Of all these “whacky-but-workable” theories the one that has perhaps generated the most interest, both in terms of scientific plausibility and practical implementation, is that of solar reflection.
The basic concept is the same as that underpinning the “white roads” idea—the development of a technology that can reflect a proportion of the sun’s radiation away from the earth’s surface and back out into space, thereby cooling the atmosphere and slowing, or even reversing the damaging effects of global climate change.
Several models have been put forward as to how such a feat of “geo-engineering” might actually be achieved, most involving the positioning of a reflective shield of some sort out in space. [...]
“No-one knows exactly what the effect would be if you pumped this enormous amount of sulphur into the atmosphere,” Dr. Benny Peiser of Liverpool’s John Moores University told CNN. “It would be a huge and risky experiment.”
Some of the possible results include debilitation of the ozone layer, acid rain and an increased incidence of human respiratory illnesses.
The sulphur would also not remain in the atmosphere permanently, gradually drifting back down to earth over a period of about two years. The shield would thus have to be constantly replenished.
Both Crutzen and Caldeira themselves, while pointing out the potential benefits of such a sulphur shield, are also candid about its drawbacks, with Crutzen saying that he hopes his “ugly baby” will never actually have to be deployed.
“Personally, as a citizen not a scientist, I don’t like geo-engineering because of the high environmental risk,” Caldeira said in a recent interview with New Scientist magazine.
“It is toying with poorly understood complex systems.”
The general consensus within the scientific community is that the idea of creating a solar-shield—whatever form it might take—should not in any way be seen as an alternative to finding ways of reducing global greenhouse gas emissions.
At the same time, however, there is also a consensus that it is crucial to explore and develop such futuristic technologies in case the worst-case global warming scenarios should become reality.
“Despite their potential drawbacks we need to look at these geo-engineering fixes because we might need them at some point,” says Dr. Benny Peiser. “It is always better to be prepared for any event.
“You insure your house against fire even though you know it probably won’t be burnt down.
“That’s what these sort of solar-shield technologies offer—an insurance policy. It is unlikely we will ever have to use them, but it is good to know we could deploy them if necessary.”
http://edition.cnn.com/2007/TECH/science/06/19/solar.shield/