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Global Warming Legislation in the 109th Congress

Note: The most recent version of this chart is available at Comparison of Legislative Climate Change Targets in the 110th Congress.

The 109th U.S. Congress considered no less than seven proposals to address global warming through the use of market-based, cap-and-trade mechanisms. The bills each specified emission caps using different formulas, such as a return to 2000 levels (McCain-Lieberman) or 1.5% reductions per year (Kerry-Snowe). Bills have different time frames; some run only through 2020, while others run through 2050, usually with reductions that increase in later years.

This graph shows how different legislative proposals would cap U.S. emissions. For comparison, the Bush administration policy—an emissions intensity target—is also shown, as is the U.S. commitment under the Kyoto Protocol had it not withdrawn. Also shown are a "business as usual" scenario, absent any policy changes, using projections from the U.S. Department of Energy's Energy Information Administration, and estimated U.S. emissions reduction paths that would be needed to stabilize global atmospheric greenhouse gas concentrations at 450 or 550ppm (parts per million) CO2 equivalent.

The number of cap-and-trade bills in the 109th Congress starkly differs from previous Congresses where McCain-Lieberman was the only formal proposal considered. Congress now has several options that are very different in their stringency. For example, there is a 2 billion ton difference in year 2020 emission caps between the least stringent (Bingaman) and the most stringent (Jeffords-Boxer and Waxman) proposals. The Jeffords-Boxer and Waxman proposals come closest to emissions trajectories that many policymakers consider necessary to avoid the worst consequences of global warming.


All proposals are assumed to have been enacted in 2006. Years between targets or projections were interpolated using a simple linear formula.

Emissions intensity is a concept where emissions are measured relative to a production level, such as CO2/GDP, as opposed to a percentage or total reduction relative to a baseline year. Total emissions can increase even under a decreasing intensity target, if GDP grows faster than emissions. For a complete analysis, see Target: Intensity. An Analysis of Greenhouse Gas Intensity Targets.

Description of Proposals and Scenarios

Business as Usual. Historical emissions from 1990-2004 come from the EPA’s U.S. Inventory of Greenhouse Gas Emissions and Sinks 1990-2004. Emissions projections through 2030 come from the Energy Information Agency's (EIA) Annual Energy Outlook 2006 (Table 15) and are extrapolated from that report for 2030-2050.

Bush Administration. Emissions intensity would be reduced 18% from 2002-2012.

Kyoto Protocol. The U.S. commitment would have been a 7% reduction from 1990 levels for 2008-2012.

McCain-Lieberman/Olver-Gilchrest. Emissions would be capped from 2010-2020 equal to 2000 levels.

Bingaman. The discussion draft is largely modeled after the emissions caps in the recommendation from the National Committee on Energy Policy (NCEP). The NCEP report recommends a 2.4% annual reduction in emissions intensity from 2010-2020 and a 2.8% intensity reduction from 2020 to 2025. The data used here is taken from the EIA report Energy Market Impacts of Alternative Greenhouse Gas Intensity Targets.

Udall-Petri. Emissions would be capped at the average annual emissions of the three years immediately following enactment (assumed here to be 2007-2009).

Feinstein. Emissions would be capped at "current levels" (assumed here to be the beginning of 2006). Emissions would be reduced 0.5% per year from 2011-2015 and 1% per year from 2016-2020.

Kerry-Snowe. Beginning in 2010, emissions would be reduced 1.5% per year until 2020, 2.5% per year until 2030, and 3.5% per year until 2050.

Waxman. Emissions would be reduced to 1990 levels from 2010-2020, with 5% annual reductions thereafter.

Jeffords-Boxer. Emissions would be reduced to 1990 levels from 2010-2020, and to 80% below 1990 levels by 2050.

Stabilize at 450/550ppm. Derived from den Elzen and Meinshausen (2005), Figure 9c.

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