By John Larsen
Note: this article is an update to Global Warming Legislation in the 109th Congress.
This graph shows how different legislative proposals would cap U.S. emissions (a variation of this graph recently appeared in a New York Times article). 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policy—an emissions intensity target—is also shown, as is the U.S. commitment under the Kyoto Protocol had it not withdrawn. The graph also shows a “business as usual” scenario, absent any policy changes, using projections from the U.S. Department of Energy’s Energy Information Administration. The blue area shows the estimated range of U.S. emissions reductions that would be needed to stabilize global atmospheric greenhouse gas concentrations between 450 and 550ppm (parts per million) CO2 equivalent.
All proposals are assumed to have been enacted in 2007. 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. Dotted lines indicate extrapolations. This projection incorporates all 6 greenhouse gases.
Bush Administration. Emissions intensity would be reduced 18% from 2002-2012. See page 60 of EIA’s Annual Energy Outlook 2006.
Kyoto Protocol. The U.S. commitment would have been a 7% reduction from 1990 levels for 2008-2012.
McCain-Lieberman. Emissions would be capped at 2004 levels from 2012-2019, 1990 levels from 2020-2029, approximately 22% below 1990 levels from 2030-2049, and 60% below 1990 levels in 2050.
Olver-Gilchrest. Emissions would be capped at 2004 levels from 2012-2019, 1990 levels from 2020-2029, approximately 33% below 1990 levels from 2030-2049, and approximately 75% below 1990 levels in 2050.
Bingaman-Specter. Emissions would be reduced by 2.6% per unit of GDP (an intensity target) from 2012-2021, and by 3% per unit of GDP from 2022 onward. The data used here is based on the EIA’s Energy Market and Economic Impacts of a Proposal to Reduce Greenhouse Gas Intensity with a Cap and Trade System report which analyzes the target through 2030. This graph extrapolates the 3% intensity target linearly through 2050 and may be somewhat conservative in its cap projections after 2030. Emissions data for the price cap projection are derived from the same EIA analysis. Dotted lines indicate extrapolations.
Sanders-Boxer. Emissions would be reduced to 1990 levels from 2010-2020, and to 80% below 1990 levels by 2050.
Kerry-Snowe. Emissions would be reduced to 1990 levels from 2010-2020, beginning in 2021, emissions would be reduced 2.5% per year until 2030, and 3.5% per year until 2050. In 2050, the emissions cap would be equal to approximately 62% below 1990 levels.
Stabilize at 450/550ppm. Derived from den Elzen et al. (2006), Figure 8-2. “Multi-stage” scenarios were used in this analysis. Full discussion of assumptions begins on page 207.
For information on the methodologies used in this graph, contact John Larsen.