WILL WE TAME THE CLIMATE OR WILL IT FINALLY TAME US?

Saturday, October 11, 2003

Lots of people worry about global warming; where and when and by how much temperatures are rising, and whether or how much human activities might be contributing to the increase. William Calvin worries on a more apocalyptic scale -- that the climatic forces that shaped our species could destroy our civilization.

Every few thousand years, the earth's climate undergoes a dramatic shift -- from wet and warm, which is what it is now and has been since the Northern Hemisphere glaciers began to recede about 15,000 years ago, to cool and dry. And back again, with the shift occurring not over centuries or millennia, but in less than a decade.

If this seems unlikely, remember there is no shortage of candidates for climate variability that have nothing to do with human activities. The sun brightens and dims, sunspots come and go, the magnetic poles move, Earth wobbles on its axis and speeds up or slows down in its orbit, and the orbit itself swings in a grand loop around the sun. And we are nowhere close to figuring out how all these things interact.

The effects of human activity, though small in comparison to these planetary forces, might just be the last push needed to trigger one of these shifts. Since we don't know enough to predict when or how the next shift will happen, Calvin says, we ought to be preparing for it. He is an affiliate professor of psychiatry and behavioral sciences at the School of Medicine at the University of Washington, and he spoke at the Accelerating Change Conference held at Stanford University in September.

Consider what would happen in Europe if the Gulf Stream were to shut down -- which is one of the ways climate can suddenly shift. The population of Europe lives much farther north than North Americans mostly do; Rome is about the same latitude as Chicago. London and Paris are close to the line separating the U.S. and Canada. Oslo, Stockholm, and St. Petersburg are about as far north as Anchorage.

Without the Gulf Stream, Europe would have the climate of Canada. Canada feeds 28 million people; Europe some 650 million. If agriculture failed -- not over 500 years, say, but five -- Calvin believes we would see resource wars, with unpaid, hungry armies going marauding in neighboring countries. There wouldn't be time to organize relief, and possibly not capacity either, if the rest of the world were also suffering from prolonged and widespread droughts.

It probably wouldn't mean the extinction of the human species, which has experienced many such episodes. But the ability of our high-tech industrial culture to survive one hasn't been tested. The prudent thing to do would be to put more resources into learning about the climate in the hopes that we can figure out how to stabilize it before the next time it gets close to flipping.

That's still a political question, but it isn't as inherently politicized as, say, deciding whether to sign the Kyoto treaty. Nobody's to blame for celestial mechanics. It's more like asking whether we should have a space program so we can deflect an asteroid heading for the earth. Sure it's a good idea, we just have to decide whether it will cost too much.

That's mostly what Calvin talked about at the conference, but it's only half the story. In his book, A Brain for All Seasons, he lays out the intriguing thesis that abrupt climate change of this kind may have been the driver of the evolutionary process that eventually produced a species capable of worrying about global climate change.

Since the time that the genus Homo split off from the rest of the primate line, about 2.5 million years ago, there have been many times, perhaps hundreds of times, when the climate suddenly changed in this fashion. The ancestral pre-human populations in Africa might have been separated into widely scattered areas where there was suitable habitat, and only some of them left descendants. It's not too much of a stretch to speculate that the cleverest and most adaptable of them were slightly more likely to make it through the genetic bottleneck. Even a small survival advantage in intelligence and brain size (not the same thing, but related) compounded over a couple of hundred iterations of severe climate stress would eventually have large effects. We can't see intelligence in the fossil record, but brain size has roughly tripled over the same length of time.

Stories like this always have a certain ``just-so'' flavor (after Kipling) but every now and then one turns out to be right. And it would make for a pleasing closure if the brain that was forged in the crucible of climate became the instrument that tames it.