Researchers say placing a “planetary sunshade” between Earth and the Sun could lower global temperatures by 1 °C. Credit: Mongpro/Getty
A proposal to place satellites between Earth and the Sun to reflect sunlight and cool the planet is gaining attention from researchers, even as experts warn that the approach remains technically difficult, risky and no substitute for cutting greenhouse-gas emissions. A new report estimates that construction of a so-called planetary sunshade could begin within 20 to 40 years if heavy-lift rocket technology advances rapidly enough.
In August, entrepreneur Elon Musk proposed sending satellites into space to provide shade from the Sun. These “sentient satellites” “could solve about a billion years of global warming,” he wrote in a social-media post.
It is unclear whether Musk, the chief executive of SpaceX, an aerospace company based in Starbase, Texas, intended the proposal to be taken seriously. But some researchers are exploring space-based methods for reflecting sunlight away from Earth as global temperatures approach increasingly dangerous levels.
The Planetary Sunshade Institute, a nonprofit organization in Los Angeles, California, published a report this month that it describes as the most detailed analysis of these geoengineering methods to date. The report was compiled by a consortium of engineers and climate scientists, including researchers from major space agencies such as NASA.
The report estimates that construction of a planetary sunshade could begin within 20 to 40 years. The timetable would depend on how quickly heavy-lift rockets capable of carrying millions of tons of material into deep space can be developed. SpaceX, which was not involved in the report, did not respond to Nature’s inquiries about whether it had conducted research on the concept.
“Many people think the idea is just a pipe dream,” said Chantal Cappelletti, a space-systems engineer at the University of Nottingham in the United Kingdom who is part of the consortium. But the falling cost of space launches has made the prospect more achievable, she said.
Not so much science fiction
Cooling Earth by blocking sunlight through solar geoengineering has long been debated. Proposals include releasing sunlight-reflecting particles into the atmosphere, which could have poorly understood effects, including inhibiting rainfall and plant growth.
Space-based approaches pose their own risks, including pollution from thousands of rocket launches. Critics also argue that focusing on geoengineering could distract from the urgent need to reduce greenhouse-gas emissions and address climate change.
Nevertheless, solar geoengineering is attracting researchers’ attention as global warming threatens to accelerate to 1.5 °C above pre-industrial reference temperatures. The “accelerating climate crisis” is moving the world towards solar geoengineering, said climate activist Morgan Goodwin, executive director of the Planetary Sunshade Institute.
The report is the institute’s largest project to date. It was funded by a £400,000 (US$530,000) grant from the United Kingdom’s Advanced Research and Inventions Agency (ARIA), a government-sponsored organization that supports high-risk, high-reward research. The grant is part of a larger £56.8 million ARIA research programme on solar geoengineering.
Daniele Visioni, a climate scientist at Cornell University in Ithaca, New York, had previously dismissed space-based approaches as science fiction. After joining the Faculty of Engineering and attending a workshop earlier this year, however, he became convinced that the idea deserved more attention. “I still don’t think this will be possible by the end of the century,” he said.
Between Earth and the Sun
Source: www.nature.com
