Good news for the ozone layer: Following a recent increase in CFC-11 pollution, emissions of this ozone-depleting chemical are declining.
Trichlorofluoromethane or CFC-11 emissions are expected to decrease after the Montreal Protocol banned the production of CFC-11 in 2010 (SN: 7/7/90). But between 2014 and 2017 he saw an unexpected blow. About half of that illegal pollution was linked to eastern China (SN: 22/05/19). Now, atmospheric data show that global CFC-11 emissions in 2019 dropped again to the average levels seen between 2008 and 2012, and about 60 percent of that decline was due to reduced emissions in eastern China, two teams reported. online on February 10 in Nature.
These findings suggest that the Earth’s ozone layer hole is still on the verge of closing in the next 50 years, rather than being delayed, as it would be if CFC-11 emissions remained at levels observed between 2014 and 2017 (SN: 14 / 12/16).
One group analyzed the concentration of CFC-11, used to make insulating foams for buildings and appliances, in the air above atmospheric control stations around the world. The team found that the world emitted about 52,000 tons of CFC-11 in 2019, a significant drop in the annual average of 69,000 tons from 2014 to 2018. Emissions from 2019 were comparable to average annual emissions from 2008 to 2012, Stephen Montzka, an atmospheric chemist with the U.S. National Oceanic and Atmospheric Administration in Boulder, Colorado, and colleagues report.
The new measurements imply that there has been a significant decrease in illicit CFC-11 production in the last two years, the researchers say, probably thanks to stricter enforcement of the regulations in China and elsewhere.
Another group confirmed that emissions from eastern China have decreased since 2018 by analyzing air samples from Hateruma, Japan and Gosan, South Korea. The region emitted about 5,000 tons of CFC-11 in 2019, which was about 10,000 tons less than its average annual emissions between 2014 and 2017 and was similar to the average from 2008 to 2012. That analysis was led by Sunyoung Park, a geochemist at Kyungpook National University in Daegu, South Korea.
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The recent drop in CFC-11 contamination demonstrates that “the Montreal Protocol is working,” says A.R. "Ravi" Ravishankara, an atmospheric scientist at Colorado State University in Fort Collins, did not participate in either study. When someone violates the treaty, the “atmospheric trap” can uncover the culprits and encourage countries to take action, he says. "China has taken action clearly because you can see the result of that action in the atmosphere."
Montzka warns that it may not always be so easy to point the finger at rogue broadcasters. “I think this time we were lucky,” he says, because atmospheric control sites in Asia have been able to track most of the illegal emissions to eastern China and monitor the situation over several years. Many places in the world, such as Africa and South America, lack atmospheric control stations, so it is still a mystery that countries other than China have been responsible for the recent rise and fall in CFC-11 emissions.