Flagstaff, AZ –
Guarded by frigid water, giant mosquito swarms and hungry grizzly bears. . .is a terrestrial journal dating back thousands of years. Recorded in the layers of Arctic lake mud is information about changes in lake water temperature, runoff from melting glaciers, and the frequency of ash fall from volcanic eruptions.
From the depths of Alaskan lakes Kaufman is hauling out 20-foot-long tubes of mud, a treasure trove of information about past environmental changes.
In his core samples, Kaufman has found evidence that the Arctic had been cooling for more than two-thousand years. There were some warm spots, . . .during the Middle Ages for example. That was demonstrated in Kaufman's core samples by an explosion of biological productivity and a retreat of glaciers. But overall, the earth has been on a decisive cooling trend. That's changed, though, in the last 60 years. Four out of five of the warmest decades in the past two millennia have occurred since 1950.
And the last ten years, were the warmest yet. The Arctic heated up by half a degree centigrade.
Kaufman says he's convinced that most of this dramatic warming is caused by greenhouse gases, Never before, he adds, have humans had such an impact on their environment.
But still, the idea of global warming is politically controversial. Kaufman will assure you, the science behind it is solid, but definitely messy.
Inquiring Minds is a production of KNAU, Arizona Public Radio. I'm Bonnie Stevens.