We have no reason to think that climate change is harmful if you look at the world as a whole. Most places, in fact, are better off being warmer than being colder. And historically, the really bad times for the environment and for people have been the cold periods rather than the warm periods.

It's better to get mugged than to live a life of fear.

I think that what the machines can do, of course, is wonderful, but it's not the same as what the brain can do.

The thing that makes me most optimistic is China and India - both of them doing well. It's amazing how much progress there's been in China, and also India. Those are the places that really matter - they're half of the world's population. They're the places where things are enormously better now than they were 50 years ago. And I don't see anything that's going to stop that.

You ask: what is the meaning or purpose of life? I can only answer with another question: do you think we are wise enough to read God's mind?

I think that the artificial-intelligence people are making a lot of noise recently, claiming that artificial intelligence is making huge progress and we're going to be outstripped by the machines.

Computer models of the climate....[are] a very dubious business if you don't have good inputs.