A quick fix for global warming

It's the stuff of science fiction, but could mirrors in space or sea water sprayed in the air be shortcuts to halt global warming?

"It's Dr Strangelove. 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.

If we don't do any research, says Professor Brian Launder of Manchester University, who is editing a new study of geo-engineering for the Royal Society, "we won't have anything that we can bring into place in 2030 say, when suddenly the world is at a crisis point".

Some forms of geo-engineering are also surprisingly cheap. That leads to fears that governments facing particular climatic problems might go it alone.

China and India, which have growing scientific capabilities, could use geo-engineering as a way of challenging international climate policy if they saw it as too skewed towards the interests of Western countries.

Or, even more alarmingly, an individual might decide to play with the global climate.

Professor David Victor, of Stanford University, imagines a scenario in which someone is frustrated at the lack of international action. "[They] could buy the aircraft and buy the rockets and just start doing some geo-engineering off their own island."

James Bond films of the future, he adds, might not feature Goldfinger. It could be Greenfinger, hand hovering over the global thermostat. - bbc