WASHINGTON — A federal appeals court on Tuesday upheld the first-ever regulations aimed at reducing the gases blamed for global warming, handing down perhaps the most significant decision on the issue since a 2007 Supreme Court ruling that greenhouse gases could be controlled as air pollutants.
The rules, which had been challenged by industry groups and several states, will reduce emissions of six heat-trapping gases from large industrial facilities such as factories and power plants, as well as from automobile tailpipes.
A three-judge panel of the US Court of Appeals in Washington said that the Environmental Protection Agency was ‘‘unambiguously correct’’ in using existing federal law to address global warming, denying two of the challenges to four separate regulations and dismissing the others.
Michael Gerrard, director of the Center for Climate Change Law at Columbia University, said no one expected the ‘‘complete slam dunk’’ issued by the court Tuesday, and said the decision was exceeded in importance only by the Supreme Court ruling five years ago.
It also lands during a presidential election year where there are sharp differences between the two candidates when it comes to how best to deal with global warming.
President Obama’s administration has come under fierce criticism from Republicans, including Mitt Romney, for pushing ahead with the regulations after Congress did not pass climate legislation and after the Bush administration resisted such steps. In 2009, the EPA concluded that greenhouse gases endanger human health and welfare, triggering controls on automobiles and other large sources. But the administration has always said it preferred to address global warming through a new law.
Carol Browner, Obama’s former energy and climate adviser, said the decision ‘‘should put an end, once and for all, to any questions about the EPA’s legal authority to protect us from dangerous industrial carbon pollution.’’
At a town hall gathering in New Hampshire last year, Romney, the presumptive Republican presidential nominee, said it was a mistake for the EPA to be involved in reducing emissions of carbon dioxide, the chief greenhouse gas.
‘‘My view is that the EPA is getting into carbon and regulating carbon has gone beyond the original intent of the legislation, and I would not go there,’’ he said.
The court on disagreed with Romney’s assessment when it denied two challenges to the administration’s rules, including one arguing that the agency erred in concluding greenhouse gases endanger human health and welfare. Lawyers for the industry groups and states argued that the EPA should have considered the policy implications of regulating heat-trapping gases along with the science.
The judges — Chief Judge David Sentelle, who was appointed by Republican President Ronald Reagan, and David Tatel and Judith Rogers, both appointed by Democrat Bill Clinton — flatly rejected those arguments.
‘‘This is how science works,’’ the unsigned opinion said. ‘‘EPA is not required to re-prove the existence of the atom every time it approaches a scientific question.’’
Industry groups vowed to fight on.
‘‘Today’s ruling is a setback for businesses facing damaging regulations from the EPA,’’ said Jay Timmons, president and CEO of the National Association of Manufacturers. ‘‘We will be considering all of our legal options when it comes to halting these devastating regulations.”
Environmentalists, meanwhile, called it a landmark decision for global warming policy, which has been repeatedly targeted by the Republican-controlled House.
‘‘Today’s ruling by the court confirms that EPA’s common-sense solutions to address climate pollution are firmly anchored in science and law,’’ said Fred Krupp, president of the Environmental Defense Fund.
It “is a grand slam for the EPA and the health of the American people, and another strikeout for the fossil fuel special interests trying to block clean energy progress,” said US Representative Edward Markey of Massachusetts, a Malden Democrat who is the ranking member on the Natural Resources Committee and a senior member of the Energy and Commerce Committee.
Massachusetts, along with 11 other states, took on the EPA in 2005 to force the agency to take action against carbon emissions and other greenhouse gases. The US Court of Appeals in the District of Columbia ruled against the states. In an appeal, the Supreme Court ruled 5-4 in 2007 in favor of Massachusetts and its partner states and against the Bush administration.
Efforts led by Democratic Senator John Kerry of Massachusetts to create a bipartisan bill laying out the nation’s policy on global warming failed in 2010.