Cars, Trucks, and Climate: EPA Regulation of Greenhouse Gases from Mobile Sources

James E. McCarthy
Specialist in Environmental Policy

Brent D. Yacobucci
Specialist in Energy and Environmental Policy

In 2011, the Obama Administration took two major steps toward reducing greenhouse gas (GHG) emissions from motor vehicles. On July 29, the White House announced that it had reached agreement with 13 auto manufacturers, the United Auto Workers, the state of California, and other interested parties under which GHG emissions from new cars and light trucks will be reduced about 50% by 2025, and average fuel economy will rise to nearly 50 miles per gallon. On November 16, the Environmental Protection Agency (EPA) and the Department of Transportation (DOT) jointly proposed regulations for those vehicles. In addition, on August 9, EPA and DOT promulgated the first GHG and fuel efficiency standards for medium and heavy duty trucks.

These steps have been taken as the Congress (particularly the House) and the Administration have reached an impasse over climate issues. The Administration has made clear that its preference would be for Congress to address the climate issue through new legislation. Nevertheless, in the wake of a 2007 Supreme Court decision, it has moved forward on several fronts to define how the CAA will be used and to promulgate regulations.

On April 1, 2010, EPA used its authority (§202 of the CAA) to set the first national GHG emission standards: the standards will control emissions from new cars and light trucks beginning in model year 2012, requiring cars, SUVs, minivans, and other light trucks to meet combined emissions levels that the agency estimates will average 250 grams/mile of carbon dioxide (CO2) in model year 2016, about a 30% reduction in emissions compared to 2010 levels. The standards will be gradually phased in, with the first reduction targets set for model year 2012. As part of an agreement brokered by the White House, EPA’s standards were issued jointly with fuel economy (CAFE) standards developed by the National Highway Traffic Safety Administration, and the state of California agreed to harmonize state-level GHG emission standards, so that the auto industry would have a single national set of standards to meet. In July 2011, the White House announced that it had reached agreement on a second phase of these standards, under which CO2 emissions will be reduced to about 160 grams/mile by 2025. Detailed standards were proposed November 16; a public comment period runs through January 30, 2012.

The key to using the CAA’s authority to control greenhouse gases was for the EPA Administrator to find that GHG emissions are air pollutants that endanger public health or welfare. Administrator Jackson promulgated such an endangerment finding in December 2009. With the endangerment finding finalized, the agency can proceed to regulate emissions from motor vehicles of all kinds. Medium- and heavy-duty trucks are next in line: EPA proposed GHG emission standards for them October 25, 2010, and finalized them August 9.

In all, EPA has received 11 petitions asking that it make endangerment findings and proceed to regulate emissions of greenhouse gases. Ten of the 11 petitions addressed mobile sources: besides motor vehicles, the petitions cover aircraft, ships, nonroad vehicles and engines, locomotives, and fuels, all of which are covered by Title II of the CAA. This report discusses the full range of EPA’s authority under Title II and provides information regarding other mobile sources that might be regulated under this authority, in addition to describing the car and truck regulations.

Regulation of GHGs from mobile sources has led the agency to establish controls for stationary sources, such as electric power plants, as well. Stationary source options, the authority for which comes from different parts of the CAA, are addressed in CRS Report R41212, EPA Regulation of Greenhouse Gases: Congressional Responses and Options.


Date of Report: December 22, 2011
Number of Pages: 22
Order Number: R40506
Price: $29.95

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