The Sahel drought, which began in the late 1960s and continued for several decades, killed at least 100,000 people and displaced many more.

"What's really striking about droughts in this area is that they last such a long time," he said.

The region has undergone multi-century droughts, most recently from 1400 A.D. to 1750 A.D., the researchers found.

Changes in the surface temperatures of the North Atlantic have a significant effect on the West African monsoon, which is a climate pattern of alternating wet-and-dry periods, the scientists said.

As global warming progresses, the increases in temperature may exacerbate the normal climate pattern, producing even more severe and prolonged droughts than those of the past, they said.

Policymakers should move fast to consider concrete strategies and contingency plans for mitigating the future dry periods, the authors said.

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Editor:Yang Jie