If steps aren't taken to stem global warming, "We'll be eight degrees hotter in 30 or 40 years and basically none of the crops will grow," Turner said during a wide-ranging, hour-long interview with PBS's Charlie Rose that aired Tuesday.

"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.