Could a giant parasol in space help solve the climate crisis?
It has come to this. Now that Earth is at its hottest point in history, and humans aren't doing nearly enough to stop its overheating, a small but growing number of astronomers and physicists are proposing a possible solution that could have jumped off the pages of science fiction: the equivalent of a gigantic parasol, floating in space.
The idea is to create a huge parasol 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 counteract global warming. Scientists have calculated that if just 2 percent of the sun's radiation were blocked, it 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 on the fringes of conversations about climate solutions for years. But as the climate crisis worsens, interest in sunscreens is gaining momentum, with more and more researchers offering variations. There is even a foundation dedicated to promoting sunscreens.
A recent study led by the University of Utah examined the scattering of dust deep in space, while a team from the Massachusetts Institute of Technology is investigating creating a shield made of 'space bubbles'. Last summer, Istvan Szapudi, an astronomer at the University of Hawaii's Institute for Astronomy, said: published a paper that suggested a large solar shield would be attached to a recycled 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 prototype to demonstrate that the idea will work.
To block the necessary amount of solar radiation, the shade would have to be about a million square kilometers, about the size of Argentina, said Dr. Roses. Such a large sunshade would weigh at least 2.5 million tons — too heavy to launch into space, he said. So the project should include a series of smaller shades. They wouldn't block sunlight completely, but rather cast a somewhat diffuse shadow on the Earth, he said.
Dr. Rozen said his team was ready to design a 1,000-square-foot prototype and is seeking between $10 and $20 million to fund the demonstration.
“We can show the world, 'Look, there is a working solution, take it and scale it up to the size necessary,'” he said.
Advocates say a solar shield would not eliminate the need to stop burning coal, oil and gas, the leading causes of climate change. Even if greenhouse gas emissions from fossil fuels were to immediately drop to zero, there is already excess heat-trapping carbon dioxide in the atmosphere.
The average temperature on Earth is on the verge of an increase of 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 more difficulty surviving, scientists say. The planet has already warmed by 1.2 degrees Celsius.
A solar shield would help stabilize the climate, proponents of the idea say, while other climate mitigation strategies are pursued.
“I'm not saying this will be the solution, but I think everyone should work on every possible solution,” says Dr. Szapudi, the astronomer who proposed attaching a sunshade to an asteroid.
It was 1989 when James Early of Lawrence Livermore National Laboratory proposed a “space-based solar shield,” placed near a fixed point between Earth and the sun called Lagrange Point One, or L1, some 932,000 miles 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, said: presented his proposal for a deflecting sunshade from the National Academy of Sciences and later won a grant from the NASA Institute for Advanced Concepts to continue his research. He proposed releasing trillions of very lightweight spacecraft at L1, using transparent film and steering technology that would prevent the devices from going out of orbit.
“It's like you just turned the dial down,” said Dr. Angel, “and you don't mess with the atmosphere.”
The parasolide has critics, among others Susanne Baur, a PhD student focusing on solar radiation modification modeling at the European Center for Research and Advanced Training in Scientific Computation in France. A solar shield would be astronomically expensive and could not be implemented in time given the rate of global warming, she said. In addition, a solar storm or collision with stray space rocks could damage the shield, resulting in sudden, rapid warming with disastrous consequences, Ms. Baur said.
Time and money would be better spent on reducing greenhouse gas emissions and removing carbon dioxide from the atmosphere, she said, with a small portion of the research going toward “more viable and cost-effective” geoengineering ideas on solar energy.
But parasol advocates say that cutting greenhouse gas emissions at this stage will not go far enough to stave off climate chaos, that removing carbon dioxide has proven extremely difficult to achieve and that every possible solution must be explored.
A fully operational sunshade should be resilient and reversible, said Dr. Szapudi. In his proposed design, he said that 99 percent of the weight would come from the asteroid, offsetting the costs. It would likely still carry a price tag of trillions of dollars, an amount far less than what is spent on military weapons, he said.
“Saving the Earth and giving up 10 percent of your weapons to destroy things is actually a pretty good deal in my opinion,” said Dr. Szapudi.
He cited Tesla as an example of an idea that once seemed wildly ambitious but grew into the world's largest electric vehicle manufacturer within 20 years of its founding.
Morgan Goodwin, executive director of the nonprofit Planetary Sunshade Foundation, said one reason sunshades haven't gained as much popularity is that climate researchers have, quite naturally, focused on what's happening in Earth's atmosphere and not on space.
But the falling costs of space launches and investments in an industrial space economy have expanded the possibilities, Mr. Goodwin said. The foundation proposes to use raw materials from space and launch solar shield ships from the moon to L1, which would cost much less than a departure from Earth.
“We think that as the idea of umbrellas becomes better understood by climate people, it will become a fairly obvious part of the discussion,” said Mr. Goodwin, who is also senior director of the Sierra Club's Angeles chapter.
The Technion model attaches lightweight solar sails to a small satellite that is sent to L1. Their prototype would move back and forth between L1 and another equilibrium point, with the sail tilting between facing the sun and being perpendicular to it, moving like a blind slat. This would help keep the satellite stable and eliminate the need for a propulsion system, said Dr. Roses.
Dr. Rozen said the team was still in the pre-design phase but was able to launch a prototype within three years of securing funding. He estimated that a full-size version would cost trillions (a tab “that the world should pick up, not a single country,” he said), but that global temperatures would drop by 1.5 degrees Celsius within two years.
“We at Technion are not going to save the planet,” said Dr. Roses. “But we are going to show that it is possible.”