Onywere rushed back to Nairobi, where he and his colleagues at several Kenyan universities studied recent satellite images of the lake. The images showed that the lake had, in the past year, flooded the area around it. Then Onywere searched for images of some of the lakes nearby: Lakes Bogoria, Naivasha and Nakuru. All of these had flooded. As he extended his search, he saw that Lake Victoria, Africa’s largest lake, had flooded, too. So had Lake Turkana, the largest desert lake in the world.