The study, published in the journal Science on Thursday, reported that for the first time, U.S. researchers have developed an almost year-by-year record of the last 3,000 years of West Africa's climate.
In that period, catastrophic droughts occurred every 30 to 65 years, and the pattern can be expected to continue in the future, the research team reported.
The research team determined the region's past climate by analyzing the annual layers of sediment deposited in Ghana's Lake Bosumtwi, geological records of the lake level, and other climate indicators.
"What's disconcerting about this record is that it suggests that the most recent drought was relatively minor in the context of the West African drought history," said Timothy Shanahan, a member of the team.
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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