"Today will be remembered as a turning point in the fight against global warming," said California Sen. Barbara Boxer, chair of the Senate Environment and Public Works Committee.

The bill requires cuts in carbon dioxide and other heat-trapping gases from electric utilities, transportation and manufacturing, accounting for about 75 percent of U.S emissions.

Lieberman issued a press release stating:

"On its own, the America's Climate Security Act (ACSA) is projected to reduce total U.S. greenhouse-gas emissions by as much as 19% below the 2005 level (4% below the 1990 level) in 2020 and by as much as 63% below the 2005 level in 2050. Lieberman and Warner presented their new bill as the core of a new federal program that Congress should pass to avert catastrophic global climate change while enhancing America's energy security."

"In my 28 years in the Senate, I have focused above all on issues of national security, and I see the problem of global climate change as fitting squarely within that focus," Warner said in the release.

Predictably, industry raised alarmist warnings. Jack Gerard, president and CEO of the American Chemistry Council, a trade group of plastic and chemical manufacturers, is quoted in the Chronicle saying the bill's proposed reductions were "too much, too soon." He warned the bill would "turn energy markets upside down, causing massive reductions in coal usage and enormous increases in natural gas and renewable fuels usage." Which is probably exactly what the senators intended, and certainly what science calls for.

But some environmentalists were unhappy with the bill's system for handling allowances. Environmental group Friends of the Earth did a study of an August draft of the legislation, and author Erich Pica concluded that, "What we're looking at is the potential for corporate giveaways that are orders of magnitude larger than anything environmentalists have ever faced -- potentially the biggest corporate giveaways in American history."

The Friends of the Earth analysis found that the coal industry in particular stands to benefit from this legislation, precisely because it is currently the industry most responsible for global warming pollution. Depending on market conditions, the coal industry could receive permits worth up to $231 billion in the first year alone, 48 percent of the total permit allocation.

Instead of giving these permits away, environmental groups would like to see them auctioned off and the proceeds go to deploying clean energy technologies, training people for "green-collar" jobs, and helping poor people pay their energy bills and weatherize their homes. "Polluters should have to pay for their pollution, not be rewarded for it," says Pica.

Warner and Lieberman have tried for a compromise that would start with auctioning off about one-quarter of the allowances, and increasing the number sold to 73 percent by 2036. Boxer said she or another senator would introduce an amendment to test support for a 100 percent auction system. "We'll see if we can get 51 votes," she said.

Thursday's announcement represents a historic opportunity for the US Government to finally take leadership on global warming, but it is far from a done deal. We'll be watching this bill closely in the coming months as the debate on global warming promises to raise some heat on Capitol Hill.