I kind of like carbon taxes because we already know how to apply them. We already have apparatus in place. When we talk about these other solutions - like a billion tons of iron filings in the ocean or putting sunshades between us and the sun - they're huge. We have no idea if they will work. We have no idea what their nasty consequences might be. And it's unlikely we can do them anyway.

I don't think scientists can dictate from above what we should do, because it's not a matter of scientific decision. If you want to have everybody living like a Beverly Hills millionaire, then 2 billion people might be too many. If we want to have a battery-chicken kind of world, with everybody having an absolute minimum diet, you might be able to support 10 billion.

There's no question at all that the population explosion will come to an end. The two basic choices are it'll come to an end because we control our reproduction, and in many areas we have started to do so, or we'll end up with a high death rate. You have to take a personal moral stand on this.

Most of the scientists I know think civilization is teetering on the brink of a global disaster. They just don't know when it's going to hit. I don't have the answer to that either. I'm scared as hell.

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.

We're never all going to agree with each other. We have to learn to value the diversity. It's one of the presumable principles of our government that isn't followed nearly enough - one of the jobs of the majority is to try and make the minority feel comfortable.

Recycling helps make people feel involved, and in some cases can be useful. Although you've got to do careful life history studies of what you're recycling. If all you're doing is recycling - if you've got three automobiles, and 10 children, and a 7,000-square-foot dot-com palace and second home up in the mountains that has to be heated - the recycling isn't making much difference.