Updated

The Environmental Protection Agency, responding complaints about its December findings about the threat of greenhouse gases, issued a statement Friday saying that the "science is settled" and "greenhouse gases pose a real threat to the American people."

The statement comes after after Virginia Attorney General Ken Cuccinelli filed a petition with the EPA and a challenge in federal appeals court over the EPA's conclusions.

With climate scientists in the hot seat recently over an e-mail scandal and mistakes in a prominent U.N. report, Cuccinelli argues the EPA should "restart the process and this time use rigorous, defensible science."

He says the EPA is expected to announces measures to cap carbon emissions, based on its climate change findings, and that will put a "staggering burden" on Virginia residents and businesses.

The EPA says it is going forward with "common sense measures that are helping to protect Americans from this threat" and said its critics are trying to "stall progress."

Some who support the EPA's efforts to enact carbon caps on vehicle emissions say Cuccinelli is just playing politics.

"It's very clear this is coming from lawyers, not scientists, and there's really no new science that needs to be resolved," said Brendan Bell, Washington representative for the Union of Concerned Scientists, a leading nonprofit environmental group.

But the science that climatologists have been using has come under fire. Recently, some parts of the 2007 United Nations Panel Report on Climate Change were found to contain mistakes, including a claim that the Himalayan glaciers would melt away by 2035.

And one of the lead scientists in the Climate-gate scandal last year, Phil Jones, acknowledged that there has been no statistically significant global warming since 1995. But he also claims most of the climate warning since 1950 is "due to human activity."