It took a Tucson resident to devise an emergency plan to fend off catastrophic global warming — shade.
University of Arizona astronomer Roger Angel, who has spent much of his life building mirrors to collect light from distant stars, has unveiled his plan to keep some of the light from our nearest star away from Earth — a permanent cloud of trillions of tiny spacecraft.
It's a solution that should only be used if we don't get a handle on global warming and reach a "tipping point" when climate change is inevitable, he said.
Angel's concept, being developed with a NASA grant, is a 600,000-mile-long cloud, consisting of trillions of one-meter-diameter spacecraft, or "flyers," each with a tiny sail to orient it properly and weighing one gram.
The flyers, thin, transparent membranes of plastic punched with holes, would deflect rather than block the light, Angel said, creating an almost unnoticeable cloud — "the very faintest wisp" — that, from our view on Earth, would cover about a quarter of the sun.
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About 10 percent of the light coming through that 600,000-mile cylinder would be deflected, allowing an estimated 1.8 percent reduction in sunlight striking the Earth.
Angel first presented the concept of a sunshade at a National Academy of Sciences gathering in April. NASA gave him a grant for further research, and the first detailed report was published Friday on the Web site of the National Academy of Sciences.
Angel is collaborating with Nick Woolf of UA's Steward Observatory, David Miller of the Space Systems Laboratory at MIT, and S. Peter Worden, director of NASA's Ames Research Center, according to a UA news release.
Angel said he has already read instant criticism of his concept on the scientific blogs.
"Most people miss the point. This is not an either/or thing," Angel said.
Planning for catastrophe is no substitute for reducing carbon emissions and finding new ways of generating renewable energy, he said. Doing research on a sunshade, he said, "is a little bit like insurance."
Angel said he intends to turn some of his attention to technology to make solar energy competitive with fossil fuels.
When he first proposed sunshades, Angel said, their weight and the expense of launching them into orbit at the $10,000 per pound cost of conventional rockets would make it necessary to assemble them on the moon.
This variation, he said, would make use of electromagnetic space launchers developed at Sandia National Laboratories. At an estimated $20 a pound, the deployment of the flyers from Earth would cost "a few trillion dollars," he said.
It would be worth it if calamity makes the shade necessary, he said, but it would be better to spend that money now on energy technology to keep it from being necessary.
Angel, who developed the world-renowned mirror lab at the UA and serves as its director, is also studying extra-solar planets orbiting stars in other solar systems.
"I spend a lot of time thinking about planets around other stars. Now I'm thinking about my own planet."
He said the motivation was simple. "My wife said, 'Can't you do something?' "
