WASHINGTON -- Democrats in Congress wasted no time in taking up President Barack Obama’s challenge Tuesday night that lawmakers take a "market-based" approach to addressing climate change, even if their effort has little hope of success.

Within hours of the president’s State of the Union address, two Democratic senators announced that they’d introduce a climate-related bill that would include a tax on carbon emissions. The legislation would tax the source of about 85 percent of U.S. greenhouse gas emissions, and would invest heavily in energy efficiency and renewable-energy research.

They acknowledged that the proposal will be challenging, even among their own colleagues in the Senate. Legislation that capped carbon emissions and set up a market for trading pollution credits failed during Obama’s first administration. There’s no possibility of even considering such legislation in the Republican-led House of Representatives.

"It is not going to be pretty. It is going to make making sausage look pretty," Sen. Barbara Boxer, D-Calif., the chairwoman of the Senate Environment and Public Works Committee, said Wednesday. She, along with Sen. Bernard Sanders, a Vermont independent, will unveil the legislation Thursday.

It’s unlikely to draw Republican support, though Obama hinted Tuesday that Congress should consider the bipartisan work that Sen. John McCain, R-Ariz., and then-Sen. Joe Lieberman, a Connecticut independent, did on a previous climate bill.

A far more likely outcome: The president will have to make good on his pledge in Tuesday’s speech to take action in the face of congressional inaction. He warned Congress that he’d act if it didn’t.

"I will direct my Cabinet to come up with executive actions we can take, now and in the future, to reduce pollution, prepare our communities for the consequences of climate change and speed the transition to more sustainable sources of energy," he said.

The most likely move will be in the Environmental Protection Agency, which is likely to use the Clean Air Act to establish tougher pollution rules for carbon emissions from older power plants. The administration already has drafted rules for new power plants.

"It’s likely to be the biggest point of conflict – or at least one of the biggest points of conflict – in this term," said Michael Levi, the director of the Program on Energy Security and Climate Change at the Council on Foreign Relations, a research center. "Using existing authority to cut emissions from existing power plants is not an easy thing to do. It’s certainly not an easy thing to do if you want to cut deeply."

The president took pains Tuesday night to reinforce the message he’d sent during his inaugural address: that climate change is real, and that the United States must respond regardless of the polarizing politics on the issue.

That was the same message from top U.S. climate scientists Wednesday, who warned a Senate panel led by Boxer that there will be growing consequences associated with climate change.

One of the scientists sounded a dire warning about the potential effects of the proposed Keystone XL pipeline, which environmental groups oppose because it would tap Canadian oil sands, which are higher in carbon emissions than other sources. Dozens of climate activists and celebrities were arrested Wednesday in front of the White House for a protest of the pipeline, which would run through the nation’s belly down to Texas.

"If we are partners to that and accelerate that activity, we’re moving this curve in the wrong direction," said James McCarthy, a professor of biological oceanography at Harvard University.

The American Petroleum Institute released a poll Wednesday that found widespread public support for the pipeline.

The Harris Interactive poll, part of the industry group’s effort to ramp up support for the project, found that 69 percent of those surveyed favored building the pipeline. Eighty-three percent thought the pipeline would strengthen the nation’s energy security, said institute President Jack Gerard. Even more – 92 percent of those surveyed – think jobs should be a consideration when the administration decides whether to approve it, Gerard said.

"Millions of people are still looking for jobs in the United States, and we still import nearly half our oil, much from suppliers far less reliable and friendly than Canada," he said.

There’s a "Cheerio effect" to climate change, said J. Marshall Shepherd, the president of the American Meteorological Society and a professor at the University of Georgia. Ordinary people see the consequences, from rising sea levels that threaten coastal communities, more severe droughts and rainfall in places that are unaccustomed to them, and higher food costs thanks to disrupted weather patterns, he said.

"It’s not just about polar bears," he said.

• Read more articles by Erika Bolstad

Order Reprint