New Study Challenges Optimistic Outlook on Ozone Hole Recovery
New study challenges the celebrated recovery of the ozone layer, suggesting it may not be healing as believed The hole in the ozone layer could potentially be expanding, raising concerns about the planet's vulnerability to harmful ultraviolet radiation
The ozone layer, located miles above the Earth's surface, is crucial in protecting the planet from harmful ultraviolet radiation. Previously celebrated as one of the greatest environmental achievements, a new study published on Tuesday challenges the belief that the ozone layer is recovering, suggesting that the hole may actually be expanding. These findings contradict widely accepted assessments, including a recent UN-backed study projecting a return to 1980s levels by 2040.
The Montreal Protocol, agreed upon in 1987, resulted in the banning or reduction of over 100 ozone-depleting chemicals that had caused a significant hole in the atmospheric layer above Antarctica. This depletion was primarily caused by the widespread use of chlorofluorocarbons (CFCs) in aerosol sprays, solvents, and refrigerants. The ban has been widely regarded as instrumental in the recovery of the ozone layer.
But the Antarctic ozone hole, which expands during spring before contracting in the summer, achieved unprecedented size in 2020 to 2022, leading researchers in New Zealand to explore the reasons behind it.
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Hannah Kessenich, a PhD Student at the University of Otago and lead author of the study, explained, "This indicates that the hole has not only remained large in area but has also deepened [i.e. has less ozone] throughout most of Antarctic spring. The particularly long-lasting ozone holes during 2020-2022 align with this pattern, as the size and depth of the hole in October were particularly noteworthy in all three years."
The scientists reached their conclusion by analyzing the behavior of the ozone layer from September to November using a satellite instrument. They compared this behavior to historical data and changing ozone levels in order to measure signs of ozone recovery and identify the driving factors behind these changes. Their findings showed that the depletion of ozone and deepening of the hole were caused by changes in the Antarctic polar vortex, a large swirl of low pressure and very cold air high above the South Pole.
The researchers did not delve further into investigating the cause of these changes, but they recognized that numerous factors could also play a role in ozone depletion, such as planet-warming pollution, minuscule airborne particles emitted from wildfires and volcanoes, and variations in the solar cycle.
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According to Kessenich, the study's findings suggest that the recent large ozone holes may not be solely due to CFCs. Despite the success of the Montreal Protocol in reducing CFCs and averting environmental disaster, the ongoing Antarctic ozone holes seem to be linked to shifts in atmospheric dynamics.
Many scientists question the reliability of the study's results, which are based primarily on observed ozone holes from 2020 to 2022 and use a short 19-year period to draw conclusions about the long-term health of the ozone layer.
According to Martin Jucker, a scientist at the Climate Change Research Centre at the University of New South Wales in Australia, previous research has already identified potential causes for these significant ozone holes, including smoke from the 2019 bushfires, a volcanic eruption (La Soufriere), and a general correlation between the polar stratosphere and El Niño Southern Oscillation.
During La Niña years, the polar vortex in the stratosphere tends to be stronger and colder, resulting in lower ozone concentrations. The years 2020-22 experienced a rare triple La Niña, but the study does not mention this relationship. The authors of the study stated that they excluded the years 2002 and 2019 from the record to avoid any bias from "exceptional events."
"Those events have been shown to have strongly decreased theâ¯ozoneâ¯hole size," he said, "so including those events would probably have nullified any long-term negative trend."
