Antarctic Ozone Hole of Mid-Spring Has Grown in Last 20 Years, Study Claims

Antarctica’s mid-spring ozone hole has grown in the last 20 years, a new study has found.

The ozone layer over Antarctica has seen a 26 percent reduction since 2004, the new study published in Nature Communications reports, a finding that contradicts the previously reported recovery trend in the ozone hole. However not all experts are convinced by the new findings.

The ozone layer protects life on Earth from the sun’s ultraviolet rays. When the ozone layer is thinner, there is more danger from these rays. This puts humans at risk of skin cancer, sunburns and cataracts. Every mid-spring, which is around September in the Southern Hemisphere, the ozone layer over Antarctica thins. The layer does not completely disappear, but its concentrations drop below a certain threshold. This creates the so-called ozone hole.

There has been evidence to suggest that the ozone layer is recovering, however. In the winter months from 2005 to 2016, scientists saw a 20 percent decrease in ozone thinning. Scientists estimate that this ozone hole will recover by 2040.

But the new research, led by Annika Seppälä and Hannah Kessenich, from the University of Otago in Dunedin, New Zealand, suggests different.

The researchers analyzed monthly and daily changes in the ozone between 2001 to 2022, taking a look at different stratospheric layers throughout the key period of September to November, when the layer is at its thinnest.

When assessed next to satellite data from 2022, the researchers concluded that these previously reported recovery trends disappeared.

The recovery of the ozone layer has largely been put down to the Montreal Protocol which was introduced in 1987, and controls the amount of ozone-harming substances allowed in to the atmosphere.

This new paper notes that between 2020 to 2022, there has been a re-emergence of large ozone holes over Antarctica during the springtime, in September.

However, not all scientists agree with the findings of this new research.

Martin Jucker, Ph.D., a lecturer at the Climate Change Research Centre at The University of New South Wales and an associate investigator at the Australian Research Council’s Centre of Excellence for Climate Extremes, said in a statement that he is “not convinced” by the study’s results.

“Their results rely heavily on the large ozone holes we have seen in 2020-2022,” Jucker said. “However, existing literature has already found reasons for these large ozone holes: Smoke from the 2019 bushfires and a volcanic eruption (La Soufriere), as well as a general relationship between the polar stratosphere and El Niño Southern Oscillation: We know that during la Niña years, the polar vortex in the stratosphere tends to be stronger and colder than usual, which means that ozone concentrations will also be lower during those years. The years 2020-22 have seen a rare triple La Niña, but this relationship is never mentioned in the study. “

Newsweek asked Seppälä and Kessenich by email for comment on Jucker’s observations.

Jucker was also concerned that the study removes two years from the record period analyzed. The researchers did not analyze 2002 and 2019, because of “sudden stratospheric warming” that broke up the ozone hole “anomalously early in these years.”

“Those events have been shown to have strongly decreased the ozone hole size, so including those events would probably have nullified any long-term negative trend in ozone concentrations. It is questionable how the authors can remove 2002 and 2019 from the record but not 2020-22, given that all of these years have been shown to be dominated by very special and rare events,” Jucker said.

“In this context, it is important to note that the ozone hole is extremely variable from year to year, meaning that it can be large one year and small the other year. It is only over longer terms that a trend can be identified. Using only 22 years and then removing two inconvenient years does not help make this study convincing.”