Wildfire Smoke Linked to Ozone Layer Damage

A new study led by chemists at the Massachusetts Institute of Technology found that wildfire smoke particles, which can remain in the stratosphere for a year, can cause chemical reactions that deplete the protective ozone layer. The findings occurred during the megafire in Australia in December 2019 to January 2020.

The study, published in the journal Nature, analyzed the atmospheric chemical composition over the Southern Hemisphere at mid-latitudes, including regions over Australia and New Zealand and parts of Africa and South America. 

The researchers noted that the wildfire smoke particles created chemical reactions in the stratosphere. They estimated that these reactions caused the megafire to contribute to a 3% to 5% depletion in the ozone in the area studied.

The study model also estimated that the wildfires impacted the ozone layer over Antarctica, widening the hole over the Antarctic by 2.5 million square kilometers by the end of 2020, or widening by 10% of its area in comparison to 2019.

“The Australian fires of 2020 were really a wake-up call for the science community,” Susan Solomon, study author and professor of environmental studies at M.I.T., said in a statement. “The effect of wildfires was not previously accounted for in [projections of] ozone recovery. And I think that effect may depend on whether fires become more frequent and intense as the planet warms.”

The wildfires analyzed in the study were the worst ever recorded in Australia, burning tens of millions of acres and emitting 1 million tons of smoke into the atmosphere, as M.I.T. reported.

Solomon and her colleagues previously identified a chemical reaction between chlorine-containing compounds, typically chlorofluorocarbons (CFCs), and fire aerosols that produced chlorine monoxide, which is known to deplete ozone. So the researchers came back to analyze molecules in the stratosphere following the megafire in Australia.

While the team found that wildfire smoke reactions with hydrochloric acid (HCl) in the stratosphere could deplete ozone, they suspect wildfire smoke could react to other chlorine-containing compounds in the atmosphere, especially when considering how long the smoke particles can remain.

“There’s now sort of a race against time,” Solomon said. “Hopefully, chlorine-containing compounds will have been destroyed, before the frequency of fires increases with climate change. This is all the more reason to be vigilant about global warming and these chlorine-containing compounds.”

In early 2023, the United Nations reported that the ozone layer was recovering following a ban on ozone-depleting chemicals, and the ozone layer was on track to recover by 2045 over the Arctic, by 2066 over the Antarctic and by 2040 for the rest of the world. But the new research raises concern over wildfire smoke and its link to ozone depletion, especially with the number of wildfires expected to increase by 50% by 2100.

The study was led by M.I.T. researchers Solomon and Kane Stone in collaboration with the Institute for Environmental and Climate Research in Guangzhou, China; the National Oceanic and Atmospheric Administration in the U.S.; the U.S. National Center for Atmospheric Research; and Colorado State University.