BBC: Severe droughts lasting centuries have happened often in West Africa’s recent history, and another one is almost inevitable, researchers say. Analysis of sediments in a Ghanaian lake shows the last of these “megadroughts” ended 250 years ago. Writing in the journal Science, the researchers suggest man-made climate change may make the situation worse. But, they say, the droughts are going to happen again anyway, and societies should begin planning for them. “It’s …