The six possible combinations of two climate models and three methods for calculating the melting of snow and ice are used to estimate current values of accumulation and ablation on the Greenland and Antarctic ice sheets. This allows the contrasting of high vs. low resolution climate input and to assess the reliability of simple temperature based parameterizations of melting when compared to a physical model of the seasonal evolution of the snow cover. In contrast to past efforts at modelling the mass balance of Greenland and Antarctica, the latter model allows an explicit calculation of the formation of meltwater, of the fraction of meltwater which refreezes and of runoff in the ablation region, this is not the case for the other two melt models. While the higher resolution GCM (ECHAM 4) does bring the estimation of accumulation closer to observations, it fails to give accurate results in its predictions of runoff. The simpler climate model (MIT 2D LO) overestimates accumulation in Antarctica but produces satisfactory estimates of runoff from the Greenland ice sheet. Both models reproduce some of the characteristics of the extent of the wet snow zone observed with satellite remote sensing, but the MIT model is closer to observations in terms of areal extent and intensity of the melting. The temperature dependent melting parameterizations generally require an accuracy in the climatic input beyond what is currently achieved to produce reliable. Because it is based on physical principles and relies on the surface energy balance as input, the snow cover model is believed to have the capability to respond adequately to the current climatic forcing as well as to future changes in climate. / Includes bibliographical references (p. 31-34). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/) / Supported by the Alliance for Global Sustainability, the MIT Joint Program on the Science and Policy of Global Change and NASA as part of the NASA GISS Interdisciplinary EOS Investigation NAG5-7204

Economic links among countries, through trade, will cause the effects of greenhouse-gas control measures taken by one set of nations to ripple through the international trade system, affecting countries that may not have agreed to share the burdens of control. So, for example, emission restrictions under the Kyoto Protocol will increase the cost to Annex B regions of using carbon-emitting fuels and raise the manufacturing cost of their energy-intensive goods, which may be exported in part to developing countries. The restrictions also will lower the global demand for these fuels and reduce their international prices. In addition, the emissions controls may depress the level of economic activity in countries under emissions restriction, lowering their demand for imports, some of which come from developing countries. In combination, these changes in trade volumes and prices can have complex consequences, harming some developing countries while benefiting others. This paper explores these consequences using a detailed Computable General Equilibrium (CGE) model of the world economy. / Includes bibliographical references (p. 26-28). / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/) / Supported in part by the U.S. Dept. of Energy 901214-HAR DE-FG02-94ER61937 DE-FG0293ER61713 Supported in part by the U.S. Environmental Protection Agency CR-820662002 Also supported by the Royal Norwegian Ministries of Energy and Industry and Foreign Affairs.

Continually increasing atmospheric concentrations of radiatively important chemical species such as CO2, CH4, N2O, tropospheric O3, and certain halocarbons most likely will cause future climate changes, which could in turn impact chemical reaction rates and thus lifetimes of many important chemical species. Complicated interactions between climate dynamics and atmospheric chemistry strongly suggest that a fully interactive, comprehensive chemistry-climate modeling system is needed to study the issue. This article reviews recent work in the new and challenging field of interactive chemistry-climate modeling, describing major efforts in model development and summarizing in detail applications of and results from these models. / Includes bibliographical references (p. 12-16). / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

We find that, on an economic basis, nuclear power could make a substantial contribution for meeting the emissions target Japan agreed to in the Kyoto Protocol. It is unlikely however that the contribution would be as large as projected in official Japanese forecasts. The economic costs of the carbon constraint rise if siting, construction, and approval problems prevent the economically desirable level of expansion of nuclear power. We also evaluate the economic effects of subsidizing nuclear power to achieve the expansion projected in official forecasts. While the subsidy required is substantial, the economic welfare effects are relatively small because of second-best considerations. We use the EPPA model, a global computable general equilibrium model, in the analysis. Our estimates thus include the effects of changing world energy prices and terms of trade as they affect competitiveness of nuclear power and economic welfare. / Includes bibliographical references (p. 12). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

This paper presents an investigation of the relations in China between farm output, the natural fertility of agricultural land, and the use of anthropogenic farm inputs. The methodology is presented as a potential increment to the analysis of the effects of climate change in agriculture. Variations of climate, soil and topographic conditions, and direct farm inputs across the prefectures of China are used to determine their effects on the output of particular crops. The study estimates crop production functions with conventional land, labor, fertilizer and mechanical inputs, and the net primary productivity (NPP) projections of the Terrestrial Ecosystems Model to reflect climatic conditions. Estimates of the NPP of the land in each prefecture are used to simulate the effects of climate and other natural growing conditions. The results suggest that there is substantial scope for increasing food production in China by increasing its irrigation of farm land and the use of farm inputs of fertilizer and mechanical power. / Includes bibliographical references (p. 15). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

Years of hard bargaining have failed to produce a policy architecture to adequately address the complexities of climate change. Very likely, such a structure will have to be sought though improvement of the partial architecture developed to date within the Framework Convention on Climate Change. We identify key architectural features that have emerged in the Convention process, and then explore extensions that will be necessary if the current approach is to serve for the long term. An important task is to break the deadlock over accession of developing countries. To this end we propose further incorporation in the negotiations of concepts of burden sharing according to ability to pay that already seem to be embedded in the Convention. The implications of alternative versions of such an approach are illustrated with a set of simple model simulations. / Includes bibliographical references (p. 23-24). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

This paper surveys and interprets the attitudes of scientists to the use of flux adjustments in climate projections with coupled Atmosphere Ocean General Circulation Models. The survey is based largely on the responses of 19 climate modellers to several questions and a discussion document circulated in 1995. We interpret the responses in terms of the following factors: the implicit assumptions which scientists hold about how the environmental policy process deals with scientific uncertainty over human-related global warming; the different scientific styles that exist in climate research; and the influence of organisations, institutions, and policy upon research agendas. We find evidence that scientists' perceptions of the policy process do play a role in shaping their scientific practices. In particular, many of our respondents expressed a preference for keeping discussion of the issue of flux adjustments within the climate modeling community, apparently fearing that climate contrarians would exploit the issue in the public domain. While this may be true, we point to the risk that such an approach may backfire. We also identify assumptions and cultural commitments lying at a deeper level which play at least as important a role as perceptions of the policy process in shaping scientific practices. This leads us to identify two groups of scientists, 'pragmatists' and 'purists,' who have different implicit standards for model adequacy, and correspondingly are or are not willing to use flux adjustments. / Includes bibliographical references. / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/) / Funded by the UK's Economic and Social Research Council as part of the "Science, Culture and the Enviroment" program at Lancaster University, UK.

Different atmosphere-ocean general circulation models produce significantly different projections of climate change in response to increases in greenhouse gases and aerosol concentrations in the atmosphere. The main reasons for this disagreement are differences in the sensitivities of the models to external radiative forcing and differences in their rates of heat uptake by the deep ocean. In this study, these properties are constrained by comparing radiosonde-based observations of temperature trends in the free troposphere and lower stratosphere with corresponding simulations of a fast, flexible climate model, using techniques based on optimal fingerprinting. Parameter choices corresponding either to low sensitivity, or to high sensitivity combined with slow oceanic heat uptake are rejected. Nevertheless, a broad range of acceptable model characteristics remains, such that climate change projections from any single model should be treated as only one of a range of possibilities. / Includes bibliographical references (p. 10-11). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

Global climate change is on the political agenda primarily as a result of science and the warnings of the scientific community, and is commonly seen as a quintessentially scientific matter. However, the development of policy on this issue in the U.S. today does not turn on the scientific evidence. Rather, policy is determined by the political and economic forces involved, with reference to the science only to support positions reached on other grounds. The reasons relate primarily to the uncertainty in the evidence, the structure and politics of the government, the economic costs and impact of change and of policies to reduce greenhouse gases, the international structure in which the issue is being confronted, the role of the media, and the effects of partisan politics. In this situation, the scientific and engineering communities (including social scientists and especially economists) have a major responsibility to maintain their professional values and objectivity so dominated at the moment by other pressures. Only that way can they retain the public trust that will be necessary if and when costly policy measures must be undertaken. / Includes bibliographical references. / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

The Kyoto Protocol is an international agreement aimed at limiting emissions of several greenhouse gases (GHGs; specifically: CO2, CH4, N2O, PFCs, HFCs, and SF6), and allows credit for approved sinks for CO2. It does not include consideration of several other trace atmospheric constituents that have important indirect effects on the radiative budget of the atmosphere. Here we show that inclusion of other GHGs and CO2 sinks greatly reduces the cost of achieving CO2 emissions reductions specified under the agreement. The Kyoto Protocol extrapolated to 2100 reduces predicted warming by only about 17%. The errors caused by simulating other GHGs with scaled amounts of CO2 on atmospheric composition, climate, and ecosystems are small. Larger errors come from failure to account for interactive and climatic effects of gases that affect atmospheric composition but are not included in the protocol (CO, NOx, and SOx). Over the period to 2100, the Global Warming Potential (GWP) indices based on a 100-year time horizon as specified in the protocol appear to be an adequate representation of trace gas climatic effects. The principal reason for the success of this simplified GWP approach in our calculations is that the mix of gas emissions resulting from a carbon-only rather than a multi-gas control strategy does not change by a large amount. / Includes bibliographical references (p. 13-14). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)