Deliberate intervention in the Earth’s climate system isn't a realistic means of tackling climate change any time soon.Nothing is quick, cheap and safe enough to be the answer. We must continue to cut greenhouse gas emissions. This was the conclusion of a lecture by Professor John Shepherd on 18 September, presenting the findings of a review of geo-engineering carried out by the UK Royal Society. See abstract, and the presentation.

There are two approaches to engineering the climate - cutting down on heat from the sun that hits the earth, and cutting the carbon dioxide in the atmosphere that stops the heat escaping. The Royal Society assessed all the suggested methods on the basis of their effectiveness, cost, safety and timeliness. A couple of ideas looked, in theory, as if they might help one day. But none would solve the problem of global warming on their own. And any form of solar geo-engineering only works for the time being. If it ever stops, the built-up warming comes back fast.