Scientists themselves readily admit that they do not fully understand the consequences of our many-faceted assault upon the interwoven fabric of atmosphere, water, land and life in all its biological diversity. But things could also turn out to be worse than the current scientific best guess. In military affairs, policy has long been based on the dictum that we should be prepared for the worst case. Why should it be so different when the security is that of the planet and our long-term future?

Humility is to make a right estimate of one's self. It is no humility for a man to think less of himself than he ought, though it might rather puzzle him to do that.

If you think about the impact of climate change, [it should be how] a doctor would deal with the problem. A scientific hypothesis is tested to absolute destruction, but medicine can't wait. If a doctor sees a child with a fever, he can't wait for [endless] tests. He has to act on what is there. The risk of delay is so enormous that we can't wait until we are absolutely sure the patient is dying.

I think we're going to find, with climate change and everything else, things like global warming and goodness knows what else and the cost of fuel for a start, that things are going to become very complicated.

Something as curious as the monarchy won't survive unless you take account of people's attitudes. After all, if people don't want it, they won't have it.

Forests are the world's air-conditioning system-the lungs of the planet-and we are on the verge of switching it off.

Climate change should be seen as the greatest challenge to face man and treated as a much bigger priority in the United Kingdom.