It is fitting that this week’s UN environment talks are in Nairobi, with Africa shaping the global climate conversation. The continent’s diplomats are dealing with the vexed question of whether it is wise to try to cool the planet by dimming the sun’s rays. While not on the formal summit agenda, on the sidelines they are arguing that it’s time to stop promoting solar geoengineering technology as a solution to global heating. It’s hard to disagree.

African nations have acted because they don’t want their continent to become a test bed for unproven schemes to spray particles into the high atmosphere to reflect sunlight away from Earth for a small, uncertain cooling gain. They point to environmental, ethical and geopolitical risks. That’s why the continent is pushing for a global “non-use” agreement that would rule out public funding, outdoor experiments, patenting and official promotion of these technologies.

The reason for a moratorium is obvious: solar geoengineering doesn’t cut greenhouse-gas emissions. The potential side-effects include altered rainfall patterns and the consequential pressure on food systems. Then there is the risk of a sharp temperature spike if the interventions were ever halted – the so-called termination shock. African nations’ opposition was such that they forced the withdrawal of a Swiss-backed resolution on solar radiation modification at last year’s UN talks.

Yet an industry is being built on the idea that someone can take charge of the global thermostat. A US–Israeli firm is developing a spraying system for future “cooling services” to offer to governments. Other nations are pushing back. Mexico banned solar geoengineering experiments in 2023, after an unauthorised trial over its territory by a US startup.

Academics have already warned that the UK became the first “major government” to significantly fund solar radiation modification (SRM) through its Advanced Research and Invention Agency (Aria). It is now backing scientists to research “climate cooling’” hardware and small-scale field tests. Other scientists describe the move as naive, poorly governed and scientifically incapable of proving SRM safe. Ministers ought to pull back.

Research programmes have politics. Hardware and careers get built. Risky tech acquires well-funded backers. The actions of the US, the world’s largest producer of oil and gas, should be studied. The Trump administration has made “American energy dominance” the core of its economic strategy. Solar geoengineering offers a way to manage temperature risk without loosening the carbon economy’s grip. Controlling both the world’s energy supply and the global thermostat has obvious appeal to the White House – and its billionaire backers.

African governments’ call for a non-use agreement for solar geoengineering – echoing the precedents of landmine and chemical weapons bans – is a recognition that some technologies shift power so sharply that they create unmanageable risks. A line has to be drawn. The precautionary principle is used with other novel technologies. Why not here? The point is clearly that this power can’t be left to a few.

Africa’s call should be taken seriously. None of this weakens climate policy. It would instead focus minds on measures that address the climate emergency: cutting fossil fuel use, investing in renewables – and paying for adaptation where damage is already baked in.