Only a year after the heart transplant that saved his life, 65-year-old glaciologist Lonnie Thompson is back at work in the Himalayas and Andes, collecting evidence about the past and future of climate.

His research means hauling equipment up mountains and working in freezing, oxygen-starved air at altitudes above 6,000 metres.

Thompson has suffered asthma and congestive heart failure and was on the brink of death two years ago, but was able to recently travel to a glacier in the Himalayas, in west-central Tibet, for a preliminary expeditition.

"We were above 20,000 feet, looking for a potential drill site, and "[the heart] worked very well," he says.

The distinguished professor in the school of earth sciences at Ohio State University has joined researchers in drilling ancient ice cores in 16 countries.

He spoke to Francine Pelletier, guest host of CBC Radio's The Sunday Edition, about his work.