With severe climate impacts becoming more and more apparent, many scientists think we should explore ways to block out solar radiation, but doing so would be risky.

Earlier this month, on the deck of a second world war aircraft carrier docked in San Francisco, a giant fan began spraying sea salt particles into the air.

A machine sprays sea salt particles from the flight deck of a decommissioned aircraft carrier in California to test a technique to make clouds brighter

New York Times/Redux/eyevine

Few people, beyond those on the ship and bystanders on the nearby dock, would have taken much notice of the resulting plume of salt spray drifting upwards.

But this fan, and the spray it pumps out, has global significance. It marks one of the first real-world trials of a climate intervention known as marine cloud brightening – essentially an attempt to cool the planet by making clouds more reflective, so that they bounce more of the sun’s energy back into space.

Our chances of limiting global warming to 1.5°C above pre-industrial levels are rapidly slipping away, with a recent analysis suggesting the world will burn through the remaining carbon budget for this temperature goal by 2029 or earlier.

Meanwhile, global temperatures rose to record levels in 2023. And that extreme heat has brought extreme impacts, with widespread coral reef bleaching, severe marine heatwaves and rapid glacier loss just some of the consequences. Time is running out, scientists agree, to avert disaster.

Could geoengineering buy us time to get our house in order?

Solar radiation modification (SRM) is a type of geoengineering that involves modifying the atmosphere to tweak how much of the sun’s radiation makes it to Earth. Essentially, it would involve pumping tiny reflective particles into the atmosphere to bounce more solar radiation back into space.

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