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Kilimanjaro ice wall retreating
The first ever ice core samples obtained from Africa — a valuable record of the continent's past climate — may also be the last, as the ice caps on Mount Kilimanjaro are predicted to vanish within the next 20 years.

A team of American scientists report in this week's issue of Science that Mount Kilimanjaro's ice fields decreased in area by around 80 per cent during the twentieth century. And if the climate remains as it is, the remaining caps are likely to disappear between 2015 and 2020.

"We found that the summit of the ice fields has lowered by at least 17 metres since 1962," says Lonnie Thompson, professor of sciences at Ohio State University and leader of the expeditions. "That's an average loss of about half a metre each year."

The researchers used aerial photographs, geographical positioning using satellites and physical markers to assess the extent of ice cover on the Tanzanian mountain. They are concerned that — due to global warming — this unique archive will soon be lost forever, and say that this is the last opportunity to establish an ice core record of African climate.

Detailed analysis of the chemical composition of six ice cores retrieved from Kilimanjaro's summit revealed that the region has experienced a number of catastrophic climatic changes over the past 10,000 years.

The researchers claim that such analyses can be used as 'fingerprints' of historical events. For example, the appearance of a layer of dust in the samples suggests a severe drought starting about 4,000 years ago. The authors say that this dry period correlates with the collapse of a number of civilisations at this time.

But others are sceptical about links being drawn between such events. "The precise timing of climate events proposed by the authors should be regarded with caution," says Françoise Gasse of the European Centre for Research into Environmental Geosciences (CEREGE) in a related article in Science.

Another member of the research team, Douglas Hardy of the University of Massachussetts Amherst, is quick to point out that human-induced global warming may not be the reason for the glaciers' retreat. "Further research is needed to determine to what extent global warming and/or natural climate variability are responsible for the demise of Kilimanjaro's glaciers," he says.

Nevertheless, it is clear that changes in the composition of Kilimanjaro's ice fields could have serious implications for local communities that depend on meltwater from the glaciers for farming and irrigation — especially during dry seasons and monsoon failures — as well as hydroelectric power.

Link to Science research paper

Science perspectives article: Kilimanjaro's secrets revealed

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Photo credit
: Lonnie Thompson
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