Stop thinking about global warming as a future threat and understand it instead as a present emergency, one that requires a far stronger policy response than we'd imagined.

A third of summer sea ice in the Arctic is gone, the oceans are 30 percent more acidic, and since warm air holds more water vapor than cold, the atmosphere over the oceans is a shocking five percent wetter, loading the dice for devastating floods.

We've built a new Earth. It's not as nice as the old one; it's the greatest mistake humans have ever made, one that we will pay for literally forever.

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.

My house is covered in solar panels, I'm a great believer in all this - we all should be doing this.

I think it's going to be a tough century; I also think people are starting to rise up, and that a growth in human solidarity will help compensate for the loss of margin in the natural world that will make life harder.

There's always the danger that people will simply sign online petitions, the way they used to just mail in checks, and there's the greater possibility we'll just spend our whole lives staring at screens and never get anything done.