The pair plan to launch a balloon to ascend 80,000 feet over Fort Sumner, New Mexico, before pumping out tens or hundreds of kilograms of sulphate aerosols into the sky. The idea is that the particles will reflect sunlight back into space, helping decrease the temperature of the Earth.
In theory, they’re replicating the effects they’ve observed as volcanoes spew out similar sulphates into the atmosphere. In practice… well, there is no practice, because nobody’s ever done it before. David Keith, one of the scientists, explained to the Guardian: