At the AGU Chapman Conference last month I met up with Lonnie Thompson, the alpine glaciologist who has spent more time above 20,000 feet than any other human. Despite being interrupted by last-minute demands from Peruvian customs officials – he was squeezing me in before taking off for a new expedition in the Andes – an unphased Thompson carefully laid out the past and present-day climate change that his work has uncovered. Here’s an extract:
What information can you garner from glaciers?
Glaciers are like sentinels, and they’re telling us that the system is changing. The first thing we look for in the ice is radioactivity from thermonuclear bomb tests in 1962–1963 and 1951–1952. Back in 2006, we drilled three cores in the southwestern Himalayas. At 6,050 metres, where those glaciers reach their highest elevation, we found that neither of these radioactive layers was preserved. The glaciers are being decapitated. Not only are they retreating up the mountain slopes, but they are thinning from the top down.
This same scenario is playing out on Mount Kilimanjaro in Africa. When we drilled there in 2000 we found the 1951 test preserved, but not the 1962 test. We’ve since continued to monitor those glaciers and we know that we’ve lost three metres of ice since 2000. If we had waited until this year to drill, we would not have found the 1951 bomb horizon, because that has now been lost.
What does that mean for climate science?
Once a glacier melts, the history it contained is gone forever, so there’s an urgency in trying to collect the records before they are lost.
The loss of tropical glaciers is very telling because they’re in such sensitive places. Half of the surface of the planet lies between 30° N and 30° S. That’s where the heat that drives the climate system is received. It’s also where 70 per cent of the 6.7 billion people on the planet live.
What’s the effect on people as these glaciers disappear?
After this meeting, we’re headed to Peru to drill new ice cores at two sites. That country contains 75 per cent of the world’s glaciers. Eighty per cent of its population is in the desert on the west coast, and 76 per cent of the electricity comes from hydropower, from streams that are fed by glaciers in the Andes, all of which are retreating. Those changes are impacting the ability to produce hydropower, to irrigate crops in the desert and to provide municipal water supplies.
Read the full interview here.
Image: © Thomas Nash 2000. All rights reserved.