All scientists who've looked at it know we have to phase away from burning fossil fuels. That means we've got to put a lot of effort into alternate energy technologies, but we're still subsidizing fossil fuels and not subsidizing most of the alternatives. It's not going to be an easy transition.

I thought if the climate was heating that CO2 was the only forcing, and it would be late in the century before we had trouble. Now that we know about the other half of the forcing, it's obvious that the trouble is coming much sooner.

If we were redesigning around people instead of around automobiles, which I think the market is more or less going to do, although too slowly, than I'd be a lot cheerier.

I see harm reduction as a way of engaging people as part of that path to recovery.

People have to decide, first of all, how they'd like to live, and how secure they want to be from disaster. After that, scientists can help determine what would be necessary to achieve that.

Too many cars, too many factories, too much detergent, too much pesticides, multiplying contrails, inadequate sewage treatment plants, too little water, too much carbon dioxide - all can be traced easily to too many people.

Stanford may be the best university in the world, but you can get all the way through here without knowing where your food came from, without being able to say where we came from, without being able to give a coherent description of why the climate is changing and why we should be concerned about it. So I started teaching a course in human evolution and the environment that's open to all Stanford students, no prerequisites.