As the threat from climate change looms ever larger, growing attention is being paid to proposals that sound as if they come straight from a sci-fi novel. One idea is to spray the stratosphere with particulates to reflect sunlight, thus reducing the temperature of planet Earth.
Stratospheric Aerosol Injection, known as SAI, is one form of solar radiation modification, a family of technologies also known as solar geoengineering.
It aims to mimic the temporary cooling that follows a volcanic eruption, bringing temperatures back down to pre-industrial levels. It would not replace the need to cut CO2 emissions, but scientists suggest it could buy more time, or help to reduce the temperature rise beyond the internationally agreed goal of 1.5C-2C.