One of the reasons that people, many people, many environmentalists are critical of President [Barack] Obama's policies towards global warming is on the one hand he says the right things and he says he's committed to trying to reduce our current emissions.

Though it might be nice to imagine there once was a time when man lived in harmony with nature, it’s not clear that he ever really did.

As best as can be determined, the world is now warmer than it has been at any point in the last two millennia, and, if current trends continue, by the end of the century it will likely be hotter than at any point in the last two million years.

Neanderthals were pretty smart, and if we actively killed them off, then probably we did so in the same way that humans kill each other.

I don't think there are too many places left that humans haven't pretty thoroughly explored.

Increasingly developing countries are asking for aid to help deal with the consequences of climate change, which we don't want to give.

You've got to do everything, everything's got to be pointing in the same direction and you've got to really turn this whole economic engine from one that's based on fossil fuels to one that isn't.