Continued from page 1

“Regulations can’t create technology that doesn’t exist or change the laws of physics and economics, so the only way to comply with EPA’s proposals would be to inflict massive increases in energy costs and massive increases in unemployment on families across our nation,” said Charles Drevna, the president of the National Petrochemical and Refiners Association said in a statement.

Mr. Segal also doubted the environmental benefits of the EPA move in the absence of “coordination with foreign nations.”

Fast-growing China has surpassed the United States as the top emitter of carbon, the most prominent greenhouse gas, but Beijing has launched an initiative to reduce emissions.

Mr. Obama last year pledged that the United States would curb emissions by 17 percent by 2020 compared with 2005 levels. The goal is modest compared to the actions of other developed economies, particularly the European Union.

Most scientists say the world is far off-track at meeting a goal - codified at UN climate talks in Mexico this month - of keeping temperatures from rising more than 3.6 degrees Fahrenheit above pre-industrial levels.

The EPA was able to act as a result of a 2007 Supreme Court ruling that gave it authority to regulate greenhouse gases under the landmark Clean Air Act.

Joe Mendelson of the National Wildlife Federation, who initiated the case, hailed the agency’s move Thursday, saying it constituted “reasonable and thoughtful steps” to fight climate change.

Bracing for a fight, Mr. Mendelson criticized “polluters that want to hold hostage America’s clean-energy future and our public health with bullying and unfounded threats of doom and gloom.”