Smoke injected high into the atmosphere by the 2019-2020 Australian bushfires led to ozone depletion, new research has found.
Scientists have found that smoke from devastating bushfires causes a loss of 1% ozone, an amount that typically takes a decade to recover.
The study, published in the Proceedings of the National Academy of Sciences, suggests that the increase in the intensity and frequency of fires due to the climate crisis could slow the recovery of the ozone layer.
The ozone layer – part of the stratosphere, the second layer of the Earth’s atmosphere – absorbs ultraviolet radiation emitted by the sun and is made up of a high concentration of ozone molecules.
Using satellite observations, the researchers found that smoke aerosols reacted with nitrogen in the stratosphere, leading to chemical shifts causing ozone depletion.
Study co-author Dr Kane Stone of the Massachusetts Institute of Technology said the reduction occurred between March and August 2020.
“As bushfire aerosols leave the stratosphere over time – they descend back to the [Earth’s] surface – ozone depletion stops,” Stone said. “This is a short-term decrease, but it is significant.
“We are currently seeing an ozone recovery of about 1% per decade.”
Ozone is continually replenished in the atmosphere over the tropics. “Sunlight reacts with oxygen and creates ozone,” Stone said.
Despite continued ozone production, concentrations had been reduced by substances such as chlorofluorocarbons, which were phased out under the 1987 Montreal Protocol.
Smoke from the 2019-2020 bushfires circled the globe, blanketing the mid-latitudes of the southern hemisphere. The pyrocumulonimbus cloud formed during the event – three times larger than anything previously recorded – ejected smoke particles miles up into the stratosphere.
The researchers did not study whether bushfire smoke affected the Antarctic ozone hole, which occurs at more southern latitudes and grows every spring in the Southern Hemisphere.
Director of the University of Wollongong’s Atmospheric Chemistry Center who was not involved in the research, Professor Clare Murphy, said more intense fires in the future – as current climate models predict – would slow the recovery of the ozone layer. .
“In the stratosphere, the pressure is very low…there aren’t a lot of molecules around, so chemistry usually happens very slowly,” Murphy said. “You put [smoke] particles up there and suddenly you provide a surface on which chemistry can occur orders of magnitude faster.
Efforts to address the ozone hole in Antarctica are a successful example of coordinated environmental action, Murphy said. “There’s no reason humanity can’t come together and solve climate problems too.”