$60 Million Sun-Dimming Startup Spurs War Game in London

London, United Kingdom — A simulation designed to test how the world would respond to solar geoengineering showed that scientific consensus breaks down fast once governments, companies and advocacy groups start competing over the technology, according to organizers and participants described by WIRED and Ars Technica.

What happened in the London war game?

The exercise, called Exploring Geopolitical Tipping Points and Climate Cooling Strategies, brought roughly two dozen foreign-relations experts, scientists, military personnel and former government officials to Queen Mary University of London last September, WIRED reported. Participants sat at tables representing national governments, climate nonprofits, Indigenous groups and tech companies, tasked with negotiating a response to a prospective global race to cool the planet by blocking sunlight.

Colleen Golja, a climate researcher assigned to provide technical advice during the game, told WIRED she expected agreement to come easily. "I thought that would be such an easy thing. Like, we can all agree to do ethical research and make sure it's for the better of all humans," she said. "And boy, was I wrong."

Why do nations disagree on solar geoengineering?

Solar radiation modification — spraying sulphur dioxide or similar particles into the atmosphere to reflect sunlight — mimics the cooling effect of large volcanic eruptions, which can lower global temperatures by half a degree or more, according to the report. But the consequences are not evenly distributed: models cited in the piece predict drying across sub-Saharan Africa and more intense Atlantic tropical storms as side effects. Because the cooling only lasts as long as the spraying continues, any interruption could send temperatures snapping back with unpredictable results, the report said.

Those asymmetric risks are what fractured the room during the war game, as governments and blocs representing the regions likely to bear the worst side effects pushed back against those eager to deploy the technology quickly.

Who is already building this technology?

The policy debate is no longer theoretical. Stardust Solutions, a US-Israeli startup, raised $60 million last year and in May detailed a suite of inventions it says could let operators dial global temperatures up or down, according to the report. In August, SpaceX founder Elon Musk wrote on X that "space satellites to control temperature and massive geo-engineering will be needed or it will be game over," the piece noted — a signal that private and commercial actors, not just governments, are moving toward deployment.

What are the risks of dimming the sun?

Beyond the uneven regional effects, researchers warn of a termination shock if deployment stops abruptly, plus the broader governance problem of who decides when and how much sunlight gets blocked. Cynthia Scharf, cited in the report as a figure tracking the policy landscape, argues the world will need to make governing decisions far sooner than most policymakers currently expect.

What happens next?

No binding international framework currently governs solar geoengineering deployment. The London exercise was designed to surface where diplomatic and scientific consensus breaks down before any government or company attempts a real-world test at scale, according to the organizers' stated goal in the WIRED report.