Our efforts have paid off: the ozone layer is on the mend
Thanks to the scientists who pushed for the Montreal Protocol in 1987, industrial production of chlorofluorocarbons (CFCs) have stopped. These chemicals contain chlorine that triggers the destruction of the stratospheric ozone. This layer is paramount in helping filter out harmful ultra-violet light that can cause cancer.
Said Susan Solomon, an atmospheric chemist at the Massachusetts Institute of Technology in Cambridge: “We can now be confident that the things we’ve done have put the planet on a path to heal,”. She was also surprised at the speed at which the healing took place, proving that collective efforts do have a major impact.
In Antarctica, ozone loss only starts getting serious around September. This is the beginning of the southern spring when light returns. During winter, nitric acid and water condense out and form wisps of clouds. The surfaces of the cloud particles host chemical reactions that release chlorine originating from CFCs, which will destroy the ozone after reacting with light.
Video courtesy of Science Magazine
Instead of measuring the size of the ozone hole in October, Solomon and her colleagues started earlier in September. They discovered that the hole has shrunk by 4 million square kilometers since 2000.
The researchers used a 3D atmospheric model to determine the cause of recovery, be it chemical or weather. This model helped explain the record ozone hole in October 2015, an outlier in the shrinking trend. It showed that this was due to the eruption of the Calbuco volcano in southern Chile just six months before, confirming that the reduction of chlorine and bromine chemicals were the factors contributing to the healing of the layer.
However, scientists have to consider that only half of the shrinkage was due to the drop in chlorine and bromine levels. Weather does play a part, such as volcanic eruptions, but these effects on average should not cause any changes or trends, meaning that the other 50% is unexplained. Paul Newman, who runs NASA’s Arctic Ozone Watch website at Goddard Space Flight Center in Greenbelt, Maryland says that Solomon has uncovered a “real scientific puzzle here”, it might suggest a problem with the model or a real shift in polar weather due to climate change.
For Solomon, this result concludes full circle the study determining stratospheric clouds as the chlorine reaction sites, hence playing a vital role in the scientific assessments of the Montreal Protocol and following reports.