Geo-Engineering: Quick, Cheap Way to Cool Planet?

There will be no climate treaty to emerge from the conference in Copenhagen this month, global leaders now concede. But there may be alternative ways to help combat global warming. Various methods of geo--engineering employ unorthodox means to cool the planet. Advocates say that some of these proposals could be implemented quickly and cheaply. One concept is known as stratospheric aerosol insertion. A primer:

How It Works
Military planes (or helium balloons) spray the stratosphere with sulfur gases, which disperse and oxidize. The particles scatter back into space some of the sunlight that would have been absorbed by the planet's surface. As more sunlight is deflected, the planet cools. It's like an artificial version of an erupting volcano.

The Bottom Line
No major technological innovation would be needed, and, according to the Council on Foreign Relations, one -kilogram of sulfur could offset the effect of several hundred thousand kilograms of carbon dioxide. Potential downsides: regional ozone depletion, shifts in weather patterns, drought.