Comment Australia’s bushfire season in late 2019 and early 2020 was extreme. It blew smoke about 20 miles into the sky, not unlike what a nuclear explosion might produce. Smoke from the fires circled the globe and hung in plumes over the Pacific. Now, a study published Thursday in the journal Scientific Reports shows that smoky aerosols have caused the warmest stratospheric temperatures in about three decades and likely destroyed the ozone layer — which has been recovering slowly since the substances that destroy it were largely removed. degree through the 1987 Montreal Protocol. The stratosphere, just above the point airplanes fly, it usually does not vary much in temperature due to events on the Earth’s surface — with the exception of volcanic eruptions. But a sudden and unexpected warming of the global stratosphere was detected in the first months of 2020 — reaching up to 3 degrees Celsius (5.4 degrees Fahrenheit) around Australia and about 0.7 degrees Celsius (1.26 degrees Fahrenheit) globally. Researchers say it was the hottest temperature recorded in the stratosphere since Mount Pinatubo in the Philippines erupted in 1991, sending sulfate aerosols and smoke high into the air. Lilly Damany-Pearce, a researcher at the University of Exeter in England who led the study, said both stratospheric warming and a fairly large ozone hole that spread across most of the Antarctic continent in 2020 were likely caused by violent fire. thunderstorms, or ‘pyrocumulonimbus’ events, which sent huge amounts of smoke into the lower stratosphere. He said smoke particles are about 50 times more effective at absorbing sunlight than volcanic sulfur particles – because of the black soot in smoke aerosols. Sunlight heats the air containing the smoke particles, causing this smoke-laden air to rise in a process similar to that which causes hot air balloons to rise. Once the particles are in the stratosphere, the researchers said, continued warming can cause changes in ozone through changes in atmospheric circulation, and chemical reactions on the surface of smoke particles can destroy the ozone layer. “It is plausible that the good work done under the Montreal Protocol … could be reversed by the impact of global warming on wildfires,” study co-author Jim Haywood, an atmospheric scientist at the University of Exeter, said in an email. The ozone layer helps absorb incoming UV radiation from the sun, protecting life on Earth from its harmful effects, such as skin cancer and cataract formation. The ozone hole that formed over Antarctica after the fires in 2020 was the longest-lasting and among the largest and deepest in decades, according to the World Meteorological Organization. Tonga’s volcano spewed an unprecedented amount of water into the atmosphere Olaf Morgenstern, a scientist at New Zealand’s National Institute for Water and Atmospheric Research, said the stratospheric impact of Australia’s wildfires – including a plume of smoke drifting over the South Pacific – was “historically unprecedented observations”. Morgenstern, who was not involved in the study, explained that smoke aerosols don’t stay in the upper atmosphere as long as harmful man-made chemicals, which can stay in the atmosphere for up to 80 years. “The big issue here is that, under global warming, the frequency and intensity of wildfires is expected to increase, which will lead to more” fire-induced stratospheric warming and ozone depletion in the future, Haywood said. . “I don’t think it’s a coincidence that we’ve had these massive fires in Australia. It’s part of the trend,” Morgenstern said he said, pointing to this the devastating summer fires in Europe — also fueled by extreme heat waves and widespread drought conditions similar to those that led to the Black Summer fires in Australia. Previous research has shown that Australia’s 2020 bushfire season was so extreme that it changed large-scale wind patterns more than 10 miles away. Another study last year looked at temperature and ozone changes from satellite data. The big contribution of the latest work, according to Martin Jucker, a climate expert at the University of New South Wales in Australia who was not involved in the study, is that the researchers put satellite observations from the period on the cutting edge of technology. climate model “to prove that bushfires were actually the reason for what we observed.” “The warming of the stratosphere doesn’t really have a direct impact for us on the surface [of the Earth], but keeping the ozone from recovering or destroying the ozone for a year has a real impact on the surface,” he said. “Before the 2019 fires, I don’t think we were even thinking [fires] could have such an impact. That a bushfire could be as impactful as a volcano.”
