Yet even Senator McCain has now walked away from his previous self, mocking President Obama for “saying that the biggest problem we have is climate change.”

“McCain was a champ,” said Gene Karpinski, head of the League of Conservation Voters, which tracks Congress members’ stance on environmental issues. “He would go around the country and talk about climate change. Even when he was the nominee, he didn’t walk away. But when a member of the Tea Party ran against him in the 2010 primary, he went south and never came back.”

This shift has made it impossible to pass any legislation in Congress to help deal with the problem. That has forced President Obama to adopt a different approach.

After the 2010 defeat in the Senate of the so-called cap-and-trade strategy, which was originally a Republican idea, Mr. Obama has taken to using the Environmental Protection Agency’s regulatory powers under the Clean Air Act, circumventing Congress entirely.

This solution is more expensive, however, and makes it more difficult to achieve necessary goals. A more efficient strategy will require bipartisan support. “We can’t win on the federal legislative policy unless we regain Republican support,” Mr. Karpinski said.

Is it possible to turn the Republican Party around?

It won’t be easy. Republican leaders like Mitch McConnell of Kentucky are wedded to defending a declining coal industry and advancing the interests of oil companies, most clearly in their support for the Keystone pipeline. Many of the party’s lawmakers and presidential candidates get a lot of money from people like the Koch brothers, who have multimillion-dollar contributions for anybody who will stand against efforts to curb the use of fossil fuels.

But there is more than money to the story. For many Republicans, climate change poses an existential quagmire. “To them it sounds like, ‘Everything we’ve been doing since the Industrial Revolution is going to kill us; the response must be a big government response and, by the way, it has to be international,’ ” said Mr. Goldston.