An Umbrella Big Enough to Cool the World

If covering an area the size of Arizona with 300-foot-high CO2-sucking trees seemed like a radical idea, how about an atmospheric sun blocker big enough to cover most of the United States?

That's the fallback plan of Roger Angel, a University of Arizona astronomer and optics expert who proposes to launch into earth's atmosphere 16 trillion reflectors, each two feet wide and shaped like a dish, that could bounce back about two percent of the sun's light.

From an engineering standpoint, it's pretty wild, cool stuff ....

At every stage, Angel has proposed high-technology solutions to staggering challenges. He would launch the refractors to escape velocity with an electromagnetic coil gun, which propels a missile based on electromagnetic repulsion, then propel them to L1 with ion thrusters using argon as fuel. Once in place, each disk would sense its position using hyper-miniature cameras that detect sun and Earth. Adjustable trim tabs (tiny mirrors) catch solar radiation pressure as needed to maintain the disk’s correct orientation and position in space.

If the disks had reflective mirror surfaces, they would quickly be pushed toward Earth by solar radiation pressure, so they will be designed to refract (bend) sunlight, not reflect it. Since they would make only a small deflection, the disks would evade most of the radiation pressure, Angel says. He estimates the disks could remain in orbit for at least 50 years, until their solar cells degraded and they could no longer position themselves.

... but do we really have any idea of how badly this could go wrong? Call me a Luddite, but it seems that some ideas are so conceivably catastrophic that they should be abandoned out of hand.

I mean, can you imagine if the same people responsible for the ballistic missile shield were given the job of blocking the sun? Goodbye global warming; hello ice age!

Pies in the Sky: A Solution to Global Warming? [Astrobiology Magazine]

Image: University of Arizona