Recently the Web site The Politico asked Nancy Pelosi, the speaker of the House, why she was blocking attempts to tack offshore drilling amendments onto appropriations bills. “I’m trying to save the planet; I’m trying to save the planet,” she replied.

I’m glad to hear it. But I’m still worried about the planet’s prospects.

True, Ms. Pelosi’s remark was a happy reminder that environmental policy is no longer in the hands of crazy people. Remember, less than two years ago Senator James Inhofe — a conspiracy theorist who insists that global warming is a “gigantic hoax” perpetrated by the scientific community — was the chairman of the Senate’s Environment and Public Works Committee.

Beyond that, Ms. Pelosi’s response shows that she understands the deeper issues behind the current energy debate.

Most criticism of John McCain’s decision to follow the Bush administration’s lead and embrace offshore drilling as the answer to high gas prices has focused on the accusation that it’s junk economics — which it is.

A McCain campaign ad says that gas prices are high right now because “some in Washington are still saying no to drilling in America.” That’s just plain dishonest: the U.S. government’s own Energy Information Administration says that removing restrictions on offshore drilling wouldn’t lead to any additional domestic oil production until 2017, and that even at its peak the extra production would have an “insignificant” impact on oil prices.

What’s even more important than Mr. McCain’s bad economics, however, is what his reversal on this issue — he was against offshore drilling before he was for it — says about his priorities.

Back when he was cultivating a maverick image, Mr. McCain portrayed himself as more environmentally aware than the rest of his party. He even co-sponsored a bill calling for a cap-and-trade system to limit greenhouse gas emissions (although his remarks on several recent occasions suggest that he doesn’t understand his own proposal). But the lure of a bit of political gain, it turns out, was all it took to transform him back into a standard drill-and-burn Republican.

And the planet can’t afford that kind of cynicism.

In themselves, limits on offshore drilling are only a modest-sized issue. But the skirmish over drilling is the opening stage of a much bigger fight over environmental policy. What’s at stake in that fight, above all, is the question of whether we’ll take action against climate change before it’s utterly too late.

It’s true that scientists don’t know exactly how much world temperatures will rise if we persist with business as usual. But that uncertainty is actually what makes action so urgent. While there’s a chance that we’ll act against global warming only to find that the danger was overstated, there’s also a chance that we’ll fail to act only to find that the results of inaction were catastrophic. Which risk would you rather run?

Martin Weitzman, a Harvard economist who has been driving much of the recent high-level debate, offers some sobering numbers. Surveying a wide range of climate models, he argues that, over all, they suggest about a 5 percent chance that world temperatures will eventually rise by more than 10 degrees Celsius (that is, world temperatures will rise by 18 degrees Fahrenheit). As Mr. Weitzman points out, that’s enough to “effectively destroy planet Earth as we know it.” It’s sheer irresponsibility not to do whatever we can to eliminate that threat.

Now for the bad news: sheer irresponsibility may be a winning political strategy.

Mr. McCain’s claim that opponents of offshore drilling are responsible for high gas prices is ridiculous — and to their credit, major news organizations have pointed this out. Yet Mr. McCain’s gambit seems nonetheless to be working: public support for ending restrictions on drilling has risen sharply, with roughly half of voters saying that increased offshore drilling would reduce gas prices within a year.

Hence my concern: if a completely bogus claim that environmental protection is raising energy prices can get this much political traction, what are the chances of getting serious action against global warming? After all, a cap-and-trade system would in effect be a tax on carbon (though Mr. McCain apparently doesn’t know that), and really would raise energy prices.

The only way we’re going to get action, I’d suggest, is if those who stand in the way of action come to be perceived as not just wrong but immoral. Incidentally, that’s why I was disappointed with Barack Obama’s response to Mr. McCain’s energy posturing — that it was “the same old politics.” Mr. Obama was dismissive when he should have been outraged.

So as I said, I’m very glad to know that Nancy Pelosi is trying to save the planet. I just wish I had more confidence that she’s going to succeed.

Copyright 2008 The New York Times Company