My father's generation's crisis was fighting fascism. Ours is fighting climate change. It is much harder because you can't see it, it is not an obvious threat. But the solution is in our hands.

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.

Meat is a wasteful use of water and creates a lot of greenhouse gases. It puts enormous pressure on the world's resources. A vegetarian diet is better.

You'd see more floods like you've seen in Mozambique in 2000, you'd see more droughts like you saw in Kenya in the late 1990s, there would be a serious threat to the water flow down the Nile on which 10 countries depend.

Climate change represents the greatest and widest-ranging market failure ever seen

If coal is going to be used, the only response - because it is the dirtiest of all fuels - is that we have to learn how to do carbon capture and storage and we have to learn how to do it quickly on a commercial scale.

Adaptation is the only means to reduce the now-unavoidable costs of climate change over the next few decades