Could a Giant Parasol in Outer Space Help Solve the Climate Crisis?

It’s come to this. With Earth at its hottest point in recorded history, and humans doing far from enough to stop its overheating, a small but growing number of astronomers and physicists are proposing a potential fix that could have leaped from the pages of science fiction: The equivalent of a giant beach umbrella, floating in outer space.

The idea is to create a huge sunshade and send it to a far away point between the Earth and the sun to block a small but crucial amount of solar radiation, enough to counter global warming. Scientists have calculated that if just shy of 2 percent of the sun’s radiation is blocked, that would be enough to cool the planet by 1.5 degrees Celsius, or 2.7 Fahrenheit, and keep Earth within manageable climate boundaries.

The idea has been at the outer fringes of conversations about climate solutions for years. But as the climate crisis worsens, interest in sun shields has been gaining momentum, with more researchers offering up variations. There’s even a foundation dedicated to promoting solar shields.

A recent study led by the University of Utah explored scattering dust deep into space, while a team at the Massachusetts Institute of Technology is looking into creating a shield made of “space bubbles.” Last summer, Istvan Szapudi, an astronomer at the Institute for Astronomy at the University of Hawaii, published a paper that suggested tethering a big solar shield to a repurposed asteroid.

Now scientists led by Yoram Rozen, a physics professor and the director of the Asher Space Research Institute at Technion-Israel Institute of Technology, say they are ready to build a prototype shade to show that the idea will work.

To block the necessary amount of solar radiation, the shade would have to be about a million square miles, roughly the size of Argentina, Dr. Rozen said. A shade that big would weigh at least 2.5 million tons — too heavy to launch into space, he said. So, the project would have to involve a series of smaller shades. They would not completely block the sun’s light but rather cast slightly diffused shade onto Earth, he said.