1 year after the intervention was -1.7 (-2.9 to -0.5) and between the warm climate and the control group -2.2 (-3.3 to -1.0). Three months after the intervention the mean difference between the warm and cold climate groups in pain distribution (McGill mannequin) was -12 (-20 to -5) and between the warm climate and the control group -11 (-18 to -3). There were comparable improvements in physical function (6MWT) between the 2 intervention groups and the control group. The mean difference (95% CI) in 6MWT 1 year after the intervention between the warm climate and the control group was 33 (7-59) m. The corresponding value between the cold climate and the control group was 29 (3-55) m. Grip Strength (95% CI) was increased by 4.6 kg (2.3-6.4) in the warm climate and by 3.2 kg (0.9-5.5) in the cold climate compared with the control group 1 year after the intervention. Conclusion: A rehabilitation programme for fibromyalgia may have a long-term effect on pain, as measured by TPC and pain distribution, when applied in a warm climatic setting, and may improve physical function regardless of the climatic setting. PMID:24788929

Clarke-Jenssen, Anne-Cathrine; Mengshoel, Anne Marit; Strumse, Yndis Staalesen; Forseth, Karin Oien

2014-06-25

94

How do weather characteristics change in a warming climate?  

NASA Astrophysics Data System (ADS)

The possible change in the characteristics of weather in the future should be considered as important as the mean climate change because the increasing risk of extremes is related to the variability on daily time scales. The weather characteristics can be represented by the climatological mean interdiurnal (day-to-day) variability (MIDV). This paper first assessed the phase five of the Coupled Model Intercomparison Project coupled climate models' capability to represent MIDV for the surface maximum and minimum temperature, surface wind speed and precipitation under the present climate condition. Based on the assessment, we selected three best models for projecting future change. We found that the future changes in MIDV are characterized by: (a) a marked reduction in surface maximum and minimum temperature over high latitudes during the cold season; (b) a stronger reduction in the surface minimum temperature than in the maximum temperature; (c) a reduction in surface wind speed over large parts of lands in Northern Hemisphere (NH) during NH spring; (d) a noticeable increase in precipitation in NH mid-high latitudes in NH spring and winter, and in particular over East Asia throughout most of the year.

Kim, Ok-Yeon; Wang, Bin; Shin, Sun-Hee

2013-12-01

95

Observed climate change constrains the likelihood of extreme future global warming  

Microsoft Academic Search

If cooling due to present-day levels of atmospheric aerosol is suppressing global temperatures, future reductions in aerosols emissions would allow the full greenhouse gas induced warming to be realised. The many uncertainties in aerosol physics and chemistry mean that a large range of present-day aerosol cooling is possible which could imply a large climate sensitivity, extremely large future warming and

Peter A. Stott; Chris Huntingford; Chris D. Jones; Jamie A. Kettleborough

2008-01-01

96

The Response of A Coupled Climate Model To Transient Fluxes From A Global Warming Experiment  

Microsoft Academic Search

The response of the UVic Earth System Climate Model to forcing from a global warm- ing run is investigated. Four additional transient experiments were performed to look at the relative contribution of fresh water and heat fluxes. The experiments consisted of prescribing freshwater fluxes, either above or below the sea ice, from a transient global warming run to a present

M. Eby; J. M. Gregory; O. A. Saenko; A. Schmittner; A. J. Weaver

2002-01-01

97

Assessing orbitally-forced interglacial climate variability during the mid-Pliocene Warm Period  

NASA Astrophysics Data System (ADS)

The traditional view of the Pliocene is one of an epoch with higher than present global mean annual temperatures (?2 to 3 °C) and stable climate conditions. Published data-model comparisons for the mid-Pliocene Warm Period (mPWP: ?3.3 to 3 million years ago) have identified specific regions of concordance and discord between climate model outputs and marine/terrestrial proxy data. Due to the time averaged nature of global palaeoenvironmental syntheses, it has been hypothesised that climate variability during interglacial events within the mPWP could contribute to site-specific data/model disagreement. The Hadley Centre Coupled Climate Model Version 3 (HadCM3) is used to assess the nature of climate variability around two interglacial events within the mPWP that have different characteristics of orbital forcing (Marine Isotope Stages KM5c and K1). Model results indicate that ±20 kyr on either side of the MIS KM5c, orbital forcing produced a less than 1 °C change in global mean annual temperatures. Regionally, mean annual surface air temperature (SAT) variability can reach 2 to 3 °C. Seasonal variations exceed those predicted for the annual mean and can locally exceed 5 °C. Simulations 20 kyr on either side of MIS K1 show considerably increased variability in relation to KM5c. We demonstrate that orbitally-forced changes in surface air temperature during interglacial events within the mPWP can be substantial, and could therefore contribute to data/model discord. This is especially likely if proxies preserve growing season rather than mean annual temperatures. Model results indicate that peak MIS KM5c and K1 interglacial temperatures were not globally synchronous, highlighting leads and lags in temperature in different regions. This highlights the potential pitfalls in aligning peaks in proxy-derived temperatures across geographically diverse data sites, and indicates that a single climate model simulation for an interglacial event is inadequate to capture peak temperature change in all regions. We conclude that the premise of sustained global warmth and stable Pliocene climate conditions is incomplete. We also contend that the likely nature of Pliocene interglacial climate variability is more akin to interglacial events within the Quaternary, where the character of interglacials is known to be diverse. In the future, the utility of Pliocene data/model comparisons is dependent upon 1) establishing precise chronology of the proxy data, 2) providing climate models with fully proxy-consistent boundary conditions and 3) in utilising ensembles of climate simulations that can adequately capture orbital variability around any studied interval.

Prescott, Caroline L.; Haywood, Alan M.; Dolan, Aisling M.; Hunter, Stephen J.; Pope, James O.; Pickering, Steven J.

2014-08-01

98

Subtropical climate change during the Pliocene warm period- The strong role of eccentricity and precessional forcing modulation during equable climates  

NASA Astrophysics Data System (ADS)

The Pliocene Epoch (5.3-1.8 Ma) is the most recent geologic period of sustained global warmth. Understanding how the world responded to these warmer conditions has important implications as an analog for future anthropogenic warming of the Earth. Past climate reconstructions of the Pliocene warm period (pWP, 4-3 Ma) suggest that mean annual temperatures were approximately 3°C warmer than present, although reconstructions from the Southern Hemisphere (SH) are sparse. The Southern Ocean plays a key role in regulating global climate, so high-resolution reconstructions from this region are important for understanding global climate processes. These processes include climate-ice-sea level interactions, as significant continental ice was only found in the Southern Hemisphere during the pWP. Very little is understood about SH ocean dynamics and climate variability under the unipolar climate conditions of the pWP. Of particular interest are the links between sea surface temperatures (SSTs) and orbital forcing of the unipolar ice sheet dynamics and changes in intermediate water mass properties via ?18O affecting the heat transport under warmer climate. We will present high-resolution (~2.5 kyr sample resolution) records of climate change in the surface and intermediate waters (1365 m. water depth) of the Southwest Pacific (ODP site 1125) during the pWP. Average alkenone-derived SSTs for the pWP at site ODP 1125 are warmer (18.6 °C) than Holocene SSTs in the region (16.3 °C, using multiple proxies for the last 10 kyr) as well as warmer than modern oceanographic data (14.6 °C). The glacial to interglacial temperatures observed in the pWP at ODP 1125 have a smaller range (21.0-15.5 °C) compared to glacial-interglacial temperatures observed in the late Pleistocene (18.0-11.5 °C) in the region, highlighting the reduced orbital-scale variability of subtropical surface waters during the pWP. Available datasets of pWP SSTs show that the reduced orbital-scale variability of surface waters is greater in the tropical regions by almost two-fold compared to higher latitudes. This high contrast of tropical versus higher latitude variability may indicate a more active role of the higher latitudes in re-distributing heat at the glacial-interglacial scales or that feedbacks at high latitudes are stronger relative to tropics in pWP relative to late Pleistocene. Our findings provide evidence for eccentricity and precessional forcing modulating the ?18O of benthic foraminifera at ODP 1125 and to a lesser degree the SSTs, while the obliquity response is not as prevalent on either surface or intermediate water signals. Relative contributions of eccentricity-precession and obliquity are higher at ODP 1125 compared to global benthic isotope stacks, underscoring the need for more high-resolution records, in the hemisphere with most ice, to detangle the controls (temperature vs. ice volume) in the benthic isotope record. Our findings of high eccentricity and precessional response in the ?18O of intermediate waters provide support for a strong control of the seasonal contrast in intermediate water formation during past warm climates.

Caballero Gill, R. P.; Herbert, T.

2012-12-01

99

Arctic climate warming and sea ice declines lead to increased storm surge activity  

NASA Astrophysics Data System (ADS)

The combined effects of climate warming (i.e., increased storminess, reduced sea ice extent, and rising sea levels) make low-lying Arctic coastal regions particularly susceptible to storm surges. The Mackenzie Delta, a biologically significant and resource-rich region in northwestern Canada, is particularly vulnerable to flooding by storm surges. To properly manage the consequences of climate warming for Arctic residents, infrastructure, and ecosystems, a better understanding of the influence of climate change on storm surge activity is required. Here we use particle size analysis of lake sediment records to show that the occurrence and magnitude of storm surges in the outer Mackenzie Delta are significantly related to temperature and that the frequency and intensity of storm surges is increasing. Our results demonstrate the effects of changing climate on storm surge activity and provide a cautionary example of the threat of inundation to low-lying Arctic coastal environments under future climate warming scenarios.

Vermaire, Jesse C.; Pisaric, Michael F. J.; Thienpont, Joshua R.; Courtney Mustaphi, Colin J.; Kokelj, Steven V.; Smol, John P.

2013-04-01

100

Uniform electron gas at warm, dense matter conditions  

NASA Astrophysics Data System (ADS)

A simple, practical model for computing the equilibrium thermodynamics and structure of the uniform electron gas (jellium) by classical strong-coupling methods is proposed. Conditions addressed are those of interest for recent studies of warm dense matter: solid densities and temperatures from zero to plasma states. An effective pair potential and coupling constant are introduced, incorporating the ideal gas, low density, and weak-coupling quantum limits. The resulting parameter-free, analytic model is illustrated by the calculation of the pair correlation function via strong-coupling classical liquid state theory. The results compare favorably with the first finite-temperature restricted path integral Monte Carlo simulations reported recently.

Dutta, Sandipan; Dufty, James

2013-06-01

101

Trend analysis of wet and dry climatic conditions for the Carpathian basin using RCM simulations  

Microsoft Academic Search

Global warming may be recognized both in shifts of regional mean climate, and also, in the frequency and intensity changes of different climatological extremes associated to both temperature and precipitation. In this poster the main focus is on the analysis of precipitation-related climatic conditions. For this purpose we use different types of drought indices, namely, precipitation index, standardized precipitation anomaly

Orsolya Torek; Judit Bartholy; Rita Pongracz; Brigitta Hollosi; Ildiko Pieczka

2010-01-01

102

Study of landscape change under forest harvesting and climate warming-induced fire disturbance  

Microsoft Academic Search

We examined tree species responses under forest harvesting and an increased fire disturbance scenario due to climate warming in northern Wisconsin where northern hardwood and boreal forests are currently predominant. Individual species response at the ecosystem scale was simulated with a gap model, which integrates soil, climate and species data, stratified by ecoregions. Such responses were quantified as species establishment

Hong S. He; David J. Mladenoff; Eric J. Gustafson

2002-01-01

103

Global Farm Animal Production and Global Warming: Impacting and Mitigating Climate Change  

Microsoft Academic Search

Background: The farm animal sector is the single largest anthropogenic user of land, contributing to many environmental problems, including global warming and climate change. Objectives: The aim of this study was to synthesize and expand upon existing data on the contribution of farm animal production to climate change. Methods: We analyzed the scientific literature on farm animal production and documented

Gowri Koneswaran; Danielle Nierenberg

2008-01-01

104

Tropical Climate Mean State and Variability during the Pliocene Warm Period (Invited)  

NASA Astrophysics Data System (ADS)

Past studies have shown that the mean climate state during the Pliocene warm period, about 3 - 4 million years ago, differed from present day climate in several ways: global temperature was about 3-4 degrees C warmer, the tropical thermocline was warmer and/or deeper, and meridional and zonal sea surface temperature gradients were reduced due to warmer high latitude temperatures but tropical sea surface temperatures that were similar to today. One of the most striking features of the Pliocene warm period is the El Niño-like (El Padre) mean state of the tropical Pacific, which is thought to have far-field impacts. In this study, we present a synthesis of new and published tropical Pacific data, detailing the mean state and higher frequency variability (e.g., using orbital scale records and measurements made on single foraminifera shells), for the purpose of meeting two main goals. First, we highlight important characteristics of the El Padre mean state, which include average Indo-Pacific warm pool temperatures that were similar and east Pacific cold tongue temperatures and cross-Pacific subsurface temperatures that were warmer than today. Because much of the paleotemperature data comes from Mg/Ca ratios measured in planktonic foraminifera, the impact of possible changes in Mg/Ca of seawater on paleotemperature estimates is addressed. We conclude that Mg/Ca-derived temperature estimates could be adjusted by no more than about 1 degree in order to account for seawater chemistry changes. Second, by examining orbital variability and temperature distributions based on single foraminifera analyses, we evaluate whether the cumulative strength of the many feedbacks that are involved in the generation of climate variability may be impacted by the mean state. Data indicate that the amplitude of orbital variability in surface temperature, and possibly the amplitude of ENSO variability, was reduced during the warm Pliocene compared to today. On orbital timescales, the reduction in the amplitude of variability could be explained by a possible reduction in orbital variations in CO2 forcing; this inference is supported by the single foraminiferal shell analyses from the west Pacific that show that the distribution of temperatures across seasons remained unchanged even as the mean temperature varied. On shorter, ENSO timescales, variability may have been affected by mean state conditions such as the reduced zonal gradient and the deeper/warmer thermocline that determine the strength of dominant feedbacks. In sum, while the mean state was radically different with reduced zonal gradients characteristic of El Padre, significant orbital, ENSO and seasonal variability was present, albeit reduced in amplitude in several datasets.

Ravelo, A. C.; Ford, H. L.; Dekens, P. S.; White, S. M.; Griffith, E. M.

2013-12-01

105

Climate science: The origin of regional Arctic warming  

NASA Astrophysics Data System (ADS)

Observational data and modelling show that the rapid warming of the northeastern Canada and Greenland sector of the Arctic over the past three decades has been strongly driven by cooling in the tropical Pacific Ocean. See Letter p.209

Bader, Jürgen

2014-05-01

106

Climatic unpredictability and parasitism of caterpillars: Implications of global warming  

PubMed Central

Insect outbreaks are expected to increase in frequency and intensity with projected changes in global climate through direct effects of climate change on insect populations and through disruption of community interactions. Although there is much concern about mean changes in global climate, the impact of climatic variability itself on species interactions has been little explored. Here, we compare caterpillar–parasitoid interactions across a broad gradient of climatic variability and find that the combined data in 15 geographically dispersed databases show a decrease in levels of parasitism as climatic variability increases. The dominant contribution to this pattern by relatively specialized parasitoid wasps suggests that climatic variability impairs the ability of parasitoids to track host populations. Given the important role of parasitoids in regulating insect herbivore populations in natural and managed systems, we predict an increase in the frequency and intensity of herbivore outbreaks through a disruption of enemy–herbivore dynamics as climates become more variable.

Stireman, J. O.; Dyer, L. A.; Janzen, D. H.; Singer, M. S.; Lill, J. T.; Marquis, R. J.; Ricklefs, R. E.; Gentry, G. L.; Hallwachs, W.; Coley, P. D.; Barone, J. A.; Greeney, H. F.; Connahs, H.; Barbosa, P.; Morais, H. C.; Diniz, I. R.

2005-01-01

107

Climate change drives warming in the Hudson River Estuary, New York (USA).  

PubMed

Estuaries may be subject to warming due to global climate change but few studies have considered the drivers or seasonality of warming empirically. We analyzed temperature trends and rates of temperature change over time for the Hudson River estuary using long-term data, mainly from daily measures taken at the Poughkeepsie Water Treatment Facility. This temperature record is among the longest in the world for a river or estuary. The Hudson River has warmed 0.945 °C since 1946. Many of the warmest years in the record occurred in the last 16 years. A seasonal analysis of trends indicated significant warming for the months of April through August. The warming of the Hudson is primarily related to increasing air temperature. Increasing freshwater discharge into the estuary has not mitigated the warming trend. PMID:21720614

Seekell, David A; Pace, Michael L

2011-08-01

108

Modelling the climate and ice sheets of the mid-Pliocene warm period: a test of model dependency  

Microsoft Academic Search

The mid-Pliocene warm period (MPWP; c. 3.0 - 3.3 million years ago) has been the subject of a large number of published studies during the last decade. It is an interval in Earth history, where conditions were similar to those predicted by climate models for the end of the 21st Century. Not only is it important to increase our understanding

Aisling Dolan; Alan Haywood; Daniel Lunt; Daniel Hill

2010-01-01

109

Warm climate isotopic simulations: what do we learn about interglacial signals in Greenland ice cores?  

NASA Astrophysics Data System (ADS)

Measurements of Last Interglacial stable water isotopes in ice cores show that central Greenland ?18O increased by at least 3‰ compared to present day. Attempting to quantify the Greenland interglacial temperature change from these ice core measurements rests on our ability to interpret the stable water isotope content of Greenland snow. Current orbitally driven interglacial simulations do not show ?18O or temperature rises of the correct magnitude, leading to difficulty in using only these experiments to inform our understanding of higher interglacial ?18O. Here, analysis of greenhouse gas warmed simulations from two isotope-enabled general circulation models, in conjunction with a set of Last Interglacial sea surface observations, indicates a possible explanation for the interglacial ?18O rise. A reduction in the winter time sea ice concentration around the northern half of Greenland, together with an increase in sea surface temperatures over the same region, is found to be sufficient to drive a >3‰ interglacial enrichment in central Greenland snow. Warm climate ?18O and ?D in precipitation falling on Greenland are shown to be strongly influenced by local sea surface condition changes: local sea surface warming and a shrunken sea ice extent increase the proportion of water vapour from local (isotopically enriched) sources, compared to that from distal (isotopically depleted) sources. Precipitation intermittency changes, under warmer conditions, leads to geographical variability in the ?18O against temperature gradients across Greenland. Little sea surface warming around the northern areas of Greenland leads to low ?18O against temperature gradients (0.1-0.3‰ per °C), whilst large sea surface warmings in these regions leads to higher gradients (0.3-0.7‰ per °C). These gradients imply a wide possible range of present day to interglacial temperature increases (4 to >10 °C). Thus, we find that uncertainty about local interglacial sea surface conditions, rather than precipitation intermittency changes, may lead to the largest uncertainties in interpreting temperature from Greenland ice cores. We find that interglacial sea surface change observational records are currently insufficient to enable discrimination between these different ?18O against temperature gradients. In conclusion, further information on interglacial sea surface temperatures and sea ice changes around northern Greenland should indicate whether +5 °C during the Last Interglacial is sufficient to drive the observed ice core ?18O increase, or whether a larger temperature increases or ice sheet changes are also required to explain the ice core observations.

Sime, Louise C.; Risi, Camille; Tindall, Julia C.; Sjolte, Jesper; Wolff, Eric W.; Masson-Delmotte, Valérie; Capron, Emilie

2013-05-01

110

Centennial- to millennial-scale climate shifts in continental interior Asia repeated between warm-dry and cool-wet conditions during the last three interglacial states: evidence from uranium and biogenic silica in the sediment of Lake Baikal, southeast Siberia  

NASA Astrophysics Data System (ADS)

We observed timescale-dependent changes in the correlations between biogenic silica (bioSi) and uranium concentrations of bulk sediment from the Buguldeika Saddle, Lake Baikal. There was a positive correlation for the glacial-interglacial (100 kyr) scales over the 180 kyr, with inverse correlations for centennial- to-millennial scales during the last three interglacial states (MIS 5, 3, and 1). The distinction of these correlations between the time scales suggests that the sedimentation processes of bioSi and U differ from each other. The Baikal bioSi concentration record is generally regarded as a paleotemperature proxy, reflecting the diatom production of the lake. On the other hand, we concluded that the temporal variation of the U concentration in the sediment reflected the weathering intensity in the south of Lake Baikal watershed associated with changes in the rainfall/moisture levels. Based on the paleoclimate proxies from Lake Baikal, climates in continental interior Asia are identified as having dry and wet conditions during the glacial and interglacial periods, respectively. This accounts for the rhythms in growth and retreat of ice sheets in Eurasia on glacial-interglacial scales. In the interglacial periods (MIS 5, 3, and 1), the continental interior is, contrary to the glacial-interglacial climate changes, characterized by alternating warm-dry and cool-wet climates with periods in tens of thousands years. In particular, such shifts in the climate stand out prominently at the beginning of MIS 5d. The detrended U record for the last 5.2 kyr shows wet events at 4.3-3.7, 3.2-2.3, 1.8-1.2, and 0.8-0.3 kyr. These events coincide with the timing of the North Atlantic ice-rafted debris events, which were possibly related to solar activity. All this evidence suggests that climate in the continental interior followed significantly different fluctuation patterns in the glacial-interglacial and shorter time scales.

Murakami, Takuma; Takamatsu, Takejiro; Katsuta, Nagayoshi; Takano, Masao; Yamamoto, Koshi; Takahashi, Yoshio; Nakamura, Toshio; Kawai, Takayoshi

2012-10-01

111

Climate warming and biomass accumulation of terrestrial plants: a meta-analysis.  

PubMed

• Growth of terrestrial plant species and functional types (PFTs) in response to climate warming determines future dynamics of terrestrial vegetation. • Here, a meta-analysis was conducted with data collected from 127 publications to reveal general patterns of biomass responses of terrestrial plants to warming. • Warming significantly increased biomass by 12.3% (with a 95% confidence interval of 8.4-16.3%) across all the terrestrial plants included. However, biomass responses were dependent upon PFTs, with significantly greater stimulation of woody (+26.7%) than herbaceous species (+5.2%). Warming effects on biomass showed quadratic relationships with both latitude and mean annual temperature, but did not change with mean annual precipitation or experimental duration. In addition, the other treatments, including CO(2) enrichment, nitrogen addition, drought and water addition, did not alter warming responses of plant biomass. • Dependence of the terrestrial plant biomass responses to warming upon PFTs, geographic and climatic factors as well as warming magnitudes will have consequent influences on community composition and structure, vegetation dynamics, biodiversity and ecosystem functioning in a warmer world. Our findings of functional type-specific responses of terrestrial plants are critical for improving predictions of climate-terrestrial carbon feedbacks. PMID:20609113

Lin, Delu; Xia, Jianyang; Wan, Shiqiang

2010-10-01

112

Energy-balance mechanisms underlying consistent large-scale temperature responses in warm and cold climates  

NASA Astrophysics Data System (ADS)

Climate simulations show consistent large-scale temperature responses including amplified land-ocean contrast, high-latitude/low-latitude contrast, and changes in seasonality in response to year-round forcing, in both warm and cold climates, and these responses are proportional and nearly linear across multiple climate states. We examine the possibility that a small set of common mechanisms controls these large-scale responses using a simple energy-balance model to decompose the temperature changes shown in multiple lgm and abrupt4 × CO 2 simulations from the CMIP5 archive. Changes in the individual components of the energy balance are broadly consistent across the models. Although several components are involved in the overall temperature responses, surface downward clear-sky longwave radiation is the most important component driving land-ocean contrast and high-latitude amplification in both warm and cold climates. Surface albedo also plays a significant role in promoting high-latitude amplification in both climates and in intensifying the land-ocean contrast in the warm climate case. The change in seasonality is a consequence of the changes in land-ocean and high-latitude/low-latitude contrasts rather than an independent temperature response. This is borne out by the fact that no single component stands out as being the major cause of the change in seasonality, and the relative importance of individual components is different in cold and warm climates.

Izumi, Kenji; Bartlein, Patrick J.; Harrison, Sandy P.

2014-06-01

113

Climate-change impact potentials as an alternative to global warming potentials  

NASA Astrophysics Data System (ADS)

For policy applications, such as for the Kyoto Protocol, the climate-change contributions of different greenhouse gases are usually quantified through their global warming potentials. They are calculated based on the cumulative radiative forcing resulting from a pulse emission of a gas over a specified time period. However, these calculations are not explicitly linked to an assessment of ultimate climate-change impacts. A new metric, the climate-change impact potential (CCIP), is presented here that is based on explicitly defining the climate-change perturbations that lead to three different kinds of climate-change impacts. These kinds of impacts are: (1) those related directly to temperature increases; (2) those related to the rate of warming; and (3) those related to cumulative warming. From those definitions, a quantitative assessment of the importance of pulse emissions of each gas is developed, with each kind of impact assigned equal weight for an overall impact assessment. Total impacts are calculated under the RCP6 concentration pathway as a base case. The relevant climate-change impact potentials are then calculated as the marginal increase of those impacts over 100 years through the emission of an additional unit of each gas in 2010. These calculations are demonstrated for CO2, methane and nitrous oxide. Compared with global warming potentials, climate-change impact potentials would increase the importance of pulse emissions of long-lived nitrous oxide and reduce the importance of short-lived methane.

Kirschbaum, Miko U. F.

2014-03-01

114

Permanent El Nino Conditions in the Early Pliocene, the Poleward Heat Transport Paradox, and Contemporary Global Warming.  

NASA Astrophysics Data System (ADS)

Proxy temperature records show that in the early Pliocene, approximately 3 to 5 million years ago, the tropics were characterized by permanently warm El Nino-like conditions. The equatorial Pacific was as warm as in the east as it is in the west today, and the zonal SST gradient along the equator was significantly reduced or absent. Concurrently, major coastal upwelling regions were up to 10 degrees C warmer than they are today. The globally averaged temperatures of the Earth's surface were also substantially higher. This climate state persisted even though the external factors that control climate were essentially the same as at present and the Earth was experiencing greenhouse conditions similar to today's, with the concentration of CO2 in the atmosphere comparable to present day values. Thus far, there is no satisfactory explanation for the climate state of the Pliocene, especially for the climate conditions in the tropics and subtropics. State-of-the-art climate models fail to reproduce a permanent El Nino even when forced by CO2 concentrations many times larger than those estimated for the early Pliocene. Predicting the impact on the tropics of global warming caused by anthropogenic factors also remains a serious challenge for climate scientists. Coupled general circulation models yield a wide range of possible scenarios for the region, but many suggest a slightly higher likelihood of an El Nino-like state in global warming. Efforts to predict future global warming should benefit enormously from a better understanding of the state of permanent El Nino which imposes a strong dynamical constraint on both oceanic and atmospheric circulations. Modeling permanent El Nino with atmospheric and oceanic GCMs reveals a poleward heat transport paradox: Calculations with ocean-only models suggest that a permanent El Nino should correspond to a reduced poleward heat transport by the ocean. This is related to a deeper thermocline in the eastern equatorial Pacific, which leads to a smaller ocean heat intake in the equatorial region. However, calculations with atmospheric GCMs suggest a weaker poleward heat transport by the atmosphere and, consequently, a strengthening of the ocean heat transport. This contradiction implies that there should be an additional mechanism for the poleward heat transport, which is absent or under-resolved in the current generation of general circulation models. This factor explains why climate models cannot replicate a permanent El Nino, and also questions whether climate GCMs can model adequately the impacts of global warming.

Fedorov, A. V.; Brierley, C.

2007-12-01

115

Constant diurnal temperature regime alters the impact of simulated climate warming on a tropical pseudoscorpion  

NASA Astrophysics Data System (ADS)

Recent theory suggests that global warming may be catastrophic for tropical ectotherms. Although most studies addressing temperature effects in ectotherms utilize constant temperatures, Jensen's inequality and thermal stress considerations predict that this approach will underestimate warming effects on species experiencing daily temperature fluctuations in nature. Here, we tested this prediction in a neotropical pseudoscorpion. Nymphs were reared in control and high-temperature treatments under a constant daily temperature regime, and results compared to a companion fluctuating-temperature study. At constant temperature, pseudoscorpions outperformed their fluctuating-temperature counterparts. Individuals were larger, developed faster, and males produced more sperm, and females more embryos. The greatest impact of temperature regime involved short-term, adult exposure, with constant temperature mitigating high-temperature effects on reproductive traits. Our findings demonstrate the importance of realistic temperature regimes in climate warming studies, and suggest that exploitation of microhabitats that dampen temperature oscillations may be critical in avoiding extinction as tropical climates warm.

Zeh, Jeanne A.; Bonilla, Melvin M.; Su, Eleanor J.; Padua, Michael V.; Anderson, Rachel V.; Zeh, David W.

2014-01-01

116

Modelling high latitude climates and ice sheets during the mid-Pliocene warm period  

Microsoft Academic Search

Reduction in the polar ice caps and associated climate feedbacks are implicated in the warming of pre- Quaternary palaeoclimates. General Circulation Model (GCM) simulations of the last such warm period, the mid- Pliocene (3.29-2.97 Ma), suggests global surface temperatures were between 1.4°C and 3.6°C warmer than today. However, the changes are amplified in the high latitudes, where the PRISM (Pliocene

D. J. Hill; A. M. Haywood; R. C. Hindmarsh; P. J. Valdes; D. J. Lunt

2007-01-01

117

Climate Conditioning for the Learning Environment.  

ERIC Educational Resources Information Center

Discusses heating, cooling, and ventilation for the classroom in relationship to students' learning abilities. It is designed to assist school boards, administrators, architects and engineers in understanding the beneficial effects of total climate control, and in evaluating the climate conditioning systems available for schools. Discussion…

Perkins and Will, Architects, Chicago, IL.

118

Climatic changes and associated impacts in the Mediterranean resulting from a 2 °C global warming  

NASA Astrophysics Data System (ADS)

Climatic changes over the Mediterranean basin in 2031-2060, when a 2 °C global warming is most likely to occur, are investigated with the HadCM3 global circulation model and their impacts on human activities and natural ecosystem are assessed. Precipitation and surface temperature changes are examined through mean and extreme values analysis, under the A2 and B2 emission scenarios. Confidence in results is obtained via bootstrapping. Over the land areas, the warming is larger than the global average. The rate of warming is found to be around 2 °C in spring and winter, while it reaches 4 °C in summer. An additional month of summer days is expected, along with 2-4 weeks of tropical nights. Increase in heatwave days and decrease in frost nights are expected to be a month inland. In the northern part of the basin the widespread drop in summer rainfall is partially compensated by a winter precipitation increase. One to 3 weeks of additional dry days lead to a dry season lengthened by a week and shifted toward spring in the south of France and inland Algeria, and autumn elsewhere. In central Mediterranean droughts are extended by a month, starting a week earlier and ending 3 weeks later. The impacts of these climatic changes on human activities such as agriculture, energy, tourism and natural ecosystems (forest fires) are also assessed. Regarding agriculture, crops whose growing cycle occurs mostly in autumn and winter show no changes or even an increase in yield. In contrast, summer crops show a remarkable decrease of yield. This different pattern is attributed to a lengthier drought period during summer and to an increased rainfall in winter and autumn. Regarding forest fire risk, an additional month of risk is expected over a great part of the basin. Energy demand levels are expected to fall significantly during a warmer winter period inland, whereas they seem to substantially increase nearly everywhere during summer. Extremely high summer temperatures in the Mediterranean, coupled with improved climate conditions in northern Europe, may lead to a gradual decrease in summer tourism in the Mediterranean, but an increase in spring and autumn.

Giannakopoulos, C.; Le Sager, P.; Bindi, M.; Moriondo, M.; Kostopoulou, E.; Goodess, C. M.

2009-08-01

119

Climatic Warming Increases Winter Wheat Yield but Reduces Grain Nitrogen Concentration in East China  

PubMed Central

Climatic warming is often predicted to reduce wheat yield and grain quality in China. However, direct evidence is still lacking. We conducted a three-year experiment with a Free Air Temperature Increase (FATI) facility to examine the responses of winter wheat growth and plant N accumulation to a moderate temperature increase of 1.5°C predicted to prevail by 2050 in East China. Three warming treatments (AW: all-day warming; DW: daytime warming; NW: nighttime warming) were applied for an entire growth period. Consistent warming effects on wheat plant were recorded across the experimental years. An increase of ca. 1.5°C in daily, daytime and nighttime mean temperatures shortened the length of pre-anthesis period averagely by 12.7, 8.3 and 10.7 d (P<0.05), respectively, but had no significant impact on the length of the post-anthesis period. Warming did not significantly alter the aboveground biomass production, but the grain yield was 16.3, 18.1 and 19.6% (P<0.05) higher in the AW, DW and NW plots than the non-warmed plot, respectively. Warming also significantly increased plant N uptake and total biomass N accumulation. However, warming significantly reduced grain N concentrations while increased N concentrations in the leaves and stems. Together, our results demonstrate differential impacts of warming on the depositions of grain starch and protein, highlighting the needs to further understand the mechanisms that underlie warming impacts on plant C and N metabolism in wheat.

Deng, Aixing; Song, Zhenwei; Zhang, Baoming; Zhang, Weijian

2014-01-01

120

The Early Climate History of Mars: "Warm and Wet" or "Cold and Icy"?  

NASA Astrophysics Data System (ADS)

The Amazonian climate (last ~66% of history) was much like today, a cold and dry climate regime, characterized by the latitudinal migration of surface ice in response to variations in spin-axis/orbital parameters. But what characterized the Noachian climate (first ~20% of history)? Some data support a "warm and wet" early Mars, but this evidence has been challenged. New models of early Mars climate (Forget, Wordsworth et al.) find that for atmospheric pressures greater than a few hundred millibars, surface temperatures vary with altitude due to atmosphere-surface thermal coupling: an adiabatic cooling effect (ACE) results in deposition of snow and ice at high altitudes, in contrast to Amazonian conditions. Without other warming mechanisms, no combination of parameters lead to mean annual surface temperatures (MAT) consistent with widespread liquid water anywhere on the planet. The ACE causes southern highland region temperatures to fall significantly below the global average leading to a "Noachian Icy Highlands" scenario: Water is transported to the highlands from low-lying regions due to the ACE and snows out to form an extended H2O ice cap at the southern pole, and altitude-dependent snow and ice deposits down to lower southern latitudes. Could the predictions of this "Noachian Icy Highlands" model be consistent with the many lines of evidence traditionally cited for a "warm, wet" early Mars? Perturbing this predominant Noachian environment with punctuated impacts and volcanism/greenhouse gases would lead to raising of global surface temperatures toward the melting point of water, with the following consequences: 1) ice above the surface ice stability line undergoes rapid altitude/latitude dependent warming during each Mars summer; 2) meltwater runoff from the continuous ice sheet drains and flows downslope to the edge of the ice sheet, where meltwater channels encounter cratered terrain, forming closed-basin and open-basin lakes; 3) seasonal top-down heating and melting of the top tens of meters of continuous ice produce a volume of water well in excess of the total volume interpreted to have occupied open-basin/closed basin lakes; 4) this meltwater initially erodes into the dry regolith down to the top of the ice table, producing a perched aquifer and more efficient erosion than infiltration alone; 5) at the end of the annual melting period, temperatures return to below 0°C, meltwater freezes and sublimes, returning to high altitudes as snowfall to replenish the snow and ice deposit; 6) this Noachian icy highlands, ACE-dominated water cycle persists until MAT drops to <0°C. The icy Noachian highlands/punctuated volcanism scenario appears to be able to account for the: 1) source and volume of water required for valley networks; 2) presence of closed/open-basin lakes; 4) evidence for recurring phases of activity over millions of years; 5) small amounts of net erosion; 6) relatively poor stream integration and lower order; 7) presence of a surface hydrological cycle that can replenish the source area and cause recurring activity with a small total budget of water; and 8) presence of melting and runoff in a Late Noachian climate compatible with other constraints (e.g., faint young Sun, low atmospheric pressure).

Head, James

2013-04-01

121

Enhanced marine productivity off western North America during warm climate intervals of the past 52 k.y  

USGS Publications Warehouse

Studies of the Santa Barbara Basin off the coast of California have linked changes in its bottom-water oxygen content to millennial-scale climate changes as recorded by the oxygen isotope composition of Greenland ice. Through the use of detailed records from a sediment core collected off the Magdalena Margin of Baja California, Mexico, we demonstrate that this teleconnection predominantly arose from changes in marine productivity, rather than changes in ventilation of the North Pacific, as was originally proposed. One possible interpretation is that the modern balance of El Nin??o-La Nin??a conditions that favors a shallow nutricline and high productivity today and during warm climate intervals of the past 52 k.y. was altered toward more frequent, deep nutricline, low productivity, El Nin??o-like conditions during cool climate intervals. ?? 2004 Geological Society of America.

Ortiz, J. D.; O'Connell, S. B.; DelViscio, J.; Dean, W.; Carriquiry, J. D.; Marchitto, T.; Zheng, Y.; van, Geen, A.

2004-01-01

122

Reconstruction of spatial patterns of climatic anomalies during the medieval warm period (AD 900-1300)  

SciTech Connect

The workshop will focus on climatic variations during the Medieval Warm Period or Little Climatic Optimum. The nominal time interval assigned to this period is AD 900--1300, but climate information available during the century or two preceding and following this episode is welcome. The aims of the workshop will be to: examine the available evidence for the existence of this episode; assess the spatial and temporal synchronicity of the climatic signals; discuss possible forcing mechanisms; and identify areas and paleoenvironmental records where additional research efforts are needed to improve our knowledge of this period. This document consists of abstracts of eighteen papers presented at the meeting.

Diaz, H.F. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Environmental Research Labs.; Hughes, M.K. [Arizona Univ., Tucson, AZ (United States). Lab. of Tree-Ring Research

1992-12-31

123

Beyond a warming fingerprint: individualistic biogeographic responses to heterogeneous climate change in California.  

PubMed

Understanding recent biogeographic responses to climate change is fundamental for improving our predictions of likely future responses and guiding conservation planning at both local and global scales. Studies of observed biogeographic responses to 20th century climate change have principally examined effects related to ubiquitous increases in temperature - collectively termed a warming fingerprint. Although the importance of changes in other aspects of climate - particularly precipitation and water availability - is widely acknowledged from a theoretical standpoint and supported by paleontological evidence, we lack a practical understanding of how these changes interact with temperature to drive biogeographic responses. Further complicating matters, differences in life history and ecological attributes may lead species to respond differently to the same changes in climate. Here, we examine whether recent biogeographic patterns across California are consistent with a warming fingerprint. We describe how various components of climate have changed regionally in California during the 20th century and review empirical evidence of biogeographic responses to these changes, particularly elevational range shifts. Many responses to climate change do not appear to be consistent with a warming fingerprint, with downslope shifts in elevation being as common as upslope shifts across a number of taxa and many demographic and community responses being inconsistent with upslope shifts. We identify a number of potential direct and indirect mechanisms for these responses, including the influence of aspects of climate change other than temperature (e.g., the shifting seasonal balance of energy and water availability), differences in each taxon's sensitivity to climate change, trophic interactions, and land-use change. Finally, we highlight the need to move beyond a warming fingerprint in studies of biogeographic responses by considering a more multifaceted view of climate, emphasizing local-scale effects, and including a priori knowledge of relevant natural history for the taxa and regions under study. PMID:24934878

Rapacciuolo, Giovanni; Maher, Sean P; Schneider, Adam C; Hammond, Talisin T; Jabis, Meredith D; Walsh, Rachel E; Iknayan, Kelly J; Walden, Genevieve K; Oldfather, Meagan F; Ackerly, David D; Beissinger, Steven R

2014-09-01

124

Climate Kids: It's Cold! Is Global Warming Over?  

NSDL National Science Digital Library

The movement of Arctic air, known as the Arctic oscillation, can and will cause periodic extreme winter weather outside the Arctic region - the harsh winter experienced in many parts of the U.S. in 2010 is a recent example. This article explains the connection between the two events. This article is part of the Climate Kids website, a NASA education resource featuring articles, videos, images and games focused on the science of climate change.

125

Clouds and climate: Unraveling a key piece of global warming  

SciTech Connect

Federal policy decisions relating to mitigation of greenhouse gas and other emissions have the potential to exert an enormous impact on industries in which chemical engineers play a prominent role. Many in these industries keep close watch on the development of scientific understanding associated with predictions of global climate change. The authors review one of the most critical, and most uncertain, pieces of the climate puzzle, the role of aerosols and clouds in the global energy balance.

Seinfeld, J.H.

2000-02-01

126

Effects of Global Warming on Predatory Bugs Supported by Data Across Geographic and Seasonal Climatic Gradients  

PubMed Central

Global warming may affect species abundance and distribution, as well as temperature-dependent morphometric traits. In this study, we first used historical data to document changes in Orius (Heteroptera: Anthocoridae) species assemblage and individual morphometric traits over the past seven decades in Israel. We then tested whether these changes could have been temperature driven by searching for similar patterns across seasonal and geographic climatic gradients in a present survey. The historical records indicated a shift in the relative abundance of dominant Orius species; the relative abundance of O. albidipennis, a desert-adapted species, increased while that of O. laevigatus decreased in recent decades by 6 and 10–15 folds, respectively. These shifts coincided with an overall increase of up to 2.1°C in mean daily temperatures over the last 25 years in Israel. Similar trends were found in contemporary data across two other climatic gradients, seasonal and geographic; O. albidipennis dominated Orius assemblages under warm conditions. Finally, specimens collected in the present survey were significantly smaller than those from the 1980’s, corresponding to significantly smaller individuals collected now during warmer than colder seasons. Taken together, results provide strong support to the hypothesis that temperature is the most likely driver of the observed shifts in species composition and body sizes because (1) historical changes in both species assemblage and body size were associated with rising temperatures in the study region over the last few decades; and (2) similar changes were observed as a result of contemporary drivers that are associated with temperature.

Schuldiner-Harpaz, Tarryn; Coll, Moshe

2013-01-01

127

Reversing climate warming by artificial atmospheric carbon-dioxide removal: Can a Holocene-like climate be restored?  

NASA Astrophysics Data System (ADS)

Most climate modeling studies of future climate have focused on the effects of carbon emissions in the present century or the long-term fate of anthropogenically emitted carbon. However, after carbon emissions cease, there may be a desire to return to a "safe" CO2 concentration within this millennium. Realistically, this implies artificially removing CO2 from the atmosphere. In this study, experiments are conducted using the University of Victoria Earth system-climate model forced with novel future scenarios to explore the reversibility of climate warming as a response to a gradual return to preindustrial radiative forcing. Due to hysteresis in the permafrost carbon pool, the quantity of carbon that must be removed from the atmosphere is larger than the quantity that was originally emitted (115-180% of original emissions). In all the reversibility simulations with a moderate climate sensitivity, a climate resembling that of the Holocene can be restored by 3000 CE.

MacDougall, Andrew H.

2013-10-01

128

Using physiology to predict the responses of ants to climatic warming.  

PubMed

Physiological intolerance of high temperatures places limits on organismal responses to the temperature increases associated with global climatic change. Because ants are geographically widespread, ecologically diverse, and thermophilic, they are an ideal system for exploring the extent to which physiological tolerance can predict responses to environmental change. Here, we expand on simple models that use thermal tolerance to predict the responses of ants to climatic warming. We investigated the degree to which changes in the abundance of ants under warming reflect reductions in the thermal niche space for their foraging. In an eastern deciduous forest system in the United States with approximately 40 ant species, we found that for some species, the loss of thermal niche space for foraging was related to decreases in abundance with increasing experimental climatic warming. However, many ant species exhibited no loss of thermal niche space. For one well-studied species, Temnothorax curvispinosus, we examined both survival of workers and growth of colonies (a correlate of reproductive output) as functions of temperature in the laboratory, and found that the range of thermal tolerances for colony growth was much narrower than for survival of workers. We evaluated these functions in the context of experimental climatic warming and found that the difference in the responses of these two attributes to temperature generates differences in the means and especially the variances of expected fitness under warming. The expected mean growth of colonies was optimized at intermediate levels of warming (2-4°C above ambient); yet, the expected variance monotonically increased with warming. In contrast, the expected mean and variance of the survival of workers decreased when warming exceeded 4°C above ambient. Together, these results for T. curvispinosus emphasize the importance of measuring reproduction (colony growth) in the context of climatic change: indeed, our examination of the loss of thermal niche space with the larger species pool could be missing much of the warming impact due to these analyses being based on survival rather than reproduction. We suggest that while physiological tolerance of temperature can be a useful predictive tool for modeling responses to climatic change, future efforts should be devoted to understanding the causes and consequences of variability in models of tolerance calibrated with different metrics of performance and fitness. PMID:23892370

Diamond, Sarah E; Penick, Clint A; Pelini, Shannon L; Ellison, Aaron M; Gotelli, Nicholas J; Sanders, Nathan J; Dunn, Robert R

2013-12-01

129

Definitions of climate and climate change under varying external conditions  

NASA Astrophysics Data System (ADS)

Commonly, definitions of climate are endorsed where the external conditions are held constant. This paper argues that these definitions risk being empirically void because in reality the external conditions vary. As a consequence, analogous definitions for varying external conditions are explored with help of the recently developed theory of non-autonomous dynamical systems, and the similarities and differences between the cases of constant and varying external conditions are discussed. It is argued that there are analogous definitions for varying external conditions which are preferable to the definitions where the external conditions are held constant. In this context, a novel definition is proposed (namely, climate as the distribution over time under a regime of varying external conditions), which is argued to be promising.

Werndl, C.

2014-06-01

130

The impact of warming climate on late summer snow cover in northwestern Finland  

NASA Astrophysics Data System (ADS)

Snowbeds and snow patches are characteristic features of arctic and alpine regions and are classified as endangered habitats due to the warming climate. We studied interannual variation of late summer snow cover and the factors affecting it in sub-arctic Enontekiö Lapland, northwestern Finland in years 2000, 2004, 2006, and 2009. Snow cover at 30 m resolution was derived from Landsat TM and ETM+ images obtained between 27 July and 4 August using a normalized difference snow index (NDSI). A generalized linear model (GLM) was constructed for the number (0 - 4) of snow occurrence years in 1-km grid squares. Explanatory variables in the model were elevation, terrain ruggedness, insolation and aspect. Variation in climatic conditions in the study region was examined using temperature and precipitation data from 1995 to 2009 (Finnish Meteorological Institute) and climate scenarios derived from the ENSEMBLES and PRUDENCE simulations extending to the period of 2070-2099. Late summer snow covered 23.0 km2 in 2000, 2.7 km2 in 2004, 1.5 km2 in 2006, and 5.0 km2 in 2009 of the 3176.5 km2 study area (mean altitude 727 m, maximum altitude 1310 m). The decline of snow cover was most prominent below 900 meters and on southern and western slopes. In year 2000, approximately a half of the snow cover was found above 900 meters (where 7% of the total study area is located) compared to circa 75% in 2004 and 2006, and 62% in 2009. Analyses at the 1-km resolution showed that in 19 % of the study squares there was late summer snow at least in one of the four years. Elevation and terrain ruggedness were the strongest explanatory variables for the number of snow occurrence year in a univariate GLM model. The GLM model including all variables explained 73% of the variation in the number of snow occurrence years. The interannual variation in late summer snow cover reflects the climatic variation in the study region. The mean annual temperature increased on average by 0.16°C per year during 1995-2009. Warming was most noticeable in November-December (0.37°C/year) and April- May (0.33°C/year). The number of frost days and the proportion of the snow of the total precipitation amount generally decreased during the study period. A higher number of frost days and a snowfall peak in 2008 probably explain the observed slight increase in the summer snow cover in 2009. ENSEMBLES models predict the greatest warming to take place in winter, from late autumn to early spring (ca 5.5°C by 2070-2099). Snowfall is predicted to increase 7-26% in November-March and to decrease notably in April-October. Further, PRUDENCE models predict a significant decrease in the number of frost days from average of 240 in 1961-1990 to 185 in 2071-2100. These results suggest that future climatic conditions in the study area will not support the summer occurrence of snowbeds and snow patches, which leads to threat to the alpine species and communities associated with snow and moist soils.

Kivinen, S.; Kaarlejärvi, E.; Jylhä, K.; Räisänen, J.

2012-04-01

131

Effects of climate warming on Olive and olive fly ( Bactrocera oleae (Gmelin)) in California and Italy  

Microsoft Academic Search

Climate change is expected to alter the geographic distribution and abundance of many species. Here we examine the potential\\u000a effects of climate warming on olive (Olea europaea) and olive fly (Bactrocera oleae) across the ecological zones of Arizona–California (AZ–CA) and Italy. A weather-driven physiologically-based demographic\\u000a model was developed from the extensive literature and used to simulate the phenology, growth and

Andrew Paul Gutierrez; Luigi Ponti; Q. A. Cossu

2009-01-01

132

Increases in flood magnitudes in California under warming climates  

NASA Astrophysics Data System (ADS)

Downscaled and hydrologically modeled projections from an ensemble of 16 Global Climate Models suggest that flooding may become more intense on the western slopes of the Sierra Nevada mountains, the primary source for California's managed water system. By the end of the 21st century, all 16 climate projections for the high greenhouse-gas emission SRES A2 scenario yield larger floods with return periods ranging 2-50 years for both the Northern Sierra Nevada and Southern Sierra Nevada, regardless of the direction of change in mean precipitation. By end of century, discharges from the Northern Sierra Nevada with 50-year return periods increase by 30-90% depending on climate model, compared to historical values. Corresponding flood flows from the Southern Sierra increase by 50-100%. The increases in simulated 50 year flood flows are larger (at 95% confidence level) than would be expected due to natural variability by as early as 2035 for the SRES A2 scenario.

Das, Tapash; Maurer, Edwin P.; Pierce, David W.; Dettinger, Michael D.; Cayan, Daniel R.

2013-09-01

133

Sensitivity of Runoff to Climate Warming over the Western U.S  

NASA Astrophysics Data System (ADS)

The response of runoff to climate warming, on annual water supply time scales or on shorter, flood event scales, are critical issues for water managers and for ecosystems. Here we summarize a set of analyses using the Variable Infiltration Capacity (VIC) hydrological model over the western U.S. to explore the sensitivity of runoff to prescribed increases in temperature. The prescribed warming is imposed upon a century long observed daily precipitation and temperature forcing dataset, developed at the University of Washington. The sensitivity of annual runoff and of relatively high runoff events varies considerably over the western U.S.. According to VIC, climate warming results in diminished annual discharge. When aggregated into streamflow within major western U.S. Rivers, the annual streamflow response ranges from as little as -1% per degree to as much as -6% per degree Celsius of warming. Total flow from California’s Sierra Nevada Rivers are not as sensitive to warming as are those in the Colorado and Pacific Northwest River basins. On the other hand, warming generally increases the frequency and magnitude of flow events in watersheds that have historically been fed by melting snowpacks. The greatest changes are found in basins with a large portion of the watershed lies just below larger changes in the region freezing point.

Das, T.; Pierce, D. W.; Cayan, D. R.; Dettinger, M.

2009-12-01

134

Dusting the climate for fingerprints. Has greenhouse warming arrived? Will we ever know?  

SciTech Connect

The topic of global warming is front page news again. Although the annual average global temperature has risen by about 0.5 C since the late 19th century, investigators have had difficulty determining whether natural forces or human actions are to blame. This article summarizes the arguments pro and con and the search for a diffinative `human fingerprint` on global warming. For example, Max-Lanck researchers find it highly imporbable (1 in 20 chance) that natural forcers have caused the temperature rise. However other scientists acknowledge that uncertainties continue to plague studies aimed at detecting the human influence in climatic change. Computer climate models are the major approach, but distiguishing between recent abnormal warming due to greenhouse gases or to other causes is elusive.

Monastersy, R.

1995-06-10

135

Population decrease of Scirpophaga incertulas Walker (Lepidoptera Pyralidae) under climate warming.  

PubMed

Scirpophaga incertulas Walker is an important agricultural pest in Asia. Only few studies are available on its long-term population dynamics under climate warming. In this study, we used the linear and generalized additive models (GAMs) to analyze the historical dataset of >50 years on this pest at Xinfeng County of Jiangxi Province, China. The main objective of this study was to explore the effects of density (delayed) dependence and minimum annual temperature (MAT), which indirectly reflects climate warming, on the population dynamics of this pest. We found that both density dependence and MAT have significant influence on the annual population growth rate. The GAMs had relatively better applicability to the dataset than the linear models. Nonparametric model provided satisfactory goodness-of-fit (R(2) > 0.5). At Xinfeng County, the MAT had a significant effect on the annual population growth rate of S. incertulas. The annual population growth rate of S. incertulas decreased with increase in MAT. Therefore, S. incertulas population becomes smaller and smaller in Southern China due to climate warming. The current study has two contributions: (1) providing a suitable method for predicting the annual population growth rate of S. incertulas, and (2) demonstrating that climate warming could decrease the S. incertulas population. PMID:22408726

Shi, Peijian; Zhong, Ling; Sandhu, Hardev S; Ge, Feng; Xu, Xiaoming; Chen, Wei

2012-01-01

136

Rapid climatic warming at the end of the last glacial: new perspectives  

Microsoft Academic Search

In this paper, an overview is given of the main considerations of an international workshop on rapid warming at the end of the last glacial. Several steps are discussed that could be taken to promote a better understanding of the abrupt climatic changes that occurred during the last glacial–interglacial transition. We focus on the following aspects: chronology, interpretation of terrestrial

H. Renssen; R. F. B. Isarin; J. F. Vandenberghe

2001-01-01

137

Geothermal Evidence From Canada for a Cold Period Before Recent Climatic Warming  

Microsoft Academic Search

Three deep boreholes in a small area in Quebec, each having two high-accuracy temperature logs separated by 22 years, allow reliable determination of the ground surface temperature history during the past few centuries. The temperature logs show that the recent climatic warming was preceded by a cold period near the end of the 19th century in this area. The presence

Kelin Wang; Trevor J. Lewis

1992-01-01

138

Sensitivity of the Ocean's Climate to Diapycnal Diffusivity in an EMIC. Part II: Global Warming Scenario  

Microsoft Academic Search

The sensitivity of the ocean's climate to the diapycnal diffusivity in the ocean is studied for a global warming scenario in which CO2 increases by 1% yr-1 for 75 yr. The thermohaline circulation slows down for about 100 yr and recovers afterward, for any value of the diapycnal diffusivity. The rates of slowdown and of recovery, as well as the

Fabio Dalan; Peter H. Stone; Andrei P. Sokolov

2005-01-01

139

Climate warming is lowering levels of dissolved carbon in the Yukon River  

NSDL National Science Digital Library

Dissolved organic carbon (DOC) export, normalized to water discharge, during the growing season from 1978 to 1980 was compared with that taken from 2001 to 2003. It was found that climate warming on frozen soils increases the flow path, residence time, and microbial mineralization of DOC in the soil's active layer and groundwater, ultimately decreasing DOC export.

Al., Striegl E.; Agu

140

Simulated climate warming alters phenological synchrony between an outbreak insect herbivore and host trees.  

PubMed

As the world's climate warms, the phenologies of interacting organisms in seasonally cold environments may advance at differing rates, leading to alterations in phenological synchrony that can have important ecological consequences. For temperate and boreal species, the timing of early spring development plays a key role in plant-herbivore interactions and can influence insect performance, outbreak dynamics, and plant damage. We used a field-based, meso-scale free-air forest warming experiment (B4WarmED) to examine the effects of elevated temperature on the phenology and performance of forest tent caterpillar (Malacosoma disstria) in relation to the phenology of two host trees, aspen (Populus tremuloides) and birch (Betula papyrifera). Results of our 2-year study demonstrated that spring phenology advanced for both insects and trees, with experimentally manipulated increases in temperature of 1.7 and 3.4 °C. However, tree phenology advanced more than insect phenology, resulting in altered phenological synchrony. Specifically, we observed a decrease in the time interval between herbivore egg hatch and budbreak of aspen in both years and birch in one year. Moreover, warming decreased larval development time from egg hatch to pupation, but did not affect pupal mass. Larvae developed more quickly on aspen than birch, but pupal mass was not affected by host species. Our study reveals that warming-induced phenological shifts can alter the timing of ecological interactions across trophic levels. These findings illustrate one mechanism by which climate warming could mediate insect herbivore outbreaks, and also highlights the importance of climate change effects on trophic interactions. PMID:24889969

Schwartzberg, Ezra G; Jamieson, Mary A; Raffa, Kenneth F; Reich, Peter B; Montgomery, Rebecca A; Lindroth, Richard L

2014-07-01

141

Climate warming feedback from mountain birch forest expansion: reduced albedo dominates carbon uptake.  

PubMed

Expanding high-elevation and high-latitude forest has contrasting climate feedbacks through carbon sequestration (cooling) and reduced surface reflectance (warming), which are yet poorly quantified. Here, we present an empirically based projection of mountain birch forest expansion in south-central Norway under climate change and absence of land use. Climate effects of carbon sequestration and albedo change are compared using four emission metrics. Forest expansion was modeled for a projected 2.6 °C increase in summer temperature in 2100, with associated reduced snow cover. We find that the current (year 2000) forest line of the region is circa 100 m lower than its climatic potential due to land-use history. In the future scenarios, forest cover increased from 12% to 27% between 2000 and 2100, resulting in a 59% increase in biomass carbon storage and an albedo change from 0.46 to 0.30. Forest expansion in 2100 was behind its climatic potential, forest migration rates being the primary limiting factor. In 2100, the warming caused by lower albedo from expanding forest was 10 to 17 times stronger than the cooling effect from carbon sequestration for all emission metrics considered. Reduced snow cover further exacerbated the net warming feedback. The warming effect is considerably stronger than previously reported for boreal forest cover, because of the typically low biomass density in mountain forests and the large changes in albedo of snow-covered tundra areas. The positive climate feedback of high-latitude and high-elevation expanding forests with seasonal snow cover exceeds those of afforestation at lower elevation, and calls for further attention of both modelers and empiricists. The inclusion and upscaling of these climate feedbacks from mountain forests into global models is warranted to assess the potential global impacts. PMID:24343906

de Wit, Heleen A; Bryn, Anders; Hofgaard, Annika; Karstensen, Jonas; Kvalevåg, Maria M; Peters, Glen P

2014-07-01

142

[Effects of climate warming and drying on millet yield in Gansu Province and related countermeasures].  

PubMed

Based on the data of air temperature, precipitation, and millet yield from Ganzhou, Anding, and Xifeng, the representative stations in Hexi moderate arid oasis irrigation area, moderate sub-arid dry area in middle Gansu, and moderate sub-humid dry area in eastern Gansu, respectively, this paper calculated the regional active accumulated temperature of > or = 0 degrees C, > or =5 degrees C, > or =10 degrees C, > or =15 degrees C, and > or =20 degrees C in millet growth period, and the average temperature and precipitation in millet key growth stages. The millet climatic yield was isolated by orthogonal polynomial, and the change characteristics of climate and millet climatic yield as well as the effects of climate change on millet yield were analyzed by statistical methods of linear tendency, cumulative anomaly, and Mann-Kendall. The results showed that warming and drying were the main regional features in the modern climatic change of Gansu. The regional temperature had a significant upward trend since the early 1990s, while the precipitation was significantly reduced from the late 1980s. There were significant correlations between millet yield and climatic factors. The millet yield in dry areas increased with the increasing temperature and precipitation in millet key growth stages, and that in Hexi Corridor area increased with increasing temperature. Warming and drying affected millet yield prominently. The weather fluctuation index of regional millet yield in Xifeng, Anding, and Ganzhou accounted for 73%, 72%, and 54% of real output coefficient variation, respectively, and the percentages increased significantly after warming. Warming was conducive to the increase of millet production, and the annual increment of millet climatic yield in Xifeng, Anding, and Ganzhou after warming was 30.6, 43.1, and 121.1 kg x hm(-2), respectively. Aiming at the warming and drying trend in Gansu Province in the future, the millet planting area in the Province should be further expanded, and the millet planting structure should be adjusted. At the same time, according to the different regional and yearly climatic types, different varieties should be selected, and various planting measures should be taken. PMID:21361020

Cao, Ling; Wang, Qiang; Deng, Zhen-yong; Guo, Xiao-qin; Ma, Xing-xiang; Ning, Hui-fang

2010-11-01

143

Climate warming and the decline of amphibians and reptiles in Europe  

Microsoft Academic Search

ABSTRACT Aim,We,explore,the relationship between,current,European,distributions,of amphibian and reptile species and observed climate, and project species potential distributions into the future. Potential impacts of climate warming,are assessed by quantifying,the magnitude,and,direction of modelled,distributional shifts for every species. In particular we ask, first, what proportion of amphibian and reptile species are projected,to lose and,gain suitable climate,space in the future? Secondly, do species projections vary

M. B. Araújo; W. Thuiller; R. G. Pearson

2006-01-01

144

Local temperatures inferred from plant communities suggest strong spatial buffering of climate warming across Northern Europe.  

PubMed

Recent studies from mountainous areas of small spatial extent (<2500 km(2) ) suggest that fine-grained thermal variability over tens or hundreds of metres exceeds much of the climate warming expected for the coming decades. Such variability in temperature provides buffering to mitigate climate-change impacts. Is this local spatial buffering restricted to topographically complex terrains? To answer this, we here study fine-grained thermal variability across a 2500-km wide latitudinal gradient in Northern Europe encompassing a large array of topographic complexities. We first combined plant community data, Ellenberg temperature indicator values, locally measured temperatures (LmT) and globally interpolated temperatures (GiT) in a modelling framework to infer biologically relevant temperature conditions from plant assemblages within <1000-m(2) units (community-inferred temperatures: CiT). We then assessed: (1) CiT range (thermal variability) within 1-km(2) units; (2) the relationship between CiT range and topographically and geographically derived predictors at 1-km resolution; and (3) whether spatial turnover in CiT is greater than spatial turnover in GiT within 100-km(2) units. Ellenberg temperature indicator values in combination with plant assemblages explained 46-72% of variation in LmT and 92-96% of variation in GiT during the growing season (June, July, August). Growing-season CiT range within 1-km(2) units peaked at 60-65°N and increased with terrain roughness, averaging 1.97 °C (SD = 0.84 °C) and 2.68 °C (SD = 1.26 °C) within the flattest and roughest units respectively. Complex interactions between topography-related variables and latitude explained 35% of variation in growing-season CiT range when accounting for sampling effort and residual spatial autocorrelation. Spatial turnover in growing-season CiT within 100-km(2) units was, on average, 1.8 times greater (0.32 °C km(-1) ) than spatial turnover in growing-season GiT (0.18 °C km(-1) ). We conclude that thermal variability within 1-km(2) units strongly increases local spatial buffering of future climate warming across Northern Europe, even in the flattest terrains. PMID:23504984

Lenoir, Jonathan; Graae, Bente Jessen; Aarrestad, Per Arild; Alsos, Inger Greve; Armbruster, W Scott; Austrheim, Gunnar; Bergendorff, Claes; Birks, H John B; Bråthen, Kari Anne; Brunet, Jörg; Bruun, Hans Henrik; Dahlberg, Carl Johan; Decocq, Guillaume; Diekmann, Martin; Dynesius, Mats; Ejrnaes, Rasmus; Grytnes, John-Arvid; Hylander, Kristoffer; Klanderud, Kari; Luoto, Miska; Milbau, Ann; Moora, Mari; Nygaard, Bettina; Odland, Arvid; Ravolainen, Virve Tuulia; Reinhardt, Stefanie; Sandvik, Sylvi Marlen; Schei, Fride Høistad; Speed, James David Mervyn; Tveraabak, Liv Unn; Vandvik, Vigdis; Velle, Liv Guri; Virtanen, Risto; Zobel, Martin; Svenning, Jens-Christian

2013-05-01

145

Forecasting flowering phenology under climate warming by modelling the regulatory dynamics of flowering-time genes.  

PubMed

Understanding how climate warming has an impact on the life cycle schedule of terrestrial organisms is critical to evaluate ecosystem vulnerability to environmental change. Despite recent advances identifying the molecular basis of temperature responses, few studies have incorporated this knowledge into predictive models. Here we develop a method to forecast flowering phenology by modelling regulatory dynamics of key flowering-time genes in perennial life cycles. The model, parameterized by controlled laboratory experiments, accurately reproduces the seasonal changes in gene expression, the corresponding timing of floral initiation and return to vegetative growth after a period of flowering in complex natural environments. A striking scenario forecast by the model under climate warming is that the shift in the return time to vegetative growth is greater than that in floral initiation, which results in a significant reduction of the flowering period. Our study demonstrates the usefulness of gene expression assessment to predict unexplored risks of climate change. PMID:23941973

Satake, Akiko; Kawagoe, Tetsuhiro; Saburi, Yukari; Chiba, Yukako; Sakurai, Gen; Kudoh, Hiroshi

2013-01-01

146

The potential for behavioral thermoregulation to buffer "cold-blooded" animals against climate warming  

PubMed Central

Increasing concern about the impacts of global warming on biodiversity has stimulated extensive discussion, but methods to translate broad-scale shifts in climate into direct impacts on living animals remain simplistic. A key missing element from models of climatic change impacts on animals is the buffering influence of behavioral thermoregulation. Here, we show how behavioral and mass/energy balance models can be combined with spatial data on climate, topography, and vegetation to predict impacts of increased air temperature on thermoregulating ectotherms such as reptiles and insects (a large portion of global biodiversity). We show that for most “cold-blooded” terrestrial animals, the primary thermal challenge is not to attain high body temperatures (although this is important in temperate environments) but to stay cool (particularly in tropical and desert areas, where ectotherm biodiversity is greatest). The impact of climate warming on thermoregulating ectotherms will depend critically on how changes in vegetation cover alter the availability of shade as well as the animals' capacities to alter their seasonal timing of activity and reproduction. Warmer environments also may increase maintenance energy costs while simultaneously constraining activity time, putting pressure on mass and energy budgets. Energy- and mass-balance models provide a general method to integrate the complexity of these direct interactions between organisms and climate into spatial predictions of the impact of climate change on biodiversity. This methodology allows quantitative organism- and habitat-specific assessments of climate change impacts.

Kearney, Michael; Shine, Richard; Porter, Warren P.

2009-01-01

147

A modeling-GIS approach for assessing irrigation effects on soil salinisation under global warming conditions  

Microsoft Academic Search

Soil salinisation is very often due to excessive irrigation. However, irrigation is absolutely essential for obtaining reliable crop yields, particularly under predicted global warming conditions. A simple methodology for assessing the salinisation risk for any water management situation and under predicted global warming conditions is presented. The methodology is illustrated by the assessment of irrigation effects on soil salinity at

Angel Utset; Matilde Borroto

2001-01-01

148

Effect of wearing an ice cooling jacket on repeat sprint performance in warm/humid conditions  

PubMed Central

Objective: To examine the effect of cooling the skin with an ice jacket before and between exercise bouts (to simulate quarter and half time breaks) on prolonged repeat sprint exercise performance in warm/humid conditions. Methods: After an initial familiarisation session, seven trained male hockey players performed two testing sessions (seven days apart), comprising an 80 minute intermittent, repeat sprint cycling exercise protocol inside a climate chamber set at 30°C and 60% relative humidity. On one occasion a skin cooling procedure was implemented (in random counterbalanced order), with subjects wearing an ice cooling jacket both before (for five minutes) and in the recovery periods (2 x 5 min and 1 x 10 min) during the test. Measures of performance (work done and power output on each sprint), heart rates, blood lactate concentrations, core (rectal) and skin temperatures, sweat loss, perceived exertion, and ratings of thirst, thermal discomfort, and fatigue were obtained in both trials. Results: In the cooling condition, chest (torso) skin temperature, thermal discomfort, and rating of thirst were all significantly lower (p<0.05), but no significant difference (p>0.05) was observed between conditions for measures of work done, power output, heart rate, blood lactate concentration, core or mean skin temperature, perceived exertion, sweat loss, or ratings of fatigue. However, high effect sizes indicated trends to lowered lactate concentrations, sweat loss, and mean skin temperatures in the cooling condition. Conclusions: The intermittent use of an ice cooling jacket, both before and during a repeat sprint cycling protocol in warm/humid conditions, did not improve physical performance, although the perception of thermal load was reduced. Longer periods of cooling both before and during exercise (to lower mean skin temperature by a greater degree than observed here) may be necessary to produce such a change.

Duffield, R; Dawson, B; Bishop, D; Fitzsimons, M; Lawrence, S

2003-01-01

149

Future Dry Spells in the Southwest US Aggravated by Climate Warming (Invited)  

NASA Astrophysics Data System (ADS)

The early 21st century drought is an example of the kinds of droughts the Southwest United States is prone to. Such droughts tend to take on large southwest footprints, although both observations and climate model simulations display different degrees of dryness in California, the Great Basin, and the Colorado basin. The early 21st century drought has been more severe in the Colorado basin than in California. As quantified by the VIC hydrological model, the historically most extreme droughts have tended to build up and finally abate over an extended multiyear period. Especially during the early 21st century, observed Southwest droughts have been exacerbated by anomalously warm summer temperatures. This tendency may continue—several different 21st century climate model simulations suggest that dry years will experience anomalously warm summer temperatures. These severe future droughts are aggravated by enhanced, globally warmed temperatures that reduce spring snowpack and late spring and summer soil moisture. As the climate continues to warm, soil moisture deficits accumulate beyond historical levels, indicating there could be larger reductions in runoff in the Colorado and other key basins of the Southwest.

Cayan, D. R.; Das, T.; Pierce, D. W.; Barnett, T. P.; Tyree, M.; Gershunov, A.

2010-12-01

150

Cold to Warm and Warm to Cold: A Comparison of rates and signatures of climate change going into and out of the Younger Dryas  

NASA Astrophysics Data System (ADS)

The most recent, very large (15 degrees C change in mean annual temperature) and very abrupt (50 years or less) climate change recorded in Greenland ice cores is the end of the Younger Dryas (YD). While this cold to warm transition has been extensively studied in ice cores using tools such as stable isotopes in ice, gas concentrations, stable isotopes in gases, snow chemistry, snow accumulation, and electrical conductivity of ice, the start of the YD has received much less attention in ice core analyses. In contrast, we have better theories for how the YD began, than how it ended. We focus here on the Greenland ice core record of the beginning of the YD, with an eye to the speed and nature of this abrupt climate change, and what the ice evidence may tell us concerning the fingerprint, and thus potential processes, of climate change left by this event. The first challenge is identifying the beginning of the YD in the ice core. Warm to cold transitions in isotopes in ice cores can be muted if winter snows are lost as a result of the colder conditions. This appears to be the case in the Greenland cores. Deuterium excess, which records ocean conditions during moisture evaporation, on the other hand, retains its sharpness. At the beginning of the YD, XS changes in NorthGRIP in a matter of years, a signal similar in size and speed to that seen at the end of the YD, but opposite in sign. Other signals are not similar in size and speed, however. These differences between the beginning and end of the YD will be discussed, and can reveal clues to the nature and timing of the climate changes. For example, continental dust does not change (increase) rapidly at the beginning of the YD cold period, but rather is delayed by decades. This suggests that there may be is a lag in the production of dust as ecosystems slowly dry and transform in response to the climate change.

Popp, T.; White, J.; Sveinbjornsdottir, A.; Masson-Delmotte, V.; Johnsen, S.; Jouzel, J.

2003-12-01

151

McMurdo Dry Valleys Climate Response to Plio-Pleistocene Warm Interglacial Climate Forcing  

NASA Astrophysics Data System (ADS)

The Antarctic Drilling Program recovered high quality Neogene sediment cores off of the coast of Ross Island recording a series of ice-contact, ice-proximal, ice-distal and marine facies suggesting grounding line migration along the sea floor. Chronology control of the core places glacial variability consistent with ~41 kyr orbital forcing. The marine facies suggests episodes of open-water conditions and elevated sea-surface temperatures in McMurdo Sound and the Ross Sea during the Pliocene. Recent Antarctic ice sheet modeling efforts have supported episodic retreat of the sea ice and possibly a frequent collapse of the West Antarctic Ice Sheet (WAIS) during the warmest intervals of the Pliocene-Pleistocene. Such repeated reduction in the Antarctic Ice Sheets occurs at a time when terrestrial records from near-by McMurdo Dry Valleys call for enduring hyper-arid cold desert conditions since the mid-to early Miocene. To assess whether hyper-arid cold desert climate could exist at high elevations within the McMurdo Dry Valleys during episodes of a diminished ice sheet (and near-by open water conditions), or if in fact these conditions are mutually exclusive, we simulated both present day (for validation) and paleo-climate conditions for Antarctic using a high resolution Regional Climate Model (RegCM3) nested within a medium resolution Global Climate Model (GCM) to predict paleo-climate as a function of ice sheet variability. RegCM3 simulations for paleo-conditions focused on the response of the Ross Sea sector to 1) orbital changes consistent with peak austral summer warmth, 2) reduction of ice shelves including the loss of the Ross and Filchner-Ronne Ice Shelves, 3) higher than modern carbon dioxide concentrations (400 - 800 ppmv) and 4) a highly diminished WAIS as predicted by the ice-sheet model. Results show mean atmospheric temperatures in the McMurdo Dry Valleys are most sensitive to loss of sea ice in McMurdo Sound / Ross Sea. If we assume a loss of marine grounded ice and remove the Antarctic ice shelves the mean atmospheric temperatures in the McMurdo Dry Valleys increases; model results suggest temperatures were 2.78°C and 2.38°C warmer than today at the coast and inland respectively although the rise in atmospheric temperatures during the summer months is typically of a smaller magnitude compared to the temperature rise predicted for the winter months. As expected the model showed warmer mean atmospheric temperatures with elevated levels of CO2. Precipitation also increased in the McMurdo Dry Valleys with increasing values of CO2. Initial model results for simulations run with a diminished WAIS predict increased atmospheric temperatures for most of the continent; temperature increase within the Transantarctic Mountains and McMurdo Dry Valleys is below the mean rise in Antarctic temperature for this simulation.

Kowalewski, D. E.; Deconto, R.; Seth, A.; Pollard, D.

2010-12-01

152

Adaptive strategies and life history characteristics in a warming climate: salmon in the Arctic?  

USGS Publications Warehouse

In the warming Arctic, aquatic habitats are in flux and salmon are exploring their options. Adult Pacific salmon, including sockeye (Oncorhynchus nerka), coho (O. kisutch), Chinook (O. tshawytscha), pink (O. gorbuscha) and chum (O. keta) have been captured throughout the Arctic. Pink and chum salmon are the most common species found in the Arctic today. These species are less dependent on freshwater habitats as juveniles and grow quickly in marine habitats. Putative spawning populations are rare in the North American Arctic and limited to pink salmon in drainages north of Point Hope, Alaska, chum salmon spawning rivers draining to the northwestern Beaufort Sea, and small populations of chum and pink salmon in Canada’s Mackenzie River. Pacific salmon have colonized several large river basins draining to the Kara, Laptev and East Siberian seas in the Russian Arctic. These populations probably developed from hatchery supplementation efforts in the 1960’s. Hundreds of populations of Arctic Atlantic salmon (Salmo salar) are found in Russia, Norway and Finland. Atlantic salmon have extended their range eastward as far as the Kara Sea in central Russian. A small native population of Atlantic salmon is found in Canada’s Ungava Bay. The northern tip of Quebec seems to be an Atlantic salmon migration barrier for other North American stocks. Compatibility between life history requirements and ecological conditions are prerequisite for salmon colonizing Arctic habitats. Broad-scale predictive models of climate change in the Arctic give little information about feedback processes contributing to local conditions, especially in freshwater systems. This paper reviews the recent history of salmon in the Arctic and explores various patterns of climate change that may influence range expansions and future sustainability of salmon in Arctic habitats. A summary of the research needs that will allow informed expectation of further Arctic colonization by salmon is given.

Nielsen, Jennifer L.; Ruggerone, Gregory T.; Zimmerman, Christian E.

2013-01-01

153

Abrupt climate change in West Antarctica and Greenland during the last deglacial warming  

NASA Astrophysics Data System (ADS)

The WAIS Divide ice core is the first Southern Hemisphere record with precision similar to ice cores from Greenland. The annually resolved timescale and small gas-age ice-age difference allow the phasing of climate change in the two hemispheres to be compared with unprecedented precision. We focus on the three abrupt climate changes in Greenland during the deglacial transition and the corresponding changes at WAIS Divide. The onset of the Antarctic Cold Reversal (ACR) is clearly defined in the WAIS Divide record and lagged the Bolling-Allerod (BA) warming by 150×50 years. The phasing of the other two abrupt climate changes cannot be distinguished from synchronous with an uncertainty of ~200 years because the transitions from warming to cooling (or cooling to warming) are not distinct in the WAIS Divide record. The lead-lag relationships of no more than a couple centuries confirm the tight coupling between hemispheres during the deglaciation. The independent timescale of WAIS Divide confirms that meltwater Pulse 1a began near-coincident with the BA and ACR although the lack of direct synchronization between the annually dated ice-core imescales and the radiometrically dated coral timescale prevents the phasing from being known to better than a couple of centuries. A new observation from WAIS Divide is that accumulation increased ~40% between 12.0 and 11.6 ka, with the accumulation increase ending approximately coincident with the warming at the end of the Younger Dryas in Greenland. Other Antarctic ice cores lack timescales with sufficient resolution to identify such abrupt changes so it is unclear how much of Antarctica was affected by the increased accumulation rates. The inter-hemispheric relationships are often limited to a discussion of warming, but the WAIS Divide records suggests that the moisture transport may be another important constraint on the mechanisms that drive abrupt climate change.

Fudge, T. J.; Steig, E. J.; Brook, E.; Buizert, C.; Conway, H.; Ding, Q.; Markle, B. R.; McConnell, J. R.; Pedro, J. B.; Schoenemann, S. W.; Severinghaus, J. P.; Sigl, M.; Sowers, T. A.; Taylor, K.; Waddington, E. D.

2013-12-01

154

Secular warming trend and climate variability of the tropical Indian Ocean  

NASA Astrophysics Data System (ADS)

Sea surface temperature (SST) has been increasingly steadily over the tropical Indian Ocean (TIO) since 1950s despite the lack of a clear trend in net surface heat flux. Fritz Schott called this the "heat flux dilemma" for the TIO warming. Scale analysis shows that for slow warming as is observed over the TIO, the time tendency term of the ocean mixed layer heat content is one order of magnitude smaller than the changes in components of surface heat flux. We then turn to the IPCC AR4 Climate of 20th Century simulations and examine how the balance among heat flux components determines the magnitude of the warming. Models are generally successful in simulating the TIO warming trend under greenhouse gas and other climate forcing. In models, the changes in net surface heat flux are indeed small and the warming is trapped in the top 125 m depth. Analysis of the model output suggests the following quasi-equilibrium adjustments among various surface heat flux components. The warming is triggered by the increased downward longwave radiation in response to the increasing greenhouse gas concentrations, amplified by the water vapor feedback and atmospheric adjustments such as weakened winds that act to suppress latent and sensible heat flux from the ocean. The sea surface temperature dependency of evaporation is the major damping mechanism. The simulated changes in surface solar radiation are highly correlated with inter-model variability in SST trend, indicating that uncertainties in cloud change are responsible for the spread in the simulated SST trend. To resolve Fritz's heat-flux dilemma, it is important to monitor changes in radiative flux and key parameters to turbulent heat flux such as relative humidity and stability. The warming of tropical oceans in response to increased greenhouse gas concentrations could cause changes in modes of climate variability. The Walker circulation, in particular, is projected to weaken, reducing the westerly winds in the equatorial Indian Ocean and raising the thermocline in the east. By itself, the thermocline shoaling would lead to an intensified Indian Ocean dipole (IOD) mode but the interannual IOD variance remains nearly constant in global warming simulations. We will present results from our analysis to resolve this dilemma of TIO climate change.

Xie, S.-P.; Du, Y.; Zheng, X.; Vecchi, G.

2009-04-01

155

Climate Warming and 21st-Century Drought in Southwestern North America  

NASA Astrophysics Data System (ADS)

Since 2000, southwestern North America has experienced widespread drought. Lakes Powell and Mead are now at less than 50% of their reservoir capacity, and drought or fire-related states of emergency were declared this past summer by governors in six western states. As with other prolonged droughts, such as the Dust Bowl during the 1930s, aridity has at times extended from northern Mexico to the southern Canadian prairies. A synthesis of climatological and paleoclimatological studies suggests that a transition to a more arid climate may be occurring due to global warming, with the prospect of sustained droughts being exacerbated by the potential reaction of the Pacific Ocean to warming.

MacDonald, Glen M.; Stahle, David W.; Diaz, Jose Villanueva; Beer, Nicholas; Busby, Simon J.; Cerano-Paredes, Julian; Cole, Julie E.; Cook, Edward R.; Endfield, Georgina; Gutierrez-Garcia, Genaro; Hall, Beth; Magana, Victor; Meko, David M.; Méndez-Pérez, Matias; Sauchyn, David J.; Watson, Emma; Woodhouse, Connie A.

2008-02-01

156

Expansion of global drylands under a warming climate  

NASA Astrophysics Data System (ADS)

Global drylands encompassing hyper-arid, arid, semiarid, and dry subhumid areas cover about 41% of the earth's terrestrial surface and are home to more than a third of the world's population. By analyzing observations for 1948-2008 and climate model simulations for 1948-2100, we show that global drylands have expanded in last sixty years and will continue to expand in the 21st century. By the end of this century, the world's drylands under a high greenhouse gas emission scenario are projected to be 5.8 × 106 km2 (or 10%) larger than in the 1961-1990 climatology. The major expansion of arid regions will occur over southwest North America, the northern fringe of Africa, southern Africa, and Australia, while major expansions of semiarid regions will occur over the north side of the Mediterranean, southern Africa, and North and South America. The global dryland expansions will increase the population affected by water scarcity and land degradations.

Feng, S.; Fu, Q.

2013-06-01

157

Potential malaria outbreak in Germany due to climate warming: risk modelling based on temperature measurements and regional climate models  

Microsoft Academic Search

Purpose  Climate warming can change the geographic distribution and intensity of the transmission of vector-borne diseases such as\\u000a malaria. The transmitted parasites usually benefit from increased temperatures as both their reproduction and development\\u000a are accelerated. Lower Saxony (northwestern Germany) has been a malaria region until the 1950s, and the vector species are\\u000a still present throughout Germany. This gave reason to investigate

Marcel Holy; Gunther Schmidt; Winfried Schröder

2011-01-01

158

Impacts of peatland forestation on regional climate conditions in Finland  

NASA Astrophysics Data System (ADS)

Climate response to anthropogenic land cover change happens more locally and occurs on a shorter time scale than the global warming due to increased GHGs. Over the second half of last Century, peatlands were vastly drained in Finland to stimulate forest growth for timber production. In this study, we investigate the biophysical effects of peatland forestation on near-surface climate conditions in Finland. For this, the regional climate model REMO, developed in Max Plank Institute (currently in Climate Service Center, Germany), provides an effective way. Two sets of 15-year climate simulations were done by REMO, using the historic (1920s; The 1st Finnish National Forest Inventory) and present-day (2000s; the 10th Finnish National Forest Inventory) land cover maps, respectively. The simulated surface air temperature and precipitation were then analyzed. In the most intensive peatland forestation area in Finland, the differences in monthly averaged daily mean surface air temperature show a warming effect around 0.2 to 0.3 K in February and March and reach to 0.5 K in April, whereas a slight cooling effect, less than 0.2 K, is found from May till October. Consequently, the selected snow clearance dates in model gridboxes over that area are advanced 0.5 to 4 days in the mean of 15 years. The monthly averaged precipitation only shows small differences, less than 10 mm/month, in a varied pattern in Finland from April to September. Furthermore, a more detailed analysis was conducted on the peatland forestation area with a 23% decrease in peatland and a 15% increase in forest types. 11 day running means of simulated temperature and energy balance terms, as well as snow depth were averaged over 15 years. Results show a positive feedback induced by peatland forestation between the surface air temperature and snow depth in snow melting period. This is because the warmer temperature caused by lower surface albedo due to more forest in snow cover period leads to a quicker and earlier snow melting. Meanwhile, surface albedo is reduced and consequently surface air temperature is increased. Additionally, the maximum difference from individual gridboxes in this area over 15 years of 11 day running means of daily mean surface air temperature reaches 2 K, which is four times as much as the maximum difference of 15-year regional average of that. This illustrates that the spring warming effect from peatland forestation in Finland is highly heterogeneous spatially and temporally.

Gao, Yao; Markkanen, Tiina; Backman, Leif; Henttonen, Helena M.; Pietikäinen, Joni-Pekka; Laaksonen, Ari

2014-05-01

159

Interfacing Single Column Lake and Atmospheric Models: Application over Lake Geneva for Observed and Climate Warming Scenario  

NASA Astrophysics Data System (ADS)

A single-column atmospheric model has been coupled to a single-column lake model to simulate present-day as well as future lake temperature profiles following global climate warming conditions. Results of multi-year climate simulations are shown for the case of the deep station SHL2 (309 m) of Lake Geneva, Switzerland. The atmospheric model termed FIZL, is a column version of a limited-area model developed for regional climate modelling based on an off-line downscaling of GCM simulations. It is physically-based and it requires outputs from a previous GCM integration. The issues of local lake climate is addressed by combining precomputed atmospheric large-scale transports of momentum, heat, and moisture, called "the dynamics," and recomputed subgrid-scale parameterized effect (solar and infrared radiation fluxes, and latent and sensible heat fluxes), called "the physics," with the explicit numerical computations of the evolving lower boundary conditions provided by the lake model. The lake model, called k-epsilon (k-e), combines a buoyancy-extended k-e model with a seiche excitation and damping model to predict the diffusivity below the surface mixed layer. In this model, the vertical turbulent diffusivities are determined from the turbulent kinetic energy and energy dissipation. Details of the atmospheric-lake interface module, and a sensitivity analysis of the simulated thermal profiles to this coupler parameters are presented. Finally statistics of the change in the lake thermal profiles is also shown for the case of an equilibrium 2xCO2 global climate warming scenario.

Goyette, S.; Perroud, M.

2008-12-01

160

Warming-induced increase in aerosol number concentration likely to moderate climate change  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles influence the climate system directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. Apart from black carbon aerosol, aerosols cause a negative radiative forcing at the top of the atmosphere and substantially mitigate the warming caused by greenhouse gases. In the future, tightening of controls on anthropogenic aerosol and precursor vapour emissions to achieve higher air quality may weaken this beneficial effect. Natural aerosols, too, might affect future warming. Here we analyse long-term observations of concentrations and compositions of aerosol particles and their biogenic precursor vapours in continental mid- and high-latitude environments. We use measurements of particle number size distribution together with boundary layer heights derived from reanalysis data to show that the boundary layer burden of cloud condensation nuclei increases exponentially with temperature. Our results confirm a negative feedback mechanism between the continental biosphere, aerosols and climate: aerosol cooling effects are strengthened by rising biogenic organic vapour emissions in response to warming, which in turn enhance condensation on particles and their growth to the size of cloud condensation nuclei. This natural growth mechanism produces roughly 50% of particles at the size of cloud condensation nuclei across Europe. We conclude that biosphere-atmosphere interactions are crucial for aerosol climate effects and can significantly influence the effects of anthropogenic aerosol emission controls, both on climate and air quality.

Paasonen, Pauli; Asmi, Ari; Petäjä, Tuukka; Kajos, Maija K.; Äijälä, Mikko; Junninen, Heikki; Holst, Thomas; Abbatt, Jonathan P. D.; Arneth, Almut; Birmili, Wolfram; van der Gon, Hugo Denier; Hamed, Amar; Hoffer, András; Laakso, Lauri; Laaksonen, Ari; Richard Leaitch, W.; Plass-Dülmer, Christian; Pryor, Sara C.; Räisänen, Petri; Swietlicki, Erik; Wiedensohler, Alfred; Worsnop, Douglas R.; Kerminen, Veli-Matti; Kulmala, Markku

2013-06-01

161

A regional response in mean westerly circulation and rainfall to projected climate warming over Tasmania, Australia  

NASA Astrophysics Data System (ADS)

Coupled ocean-atmosphere general circulation models (GCMs) lack sufficient resolution to model the regional detail of changes to mean circulation and rainfall with projected climate warming. In this paper, changes in mean circulation and rainfall in GCMs are compared to those in a variable resolution regional climate model, the Conformal Cubic Atmospheric Model (CCAM), under a high greenhouse gas emissions scenario. The study site is Tasmania, Australia, which is positioned within the mid-latitude westerlies of the southern hemisphere. CCAM projects a different response in mean sea level pressure and mid-latitude westerly circulation to climate warming to the GCMs used as input, and shows greater regional detail of the boundaries between regions of increasing and decreasing rainfall. Changes in mean circulation dominate the mean rainfall response in western Tasmania, whereas changes to rainfall in the East Coast are less related to mean circulation changes. CCAM projects an amplification of the dominant westerly circulation over Tasmania and this amplifies the seasonal cycle of wet winters and dry summers in the west. There is a larger change in the strength than in the incidence of westerly circulation and rainfall events. We propose the regional climate model displays a more sensitive atmospheric response to the different rates of warming of land and sea than the GCMs as input. The regional variation in these results highlight the need for dynamical downscaling of coupled general circulation models to finely resolve the influence of mean circulation and boundaries between regions of projected increases and decreases in rainfall.

Grose, Michael R.; Corney, Stuart P.; Katzfey, Jack J.; Bennett, James C.; Holz, Gregory K.; White, Christopher J.; Bindoff, Nathaniel L.

2013-04-01

162

Global warming impacts of ozone-safe refrigerants and refrigeration, heating, and air-conditioning technologies  

SciTech Connect

International agreements mandate the phase-out of many chlorine containing compounds that are used as the working fluid in refrigeration, air-conditioning, and heating equipment. Many of the chemical compounds that have been proposed, and are being used in place of the class of refrigerants eliminated by the Montreal Protocol are now being questioned because of their possible contributions to global warming. Natural refrigerants are put forth as inherently superior to manufactured refrigerants because they have very low or zero global warming potentials (GWPs). Questions are being raised about whether or not these manufactured refrigerants, primarily hydrofluorocarbons (HFCs), should be regulated and perhaps phased out in much the same manner as CFCs and HCFCs. Several of the major applications of refrigerants are examined in this paper and the results of an analysis of their contributions to greenhouse warming are presented. Supermarket refrigeration is shown to be an application where alternative technologies have the potential to reduce emissions of greenhouse gases (GHG) significantly with no clear advantage to either natural or HFC refrigerants. Mixed results are presented for automobile air conditioners with opportunities to reduce GHG emissions dependent on climate and comfort criteria. GHG emissions for hermetic and factory built systems (i.e. household refrigerators/freezers, unitary equipment, chillers) are shown to be dominated by energy use with much greater potential for reduction through efficiency improvements than by selection of refrigerant. The results for refrigerators also illustrate that hydrocarbon and carbon dioxide blown foam insulation have lower overall effects on GHG emissions than HFC blown foams at the cost of increased energy use.

Fischer, S.; Sand, J.; Baxter, V.

1997-12-01

163

Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions  

Microsoft Academic Search

Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by

Jinlun Zhang

2007-01-01

164

Greenhouse gas release from arctic permafrost: positive feedback to climate warming (Invited)  

NASA Astrophysics Data System (ADS)

The release of carbon (C) in the form of greenhouse gases from thawing permafrost is one of the most likely and important positive feedbacks from the land to the atmosphere in a warmer world. Perennially frozen ground, known as permafrost, covers 20 percent of the Earth’s land surface. Recent accounting for C stored as far as 80m beneath the surface in permafrost (950 billion tons) more than doubles previous inventory estimates and is comparable to the current atmospheric CO2 burden of 750 billion tons. Permafrost organic C accumulated over tens of thousands of years. In its frozen state this C is sequestered from the atmosphere, mitigating climate warming. Long term borehole from Siberia and North America attest that permafrost is thawing. A third to half of permafrost is now within a degree to a degree and a half of thawing. In places where permafrost temperature crosses the critical 0°C threshold, ice melts causing thermokarst (ground surface collapse). Thermokarst features such as sink holes, pits, slope failure, mud flows, and the formation, expansion, and drainage of thaw lakes are widespread, up to 90% of the land area in some areas of the Arctic. Dating of features revealed that this process has been going on for the past 10,000 years, since the Earth entered the most recent interglacial warm period. However, satellite records during the past 55 years suggest that permafrost thaw in some regions is accelerating. What will happen to the climate as the rest of the permafrost thaws? When permafrost thaws, organic C is made available to microbes, which rapidly degrade it, producing greenhouse gases such as CO2 and methane (CH4, 25 times the global warming potential of CO2 over 100 years). A particularly important region for greenhouse gas emissions is the Siberian Yedoma Ice Complex (10^6 km2), a Pliestocene-aged permafrost type that contains roughly half of the Arctic’s permafrost C stock. Based on patterns of yedoma degradation during the present interglacial period, estimates of the amount of C remaining in permafrost today, long term field measurements, laboratory incubation experiments, and mass balance calculations of the efficiency of CH4 production from thawed permafrost, we predict that at least 50 billion tons of CH4 (equivalent to 10 times the current atmospheric methane burden) will escape from thermokarst lakes in Siberia as yedoma thaws. More CH4 will be released from the remainder of arctic lakes. Under current projections of warming and thaw in the Arctic (7-8 deg C by 2100), thermokarst will release 0.1-0.2 billion tons CH4 yr-1 by 2100, an order of magnitude more than its current source strength, adding another 20-40% of all human and natural sources of CH4 to the atmosphere. Frozen soils which thaw under aerobic conditions will produce CO2 with projected emissions of ~0.5-1.0 billion tons C yr-1, constituting approximately 10% of modern anthropogenic emission.

Walter Anthony, K. M.; Zimov, S. A.

2009-12-01

165

Improving golf performance with a warm up conditioning programme  

PubMed Central

Objectives: To determine whether a golf specific warm up programme (both immediately prior to play and after performing it five times a week for 5 weeks) improved performance in 10 male golfers compared with 10 controls matched for age, sex, and handicap. Methods: Twenty male golfers were matched for age (±2 years) and handicap (±1 stroke). Club head speed was assessed by two dimensional video analysis in a laboratory setting. In week 1, all golfers performed 10 strokes. In weeks 2 and 7, the controls underwent the same procedure as in week 1. The exercise group performed the golf specific warm up followed by their 10 strokes. Between weeks 2 and 7, the exercise group performed the specially designed warm up five times a week for 5 weeks. Results: The mean club head speeds of the exercise group improved at each testing week. Between weeks 1 and 2, golfers in the exercise group improved their club head speed on average by 3–6 m/s (12.8%), and between weeks 1 and 7, they increased their club head speeds by 7–10 m/s (24.0%). With the exception of one golfer whose club head speed varied by 1.7 m/s, the mean club head speeds of the golfers in the control group hardly varied over the testing period (range: 0.3–0.8 m/s). A significant difference (p = 0.029) was found between the mean club head speeds of the exercise and control groups over the duration of the study, and a significant interaction over time (p<0.001) was also found. Conclusions: This study has shown that golfers' performances will be significantly improved by undertaking a golf specific warm up programme compared with not performing the warm up.

Fradkin, A; Sherman, C; Finch, C

2004-01-01

166

Above- and belowground linkages in Sphagnum peatland: climate warming affects plant-microbial interactions.  

PubMed

Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above- and belowground linkages that regulate soil organic carbon dynamics and C-balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top-predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum-polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above- and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands. PMID:23504838

Jassey, Vincent E J; Chiapusio, Geneviève; Binet, Philippe; Buttler, Alexandre; Laggoun-Défarge, Fatima; Delarue, Frédéric; Bernard, Nadine; Mitchell, Edward A D; Toussaint, Marie-Laure; Francez, André-Jean; Gilbert, Daniel

2013-03-01

167

Spatiotemporal change in geographical distribution of global climate types in the context of climate warming  

NASA Astrophysics Data System (ADS)

After standardizing global land climate gridded data from the Climatic Research Unit TS (time-series) 3.1 dataset for the period 1901-2009, cluster analysis is used to objectively classify world climates into 14 climate types. These climate types establish a baseline classification map and the types are named according to Köppen-Geiger climate classifications. Although the cluster analysis and Köppen classification methods are very different, the distributions of climate types obtained by the two methods are similar. Moreover, the climate types we identify also coincide well with their corresponding vegetation types. Thus, cluster analysis can be used as an effective alternative to the Köppen classification method for classifying world climate types. The spatial and temporal changes in geographical distribution of global climate types were investigated in 25-year intervals, and Cohen's kappa coefficient is used to detect agreement between the periods. Globally, although an obvious trend in increasing global temperature is found, distribution of climate types overall show no distinct changes over the periods. However, at the regional scale, spatial change in distribution of climate types is evident in South America and Africa. In South America, larger areas of the "fully humid equatorial rainforest" (Af) and "equatorial savannah with dry winter" (Aw) climate types have changed types. In Africa, changes mainly occurred in the Af, "equatorial savannah with dry summer" (As), Aw, "steppe climate" (BS), and "desert climate" (BW) climate types. Moreover, some climate types, including Af, "equatorial monsoon" (Am), BS, BW, and "tundra climate" (ET), were susceptible to temporal climate changes, especially in the period 1976-2009.

Zhang, Xianliang; Yan, Xiaodong

2013-12-01

168

Expansion of global drylands under a warming climate  

NASA Astrophysics Data System (ADS)

Global drylands encompassing hyper-arid, arid, semiarid, and dry subhumid areas cover about 41 percent of the earth's terrestrial surface and are home to more than a third of the world's population. By analyzing observations for 1948-2008 and climate model simulations for 1948-2100, we show that global drylands have expanded in the last sixty years and will continue to expand in the 21st~century. By the end of this century, the world's drylands (under a high greenhouse gas emission scenario) are projected to be 5.8 × 106 km2 (or 10%) larger than in the 1961-1990 climatology. The major expansion of arid regions will occur over southwest North America, the northern fringe of Africa, southern Africa, and Australia, while major expansions of semiarid regions will occur over the north side of the Mediterranean, southern Africa, and North and South America. The global dryland expansions will increase the population affected by water scarcity and land degradations.

Feng, S.; Fu, Q.

2013-10-01

169

Potential impacts of climate warming on water supply reliability in the Tuolumne and Merced River Basins, California.  

PubMed

We present an integrated hydrology/water operations simulation model of the Tuolumne and Merced River Basins, California, using the Water Evaluation and Planning (WEAP) platform. The model represents hydrology as well as water operations, which together influence water supplied for agricultural, urban, and environmental uses. The model is developed for impacts assessment using scenarios for climate change and other drivers of water system behavior. In this paper, we describe the model structure, its representation of historical streamflow, agricultural and urban water demands, and water operations. We describe projected impacts of climate change on hydrology and water supply to the major irrigation districts in the area, using uniform 2 °C, 4 °C, and 6 °C increases applied to climate inputs from the calibration period. Consistent with other studies, we find that the timing of hydrology shifts earlier in the water year in response to temperature warming (5-21 days). The integrated agricultural model responds with increased water demands 2 °C (1.4-2.0%), 4 °C (2.8-3.9%), and 6 °C (4.2-5.8%). In this sensitivity analysis, the combination of altered hydrology and increased demands results in decreased reliability of surface water supplied for agricultural purposes, with modeled quantity-based reliability metrics decreasing from a range of 0.84-0.90 under historical conditions to 0.75-0.79 under 6 °C warming scenario. PMID:24465455

Kiparsky, Michael; Joyce, Brian; Purkey, David; Young, Charles

2014-01-01

170

Potential Impacts of Climate Warming on Water Supply Reliability in the Tuolumne and Merced River Basins, California  

PubMed Central

We present an integrated hydrology/water operations simulation model of the Tuolumne and Merced River Basins, California, using the Water Evaluation and Planning (WEAP) platform. The model represents hydrology as well as water operations, which together influence water supplied for agricultural, urban, and environmental uses. The model is developed for impacts assessment using scenarios for climate change and other drivers of water system behavior. In this paper, we describe the model structure, its representation of historical streamflow, agricultural and urban water demands, and water operations. We describe projected impacts of climate change on hydrology and water supply to the major irrigation districts in the area, using uniform 2°C, 4°C, and 6°C increases applied to climate inputs from the calibration period. Consistent with other studies, we find that the timing of hydrology shifts earlier in the water year in response to temperature warming (5–21 days). The integrated agricultural model responds with increased water demands 2°C (1.4–2.0%), 4°C (2.8–3.9%), and 6°C (4.2–5.8%). In this sensitivity analysis, the combination of altered hydrology and increased demands results in decreased reliability of surface water supplied for agricultural purposes, with modeled quantity-based reliability metrics decreasing from a range of 0.84–0.90 under historical conditions to 0.75–0.79 under 6°C warming scenario.

Kiparsky, Michael; Joyce, Brian; Purkey, David; Young, Charles

2014-01-01

171

Climate warming increases Greenland Ice Sheet surface mass balance variability  

NASA Astrophysics Data System (ADS)

We analyze Greenland Ice Sheet (GIS) surface mass balance (SMB) trends generated by the Community Earth System Model for the time period 1850-2100. In addition to the expected decrease in the mean SMB, our analysis reveals a significant secular increase in temporal, integrated SMB variability. The largest variability increase occurs during the 21st century, and arises primarily from growth of the GIS ablation zone (i.e., a decrease in the accumulation area ratio, AAR) in conjunction with a high ratio of ablation-zone to accumulation-zone specific SMB variability. A secondary cause of the overall variability increase is a rise in specific SMB variability itself in both the accumulation and ablation zones, due to increased accumulation variability and lengthened melt seasons. Simple sensitivity experiments indicate that neither mechanism (decrease in the AAR, and increased specific SMB variability) in isolation is capable of causing the overall increase in integrated SMB variability. However, by exposing more of the ice sheet to high-variability ablation, the decrease in the AAR is about twice as effective as increased specific SMB variability in causing the overall variability increase. Ablation-zone SMB variability is driven largely by variability in summertime melting which is in turn regulated by variability in summertime surface energy fluxes. Broader climate processes that regulate these fluxes will therefore exert increasing control on GIS SMB variability in the future. This future increase in SMB variability can be expected to impact GIS-sourced freshwater fluxes and GIS ice dynamic variability, and may also make it more difficult to diagnose future secular trends in GIS volume.

Fyke, J. G.; Vizcaino, M.; Lipscomb, W. H.; Sacks, W.

2013-12-01

172

Enhanced Climatic Warming in the Tibetan Plateau Due to Double CO2: A Model Study  

NASA Technical Reports Server (NTRS)

The NCAR (National Center for Atmospheric Research) regional climate model (RegCM2) with time-dependent lateral meteorological fields provided by a 130-year transient increasing CO2 simulation of the NCAR Climate System Model (CSM) has been used to investigate the mechanism of enhanced ground temperature warming over the TP (Tibetan Plateau). From our model results, a remarkable tendency of warming increasing with elevation is found for the winter season, and elevation dependency of warming is not clearly recognized in the summer season. This simulated feature of elevation dependency of ground temperature is consistent with observations. Based on an analysis of surface energy budget, the short wave solar radiation absorbed at the surface plus downward long wave flux reaching the surface shows a strong elevation dependency, and is mostly responsible for enhanced surface warming over the TP. At lower elevations, the precipitation forced by topography is enhanced due to an increase in water vapor supply resulted from a warming in the atmosphere induced by doubling CO2. This precipitation enhancement must be associated with an increase in clouds, which results in a decline in solar flux reaching surface. At higher elevations, large snow depletion is detected in the 2xCO2run. It leads to a decrease in albedo, therefore more solar flux is absorbed at the surface. On the other hand, much more uniform increase in downward long wave flux reaching the surface is found. The combination of these effects (i.e. decrease in solar flux at lower elevations, increase in solar flux at higher elevation and more uniform increase in downward long wave flux) results in elevation dependency of enhanced ground temperature warming over the TP.

Chen, Baode; Chao, Winston C.; Liu, Xiao-Dong; Lau, William K. M. (Technical Monitor)

2001-01-01

173

Warm-water decapods and the trophic amplification of climate in the North Sea  

PubMed Central

A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Here, we show that in the southern North Sea the proportion of decapods to bivalves doubled following a temperature-driven, abrupt ecosystem shift during the 1980s. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii now found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime.

Lindley, J. A.; Beaugrand, G.; Luczak, C.; Dewarumez, J.-M.; Kirby, R. R.

2010-01-01

174

Warm-water decapods and the trophic amplification of climate in the North Sea.  

PubMed

A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Here, we show that in the southern North Sea the proportion of decapods to bivalves doubled following a temperature-driven, abrupt ecosystem shift during the 1980s. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii now found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime. PMID:20554562

Lindley, J A; Beaugrand, G; Luczak, C; Dewarumez, J-M; Kirby, R R

2010-12-23

175

Warming climate extends dryness-controlled areas of terrestrial carbon sequestration  

PubMed Central

At biome-scale, terrestrial carbon uptake is controlled mainly by weather variability. Observational data from a global monitoring network indicate that the sensitivity of terrestrial carbon sequestration to mean annual temperature (T) breaks down at a threshold value of 16°C, above which terrestrial CO2 fluxes are controlled by dryness rather than temperature. Here we show that since 1948 warming climate has moved the 16°C T latitudinal belt poleward. Land surface area with T > 16°C and now subject to dryness control rather than temperature as the regulator of carbon uptake has increased by 6% and is expected to increase by at least another 8% by 2050. Most of the land area subjected to this warming is arid or semiarid with ecosystems that are highly vulnerable to drought and land degradation. In areas now dryness-controlled, net carbon uptake is ~27% lower than in areas in which both temperature and dryness (T < 16°C) regulate plant productivity. This warming-induced extension of dryness-controlled areas may be triggering a positive feedback accelerating global warming. Continued increases in land area with T > 16°C has implications not only for positive feedback on climate change, but also for ecosystem integrity and land cover, particularly for pastoral populations in marginal lands.

Yi, Chuixiang; Wei, Suhua; Hendrey, George

2014-01-01

176

Warming climate extends dryness-controlled areas of terrestrial carbon sequestration.  

PubMed

At biome-scale, terrestrial carbon uptake is controlled mainly by weather variability. Observational data from a global monitoring network indicate that the sensitivity of terrestrial carbon sequestration to mean annual temperature (T) breaks down at a threshold value of 16°C, above which terrestrial CO2 fluxes are controlled by dryness rather than temperature. Here we show that since 1948 warming climate has moved the 16°C T latitudinal belt poleward. Land surface area with T > 16°C and now subject to dryness control rather than temperature as the regulator of carbon uptake has increased by 6% and is expected to increase by at least another 8% by 2050. Most of the land area subjected to this warming is arid or semiarid with ecosystems that are highly vulnerable to drought and land degradation. In areas now dryness-controlled, net carbon uptake is ~27% lower than in areas in which both temperature and dryness (T < 16°C) regulate plant productivity. This warming-induced extension of dryness-controlled areas may be triggering a positive feedback accelerating global warming. Continued increases in land area with T > 16°C has implications not only for positive feedback on climate change, but also for ecosystem integrity and land cover, particularly for pastoral populations in marginal lands. PMID:24980649

Yi, Chuixiang; Wei, Suhua; Hendrey, George

2014-01-01

177

Medieval Warm Period, Little Ice Age, and 20th Century Climate Variability From Chesapeake Bay  

Microsoft Academic Search

We investigated late Holocene climate variability during the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century in the Mid-Atlantic region of the U. S. using Marion-Dufresne core MD99-2209 from Chesapeake Bay. Mg\\/Ca ratios in the ostracode Loxoconcha and oxygen and carbon isotopes in the benthic foraminifer Elphidium were used to reconstruct spring\\/early summer temperature (influenced by oceanic

T. M. Cronin; G. S. Dwyer; R. C. Thunell; H. J. Dowsett; E. J. Tappa; C. D. Vann

2001-01-01

178

The ice-core record - Climate sensitivity and future greenhouse warming  

Microsoft Academic Search

The prediction of future greenhouse-gas-warming depends critically on the sensitivity of earth's climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial-interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the

C. Lorius; D. Raynaud; J. Jouzel; J. Hansen; H. Le Treut

1990-01-01

179

Impacts of climate warming on lake fish community structure and potential effects on ecosystem function  

Microsoft Academic Search

Fish play a key role in the trophic dynamics of lakes, not least in shallow systems. With climate warming, complex changes\\u000a in fish community structure may be expected owing to the direct and indirect effects of temperature, and indirect effects\\u000a of eutrophication, water-level changes and salinisation on fish metabolism, biotic interactions and geographical distribution.\\u000a We review published and new data

Erik Jeppesen; Mariana Meerhoff; Kerstin Holmgren; Ivan González-Bergonzoni; Franco Teixeira-de Mello; Steven A. J. Declerck; Luc De Meester; Martin Søndergaard; Torben L. Lauridsen; Rikke Bjerring; José Maria Conde-Porcuna; Néstor Mazzeo; Carlos Iglesias; Maja Reizenstein; Hilmar J. Malmquist; Zhengwen Liu; David Balayla; Xavier Lazzaro

2010-01-01

180

500-year climate cycles stacking of recent centennial warming documented in an East Asian pollen record  

PubMed Central

Here we presented a high-resolution 5350-year pollen record from a maar annually laminated lake in East Asia (EA). Pollen record reflected the dynamics of vertical vegetation zones and temperature change. Spectral analysis on pollen percentages/concentrations of Pinus and Quercus, and a temperature proxy, revealed ~500-year quasi-periodic cold-warm fluctuations during the past 5350 years. This ~500-year cyclic climate change occurred in EA during the mid-late Holocene and even the last 150 years dominated by anthropogenic forcing. It was almost in phase with a ~500-year periodic change in solar activity and Greenland temperature change, suggesting that ~500-year small variations in solar output played a prominent role in the mid-late Holocene climate dynamics in EA, linked to high latitude climate system. Its last warm phase might terminate in the next several decades to enter another ~250-year cool phase, and thus this future centennial cyclic temperature minimum could partially slow down man-made global warming.

Xu, Deke; Lu, Houyuan; Chu, Guoqiang; Wu, Naiqin; Shen, Caiming; Wang, Can; Mao, Limi

2014-01-01

181

Is climate warming more consequential towards poles? The phenology of Lepidoptera in Finland.  

PubMed

The magnitude and direction of phenological shifts from climate warming could be predictably variable across the planet depending upon the nature of physiological controls on phenology, the thermal sensitivity of the developmental processes and global patterns in the climate warming. We tested this with respect to the flight phenology of adult nocturnal moths (3.33 million captures of 334 species) that were sampled at sites in southern and northern Finland during 1993-2012 (with years 2005-2012 treated as an independent model validation data set). We compared eight competing models of physiological controls on flight phenology to each species and found strong support for thermal controls of phenology in 66% of the species generations. Among species with strong thermal control of phenology in both the south and north, the average development rate was higher in northern vs. southern populations at 10 °C, but about the same at 15 and 20 °C. With a 3 °C increase in temperature (approximating A2 scenario of IPPC for 2090-2099 relative to 1980-1999) these species were predicted to advance their phenology on average by 17 (SE ± 0.3) days in the south vs. 13 (±0.4) days in the north. The higher development rates at low temperatures of poleward populations makes them less sensitive to climate warming, which opposes the tendency for stronger phenological advances in the north from greater increases in temperature. PMID:24115266

Valtonen, Anu; Leinonen, Reima; Pöyry, Juha; Roininen, Heikki; Tuomela, Jukka; Ayres, Matthew P

2014-01-01

182

Influence of a warm ocean current on regional climate in winter  

NASA Astrophysics Data System (ADS)

In East Asia, the Siberian high pressure system expels a cold northerly monsoon, resulting in the lower atmosphere receiving plenty of moisture when it meets the ocean. From this, every winter a huge amount of snow is provided from cumulus clouds for the north and west side of the Japanese Islands. But we also find that the winter precipitation in many locations in Japan can be predicted by a simple regression from the volume transport of the Tsushima Warm Current, which is a branch of Kuroshio. The correlation with 3-month lag is shown to exceed 0.8 in some cities. The meridional heat transport in the ocean may contribute to the changes of latent heat supply from the sea surface. Furthermore, the Tsushima Warm Current precedes the western Pacific teleconnection pattern based on an analysis conducted over the past 30 years. The western Pacific index in winter sharply succeeds the volume transport of the Tsushima Warm Current in autumn, but rather smoothly connects with the El Nino indices, indicating a considerable role of the warm current in the regional climate system. This ocean-to-atmosphere feedback also leads the synoptic variability and precipitation patterns in the region. Monitoring the warm current must improve long-range weather forecast.

Hirose, N.; Fukudome, K.; Nishimura, K.; Yamamoto, M.

2010-12-01

183

Impact of CO2Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization  

Microsoft Academic Search

Previous studies have found that idealized hurricanes, simulated under warmer, high-CO 2 conditions, are more intense and have higher precipitation rates than under present-day conditions. The present study explores the sensitivity of this result to the choice of climate model used to define the CO2-warmed environment and to the choice of convective parameterization used in the nested regional model that

Thomas R. Knutson; Robert E. Tuleya

2004-01-01

184

Changes in the structural composition and reactivity of Acer rubrum leaf litter tannins exposed to warming and altered precipitation: climatic stress-induced tannins are more reactive.  

PubMed

Climate change could increase the frequency with which plants experience abiotic stresses, leading to changes in their metabolic pathways. These stresses may induce the production of compounds that are structurally and biologically different from constitutive compounds. • We studied how warming and altered precipitation affected the composition, structure, and biological reactivity of leaf litter tannins in Acer rubrum at the Boston-Area Climate Experiment, in Massachusetts, USA. • Warmer and drier climatic conditions led to higher concentrations of protective compounds, including flavonoids and cutin. The abundance and structure of leaf tannins also responded consistently to climatic treatments. Drought and warming in combination doubled the concentration of total tannins, which reached 30% of leaf-litter DW. This treatment also produced condensed tannins with lower polymerization and a greater proportion of procyanidin units, which in turn reduced sequestration of tannins by litter fiber. Furthermore, because of the structural flexibility of these tannins, litter from this treatment exhibited five times more enzyme (?-glucosidase) complexation capacity on a per-weight basis. Warmer and wetter conditions decreased the amount of foliar condensed tannins. • Our finding that warming and drought result in the production of highly reactive tannins is novel, and highly relevant to climate change research as these tannins, by immobilizing microbial enzymes, could slow litter decomposition and thus carbon and nutrient cycling in a warmer, drier world. PMID:21371041

Tharayil, Nishanth; Suseela, Vidya; Triebwasser, Daniella J; Preston, Caroline M; Gerard, Patrick D; Dukes, Jeffrey S

2011-07-01

185

Warm climates of the past--a lesson for the future?  

PubMed Central

This Discussion Meeting Issue of the Philosophical Transactions A had its genesis in a Discussion Meeting of the Royal Society which took place on 10–11 October 2011. The Discussion Meeting, entitled ‘Warm climates of the past: a lesson for the future?’, brought together 16 eminent international speakers from the field of palaeoclimate, and was attended by over 280 scientists and members of the public. Many of the speakers have contributed to the papers compiled in this Discussion Meeting Issue. The papers summarize the talks at the meeting, and present further or related work. This Discussion Meeting Issue asks to what extent information gleaned from the study of past climates can aid our understanding of future climate change. Climate change is currently an issue at the forefront of environmental science, and also has important sociological and political implications. Most future predictions are carried out by complex numerical models; however, these models cannot be rigorously tested for scenarios outside of the modern, without making use of past climate data. Furthermore, past climate data can inform our understanding of how the Earth system operates, and can provide important contextual information related to environmental change. All past time periods can be useful in this context; here, we focus on past climates that were warmer than the modern climate, as these are likely to be the most similar to the future. This introductory paper is not meant as a comprehensive overview of all work in this field. Instead, it gives an introduction to the important issues therein, using the papers in this Discussion Meeting Issue, and other works from all the Discussion Meeting speakers, as exemplars of the various ways in which past climates can inform projections of future climate. Furthermore, we present new work that uses a palaeo constraint to quantitatively inform projections of future equilibrium ice sheet change.

Lunt, D. J.; Elderfield, H.; Pancost, R.; Ridgwell, A.; Foster, G. L.; Haywood, A.; Kiehl, J.; Sagoo, N.; Shields, C.; Stone, E. J.; Valdes, P.

2013-01-01

186

Seasonal rainfall and ecohydrological feedbacks ameliorate the potential hydrological impact of climate warming in a Mediterranean ecosystem  

NASA Astrophysics Data System (ADS)

A critical challenge for ecohydrologists is to improve our knowledge of how the hydrologic cycle will respond to environmental stimuli such as climate warming. In particular, we have an incomplete understanding of how climate warming may impact the partitioning of annual precipitation to evapotranspiration (ET) and groundwater recharge (R). This problem has evaded experimentalists due to the overwhelming challenge of measuring the entire water budget in systems with known boundary conditions, and under forecasted alterations in surface air temperatures. Yet, experimental results are critical for qualitatively evaluating model formulations and for identifying key system interactions. Here we present new data from a manipulative-microcosm experiment that examined the combined responses of ET, soil moisture (?), and deep percolation (a surrogate for R) to a 3.5 degree C temperature increase in a Mediterranean climate. The temperature increase was applied both symmetrically throughout the day, and asymmetrically such that daily minimum temperature was 5 degrees C greater than ambient and daily maximum temperature was 2 degrees C greater than ambient. We hypothesized that increasing air temperatures would accelerate and enhance plant growth and ET during the spring season, causing an associated reduction in R. Additionally, we anticipated greater soil desiccation during the summer drought period, resulting in a greater cumulative rainfall requirement to initiate R at the onset of the fall rains-both effects resulting in increased ET and reduced R at the annual time scale. Our results, spanning October 2007 through June 2010, showed that symmetric and asymmetric warming treatments enhanced ET by an average of 21.5 mm and 18.3 mm, respectively, during spring (April), with corresponding reductions in ?. This perturbation reduced R during late-spring storms, though the reductions amounted to less than 4% of annual R among all years. As a consequence of greater water use earlier in the spring, grasslands experiencing warming treatments also senesced earlier in the summer, whereas transpiration in grasslands experiencing ambient temperatures persisted later in the summer. This negative ecohydrological feedback caused ? to converge on similar residual values at the end of the summer drought under both ambient and imposed-warming conditions. The net result was no alteration of annual partitioning of rainfall to ET or R associated with the imposed warming scenarios-contrary to our initial expectation. These findings emphasize the predominant influence of the Mediterranean rainfall regime, where the plant growing season and ET occur largely out of phase with annual rainfall and R. Our results suggest that a 3.5 degree C warming signal may marginally accelerate the plant growing season, but with no significant reduction in R during the spring. Further, the seasonal-summer drought leads to water limited soil conditions that truncate the plant growing season, and ultimately negate the enhancement of ET observed during the spring.

Pangle, L. A.; McDonnell, J. J.; Gregg, J. W.

2011-12-01

187

Earlier wine-grape ripening driven by climatic warming and drying and management practices  

NASA Astrophysics Data System (ADS)

Trends in phenological phases associated with climate change are widely reported--yet attribution remains rare. Attribution research in biological systems is critical in assisting stakeholders to develop adaptation strategies, particularly if human factors may be exacerbating impacts. Detailed, quantified attribution helps to effectively target adaptation strategies, and counters recent tendencies to overattribute phenological trends to climate shifts. Wine grapes have been ripening earlier in Australia in recent years, often with undesirable impacts. Attribution analysis of detected trends in wine-grape maturity, using time series of up to 64 years in duration, indicates that two climate variables--warming and declines in soil water content--are driving a major portion of this ripening trend. Crop-yield reductions and evolving management practices have probably also contributed to earlier ripening. Potential adaptation options are identified, as some drivers of the trend to earlier maturity can be manipulated through directed management initiatives, such as managing soil moisture and crop yield.

Webb, L. B.; Whetton, P. H.; Bhend, J.; Darbyshire, R.; Briggs, P. R.; Barlow, E. W. R.

2012-04-01

188

Estimating thermal regimes of bull trout and assessing the potential effects of climate warming on critical habitats  

USGS Publications Warehouse

Understanding the vulnerability of aquatic species and habitats under climate change is critical for conservation and management of freshwater systems. Climate warming is predicted to increase water temperatures in freshwater ecosystems worldwide, yet few studies have developed spatially explicit modelling tools for understanding the potential impacts. We parameterized a nonspatial model, a spatial flow-routed model, and a spatial hierarchical model to predict August stream temperatures (22-m resolution) throughout the Flathead River Basin, USA and Canada. Model comparisons showed that the spatial models performed significantly better than the nonspatial model, explaining the spatial autocorrelation found between sites. The spatial hierarchical model explained 82% of the variation in summer mean (August) stream temperatures and was used to estimate thermal regimes for threatened bull trout (Salvelinus confluentus) habitats, one of the most thermally sensitive coldwater species in western North America. The model estimated summer thermal regimes of spawning and rearing habitats at <13 C° and foraging, migrating, and overwintering habitats at <14 C°. To illustrate the useful application of such a model, we simulated climate warming scenarios to quantify potential loss of critical habitats under forecasted climatic conditions. As air and water temperatures continue to increase, our model simulations show that lower portions of the Flathead River Basin drainage (foraging, migrating, and overwintering habitat) may become thermally unsuitable and headwater streams (spawning and rearing) may become isolated because of increasing thermal fragmentation during summer. Model results can be used to focus conservation and management efforts on populations of concern, by identifying critical habitats and assessing thermal changes at a local scale.

Jones, Leslie A.; Muhlfeld, Clint C.; Marshall, Lucy A.; McGlynn, Brian L.; Kershner, Jeffrey L.

2013-01-01

189

Sensitivity of spring phenology to warming across temporal and spatial climate gradients in two independent databases  

NASA Astrophysics Data System (ADS)

Disparate ecological datasets are often organized into databases post-hoc and then analyzed and interpreted in ways that may diverge from the purposes of the original data collections. Few studies, however, have attempted to quantify how biases inherent in these data (e.g., species richness, replication, climate) affect their suitability for addressing broad scientific questions, especially in under-represented systems (e.g., deserts, tropical forests) and wild communities. Here, we quantitatively compare the sensitivity of species first flowering and leafing dates to spring warmth in two phenological databases from the Northern Hemisphere. One—PEP725—has high replication within and across sites, but has low species diversity and spans a limited climate gradient. The other—NECTAR—includes many more species and a wider range of climates, but has fewer sites and low replication of species across sites. PEP725, despite low species diversity and relatively low seasonality, accurately captures the magnitude and seasonality of warming responses at climatically similar NECTAR sites, with most species showing earlier phenological events in response to warming. In NECTAR, the prevalence of temperature responders significantly declines with increasing mean annual temperature, a pattern that cannot be detected across the limited climate gradient spanned by the PEP725 flowering and leafing data. Our results showcase broad areas of agreement between the two databases, despite significant differences in species richness and geographic coverage, while also noting areas where including data across broader climate gradients may provide added value. Such comparisons help to identify gaps in our observations and knowledge base that can be addressed by ongoing monitoring and research efforts. Resolving these issues will be critical for improving predictions in understudied and undersampled systems outside of the temperature seasonal midlatitudes.

Cook, B. I.; Wolkovich, E. M.; Davies, J.; Ault, T. R.; Betancourt, J. L.; Allen, J.; Bolmgren, K.; Cleland, E. E.; Crimmins, T. M.; Kraft, N.; Lancaster, L.; Mazer, S.; McCabe, G. J.; McGill, B.; Parmesan, C.; Pau, S.; Regetz, J.; Salamin, N.; Schwartz, M. D.; Travers, S.

2012-12-01

190

Tittel: An Alternative to the Global Warming Potential for Comparing Climate Impacts of Emissions of Greenhouse Gases Title: An Alternative to the Global Warming Potential for Comparing Climate Impacts of Emissions of Greenhouse Gases  

Microsoft Academic Search

The Global Warming Potential (GWP) is used within the Kyoto Protocol to the United Nations Framework Convention on Climate Change as a metric for weighting the climatic impact of emissions of different greenhouse gases. The GWP has been subject to many criticisms because of its formulation, but nevertheless it has retained some favour because of the simplicity of its design

Keith P. Shine; Jan S. Fuglestvedt; Nicola Stuber

191

Modeling the subsurface thermal impact of Arctic thaw lakes in a warming climate  

NASA Astrophysics Data System (ADS)

Warming air temperatures in the Arctic are modifying the rates of thermokarst processes along Alaska's Arctic Coastal Plain. The Arctic Coastal Plain is dominated by thaw lakes. These kilometer-scale lakes are the most visible surface features in the region, and they provide important habitats for migratory birds. The lakes are formed by thermokarst processes, and are therefore susceptible to change as warming continues. We present a 1D numerical model of permafrost and subsidence processes in order to investigate the subsurface thermal impact of thaw lakes of various depths, and to evaluate how this impact might change in a warming climate. Currently, most thaw lakes in the region are shallow (<˜2 m deep), freeze to their base each winter, and are not underlain by permanently unfrozen ground (taliks). Field observations indicate that these shallow lakes have not greatly altered the thermal structure of the subsurface. Our model suggests that under a warming scenario, the number of lakes that do not freeze to their base during the winter, and are therefore underlain by taliks, will increase. Such changes could substantially alter the hydrology of the Arctic Coastal Plain.

Matell, N.; Anderson, R. S.; Overeem, I.; Wobus, C.; Urban, F. E.; Clow, G. D.

2013-04-01

192

Variability of terrestrial carbon cycle and its interaction with climate under global warming  

NASA Astrophysics Data System (ADS)

Land-atmosphere carbon exchange makes a significant contribution to the variability of atmospheric CO2 concentration on time scales of seasons to centuries. In this thesis, a terrestrial vegetation and carbon model, VEgetation-Global-Atmosphere-Soil (VEGAS), is used to study the interactions between the terrestrial carbon cycle and climate over a wide-range of temporal and spatial scales. The VEGAS model was first evaluated by comparison with FLUXNET observations. One primary focus of the thesis was to investigate the interannual variability of terrestrial carbon cycle related to climate variations, in particular to El Nino-Southern Oscillation (ENSO). Our analysis indicates that VEGAS can properly capture the response of terrestrial carbon cycle to ENSO: suppression of vegetative activity coupled with enhancement of soil decomposition, due to predominant warmer and drier climate patterns over tropical land associated with El Nino. The combined affect of these forcings causes substantial carbon flux into the atmosphere. A unique aspect of this work is to quantify the direct and indirect effects of soil wetness vegetation activities and consequently on land-atmosphere carbon fluxes. Besides this canonic dominance of the tropical response to ENSO, our modeling study simulated a large carbon flux from the northern mid-latitudes, triggered by the 1998-2002 drought and warming in the region. Our modeling indicates that this drought could be responsible for the abnormally high increase in atmospheric CO2 growth rate (2 ppm/yr) during 2002-2003. We then investigated the carbon cycle-climate feedback in the 21 st century. A modest feedback was identified, and the result was incorporated into the Coupled Carbon Cycle Climate Model Inter-comparison Project (C4MIP). Using the fully coupled carbon cycle-climate simulations from C4MIP, we examined the carbon uptake in the Northern High Latitudes poleward of 60°N (NHL) in the 21st century. C4MIP model results project that the NHL will be a carbon sink by 2100, as CO2 fertilization and warming stimulate vegetation growth, canceling the effect of enhancement of soil decomposition by warming. However, such competing mechanisms may lead to a switch of NHL from a net carbon sink to source after 2100. All these effects are enhanced as a result of positive carbon cycle-climate feedbacks.

Qian, Haifeng

193

Is equilibrium climate sensitivity the best predictor for future global warming? (Invited)  

NASA Astrophysics Data System (ADS)

When the climate system is subject to radiative forcing the planet is brought out of radiative balance and the thermal inertia of the planet makes the surface temperature lag behind the forcing. The time constant, which is the time for relaxation to a new equilibrium after a sudden change in forcing, has been considered to be an important parameter to determine. The equilibrium climate sensitivity Seq, the temperature raise per unit forcing after relaxation is complete, is another. In the industrialized epoch a major source for the present energy imbalance is the steady increase in anthropogenic forcing. If the climate system can be modeled as a hierarchy of interacting subsystems with increasing heat capacities and response times there will also be a hierarchy of climate sensitivities. One way of modeling this feature is to replace the standard exponentially decaying impulse-response function with one that is scale free, i.e., decaying like a power law. For a climate system which is subject only to random forcing modeled as a white Gaussian noise, the resulting climate variable is then a long-memory fractional Gaussian noise with a scale-free power spectral density. The final response to a step increase in the forcing is infinite for such a perfectly scale-free response function, since the response to an increase in the forcing will never saturate. This is of course unphysical, but rather than invalidating the scale-free response model it suggests the introduction of a frequency-dependent climate sensitivity S(f). Even in the exponential response model the amplitude response to an oscillation vanishes for high frequencies, but converges to Seq in the limit of low frequencies f. In the scale-free response model S(f) diverges in the low-frequency limit. We demonstrate that long-memory responses can explain important aspects of Northern hemisphere temperature variability over the last millennium and lead to new predictions of how much more warming there will be 'in the pipeline' in any given forcing scenario. The relation to scaling properties of local temperature data and spatial correlations in climate data is also discussed. References: Rypdal, M. and Rypdal, K.: Long-memory effects in linear-response models of Earth's temperature and implications for future global warming, submitted to J. Climate, http://arxiv.org/pdf/ 1305.5080v1.pdf, 2013. Rypdal, M. and Rypdal, K.: 'Predicting' northern hemisphere temperature for the previous millennium based on a parametric stochastic-dynamic model trained on the instrumental global temperature and forcing records, session PP012, this conference.

Rypdal, M.; Rypdal, K.

2013-12-01

194

The Sensitivity of Deep Convection to Environmental Humidity in Warm and Cold Climates  

NASA Astrophysics Data System (ADS)

Observations and theory indicate that column relative humidity is a powerful control on the prevalance of deep convection. A drier column implies that mixing between a saturated convecting parcel and its environment will lead to greater evaporative cooling and loss of buoyancy. Since the water vapor profile is a strong function of temperature, the absolute water vapor difference between cloud and environment is expected to increase in a warmer climate. Assuming no change in cloud properties, this implies that a given rate of fractional mixing will more rapidly deplete cloud buoyancy, enhancing the sensitivity of deep convection to variations in humidity in warmer climates. Here we use a Cloud Resolving Model to estimate the linear response of a cumulus ensemble to perturbations in environmental humidity within relatively cold and warm mean states. The System for Atmospheric Modeling is run over a uniform ocean with SST fixed at 297K and 303K, and states of radiative-convective equilibrium are perturbed with a set of steady large-scale moisture tendencies. The perturbed state vector of the domain-average moisture and temperature, along with the anomalous convective tendencies, are then used to define a matrix equation which may be inverted to yield estimates of the convective response to moisture perturbations. Differences in the modeled convective response between warm and cold climates are compared with simple scaling arguments. We also consider potential consequences for tropical intraseasonal variability, which is known to depend on the sensitivity of deep convection to its environment.

Arnold, N.; Kuang, Z.

2013-12-01

195

Arctic climate change with a 2 ? C global warming: Timing, climate patterns and vegetation change  

Microsoft Academic Search

The signatories to United Nations Framework Convention on Climate Change are charged with stabilizing the concentrations of\\u000a greenhouse gases in the atmosphere at a level that prevents dangerous interference with the climate system. A number of nations,\\u000a organizations and scientists have suggested that global mean temperature should not rise over 2 ?C above preindustrial levels. However, even a relatively moderate

Jed O. Kaplan; Mark New

2006-01-01

196

Climate Extremes Triggered State Shifting of US Great Plains Prairie under Experimental Warming  

NASA Astrophysics Data System (ADS)

Ecosystems can exist under multiple stable states. Transition from one stable state to another is usually triggered by perturbations such as climate extremes, which should be large enough to push the ecosystem over a threshold. Ecosystem state changes can alter ecosystem functions and services as dramatically as in Sahara with vegetation changes from tropical forests to grassland and deserts over 6000 years. Thus it is crucial to understand mechanisms underlying ecosystem state changes. State changes of ecosystem vegetation have been well documented in paleo-records and predicted to occur under climate change by dynamic global vegetation models. Paleo-records usually offer broad-scale patterns of ecosystem state changes over time and rarely offer much insight into fundamental mechanisms underlying the state changes. Model predictions may be calibrated against contemporary and paleo vegetation distributions but have not been carefully tested against experimental evidence. The latter, however, is extremely rare largely because global chance experiments are mostly short term. We have observed state shifting of a US Great Plains prairie under long-term experimental warming and clipping treatments. Our analysis of 11-year data from the experiment showed two-stage stimulations of aboveground net primary production (ANPP) with small increases in the first 7 followed by distinctly large increases under experimental warming in comparison with those under control. The two-stage ANPP simulations were corresponded with species reordering with the plant community over time but not related to warming-induced changes in temperature, soil moisture and nitrogen dynamics in the grassland. The state shifting of the grassland under the experimental warming was partly because our experimental site locates in an ecotone between the mixed and tall grass prairies. Under the experimental warming, the prairie was shifting from the mixed prairie as dominated by Schizachyrium scoparium (little blue stem) with a typical height of about 1 m to a typical tallgrass prairie dominated by Sorghastrum nutans (Indian grass) of about 2 m tall. Our results suggested that chronic experimental treatments differentially exerted impacts on individual species to certain thresholds, beyond which plant community structure and ecosystem functions were changing to a different state. , The threshold change was triggered by climate extremes with two consecutive drought years in 2005 and 2006 followed by a very wet year in 2007.

Luo, Y.; Xu, X.; Sherry, R.; Niu, S.; Li, D.; Xia, J.

2012-04-01

197

Science blogging: RealClimate.org and the Global Warming debate  

NASA Astrophysics Data System (ADS)

The media and public policy debate suffer from an extreme form of Attention Deficit Disorder. Compared to the daily news cycle, the progress of scientific debate within the peer-reviewed literature is extremely slow. This puts serious scientists who work in relatively politicised fields (global warming, evolution, stem cell research and the like) at a huge disadvantage when it comes to having their voices heard above the noise. Since Dec 2004, RealClimate.org has been operating as a group blog (a web-based journal) run by climate scientists for interested members of the public and the media. The aim has been to provide the context for climate-related news stories that is often missing in the mainstream media and to explain the basics of our field to the often confused, but curious, members of the public. In particular, it has provided rapid reaction to mis-uses and abuses of scientific results by policy advocates across the spectrum. Reactions to the blog have been overwhelmingly (but not uniformly) positive from both professionals in the media, the scientific community and the public. It has been described as the 'go-to site' for climate science in the New York Times, and received a Scientific American Science and Technology Web award in 2005. I will discuss what impacts RealClimate may have had and the pluses and minuses of trying to reach the public through this kind of outlet.

Schmidt, G. A.

2006-12-01

198

Competitive and demographic leverage points of community shifts under climate warming  

PubMed Central

Accelerating rates of climate change and a paucity of whole-community studies of climate impacts limit our ability to forecast shifts in ecosystem structure and dynamics, particularly because climate change can lead to idiosyncratic responses via both demographic effects and altered species interactions. We used a multispecies model to predict which processes and species' responses are likely to drive shifts in the composition of a space-limited benthic marine community. Our model was parametrized from experimental manipulations of the community. Model simulations indicated shifts in species dominance patterns as temperatures increase, with projected shifts in composition primarily owing to the temperature dependence of growth, mortality and competition for three critical species. By contrast, warming impacts on two other species (rendering them weaker competitors for space) and recruitment rates of all species were of lesser importance in determining projected community changes. Our analysis reveals the importance of temperature-dependent competitive interactions for predicting effects of changing climate on such communities. Furthermore, by identifying processes and species that could disproportionately leverage shifts in community composition, our results contribute to a mechanistic understanding of climate change impacts, thereby allowing more insightful predictions of future biodiversity patterns.

Sorte, Cascade J. B.; White, J. Wilson

2013-01-01

199

Changing hydrological conditions in the Po basin under global warming.  

PubMed

The Po River is a crucial resource for the Italian economy, since 40% of the gross domestic product comes from this area. It is thus crucial to quantify the impact of climate change on this water resource in order to plan for future water use. In this paper a mini ensemble of 8 hydrological simulations is completed from 1960 to 2050 under the A1B emission scenario, by using the output of two regional climate models as input (REMO and RegCM) at two different resolutions (25km-10km and 25km-3km). The river discharge at the outlet point of the basin shows a change in the spring peak of the annual cycle, with a one month shift from May to April. This shift is entirely due to the change in snowmelt timing which drives most of the discharge during this period. Two other important changes are an increase of discharge in the wintertime and a decrease in the fall from September to November. The uncertainty associated with the winter change is larger compared to that in the fall. The spring shift and the fall decrease of discharge imply an extension of the hydrological dry season and thus an increase in water stress over the basin. The spatial distributions of the discharge changes are in agreement with what is observed at the outlet point and the uncertainty associated with these changes is proportional to the amplitude of the signal. The analysis of the changes in the anomaly distribution of discharge shows that both the increases and decreases in seasonal discharge are tied to the changes in the tails of the distribution, i.e. to the increase or decrease of extreme events. PMID:24656403

Coppola, Erika; Verdecchia, Marco; Giorgi, Filippo; Colaiuda, Valentina; Tomassetti, Barbara; Lombardi, Annalina

2014-09-15

200

Changing hydrological conditions in the Po basin under global warming  

NASA Astrophysics Data System (ADS)

The Po River is a crucial resource for the Italian economy since 40% of the gross domestic product comes from this area. To quantify the impact of climate change on this water resource is then crucial for planning the water use and distribution in the near future. In this paper a mini ensemble of 8 hydrological simulations are completed from 1960 to 2050 under the A1B scenario, by using as input the output of two regional climate models (REMO and RegCM) at two different resolutions (25 km -10km and 25km-3km). The river discharge at the closing point of the basin shows a change in the spring pick of annual cycle and one month shift is evident from May to April. This shift is entirely due to the changing in the snowmelt timing because that drives most of the discharge in this period. The others two important changes are the increase of discharge in the wintertime and the decrease in fall from September to November. The uncertainty associated with the winter change is bigger compared to that in fall. The spring shift and the fall decrease of discharge imply an extension of the hydrological dry seasons and thus increasing water stress over the basin. The spatial distribution of the discharge changes are in agreement with what is observed at the closing point and the uncertainty associated with these changes are proportional to the amplitude of the signal. By looking at the changes in the anomaly distribution of discharge it seems evident that either the increase or decrease of seasonal discharge is tied to the changes in the tails of the distribution, namely to the increase or decrease of the extreme events.

Coppola, Erika; Verdecchia, Marco; Giorgi, Filippo; Colaiuda, Valentina; Tomassetti, Barbara; Lombardi, Annalina

2014-05-01

201

Changing forest water yields in response to climate warming: Results from long-term experimental watershed sites across North America  

NASA Astrophysics Data System (ADS)

Climate warming is projected to affect forest catchment water yields, but effects may vary among biomes. We hypothesized that catchments where water yields have varied relatively little in response to climate warming would be more resilient to warming effects than other types of catchments are. To test this hypothesis, we examined the variability in historical catchment water yields at long-term experimental watershed sites across Canada and the United States. Using the theoretical framework of the Budyko curve, which estimates catchment evaporation as a function of catchment dryness, we calculated the effects of climate warming on the annual partitioning of precipitation (P) into evapotranspiration (ET) and water yield. Deviation was defined as a catchment's change in actual ET divided by P (AET/P) coincident with a shift from a cool to warm period. Elasticity was defined as the ratio of inter-annual variation in potential ET divided by P (PET/P, the dryness index) to inter-annual variation in actual ET divided by P (AET/P, the evaporative index). Deviation in water yields was related to elasticity. Alpine sites showed greatest sensitivity to climate warming with any warming leading to increased water yields. Conifer sites included catchments with lowest elasticity and had stable to higher water yields, deciduous sites included catchments with intermediate elasticity and had stable to lower water yields, and mixed forests included catchments with highest elasticity and had stable water yields. For all forest types, there was a tendency for elasticity to converge to 1.0 with forest age. Both forest type and age were determinants of elasticity, which leads to resilience of catchment water yields to climate warming.

Jones, J. A.; Creed, I. F.; Spargo, A.; Buttle, J. M.; Adams, M.; Beall, F. D.; Booth, E.; Campbell, J. L.; Clow, D. W.; Elder, K.; Ford, C. R.; Grimm, N. B.; Ramlal, P.; Saha, A.; Sebestyen, S. D.; Spittlehouse, D.; Sterling, S. M.; Williams, M. W.; Winkler, R. D.; Yao, H.

2013-12-01

202

Global Farm Animal Production and Global Warming: Impacting and Mitigating Climate Change  

PubMed Central

Background The farm animal sector is the single largest anthropogenic user of land, contributing to many environmental problems, including global warming and climate change. Objectives The aim of this study was to synthesize and expand upon existing data on the contribution of farm animal production to climate change. Methods We analyzed the scientific literature on farm animal production and documented greenhouse gas (GHG) emissions, as well as various mitigation strategies. Discussions An analysis of meat, egg, and milk production encompasses not only the direct rearing and slaughtering of animals, but also grain and fertilizer production for animal feed, waste storage and disposal, water use, and energy expenditures on farms and in transporting feed and finished animal products, among other key impacts of the production process as a whole. Conclusions Immediate and far-reaching changes in current animal agriculture practices and consumption patterns are both critical and timely if GHGs from the farm animal sector are to be mitigated.

Koneswaran, Gowri; Nierenberg, Danielle

2008-01-01

203

Response of global warming on regional climate change over Korea: An experiment with the MM5 model  

NASA Astrophysics Data System (ADS)

This study is to investigate changes in regional surface climate arising from global warming with MM5 downscaling simulation for the period 1971-2100. The main focus is on the drought conditions over Korea. Palmer Drought Severity Index (PDSI) is utilized as a measure of drought severity. The important findings show the increase of surface air temperature by 6°C and precipitation by 25% over Korea at the end of the 21st century. The increasing trend of temperature is associated with an increasing trend of evapotranspiration and precipitation. Climatological precipitation amount appropriate for existing conditions is larger than the precipitation amounts. Hence, it actually produces deficit in precipitation. This exhibits a negative PDSI. As a result droughts are expected to be severe and frequent. Better resolved topography in MM5 induces large changes in local precipitation compared with temperature. Consequently peaks of negative PDSI anomalies appear over southern parts of Korea, where a large reduction in precipitation is noticed in addition to warming.

Boo, Kyung-On; Kwon, Won-Tae; Oh, Jai-Ho; Baek, Hee-Jeong

2004-11-01

204

Coupled Climate Model Simulations of a Late Cretaceous (Maastrichtian) Greenhouse Climate: Comparison with Proxy Data  

Microsoft Academic Search

Earth's future climate is expected to warm considerably due to increased atmospheric carbon dioxide. Paleoclimate records indicate that pre-Quaternary time periods provide the best possible view of Earth under warm greenhouse conditions. Thus, past warm greenhouse climates provide an important tool to evaluate fully coupled climate models that are currently used to study future climate change. In this study, we

G. R. Upchurch; J. T. Kiehl; C. A. Shields; C. Scotese

2009-01-01

205

Impact of a permanent El Niño (El Padre) and Indian Ocean Dipole in warm Pliocene climates  

NASA Astrophysics Data System (ADS)

Pliocene sea surface temperature data, as well as terrestrial precipitation and temperature proxies, indicate warmer than modern conditions in the eastern equatorial Pacific and imply permanent El Niño-like conditions with impacts similar to those of the 1997/1998 El Niño event. Here we use a general circulation model to examine the global-scale effects that result from imposing warm tropical sea surface temperature (SST) anomalies in both modern and Pliocene simulations. Observed SSTs from the 1997/1998 El Niño event were used for the anomalies and incorporate Pacific warming as well as a prominent Indian Ocean Dipole event. Both the permanent El Niño (also called El Padre) and Indian Ocean Dipole (IOD) conditions are necessary to reproduce temperature and precipitation patterns consistent with the global distribution of Pliocene proxy data. These patterns may result from the poleward propagation of planetary waves from the strong convection centers associated with the El Niño and IOD.

Shukla, Sonali P.; Chandler, Mark A.; Jonas, Jeff; Sohl, Linda E.; Mankoff, Ken; Dowsett, Harry

2009-06-01

206

A paleoscience approach to estimating the effects of climatic warming on salmonid fisheries of the Columbia River Basin  

SciTech Connect

To understand how climatic warming might affect salmonid populations, we are following a four-step procedure, incorporating paleoenvironmental data at the beginning and ending points, as follows. First, we used geomorphic, paleobotanical, and paleomalacological data to reconstruct stream conditions during the last 8000 years. Second, we estimated the effect on salmon of conditions extant approximately 6000 to 7000 radiocarbon years before present (B.P.), when temperatures were as much as 2[degrees]C warmer than at present. This became an analog of future warmer climate and its effects on spawning, incubation, and rearing parameters of the NPPC's Tributary Parameter Model (TPM) for estimating salmoned production. Third, we ran the TPM in conjunction with the NPPC System Planning Model (SPM) to calculate the effect of these analog conditions on the population of returning adult fish in selected stream systems. Ultimately, we will run the models for all salmon-accessible subbasins of the Columbia River system. Finally, we are identifying fish remains obtained from archaeological sites along the Columbia River to compare variations in the taxonomic composition of ancient fish assemblages with model predictions.

Chatters, J.C.; Butler, V.L.; Scott, M.J.; Anderson, D.M.; Neitzel, D.A.

1992-10-01

207

A paleoscience approach to estimating the effects of climatic warming on salmonid fisheries of the Columbia River Basin  

SciTech Connect

To understand how climatic warming might affect salmonid populations, we are following a four-step procedure, incorporating paleoenvironmental data at the beginning and ending points, as follows. First, we used geomorphic, paleobotanical, and paleomalacological data to reconstruct stream conditions during the last 8000 years. Second, we estimated the effect on salmon of conditions extant approximately 6000 to 7000 radiocarbon years before present (B.P.), when temperatures were as much as 2{degrees}C warmer than at present. This became an analog of future warmer climate and its effects on spawning, incubation, and rearing parameters of the NPPC`s Tributary Parameter Model (TPM) for estimating salmoned production. Third, we ran the TPM in conjunction with the NPPC System Planning Model (SPM) to calculate the effect of these analog conditions on the population of returning adult fish in selected stream systems. Ultimately, we will run the models for all salmon-accessible subbasins of the Columbia River system. Finally, we are identifying fish remains obtained from archaeological sites along the Columbia River to compare variations in the taxonomic composition of ancient fish assemblages with model predictions.

Chatters, J.C.; Butler, V.L.; Scott, M.J.; Anderson, D.M.; Neitzel, D.A.

1992-10-01

208

CMIP5 Model Assessments of the Ongoing Global Warming Hiatus and Two Extreme 2012 Climate Events  

NASA Astrophysics Data System (ADS)

Several recent climate phenomena are assessed using a 23-model CMIP5 multi-model ensemble. The pause in global warming since 1998 represents an important ongoing test for climate models. We find that the observed global mean temperature trend (1998-2010) is still within the 5th to 95th percentile of the distribution of trends formed by the CMIP5 ensemble. The CMIP5 ensemble is also used to assess two extreme climate events that occurred in 2012. For Arctic sea ice extent, both the trend over 2000-2012 and the 2012 extreme low are outside the 5th to 95th percentile range of the multi-model CMIP5 ensemble that uses historical forcing. These changes are also far outside the corresponding range of the control runs alone, strongly suggesting a role for anthropogenic forcing in the ice loss. Potential causes of the under-prediction of 2012 Arctic ice loss by the models include: underestimation of natural variability in the Arctic; underestimation of the models' Arctic ice response to forcing; errors in or missing historical forcings; or the extreme ice loss may simply have been an extremely rare event. For the eastern U.S., 2012 produced record temperature anomalies in March-May (MAM), according to the HadCRUT4 gridded data set. Based on the CMIP5 model assessment, we find a significant anthropogenic component to a long-term (multi-decadal to century scale) warming in this region during MAM. According to the ensemble mean of the CMIP5 historical runs, and using a baseline period of 1881-1920, we estimate that about one third of the 2012 warm anomaly was attributable to external forcing (principally anthropogenic). Eastern U.S. MAM warm anomalies exceeding those of 2012 occur about 12 times more often in the CMIP5 historical runs than in the control runs, suggesting that external forcing (principally anthropogenic) has substantially increased the risk of occurrence of such an event.

Knutson, T. R.; Zhang, R.; Wittenberg, A. T.; Zeng, F. J.

2013-12-01

209

Modeling dynamics of circum-arctic tundra plant communities in response to climate warming and grazing pressure  

NASA Astrophysics Data System (ADS)

The Arctic is a complex system with strong interconnectedness among system components. Understanding the responses of the arctic tundra biome to a changing climate requires knowledge of the complex interactions among climate, soils, and the biological system. In this study, we investigate the individual and interactive effects of projected climate change and reindeer/caribou grazing across a variety of climate zones and soil nutrient levels on tundra plant community dynamics using an arctic vegetation model - ArcVeg. Our research questions include: 1) How does soil nutrient availability affect tundra vegetation responses to projected climate warming? 2) How does grazing affect tundra vegetation responses? 3) How do interactions of soil nutrients, climate warming and grazing affect tundra vegetation? We based our simulations on A1B scenario temperature data from the Intergovernmental Panel on Climate Change (IPCC), soil organic nitrogen data from Terrestrial Ecosystem Model (TEM) simulations and grazing pressure derived from reindeer/caribou population data from the CircumArctic Rangifer Monitoring and Assessment Network (CARMA). We found that in general tundra communities responded to warming with increased plant biomass, but the magnitude of the response is affected by the bioclimate zones, warming magnitude, available soil nutrients and grazing pressures. Regions with greater soil organic nitrogen responded to warming with greater biomass increase, Low Arctic tundra tended to have greater biomass increase than High Arctic tundra due to greater shrub abundance. However, such responses are mitigated by grazing. Regions with greater reindeer population and thus greater grazing intensity tended to have stronger negative effects on plant responses to warming than regions with less grazing. For example, in Subzone D, total biomass and NPP increases due to warming were about 71% and 43% in an Alaskan low grazing-intensity region, but 63% and 36% in a northwestern Canada high grazing-intensity region. In Subzone C, although with similar warming magnitude, Yamal and Taymyr region being intensely grazed by reindeer responded with smaller total biomass increase (~68%) than a northwestern Canada low grazing-intensity region (~93%). Plant responses to warming may be a factor that determines the size of reindeer population and understanding how tundra plants respond to warming, grazing and their interactions will contribute to reindeer management practices.

Yu, Q.; Epstein, H. E.; Walker, D. A.; Forbes, B. C.; Vors, L. S.

2011-12-01

210

Biogeochemical plant-soil microbe feedback in response to climate warming in peatlands  

NASA Astrophysics Data System (ADS)

Peatlands act as global sinks of atmospheric carbon (C) through the accumulation of organic matter, primarily made up of decay-resistant litter of peat mosses. However, climate warming has been shown to promote vascular plant growth in peatlands, especially ericaceous shrubs. A change in vegetation cover is in turn expected to modify above-ground/below-ground interactions, but the biogeochemical mechanisms involved remain unknown. Here, by selecting peatlands at different altitudes to simulate a natural gradient of soil temperature, we show that the expansion of ericaceous shrubs with warming is associated with an increase of polyphenol content in both plant litter and pore water. In turn, this retards the release of nitrogen (N) from decomposing litter, increases the amount of dissolved organic N and reduces N immobilization by soil microbes. A decrease of soil water content with increasing temperature promotes the growth of fungi, which feeds back positively on ericaceous shrubs by facilitating the symbiotic acquisition of dissolved organic N. We also observed a higher release of labile C from vascular plant roots at higher soil temperatures, which promotes the microbial investment in C-degrading enzymes. Our data suggest that climate-induced changes in plant cover can reduce the productivity of peat mosses and potentially prime the decomposition of organic matter by affecting the stoichiometry of soil enzymatic activity.

Bragazza, Luca; Parisod, Julien; Buttler, Alexandre; Bardgett, Richard D.

2013-03-01

211

Climate warming during Antarctic ice sheet expansion at the Middle Miocene transition  

NASA Astrophysics Data System (ADS)

During the Middle Miocene climate transition about 14 million years ago, the Antarctic ice sheet expanded to near-modern volume. Surprisingly, this ice sheet growth was accompanied by a warming in the surface waters of the Southern Ocean, whereas a slight deep-water temperature increase was delayed by more than 200 thousand years. Here we use a coupled atmosphere-ocean model to assess the relative effects of changes in atmospheric CO2 concentration and ice sheet growth on regional and global temperatures. In the simulations, changes in the wind field associated with the growth of the ice sheet induce changes in ocean circulation, deep-water formation and sea-ice cover that result in sea surface warming and deep-water cooling in large swaths of the Atlantic and Indian ocean sectors of the Southern Ocean. We interpret these changes as the dominant ocean surface response to a 100-thousand-year phase of massive ice growth in Antarctica. A rise in global annual mean temperatures is also seen in response to increased Antarctic ice surface elevation. In contrast, the longer-term surface and deep-water temperature trends are dominated by changes in atmospheric CO2 concentration. We therefore conclude that the climatic and oceanographic impacts of the Miocene expansion of the Antarctic ice sheet are governed by a complex interplay between wind field, ocean circulation and the sea-ice system.

Knorr, Gregor; Lohmann, Gerrit

2014-05-01

212

Spatial heterogeneity in the timing of birch budburst in response to future climate warming in Ireland  

NASA Astrophysics Data System (ADS)

In order to predict the impact of future climate warming on trees it is important to quantify the effect climate has on their development. Our understanding of the phenological response to environmental drivers has given rise to various mathematical models of the annual growth cycle of plants. These models simulate the timing of phenophases by quantifying the relationship between development and its triggers, typically temperature. In addition, other environmental variables have an important role in determining the timing of budburst. For example, photoperiod has been shown to have a strong influence on phenological events of a number of tree species, including Betula pubescens (birch). A recently developed model for birch (DORMPHOT), which integrates the effects of temperature and photoperiod on budburst, was applied to future temperature projections from a 19-member ensemble of regional climate simulations (on a 25 km grid) generated as part of the ENSEMBLES project, to simulate the timing of birch budburst in Ireland each year up to the end of the present century. Gridded temperature time series data from the climate simulations were used as input to the DORMPHOT model to simulate future budburst timing. The results showed an advancing trend in the timing of birch budburst over most regions in Ireland up to 2100. Interestingly, this trend appeared greater in the northeast of the country than in the southwest, where budburst is currently relatively early. These results could have implications for future forest planning, species distribution modeling, and the birch allergy season.

Caffarra, Amelia; Zottele, Fabio; Gleeson, Emily; Donnelly, Alison

2014-05-01

213

Climate warming and eco-hydrology of forested watersheds in the California Sierra (Invited)  

NASA Astrophysics Data System (ADS)

Coupled models of hydrologic and ecosystem biogeochemical cycling are key tools used to generalize results from field based analysis at the CZO to other watersheds and future climate and land management scenarios. The CZO continues to provide an excellent opportunity to assess the performance of coupled models and highlight strategies for improvement and/or situations where model limitations or specific parameterization approaches are likely to alter eco-hydrologic predictions. At the Sierra CZO we have used RHESSys (the Regional Hydro-Ecologic Simulation System) as a modeling framework to look at interactions among climate variability and change, and vegetation dynamics and hydrology at daily, and seasonal to inter-annual time scales. Geophysical information provides a template that influences these interactions through topography, flowpath distributions, and soil properties. We present an implementation of RHESSys. We use the model to examine spatial-temporal patterns in the sensitivity of snow-dominated systems to climate warming and show how earlier snowmelt alters not only hydrology, but also forest carbon and nutrient cycling. Model results emphasize the importance of accounting for feedbacks between climate driven changes in hydrology and ecosystem responses.

Tague, C.; Son, K.; Brandt, T.; Dugger, A. L.

2013-12-01

214

Spatial heterogeneity in the timing of birch budburst in response to future climate warming in Ireland.  

PubMed

In order to predict the impact of future climate warming on trees it is important to quantify the effect climate has on their development. Our understanding of the phenological response to environmental drivers has given rise to various mathematical models of the annual growth cycle of plants. These models simulate the timing of phenophases by quantifying the relationship between development and its triggers, typically temperature. In addition, other environmental variables have an important role in determining the timing of budburst. For example, photoperiod has been shown to have a strong influence on phenological events of a number of tree species, including Betula pubescens (birch). A recently developed model for birch (DORMPHOT), which integrates the effects of temperature and photoperiod on budburst, was applied to future temperature projections from a 19-member ensemble of regional climate simulations (on a 25 km grid) generated as part of the ENSEMBLES project, to simulate the timing of birch budburst in Ireland each year up to the end of the present century. Gridded temperature time series data from the climate simulations were used as input to the DORMPHOT model to simulate future budburst timing. The results showed an advancing trend in the timing of birch budburst over most regions in Ireland up to 2100. Interestingly, this trend appeared greater in the northeast of the country than in the southwest, where budburst is currently relatively early. These results could have implications for future forest planning, species distribution modeling, and the birch allergy season. PMID:24037345

Caffarra, Amelia; Zottele, Fabio; Gleeson, Emily; Donnelly, Alison

2014-05-01

215

Functional traits predict relationship between plant abundance dynamic and long-term climate warming  

PubMed Central

Predicting climate change impact on ecosystem structure and services is one of the most important challenges in ecology. Until now, plant species response to climate change has been described at the level of fixed plant functional types, an approach limited by its inflexibility as there is much interspecific functional variation within plant functional types. Considering a plant species as a set of functional traits greatly increases our possibilities for analysis of ecosystem functioning and carbon and nutrient fluxes associated therewith. Moreover, recently assembled large-scale databases hold comprehensive per-species data on plant functional traits, allowing a detailed functional description of many plant communities on Earth. Here, we show that plant functional traits can be used as predictors of vegetation response to climate warming, accounting in our test ecosystem (the species-rich alpine belt of Caucasus mountains, Russia) for 59% of variability in the per-species abundance relation to temperature. In this mountain belt, traits that promote conservative leaf water economy (higher leaf mass per area, thicker leaves) and large investments in belowground reserves to support next year’s shoot buds (root carbon content) were the best predictors of the species increase in abundance along with temperature increase. This finding demonstrates that plant functional traits constitute a highly useful concept for forecasting changes in plant communities, and their associated ecosystem services, in response to climate change.

Soudzilovskaia, Nadejda A.; Elumeeva, Tatiana G.; Onipchenko, Vladimir G.; Shidakov, Islam I.; Salpagarova, Fatima S.; Khubiev, Anzor B.; Tekeev, Dzhamal K.; Cornelissen, Johannes H. C.

2013-01-01

216

Impact of climate warming-induced increase in drought stress on successional dynamic of a coniferous forest within a dry inner Alpine environment  

NASA Astrophysics Data System (ADS)

Climate sensitivity of tree growth will effect the development of forest ecosystems under a warmer and drier climate by changing species composition and inducing shifts in forest distribution. We applied dendroclimatological techniques to determine impact of climate warming on radial stem growth of three native and widespread coniferous tree species of the central Austrian Alps (Norway spruce, Picea abies; European larch, Larix decidua; Scots pine, Pinus sylvestris), which grow intermixed at dry-mesic sites within a dry inner Alpine environment (750 m a.s.l., Tyrol, Austria). Time series of annual increments were developed from > 250 saplings and mature trees. Radial growth response to recent climate warming was explored by means of moving response functions (MRF) and evaluation of trends in basal area increment (BAI) for the period 1911 - 2009. Climate-growth relationships revealed significant differences among species in response to water availability. While precipitation in May - June favoured radial growth of spruce and larch, Scots pine growth mainly depended on April - May precipitation. Spruce growth was most sensitive to May - June temperature (inverse relationship). Although MRF coefficients indicated increasing drought sensitivity of all species, which is most likely related to intensified belowground competition for scarce water with increasing stand density and higher evapotranspiration rates due to climate warming, recent BAI trends strikingly differed among species. While BAI of larch was distinctly declining, spruce showed steadily increasing BAI and quite constant BAI was maintained in drought adapted Scots pine, although at lowest level of all species. Furthermore, more favourable growing conditions of spruce in recent decades are indicated by scattered natural regeneration and higher growth rates of younger trees during first decades of their lifespan. Because human interference and wildlife stock is negligible within the study area, results suggest a competitive advantage of shade-tolerant and shallow-rooted late successional spruce over early successional species, whereby the spruce`s competitive strength is most likely related to synergistic effects of shade-tolerance and efficient uptake of small rainfall events by fine roots distributed primarily in upper soil layers. On the other hand, strikingly decreasing trend in BAI of larch is suggested to be due to negative influence of climate warming on tree water status. We conclude that climate warming-induced increase in drought sensitivity changed competitive strength of co-occurring conifers due to differences in inherent adaptive capacity at a drought-prone inner Alpine site.

Schuster, R.; Zeisler, B.; Oberhuber, W.

2012-04-01

217

Recent rapid warming of the Antarctic Peninsula set in context with regional Holocene climate records (Invited)  

NASA Astrophysics Data System (ADS)

The Antarctic Peninsula is one of the most rapidly warming regions on Earth, with historical observations from local meteorological stations documenting warming equivalent to around 3.5°C per century. During recent decades ice shelves to the north-east of Antarctic Peninsula have been lost, causing an acceleration of the feeder glaciers that drain ice from the Antarctic Peninsula. However, marine sediment records taken from beneath the former Prince Gustav Channel and Larsen B ice shelves suggest that they were also absent during the middle of the Holocene, presumably before then being re-established, and then lost again recently. The paradox between modern observations of rapid climate change and retreating ice shelves, and yet an apparent absence of those same ice shelves only a few thousand years before today, cries out for a local paleoclimate record. This was achieved by a joint UK-French team who recovered an ice core to bedrock in 2008 from James Ross Island, situated at the north of the Antarctic Peninsula, close to the area where ice shelves have retreated. The 364m long core spans the whole of the period from the Last Glacial Maximum through to the present. Our temperature estimates, based on the record of water deuterium isotope variations in the ice, show that the northern Antarctic Peninsula experienced an early-Holocene climate optimum about 1.3°C warmer than present, followed by cooler stable temperatures, from about 9,200 to 2,500 years ago, that were similar to the modern-day levels. We find that the late Holocene development of ice shelves near James Ross Island was coincident with pronounced cooling from 2,500 to 600 years ago. Warming of the northern Antarctic Peninsula began around 600 years ago, with the rate becoming more rapid during the 20th century. We discuss the temperature record from the James Ross Island ice core together with other paleoclimate references from this region.

Mulvaney, R.; Abram, N.; Arrowsmith, C.

2013-12-01

218

Aerosol microphysical effects on warm cloud in Eastern China: impacts of meteorological conditions  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol particles can alter the droplet size and number concentration of clouds, thereby changing the Earth's climate system. The aerosol indirect effect has been proved climatically significant after decades of research, albeit uncertain. This is partially due to the frustrating difficulty in decoupling the aerosol effect from meteorology influences on cloud properties. This study attempts to probe into the aerosol indirect effect on the warm clouds of summertime the Yangtze River Delta (YRD) of eastern China and East China Sea (ECS), respectively. It is based on simultaneously observed aerosol and cloud properties from MODIS/Aqua Level 3 datasets, along with meteorological properties from NCEP Final Analyses Operational Global Analysis datasets. Statistic analysis is employed to analyze the aerosol cloud interaction, constrained by multiple meteorological conditions, such as cloud top pressure (CTP), relative humidity (RH), pressure vertical velocity (PVV) and lower tropospheric stability (LTS), expected to minimize meteorological impact. The reduction of cloud droplet radius (CDR) with increasing aerosol optical depth (AOD) is revealed over ECS. In contrast, anti-Twomey effect is detected over YRD. The aerosol effects on cloud fraction (CF) are further investigated, taking CTP and RH into account. CF is found to increase more sharply over YRD than over ECS in response to aerosol enhancement, regardless of RH conditions. In addition, the horizontal extension of cloud is prone to be driven by aerosol rather than RH in the summertime over YRD. Meanwhile, CTP effect on AOD-CF is eliminated, indicating CTP make little contribution to the observed AOD-CF relationship. Also, CDR variation in response to AOD, constrained by LTS and PVV (750hPa) is analyzed. In general, aerosol tends to observe the law of Twomey's effect except for the unstable condition over land. Regarding dynamic effect, the rising atmospheric environment is subject to larger CDR than the subsidence environment under the same aerosol abundance, irrespective of over land and ocean, which can be attributed to the rising motion favoring the growth of cloud droplet. Overall, the observed cloud response to aerosol reflects the combined effects of dynamic, thermodynamic, and microphysical processes in cloud systems.

Guo, J.; Wang, F.; Li, Z.

2013-12-01

219

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

NASA Astrophysics Data System (ADS)

A new high-resolution reconstruction of the temperature and salinity of the subsurface waters using paired Mg/Ca-?18O 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 Atlantic on ice sheet dynamics at the Mid-Pleistocene Transition. Paleoceanography 27, PA3214. Marcott, S.A., Clark, P.U., Padman, L., Klinkhammer, G.P., Springer, S.R., Liu, Z., Otto-Bliesner, B.L., Carlson, A.E., Ungerer, A., Padman, J., He, F., Cheng, J., Schmittner, A., 2011. Ice-shelf collapse from subsurface warming as a trigger for Heinrich events. Proceedings of the National Academy of Sciences 108, 13415-13419

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

2014-05-01

220

The Arctic freshwater cycle during a naturally and an anthropogenically induced warm climate  

NASA Astrophysics Data System (ADS)

The Arctic freshwater cycle plays an important role in regulating regional and global climate. Current observations suggest that an intensification of the high-northern latitude hydrological cycle has caused a freshening of the Arctic and sub-Arctic seas, increasing the potential of weakening overturning strength in the Nordic seas, and reducing temperatures. It is not known if this freshening is a manifestation of the current anthropogenic warming and if the Arctic freshwater cycle has exhibited similar changes in the past, in particular as a response to naturally induced periods of warming, for example during the mid-Holocene hypsithermal. Thus, we have used an earth model of intermediate complexity, LOVECLIM, to investigate the response of the Arctic freshwater cycle, during two warm periods that evolved under different sets of forcings, the mid-Holocene and the twenty-first century. A combination of proxy reconstructions and modelling studies have shown these two periods to exhibit similar surface temperature anomalies, compared to the pre-industrial period, however, it has yet to be determined if the Arctic freshwater cycle and thus, the transport and redistribution of freshwater to the Arctic and the sub-Arctic seas, during these two warm periods, is comparable. Here we provide an overview that shows that the response of the Arctic freshwater cycle during the first half of the twenty-first century can be interpreted as an `extreme' mid-Holocene hydrological cycle. Whilst for the remainder of the twenty-first century, the Arctic freshwater cycle and the majority of its components will likely transition into what can only be described as truly anthropogenic in nature.

Davies, Frazer J.; Renssen, Hans; Goosse, Hugues

2014-04-01

221

Regional climate response to land surface changes after harvest in the North China Plain under present and possible future climate conditions  

NASA Astrophysics Data System (ADS)

this study, we investigated the impacts of land use alterations from harvesting practices on the regional surface climate over the North China Plain. The surface climate responses after harvest in June in regions where double-cropping is practiced were evaluated using observations and model simulations with the global climate model HadGEM2-Atmosphere. Responses were modeled under both present and possible future climate conditions. In the model, double-cropping was represented using the monthly varying fraction of vegetation. This contributed to an improvement in the model simulation over East Asia. Modeling results showed that the land surface was warmer and drier after harvest, and these simulation results were consistent with observations. The bare soil surface after harvest in June had biophysical impacts on the surface climate that were mediated by decreasing evapotranspiration and latent heat flux effects, which increased surface air temperatures and decreased surface humidity. An increase in shortwave radiation also contributed to the rise in temperatures. Under two Representative Concentration Pathways (RCP) scenarios for possible future climate conditions, land conversion induced additional warming in addition to greenhouse gases induced global warming. The RCP 8.5 and RCP 2.6 scenarios demonstrated a warming of 1.0°C and 1.4°C due to harvesting practices in June, respectively. The response magnitude was affected by the climate conditions in each RCP. Our results suggest that potential impacts of harvest on the local climate need to be considered in future projections of CO2-induced warming on a regional scale.

Cho, Mee-Hyun; Boo, Kyung-On; Lee, Johan; Cho, Chunho; Lim, Gyu-Ho

2014-04-01

222

Plants, birds and butterflies: short-term responses of species communities to climate warming vary by taxon and with altitude.  

PubMed

As a consequence of climate warming, species usually shift their distribution towards higher latitudes or altitudes. Yet, it is unclear how different taxonomic groups may respond to climate warming over larger altitudinal ranges. Here, we used data from the national biodiversity monitoring program of Switzerland, collected over an altitudinal range of 2500 m. Within the short period of eight years (2003-2010), we found significant shifts in communities of vascular plants, butterflies and birds. At low altitudes, communities of all species groups changed towards warm-dwelling species, corresponding to an average uphill shift of 8 m, 38 m and 42 m in plant, butterfly and bird communities, respectively. However, rates of community changes decreased with altitude in plants and butterflies, while bird communities changed towards warm-dwelling species at all altitudes. We found no decrease in community variation with respect to temperature niches of species, suggesting that climate warming has not led to more homogenous communities. The different community changes depending on altitude could not be explained by different changes of air temperatures, since during the 16 years between 1995 and 2010, summer temperatures in Switzerland rose by about 0.07°C per year at all altitudes. We discuss that land-use changes or increased disturbances may have prevented alpine plant and butterfly communities from changing towards warm-dwelling species. However, the findings are also consistent with the hypothesis that unlike birds, many alpine plant species in a warming climate could find suitable habitats within just a few metres, due to the highly varied surface of alpine landscapes. Our results may thus support the idea that for plants and butterflies and on a short temporal scale, alpine landscapes are safer places than lowlands in a warming world. PMID:24416144

Roth, Tobias; Plattner, Matthias; Amrhein, Valentin

2014-01-01

223

Evidence for external forcing on 20th-century climate from combined ocean-atmosphere warming patterns  

NASA Astrophysics Data System (ADS)

Of the additional energy absorbed by the Earth over the past decades, by far the largest fraction is taken up by the oceans. Yet most attribution studies focus on the surface warming, and only few have used patterns of ocean warming to attribute changes to external forcing or internal variability. Here we use the combined observed evidence from warming of the atmosphere and ocean with the latest climate model simulations to demonstrate that both the depth profiles and spatial warming patterns near the surface are very heterogeneous when resulting from internal unforced variability. In the 20th-century simulations on the other hand, the observed spatial pattern is smooth, and the warming decreases almost gradually with depth in the ocean, consistent with observations and a penetration of the surface warming to intermediate depth by diffusion and advection. We argue that such physically motivated arguments combining different lines of evidence and types of observations offer insight that is complementary to existing attribution methods. We conclude that the simultaneous warming of the atmosphere and mixed layer is uninformative for attribution, but the homogeneity of the spatial pattern and the distribution of warming below the mixed layer strongly argue for the 20th-century warming being largely externally forced.

Sedlacek, J.; Knutti, R.

2012-12-01

224

A warm and wet Little Climatic Optimum and a cold and dry Little Ice Age in the southern Rocky Mountains, USA  

SciTech Connect

In the next century, increases in atmospheric trace gas concentration could warm the global average temperature beyond what it has ranged during the past century. Examination of larger-than-historic climatic changes that have occurred in the past in specific regions provides realistic context for evaluating such potential future changes. This paper has contrasted the climatic manifestation of the Little Climatic Optimum or Medieval Warm Period (AD 900--1300) with that of the Little Ice Age (AD 1300--1850) in the northern Colorado Plateau region of the southwestern USA. The zenith of the Anasazi occupation coincides with the former and their demise coincides with the latter, when conditions became too cold and especially dry (in the summer) to support upland dry farming. During the height of the Little Climatic Optimum the region was characterized by a relatively long growing season and greater winter and summer precipitation than that of today. This resulted in a relatively rapid development of a potential dry-farming belt that was twice as wide as the present and areas that cannot be dry farmed today were routinely farmed by the Anasazi. Such conditions would be beneficial to dry farmers in the Four Corners region if those conditions were repeated in the near future.

Petersen, K.L.

1992-05-01

225

Variability in Eastern North American surface ozone under climate warming scenarios: Key role for jet position  

NASA Astrophysics Data System (ADS)

Climate warming is generally expected to degrade air quality in many polluted regions. Model estimates of the magnitude, and in some cases the sign, of the surface ozone response to projected warming, however, disagree regionally. These discrepancies underscore a need for improved process-level understanding of the factors controlling the regional ozone response to warming. Furthermore, developing accurate approaches to estimate regional surface ozone changes directly from projected changes in regional climate requires this process understanding. Over Eastern North America, synoptic variability is known to be a key driver of summertime ozone pollution episodes. We investigate the hypothesis that this variability depends on the position of the jet within this region by analyzing June-August (JJA) daily surface ozone in a suite of CMIP5 and related sensitivity simulations from 1860 to 2100 in the GFDL CM3 chemistry-climate model. Specifically, we use the CM3 CMIP5 Historical (1860-2005; 5-member) and RCP4.5 (2006-2100; 3-member) ensemble simulations. An additional scenario with evolving well-mixed greenhouse gases following the RCP4.5 scenario but emissions of aerosol and ozone precursors held constant at 2005 levels, denoted RCP4.5*, enables us to isolate the impact of climate warming alone from the impact of large decreases in ozone precursor emissions occurring under RCP4.5. We demonstrate that the daily variability of JJA surface ozone is a strong function of the position of the jet-stream over Eastern North America in all three scenarios. The jet stream moves poleward with climate change under the RCP4.5 and RCP4.5* scenarios, and we show that ozone variability follows the position of the jet. The consistent response in both the RCP4.5 and RCP4.5* simulations demonstrates that the large decreases in ozone precursor emissions under RCP4.5 (North American nitrogen oxides (NOx) decrease by about a factor of 5 over the 21st century) are not driving the northward shift of ozone variability. While the relationship with jet latitude remains, the decrease in ozone precursor emissions under RCP4.5 leads to a reduction in variability over the entire region. We further show that the strength of the correlation between ozone and temperature is a strong function of the jet position. The quantitative relationship (slope between ozone and temperature), however, depends strongly on NOx emissions, consistent with recent observation-based work. These findings demonstrate that historical relationships between surface ozone and meteorological quantities such as temperature are unlikely to apply in the future. Although this study focuses solely on Eastern North America, the relationships found here are likely also present in other mid-latitude regions influenced by the mid-latitude jet. The strong dependence of surface ozone variability on jet latitude, a quantity easily computed from climate models, implies that understanding future changes in jet location can be used to derive changes in summertime surface ozone variability and the ozone-temperature correlation. Our results further imply that inter-model discrepancies in jet location likely contribute to the wide range of current estimates for changes in surface ozone in northern mid-latitude regions.

Barnes, Elizabeth; Fiore, Arlene

2013-04-01

226

Variability in Eastern North American surface ozone under climate warming scenarios: Key role for jet position  

NASA Astrophysics Data System (ADS)

Climate warming is generally expected to degrade air quality in many polluted regions. Model estimates of the magnitude, and in some cases the sign, of the surface ozone response to projected warming, however, disagree regionally. These discrepancies underscore a need for improved process-level understanding of the factors controlling the regional ozone response to warming. Furthermore, developing accurate approaches to estimate regional surface ozone changes directly from projected changes in regional climate requires this process understanding. Over Eastern North America, synoptic variability is known to be a key driver of summertime ozone pollution episodes. We investigate the hypothesis that this variability depends on the position of the jet within this region by analyzing June-August (JJA) daily surface ozone in a suite of CMIP5 and related sensitivity simulations from 1860 to 2100 in the GFDL CM3 chemistry-climate model. Specifically, we use the CM3 CMIP5 Historical (1860-2005; 5-member) and RCP4.5 (2006-2100; 3-member) ensemble simulations. An additional scenario with evolving well-mixed greenhouse gases following the RCP4.5 scenario but emissions of aerosol and ozone precursors held constant at 2005 levels, denoted RCP4.5*, enables us to isolate the impact of climate warming alone from the impact of large decreases in ozone precursor emissions occurring under RCP4.5. We demonstrate that the daily variability of JJA surface ozone is a strong function of the position of the jet-stream over Eastern North America in all three scenarios. The jet stream moves poleward with climate change under the RCP4.5 and RCP4.5* scenarios, and we show that ozone variability follows the position of the jet. The consistent response in both the RCP4.5 and RCP4.5* simulations demonstrates that the large decreases in ozone precursor emissions under RCP4.5 (North American nitrogen oxides (NOx) decrease by about a factor of 5 over the 21st century) are not driving the northward shift of ozone variability. While the relationship with jet latitude remains, the decrease in ozone precursor emissions under RCP4.5 leads to a reduction in variability over the entire region. We further show that the strength of the correlation between ozone and temperature is a strong function of the jet position. The quantitative relationship (slope between ozone and temperature), however, depends strongly on NOx emissions, consistent with recent observation-based work. These findings demonstrate that historical relationships between surface ozone and meteorological quantities such as temperature are unlikely to apply in the future. Although this study focuses solely on Eastern North America, the relationships found here are likely also present in other mid-latitude regions influenced by the mid-latitude jet. The strong dependence of surface ozone variability on jet latitude, a quantity easily computed from climate models, implies that understanding future changes in jet location can be used to derive changes in summertime surface ozone variability and the ozone-temperature correlation. Our results further imply that inter-model discrepancies in jet location likely contribute to the wide range of current estimates for changes in surface ozone in northern mid-latitude regions.

Barnes, E. A.; Fiore, A. M.

2012-12-01

227

Modeling the potential change in yield and distribution of the earth's crops under a warmed climate  

Microsoft Academic Search

The large scale distribution of crops is largely determined by climate. The authors present the results of a climate-crop prediction model based on the U.N. Food and Agriculture Organization crop-suitability approach, implemented in a geographic information system (GIS) environment using several global environmental databases. The model utilizes daily temperature and moisture conditions to determine the properties of the growing period.

R. Leemans; A. M. Solomon

1993-01-01

228

Does climate warming stimulate or inhibit soil protist communities? A test on testate amoebae in high-arctic tundra with free-air temperature increase.  

PubMed

Soil testate amoebae assemblages in a grassland area at Zackenberg (Northeast Greenland) were subjected to simulated climate-warming during the growing season using the Free-Air Temperature Increase technique. Samples were collected in upper (0 - 3cm) and deeper (3 - 6cm) soil horizons. Mean temperature elevations at 2.5 and 7.5 cm depth were 2.58 ± SD 1.11 and 2.13±SD 0.77°C, respectively, and did not differ significantly. Soil moisture in the top 11cm was not affected by the warming. During the manipulation, the densities of living amoebae and empty shells were higher in the experimental plots but only in the upper layer. Possibly, testate amoebae in the deeper layer were limited by other factors, suggesting that warming enhances the carrying capacity only in favourable conditions. Species richness, on the other hand, was only increased in the deeper horizon. Warming did not change the percentage of individuals belonging to small-sized species in any of the living assemblages, contrary to our expectation that those species would quickly increase their density. However, in the empty shell assemblages, the proportion of small-sized individuals in the experimental plots was higher in both layers, indicating a rapid, transient increase in small amoebae before the first sampling date. Changes in successional state of testate amoebae assemblages in response to future climate change might thus be ephemeral, whereas alterations in density and species richness might be more sustained. PMID:20708962

Tsyganov, Andrey N; Nijs, Ivan; Beyens, Louis

2011-04-01

229

Numerical and Experimental Investigations on Deformation Behavior of Aluminum 5754 Sheet Alloy under Warm Hydroforming Conditions  

Microsoft Academic Search

Material behavior of Al5754 was characterized using both tensile and hydraulic bulge tests under both room and warm temperature conditions. Response of Al5754 to different process conditions such as pressurization rates (0.022 and 0.2 s-1 strain rate), variable strain rates (increasing and decreasing profiles), forming temperature (room to 260° C), and loading conditions (uniaxial vs. biaxial) were presented. The results

M. Koç; S. Mahabunphachai; J. E. Carsley

2010-01-01

230

Forest Dynamics and Their Phenological Response to Climate Warming in the Khingan Mountains, Northeastern China  

PubMed Central

The Khingan Mountain region, the most important and typical natural foci of tick-borne encephalitis (TBE) in China, is the largest and northernmost forest area and the one more sensitive to climate change. Taking this region as the study area, we investigated the spatio-temporal dynamics of deciduous broadleaf forest (DBF) and its phenology changes in relation to climate change and elevation. Based on MODIS Enhanced Vegetation Index (EVI) time series over the period of 2001 to 2009, the start-of-season (SOS), length-of-season (LOS) and another two vegetation variables (seasonal amplitude (SA) and integrated EVI (SI)) were derived. Over the past decade, the DBF in Khingan Mountains has generally degraded and over 65% of DBF has experienced negative SA and SI trends. Earlier trends in SOS and longer trends in LOS for DBF were observed, and these trends were mainly caused by climate warming. In addition, results from our analysis also indicated that the effects of temperature on DBF phenology were elevation dependent. The magnitude of advancement in SOS and extension in LOS with temperature increase significantly increased along a raising elevation gradient.

Cai, Hongyan; Zhang, Shuwen; Yang, Xiaohuan

2012-01-01

231

Aerosol contribution to the rapid warming of near-term climate under RCP 2.6  

NASA Astrophysics Data System (ADS)

The importance of aerosol emissions for near term climate projections is investigated by analysing simulations with the HadGEM2-ES model under two different emissions scenarios: RCP2.6 and RCP4.5. It is shown that the near term warming projected under RCP2.6 is greater than under RCP4.5, even though the greenhouse gas forcing is lower. Rapid and substantial reductions in sulphate aerosol emissions due to a reduction of coal burning in RCP2.6 lead to a reduction in the negative shortwave forcing due to aerosol direct and indirect effects. Indirect effects play an important role over the northern hemisphere oceans, especially the subtropical northeastern Pacific where an anomaly of 5-10 Wm-2 develops. The pattern of surface temperature change is consistent with the expected response to this surface radiation anomaly, whilst also exhibiting features that reflect redistribution of energy, and feedbacks, within the climate system. These results demonstrate the importance of aerosol emissions as a key source of uncertainty in near term projections of global and regional climate.

Chalmers, N.; Highwood, E. J.; Hawkins, E.; Sutton, R.; Wilcox, L. J.

2012-09-01

232

3D Numerical Simulation of the Geothermal Field of Permafrost at Salluit in Nunavik, Québec, in Response to Climate Warming. Research in Progress.  

NASA Astrophysics Data System (ADS)

The village of Salluit is located in the continuous permafrost zone in Nunavik, Québec. This Inuit community of about 1100 people is characterized by a fast population growth. The village lies in the bottom of a restricted valley flanked by steep rock walls. Most village infrastructures are built on frozen saline and ice-rich marine silts creating problematic ground conditions for infrastructures construction. For satisfying the fast population growth, a housing program is in progress but the available terrain with proper ground conditions for stable foundation is scarce and little is known on the permafrost conditions in the valley. During the construction of the airport of Salluit, a thermistor cable has been permanently buried in a rock outcrop. Regular temperature measurements have been carried out from 1987 and 1994, and from 2001 until now. During the first measurement interval, the permafrost temperature decreased steadily from -8 to -8.5 °C at a depth of 8 m. According to Environment Canada, the climate in that region of Canada was slowly cooling. However, this trend was reversed around 1997-1998 and some important warming recently occurred. In August 2001, the temperature measurements showed an increase of about 1.9 °C at the same depth. Moreover, a major active layer detachment failure occurred in the valley uphill in 1998 forcing the moving of twenty houses recently built. This landslide was probably triggered by the climate warming. Proper assessment of available terrain for the village expansion is therefore a major concern for the Inuit community of Salluit. Following the request of the provincial government, a thorough study for mapping the permafrost conditions and assessing the impacts of climate warming on permafrost conditions has been undertaken in 2002. The surveys carried out included deep sampling of permafrost, seismic reflection and ground penetrating radar profiling, and surface mapping supported by a detailed photo interpretation. The survey aims at providing information on the geological and geotechnical characteristics of permafrost. Thermistor cables in deep boreholes, meteorological stations, dataloggers for the measurement of surface temperature, and thermal probes have been also installed in the valley. Air photographs will be used to produce a digital terrain model of the valley. This integrated multi-technique approach is essential for properly assessing the permafrost conditions in the valley. The study will provide the data needed for the development of a 3D model of permafrost conditions in the valley. A 3D numerical simulation of the geothermal field of permafrost in the valley will be then undertaken. This simulation is a major challenge giving the size of the thermal field and the variability in permafrost conditions. The impacts of climate warming on the thermal field of permafrost will be simulated and predicted by forcing the surface temperature to increase following different scenarios of climate warming. It is planned to combine the geotechnical properties and the simulation of the geothermal field of permafrost in order to define threshold values of permafrost strength and slope instability and set a pre-warning scheme of permafrost temperature in case of further warming in the coming years. The monitoring of permafrost temperature will be continued in the future. If the scheme is reached, actions can be then undertaken to mitigate the impacts of climate warming on the infrastructures and protect the population of Salluit.

Fortier, R.; Allard, M.; Gagnon, O.

2002-12-01

233

The palaeoclimatic significance of Eurasian Giant Salamanders (Cryptobranchidae: Zaissanurus, Andrias) - indications for elevated humidity in Central Asia during global warm periods (Eocene, late Oligocene warming, Miocene Climate Optimum)  

NASA Astrophysics Data System (ADS)

Cryptobranchids represent a group of large sized (up to 1.8 m) tailed amphibians known since the Middle Jurassic (Gao & Shubin 2003). Two species are living today in eastern Eurasia: Andrias davidianus (China) and A. japonicus (Japan). Cenozoic Eurasian fossil giant salamanders are known with two genera and two or three species from over 30 localities, ranging from the Late Eocene to the Early Pliocene (Böhme & Ilg 2003). The Late Eocene species Zaissanurus beliajevae is restricted to the Central Asian Zaissan Basin (SE-Kazakhstan, 50°N, 85°E), whereas the Late Oligocene to Early Pliocene species Andrias scheuchzeri is distributed from Central Europe to the Zaissan Basin. In the latter basin the species occur during two periods; the latest Oligocene and the late Early to early Middle Miocene (Chkhikvadse 1982). Andrias scheuchzeri is osteological indistinguishable from both recent species, indicating a similar ecology (Westfahl 1958). To investigate the palaeoclimatic significance of giant salamanders we analyzed the climate within the present-day distribution area and at selected fossil localities with independent palaeoclimate record. Our results indicate that fossil and recent Andrias species occur in humid areas where the mean annual precipitation reach over 900 mm (900 - 1.300 mm). As a working hypothesis (assuming a similar ecology of Andrias and Zaissanurus) we interpret occurrences of both fossil Eurasian giant salamanders as indicative for humid palaeoclimatic conditions. Based on this assumption the Late Eocene, the latest Oligocene (late Oligocene warming) and the late Early to early Middle Miocene (Miocene Climatic Optimum) of Central Asia (Zaissan Basin) are periods of elevated humidity, suggesting a direct (positive) relationship between global climate and Central Asian humidity evolution. Böhme M., Ilg A. 2003: fosFARbase, www.wahre-staerke.com/ Chkhikvadze V.M. 1982. On the finding of fossil Cryptobranchidae in the USSR and Mongolia. Vertebrata Hungarica, 21: 63-67. Gao K.-Q., Shubin N.H. 2003. Earliest known crown-group Salamanders. Nature, 422: 424-428. Westphal F. 1958. Die Tertiären und rezenten Eurasiatischen Riesensalamander. Palaeontolographica Abt. A, 110: 20-92.

Vasilyan, Davit; Böhme, Madelaine; Winklhofer, Michael

2010-05-01

234

Summertime land-sea thermal contrast and atmospheric circulation over East Asia in a warming climate—Part II: Importance of CO2-induced continental warming  

NASA Astrophysics Data System (ADS)

In this the second of a two-part study, we examine the physical mechanisms responsible for the increasing contrast of the land-sea surface air temperature (SAT) in summertime over the Far East, as observed in recent decades and revealed in future climate projections obtained from a series of transient warming and sensitivity experiments conducted under the umbrella of the Coupled Model Intercomparison Project phase 5. On a global perspective, a strengthening of land-sea SAT contrast in the transient warming simulations of coupled atmosphere-ocean general circulation models is attributed to an increase in sea surface temperature (SST). However, in boreal summer, the strengthened contrast over the Far East is reproduced only by increasing atmospheric CO2 concentration. In response to SST increase alone, the tropospheric warming over the interior of the mid- to high-latitude continents including Eurasia are weaker than those over the surrounding oceans, leading to a weakening of the land-sea SAT contrast over the Far East. Thus, the increasing contrast and associated change in atmospheric circulation over East Asia is explained by CO2-induced continental warming. The degree of strengthening of the land-sea SAT contrast varies in different transient warming scenarios, but is reproduced through a combination of the CO2-induced positive and SST-induced negative contributions to the land-sea contrast. These results imply that changes of climate patterns over the land-ocean boundary regions are sensitive to future scenarios of CO2 concentration pathways including extreme cases.

Kamae, Youichi; Watanabe, Masahiro; Kimoto, Masahide; Shiogama, Hideo

2014-04-01

235

Zonobiomes, forests, and major forest-forming conifers across Northern Eurasia by the end of the century under climate warming  

NASA Astrophysics Data System (ADS)

Simulations of terrestrial ecosystems demonstrated globally the profound effects of the GCM-predicted climate change on their distribution at all hierarchical levels: zonobiomes, forests, and forest-forming tree species. We investigated progressions of potential vegetation cover, forest cover and ranges of forest-forming conifers across Northern Eurasia and Russia in the warming climate during the current century. We developed envelope-type static large-scale bioclimatic models predicting zonobiomes NEBioCliM, forests (ForCliM) and primary forest-forming conifer trees (TreeCliM)) from three bioclimatic indices (1) growing degree-days above 5oC, GDD5; (2) negative degree-days below 0oC, NDDo; and (3) an annual moisture index (ratio of growing degree days above 5oC to annual precipitation), AMI. No soil conditions except presence/absence of permafrost were taken into account in our models. Continuous permafrost was included in the models as limiting the forests and tree species distribution in interior Siberia. Each zonobiome, forest type and conifer distribution was mapped for the basic period 1960-1990 and for 2080 by coupling our bioclimatic models with bioclimatic indices and the permafrost distribution for the 1960-1990 and 2080 simulations. Climatic departures for the 2080 climate were derived from two climate change scenarios, the HadCM3 A2 and B1 (IPCC, 2007). Kappa (K) statistics were used to compare both the modeled vegetation and the conifer distributions in the contemporary climate to actual vegetation and forest maps. K-statistics proved that NEBioCliM accomplished a fair work in modeling zonobiomes across Russia. The tree species distributions also showed good match with the modeled ranges: 41% (Abies sibirica), 46% (Pinus sibirica), 71% (Pinus sylvestris), 75% (Picea spp.) and 78% (Larix spp.). Those matches might be higher because historically part of the primary conifer forests were replaced by secondary birch and aspen forests after large disturbances (clearcuts and wildfire). With these projected climates, the zonobiomes would need to shift far to the north in order to reach an equilibrium with the change in climate. Because future climate is predicted to be much warmer and drier, the future climate would be suitable for the forest-steppe ecotone and grasslands (up to 80%) rather than forests (less than 20%). Water stress tolerant light-needled taiga would have advantage over water-loving dark-needled taiga in a new climate. Permafrost wiould not retreat fast enough to make favorable habitats for dark taiga and L. dahurica taiga withstanding permafrost would remain the dominant forest type. Accumulated fire load due to increased tree mortality, especially at the southern forest border and in interior Siberia (Yakutia), together with an increase in fire weather would also initiate large fires facilitating vegetation progression towards an equilibrium with the climate.

Tchebakova, N.; Parfenova, E. I.; Shvetsov, E.; Soja, A. J.; Conard, S. G.

2012-12-01

236

Global warming impacts of ozone-safe refrigerants and refrigeration, heating, and air-conditioning technologies  

Microsoft Academic Search

International agreements mandate the phase-out of many chlorine containing compounds that are used as the working fluid in refrigeration, air-conditioning, and heating equipment. Many of the chemical compounds that have been proposed, and are being used in place of the class of refrigerants eliminated by the Montreal Protocol are now being questioned because of their possible contributions to global warming.

S. Fischer; J. Sand; V. Baxter

1997-01-01

237

Can warm climate-related structure of littoral predator assemblies weaken the clear water state in shallow lakes?  

Microsoft Academic Search

Shallow lakes, the most abundant lake type in the world, are very sensitive to climatic changes. The structure and functioning of shallow lakes are greatly impacted by sub- merged plants, and these may be affected by climate warming in various, contrasting, ways. Following a space-for-time substitution approach, we aimed to analyse the role of aquatic (submerged and free-floating) plants in

J UAN; CARLOS I GLESIAS; R. P EDERSEN; Ole Worms

2007-01-01

238

Climate warming and changes in habitat suitability for Boophilus microplus (Acari: Ixodidae) in Central America.  

PubMed

Remote sensing on the basis of AVHRR (advanced very high resolution radiometer) satellite imagery was used, together with standard geostatistical methods (cokriging), to estimate the distribution of habitat suitability (HS) for the tick Boophilus microplus (Canestrini) in Central America. Most attention was paid to the expected limits of tick distribution as well as the temperature and vegetation values responsible for different HS zones and their variability within the year. The highest HS extended through wide areas of southeastern United States, much of Mexico, and other countries of Central America. Areas with higher HS had relatively stable temperatures (within 20-25 C) throughout the year, and had a NDVI (normalized derived vegetation index) of around 0.4. These areas need to be targeted to ensure acaricide usage at optimum intervals and to avoid the formation of areas with enzootic instability. A seasonal analysis of the climate trend through the study period (1982-1999) revealed a warming cycle, together with a rise in NDVI index values. The main consequence of this trend is the gradual increase in unsuitability in areas where the tick is already established, with the establishment of new foci in zones currently too cold to support tick populations. The cooling periods of 1-2 yr that were observed between warming cycles may also lead to enzootic instability when warm zones cool to within the suitability range. As the model is remotely sensed, a continuous update of the B. microplus distribution could be performed, assuring maximum efficiency in developing management strategies. PMID:11695419

Estrada-Peña, A

2001-10-01

239

Sensitivity of the Ocean's Climate to Diapycnal Diffusivity in an EMIC. Part II: Global Warming Scenario.  

NASA Astrophysics Data System (ADS)

The sensitivity of the ocean's climate to the diapycnal diffusivity in the ocean is studied for a global warming scenario in which CO2 increases by 1% yr-1 for 75 yr. The thermohaline circulation slows down for about 100 yr and recovers afterward, for any value of the diapycnal diffusivity. The rates of slowdown and of recovery, as well as the percentage recovery of the circulation at the end of 1000-yr integrations, are variable, but a direct relation with the diapycnal diffusivity cannot be found. At year 70 (when CO2 has doubled) an increase of the diapycnal diffusivity from 0.1 to 1.0 cm2s-1 leads to a decrease in surface air temperature of about 0.4 K and an increase in sea level rise of about 4 cm. The steric height gradient is divided into thermal component and haline component. It appears that, in the first 60 yr of simulated global warming, temperature variations dominate the salinity ones in weakly diffusive models, whereas the opposite occurs in strongly diffusive models.The analysis of the vertical heat balance reveals that deep-ocean heat uptake is due to reduced upward isopycnal diffusive flux and parameterized-eddy advective flux. Surface warming, induced by enhanced CO2 in the atmosphere, leads to a reduction of the isopycnal slope, which translates into a reduction of the above fluxes. The amount of reduction is directly related to the magnitude of the isopycnal diffusive flux and parameterized-eddy advective flux at equilibrium. These latter fluxes depend on the thickness of the thermocline at equilibrium and hence on the diapycnal diffusion. Thus, the increase of deep-ocean heat uptake with diapycnal diffusivity is an indirect effect that the latter parameter has on the isopycnal diffusion and parameterized-eddy advection.

Dalan, Fabio; Stone, Peter H.; Sokolov, Andrei P.

2005-07-01

240

Marine Ecosystem Response to Rapid Climate Warming on the West Antarctic Peninsula (Invited)  

NASA Astrophysics Data System (ADS)

The Palmer, Antarctica LTER builds on meteorological, ocean color and seabird observations since the late 1970s. It occupies annually in summer a regional-scale grid extending 700 km northward from Charcot Island to Anvers Island, and 200 km cross-shelf from the coast to the shelfbreak. In addition to routine CTD profiles and zooplankton tows throughout the grid, the observing system also includes Slocum Glider surveys and thermistor moorings. Geophysical changes include +6C atmospheric warming in winter since 1950, a 20% increase in heat content over the continental shelf since 1990, a surface ocean warming of +1C since 1950, an 83-day reduction in sea ice duration (advance 48 days later, retreat 35 days earlier) over the greater southern Bellingshausen Sea region from 1979-2007, intensification of westerly winds and differential changes in cloudiness. In response to these large changes in the regional climate, the marine ecosystem of the western Peninsula is changing at all trophic levels from diatoms to penguins. Ocean color indicates differential changes in phytoplankton stocks in response to regional decreases in sea ice cover. Surface chlorophyll has declined 89% in the north and increased 67% in the south. Antarctic krill and salps have declined and increased in our study area, respectively. Penguin diet sampling suggests changes in populations or distributions of the Antarctic Silverfish in the Anvers Island vicinity, possibly in response to ocean warming. Adélie penguins have declined 75% from 15000 to <3000 pairs at since 1975 in response to changes in food availability and increased late spring snow accumulation. Changes in pygoscelid penguin breeding populations in the Anvers Island vicinity of the West Antarctic Peninsula

Ducklow, H.; Baker, K. S.; Doney, S. C.; Fraser, B.; Martinson, D. G.; Meredith, M. P.; Montes-Hugo, M. A.; Sailley, S.; Schofield, O.; Sherrell, R. M.; Stammerjohn, S. E.; Steinberg, D. K.

2010-12-01

241

The role of climate change and ozone recovery for the future timing of major stratospheric warmings  

NASA Astrophysics Data System (ADS)

Future changes in the occurrence rates of major stratospheric warmings (MSWs) have recently been identified in chemistry-climate model (CCM) simulations, but without reaching a consensus, potentially due to the competition of different forcings. We examine future variations in the occurrence rates of MSWs in transient and timeslice simulations of the ECHAM/MESSy atmospheric chemistry (EMAC) CCM, with a focus on the individual effect of different external factors. Although no statistically significant variation is found in the decadal-mean frequency of MSWs, a shift of their timing toward midwinter is detected in the future. The strengthening of the polar vortex in early winter is explained by recovering ozone levels following the future decrease in ozone-depleting substances. In midwinter, a stronger dynamical forcing associated with changes in tropical sea surface temperatures will lead to more MSWs, through a similar mechanism that explains the stratospheric response to El Niño-Southern Oscillation (ENSO).

Ayarzagüena, Blanca; Langematz, Ulrike; Meul, Stefanie; OberläNder, Sophie; Abalichin, Janna; Kubin, Anne

2013-05-01

242

Response of high-mountain Altai thermal regime to climate global warming of recent decades  

NASA Astrophysics Data System (ADS)

The paper presents a brief climatic characteristic and statistical analysis on dynamics of thermal regime in Altai Mountains. The close correlation between temperature series of the Russian and northern part of Mongolian Altai was determined. It was found that the rate of temperature increase for the period under consideration (1940-2008) ranged from 0.19 to 0.53 °?/10 years, and the most significant increase was registered during the cold seasons. During the maximum global warming (1980-1999), a 2-4.5 times increase of annual average temperature was observed as compared to the period of 1940-1979. The temperature series variations obtained with the Welch's method and wavelet analysis correspond to the periods of North Atlantic Oscillation and solar activity variation.

Bezuglova, N. N.; Zinchenko, G. S.; Malygina, N. S.; Papina, T. S.; Barlyaeva, T. V.

2012-12-01

243

Warm to cold polar climate transitions over the last 15,000 years: A paleoclimatology record from the raised beaches of northern Norway  

SciTech Connect

Because of the strength of the cold, dry arctic high pressure vortex, and the absence of multiple air-mass sources, climate records from the polar region tend to display a cleaner signal than those from mid-latitude settings. The high arctic presents unique opportunities for the prediction of the natural background pattern of climate change prior to the disturbances generated by manmade atmospheric pollutants. The Varanger Peninsula of northernmost Norway was extensively depressed by an ice dome during the last glacial stage. Deglaciation was accompanied by isostatic recovery at a steady though exponentially decaying rate. Superimposed on the rising land is a discontinuous staircase of cobble beach ridges, deposited during the postglacial period by storms at the coast. The ridges are constructed during brief episodes of weather- and tide-related elevation of sea level and wave run-up. Storminess periods can only occur in the absence of sea ice associated with several decades of mild, relatively warm temperatures. A history of local relative sea level is constructed from over 70 radiocarbon dates of various water-level indicators. The sea-level history is used to construct a chronology of beach-ridge building that documents the cyclic, a periodic nature of arctic storminess conditions. The authors date a dynamic signal with multiple climate transitions from warm, stormy conditions to cool, calm conditions occurring roughly every 200 years between 15,000 years ago to 10,000 years ago. Throughout the Holocene the climate is more settled with longer periods separating the major warm to cool transitions.

Fletcher, C.H. (Univ. of Hawaii, Honolulu (United States)); Fairbridge, R.H. (NASA-Goddard Inst. for Space Studies, New York, NY (United States)); Moeller, J.K. (Univ. of Tromso (Norway)); Long, A.J. (Univ. of Durham (United Kingdom))

1991-03-01

244

Is the impact of future climate change on hydro-climatic conditions significant? - A climate change study for an Eastern European catchment area.  

NASA Astrophysics Data System (ADS)

The future change of climatic conditions is, among others, closely linked to future hydrological changes. One important aspect of these issues is the question of future availability of water resources. A changed climatic water balance, as indicator for potential water availability, has far-reaching consequences for the water cycle, hydrological conditions, ecology, water management, the energy business, agriculture and forestry, and for anthropogenic use of the river. We generated regional climate projections via dynamic downscaling for the catchment area of the Western Bug river in the border area of Poland, Belarus, and Ukraine. The hydro-climatic conditions of the past and their projected future changes in the catchment were analyzed based on 2m-temperature, precipitation, potential evaporation and climatic water balance. Up to the end of the century, the used IPCC scenarios B1 and A2 lead to warming for each month in the long-term mean, with highest warming rates in winter. Instead, precipitation does not change in the long-term yearly mean. However, the intra-annual distribution of monthly precipitation sums shifts with an increase in winter and a strong decrease in summer. Combined, this leads to a changed climatic water balance with a stronger deficit in summer and a higher gain in winter. Particular in the south-eastern part of the catchment, the summer deficit cannot be compensated within the annual cycle. It raised the question: are these changes statistically significant and thus robust for use in further impact studies? Using a significance analysis, we found, that climatic changes in temperature, precipitation and potential evaporation and thus the climatic water balance change is most significant for scenario A2 from 2071 to 2100. The temperature changes are significant throughout the year. For the other variables changes are most significant in the late summer months (July, August, and September) and the winter months (December, January, and February). In contrast, projected changes are hardly significant in the first period from 2021 to 2050. Only temperatures show most statistically significant changes. Weaker change signals in temperature, precipitation and potential evaporation lead also to weak climatic water balance changes in the first period. However, the projected changes in the first period are already indications of impending climatic changes in the catchment.

Pavlik, Dirk; Söhl, Dennis; Bernhofer, Christian

2014-05-01

245

Rainfall seasonality and an ecohydrological feedback offset the potential impact of climate warming on evapotranspiration and groundwater recharge  

NASA Astrophysics Data System (ADS)

potential impact of projected climate warming on the terrestrial hydrologic cycle is uncertain. This problem has evaded experimentalists due to the overwhelming challenge of measuring the entire water budget and introducing experimental warming treatments in open environmental systems. We present new data from a mesocosm experiment that examined the combined responses of evapotranspiration (ET), soil moisture, and potential groundwater recharge (R; lysimeter drainage) to a 3.5°C temperature increase in a grassland ecosystem experiencing a Mediterranean climate. The temperature increase was applied both symmetrically throughout the day, and asymmetrically such that daily minimum temperature was 5°C greater than ambient and daily maximum temperature was 2°C greater than ambient. Our results span 3 water years and show that symmetric and asymmetric warming-enhanced ET during the spring. However, this increase in ET reduced soil moisture more rapidly, resulting in less ET during the summer than occurred under ambient temperature, and no difference in total ET during the combined spring and summer (March to October). Groundwater recharge was reduced during late-spring storms relative to the ambient temperature treatment, but these reductions were less than 4% of total annual R, and were offset by slightly greater R in the fall under both warming treatments. The results highlight the potential for local interactions between temperature, vegetation, and soils to moderate the hydrological response to climate warming, particularly in environments where precipitation is seasonal and out of phase with the vegetation growing season.

Pangle, Luke A.; Gregg, Jillian W.; McDonnell, Jeffrey J.

2014-02-01

246

Diagnosing Warm Frontal Cloud Formation in a GCM: A Novel Approach using Conditional Subsetting  

NASA Astrophysics Data System (ADS)

This study analyzes characteristics of clouds and vertical motion across extratropical cyclone warm fronts in the NASA Goddard Institute for Space Studies General Circulation Model. The validity of the modeled clouds is assessed using a combination of satellite observations from CloudSat, CALIPSO and AMSR-E and the NASA-MERRA reanalysis. The analysis focuses on developing cyclones, to test the model's ability to generate their initial structure. To begin, the extratropical cyclones and their warm fronts are objectively identified and cyclone-local fields are mapped into a vertical transect centered on the surface warm front. To further isolate specific physics, the cyclones are separated using conditional subsetting based on additional cyclone-local variables, and the differences between the subset means are analyzed. Conditional subsets are created based on: (1, 2) the transect clouds and vertical motion, (3) the strength of the temperature gradient along the warm front, as well as the storm-local (4) wind speed and (5) precipitable water (PW). The analysis shows that the model does not generate enough frontal cloud, especially at low altitude. The subsetting results reveal that compared to the observations, the model exhibits a decoupling between cloud formation at high and low altitudes across warm fronts and a weak sensitivity to moisture. These issues are caused in part by the parameterized convection and assumptions in the stratiform cloud scheme that are valid in the subtropics. On the other hand, the model generates proper co-variability of low-altitude vertical motion and cloud at the warm front, and a joint dependence of cloudiness on wind and PW.

Booth, J. F.; Naud, C. M.; Del Genio, A. D.

2013-12-01

247

Rapid Peatland Expansion and Carbon Accumulation in Alaska Caused by a Warm Climate and High Seasonality in the Early Holocene  

Microsoft Academic Search

In order to understand how peatlands respond to past climate warming, here we compiled basal dates from nearly 300 peatlands from across Alaska to examine the timing and spatial pattern of peatland initiation during the late glacial and Holocene. We also calculated Holocene carbon accumulation rates from four peatlands on the Kenai Peninsula, Alaska that have high-resolution dating and carbon

Miriam C. Jones; Zicheng Yu

248

Mid?latitude (30°–60° N) climatic warming inferred by combining borehole temperatures with surface air temperatures  

Microsoft Academic Search

We construct a mid-latitude (30 ? -60 ? N) re- duced temperature-depth profile from a global borehole tem- perature database compiled for climate reconstruction. This reduced temperature profile isinterpreted in termsof pas t surface ground temperature change and indicates warming on the order of 1 ? C over the past 100 to 200 years. The combination of an initial temperature

Robert N. Harris; David S. Chapman

2001-01-01

249

Differential effects of past climate warming on mountain and flatland species distributions: a multispecies North American mammal assessment  

Microsoft Academic Search

Aim The magnitude of predicted range shifts during climate change is likely to be different for species living in mountainous environments compared with those living in flatland environments. The southern edges of ranges in mountain species may not shift northwards during warming as populations instead migrate up available elevational gradients; overall latitudinal range appears therefore to expand. In contrast, flatland

Robert Guralnick

2006-01-01

250

The Effect of Warming Arctic Climate on Coupling Between the Sea Ice Cover and the Upper Ocean  

Microsoft Academic Search

The recent accelerating climate warming and sea ice melt in the Arctic has been often associated with the changes in atmospheric forcing and ice-albedo feedback. However, the causes of ice melt and its rate are not fully understood. Recent observational and modeling studies suggest that the increasing duration and area of open water during the melt season allows significant accumulation

W. Maslowski; J. Clement Kinney; J. E. Haynes; S. R. Okkonen; R. Osinski

2010-01-01

251

Vegetation limits the impact of a warm climate on boreal wildfires.  

PubMed

Strategic introduction of less flammable broadleaf vegetation into landscapes was suggested as a management strategy for decreasing the risk of boreal wildfires projected under climatic change. However, the realization and strength of this offsetting effect in an actual environment remain to be demonstrated. Here we combined paleoecological data, global climate models and wildfire modelling to assess regional fire frequency (RegFF, i.e. the number of fires through time) in boreal forests as it relates to tree species composition and climate over millennial time-scales. Lacustrine charcoals from northern landscapes of eastern boreal Canada indicate that RegFF during the mid-Holocene (6000-3000 yr ago) was significantly higher than pre-industrial RegFF (AD c. 1750). In southern landscapes, RegFF was not significantly higher than the pre-industrial RegFF in spite of the declining drought severity. The modelling experiment indicates that the high fire risk brought about by a warmer and drier climate in the south during the mid-Holocene was offset by a higher broadleaf component. Our data highlight an important function for broadleaf vegetation in determining boreal RegFF in a warmer climate. We estimate that its feedback may be large enough to offset the projected climate change impacts on drought conditions. PMID:23691916

Girardin, Martin P; Ali, Adam A; Carcaillet, Christopher; Blarquez, Olivier; Hély, Christelle; Terrier, Aurélie; Genries, Aurélie; Bergeron, Yves

2013-09-01

252

McMurdo Dry Valleys Climate Response to Plio-Pleistocene Warm Interglacial Climate Forcing  

Microsoft Academic Search

The Antarctic Drilling Program recovered high quality Neogene sediment cores off of the coast of Ross Island recording a series of ice-contact, ice-proximal, ice-distal and marine facies suggesting grounding line migration along the sea floor. Chronology control of the core places glacial variability consistent with ~41 kyr orbital forcing. The marine facies suggests episodes of open-water conditions and elevated sea-surface

D. E. Kowalewski; R. Deconto; A. Seth; D. Pollard

2010-01-01

253

Geopolitics of Climate Change.  

National Technical Information Service (NTIS)

This report analyzes the consequences of climate change and global warming for international politics in general and international security in particular. The report focuses on whether and in what way climate change may alter the conditions of internation...

P. Halden

2007-01-01

254

Mechanisms producing warm-climate ice retreat in East Antarctic subglacial basins  

NASA Astrophysics Data System (ADS)

Geological data indicate that global sea level has fluctuated on O(10,000) to O(1,000,000) year time scales during the last ~25 million years. Peak levels are uncertain, but some estimates suggest high stands of ~20 m or more above modern, for instance during the mid Pliocene. If correct, this implies substantial variations in the size of the East Antarctic Ice Sheet (EAIS). However, climate and ice-sheet models have not been able to simulate significant EAIS retreat from continental size, given low proxy atmospheric CO2 levels during this time. Here, we use a continental Antarctic ice-sheet model with two new mechanisms based on previous studies and observations: (1) structural failure of large tidewater ice cliffs, and (2) enhanced ice-shelf calving due to meltwater drainage into crevasses. With atmospheric and oceanic forcing representing Pliocene warm periods, the new mechanisms greatly accelerate the expected collapse of marine ice in West Antarctica, and also cause drastic retreat into 3 major East Antarctic subglacial basins, producing ~15 m global sea-level rise within a few thousand years. Basic results are presented, along with details of the cliff-failure numerics, and a simple parameterization of the clogging effects of ice melange in narrow seaways, which aids in ice-sheet recovery after colder climates resume.

Pollard, David; DeConto, Robert

2014-05-01

255

Multiscale hydrologic impacts of dust deposition and climate warming in the Upper Colorado River Basin  

NASA Astrophysics Data System (ADS)

The Colorado River provides water to 30 million people in seven states and two countries. Climate models project runoff losses of 7-20% from the basin in this century due to human-induced climate change. Recent work has shown that decreased snow albedo from anthropogenic disturbance-induced dust loading to the CO mountains shortens the duration of snow cover by several weeks, and advances peak runoff at Lees Ferry, Arizona by an average of 3 weeks. Increases in evapotranspiration from earlier exposure of vegetation and soils decreases annual runoff by more than 1.0 billion cubic meters or ~5% of the annual average. This prior work was based on observed dust loadings during 2003-2008, however 2009 and 2010 saw unprecedented levels of dust loading on snowpacks in the Upper Colorado River basin on the order of 5 times the 2003-2008 loading. We examine the hydrologic impact of extreme dust years such as 2009/2010, and interactions with projected regional warming on the Upper Colorado River Basin and selected sub-basins.

Deems, J. S.; Painter, T.; Barsugli, J.

2012-12-01

256

Projected climate regime shift under future global warming from multi-model, multi-scenario CMIP5 simulations  

NASA Astrophysics Data System (ADS)

This study examined shifts in climate regimes over the global land area using the Köppen-Trewartha (K-T) climate classification by analyzing observations during 1900-2010, and simulations during 1900-2100 from twenty global climate models participating in Phase 5 of the Coupled Model Inter-comparison Project (CMIP5). Under the Intergovernmental Panel on Climate Change Representative Concentration Pathways 8.5 (RCP8.5) scenario, the models projected a 3°-10 °C warming in annual temperature over the global land area by the end of the twenty-first century, with strong (moderate) warming in the high (middle) latitudes of the Northern Hemisphere and weaker warming in the tropics and the Southern Hemisphere. The projected changes in precipitation vary considerably in space and present greater uncertainties among the models. Overall, the models are consistent in projecting increasing precipitation over the high-latitude of the Northern Hemisphere, and reduced precipitation in the Mediterranean, southwestern North America, northern and southern Africa and Australia. Based on the projected changes in temperature and precipitation, the K-T climate types would shift toward warmer and drier climate types from the current climate distribution. Regions of temperate, tropical and dry climate types are projected to expand, while regions of polar, sub-polar and subtropical climate types are projected to contract. The magnitudes of the projected changes are stronger in the RCP8.5 scenario than the low emission scenario RCP4.5. On average, the climate types in 31.4% and 46.3% of the global land area are projected to change by the end of the twenty-first century under RCP4.5 and RCP8.5 scenarios, respectively. Further analysis suggests that changes in precipitation played a slightly more important role in causing shifts of climate type during the twentieth century. However, the projected changes in temperature play an increasingly important role and dominate shifts in climate type when the warming becomes more pronounced in the twenty-first century.

Feng, Song; Hu, Qi; Huang, Wei; Ho, Chang-Hoi; Li, Ruopu; Tang, Zhenghong

2014-01-01

257

Do variations in the ?13C of soil phospholipid fatty acids indicate changes in substrate use with climate warming?  

NASA Astrophysics Data System (ADS)

The effect of climate warming on the microbial mineralization of soil organic carbon (SOC) remains a key uncertainty in biogeochemical models. In particular, it remains unclear whether microbial substrate use patterns change with climate. The carbon isotopic signature (?13C) of soil microbial phospholipid fatty acids (?13CPLFA) can provide insight into substrate utilization patterns in situ without manipulations unavoidable in soil incubation experiments. The interpretation of ?13CPLFA, however, is limited by gaps in our understanding of the isotopic fractionation associated with PLFA biosynthesis, and in particular, whether this fractionation changes with growth temperature. Characterizing the principles controlling ?13CPLFA under controlled laboratory conditions can help with the interpretation of field measurements of temperature effects on microbial SOC assimilation. We measured ?13CPLFA from field soils in two regions along a boreal climate transect, which differ by 4.5 °C mean annual temperature. In each region, the organic (L, F, H) and mineral (B; top 10cm) soil horizons were sampled at three locations chosen for similar vegetation (balsam fir), stand age, elevation, and soil type (humo-ferric podzol). Soils from both regions had similar bulk SOC ?13C and exhibited an increase with depth from -29.5±0.4 to -26.5±0.6o. Despite the similar ?13C of SOC, PLFA in the organic horizons from the warmer region were more enriched in 13C relative to those from the colder region.In a model that used region, horizon and the individual PLFA as predictors, we found that region had a subtle (0.7o), but highly significant (p

Kohl, Lukas; Laganière, Jérôme; Edwards, Kate; Lehmeier, Christoph; Min, Kyungjin; Billings, Sharon A.; Ballantyne, Ford; Van Biesen, Geert; Morrill, Penny L.; Ziegler, Susan E.

2014-05-01

258

Dinoflagellate cyst evidence for warm interglacial conditions at the northern Barents Sea margin during marine oxygen isotope stage 5  

Microsoft Academic Search

Dinoflagellate cyst analysis has been conducted on a sediment core from the northern Barents Sea margin (eastern Arctic Ocean) to reconstruct sea-surface conditions during marine oxygen isotope stage 5. Cyst concentrations and composition of assemblages display a distinct variability reflecting deglacial warming and the onset of relatively warm interglacial conditions in early stage 5. Dinoflagellate cyst assemblages of the last

Jens Matthiessen; Jochen Knies

2001-01-01

259

Conditional Uncertainty in Anthropogenic Global Climate Change  

NASA Astrophysics Data System (ADS)

Although, the uncertainty associated with human-induced climate change is less that in many other human activities such as economic management and warfare, the uncertainties in the climate system have assumed a disproportionate profile in public debate. Achieving improved public understanding is dependent on consistent use of the various categories of change and their respective uncertainties. Probably the most important distinction to be made is between uncertainties associated with uncertain societal choices and uncertainties associated with the consequences of such choices. For the biogeochemical system, categories of uncertainty are adapted from those used in the study of uncertainty for the REgional Carbon Assessment and Processes (RECCAP) study. These are then extended and applied to the discussion of the combined carbon-climate system. Characterising uncertainties in future change requires a consistent approach to propagating into the future the uncertainties associated with the past and present state of the climate system. Again, previous analysis for the carbon system is extended to the carbon-climate system. The potential category ambiguities that arise from feedbacks between climate and carbon are identified and resolved. A consistent characterisation of the uncertainties in the earth system provides a basis for factoring the overall uncertainty into human and natural contributions.

Enting, I. G.

2012-12-01

260

Stratosphere key for wintertime atmospheric response to warm Atlantic decadal conditions  

NASA Astrophysics Data System (ADS)

There is evidence that the observed changes in winter North Atlantic Oscillation (NAO) drive a significant portion of Atlantic Multi Decadal Variability (AMV). However, whether the observed decadal NAO changes can be forced by the ocean is controversial. There is also evidence that artificially imposed multi-decadal stratospheric changes can impact the troposphere in winter. But the origins of such stratospheric changes are still unclear, especially in early to mid winter, where the radiative ozone-impact is negligible. Here we show, through observational analysis and atmospheric model experiments, that large-scale Atlantic warming associated with AMV drives high-latitude precursory stratospheric warming in early to mid winter that propagates downward resulting in a negative tropospheric NAO in late winter. The mechanism involves stratosphere/troposphere dynamical coupling, and can be simulated to a large extent, but only with a stratosphere resolving model (i.e., high-top). Further analysis shows that this precursory stratospheric response can be explained by the shift of the daily extremes toward more major stratospheric warming events. This shift cannot be simulated with the atmospheric (low-top) model configuration that poorly resolves the stratosphere and implements a sponge layer in upper model levels. While the potential role of the stratosphere in multi-decadal NAO and Atlantic meridional overturning circulation changes has been recognised, our results show that the stratosphere is an essential element of extra-tropical atmospheric response to ocean variability. Our findings suggest that the use of stratosphere resolving models should improve the simulation, prediction, and projection of extra-tropical climate, and lead to a better understanding of natural and anthropogenic climate change.

Omrani, N.-E.; Keenlyside, N. S.; Bader, Jürgen; Manzini, Elisa

2014-02-01

261

Influence of Climate Warming on Arctic Mammals? New Insights from Ancient DNA Studies of the collared lemming Dicrostonyx torquatus.  

NASA Astrophysics Data System (ADS)

Global temperature increased by approximately half a degree (Celsius) within the last 150 years. Even this moderate warming had major impacts on Earth's ecological and biological systems, especially in the Arctic where the magnitude of abiotic changes even exceeds those in temperate and tropical biomes. Therefore, understanding the biological consequences of climate change on high latitudes is of critical importance for future conservation of the species living in this habitat. The past 25,000 years can be used as a model for such changes, as they were marked by prominent climatic changes that influenced geographic distribution, demographic history and pattern of genetic variation of many extant species. We sequenced ancient and modern DNA of the collared lemming (Dicrostonyx torquatus), which is a key species of the arctic biota, from a single site (Pymva Shor, Northern Pre Urals, Russia) to see if climate warming events after the Last Glacial Maximum (LGM) had detectable effects on the genetic variation of this arctic rodent species, which is strongly associated with cold and dry climate. Using three dimensional network reconstruction and model-based approaches such as Approximate Bayesian Computation and Markov Chain Monte Carlo based Bayesian inference we show that there is evidence for a population decline in the collared lemming following the LGM, with the population size dropping to a minimum during the Greenland Interstadial 1 (Blling/Allerd) warming phase at 14.5 kyrs BP. Our results show that previous climate warming events had a strong influence on collard lemming populations. A similar population reduction due to predicted future climate change would have severe effects on the arctic ecosystem, as collared lemmings are a key species in the trophic interactions and ecosystem processes in the Arctic.

Prost, Stefan; Smirnov, Nickolay; Fedorov, Vadim B.; Sommer, Robert S.; Stiller, Mathias; Nagel, Doris; Knapp, Michael; Hofreiter, Michael

2010-05-01

262

Influence of Climate Warming on Arctic Mammals? New Insights from Ancient DNA Studies of the Collared Lemming Dicrostonyx torquatus  

PubMed Central

Background Global temperature increased by approximately half a degree (Celsius) within the last 150 years. Even this moderate warming had major impacts on Earth's ecological and biological systems, especially in the Arctic where the magnitude of abiotic changes even exceeds those in temperate and tropical biomes. Therefore, understanding the biological consequences of climate change on high latitudes is of critical importance for future conservation of the species living in this habitat. The past 25,000 years can be used as a model for such changes, as they were marked by prominent climatic changes that influenced geographical distribution, demographic history and pattern of genetic variation of many extant species. We sequenced ancient and modern DNA of the collared lemming (Dicrostonyx torquatus), which is a key species of the arctic biota, from a single site (Pymva Shor, Northern Pre Urals, Russia) to see if climate warming events after the Last Glacial Maximum had detectable effects on the genetic variation of this arctic rodent species, which is strongly associated with a cold and dry climate. Results Using three dimensional network reconstructions we found a dramatic decline in genetic diversity following the LGM. Model-based approaches such as Approximate Bayesian Computation and Markov Chain Monte Carlo based Bayesian inference show that there is evidence for a population decline in the collared lemming following the LGM, with the population size dropping to a minimum during the Greenland Interstadial 1 (Bølling/Allerød) warming phase at 14.5 kyrs BP. Conclusion Our results show that previous climate warming events had a strong influence on genetic diversity and population size of collared lemmings. Due to its already severely compromised genetic diversity a similar population reduction as a result of the predicted future climate change could completely abolish the remaining genetic diversity in this population. Local population extinctions of collared lemmings would have severe effects on the arctic ecosystem, as collared lemmings are a key species in the trophic interactions and ecosystem processes in the Arctic.

Prost, Stefan; Smirnov, Nickolay; Fedorov, Vadim B.; Sommer, Robert S.; Stiller, Mathias; Nagel, Doris; Knapp, Michael; Hofreiter, Michael

2010-01-01

263

Understanding the causes of recent warming of mediterranean waters. How much could be attributed to climate change?  

PubMed

During the past two decades, Mediterranean waters have been warming at a rather high rate resulting in scientific and social concern. This warming trend is observed in satellite data, field data and model simulations, and affects both surface and deep waters throughout the Mediterranean basin. However, the warming rate is regionally different and seems to change with time, which has led to the question of what causes underlie the observed trends. Here, we analyze available satellite information on sea surface temperature (SST) from the last 25 years using spectral techniques and find that more than half of the warming tendency during this period is due to a non-linear, wave-like tendency. Using a state of the art hydrodynamic model, we perform a hindcast simulation and obtain the simulated SST evolution of the Mediterranean basin for the last 52 years. These SST results show a clear sinusoidal tendency that follows the Atlantic Multidecadal Oscillation (AMO) during the simulation period. Our results reveal that 58% of recent warming in Mediterranean waters could be attributed to this AMO-like oscillation, being anthropogenic-induced climate change only responsible for 42% of total trend. The observed acceleration of water warming during the 1990s therefore appears to be caused by a superimposition of anthropogenic-induced warming with the positive phase of the AMO, while the recent slowdown of this tendency is likely due to a shift in the AMO phase. It has been proposed that this change in the AMO phase will mask the effect of global warming in the forthcoming decades, and our results indicate that the same could also be applicable to the Mediterranean Sea. Henceforth, natural multidecadal temperature oscillations should be taken into account to avoid underestimation of the anthropogenic-induced warming of the Mediterranean basin in the future. PMID:24312322

Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

2013-01-01

264

Understanding the Causes of Recent Warming of Mediterranean Waters. How Much Could Be Attributed to Climate Change?  

PubMed Central

During the past two decades, Mediterranean waters have been warming at a rather high rate resulting in scientific and social concern. This warming trend is observed in satellite data, field data and model simulations, and affects both surface and deep waters throughout the Mediterranean basin. However, the warming rate is regionally different and seems to change with time, which has led to the question of what causes underlie the observed trends. Here, we analyze available satellite information on sea surface temperature (SST) from the last 25 years using spectral techniques and find that more than half of the warming tendency during this period is due to a non-linear, wave-like tendency. Using a state of the art hydrodynamic model, we perform a hindcast simulation and obtain the simulated SST evolution of the Mediterranean basin for the last 52 years. These SST results show a clear sinusoidal tendency that follows the Atlantic Multidecadal Oscillation (AMO) during the simulation period. Our results reveal that 58% of recent warming in Mediterranean waters could be attributed to this AMO-like oscillation, being anthropogenic-induced climate change only responsible for 42% of total trend. The observed acceleration of water warming during the 1990s therefore appears to be caused by a superimposition of anthropogenic-induced warming with the positive phase of the AMO, while the recent slowdown of this tendency is likely due to a shift in the AMO phase. It has been proposed that this change in the AMO phase will mask the effect of global warming in the forthcoming decades, and our results indicate that the same could also be applicable to the Mediterranean Sea. Henceforth, natural multidecadal temperature oscillations should be taken into account to avoid underestimation of the anthropogenic-induced warming of the Mediterranean basin in the future.

Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

2013-01-01

265

The interplay between knowledge, perceived efficacy, and concern about global warming and climate change: a one-year longitudinal study.  

PubMed

If the long-term goal of limiting warming to less than 2°C is to be achieved, rapid and sustained reductions of greenhouse gas emissions are required. These reductions will demand political leadership and widespread public support for action on global warming and climate change. Public knowledge, level of concern, and perceived personal efficacy, in positively affecting these issues are key variables in understanding public support for mitigation action. Previous research has documented some contradictory associations between knowledge, personal efficacy, and concern about global warming and climate change, but these cross-sectional findings limit inferences about temporal stability and direction of influence. This study examines the relationships between these three variables over a one-year period and three waves with national data from New Zealand. Results showed a positive association between the variables, and the pattern of findings was stable and consistent across the three data points. More importantly, results indicate that concern mediates the influence of knowledge on personal efficacy. Knowing more about global warming and climate change increases overall concern about the risks of these issues, and this increased concern leads to greater perceived efficacy and responsibility to help solving them. Implications for risk communication are discussed. PMID:22489642

Milfont, Taciano L

2012-06-01

266

Physiological effects of climate warming on flowering plants and insect pollinators and potential consequences for their interactions  

PubMed Central

Growing concern about the influence of climate change on flowering plants, pollinators, and the mutualistic interactions between them has led to a recent surge in research. Much of this research has addressed the consequences of warming for phenological and distributional shifts. In contrast, relatively little is known about the physiological responses of plants and insect pollinators to climate warming and, in particular, how these responses might affect plant-pollinator interactions. Here, we summarize the direct physiological effects of temperature on flowering plants and pollinating insects to highlight ways in which plant and pollinator responses could affect floral resources for pollinators, and pollination success for plants, respectively. We also consider the overall effects of these responses on plant-pollinator interaction networks. Plant responses to warming, which include altered flower, nectar, and pollen production, could modify floral resource availability and reproductive output of pollinating insects. Similarly, pollinator responses, such as altered foraging activity, body size, and life span, could affect patterns of pollen flow and pollination success of flowering plants. As a result, network structure could be altered as interactions are gained and lost, weakened and strengthened, even without the gain or loss of species or temporal overlap. Future research that addresses not only how plant and pollinator physiology are affected by warming but also how responses scale up to affect interactions and networks should allow us to better understand and predict the effects of climate change on this important ecosystem service

SCAVEN, Victoria L.; RAFFERTY, Nicole E.

2013-01-01

267

A mechanism for land-ocean contrasts in global monsoon trends in a warming climate  

NASA Astrophysics Data System (ADS)

A central paradox of the global monsoon record involves reported decreases in rainfall over land during an era in which the global hydrologic cycle is both expected and observed to intensify. It is within this context that this work develops a physical basis for both interpreting the observed record and anticipating changes in the monsoons in a warming climate while bolstering the concept of the global monsoon in the context of shared feedbacks. The global-land monsoon record across multiple reanalyses is first assessed. Trends that in other studies have been taken as real are shown to likely be spurious as a result of changes in the assimilated data streams both prior to and during the satellite era. Nonetheless, based on satellite estimates, robust increases in monsoon rainfall over ocean do exist and a physical basis for this land-ocean contrast remains lacking. To address the contrast's causes, simulated trends are therefore assessed. While projections of total rainfall are inconsistent across models, the robust land-ocean contrast identified in observations is confirmed. A feedback mechanism is proposed rooted in the facts that land areas warm disproportionately relative to ocean, and onshore flow is the chief source of monsoonal moisture. Reductions in lower tropospheric relative humidity over land domains are therefore inevitable and these have direct consequences for the monsoonal convective environment including an increase in the lifting condensation level and a shift in the distribution of convection generally towards less frequent and potentially more intense events. The mechanism is interpreted as an important modulating influence on the "rich-get-richer" mechanism. Caveats for regional monsoons exist and are discussed.

Fasullo, J.

2012-09-01

268

Climate Impacts of Land Cover and Land Use Changes in a Tropical Montane Cloud Forest under Conditions of Global Climate Change  

NASA Astrophysics Data System (ADS)

The main objective of this research is to gain a better understanding of the climate impacts caused by the combined effects of land cover and land use (LCLU) changes and global climate change (i.e., global warming) in tropical montane cloud forests (TMCF). To achieve this goal an ensemble of climate simulations were performed, combining two LCLU and two global warming scenarios, using the Regional Atmospheric Modeling System (RAMS) as the main research tool and taking the northeastern region of the Caribbean island of Puerto Rico as the test case. Reconstructed agricultural maps combined with reconstructed sea surface temperatures (SST) form the Past (1951-1956) climate scenario, while the Present (2000-2004) scenario was supported with high-resolution remote sensing data. The climate reconstruction approach is validated with observational data from surface weather stations for both timeframes. Results indicate that LCLU changes produced the largest air temperature differences over heavily urbanized regions and that these changes occur near the surface. The influence of the global warming signal is to induce a positive inland gradient for maximum temperature, possibly due to increased trade winds in the present climatology. The minimum surface temperatures are dominated by the warming signal inducing temperature increases along the coastal plains and inland lowlands. The global warming signal also produces stronger trade winds with an easterly-southeasterly direction. These changes cause a shift in the location of a convergence zone north of the Central Mountains and east of El Yunque National Forest, also known as the Luquillo Experimental Forest. This produces an extra orographic lifting and additional latent heat released by the vegetation, resulting in higher cloud bases, reducing the total column of liquid water content above higher elevations in all TMCF located within the domain. This combination of factors translates into a dramatic decrease in surface accumulated precipitation in the highlands of the region of interest due to global climate change. The combined effects of LCLU changes and global warming indicate that the impact of LCLU changes on temperatures, total column liquid water content, and surface accumulated precipitation are relatively independent of the large-scale climate conditions, and vice versa. The aggregate effects on surface temperatures is, however, additive with LCLU increasing the regional warming signal in the local urban region.

Comarazamy, D.; González, J. E.

2011-12-01

269

Sequential chilling-forcing models predict budburst phenology best in deciduous trees: results from a climate warming experiment  

NASA Astrophysics Data System (ADS)

Modeling budburst phenology is important for assessing the impact of climate change on ecosystem processes. Based on historical datasets, the simple growing degree days models were thought to successfully reproduce budburst date. However, many tree species require a certain amount of winter chilling and the future warming may result in insufficient chilling. Therefore, modeling future phenology shifts needs evaluation of the budburst process based on warming experiments. In this study, we conducted a 2-year warming experiment, with different warming levels. The main aims of this study were to assess the budburst response to winter and spring warming and to estimate the accuracy of five budburst models. One-meter-high saplings of three deciduous tree species were used, i.e. birch (Betula pendula L.), oak (Quercus robur L.) and beech (Fagus sylvatica L.). The results showed that the manipulated warming results in a wide range of budburst dates across the three studied species. Both warming winter and spring substantially advanced the timing of budburst. Model evaluation shows that both one-(without chilling) and two-(with chilling) phase models are able to accurately predict the observation date. The best performing model differed among the three species. The growing degree days model performed best for oak and birch. The model with sequential chilling and forcing yielded similar good results for these two species, but was by far the best model for beech. Therefore, a model with a sequential budburst pattern may be more appropriate to simulate budburst data in a future warmer climate in which chilling progressively becomes more limiting.

Fu, Y. S. H.; Campioli, M.; Deckmyn, G.; Janssens, I. A.

2012-04-01

270

Potential increase of flood hazards in Korea due to global warming from a high-resolution regional climate simulation  

NASA Astrophysics Data System (ADS)

Because of the importance of the changes in the hydrologic cycle, accurate assessment of precipitation characteristics is essential to understand the impact of climate change due to global warming. This study investigates the changes in extreme precipitation with sub-daily and daily temporal scales. For a fine-scale climate change projection focusing on the Korean peninsula (20 km), we performed the dynamical downscaling of the global climate scenario covering the period 1971-2100 (130-year) simulated by the Max-Planck-Institute global climate model, ECHAM5, using the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model, RegCM3. While annual mean precipitation exhibits a pronounced interannual and interdecadal variability, with the increasing or decreasing trend repeated during a certain period, extreme precipitation with sub-daily and daily temporal scales estimated from the generalized extreme value distribution shows consistently increasing pattern. The return period of extreme precipitation is significantly reduced despite the decreased annual mean precipitation at the end of 21st century. The decreased relatively weak precipitation is responsible for the decreased total precipitation, so that the decreased total precipitation does not necessarily mean less heavy precipitation. Climate change projection based on the ECHAM5-RegCM3 model chain clearly shows the effect of global warming in increasing the intensity and frequency of extreme precipitation, even without significantly increased total precipitation, which implies an increased risk for flood hazards.

Im, Eun-Soon; Lee, Byong-Ju; Kwon, Ji-Hye; in, So-Ra; Han, Sang-Ok

2012-02-01

271

Increasing contaminant burdens in an arctic fish, Burbot ( Lota lota ), in a warming climate.  

PubMed

The temporal patterns of mercury (Hg), polychlorinated biphenyls (PCBs), and other contaminants in Arctic aquatic biota are usually attributed to changing atmospheric sources. However, climate variability and change is another means of altering contaminant fate and bioavailability. We show here that the concentrations of Hg and PCBs in Mackenzie River burbot ( Lota lota ), a top predator fish and important staple food for northern Canadian communities, have increased significantly over the last 25 years despite falling or stable atmospheric concentrations, suggesting that environmental processes subsequent to atmospheric transport are responsible. Using a dated sediment core from a tributary lake near the Mackenzie River sampling site, we show that variations in Hg concentrations downcore are strongly associated with labile, algal-derived organic matter (OM). Strong temporal correlations between increasing primary productivity and biotic Hg and PCBs as reflected by burbot suggest that warming temperatures and reduced ice cover may lead to increased exposure to these contaminants in high trophic level Arctic freshwater biota. PMID:19957995

Carrie, J; Wang, F; Sanei, H; Macdonald, R W; Outridge, P M; Stern, G A

2010-01-01

272

Managing Stream Temperatures for Climate Warming Adaptation with Selective Withdrawal from Reservoirs  

NASA Astrophysics Data System (ADS)

Climate warming is altering the flow and temperature regimes in California's Sierra Nevada mountain range by reducing snowpack, causing earlier runoff and raising stream temperatures. Managing reservoir releases for downstream temperatures is a promising adaptation option. In this study, we developed a linear programming model to optimally release water from multiple thermal layers in a seasonally stratified reservoir to minimize deviations from desired downstream temperatures. An explicit objective of the work was to develop a method that can be readily integrated into a watershed-scale, multi-reservoir optimization model using a node-link representation of system features. The objective function is to minimize managed temperature deviations from target temperatures based on the natural temperature regime. Thermal dynamics of reservoirs and streams are included in the constraint set. For a case study, the model is applied to Lake Spaulding, a multi-purpose reservoir in the western Sierra Nevada that thermally stratifies seasonally and that could be used to manage temperatures for a downstream cold water fishery. We demonstrate how the model can effectively manage releases from thermal pools when compared to only a single, low-level outlet (no selective withdrawal). The model hedges the release of cold water to decrease summer stream temperatures, but at a cost of warmer stream temperatures in the winter. This method can be extended to include other nearby reservoirs to optimally manage releases from multiple reservoirs for multiple downstream temperature targets to help buffer aquatic ecosystems against anticipated stream temperature increases.

Rheinheimer, D. E.; Lund, J. R.; Null, S.; Viers, J. H.

2011-12-01

273

Predicting organismal vulnerability to climate warming: roles of behaviour, physiology and adaptation  

PubMed Central

A recently developed integrative framework proposes that the vulnerability of a species to environmental change depends on the species' exposure and sensitivity to environmental change, its resilience to perturbations and its potential to adapt to change. These vulnerability criteria require behavioural, physiological and genetic data. With this information in hand, biologists can predict organisms most at risk from environmental change. Biologists and managers can then target organisms and habitats most at risk. Unfortunately, the required data (e.g. optimal physiological temperatures) are rarely available. Here, we evaluate the reliability of potential proxies (e.g. critical temperatures) that are often available for some groups. Several proxies for ectotherms are promising, but analogous ones for endotherms are lacking. We also develop a simple graphical model of how behavioural thermoregulation, acclimation and adaptation may interact to influence vulnerability over time. After considering this model together with the proxies available for physiological sensitivity to climate change, we conclude that ectotherms sharing vulnerability traits seem concentrated in lowland tropical forests. Their vulnerability may be exacerbated by negative biotic interactions. Whether tropical forest (or other) species can adapt to warming environments is unclear, as genetic and selective data are scant. Nevertheless, the prospects for tropical forest ectotherms appear grim.

Huey, Raymond B.; Kearney, Michael R.; Krockenberger, Andrew; Holtum, Joseph A. M.; Jess, Mellissa; Williams, Stephen E.

2012-01-01

274

The effect of climate warming and permafrost thaw on desertification in the Qinghai-Tibetan Plateau  

NASA Astrophysics Data System (ADS)

Four sets of remote sensing images from 1987, 1994, 2000, and 2006, 50 years of meteorological and soil moisture data corresponding to different desertified lands were combined with populations and livestock data to analyze the process and cause of desertification in a portion of the Qinghai-Tibetan Plateau (QTP). It showed that surface soil temperature in the region has increased at an average rate of 0.6 °C per decade between 1980 and 2005, the thawing days on the surface have increased by 60 days from 1983 to 2001, and the depth of the seasonal thawing layer has increased by 54 cm, 102 cm and 77 cm in April, May and June, respectively, from 1983 to 2003. As a result, the upper soil layer has become drier due to the thickening active layer and soil water infiltration. These changes, in turn, have inhibited the growth of alpine meadow vegetation that has shallow root systems. It is concluded that climate warming and permafrost thawing have caused desertification in grazing regions of the Qinghai-Tibetan Plateau (QTP).

Xue, Xian; Guo, Jian; Han, Bangshuai; Sun, Qingwei; Liu, Lichao

2009-07-01

275

Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests  

NASA Astrophysics Data System (ADS)

Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

Lapenis, Andrei G.; Lawrence, Gregory B.; Heim, Alexander; Zheng, Chengyang; Shortle, Walter

2013-01-01

276

Anticyclonic atmospheric circulation as an analogue for the warm and dry mid-Holocene summer climate in central Scandinavia  

Microsoft Academic Search

Climate reconstructions from central Scandinavia suggest that annual and summer temperatures were rising during the early Holocene and reached their maximum after 8000 cal yr BP. The period with highest temperatures was characterized by increasingly low lake-levels and dry climate, with driest and warmest conditions at about 7000 to 5000 cal yr BP. We compare the reconstructed climate pattern with

K. Antonsson; D. Chen; H. Seppä

2008-01-01

277

Effects of airflow on body temperatures and sleep stages in a warm humid climate  

NASA Astrophysics Data System (ADS)

Airflow is an effective way to increase heat loss—an ongoing process during sleep and wakefulness in daily life. However, it is unclear whether airflow stimulates cutaneous sensation and disturbs sleep or reduces the heat load and facilitates sleep. In this study, 17 male subjects wearing short pyjamas slept on a bed with a cotton blanket under two of the following conditions: (1) air temperature (Ta) 26°C, relative humidity (RH) 50%, and air velocity (V) 0.2 m s-1; (2) Ta 32°C, RH 80%, V 1.7 m s-1; (3) Ta 32°C; RH 80%, V 0.2 m s-1 (hereafter referred to as 26/50, 32/80 with airflow, and 32/80 with still air, respectively). Electroencephalograms, electrooculograms, and mental electromyograms were obtained for all subjects. Rectal (Tre) and skin (Ts) temperatures were recorded continuously during the sleep session, and body-mass was measured before and after the sleep session. No significant differences were observed in the duration of sleep stages between subjects under the 26/50 and 32/80 with airflow conditions; however, the total duration of wakefulness decreased significantly in subjects under the 32/80 with airflow condition compared to that in subjects under the 32/80 with still air condition ( P < 0.05). Tre, Tsk, Ts, and body-mass loss under the 32/80 with airflow condition were significantly higher compared to those under the 26/50 condition, and significantly lower than those under the 32/80 with still air condition ( P < 0.05). An alleviated heat load due to increased airflow was considered to exist between the 32/80 with still air and the 26/50 conditions. Airflow reduces the duration of wakefulness by decreasing Tre, Tsk, Ts, and body-mass loss in a warm humid condition.

Tsuzuki, Kazuyo; Okamoto-Mizuno, Kazue; Mizuno, Koh; Iwaki, Tatsuya

2008-03-01

278

AMOC response to global warming: dependence on the background climate and response timescale  

NASA Astrophysics Data System (ADS)

This paper investigates the response of the Atlantic meridional overturning circulation (AMOC) to a sudden doubling of atmospheric CO2 in the National Center for Atmospheric Research Community Climate System Model version 3, with a focus on differences under different background climates. The findings reveal that the evolution of the AMOC differs significantly between the modern climate and the last glacial maximum (LGM). In the modern climate, the AMOC decreases (by 25 %, 4 Sv) in the first 100 years and then recovers slowly (by 6 %, 1 Sv) by the end of the 1,500-year simulation. At the LGM, the AMOC also weakens (by 8 %, 1 Sv) in the initial 90 years, but then recovers, first rapidly (by 30 %, 4 Sv) over the following 300 years, and then slowly (by 13 %, 1.6 Sv) during the remainder of the integration. These results suggest that the responses of the AMOC under both climates have a similar initial rapid weakening period of ~100 years and a final slow strengthening period over 1,000 years long. However, additional intermediate period of ~300 years does occur for the LGM, with rapid intensification in the AMOC. Analyses suggest that the rapid intensification is triggered and sustained primarily by a coupled sea ice-ocean feedback: the reduction of meltwater flux in the northern North Atlantic—associated with the remarkable sea-ice retreat at the LGM—intensifies the AMOC and northward heat transport, which, in turn, causes further sea-ice retreat and more reduction of meltwater. These processes are insignificant under modern conditions.

Zhu, Jiang; Liu, Zhengyu; Zhang, Jiaxu; Liu, Wei

2014-05-01

279

Modeling the potential change in yield and distribution of the earth's crops under a warmed climate  

SciTech Connect

The large scale distribution of crops is largely determined by climate. The authors present the results of a climate-crop prediction model based on the U.N. Food and Agriculture Organization crop-suitability approach, implemented in a geographic information system (GIS) environment using several global environmental databases. The model utilizes daily temperature and moisture conditions to determine the properties of the growing period. Crops are characterized by their variety-specific minimum growing period requirements and photosynthesis and respiration properties. Temperature and solar radiation during the growing period control the development of each crop. The model simulates crop-specific geographic distributions by demarcating the region where productivity is possible. The model takes only non-irrigated crop productivity into account and the potential increase in productivity by technological means is not considered. The model therefore shows no crop growth along major rivers in arid, often irrigated, regions. (Copyright (c) Inter-Research 1993.)

Leemans, R.; Solomon, A.M.

1993-01-01

280

Arctic land hydrothermal sensitivity under warming: Idealized off-line evaluation of a physical terrestrial scheme in a global climate model  

NASA Astrophysics Data System (ADS)

A series of idealized one-dimensional off-line sensitivity experiments for the Arctic hydroclimate under a transitional warming environment were conducted to investigate the impact of different internal mechanisms and external forcing (excessive water input) in a physical terrestrial scheme, Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO), used in a global climate model. The scheme has freeze/thaw processes and was run with the column depth greater than 50 m. The inclusion of the top organic layers and the physically based parameterization of soil hydrothermal properties led to a realistic seasonal amplitude of a subsurface thermal regime and mitigated the warming and deepening of the maximum active layer thickness (ALT). After a 6-K warming over 100 years, ALT increases by 67% (from 9.6 to 16 cm) with the top organic layers and increases by more than a factor of 2 for the default mineral layers (122% from 45 cm to 1.0 m). With the more realistic thermal property profile, the physically based parameterizations projected ALT after the 100-year warming to be about a half of what the original parameterization did (2.0 against 3.5 m). Finer soil layer thickness near the surface had impacts on the near-surface wetness and the energy and water exchange between the atmosphere and also showed greater tolerance to the misconfiguration of porosity profile, whose global-scale distribution is poorly known for global climate model applications. With much wetter forcing, water infiltration kept the soil close to the saturation, degradation of the frozen state proceeded faster, and the adaptation back to a drier condition occurred on a decadal time scale.

Saito, Kazuyuki

2008-11-01

281

Impacts of climate warming and permafrost thaw on the riverine transport of nitrogen and phosphorus to the Kara Sea  

Microsoft Academic Search

Measurements of nitrogen and phosphorus (N and P) concentrations from previously unstudied streams and rivers throughout west Siberia suggest that climate warming and\\/or associated permafrost thaw will likely amplify the transport of N and P to the Kara Sea and adjacent Arctic Ocean. We present concentrations of dissolved organic nitrogen (DON), ammonium (NH4-N), nitrate (NO3-N), total dissolved nitrogen (TDN), and

Karen E. Frey; James W. McClelland; Robert M. Holmes; Laurence C. Smith

2007-01-01

282

Impacts of climate warming and permafrost thaw on the riverine transport of nitrogen and phosphorus to the Kara Sea  

Microsoft Academic Search

(1) Measurements of nitrogen and phosphorus (N and P) concentrations from previously unstudied streams and rivers throughout west Siberia suggest that climate warming and\\/or associated permafrost thaw will likely amplify the transport of N and P to the Kara Sea and adjacent Arctic Ocean. We present concentrations of dissolved organic nitrogen (DON), ammonium (NH4-N), nitrate (NO3-N), total dissolved nitrogen (TDN),

Karen E. Frey; James W. McClelland; Robert M. Holmes; Laurence C. Smith

2007-01-01

283

24 CFR 3285.404 - Severe climatic conditions.  

Code of Federal Regulations, 2013 CFR

...COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Anchorage Against Wind § 3285.404 Severe climatic conditions. In frost-susceptible soil locations, ground anchor augers must be...

2013-04-01

284

Warm-season rainfall variability over the U.S. Great Plains and its correlation with evapotranspiration in a climate simulation  

NASA Astrophysics Data System (ADS)

The warm-season rainfall variability over the US Great Plains is examined in a climate simulation and compared with observations to explore the role of land-atmosphere interaction in the model. The results show that compared to observations, the model simulations underestimate summertime rainfall by more than 12% but overestimate its standard deviation by 25-54%, with the larger value referring to interannual variability. Linear regression shows that the rainfall variability is connected with evapotranspiration (ET) anomalies, but mostly to evaporation rather than transpiration. Since the evaporation represents an immediate response of the land surface to atmospheric conditions but the transpiration reflects soil moisture memory with considerably longer time scales, the realism of the correlated variability between separate ET components and precipitation is an important aspect of how climate models realistically address land-atmosphere interaction.

Wu, Wanru; Dickinson, Robert E.

2005-09-01

285

Diagnosis of the summertime warm and dry bias over the U. S. Southern Great Plains in the GFDL climate model using a weather forecasting approach  

SciTech Connect

Weather forecasts started from realistic initial conditions are used to diagnose the large warm and dry bias over the United States Southern Great Plains simulated by the GFDL climate model. The forecasts exhibit biases in surface air temperature and precipitation within 3 days which appear to be similar to the climate bias. With the model simulating realistic evaporation but underestimated precipitation, a deficit in soil moisture results which amplifies the initial temperature bias through feedbacks with the land surface. The underestimate of precipitation is associated with an inability of the model to simulate the eastward propagation of convection from the front-range of the Rocky Mountains and is insensitive to an increase of horizontal resolution from 2{sup o} to 0.5{sup o} latitude.

Klein, S A; Jiang, X; Boyle, J; Malyshev, S; Xie, S

2006-07-11

286

Trend analysis of wet and dry climatic conditions for the Carpathian basin using RCM simulations  

NASA Astrophysics Data System (ADS)

Global warming may be recognized both in shifts of regional mean climate, and also, in the frequency and intensity changes of different climatological extremes associated to both temperature and precipitation. In this poster the main focus is on the analysis of precipitation-related climatic conditions. For this purpose we use different types of drought indices, namely, precipitation index, standardized precipitation anomaly index (SAI), De Martonne aridity index, Thornthwaite index, Lang's rainfall index, Ped's drought index and Foley's anomaly index (FAI). In order to calculate the time series of these indices, temperature and precipitation datasets of PRECIS simulations were used. The model PRECIS is a hydrostatic regional climate model HadRM3P developed at the UK Met Office, Hadley Centre, and nested in HadCM3 global climate model (GCM). It uses 25 km horizontal resolution transposed to the Equator and 19 vertical levels with sigma coordinates. In this research simulations for the periods 1961-1990 (as the reference period) and 2071-2100 (using the HadCM3 GCM outputs as boundary conditions taking into account the SRES A2 and B2 emission scenario) were analyzed. The results suggest that the climate of the Carpathian basin is expected to become wetter in winter and drier in the other seasons, the largest drying is projected to occur in summer.

Torek, Orsolya; Bartholy, Judit; Pongracz, Rita; Hollosi, Brigitta; Pieczka, Ildiko

2010-05-01

287

Groundwater recharge simulation under the steady-state and transient climate conditions  

NASA Astrophysics Data System (ADS)

Groundwater recharge simulation under the steady-state and transient climate conditions Diffusive groundwater recharge is a vertical water flux through the water table, i.e. through the boundary between the unsaturated and saturated zones. This flux features temporal and spatial changes due to variations in the climatic conditions, landscape the state of vegetation, and the spatial variability of vadoze zone characteristics. In a changing climate the non-steady state series of climatic characteristics will affect on the groundwater recharge.. A well-tested approach to calculating water flux through the vadoze zone is the application of Richard’s equations for a heterogeneous one-domain porosity continuum with specially formulated atmospheric boundary conditions at the ground surface. In this approach the climatic parameters are reflected in upper boundary conditions, while the recharge series is the flux through the low boundary. In this work developed by authors code Surfbal that simulates water cycle at surface of topsoil to take into account the various condition of precipitation transformation at the surface in different seasons under different vegetation cover including snow accumulation in winter and melting in spring is used to generate upper boundary condition at surface of topsoil for world-wide known Hydrus-1D code (Simunek et al, 2008). To estimate the proposal climate change effect we performed Surfbal and Hydrus simulation using the steady state climatic condition and transient condition due to global warming on example of Moscow region, Russia. The following scenario of climate change in 21 century in Moscow region was selected: the annual temperature will increase on 4C during 100 year and annual precipitation will increase on 10% (Solomon et al, 2007). Within the year the maximum increasing of temperature and precipitation falls on winter time, while in middle of summer temperature will remain almost the same as observed now and monthly precipitation. For simulating climate input the weather generator LARSWG (Semenov and Barrow 1997) was trained for generation daily meteorological records for both steady state and transient climatic conditions and two 100 year of meteorological series of minimum and maximum of air temperature, solar radiation and precipitation were generated. The numerical experiment for studying of transient climate on groundwater was performed for typical vadoze zone parameters of western part of Moscow Artesian basin. As the result, the 100 years series of recharge were simulated. Examination of stochastic properties of simulated time-series and comparative analysis series for the transient and for the steady state conditions shows the trend of increasing of recharge in this region in transient climate. Analysis of daily and monthly simulated water balance shows that this increasing is result of winter snow melting and winter infiltration into thaw topsoil. This work was supported by Russian Foundation for Basic Research via grant 08-05-00720a REFERENCES Semenov M.A and Barrow E.M., 1997. Use of a stochastic weather generator in the development of climate change scenarios. Climatic Change, 35:397-414 Šim?nek, J., M. Th. van Genuchten, and M. Šejna, 2008. Development and applications of the HYDRUS and STANMOD software packages, and related codes, Vadose Zone Journal, doi:10.2136/VZJ2007.0077, Special Issue "Vadose Zone Modeling", 7(2), 587-600. Solomon, S., D. Qin, M. Manning, Technical Summary. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Pozdniakov, S.; Lykhina, N.

2010-03-01

288

Numerical and Experimental Investigations on Deformation Behavior of Aluminum 5754 Sheet Alloy under Warm Hydroforming Conditions  

NASA Astrophysics Data System (ADS)

Material behavior of Al5754 was characterized using both tensile and hydraulic bulge tests under both room and warm temperature conditions. Response of Al5754 to different process conditions such as pressurization rates (0.022 and 0.2 s-1 strain rate), variable strain rates (increasing and decreasing profiles), forming temperature (room to 260° C), and loading conditions (uniaxial vs. biaxial) were presented. The results from tensile and hydraulic bulge tests as well as closed-die hydroforming experiments suggested that, in general, formability of Al5754 could be improved with slow forming rates (<0.02 s-1), high forming temperature (>200° C), and biaxial loading (hydoforming) due to the delay of necking. However, decreasing forming rate conditions did not show any improvement in formability for temperature levels below 200° C.

Koç, M.; Mahabunphachai, S.; Carsley, J. E.

2010-06-01

289

Impact of a permanent El Ni?? (El Padre) and Indian Ocean Dipole in warm Pliocene climates  

USGS Publications Warehouse

Pliocene sea surface temperature data, as well as terrestrial precipitation and temperature proxies, indicate warmer than modern conditions in the eastern equatorial Pacific and imply permanent El Ni??o-like conditions with impacts similar to those of the 1997/1998 El Ni??o event. Here we use a general circulation model to examine the global-scale effects that result from imposing warm tropical sea surface temperature (SST) anomalies in both modern and Pliocene simulations. Observed SSTs from the 1997/1998 El Ni??o event were used for the ,anomalies and incorporate Pacific wanning as well as a prominent Indian Ocean Dipole event. Both the permanent El Ni??o (also called El Padre) and Indian Ocean Dipole (IOD) conditions are necessary to reproduce temperature and precipitation patterns consistent with the global distribution of Pliocene proxy data. These patterns may result from the poleward propagation of planetary waves from the strong convection centers associated with the El Ni??o and IOD. Copyright 2009 by the American Geophysical Union.

Shukla, S. P.; Chandler, M. A.; Jonas, J.; Sohl, L. E.; Mankoff, K.; Dowsett, H.

2009-01-01

290

The dynamic response of the Greenland and Antarctic ice sheets to multiple-century climatic warming  

SciTech Connect

New calculations were performed to investigate the combined response of the Greenland and Antarctic ice sheets to a range of climatic warming scenarios over the next millennium. Use was made of fully dynamic 3D thermomechanic ice sheet models, which were coupled to a two-dimensional climate model. The experiments were initialized with simulations over the last two glacial cycles to estimate the present evolution and were subsequently forced with temperature scenarios resulting from greenhouse emission scenarios which assume equivalent CO{sub 2} increases of two, four, and eight times the present (1990 A.D.) value by the year 2130 A.D. and a stabilization after that. The calculations brought to light that during the next century (short-term effect), the background evolution trend would dominate the response of the Antarctic ice sheet but would be negligible for the Greenland ice sheet. On that timescale, the Greenland and Antarctic ice sheets would roughly balance one another for the middle scenario (similar to the IPCC96 IS92a scenario), with respective contributions to the worldwide sea level stand on the order of about {+-}10 cm. On the longer term, however, both ice sheets would contribute positively to the worldwide sea level stand and the most important effect would come from melting on the Greenland ice sheet. Sensitivity experiments highlighted the role of ice dynamics and the height-mass-balance feedback on the results. It was found that ice dynamics cannot be neglected for the Greenland ice sheet, not even on a century timescale, but becomes only important for Antarctica on the longer term. The latter is related to an increased outflow of ice into the ice shelves and to the grounding-line retreat of the west Antarctic ice sheet, which are both found to be sensitive to basal melting below ice shelves and the effective viscosity of the ice shelves. Stretching parameters to their limits yielded a combined maximum rate of sea level rise of 85 cm century{sup {minus}1}, of which 60 cm would originate from the Greenland ice sheet alone.

Huybrechts, P. [Vrije Universiteit Brussel, Brussels (Belgium). Dept. Geografie] [Vrije Universiteit Brussel, Brussels (Belgium). Dept. Geografie; Wolde, J. de [Universiteit Utrecht (Netherlands). Instituut voor Marien en Atmosferische Onderzoek] [Universiteit Utrecht (Netherlands). Instituut voor Marien en Atmosferische Onderzoek

1999-08-01

291

No Evidence for Recent Climatic Warming From Borehole Temperatures in the Canadian Cordillera  

NASA Astrophysics Data System (ADS)

Inversions of temperature data from 60 boreholes at 20 sites spanning 13 degrees of latitude in the Canadian Cordillera show that there was no significant unexplained change in the GST (ground surface temperature) over the last two centuries. There were no changes in the GST at undisturbed sites, and at sites where a known event altered the terrain surrounding them, the modelled changes in GST were in agreement with the site histories. These boreholes were chosen for analysis from over 500 in this region in the GSC data base. The others were excluded because of unknown terrain histories, obvious effects of water flow in crystalline rocks, low water tables, or penetration of sedimentary rocks that might have bulk permeability. From a consideration of the heat budget at the surface of the earth, the change in the average surface temperature expected due to permanent deforestation and/or drainage of surface waters is approximately 2 K. This is due to the greater run off of water and the smaller amount of heat required, principally in the summer time, for evaporation and transpiration. This is equivalent to the average amount detected at such sites. The GST tracks the SAT (surface air temperature) in this region, except when it is below 0° C. Climatic warming in the winter time would not be detected by this method, except in the very southern, coastal part of this region. Proxy data indicate that winter temperatures have not changed significantly in the north. Therefore I suggest changing amounts of precipitation and their distribution in time are causing glacial recession.

Lewis, T.

2004-05-01

292

Nematode community shifts in response to experimental warming and canopy conditions are associated with plant community changes in the temperate-boreal forest ecotone.  

PubMed

Global climate warming is one of the key forces driving plant community shifts, such as range shifts of temperate species into boreal forests. As plant community shifts are slow to observe, ecotones, boundaries between two ecosystems, are target areas for providing early evidence of ecological responses to warming. The role of soil fauna is poorly explored in ecotones, although their positive and negative effects on plant species can influence plant community structure. We studied nematode communities in response to experimental warming (ambient, +1.7, +3.4 °C) in soils of closed and open canopy forest in the temperate-boreal ecotone of Minnesota, USA and calculated various established nematode indices. We estimated species-specific coverage of understory herbaceous and shrub plant species from the same experimental plots and tested if changes in the nematode community are associated with plant cover and composition. Individual nematode trophic groups did not differ among warming treatments, but the ratio between microbial-feeding and plant-feeding nematodes increased significantly and consistently with warming in both closed and open canopy areas and at both experimental field sites. The increase in this ratio was positively correlated with total cover of understory plant species, perhaps due to increased predation pressure on soil microorganisms causing higher nutrient availability for plants. Multivariate analyses revealed that temperature treatment, canopy conditions and nematode density consistently shaped understory plant communities across experimental sites. Our findings suggest that warming-induced changes in nematode community structure are associated with shifts in plant community composition and productivity in the temperate-boreal forest ecotones. PMID:24668014

Thakur, Madhav Prakash; Reich, Peter B; Fisichelli, Nicholas A; Stefanski, Artur; Cesarz, Simone; Dobies, Tomasz; Rich, Roy L; Hobbie, Sarah E; Eisenhauer, Nico

2014-06-01

293

Efficacy of Wrist/Palm Warming as an EVA Countermeasure to Maintain Finger Comfort in Cold Conditions During EVA  

NASA Technical Reports Server (NTRS)

This study explored the effectiveness of local wrist/palm warming as a potential countermeasure for providing finger comfort during extended duration EVA. Methods: Six subjects (5 males and 1 female) were evaluated in a sagitally divided liquid cooling/warming garment (LCWG) with modified liquid cooling/warming (LCW) gloves in three different experimental conditions. Condition 1: Stage 1- no LCWG; chamber adaptation with LCW glove inlet water temperature 33 C; Stage 2-LCW glove inlet water temperature cooled to 8 C; Stage 3-LCW glove inlet water temperature warmed to 45 C; Condition 2: Stage1-LCWG and LCW glove inlet water temperature 33 C; Stage 2-LCWG inlet temperature cooled to 31 C, LCW gloves, 8 C; Stage 3-LCWG inlet water temperature remains at 31 C, LCW glove inlet water temperature warmed to 45 C; Condition 3: Stage l -LCWG and LCW gloves 33 C; Stage 2-LCWG inlet water temperature cooled to 28 C, LCW gloves, 8 C; Stage 3-LCWG remains at 28 C, LCW glove water temperature warmed to 45 C. Results: Wrist/palm area warming significantly increased finger temperature (Tfing) and blood perfusion in Stage 3 compared to Stage 2. The LCW gloves were most effective in increasing Stage 3 Tfing in Condition 1; and in increasing blood perfusion in Conditions 1 and 2 compared to Condition 3. Ratings of subjective perception of heat in the hand and overall body heat were higher at Stage 3 than Stage 2, with no significant differences across Conditions. Conclusions: Local wrist/palm warming was effective in increasing blood circulation to the distal extremities, suggesting the potential usefulness of this technique for increasing astronaut thermal comfort during EVA while decreasing power requirements. The LCW gloves were effective in heating the highly cooled fingers when the overall body was in a mild heat deficit.

Koscheyev, Victor S.; Leon, Gloria R.; Trevino, Robert C.

2000-01-01

294

Spatiotemporal distribution of threatened high-latitude snowbed and snow patch habitats in warming climate  

NASA Astrophysics Data System (ADS)

We studied the interannual variation of late summer snow covered area (SCA), i.e. snowbeds and permanent snow patches, in northern Finland and analyzed the role of topographical factors and climatic conditions on the recent and future occurrence of summer snow. SCA for the years 2000, 2004, 2006 and 2009 was derived from Landsat images using a normalized difference snow index (NDSI). Late summer SCA varied notably between the years (1.5-23.0 km2). A major part of the late summer snow was located above 900-1000 m and on northern and eastern slopes. A generalized additive model (GAM) showed that the number of years with snow present in 1 km grid squares was strongly positively related to altitude and terrain ruggedness. Parallel examination of interannual variation of SCA and climatic conditions showed that snow cover declines were linked to relatively low snowfall-to-rainfall ratios. Annual mean air temperatures, particularly spring and early winter temperatures, showed increasing trends during the study period. Projected increases in air temperatures and rainfall suggest earlier and more efficient snow melt in the future. This may threaten the occurrence of species and communities related to snowbeds and decrease the ?-diversity of the landscape, and could also affect ecosystem services of the region.

Kivinen, Sonja; Kaarlejärvi, Elina; Jylhä, Kirsti; Räisänen, Jouni

2012-09-01

295

Climatic warming changes plant photosynthesis and its temperature dependence in a temperate steppe of northern China  

Microsoft Academic Search

Warming responses of photosynthesis and its temperature dependence in two C3 grass (Agropyron cristatum, Stipa krylovii), one C4 grass (Pennisetum centrasiaticum), and two C3 forb (Artemisia capillaris, Potentilla acaulis) species in a temperate steppe of northern China were investigated in a field experiment. Experimental warming with infrared heater significantly increased daily mean assimilation rate (A) in P. centrasiaticum and A.

Shuli Niu; Zhixiong Li; Jianyang Xia; Yi Han; Mingyu Wu; Shiqiang Wan

2008-01-01

296

Recent observations of warming in the North Pacific: Is this evidence of anthropogenic climate change?  

Microsoft Academic Search

A transbasin survey of the North Pacific Ocean in 2004 reveals sizable warming of the upper ocean. Temperature observations from the 2004 CLIVAR P2 occupation along 30 degrees north are compared with 1994 WOCE occupation of the same line. The greatest observed warming (about 0.5 C) is observed in the lower ventilated layers of the subtropical thermocline. Analysis of the

P. E. Robbins; J. Swift; R. Fine; A. Thurnherr; D. Min

2004-01-01

297

Potential increase of flood hazards in Korea due to global warming from a high-resolution regional climate simulation  

NASA Astrophysics Data System (ADS)

Because of the importance of the changes in the hydrologic cycle, accurate assessment of precipitation characteristics is essential to understand the impact of climate change due to global warming. This study investigates the changes in extreme precipitation with sub-daily and daily temporal scales. For a fine-scale climate change projection focusing on the Korean peninsula (20 km), we performed the dynamical downscaling of the global climate scenario covering the period 1971-2000 (130-year) simulated by the Max-Planck-Institute global climate model, ECHAM5, using the latest version of the International Centre for Theoretical Physics (ICTP) regional climate model, RegCM3. While annual mean precipitation exhibits a pronounced interannual and interdecadal variability, with the increasing or decreasing trend repeated during a certain period, extreme precipitation with sub-daily and daily temporal scales estimated from the generalized extreme value distribution shows consistently increasing pattern. The return period of extreme precipitation is significantly reduced despite the decreased annual mean precipitation at the end of 21st century. The decreased relatively weak precipitation is responsible for the decreased total precipitation, so that the decreased total precipitation does not necessarily mean less heavy precipitation. Climate change projection based on the ECHAM5-RegCM3 model chain clearly shows the effect of global warming in increasing the intensity and frequency of extreme precipitation, even without significantly increased total precipitation, which implies an increased risk for flood hazards. [Acknowledgements] This work was supported by a grant (code#3100-3136-442) funded by the National Institute of Meteorological Research (NIMR), the Korea Meteorological Administration (KMA).

Im, E.-S.; Kwon, J.-H.; Lee, B.-J.; In, S.-R.; Han, S.-O.

2012-04-01

298

Energy and global warming impacts of next generation refrigeration and air conditioning technologies  

SciTech Connect

Significant developments have occurred in hydrofluorocarbon (HFC) and the application of ammonia and hydrocarbons as refrigerant working fluids since the original TEWI (Total Equivalent Warming Impact) report in 1991. System operating and performance data on alternative refrigerants and refrigeration technologies justify and updated evaluation of these new alternative refrigerants and competing technologies in well-characterized applications. Analytical and experimental results are used to show quantitative comparisons between HFCS, HFC blends, hydrocarbons, and ammonia, used as refrigerants. An objective evaluation is presented for commercial and near commercial non-CFC refrigerants/blowing agents and alternative refrigeration technologies. This information is needed for objective and quantitative decisions on policies addressing greenhouse gas emissions from refrigeration and air conditioning equipment. The evaluation assesses the energy use and global warming impacts of refrigeration and air conditioning technologies that could be commercialized during the phase out of HCFCS. Quantitative comparison TEWI for two application areas are presented. Opportunities for significant reductions in TEWI are seen with currently known refrigerants through improved maintenance and servicing practices and improved product designs.

Sand, J.R.; Fischer, S.K.; Baxter, V.D.

1996-10-01

299

Fungal Diversity in Permafrost and Tallgrass Prairie Soils under Experimental Warming Conditions  

PubMed Central

Soil fungi play a major role in terrestrial ecosystem functioning through interactions with soil structure, plants, micro- and mesofauna, and nutrient cycling through predation, pathogenesis, mutualistic, and saprotrophic roles. The diversity of soil fungi was assessed by sequencing their 28S rRNA gene in Alaskan permafrost and Oklahoma tallgrass prairie soils at experimental sites where the effect of climate warming is under investigation. A total of 226,695 reads were classified into 1,063 genera, covering 62% of the reference data set. Using the Bayesian Classifier offered by the Ribosomal Database Project (RDP) with 50% bootstrapping classification confidence, approximately 70% of sequences were returned as “unclassified” at the genus level, although the majority (?65%) were classified at the class level, which provided insight into these lesser-known fungal lineages. Those unclassified at the genus level were subjected to BLAST analysis against the ARB-SILVA database, where ?50% most closely matched nonfungal taxa. Compared to the more abundant sequences, a higher proportion of rare operational taxonomic units (OTU) were successfully classified to genera at 50% bootstrap confidence, indicating that the fungal rare biosphere in these sites is not composed of sequencing artifacts. There was no significant effect after 1 year of warming on the fungal community structure at both sites, except perhaps for a few minor members, but there was a significant effect of sample depth in the permafrost soils. Despite overall significant community structure differences driven by variations in OTU dominance, the prairie and permafrost soils shared 90% and 63% of all fungal sequences, respectively, indicating a fungal “seed bank” common between both sites.

StLouis, Derek; Cole, James R.; Luo, Yiqi; Wu, Liyou; Schuur, E. A. G; Zhou, Jizhong; Tiedje, James M.

2013-01-01

300

Regional Warming from Aerosol Removal over the United States: Results from a Transient 2010-2050 Climate Simulation  

NASA Technical Reports Server (NTRS)

We use a general circulation model (NASA Goddard Institute for Space Studies GCM 3) to investigate the regional climate response to removal of aerosols over the United States. We perform a pair of transient 2010e2050 climate simulations following a scenario of increasing greenhouse gas concentrations, with and without aerosols over the United States and with present-day aerosols elsewhere. We find that removing U.S. aerosol significantly enhances the warming from greenhouse gases in a spatial pattern that strongly correlates with that of the aerosol. Warming is nearly negligible outside the United States, but annual mean surface temperatures increase by 0.4e0.6 K in the eastern United States. Temperatures during summer heat waves in the Northeast rise by as much as 1e2 K due to aerosol removal, driven in part by positive feedbacks involving soil moisture and low cloud cover. Reducing U.S. aerosol sources to achieve air quality objectives could thus have significant unintended regional warming consequences.

Mickley, L. J.; Leibensperger, E. M.; Jacob, D. J.; Rind, D.

2012-01-01

301

Simulating Freshwater Availability under Future Climate Conditions  

NASA Astrophysics Data System (ADS)

Freshwater availability is a key factor for regional development. Precipitation, evaporation, river inflow and outflow are the major terms in the estimate of regional water supply. In this study, we aim to obtain a realistic estimate for these variables from 1901 to 2100. First we calculated the ensemble mean precipitation using the 2011-2100 RCP4.5 output (re-sampled to half-degree spatial resolution) from 16 General Circulation Models (GCMs) participating the Coupled Model Intercomparison Project Phase 5 (CMIP5). The projections are then combined with the half-degree 1901-2010 Climate Research Unit (CRU) TS3.2 dataset after bias correction. We then used the combined data to drive our UMD Earth System Model (ESM), in order to generate evaporation and runoff. We also developed a River-Routing Scheme based on the idea of Taikan Oki, as part of the ESM. It is capable of calculating river inflow and outflow for any region, driven by the gridded runoff output. River direction and slope information from Global Dominant River Tracing (DRT) dataset are included in our scheme. The effects of reservoirs/dams are parameterized based on a few simple factors such as soil moisture, population density and geographic regions. Simulated river flow is validated with river gauge measurements for the world's major rivers. We have applied our river flow calculation to two data-rich watersheds in the United States: Phoenix AMA watershed and the Potomac River Basin. The results are used in our SImple WAter model (SIWA) to explore water management options.

Zhao, F.; Zeng, N.; Motesharrei, S.; Gustafson, K. C.; Rivas, J.; Miralles-Wilhelm, F.; Kalnay, E.

2013-12-01

302

Keeping up with a warming world; assessing the rate of adaptation to climate change  

PubMed Central

The pivotal question in the debate on the ecological effects of climate change is whether species will be able to adapt fast enough to keep up with their changing environment. If we establish the maximal rate of adaptation, this will set an upper limit to the rate at which temperatures can increase without loss of biodiversity. The rate of adaptation will primarily be set by the rate of microevolution since (i) phenotypic plasticity alone is not sufficient as reaction norms will no longer be adaptive and hence microevolution on the reaction norm is needed, (ii) learning will be favourable to the individual but cannot be passed on to the next generations, (iii) maternal effects may play a role but, as with other forms of phenotypic plasticity, the response of offspring to the maternal cues will no longer be adaptive in a changing environment, and (iv) adaptation via immigration of individuals with genotypes adapted to warmer environments also involves microevolution as these genotypes are better adapted in terms of temperature, but not in terms of, for instance, photoperiod. Long-term studies on wild populations with individually known animals play an essential role in detecting and understanding the temporal trends in life-history traits, and to estimate the heritability of, and selection pressures on, life-history traits. However, additional measurements on other trophic levels and on the mechanisms underlying phenotypic plasticity are needed to predict the rate of microevolution, especially under changing conditions. Using this knowledge on heritability of, and selection on, life-history traits, in combination with climate scenarios, we will be able to predict the rate of adaptation for different climate scenarios. The final step is to use ecoevolutionary dynamical models to make the link to population viability and from there to biodiversity loss for those scenarios where the rate of adaptation is insufficient.

Visser, Marcel E

2008-01-01

303

Climate variability during warm and cold phases of the Atlantic Multidecadal Oscillation (AMO) 1871–2008  

NASA Astrophysics Data System (ADS)

An extended reanalysis, a combination of observations and model output, is used to examine the spatial patterns of physical variables associated with the Atlantic Multidecadal Oscillation (AMO) from 1871 to 2008. The results are presented as anomalies during positive and negative phases of the AMO. As in previous studies, during positive (negative) AMO phases the sea surface temperature (SST) is anomalously warm (cold) over most of the North Atlantic, with the exception of the east coast of the United States. The atmospheric patterns, associated with the positive phase of the AMO, include anomalous low pressure over the Atlantic between 20°S and 50°N, cyclonic surface winds around the low, reduced wind speeds over the tropical Atlantic and enhanced precipitation in the eastern tropical Atlantic, with roughly opposite conditions during negative AMO phases. There are, however, substantial differences in the SST and the atmospheric anomalies between periods of the same phase, especially in the extratropics. Correlations between the AMO and air temperature anomalies are positive over much of the globe between 40°S and 50°N, with correlations exceeding 0.6 (~ 95% significance level) over the Maritime Continent and northern rim of the Pacific Ocean. Most of the sea level pressure (SLP) anomalies beyond the Atlantic are not statistically significant.

Alexander, Michael A.; Halimeda Kilbourne, K.; Nye, Janet A.

2014-05-01

304

Possible land cover change feedbacks to surface albedo and net radiation over Siberia in a warming climate  

NASA Astrophysics Data System (ADS)

Our goal was to simulate vegetation cover and hot spots of vegetation change in the changing climate of Siberia by the end of the 21st century and to insight regarding vegetation change feedbacks on the alteration of surface albedo and energy. We applied the Siberian BioClimatic Model (SiBCliM) to the HadCM3 A2 (with the highest temperature increase) and B1 (with the lowest temperature increase) scenarios of the Hadley Centre (IPCC, 2007) to highlight possible vegetation change. SiBCliM predicts a biome (a zonal vegetation class) from three climatic indices (growing degree-days, negative degree-days, and an annual moisture index) and permafrost. Large changes in land cover are predicted from the A2 scenario: coverage by northern vegetation types (tundra, forest-tundra, and taiga) would decrease from 70 to some 30% enabling southern habitats (forest-steppe, steppe and semidesert) to expand coverage from 30 to 70%. Altered land cover would feedback to the climate system resulting in a potential non-linear response to changes in climate. We investigated the effects of land cover change on surface reflectivity (albedo) resulting in net radiation alterations. We calculated annual albedo as the mean of summer albedo during months with no snow cover and winter albedo during months with snow cover. Snow cover appearance and dissappearance were related to surface temperature thresholds 0, 3 and 5 Celsius degrees. Albedo change by 2080 was calculated as the differences between albedo ascribed to each pixel (between 60oE -140oE and 50oN -75oN) according to a vegetation type and snow cover presence/absence in the current and the 2080 climates. In a warmed climate, by 2080, albedo would increase in the southern and middle latitudes in Siberia due to the forest retreat. In the northern latitudes and highlands, tundra would be replaced by the forest with decreased albedo. The total would result in about a 1% albedo increase over the entire area. Under the predicted warmer climate, these calculations suggest that the annual shortwave and consequently net radiation would decrease in 2/3 of the area in the south and would increase in 1/3 of the area in the north resulting in an even greater warming than currently predicted in the high latitudes. Thus, the regional effects of land cover change on climate would be non-linear. This land change projection suggests that the interactive biosphere should be included in global and regional circulation models to get more reliable projections.

Tchebakova, N.; Parfenova, E.; Soja, A. J.

2009-12-01

305

Design and Build of the Qinghai-Tibet Railway considering the Impacts of Warming Climate and Permafrost  

NASA Astrophysics Data System (ADS)

During the period from 1960 to 2000, an 1°C increase of air temperature has been observed along the Qinghai-Tibet Railway (QTR) traversing 632 km of warm and ice-rich permafrost through the interior of the Qinghai-Tibet Plateau. Correspondingly, mean annual ground temperatures (MAGTs) of warm (>-1 °C) permafrost on average increased about 0.3 to 0.5°C during 1970s-1990, while that of colder permafrost had increased by 0.1 to 0.3°C. During 1996-2004, ground temperatures at the permafrost table were increasing at the rates of 0.01-0.08°C a-1, and the permafrost table was lowering at the rates of 2.6 to 6.6 cm a-1; and the ground temperatures at depths of 6 to 8 m were warming at the rates of 0.02 to 0.05°C a-1. Consequently, the strengths of permafrost as the foundation of the QTR would be weakened if proper engineering measures were not taken. Based on the experiences and lessons learned from the road construction in permafrost regions from Alaska, Canada and Russia, and northeastern China, and taking into consideration of possible climatic warming along the QTR during the next 100 years, the design and construction of the QTR adopted the principle of``cooling the roadbed'' because most of the permafrost along the route is too deep to be thawed, too thermally sensitive to climatic warming and too critical to have appreciable thaw settlements. About 550 km of QTR is in continuous permafrost zone, 82 km is in discontinuous permafrost zone; 275 km is in warm permafrost areas, and 110 km of permafrost is ice-rich. The QTR is designed for safe operations during the next 100 years during which a warming of 2.2 to 2.6°C by 2050 is projected. Without engineering measures to keep ground frozen or maintain the settlement within the acceptable limits, thaw settlement in the foundation soils, and induced environmental instability would threaten the integrity and safety of QTR operation. However, only increasing therma resistance, such as increasing fill thickness or using insulation materials is a passive method of permafrost protection and inadequate to ensure the engineering reliability and long-term stability of foundation soils under a persistent warming climate. Therefore, the design of the QTR has to adopt the principle of active cooling by controlling radiation, convection and conduction through modifying road structures. The measures for controlling radiation include the applications of ligh-color fill materials and side-slope materials, and awnings. The measures fo controlling the convection include air ducts, coarse rock roadbed and sideslope structures, and thermosyphons. The methods for controlling the conduction include insulation materials with strong thermal offsets and sufficient strength and durability, grassing of side slopes. Some of the abovementioned methods are combined to enhance the cooling effect in critical sections with warm and ice rich permafrost. These engineering measures based on extensive field and laboratory scientific experimental and simulation research have been adopted by the design and construction of the QTR. The preliminary results indicate that they have been quite effective in maintaining permafrost table positions and the strength of frozen soils at desired levels and thaw settlements at acceptable limits.

Ma, W.; Jin, H.; Cheng, G.; Wu, Q.; Lai, Y.

2005-12-01

306

Modeling the impact of climate warming on the range of brook trout in the Blue Ridge Mountains, USA  

NASA Astrophysics Data System (ADS)

Brook trout in the Eastern United States (Salvelinus fontinalis) thrive in a relatively narrow range of stream temperatures. Over the past several centuries, the introduction of competitive species has pushed brook trout to the cooler, upstream margins of what use to be a much more extensive range within most drainages. Over the next several decades, climate change may put further thermal pressure on the species, increasing the fragmentation of their distribution and shrinking their present range. Because the size and connectivity of habitats seem to influence the persistence of local populations, climate warming leading to increased fragmentation of remaining habitats could accelerated species decline. Using the Regional Hydrological and Ecological Simulation System (RHYSSys), I modeled the projected habitat changes for a group of native brook trout streams in the Blue Ridge Mountains of South-Central Virginia, USA. The modeling process is illustrative of the need for better understanding of the couplings that exist between geomorphology, hydrology, and ecology, particularly in mountain environments. Model results are quantified according to the degree of decrease in stream-miles of habitat and the increase in the fragmentation of the habitat as a function of the warming rate (degrees per decade). These results may help inform habitat management strategies for the coming several decades in the region, and the modeling process helps highlight the need for more refined understanding of climate change's impacts on habitability.

Bartlett, M. G.

2012-12-01

307

Assessing the Response of Nematode Communities to Climate Change-Driven Warming: A Microcosm Experiment  

PubMed Central

Biodiversity has diminished over the past decades with climate change being among the main responsible factors. One consequence of climate change is the increase in sea surface temperature, which, together with long exposure periods in intertidal areas, may exceed the tolerance level of benthic organisms. Benthic communities may suffer structural changes due to the loss of species or functional groups, putting ecological services at risk. In sandy beaches, free-living marine nematodes usually are the most abundant and diverse group of intertidal meiofauna, playing an important role in the benthic food web. While apparently many functionally similar nematode species co-exist temporally and spatially, experimental results on selected bacterivore species suggest no functional overlap, but rather an idiosyncratic contribution to ecosystem functioning. However, we hypothesize that functional redundancy is more likely to observe when taking into account the entire diversity of natural assemblages. We conducted a microcosm experiment with two natural communities to assess their stress response to elevated temperature. The two communities differed in diversity (high [HD] vs. low [LD]) and environmental origin (harsh vs. moderate conditions). We assessed their stress resistance to the experimental treatment in terms of species and diversity changes, and their function in terms of abundance, biomass, and trophic diversity. According to the Insurance Hypothesis, we hypothesized that the HD community would cope better with the stressful treatment due to species functional overlap, whereas the LD community functioning would benefit from species better adapted to harsh conditions. Our results indicate no evidence of functional redundancy in the studied nematofaunal communities. The species loss was more prominent and size specific in the HD; large predators and omnivores were lost, which may have important consequences for the benthic food web. Yet, we found evidence for alternative diversity–ecosystem functioning relationships, such as the Rivets and the Idiosyncrasy Model.

Gingold, Ruth; Moens, Tom; Rocha-Olivares, Axayacatl

2013-01-01

308

Microclimate impacts of passive warming methods in Antarctica: implications for climate change studies  

Microsoft Academic Search

Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the\\u000a growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance.\\u000a In this review, we synthesise and discuss the microclimate impacts of passive warming chambers (closed, ventilated and Open\\u000a Top Chamber—OTC) commonly used in

Stef Bokhorst; A. H. L. Huiskes; Peter Convey; Brent J. Sinclair; Marc Lebouvier; Bart Van de Vijver; Diana H. Wall

2011-01-01

309

From Vegetation Zones to Climatypes: Effects of Climate Warming on Siberian Ecosystems  

Microsoft Academic Search

\\u000a Evidence for global warming over the past 200 years is overwhelming, based on both direct weather observation and indirect\\u000a physical and biological indicators such as retreating glaciers and snow\\/ice cover, increasing sea level, and longer growing\\u000a seasons (IPCC 2001, 2007). On the background of global warming at a rate of 0.6°C during the twentieth century (IPCC 2001),\\u000a the temperature increase

N. M. Tchebakova; G. E. Rehfeldt; E. I. Parfenova

310

Investigating climatic drivers of the warming hole through empirical downscaling of eastern U.S. summertime maximum temperatures  

NASA Astrophysics Data System (ADS)

Global average temperatures have increased over the past century, but not all regions of the world have experienced warming. The central United States has experienced less warming than western and eastern portions of the country, with some stations experiencing cooling trends during the period of 1948-2009, leading researchers to dub the area a "warming hole." The causes of this anomaly have been investigated via general circulation models (GCMs) and regional climate model downscaling of GCM output, but conclusions have been limited. This research identifies important drivers of June, July, and August (JJA) mean maximum daily temperature (Tmax) in the region which includes the "warming hole" by developing a model for Tmax using empirical downscaling of large scale variables and local precipitation. First, robust trend analysis is used to determine temperature trends across the country for two time periods: 1948--2009, and 1978--2009; and to locate stations which have experienced cooling, or minimal warming. Second, 19 surface and upper air variables are investigated to identify the optimal independent predictors of Tmax. Station-by-station models of T max are produced from National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis sea level pressure, 500 mb geopotential heights, total (meridional and zonal) 850 mb winds in the area of frequent LLJs, as well as station precipitation and assessed for quality. Measures of skill include analysis of error and variance in the modeled time series, as well values of beta-weighted regression coefficients. Third, trends from the modeled time series are calculated and compared with the observed trends. The models show that 500 mb heights have a strong positive correlation with Tmax across the study area, while precipitation widely and uniformly correlates with lower Tmax. Sea level pressure has a negative correlation with Tmax in much of the study area. The LLJ predictor provides novel insight into the climatic drivers in the vicinity of the warming hole, indicating that moisture advection driving nocturnal precipitation plays a role in depressing Tmax.

Wagner, Audrey Romaine

311

Assessing the impacts of extended drought conditions and global warming on groundwater resources in Iowa  

NASA Astrophysics Data System (ADS)

Extended drought conditions that affected much of the U.S. throughout 2012 and continued into 2013 are bringing climate change to the forefront of public attention. Long-term effects of an extended dry spell on groundwater is especially concerning as these resources are essential for meeting drinking water demands, supporting agricultural and industrial activities, and maintaining water levels in rivers and lakes. Thus, the impact of extended drought conditions on the entire hydrologic cycle needs to be well understood to guide future resource and land management decisions. This study aims to explore the impact of extended drought conditions on groundwater resources in a representative Iowa watershed using Regional Climate Model scenarios implemented through HydroGeoSphere, a physically-based, surface water-groundwater model. Estimating the impacts of climate changes on groundwater resources requires representation of the full hydrological system, i.e. the connection between the atmospheric and surface-subsurface processes, in a realistic way. In the HydroGeoSphere model, surface and subsurface flow equations are solved simultaneously, and the interdependence of processes like actual evapotranspiration and recharge is handled explicitly. Using such state-of-the-art modeling tools, we seek to address the consequences of changing climate extremes (that have already been experienced and expected to continue over long periods in the future) on the hydrologic cycle of our pilot study area, the South Fork watershed in north-central Iowa. The results will provide a baseline for investigating mitigation strategies in agricultural practices and water use due to changes in the wet and dry cycles of the regional hydrologic cycle.

Acar, O.; Franz, K.; Simpkins, W. W.

2013-12-01

312

A method to treat climate changes of year-to-year variations in the pseudo-global-warming method as a dynamical downscaling  

NASA Astrophysics Data System (ADS)

The pseudo-global-warming (PGW) method is a time-slice dynamical downscaling one developed by Kimura and Kitoh (2007) to obtain regional climate change information with finer resolutions. In the present climate experiment, regional climate model (RCM) experiment is carried out with objective analysis data (ANAL) as the lateral boundary conditions. On the other hand, in the future climate experiment, the lateral boundary conditions are the sum of the ANAL and the difference between the present and future climates by an atmosphere-ocean general circulation model (AOGCM). The advantage of this method is that the influences of biases of the AOGCMs are reduced. In addition, the number of downscaling experiments could be reduced in multi-model problems, namely, a RCM experiment result with the boundary conditions created by a multi-model ensemble mean of AOGCMs seems to be similar to the average of the results of RCMs with their AOGCMs. However, PGW method involves some problems. One of them is that climate changes in year-to-year variations are ignored. To overcome this problems, a new method is introduced. In the new method, a mean climatological difference of a AOGCM is added to ANAL in future climate experiment, which is the same as PGW method. Next, the year-to-year variation term of ANAL, AOGCM in the present climate (GCM-P), and that in the future climate (GCM-F) are normalized in each level and element of ANAL to X’a, X’p, and X’f, respectively. The eigenvector of X’a (Va) is extracted by Principal Component Analysis (PCA). Only Va is trusted among the variations of ANAL, GCM-P, and GCP-F. Thus, the coefficients (Ta, Tp, and Tf) of the Multiple Regression Analysis (MRA) with Va are examined, and a coefficient (Tw) for Va are newly estimated as the variation term of boundary conditions of RCM in the future climate (X’w). To create Tw, three-step calculations are included in the estimation. First, a matrix operator, that the covariance of coefficients matrix of GCM-P is changed into that of GCM-P, is calculated using the lower triangle matrix made by the Cholesky decomposition. The operation is carried out for Ta, and Tw1 and its covariance Cw1 are estimated. Second, the reliability of Tw1 and Cw1 are investigated. The Cw1 is modified using a weight matrix W into Cw2. The details are omitted, but the unreliable variation mode is mostly replaced by that of the ANAL. Tw2 are calculated from Cw2. Third, The total amplitude of the variations is adjusted. The total amplitude of Cw2 (Pw), that is a trace of orthogonalized Cw2, is somewhat small, because all variations of Tw could not be expressed by Va. To amplify Pw, Cw is defined as Qw/Pw*Cw2. Here, Qw=Qf/Qp*Qa. Qa (Qp, Qf) is a trace of covariance of coefficient, which is estimated by a PCA and a MRA with ANAL (GCM-P, GCM-F). The final coefficient Tw is calculated by Cw. Consequently, a suitable year-to-year variation pattern is created for the boundary conditions of PGW experiment in the future climate. Here, differences of the boundary conditions between the present and future climate are constant in the normal PGW method. However, these vary with year in the new method. In the multi-model downscaling problem, the statistical operations such as the average are carried out for Cw.

Wakazuki, Y.; Hara, M.; Kimura, F.; Regional Climate Modeling Research Team

2010-12-01

313

Warm-up with weighted bat and adjustment of upper limb muscle activity in bat swinging under movement correction conditions.  

PubMed

The effects of weighted bat warm-up on adjustment of upper limb muscle activity were investigated during baseball bat swinging under dynamic conditions that require a spatial and temporal adjustment of the swinging to hit a moving target. Seven male college baseball players participated in this study. Using a batting simulator, the task was to swing the standard bat coincident with the arrival timing and position of a moving target after three warm-up swings using a standard or weighted bat. There was no significant effect of weighted bat warm-up on muscle activity before impact associated with temporal or spatial movement corrections. However, lower inhibition of the extensor carpi ulnaris muscle activity was observed in a velocity-changed condition in the weighted bat warm-up, as compared to a standard bat warm-up. It is suggested that weighted bat warm-up decreases the adjustment ability associated with inhibition of muscle activation under movement correction conditions. PMID:24724516

Ohta, Yoichi; Ishii, Yasumitsu; Ikudome, Sachi; Nakamoto, Hiroki

2014-02-01

314

The hydroclimatological response to global warming based on the dynamically downscaled climate change scenario  

Microsoft Academic Search

Given the discernable evidences of climate changes due to human activity, there is a growing demand for the reliable climate change scenario in response to future emission forcing. One of the most significant impacts of climate changes can be that on the hydrological process. Changes in the seasonality and increase in the low and high rainfall extremes can severely influence

Eun-Soon Im; Erika Coppola; Felippo Giorgi

2010-01-01

315

Spatiotemporal Variability in Distributions of Western Streamflow Conditioned on Climate Indices  

NASA Astrophysics Data System (ADS)

We investigated spatial and temporal variations in the mean and distributions of annual streamflows in the Western US conditioned on indices for ENSO, PDO, and AMO and their interactions for water years 1912 through 2010. Distribution properties were quantified using the 10%, 25%, 50%, 75% and 90% quantiles. Although others have examined the spatiotemporal variations in anomalies of precipitation means for the Western US that were conditioned on indices for ENSO, PDO, and AMO, no parallel studies have been conducted for streamflow. Spatial and temporal patterns in negative and positive anomalies of the mean in annual flows conditioned on individual climate indices for AMO, PDO, and Darwin sea level pressure (SLP), our ENSO indicator, differed from the annual streamflow anomalies of the quantiles examined. North-south bipolar differences in streamflow anomalies for low Darwin SLP occurred in the 90th quantile of annual flow anomalies, but were not evident in the anomalies of the mean. No distinct bipolar effects of PDO were apparent in our results. AMO had limited effect on anomalies of the mean in annual streamflow in the West. But in the southern half of the west (S-W) and along the Rocky Mountains, large positive anomalies occurred in quantiles above the median during cool AMO and large negative anomalies occurred during warm AMO. Effects of interactions between PDO and ENSO were constructive or destructive. So depending on the PDO phase, effects may have appeared opposite of the expected for ENSO. Since effects of AMO were largest in the S-W and along the Rockies, warm AMO in combination with PDO and ENSO resulted in large areas of the West with negative flow anomalies in quantiles above the median. The greatest area in the Western US affected by drier and intensely dry conditions occurred during positive AMO, negative PDO, and positive Darwin SLP, similar to current climate conditions and those of the 1950's. Our results reveal differences between mean streamflows and streamflow distributions as quantified by quantiles in the Western US. These differences add to and transform our understanding of effects of climate conditions on the full distribution of streamflows. Enhanced understanding of streamflow variability associated with climate interactions has direct applications in improving water supply forecasting and managing water and related resources.

Matter, M. A.; Luce, C.; Tarboton, D. G.

2012-12-01

316

The Effects of Urban Warming on Herbivore Abundance and Street Tree Condition  

PubMed Central

Trees are essential to urban habitats because they provide services that benefit the environment and improve human health. Unfortunately, urban trees often have more herbivorous insect pests than rural trees but the mechanisms and consequences of these infestations are not well documented. Here, we examine how temperature affects the abundance of a scale insect, Melanaspis tenebricosa (Comstock) (Hemiptera: Diaspididae), on one of the most commonly planted street trees in the eastern U.S. Next, we examine how both pest abundance and temperature are associated with water stress, growth, and condition of 26 urban street trees. Although trees in the warmest urban sites grew the most, they were more water stressed and in worse condition than trees in cooler sites. Our analyses indicate that visible declines in tree condition were best explained by scale-insect infestation rather than temperature. To test the broader relevance of these results, we extend our analysis to a database of more than 2700 Raleigh, US street trees. Plotting these trees on a Landsat thermal image of Raleigh, we found that warmer sites had over 70% more trees in poor condition than those in cooler sites. Our results support previous studies linking warmer urban habitats to greater pest abundance and extend this association to show its effect on street tree condition. Our results suggest that street tree condition and ecosystem services may decline as urban expansion and global warming exacerbate the urban heat island effect. Although our non-probability sampling method limits our scope of inference, our results present a gloomy outlook for urban forests and emphasize the need for management tools. Existing urban tree inventories and thermal maps could be used to identify species that would be most suitable for urban conditions.

Dale, Adam G.; Frank, Steven D.

2014-01-01

317

Weakening and strengthening structures in the Hadley Circulation change under global warming and implications for cloud response and climate sensitivity  

NASA Astrophysics Data System (ADS)

has long been recognized that differences in climate model-simulated cloud feedbacks are a primary source of uncertainties for the model-predicted surface temperature change induced by increasing greenhouse gases such as CO2. Large-scale circulation broadly determines when and where clouds form and how they evolve. However, the linkage between large-scale circulation change and cloud radiative effect (CRE) change under global warming has not been thoroughly studied. By analyzing 15 climate models, we show that the change of the Hadley Circulation exhibits meridionally varying weakening and strengthening structures, physically consistent with the cloud changes in distinct cloud regimes. The regions that experience a weakening (strengthening) of the zonal-mean circulation account for 54% (46%) of the multimodel-mean top-of-atmosphere (TOA) CRE change integrated over 45°S-40°N. The simulated Hadley Circulation structure changes per degree of surface warming differ greatly between the models, and the intermodel spread in the Hadley Circulation change is well correlated with the intermodel spread in the TOA CRE change. This correlation underscores the close interactions between large-scale circulation and clouds and suggests that the uncertainties of cloud feedbacks and climate sensitivity reside in the intimate coupling between large-scale circulation and clouds. New model performance metrics proposed in this work, which emphasize how models reproduce satellite-observed spatial variations of zonal-mean cloud fraction and relative humidity associated with the Hadley Circulation, indicate that the models closer to the satellite observations tend to have equilibrium climate sensitivity higher than the multimodel mean.

Su, Hui; Jiang, Jonathan H.; Zhai, Chengxing; Shen, Tsaepyng J.; Neelin, J. David; Stephens, Graeme L.; Yung, Yuk L.

2014-05-01

318

Predicting Weather Conditions and Climate for Mars Expeditions  

NASA Astrophysics Data System (ADS)

Weather and climatic conditions are among the most important factors to be taken into account when planning expeditions to remote and challenging locations on Earth. This is likely to be equally the case for expedition planners on Mars, where conditions (in terms of extremes of temperature, etc.) can be at least as daunting as back on Earth. With the success of recent unmanned missions to Mars, such as NASA's Mars Pathfinder, Mars Global Surveyor and Mars Odyssey, there is now a great deal of information available on the range of environ- mental conditions on Mars, from the tropics to the CO2 ice-covered polar caps. This has been further supple- mented by the development of advanced numerical models of the Martian atmosphere, allowing detailed and accurate simulations and predictions of the weather and climate across the planet. This report discusses the main weather and climate variables which future Martian human expedition planners will need to take into account. The range of conditions likely to be encountered at a variety of typical locations on Mars is then considered, with reference to predictions from the ESA Mars Climate Database.

Read, P. L.; Lewis, S. R.; Bingham, S. J.; Newman, C. E.

319

Energy-balance and circulation controls of consistent large-scale temperature responses in warm and cold climates  

NASA Astrophysics Data System (ADS)

The Coupled Modelling Intercomparison Project Phase 5 (CMIP5), which requires the same version of models for paleo, historical, and future simulations, combined with large-scale paleoclimatic data syntheses (e.g., the Multiproxy Approach for the reconstruction of Glacial Ocean (MARGO) project, and the quantitative climate reconstructions based on the pollen and plant macrofossil data) allow diagnostic analyses of the mechanisms responsible for the large-scale spatial patterns of temperature that consistently occur in simulations of warm and cold climates. Comparison with the large-scale temperature changes shown by historical observations and by paleoclimate reconstructions also allows us to determine the realism of these responses. We have examined temperature responses in several CMIP5 experiments (lgm, midHolocene, historical, 1pctCO2, and abrupt4xCO2), and used six models (IPSL-CM5A-LR, MPI-ESM-P, MIROC-ESM, CCSM4, MRI-CGCM3, and GISS-E2-R). The simulations show major patterns of past and modern climates changes including 1) the differential response of land-ocean to warming/cooling, 2) the tendency for temperature changes in the higher latitudes to be more extreme than changes in the tropics, and 3) the amplification of seasonality in both warmer/cooler climates. The consistency among simulated and observed large-scale temperature responses shows that these are features of the real climate system that are simulated successfully by models. Moreover, consistency in the simulated patterns of past (e.g., lgm) and future (e.g., abrupt4xCO2) temperature changes implies that a small set of common mechanisms controls the response of the climate system across multiple states. In this study, we explore the key controls for the three large-scale temperature responses in both warmer and cooler climates using a simple energy balance model and analyses of atmospheric circulation changes. Overall, across the range of simulations, variations in clear-sky downward longwave radiation are responsible for the patterns in large-scale temperature anomalies, and in the lgm simulation, this mechanism is augmented by surface albedo feedback.

Izumi, K.; Bartlein, P. J.

2013-12-01

320

Forecasting conditional climate-change using a hybrid approach  

USGS Publications Warehouse

A novel approach is proposed to forecast the likelihood of climate-change across spatial landscape gradients. This hybrid approach involves reconstructing past precipitation and temperature using the self-organizing map technique; determining quantile trends in the climate-change variables by quantile regression modeling; and computing conditional forecasts of climate-change variables based on self-similarity in quantile trends using the fractionally differenced auto-regressive integrated moving average technique. The proposed modeling approach is applied to states (Arizona, California, Colorado, Nevada, New Mexico, and Utah) in the southwestern U.S., where conditional forecasts of climate-change variables are evaluated against recent (2012) observations, evaluated at a future time period (2030), and evaluated as future trends (2009–2059). These results have broad economic, political, and social implications because they quantify uncertainty in climate-change forecasts affecting various sectors of society. Another benefit of the proposed hybrid approach is that it can be extended to any spatiotemporal scale providing self-similarity exists.

Esfahani, Akbar Akbari; Friedel, Michael J.

2014-01-01

321

Low cloud reduction in a greenhouse-warmed climate: Results from Lagrangian LES of a subtropical marine cloudiness transition  

NASA Astrophysics Data System (ADS)

large-eddy simulations of a composite stratocumulus to cumulus transition case over the subtropical northeast Pacific Ocean are subject to perturbed forcings that isolate the cloud response to CO2, to overall tropical warming, and to increased inversion stability over the subtropical subsidence regions. These simulations show that a tropical surface warming of 4 K induces substantial stratocumulus thinning via a thermodynamic mechanism: increased cloud layer humidity flux in a warmer climate induces an entrainment liquid-flux adjustment that dries the stratocumulus cloud layer, whether well mixed or cumulus coupled. A radiative mechanism amplifies this response: increased emissivity of the free troposphere due to increased CO2 and water vapor reduces radiative driving of turbulence in a stratocumulus-capped boundary layer; a thinner stratocumulus layer accompanies less turbulence. In combination, a 4 K warming and CO2 quadrupling greatly reduce low cloud and weaken the simulated shortwave cloud radiative effect by over 50%. Large increases in inversion stability in the stratocumulus regions could counter much of this cloudiness reduction.

Bretherton, Christopher S.; Blossey, Peter N.

2014-03-01

322

Recent warming in a small region with semi-oceanic climate, 1949 1998: what is the ground truth?  

NASA Astrophysics Data System (ADS)

Trends of monthly air temperature extremes were investigated in five meteorological stations of the Grand-Duchy of Luxembourg during the period 1949 1998. The application of an innovative homogenization method based on the concept of relative homogeneity to climatic time series allows identifying multiple break points, as well as correcting data series in an objective and robust statistical way. The rise of maximum temperature (Tmax) has occurred at a rate of 1.5 times that of the minimum temperature (Tmin) in winter (+1.4 °C versus +0.9 °C) and summer (+1.4 °C versus +0.8 °C). No trend in temperature extremes was found in autumn, while spring was affected by a small warming (+0.3 °C) of Tmin and no change in Tmax resulting in a decrease of the diurnal temperature range (DTR) (-0.3 °C). In spring, a strong positive linear relationship between Tmin warming and local terrain slope could be found. Comparison to new-gridded large-scale climatologies indicates generally close agreement to temperature trends during the 1949 1998 period, while a lower local warming was observed in summer during the post-1975 period following the changing-point year of atmospheric circulation over North-western Europe. This study shows that the question of data homogeneity is not trivial and should receive careful attention before quantifying historical temperature trends and identifying their spatial patterns at regional scale.

Drogue, G.; Mestre, O.; Hoffmann, L.; Iffly, J.-F.; Pfister, L.

2005-06-01

323

Attribution of soil moisture dynamics - Initial conditions vs. atmospheric forcing and the role of climate change  

NASA Astrophysics Data System (ADS)

The world's climate has started to change more quickly in recent decades and a stronger and faster shift is expected in the future. Even if the public perception is mostly limited to a widespread warming, climate change is a complex phenomenon impacting numerous variables of the climate system in different ways, also depending on time and location. Furthermore, extreme events may change more drastically than the mean climate. There is growing evidence that climate change is mostly man-made. However, it is still a matter of debate to which extent changes of the mean climate but also of particular (extreme) events are due to human impact. These questions are addressed by the growing science of climate attribution. Pointing out the anthropogenic influence on extreme events such as the 2010 Russian heatwave or the 2002 floods in Central Europe may help to support adaptation to climate change. This study investigates soil moisture in Europe in the context of climate change, because of its role as a key variable of the land-climate system and its practical importance for instance to agriculture. To derive soil moisture dynamics from 1984-2007 we use E-OBS forcing data together with SRB radiation data and employ an observation-based approach where soil moisture is computed from a water balance equation in which runoff (normalized with precipitation) and ET (normalized with net radiation) are simple functions of soil moisture. The constant runoff function is prescribed for the whole continent, and the ET function is calibrated using temperature data. After performing a validation of the inferred soil moisture data we use it in order to analyze changes in the likelihood of droughts. Our results show increased drought risk especially in north-eastern Europe and the Mediterranean, whereby the probability of extreme droughts increases stronger as for mild dryness episodes. To assess the potential for drought forecasting we furthermore study the importance of the initial conditions versus the atmospheric forcing for monthly soil moisture variations. We find that initial soil moisture anomalies are overall more important than the forcing, even if less pronounced in summer. Especially in southern Europe we show high drought forecasting potential, whereas the forcing is more important in Central and North-eastern Europe.

Orth, Rene; Seneviratne, Sonia I.

2014-05-01

324

Response to CO2 Transient Increase in the GISS Coupled Model: Regional Coolings in a Warming Climate  

NASA Technical Reports Server (NTRS)

The (GISS) Goddard Institute for Space Studies coupled atmosphere-ocean model is used to investigate the effect of increased atmospheric CO2 by comparing a compounded 1 percent CO2 increase experiment with a control simulation. After 70 years of integration, the global surface air temperature in the 1 percent CO2 experiment is 1.43 C warmer. In spite of this global warming, there are two distinct regions, the northern Atlantic Ocean and the southern Pacific Ocean, where the surface air temperature is up to 4 C cooler. This situation is maintained by two positive feedbacks: a local effect on convection in the South Pacific and a non-local impact on the meridional circulation in the North Atlantic. The poleward transport of latent energy and dry static energy by the atmosphere is greater in the 1 percent CO2 experiment, caused by warming and therefore increased water vapor and greater greenhouse capacity at lower latitudes. The larger atmospheric transports tend to reduce upward vertical fluxes of heat and moisture from the ocean surface at high latitudes, which has the effect of stabilizing the ocean, reducing both convection and the thermohaline circulation. With less convection, less warm water is brought up from below, and with a reduced North Atlantic thermohaline circulation (by 30 percent at time of CO2 doubling), the poleward energy transport by the oceans decreases. The colder water then leads to further reductions in evaporation, decreases of salinity at high latitudes, continued stabilization of the ocean, and maintenance of reduced convection and meridional overturning. Although sea ice decreases globally, it increases in the cooling regions which reduces the overall climate sensitivity; its effect is most pronounced in the Southern Hemisphere. Tropical warming has been observed over the past several decades; if modeling studies such as this and others which have produced similar effects are valid, these processes may already be beginning.

Russell, Gary L.; Rind, David

1999-01-01

325

Response to CO{sub 2} transient increase in the GISS coupled model: Regional coolings in a warming climate  

SciTech Connect

The GISS coupled atmosphere-ocean model is used to investigate the effect of increased atmospheric CO{sub 2} by comparing a compounded 1% CO{sub 2} increase experiment with a control simulation. After 70 yr of integration, the global surface air temperature in the 1% CO{sub 2} experiment is 1.43 C warmer. In spite of this global warming, there are two distinct regions, the northern Atlantic Ocean and the southern Pacific Ocean, where the surface air temperature is up to 4 C cooler. This situation is maintained by two positive feedbacks: a local effect on convection in the South Pacific and a nonlocal impact on the meridional circulation in the North Atlantic. The poleward transport of latent energy and dry static energy by the atmosphere is greater in the 1% CO{sub 2} experiment, caused by warming and therefore increased water vapor and greater greenhouse capacity at lower latitudes. The larger atmospheric transports tend to reduce upward vertical fluxes of heat and moisture from the ocean surface at high latitudes, which has the effect of stabilizing the ocean, reducing both convection and the thermohaline circulation. With less convection, less warm water is brought up from below, and with a reduced North Atlantic thermohaline circulation, the poleward energy transport by the oceans decreases. The colder water then leads to further reductions in evaporation, decreases of salinity at high latitudes, continued stabilization of the ocean, and maintenance of reduced convection and meridional overturning. Although sea ice decreases globally, it increases in the cooling regions, which reduces the overall climate sensitivity, especially in the Southern Hemisphere. Tropical warming has been observed over the past several decades; if modeling studies such as this and others that have produced similar effects are valid, these processes may already be beginning.

Russell, G.L.; Rind, D. [NASA/Goddard Space Flight Center, New York, NY (United States). Inst. for Space Studies] [NASA/Goddard Space Flight Center, New York, NY (United States). Inst. for Space Studies

1999-02-01

326

Patterns of Indian Ocean sea-level change in a warming climate  

Microsoft Academic Search

Global sea level has risen during the past decades as a result of thermal expansion of the warming ocean and freshwater addition from melting continental ice. However, sea-level rise is not globally uniform. Regional sea levels can be affected by changes in atmospheric or oceanic circulation. As long-term observational records are scarce, regional changes in sea level in the Indian

Weiqing Han; Gerald A. Meehl; Balaji Rajagopalan; John T. Fasullo; Aixue Hu; Jialin Lin; William G. Large; Jih-Wang Wang; Xiao-Wei Quan; Laurie L. Trenary; Alan Wallcraft; Toshiaki Shinoda; Stephen Yeager

2010-01-01

327

CLIMATE WARMING AND THE CARBON CYCLE IN THE PERMAFROST ZONE OF THE FORMER SOVIET UNION  

EPA Science Inventory

The continuous permafrost zone of the former Soviet Union occupies 5% of the land surface area of the earth and stores a significant amount of carbon. limate warming could disrupt the balance between carbon (C) accumulation and decomposition processes within the permafrost zone. ...

328

Science blogging: RealClimate.org and the Global Warming debate  

Microsoft Academic Search

The media and public policy debate suffer from an extreme form of Attention Deficit Disorder. Compared to the daily news cycle, the progress of scientific debate within the peer-reviewed literature is extremely slow. This puts serious scientists who work in relatively politicised fields (global warming, evolution, stem cell research and the like) at a huge disadvantage when it comes to

G. A. Schmidt

2006-01-01

329

Experimental Warming and Precipitation Effects on Plant Community Composition, Productivity, Nutrient Availability, and Soil Respiration in Pacific Northwest Prairies along a Natural Climate Gradient  

NASA Astrophysics Data System (ADS)

Climate change effects on soil respiration and carbon stores in grasslands globally may have significant implications for future atmospheric carbon dioxide concentrations. Climate change may also may negatively impact native plant species and favor exotic species. We are experimentally increasing temperature by 3 degrees C and increasing precipitation by 25% above ambient in three upland prairie sites along a natural climate gradient from southwestern Oregon to central-western Washington to determine how future climate change will affect (i) plant community composition and the relative success of native versus introduced plant species and (ii) above- and belowground carbon and nutrient dynamics. Sixty plots (20 at each site) were restored by mowing, raking, and herbicide application followed by the sowing of the same 34 native grass and forb species in each plot. Differences in total cover, net primary productivity, and community composition were much greater among sites than among treatments within sites in both 2010--the establishment year, and 2011-the first full year of treatment. Strong successional dynamics occurred over the two years as competition intensified, but these were dependent on a site-treatment interaction, with lower native plant survival in heated plots because of competitive exclusion by exotic, invasive plants. A strong treatment - season interaction in canopy cover (as determined by canopy reflectance) also occurred, with heating causing greater cover during the wet season and lower cover during the dry season. This effect was strongest in the southernmost site which experiences earlier and more intense drought conditions. There were also strong site, treatment, and season interactions on nutrient availability as determined by cation-anion exchange resins. Heating increased nutrient availability in all but the northernmost site during the growing season, and that site also had much lower nutrient availability, but overall availability and site and treatment effects were less during the winter. Plant dynamics among the sites are likely strongly controlled by these differences in nutrient availability. In the winter, heating increased soil respiration, but this effect was lost as the sites warmed and dried during the growing season, with this switch in treatment effect occurring earlier in the spring in the southernmost site. Overall, we have observed many significant effects of the warming and precipitation treatments on plant and ecosystem dynamics, but these effects are often seasonally dependent and of lesser importance than strong differences among sites, driven by differences in soils and the pressure from invasive species. Our experiment shows the importance of placing climate change impacts on natural ecosystems within a context of local ecosystem controls.

Bridgham, S. D.; Pfeifer-Meister, L.; Tomaszewski, T.; Reynolds, L.; Goklany, M.; Wilson, H.; Johnson, B. R.

2011-12-01

330

Impact of the Medieval Climate Anomaly, Little Ice Age, and Recent Warming on Hydrology and Carbon Accumulation in the James Bay Lowland  

NASA Astrophysics Data System (ADS)

Reconstructing late-Holocene hydroclimatic variations can be useful to understand the sensitivity of peatland soil carbon (C) to climate change (Bunbury et al., 2012). We reconstructed water table depth (WTD), using testate amoebae, for a four-core north to south transect of the James Bay Lowland and Boreal Shield of Ontario, Canada, and compared WTD to long-term apparent rate of C accumulation (LARCA). The three southern sites indicate that WTD fluctuated relative to the mean, with a wetter Medieval Climate Anomaly (MCA) and drier Little Ice Age (LIA) (Fig. 1). However, the most northern site recorded a wet LIA and dry MCA (Fig. 1). All four cores recorded drying coincident with modern warming (Fig. 1). Increased Medieval moisture detected in the three southern sites is consistent with a geographic pattern of precipitation anomalies associated with La Niña-like conditions, which cause drought in the American southwest and central plains regions coupled with increased moisture in the Pacific Northwest and north of the Great Lakes (Feng et al., 2008; Seager et al., 2008). Despite the hydroclimatic sensitivity of the region, we observed no consistent relationship between variations in WTD and LARCA from the same cores. At these particular sites, at least, C accumulation has not been sensitive to the range of climatic variability associated with the MCA, LIA and recent warming. Bunbury, J., Finkelstein, S. A., & Bollmann, J. (2012). Holocene hydro-climatic change and effects on carbon accumulation inferred from a peat bog in the Attawapiskat River watershed, Hudson Bay Lowlands, Canada. Quaternary Research: 275-284. Feng, S., Oglesby, R. J., Rowe, C. M., Loope, D. B., & Hu, Q. (2008). Atlantic and Pacific SST influences on Medieval drought in North America simulated by the Community Atmospheric Model. Journal of Geophysical Research: Atmospheres (1984-2012), 113(D11). Seager, R., Burgman, R., Kushnir, Y., Clement, A., Cook, E., Naik, N., & Miller, J. (2008). Tropical Pacific Forcing of North American Medieval Megadroughts: Testing the Concept with an Atmosphere Model Forced by Coral-Reconstructed SSTs. Journal of Climate, 21(23), 6175-6190. The upper plot indicates the most northern site from the discontinuous permafrost zones, The lower plot represents southern sites from the non-permafrost zone.

Holmquist, J. R.; Booth, R. K.; MacDonald, G. M.

2013-12-01

331

Persistent millennial-scale link between Greenland climate and northern Pacific Oxygen Minimum Zone under interglacial conditions  

NASA Astrophysics Data System (ADS)

The intensity and/or extent of the northeastern Pacific Oxygen Minimum Zone (OMZ) varied in-phase with the Northern Hemisphere high latitude climate on millennial timescales during the last glacial period, indicating the occurrence of atmospheric and oceanic connections under glacial conditions. While millennial variability was reported for both the Greenland and the northern Atlantic Ocean during the last interglacial period, the climatic connections with the northeastern Pacific OMZ has not yet been observed under warm interglacial conditions. Here we present a new geochemical dataset, spanning the past 120 ka, for major components (terrigenous fraction, marine organic matter, biogenic opal, and carbonates) generated by X-ray fluorescence scanning alongside with biological productivity and redox sensitive trace element content (Mo, Ni, Cd) of sediment core MD02-2508 at 23° N, retrieved from the northern limit of the modern OMZ. Based on elemental ratios Si / Ti (proxy for opal), Cd / Al and Ni / Al, we suggest that biological productivity was high during the last interglacial (MIS5). Highly resolved opal reconstruction presents millennial variability corresponding to all the Dansgaard-Oeschger interstadial events over the last interglacial, while the Mo / Al ratio indicates reduced oxygenation during these events. Extremely high opal content during warm interstadials suggests high diatom productivity. Despite the different climatic and oceanic background between glacial and interglacial periods, rapid variability in the northeastern Pacific OMZ seems to be tightly related to Northern Hemisphere high latitude climate via atmospheric and possibly oceanic processes.

Cartapanis, O.; Tachikawa, K.; Romero, O. E.; Bard, E.

2014-02-01

332

Modeling the Potential Change in Yield and Distribution of the Earth's Crops under a Warmed Climate.  

National Technical Information Service (NTIS)

The large scale distribution of crops is largely determined by climate. The authors present the results of a climate-crop prediction model based on the U.N. Food and Agriculture Organization crop-suitability approach, implemented in a geographic informati...

R. Leemans A. M. Solomon

1993-01-01

333

Linking climate change and biological invasions: Ocean warming facilitates nonindigenous species invasions  

Microsoft Academic Search

The spread of exotic species and climate change are among the most serious global environmental threats. Each independently causes considerable ecological damage, yet few data are available to assess whether changing climate might facilitate invasions by favoring introduced over native species. Here, we compare our long-term record of weekly sessile marine invertebrate recruitment with interannual variation in water temperature to

John J. Stachowicz; Jeffrey R. Terwin; Robert B. Whitlatch; Richard W. Osman

2002-01-01

334

Global Climate Highlights and Anomalies  

NSDL National Science Digital Library

NOAA's Global Climate Highlights and Anomalies page offers weekly summaries of global climate highlights and anomalies (warm, cold, wet, dry). Areas experiencing climate anomalies are color-marked on a global map, followed by written summaries of each region's climate conditions. All weeks are posted for the year 2000 (to present), and a link points users to the complete 1999 archive.

1999-01-01

335

Comparing Observed Hurricane Conditions Against Potential Future Climate Change Influences  

NASA Astrophysics Data System (ADS)

Climate Adaptation Science Investigators: (CASI) is to advance and apply NASA's scientific expertise and products to develop climate adaptation strategies that support NASA's overall mission by minimizing risks to each center's operations, physical assets, and personnel. Using Hurricane Katrina observations as a baseline, we use ADCIRC to model surge extent with simple modifications of the storm track. We examine two time now (T0) scenarios of present-day climatological factors: 1) translating the 2005 path 7 km west; and 2) rotating the approach angle from due-north to WNW. Second, we examine two future time scenarios (TX) by infusing climate change conditions, such as sea level rise and increased storm intensity, into a T0 baseline to assess future impacts. The primary goal of this work entails planning and protecting NASA assets and infrastructure. The adjacent communities, state and local emergency managers, gain benefit from this NASA work as data and analysis includes the surrounding geography.

Graham, W. D.

2012-12-01

336

Paleoclimate. Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming.  

PubMed

Some proposed mechanisms for transmission of major climate change events between the North Pacific and North Atlantic predict opposing patterns of variations; others suggest synchronization. Resolving this conflict has implications for regulation of poleward heat transport and global climate change. New multidecadal-resolution foraminiferal oxygen isotope records from the Gulf of Alaska (GOA) reveal sudden shifts between intervals of synchroneity and asynchroneity with the North Greenland Ice Core Project (NGRIP) ?(18)O record over the past 18,000 years. Synchronization of these regions occurred 15,500 to 11,000 years ago, just prior to and throughout the most abrupt climate transitions of the last 20,000 years, suggesting that dynamic coupling of North Pacific and North Atlantic climates may lead to critical transitions in Earth's climate system. PMID:25061208

Praetorius, Summer K; Mix, Alan C

2014-07-25

337

Regression tree modeling of forest NPP using site conditions and climate variables across eastern USA  

NASA Astrophysics Data System (ADS)

As evidence of global warming continue to increase, being able to predict forest response to climate changes, such as expected rise of temperature and precipitation, will be vital for maintaining the sustainability and productivity of forests. To map forest species redistribution by climate change scenario has been successful, however, most species redistribution maps lack mechanistic understanding to explain why trees grow under the novel conditions of chaining climate. Distributional map is only capable of predicting under the equilibrium assumption that the communities would exist following a prolonged period under the new climate. In this context, forest NPP as a surrogate for growth rate, the most important facet that determines stand dynamics, can lead to valid prediction on the transition stage to new vegetation-climate equilibrium as it represents changes in structure of forest reflecting site conditions and climate factors. The objective of this study is to develop forest growth map using regression tree analysis by extracting large-scale non-linear structures from both field-based FIA and remotely sensed MODIS data set. The major issue addressed in this approach is non-linear spatial patterns of forest attributes. Forest inventory data showed complex spatial patterns that reflect environmental states and processes that originate at different spatial scales. At broad scales, non-linear spatial trends in forest attributes and mixture of continuous and discrete types of environmental variables make traditional statistical (multivariate regression) and geostatistical (kriging) models inefficient. It calls into question some traditional underlying assumptions of spatial trends that uncritically accepted in forest data. To solve the controversy surrounding the suitability of forest data, regression tree analysis are performed using Software See5 and Cubist. Four publicly available data sets were obtained: First, field-based Forest Inventory and Analysis (USDA, Forest Service) data set for the 31 eastern most United States. Second, 8-day composite of MODIS Land Cover, FPAR, LAI and GPP/NPP data were obtained from Jan 2001 to Dec 2004 (total 182 composite) and each product were filtered by pixel-level quality assurance data to select best quality pixels. Third, 30-year averaged climate data were collected from National Oceanic and Atmospheric Administration (NOAA) and five climatic variables were obtained: Monthly temperature, precipitation, annual heating and cooling days, and annual frost-free days. Forth, topographic data were obtained from digital elevation model (1km by 1km). This research will provide a better understanding of large-scale forest responses to environmental factors that will be beneficial for the development of important forest management applications.

Kwon, Y.

2013-12-01

338

Is bias correction of Regional Climate Model (RCM) simulations possible for non-stationary conditions?  

NASA Astrophysics Data System (ADS)

Regional Climate Models (RCMs) are commonly used in climate-change impact studies to transfer large-scale Global Climate Model (GCM) values to smaller scales and to provide more detailed regional information. There is, however, the problem that RCM simulations often show considerable deviations from local observations due to systematic and random model errors. This issue has caused the development of several correction approaches, that can be classified according to their degree of complexity and include simple-to-apply methods such as linear transformations but also more advanced methods such as distribution mapping. Most of these common correction approaches are based on the assumption that RCM errors do not change over time. It is in principle not possible to test whether this underlying assumption of error stationarity is actually fulfilled for future climate conditions. In this contribution, however, we show that it is possible to evaluate how well correction methods perform for conditions different from those that they were calibrated to. This can be done with the relatively simple differential split-sample test, originally proposed by Klemeš ["Operational testing of hydrological simulation models", Hydrological Sciences Journal 31, no. 1 (1986): 13-24]. For five Swedish catchments, precipitation and temperature time series from 15 different ERA40-driven RCM simulations were corrected with different commonly-used bias correction methods. We then performed differential split-sample tests by dividing the data series into cold and warm respective dry and wet years. This enabled us to cross-evaluate the performance of different correction procedures under systematically varying climate conditions. The differential split-sample test identified major differences in the ability of the applied correction methods to reduce model errors and to cope with non-stationary biases. More advanced correction methods performed better, whereas large deviations remained for climate model simulations corrected with simpler approaches. Therefore, we question the use of simple correction methods such as the widely used delta-change approach and linear transformation for RCM-based climate-change impact studies. Instead, we recommend using higher-skill correction methods such as distribution mapping.

Teutschbein, Claudia; Seibert, Jan

2014-05-01

339

How the West Was Warmed  

NASA Astrophysics Data System (ADS)

Is the West getting warmer? To be sure, the summer of 2005 was one of record heat in the West, and recent period of western US drought during 1998-2004 was also accompanied by unusual warmth. But warm conditions accompanied the Dust Bowl era of the 1930s and the 1950s. The question remains open whether recent western warming has been part of a externally forced climate trend, or whether other processes have been at play like urbanization or the inherent natural fluctuations of climate paterns? We perform analysis of the Fourth Assessment coupled ocean-atmosphere models for the period 1895-2005, together with atmospheric general circulation model experiments. These reveal that the recent warming of the West has very likely been a consequence of increasing greenhouse gases. In fact, no single member of 40 availabl GHG-forced simulations failed to warm the West during the past century. We further show that a warming of the tropical oceanic warm pool regions, itself a greenhouse gas forced response, has been a major contributor to the warming of the West since 1970.

Hoerling, M.; Eischeid, J.

2006-05-01

340

Sensitivity of salmonid freshwater life history in western US streams to future climate conditions.  

PubMed

We projected effects of mid-21st century climate on the early life growth of Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) in western United States streams. Air temperature and snowpack trends projected from observed 20th century trends were used to predict future seasonal stream temperatures. Fish growth from winter to summer was projected with temperature-dependent models of egg development and juvenile growth. Based on temperature data from 115 sites, by mid-21st century, the effects of climate change are projected to be mixed. Fish in warm-region streams that are currently cooled by snow melt will grow less, and fish in suboptimally cool streams will grow more. Relative to 20th century conditions, by mid-21st century juvenile salmonids' weights are expected to be lower in the Columbia Basin and California Central Valley, but unchanged or greater in coastal and mountain streams. Because fish weight affects fish survival, the predicted changes in weight could impact population fitness depending on other factors such as density effects, food quality and quantity changes, habitat alterations, etc. The level of year-to-year variability in stream temperatures is high and our analysis suggests that identifying effects of climate change over the natural variability will be difficult except in a few streams. PMID:23640715

Beer, W Nicholas; Anderson, James J

2013-08-01

341

Features of the ocean-atmosphere exchange and its effect on terrestrial climate conditions  

NASA Astrophysics Data System (ADS)

The climatic changes on Earth are to a large extent influenced by the intensity of ocean-atmosphere-land interactions Energy exchange in the atmosphere-ocean system depends on the transfer of warm and cold water masses by stream flows Interaction of water masses leads to formation of frontal zones with high temperature gradients Such zones are easily detected by temperature gradients which are calculated according to AVHRR MCSST satellite data for the 1982 -- 1986 average monthly and 1990 -- 2001 average weekly periods The spatial extension and the size of the frontal zone formed by Gulf Stream in North Atlantic affects the evaporation mode Such interaction with atmosphere leads to changes in the cyclonic and anticyclonic activity in the North Atlantic Oscillation NAO zone In this work the seasonal North Atlantic Oscillations are compared with the temperature gradients in North Atlantic for the period of satellite measurements Besides the investigation is made of the connection between the changes of NAO and climatic parameters overland We used the weather stations data concerning the average monthly air temperature and precipitation for the territory of Eurasia for the period of 1900-2004 This work analyses the features of ocean-atmosphere interaction and the effect of such interaction on the climatic conditions We developed software for the analysis of climagrams in graphic form in which the air temperature and amount of precipitation are averaged over the whole observation period and also for separate periods The average seasonal

Kartushinsky, A.; Sashko, L.

342

Cloud tuning in a coupled climate model: Impact on 20th century warming  

NASA Astrophysics Data System (ADS)

Climate models incorporate a number of adjustable parameters in their cloud formulations. They arise from uncertainties in cloud processes. These parameters are tuned to achieve a desired radiation balance and to best reproduce the observed climate. A given radiation balance can be achieved by multiple combinations of parameters. We investigate the impact of cloud tuning in the CMIP5 GFDL CM3 coupled climate model by constructing two alternate configurations. They achieve the desired radiation balance using different, but plausible, combinations of parameters. The present-day climate is nearly indistinguishable among all configurations. However, the magnitude of the aerosol indirect effects differs by as much as 1.2 Wm - 2, resulting in significantly different temperature evolution over the 20th century.

Golaz, J.-C.; Golaz, Jean-Christophe; Levy, Hiram

2013-05-01

343

The borehole temperature record of climate warming in the mid-continent of North America  

Microsoft Academic Search

Ground-surface temperature (GST) histories, determined from a carefully selected set of twenty-nine borehole temperature profiles, show a warming trend over the last century that increases systematically with latitude in the mid-continent of North America. Except one site in north Texas, the borehole locations lie within a 500 × 1000 km transect that extends from the Kansas-Nebraska border into southern Manitoba.

W. D. Gosnold; P. E. Todhunter; W. Schmidt

1997-01-01

344

Coral-based climate variability in the Western Pacific Warm Pool since 1867  

Microsoft Academic Search

We have generated monthly resolved, stable isotope (?18O and ?13C) and Sr\\/Ca time series from a massive Porites coral from Rabaul (4°S, 152°E): a site located in the warmest sector of the Western Pacific Warm Pool (WPWP). The coral ?18O and Sr\\/Ca time series are well correlated to each other and positive excursions in both records coincide with times of

Terrence M. Quinn; Frederick W. Taylor; Thomas J. Crowley

2006-01-01

345

Climatic Warming and the Decline of Zooplankton in the California Current  

Microsoft Academic Search

Since 1951, the biomass of macrozooplankton in waters off southern California has decreased by 80 percent. During the same period, the surface layer warmed-by more than 1.5^circC in some places-and the temperature difference across the thermocline increased. Increased stratification resulted in less lifting of the thermocline by wind-driven upwelling. A shallower source of upwelled waters provided less inorganic nutrient for

Dean Roemmich; John McGowan

1995-01-01

346

Climate change in cities due to global warming and urban effects  

Microsoft Academic Search

Urbanisation is estimated to result in 6 billion urban dwellers by 2050. Cities will be exposed to climate change from greenhouse gas induced radiative forcing, and localised effects from urbanisation such as the urban heat island. An urban land-surface model has been included in the HadAM3 Global Climate Model. It shows that regions of high population growth coincide with regions

Mark P. McCarthy; Martin J. Best; Richard A. Betts

2010-01-01

347

Proxy records of Late Holocene climate events in the eastern United States: Medieval Warm Period and Little Ice Age  

NASA Astrophysics Data System (ADS)

We are conducting a multiproxy, regional reconstruction of climate variability during the last two millennia including the Medieval Warm Period (MWP) and Little Ice Age (LIA) in eastern North America. Pollen, benthic foraminifers, ostracodes, and other proxies were analyzed from high-resolution sampling of continuous sedimentary records from lakes, wetlands, and estuaries in Florida, North Carolina, Chesapeake Bay, and Lake Champlain. These records document multi-decadal changes in vegetation, temperature, precipitation, and estuarine salinity across a latitudinal transect. During both the MWP and LIA, decreased precipitation altered plant community composition and distribution in the southeastern United States, and the LIA triggered threshold changes in vegetation that persisted until anthropogenic land-cover change overwhelmed the climate signature. In the mid-Atlantic region, progressively cooler and wetter late Holocene springs culminated in a cool, wet LIA; this trend correlates with observed oceanic changes. Trend analysis of the data suggest that inter-regional correlation of multi-decadal and centennial-scale Holocene climate events will be forthcoming.

Willard, D. A.; Cronin, T. M.; Hayo, K. M.

2006-12-01

348

The transferability of hydrological models under nonstationary climatic conditions  

NASA Astrophysics Data System (ADS)

This paper investigates issues involved in calibrating hydrological models against observed data when the aim of the modelling is to predict future runoff under different climatic conditions. To achieve this objective, we tested two hydrological models, DWBM and SIMHYD, using data from 30 unimpaired catchments in Australia which had at least 60 yr of daily precipitation, potential evapotranspiration (PET), and streamflow data. Nash-Sutcliffe efficiency (NSE), modified index of agreement (d1) and water balance error (WBE) were used as performance criteria. We used a differential split-sample test to split up the data into 120 sub-periods and 4 different climatic sub-periods in order to assess how well the calibrated model could be transferred different periods. For each catchment, the models were calibrated for one sub-period and validated on the other three. Monte Carlo simulation was used to explore parameter stability compared to historic climatic variability. The chi-square test was used to measure the relationship between the distribution of the parameters and hydroclimatic variability. The results showed that the performance of the two hydrological models differed and depended on the model calibration. We found that if a hydrological model is set up to simulate runoff for a wet climate scenario then it should be calibrated on a wet segment of the historic record, and similarly a dry segment should be used for a dry climate scenario. The Monte Carlo simulation provides an effective and pragmatic approach to explore uncertainty and equifinality in hydrological model parameters. Some parameters of the hydrological models are shown to be significantly more sensitive to the choice of calibration periods. Our findings support the idea that when using conceptual hydrological models to assess future climate change impacts, a differential split-sample test and Monte Carlo simulation should be used to quantify uncertainties due to parameter instability and non-uniqueness.

Li, C. Z.; Zhang, L.; Wang, H.; Zhang, Y. Q.; Yu, F. L.; Yan, D. H.

2012-04-01

349

Potential impacts of climate warming on runoff from snowmelt: a case study of two mountainous basins in the Upper Rio Grande  

NASA Astrophysics Data System (ADS)

We used historical climate, snow cover and streamflow data in the Snowmelt Runoff Model (SRM) to drive simulations of runoff from two mountainous basins in the Upper Rio Grande. The basins selected for this study are El Rito and Santa Fe. With climate warming, both have been shown to be at risk of losing annual snowpack and the associated peak in the spring hydrograph caused by snowmelt. Historical flow simulations supplied model parameters specific to each basin (runoff coefficients, degree day factors, temperature lapse rates, critical temperature and recession coefficients). These parameters were then used in applying SRM under changed climate conditions (scenario A2, ECHAM-5 general circulation model, 2046-2100). Although there is some interannual variability, under the A2 scenario the SRM simulations imply (i) a profound loss of annual snowpack at all but the highest elevations; (ii) decline in springtime streamflow (fraction of flow occurring between April and July) and (iii) earlier occurrence of winter-spring center of volume (half total runoff volume for January 1 to May 31). Our results have profound implications for the rural acequia community in El Rito for whom the annual snowpack acts as a natural reservoir releasing water to the acequias (irrigation canals) concurrent with the beginning of the growing season. In El Rito, the only alternative to water from snowmelt runoff is groundwater, but this source of water will also be affected by the accumulation, quantity and duration of annual snowpack. With two reservoirs, the urban area of Santa Fe is less dependent on the timing of snowmelt than El Rito. Additionally, Santa Fe has access to alternate sources of surface water (e.g., from the San Juan-Chama Project). Nevertheless, climate-change induced scarcity of water throughout the region will also have important socio-economic and political impacts on the City of Santa Fe.

Rango, A.; Steele, C. M.; Elias, E.; Mejia, J.; Fernald, A.

2013-12-01

350

U.S. Federal Investments in Climate Change Education: They're Warming Up! (Invited)  

NASA Astrophysics Data System (ADS)

Many similarities exist between the U.S. federal government and the climate system, in terms of their complexity. Government operates through a dynamic interplay of sub-systems (different agencies), pressure gradients (political interests), energy transformations (converting dollars into activity through Congressional appropriations, grants and contracts), and non-linear positive and negative feedback mechanisms (MOU’s, competing agency missions). ‘Viscosity’ in the system makes progress difficult. The good news is that, like the climate, federal investments in climate change education are heating up, due to man-made inputs. Individual agency investments in projects to improve and monitor public understanding of climate change and its impacts are rapidly becoming more coupled and coherent. This paper will discuss several efforts now underway. In FY 2009, dedicated, multi-million dollar funding led to creation of NSF’s Climate Change Education (CCE) and NASA’s Global Climate Change Education (GCCE) grant programs, which are funding a projects to develop pedagogically-sound learning resources, professional development strategies, tool kits, and web-based clearinghouses offering scientifically accurate information about climate change to different learner audiences. NOAA has been able to firmly establish their Environmental Literacy Grant (ELG) program because of the America COMPETES Act. Related programs are being developed within the EPA and USDA’s NIFA and U.S. Forest Service. Several other agencies have revamped their strategic plans to increase focus on communicating with and educating teachers, students, policymakers, and the general public about climate change