Barack Obama will fly to Copenhagen at the end of this week for a brief visit. His mission: to plead Chicago's case to the International Olympic Committee, which is deciding whether the Windy City, Madrid, Rio de Janeiro, or Tokyo will get the honor (and questionable economic benefits) of hosting the 2016 Games. The minor scheduling decision has set off a small tempest in a teapot. The attention-starved Danes (they're even paying for me to visit next week to learn about their domestic environmental policy) are excited to play host to a U.S. president. And the American right wing is eager to offer absurd political attacks, like Michael Goldfarb from The Weekly Standard making the claim that lobbying on behalf of his hometown -- and the United States of America -- is some kind of corrupt payoff to an insidious "Chicago machine."

This is silly, but the brief moment of international political attention to the city of Copenhagen prefigures a much more serious meeting in December -- a major international conference on climate change. It's long been clear that the summit was unlikely to immediately result in global adoption of a comprehensive agreement on curbing greenhouse gas emissions -- the issue of exactly how to handle the large economies of the developing world is too thorny.

But as of 12 months ago there were high hopes that the meeting could be a productive one, in particular by incorporating the United States into the family of countries trying to work constructively on the climate issue.

After all, not only was Barack Obama promising to limit emissions through a cap-and-trade system, his Republican opponent John McCain was promising something similar. The two contenders' plans had substantial differences, but on some level the differences seemed not so important. After all, Congress would be determining the details of climate policy anyway, and the real limits of how much can be done are also determined by Congress.

Now, however, the "limits" imposed by Congress -- and especially the United States Senate -- look nearly insurmountable. McCain, in some kind of fit of pique, has completely abandoned his former support for action on climate. Republican John Warner, formerly someone willing to lead his party to sense on this issue, is no longer with us. The health-care debate has revealed a GOP prepared to treat legislation as a blood sport. Republicans are just trying to deliver defeats wherever possible. And if progressives think they've had a hard time keeping Democratic senators united during the health debate, they'll have a real nightmare on their hands when it comes to getting senators who represent coal (Rockefeller, Byrd, Conrad, Dorgan, Baucus) or oil (Landrieu) or automotive (Levin, Stabenow) interests to say nothing of those who are just very electorally vulnerable (Lincoln, Pryor, Nelson) to vote for meaningful carbon-dioxide reductions. With health care, the big question has been whether progressives can round up 60 votes for a public option -- and the answer is apparently "no." On climate it's not clear you can even find 50 for anything approaching a serious bill. The House of Representatives passed a historic, though deeply flawed, bill before the summer recess. In the Senate, Barbara Boxer and John Kerry introduced a bill this week, but nobody expects anything to go anywhere this year, if ever.

This is going to create, to put it mildly, an embarrassing situation for the Obama administration at the Copenhagen conference. Unlike the Bush administration, it won't be there to try to deliberately sabotage things. But it won't really be able to play the role you expect from the United States of America at such a gathering, the role of leader. After all, how can Obama lead the world into the clean-energy future when he can't lead the Democratic majority in the U.S. Congress?

There's been some talk lately of the idea of climate change as a national-security issue, mostly focused on the hard security risks that could stem from climate-induced political destabilization in the developing world. There's something to this approach, but realistically it casts the issue too narrowly. Carbon emissions and their impact on the planet are intrinsically a national-security issue because they can only be dealt with on an international basis. To our closest allies, the situation is baffling. The right is ascendant in most of Europe, but neither Nicholas Sarkozy nor Angela Merkel see a commitment to right-of-center politics as requiring them to deny the clear facts about the threat. I met with a senior German foreign ministry official as part of a group of American journalists right after Germany's election earlier this week, and he listed climate as right at the top of his country's international agenda. It's the same with France, Japan, and the U.K. Even China is starting to make promises about emission cuts. But the United States is nowhere to be found.

This is not only a profound crisis for the world but a much more profound crisis for American global leadership than is generally recognized in Washington. Our position in the world is largely determined by the enormous size of our economic output, land mass, and population. But to a critical extent the United States leads a coalition of friendly nations -- and has done so for decades -- because we're generally perceived as the "good guys" of international politics. Better us than the Nazis, then better us than the Communists, and more recently better us than Islamist fanatics. The premise here is that whatever disputes may arise between friends, the U.S. and its major allies are generally on the same side of the biggest disputes of the era.

On climate, that doesn't seem to be the case. The United States is, historically speaking, by far the largest contributor to the problem. And it's not a minor problem -- the quantity of lives at stake far exceeds the number threatened by conventional terrorist attacks -- and rather than be a part of the solution, we've been steadily making things worse.

Foreign elites have a reasonable understanding of American politics and will forgive Obama for not being able to show up in Copenhagen with a fully formed piece of legislation. But unless some kind of realistic roadmap exists where people can see how a serious climate bill might be enacted, we're hurtling toward ecological and diplomatic disaster. It’s not too late for the climate crisis to join the list of serious international problems solved by a U.S.-led coalition. But for it to happen, conservative and "moderate" U.S. politicians need to ask themselves if they really want America's future to be that of an isolated country, despised by all for having wrecked the planet.