How a giant space umbrella could fight global warming

The race to find a solution to a rapidly warming world is one of the most pressing challenges facing our planet today. One proposal to try to halt this warming is literally out-of-this-world: a giant, space-based sunshade, says a BBC report.

It’s a radical idea, and it might just work. Reducing the amount of light reaching our planet could cool the Earth quickly, even with rising carbon dioxide levels. While the asteroid which helped wipe out the dinosaurs blocked out 90% of the Sun’s rays, we would need to divert just 2-4%, it’s believed, to take the Earth back to its pre-industrial climate.

Space sunshades have support in high places, from the Royal Society to Nasa, to the European Union. It’s even roused the interest of the most respected authority on global warming, the Intergovernmental Panel on Climate Change (IPCC).

The concept may be increasingly mainstream, but how we’d do it sounds more far-fetched. To uniformly cool the planet in a system that’s always on the move, the shade would be installed in an area of outer space that’s balanced between the gravity of the Earth and the Sun – the L1 point – about a million miles away.

First conceived by engineer James Early in 1989, the original design was a vast, 2,000 km-wide glass shield – a structure so heavy, it would need to be constructed on the Moon. More recent suggestions include clouds of Moon dust, 55,000 wire-mesh mirrors or a planet-girdling ring of tiny umbrellas.

By far the greatest challenge is getting the sunshade into outer space. It currently costs at least $10,000 (£6,930) to launch a pound of payload into orbit, and we haven’t put a man on the Moon since 1972. To be a viable option, the technology would need to be wafer-light and it would have to be assembled here on Earth.

Astronomer Roger Angel believes he has the answer: 16 trillion flying space robots. Each would weigh about a gram – the same as a large butterfly – and deflect sunlight with a transparent film pierced with tiny holes. To keep the burden low, the lenses would be less than a hundredth of the thickness of a human hair. “You can’t stop sunlight with anything thinner than that,” he says.

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