Elon Musk Wants to Block Out the Sun

Earth’s average temperature is nearing critical thresholds as the international community lags behind its emissions goals. As a result, bold technological strategies to cool the planet have gained attention in recent years, and now, Elon Musk is weighing in.

Early Monday morning, Musk took to X to share his two cents on how to address the climate crisis. He claimed that using satellites for solar radiation management (SRM)—a theoretical geoengineering technique that would allow humans to control the amount of sunlight reaching Earth—would be an effective solution.

“A large solar-powered AI satellite constellation would be able to prevent global warming by making tiny adjustments in how much solar energy reached Earth,” Musk wrote.

When asked how this would ensure precise, equitable adjustments to solar energy across the planet—while also accounting for seasonal variations and potential geopolitical conflicts over control—Musk replied: “Yes. It would only take tiny adjustments to prevent global warming or global cooling for that matter. Earth has been a snowball [many] times in the past.”

So, it would appear he doesn’t quite have all the answers. That said, it’s certainly notable that the wealthiest man on Earth and the CEO of the world’s largest satellite company, is advocating for space-based SRM. Experts warn, however, that this strategy is both highly unrealistic and dangerous.

Is SpaceX eyeing a new orbital venture?

Musk isn’t the only entrepreneur interested in blocking out the Sun. A growing number of companies are exploring different approaches to SRM, from using atmospheric aerosols to mimic the sunlight-blocking effects of volcanic eruptions to launching thousands of mirrors into orbit.

While some of these companies have raised significant capital and have set ambitious near-term targets for development and testing, none are anywhere close to deploying their technology at scale. If Musk’s SpaceX wades into this burgeoning industry, these startups will suddenly find a very big fish in their very small pond.

But to be clear, Musk has not shared any plans for SpaceX to develop SRM-capable satellites. And even with the company’s billion-dollar valuation and the enormous Starlink constellation it has already deployed, doing so would be far easier said than done.

Could Musk actually do it?

The first hurdle SpaceX would face is a pivot away from producing Starlink communications satellites to developing the artificially intelligent, solar-powered, SRM-capable satellites Musk described. And no, the nearly 9,000 operational Starlinks currently in orbit could not be adapted for this purpose. Alternatively, SpaceX could launch an entirely new satellite division devoted to this geoengineering project while simultaneously managing Starlink.

While Musk did not share specifics on how these satellites would work, they would likely be equipped with mirrors or sunshades that come together in formation to create a gigantic, manipulatable barrier between Earth and the Sun. When we say gigantic—we really mean it.

Scientists don’t know exactly how many SRM satellites it would take to make a meaningful difference in Earth’s average temperature, but estimates range so high that many experts consider this solution infeasible. The cost of deployment alone would likely prove insurmountable even for Musk, with estimates in the multi-trillion-dollar range.

Even if Musk could make this happen, that doesn’t mean he should. Experts have long warned of the potential consequences of space-based SRM, which could trigger major, unintended changes in Earth’s climate, the day-night cycle, biodiversity, geopolitical tensions, and more.

Avoiding these consequences—and actually mitigating global warming—would require unprecedented technological control and international governance over the largest and most impactful satellite constellation ever deployed.

Needless to say, it’s not happening anytime soon. Still, Musk’s growing interest in this technology will undoubtedly attract attention to this nascent industry, potentially fueling innovation and debate over how geoengineering can and should go.