Humans Are Destroying the Ozone Layer Again

The Montreal Protocol has been the shining success story of international climate agreements: Scientists realized human chemicals were eating a giant hole in the ozone layer that blocks the sun's damaging ultraviolet radiation, then governments around the globe came together to fix the problem. The result was a pact enacted at the beginning of 1989 to gradually stop using the chemicals responsible for the gaping hole. Three decades after the initial agreement was hammered out, it's still in effect with amendments.

But according to a new paper published in the journal Atmospheric Chemistry and Physics, a hole in the Montreal Protocol itself may be leaving the ozone layer open to previously unrecognized damage—which could mean bad news for all life on Earth.

Ozone is a form of oxygen that includes three atoms stuck together—the oxygen we breathe to survive is built of only two atoms. It's created naturally in the top layers of Earth's atmosphere as sunlight breaks down two-atom oxygen and sticks the singletons onto other molecules of oxygen. (It can also be created near Earth's surface from reactions of human-made chemicals, but it's dangerous to breathe.) All told, there's more than 3 billion tons of the stuff floating more than six miles above our heads.

That's a good thing: High above Earth, ozone acts basically as a sunshield for the entire planet, soaking up most ultraviolet light. What does make it through the ozone layer can give you a bad sunburn, but without ozone, living things wouldn't survive on Earth.

But a range of chemicals humans produce break ozone down, particularly over the north and south poles, creating the so-called "hole in the ozone layer." The Montreal Protocol governs dozens of these chemicals—compounds of chlorine, fluorine or both. That includes chemicals that had once been common in a range of consumer products, like the freon that powered a half century of refrigerators.

But the Montreal Protocol focused on gases that linger in the atmosphere—and that may have been a mistake, according to the new study. In it, scientists looked at shorter-lived chemicals, including one called dichloromethane, which is used in products including adhesives, paints and pharmaceuticals, and one called 1,2-dichloroethane, which is used to make polyvinyl chloride (PVC, as in the pipes). The new study argues that these chemicals are the result of industrial processes in in Eastern Asia.

In the case of both these chemicals, the scientists found higher levels than they had expected, and higher up in the atmosphere, closer to the ozone layer. That could slow down the continuing recovery of the hole in the ozone, according to Lucy Carpenter, an atmospheric chemist at the University of York in the U.K. who was not involved in the paper.

Precisely how much of an impact these previously unrecognized chemicals could have on the ozone layer is still unclear, Ryan Hossaini, an atmospheric scientist at Lancaster University also not involved in the study, told Newsweek in an email. "While their impact on the ozone layer is expected to be relatively small at present, it would be prudent to continue to monitor these compounds."