THE last eco-warrior to win the Nobel peace prize, Wangari Maathai (a tree-planting conservationist who won in 2004), was barely known outside her native Kenya. Al Gore is a flashier shade of green. His trophy cabinet is already bulging—the Nobel medal will have to jostle for space with an Oscar and an Emmy, all won this year. His political career has probably attracted more attention than that of any other living non-president. Billions watched the drama of Bush v Gore unfold in 2000. So last week's announcement in Norway has naturally ignited speculation that Mr Gore will mount another bid for the White House.

Don't hold your breath. As Mr Gore well knows, running for president is not much fun. You have to make small talk with thousands of people you don't know. You are attacked often, viciously and sometimes unfairly. And you have to forgo that comforting extra scoop of ice-cream. Why would Mr Gore re-subject himself to such an ordeal? Currently, as the prophet of the planet's most fashionable cause—preventing climate change—he is showered with adulation wherever he goes. The more the world recoils from George Bush, the more it embraces the man he beat (or didn't, if you believe some diehard Gorephiles). Mr Gore advocated tackling global warming and staying out of Iraq before either cause was popular in America. Foreigners love him. So do Democrats.

But were he to heed the 200,000 petitioners who have signed up at www.draftgore.com, he would lose his saintly aura. He would have to raise money and trash his opponents again (it was he who first attacked Michael Dukakis for freeing violent jailbirds for the weekend). His tendency to over-dramatise the likely consequences of climate change—will the oceans rise by two feet or 20?—would be ruthlessly pilloried. Worst of all, he would probably lose again. A Gallup poll taken after the Nobel announcement found that if he ran for the Democratic nomination, Hillary Clinton would thrash him by 30 points and Barack Obama would pip him by five. Only 48% of Democrats said they wanted him to run—six points less than seven months ago. Mr Gore has repeatedly, though not absolutely definitively, said he is not planning to run, and did so quite firmly again this week. The chances must now be remote that he will change his mind.

Far more likely is that Mr Gore will carry on as before, agitating from outside the political system for America to emit less carbon. He may succeed. The Senate will soon consider a bill, co-sponsored by Mr Gore's former running mate, Joe Lieberman, to set up a cap-and-trade system for greenhouse-gas emissions. Similar proposals are working their way through the House of Representatives. If both arms of Congress present Mr Bush with a cap-and-trade bill, he may well sign it. If none of this happens before next year's election, it will probably do so afterwards.

Turning up the heat

Public opinion is shifting. The proportion of Americans who say they worry “a great deal” about global warming has risen from 28% to 41% in the past four years. Over the same period, the proportion favouring “immediate, drastic action” to protect the environment has risen from 23% to 38%. How much of this is due to Mr Gore is impossible to say. Others crunched the numbers (including the UN's Intergovernmental Panel on Climate Change, with which he shared the Nobel). Hurricane Katrina, some reckon, did more than Mr Gore to make Americans fear global warming. (Illogically, since one storm proves nothing.) And Mr Gore's political past sometimes hinders his message. Granted, many Americans take him more seriously because he used to be vice-president. But others dismiss him because he was part of an administration that often twisted the truth. Nearly half of Republicans think the environment is in good shape; only 9% of Democrats agree.

Despite all these caveats, Mr Gore has surely helped to pave the way for American action against climate change. American voters are hardly demanding such action—only 2% say that climate change is one of the most important issues they will take into account when voting next year. But all the main Democratic candidates favour a cap-and-trade system. They also favour auctioning the emissions permits rather than giving them away. Mr Obama uses religious language to make the case, arguing that “we are not acting as good stewards of God's earth.” On the Republican side, John McCain has long pushed for cap-and-trade. His main rivals have not so far felt pressed by their Republican electorate to say much about it. But whoever clinches the nomination will be forced to take a stance.

Besides Mr Gore, however, no plausible candidate of either party favours a carbon tax, the most efficient way to tackle emissions. (Chris Dodd, a Democrat, does, but he surely won't win.) Voters prefer solutions that are either cheap or that they think will be paid for by someone else. A poll for the New Scientist magazine in June tried to quantify this, with sobering results. Only half of Americans would favour rules to force power companies to emit less if that raised their monthly electricity bill from $85 (the average in 2005) to $155 (an estimate of the hike needed to lower American emissions by 5% by 2020). And only 37% could stomach a tax that raised petrol (gasoline) prices to $4 a gallon. That would be an unprecedented hardship for Americans but barely half what the stuff now costs in Britain.

This is why Mr Gore talks more bluntly now than he ever did on the campaign trail, and why no serious presidential contender echoes him. You cannot win the White House by telling Americans that they must pay more to drive, or by telling Midwestern coalminers that their industry must clean up or die. But if candidates do not prepare America for the cost of tackling climate change, the next president will have no mandate to impose it. Now that's an inconvenient truth.