Is China Emitting a Climate Super Pollutant in Violation of an International Environmental Agreement?

Concentrations of HFC-23, one of the world’s most potent greenhouse gases, remained elevated in East Asia after China, a known past polluter, agreed to curb emissions.

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Former Secretary of State John Kerry and Chinese Deputy Minister of Environmental Protection Zhai Qing arrive for a bilateral meeting on the sidelines of the 28th Meeting of the Parties to the Montreal Protocol in Kigali on October 14, 2016. Credit: Cyril Ndegeya/AFP via Getty Images
Then Secretary of State John Kerry and Chinese Deputy Minister of Environmental Protection Zhai Qing arrive for a bilateral meeting on the sidelines of the 28th Meeting of the Parties to the Montreal Protocol in Kigali on October 14, 2016. Credit: Cyril Ndegeya/AFP via Getty Images

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Preliminary atmospheric monitoring data from a remote South Korean island off China’s east coast shows elevated concentrations of hydrofluorocarbon-23 (HFC-23), a greenhouse gas 14,700 times more potent than carbon dioxide on a pound-for-pound basis, according to the World Meteorological Association. 

The gas concentrations remain elevated in air samples collected at the Gosan atmospheric monitoring station on South Korea’s Jeju Island in 2022 even after China, previously identified as the source of HFC-23 pollution detected at this site, was supposed to have ceased emitting it under an international agreement.

In June 2021, China ratified the Kigali Amendment to the Montreal Protocol, a binding international agreement that seeks to curb emissions of climate-warming HFCs, synthetic gases primarily used for air conditioning and refrigerating. The agreement entered into force in China on September 15, 2021, requiring the country to reduce HFC-23 emissions “to the extent practicable” by the end of 2021.

The primary source of HFC-23 emissions in China was as a byproduct in the manufacturing of HCFC-22, which is used to produce other fluorinated chemicals including polytetrafluoroethylene (PTFE), or Teflon. More than half of all HCFC-22 has been produced in China since 2009, according to a United Nations Environment Programme report


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To comply with the Montreal Protocol, HCFC-22 manufacturers must install mitigation technologies, at relatively low cost, to destroy the by-product HFC-23. 

However, air samples collected at Gosan contained elevated concentrations of HFC-23, with some measurements roughly twice that of global background levels measured at other remote locations. The elevated concentrations continued through June 2022, the most recent month for which data is available.  

The preliminary data from Gosan suggests there were likely significant emissions of HFC-23 that continued to be released from somewhere in the region throughout the sampling period.

The data, which relies on monitoring equipment capable of measuring trace volumes of pollution down to the parts-per-trillion level, is posted on the website of the Advanced Global Atmospheric Gases Experiment, or AGAGE, a publicly funded international atmospheric monitoring network. AGAGE is sponsored by NASA and other federal agencies including the National Research Foundation of Korea. 

The volume and source of emissions that led to the elevated concentrations of the climate pollutant remain unknown. However, a study published in August in the journal Atmospheric Chemistry and Physics concluded that similarly elevated HFC-23 concentrations detected at the same monitoring station from 2008 to 2019 came almost exclusively from eastern China. Ninety four percent of emissions in East Asia in 2019 could be traced back to eastern China, the study concluded.  

HFC-23 emissions from eastern China in 2019 equaled 9,450 metric tons, according to the study, which was equal to the annual greenhouse gas emissions of 31 million cars or 37 coal fired power plants, according to the EPA’s greenhouse gas equivalency calculator.

Yuan Liu, the director of the Montreal Protocol division for the Foreign Environmental Cooperation Center of China’s Ministry of Ecology and Environment, said the ministry is looking into the issue.

“We note that HFC-23 emission is an important and complex issue, which has raised concerns by scientists in both China and abroad,” Yuan said in an emailed response to Inside Climate News. “Scientists are carrying out a great deal of research and investigation work now.”

AGAGE scientists will now analyze the air samples collected at Gosan from 2020 to mid-2022, said Ronald Prinn, an atmospheric science professor at MIT and one of two principal investigators overseeing the AGAGE network. The assessment will include detailed meteorological modeling that should allow scientists to determine the source and volume of any regional HFC-23 emissions that led to the elevated concentrations detected at Gosan.

However, given the time it took to publish the 2008 to 2019 data, it could be years before the assessment is complete and the findings are published in a peer-reviewed academic journal. In the meantime, the elevated atmospheric concentrations collected at Gosan suggest chemical plants in China may not have stopped emitting the climate pollutant in 2021 as required under the Kigali Amendment.

“China itself has played an important role in the reaching of the Kigali Amendment,” Liu Pengyu, the spokesman for China’s embassy in Washington, said on Friday. “Domestically, China has made solid efforts of compliance.”

“China will continue to earnestly implement the protocol and amendment, and promote global efforts on climate and environment,” Liu added.

The U.S. closely tracks China’s compliance with the Kigali Amendment, including HFC-23 by-product emissions, a senior State Department official, who asked not to be quoted by name, said.  

A South Korean researcher who is familiar with the air sampling and analysis at Gosan declined to comment and asked not to be named, given the preliminary nature of the data.

Prinn declined to draw any conclusions about the HFC-23 atmospheric concentration data and what it might reveal about the source or volume of emissions before a full analysis and the peer review process are complete.

HFC-23 atmospheric concentration data from Gosan from January 2021 through June 2022 was removed from the AGAGE website after Inside Climate News first contacted AGAGE researchers about the data. Prinn and the South Korean researcher familiar with the project did not respond to requests for comment about why the data was removed.

However, other climate scientists said the data from 2020 to mid-2022 suggests emissions of HFC-23, from somewhere in East Asia, likely persisted beyond 2021.

“You can’t say exactly where it’s coming from,” said Megan Lickley, a climate science professor at Georgetown University. “But you can say that, qualitatively, it looks like the trend of there being a pollution source close to Gosan appears to be continuing.” 

A graph prepared by Inside Climate News shows the atmospheric concentrations of HFC-23 in the air collected at Gosan compared to concentrations collected at other monitoring sites around the world.

Concentrations from the South Korean island appear as red dots or points on the graph and are higher than HFC-23 concentrations collected at remote sites in Ireland and Australia, suggesting HFC-23 was emitted somewhere in East Asia. The visualization shows there may be a gradual decrease in atmospheric concentrations of HFC-23 at Gosan following China’s entry into the Kigali Amendment, but not a sudden drop signifying an abrupt decrease in emissions.  

“I would have fully expected those red points to drop, you know, after 2021, but we do have these important caveats to keep in mind,” said Stephen Montzka, a senior scientist with the National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory and a member of the Montreal Protocol’s Scientific Assessment Panel. 

Montzka noted that even if China did dramatically reduce its HFC-23 emissions in 2021, it is possible that relatively low levels of emissions from South Korea or western Japan that are closer to Gosan could, potentially, account for the ongoing elevated concentrations detected at the monitoring station.

Matthew Rigby, an atmospheric scientist at the University of Bristol, said the measurements from Gosan suggest significant emissions from somewhere in the region that persisted at a similar or slightly lower magnitude after China’s entry into the Kigali amendment, but added that additional analysis is required to pinpoint the source.

“We really need to continue the analysis of this data so that we can, first of all, find which wind directions are responsible for these elevated pollution events and then also put some numbers on the emissions that could be responsible,” Rigby said.  

Durwood Zaelke, president of the Institute for Governance and Sustainable Development, an environmental organization based in Washington, D.C. said the potential magnitude of the emissions makes it worth raising the issue to the member countries or “parties” of the Montreal Protocol now, rather than waiting for final confirmation.  

“It’s a heads up,” Zaelke said. “While you do have to explain that it’s preliminary, it’s important enough to be brought to the attention of parties right now.”

Avipsa Mahapatra, climate campaign director at the Environmental Investigation Agency, a nonprofit environmental organization based in Washington, D.C., agreed.

“We need to find out where these emissions are coming from and address them immediately,” Mahapatra said.

Megumi Seki Nakamura, the executive secretary of the U.N.’s Ozone Secretariat, which oversees the Montreal Protocol, said all cases of potential non-compliance with the Kigali Amendment will be reviewed. 

Potential actions that members of the protocol could take range from providing assistance—including help with the collection and reporting of data—to issuing warnings, and, if necessary, imposing trade restrictions. 

A report published by the Montreal Protocol’s Technology and Economic Assessment Panel in September concluded that 95 percent of the HFC-23 generated worldwide comes from HCFC-22 production. However, the report noted there was insufficient information on potential HFC-23 byproduct production in the manufacturing of some other chemicals.

“There are potentially other pathways that are generating HFC-23 that we don’t have a good handle on as a global community,” Mahapatra, of EIA, said.

Montreal Protocol members requested that its scientific and technical expert panels provide updated estimates on HFC-23 emissions at its annual Meeting of the Parties in Nairobi, Kenya last month.  

HFC-23 emissions from chemical plants manufacturing HCFC-22 have been prohibited in China since September 2021, but the central government is still developing monitoring, reporting and verification standards for the pollutant.

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China’s Ministry of Ecology and Environment (MEE) issued a notice in September 2021 stating that chemical manufacturers in China could no longer vent HFC-23 directly into the air.  The notice stated that they must destroy HFC-23 as much as possible using destruction technology approved by the Montreal Protocol, which can destroy more than 99 percent of HFC-23 emissions.  

“Everybody knows that the technology is readily available and inexpensive and most people are using it to destroy [HFC-]23,” Zaelke said.  “There’s no defense that ‘we don’t have the technology, we don’t know how to use the technology, [or it’s] too expensive.’  That is definitely not the case here.”

MEE issued a notice on HFCs that reaffirmed the ban on HFC-23 emissions on Nov. 6 and included a list of the 21 chemical plants in China that produce HCFC-22.  

However, Zheng Tan, an industry program officer with Energy Foundation China, a nonprofit with offices in San Francisco and Beijing that funds projects addressing climate change in China, noted that China’s central government hasn’t yet published a standard method for monitoring, reporting and verifying HFC-23 emissions.

Such a standard would likely be required before any enforcement action could be taken against companies that fail to curb emissions.

“The standard is under development and will be released soon,” Zheng said.

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