Use smoke, mirrors to combat global warming?

For far-out concepts, it’s hard to beat Roger Angel’s. Last fall, the University of Arizona astronomer proposed what he called a “sun shade.” It would be a cloud of small Frisbee-like spaceships that go between Earth and the sun and act as an umbrella, reducing heat from the sun.

“It really is just like turning down the knob by 2 percent of what’s coming from the sun,” he said.

The science for the ships, the rocketry to launch them, and the materials to make the shade are all doable, Angel said.

Tom Connors / University of Arizona via AP This graphic illustration provided by Roger Angel of the University of Arizona shows a sunshade or solar umbrella composed of small discs designed reduce global warming.

These nearly flat discs would each weigh less than an ounce and measure about a yard wide with three tab-like “ears” that are controllers sticking out just a few inches.

About 800,000 of these would be stacked into each rocket launch. It would take 16 trillion of them — that’s million million — so there would be 20 million launches of rockets. All told, Angel figures 20 million tons of material to make the discs that together form the solar umbrella.

And then there’s the cost: at least $4 trillion over 30 years, probably more.

“I compare it with sending men to Mars. I think they’re both projects on the same scale,” Angel said. “Given the danger to Earth, I think this project might warrant some fraction of the consideration of sending people to Mars.”

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