Scores of climate change bills are stacking up in the legislative queue. Numerous hearings, the most recent on the polar bear, are highlighting the issue. And some regulation-averse corporate executives have even called on Congress to step in.
But despite the dramatic shift in the Capitol in favor of doing something to reduce greenhouse gas emissions, global warming legislation remains a long shot for this year.
Proponents always knew it would be tough to get a bill with mandatory limits through a narrowly divided Congress and past President Bush. But the first bill to advance since Democrats won an effective majority in 2006 has run into unexpected roadblocks.
Some environmentalists are complaining that it isn't strong enough, and they worry that it may even be watered down. They want to wait to take up a bill after the November election, when Democrats might capture more seats in Congress, as well as the White House.
Many business groups are no more enthusiastic, saying the bill would drive up costs and make it harder for them to compete globally at a time of anxiety about the economy.
And if the criticism from both sides isn't enough, this is of course an election year -- a time when partisan tensions heighten in Congress, making it difficult to pass anything controversial.
Still, congressional leaders are determined to press ahead.
"We must pass the strongest bill we can," said Sen. Barbara Boxer (D-Calif.), the chairwoman of the Senate Environment and Public Works Committee, "but we must remember that the perfect cannot be the enemy of the very good."
Those hoping to pass the bill point out that just a year ago it was unimaginable that environmentalists would win a decades-long fight for tougher fuel economy standards. After the auto industry relented, the measure passed and Bush signed it.
Environmentalists hope that scenario will be repeated with global warming.
"You now have a big chunk of industry saying, 'Let's just get this done,' " said Manik Roy, director of congressional affairs for the Pew Center on Global Climate Change.
The Senate has moved faster than the House. Boxer's committee has approved a bill by Sens. Joe Lieberman (I-Conn.) and John W. Warner (R-Va.) that would cap greenhouse gas emissions from power plants, factories, oil refineries and other polluters.
The bill, called America's Climate Security Act, would require companies that exceed the limits to buy credits from other companies that more than meet them.
The House is still working on its bill. Its leaders say they are determined to try to send a bill to the president before Congress adjourns this year, but they acknowledge that it will be difficult.
More senators support mandatory emission reductions than the last time the issue came up for a vote. That was in 2005, when a bill drew the support of 38 senators.
With Democrats holding a narrow working majority in the Senate (the two independent senators generally vote with them), the bill's supporters need Republican votes to reach the 60 required to overcome a filibuster. But when the measure passed the Senate's environment committee, it received the support of only one Republican: Warner.
And a prominent Republican who was an early advocate of mandatory emission reductions opposes the bill. Sen. John McCain of Arizona objects that the measure doesn't promote nuclear power, a low-emission energy source he sees as a crucial part of the solution.
The bill has generated concern from industry groups such as airlines and oil and gas producers. The American Iron and Steel Institute said the bill would make U.S. businesses less competitive, saying that it "applies an uneven standard to American manufacturers, while not addressing the carbon footprint of our major foreign competitors."
William Kovacs, vice president for environment, technology and regulatory affairs at the U.S. Chamber of Commerce, dared Democrats to pass a bill he said would drive up utility costs at a time of high economic anxiety.
"Go for it," he said, warning that lawmakers could expect their votes to become a campaign issue.
In a sign of the difficult road ahead, Duke Energy Co., one of the companies that has supported an emissions cap, objects that the measure "unduly penalizes consumers in the Midwest, Great Plains and Southeast who depend on coal for much of their electricity."
Opposition from coal-using utilities is important because a large number of senators hail from states that produce coal or rely on it to produce electricity.
Still, there are companies, including Alcoa, that see the bill as a way to end the uncertainty over regulation they think is inevitable. The aluminum producer called the bill a "strong enough start."
Some environmentalists agree with Boxer that the time to act is now, noting that the bill is the strongest yet to come before the Senate. They are hopeful that it could pass, citing senators who voted against the 2005 bill -- including Elizabeth Dole (R-N.C.) and Max Baucus (D-Mont.) -- who support this year's bill. And they think it's important to bring up the bill to keep climate change in the forefront of the election debate.
"If you believe that action on global warming is increasingly urgent, a sit-back-and-wait strategy doesn't make a lot of sense, particularly when we have an opportunity to move good legislation now," said Jeremy Symons, director of the National Wildlife Federation's global warming program.
But others complain that the measure doesn't go far enough.
"This bill doesn't do the job that science tells us we need to do," said Melinda Pierce, a Sierra Club lobbyist.
Brent Blackwelder, president of Friends of the Earth, called it "an embarrassment."
The measure would reduce greenhouse gas emissions by mid-century to 70% below 2005 levels, but environmental groups claim that is short of the 80% scientists say is needed. A number of groups also object that the bill would, at least initially, give away pollution allowances to companies, reducing the incentive to cut emissions.
Environmental groups hope to strengthen the measure. But that is likely to be difficult in the narrowly divided Senate. And some fear that the bill's sponsors will make "further concessions to an already compromised bill," said Frank O'Donnell of Clean Air Watch.
Some environmentalists worry that industry groups are eager for action this year only because they think they stand a better chance of shaping a bill to their liking than if a measure were to be crafted after the November election.
"The political reality is -- and I think it's unfortunate -- today in the United States Senate, we do not have a 60-vote majority on a strong global warming bill," said Chris Miller, director of Greenpeace USA's global warming campaign. "The only way you move anywhere close to getting the 60 votes you need is to weaken the bill even further."
For that reason, some want to wait.
"The odds are pretty good that whoever is the next president is going to take a better position on global warming than Bush," O'Donnell said. "That in itself makes you wonder, is it wise to race ahead?"
But Tony Kreindler of Environmental Defense warned that environmentalists should push for action now rather than "rolling the dice" on whether the political climate will improve. "Climate right now is very much at the top of the congressional agenda," he said, "and you've got to ride that momentum when you have it."