Dec. 6 (UPI) -- The hole in the ozone layer isn't yet gone, but it's been slowly shrinking for the last few decades, mostly thanks to the Montreal Protocol, passed in 1987, which helped phase out the use of ozone-eating chlorofluorocarbons around the world.
New research suggests the Montreal Protocol also helped slow global warming. Chlorofluorocarbons, a class of chemicals that destroy the ozone layer, are also greenhouse gases.
For the new study, published this week in the journal Environmental Research Letters, scientists calculated the amount of warming that was prevented by slowing the release of CFCs into Earth's atmosphere. The analysis showed that by mid-century, Earth will be at least 1 degree Celsius cooler than it would have been without the Montreal Protocol.
"By mass CFCs are thousands of times more potent a greenhouse gas compared to CO2, so the Montreal Protocol not only saved the ozone layer but it also mitigated a substantial fraction of global warming," lead study author Rishav Goyal, a doctoral student at the University of New South Wales' Climate Change Research Center in Australia, said in a news release. "Remarkably, the Protocol has had a far greater impact on global warming than the Kyoto Agreement, which was specifically designed to reduce greenhouse gases."
At first, Goyal and his research partners weren't actually trying to measure the cooling effects of the Montreal Protocol. Instead, the research team set out to measure the effects of international agreement and subsequent CFC emissions reductions on atmospheric circulation around Antarctica.
The models they built to quantify climate dynamics and atmospheric chemistry with and without the Montreal Protocol revealed a surprising discrepancy in average global temperatures.
The commitment to curbing CFC emissions has helped some places avoid warming more than others. For example, the models -- which assume a conservative estimate of 3 percent annual increases in CFC emissions without the Protocol -- suggest Antarctica will avoid as much as 3 degrees Celsius of warming by mid-Century.
The latest research also showed there would likely be even less Arctic sea ice than there is now if it wasn't for the Montreal Protocol.
"Without any fanfare the Montreal Protocol has been mitigating global warming impacts for more than three decades, surpassing some treaties that were specifically aimed to ameliorate climate change impacts," said researcher Martin Jucker.
Of course, the progress made by the Montreal Protocol isn't necessarily permanent. Last year, scientists observed rising CFC emissions in Asia. Investigators determined the continued production and use of CFCs in China and its foam industry were to blame for the emissions increase.
Scientists have also found evidence that the increased use of dichloromethane, a popular substitute for CFCs, could also undermine the recovery of the ozone layer. Though the ozone-eating chemical has a much shorter lifespan than chlorofluorocarbons, its use remains unregulated.