Over the last year, we've reported on federal and state efforts to cut greenhouse-gas emissions. In October, for instance, "EPA Sets Lower Emissions Regulations for Mowers" covered regulations to go into effect in 2011. And in December, we covered efforts in California to reduce greenhouse-gas emissions in the state to 1990 levels by 2020 and 80 percent below 1990 levels by 2050.

Now comes news that the Environmental Protection Agency last week sent the White House Office of Management and Budget a proposed finding—the Proposal for Endangerment Finding for Greenhouse Gases under the Clean Air Act—that carbon dioxide is a public-health danger.

The finding grew out of 2007 decision by the U.S. Supreme Court that ordered the EPA to determine how to regulate carbon emissions from under the Clean Air Act.

The Wall Street Journal reported that "if approved by the White House Office of Management and Budget, the endangerment finding could clear the way for the EPA to use the Clean Air Act to control emissions of carbon dioxide and other greenhouse gases believed to contribute to climate change. In effect, the government would treat carbon dioxide as a pollutant."

"This is historic news. It will set the stage for the first-ever national limits on global warming pollution and is likely to help light a fire under Congress to get moving," wrote Frank O'Donnell, president of Clean Air Watch, in a March 23 post on that advocacy group's blog.

"This finding will officially end the era of denial on global warming. Instead of allowing political interference in scientific and legal decisions, as was the case in the previous administration, the Obama administration is letting the sun shine in on the dangerous realities of global warming," said Representative Ed Markey, the Massachusetts Democrat who is the chair of the House Select Committee on Energy Independence and Global Warming.

Not everyone embraces the EPA's finding. The New York Times reported reported that "Bill Kovacs, a specialist on global warming issues with the United States Chamber of Commerce, said that an endangerment finding would automatically provoke a tangle of regulatory requirements for businesses large and small," including those involved in transportation, power generation, oil refining, and cement manufacture.

The EPA has not yet issued a public comment on its finding.