It sounds contradictory, but the idea is actually based on a natural polluter -- volcanoes. Kintisch points out that nearly 20 years before the eruption of Eyjafjallajokull in Iceland shut down air traffic across Europe, a much bigger volcano in the Philippines affected the climate over a much broader area.
"In 1991, when Mount Pinatubo erupted, it put tons of sulfur into the stratosphere," he says. "Those sulfur aerosols cooled the planet."
So if we found ourselves in a climate crisis where oceans were rising rapidly and coastal areas were flooding, some scientists think "we could mimic the cooling effect of natural volcanoes and make man-made volcanoes by putting our own gunk, essentially, up in the upper atmosphere," Kintisch says
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