Showing papers on "Climate change published in 1992"

Climate change : the IPCC scientific assessment

Abstract: Book review of the intergovernmental panel on climate change report on global warming and the greenhouse effect. Covers the scientific basis for knowledge of the future climate. Presents chemistry of greenhouse gases and mathematical modelling of the climate system. The book is primarily for government policy makers.

Climate Forcing by Anthropogenic Aerosols

Abstract: Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be –1 to –2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.

Biological invasions by exotic grasses, the grass/fire cycle, and global change

Abstract: Biological invasions into wholly new regions are a consequence of a far reaching but underappreciated component of global environmental change, the human-caused breakdown of biogeographic barriers to species dispersal . Human activity moves species from place to place both accidentally and deliberately-and it does so at rates that are without precedent in the last tens of millions of years. As a result , taxa that evolved in isolation from each other are being forced into contact in an instant of evolutionary time. This human-caused breakdown of barriers to dispersal sets in motion changes that may seem less important than the changing composition of the atmosphere , climate change , or tropical deforestation-but they are significant for several reasons. First , to date , biological invasions have caused more species extinctions than have resulted from human-caused climatic change or the changing composition of the atmosphere . Only land use change probably has caused more extinction, and (as we later discuss) land use change interacts strongly with biological invasions. Second, the effects of human-caused biological invasions are long-term: changes in climate, the atmosphere, and land use may be reversible in hundreds to thousands of years, but the breakdown of biogeographic barriers has resulted in self-maintaining and evolving

Tectonic forcing of late Cenozoic climate

Abstract: Global cooling in the Cenozoic, which led to the growth of large continental ice sheets in both hemispheres, may have been caused by the uplift of the Tibetan plateau and the positive feedbacks initiated by this event. In particular, tectonically driven increases in chemical weathering may have resulted in a decrease of atmospheric C02 concentration over the past 40 Myr.

Climate change 1992 : the supplementary report to the IPCC scientific assessment

Abstract: Foreword Preface 1992 Supplement A. Greenhouse gases A1. Sources and sinks A2. Radiative forcing of climate A3. Emissions scenarios for IPCC: an update B. Climate modelling, climate prediction and model validation C. Observed climate variability and change Annex Appendices. Sponsored jointly by the World Meteorological Organization and the United Nations Environment Programme

An optimal transition path for controlling greenhouse gases.

Abstract: Designing efficient policies to slow global warming requires an approach that combines economic tools with relations from the natural sciences. The dynamic integrated climate-economy (DICE) model presented here, an intertemporal general-equilibrium model of economic growth and climate change, can be used to investigate alternative approaches to slowing climate change. Evaluation of five policies suggests that a modest carbon tax would be an efficient approach to slow global warming, whereas rigid emissions- or climate-stabilization approaches would impose significant net economic costs.

Discrimination among semi-arid landscape endmembers using the Spectral Angle Mapper (SAM) algorithm

Abstract: Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were acquired during three consecutive seasons of the year (26 Sep. 1989, 22 Mar. 1990, and 7 Aug. 1990) over an area of the High Plains east of Greeley, Colorado. This region contains extensive eolian deposits in the form of stabilized dune complexes (small scale parabolic dunes superimposed on large scale longitudinal and parabolic dunes). Due to the dunes' large scale (2-10 km) and low relief (1-5 m), the scaling relationships that contribute to the evolution of this landscape are nearly impossible to understand without the use of remote sensing. Additionally, climate models indicate that the High Plains could be one of the first areas to experience changes in climate caused by either global warming or cooling. During the past 10,000 years there were at least three periods of extensive sand activity, followed by periods of landscape stability, as shown in the stratigraphic record of this area. Therefore, if the past is an indication of the future, the monitoring of this landscape and its sensitive ecosystem is important for early detection of regional and global climate change.

The hydrological cycle and its influence on climate

Abstract: The current theoretical and observational understanding of the roles of the hydrological cycle in the climate system and its intimate connection to the energy cycle is evaluated. An attempt is made to show why the hydrological cycle has emerged as the central element in studies of climate change and to anticipate the main advances expected in modeling and observations in the coming decade.

Implications for climate and sea level of revised IPCC emissions scenarios

Abstract: A new set of greenhouse gas emissions scenarios has been produced by the Intergovernmental Panel on Climate Change (IPCC). Incorporating these into models that also include the effects of C02 fertilization, feedback from stratospheric ozone depletion and the radiative effects of sulphate aerosols yields new projections for radiative forcing of climate and for changes in global-mean temperature and sea level. Changes in temperature and sea level are predicted to be less severe than those estimated previously, but are still far beyond the limits of natural variability.

Continuous 500,000-year climate record from vein calcite in devils hole, nevada.

Abstract: Oxygen-18 (δ18O) variations in a 36-centimeter-long core (DH-11) of vein calcite from Devils Hole, Nevada, yield an uninterrupted 500,000-year paleotemperature record that closely mimics all major features in the Vostok (Antarctica) paleotemperature and marine δ18O ice-volume records. The chronology for this continental record is based on 21 replicated mass-spectrometric uranium-series dates. Between the middle and latest Pleistocene, the duration of the last four glacial cycles recorded in the calcite increased from 80,000 to 130,000 years; this variation suggests that major climate changes were aperiodic. The timing of specific climatic events indicates that orbitally controlled variations in solar insolation were not a major factor in triggering deglaciations. Interglacial climates lasted about 20,000 years. Collectively, these observations are inconsistent with the Milankovitch hypothesis for the origin of the Pleistocene glacial cycles but they are consistent with the thesis that these cycles originated from internal nonlinear feedbacks within the atmosphere-ice sheet-ocean system.

Global warming and biological diversity

Abstract: This book discusses in detail the consequences of global warming for ecosystems and includes commentary by distinguished scientists on many aspects of this critical problem Considering a variety of specific ecosystems (tropical forests, the deciduous forests of eastern North America, the forests of the Pacific Northwest, Mediterranean-type ecosystems in California, arctic tundra and arctic marine systems), experts describe responses of animals and plants to previous climate changes, interactions between various environmental components, and synergies between climate change and human activites such as deforestation The theme of the book is that global warming could cause profound disruption of natural ecosystems and could threaten many species with extinction Warming, coupled with the effects of habitat destruction, could cause massive waves of extinctions such as have not been seen for millions of years The goal of the book is therefore to ensure that furtuer scientific and policy discussions of global warming pay adequate attention to natural ecosystems

Potential climate impact of Mount Pinatubo eruption

Abstract: The GISS global-climate model is used to make a preliminary estimate of Mount Pinatubo's climate impact. Assuming the aerosol optical depth is nearly twice as great as for the 1982 El Chichon eruption, the model forecasts a dramatic but temporary break in recent global warming trends. The simulations indicate that Pinatubo occurred too late in the year to prevent 1991 from becoming one of the warmest years in instrumental records, but intense aerosol cooling is predicted to begin late in 1991 and to maximize late in 1992. The predicted cooling is sufficiently large that by mid 1992 it should even overwhelm global warming associated with an El Nino that appears to be developing, but the El Nino could shift the time of minimum global temperature into 1993. The model predicts a return to record warm levels in the later 1990s. The effect is estimated of the predicted global cooling on such practical matters as the severity of the coming Soviet winter and the dates of cherry blossoming next spring.

Climate at the equilibrium line of glaciers

Abstract: The relationships between temperature, precipitation and radiation on glacier equilibrium lines are investigated, using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods. It is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months’ temperature in a free atmosphere, annual total precipitation, and the sum of global and long-wave net radiation. All of these are measured at or very near the equilibrium-line altitudes. Then, it is shown how the shift of the equilibriumline will occur as a result of a climatic change. Finally, the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations. The present results make it possible to identify the altitudes in climate models where glacierization should begin, and to evaluate the mass-balance changes as a result of possible future changes in the climate.

Sensitivity of glaciers and small ice caps to greenhouse warming.

Abstract: Recent field programs on glaciers have supplied information that makes simulation of glacier mass balance with meteorological models meaningful. An estimate of world-wide glacier sensitivity based on a modeling study of 12 selected glaciers situated in widely differing climatic regimes shows that for a uniform 1 K warming the area-weighted glacier mass balance will decrease by 0.40 meter per year. This corresponds to a sea-level rise of 0.58 millimeter per year, a value significantly less than earlier estimates.

Adapting stochastic weather generation algorithms for climate change studies

Abstract: While large-scale climate models (GCMs) are in principle the most appropriate tools for predicting climate changes, at present little confidence can be placed in the details of their projections. Use of tools such as crop simulation models for investigation of potential impacts of climatic change requires daily data pertaining to small spatial scales, not the monthly-averaged and large-scale information typically available from the GCMs. A method is presented to adapt stochastic weather generation models, describing daily weather variations in the present-day climate at particular locations, to generate synthetic daily time series consistent with assumed future climates. These assumed climates are specified in terms of the commonly available monthly means and variances of temperature and precipitation, including time-dependent (so-called ‘transient’) climate changes. Unlike the usual practice of applying assumed changes in mean values to historically observed data, simulation of meteorological time series also exhibiting changes in variability is possible. Considerable freedom in climate change ‘scenario’ construction is allowed. The results are suitable for investigating agricultural and other impacts of a variety of hypothetical climate changes specified in terms of monthly-averaged statistics.

Volcanic winter and accelerated glaciation following the Toba super-eruption

Abstract: Model calculations that investigate the possible climatic effects of the Toba volcanic cloud are presented. The increase in atmospheric opacity might have produced a 'volcanic winter', followed by a few years with maximum estimated annual hemispheric surface-temperature decreases of 3-5 C. The eruption occurred during the stage 5a-4 transition of the oxygen isotope record, a time of rapid ice growth and falling sea level. It is suggested that the Toba eruption may have greatly accelerated the shift to glacial conditions that was already under way, by inducing perennial snow cover and increased sea-ice extent at sensitive northern latitudes. As the onset of climate change may have helped to trigger the eruption itself, it is proposed that the Toba event may exemplify a more general climate-volcano feedback mechanism.

Time-dependent greenhouse warming computations with a coupled ocean-atmosphere model

Abstract: Climate changes during the next 100 years caused by anthropogenic emissions of greenhouse gases have been simulated for the Intergovernmental Panel on Climate Change Scenarios A (“business as usual”) and D (“accelerated policies”) using a coupled ocean-atmosphere general circulation model. In the global average, the near-surface temperature rises by 2.6 K in Scenario A and by 0.6 K in Scenario D. The global patterns of climate change for both IPCC scenarios and for a third step-function 2 x CO2 experiment were found to be very similar. The warming delay over the oceans is larger than found in simulations with atmospheric general circulation models coupled to mixed-layer models, leading to a more pronounced land-sea contrast and a weaker warming (and in some regions even an initial cooling) in the Southern Ocean. During the first forty years, the global warming and sea level rise due to the thermal expansion of the ocean are significantly slower than estimated previously from box-diffusion-upwelling models, but the major part of this delay can be attributed to the previous warming history prior to the start of present coupled ocean-atmosphere model integration (cold start).

Deep-sea food chains and the global carbon cycle

Abstract: Carbon dioxide and other "greenhouse" gases are increasing in the atmosphere due to the burning of fossil fuels, the destruction of rain forests, etc, leading to predictions of a gradual global warming which will perturb the global biosphere. An important process which counters this trend toward potential climate change is the removal of carbon dioxide from the surface ocean by photosynthesis. This process packages carbon in phytoplankton which enter the food chain or sink into the deep sea. Their ultimate fate is a "rain" or organic debris out of the surface-mixed layer of the ocean. On a global scale, the mechanisms and overall rate of this process are relatively little known. The authors of the 25 papers in this volume present their state-of-the-art approaches to quantifying the mechanisms by which the "rain" of biogenic debris nourishes deep ocean life. Prominent deep sea ecologists, geochemists and modellers address relationships between data and models of carbon fluxes and food chains in the deep ocean. An attempt is made to estimate the fate of carbon in the deep sea on a global scale by summing up the utilization of organic matter among all the populations of the abyssal biosphere. Comparisons are made been these ecological approaches and estimates of geochemical fluxes based on sediment trapping, one-dimensional geochemical models and horizontal (physical) input from continental margins. Planning interdisciplinary enterprises between geochemists and ecologists, including new field programmes, are summarized in the final chapter. The summary includes a list of the important gaps in understanding which must addressed before the role of the deep-sea biota in global-scale processes can be put in perspective.

Winter warming from large volcanic eruptions

Abstract: An examination of the Northern Hemisphere winter surface temperature patterns after the 12 largest volcanic eruptions from 1883-1992 shows warming over Eurasia and North America and cooling over the Middle East which are significant at the 95 percent level. This pattern is found in the first winter after tropical eruptions, in the first or second winter after midlatitude eruptions, and in the second winter after high latitude eruptions. The effects are independent of the hemisphere of the volcanoes. An enhanced zonal wind driven by heating of the tropical stratosphere by the volcanic aerosols is responsible for the regions of warming, while the cooling is caused by blocking of incoming sunlight.

Mapping eastern North American vegetation change of the past 18 ka: No-analogs and the future

Abstract: The method of modern analogs and an extensive data base of modern and fossil pollen data were used to generate a new series of paleovegetation maps for eastern North America spanning the past 18 ka. The maps illustrate the continuous nature of climate-induced vegetation change and the development, after about 10 ka, of modern regional vegetation patterns. Before the Holocene, vegetation biomes without modern analogs were widespread in response to climate conditions without modern analogs and, to a lesser extent, to the rapidity of climate change over the last glacial-interglacial transition. This geological perspective suggests that possible future climate changes could force similarly complex changes in natural vegetation, including the development of biomes without modern analogs.

Greenhouse Gas–induced Climate Change Simulated with the CCC Second-Generation General Circulation Model

Abstract: The Canadian Climate Centre second-generation atmospheric general circulation model coupled to a mixed-layer ocean incorporating thermodynamic sea ice is used to simulate the equilibrium climate response to a doubling of C02. Features of the simulation include the use of higher model resolution than previously for studies of this kind, specification of ocean heat transport for the open ocean and under sea ice, incorporation of information on vegetation and soil type in the treatment of land surface processes, and the inclusion of a parameterization of variable cloud optical properties. The results of the simulation indicate a global annual warming of 3.5°C with enhanced warming found over land and at higher latitudes. Precipitation and evaporation rates increase by about 4%, and cloud cover decreases by 2.2%. Soil moisture decreases over continental Northern Hemisphere land areas in summer. The frozen component of soil moisture decreases and the liquid component increases in association with the ...

Atmospheric Change: An Earth System Perspective

Abstract: Earth and Its Driving Forces. The Atmospheric Radiation Budget. The Atmospheric Circulation: Transorters of Chemical Constituents. Aerosols and Hydrosols. The Water Cycle and Climate. Chemical Principles. The Chemistry of the Atmosphere. Aquatic Chemistry. Ancient Earth: Climate Histories. Ancient Earth:Chemical Histories. Global Change: The Last Few Centuries. Global Change: The Last Several Decades. Budgets and Cycles. Building Environmental Chemical Models. Regional Futures. Global Futures. The Climate of the Far Future. On Change and Sustainability. Units of Measurement in Environmental Chemistry. Earth Data and Physical Constants. Answers to Selected Exercises.

The Southern Ocean Benthic Fauna and Climate Change: A Historical Perspective

Abstract: Environmental change is the norm and it is likely that, particularly on the geological timescale, the temperature regime experienced by marine organisms has never been stable. These temperature changes vary in timescale from daily, through seasonal variations, to long-term environmental change over tens of millions of years. Whereas physiological work can give information on how individual organisms may react phenotypically to short-term change, the way benthic communities react to long-term change can only be studied from the fossil record. The present benthic marine fauna of the Southern Ocean is rich and diverse, consisting of a mixture of taxa with differing evolutionary histories and biogeographical affinities, suggesting that at no time in the Cenozoic did continental ice sheets extend sufficiently to eradicate all shallow-water faunas around Antarctica at the same time. Nevertheless, certain features do suggest the operation of vicariant processes, and climatic cycles affecting distributional ranges and ice-sheet extension may both have enhanced speciation processes. The overall cooling of southern high-latitude seas since the mid-Eocene has been neither smooth nor steady. Intermittent periods of global warming and the influence of Milankovitch cyclicity is likely to have led to regular pulses of migration in and out of Antarctica. The resultant diversity pump may explain in part the high species richness of some marine taxa in the Southern Ocean. It is difficult to suggest how the existing fauna will react to present global warming. Although it is certain the fauna will change, as all faunas have done throughout evolutionary time, we cannot predict with confidence how it will do so.

Ethics, Public Policy, and Global Warming:

Abstract: There are many uncertainties concerning climate change, but a rough international consensus has emerged that a doubling of atmospheric carbon dioxide from its pre-industrial baseline is likely to lead to a 2.5 degree centigrade increase in the earth's mean surface temperature by the middle of the next century. Such a warming would have diverse impacts on human activities and would likely be catastrophic for many plants and nonhuman animals. The author's contention is that the problems engendered by the possibility of climate change are not purely scientific but also concern how we ought to live and how humans should relate to each other and to the rest of nature; and these are problems of ethics and politics.