China’s emissions of a banned gas that damages the Earth’s ozone layer have decreased dramatically after increasing for several years, two teams of scientists said on Wednesday, a sign that the Beijing government has kept promises to crack down on illegal production of the industrial chemist.
The findings lessen concerns that increasing emissions of the gas, CFC-11, would slow progress in the decades-long environmental struggle to repair the ozone layer, which filters out the sun’s ultraviolet radiation that can cause skin cancer and damage crops .
“We see a big decline in global emission rates and what comes from eastern China,” said Stephen A. Montzka, a research chemist with the National Oceanic and Atmospheric Administration and lead author of one of the studies. The work of Dr. Montzka and others three years ago revealed illegal emissions for the first time.
“It looks like there was a substantial response, potentially as a result of raising a flag and saying, ‘Hey, something is not going as it should,'” said Montzka.
Matthew Rigby, an atmospheric chemist at the University of Bristol, England, and author of the second study, said that if emissions had not decreased, “we could be seeing a years delay in ozone recovery.” As of now, full recovery is still expected in the middle of the century.
Chinese government officials did not immediately respond to requests for comment.
Chemical traders in Shandong, a heavily industrialized province in eastern China where CFC-11 was widely used to make insulating foams, said the prohibited gas trade had practically dried up. “It has not disappeared entirely, but it is much scarcer than before,” said Gao Shang, a chemical trader in Shandong, in a telephone interview.
CFC-11 was declared illegal a decade ago by the Montreal Protocol, the treaty established in the 1980s, when research revealed its effects on atmospheric ozone, along with the effects of similar widely used chemicals.
The revelation in a 2018 study of China’s harmful emissions that began five years earlier came as a shock to scientists, lawmakers, environmentalists and others who monitor the protocol, which is widely regarded as the most effective environmental treaty in history.
Meg Seki, interim executive secretary of the Ozone Secretariat, the United Nations body that administers the treaty, said the organization was pleased to see that emissions have fallen and that the effect on the ozone layer is likely to be limited. “It is important, however, to avoid such unexpected emissions in the future through continuous monitoring of a high standard by the scientific community,” she said in a statement.
The 2018 survey did not identify the source of most emissions, and located them as coming from East Asia. But that year’s investigations by the Environmental Investigation Agency, an independent defense group based in Washington, DC, and The New York Times found evidence that the gas was still being produced and used in eastern China, particularly in Shandong.
An atmospheric analysis conducted by Dr. Rigby in 2019 found that Shandong, as well as a neighboring province, Hebei, were the main sources.
When confronted with the evidence for the first time, Chinese environmental authorities sidestepped and raised doubts about the findings, suggesting that there could be other unregistered sources of the chemical or that insulating foam manufacturers would not use as much CFC-11.
At the same time, China’s Ministry of Ecology and Environmental Protection has promised “zero tolerance” for companies that manufacture or use CFC-11 illegally.
Policy announcements, industry reports and court decisions indicate that the Chinese government has cracked down on illicit trade, although it continued to deny that there was ever a serious problem. Last year, the government publicized the conviction of a businessman, Qi Erming, as the first case in China of a criminal case for illegal trade in chemicals harmful to the ozone layer.
In addition to the processes, the government tightened the rules and monitoring of the chemical and foaming industries, and promised to create a comprehensive data system to track the movement of chemicals that could be used to make CFC-11.
There are legal gases that can replace CFC-11 in foam production. Gao, the chemicals dealer in Shandong, said his company specializes in one.
The availability of substitutes may have helped China’s efforts to reduce emissions of CFC-11. Zhu Xiuli, sales manager at another company in Shandong that sells sparkling agents, said customers had already asked if they had CFC-11. But “in recent years, there have been fewer and fewer consultations,” she said.
CFC-11 has also been used in refrigeration equipment. As the gear ages and the CFC-11 containing foams degrade over time, the gas is released slowly. Although the size of this CFC-11 “bank” is not known precisely, it is accounted for by the protocol and is one of the reasons why total ozone recovery will take decades.
The new articles, which were published in the journal Nature, also do not account for the entire global increase in CFC-11 emissions that has occurred since 2013. The gas may still be being produced or used in other countries or in other parts of China, but the researchers said there are not enough air sampling stations in the world to know for sure.
“This is a useful lesson that we really need to expand our monitoring capabilities,” said Dr. Rigby.
Avipsa Mahapatra, leader of the Environmental Research Agency’s climate campaign, said of the new findings that it was “exciting to see atmospheric studies confirming that local intelligence and subsequent application culminated in a spectacular climate victory.” But she said her group had indications that the inspection may have been more successful in some parts of China than in others. “This is not the time for complacency,” she said.
Susan Solomon, an atmospheric chemist at the Massachusetts Institute of Technology who was not involved in the research, said the work was “a real triumph for science”.
But the problem is not over, Solomon said, because in addition to CFC-11, there are other similar chemicals being emitted. “There is an entire zoo of molecules,” she said, and although the quantities are smaller, they add up.
They are also potent greenhouse gases, she said, although their contribution to warming is much less than the much more prevalent gases that retain heat, such as carbon dioxide and methane. “The global chemical industry is not yet monitored closely enough that we can really be confident in the amount of greenhouse gases they are producing and the amount of gases that destroy the ozone layer,” she said.
Liu Yi contributed research.