I think it's important that people think about what they are doing and that includes what they are eating. I am 61 now and attitudes towards drinking and driving have changed radically since I was a student. People change their notion of what is responsible. They will increasingly ask about the carbon content of their food.

Climate change will affect the basic elements of life for people around the world - access to water, food production, health, and the environment. Hundreds of millions of people could suffer hunger, water shortages and coastal flooding as the world warms.

Looking back, I underestimated the risks. The planet and the atmosphere seem to be absorbing less carbon than we expected, and emissions are rising pretty strongly. Some of the effects are coming through more quickly than we thought then.

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.

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.

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.

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.