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Megafires like those in Australia’s Black Summer can damage the ozone layer that protects life on Earth, new research suggests.
The findings are sobering given longstanding warnings that climate change will cause more frequent and intense wildfires.
Atmospheric scientists at the Massachusetts Institute of Technology in the United States believe that the composition of smoke from wildfires promotes chemical reactions that contribute to the destruction of stratospheric ozone.
Stratospheric ozone, commonly known as the ozone layer, is found in high concentrations 15 to 30 kilometers above the earth’s surface and protects life by filtering out harmful ultraviolet radiation from the sun.
Without it, the planet would be uninhabitable.
When the Black Summer fires raged across Australia in 2019-2020, they produced pyrocumulonimbus towers that released bushfire smoke into the stratosphere.
The smoke was associated with changes in the chemical composition of the upper atmosphere, including a depletion of ozone.
But how the smoke might be contributing to ozone depletion remains uncertain.
Now Professor Susan Solomon, who in the 1980s also explained the hole in the ozone layer, suggests that the mixture of chemicals in the smoke enhances the activation of chlorine radicals, the molecules that can destroy ozone.
Roger Dargaville of Victoria’s Monash University has also studied stratospheric ozone depletion and says the research shows the dangers of climate change are still being revealed.
He fears that more mega-fires could undermine successes achieved under a landmark 1987 pact that calls for a global reduction in consumption and production of around 100 ozone-depleting man-made chemicals.
“The (new paper) shows that smoke from extreme wildfires entering the stratosphere increases the potency of chlorine in the atmosphere, jeopardizing the progress achieved through the Montreal Protocol to date,” he said.
Professor Ian Rae is an expert on chemicals in the environment at the University of Melbourne’s School of Chemistry and contributed to the work behind the Montreal Protocol.
“Once you find this kind of ozone-damaging side effect of fires, not as bad as chlorofluorocarbons, but enough to measure, then you start to think we might have solved a problem for the ozone layer, but there is another. one that lurks now,” he said.
“So what are the consequences? At the moment it is not bad at all but it is an impact that is not going to disappear.
“And certainly if there are more wildfires, there will be more disturbances in the ozone layer.”
Martin Jucker, from the University of NSW and ARC Center of Excellence for Extreme Climates, says the research is of particular relevance to Australia.
While the ozone hole usually forms over Antarctica, due to low temperatures helping chlorine attack ozone, smoke from wildfires appears to be capable of causing ozone depletion in relatively warmer temperatures.
And that could cause the ozone hole to extend further towards the equator, endangering many Australians.
“If this were to happen more frequently and possibly more strongly, it would actually be right above us, so we would have more ultraviolet radiation directly hitting regions of Australia where a lot of people live,” said Dr Jucker.
“The study confirms once again that when it comes to the weather, all things are connected.”
The research work has been published in the journal Nature.
-AAP