The Montreal Protocol (Canada), approved in 1987 for the protection of the ozone layer, is considered one of the most important international agreements on environmental matters of all time. The limits established in this agreement on the production and use of gases such as CFCs (and others incorporated into the agreement in subsequent amendments) are allowing the recovery of ozone in the upper layers of the atmosphere, a kind of filter for the most harmful solar radiation. for living beings.
Despite the undeniable success of this commitment framed in the Vienna Convention (sponsored by the UN), data continues to appear that suggests that the expected success (complete recovery around the year 2050) may be more complicated than expected. On the one hand, in recent years new ozone-depleting substances (OSDS) and undeclared or fraudulent emissions have been discovered in countries that are difficult to supervise, such as China.
In addition, it now seems to be confirmed that climate change and the alteration of the polar vortex are damaging the ozone layer in areas such as Antarctica much more than previously thought possible.
A study carried out by Hannah E. Kessenich, Annika Seppälä and Craig J. Rodgers, researchers at the University of Otago (New Zealand), in this sense, review the state of the ozone layer in Antarctica and propose an explanation for the ozone holes (large decreases in the concentration of this molecule) detected in the last three years in the South Pole region. The results of this study have been published in the journal Nature Communications.
The lead author of the new study, Hannah Kessenich, a PhD student in the Department of Physics at the University of Otago, highlights that in their work they found that there is now much less ozone in the center of the Antarctic ozone hole compared to 19 years ago. .
“This means that the hole is not only larger [extension], but also deeper [lower concentration of these types of molecules] during most of the spring.”
“We made connections between this drop in ozone and changes in the air reaching the polar vortex over Antarctica. “This reveals that the recent large ozone holes may not be caused only by CFCs [and the like],” says this co-author.
"Most of the important communications on the ozone layer in recent years have given the public the impression that the 'ozone problem' has been solved," explains the University of Otago in a note disclosing the results of its researchers.
While the Montreal Protocol has greatly improved our situation with respect to ozone destruction by SACOs, the hole has been among the largest on record in the last three years, and in two of the five years before that.
"Our analysis ended with data from 2022, but as of today the 2023 ozone hole has already exceeded the size of the previous three years: at the end of last month it was more than 26 million km², almost double the area of Antarctica," says this researcher.
Hannah Kessenich believes that understanding ozone variability is important because of the important role it plays in the climate of the Southern Hemisphere. “We are all aware of the recent wildfires and cyclones in Australia and New Zealand, and the ozone hole in Antarctica is part of this picture.
Although it is a different problem than climate change, the hole in the ozone layer interacts with the delicate balance of the atmosphere, Kessenich recalls. Thus, because ozone generally absorbs ultraviolet light, a hole in the ozone layer can not only cause extreme levels of ultraviolet radiation on the surface of Antarctica, but can also dramatically affect where heat is stored in the atmosphere.
The new study presents a hypothesis that has been partially questioned by experts from other universities. It cannot be forgotten that science is based on the proposal and discussion of hypotheses, with results that can change over time based on new knowledge and results.
American professor Susan Solomon, one of the most recognized experts in ozone studies, for example, has indicated in statements collected by AFP that it must also be taken into account that the conditions in "recent years have been quite unusual."
Solomon led previous research showing that the 2020 ozone hole widened by 10% due to the massive wildfires in Australia.
The gigantic eruption of the Hunga-Tonga-Hunga-Ha'apai volcano off Tonga in 2022 is also believed to have affected recent ozone levels.
Martin Jucker, an expert at the University of New South Wales in Australia, is also not convinced by the study's results. "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," Martin Jucker told AFP.
