A solar shield could save us from climate change. But its sudden collapse would doom the planet

By Katie Langin

Last year, the planet was plagued by powerful hurricanes, blistering fires, and temperatures that ranked as some of the hottest on record—ratcheting up concern that we’re already knee-deep in climate change. To stave off the heat, some scientists have proposed blanketing Earth in a sheet of sunlight-reflecting particles called aerosols. This solar shield could cool the planet and buy us time, but a new study suggests that if politicians turned off the hypothetical cloud, they could plunge the planet into a sudden ecological Armageddon.

The idea of injecting aerosols into the atmosphere first came to prominence in 2006, when Nobel Prize-winning atmospheric chemist Paul Crutzen argued that scientists should actively explore the possibility. He said it would be similar to what happens naturally following some volcanic eruptions. For example, the 1991 Mount Pinatubo eruption cooled the planet by 0.5⁰C, after spewing some 20 million tons of sulfur dioxide into the stratosphere. The gas created a sulfate aerosol cloud that reflected sunlight back to space for 2 years.

But injecting aerosols would require constant maintenance—and continuous global support. If a severe drought, a new government, or an economic downturn triggered its sudden collapse, the planet would rapidly warm to the steamy temperatures we otherwise would have been facing. “The minute you stop it you get the full force of the total emissions you’ve put out and that are still in the atmosphere,” says Camille Parmesan, a climate change biologist at the University of Plymouth in the United Kingdom and the University of Texas at Austin who was not involved in the new study.

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