Environment
Injecting aerosols into the atmosphere – but at higher altitudes than planes can reach – could cool the climate while avoiding some of the downsides of lower-altitude solar geoengineering
By James Dinneen
Rockets could carry cooling aerosols to high altitudes
Kevin Dietsch/Getty Images
Reusable rockets that deliver sun-reflecting aerosols to the top of the stratosphere could cool the planet – with fewer negative side effects than lower-altitude solar geoengineering. But a fleet of climate-cooling rockets would come with its own downsides.
The rise in global average temperatures has focused more research attention on solar geoengineering, the controversial notion of cooling the climate by reflecting sunlight away from the planet. The best-known approach, called stratospheric aerosol injection (SAI), would involve releasing a constant supply of reflective particles like sulphur dioxide into the stratosphere.
In SAI scenarios, researchers normally envision using specialised high-flying cargo planes to inject aerosols at an altitude of around 20 kilometres. According to climate models, this would mask the warming due to rising concentrations of greenhouse gases. But it would create numerous other climate risks, both known and unknown.
One major issue is that the aerosols would absorb sunlight and heat up the stratosphere itself, even as surface temperatures cooled below. Due to wind patterns, the aerosols would accumulate in the tropical stratosphere, causing greater