A couple of months before heading off for Naimona'nyi, Thompson says, he revisited Peru's Quelccaya, where the ice is now receding at an alarming rate. Qori Kalis, the outlet glacier he's regularly measured for the past 28 years, has thinned so much that he expects it will have vanished by the time he returns this year. As for Mount Kilimanjaro, the highest peak in Africa, he says, "its ice fields are now just spikes. And once you lose the ice, you lose the history, you lose the record." Fortunately, Thompson got to that iconic mountain just in time; seven years ago he mounted an expedition that pulled out an 11,700-year record of the climate swings in East Africa, including a drought 4,000 years ago that coincided with the collapse of Egypt's fabled Old Kingdom. He keeps a list in his head of 13 more high-elevation ice fields that he'd like to drill before it's too late, including the rapidly shrinking Carstensz glacier on 16,023-foot Mount Jaya, New Guinea's highest peak. He admits he probably can't get to them all.
Perhaps not surprisingly for a native West Virginian who once considered a career in coal geology, Thompson often draws an analogy between glaciers and the proverbial canary in the coal mine. Like the bird, glaciers are warning us of the buildup of dangerous gases. But there is one important difference. "In the past, when the canaries stopped singing and died, the miners knew to get out of the mine. Our problem is, we live in the mine."
J. Madeleine Nash is the author of El Niño: Unlocking the Secrets of the Master Weather-Maker. Thomas Nash is a physicist and photographer. They live in San Francisco.