That Rolling Stones article throws up a figure of 100 million dollars. The estimate I read had a figure of 40 billion dollars a year. To me the 40 billion dollar figure seemed reasonable for the amount of material and the number of flights that would be required.

The article also has some stupid sentences in it: "Until recently, discussion of geoengineering -- intentional, large-scale manipulation of the Earth's climate -- has been taboo among scientists."

Gee, the council of witch doctors that determines what is and isn't taboo in science must have changed their minds.