Sun-cancellation cloud

Will "a swarm of umbrellas" protect the Earth from global warming? Roger Angel, at the University of Arizona, apparently hopes so. In Angel's plan, "a trillion miniature spacecraft, each about a gram in mass and carrying a half-meter-diameter sunshade... would act as a mostly transparent umbrella for the entire planet."

[Image: The anti-sun space-umbrella cloud, by Roger Angel. Because of the cloud, sunlight is "spread out, so it misses the Earth" – leaving everyone down here pale and confused (but free of global warming)].

The whole thing "could be deployed in about 25 years at a cost of several trillion dollars," and it "would be accelerated into space by a large magnetic field applied along 2,000-m-long tracks. With each such launch sending out 800,000 flyers, the project would require 20 million launches over a decade." According to EurekAlert!, this actually means "launching a stack of flyers every 5 minutes for 10 years."
So will this flying sun-cancellation machine really go live? Shouldn't we perhaps use derelict buildings instead, hurling gigantic anti-sun clouds of ruined architecture into space – empty tower blocks and football stadia and Thames Water filtration plants, all blocking out the harmful rays? Sunlight passing through the windows of churches casts shadows on farms, affecting harvests... and the temperature on earth will never change.

(Via Roland Piquepaille, on a tip from Bryan Finoki).