Showing papers on "Climate change published in 1998"

The Regional Impacts of Climate Change: An Assessment of Vulnerability

Abstract: The Intergovernmental Panel on Climate Change (IPCC) was jointly established by the World Meteorological Organization and the United Nations Environment Programme in 1988 to assess the scientific and technical literature on climate change, the potential impacts of changes in climate, and options for adaption to and mitigation of climate change. Since its inception, the IPCC has produced a series of Assessment Reports, Special Reports, Technical Papers, methodologies and other products which have become standard works of reference, widely used by policymakers, scientists and other experts. This Special Report, which has been produced by Working Group II of the IPCC, builds on the Working Group's contribution to the Second Assessment Report (SAR), and incorporates more recent information made available since mid-1995. It has been prepared in response to a request from the Subsidiary Body for Scientific and Technological Advice (SBSTA) of the UN Framework Convention on Climate Change (UNFCCC). It addresses an important question posed by the Conference of the Parties (COP) to the UNFCCC, namely, the degree to which human conditions and the natural environment are vulnerable to the potential effects of climate change. The report establishes a common base of information regarding the potential costs and benefits of climatic change, including the evaluation of uncertainties, to help the COP determine what adaptation and mitigation measures might be justified. The report consists of vulnerability assessments for 10 regions that comprise the Earth's entire land surface and adjoining coastal seas: Africa, Arid Western Asia (including the Middle East), Australasia, Europe, Latin America, North America, the Polar Regions (The Arctic and the Antarctic), Small Island States, Temperate Asia and Tropical Asia. It also includes several annexes that provide information about climate observations, climate projections, vegetation distribution projections and socioeconomic trends.

Making mistakes when predicting shifts in species range in response to global warming

Abstract: Many attempts to predict the biotic responses to climate change rely on the 'climate envelope' approach, in which the current distribution of a species is mapped in climate-space and then, if the position of that climate-space changes, the distribution of the species is predicted to shift accordingly. The flaw in this approach is that distributions of species also reflect the influence of interactions with other species, so predictions based on climate envelopes may be very misleading if the interactions between species are altered by climate change. An additional problem is that current distributions may be the result of sources and sinks, in which species appear to thrive in places where they really persist only because individuals disperse into them from elsewhere. Here we use microcosm experiments on simple but realistic assemblages to show how misleading the climate envelope approach can be. We show that dispersal and interactions, which are important elements of population dynamics, must be included in predictions of biotic responses to climate change.

Climate Change 1995

Abstract: Climate Change 1995 is a scientific assessment that was generated by more than 1 000 contributors from over 50 nations. It was jointly co-ordinated through two international agencies; the World Meteorological Organization and the United Nations Environment Programme. The assessment was completed by the Intergovernmental Panel on Climate Change (IPCC) with a primary aim of reviewing the current state of knowledge concerning the impacts of climate change on physical and ecological systems, human health, and socioeconomic factors. The second aim was to review the available information on the technical and economic feasibility of the potential mitigation and adaptation strategies.

Drought-induced shift of a forest–woodland ecotone:Rapid landscape response to climate variation

Abstract: In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects—particularly those caused by mortality—largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon–juniper woodland shifted extensively (2 km or more) and rapidly (<5 years) through mortality of ponderosa pines in response to a severe drought. This shift has persisted for 40 years. Forest patches within the shift zone became much more fragmented, and soil erosion greatly accelerated. The rapidity and the complex dynamics of the persistent shift point to the need to represent more accurately these dynamics, especially the mortality factor, in assessments of the effects of climate change.

Simulated response of the ocean carbon cycle to anthropogenic climate warming

Abstract: A 1995 report1 of the Intergovernmental Panel on Climate Change provides a set of illustrative anthropogenic CO2 emission models leading to stabilization of atmospheric CO2 concentrations ranging from 350 to 1,000 p.p.m. (1–4). Ocean carbon-cycle models used in calculating these scenarios assume that oceanic circulation and biology remain unchanged through time. Here we examine the importance of this assumption by using a coupled atmosphere–ocean model of global warming5 for the period 1765 to 2065. We find a large potential modification to the ocean carbon sink in a vast region of the Southern Ocean where increased rainfall leads to surface freshening and increased stratification6. The increased stratification reduces the downward flux of carbon and the loss of heat to the atmosphere, both of which decrease the oceanic uptake of anthropogenic CO2 relative to a constant-climate control scenario. Changes in the formation, transport and cycling of biological material may counteract the reduced uptake, but the response of the biological community to the climate change is difficult to predict on present understanding. Our simulation suggests that such physical and biological changes might already be occurring, and that they could substantially affect the ocean carbon sink over the next few decades.

Human choice and climate change

Abstract: This is four-part work providing an international view of climate change which is designed to complement the Intergovernmental Panel on Climate Change Second Assessment report. The complete work is a benchmark document summarising current understanding of of the contributions of the social sciences to the interdisciplinary issues of global climate change. It brings together widely scattered information and highlights both current research strengths and key areas for further research. The books survey the state of the art of the social sciences with regard to global climate change research; recognise global climate change research as policy relevant; review what is currently known, uncertain, and unknown in the social science areas relevant to global change; assemble and summarise findings from the international research community; report these findings within behavioural and interpretive frameworks as appropriate; and assemble this information to enlighten the future formulation and conduct of policy-relevant scientific research. The volumes in this four-part work cover resources and technology (Volume 2); tools for policy analysis (Volume 3); and, in Volume 1, begin with the societal framework. Volume 4 is presented as a readable summary for non-professionals. The first chapter of Volume 4 comprises the introductory section of each of the three more specialist volumes.

Asynchrony of Antarctic and Greenland climate change during the last glacial period

Abstract: A central issue in climate dynamics is to understand how the Northern and Southern hemispheres are coupled during climate events. The strongest of the fast temperature changes observed in Greenland (so-called Dansgaard–Oeschger events) during the last glaciation have an analogue in the temperature record from Antarctica. A comparison of the global atmospheric concentration of methane as recorded in ice cores from Antarctica and Greenland permits a determination of the phase relationship (in leads or lags) of these temperature variations. Greenland warming events around 36 and 45 kyr before present lag their Antarctic counterpart by more than 1 kyr. On average, Antarctic climate change leads that of Greenland by 1–2.5 kyr over the period 47–23 kyr before present.

Predicting abundance of 80 tree species following climate change in the eastern united states

Abstract: Projected climate warming will potentially have profound effects on the earth's biota, including a large redistribution of tree species. We developed models to evaluate potential shifts for 80 individual tree species in the eastern United States. First, environmental factors associated with current ranges of tree species were assessed using geographic information systems (GIS) in conjunction with regression tree analysis (RTA). The method was then extended to better understand the potential of species to survive and/ or migrate under a changed climate. We collected, summarized, and analyzed data for climate, soils, land use, elevation, and species assemblages for .2100 counties east of the 100th meridian. Forest Inventory Analysis (FIA) data for .100 000 forested plots in the East provided the tree species range and abundance information for the trees. RTA was used to devise prediction rules from current species-environment relationships, which were then used to replicate the current distribution as well as predict the future potential distri- butions under two scenarios of climate change with twofold increases in the level of at- mospheric CO2. Validation measures prove the utility of the RTA modeling approach for mapping current tree importance values across large areas, leading to increased confidence in the predictions of potential future species distributions. With our analysis of potential effects, we show that roughly 30 species could expand their range and/or weighted importance at least 10%, while an additional 30 species could decrease by at least 10%, following equilibrium after a changed climate. Depending on the global change scenario used, 4-9 species would potentially move out of the United States to the north. Nearly half of the species assessed (36 out of 80) showed the potential for the ecological optima to shift at least 100 km to the north, including seven that could move .250 km. Given these potential future distributions, actual species redistributions will be controlled by migration rates possible through fragmented landscapes.

Correlation between Arabian Sea and Greenland climate oscillations of the past 110,000 years

Abstract: Palaeoclimate studies have revealed the general high-frequency instability of Late Pleistocene climate—for example, the so-called Dansgaard–Oeschger and Heinrich events—on timescales of a few millennia, centuries or even decades1,11. Here we present evidence for a general relationship between low-latitude monsoonal climate variability and the rapid temperature fluctuations of high northern latitudes that are recorded in the Greenland ice records. Sediment cores from the northeastern Arabian Sea show laminated, organic-carbon-rich bands, reflecting strong monsoon-induced biological productivity, that correlate with the mild interstadial climate events in the northern North Atlantic region. In contrast, periods of lowered southwest monsoonal intensity, indicated by bioturbated, organic-carbon-poor bands, are associated with intervals of high-latitude atmospheric cooling and the injection of melt water into the North Atlantic basin. Our records suggest that Dansgaard–Oeschger and Heinrich events are strongly expressed in low-latitude (monsoonal) climate variability, suggesting the importance of common forcing agents such as atmospheric moisture and other greenhouse gases.

Climate Change and Forest Fire Potential in Russian and Canadian Boreal Forests

Abstract: In this study outputs from four current General Circulation Models (GCMs) were used to project forest fire danger levels in Canada and Russia under a warmer climate. Temperature and precipitation anomalies between 1 × CO2 and 2 × CO2 runs were combined with baseline observed weather data for both countries for the 1980–1989 period. Forecast seasonal fire weather severity was similar for the four GCMs, indicating large increases in the areal extent of extreme fire danger in both countries under a 2 × CO2 climate scenario. A monthly analysis, using the Canadian GCM, showed an earlier start to the fire season, and significant increases in the area experiencing high to extreme fire danger in both Canada and Russia, particularly during June and July. Climate change as forecast has serious implications for forest fire management in both countries. More severe fire weather, coupled with continued economic constraints and downsizing, mean more fire activity in the future is a virtual certainty. The likely response will be a restructuring of protection priorities to support more intensive protection of smaller, high-value areas, and a return to natural fire regimes over larger areas of both Canada and Russia, with resultant significant impacts on the carbon budget.

World Carbon Dioxide Emissions: 1950–2050

Abstract: Emissions of carbon dioxide from the combustion of fossil fuels, which may contribute to long-term climate change, are projected through 2050 using reduced-form models estimated with national-level panel data for the period of 1950–1990. Using the same set of income and population growth assumptions as the Intergovernmental Panel on Climate Change (IPCC), we find that the IPCC's widely used emissions growth projections exhibit significant and substantial departures from the implications of historical experience. Our model employs a flexible form for income effects, along with fixed time and country effects, and we handle forecast uncertainty explicitly. We find clear evidence of an “inverse U” relation with a within-sample peak between carbon dioxide emissions (and energy use) per capita and per-capita income.

Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice

Abstract: Rapid temperature change fractionates gas isotopes in unconsolidated snow, producing a signal that is preserved in trapped air bubbles as the snow forms ice The fractionation of nitrogen and argon isotopes at the end of the Younger Dryas cold interval, recorded in Greenland ice, demonstrates that warming at this time was abrupt This warming coincides with the onset of a prominent rise in atmospheric methane concentration, indicating that the climate change was synchronous (within a few decades) over a region of at least hemispheric extent, and providing constraints on previously proposed mechanisms of climate change at this time The depth of the nitrogen-isotope signal relative to the depth of the climate change recorded in the ice matrix indicates that, during the Younger Dryas, the summit of Greenland was 15 ± 3 °C colder than today

Dynamic responses of terrestrial ecosystem carbon cycling to global climate change

Abstract: Terrestrial ecosystems and the climate system are closely coupled, particularly by cycling of carbon between vegetation, soils and the atmosphere. It has been suggested1,2 that changes in climate and in atmospheric carbon dioxide concentrations have modified the carbon cycle so as to render terrestrial ecosystems as substantial carbon sinks3,4; but direct evidence for this is very limited5,6. Changes in ecosystem carbon stocks caused by shifts between stable climate states have been evaluated7,8, but the dynamic responses of ecosystem carbon fluxes to transient climate changes are still poorly understood. Here we use a terrestrial biogeochemical model9, forced by simulations of transient climate change with a general circulation model10, to quantify the dynamic variations in ecosystem carbon fluxes induced by transient changes in atmospheric CO2 and climate from 1861 to 2070. Wepredict that these changes increase global net ecosystem production significantly, but that this response will decline as the CO2 fertilization effect becomes saturated and is diminished by changes in climatic factors. Thus terrestrial ecosystem carbon fluxes both respond to and strongly influence the atmospheric CO2 increase and climate change.

Interactions between the atmosphere and terrestrial ecosystems: influence on weather and climate

Abstract: This paper overviews the short-term (biophysical) and long-term (out to around 100 year timescales; biogeochemical and biogeographical) influences of the land surface on weather and climate. From our review of the literature, the evidence is convincing that terrestrial ecosystem dynamics on these timescales significantly influence atmospheric processes. In studies of past and possible future climate change, terrestrial ecosystem dynamics are as important as changes in atmospheric dynamics and composition, ocean circulation, ice sheet extent, and orbit perturbations.

New Estimates of the Damage Costs of Climate Change

Abstract: Monetised estimates of the impact of climate change are derived. Impacts are expressed as functions of climate change and 'vulnerability'. Vulnerability is measured by a series of indicators, such as per capita income, population above 65, and economic structure. Impacts are estimated for nine world regions, for the period 2000-2200, for agriculture, forestry, water resources, energy consumption, sea level rise, ecosystems, fatal vector- borne diseases, and fatal cardiovascular and respiratory disorders. Uncertainties are large, often including sign switches. In the short term, the estimated sensitivity of a sector to climate change is found to be the crucial parameter. In the longer term, the change in the vulnerability of the sector is often more important for the total impact. Impacts can be negative or positive, depending on the time, region, and sector one is looking at. Negative impacts tend to dominate in the later years and in the poorer regions.

Effects of global climate change on agriculture: an interpretative review

Abstract: Climate is the primary determinant of agricultural productivity. Concern over the poten- tial effects of long-term climatic change on agriculture has motivated a substantial body of research over the past decade. This body of research addresses possible physical effects of climatic change on agriculture, such as changes in crop and livestock yields, as well as the economic consequences of these potential yield changes. This paper reviews the extant literature on these physical and economic effects and interprets this research in terms of common themes or findings. Of particular interest are findings concerning the role of human adaptations in responding to climate change, possible regional impacts to agricultural systems and potential changes in patterns of food production and prices. Limi- tations and sensitivities of these findings are discussed and key areas of uncertainty are highlighted. Finally, some speculations regarding issues of potential importance in interpreting and using informa- tion on climate change and agriculture are presented.

An Interim Evaluation of Sulfur Dioxide Emissions Trading

Abstract: ide IV of the 1990 Clean Air Act Amendments established the first large-scale, long-term environmental program to rely on tradable emissions permitscalled "allowances" in this program-to control pollution. This program was designed to cut acid rain by reducing sulfur dioxide (SO2) emissions from electric generating plants to about half their 1980 level, beginning in 1995. It is of interest both as a response to an important environmental issue and as a landmark experiment in environmental policy. This experiment comes at a particularly important time, since emission trading is under serious consideration, with strong U.S. backing, for use to deal with global climate change by curbing emissions of carbon dioxide (CO2). The economic stakes in climate change surpass those in acid rain by several orders of magnitude (Intergovernmental Panel on Climate Change, 1996). This article summarizes the results to date of our ongoing empirical analysis of compliance costs and allowance market performance under the U.S. acid rain program.'

Effects of climate and atmospheric CO2 partial pressure on the global distribution of C4 grasses: present, past, and future

Abstract: C4 photosynthetic physiologies exhibit fundamentally different responses to temperature and atmospheric CO2 partial pressures (pCO2) compared to the evolutionarily more primitive C3 type. All else being equal, C4 plants tend to be favored over C3 plants in warm humid climates and, conversely, C3 plants tend to be favored over C4 plants in cool climates. Empirical observations supported by a photosynthesis model predict the existence of a climatological crossover temperature above which C4 species have a carbon gain advantage and below which C3 species are favored. Model calculations and analysis of current plant distribution suggest that this pCO2-dependent crossover temperature is approximated by a mean temperature of 22°C for the warmest month at the current pCO2 (35 Pa). In addition to favorable temperatures, C4 plants require sufficient precipitation during the warm growing season. C4 plants which are predominantly graminoids of short stature can be competitively excluded by trees (nearly all C3 plants) - regardless of the photosynthetic superiority of the C4 pathway - in regions otherwise favorable for C4. To construct global maps of the distribution of C4 grasses for current, past and future climate scenarios, we make use of climatological data sets which provide estimates of the mean monthly temperature to classify the globe into areas which should favor C4 photosynthesis during at least 1 month of the year. This area is further screened by excluding areas where precipitation is <25 mm per month during the warm season and by selecting areas classified as grasslands (i.e., excluding areas dominated by woody vegetation) according to a global vegetation map. Using this approach, grasslands of the world are designated as C3, C4, and mixed under current climate and pCO2. Published floristic studies were used to test the accuracy of these predictions in many regions of the world, and agreement with observations was generally good. We then make use of this protocol to examine changes in the global abundance of C4 grasses in the past and the future using plausible estimates for the climates and pCO2. When pCO2 is lowered to pre-industrial levels, C4 grasses expanded their range into large areas now classified as C3 grasslands, especially in North America and Eurasia. During the last glacial maximum (∼18 ka BP) when the climate was cooler and pCO2 was about 20 Pa, our analysis predicts substantial expansion of C4 vegetation - particularly in Asia, despite cooler temperatures. Continued use of fossil fuels is expected to result in double the current pCO2 by sometime in the next century, with some associated climate warming. Our analysis predicts a substantial reduction in the area of C4 grasses under these conditions. These reductions from the past and into the future are based on greater stimulation of C3 photosynthetic efficiency by higher pCO2 than inhibition by higher temperatures. The predictions are testable through large-scale controlled growth studies and analysis of stable isotopes and other data from regions where large changes are predicted to have occurred.

The Sun's total irradiance: Cycles, trends and related climate change uncertainties since 1976

Abstract: A composite record of the Sun's total irradiance compiled from measurements made by five independent space-based radiometers since 1978 exhibits a prominent 11-year cycle with similar levels during 1986 and 1996, the two most recent minimum epochs of solar activity. This finding contradicts recent assertions of a 0.04% irradiance increase from the 1986 to 1996 solar minima and suggests that solar radiative output trends contributed little of the 0.2°C increase in the global mean surface temperature in the past decade. Nor does our 18-year composite irradiance record support a recent upward irradiance trend inferred from solar cycle length, a parameter used to imply a close linkage in the present century between solar variability and climate change.

Effect of interannual climate variability on carbon storage in Amazonian ecosystems

Abstract: The Amazon Basin contains almost one-half of the world's undisturbed tropical evergreen forest as well as large areas of tropical savanna1,2. The forests account for about 10 per cent of the world's terrestrial primary productivity and for a similar fraction of the carbon stored in land ecosystems2,3, and short-term field measurements4 suggest that these ecosystems are globally important carbon sinks. But tropical land ecosystems have experienced substantial interannual climate variability owing to frequent El Nino episodes in recent decades5. Of particular importance to climate change policy is how such climate variations, coupled with increases in atmospheric CO2 concentration, affect terrestrial carbon storage6,7,8. Previous model analyses have demonstrated the importance of temperature in controlling carbon storage9,10. Here we use a transient process-based biogeochemical model of terrestrial ecosystems3,11 to investigate interannual variations of carbon storage in undisturbed Amazonian ecosystems in response to climate variability and increasing atmospheric CO2 concentration during the period 1980 to 1994. In El Nino years, which bring hot, dry weather to much of the Amazon region, the ecosystems act as a source of carbon to the atmosphere (up to 0.2 petagrams of carbon in 1987 and 1992). In other years, these ecosystems act as a carbon sink (up to 0.7 Pg C in 1981 and 1993). These fluxes are large; they compare to a 0.3 Pg C per year source to the atmosphere associated with deforestation inthe Amazon Basin in the early 1990s12. Soil moisture, which is affected by both precipitation and temperature, and which affects both plant and soil processes, appears to be an important control on carbon storage.

Simulation of modern and glacial climates with a coupled global model of intermediate complexity

Abstract: A global coupled ocean–atmosphere model of intermediate complexity is used to simulate the equilibrium climate of both today and the Last Glacial Maximum, around 21,000 years ago. The model successfully predicts the atmospheric and oceanic circulations, temperature distribution, hydrological cycle and sea-ice cover of both periods without using ‘flux adjustments’. Changes in oceanic circulation, particularly in the Atlantic Ocean, play an important role in glacial cooling.

Climate change and its impacts on glaciers and permafrost in the Alps

Abstract: Climate change in the European Alps during the 20th century has been characterized by increases in minimum temperatures of about 20C, a more modest increase in maximum temperatures, little trend in precipitation data, and a general decrease of sunshine duration through to the mid-1980s. Temperature increase has been most intense in the 1 940s, followed by the 1 980s. The warming experienced since the early 1980s, while synchronous with the global warming, is of far greater amplitude and reaches close to 1 OC for this ensemble average and up to 20C for individual sites. Such changes caused pronounced effects in the glacial and periglacial belts. Since the middle of the past century-the end of the Little Ice Age-the glacierization of the European Alps has lost about 30 to 40% in surface area and around half its original volume. The estimated total glacier volume in the European Alps was some 130 km3 for the mid-1 970s, but strongly negative mass balances have caused an additional loss of about 10 to 20% of this remaining ice volume since 1980. Periglacial permafrost in the Alps today occupies an area comparable to the glacierized area and must have been affected as well, but its secular evolution is much less well known. Simulations of high-resolution climatologies for double-CO2 situations using regional climate models (RCM) with a 20-km horizontal grid give generally higher winter temperatures, a more marked increase in summer temperatures, indications that temperature increases more at higher elevations than at lower altitudes, and higher/ more intense precipitation in winter, but much dryer conditions in summer. Under such conditions, the Alps would lose major parts of their glacier cover within decades, warming of cold firn areas at high altitudes could become pronounced and lower limits of permafrost occurrence in the Alps could rise by several hundred meters. Pronounced disequilibria could result, in the water cycle, in mass wasting processes, and in sediment flux as well as in growth conditions of vegetation. For those directly involved with such changes, the main challenge would be to adapt to high and accelerating rates of environment evolution. Empirical knowledge would have to be replaced increasingly by improved process understanding, especially concerning runoff formation and slope stability. In view of the uncertainties involved with future projections, highest priority should be given to appropriate monitoring programs.

The timing of Pleistocene glaciations from a simple multiple-state climate model

Abstract: The Earth's climate over the past million years has been characterized by a succession of cold and warm periods, known as glacial–interglacial cycles, with periodicities corresponding to those of the Earth's main orbital parameters; precession (23 kyr), obliquity (41 kyr) and eccentricity (100 kyr). The astronomical theory of climate, in which the orbital variations are taken to drive the climate changes, has been very successful in explaining many features of the palaeoclimate records1. Nevertheless, the timing of the main glacial and interglacial periods remains puzzling in many respects2,3,4,5. In particular, the main glacial–interglacial switches occur approximately every 100 kyr, but the changes in insolation forcing are very small in this frequency band. Similarly, an especially warm interglacial episode, about 400,000 years ago7, occurred at a time when insolation variations were minimal. Here I propose that multiple equilibria in the climate system can provide a resolution of these problems within the framework of astronomical theory. I present two simple models that successfully simulate each glacial–interglacial cycle over the late Pleistocene epoch at the correct time and with approximately the correct amplitude. Moreover, in a simulation over the past 2 million years, the onset of the observed prominent ∼100-kyr cycles around 0.8 to 1 million years ago is correctly reproduced.

Changes in the Extremes of the Climate Simulated by CCC GCM2 under CO2 Doubling

Abstract: Changes due to CO2 doubling in the extremes of the surface climate as simulated by the second-generation circulation model of the Canadian Centre for Climate Modelling and Analysis are studied in two 20-yr equilibrium simulations. Extreme values of screen temperature, precipitation, and near-surface wind in the control climate are compared to those estimated from 17 yr of the NCEP‐NCAR reanalysis data and from some Canadian station data. The extremes of screen temperature are reasonably well reproduced in the control climate. Their changes under CO2 doubling can be connected with other physical changes such as surface albedo changes due to the reduction of snow and sea ice cover as well as a decrease of soil moisture in the warmer world. The signal in the extremes of daily precipitation and near-surface wind speed due to CO 2 doubling is less obvious. The precipitation extremes increase almost everywhere over the globe. The strongest change, over northwest India, is related to the intensification of the summer monsoon in this region in the warmer world. The modest reduction of wind extremes in the Tropics and middle latitudes is consistent with the reduction of the meridional temperature gradient in the 23CO2 climate. The larger wind extremes occur in the areas where sea ice has retreated.

Rethinking the role of adaptation in climate policy

Abstract: Since the late 1980s, scientists and policy makers have devoted considerable attention and resources to the issue of global climate change. Domestic and international policies in response focus primarily on prevention of future climate impacts on society through the mitigation of carbon dioxide emissions. Academic and political attention is also largely focused on issues of mitigation. Adaptation refers to adjustments in individual, group, and institutional behavior in order to reduce society’s vulnerabilities to climate, and thus reduce its impacts. In 1996, the Intergovernmental Panel on Climate Change (IPCC) wrote that adaptation offers a ‘very powerful option’ for responding to climate change and ought to be viewed as a ‘complement’ to mitigation efforts. Yet, the IPCC also wrote that ‘little attention has been paid to any possible tradeoff between both types of options’. This paper discusses the limitations of mitigation responses and the need for adaptation to occupy a larger role in climate policy.

Climate forcings in the Industrial era

Abstract: The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHGs alone. Current trends in GHG climate forcings are smaller than in popular "business as usual" or 1% per year CO2 growth scenarios. The summary implication is a paradigm change for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.

Modelling the response of glaciers to climate warming

Abstract: Dynamic ice-flow models for 12 glaciers and ice caps have been forced with various climate change scenarios The volume of this sample spans three orders of magnitude Six climate scenarios were considered: from 1990 onwards linear warming rates of 001, 002 and 004 K a-1, with and without concurrent changes in precipitation The models, calibrated against the historic record of glacier length where possible, were integrated until 2100 The differences in individual glacier responses are very large No straightforward relationship between glacier size and fractional change of ice volume emerges for any given climate scenario The hypsometry of individual glaciers and ice caps plays an important role in their response, thus making it difficult to generalize results For a warming rate of 004 K a-1, without increase in precipitation, results indicate that few glaciers would survive until 2100 On the other hand, if the warming rate were to be limited to 001 K a-1 with an increase in precipitation of 10% per degree warming, we predict that overall loss would be restricted to 10 to 20% of the 1990 volume

Dengue fever epidemic potential as projected by general circulation models of global climate change

Abstract: Climate factors influence the transmission of dengue fever, the world's most widespread vector-borne virus. We examined the potential added risk posed by global climate change on dengue transmission using computer-based simulation analysis to link temperature output from three climate general circulation models (GCMs) to a dengue vectorial capacity equation. Our outcome measure, epidemic potential, is the reciprocal of the critical mosquito density threshold of the vectorial capacity equation. An increase in epidemic potential indicates that a smaller number of mosquitoes can maintain a state of endemicity of disease where dengue virus is introduced. Baseline climate data for comparison are from 1931 to 1980. Among the three GCMs, the average projected temperature elevation was 1.16 degrees C, expected by the year 2050. All three GCMs projected a temperature-related increase in potential seasonal transmission in five selected cities, as well as an increase in global epidemic potential, with the largest area change occurring in temperate regions. For regions already at risk, the aggregate epidemic potential across the three scenarios rose on average between 31 and 47% (range, 24-74%). If climate change occurs, as many climatologists believe, this will increase the epidemic potential of dengue-carrying mosquitoes, given viral introduction and susceptible human populations. Our risk assessment suggests that increased incidence may first occur in regions bordering endemic zones in latitude or altitude. Endemic locations may be at higher risk from hemorrhagic dengue if transmission intensity increases.

The implications of predicted climate change for insect pests in the UK, with emphasis on non‐indigenous species

Abstract: Recent estimates for global warming predict increases in global mean surface air temperatures (relative to 1990) of between 1 and 3.5 °C, by 2100. The impact of such changes on agricultural systems in mid- to high-latitude regions are predicted to be less severe than in low-latitude regions, and possibly even beneficial, although the influence of pests and diseases is rarely taken into account. Most studies have concluded that insect pests will generally become more abundant as temperatures increase, through a number of inter-related processes, including range extensions and phenological changes, as well as increased rates of population development, growth, migration and over-wintering. A gradual, continuing rise in atmospheric CO2 will affect pest species directly (i.e. the CO2 fertilization effect) and indirectly (via interactions with other environmental variables). However, individual species responses to elevated CO2 vary: consumption rates of insect herbivores generally increase, but this does not necessarily compensate fully for reduced leaf nitrogen. The consequent effects on performance are strongly mediated via the host species. Some recent experiments under elevated CO2 have suggested that aphids may become more serious pests, although other studies have discerned no significant effects on sap-feeding homopterans. However, few, if any of these experiments have fully considered the effects on pest population dynamics. Climate change is also considered from the perspective of changes in the distribution and abundance of species and communities. Marked changes in the distribution of well-documented species – including Odonata, Orthoptera and Lepidoptera – in north-western Europe, in response to unusually hot summers, provide useful indications of the potential effects of climate change. Migrant pests are expected to respond more quickly to climate change than plants, and may be able to colonize newly available crops/habitats. Range expansions, and the removal of edge effects, could result in the increased abundance of species presently near the northern limits of their ranges in the UK. However, barriers to range expansions, or shifts, may include biotic (competition, predation, parasitism and disease), as well as abiotic, factors. Climatic phenomena, ecosystem processes and human activities are interactive and interdependent, making long-term predictions extremely tenuous. Nevertheless, it appears prudent to prepare for the possibility of increases in the diversity and abundance of pest species in the UK, in the context of climate change.

Soil processes and global change

Abstract: Contributors to the Intergovernmental Panel on Climate Change (IPCC) generally agree that increases in the atmospheric concentration of greenhouse trace gases (i.e., CO2, CH4, N2O, O3) since preindustrial times, about the year 1750, have led to changes in the earth's climate. During the past 250 years the atmospheric concentrations of CO2, CH4, and N2O have increased by 30, 145, and 15%, respectively. A doubling of preindustrial CO2 concentrations by the end of the twenty-first century is expected to raise global mean surface temperature by about 2 °C and increase the frequency of severe weather events. These increases are attributed mainly to fossil fuel use, land-use change, and agriculture. Soils and climate changes are related by bidirectional interactions. Soil processes directly affect climatic changes through the production and consumption of CO2, CH4, and N2O and, indirectly, through the production and consumption of NH3, NOx, and CO. Although CO2 is primarily produced through fossil fuel combustion, land-use changes, conversion of forest and grasslands to agriculture, have contributed significantly to atmospheric increase of CO2. Changes in land use and management can also result in the net uptake, sequestration, of atmospheric CO2. CH4 and N2O are produced (30% and 70%, respectively) in the soil, and soil processes will likely regulate future changes in the atmospheric concentration of these gases. The soil-atmosphere exchange of CO2, CH4, and N2O are interrelated, and changes in one cycle can impart changes in the N cycle and resulting soil-atmosphere exchange of N2O. Conversely, N addition increases C sequestration. On the other hand, soil processes are influenced by climatic change through imposed changes in soil temperature, soil water, and nutrient competition. Increasing concentrations of atmospheric CO2 alters plant response to environmental parameters and frequently results in increased efficiency in use of N and water. In annual crops increased CO2 generally leads to increased crop productivity. In natural systems, the long-term impact of increased CO2 on ecosystem sustainability is not known. These changes may also result in altered CO2, CH4, and N2O exchange with the soil. Because of large temporal and spatial variability in the soil-atmosphere exchange of trace gases, the measurement of the absolute amount and prediction of the changes of these fluxes, as they are impacted by global change on regional and global scales, is still difficult. In recent years, however, much progress has been made in decreasing the uncertainty of field scale flux measurements, and efforts are being directed to large scale field and modeling programs. This paper briefly relates soil process and issues akin to the soil-atmosphere exchange of CO2, CH4, and N2O. The impact of climate change, particularly increasing atmospheric CO2 concentrations, on soil processes is also briefly discussed.