Researchers are examining whether a vast “planetary sunshade” placed between Earth and the Sun could reduce global temperatures by about 1°C. A report from the Planetary Sunshade Institute says construction might begin within 20 to 40 years if heavy-lift rockets become capable of transporting millions of tons of material into deep space, although scientists emphasize that the concept remains uncertain and controversial.
Researchers say that placing a “planetary sunshade” between Earth and the Sun could lower global temperatures by 1°C. Credit: Mongpro/Getty
In August, entrepreneur Elon Musk suggested in a social media post that Earth could be cooled by launching satellites into space to shade the planet from the Sun. These “sentient satellites” “could solve about a billion years of global warming,” he wrote.
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It is unclear whether Musk, the chief executive of aerospace company SpaceX in Starbase, Texas, intended the proposal to be taken seriously. However, some researchers are interested in exploring space-based methods of reflecting sunlight away from Earth as global temperatures approach increasingly dangerous levels.
The Planetary Sunshade Institute, a nonprofit organization based in Los Angeles, California, published a report this month that it describes as the most detailed analysis of these geoengineering methods to date. Compiled by a consortium of engineers and climate scientists, including some from major space agencies such as NASA, the report estimates that construction of a “planetary sunshade” could begin within 20 to 40 years.
The timeline would depend on the development of heavy-lift rockets capable of carrying millions of tons of material into deep space to build the sunshade. 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 UK 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 particles into the atmosphere that reflect sunlight, but these could have poorly understood effects, including suppressing rainfall and reducing plant growth.
Space-based approaches carry their own risks, including pollution from thousands of rocket launches. Critics also argue that focusing on geoengineering could distract from the urgent need to cut greenhouse-gas emissions to address climate change.
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But as global warming threatens to accelerate beyond 1.5°C above pre-industrial reference temperatures, solar geoengineering is attracting more attention from researchers. 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 UK’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, he attended a workshop earlier this year and was persuaded that the approach deserved more attention. However, “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