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 are lots of excellent analysts out there. John Holdren at the Harvard Kennedy School, who was just president of the American Association for the Advancement of Science, has been talking about this stuff for years. There are lots of people out there who understand what’s going on. The problem is, they aren’t much picked up on Fox News.

Chinese are already more on board than we are. China is the only country that actually discussed in formal government documents how important it is to control the size of your populations if you’re going to limit emissions.

The drilling idea is spherically senseless - it's senseless from whatever point of view you look at it. It'd take 10 years to bring any oil online, and it would probably go to Japan. It sure wouldn't help gasoline prices here. All the economists say gasoline is still too cheap in the United States anyway. So here we're having this huge debate over offshore drilling that is just straightforward nonsense, which won't surprise you.

My first policy move would be to try to get a conversation going in the US about what people stand for and what we really want. Do we want to keep adding people to the world and to our country until we move to a battery-chicken kind of existence and then collapse? Or do we want to think hard about what really is valuable to us, and figure out how many people we can supply that to sustainably?

I'm sort of optimistic about what we could do, but I'm very pessimistic about what we will do. I can't tell you that Al Gore's 10-year plan is impossible. I'm old enough to remember the Second World War - if we had a World War II-type mobilization, we might accomplish Gore's plan. In 1940 we were making tens of thousands of automobiles, and in 1941 we were making tens of thousands of airplanes. We mobilized as a nation. If we get that kind of mobilization as a nation or globally, then we could solve a lot of these problems.

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.