In 2019 and 2020, huge wildfires erupted in Australia, injecting over one million tons of smoke particles into the atmosphere - and destroying the ozone.
Now MIT scientists have warned that if wildfires continue or become more frequent, they could delay the recovery of the ozone layer for years.
The smoke from the ‘Black Summer’ fires - which also killed or displaced almost three billion animals - set off chemical reactions in the stratosphere that contributed to the destruction of ozone, which shields the Earth from incoming ultraviolet radiation.
In March 2020, shortly after the fires subsided, the team observed a sharp drop in nitrogen dioxide in the stratosphere, which is the first step in a chemical cascade that is known to end in ozone depletion.
The researchers found that this drop in nitrogen dioxide directly correlates with the amount of smoke that the fires released into the stratosphere.
They estimate that this smoke-induced chemistry depleted ozone by 1%.
The phaseout of ozone-depleting gases under a worldwide agreement to stop their production has led to about a one percent ozone recovery from earlier ozone decreases over the past 10 years
So, the wildfires cancelled those hard-won diplomatic gains for a short period.
If future wildfires grow stronger and more frequent, as they are predicted to do with climate change, ozone’s projected recovery could be delayed by years.
Lead author Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies at MIT said: “The Australian fires look like the biggest event so far, but as the world continues to warm, there is every reason to think these fires will become more frequent and more intense.
“It’s another wakeup call, just as the Antarctic ozone hole was, in the sense of showing how bad things could actually be.”
Massive wildfires are known to generate pyrocumulonimbus - towering clouds of smoke that can reach into the stratosphere.
The smoke from Australia’s wildfires reached well into the stratosphere, as high as 21 miles.
In 2021, Solomon’s co-author, Pengfei Yu at Jinan University, carried out a separate study of the fires’ impacts and found that the accumulated smoke warmed parts of the stratosphere by as much as 2 degrees Celsius.
The warming persisted for six months.
The study also found hints of ozone destruction in the Southern Hemisphere following the fires.
“Wildfire smoke is a toxic brew of organic compounds that are complex beasts,” Solomon says. “And I’m afraid ozone is getting pummeled by a whole series of reactions that we are now furiously working to unravel.”
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