We’ve come to this. With Earth at its hottest point in history and humans doing little to stop it from overheating, a small but growing number of astronomers and physicists are proposing a potential solution that could have come straight from the pages of science fiction: the equivalent to a giant parasol, floating in space.
The idea is to create a huge shadow and send it to a distant point between the Earth and the Sun to block a small but crucial amount of solar radiation, enough to combat global warming. Scientists have calculated that if we block just under 2% of solar radiation, that would be enough to cool the planet by 1.5 degrees Celsius, or 2.7 Fahrenheit, and keep Earth within manageable climate limits.
The idea has been appearing in conversations about climate solutions for years. But as the climate crisis worsens, interest in solar shadows has gained momentum, with more researchers coming up with variations. There’s even a foundation dedicated to promoting solar shields.
A recent study led by the University of Utah explored the dispersal of dust in deep space, while a team at the Massachusetts Institute of Technology studies creating a shield made of “space bubbles.” Last summer, Istvan Szapudi, an astronomer at the University of Hawaii’s Institute for Astronomy, published a paper suggesting strapping a large solar shield to a repurposed asteroid.
Now, scientists led by Yoram Rozen, professor of physics and director of the Asher Space Research Institute at the Technion-Israel Institute of Technology, say they are ready to build a shadow prototype to show that the idea will work.
To block the necessary amount of solar radiation, the shadow would have to be the size of an Argentina, Rozen said. Such a shadow would weigh at least 2.5 million tons — too heavy to be launched into space, according to him. Therefore, the project would have to involve a series of smaller shadows. They would not completely block the Sun’s light, but they would cast a slightly diffuse shadow on Earth, he said.
Rozen said his team is ready to design a 100-square-foot shade prototype and is seeking between $10 million and $20 million to fund the demonstration.
Advocates say an umbrella 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 is already excess carbon dioxide in the atmosphere trapping heat.
Earth’s average temperature is about to rise 1.5 degrees Celsius compared to the pre-industrial average. That’s the point beyond which the chances of extreme storms, droughts, heat waves and wildfires would increase significantly, and humans and other species would have a harder time surviving, scientists say. The planet has already warmed by 1.2 degrees Celsius.
An umbrella would help stabilize the climate, proponents of the idea say, while other climate mitigation strategies are being pursued.
“I’m not saying this will be the solution, but I think everyone should work toward all possible solutions,” said Szapudi, the astronomer who proposed tying an umbrella to an asteroid.
It was in 1989 that James Early of Lawrence Livermore National Laboratory suggested a “space-based solar shield” positioned near a fixed point between the Earth and the Sun called Lagrange Point One, or L1, about 1,500 km away. , four times the average distance between the Earth and the Moon. There, the gravitational forces of the Earth and the Sun cancel each other out.
In 2006, Roger Angel, an astronomer at the University of Arizona, presented his proposal for a deflecting solar shield to the National Academy of Sciences and subsequently won a grant from NASA’s Institute for Advanced Concepts to continue his research. He suggested releasing trillions of very light spacecraft into L1, using transparent film and steering technology that would prevent the devices from straying from orbit.
“It’s like you just turned a dial on the sun,” Angel said, “and you don’t mess with the atmosphere.”
The parasol idea has its critics, among them Susanne Baur, a doctoral candidate who focuses on modeling solar radiation modification at the European Center for Advanced Research and Training in Scientific Computing in France.
A beach umbrella would be astronomically expensive and could not be implemented in time, given the speed of global warming, she said. Additionally, a solar storm or collision with space rocks could damage the shield, resulting in sudden, rapid heating with disastrous consequences, Baur 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 “more viable and cost-effective” solar geoengineering ideas.
But solar shading advocates say that at this stage, reducing greenhouse gas emissions will not be enough to prevent climate chaos, that carbon dioxide removal has proven extremely difficult to accomplish, and that any potential solution must be explored.
Morgan Goodwin, executive director of the nonprofit Planetary Solar Shading Foundation, said one of the reasons solar shading hasn’t gained as much attention is that climate researchers have naturally focused on what’s happening in the atmosphere. on Earth and not in space.
However, the falling costs of space launches and investments in a space industrial economy have expanded the possibilities, Goodwin said. The foundation suggests using raw materials from space and launching solar shaders to L1 from the Moon, which would cost much less than starting from Earth.
“We think that as the idea of solar shading becomes more understood by climate experts, it will become a pretty obvious part of the discussion,” said Goodwin, who is also senior director of the Angeles chapter of the Sierra Club.
The Technion’s model involves attaching lightweight solar sails to a small satellite sent to L1. Its prototype would move back and forth between L1 and another equilibrium point, with the sail tilting between pointing at the Sun and being perpendicular to it, moving like a shutter. This would help keep the satellite stable and eliminate the need for a propulsion system, Rozen said.
Rozen said the team was still in the pre-design phase, but could launch a prototype within three years after securing funding. He estimated that a full-size version would cost trillions (a bill “for the world to pay, not a single country,” he said), but would reduce Earth’s temperature by 1.5 Celsius in two years.
“We at the Technion are not going to save the planet,” Rozen said. “But we’re going to show that it can be done.”