I think all countries need to aim to cut the CO2 emissions per person, taking account of externalities like imports and exports.

Devastation could arise insidiously, rather than suddenly, through unsustainable pressure on energy supplies, food, water and other natural resources. Indeed, these pressures are the prime 'threats without enemies' that confront us.

Let me say that I don't see any conflict between science and religion. I go to church as many other scientists do. I share with most religious people a sense of mystery and wonder at the universe and I want to participate in religious ritual and practices because they're something that all humans can share.

Indeed, our everyday world presents intellectual challenges just as daunting as those of the cosmos and the quantum, and that is where 99 per cent of scientists focus their efforts. Even the smallest insect, with its intricate structure, is far more complex than either an atom or a star.

Absence of evidence is not evidence of absence.

It used to be controversial whether smoking caused lung cancer, it used to be controversial whether HIV caused AIDS. Now, there are a few mavericks who deny those things. In the case of climate change, I think the debate is going the same way in that there is a strong consensus that it is a serious matter.

The 'clean energy' challenge deserves a commitment akin to the Manhattan project or the Apollo moon landing.