Sunday, June 19, 2005

The Iceman Cometh

Ulrich Joerin, a Swiss scientist, does climatology without fear. Retreating glaciers supposedly are sure signs of global warming. But Joerin has assembled heavy evidence that Swiss glaciers have advanced and retreated dramatically over the last few thousand years. In fact, for much of that time, they were smaller than they are today, and about 7,000 years ago they all but disappeared.

He takes a journalist up to the edge of a glacier and says, "Back then we would have been standing in the middle of a forest." The proof is beneath his feet: he kicks up a blackened tree stump. It must have been carried down by the glacier. But that means the forest must have been there before the ice. He's collected hundreds of similar tree remains, and dated them carefully.

The fact that the Alpine glaciers are melting right now appears to be part of regular cycle in which snow and ice have been coming and going for thousands of years.

The glaciers, according to the new hypothesis, have shrunk down to almost nothing at least ten times since the last ice age 10,000 years ago. "At the time of the Roman Empire, for example, the glacier tongue was about 300 meters higher than today," says Joerin. Indeed, Hannibal probably never saw a single big chunk of ice when he was crossing the Alps with his army.

Aha! Or not. What does this have to do with global warming? Almost nothing, except that, if he is right, one of the supposedly obvious evidence for it may be no such thing.

Joerin is quick to explain that he is not trying to explain away the effects of man-made warming of the past few years: "Our findings so far could also be seen as giving the exact opposite of a climatic all-clear," he says. "If we can prove that there were ancient forests where the glaciers are today, it means one thing in particular: that the climate can change more suddenly than we thought."

Up on the Tschierva Glacier the two scientists are especially keen on finding the answers to the most pressing questions of the day: How quickly did the climate change? How quickly did the balance of ice slip from a plus into a minus and back again? The carbon dating method they've been using is far too imprecise for this, which is why the scientists plan to compare their results to the analysis of the carbon rings. For that they need more samples like TSC-160.

Joerin spots the ideal specimen. "Up there, that is a prime example," he says, pointing to a tree trunk in the ice, deep and unreachable. The scientists will have to return at another time, but they have already set a date. By October the glacier will have receded another 50 meters, freeing the tree trunk for the chainsaw and the microscope.

And that's the way science is supposed to work; dig the sodden tree stump out of the dirty ice, count the rings, report the results. If it adds to the theory, the theory gains. If it doesn't, go back to the drawing board. The only thing a scientific statement should do is fit the facts and be internally consistent. Politics don't have a place.