The U.S. Supreme Court often hears disputes over how much authority the federal government has to stop businesses from polluting.
But rarely, if ever, in nearly four decades of environmental regulation has the government argued that it has no power over an entire category of potential pollutants -- or that if it had the power, it wouldn't use it.
That's the position, though, that the Bush administration is taking in a lawsuit seeking federal limits on vehicles' emissions of greenhouse gases. The Supreme Court is to hear arguments Wednesday in the case, which was filed by California, 11 other states and most of the nation's major environmental organizations.
The court's ruling, due by next summer, also will resolve a similar lawsuit over the government's power to regulate greenhouse gases emitted by factories and other industrial sources. And it may decide a challenge by automakers of a California law requiring them to limit tailpipe emissions of greenhouse gases starting in 2009. That law has inspired similar statutes in 10 other states.
An overwhelming majority of scientists agree carbon dioxide and other common substances known as greenhouse gases trap heat in the atmosphere and are causing worldwide temperature increases that threaten to become catastrophic in coming decades.
The U.S. Environmental Protection Agency argues in the case before the Supreme Court that greenhouse gases are not air pollutants, and therefore are not subject to government regulation. Even if the common gases are pollutants, the EPA says, nationwide regulation would be premature at best and might cause more harm than good.
The agency's position is consistent with President Bush's policy of relying on industry to reduce emissions voluntarily, and withdrawing the United States from the Kyoto Protocol, which requires industrial nations to cut greenhouse gas emissions 5 percent below 1990 levels by 2012.
Justice Department lawyers argue that a one-nation solution, particularly if imposed by a court, is inappropriate for a global problem.
Greenhouse gases are evenly spread around the world, so a nation that regulates on its own "may bear a substantial economic burden but will receive only a small share of any resulting benefit,'' the lawyers wrote in papers they filed with the Supreme Court. "Countries -- particularly developing countries -- may seek a 'free ride' from expensive regulation self-imposed by other nations,'' they wrote.
What's more, they said, the causes of global warming remain a subject of "substantial scientific uncertainties'' -- and the Clean Air Act allows the government to make that call.
Such assertions dismay the plaintiffs and their supporters, who say the EPA is fiddling while the planet burns.
"Global warming is not merely a future threat, but a present deadly reality,'' said a supporting brief submitted by organizations representing mayors, county governments and several cities across the country, including San Francisco.
The brief cited a World Health Organization estimate that already 150,000 deaths caused each year by malnutrition, malaria and other illnesses can be traced to global warming. And scientists cite forecasts of increasing air pollution, droughts, melting snowpacks and more intense hurricanes.
Nicholas Burns, a deputy California attorney general, said the court should give little weight to the EPA's assertion of scientific uncertainty about the exact causes of global warming. Under the law, "they're required to regulate even in the face of some uncertainty,'' he said.
"There's always going to be some uncertainty," Burns said. "The level of uncertainty as to whether or not global warming is occurring is very low.''
The ultimate issue in the case is whether the federal government must regulate vehicle emissions of greenhouse gases under the provision of the Clean Air Act mandating regulation of pollutants that "may reasonably be anticipated to endanger public health or welfare.'' The law includes climate and weather in its definition of welfare.
The EPA said in 2003 that the law did not even authorize it to regulate greenhouse gases, let alone require it to.
The plaintiffs want the court to order the agency to reconsider its position in new proceedings that would include only scientific evidence, not political or financial arguments.
But first the court will face the question of whether greenhouse gases should be classified as air pollutants. And, for California and other states with their own global warming laws, that is the most critical issue in the case.
If the substances are pollutants, state lawyers say, the EPA -- regardless of its own regulatory stance -- is compelled to grant waivers from more lax federal standards and allow the states to enforce their laws.
But if the substances aren't defined as pollutants, federal approval of state regulation is unlikely.
The Clean Air Act defines a pollutant as a potentially harmful physical or chemical substance emitted into the air. The states and environmental groups, represented by Massachusetts Attorney General Tom Reilly, say carbon dioxide and other greenhouse gases -- methane, nitrous oxide and hydrofluorocarbons -- "fit easily within the (law's) definition.''
But the EPA and its backers say it's not so simple.
The air pollution law, passed in 1970 to combat specific sources of smog and contaminants, is "not appropriate for addressing a global problem believed to be caused by ... a wide range of human activity and natural processes around the world,'' said a brief filed by major U.S. industries.
Martin Kaufman, general counsel of the Atlantic Legal Foundation, representing a group of scientists who oppose federal regulation of greenhouse gases, said carbon dioxide, "an essential and inevitable product of metabolism,'' isn't necessarily a pollutant.
But he said the definition is less important than the question of whether greenhouse gases are pollutants that one nation should regulate -- a decision, he contended, that should be left to the EPA.
The federal government and its supporters also argue that the suit should be dismissed because states can't show they are being harmed by the absence of federal regulation. If they aren't being harmed, the states and their residents lack legal standing to challenge the EPA's inaction.
The United States is the largest single source of greenhouse gases, but regulation of new motor vehicles sold in the United States would achieve "at most a tiny percentage reduction in worldwide greenhouse gas emissions,'' government lawyers said. They argue that individual states would not notice the reduction.
In response, plaintiffs' lawyers catalogued the harm that they said states already suffer because of global warming -- loss of coastal land, worsening smog, dwindling glaciers -- and said there's little question that one cause is motor vehicles sold in the United States, which contribute 6 percent of the world's greenhouse emissions.
Although California and other states have adopted their own laws, they have a stake in federal action because the issue is too monumental for them to tackle without federal help, said Doug Kendall, executive director of the Community Rights Council, which filed arguments on behalf of local government officials.
"No matter how much they do, state and local action alone will not fully address this problem,'' he said.