Scientists at Nasa and Niwa have been studying the effects of the wildfire’s smoke on our ozone, and found there was a gap in scientists’ understanding of ozone chemistry.
The changes involved several chlorine-containing gases, which do not usually change much in the stratosphere.
The main differences involved hydrogen chloride (HCl) - a gas that can be converted into a reactive form that destroys ozone.
In the months following the bushfires, Nasa’s Aura satellite also observed HCl levels had dropped by about half, and there were also increases in chlorine monoxide (ClO).
Niwa’s station at Lauder in Central Otago was perfectly placed to make the observations.
New Zealand experienced apocalyptic orange skies and brown snow-peaked mountains as the smoke blew over the country.
Niwa researcher Dan Smale, of Lauder, said the smoke offered a great chance to study the impact of massive wildfire events on the atmosphere.
"Nothing like this has ever been seen in the Lauder data record before.
"The Australian bushfires were the biggest and most destructive ever recorded and seem to have caused unknown reactions affecting ozone chemistry, which is both tantalising from a science point of view and worrying from an environmental point of view.
"Our findings identify a knowledge gap in the processes that control ozone."
Wildfires were predicted to become more frequent and intense as the planet warmed, and the likelihood of ozone depletion would increase, he said.
"Laboratory studies on the chemical reactivity of wildfire smoke particles are urgently needed."
Research leader and Nasa Goddard Flight Centre senior research scientist Susan Strahan agreed the discovery had revealed an important gap in our understanding of ozone chemistry.
"We were unable to replicate what we were seeing in any models, meaning that the reactions taking place in the stratosphere on these smoke aerosols are unknown," Dr Strahan said.
"This is worrying because anything that messes with the chlorine family of gases — like HCl — has the potential to harm the ozone.
"Just one atom of chlorine can destroy over 100,000 ozone molecules before it is removed from the atmosphere.
"From the observations of elevated chlorine monoxide (ClO), we think that ozone in the mid latitudes experienced some depletion following the 2020 fires," she said.
The 2020 wildfires burnt about 14.3 million hectares of land, destroyed 3000 homes, killed at least 34 people and up to three billion animals.
