Space sunshade may one day  reduce global warming

Global warming is a reality and increasingly itsreached L1, they would be dealt off the stack into a
consequences are upon us. We may think that globalcloud. There's nothing to assemble in space." Angel
warming does not affect us but the fact is it hasproposes to design lightweight flyers made of
already started to have disastrous consequences.transparent film pierced with small holes and would be
Flash floods, droughts, receding icebergs, cyclones aretwo feet in diameter, 1/5000 of an inch thick and weigh
some of the manifestations of global warming.about a gram, the same as a large butterfly. He
Although we are aware and worried about it andsuggests using "MEMS" technology mirrors as tiny sails
trying our best to control it but no significant impactthat tilt to hold the flyers position in the orbiting
could be seen. Scientists have come up with newconstellation. The weight of all flyers would be 20
strategies to tackle the problem. Now a scientist hasmillions tons. But conventional rocket launch system at
suggested an ambitious idea to contain global warming.$10,000 a pound would be too prohibitive. His
Put sunshades in space. That's right. University ofalternative would cost only around $20 a pound.
Arizona astronomer Roger Angel suggests putting He suggests deploying a total 20
sunshades in space and has detailed his idea in aelectromagnetic launchers launching a stack of flyers
paper "Feasibility of cooling the Earth with a cloud ofevery 5 minutes for 10 years. The electromagnetic
small spacecraft near L1" in the Proceedings of thelaunchers would use hydroelectric power but even if it
National Academy of Sciences. He suggests launchinguses coal-generated electricity, each ton of carbon
a constellation of trillions of small free-flying spacecraftused would reduce the effect of 1000 tons of
a million miles above Earth into an orbit aligned with theatmospheric carbon. Â Once propelled beyond
sun, called the L-1 orbit. This spacecraft would form aEarth's atmosphere the flyer stacks would be steered
long, cylindrical cloud and would have a diameter aboutto L-1 orbit by solar-powered ion propulsion, pioneered
half that of Earth, and about 10 times longer. It isby European Space Agency's SMART-1 moon orbiter
suggested that about 10 percent of the sunlight passingand NASA's Deep Space 1 probe. "The concept builds
through the 60,000-mile length of the cloud, pointingon existing technologies," Angel said. "It seems feasible
lengthwise between the Earth and the sun, would bethat it could be developed and deployed in about 25
diverted away from our planet. This would result inyears at a cost of a few trillion dollars. With care, the
uniformly reduced sunlight by about 2 percent over thesolar shade should last about 50 years. So the
entire planet and would balance the heating of carbonaverage cost is about $100 billion a year, or about
dioxide in Earth's atmosphere. Â The use oftwo-tenths of one percent of the global domestic
space shade was first mooted by James Early of theproduct." He added, "The sunshade is no substitute for
Lawrence Livermore National Laboratory in 1989.developing renewable energy, the only permanent
 "The earlier ideas were for bigger, heaviersolution. A similar massive level of technological
structures that would have needed manufacture andinnovation and financial investment could ensure that.
launch from the moon, which is pretty futuristic," Angel"But if the planet gets into an abrupt climate crisis that
said. "I wanted to make the sunshade from smallcan only be fixed by cooling, it would be good to be
'flyers,' small, light and extremely thin spacecraft thatready with some shading solutions that have been
could be completely assembled and launched fromworked out.
Earth, in stacks of a million at a time. When they