Do I think that people should in the best of all possible worlds have to go to jail for wanting the US government to pay attention to the warnings of scientists about climate change? Not really. I mean, in a rational world, if all the scientists said, "The worst thing that ever happened is about to happen and here's what you should do to stop it," you would expect any rational system to say, "Oh, sure, OK, let's do something about it." But that's not the world we live in. In the world we live in, you do need people willing to stand up, fight, march and sometimes go to jail.

There are so many symptoms of this disease it's hard to know where to start to catalogue them, but just look at the effects on hydrology - on the way water moves around the planet.

I think fracking for gas will reduce the incentive to turn to renewables, and I think it will do a lot of other damage across the countryside.

Between [Speaker of the House] Paul Ryan, [Senate Majority Leader] Mitch McConnell, and Donald Trump's team, I don't see a lot of openings for making real progress.

There is no real scientific debate over what is happening; of course there is debate over exactly how it is going to play out in the decades ahead, because this is a large experiment that we haven't done before, and no one knows precisely how one can ever precisely predict what effects this heat will have. But all the science in the last few years, or almost all of it, really serves to show that the effects are larger and more rapid than we had thought even a decade ago.

I think [George W.] Bush has done nothing right about global warming.

In the scientific community, the debate is over, for all intents and purposes, about whether or not the planet is heating and who is causing it. In fact, it's more or less been over since 1995.