A giant sunshade placed in space, between Earth and the Sun, to cool the planet. Until recently it looked like science fiction, but a group of engineers and climate scientists is now evaluating it seriously, and the topic gained attention after entrepreneur Elon Musk raised it in a social-media post in August.
The post said "sentient satellites" could "solve global warming for ~1B years". It is unclear whether Musk meant it seriously. What is clear is that his provocation brought visibility to a line of research once dismissed as unrealistic.
Image: room.eu.com — https://room.eu.com/article/sunshades-in-space-could-help-alleviate-earths-climate-crisis
The most detailed work on the subject comes from the Planetary Sunshade Institute, a nonprofit based in Los Angeles. Its report summarizes studies from a consortium of engineers and climate scientists, some linked to space agencies such as NASA. According to the report's estimates, building such a shade could become viable in 20 to 40 years. The timeline, however, depends on one factor: the development of heavy-lift rockets able to haul millions of tonnes of material into deep space.
The project's most difficult questions are economic and environmental. The report was funded with £400,000 (about $530,000) from the UK Advanced Research and Invention Agency, a government body that backs high-risk, high-reward research.
The idea rests on blocking part of sunlight to lower temperatures. In the debate over solar geoengineering, it has long been controversial. Earth-based proposals could alter the climate in poorly understood ways, for instance by changing rainfall and plant growth. Space-based approaches carry their own risks, starting with the pollution from thousands of rocket launches. Some also argue that focusing on geoengineering takes attention away from cutting emissions, which remains the priority.
Image: Space.com — https://www.space.com/sunshade-earth-orbit-climate-change
The push to consider these options is also fuelled by warming already under way. The ongoing warming has also been confirmed by the UNEP, which declared that exceeding the 1.5 °C threshold is inevitable, with current policies heading towards 2.8 °C. Cooling in the orbital vacuum remains a serious technical problem, as shown by the SpaceX and NVIDIA Starmind AI1 satellite launched in August. Morgan Goodwin, a climate activist and executive director of the institute, describes an accelerating climate crisis that pushes toward such solutions.
Even among researchers, views are shifting. Daniele Visioni, a climate scientist at Cornell University, admits he long dismissed space-based approaches as science fiction. After an engineering workshop on the topic earlier this year, he changed his mind and now believes they deserve more attention. He still does not think they will be feasible before the end of the century.
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