"Most of the people will have died and the rest of us will be cannibals," said Turner, 69. "Civilization will have broken down. The few people left will be living in a failed state — like Somalia or Sudan — and living conditions will be intolerable."
One way to combat global warming, Turner said, is to stabilize the population.
"We're too many people; that's why we have global warming," he said. "Too many people are using too much stuff."
Turner suggested that "on a voluntary basis, everybody in the world's got to pledge to themselves that one or two children is it."