May 31, 2016 This article is more than 2 years old.

Stephen Hawking, one of the world’s most brilliant physicists, has spent his life elucidating the workings of space and time.

But asked to explain the phenomenon of Donald Trump, he was stumped. “I can’t,” was Hawking’s response when he was asked to do so by ITV News on Tuesday morning (May 31).

“He is a demagogue, who seems to appeal to the lowest common denominator,” said Hawking, who directs research at the Centre for Theoretical Cosmology at the University of Cambridge, UK.

But asked what was the greatest threat to the world right now, Hawking didn’t mention the US presidential hopeful or any of the security concerns that typically preoccupy him. Hawking said climate change would be more catastrophic than any single factor other than an asteroid collision, the last of which happened 70 million years ago, and killed the dinosaurs, he said.

“A more immediate danger is runaway climate change,” Hawking continued. “A rise in ocean temperature would melt the ice-caps, and cause a release of large amounts of carbon dioxide from the ocean floor. Both effects could make our climate like that of Venus, with a temperature of 250 degrees.”