The quest for cleaner cars got a big boost on Apr. 2, 2007, when the U.S. Supreme Court ruled that global warming pollution from automobiles can be regulated under the Clean Air Act. "The debate over global warming has ended,” said Joe Mendelson, legal director of the International Center for Technology Assessment (ICTA). The decision establishes carbon dioxide (CO2) and other heat-trapping gases as “air pollution” under the Clean Air Act.

Despite enthusiasm from environmental organization, the Supreme Court’s decision doesn’t actually set new car standards. However, it does remove a key legal question that has been hanging over national and state-based greenhouse gas standards. Moreover, it pressures Congress to enact a national cap on carbon emissions that might trigger big changes in car technology. Binding new car standards are still at least a few years away.

The Supreme Court decision is the culmination of eight years of legal back-and-forth, which began in 1999, when the ICTA filed a legal petition calling upon the Environmental Protection Agency (EPA) to regulate the greenhouse gases emitted by automobiles. First passed in 1970, the Clean Air Act spelled out a very broad definition of air pollution: any physical or chemical substance emitted into the air that is "reasonably anticipated to endanger public health or welfare." The EPA is now legally responsible for setting limits on greenhouse gases from cars.

Environmental groups cheered the decision for three reasons, according to John DeCicco, senior fellow at Environmental Defense. “It compels EPA to start addressing global warming, it opens the door for state policies such as California’s greenhouse gas emissions standards for cars to get past court challenges they face, and it puts added pressure on the U.S. Congress to enact national climate protection legislation sooner rather than later,” said DeCicco.

Why Cars?

Cars were one of the first targets of the original Clean Air Act and the law specifically requires EPA to set standards to limit auto pollution. The focus on cars was a natural starting point, but similar petitions were since directed at other sources of global warming pollution such as power plants. Scientific evidence is now overwhelming that carbon pollution from cars and other uses of fossil fuel represents a clear and present danger to public health and welfare. No single source accounts for a majority of the pollution, but cars are one of the larger sources both in the United States and worldwide. America’s automobiles alone contribute more CO2 than the entire emissions of all but three other countries of the world.

Automakers have been inching closer to a constructive position on these issues, and the Supreme Court decision is another prod. The industry is still legally blocking state action to cut global warming effects from cars, but their position is starting to change. Dave McCurdy, chief executive of the Alliance of Automobile Manufacturers, representing most big US and foreign carmakers, said “there needs to be a national, federal, economy-wide approach to addressing greenhouse gases”. The Supreme Court ruling, Mr. McCurdy added, means that “the EPA will be part of this process.”

The battle over greenhouse gas emissions from cars now becomes a road show as courts at the state level decide cases in which automakers attempt to legally block efforts by individual states to establish their own CO2 standards, prior to the EPA setting federal guidelines.