Contrary to popular belief, the general trend shows that the hole in the ozone layer is shrinking

The hole in the ozone layer above Antarctica reached its annual peak of 26.4 million square kilometers on October 5. Although this is the third year in a row that the hole in the ozone layer has reached this size, the general trend shows that contrary to popular belief, it is in fact continuing to shrink.

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According to a statement from Paul Newman, Earth Science Manager at NASA's Goddard Space Flight span, “All data points to ozone being on the mend. » While the hole is still deepening between August and October, the researcher told our colleagues at the Associated Press (AP) that “It was a little more serious this year because it was a little colder. »

Ozone depletion over the southern polar region is caused by chlorine compounds elevated in the stratosphere, most of which can be attributed to the historical use of chlorofluorocarbons (CFCs). During the cold winter of the Antarctic , temperatures are low enough for polar stratospheric clouds (PSC) to form at high altitudes. These then provide a surface for the chemical reactions that convert the chlorofluorocarbons into more active forms like chlorine gas.

When sunlight returns in early spring, ultraviolet radiation splits these chlorine gas molecules and releases chlorine atoms, which then interact with and destroy ozone molecules. This explains why the hole in Antarctica's ozone layer always widens in the spring, only to level off when temperatures get too high for PSCs to exist.

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The colder the spring, the greater the potential damage, which is why ozone holes have been particularly prominent lately. This year, for example, stratospheric temperatures reached 179 Kelvin (-94 degrees Celsius) on August 11, then 191 Kelvin (-82 degrees Celsius) on October 11. However, this figure remains below the minimum temperature required for the formation of PSCs.

NASA measurements of the ozone hole itself showed it had shrunk to 22.67 million square kilometers (8.75 million square miles) on October 11. Minimum ozone thickness over the south polar region was recorded at 97 Dobson units on October 1, but increased to 105 Dobson units ten days later. As a rough guide, the Earth is surrounded by an ozone layer with a standard thickness of 220 Dobson units. Values ​​below this amount were not observed in Antarctica until 1979, and are still associated with ozone destruction by CFCs.

Credit: AP

Holes in the ozone layer are shrinking

Fortunately, the ozone layer has been recovering for several decades, largely thanks to the Montreal Protocol of 1987 which banned the use of CFCs. Although annual levels fluctuate, the size of the hole has steadily decreased since reaching an all-time high of 29.9 million square kilometers (11.5 million square miles) in September 2000.

However, if the temperatures Cold temperatures are likely largely responsible for this year's relatively large ozone hole, with some speculating that illegal use of CFCs by factories in China may be partly responsible. Additionally, Brian Toon, a scientist affiliated with the University of Colorado, says the large wildfires in Australia and the recent underwater volcanic eruption in the Tonga Islands could have a direct effect.