This past Sunday was the 25th anniversary of the signing of the Montreal Protocol, an international treaty to ban the use of chlorofluorocarbons (CFCs) and other ozone-depleting substances that were responsible for the depletion of the ozone layer. To honour the date, the World Meteorological Organization (WMO) released a report on Friday stating that the Antarctic ozone hole will be smaller this year than it was last year, giving hope that ozone layer is now on the mend.
A few years ago, NASA scientists developed a simulation showing the world we avoided by signing the Montreal Protocol into effect. In the simulation, another ozone hole would have opened up over the Arctic by the year 2020, and by 2065 the ozone layer would have been completely gone.
The expansion of this year's ozone hole, which typically reaches its maximum size sometime in late September or early October, had a late start compared to previous years. Also, current observations and the 5-day forecast show that it may have already reached its maximum for the year, although they also include a warning that there is no way to tell for sure if ozone depletion has actually peaked for the year.
Currently at around 18.5 million square kilometres, the ozone hole is still larger than it was in 2010 at this time. However, the 2010 ozone hole reached its maximum area of around 22 million square kilometres in late September, so if the WMO forecast turns out to be right, this year's peak may be smaller than in 2010, and possibly the smallest in quite a few years. Looking back through the records, the last time the ozone hole maximum area stayed below 20 million square kilometers was back in 1988, a year after the Montreal Protocol was signed.
In addition to the intended protection of the ozone layer, an unexpected benefit of the Montreal Protocol was its effect on climate change.
"Given that many substances that deplete the ozone layer are also potent greenhouse gases, the Montreal Protocol has proved to be a double bonus for our atmosphere and climate system," said Michel Jarraud, Secretary-General of the World Meteorological Organization.
"The monitoring activities of WMO's Global Atmosphere Watch programme have strengthened our understanding of this relationship between ozone depletion and climate change," said Jarraud. "As we celebrate this 25th anniversary, we therefore pay tribute to the hundreds of scientists who have braved inhospitable terrain — including the Antarctic with temperatures down to -50 degrees Centigrade — to conduct the observations and research needed to understand our changing environment."