Climate change sceptics have seized on several scientific studies in recent years that have appeared to cast doubt on whether Mount Kilimanjaro’s diminishing glaciers are evidence of global warming.

Al Gore is the sceptics’ bête noire and they like claiming to have found inaccuracies in his documentary An Inconvenient Truth. The former US Vice-President presented the melting snows on Africa’s tallest peak as one of the most dramatic visible signs of the impact of man-made greenhouse gases.

The studies have not questioned that the glaciers are rapidly melting but have suggested that the cause is more likely to be regional factors, such as deforestation of the foothills owing to extensive farming. Lack of trees has contributed to a loss of humidity and cloud cover, resulting in drier conditions. There are fewer clouds to protect Kilimanjaro from solar radiation and there is less snowfall to replenish the ice fields.

Philip Mote, a climate expert at the University of Washington, wrote in 2007: “Kilimanjaro is a grossly overused mis-example of the effects of climate change.” He attributed the glacier loss largely to sunlight and dry air causing sublimation, when ice is converted directly to water vapour without passing through the liquid phase.

Yet a study, published yesterday, is a serious blow to the sceptics. It not only supplies new evidence that global warming is contributing to the melting but it is co-authored by Doug Hardy, a climatologist previously quoted by sceptics as supporting their case.

If drier conditions were to blame, it would be reasonable to expect a 300-year drought that afflicted Kilimanjaro 4,200 years ago to have resulted in significant ice loss. But cross-sections of ice examined by Dr Hardy show that the only sustained melting in the past 11,700 years began about 40 years ago.

The study admits that landscape changes could be playing a part in the ice loss but suggests that warmer temperatures are also likely to be “playing an important role”.

Will this study alter the opinions of many sceptics? Probably not, especially when they learn that it was edited by James Hansen, head of the Nasa Goddard Institute for Space Studies. He is one of the original proponents of the theory that man-made emissions are causing climate change.

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