Science doi:10.1126/science.1153966 (2008)


Proposed 'geoengineering' schemes to counteract climate change could pose a serious threat to the Earth's ozone layer, warn scientists. One of the more popular ideas for rapidly cooling the planet involves simulating a volcanic eruption by releasing bursts of sulphur into the atmosphere to increase the amount of sunshine reflected back into space.

Now Simone Tilmes of the National Center for Atmospheric Research in the US and colleagues have calculated the impact on polar ozone of a sulphur injection large enough to compensate for the warming effect of doubling atmospheric carbon dioxide levels. They base their estimates on historical records of the relationship between ozone loss and atmospheric aerosols in polar regions, as well as accounting for anticipated future depletion of ozone by anthropogenic pollutants such as halogens, expected to decline in coming years owing to a prohibition on their use.

Assuming the scheme began in 2010 and steadily saturated the atmosphere with sulphate over the following five years using annual injections, it would greatly enhance ozone loss over the Arctic during the next century, especially if winters were cold, they found. In addition, they say the recovery of the ozone layer over the Antarctic could be delayed by 30 to 70 years.