Carolyn Gramling writes:

Towering clouds of smoke sent into the stratosphere by ferocious wildfires can eat away at Earth’s ozone layer thanks to a potent mix of smoke, atmospheric chemistry and ultraviolet light, a new study finds.

During late 2019 and early 2020, Australia’s skies turned black, darkened by thick columns of wildfire smoke that reached into the stratosphere. In the aftermath, satellite data revealed that the smoke was somehow reacting with atmospheric molecules to eat away at Earth’s ozone layer. But how exactly that was happening wasn’t clear.

Now, scientists have put together the pieces of that chemical puzzle. Once in the stratosphere, the team says, the smoke particles were able to interact with stratospheric gases as well as lingering emissions of ozone-destroying chemicals. Add in solar radiation, and that smoky brew churned out chlorine radicals, a type of chemical with an affinity for attacking ozone, researchers report in the March 9 Nature.

This series of events was responsible for depleting about 3 to 5 percent of the ozone layer in parts of the Southern Hemisphere during 2020, the researchers estimate. That’s a small fraction of the whole — but it rivals the scale of the impact of human emissions of ozone-eating chlorofluorocarbons in their heyday, says MIT atmospheric chemist Susan Solomon. [Continue reading…]