Why does the ozone layer heal
The ozone hole closes
The researchers also found that the observations were predictive and that more than half of the shrinkage was due to a decrease in chlorine in the atmosphere.
According to Donald Blake, a professor of chemistry at the University of California at Irvine, this research represents the most comprehensive study of polar ozone to date.
FIGHTING THE PROBLEM
Then in the 1980s the ozone levels dropped suddenly. The entry into force of the Montreal Protocol in 1987 was widely regarded as a triumph of international cooperation. It ensured the rapid cessation of production of industrial CFCs. The ozone layer stabilized but was still depleted.
The size of the ozone hole varies from year to year. It is affected by changes in weather and volcanism, making it difficult to see a trend towards the closure of the hole. Scientists believe it has remained relatively stable since the turn of the millennium. However, in October 2015 the hole reached its greatest extent to date.
Scientists have long suspected that the ozone layer is slowly recovering. However, Solomon and her team - made up of researchers from MIT, the US National Atmospheric Research Center, and the University of Leeds - are the first to find evidence of the healing process.
Although the size of the hole was unusual in 2015, Solomon attributes it to the Calbuco eruption in Chile in April 2015. Volcanoes do not eject chlorine molecules into the atmosphere, but small particles. These create more clouds in the stratosphere over the poles, which react with the chlorine generated by humans.
VIEW IN THE FUTURE
The evidence suggests that the healing of the ozone layer is proceeding as predicted. According to Blake, that signals a decline in atmospheric gases that affect the ozone layer.
Both Solomon and Blake expect this slow healing trend to continue. However, a full recovery is not expected until the middle of the century. CFC production was discontinued in 1990, but the gases have a lifespan of 50 to 100 years. So the chlorine molecules that were made in the 70s and 80s are still in the atmosphere.
Nonetheless, the findings are a happy culmination of decades of work - not just that of scientists, but also of engineers, diplomats, and the whole world.
"That was a pretty remarkable story," says Solomon. "This gives us hope that we shouldn't be afraid of tackling major environmental problems."
“It's wonderful,” Blake adds, “to have a treatise that says so precisely: This is what we expected, and this is what we got. That makes me very happy. I wish Sherry [Sherwood Rowland] were still alive ... he would be very happy to read this. "
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