Back in the late 1990s, Ken Caldeira set out to disprove the “ludicrous” idea that we could reverse global warming by filling the sky with chemicals that would partially block the sun. A few years earlier, Mount Pinatubo had erupted in the Philippines, sending tiny sulfate particles—known as aerosols—into the stratosphere, where they reflected sunlight back into space and temporarily cooled the planet. Some scientists believed that an artificial version of this process could be used to cancel out the warming effect of greenhouse gases. “Our original goal was to show that it was a crazy idea and wouldn’t work,” says Caldeira, who at the time was a climate scientist at the Lawrence Livermore National Laboratory. But when Caldeira and a colleague ran a model to test out this geoengineering scenario, they were shocked by what they found. “Much to our surprise, it worked really well,” he recalls. “Our results indicate that geoengineering schemes could markedly diminish regional and seasonal climate change from increased atmospheric CO2,” they wrote in a 2000 paper. You might think that the volume of aerosols needed to increase the Earth’s reflectivity (known as albedo) enough to halt global climate change would be enormous. But speaking to Kishore Hari on this week’s Inquiring Minds podcast, Caldeira explains that “if you had just one firehose-worth of material constantly spraying into the stratosphere, that would be enough to offset all of the global warming anticipated for the rest of this century.” So does Caldeira think it’s time to start blasting aerosols into the air? Nope. “It’s a funny situation that I feel like I’m in,” he says. “Most of our published results show that it would actually work quite well, but personally I think it would be a crazy thing to do.” He thinks there’s just too much risk. More via Climate Desk.
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