Key uncertainties in the global carbon cycle are explored with a 2-D model for the oceanic carbon sink. By calibrating the key parameters of this ocean carbon sink model to widely referenced values, it produces an average oceanic carbon sink during the 1980s of 1.94 Pg/yr, consistent with the range estimated by the IPCC of 2.0 Pg/yr +/- 0.8 Pg/yr. A sensitivity analysis of the parameter values used as inputs to the 2-D ocean carbon sink model developed for this study suggests that the IPCC's range for the oceanic carbon sink of 1.2 to 2.8 Pg/yr during the 1980s may be too conservative. By applying the Probabilistic Collocation Method to this simple ocean carbon sink model, the uncertainty in the size of the oceanic sink for carbon and hence future atmospheric CO₂ concentrations is quantitatively examined. An average 1980s oceanic carbon sink of 2.06 ± 0.9 Pg/y (with 67% confidence) is estimated. This uncertainty is found to be dominated the uncertainty in by the rate of vertical mixing of dissolved carbon from the surface into the deep ocean which is parameterized in this study by vertical diffusion. It is observed that a wide range of parameter values can be used to balance the contemporary carbon cycle due to the large uncertainties in the total oceanic and terrestrial sinks. For a reference set of emissions similar to the IS92a scenario of the IPCC, the uncertainty in the atmospheric CO₂ concentration in 2100 is found to be 659 ppm +/- 35 ppm (with 67% confidence). This uncertainty is solely due to uncertainties identified in the "solubility pump" mechanism of the oceanic sink, which is only one of the many large uncertainties lacking a quantitative examination in the global carbon cycle. Such uncertainties have implications for the predictability of atmospheric CO₂ levels, a necessity for gauging the impact of different rates of anthropogenic CO₂ emissions on climate and for policy-making purposes. Because of the negative feedback between the natural carbon uptake by the terrestrial ecosystem and atmospheric CO₂ concentration, taking changes in the former into account leads to a smaller uncertainty in the latter compared to that in the case with the fixed terrestrial uptake. / 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/) / Includes bibliographical references (p. 22-25).

Future global climate projections are subject to large uncertainties. Major sources of this uncertainty are projections of anthropogenic emissions. We evaluate the uncertainty in future anthropogenic emissions using a computable general equilibrium model of the world economy. Results are simulated through 2100 for carbon dioxide (CO₂), methane (CH4), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6), sulfur dioxide (SO₂), black carbon (BC) and organic carbon (OC), nitrogen oxides (NOx), carbon monoxide (CO), ammonia (NH3) and non-methane volatile organic compounds (NMVOCs). We construct mean and upper and lower 95% emissions scenarios (available from the authors at 1 degree by 1 degree latitude-longitude grid). Using the MIT Integrated Global System Model (IGSM), we find a temperature change range in 2100 of 0.9 to 4.0 degrees C, compared with the Intergovernmental Panel on Climate Change emissions scenarios that result in a range of 1.3 to 3.6 degrees C when simulated through MIT IGSM. / 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/) / Includes bibliographical references (p. 23-25).

We apply the optimal fingerprint detection algorithm to three independent diagnostics of the recent climate record and derive joint probability density distributions for three uncertain properties of the climate system. The three properties are climate sensitivity, the rate of heat uptake by the deep ocean, and the strength of the net aerosol forcing. Knowing the probability distribution for these properties is essential for quantifying uncertainty in projections of climate change. We briefly describe each diagnostic and indicate its role in constraining these properties. Based on the marginal probability distributions, the 5 to 95% confidence intervals are 1.4 to 7.7K for climate sensitivity and 0.30 to 0.95 W/m^2 for the net aerosol forcing using uniform priors; and 1.3 to 4.2K and 0.26 to 0.88 W/m^2 using an expert prior for climate sensitivity. The oceanic heat uptake is not so well constrained. The uncertainty in the net aerosol forcing in either case is much less than the uncertainty range usually quoted for the indirect aerosol forcing alone. / Includes bibliographical references (p. 8-11). / 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 NOAA Office of Global Programs (NA06GP0061). Supported in part by the UK Natural Environment Research Council, and by UK DETR (PECD 7/12/37).

Controlling multiple substances that jointly contribute to climate warming requires some method to compare the effects of the different gases because the physical properties (radiative effects, and persistence in the atmosphere) of the greenhouse gases are very different. We cast such indices as the solution to a dynamic, general equilibrium cost-benefit problem where the correct indices are the relative shadow values of control on the various substances. We find that use of declining discount rate, as recommended by recent research, suggests that the current physical-based indices adopted in international negotiations overestimate the value of control of short-lived gases and underestimates the value of control of very long-lived species. Moreover, we show that such indices will likely need to be revised over time and this will require attention to the process by which decisions are made to revise them and how revisions are announced. / Includes bibliographical references (p. 18-19). / 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/)

Multi-fueled electric utilities are commonly seen as offering relatively greater opportunities for reasonably priced carbon abatement through changes in the dispatch of generating units from capacity using high emission fuels, coal or oil, to capacity using lower emitting fuels, natural gas (LNG) or nuclear. This paper examines the potential for such abatement using Japanese electric utilities as an example. We show that the potential for abatement through re-dispatch is determined chiefly by the amount of unused capacity combining low emissions and low operating cost, which is typically not great. Considerably more abatement potential lies in changing planned, base load, fossil-fuel fired capacity additions to nuclear capacity. Our results are at odds with the common view that the demand for natural gas or LNG would increase, or at least not fall, as the result of a carbon constraint; and our analysis suggests that this result may not be limited to Japan. / 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/) / Includes bibliographical references (p. 31).

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/) / Includes bibliographical references (p. 31). / Supported in part by the Univ. of Washington's Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement (NA67RJ0155 841). Also supported in part by MIT's Joint Program on the Science and Policy of Global Change, with support from the U.S. Dept. of Energy's Office of Biological and Environmental Research to (DE-FG02-93ER61677).

To what extent do the welfare costs associated with the implementation of the Burden Sharing Agreement in the European Union depend on sectoral allocation of emissions rights? What are the prospects for strategic climate policy to favor domestic production? This paper attempts to answer those questions using a CGE model featuring a detailed representation of the European economies. First, numerical simulations show that equalizing marginal abatement costs across domestic sectors greatly reduces the burden of the emissions constraint but also that other allocations may be preferable for some countries because of pre-existing tax distortions. Second, we show that the effect of a single country's attempt to undertake a strategic policy to limit impacts on its domestic energy-intensive industries has mixed effects. Exempting energy-intensive industries from the reduction program is a costly solution to maintain the international competitiveness of these industries; a tax-cum-subsidy approach is shown to be better than exemption policy to sustain exports. The welfare impact either policy -- exemption or subsidy -- on other European countries is likely to be small because of general equilibrium effects. / 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/) / Includes bibliographical references (p. 17-18).

We extend an analytical general equilibrium model of environmental policy with pre-existing labor tax distortions to include pre-existing monopoly power as well. We show that the existence of monopoly power has two offsetting effects on welfare. First, the environmental policy reduces monopoly profits, and the negative effect on income increases labor supply in a way that partially offsets the pre-existing labor supply distortion. Second, environmental policy raises prices, so interaction with the pre-existing monopoly distortion further exacerbates the labor supply distortion. This second effect is larger, for reasonable parameter values, so the existence of monopoly reduces the welfare gain (or increases the loss) from environmental restrictions. / 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/) / Includes bibliographical references (p. 17-19). / Supported in part by the Joint Program on the Science and Policy of Global Change at MIT and the National Science Foundation (NFS SBR-9811324).

The Emissions Prediction and Policy Analysis (EPPA) model is a component of the MIT Integrated Earth Systems Model (IGSM). Here, we provide an overview of the model accessible to a broad audience and present the detailed structure, data, and parameterization of the model for specialists in economic modeling. EPPA projects emissions of most of the climatically important substances emitted as a result of human activities including carbon dioxide (CO₂), carbon monoxide (CO), methane (CH4), nitrous oxide (N₂O), nitrogen oxides (NOx), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), sulfate aerosols (SOx), non-methane volatile organic compounds (NMVOCs), black carbon, organic carbon, and ammonia (NH3). We present an updated and consistent inventory for 1995 of all of these emissions disaggregated to the regional and sectoral levels we use in EPPA. This more complete inventory of climatically important substances shows non-energy sources (e.g. agriculture, biomass burning) and developing countries to be important current sources of many of these emissions. A major use of EPPA, a computable general equilibrium model of the world economy with regional and sectoral detail, is to estimate the cost of greenhouse gas emissions control over the 100-year horizon of the model. Reference projections show rates of improvement in energy use per unit of output (Gross Domestic Product) consistent with historical rates although in EPPA we do not attempt to model short-term business cycle behavior so that our projections do not show the same variability as the historical data. Emissions of climatically important substances mostly grow over time in our reference projection (although rates differ substantially among them) despite considerable improvements in energy efficiency and reductions in emissions coefficients for other substances. Developing countries as group become larger sources of all greenhouse gas emissions than developed or transition economies by the middle of the century as their economies and populations are projected to grow more rapidly. There remain many uncertainties in projections of this type. The projections presented in this report are a starting point (i.e. reference) for evaluating alternative scenarios and climate policies. / Includes bibliographical references (p. 84-90). / 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 estimate reference CO₂ emission projections in the European Union, and quantify the economic impacts of the Kyoto commitment on Member States. We consider the case where each EU member individually meets a CO₂ emissions target, applying a country-wide cap and trade system to meet the target but without trade among countries. We use a version of the MIT Emissions Prediction and Policy Analysis (EPPA) model, here disaggregated to separately include 9 European Community countries and commercial and household transportation sectors. We compare our results with that of four energy-economic models that have provided detailed analyses of European climate change policy. In the absence of specific additional climate policy measures, the EPPA reference projections of carbon emissions increase by 14% from 1990 levels. The EU-wide target under the Kyoto Protocol to the Framework Convention on Climate Change is a reduction in emissions to 8% below 1990 levels. EPPA emissions projections are similar to other recent modeling results but there are underlying differences in energy and carbon intensities among the projections. If EU countries were to individually meet the EU allocation of the Community-wide carbon cap specified in the Kyoto Protocol, we find using EPPA that carbon prices vary from $91 in the United Kingdom to $385 in Denmark; welfare costs range from 0.6 to 5%. / Includes bibliographical references (p. 30-32). / 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 Institut Français de l'Energie