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China's clampdown on harmful emissions puts ozone layer rescue back on track

Posted February 11, 2021 7:31 a.m. EST

— Here's some good news: when people put their mind to it, they can act on climate.

Research published on Wednesday has shown a significant drop in emissions of a banned ozone-depleting chemical after China clamped down on its illegal production. As a result of this drop, the recovery of the ozone layer has resumed.

The ozone layer is the world's shield against ultraviolet radiation, which is known to cause skin cancer. It has been significantly damaged by dangerous man-made chemicals, including those known as CFCs.

Two studies that were published in Nature on Wednesday and conducted primarily by scientists at MIT, in the United States, and the University of Bristol, in England, show that after a worrying spike in recent years, the emissions of one of these ozone-harming gases, CFC-11, have dropped back to much lower levels.

Ronald Prinn, the director of the Center for Global Change Science at MIT and a co-author of the new research, said the data was "tremendously encouraging." CFC gases are also potent greenhouse gases and they stay in the atmosphere for a long time, which is why the recovery of the ozone layer will take decades.

"If emissions of CFC-11 had continued to rise or even just leveled off, there would have been a much bigger problem building up," Prinn said.

Ozone molecules are made of three oxygen atoms. When CFC-11 is released into the atmosphere, radiation breaks it down into chlorine, which then eats into the ozone molecules, breaking them down and creating the more stable oxygen molecules made of two atoms.

Once commonly used in refrigeration and insulation, CFC-11 was banned by global agreement in the late 1980s, and was meant to be phased out internationally by 2010. Initially, the agreement worked: the concentration of the substance was declining and scientists estimated the ozone layer would recover by 2050.

But then in 2018, a team of scientists looking at data from the National Oceanographic and Atmospheric Administration and Advanced Global Atmospheric Gases Experiment, noticed the downward trend had abruptly stopped. In fact, their measurements pointed to an unexpected spike in the CFC-11 concentration.

The scientists were able to see the bulk of the emissions came from eastern China's Shandong and Hebie industrial provinces and environmental activists, including the Environmental Investigation Agency, then traced the emissions to factories producing polyurethane foam.

The researchers said that after it became apparent the emissions were coming from China, Chinese authorities were quick to react, putting in new enforcement measures which led to the decline of the emissions.

"The global monitoring networks really caught this spike in time, and subsequent actions have lowered emissions before they became a real threat to recovery of the ozone layer," Prinn said.

While the study says the emissions coming from China have declined, those only account for roughly half the global total. Figuring out where the rest is coming from is the scientists' next challenge.

"We will need to expand measurements and modeling to identify new sources, and continue to keep watch," Prinn said. "Clearly this story shows that ... continuous vigilance is required. You can't stop measuring these chemical species and assume the problem is solved."

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