Does Atlantic ocean cause African droughts?

Devastating spells of extremely arid weather worse than the infamous Sahel drought are part of the normal climate regime for sub-Saharan West Africa, according to a research team led by the University of Texas, Austin. For the first time, researchers have developed an almost year-by-year record of the last 3,000 years of West Africa's climate.

"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," notes Timothy Shanahan, who conducted the research while he was a doctoral student. The Sahel drought, which began in the late 1960s and continued for three 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. You have droughts that last 30 to 60 years, and then some that last four times as long."

The region even has undergone multicentury droughts, most recently from 1400-1750. "If we were to switch into one of these century-scale patterns of drought, it would be a lot more severe, and it would be very difficult for people to adjust to the change," relays Shanahan, assistant professor of geosciences.

Changes in the North Atlantic sea-surface temperatures have a significant effect on the West African monsoon, which is a climate pattern of alternating wet-and-dry segments. "This area switched between very long wet periods and long, very severe dry periods," Shanahan relates.

Many of the Earth's climate patterns are influenced by sea-surface temperatures. Climate scientists have proposed that temperatures in the North Atlantic rise and fall naturally in an approximately 60-year cycle called the Atlantic Multidecadal Oscillation. If it exists, the oscillation should have a strong effect on the West African monsoon.