Efforts to heal hole in ozone layer also helped Arctic sea ice, study suggests

An international policy struck decades ago is healing a hole in the ozone layer above the Antarctic — but according to a new study, it's also having an unintended climate benefit on the opposite side of the world. 

Climate researchers at Columbia University and the University of Exeter have found the Montreal Protocol — signed in 1987 — is delaying the Arctic's first ice-free summer by up to 15 years.

Mark England, one of the study's co-authors, describes it as a "fantastic by-product."

"The climate benefits are happening today and over the next few decades," England said.

The Montreal Protocol was a significant international effort that unfolded after the discovery of a hole developing in the ozone layer above Antarctica. Widely considered a great environmental success story, it helped to protect and repair the ozone layer by banning the use of chlorofluorocarbons (CFCs) — a type of greenhouse gas that contributes to ozone depletion. 

Before that, CFCs were being used in products like cleaning agents, aerosol sprays and refrigerators. 

Earlier this year, the United Nations issued a report saying the hole over Antarctica is slowly but noticeable healing, and should be fully mended in about 43 years. 

The peer-reviewed study, published last month in the journal Proceedings of the National Academy of Sciences, used climate models to see what would happen, with and without the Montreal Protocol, in a medium and high emission scenario between 1985 and 2050. 

Researchers found that had the protocol not been enacted, the world's mean surface temperature would be half a degree warmer, and the Arctic polar cap could be almost one degree warmer by 2050. 

"By enacting the Montreal Protocol, we were able to delay when the Arctic becomes ice free by somewhere between seven and 15 years, depending on kind of assumptions you make about other emissions," England said.

He said although policy makers probably weren't thinking about Arctic sea ice when the protocol was signed, it does carry lessons for changing the course of a warming planet. 

"It was such a successful piece of climate mitigation action because it happened so rapidly. Only after a couple years of finding out about the development of the ozone hole, the international community took action," he said. 

"Because these substances last so long in the atmosphere, it's really key to kind of stop it early," 

England said the policy also "had teeth" because it punished violations of the protocol with trade sanctions.