Global Warming Could End Sahara Droughts, Says Study

Global warming could significantly increase rainfall in Saharan Africa within a few decades, potentially ending the severe droughts that have devastated the region, a new study suggests.

The discovery was made by climate experts at the Royal Meteorological Institute in De Bilt, the Netherlands, who used a computer model to predict changes in the Sahel region - a wide belt stretching from the Atlantic to the horn of Africa that includes Ethiopia, Somalia and Djibouti.

Global warming will heat the land more than the sea, leading to changes in air pressure and weather. When the Netherlands team simulated this effect and combined it with warming caused by the expected rises in greenhouse gas emissions between 1980 and 2080, they found Sahel rainfall in the July to September period jumped 1-2mm a day.

Some scientists suspected that global warming might increase rainfall in the region, causing the so-called greening of the Sahara, but these are the biggest predicted increases so far.

Writing in the journal Geophysical Research Letters, the scientists say the increased rainfall could "strongly reduce the probability of prolonged droughts".

Reindert Haarsma, who led the research, said: "We were surprised that it was such a big rainfall signal. There is a lot of uncertainty in this kind of prediction but it is possible the Sahara region could benefit from climate change."

Sediments from the region suggest the semi-arid Sahel region, which borders the southern edge of the Sahara desert, was filled with lakes and lush vegetation as recently as 5,500 years ago. Countries in the Sahel have suffered unpredictable swings in rainfall, leading to severe drought between the 1970s and 1990s.

The cause of the droughts remains a mystery: some blame climate change and others say it is down to farmers destroying surface vegetation. Satellite images suggest vegetation in the region has recovered significantly over the last 15 years, pushing the southern Sahara into retreat.

Professor Haarsma cautioned against reading too much into the new results. The computer models were simple and did not include confounding factors like vegetation.

Peter Cox, of the Centre for Ecology and Hydrology in Dorset, said: "This looks like an interesting study. However, the conclusion that Sahellian rainfall will increase under climate change must be considered as highly uncertain. Models differ in their predictions, with about as many showing decreases in rainfall as increases."