Since 2013, annual emissions of the banned chlorofluorocarbon CFC-11 have increased by around 7,000 metric tons from eastern China, according to a new study by an international team of scientists including Empa researchers, published in «Nature» today.
The new discovery follows a finding in 2018 that emissions of this very important ozone-depleting substance had increased. This surprise finding indicated to researchers and policy makers around the world that someone somewhere was likely producing and emitting thousands of metric tons of this substance, despite a global phase-out since 2010 under the Montreal Protocol (see box).
Matt Rigby, a lead author of the study of the University of Bristol, says: "Through global monitoring networks such as the Advanced Global Atmospheric Gases Experiment ( AGAGE ) and the National Oceanic and Atmospheric Administration Global Monitoring Division ( NOAA GMD ), scientists have been making measurements of CFCs in the atmosphere for over 40 years. 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 (UV) 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.
To pinpoint the sources, measurements are required closer to industrialized regions. In this case, the clue to the location of the new CFC-11 emissions came from two monitoring stations in eastern Asia. Sunyoung Park, a lead author of the study from Kyungpook National University in South Korea, who leads the Gosan measurement station on Jeju Island to the south of the Korean peninsula, 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 a Japanese National Institute of Environmental Science station on Hateruma Island close to Taiwan.To establish which countries were responsible for the growing pollution levels at the Korean and Japanese monitoring stations, an international team of researchers from 13 research institutions including the University of Bristol, the South Korean Kyungpook National University, the UK Met Office, the Swiss Federal Laboratories for Materials Science and Technology (Empa) and the Massachusetts Institute of Technology (MIT) ran sophisticated computer models to determine the origin of air samples measured at Gosan and Hateruma. "This cooperation between world-leading groups in the field is an excellent demonstration of the power of combining continuous measurements and atmospheric modelling to identify unknown or forbidden emissions. We were thus able to unambiguously trace back renewed CFC-11 emissions to China. For this purpose we had to rely on measurements from Gosan, an island off the coast of South Korea, as the use of Chinese measurement data is still strongly restricted", says Empa researcher Stephan Henne, a co-author of the study.
Whilst the new study has identified a substantial fraction of the global rise in CFC-11 emissions, it is possible that smaller increases have also taken place in other countries, or even in other parts of China. "Our measurements are sensitive only to the eastern part of China, western Japan and the Korean peninsula and the remainder of the AGAGE network (see box) sees parts of North America, Europe and southern Australia", explains Sunyoung Park. "There are large swathes of the world, for which we have 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 Ray Weiss, a geochemist at Scripps Institution of Oceanography at the University of California San Diego and co-author of the study.
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. Whilst this new study cannot determine which industry or industries are responsible, it does provide very strong evidence that substantial new emissions of CFC-11 have occurred from China. "It is almost certain that these CFC-11 emissions, which have been located in Eastern China, are violating the Montreal Protocol, which forbids emissive usage of this substance", says Empa researcher Stefan Reimann. "The most likely process is the emission during foam blowing, during which a considerable part of the substance does not remain in the foam but immediately escapes to the atmosphere", he adds. Since 2010, CFC-11 has been banned worldwide to be used in foam blowing by the Montreal Protocol.
To detect further emissions of forbidden gases the Empa researcher suggests strengthening the global measurement network at regional and local scales targeting all industrialized areas of the world. "Such a network will not only be highly valuable for detecting forbidden ozone-depleting gases, such as CFC-11; it could also be used for monitoring reported inventories of greenhouse gas emissions", Reimann says. In fact, the World Meteorological Organization (WMO) is currently endorsing the Integrated Global Greenhouse Gas Information System (IG3IS). This initiative and similar actions will build additional trust between signatory countries of the Paris Agreement to limit emissions of greenhouse gases and their effect on climate change.
The Montreal Protocol is an agreement among countries to protect the Earth’s ozone layer, which shields the planet from UV radiation. It was signed in 1987 and entered into force in 1989. It was ratified by 196 countries and the European Union, making it the first universally ratified treaty in United Nations history. The "Advanced Global Atmospheric Gases Experiment" (AGAGE) was created in 1990, though predecessor programs date back to 1978. A consortium of 11 research centers from around the world makes measurements of more than 50 gases emitted to the atmosphere by human activities that contribute to greenhouse warming of the planet and/or depletion of its ozone layer.