They were once abundant, in our hairsprays, bug sprays, and refrigerators. And then scientists figured out these substances ripped a hole in the ozone layer, leading to a 1987 plan to phase them out that over time would be agreed to by every country in the world.
More than three decades later, researchers have made a new discovery.
Ozone-depleting substances do more than just gnaw at Earth's protective layer. They're also greenhouse gases, so they contribute to the planet's overall warming by trapping heat, too. And now we may know just how much these substances have contributed to Arctic warming, thanks to a study published in the science journal Nature on Monday.
Between 1955 and 2005, ozone-depleting gases caused half of Arctic climate change (and a third of overall global warming), the study finds. This is primarily due to their heat-trapping qualities, not their ozone munching. The Arctic has seen rapidly melting sea ice for years and is warming faster than the rest of the world.
Critically, the vanishing sea ice causes the Arctic waters to absorb even more sunlight, which amplifies historically unprecedented heating in the region.
Between 1955 and 2005, ozone-depleting gases caused half of Arctic climate change.
These ozone-depleting gases include chlorofluorocarbons (CFCs), which we've been cracking down on since the global agreement known as the Montreal Protocol was finalized 33 years ago. CFCs, which include propellants and refrigerants, have been around since the 1920s and 1930s. Their popularity peaked in the late 20th century and have been on the decline since the Montreal Protocol.
To quantify the climate impact of ozone-depleting gasses, scientists from Columbia University, the Institute for Atmospheric and Climate Sciences in Switzerland, and University of Toronto used climate models to run a variety of simulations. In one, they tested what would happen if stratospheric ozone and the pesky gases that hurt it stayed at 1955 levels. Research on CFCs' climate impacts beyond ozone depletion is scant, even though they can trap more heat than climate change poster child carbon dioxide, the study notes.
The study's findings not only give an extra gold star to the much-acclaimed Montreal Protocol, but also provide a bit of hope when so much climate change research focuses on doom and gloom.
"Our findings also have implications for the future because the phase-out of [ozone-depleting substances], which is well under way, will substantially mitigate Arctic warming and sea-ice melting in the coming decades," the study explains.
Indeed, Cecilia Bitz, a climate scientist at the University of Washington in Seattle who was not involved in the study, told Nature, “It’s a very important paper because it has a little shred of optimism.”
Don't get too excited just yet, though. More studies that replicate these findings need to be done to corroborate the evidence, Bitz, the study authors, and other scientists say.
Then there's also the problem of CFCs still being used despite global crackdowns. For example, China is struggling to tamp down on illegal CFC production. In addition, we've just begun to tackle hydrofluorocarbons (HFCs), which air conditioner and refrigerator manufacturers turned to when they were blocked from CFCs, on a global scale. HFCs are less harmful for the ozone than CFCs, but like their loathed counterpart, they're more powerful than carbon dioxide when it comes to trapping heat. Let's also not forget the alarming carbon dioxide concentration record announced last year.
And to be clear, weakening the ozone is still a very bad trait to have. Scientists expect it'll take another 50 years before the ozone hole over Antarctica is back to its 1980 level.
Sorry to be a downer.
UPDATE: Jan. 21, 2020, 11:40 a.m. EST : This story originally stated melting Arctic sea ice results in sea level rise. While the impacts of Arctic warming are many, melting Arctic sea ice does not raise sea levels, so this reference was omitted.
