Could a giant umbrella in outer space help solve the climate crisis?

It has come to this. With Earth reaching its hottest point in recorded history, and humans making insufficient efforts to stop its warming, a small but growing number of astronomers and physicists are proposing a potential solution that could have jumped from the pages of science fiction: the equivalent of a giant beach umbrella, floating in Outer Space.

The idea is to create a huge solar umbrella and send it to a remote point between the Earth and the sun to block a small but crucial amount of solar radiation, enough to counteract global warming. Scientists have calculated that if roughly 2% of the sun's radiation was blocked, that would be enough to cool the planet by 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, and keep Earth within manageable climate limits.

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

A recent study led by the University of Utah explored the dispersal of 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 Chabudi, an astronomer at the University of Hawaii's Institute of Astronomy, Published paper Which proposes attaching a large solar shield to a reused asteroid.

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

To block the necessary amount of solar radiation, the shadow area would need to be about 1 million square miles, roughly the size of Argentina, Dr. Rosen said. A shadow of that size would weigh at least 2.5 million tons, too heavy to be launched into space, he said. Therefore, the project should include a series of smaller shades. He said that it would not completely block sunlight, but rather would cast slightly spreading shadows on the ground.

Dr. Rosen said his team is ready to design a 100-square-foot prototype and is seeking $10 million to $20 million to fund the demonstration.

“We can show the world: Look, there is a workable solution, take it and scale it up,” he said.

Supporters say a sunshade would not eliminate the need to stop burning coal, oil and gas, the main drivers of climate change. Even if greenhouse gas emissions from fossil fuels were immediately reduced to zero, there are already large amounts of carbon dioxide trapping heat in the atmosphere.

The Earth's average temperature is about to rise 1.5°C above the pre-industrial average. Scientists say this is the point beyond which the chances of severe storms, droughts, heat waves and wildfires will increase dramatically and humans and other species will struggle to survive. The planet has already warmed by 1.2 degrees Celsius.

Supporters of the idea say the canopy would help stabilize the climate, while other strategies to mitigate the effects of climate change are being pursued.

“I'm not saying this will be the solution, but I think everyone should work on finding all possible solutions,” said Dr. Chabuddy, the astronomer who proposed attaching the sun's parachute to an asteroid.

It was in 1989 when James Early of Lawrence Livermore National Laboratory proposed creating a “space sun shield” that would be placed near a fixed point between Earth and the sun called Lagrange Point One, or L1, about 932,000 miles away, four times the average distance. . Between the Earth and the Moon. There, gravitational forces from the Earth and the Sun cancel each other out.

In 2006, Roger Angell, an astronomer at the University of Arizona, He presented his proposal for a deflector sun shield He joined the National Academy of Sciences and later received a grant from the NASA Institute for Advanced Concepts to continue his research. He proposed launching trillions of ultra-light spacecraft at L1, using a transparent film and guidance technology that would prevent the hardware from drifting out of orbit.

“It's as if you just turned a knob on the sun, and you're not messing with the atmosphere,” Dr. Angel said.

The umbrella idea has its critics, including… Susan Burr, PhD candidate focusing on modeling solar radiation modulation at the European Center for Advanced Research and Training in Scientific Computation in France. She said the parachute would be too expensive to implement in time, given the speed of global warming. In addition, a solar storm or collision with errant space rocks could damage the shield, leading to a sudden, rapid rise in temperatures with disastrous consequences, Ms. Power said.

She said time and money would be better spent working to reduce greenhouse gas emissions and remove carbon dioxide from the atmosphere, with a small portion of research devoted to solar geoengineering ideas that are “most feasible and cost-effective.”

But Umbrella proponents say that reducing greenhouse gas emissions at this stage will not be enough to calm climate chaos, and that removing carbon dioxide has proven extremely difficult to achieve, and that all potential solutions must be explored.

A fully functional sunshade must be flexible and reversible, Dr. Chabudi said. In his proposed design, he said 99% of its weight would come from the asteroid, which would help offset the cost. He added that its price would likely reach trillions of dollars, an amount much less than what is spent on military weapons.

“Saving the Earth and giving up 10 percent of your weapons to destroy things is actually a pretty good deal in my book,” Dr. Sabaody said.

He gave Tesla as an example of an idea that once seemed very ambitious, but within 20 years of its founding it had become the world's largest electric car manufacturer.

One reason sunshades haven't gained as much attention is that climate researchers have, quite naturally, focused on what's happening inside Earth's atmosphere rather than in space, said Morgan Goodwin, executive director of the Planetary Sunshade Foundation, a nonprofit.

But Goodwin said falling space launch costs and investments in the space industrial economy have expanded the possibilities. The Foundation proposes to use raw materials from space and launch solar shadow ships to L1 from the Moon, which would be much less expensive than launching from Earth.

“We believe that as the idea of ​​solar canopies becomes increasingly understood by climate workers, they will be a very visible part of the discussion,” said Mr. Goodwin, who is also senior director of the Sierra Club's Los Angeles chapter.

The Technion model involves attaching lightweight solar sails to a small satellite that is transmitted to L1. Their prototype would move back and forth between L1 and another balance point, tilting the sail between pointing at the sun and being perpendicular to it, moving like a slat on a metal curtain. This would help keep the satellite stable and eliminate the need for a propulsion system, Dr. Rosen said.

Dr. Rosen said the team is still in the pre-design phase but could launch a prototype within three years after securing funds. He estimated that a full-sized version would cost trillions of dollars (it's a tab “the world has to pick up, not one country,” he said), but would lower the Earth's temperature by 1.5 degrees Celsius within two years.

“We at the Technion are not going to save the planet,” Dr. Rosen said. “But we will show that it can be done.”