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According to data from Copernicus, the EU observation program, the hole in the ozone layer is one of the largest on record this year, a sign that its recovery will come to a standstill and be slow.
The hole in the layer above Antarctica stretched in September over an area of just over 24m square kilometers, which is equivalent to the 27m square kilometers recorded in 2006.
The measure this year was “within 25 percent of the largest” ever recorded, says Vincent-Henri Peuch, director of the Copernicus Atmosphere Monitoring Service. This does not mean that the recovery of the ozone layer is “threatened. It just means it takes time. ”
A full recovery can be restored within 50 years, he added.
The earth’s ozone layer protects the earth from harmful ultraviolet rays, but is damaged by chlorofluorocarbons (CFCs) – long-lived and powerful pollutants, often found in aerosols and coolants, which were banned worldwide by the late 1980s.
Every year, a hole forms in the ozone layer of the stratosphere during the spring season of the southern hemisphere, when sunlight causes the destruction of ozone by catalysts derived from man-made chemicals, mainly CFCs.
These catalysts, which consist of compounds containing chlorine or bromine, appear on polar stratospheric clouds that form during the winter night at the very low temperatures within the polar vortex.
While these catalysts are inactive in the dark, they quickly destroy ozone as the sun reaches the polar region.
The volume of CFCs in the stratosphere does not vary much from year to year, but has begun to decline, according to Copernicus, due to the Montreal Protocol introduced in 1987 to ban its use from 1989 onwards.
Natural variability also plays a role in the size of the ozone layer: lower temperatures mean more polar stratospheric clouds and a stronger vortex, which is likely to cause a larger hole.
Conversely, sudden stratospheric heating and an unstable polar vortex can mean that ozone-depleting chemicals are mixed with air from outside the vortex, reducing their destructive effect. This happens in 2019, when the ozone hole was significantly smaller.
“It takes a very long time before the atmosphere is clean,” Peuch said. But as the amount of depleting substances decreases, the hole in the ozone layer becomes smaller “regardless of the variability from one year to the next”.
The big holes recorded over the past two years “do not dispute our understanding of the ozone recovery process,” Peuch added.