2023-11-22 02:14:15
The hole in the ozone layer above Antarctica has been growing every austral spring for around twenty years, according to a study published Tuesday, November 21, despite the ban on chemical substances that destroy the shield protecting the Earth dangerous solar radiation.
The stratospheric ozone layer, located between 11 and 40 km above the earth’s surface, filters the Sun’s ultraviolet rays which can cause cancer, alter the immune system and even damage the DNA of living beings.
In the mid-1970s, chlorofluorocarbons (CFCs), once widely used in aerosols and refrigerators, were identified as the main culprits in the thinning of the ozone layer, creating emissions each year. “holes”including a particularly large one over Antarctica.
The 1987 Montreal Protocol, which banned CFCs to close these gaps, is considered a success story in global environmental cooperation. In January, experts commissioned by the UN judged the agreement effective: according to their forecasts, the ozone layer should recover by around 2066 over the Antarctic, 2045 over the Arctic and 2040 in the rest of the world.
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But despite the decline in CFCs, the hole above Antarctica has not yet been significantly reduced, according to the authors of a study published in Nature Communications. “Six of the last nine years have seen very low ozone levels and extremely large ozone holesexplained to Agence France-Presse (AFP) Annika Seppala, from the physics department at the New Zealand University of Otago, co-author of the study. It could be that something else is happening in the atmosphere – perhaps because of climate change – and masking some of the recovery. »
“The last few years have been quite unusual”
The hole in the ozone layer over Antarctica usually opens in September and lasts until November, during the austral spring, before gradually filling up. According to the researchers, it opened later in September, a sign of a recovery undoubtedly attributable to the reduction of CFCs. But in October, the period when it reaches its maximum size, the level of ozone in the middle stratospheric layer fell by 26% between 2004 and 2022, according to the work of this team, which is based on satellite data.
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The reduction in CFCs in the atmosphere decided by the Montreal Protocol nevertheless remains ” on the right track “, underlines Hannah Kessenich, the main author. But “our conclusions reveal that these large holes, formed recently, are not solely caused” par ces substances.
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For Susan Solomon, an eminent ozone specialist who was not involved in this research, the results of this study must be read in light of the fact that “the last few years have been quite unusual”. The chemist had previously shown that in 2020, the hole in the ozone layer widened by 10% under the effect of the huge bushfires in Australia. The gigantic eruption of the Hunga-Tonga-Hunga-Ha’apai underwater volcano in the Pacific in January 2022 also reduced ozone levels in the stratosphere, reveals a recent study published in the journal PNAS.
Our graphics. Thirty years of (weak) resorption of the hole in the ozone layer in graphs
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