The new trend was confirmed by a study published in Science.
It seems to be the beginning of the end for the Antarctic ozone hole!
A new analysis shows that the hole in the ozone layer is now, on average, smaller and appears later than it did in the year 2000.
The hole in the ozone layer, in fact, occurs every spring in the southern hemisphere, letting in a lot of harmful ultraviolet rays.
The Montreal Protocol, signed in 1987 and in force since 1989, provided for measures aimed at reducing the ozone hole, including the banning of chlorofluorocarbons, the chemical compounds that contain chlorine and are used as refrigerants in products such as air conditioners. Chlorofluorocarbons have been identified as one of the factors accelerating ozone loss in the stratosphere.
The results of the study, conducted by Dr Susan Solomon and her colleagues at the Massachusetts Institute of Technology in Cambridge, were published in the June issue of the journal Science and prove that this ban worked.
Dr Solomon said, 'We avoided what would have been an environmental catastrophe for the planet.
As early as 2008, an initial study by Yang et al. reported that the rate of depletion of the atmospheric ozone layer had begun to decline, and in 2014 the Assessment by the World Meteorological Organisation had shown that the reparative process had begun, at high altitudes, in the middle and low latitudes.
In October 2015, however, a counter-trend was recorded: the ozone hole in the Antarctic had reached a record level at that time, with a peak extent of 28.2 million square kilometres. However, the alarming phenomenon could be linked to large volcanic eruptions that would have an impact on the chemical composition of the ozone layer, which Dr Solomon's team then decided to ascertain.
The researchers discovered that Chile's Calbuco volcano was largely responsible for the phenomenon, as it had erupted in April 2015 and filled the stratosphere with sulphurous particles that triggered ozone-depleting reactions.
The climate model carefully developed by scientists also found that the ozone hole in Antarctica in September had shrunk by an average of 4.5 million square kilometres between 2000 and 2015. September is an important reference period, as it is the month when sunlight returns in full force to the Antarctic after winter, setting in motion the chemical reactions that destroy the atmospheric ozone layer. "The trend is significant and is exactly what we expect from chlorine chemistry," said Dr Solomon. Until now, scientists had focused on October, which was the time when the largest ozone hole was recorded, but Dr Solomon pointed out that the signs of the repair process are to be detected in September, as the hole now opens on average 10 days later than in the past. It will take several decades for the Antarctic ozone hole to fully heal.
"The hole in the ozone layer still remains massive and we cannot expect it to disappear before the end of the century, with all the consequent implications for human and ecosystem health," said Michaela Hegglin, atmospheric scientist at the University of Reading (UK).
Furthermore, unfortunately, the ozone hole in the Arctic above the North Pole, which fluctuates more than in the southern part, has not yet shown any trend towards reduction.
Dr. Carmelo Chines
Direttore responsabile
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