Kilimanjaro ice loss likely due to warming, not drought
Tuesday, November 3rd, 2009
When I was in grad school, I saw a talk by Lonnie Thompson—a paleoclimatologist who climbs the most remote mountain peaks in the world to take ice cores from glaciers. Over the past several decades, he has used ice layers to generate historical records of environmental change at low latitudes (near the tropics) as a useful comparison to the ice core work at Greenland and Antarctica. Hands down, Lonnie has some of the most amazing and treacherous expeditions in the world. If you ever get a chance to see a photo of how they traverse ice crevasses with field gear, it’s amazing.
In a forthcoming article in the Proceedings of the National Academy of Sciences (open access), Thompson’s team climbed Mt. Kilimanjaro in Africa to assess the rate of ice loss on this mountain. Kiliminanjaro has been losing significant ice for decades–as much as 80% gone by 2000.
Although this seems like obvious evidence of climate warming, there has been considerable debate about the additional role of drought. Glacier growth is controlled by precipitation, and if east Africa has experienced drought for the last few decades, this might also be affecting the Kilimanjaro glaciers through (1) reduced snowfall and (2) increased solar radiation.
The team collected 6 cores dating back 11,700 years ago. What did they find?
- Based on the rates of ice loss, they expect the disappearance of all Kilimanjaro ice between 2022-2033.
- 26% of the ice was lost between 2000-2007.
- Based on meteorological data, they argue that there is a distinct warming trend in the region over the 20th century but not clear evidence for extensive droughts.
- Since glaciers are also being lost in other low-latitude sites (Indonesia, Tibet, and the Himilayas), this suggests a global warming effect rather than regional droughts.
- Also, the Kilimanjaro ice survived a past drought around 4,200 years ago that lasted for almost 300 years, and the ice has persisted for the last 11,700 years, suggesting it has weathered many past climate changes during our current, warm interglacial period known as the Holocene.
- All of these lines of evidence suggest that less cloudy and drier conditions are not likely driving ice loss.
This is another amazing example of something that is going extinct in our lifetime because of global change.
photo credit: http://www.flickr.com/photos/appenz/ / CC BY 2.0
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[...] and can measure well—like thermal expansion of the ocean and melting of land glaciers (see here for a discussion of the Kilimanjaro example). What it doesn’t do so well is account for all [...]