Stratosphere, just above the place Airplanes fly, temperatures usually don’t vary much due to events on Earth’s surface – except for volcanic eruptions.
But a sudden, unexpected rise in the global stratosphere was detected in the first few months of 2020 – as high as 3°C (5.4°F) around Australia and about 0.7°C (1.26°F) globally. Researchers say it’s the highest temperature ever recorded in the stratosphere since the 1991 eruption of Mount Pinatubo in the Philippines, sending a mist of sulfates and smoke into the air.
Both stratospheric warming and the large ozone hole that has spread, said Lily Damani-Pearce, the researcher at the University of Exeter in England who led the study. Most of Antarctica In 2020 it was probably caused by violence Thunder cloud caused by fireor “pyrocumulonimbus” events, which inject huge plumes of smoke into the lower stratosphere.
She said smoke particles are about 50 times more efficient at absorbing sunlight than volcanic sulfate particles – due to the black soot in smoke mist. The sun’s rays heat 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 enter the stratosphere, the researchers said, continuous heating can cause changes in ozone through changes in atmospheric circulation, and chemical reactions at the surface of smoke particles can deplete the ozone layer.
“It is plausible that the good work done under the Montreal Protocol … could be set back by the global warming effect on intense fires,” study co-author Jim Haywood, an atmospheric scientist at the University of Exeter, said in an email.
The ozone layer helps absorb ultraviolet rays from the sun, protecting life on Earth from its harmful effects, such as skin cancer and cataract formation. The ozone hole that formed Antarctica After the fires of 2020, they were the longest lasting and among the largest and deepest in decades, according to of the World Meteorological Organization.
Olaf Morgenstern, a scientist at New Zealand’s National Institute of Water and Atmospheric Research, said the impact of the Australian fires on the stratosphere – including the plume of smoke that drifted over the South Pacific Ocean – is “unprecedented in terms of the observational record”.
Morgenstern, who was not involved in the study, explained that smoke mist does not stay in the upper atmosphere as long as harmful man-made chemicals, which can remain in the atmosphere for up to 80 years.
“The big issue here is that with global warming, wildfires are expected to increase in frequency and intensity, which could lead to more fire-induced warming and ozone depletion in the future,” Haywood said.
“I don’t think it is a coincidence that we have these wildfires in Australia. They are part of the trend,” Morgenstern He said referring to this Europe’s devastating summer fires – which also fueled them waves of intense heat Extensive drought conditions are similar to those that led to Australia Black summer fires.
Previous research has shown that the 2020 Australian fire season was very severe Extensive wind patterns change More than 10 miles up. Another study last year note Temperature and ozone changes from satellite data.
The large contribution of the last paper, according to Martin Jokera climate expert at Australia’s University of New South Wales who was not involved in the study, is that the researchers put satellite observations from that period in modern climate model “To prove that the bushfires were in fact the cause of what we observed.”
“The heating of the stratosphere has no direct effect on us at the surface [of the Earth]but preventing ozone from restoring or destroying ozone for a year has a real impact on the surface,” he said. “Before the 2019 wildfires, I don’t think we even thought [fires] It can have such an effect. That a bush fire can have the same effect as a volcano.”
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