The U.S. Environmental Protection Agency (EPA) should limit greenhouse gases emitted from cars, a coalition of 12 states, a number of cities, and several nonprofit organizations said today in filings for a landmark Supreme Court case on climate change. The case, Massachusetts v. EPA, is expected to be heard later this year or early 2007.
The Clean Air Act requires EPA to set emission standards for substances that could "reasonably be anticipated to endanger public health or welfare." It does so for the components of smog but not for C02 and other greenhouse gases. Led by the state of Massachusetts, the petitioners cite scientific studies linking these emissions to wide-ranging impacts including droughts and flooding along the U.S. coasts. Those effects on climate, they argue, should impel the agency to regulate greenhouse emissions.
"The federal government is shirking its responsibility to enforce the law," said Massachusetts Attorney General Tom Reilly in a conference call with reporters today. And the science of climate impacts, say a group of climate researchers in a friend-of-the-court brief, are "clearly sufficient to support a finding of 'reasonable anticipation' " of the risks of greenhouse gases.
EPA, which prevailed last year in a federal appeals court, says the health impacts of climate change are uncertain and that it's difficult to separate the effects of human activity from natural cycles. Those uncertainties, compounded by the need to abide by U.S. obligations under several international agreements, explain why EPA has avoided tackling greenhouse gases, it says. The agency's arguments must be filed by 5 October.
The states' arguments are "cogent," as they directly address what standards the agency should use in deciding what to regulate, says David Hodas, a professor at Widener University School of Law in Wilmington, Delaware. But he says "it's hard to predict" what the court will do. In 2000, for example, the nine justices surprised experts by stopping the Food and Drug Administration from regulating nicotine in tobacco.
For a more detailed news story on this topic, stay tuned for the 8 September issue of Science.