Assessment of U.S. Cap-and-Trade Proposals

The MIT Emissions Prediction and Policy Analysis model is applied to synthetic policies that match key attributes of a set of cap-and-trade proposals being considered by the U.S. Congress in spring 2007. The bills fall into two groups: one specifies emissions reductions of 50% to 80% below 1990 levels by 2050; the other establishes a tightening target for emissions intensity and stipulates a time-path for a "safety valve" limit on the emission price that approximately stabilizes U.S. emissions at the 2008 level. Initial period prices are estimated between $7 and$50 per ton CO2-e with these prices rising by a factor of four by 2050. Welfare costs vary from near zero to less than 0.5% at the start, rising in the most stringent case to near 2% in 2050. If allowances were auctioned these proposals could produce revenue between $100 billion and$500 billion per year depending on the case. Outcomes from U.S. policies depend on mitigation effort abroads, and simulations are provided to illuminate terms-of-trade effects that influence the emissions prices and welfare effects, and even the environmental effectiveness, of U.S. actions. Sensitivity tests also are provided of several of key design features. Finally, the U.S. proposals, and the assumptions about effort elsewhere, are extended to 2100 to allow exploration of the potential role of these bills in the longer-term challenge of reducing climate change risk. Simulations show that the 50% to 80% targets are consistent with global goals of atmospheric stabilization at 450 to 550 ppmv CO2 but only if other nations, including the developing countries, follow suit.

Analysis of U.S. Greenhouse Gas Tax Proposals

The U.S. Congress is considering a set of bills designed to limit the nation's greenhouse gas (GHG) emissions. This paper complements the analysis by Paltsev et al. (2007) of cap-and-trade bills and applies the MIT Emissions Prediction and Policy Analysis (EPPA) model to carry out an analysis of the tax proposals. Several lessons emerge from this analysis. First, a low starting tax rate combined with a low rate of growth in the tax rate will not reduce emissions significantly. Second, the costs of GHG reductions are reduced with the inclusion of non-CO2 gases in the carbon tax scheme. Third, welfare costs of the policies can be affected by the rate of growth of the tax, even after controlling for cumulative emissions. Fourth, a carbon tax -- like any form of carbon pricing -- is regressive. However, general equilibrium considerations suggest that the short-run measured regressivity may be overstated. Additionally, the regressivity can be offset with a carefully designed rebate of some or all of the revenue. Finally, the carbon tax bills that have been proposed or submitted are for the most part comparable to many of the carbon cap-and-trade proposals that have been suggested. Thus the choice between a carbon tax and cap-and-trade system can be made on the basis of considerations other than their effectiveness at reducing emissions over some control period.

Assessment of U.S. Cap-and-Trade Proposals

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/).The MIT Emissions Prediction and Policy Analysis model is applied to an assessment of a set of cap-and-trade proposals being considered by the U.S. Congress in spring 2007. The bills specify emissions reductions to be achieved through 2050 for the standard six-gas basket of greenhouse gases. They fall into two groups: one specifies emissions reductions of 50% to 80% below 1990 levels by 2050; the other establishes a tightening target for emissions intensity and stipulates a time-path for a “safety valve” limit on the emission price that approximately stabilizes U.S. emissions at the 2008 level. A set of three synthetic emissions paths are defined that span the range of stringency of these proposals, and these “core” cases are analyzed for their consequences in terms of emissions prices, effects on energy markets, welfare cost, the potential revenue generation if allowances are auctioned and the gains if permit revenue were used to reduce capital or labor taxes. Initial period prices for the first group of proposals, in carbon dioxide equivalents, are estimated between $30 and$50 per ton CO2-e depending on where each falls in the 50% to 80% range, with these prices rising by a factor of four by 2050. Welfare costs are less than 0.5% at the start, rising in the most stringent case to near 2% in 2050. If allowances were auctioned these proposals could produce revenue between $100 billion and$500 billion per year depending on the case. Emissions prices for the second group, which result from the specified safety-valve path, rise from $7 to$40 over the study period, with welfare effects rising from near zero to approximately a 0.5% loss in 2050. Revenue in these proposals depends on how many allowances are freely distributed. To analyze these proposals assumptions must be made about mitigation effort abroad, and simulations are provided to illuminate terms-of-trade effects that influence the emissions prices and welfare effects, and even the environmental effectiveness, of U.S. actions. Sensitivity tests also are provided of several of the design features imposed in the “core” scenarios including the role of banking, the specification of less than complete coverage of economic sectors, and the development of international permit trading. Also, the effects of alternative assumptions about nuclear power development are explored. Of particular importance in these simulations is the role of biofuels, and analysis is provided of the implications of these proposals for land use and agriculture. Finally, the U.S. proposals, and the assumptions about effort elsewhere, are extended to 2100 to allow exploration of the potential role of these bills in the longer-term challenge of reducing climate change risk. Simulations using the MIT Integrated System Model show that the 50% to 80% targets are consistent with global goals of atmospheric stabilization at 450 to 550 ppmv CO2 but only if other nations, including the developing countries, follow.Development of the underlying analysis models and other research-based tools used in this study was supported separately by the U.S. Department of Energy, Office of Biological and Environmental Research [BER] (DE-FG02-94ER61937), the U.S. Environmental Protection Agency (XA-83042801-0), the Electric Power Research Institute, and by a consortium of industry and foundation sponsors