Montreal Protocol helped slow down ozone depletion

The Antarctic ozone hole would have been 40 per cent bigger by now if ozone-depleting chemicals had not been restricted in the 1980s in accordance with the Montreal Protocol, a new research claims.
We are already reaping the rewards of the protocol, with the ozone layer in much better shape than it would have been without the UN treaty, researchers said.
"Our research confirms the importance of the Montreal Protocol and shows that we have already had real benefits," study lead author Professor Martyn Chipperfield, from the School of Earth & Environment at the University of Leeds, said.
"We knew that it would save us from large ozone loss 'in the future', but in fact we are already past the point when things would have become noticeably worse," said Chipperfield.

Although the Montreal Protocol came into force in 1987 and restricted the use of ozone-depleting substances, atmospheric concentrations of these harmful substances continued to rise as they can survive in the atmosphere for many years.
Concentrations peaked in 1993 and have subsequently declined.

In the new study, the researchers used a state-of-the-art 3D computer model of atmospheric chemistry to investigate what would have happened to the ozone layer if the Montreal Protocol had not been implemented.
"Ozone depletion in the polar regions depends on meteorology, especially the occurrence of cold temperatures at about 20km altitude - colder temperatures cause more loss," Chipperfield said.

"We have used actual observed meteorological conditions for the past few decades. This gives a more accurate simulation of the conditions for polar ozone loss," said Chipperfield.
The researchers suggest that the hole in the ozone layer over the Antarctic would have grown in size by an additional 40 per cent by 2013.
Their model also suggests that had ozone-depleting substances continued to increase, the ozone layer would have become significantly thinner over other parts of the globe.
Chipperfield said he undertook this study because of the exceptionally cold Arctic winter of 2010/11.
Without the Montreal Protocol, the new study shows that a very large ozone hole over the Arctic would have occurred during that cold winter and smaller Arctic ozone holes would have become a regular occurrence.

The study was published in the journal Nature Communication.