Showing papers on "Climate change published in 1987"
TL;DR: In this paper, the authors reviewed the available information on El Nino occurrences, a regional manifestation of the large-scale (El Nino-Southern Oscillation (ENSO)) event, based on evidence obtained from the west coast region of northern South America and its adjacent Pacific Ocean waters.
Abstract: Applicable publications, involving five languages, have been reviewed to obtain information on El Ninos that occurred over the past four and a half centuries. Since this information refers strictly to El Nino occurrences, a regional manifestation of the large-scale (El Nino-Southern Oscillation (ENSO)) event, it is based primarily on evidence obtained from the west coast region of northern South America and its adjacent Pacific Ocean waters. Authored lists of events were not acceptable without referenced valid information sources. It was desirable to have cross-correlated reports from independent sources. Relative strengths of events are based on such considerations as wind and current effects on travel times of ancient sailing ships, degree of physical damage and destruction, amounts of rainfall and flooding, mass mortality of endemic marine organisms and guano birds, extent of invasion by tropical nekton, rises in sea temperatures and sea levels, affects on coastal fisheries and fish meal production, etc. Emphasis is placed on strong and very strong events. For example, the 1940–1941, 1957–1958, and 1972–1973 events fall into the strong category, whereas the 1891, 1925–1926 and 1982–1983 events are considered very strong. Over our period of study, 47 El Nino events were placed in the strong or very strong categories. Over the period 1800-present, we noted 32 El Nino events of moderate or near moderate intensity. Weak events are not included here. The approach used here caused us to revise many of our earlier evaluations concerning event occurrences and intensities. Our tropical Pacific thickness analyses and cumulative plots of Southern Oscillation index anomalies over the southeast Pacific trade wind zone showed additional evidence as to the unusual strength of the 1982–1983 event. Also, in our investigation we noted several periods of long-term (near decadal or longer) climatic change.
693 citations
TL;DR: In this article, the first assessment of the potential climatic effects of increased CO2 were performed using simplified climate models, namely, energy balance models (EBMs) and radiative-convective models (RCMs).
Abstract: The first assessments of the potential climatic effects of increased CO2 were performed using simplified climate models, namely, energy balance models (EBMs) and radiative-convective models (RCMs). A wide range of surface temperature warming has been obtained by surface EBMs as a result of the inherent difficulty of these models in specifying the behavior of the climate system away from the energy balance level. RCMs have given estimates of ΔTs for a CO2 doubling that range from 0.48° to 4.2°C. This response can be characterized by ΔTs = ΔRTG0/(1 - f), where ΔRT is the radiative forcing at the tropopause due to the CO2 doubling (∼4 W m−2), G0 is the gain of the climate system without feedbacks (∼0.3°C/(W m−2)), and f is the feedback. The feedback processes in RCMs include water vapor feedback (f is 0.3 to 0.4), moist adiabatic lapse rate feedback (f is −0.25 to −0.4), cloud altitude feedback (f is 0.15 to 0.30), cloud cover feedback (f is unknown), cloud optical depth feedback (f is 0 to −1.32), and surface albedo feedback (f is 0.14 to 0.19). However, these feedbacks can be predicted credibly only by physically based models that include the essential dynamics and thermodynamics of the feedback processes. Such physically based models are the general circulation models (GCMs). The earliest GCM simulations of CO2-induced climate change were performed without the annual insolation cycle. These “annual mean” simulations gave for a CO2 doubling a global mean surface air temperature warming of 1.3° to 3.9°C, an increase in the global mean precipitation rate of 2.7 to 7.8%, and an indication of a soil moisture drying in the middle latitudes. The first GCM simulation of the seasonal variation of CO2-induced climate change was performed for a CO2 quadrupling and obtained annual global mean surface temperature and precipitation changes of 4.1°C and 6.7%, respectively. Substantial seasonal differences in the CO2-induced climate changes were found, especially in polar latitudes where the warming was maximum in winter and in the middle latitudes of the northern hemisphere where a soil moisture desiccation was found in summer. Recently, three CO2-doubling experiments have been performed with GCMs that include the annual insolation cycle. These seasonal simulations give an annual global mean warming of 3.5° to 4.2°C and precipitation increases of 7.1 to 11%. These changes are approximately twice as large as those implied for a CO2 doubling by the earliest seasonal simulation, apparently as a result of a positive cloud feedback. The geographical distributions of the CO2-induced warming obtained by the recent simulations agree qualitatively but not quantitatively. Furthermore, the precipitation and soil moisture changes do not agree quantitatively and even show qualitative differences. In particular, the summertime soil moisture drying in middle-latitudes is simulated by only one of the GCMs. In order to improve the state of the art in simulating the equilibrium climatic change induced by increased CO2 concentrations, it is recommended first that the contemporary GCM simulations be analyzed to determine the feedback processes responsible for their differences and second that the parameterization of these processes in the GCMs be validated against highly detailed models and observations.
474 citations
TL;DR: In this paper, the authors consider the role of oceans in governing the transient climate responses and a time-dependent estimate of the potential trace gas warming from the preindustrial era to the early 21st century.
Abstract: The paper considers trace gas-climate effects including the greenhouse effect of polyatomic trace gases, the nature of the radiative-chemical interactions, and radiative-dynamical interactions in the stratosphere, and the role of these effects in governing stratospheric climate change. Special consideration is given to recent developments in the investigations of the role of oceans in governing the transient climate responses, and a time-dependent estimate of the potential trace gas warming from the preindustrial era to the early 21st century. The importance of interacting modeling and observational efforts is emphasized. One of the problems remaining on the observational front is the lack of certainty in current estimates of the rate of growth of CO, O3, and NOx; the primary challenge is the design of a strategy that will minimize the sampling errors.
249 citations
TL;DR: In this paper, a statistical test for detecting a change in the behavior of an annual temperature series is presented based on the two-phase regression model by trading the hypothesized time of change as an unknown parameter.
Abstract: A statistical test for detecting a change in the behavior of an annual temperature series is presented The test is based on the two-phase regression model By trading the hypothesized time of change as an unknown parameter, the approach allows an inference to be made about the time of change The approach also avoids a serious problem, called data-dredging, that can arise in testing for change occurring at a specified time The test is applied to a series of Southern Hemisphere temperatures, and the hypothesis of no change cannot be rejected
178 citations
TL;DR: In this paper, an approximately 260 kyr record of Melosira accumulation in an equatorial Atlantic sediment core was reported, and demonstrated significant influence of the Earth's precessional cycle on the climate of tropical Africa.
Abstract: High abundances of the freshwater diatom Melosira spp., reflecting eolian input from dry lake beds in tropical Africa, occur in deep-sea sediments of the equatorial Atlantic at discrete times during the late Quaternary1,2. We report here an approximately 260 kyr record of Melosira accumulation in an equatorial Atlantic sediment core, and demonstrate significant influence of the Earth's precessional cycle on the climate of tropical Africa.
161 citations
TL;DR: It is indicated that the observed growth decreases of surviving red spruce trees at northeastern sites with high mortality have been anomalous during the past 20 to 25 years with respect to both historical annual growth patterns and past relationships to climate or stand development at these sites.
Abstract: Long-term growth patterns of red spruce (Picea rubens Sarg.) were analyzed from increment cores collected from over 1000 trees at 48 sites in the eastern United States. Principal objectives were the evaluation of the distribution, timing, and uniqueness of observed patterns of decreasing radial growth during the past 25 years and the examination of stand competition and climate as factors contributing to observed changes. Our analyses focused on historical records of spruce mortality and approximately 200 years of radial growth data to search for historical precedents for current trends. In this work we have used time series analysis to detect the temporal frequency of significant negative or positive shifts in radial growth rates, an analysis of relationships between a stand competition index and observed changes in growth and mortality, and modeling of past growth-climate relationships to determine whether recent growth changes could be predicted based on climate. Collectively, these analyses indicate that the observed growth decreases of surviving red spruce trees at northeastern sites with high mortality have been anomalous during the past 20 to 25 years with respect to both historical annual growth patterns and past relationships to climate or stand development at these sites. In general, reductions in radial increment that have also been noted at southern high elevation sites but not at low elevations occurred 5 to 10 years later than at northern sites and represent less substantive departures from growth trends predicted by linear climate models. These results suggest that regional and not local stresses have triggered the observed decline in radial growth of red spruce at these sites. While climatic change may have contributed to observed changes, the degree of radial growth suppression observed is greater than would be expected based on past growth-climate relationships. This unique relationship of growth to climate suggests the influences of either recent, unique combinations of climatic stresses or the possibly interactive intervention of other regional-scale stresses, such as atmospheric pollution.
156 citations
TL;DR: In this paper, the authors present evidence for late-glacial climatic cooling in southernmost South America from studies of radiocarbon-dated glacial and pollen stratigraphy at sites along the Beagle Channel in Tierra del Fuego, where a forest-tundra tension zone is especially sensitive to shifting climate.
Abstract: Pronounced climatic change during the last glacial maximum is recognized as global in extent, and has been attributed to orbital forcing1. Not readily explained in a global context because of the equivocal nature of the evidence are the late-glacial climatic events of short (100–1,000-yr) duration. The cold climate of the Younger Dryas chron (∼11,000–10,000 yr BP), for example, is known to have been particularly pronounced over the North Atlantic and parts of Europe and North America2,3, whereas in the Southern Hemisphere, cold conditions for that time are not well established. Here we present evidence for late-glacial climatic cooling in southernmost South America from studies of radiocarbon-dated glacial and pollen stratigraphy at sites along the Beagle Channel in Tierra del Fuego, where a forest–tundra tension zone in the region is especially sensitive to shifting climate. We conclude that the cold episode corresponds with the time of the Younger Dryas in Europe, when a drop in temperature, ascribed most recently to colder sea surface temperatures and production rate of deep water in the North Atlantic4,5, apparently occurred worldwide.
151 citations
01 Jan 1987
140 citations
01 Jan 1987
TL;DR: In this article, a new equation to calculate the local ocean paleoproductivity has been developed, based on the relationships between carbon accumulation rate, water depth, and carbon-free bulk sedimentation rates (as a "sealing factor") of deep-sea sediments, and is independent of a large range of bottom water 02 concentration.
Abstract: In addition to variations in the Earth’s orbit, changes in atmospheric pC02 represent an important factor in creating global climatic and ice volume changes. Atmospheric pC02 fluctuations are largely controlled by the exchange rates of C02 between the atmosphere and ocean reservoirs, an exchange which greatly depends upon plankton primary productivity in oceanic upwelling regions, where the carbon to carbonate “Rain Ratio” (Berger and Keir, 1984) is high. In order to test this model, a new equation to calculate the local ocean paleoproductivity has been developed. The formula is based on the relationships between carbon accumulation rate, water depth, and carbon-free bulk sedimentation rates (as a “sealing factor”) of deep-sea sediments, and is independent of a large range of bottom water 02 concentration. For comparison with paleoproductivity, δ13C fluctuations of Cibicidoides wuellerstorfi serve to record the total C02 dissolved in North Atlantic Deep Water (NADW). In the region of coastal upwelling off northwest Africa, paleoproductivity increased by a factor of three from interglacial to glacial stages depicting a clear 100,000 year cycle. In oceanic “deserts”, the productivity varied much less, but approximately with the same cycle during the last 0.5 my. Phase relationships during the last two Terminations show that trade wind strength and related productivity due to upwelling in the east Atlantic started to decrease slightly prior to or simultaneously with global ice melting, synchronously with a drastic increase in atmospheric pC02 (after Neftel et al., 1982). On the other hand, C02 depletion in the NADW only followed after some 2500 to 4500 years, and thus, cannot have caused the change in atmospheric C02. The high latitude insolation balance which causes changes in sea-ice cover and thus, of meridional trade wind intensity, is regarded as the prime factor responsible for this massive feedback mechanism for climatic change.
139 citations
TL;DR: In this paper, an original method based on best analogs estimation and multiple regression was performed to calculate a relationship between climate (monthly temperature and precipitation) and modern pollen spectra for data from 182 sites.
TL;DR: In this article, the authors examined the effect of cloud optical properties on surface temperature in a climate model where clouds are simulated interactively with dynamics, radiation, and hydrological cycle, and the results showed the anticipated increase of cloud liquid water and cloud optical depth.
Abstract: Recent general circulation model studies1–3 performed to assess the equilibrium climate response to doubling atmospheric CO2 suggested a global mean surface warming of 3.5–4.2 °C. Part of this warming was attributed to a change in cloud cover1. But all of these studies neglected changes of cloud optical properties which were shown to provide a substantial negative feedback in radiative-convective models if the cloud liquid water content was assumed to increase with increasing temperature4,5. This hypothesis is examined in a climate model where clouds are simulated interactively with dynamics, radiation and hydrological cycle6. The thermal forcing is introduced by a 2% increase of the solar constant which is equivalent to a doubling of CO21. The results show the anticipated increase of cloud liquid water and cloud optical depth. A feedback analysis of the simulated climate change supports earlier suggestions of the importance of cloud optical depth feedbacks4,5. The net effect of clouds is to provide a negative feedback on surface temperature, rather than the positive feedback found in earlier general circulation model studies without considering cloud optical depth feedbacks1.
TL;DR: In this paper, the authors analyzed 7 lakes with annually laminated sediments sampled at 40-year intervals to isolate the climatic effects from other effects on the long-term dynamics of vegetation during the past 1000-2000 years along a transect from Maine to Minnesota.
Abstract: Pollen diagrams from seven lakes with annually laminated sediments sampled at 40-year intervals are analyzed to isolate the climatic effects from other effects on the long-term dynamics of vegetation during the past 1000–2000 years along a transect from Maine to Minnesota. Principal components analysis is used to reduce the dimensionality of the pollen data. The pollen records from all lakes show long-term trends, medium frequency oscillations, and higher frequency fluctuations. The long-term trend is associated with the neoglacial expansion of the boreal forest. The mechanism causing this replacement is a change in frequency of air masses in the area. The medium-frequency oscillations are also associated with climate changes, the most recent of which is the ‘Little Ice Age’. The climate-related mechanism causing the medium-frequency changes may be changes in disturbance frequency. The higher frequency fluctuations may also be related to disturbance. This analysis of pollen diagrams into time scales of variation has enabled the separation of climate from other factors affecting vegetation dynamics. By comparing the principal components across a transect of sites it proved possible to interpret the climatic effects on vegetation at most sites and not only at range boundaries and ‘sensitive’ sites.
TL;DR: A better understanding of the action of the climate forcing factors is required before possible climatic change can be included in determining reliability of cropping.
TL;DR: The first inklings of an understanding of the role played by infrared absorbing gases in maintaining the warmth of the surface of our planet were voiced early in the 19th century, and by the turn of this century quantitative calculations had been carried out that demonstrated how a change in atmospheric carbon dioxide would alter the earth's mean temperature.
Abstract: The first inklings of an understanding of the role played by infraredabsorbing gases in maintaining the warmth of the surface of our planet were voiced early in the 19th century, and by the turn of this century quantitative calculations had been carried out that demonstrated how a change in atmospheric carbon dioxide would alter the earth's mean temperature. However, it was not until the 1960s that much attention was paid to this matter, and in the early 1970s two important summer studies dealing with environmental change fired the imagination of the scientific community. Since then the science (or art) of modeling the climate system has made great strides, aided by faster computers, greater knowledge of the factors involved, and global observations from space of the atmosphere, oceans, and biosphere. This effort has also been bolstered by studies of the behavior of the climate system in the past. There is now a strong consensus that the observed increase in the atmospheric concentrations of carbon dioxide and other infrared-absorbing trace gases is indeed warming the earth, and that this change is caused by mankind. The next set of questions are now being seriously addressed in national and international forums: what are the regional patterns of the changes to be anticipated, especially in terms of rainfall and soil moisture? And what should the countries of the world do about the situation? There is already a sharp debate between the activists, who would take action worldwide to avoid the climate change (or at least slow its advance), and those who would simply wait and see what happens and perhaps take what local measures are necessary to mitigate the effects.
TL;DR: In this paper, the use of a relatively high resolution general circulation model (the Meteorological Office 5-layer model) to determine climate changes for impact studies is evaluated by comparing not only different seasons with climatological data, but also the mean annual cycle and the frequency of extreme events.
Abstract: The use of a relatively high resolution general circulation model (the Meteorological Office 5-layer model) to determine climate changes for impact studies is evaluated. The simulation of present day climate over Western Europe is assessed by comparing not only different seasons with climatological data, but also the mean annual cycle and the frequency of extreme events. It is found that while the broad features of the simulation are satisfactory, the model produces too many cold episodes in spring, and an excessive number of wet days over northern Europe. When atmospheric CO2 concentrations are quadrupled, and sea surface temperatures and sea ice extents changed appropriately, the number of cold episodes is reduced and precipitation is less frequent in summer and autumn over much of Europe, and throughout the year in the south. The relevance of both the model data and the statistical tests to climate impact studies is discussed.
TL;DR: In this paper, a two-dimensional energy balance climate model has been used to simulate the seasonal temperature cycle on a supercontinent-sized land mass, and experiments with idealized and realistic geography indicate that the land-sea configuration in high latitudes exerts a strong influence on the magnitude of summer warming.
Abstract: A two-dimensional energy balance climate model has been used to simulate the seasonal temperature cycle on a supercontinent-sized land mass. Experiments with idealized and realistic geography indicate that the land-sea configuration in high latitudes exerts a strong influence on the magnitude of summer warming. These simulations provide significant insight into the evolution of climate during the Palaeozoic, and raise questions about the presumed pre-eminent role of carbon dioxide in explaining long-term climate change.
Book•
01 Jan 1987
TL;DR: In this article, the authors present a model for climate change in the terrestrial world, which is based on the concept of meteorological anomalies and is called meteorological anomaly detection (SIDA).
Abstract: Acid Rain. Adiabatic Phenomena. Aerology. Aerosols. Africa, Climate of. Agroclimatology. Airmass Climatology. Air Pollution Climatology. Albedo and Reflectivity. Aleutian Low. Angular Momentum, Angular Velocity. Antarctic Climates. Applied Climatology. Architecture and Climate. Arctic Climates. Arctic Front. Arid Climates. Aridity Indexes. Art and Climate. Asia, Climate of. Atmosphere, Evolution of. Atmospheric Circulation, Global. Atmospheric Nomenclature. Atmospheric Nuclei and Dust. Australia, Climate of. Azores (Bermuda) High. Beaufort Wind Scale. Bioclimatology. Blocking. Boreal Zone. Boundary Layer Climatology. Bowen Ratio. Bruckner Cycle. Carbon Dioxide and Climate. Carbon-14 Dating. Centers of Action. Central America and West Indies, Climate of. Climatic Change and Ancient Civilization. Climatic Change Theories. Climatic Classification. Climatic Data, Nature of. Climatic Data, Sample of. Climatic Data, Sources of. Climatic Forecasting, Monthly and Seasonal. Climatic Hazards. Climatic Modification, Inadvertent. Climatic Variation, Geological Record. Climatic Variation, Historical Record. Climatic Variation, Instrumental Data. Climatology. Climatology, History of. Climatotherapy. Clouds and Cloudiness. Coastal Climate. Cold Pole. Condensation. Confluence and Diffluence. Continental Climate. Continentality. Convergence and Divergence. Coriolis Effect. Crime and Climate. Cycles and Periodicities. Desertification. Determinism, Climatic. Dew. Dew Point. Doldrums. Drought. Dynamic Climatology. Earth Motions. Easterly Waves. Electromagnetic Radiation. El Nino. Energy Budget Climatology. Energy Transfer in the Atmosphere. Europe, Climate of. Evaporation. Evapotranspiration. Ferrel Cell. Fog and Mist. Frost. Geomorphology and Climate. Glacial Anticyclone Theory. Greenhouse Effect. Hadley Cell, Hadley Regime. Hail. Health and Climate. Heat Low. Horse Latitudes. Humid Climates. Humidity. Hurricanes. Hurricanes, Beach Effects of. Hydroclimatology. Ice Age Theory. Icelandic Low. Indian Summer. Intertropical Convergence Zone. Inversion. "Iso" Terms. Jet Streams. Katabatic (Gravity) Winds. Kepler's Laws. Koniology. Koppen-Supan Line. Krakatoa Winds. Lakes, Effects on Climate. Land and Sea Breezes. Lapse Rate. Latent Heat. Lightning. Little Ice Age. Local Climatology. Local Winds. Maritime Climate, Oceanicity. Maunder Minimum. Mediterranean Climate. Mesosphere. Microclimatology. Middle Latitude Climates. Models, Climatic. Monsoon Climates. Mountain and Valley Winds. Mountain Climates, Upland. National Center for Atmospheric Research. National Climate Program Act. Nephanalysis. North America, Climate of. North American High. Nuclear Winter. Ocean-Atmosphere Interaction. Ocean Circulation. Oceans, Climate of. Orographic Precipitation. Oscillation. Oxygen, Evolution in Atmosphere. Ozone. Pacific (Hawaiian) High. Paleoclimatology. Paleoclimatology, Isotopic. Paleohydrology. Palmer Index. Phase Changes. Precession. Precipitation. Precipitation Distribution. Pressure, Principles of. Pressure, Surface. Pressure, Upper Air. Pressure Gradient. Radar, Climatic Applications. Radiation Laws. Rain Shadow. Relative Humidity. Rossby Number. Rossby Regime. Rossby Wave. Satellite Climatology. Satellites, Weather and Climate. Savanna Climate. Scales of Climate. Scattering. Sea Ice, Climatic Changes. Sea Level, Mean. Seasons. Semiarid Regions, Hydroclimatology. Siberian (Asiatic) High. Soils and obClimate. Solar Activity and Climatic Change. Solar Radiation. Solar Wind. South America, Climate of. Southern Oscillation. Spherics. Spiral (Ekman) Layer. Standard Atmosphere. Stemflow. Stratosphere. Streamlines. Sunspot Cycles. Sunspots. Synoptic Climatology. Taiga Climate. Temperature Distribution. Temperature-Humidity Index. Terrestrial Radiation. Thunder. Thunderstorms. Tornadoes. Trade Winds. Tree-Ring Analysis. Tropical and Equatorial Climates. Troposphere. Tundra Climate. Turbulence and Diffusion. Ultraviolet Radiation. Units, Constants, and Symbols. Urban Climatology. Vegetation and Climate. Visibility. Vorticity. Walker Circulation. Water Budget Analysis. Waterspouts. Wave Climate. Weather. Westerlies, Middle Latitude West Winds. Wind Chill. Wind Principles. Winds and Wind Systems. Zonal Circulation and Index. Climatic Zones.
TL;DR: In this paper, the authors investigated the possible effects of climate change on surface runoff in the Great Basin Region of the western United States by applying water balance models to four watersheds in Nevada and Utah.
Abstract: There is mounting evidence that increasing amounts of atmospheric carbon dioxide may lead to significant changes in global climate during the next century. The possible effects of such climatic changes on surface runoff in the Great Basin Region of the western United States has been investigated by applying water balance models to four watersheds in Nevada and Utah. The most probable change, a 2°C increase in average annual temperature coupled with a 10 percent decrease in precipitation, would reduce runoff from 17 to 28 percent of the present mean, with drier basins showing the greatest change. Decreasing precipitation by 25 percent causes runoff reductions of 33 to 51 percent. Equivalent changes to a cooler and wetter climate show corresponding increases in runoff of approximately the same magnitude, but such a shift is not considered likely. Based on projected water requirements for the year 2000, a change to a warmer and drier climate would cause severe water shortages in many parts of the Great Basin.
Journal Article•
TL;DR: In this article, the most important cause for a shift in the isotopic composition of meteoric waters appears to be a modification in the weighting factor in the annual average for each contributing synoptic pathway (each with its distinct isotopic signature).
Abstract: In a climatic transition zone such as the Eastern Mediterranean Sea area, in which storm tracks and moisture origin is quite varied, the most important cause for a shift in the isotopic composition of meteoric waters appears to be a modification in the weighting factor in the annual average for each contributing synoptic pathway (each with its distinct isotopic signature). Changes in local meteorologie parameters affect the isotopic composition of rain only to a limited extent, with rain intensity as the most effective parameter. The effects of global temperature and humidity changes express themselves primarily by means of the "d"-excess parameters. All-inall, the reduced role of the Mediterranean Sea as a dominant vapor source for the region's precipitation in the past, appears to be the dominant factor in the change of isotopic composition between present-day precipitation and the paleowaters of the Levant. Effet des changements climatiques sur les modes de precipitation et sur la composition isotopique de l'eau dans une zone climatique transitaire Cas de la region de la Mer Mediterranee Orientale Resume Dans une zone climatique transitaire, tel que la Mer Mediterranee Orientale dans lequel le cours des tempetes et l'humidite sont d'origines variees, la raison principale d'une variation de la composition isotopique des eaux meteoriques est le changement du facteur-poids de la moyenne annuelle des pluies pour chaque trajet meteorologique (ayant chacun sa propre empreinte isotopique). Les changements des parametres meteorologiques locaux n'affectent que dans une certaine mesure la composition isotopique des pluies, l'intensite des pluies etant le parametre le plus influencant. Les effets de la temperature du globe et des changements d'humidite sont exprime's par le parametre "d-excess". En fait, la Mer Mediterranee, dont le role de principale source de vapeur dans la region etait mineur dans le passe, devient le facteur dominant du changement de la composition isotopique entre les precipitations actuelles et les eaux anciennes dans le Levant.
TL;DR: In this article, the authors evaluate whether it would be worthwhile to insure that new systems are not vulnerable to the risks of climate change and sea level rise and suggest that the cost of designing a new system to accommodate a rise in sea level will sometimes be small compared with the retrofit cost that may ultimately be necessary if new systems were not designed for a rise.
Abstract: Increasing concentrations of carbon dioxide and other gases are expected to warm the earth several degrees in the next century, which would raise sea level a few feet and alter precipitation patterns. Both of these changes would have major impacts on the operation of coastal drainage systems. However, because sea level rise and climate change resulting from the greenhouse effect are still uncertain, most planners and engineers are ignoring the potential implications. Case studies of the potential impact on watersheds in Charleston, South Carolina, and Fort Walton Beach, Florida, suggest that the cost of designing a new system to accommodate a rise in sea level will sometimes be small compared with the retrofit cost that may ultimately be necessary if new systems are not designed for a rise. Rather than ignore the greenhouse effect until its consequences are firmly established, engineers and planners should evaluate whether it would be worthwhile to insure that new systems are not vulnerable to the risks of climate change and sea level rise.
TL;DR: In this article, the influence of the Benguela Current near the equator was strongest during stage 2; a separate regime of coastal upwelling may have existed in the Gulf of Guinea at this time.
Abstract: Over the last 160,000 years, diatom productivity in the equatorial Atlantic has been high during glacial stages 2, 4, and 6, and moderate during parts of substages 5b and 5d (approximately 96,000 and 117,000 years B.P.). Productivity of diatoms is particularly low in substage 5e and in the middle of stage 1. Higher productivity implies more vigorous trade winds during glacial intervals, leading to stronger upwelling and enhanced lateral advection of surface waters. The influence of the Benguela Current near the equator was strongest during stage 2; a separate regime of coastal upwelling may have existed in the Gulf of Guinea at this time. Upwelling and advection may not always respond to the same forcing as sea surface temperature. Results support the hypothesis that Ethmodiscus rex oozes result from high diatom productivity. Runoff from the Zaire and Niger rivers was highest at the stage 2/1 transition and just prior to the stage 6/5 transition, due to intensification of the African Monsoon. Several other times of increased runoff are indicated. Periods of increased surface water circulation in the eastern equatorial Atlantic appear to correspond to times of aridity in tropical Africa. Conversely, intervals of decreased circulation in the eastern equatorial Atlantic coincide with times of humidity in tropical Africa. Precessional forcing of continental climate is suggested; however, precessional forcing of surface ocean circulation can be neither confirmed nor refuted based on the records examined here. Influx of Antarctic Bottom Water to the eastern equatorial Atlantic has been insignificant throughout the last 160,000 years.
TL;DR: In this article, a dynamical model for the late-Quaternary global variations of δ18O, mean ocean surface tempeature τ, ice mass I, deep ocean temperature θ, and atmospheric carbon dioxide concentration μ, is constructed.
Abstract: A dynamical model for the late-Quaternary global variations of δ18O, mean ocean surface tempeature τ, ice mass I, deep ocean temperature θ, and atmospheric carbon dioxide concentration μ, is constructed. This model consists of two diagnostic equations (for δ18O and τ), and three prognostic equations (for I, θ, and μ) of a form studied extensively in previous articles. The carbon dioxide equation includes forcing by a representation of the Milankovitch earth-orbital radiation effects, and contains a basic instability that drives a free oscillation of period near 100,000 years. The system is constrained to conserve mass and energy, contain physically plausible feedbacks including a system time constant no greater than 10.000 years, and be robust (i. e., structurally stable in the presence of expected noise levels and uncertainties in values of coefficients). Within the limits of these constraints, coefficients are chosen such that (i) the solution gives a good fit to the observed SPECMAP δ18O variations, and (ii) the ice mass variations are qualitatively similar to the δ18O variations. The predicted long term variations of sea surface temperature and atmospheric carbon dioxide are in reasonably good agreement with the limited observational evidence available for these quantities, while the predicted variations of deep ocean temperature remain to be verified when paleoclimatic estimates of this quantity become available. The relative contributions of ice mass changes and surface water temperature changes to the variations of δ18O at any time are given by the model.
TL;DR: The earth's climate is constantly changing as discussed by the authors, and despite changes in the sun's radiant intensity over the past 4.5 billion years, the average temperature of the earth's surface has remained remarkably constant, hovering near 15 °C. This implies the presence of strong negative feedbacks reacting to any major environmental change.
Abstract: The earth's climate is constantly changing. Climatic change is effected by many factors: the influence of continental drift, variations in solar intensity, volcanism, the impact of meteors and comets, changes in the earth's orbital parameters, ice accumulation and depletion, variations in oceanic circulations and chemistry, changes in terrestrial and aquatic life, and changes in atmospheric composition and circulation. Despite these influences, many of them large, and despite changes in the sun's radiant intensity over the past 4.5 billion years, the average temperature of the earth's surface has remained remarkably constant, hovering near 15 °C. This implies the presence of strong negative feedbacks reacting to any major environmental change. During the past century, man's influence on his environment has been increasing at an unprecedented rate. Under this influence, and particularly because of the effect of the so-called "greenhouse gases," the global mean temperature is expected to rise approximately ...
01 Jan 1987
TL;DR: In this article, the tropical Quelccaya ice cap in Peru (5,670m) has provided a 1500-year record of climatic variability and abrupt events are recorded in this ice by microparticle concentrations, conductivities and oxygen isotopes.
Abstract: Reliable observations of climatic variation prior to 1850 are limited or absent for many regions, especially South America. Ice sheet and ice caps can provide a valuable supplement to historical and other proxy records. The tropical Quelccaya ice cap in Peru (5,670m) has provided a 1500-year record of climatic variability. Abrupt climatic events are recorded in this ice by microparticle concentrations, conductivities and oxygen isotopes which are discussed in detail for three periods: A.D. 1928–1947, 1864–1905 and 1452–1550. These data suggest that both the onset and termination of the “Little Ice Age” were abrupt in tropical South America.
TL;DR: In this article, the authors used soil profiles, pollen analysis of stratified soil samples, and 14C dating of charcoal samples found at various soil depths in the Sagarmatha (Mt. Everest) National Park, Khumbu, Nepal.
Abstract: Popular and policy-influencing hypotheses concerning historical, post-1950, and current landscape degradation within the Sagarmatha (Mt. Everest) National Park, Khumbu, Nepal, were tested through a number of complementary measures. Historical perspectives were provided by the assessment of soil profiles, pollen analysis of stratified soil samples, and the identification and 14C dating of charcoal samples found at various soil depths. Repeat photography, combined with ground-truth verification, enabled an assessment of existing claims that large-scale vegetation and geomorphic change had occurred in the Park during the past 29-34 years. Soil-loss study plots were installed on a stratified and replicated basis throughout the Imja Khola valley and monitored on a weekly basis between 6 April and 1 November 1984. Results suggested that man may have been frequenting and modifying the Khumbu landscape for considerably longer than the 400-year period generally assumed, and that substantial climatic change has occurred during the past 4,000 years. Since the 1950s, far less forest removal and geomorphic damage has occurred in the Khumbu than has been hitherto assumed; most shrub/grassland and forested slopes below 4,000 m are surficially stable, but high soil loss occurs in certain degraded alpine summer settlement areas because of continued shrub harvesting for fuelwood, grazing pressures, and natural freeze-thaw processes. Project results suggest that previous claims of serious landscape degradation in the Khumbu have been overstated. Similar mis- understandings are likely to exist for other regions of Nepal and contain the potential for adversely affecting development and land management policies there. Long-term, region-specific, and quantitative research is suggested to facilitate the better understanding, and thus better management, of the diverse environments characteristic of Nepal, the Himalaya, and the mountain world in general.
TL;DR: In this article, the effects of a changing (rather than changed) climate and the potential adaptations of society to that changing climate are analyzed from a decision-analytic perspective, using both physical and economic models of differing levels of aggregation.
Abstract: Climatic change and its societal impacts have been a topic of considerable concern over the last decade. Economic analysis would seem to have much to contribute to society's understanding of the importance of this issue, yet the contributions of prior analyses have been limited. Consideration from a decision-analytic perspective suggests that more useful insights could be gained by evaluating the effects of a changing (rather than changed) climate and the potential adaptations of society to that changing climate. Linking physical and economic models of differing levels of aggregation can be useful in analyzing a changing climate.
TL;DR: In this article, two scenarios of CO/sub 2/-induced climatic change are used to estimate changes in water use for a number of municipalities in the Great Lakes region of Canada and the US.
Abstract: Two scenarios of CO/sub 2/-induced climatic change are used to estimate changes in water use for a number of municipalities in the Great Lakes region of Canada and the US. Both scenarios, based on General Circulation Models produced by the Goddard Institute for Space Studies (GISS) and Geophysical Fluid Dynamics Lab (GFDL), project warmer temperatures for the region. Using regression models based on monthly potential evapotranspiration for individual cities, it is projected that annual per capita water use will increase by a small amount, which will probably have only a marginal effect on water supplies in the Great Lakes basin. This method could also be used to assess the potential impacts of CO/sub 2/-induced climatic change on water use by the agriculture and power sectors, as well as the effectiveness of water policy initiatives, such as price changes. More work is needed to project water use during peak periods (warm dry spells), which may occur more frequently in a 2 x CO/sub 2/ climate in this region.