Thirty-five years ago, scientists reported a massive opening in the ozone layer above Antarctica. That breakdown of the ozone layer, life’s protective shield from the Sun’s harmful ultraviolet light, was caused by man-made substances called chlorofluorocarbons or CFCs. In a remarkably quick movement by the world, CFCs were banned via the Montreal Protocol in 1987. Their full phase-out went into effect in 2010. China was one of the many countries to ratify this agreement, but in 2013, scientists discovered that thousands of tons of CFCs started coming from eastern China, due to the illegal production of this ozone-destroying gas. Alarms went off all over the world. If these emissions didn’t stop, the ozone layer’s recovery would be stymied. Fortunately, this article bears good news. The CFC emissions from eastern China appear to have largely stopped, according to a new finding published in the journal Nature this February.

The core of the study’s conclusions relies on fairly straightforward evidence: direct measurements of CFC levels in the air we breathe. There are stations throughout the world that continuously measure a portfolio of gases in our air. Carbon dioxide is a classic one. CFCs are another. There are many types of CFCs, which differ by the combination of carbon and chlorine atoms that compose them. Eastern China had been specifically emitting CFC-11.

To pinpoint whether China’s CFC-11 emissions were declining, the study’s lead author Professor Sunyoung Park and her colleagues snagged records from two atmospheric monitoring stations near eastern China: one on an island in Japan, and the other on an island in South Korea (which were also used to find east China’s emissions in the first place). They found that CFC concentrations in 2018 and 2019 were less enhanced than 2017 levels, suggesting decreased emissions. They also used atmospheric circulation simulations to roughly tie that decline to eastern China. Finally, by tracking other chemicals that are byproducts of CFC-11 production, they could confirm that the decline likely means that whoever was producing the banned substance in China has stopped. Park and her colleagues found that annual emissions of CFCs from the Chinese region dropped by a little over one thousand tons in 2019, and the emissions are back to levels seen around 2010 before the detected spike in production. The reduction in China’s recent emissions has cut global CFC emissions roughly in half, with the remaining emissions likely from the leaking of abandoned CFC reserves across the world.

The effects are seen across the world. An accompanying study, led by atmospheric chemist Stephen Montzka and published in Nature on the same day, shows that global CFC-11 concentrations are dropping faster in 2018 and 2019 compared to trends in 2013-2017. The rogue emissions in China likely would have continued, if not for the efforts of the atmospheric scientists who discovered them and notified the world.

Sunyoung Park is an atmospheric science professor at Kyungpook National University in South Korea. Stephen Montzka is a research scientist at the U.S. National Oceanic and Atmospheric Administration Global Monitoring Laboratory.

Managing Correspondent: Jordan Wilkerson

Original Science Articles: 1.A decline in global CFC-11 emissions during 2018-2019

2. A decline in emissions of CFC-11 and related chemicals from eastern China

Image Credit: NASA’s Marshall Space Flight Center

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