Good article on geoengineering cost analysis, etc for sulfur injection . . .

Geoengineering Could Be Essential to Reducing the Risk of Climate Change

Using technology to cool the planet may be the only way to deal with the greenhouse gases already in the atmosphere, argues scientist David Keith.

[link to www.technologyreview.com]

Keith and some of his colleagues recently hired engineers to estimate how much one approach to sulfate injection might work, and how much it might cost. It could be done at first with existing airplanes—certain business jets can fly high enough to inject the particles into the upper atmosphere. Eventually we would need new planes that can fly higher. All in all, once the procedure is scaled up it would cost about a billion dollars a year and require about 100 aircraft. That’s cheap enough for most countries to pull off on their own.