Chemicals used in refrigerators and freezers may have been responsible for half of Arctic climate change in the past 50 to 60 years, scientists say.
And while that might sound like bad news, it’s actually good news, they suggest, because the culprits were banned more than 30 years ago by an international accord known as the Montreal Protocol.
At issue is the class of chemicals known as chlorofluorocarbons (CFCs), once widely used as refrigerants, solvents, and propellants for aerosol sprays. Invented in the 1920s and 1930s, they were being released into the atmosphere in large quantities by the 1950s.
A few decades later, it was realised they were destroying ozone in the upper atmosphere, particularly at the poles, where they were linked to the growth of a dramatic “ozone hole” over Antarctica.
Because ozone provides crucial protection from dangerous ultraviolet radiation, 197 nations rallied in 1987 to phase these chemicals out via the Montreal Protocol.
At the time, the goal was simply to protect the ozone layer. But CFCs, and related chemical known as ozone-depleting substances (ODSs), aren’t just ozone-destroyers.
They are also super-potent planet-warming “greenhouse” gases, 19,000 to 23,000 times more powerful, molecule for molecule, than carbon dioxide, says Mark England, a polar climate scientist at Scripps Institution of Oceanography and the University of North Carolina, US.
That potency, he says, makes them second only to carbon dioxide as the main drivers of global warming.
They also appear to be particularly powerful contributors to the warming of the Arctic, which has been warming more than twice as quickly at the rest of the globe.
To see just how big a role these substances have played, England’s team modelled the Arctic climate from 1955 to 2005, looking to see what would have happened if releases of them had not increased during the 1950s, ’60s, ‘70s and ‘80s.
What they found, he says, is that without these chemicals, there would have been only half as much Arctic warming in that 50-year period as there was with them. Similarly, he says, without them, there would only have been about half as much melting of sea ice.
On a global scale, his team adds, these chemicals contributed fully one-third of the total global warming seen during that time period.
But, he stresses, CFCs and other ozone-depleting chemicals don’t last forever. Already the ozone hole is shrinking, and by the middle of this century – or “maybe a bit later” – there will also be reductions in these chemicals’ impact on Arctic warming.
Not that it will be enough to bring climate change to a halt. “Carbon dioxide is definitely the biggest contributor,” England says. “That is still true. But… it would warm less.”
The bottom line, he adds, is that the Montreal Protocol may be an unsung hero in the history of the fight against climate change.
“We haven’t had many wins in terms of climate protocols,” he says, “but that is really our biggest win. More research should be done about the positive effects of it.”
His team’s research is published in the journal Nature Climate Change.
Richard A Lovett
Richard A Lovett is a Portland, Oregon-based science writer and science fiction author. He is a frequent contributor to Cosmos.
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