A $2,500 billion sun umbrella?

The global warming effect could trim about $7,000 billion to the global economy if nothing is done about it (check here for details). A University of Arizona professor thinks he has a solution if we don't act fast enough to develop renewable sources of energy. He wants to reduce the temperature on Earth by building a massive space sunshade made of — hold your breath — 20,000 billions of very small spacecraft weighing about a gram and orbiting a million miles above our heads. This plan would cost $100 billion per year and would be deployed over a period of 25 years. Is this a joke? Not at all, but read more about this project.
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