May 24 2019
Since 2013, annual emissions of a banned chlorofluorocarbon (CFC) have increased by nearly 8,000 tons from eastern China, according to new research published in Nature by an international team of scientists from the United Kingdom, South Korea, Japan, the United States, Australia, and Switzerland.
Last year it was reported that emissions of one of the most important ozone-depleting substances, CFC-11, had increased. This chemical was used primarily as a foaming agent for building insulation, refrigerators, and other consumer products. The surprise finding indicated that someone, somewhere was likely producing thousands of tons of CFC-11, despite a global phase-out since 2010 under the Montreal Protocol.
"Through global monitoring networks such as the Advanced Global Atmospheric Gases Experiment (AGAGE) and the National Oceanic and Atmospheric Administration Global Monitoring Division, scientists have been making measurements of CFCs in the atmosphere for over 40 years," says Matt Rigby, a lead author of the study and reader in atmospheric chemistry at the University of Bristol. "In recent decades, we've primarily seen declining CFC emissions reflected in these measurements, because of the Montreal Protocol. Therefore, it was unexpected when it was reported last year that, starting around 2013, global emissions of one of the most important CFCs suddenly began to grow."
This finding was concerning because CFCs are the main culprits in depletion of the stratospheric ozone layer, which protects us from the sun's ultraviolet radiation. Any increase in emissions of CFCs will delay the time it takes for the ozone layer, and the Antarctic ozone "hole," to recover.
But where were these new emissions coming from? Until now, researchers only had an indication that at least part of the source was located somewhere in eastern Asia.
"Initially our monitoring stations were set up in remote locations, far from potential sources," says Ronald Prinn, co-author of the study, leader of the AGAGE network, and professor of atmospheric science and co-director of MIT's Joint Program on the Science and Policy of Global Change. "This was because we were interested in collecting air samples that were representative of the background atmosphere, so that we could monitor global changes in concentration and determine their atmospheric lifetimes."
To better pinpoint emissions sources, more recent measurement stations have been located closer to industrialized regions. In this case, the clue to the location of the new CFC-11 emissions came from an AGAGE station in South Korea and an AGAGE-affiliated station run by the National Institute of Environmental Studies (NIES) in Japan.
Professor Sunyoung Park from Kyungpook National University in South Korea, a lead author on the study, who runs the South Korean Gosan measurement station, explains: "Our measurements show 'spikes' in pollution, when air arrives from industrialized areas. For CFC-11, we noticed that the magnitude of these spikes increased after 2012, indicating that emissions must have grown from somewhere in the region."
Similar signals had also been noticed at the NIES station on the Japanese island of Hateruma, close to Taiwan. To establish which countries were responsible for the growing pollution levels at these stations, an international team of modeling groups at University of Bristol, the U.K. Met Office, the Swiss Federal Laboratories for Materials Science and Technology, and MIT ran sophisticated computer simulations that determined the origin of the polluted air samples.
"From the atmospheric observation data of CFC-11 at the Korean and Japanese stations and models, we found that emissions of CFC-11 from eastern China had increased by around 7,700 tons per year after 2013 — primarily around the northeastern provinces of Shandong and Hebei — while no evidence of increasing emissions had been found for Japan and the Korean peninsula in that period," says Xuekun Fang, a lead author on the study and a postdoc at MIT.
To investigate the possibility that the new emissions from China could be the result of a release to the atmosphere of CFC-11 that was produced before the ban, the team considered a range of possibilities. CFC-11 was used primarily in foam blowing, so researchers looked at estimates of the amount of CFC-11 that could be locked up in insulating foams in buildings or refrigerators made before 2010, but the quantities were far too small to explain the recent rise.
"The most likely explanation is that new production has taken place, at least prior to the end of 2017, which is the period covered in our work," says Rigby.
While the study has identified a substantial fraction of the global emissions rise, it is possible that smaller increases have also taken place in other countries, or even in other parts of China. According to Park, the Korean and Japanese measurements are sensitive only to the eastern part of China, western Japan, and the Korean peninsula; the remainder of the AGAGE network sees parts of North America, Europe, and southern Australia. Thus there are large swathes of the world for which there is very little detailed information on the emissions of ozone-depleting substances.
Nevertheless, this study "represents an important and particularly policy-relevant milestone in atmospheric scientists' ability to tell which regions are emitting ozone-depleting substances, greenhouse gases, or other chemicals, and in what quantities," says Professor Ray Weiss, a geochemist at Scripps Institution of Oceanography at the University of California at San Diego and study co-author.
Rigby stresses the urgent need to identify which industries are responsible for the new emissions.
"If the emissions are due to the manufacture and use of products such as foams, it is possible that we have only seen part of the total amount of CFC-11 that was produced," he says. "The remainder could be locked up in buildings and chillers and will ultimately be released to the atmosphere over the coming decades."
Previous reports by the Environmental Investigation Agency and The New York Times had suggested that Chinese foam manufacturers were using CFC-11 after the global ban, and Chinese authorities have identified and closed down some illegal production facilities.
While this new study cannot determine which industry or industries are responsible, it provides a clear indication of large increases in emissions of CFC-11 from China in recent years. These increases, likely from new production, account for a substantial fraction of the concurrent global emission rise.