The US Supreme Court decided it will weigh whether the federal government must regulate emissions of new cars to combat global warming as demanded by environmental groups and some state and city authorities. The case could open the way for the high court to deliver a crucial ruling on how the US government enforces environmental laws. Since 2003, 12 US states, several cities and a dozen environmental groups have waged a legal battle against the federal Environmental Protection Agency (EPA), which has chosen not to curb greenhouse emissions on new cars. The EPA maintains that the federal Clean Air Act does not address global climate change and that carbon dioxide is not defined as a pollutant under the law. The administration of President George W. Bush has advocated voluntary controls instead of mandatory limits on emissions. The plaintiffs in the suit, which include the states of California, Massachusetts and New York, argue that the Clean Air Act obliges the EPA to regulate emissions from cars and power plants such as carbon dioxide and three other gases linked to global warming. Carbon dioxide and similar emissions are believed to trap heat in the earth’s atmosphere, causing […]