But it's the kind of Dr Strangelove you could see governments really using." That's how one expert describes geo-engineering - the idea that we can use a kind of technical quick fix to cool the planet if global warming accelerates. Plans for geo-engineering can sound bizarre. They range from placing millions of tiny mirrors in space to reflect back some of the sun's rays, to using rockets to launch tons of sulphur into the stratosphere to create a kind of planetary sun shade. That plan was inspired by watching what happened after the eruption of the Mount Pinatubo volcano in the Philippines in 1991. Sulphur ejected into the atmosphere spread around in subsequent months to create a layer believed to have had a temporary cooling effect as it blocked some of the sun's warmth. Other suggestions include spraying sea water into the atmosphere to make it cloudier, or pumping carbon dioxide out of the atmosphere or out of the oceans. Until recently, policymakers have dismissed this as science fiction, a complete distraction from the fight against global warming. Now, attitudes seem to be changing. "I think we're faced with such an enormous problem that we need to do all the research we can to see if there are any geo-engineering proposals which work through to the marketplace," says Professor Sir David King, until recently the government's chief scientific adviser.
There are still many scientific doubts about geo-engineering. What might the side effects be? Are such schemes irreversible? Plan B: But as there is now so much pessimism about whether governments will ever agree to reduce carbon emissions enough, more and more scientists say we need to know exactly what our other options are.
