Smoke from Australia’s monster wildfires triggered a chemical reaction that widened the ozone hole by 10 percent, researchers said Wednesday, raising fears that an increase in wildfires could delay the recovery of Earth’s atmospheric protection from the deadly ultraviolet radiation.
Intense summer heat and drought helped drive the deadly ‘Black Summer’ fires from late 2019 to early 2020, which destroyed vast areas of eucalyptus forest and shrouded Sydney and other cities in smoke and ash for months .
Previous research concluded that the more than one million metric tons of smoke pumped into the atmosphere by the fires extended the Antarctic ozone hole that opens over Antarctica each spring.
In a new study, published in the journal Natureresearchers in the United States and China have identified a newly identified chemical reaction in wildfire smoke that increased ozone depletion—the atmospheric gas that reduces the amount of ultraviolet radiation that reaches the Earth’s surface.
Susan Solomon, the MIT professor who led the research, said this reaction had died out at the edges of the ozone hole over Antarctica, expanding the hole by more than two million square kilometers (770,000 square miles)— 10 percent of its area compared to the previous year.
“These chemical reactions happen right at the edge of the region where the ozone hole is happening,” he said, explaining that “the particles give it a little extra push.”
The ozone hole was first created by human pollution—particularly the chlorofluorocarbons (CFCs) emitted by many refrigerators—but in recent decades, a global agreement on these chemicals has given the ozone layer a chance to heal.
The 1987 Montreal Protocol, ratified by 195 countries, sharply reduced the amount of CFCs pumped into the atmosphere, although the molecules remain for decades.
UN modeling predicts that the ozone layer over the Southern Hemisphere should fully heal by 2060.
But Solomon, who first identified the chemicals responsible for the Antarctic ozone hole in the 1980s, expressed concern that the effects of climate change could slow that recovery.
“We think the fires will become more frequent and intense,” he told AFP, adding that the ozone hole “will improve eventually, I believe, but it is conceivable that the fires could certainly slow it down.
“I don’t think it’s going to stop the recovery completely. But it could stop it from really recovering when we think it should.”
Scientists have long associated the formation of the ozone hole with extreme cold, as clouds at these very cold temperatures provide a surface with which lingering CFCs react, turning them into other chemicals that make chlorine more harmful to the ozone layer than it would otherwise be.
But Solomon said the new research shows that fire smoke particles rising into the atmosphere also act to absorb these molecules and trigger a series of chemical reactions that produce ozone-depleting chlorine monoxide.
This can happen, they found, without the need for extreme cold temperatures.
Provoking this reaction, the new study found that the fires likely contributed to a temporary 3 to 5 percent decrease in total ozone in the mid-latitudes of the Southern Hemisphere, over Australia, New Zealand and parts of Africa and South America.
“Honestly, I’ve never seen anything like what happened after the fires in Australia and I never expected it,” said Solomon, a leading climate scientist.
“It’s another shock.”
Research published in August by researchers in Britain found that the accumulation of smoke particles from the Black Summer fires caused changes in atmospheric temperatures that extended the Antarctic ozone hole.
More than 30 people died in the Black Summer fires, which killed or displaced an estimated one to three billion animals.
Climate change caused by fossil fuel pollution is expected to create warmer and drier conditions associated with more intense wildfires.
Susan Solomon, Chlorine Activation and Enhanced Ozone Depletion by Fire Aerosols, Nature (2023). DOI: 10.1038/s41586-022-05683-0. www.nature.com/articles/s41586-022-05683-0
© 2023 AFP
Reference: Massive Australian wildfires increased Antarctic ozone hole: Study (2023, March 11) Retrieved March 11, 2023, from https://phys.org/news/2023-03-massive-australia-wildfires- antarctic-ozone.html
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