Bill McKibben, author of the first global warming book for a general audience, was none too impressed with President Obama's speech to the U.N.'s climate summit on Tuesday. Obama stressed the urgency of the climate crisis and the need for diplomatic cooperation by industrial giants but also by developing countries. While many listeners appreciated the president's strong-handed rhetoric, McKibben thought he set the bar too low. Or, actually, not low enough.

The environmental writer and activist (and erstwhile Atlantic contributor) spearheads a global movement to embrace an atmospheric carbon target of 350 parts per million (ppm). This figure is a good 20 percent below the 450 ppm target that's recently populated pragmatic debate and that was espoused in the climate bill the House passed over the summer. But just ten months ago, leading climatologist Jim Hansen presented a paper stating that "if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted," atmospheric carbon must inch no higher than 350. A bit disconcerting, given the current level of around 390.

McKibben was an early adopter of the 350 goal, founding a movement called that calls upon citizens across the world to pressure their leaders into embracing the new target. The movement is building to a global "day of action," when people in upwards of 125 countries will perform upwards of 1,500 demonstrations of their support. Thousands of bodies will spell out "350" on deserts and beaches from China to New Mexico, musicians will play a total of 350 concerts across multiple continents, and, my personal favorite, the president of the Maldives will host a cabinet meeting underwater (cabinet members are currently in scuba training).  

On Thursday, I spoke with the understated mastermind behind this enormous activist campaign. We covered his Obama malaise, China's wake-up call, and the resurgence of the political protest--a lightly edited transcript follows.

What was your reaction to Obama's speech at the climate summit on Tuesday?

I thought Obama was quite disappointing. It felt to me like he was pre-excusing failure both in Washington and in Copenhagen. If this is as important as he says it is--and in fact, it's far more important than he says it is--then you've got to do more than the occasional speech or reference. You've got to go out and campaign. This guy knows how to campaign. I think we'll know he's completely serious the day he fires up Air Force One and the day begins with the whole press corps in tow in Barrow, Alaska and ends in McMurdo Station in the Antarctic.

Do you think Obama made a mistake by frontloading the Congressional agenda with health care?

God only knows. I'm a big Obama guy--I was one of the first names on Environmentalists for Obama. I don't know what the problem is, but it's clearly not getting done yet on climate in the Obama administration. It's a great shame because the science is clearer than it's ever been. And in certain ways, the politics is more possible than it's been before, too. It's quite astonishing to see the developing nations. No one would have predicted a year ago that an Obama-led U.S. would look less flexible and able to deal with this than China. But that's what it looked like after the U.N.

So you were happy with President Hu's speech?

Eh, happy--look, China is a lot further along than one would have thought on embracing this. The reason is, I think, that they've seriously internalized the deep danger that they're in. I don't think it has much to do with world opinion--they're happy to flout world opinion. But they're well aware that if the glaciers of Tibet melt, that's where the Yangtze and the Yellow [Rivers] come from.

In a roundtable discussion The Atlantic hosted in 2000, you posited that political change on climate issues was going to come "the old-fashioned way... Enough folks are going to look around them and say--holy cow, something bad is going down. They are going to organize, they are going to protest, they are going to make the political system bend." I'm wondering where is on this journey.

I didn't do really serious, fulltime--albeit volunteer--organizing about this until three years ago. 350 is a way to globalize the movement and to bring it up to date with the science of the moment. I'm not promising you in any way that it's going to work. It frightens me intensely that we're seeing change on the scale that we're seeing, with about a degree Celsius increase in temperature. That doesn't bode well. But, at some level, all of this is relative, and if the last twenty years has proved anything, it's that in the absence of a strong movement, nothing will happen--because nothing has happened.

With the health care debate this summer, there's been a real resurgence in the protest as a way of getting things done. Where do you think 350 fits into this trend, and do you have any ideas as to why people might be more energized to take group action now than they were even just five or ten years ago?

On this issue, the scale of the consequences has become clear enough that people are ready to act. And it didn't hurt that Obama's background as a community organizer in this country kind of lent legitimacy to this. The skills that people acquired in his campaign have been helpful, too.

It feels to me that the immune system of the planet is finally kicking in. After twenty years of waiting to see if a climate movement would develop, one's developing.