In pushing other species to extinction, humanity is busy sawing off the limb on which it perches.

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.

You take the huge income that comes with a big gas tax, and you use it to pay off regressive taxes like the FICA [Federal Insurance Contributions Act] tax. You can help the poor in other ways besides giving them cheap gas. You want to send the message that people want to be as efficient as possible using gasoline until we can transition away from that need entirely.

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

Here's the scientific community saying, fundamentally, "If we don't change our ways, we're screwed." And they got no attention at all. Even though the Union of Concerned Scientists put out this statement which was signed by more than half of all the Nobel laureates in science and another 1,500 distinguished scientists.

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.