Abstract: Excess carbon dioxide, methane, and other gases which trap heat are accumulating in the troposphere, the earth's lower atmosphere, because of the scale and type of human economic activity Climate scientists predict that the resultant increase in the troposphere's “radiative forcing” will warm the earth's surface1 2 3 Indeed, in its recent second assessment report, the Intergovernmental Panel on Climate Change—a multidisciplinary scientific body established by the United Nations in 1988 to advise governments—concluded that on balance an anthropogenic influence upon the global climate was now “discernible” 1 The intergovernmental panel forecasts an increase in the average world temperature of 10-35°C over the coming century1 This forecast is necessarily uncertain because the sensitivity of climate to atmospheric change is imperfectly understood and because future trends in gaseous emissions and modulating processes (for example, the cooling effects of industrial aerosol emissions) cannot be foreseen accurately Nevertheless, the expected rate of climate change over the coming century would be far greater than any natural change in world climate since the advent of agriculture 10 000 years ago Anthropogenic climate change signifies that for the first time the aggregate global impact of humankind exceeds the physical and ecological limits of the biosphere4 The potential consequences of this and other global changes (including stratospheric ozone depletion, loss of biodiversity, worldwide land degradation, and depletion of aquifers) are wide ranging We can expect that climate change will affect the health and wellbeing of human populations in diverse ways This greatly extends the temporo-spatial scale of environmental health beyond our usual concern with localised and immediate exposures to toxic or infectious agents4 A major research task, therefore, is the application of current knowledge to forecasting probable health effects The primary objective is to provide indicative forecasts of an important consequence that will …

Abstract: Observed climate change is consistent with radiative forcings on several time-scales for which the dominant forcings are known, ranging from the few years after a large volcanic eruption to glacial-to-interglacial changes. In the period with most detailed data, 1979 to the present, climate observations contain clear signatures of both natural and anthropogenic forcings. But in the full period since the industrial revolution began, global warming is only about half of that expected due to the principal forcing, increasing greenhouse gases. The direct radiative effect of anthropogenic aerosols contributes only little towards resolving this discrepancy. Unforced climate variability is an unlikely explanation. We argue on the basis of several lines of indirect evidence that aerosol effects on clouds have caused a large negative forcing, at least -1 Wm-2, which has substantially offset greenhouse warming. The tasks of observing this forcing and determining the microphysical mechanisms at its basis are exceptionally difficult, but they are essential for the prognosis of future climate change.

Abstract: The realistic physical functioning of the greenhouse effect is reviewed, and the role of dynamic transport and water vapor is identified. Model errors and uncertainties are quantitatively compared with the forcing due to doubling CO2, and they are shown to be too large for reliable model evaluations of climate sensitivities. The possibility of directly measuring climate sensitivity is reviewed. A direct approach using satellite data to relate changes in globally averaged radiative flux changes at the top of the atmosphere to naturally occurring changes in global mean temperature is described. Indirect approaches to evaluating climate sensitivity involving the response to volcanic eruptions and Eocene climate change are also described. Finally, it is explained how, in principle, a climate that is insensitive to gross radiative forcing as produced by doubling CO2 might still be able to undergo major changes of the sort associated with ice ages and equable climates.

Abstract: A climate change resulting from recent increases in the atmospheric greenhouse gases (GHGs) is supposed to occur sometime in the middle of the next century. This climate change induced by GHGs would be caused by radiative forcing through the greenhouse effect and would lead to global warming and eventually to sea-level rise. This paper presents a climate change scenario for the greater Caribbean as simulated by the Canadian Climate Centre (CCC) general circulation model (GCM). The CCC GCM projects a GHG induced temperature increase of about 2°C and more extreme rainfall conditions for the greater Caribbean. The climate records of temperature, rainfall and cloudiness for several stations on the island of Trinidad are then examined in an attempt to detect GHG climate change signals. The temperature change to date, close to 1°C, and the fluctuations in rainfall patterns, over the last five decades, seem to be indicative of early greenhouse signals. © 1997 The Royal Meteorological Society.

Abstract: Global climate change related to natural and anthropogenic processes has been the topic of concern and interest world wide. Despite ongoing research efforts, the climate predictions cannot be rated any better than speculative or possible scenarios whose probability of occurrence is, at the present stage, impossible to assess. One of the most significant impacts of the ‘greenhouse effect’ is anticipated to be on water resources, including different elements of the hydrologic cycle, water supply and demand, regional vulnerability, and water quality. Thus, the impact of climate change appears to be an additional component on top of the large number of existing water-related problems. The existence of the greenhouse effect, the increase of greenhouse gas emissions, and the rise of corresponding concentrations are things that are certain. However, their impacts on hydrology and water management are highly uncertain. In the latter area, one needs information on much smaller spatial and temporal scales than those used in climate studies. The objective of the present paper is to analyze the climate change impact on water resources in a system's perspective, to discuss scientific gaps, and challenge scientific issues. The role of different scales and uncertainties, as well as the hydrological view of global circulation models are also discussed. Our preparedness for probable global (climate) change is reviewed in terms of assessment, planning, design and adaptation.

Abstract: A year and a half ago, an international panel suggested that global warming had arrived. But as negotiators prepare to gather in Bonn in July to discuss a climate treaty that could require nations to adopt expensive policies for limiting emissions of greenhouse gases, many climate experts caution that it is not at all clear yet that human activities have begun to warm the planet--or how bad greenhouse warming will be when it arrives.

Abstract: Several time series investigations of global climate change have been published, but the time series properties of the variables has received little attention with a few exceptions in the case of global temperature series. We focus on the presence or absence of stochastic trends. We use three different tests to determine the presence of stochastic trends in a selected group of global climate change data for the longest time series available. The test results indicate that the radiative forcing due to changes in the atmospheric concentrations of CO2, CH4, CFCs, and N2O, emissions of SOX, CO2, CH4, and CFCs and solar irradiance contain a unit root while most tests indicate that temperature does not. The concentration of stratospheric sulfate aerosols emitted by volcanoes is stationary. The radiative forcing variables cannot be aggregated into a deterministic trend which might explain the changes in temperature. Taken at face value our statistical tests would indicate that climate change has taken place over the last 140 years but that this is not due to anthropogenic forcing. However, the noisiness of the temperature series makes it difficult for the univariate tests we use to detect the presence of a stochastic trend. We demonstrate that multivariate cointegration analysis can attribute the observed climate change directly to natural and anthropogenic forcing factors in a statistically significant manner between 1860 and 1994.

Abstract: Climate models are distinguished by the relative importance they attach to the different components and processes of the climate system. One finds the so-called energy balance climate models at the bottom on a scale of models of increasing complexity, and coupled general circulation models of atmosphere and oceans at the top on that scale.

Abstract: Among the key issues of concern to the Climate Convention is the stabilization of greenhouse gas concentrations and the minimization of impacts to global agriculture, natural ecosystems and economic development. The purpose of this paper is to couple these issues in consistent, integrated scenarios, using the IMAGE 2.0 model as an integrating tool. Scenarios of gradual stabilization of atmospheric CO2 at 350 and 450 ppm are compared to a baseline of no policy action in which CO2 concentration increases to 777 ppm. Under the stabilization scenarios substantially smaller areas of wheat and millet, as well as nature reserves, are threatened by climate change, especially in temperate regions. The amount of sea level rise is also reduced under the stabilization scenarios. However, climate continues to change under the stabilization scenarios and therefore some ‘residual’ climate impacts occur. Hence the integrated scenarios indicate that stabilizing greenhouse gas concentrations at or slightly above current levels will lessen impacts as compared to baseline levels, but not eliminate them.

Abstract: Climate change associated with increasing concentrations of the greenhouse gas, carbon dioxide(CO2), is expected to lead to an increase in global mean temperature of between 1 and 3.5 deg C by the end of the 21st century, with regional changes in rainfall and humidity. This thesis is concerned with modelling the effects of a changing climate and atmospheric C02 concentration on global vegetation. The process-based model, DOLY (Dynamic glObal phtogeographY), is used. It is able to operate using three climate variables, two soil variables and an atmospheric CO2 concentration. Its outputs are leaf area index (LAI), and net primary productivity (NPP). The LAI and NPP values predicted by DOLY were used to run a life-form model with a climate change scenario. It was found that warming led to the spread of trees into the tundra region. The DOLY model was also coupled with the Hadley Centre general circulation model to determine the feedbacks of vegetation on climate. With a global warming of 2◦C, the global feedback of vegetation on temperature was a decrease of 0.1 deg C. However at the regional scale the feedback was +/-2 ◦C, of similar magnitude to the driving temperature change. Finally, the DOLY model was run with transient climate data from the Hadley Centre. The boreal forest moved north, and the Gobi desert and the southern steppes in the former Soviet Union shrank in area. The sensitivity of the model to its soil and climate inputs have also been analysed over a range of environments and the model has been validated with reference to satellite data and experimental data. It was found to perform well. This thesis has shown that it is possible to predict current and possible future distributions of vegetation with climate change using a vegetation model.

Abstract: The realistic physical functioning of the greenhouse effect is reviewed, and the role of dynamic trans- port and water vapor is identified. Model errors and uncer- tainties are quantitatively compared with the forcing due to doubling CO2, and they are shown to be too large for reliable model evaluations of climate sensitivities. The possibility of directly measuring climate sensitivity is reviewed. A direct approach using satellite data to relate changes in globally averaged radiative f lux changes at the top of the atmosphere to naturally occurring changes in global mean temperature is described. Indirect approaches to evaluating climate sensitiv- ity involving the response to volcanic eruptions and Eocene climate change are also described. Finally, it is explained how, in principle, a climate that is insensitive to gross radiative forcing as produced by doubling CO2 might still be able to undergo major changes of the sort associated with ice ages and equable climates. The title suggested for this paper (by Dave Keeling) is tanta- lizing for its ambiguity. At some level, the answer is philo- sophically trivial. After all, our knowledge is rarely so perfect that we can say anything is absolutely impossible. In connec- tion with this question we can go a bit further, and state that increasing CO2 is likely to cause some climate change, and that the resulting change will involve average warming of the earth. However, this answer is almost as trivial as the first. The climate is always undergoing change, and if the changes due to increasing CO2 are smaller than the natural variability, then these changes will be of only modest concern except as an exercise in weak signal detection. The more serious question then is do we expect increasing CO2 to produce sufficiently large changes in climate so as to be clearly discernible and of consequence for the affairs of humans and the ecosystem of which we are part. This is the question I propose to approach in this paper. I will first consider the question of whether current model predictions are likely to be credible. We will see why this is unlikely at best. I will then show how we might estimate and bound climate sensitivity both directly and indi- rectly from existing data. Finally, I will consider the relation- ship of changes in mean temperature to changes in the structure of climate. It has been suggested that small changes in mean temperature are important because major changes in past climate were associated with major changes in the equa- tor-to-pole temperature difference, but only small changes in the mean temperature. I will argue that the changes in mean temperature may be only residuals of the changes in the meridional temperature distribution rather than the cause. Current Forecasts

Abstract: The aim of this paper is to report on the development of regional climate change scenarios for Kazakhstan as the result of increasing of CO2 concentration in the global atmosphere. These scenarios are used in the assessment of climate change impacts on the agricultural, forest and water resources of Kazakhstan. Climate change scenarios for Kazakhstan to assess both long-term (2× CO2 in 2075) and short-term (2000, 2010 and 2030) impacts were prepared. The climate conditions under increasing CO2 concentration were estimated from three General Circulation Models (GCM) outputs: the model of the Canadian Climate Center Model (CCCM), the model of the Geophysical Fluid Dynamics Laboratory (GFDL) and the 1% transient version of the GFDL model (GFDL-T). The near-term climate scenarios were obtained using the probabilistic forecast model (PFM) to the year 2010 and the results of GFDL-T for years 2000 and 2030. A baseline scenario representing the current climate conditions based on observations from 1951 to 1980 was developed. The assessment of climate change in Kazakhstan based on the analysis of 100-years observations is given too. As a result of comparisons of the current climate (based on observed climate) the 1× CO2 output from GCMs showed that the GFDL model best matches the observed climate. The GFDL model suggests that the minimum increase in temperature is expected in winter, when most of the territory is expected to have temperatures 2.3–4.5 °C higher. The maximum (4.3 to 8.2 °C) is expected to be in spring. CCCM scenario estimates an extreme worming above 11 °C in spring months. GFDL-T outputs provide an ‘intermediate’ scenario.

Abstract: Increased atmospheric greenhouse gases resulting from human activities have produced a sharp increase in the potential to warm the climate to levels that may have serious implications. Predictions of future climate changes in response to these greenhouse gas increases depend almost completely upon physically based mathematical models of the climate system. The strengths and weaknesses of these models to project various aspects of climate change are evaluated in terms of a "betting odds" approach to provide guidance to the policy deliberation process.

Abstract: This is the first major textbook to encompass the true complexity of climate change. Whilst 'greenhouse' warming dominates most of the literature, Ted Bryant presents numerous reasons for the observed climate change of the past century. He argues that changes in climate, more dramatic than those of the last 150 years, have been a predominant aspect of the Earth's climate over the past two million years. Bryant highlights human impacts on climate other than 'greenhouse' gases, including sulphate air pollutants, dust and urban heat islands. He also explains the natural components forcing climate change.Bryant presents, in simple terms, the processes that drive the Earth's present climate system. He outlines the nature and reasons for temperature fluctuations over millennia, including recent human-induced climate change. Finally, he discusses the impact of climate change upon human health and the world's ecosystems.

Abstract: Climate is discussed as an integral part of ‘System Earth’, determined by a complex interplay of numerous geological, biological and solar processes. The historical and geological record of changing climate and atmospheric CO2 pressure does not support the current popular vision that this greenhouse gas is the dominant climate controlling agent. When empirically ante post tested against past global climate changes, the ‘forecasts’ of the climate models mainly based on forcing by atmospheric CO2 are not borne out. On the other hand, recent studies show that solar variability rather than changing CO2 pressure is an important, probably the dominant climate forcing factor.