The hole in the ozone has widened and deepened in recent years, a new study has found, throwing into question research from earlier this year that claimed the stratospheric layer was healing.
The ozone absorbs ultraviolet light, acting as a kind of natural sunscreen for the Earth. The ozone hole is a region of highly depleted ozone in the stratosphere over the Antarctic.
In the 1980s scientists observed the ozone had started to thin each spring.
Researchers initially thought chlorofluorocarbons (CFCs) – a group of chemicals widely used as refrigerant gases and propellants in aerosol sprays that have since been banned – were solely to blame.
But they now think something else might be going on, worsening the problem.
The study of changes from 2004 to 2022 has found that there is much less ozone in the area compared to 19 years ago.
“This means that the hole is not only larger in area, but also deeper throughout most of spring,” said lead author Hannah Kessenich, a PhD candidate in the Department of Physics at the University of Otago.
“We made connections between this drop in ozone and changes in the air that is arriving into the polar vortex above Antarctica. This reveals the recent, large ozone holes may not be caused just by CFCs,” she says.
Last year Nasa also said the ozone layer was healing.
The new study, published in Nature Communications, analysed the monthly and daily ozone changes, at different altitudes and latitudes within the Antarctic ozone hole during the 18-year period.
The researchers said while the Montreal Protocol on Substances that Deplete the Ozone Layer, which has been in place since 1987, has vastly improved the situation with CFCs, the hole in the ozone has continued to grow – despite a public perception the problem has been solved.
“Most major communications about the ozone layer over the last few years have given the public the impression that the ‘ozone issue’ has been solved,” said Ms Kessenich.
“While the Montreal Protocol has vastly improved our situation with CFCs destroying ozone, the hole has been amongst the largest on record over the past three years, and in two of the five years prior to that.
“Our analysis ended with data from 2022, but as of today the 2023 ozone hole has already surpassed the size of the three years prior – late last month it was over 26 million km2, nearly twice the area of Antarctica.
She said understanding ozone variability is important because of the major role it plays in the Southern Hemisphere’s climate.
“While separate from the impact of greenhouse gases on climate, the ozone hole interacts with the delicate balance in the atmosphere,” said Ms Kessenich.
“Because ozone usually absorbs UV light, a hole in the ozone layer cannot only cause extreme UV levels on the surface of Antarctica, but it can also drastically impact where heat is stored in the atmosphere.
“Downstream effects include changes to the Southern Hemisphere’s wind patterns and surface climate, which can impact us locally.”
In August the Copernicus Atmosphere Monitoring Service said the ozone hole developed slightly earlier this year.
The EU's Earth Observation Programme said lower ozone column values in comparison to the previous 43 years of satellite observations, together with other key indicators, marked an early start to the ozone hole.