Under a White Sky: The Nature of the Future

by Elizabeth Kolbert

“But one of the things to think about is that all the material comes back down,” Keutsch continued. “Does that mean that people are inhaling these little diamond particles? It’s very likely that the amount would be so small it wouldn’t be a problem. But, somehow, I really don’t like that idea.”

Mathematical modeling has confirmed the mineral’s advantages, Keutsch told me. But until someone actually throws calcium carbonate into the stratosphere, it’s hard to know how much to trust the models. “There’s no other way around it,” he said.

melting the Arctic ice cap with a dam across the Bering Strait. Hundreds of cubic miles’ worth of cold water could then, somehow or other, be pumped from the Arctic Ocean into the Bering Sea, which would draw in warmer water from the North Atlantic and, according to Borisov’s calculations, produce milder winters not just in the polar regions but also in the mid-latitudes.

If the SAILs flew for a few decades and then, for whatever reason—a war, a pandemic, unhappiness with the results—they stopped, the effect would be like opening a globe-sized oven door. All the warming that had been masked would suddenly manifest itself in a rapid and dramatic temperature run-up, a phenomenon that’s become known as “termination shock.”

According to this scheme, a fleet of ships would be dispatched to the Arctic Ocean to shoot very fine droplets of salt water into the sky. The salt crystals, it’s theorized, would increase the clouds’ reflectivity, thus reducing the amount of sunlight striking the ice. “The hope is to preserve the layer of sea ice that is formed during the polar winter,” King said. “And if you proceed with that year on year, you rebuild the ice, layer by layer.”