Good news on the environmental front is rare enough to be highlighted. The ozone layer is expected to fully recover over the next four decades, and the gradual elimination of the chemicals that destroy it is helping to limit climate change. Even if points of vigilance remain, it is a major success for the international community. These are the conclusions of a group of experts sponsored by the United Nations, presented Monday, January 9.
Ce evaluation report constitutes the most complete state of scientific knowledge on ozone, like the reports of the Intergovernmental Panel on Climate Change (IPCC). It is produced every four years by the Montreal Protocol Scientific Evaluation Group, under the auspices 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 thirty-five years, the protocol has become a real spearhead in the defense of the environment”said Meg Seki, Executive Secretary of UNEP’s Ozone Secretariat.
It all started in the 1970s, when scientists warned about the degradation of the ozone layer, this protective barrier that filters UV rays from the sun. In the early 1980s, they discovered a “hole” over Antarctica, as big as the polar continent, which formed every year between July and September and closed in November. This phenomenon is caused by gases, such as chlorofluorocarbons (CFCs) and halons, which contain chlorine and bromine, capable of destroying ozone. They were at that time massively used in the manufacture of everyday products, such as refrigerators, air conditioners, aerosols or insulation foams.
The hole appeared over Antarctica because the extremely low temperatures of this region in winter allow the formation of polar stratospheric clouds, on the surface of which certain reactions then promote the destruction of ozone in the polar spring.
The Montreal Protocol, signed in 1987 and now ratified by 198 countries, has banned ozone-depleting substances (ODS) – since 1996 for developed countries and since 2010 for developing ones. Due to their long lifespan (between fifty and a hundred years), however, they have not disappeared from the stratosphere, the region of the atmosphere extending from 15 km to 50 km in altitude, which contains the layer of ozone. The report confirms that chlorine and bromine concentrations are continuing their – slow – decline.
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