UK researchers have revealed Australia's Black Summer bushfires likely damaged the ozone layer and caused the highest temperatures in the stratosphere in 30 years.
The fires scorched more than 24 million hectares, killed 33 people directly, and almost 450 more lost their lives from the effects of smoke inhalation.
A study published Thursday in the journal Scientific Reports revealed the temperature in the stratosphere rose by 0.7 degrees Celsius. Above Australia, it rose by 3C.
The study's co-author, atmospheric science professor Jim Haywood, said the findings were statistically significant and worrying.
"The implications might be quite alarming, because the future climate is predicted to get warmer and drier and we're expecting higher frequencies of wildfires and we're also expecting them to be at greater intensity," he said.
The University of Exeter researchers also discovered the bushfires appeared to have depleted the Earth's ozone layer and led to "a very large, deep and long-lived ozone hole".
The ozone layer has managed to make some recovery since the 1980s as a result of a landmark multilateral agreement, the Montreal Protocol, phasing out the use of some chemicals.
The stratosphere, which contains the ozone layer, is around 12 to 50 km above the Earth's surface.
It doesn't usually vary much in temperature, except in events like volcanic eruptions or extreme prolonged bushfire events.
Professor Hayward said global efforts to restore the ozone layer could be rapidly be put at risk.
"All the hard work that we've been putting into getting rid of ozone-depleting substances in order to protect the ozone layer might be undone by global warming," he said.
'Really scary' fire thunderstorms accelerating climate change
Professor of pyrogeography and fire science at the University of Tasmania David Bowman said fire thunderstorms could push aerosols into the stratosphere, and they're becoming more common.
"These fire thunderstorms are very scary because, locally, they generate their own weather conditions," he said.
"They actually increase the number of fires by spreading lighting, incredible winds, unpredictable winds, so they're horribly terrifying for firefighters that can't fight them.
"You can't even predict what they're doing. They're really scary."
Professor Bowman said scientists were worried about the idea of a "feedback loop", in which fires create conditions that accelerate climate change.
"At a global scale, as we saw in the 2019-20 fires, these things are beginning to affect the Earth's system.
"They're ejecting smoke into the stratosphere, they're spreading minerals into the ocean and causing algal blooms.
"And what we're worried about is if these fires become more frequent, more intense, that wildfire is going to erode the carbon stocks in the landscape and it'll start amplifying climate change."
He said the Black Summer bushfires offered scientists a window into the future of extreme fires, but now there are so many unusual fire events it's impossible to keep up.
"We're at a point where … all of the switches and the dials and the lights on the control panel are telling us we've got a real problem," he said.
