Showing papers on "Climate change published in 1993"
TL;DR: In this paper, a process-based model was used to estimate global patterns of net primary production and soil nitrogen cycling for contemporary climate conditions and current atmospheric CO2 concentration, with most of the production attributable to tropical evergreen forest.
Abstract: A process-based model was used to estimate global patterns of net primary production and soil nitrogen cycling for contemporary climate conditions and current atmospheric CO2 concentration. Over half of the global annual net primary production was estimated to occur in the tropics, with most of the production attributable to tropical evergreen forest. The effects of CO2 doubling and associated climate changes were also explored. The responses in tropical and dry temperate ecosystems were dominated by CO2, but those in northern and moist temperate ecosystems reflected the effects of temperature on nitrogen availability.
1,929 citations
TL;DR: In this article, the low-frequency variability of the surface climate over the North Atlantic during winter is described, using 90 years of weather observations from the Comprehensive Ocean-Atmosphere Data Set.
Abstract: The low-frequency variability of the surface climate over the North Atlantic during winter is described, using 90 years of weather observations from the Comprehensive Ocean–Atmosphere Data Set. Results are based on empirical orthogonal function analysis of four components of the climate system: sea surface temperature (SST), air temperature, wind, and sea level pressure. An important mode of variability of the wintertime surface climate over the North Atlantic during this century is characterized by a dipole pattern in SSTs and surface air temperatures, with anomalies of one sign cast of Newfoundland, and anomalies of the opposite polarity off the southeast coast of the United States. Wind fluctuations occur locally over the regions of large surface temperature anomalies, with stronger-than-normal winds overlying cooler-than-normal SSTs. This mode exhibits variability on quasi-decadal and biennial time scales. The decadal fluctuations are irregular in length, averaging ∼9 years before 1945 and ∼1...
782 citations
TL;DR: Using historical, tree-ring and ice core data, the authors examined climatic variations during the period commonly called the "Little Ice Age", and found that unusually warm conditions have prevailed since the 1920s, probably related to a relative absence of major explosive volcanic eruptions and higher levels of greenhouse gases.
Abstract: Climatic changes resulting from greenhouse gases will be superimposed on natural climatic variations. High-resolution proxy records of past climate can be used to extend our perspective on regional and hemispheric changes of climate back in time by several hundred years. Using historical, tree-ring and ice core data, we examine climatic variations during the period commonly called the 'Little Ice Age'. The coldest conditions of the last 560 years were between AD 1570 and 1730, and in the nineteenth century. Unusually warm conditions have prevailed since the 1920s, probably related to a relative absence of major explosive volcanic eruptions and higher levels of greenhouse gases.
694 citations
TL;DR: In this paper, a statistical strategy to deduct regional-scale features from climate general circulation model (GCM) simulations has been designed and tested and the skill of the resulting statistical model is shown by reproducing, to a good approximation, the winter mean Iberian Peninsula rainfall from 1900 to present from the observed North Atlantic mean SLP distributions.
Abstract: A statistical strategy to deduct regional-scale features from climate general circulation model (GCM) simulations has been designed and tested. The main idea is to interrelate the characteristic patterns of observed simultaneous variations of regional climate parameters and of large-scale atmospheric flow using the canonical correlation technique. The large-scale North Atlantic sea level pressure (SLP) is related to the regional, variable, winter (DJF) mean Iberian Peninsula rainfall. The skill of the resulting statistical model is shown by reproducing, to a good approximation, the winter mean Iberian rainfall from 1900 to present from the observed North Atlantic mean SLP distributions. It is shown that this observed relationship between these two variables is not well reproduced in the output of a general circulation model (GCM). The implications for Iberian rainfall changes as the response to increasing atmospheric greenhouse-gas concentrations simulated by two GCM experiments are examined with...
665 citations
Book•
01 Jan 1993
TL;DR: In this paper, the effects of global climate change on North American birds and their communities were investigated. But the authors focused on the effects on the distribution of species in the wild and not on the communities themselves.
Abstract: Part 1 Patterns and determinants of climate and landscape change: scenarios of global warming, Stephen H. Schneider evaluating landscape change - patterns of worldwide deforestation and local fragmentation, Martha J. Groom and Nathan Schumaker population and community processes in the response of terrestrial ecosystems to global change, David S. Schimel. Part 2 Physiology and population responses to environmental change: terrestrial vegetation and climate change - integrating models and experiments, Stephen W. Pacala and George C. Hurtt plant defense, herbivory, and climate change, Matthew P. Ayres population responses to environmental change - operative environments, physiologically structured models, and population dynamics, Arthur E. Dunham climate change and ecological interactions, Anthony R. Ives and George Gilchrist individual-based models for predicting effects of global change, William W. Murdoch. Part 3 Evolutionary responses to environmental change: evolutionary genetics and climatic change - will animals adapt to global warming?, Ary A. Hoffmann and Mark W. Blows evolutionary responses of plants to global change, Monica A. Gever and Todd E. Dawson the evolutionary dynamics of fragmented plant populations, Kent S. Holsinger genetic consequences of extinction and recolonization in fragmented habitats, David E. McCauley evolution and extinction in response to environmental change, Michael Lynch and Russell Lande global change - lessons from and for evolutionary biology, Joseph Travis and Douglas J. Futuyma. Part 4 Community responses to environmental change: species dynamics and global environmental change - a perspective from ecosystem experiments, Stephen R. Carpenter, et al effects of global climate change on North American birds and their communities, Terry L. Root implications of climate change for stream communities, Nancy B. Grimm paleoecological perspectives on modeling broad-scale responses to global change, James S. Clark carbon dioxide limitation and potential direct effects of its accumulation on plant communities, David Tilman a salty and salutary perspective on global change, Robert T. Paine forecasting ecological responses to global change - the need for large-scale comparative studies, Michael L. Pace. Part 5 Landscape change and habitat fragmentation: species invasions and deletions - community effects and responses to climate and habitat change, David M. Lodge species diversity, spatial scale, and global change, Susan Harrison effects of global change on the dynamics of insect host-parasitoid interactions, M.P. Hassell, et al conservation planning for species occupying fragmented landscapes - the case of the Northern Spotted Owl, Kevin McKelvey, et al part contents.
653 citations
TL;DR: In this article, a 27-year record of Northern Hemisphere continental snow cover produced by the National Oceanic and Atmospheric Administration (NOAA) is the longest such environmental record available, and the visible imagery charting technique used to generate these data provides information on snow extent but not on snow volume.
Abstract: Accurate monitoring of the large-scale dimensions of global snow cover is essential for understanding details of climate dynamics and climate change. Presently, such information is gathered individually from ground station networks and satellite platforms. Efforts are in progress to consolidate and analyze long-term station records from a number of countries. To gain truly global coverage, however, satellite-based monitoring techniques must be employed. A 27-year record of Northern Hemisphere continental snow cover produced by the National Oceanic and Atmospheric Administration (NOAA) is the longest such environmental record available. Records of Southern Hemisphere continental cover and snow on top of Arctic sea ice have been produced by similar means for a portion of this interval. The visible imagery charting technique used to generate these data provides information on snow extent but not on snow volume. Satellite microwave analyses over Northern Hemisphere lands show some promise in this regard, howe...
629 citations
TL;DR: In this paper, the authors studied the potential for change in the Arctic Flora and Vegetation in a changing climate, and proposed a model for the response of Arctic plants to changing climate.
Abstract: F.S. Chapin III, R.L. Jefferies, J.F. Reynolds, G.R. Shaver, and J. Svoboda, Arctic Plant Physiological Ecology: A Challenge for the Future. The Arctic System: B. Maxwell, Arctic Climate: Potential for Change under Global Warming. D.L. Kane, L.D. Hinzman, M. Woo, and K.R. Everett, Arctic Hydrology and Climate Change. L.C. Bliss and N.V. Matveyeva, Circumpolar Arctic Vegetation. W.D. Billings, Phytogeographic and Evolutionary Potential for the Arctic Flora and Vegetation in a Changing Climate. L.C. Bliss and K.M. Peterson, Plant Succession, Competition, and the Physiological Constraints of Species in the Arctic. Carbon Balance: W.C. Oechel and W.D. Billings, Effects of Global Change on the Carbon Balance of Arctic Plants and Ecosystems. O.A. Semikhatova, T.V. Gerasimenko, and T.I. Ivanova, Photosynthesis, Respiration, and Growth of Plants in the Soviet Arctic. G.R. Shaver and J. Kummerow, Phenology, Resource Allocation, and Growth of Arctic Vascular Plants. J.D. Tenhunen, O.L. Lange, S. Hahn, R. Siegwolf, and S.F. Oberbauer, The Ecosystem Role of Poikilohydric Tundra Plants. B. Sveinbj~adornsson, Arctic Tree Line in a Changing Climate. Water and Nutrient Balance: S.F. Oberbauer and T.E. Dawson, Water Relations of Arctic Vascular Plants. K.J. Nadelhoffer, A.E. Giblin, G.R. Shaver, and A.E. Linkins, Microbial Processes and Plant Nutrient Availability in Arctic Soils. D.M. Chapin and C.S. Bledsoe, Nitrogen Fixation in Arctic Plant Communities. K. Kielland and F.S. Chapin III, Nutrient Absorption and Accumulation in Arctic Plants. F. Berendse and S. Jonasson, Nutrient Use and Nutrient Cycling in Northern Ecosystems. Interactions: J.B. McGraw and N. Fetcher, Response of Tundra Plant Populations to Climatic Change. J.P. Bryant and P.B. Reichardt, Controls over Secondary Metabolite Production by Arctic Woody Plants. R.L. Jefferies, J. Svoboda, G. Henry, M. Raillard, and R. Ruess, Tundra Grazing Systems and Climatic Change. J.F. Reynolds and P.W. Leadley, Modeling the Response of Arctic Plants to Changing Climate. F.S. Chapin III, R.L. Jefferies, J.F. Reynolds, G.R. Shaver, and J. Svoboda, Arctic Plant Physiological Ecology in an Ecosystem Context. Index.
587 citations
TL;DR: In this paper, electrical conductivity measurements from a new Greenland ice core, which confirm these previous observations, and reveal a hitherto unrecognized mode of rapid climate variation, are reported.
Abstract: POLAR ice contains a unique record of past climate variations; previous Greenland ice cores have documented relatively warm ‘interstadial’ periods during the last glaciation and short (centuryscale) returns to colder conditions during the glacial to interglacial warming (see, for example, ref. 1). These climate features have also been observed to varying degrees in ocean sediment cores2–4 and terrestrial pollen and insect records5–7. Here we report electrical conductivity measurements from a new Greenland ice core, which confirm these previous observations, and also reveal a hitherto unrecognized mode of rapid climate variation. Fluctuations in ice conductivity on the scales of <5–20 years reflect rapid oscillations in the dust content of the atmosphere. This ‘flickering’ between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation.
567 citations
TL;DR: This paper used a coupled ocean-atmosphere climate model to study the evolution of the world's climate over the next few centuries, driven by doubling and quadrupling of the concentration of atmospheric CO2.
Abstract: SEVERAL studies have addressed the likely effects of CO2-induced climate change over the coming decades1–10, but the longer-term effects have received less attention. Yet these effects could be very significant, as persistent increases in global mean temperatures may ultimately influence the large-scale processes in the coupled ocean–atmosphere system that are thought to play a central part in determining global climate. The thermohaline circulation is one such process—Broecker has argued11 that it may have undergone abrupt changes in response to rising temperatures and ice-sheet melting at the end of the last glacial period. Here we use a coupled ocean-atmosphere climate model to study the evolution of the world's climate over the next few centuries, driven by doubling and quadrupling of the concentration of atmospheric CO2. We find that the global mean surface air temperature increases by about 3.5 and 7 °C, respectively, over 500 years, and that sea-level rise owing to thermal expansion alone is about 1 and 2 m respectively (ice-sheet melting could make these values much larger). The thermal and dynamical structure of the oceans changes markedly in the quadrupled-CO2 climate—in particular, the ocean settles into a new stable state in which the thermohaline circulation has ceased entirely and the thermocline deepens substantially. These changes prevent the ventilation of the deep ocean and could have a profound impact on the carbon cycle and biogeochemistry of the coupled system.
TL;DR: It is investigated the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.
Abstract: Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.
TL;DR: Prentice et al. as discussed by the authors presented a simulation model for the transient effects of climate change on forest landscapes, where tree establishment and growth rates were modified by species-specific functions describing the effects of winter and summer temperature limitations, accumulated annual foliage net assimilation and sapwood respiration as functions of temperature, CO 2 fertilization, and growing-season drought.
TL;DR: In this article, experiments with climate models are used to illustrate how earth's climate could be expected to change if surface uplift occurred, and the experiments contrast two climate simulations: one with all continents at sea level and one with present-day mountains and plateaus.
Abstract: Experiments with climate models are used to illustrate how earth's climate could be expected to change if surface uplift occurred. The experiments contrast two climate simulations: one with all continents at sea level and one with present-day mountains and plateaus. The simulations in the Eurasia sector show that surface uplift (increased elevation) produces marked increases in the intensity of summer and winter monsoons of Asia, with development of wetter climates to the south and east of the Tibetan plateau and drier climates to the north and west of the plateau; there is a general cooling in northern polar latitudes. Comparison of simulations from two different models shows that the magnitude of the simulated changes depends upon how the models calculate the land surface hydrology and the ocean temperature. The simulated changes produced by surface uplift agree in a general way with many geologic indicators of late Cenozoic climate change. The results suggest that surface uplift of mountains and platea...
Abstract: A tropical deforestation experiment has been conducted in which the tropical moist forest throughout the Amazon Basin and SE Asia has been replaced by scrub grassland in a version of the National Center for Atmospheric Research Community Climate Model (Version 1), which also incorporates a mixed layer ocean and the Biosphere-Atmosphere Transfer Scheme. In both regions we find a smaller temperature increase than did all other previous experiments except that of Henderson-Sellers and Gornitz (1984); indeed, temperatures decrease in some months. On the other hand, we find larger runoff decreases and a larger difference between the changes in evaporation and precipitation than all earlier experiments indicating a basin-wide decrease in moisture convergence. Disturbances in South America extend beyond the region of land-surface change causing temperature reductions and precipitation increases to the south of the deforested Amazon. Changes to the surface climate in the deforested area take between 1 to 2 years to become fully established although the root zone soil moisture is still decreasing in year 3 and the variability of soil moisture and total cloud amount continue increasing throughout the 6-year integration. Besides temperature and precipitation, other fields show statistically significant alterations, especially evaporation and net surface radiation (both decreased).
TL;DR: Gases trapped in polar ice proved our most direct record of the changes in greenhouse gas levels during the past 150,000 years, and the best documented trace-gas records are for CO[sub 2] and CH[sub 4] as mentioned in this paper.
Abstract: Gases trapped in polar ice proved our most direct record of the changes in greenhouse gas levels during the past 150,000 years. The best documented trace-gas records are for CO[sub 2] and CH[sub 4]. The measurements corresponding to the industrial period document the recent changes in growth rate. The variability observed over the last 1000 years constrains the possible feedbacks of a climate change on the trace gases under similar conditions as exist today. Changes in the levels of greenhouse gases during the glacial-interglacial cycle overall paralleled, at least at high southern latitudes, changes in temperature; this relation suggests that greenhouse gases play an important role as an amplifier of the initial orbital forcing of Earth's climated and also helps to assess the feedbacks on the biogeochemical cycles in a climate system in which the components are changing at different rates.
TL;DR: Oscillations of Pinus (pine) pollen in a 50,000-year sequence from Lake Tulane, Florida, indicate that there were major vegetation shifts during the last glacial cycle and seems to be temporally correlated with the North Atlantic Heinrich events.
Abstract: Oscillations of Pinus (pine) pollen in a 50,000-year sequence from Lake Tulane, Florida, indicate that there were major vegetation shifts during the last glacial cycle. Episodes of abundant Pinus populations indicate a climate that was more wet than intervening phases dominated by Quercus (oak) and Ambrosia-type (ragweed and marsh-elder). The Pinus episodes seem to be temporally correlated with the North Atlantic Heinrich events, which were massive, periodic advances of ice streams from the eastern margin of the Laurentide Ice Sheet. Possible links between the Tulane Pinus and Heinrich events include hemispheric cooling, the influences of Mississippi meltwater on sea-surface temperatures in the Gulf of Mexico, and the effects of North Atlantic thermohaline circulation on currents in the Gulf.
TL;DR: A 5000-year regional paleoflood chronology, based on flood deposits from 19 rivers in Arizona and Utah, reveals that the largest floods in the region cluster into distinct time intervals that coincide with periods of cool, moist climate and frequent El Ni�o events.
Abstract: A 5000-year regional paleoflood chronology, based on flood deposits from 19 rivers in Arizona and Utah, reveals that the largest floods in the region cluster into distinct time intervals that coincide with periods of cool, moist climate and frequent El Nino events. The floods were most numerous from 4800 to 3600 years before present (B.P.), around 1000 years B.P., and after 500 years B.P., but decreased markedly from 3600 to 2200 and 800 to 600 years B.P. Analogous modern floods are associated with a specific set of anomalous atmospheric circulation conditions that were probably more prevalent during past flood epochs.
TL;DR: Spectral analysis suggests that the distribution of variance in this record has shifted among annual to interannual periods during the present century, concurrent with observed changes in the strength of the Southern Oscillation.
Abstract: In the western tropical Pacific, the interannual migration of the Indonesian Low convective system causes changes in rainfall that dominate the regional signature of the El Nino—Southern Oscillation (ENSO) system. A 96-year oxygen isotope record from a Tarawa Atoll coral (1°N, 172°E) reflects regional convective activity through rainfall-induced salinity changes. This monthly resolution record spans twice the length of the local climatological record and provides a history of ENSO variability comparable in quality with those derived from instrumental climate data. Comparison of this coral record with a historical chronology of EI Nino events indicates that climate anomalies in coastal South America are occasionally decoupled from Pacific-wide ENSO extremes. Spectral analysis suggests that the distribution of variance in this record has shifted among annual to interannual periods during the present century, concurrent with observed changes in the strength of the Southern Oscillation.
TL;DR: A hierarchic geographic information system (HGIS) which helps examine links between species distributions at the plot level, at the level of landscape patterns of plant communities, and at thelevel of regional patterns of greeness is presented.
Abstract: Relationships among vegetation, wind, snow, and temperature regimes may help predict effects of climate change. This paper presents a hierarchic geographic information system (HGIS) which helps examine links between species distributions at the plot level, at the level of landscape patterns of plant communities, and at the level of regional patterns of greeness. Geographically referencing ecological data, mapping techniques, landscape and regional scale mapping, and linking ground-level observations to remotely sensed information are all discussed. Results include discussion of specific plant species-snow relationships, landscape-level patterns of specific plant communities, regional patterns of the normalized difference vegetation index (NDVI), and linking patterns to variations in climate or direct anthropogenic impacts. 50 refs., 12 figs., 3 tabs.
TL;DR: In this article, an optimal linear filter (fingerprint) is derived for the detection of a given time-dependent, multivariate climate change signal in the presence of natural climate variability noise.
Abstract: An optimal linear filter (fingerprint) is derived for the detection of a given time-dependent, multivariate climate change signal in the presence of natural climate variability noise. Application of the fingerprint to the observed (or model simulated) climate data yields a climate change detection variable (detector) with maximal signal-to-noise ratio. The optimal fingerprint is given by the product of the assumed signal pattern and the inverse of the climate variability covariance matrix. The data can consist of any, not necessarily dynamically complete, climate dataset for which estimates of the natural variability covariance matrix exist. The single-pattern analysis readily generalizes to the multipattern case of a climate change signal lying in a prescribed (in practice relatively low dimensional) signal pattern space: the single-pattern result is simply applied separately to each individual base pattern spanning the signal pattern space. Multipattern detection methods can be applied either t...
Book•
01 Jan 1993
TL;DR: This book discusses the ecological framework, system overload: ancient and modern, population increase, poverty and health, and the growth of cities in the modern world.
Abstract: Preface Introduction 1. First things 2. The ecological framework 3. The health of populations 4. System overload: ancient and modern 5. Population increase, poverty and health 6. Greenhouse warming and climate change 7. The thinning ozone layer 8. Soil and water: loaves and fishes 9. Biodiversity: forests, food and pharmaceuticals 10. The growth of cities 11. Impediments I: conceptual blocks 12. Impediments II: relationships 13. The way ahead Glossary Index.
Book•
01 Jan 1993
TL;DR: In this paper, the authors discuss butterfly populations and distributions adaptations to climatic gradients and evolutionary history greenhouse gases, climatic change and butterfly populations, including butterflies and caterpillars.
Abstract: Weather, climate and butterfly biology climate, butterfly populations and distributions adaptations to climatic gradients climatic changes and evolutionary history greenhouse gases, climatic change and butterfly populations.
TL;DR: The developmental processes of seed production were shown to be highly sensitive, even within one growing season, to specific environmental perturbations which differed between sites.
Abstract: The effects of temperature, precipitation and nutrient perturbations, and their interactions, are being assessed on two contrasting arctic ecosystems to simulate impacts of climate change. One, a high arctic polar semi-desert community, is characterised by a sparse, low and aggregated vegetation cover where plant proliferation is by seedlings, whereas the other, a sub-arctic dwarf shrub heath, is characterised by a complete vegetation cover of erect, clonal dwarf shrubs which spread vegetatively. The developmental processes of seed production were shown to be highly sensitive, even within one growing season, to specific environmental perturbations which differed between sites
TL;DR: High-resolution, continuous glaciochemical records, newly retrieved from central Greenland, record the chemical composition of the arctic atmosphere at this time, showing that both the onset and termination of the Younger Dryas occurred within 10 to 20 years and that massive, frequent, and short-term changes in atmospheric composition occurred throughout this event.
Abstract: One of the most dramatic climate change events observed in marine and ice core records is the Younger Dryas, a return to near-glacial conditions that punctuated the last deglaciation. High-resolution, continuous glaciochemical records, newly retrieved from central Greenland, record the chemical composition of the arctic atmosphere at this time. This record shows that both the onset and the termination of the Younger Dryas occurred within 10 to 20 years and that massive, frequent, and short-term (decadal or less) changes in atmospheric composition occurred throughout this event. Changes in atmospheric composition are attributable to changes in the size of the polar atmospheric cell and resultant changes in source regions and to the growth and decay of continental biogenic source regions.
TL;DR: In this article, the authors use two general circulation models to estimate the transient response of the terrestrial surface to a step doubling of atmospheric CO2, and find that vegetation and soil changes could prove to be a significant source of CO2 in the first 50 to 100 years following a climate warming, increasing the atmospheric CO 2 concentration by up to a third of the present level.
Abstract: MODEL simulations suggest that at equilibrium, global warming driven by higher atmospheric concentrations of greenhouse gases will lead to increased terrestrial carbon storage1,2, implying a negative feedback between the global vegetation/soil system and the atmospheric CO2 concentration. But changes in vegetation and soil type that result in a net release of CO2 to the atmosphere (such as those caused by wildfires) could be more rapid than changes that result in a net increase in terrestrial carbon storage (such as species immigration and soil formation), so that in its transient response to climate change, the terrestrial vegetation/soil system could be a net source of carbon to the atmosphere. Here we use two general circulation models3,4 to estimate the transient response of the terrestrial surface to a step doubling of atmospheric CO2. We find that vegetation and soil changes could prove to be a significant source of CO2 in the first 50–100 years following a climate warming, increasing the atmospheric CO2 concentration by up to a third of the present level.
TL;DR: In this article, the authors present a δ13C record spanning the past 20 kyr from peats in the Nilgiri hills, southern India, and observe the key climate shifts that are already known to have occurred during the last glacial maximum (18 kyr ago) and the subsequent deglaciation.
Abstract: STABLE-ISOTOPE ratios of carbon in soils or lake sediments1–3 and of oxygen and hydrogen in peats4,5 have been found to reflect past moisture variations and hence to provide valuable palaeoclimate records. Previous applications of the technique to peat have been restricted to temperate regions, largely because tropical climate variations are less pronounced, making them harder to resolve. Here we present a δ13C record spanning the past 20 kyr from peats in the Nilgiri hills, southern India. Because the site is at high altitude (>2,000 m above sea level), it is possible to resolve a clear climate signal. We observe the key climate shifts that are already known to have occurred during the last glacial maximum (18 kyr ago) and the subsequent deglaciation. In addition, we observe an arid phase from 6 to 3.5 kyr ago, and a short, wet phase about 600 years ago. The latter appears to correspond to the Mediaeval Warm Period, which previously was believed to be confined to Europe and North America6,7. Our results therefore suggest that this event may have extended over the entire Northern Hemisphere.
TL;DR: In this article, the increase in the vigor of the hydrological cycle simulated in a 2 × CO2 experiment with the Canadian Climate Centre general circulation model is smaller than that obtained by other models which have similar increases in mean surface temperature.
Abstract: The increase in the vigor of the hydrological cycle simulated in a 2 × CO2 experiment with the Canadian Climate Centre general circulation model is smaller than that obtained by other models which have similar increases in mean surface temperature. The surface energy budget, which encompasses also the moisture budget for the oceans, is analyzed. Changes in the net radiative input to and sensible heat flux from the surface act to warm it. This is balanced, at the new equilibrium, by a change in the latent heat flux which acts to cool it. Although this same general behavior is seen in other models, the increase in radiative input to the surface in the CCC GCM is smaller than in other models while the change in the sensible heat flux is of similar size. As a consequence, the latent heat flux required for balance is smaller. The comparatively small increase in the net radiative input at the surface occurs because of a decrease in the solar component. On average the decrease in solar input in the tropical region outweighs the higher latitude increase associated with the snow/ice albedo feedback. The notable tropical decrease in solar input occurs because the albedo of the clouds increase enough in this region to outweigh a small decrease in cloud amount. The increase in cloud albedo in the warmer and moister tropical atmosphere is a consequence of the parameterized cloud optical properties in the model which play an important role in the regulation of the surface energy and moisture budgets. The results demonstrate some of the consequences of the negative feedback mechanism associated with increasing cloud albedo in the model. They also suggest that the simulated change in the vigor of the hydrological cycle is not a simple function of the average increase in surface temperature but is a consequence of all of the processes in the model which control the available energy at the surface as a function of latitude.
TL;DR: In this paper, the potential economic and agronomic impacts of gradual climate warming are examined at the farm level, and three models of the relevant climatic, agRONomic, and economic processes are developed and linked to address climate change impacts and agricultural adaptability.
Abstract: The potential economic and agronomic impacts of gradual climate warming are examined at the farm level. Three models of the relevant climatic, agronomic, and economic processes are developed and linked to address climate change impacts and agricultural adaptability. Several climate warming severity. The results indicate that grain farmers in southern Minnesota can effectively adapt to a gradually changing climate (warmer and either wetter or drier) by adopting later maturing cultivars, changing crop mix, and altering the timing of field operations to take advantage of a longer growing season resulting from climate warming.
TL;DR: In this paper, a detailed record of climate change in lowland equatorial Africa throughout the last deglaciation (12,800& ndash;10,000 14C yr BP) was presented based on analyses of diatom assemblages, geochemistry and magnetic mineralogy.
Abstract: THE last deglaciation was interrupted by an abrupt cooling event, the Younger Dryas, at 11,000& ndash;10,000 yr BP (uncalibrated radiocarbon timescale)1. Originally recognized in climate records from northwest Europe, the Younger Dryas has now been identified in marine and ice-core records worldwide2–6. In the tropics, a broadly contemporaneous change in climate is recorded by decreases in water levels and increased salinity of lakes7–9,14, indicating a period of arid climate caused by a reduction in ocean-to-land moisture flux. The exact timing of these changes in relation to the Younger Dryas event in high-latitude records has remained unclear, however. Here we present climate records based on analyses of diatom assemblages, geochemistry and magnetic mineralogy of radiocarbon-dated sequences of laminated lake sediments from Lake Magadi in the East African rift. These records provide a detailed record of climate change in lowland equatorial Africa throughout the last deglaciation (12,800& ndash;10,000 14C yr BP). We find that lake-level and humidity maxima coincide with the most rapid phases of ice melting in the Northern Hemisphere, and that the climate changes, including the Younger Dryas event, were synchronous at low and high latitudes. Thus, the effects of abrupt climate change appear to be felt at both high and low latitudes without a significant time lag.