Elisabeth Rosenthal. The New York Times.

IN 2008, both the Democratic and Republican candidates for president, Barack Obama and John McCain, warned about man-made global warming and supported legislation to curb emissions. After he was elected, President Obama promised “a new chapter in America’s leadership on climate change,” and arrived cavalry-like at the 2009 United Nations Climate Conference in Copenhagen to broker a global pact.

But two years later, now that nearly every other nation accepts climate change as a pressing problem, America has turned agnostic on the issue.

In the crowded Republican presidential field, most seem to agree with Gov. Rick Perry of Texas that “the science is not settled” on man-made global warming, as he said in a debate last month. Alone among Republicans onstage that night, Jon M. Huntsman Jr. said that he trusted scientists’ view that the problem was real. At the moment, he has the backing of about 2 percent of likely Republican voters.

Though the evidence of climate change has, if anything, solidified, Mr. Obama now talks about “green jobs” mostly as a strategy for improving the economy, not the planet. He did not mention climate in his last State of the Union address. Meanwhile, the administration is fighting to exempt United States airlines from Europe’s new plan to charge them for CO2 emissions when they land on the continent. It also seems poised to approve a nearly 2,000-mile-long pipeline, from Canada down through the United States, that will carry a kind of oil. Extracting it will put relatively high levels of emissions into the atmosphere.

“In Washington, ‘climate change’ has become a lightning rod, it’s a four-letter word,” said Andrew J. Hoffman, director of the University of Michigan’s Erb Institute for Sustainable Development.

Across the nation, too, belief in man-made global warming, and passion about doing something to arrest climate change, is not what it was five years or so ago, when Al Gore’s movie had buzz and Elizabeth Kolbert’s book about climate change, “Field Notes From a Catastrophe,” was a best seller. The number of Americans who believe the earth is warming dropped to 59 percent last year from 79 percent in 2006, according to polling by the Pew Research Group. When the British polling firm Ipsos Mori asked Americans this past summer to list their three most pressing environmental worries, “global warming/climate change” garnered only 27 percent, behind even “overpopulation.”

This fading of global warming from the political agenda is a mostly American phenomenon. True, public enthusiasm for legislation to tackle climate change has flagged somewhat throughout the developed world since the recession of 2008. Nonetheless, in many other countries, legislation to control emissions has rolled out apace. Just last Wednesday, Australia’s House of Representatives passed a carbon tax, which is expected to easily clear the country’s Senate. Europe’s six-year-old carbon emissions trading system continues its yearly expansion. In 2010, India passed a carbon tax on coal. Even China’s newest five-year plan contains a limited pilot cap-and-trade system, under which polluters pay for excess pollution.

The United States is the “one significant outlier” on responding to climate change, according to a recent global research report produced by HSBC, the London-based bank. John Ashton, Britain’s special representative for climate change, said in an interview that “in the U.K., in Europe, in most places I travel to” — but not in the United States — “the starting point for conversation is that this is real, there are clear and present dangers, so let’s get a move on and respond.” After watching the Republican candidates express skepticism about global warming in early September, former President Bill Clinton put it more bluntly, “I mean, it makes us — we look like a joke, right?”

Americans — who produce twice the emissions per capita that Europeans do — are in many ways wired to be holdouts. We prefer bigger cars and bigger homes. We value personal freedom, are suspicious of scientists, and tend to distrust the kind of sweeping government intervention required to confront rising greenhouse gas emissions.

“Climate change presents numerous ideological challenges to our culture and our beliefs,” Professor Hoffman of the Erb Institute says. “People say, ‘Wait a second, this is really going to affect how we live!’ ”

There are, of course, other factors that hardened resistance: America’s powerful fossil-fuel industry, whose profits are bound to be affected by any greater control of carbon emissions; a cold American winter in 2010 that made global warming seem less imminent; and a deep recession that made taxes on energy harder to talk about, and job creation a more pressing issue than the environment — as can be seen in the debate over the pipeline from Canada.

But it is also true that Europe has endured a deep recession and has had mild winters. What’s more, some of the loudest climate deniers are English. Yet the European Union is largely on target to meet its goal of reducing emissions by at least 20 percent over 1990 levels by 2020.

Connie Hedegaard, the European Union’s commissioner on climate action, told me recently: “Look, it was not a piece of cake here either.”

In fact, many countries in Europe have come to see combating climate change and the move to a “greener” economy as about “opportunities rather than costs,” Mr. Ashton said. In Britain, the low-carbon manufacturing sector has been one of the few to grow through the economic slump.

“One thing I’ve been pleasantly surprised about in the E.U. is that despite the economic and financial crisis, the momentum on climate change has more or less continued,” Mr. Ashton said.

And Conservatives, rather than posing an obstacle, are directing aggressive climate policies in much of the world. Before becoming the European Union’s commissioner for climate action, Ms. Hedegaard was a well-known Conservative politician in her native Denmark. In Britain, where a 2008 law required deep cuts in emissions, a coalition Conservative government is now championing a Green Deal.

In the United States, the right wing of the Republican Party has managed to turn skepticism about man-made global warming into a requirement for electability, forming an unlikely triad with antiabortion and gun-rights beliefs. In findings from a Pew poll this spring, 75 percent of staunch conservatives, 63 percent of libertarians and 55 percent of Main Street Republicans said there was no solid evidence of global warming.

“This has become a partisan political issue here in a way it has not elsewhere,” said Andrew Kohut, president of the Pew Research Center. “We are seeing doubts in the U.S. largely because the issue has become a partisan one, with Democrats” — 75 percent of whom say they believe there is strong evidence of climate change — “seeing one thing and Republicans another.”

Europeans understand the challenges in the United States, though they sound increasingly impatient. “We are very much aware of the political situation in the United States and we don’t say ‘do this,’ when we know it can’t get through Congress,” said Ms. Hedegaard, when she was in New York for the United Nations General Assembly last month. But she added:

“O.K. if you can’t commit today, when can you? When are you willing to join in? Australia is making a cap-and-trade system. South Korea is introducing one. New Zealand and the E.U. have it already. So when is the time? That’s the question for the U.S.”

MEANWHILE, in the developing world, emerging economies like India and China are now pursuing aggressive climate policies. “Two years ago the assumption was that the developed world would have to lead, but now China, India and Brazil have jumped in with enthusiasm, and are moving ahead,” said Nick Robins of HSBC Global Research.

Buffeted by two years of treacherous weather that they are less able to handle than richer nations — from floods in India to water shortages in China — developing countries are feeling vulnerable. Scientists agree that extreme weather events will be more severe and frequent on a warming planet, and insurance companies have already documented an increase.

So perhaps it is no surprise that regard for climate change as “a very serious problem” has risen significantly in many developing nations over the past two years. A 2010 Pew survey showed that more than 70 percent of people in China, India and South Korea were willing to pay more for energy in order to address climate change. The number in the United States was 38 percent. China’s 12th five-year plan, for 2011-2015, directs intensive investment to low carbon industries. In contrast, in the United States, there is “no prospect of moving ahead” at a national legislative level, Mr. Robins said, although some state governments are addressing the issue.

In private, scientific advisers to Mr. Obama say he and his administration remain committed to confronting climate change and global warming. But Robert E. O’Connor, program director for decision, risk and management sciences at the National Science Foundation in Washington, said a bolder leader would emphasize real risks that, apparently, now feel distant to many Americans. “If it’s such an important issue, why isn’t he talking about it?”