My real worry with Bill Gates is that he has too much influence. By putting out a book promoting an engineering approach to combating climate change he is subtly nullifying all of the more organic solutions, such as reforestation and reduction in consumption. His smug, we can fix this with technology, message leads to climate apathy. "No need to worry or change my habits, Bill has got a technological answer up his sleeve".

For him, the answer is always about making some high tech gadget and selling it. For example he proposes building an enormous sunscreen, floating around in space, to shade the earth and lower the global temperature. This solution always puts my in mind of that episode of the Simpsons, where Mr Burns build a huge sun shield to make everyone use more electricity from his nuclear power plant.

It sounds like a solution until you realise that up till now we have barely put more than some tiny satellites into space with solar arrays that can be measured in square metres, not square miles. For a sun shade to be anywhere near effective it would have to approach the same diameter as the moon. I suspect there isn't enough resources on the entire planet that could be used to build that and fly it into space. If you doubt my maths, just look at the sky for the largest manmade space, Skylab, to see how much shade it produces. You will probably need to use a telescope to see it though. On a clear night you can just about see it with the naked eye as a small bright dot moving across the sky.

I would be more optimistic if he wrote that he was going to spend all his millions on reforestation, restoring degraded land, cleaning the oceans and stopping the fossil fuel companies from destroying the planet in the name of profit. There are many climate solutions out there that don't involve high tech, just investment without short term gains.