Heroes of the Environment 2008

Lonnie Thompson

In the early 1970s, Lonnie Thompson was looking for a job. He came to Ohio State University, ostensibly to work on the geology of coal, but the first meaningful position he was offered involved polar studies. "I thought: Glaciers only cover 10% of the planet," Thompson recalls. "How important could they be?"

Very important, it turned out, and Thompson — still at Ohio State and now the world's most distinguished paleoclimatologist — would be instrumental in showing why. As ice forms in the polar regions and the mountain glaciers of the world, bits of the atmosphere are trapped inside the frozen water. Scientists can drill thousands of meters deep in places like Greenland or Antarctica and find ice that was formed hundreds of thousands of years ago. They can then analyze those ice cores to find out how warm the earth's atmosphere was at a particular time. Ice cores are key to decoding the earth's climatic past, helping us understand how we are warming it today, and what might happen in the future.

Until Thompson came along, almost all ice cores were taken from relatively accessible polar regions. He decided to drill where others were not venturing: in the glaciers that crown tropical mountain ranges in places like Ecuador, Nepal and Tibet. It was intensely challenging work, involving such logistical nightmares as getting a drill up to the Quelccaya ice cap at an altitude of 18,600 ft. (5,670 m). But eventually, says Thompson, "We did enough to show that there is important climatic history in tropical glaciers."

The mountain ice cores he has analyzed have added immeasurably to our understanding of the earth's climate by broadening research to the tropics, where 70% of the world's population resides. But Thompson's most lasting accomplishment may be his powerful eyewitness record of climate change: the rapid retreat of alpine glaciers over the past few decades is one of the most unequivocal signs of global warming in action.

The fact that the very stuff of Thompson's work is literally vanishing might be depressing to some, but not to him. "I believe when it's clear what we have to do, we'll work together," he says. If we do, the man who once thought glaciers weren't very important will deserve to be remembered as one of their saviors.