The stratospheric ozone layer, located between 11 and 40 kilometers above the Earth’s surface, filters out the sun’s ultraviolet rays that can cause cancer, alter the immune system, and even damage the DNA of living organisms.
In the mid-1970s, chlorofluorocarbons (CFCs), once widely used in aerosols and refrigerators, were identified as the main cause of ozone depletion, creating “holes” every year, including a particularly large hole over the continent. Antarctica.
The 1987 Montreal Protocol, which banned the use of CFCs to fill these gaps, is considered a success story in global environmental cooperation.
In January, experts appointed by the United Nations deemed the agreement effective: according to their forecasts, the ozone layer is expected to recover around 2066 in Antarctica, 2045 in the Arctic, and 2040 in the rest of the world.
But despite the decline in CFCs, the hole over Antarctica has not yet been significantly reduced, according to the authors of a study published Tuesday in the journal Nature Communications.
“Six of the past nine years have seen very low levels of ozone and very large ozone holes,” Anika Seppala, from the Department of Physics at the University of Otago in New Zealand, who co-authored the study, told AFP. ). .
“It is possible that there is something else going on in the atmosphere – perhaps due to climate change – that is masking part of the recovery,” he added.
The hole in the ozone layer over Antarctica usually opens in September and lasts until November, during the austral spring, that is, in the Southern Hemisphere, before gradually filling up.
According to researchers, the crater opened at the end of September, a sign of recovery, which is undoubtedly due to the decline in CFCs.
But in October, the period when the hole reaches its maximum size, the level of ozone in the middle stratosphere fell by 26% between 2004 and 2022, according to their work based on satellite data.
However, the reduction of CFCs in the atmosphere mandated by the Montreal Protocol is still “on track,” as Hanna Kessenich, the lead author, explained.
But he stressed that “our conclusions reveal that these large holes, which formed recently, will not be caused solely” by these materials.
Susan Solomon, an ozone expert who was not involved in this research, said the results of this study should be read in light of the fact that “the last few years have been quite extraordinary.”
The expert previously explained that in 2020, the hole in the ozone layer increased by 10% due to massive forest fires in Australia.
A recent study published in the journal PNAS revealed that the massive eruption of the underwater volcano Honga-Tonga-Hunga-Haapi, in the Pacific Ocean, in January 2022, also led to a decline in ozone levels in the stratosphere.
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