On a Tuesday in August, Luke Iseman drove two hours east of Oakland in drought-stricken California to a remote spot where he launched a handful of balloons filled with sulphur dioxide and helium high into the sky.

From there, he used GPS to try to track the balloons as they rose into the stratosphere,
the layer of Earth’s atmosphere that begins about 12km high and contains the ozone
layer that protects the planet from solar radiation. Once there, they would burst and
release the gas.

Iseman’s start-up, Make Sunsets, is piloting small-scale stratospheric aerosol
injections: the sulphur dioxide released by the balloons oxidises to form an aerosol, or
fine mist, of sulphate particles that deflect some of the sun’s radiation. So far it has
launched 28, each the size of a small weather balloon. “The company’s mission is to
cool the Earth as quickly as we safely can”, he says.

Read more: ft.com

Photo: ft.com