Nearly three decades after the world banned chemicals that were destroying the atmosphere’s protective ozone layer, signs of recovery have been welcomed by Irish scientists.
Ozone protects life on Earth by absorbing damaging ultraviolet rays from the sun. Without it, increased ultraviolet radiation could lead to increased incidence of skin cancers, cataracts and impacts on biodoversity and agriculture.
Ireland and northern Europe faced a particular problem when it was noted northern Europe was experiencing “swirls of depletion” effectively a weakening of the ozone layer close to the artic circle.
Although the improvement has been slight so far, it is an indication that the Montreal Protocol, the 1987 world-wide ban on the use of chemicals known as chlorofluorocarbons, or CFCs, is having its intended effect.
According to Dr. John Sweeney Emeritus Professor of Geography at the National University of Ireland the recovery is slow, but should be complete sometime in mid century.
Professor Sweeney who is a founder the Irish Climate Analysis and Research Unit Icarus, said the “swirls of depletion” were a worry for Ireland and recovery was “a good news stroy”. He said recovery was a testament to what can be done by international cooperation.
But he warned banning CFCs was a much more simple exercise than dealing with climate change, as banning CFC producing aerosols is seen to be much easier than, for example, getting people not use their cars.
Mistaking climate change and the problem of greenhouse gas emissions with the hole in the ozone layer was a simplistic error and tackling global warming was a much more significant task, he warned.
Professor Sweeney also warned people in Ireland to continue to use sunscreen especially on children and not to think that because of the dull climate that there was no risk of melanoma.
Many scientists who pushed for the Montreal Treaty always acknowledged that recovery of the ozone layer would be very slow, because CFCs linger in the stratosphere for a long time.
But international researchers have now said they had found “fingerprints” indicating that the seasonal ozone hole over Antarctica, a cause of concern since it was discovered in 1984, was getting smaller.
“This is just the beginning of what is a long process,” said Susan Solomon, an atmospheric chemist at the Massachusetts Institute of Technology and lead author of a study on the ozone layer, published in the journal Science.
“Think of it like a patient with a disease,” Ms Solomon said. “First, it was getting worse. Then it stopped ? it was stable but still in bad shape.” Now, she said, “as molecules slowly decay away from the atmosphere, it’s getting just a little bit better.”
David Fahey, a research physicist at the National Oceanic and Atmospheric Administration who was not involved in the study, said the news “gives us a critical level of confidence that we are moving in the direction we want to see.”
It also reinforces that the Montreal Protocol has been a “resounding success,” Mr Fahey said. “It stands head and shoulders above any other environmental treaty.”
While ozone has been depleted in the Arctic and mid-latitude regions as well, the destruction over Antarctica is greater, in part because temperatures there are so cold.
Because the reactions that cause ozone to be destroyed require sunlight, thinning of the ozone layer begins each year in late August, when winter in the Southern Hemisphere is ending, and reaches its maximum by September and October. The ozone layer recovers later in the year, and then the cycle repeats itself.
Ozone depletion is a complex process that is affected by variables like temperature, wind and volcanic activity.
Ms Solomon’s study found that the ozone hole had shrunk by about 1.5 million square miles, or about one-third the area of the United States, from 2000 to 2015. This reduction occurred despite the effects of some volcanic eruptions, including one last year in the Chilean Andes that led to one of the largest holes ever measured.
Geir Braathen, a senior scientific officer at the World Meteorological Organization, said that the use of computer models by Ms Solomon and her colleagues was important. “Just looking at observational data, even if you see some hint of improvement, you can’t say if it’s due to ozone-depleting gases,” he said. “That’s why they used the models.”
A 2009 analysis by NASA scientists showed what the world would have been like had there been no Montreal Protocol, and CFC production and use had continued. By midcentury, their simulations showed, the ozone hole would have covered the world, and at noon on a clear summer day in a city like New York, the UV index, a measure of the damage the sun can do, would have caused a noticeable sunburn on unprotected skin in 10 minutes.
That dire situation has been avoided thanks to the collective efforts of society, Solomon said. “We are seeing the planet respond as expected to the actions of people,” she said. “It’s really a story of the public getting engaged, policymakers taking action, and business getting engaged.”
Additional material : New York Times