Type I and II polar stratospheric clouds seen at an altitude of 15,300 m from a NASA DC-8 research aircraft. NASA/SCIENCE PHOTO LIBRARY
Good news on the environmental front is rare enough to be highlighted. The ozone layer should recover fully over the next four decades, and the progressive elimination of the chemicals that destroy it is helping to limit climate change. Even if there is still vigilance, it is a great achievement for the international community. These are the conclusions of a United Nations-sponsored panel of experts unveiled on Monday, January 9th.
This assessment report represents the most complete body of scientific knowledge about ozone, such as reports from the Intergovernmental Panel on Climate Change (IPCC). It is prepared every four years by the Montreal Protocol Scientific Assessment Panel under the aegis of the World Meteorological Organization and the United Nations Environment Program (UNEP). This 2022 edition was written and reviewed by 230 researchers from 30 countries. “Over the past 35 years, the Protocol has become a veritable spearhead of environmental protection,” said Meg Seki, Executive Secretary of UNEP’s Ozone Secretariat.
It all started in the 1970s when scientists warned about the depletion of the ozone layer, that protective barrier that filters the sun’s UV rays. In the early 1980s, they discovered a “hole” over Antarctica the size of the polar continent that formed between July and September each year and closed in November. This phenomenon is caused by gases such as chlorofluorocarbons (CFCs) and halons, which contain chlorine and bromine and can destroy ozone. At that time, they were used extensively in the manufacture of everyday products such as refrigerators, air conditioners, aerosols and insulating foams.
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The Montreal Protocol, signed in 1987 and now ratified by 198 countries, has banned ozone-depleting substances (ODS) – since 1996 for industrialized countries and since 2010 for developing countries. However, because of their long lifespans (between fifty and one hundred years), they have not disappeared from the stratosphere, the region of the atmosphere that extends 15 to 50 km above sea level and contains the ozone layer. The report confirms that chlorine and bromine concentrations continue their – slow – decline.
If current guidelines are maintained, the ozone layer is expected to return to its pre-1980 levels by 2066 over Antarctica, 2045 over the Arctic, and as early as 2040 in the rest of the world. “It’s a threat to humanity that was avoided,” recalls Sophie Godin-Beekmann, Director of Research (CNRS), President of the International Commission on Ozone and one of the authors of the report. In the United States alone, the protocol is expected to prevent more than 400 million skin cancers by the end of the century.
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