Hunt for tree rings could yield Africa’s first drought atlas
By Paul Voosen, Science.
Excerpt: For decades, a climatological mystery has haunted West Africa. In the 1970s and ’80s, a vicious drought, perhaps the worst worldwide in the 20th century, struck the region...just south of the Sahara Desert. The disaster killed tens of thousands of people in Senegal and other countries and caused a mass migration to cities. But then the drought stopped, and nothing like it has occurred since. Still the question has lingered: Could the great drought return? Climate researchers led by Edward Cook and Michela Biasutti of Columbia University want to glean an answer from trees, using tree-ring records to create the first comprehensive, multicentury drought atlas for any region of Africa. They’re now mounting an arduous search for the few West African trees that capture the whispers of past rainfall in their annual growth. “We want to tell people what to expect in the next few decades,” Biasutti says. Climate change will surely affect future droughts, but any forecast requires knowing what happened in the past. ...Much evidence now suggests the Sahel drought was caused, at least in part, by air pollution from the United States and Europe, Biasutti says. As economies boomed following World War II, coal-fired power plants belched sulfur gas, which formed sulfate particles that reflected sunlight and cooled the North Atlantic. The cooling fed the drought by suppressing a natural tendency for the tropical rain bands that form in West Africa’s wet season to shift northward....