If Hurricane Katrina was a shot across the bow, it seems as if the war has now begun in earnest. A war between people and a planet that no longer behaves in any of the ways we expect. This, it turns out, is what global warming feels like. The great fraying is underway.
You can see it in the fire-ridden canyons of southern California, where the land was drier than it had been in 90 years. You can see it in the cracking earth of the southeast, where Atlanta stands a few weeks away from running out of water. You can see it in the southwest, where bathtub rings line the great reservoirs, and in the Sierras where the snowpack shrivels. You can see it in the streets of New Orleans, where eight inches of rain fell in a few hours the other day.
None of these events can be linked directly to climate change. This isn't CSI; there's no DNA test to prove paternity. But these are precisely the things we expect would happen as the climate changes. Warm air holds more water vapor than cold air, so evaporation increases and we get drought. Once that water's up there, it's got to come down someplace, and we get floods.
Systems on earth have begun to show this same kind of unsettling change. In late August and September Arctic ice melt was setting records. For the first time ever recorded, the Northwest Passage opened. Meanwhile, observers on flights above Greenland reported that meltwater "cascades" the size of Niagara Falls, were pouring water into the bottom of its great ice sheet. A deep lake may now be forming at the base of the glaciers, speeding their slide into the sea.
And according to a new study in the Proceedings of the National Academy of Sciences published earlier this week, something even scarier has started to happen: the earth's natural "sinks" for storing excess carbon dioxide have begun to lose their effectiveness. Sea water, for instance, is suddenly absorbing less CO2, because stronger winds are mixing carbon-rich deep water into the surface layer. As Dr. Corinne Le Quere of the British Antarctic Survey put it: "Only the most extreme climate models predicted this. We didn't think it would happen until the second half of the century."
All this, by the way, has happened with just a single degree of global warming. The Intergovernmental Panel on Climate Change, which won the Nobel Prize for its work, has predicted that the planet will add another five degrees or so in the course of the century. The great fraying has begun, but it's nowhere near finished.
The only remaining variable is how fast and how well humans will respond. Americans, by far the biggest source of the problem, need to lead the way. So far, Congress has done nothing. At all. Having waited this long, half-measures simply won't do the trick.
A popular movement is finally arising to force that change -- a movement that grows stronger with each passing tragedy. Last spring we at Stepitup07.org organized an historic 1,400 demonstrations in all 50 states; a week from Saturday we'll host another round of big national demonstrations, which will coincide with the largest gathering of college students yet who want to fight global warming.
We know we're not going to prevent all climate change -- it's too late for that. But we cling firmly to the hope that, working together to win rapid federal action, we can slow it down, and keep it from getting completely out of control. We're calling for serious reductions in American carbon emissions -- 80 percent by mid-century -- and for an end to new coal-fired power plants. It's the minimum that scientists tell us makes sense.
Most of us can't go fight the blazes in the hills above Los Angeles. But we can damp down the great central fire of global warming that keeps sparking all these other disasters. It's a fight that seems more necessary with each passing hour.
Bill McKibben, a scholar in residence at Middlebury College, is the co-author of the new book Fight Global Warming Now, and co-founder of StepItUp07.org.