Lashed by solar flares and rising CFCs, the ozone layer isn’t safe yet
The concentrations of five ozone-depleting CFC chemicals have reached a 40-year peak in the atmosphere despite a 2010 ban on the chemicals under the Montreal Protocol.
The revelation comes as scientists prepare for a burst of solar activity as the sun approaches its “solar maximum”, the peak of the star’s 11-year magnetic cycle that sees Earth hammered by more radiation and solar flares.
Solar flares, captured here by NASA in 2015, are expected to increase in the lead up to 2025 as the sun enters a more active phase.Credit:NASA
In addition to dismantling molecules of ozone, which shield the earth from harmful solar radiation, the rising CFCs are also powerful greenhouse gases equivalent to about 47 million tonnes of CO2.
Dr Paul Krummel, a CSIRO expert in ozone depleting substances and lead scientist of Tasmania’s Cape Grim atmospheric gas observatory, was part of the team that raised the alarm during a four-yearly check-up of the ozone layer.
“That’s when we realised these five minor CFCs were rising,” Krummel said. “With the level they’re at now, it’s a pretty modest, small risk in terms of ozone depletion.
“But CFCs are strong greenhouse gases as well as ozone-depleters. Our concern is if the trends continue, then it may become significant down the track.”
The Montreal Protocol allows CFCs to be used as a feedstock to manufacture other chemicals, which explains some of the CFCs’ rising presence. But one of the chemicals, CFC-13, has no known uses, baffling researchers as to why it’s increasing in the atmosphere.
One theory holds that CFC-13 is a by-product from the breakdown of another major ozone-depleting chemical, CFC-12. The chemical is subjected to a process called “plasma arc destruction” to break it down.
“It uses very high voltage to produce extremely high temperatures which then destroy the chemicals,” said Krummel.
“Through that physical and chemical process, there can be some minor production of CFC 13.”
Although current concentrations of the CFCs pose no major threat to the ozone layer, the authors of the research, published in Nature Geoscience, warn CFCs’ intense warming effect and the fact that the chemicals can linger in the atmosphere for 640 years mean processes that continue to relinquish CFCs should be scrutinised.
The ozone hole above Antarctica has gradually decreased in size over the last 20 years and is on track to fully recover by 2066. But in recent years the hole has been larger than expected, said Krummel.
Cape Grim gas monitoring station in Tasmania, where Dr Paul Krummel is the lead scientist, supplied data on CFC levels for the research findings.Credit:Australian Bureau of Meteorology
“There might be multiple factors affecting it,” he said. “Things like the volcano in Hunga Tonga, and the Australian bushfires in 2019-20 injected a huge amount of stuff into the stratosphere.
“We’ve also just been through three La Niña years. Overall atmospheric dynamics change when those events are happening as well. It’ll be interesting to see what happens this year with the ozone hole.”
The ozone layer can also be affected by solar activity. Last week two giant “coronal holes”, 20 times larger than Earth, opened up on the sun, indicating the star is ramping up to a more active stage that will peak in 2025.
“There is an increase in the brightness in the sun, in the extreme ultraviolet part of the spectrum,” said space weather expert at RMIT, Associate Professor Brett Carter. “That actually results in a slight decrease in the amount of ozone in the Earth’s atmosphere.”
We could see an increase in solar flares lashing the Earth over the next few years, which sees solar protons travelling close to the speed of light pelt our atmosphere. The protons break apart nitrogen and hydrogen oxides, creating free atoms that react with ozone and deplete the radiation-absorbing molecules.
“[The protons] will go ahead and collide with various constituents inside the atmosphere, and they ultimately end up leading to a bit of a breakup of ozone in the short term,” Carter said.
In 2000, a powerful “X-Class” solar flare slammed the Earth in an event known by solar scientists as Bastille Day. The flare reduced the amount of protective ozone in the upper atmosphere, the mesosphere, by 30 per cent.
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