“We’ve been around for 300,000 years. We’ve had agriculture for 12,000 years,” the 77-year-old money manager said on Monday in Carlsbad, Calif. “Yet we’ve come down to just 100 years where the whole game is playing out.” He said it’s not just that the climate is warming, but that climate warming is accelerating.

Grantham says he is far more optimistic about technology’s ability to solve energy problems than most environmentalists. But he is also far more pessimistic about the ability to feed a rapidly growing global population, given changing climate patterns, than most technologists. “Both groups underestimate the good news or the bad news.” As a result, he said, “it’s going to be quite a horse race.”

Asked by Fortune Editor Brian O’Keefe who would win, Grantham replied: “It’s fifty-fifty.”