It came to that. With the Earth at its hottest point in recorded history and humans not doing enough to stop its warming, a small but growing number of astronomers and physicists are proposing a possible solution that could have leaped from the pages of science fiction: The equivalent of a giant beach umbrella, floating in space.
The idea is to create a giant sunshade and send it to a distant point between the Earth and the sun to block a small but critical amount of solar radiation, enough to combat global warming. Scientists have calculated that if it blocked just 2 percent of the sun’s 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 on the sidelines of climate solutions discussions for years. But as the climate crisis worsens, interest in sun shields is gaining momentum, with more researchers offering variations. There is even a foundation dedicated to promoting sun shields.
A recent study led by the University of Utah explored dust scattering in deep space, while a team at the Massachusetts Institute of Technology is looking at creating a shield from “space bubbles.” Last summer, Istvan Szapudi, an astronomer at the Institute for Astronomy at the University of Hawaii, posted a job who proposed attaching a large solar shield to a redesigned asteroid.
Now scientists led by Yoram Rozen, 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 shade to show the idea will work.
To block the necessary amount of solar radiation, the shadow would have to be about a million square miles, roughly the size of Argentina, Dr. Rosen said. Such a large shadow would weigh at least 2.5 million tons — too heavy to launch into space, he said. Thus, the work should include a series of smaller nuances. They wouldn’t block sunlight completely, but would rather cast a slightly diffused shadow on Earth, he said.
Dr. Rosen said his team was ready to design a prototype 100-square-foot shade and was seeking between $10 million and $20 million to fund the demonstration.
“We can show the world, ‘Look, there’s a working solution, take it, scale it up,'” he said.
Proponents say a sunshade won’t eliminate the need to stop burning coal, oil and natural gas, the main drivers of climate change. Even if greenhouse gas emissions from fossil fuels drop immediately to zero, there is already too much heat-trapping carbon dioxide in the atmosphere.
The Earth’s average temperature is on the verge of increasing by 1.5 degrees Celsius over the pre-industrial average. That’s the point beyond which the chances of extreme storms, droughts, heatwaves and wildfires would increase significantly, and humans and other species would struggle harder to survive, scientists say. The planet has already warmed 1.2 degrees Celsius.
A sunshade would help stabilize the climate, proponents say, while other climate mitigation strategies are being pursued.
“I’m not saying this is going to be the solution, but I think everyone should work toward every possible solution,” said Dr. Szapudi, the astronomer who proposed attaching an asteroid to an asteroid.
It was in 1989 that 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, about 932,000 miles away, four times the average distance. between the Earth and the Moon. There, the gravitational pulls from Earth and the sun cancel each other out.
In 2006, Roger Angel, an astronomer at the University of Arizona, presented his proposal for a sun shield diversion to the National Academy of Sciences and later won a grant from NASA’s Institute for Advanced Concepts to continue his research. He proposed releasing trillions of very light spacecraft at L1, using transparent film and steering technology that would prevent the devices from drifting out of orbit.
“It’s just like turning a knob on the sun,” said Dr. Angell, “and you don’t mess with the atmosphere.”
The shader idea has its detractors, among them Susanne Baur, PhD candidate focusing on solar radiation modification modeling at the European Center for Research and Advanced Training in Scientific Computing in France. A sunshade would be astronomically expensive and could not be implemented in time given the speed of global warming, he said. In addition, a solar storm or collision with stray space rocks could damage the shield, resulting in sudden, rapid heating with catastrophic consequences, Ms. Baur said.
Time and money would be better spent on reducing greenhouse gas emissions and removing carbon dioxide from the atmosphere, he said, with a small portion of research devoted to “more sustainable and cost-effective” solar geoengineering ideas.
But shade advocates say that at this stage, reducing greenhouse gas emissions won’t go far enough to reduce climate chaos, that removing carbon dioxide has proven extremely difficult and that every possible solution should be explored .
A fully functional sunshade would need to be durable and reversible, Dr. Szapudi said. In his proposed design, he said 99 percent of its weight would come from the asteroid, helping to offset the cost. It would still have a price tag of trillions of dollars, an amount that is far less than what is spent on military weapons, he said.
“Saving the Earth and giving away 10 percent of your weapons to destroy things is actually a pretty good deal in my book,” Dr. Szapudi said.
He held up Tesla as an example of an idea that once seemed wildly ambitious, but within 20 years of its founding has become the world’s leading electric vehicle maker.
Morgan Goodwin, executive director of the Planetary Sunshade Foundation, a nonprofit organization, said one reason sunshades haven’t gained as much traction is that climate researchers have focused, of course, on what’s happening in Earth’s atmosphere rather than space.
But the falling cost of space launches and investment in a space-based industrial economy have widened the possibilities, Mr Goodwin said. The foundation proposes using raw materials from space and launching sunshade ships to L1 from the moon, which would cost much less than starting from Earth.
“We think that as the idea of sunshades becomes more understood by climate people, it will be a fairly obvious part of the conversation,” said Mr. Goodwin, who is also senior director of the Sierra Club’s Angeles chapter.
The Technion model involves attaching lightweight solar sails to a small satellite sent to L1. Their prototype would move back and forth between L1 and another balance point, with the sail tilted between pointing toward the sun and being perpendicular to it, moving like a slat on a blind. This would help keep the satellite stable and eliminate the need for a propulsion system, Dr. Rosen said.
Dr. Rosen said the team was still in the preliminary design phase, but could launch a prototype within three years after securing funds. He estimated that a full-size version would cost trillions (a tab “for the world to pick up, not one country,” he said) but would lower the Earth’s temperature by 1.5C within two years.
“We at the Technion are not going to save the planet,” said Dr. Rosen. “But we will show that it can be done.”