Tweaking Earth's climate to combat global warming seems like a great idea. Giant mirrors or shades in space, artificially enhanced cloud cover, and regular injections of reflective sulfate particles into the stratosphere could all help cool the planet enough for us to ignore all of the CO2 we're pumping into the atmosphere. But a new study says one of the most popular ideas — the sulfate particles — would devastate the ozone layer, leaving us all to fry from exposure to ultraviolet radiation even as the planet cooled.
Scientists got the idea for injecting sulfate particles into the atmosphere from watching massive volcanoes blow their top. When big boomers like Mount St. Helens or Pinatubo go, they throw huge plumes of sulfur-rich gunk into the atmosphere, and climate around the globe can cool significantly for up to a few years. The ozone layer also thins significantly.
Simone Tilmes of the National Center for Atmospheric Research (NCAR) and her colleagues calculated that if humans started artificially pumping two different sizes of sulfate molecules into the atmosphere, we could lose as much as 3/4 of the ozone layer:
The study found that injections of small particles, over the next 20 years, could reduce the ozone layer by 100 to 230 Dobson Units. This would represent a significant loss of ozone because the average thickness of the ozone layer in the Northern Hemisphere is 300 to 450 Dobson Units. (A Dobson Unit is equivalent to the number of ozone molecules that would create a layer 0.01 millimeters thick under conditions at Earth's surface).
With large particles, the Arctic loss would range from 70 to 150 Dobson Units. In each case, the larger figure is correlated with colder winters.
The ozone loss would drop in the later part of the century to about 60 to 150 Dobson Units, depending on the size of the sulfates and the severity of winters.
In the Antarctic, most of the ozone is already depleted and the sulfate injections would not significantly reduce the thickness of the ozone layer. Instead, they would significantly delay the recovery of the ozone hole.
The authors caution that the actual impacts on ozone could be somewhat different than estimated if atmospheric changes led to unusually warm or cold polar winters. They also warn that a geoengineering project could lead to even more severe ozone loss if a major volcanic eruption took place at the same time.