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

One of the computer models for a four degree temperature rise would give rise to a 10 degree temperature rise in Africa. And bear in mind also that in the depth of an ice age the mean temperature drop compared to the present was five degrees.

During the 20th century, we came to understand that the essence of all substances - their colour, texture, hardness and so forth - is set by their structure, on scales far smaller even than a microscope can see. Everything on Earth is made of atoms, which are, especially in living things, combined together in intricate molecular assemblages.

Crucial to science education is hands-on involvement: showing, not just telling; real experiments and field trips and not just "virtual reality".

It's better to read first rate science fiction than second rate science-it's a lot more fun, and no more likely to be wrong.

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

Once the threshold is crossed when there is a self-sustaining level of life in space, then life's long-range future will be secure irrespective of any of the risks on Earth. Will this happen before our technological civilization disintegrates, leaving this as a might-have-been? Will the self-sustaining space communities be established before a catastrophe sets back the prospect of any such enterprise, perhaps foreclosing it forever? We live at what could be a defining moment for the cosmos.