New research from the University of Otago shows that the Antarctic ozone hole is much larger and more persistent than commonly thought, and that the complex factors responsible for the hole's persistence and impact on the southern hemisphere's climate are not just chlorofluorocarbons. Despite the efforts of the Montreal Protocol, this study still links the ozone hole to changes in climate and weather patterns in the Southern Hemisphere.
Researchers at the University of Otago believe chlorofluorocarbons (CFCs) are not the only culprit. In a study published today (November 21) in the journal Nature Communications, the team analyzed monthly and daily ozone changes at different altitudes and latitudes in the Antarctic ozone hole from 2004 to 2022.
Hannah Kessenich, author of the paper and a doctoral student in the Department of Physics, said they found that there is much less ozone in the center of the ozone hole than it was 19 years ago. This means that during much of the spring, the ozone hole is not only larger, but also deeper.
"We linked the decrease in ozone to changes in the air in the polar vortex over Antarctica," she said. "This reveals that the recent giant ozone hole may not just be caused by chlorofluorocarbons."
The Montreal Protocol has been in place for a long time, but the ozone hole still exists
Although the Montreal Protocol on Substances that Deplete the Ozone Layer, in force since 1987, regulates the production and consumption of man-made chemicals known to deplete ozone, researchers believe that other complicating factors are also responsible for the ozone hole.
Researchers believe other complex factors are also responsible for the ozone hole. "Most of the major publicity about the ozone layer over the past few years has given the public the impression that the 'ozone problem' has been solved. Although the Montreal Protocol greatly improved the situation of ozone destruction by chlorofluorocarbons, the ozone hole has been shrinking for the past three years and two of the five years before that. It has been one of the largest holes on record. Our analysis ended with 2022 data, but as of today, the 2023 ozone hole has already exceeded the size of the previous three years - at the end of last month, the ozone hole exceeded 26 million square kilometers, almost twice the size of Antarctica."
Ozone changes and climate impacts
Kessenich believes it's important to understand changes in ozone because it plays an important role in the Southern Hemisphere's climate. We all know about the recent wildfires and cyclones in Australia and New Zealand, and the Antarctic ozone hole was part of that. While the ozone hole has a different impact on climate than greenhouse gases, it interacts with the delicate balance in the atmosphere. Since ozone normally absorbs ultraviolet light, a hole in the ozone layer would not only cause ultraviolet levels to reach extreme levels on Antarctica's surface, but would also severely affect where heat is stored in the atmosphere.
Downstream impacts include changes in wind patterns and surface climate in the Southern Hemisphere, which have consequences for us locally.
However, she was quick to dismiss concerns about extreme UV rays from people living outside Antarctica.
"New Zealanders don't have to worry about applying extra sunscreen this year because the Antarctic ozone hole doesn't generally open over New Zealand - it's mainly located directly above Antarctica and the South Pole."