The Environmental Protection Agency on Monday declared carbon blamed for global warming a public health threat, paving the way to regulate the emissions for the first time.

Administrator Lisa Jackson said that the agency was “now authorized and obligated to make reasonable efforts” to cut greenhouse gas emissions.

“These long-overdue findings cement 2009’s place in history as the year when the United States government began addressing the challenge of greenhouse-gas pollution,” she told a news conference.

The announcement came on the first day of a major climate conference in Copenhagen that aims to forge a new global deal on fighting global warming.

Jackson hit back at conservative critics who question the science behind climate change, saying there was “overwhelming evidence” pointing to global warming.

The agency said it was classifying six greenhouse gases—carbon dioxide along with methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride—as public health threats under the U.S. Clean Air Act.

Jackson said that the agency was not immediately imposing new regulations but that the finding would allow it to finalize emissions standards for light-duty vehicles.

President Obama’s administration took the step as Congress debates the first-ever system to restrict carbon emissions, with most Republicans fighting the legislation.

Jackson said that the Obama administration still believed it was important that the legislation go ahead, as such laws would affect the entire economy.

“I don’t want anyone coming out of here believing it’s an either/or,” she said.  (link)