Perhaps the single most important thing that we can do to undo the harm we have done is to fix firmly in our minds the thought: the earth is alive.

The climate is doing its usual tricks. There's nothing much really happening yet. We were supposed to be halfway toward a frying world now.

NASA will send up a big sun shade that will be in orbit between the earth and sun and deflect 2 or 3 percent of the sunshine back into space. It would be cheaper than the international space station.

For each of our actions there are only consequences.

One thing that being a scientist has taught me is that you can never be certain about anything. You never know the truth. You can only approach it and hope to get a bit nearer to it each time. You iterate towards the truth. You don't know it.

Humans are too stupid to prevent climate change from radically impacting on our lives over the coming decades.

We thought we knew 20 years ago. That led to some alarmist books – mine included – because it looked clear-cut, but it hasn’t happened. The climate is doing its usual tricks. There’s nothing much really happening yet. We were supposed to be halfway toward a frying world now. The world has not warmed up very much since the millennium. Twelve years is a reasonable time. The temperature has stayed almost constant, whereas it should have been rising - carbon dioxide is rising, no question about that.