SOURCE: Yale e360

DATE: Aug 14, 2017

SNIP: Did the Montreal Protocol fix the ozone hole? It seemed so. With chlorofluorocarbons (CFCs) and other ozone-eating chemicals banned, many scientists said it was only a matter of time before the ozone layer recharged, and the annual hole over Antarctica healed for good.

But 30 years on, some atmospheric chemists are not so sure. The healing is proving painfully slow. And new discoveries about chemicals not covered by the protocol are raising fears that full recovery could be postponed into the 22nd century – or possibly even prevented altogether.

…[I]n the past five years, evidence has emerged that potential ozone-eating compounds can reach the ozone layer much faster than previously thought. Under some weather conditions, just a few days may be enough. And that means a wide range of much more short-lived compounds threaten the ozone layer – chemicals not covered by the Montreal Protocol.

These compounds are all around us. They are widely used as industrial solvents for tasks like degreasing and dry cleaning. And their releases into the atmosphere are increasing fast.

[Jonathan Shanklin of the British Antarctic Survey] says an important reason for the sluggish recovery of the ozone layer is global warming. As increased levels of greenhouse gases such as carbon dioxide trap more solar heat radiating from the Earth’s surface, less warmth reaches the stratosphere, which cools as a result. This trend has been evident for almost 40 years. A colder stratosphere improves conditions for ozone loss. Climate change “could delay the recovery of the ozone hole well into the second half of this century,” he says.

Protecting the ozone layer “presents a much greater industrial and political challenge than previously thought,” says [David Rowley, an atmospheric chemist at the University College London]. Thirty years on, there is evidently still a lot to do.