The greenhouse effect is something you can observe experimentally - and most people have observed the greenhouse effect themselves, in greenhouses. Yes?

This [climate change] is potentially so dangerous that we have to act strongly. Do we want to play Russian roulette with two bullets or one?

Unfortunately, the current pace of progress is not nearly rapid enough, with many rich industrialised countries being slow to make the transition to cleaner and more efficient forms of economic growth.

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.

Do politicians understand just how difficult it could be, just how devastating rises of 4C, 5C or 6C could be? I think, not yet

The basic scientific conclusions on climate change are very robust and for good reason. The greenhouse effect is simple science: greenhouse gases trap heat, and humans are emitting ever more greenhouse gases.

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.