Some scientists have challenged Dr. Thompson’s analysis of the signals in his ice cores, saying that the chemical changes he interprets as temperature swings probably reflect a more complicated mix of changes in temperature, precipitation and atmospheric circulation patterns. Mathias Vuille, an atmospheric scientist at the State University at Albany, who admires Dr. Thompson’s achievements, said that his analysis on this point “is hard to reconcile with other evidence.”

And an especially intense controversy has erupted about Dr. Thompson’s interpretation of ice he recovered atop Mount Kilimanjaro. Though Dr. Thompson sees the rapid disappearance of ice there as a reflection of climate change, his critics cite more regional than global factors, like precipitation.

While Dr. Thompson has defended his interpretations on these points, he does have some regrets. One is that those years of frenzied drilling led him to fall behind in publishing his data, so some of the evidence he has gathered is not yet available to the broader scientific community.

Still, it is clear that Dr. Thompson managed to retrieve ice cores from a half-dozen places in the world where they can no longer be found in pristine form today. Some of the ice he drilled on Kilimanjaro, for instance, has since disappeared entirely.

Ellen Mosley-Thompson does most of her fieldwork in Antarctica, but she has played a major role in interpreting the ice her husband recovered. Both are convinced that their own analysis is merely a start, and they have put money they have won from scientific prizes into an endowment to preserve the ice cores for future generations.

‘It’s Not Your Time’

As a young man, Dr. Thompson stayed in shape by training for and running marathons. He now realizes his health began a slow decline sometime in his 40s.

Dr. Bowen, a physicist and mountain climber, accompanied Dr. Thompson on several expeditions to write the definitive book about him. He said that atop Mount Kilimanjaro, “my heart went out to Lonnie as I lay in my tent at 20,000 feet and listened to him just hack away, coughing his lungs out. It happened almost every night for four weeks, yet we were all amazed when he got up during the day and was still as productive as four normal people.”