What we are talking about is extended world war...People would move on a massive scale. Hundreds of millions, probably billions of people would have to move.

Failing to curb the impact of climate change could damage the global economy on the scale of the Great Depression or the world wars by spawning environmental devastation that could cost 5 to 20 percent of the world's annual gross domestic product.

We run enormous risks and we know what kind of reductions of greenhouse gases are necessary to drastically reduce risks. Reducing emissions by half by 2050 is roughly in the right ballpark. It would bring us below 550 ppm.

Adaptation is a vital part of a response to the challenge of climate change

Those who say that climate change doesn't exist are being understood as the flat-earthers that they are, as the people who deny the link between smoking and cancer, as the people who denied the link between HIV and AIDS.

Give up meat to save the planet.

It's very important that there should be cross-fertilisation between government and academia. Both parties can benefit from having a better understanding of how the other works.