The politics is far harder than the science. And even if we accept the science we have a big issue of how to deal with it.

Scientists habitually moan that the public doesn't understand them. But they complain too much: public ignorance isn't peculiar to science. It's sad if some citizens can't tell a proton from a protein. But it's equally sad if they're ignorant of their nation's history, can't speak a second language, or can't find Venezuela or Syria on a map.

There may be organic life out there, or maybe machines created by long-dead civilizations, but any signals, even if they are difficult to decode, would tell us that the concepts of logic and physics are not limited to the hardware in human skulls, and will transform our view of the universe.

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

Scientists surely have a special responsibility. It is their ideas that form the basis of new technology. They should not be indifferent to the fruits of their ideas. They should forgo experiments that are risky or unethical.

The important point there is that when people talk about a mean temperature rise of say two, three or four degrees that's a sort of global average which really is a signature of large scale change in climatic patterns.

We should all oppose - as Darwin did - views manifestly in conflict with the evidence, such as creationism... But we shouldn't set up this debate as 'religion v science'; instead we should strive for peaceful coexistence with at least the less dogmatic strands of mainstream religions, which number many excellent scientists among their adherents.