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.

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

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.

I'm a technological optimist in that I do believe that technology will provide solutions that will allow the world in 2050 to support 9 billion people at an acceptable standard of living. But I'm a political pessimist in that I am concerned about whether the science will be appropriately applied.

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.

God invented space so that not everything had to happen in Princeton.

To ensure continuing prosperity in the global economy, nothing is more important than the development and application of knowledge and skills.