This figure depicts the cumulative greenhouse gas emissions budgets for the proposals over two time periods. While the speed with which emissions reductions are implemented is an important determinant of the efficacy of climate change legislation, cumulative emissions reductions are also an essential indicator of the overall environmental stringency of a policy proposal. Time periods of 2010-2030 and 2010-2050 were chosen to evaluate how ambitious the proposals are in both the short and long term. In addition, for the Boxer-Lieberman-Warner, Bingaman-Specter, Doggett and Markey proposals, maximum and minimum reduction scenarios are presented to account for changes in U.S. emissions that may result from conditional targets and complementary policies included in these bills. These estimates do not include changes to the targets or annual emissions levels that may result from the use of cost-containment provisions included in some proposals.

For a full discussion of underlying methodology, assumptions and references, please see WRI does not endorse any of these bills. This analysis is intended to fairly and accurately compare explicit carbon caps in Congressional climate proposals and uses underlying data that may differ from other analyses. Price caps and circuit breakers contained in some bills may allow emissions to exceed what is depicted in this analysis.