Atmospheric measurements of CFC-11 through most of 2019: Are global CFC-11 emissions back on the decline?
Abstract
Since we announced a renewed increase in global CFC-11 emission in May of 2018 (https:doi.org/10.1038/s41586-018-0106-2), scientists, policymakers, and industry experts worldwide have sought to improve understanding of the underlying causes of this apparent violation of the Montreal Protocol and consider what international-scale policy changes could prevent similar violations in the future. An important additional finding from this study was that some portion of the detected emission increase was attributable to eastern Asia. Perhaps in response to this finding, which a second paper confirmed and refined by indicating in May of 2019 that China was responsible for at least 40 to 60% of the global emission increase (https://doi.org/10.1038/s41586-019-1193-4), China promptly devised a broad-reaching plan to address the issue. Their plan included strengthening enforcement of controls on production, use, and trade of ozone-depleting substances (ODSs), improvements in tracking production, use, and sales of the main precursor chemical (CCl4), and an intention to build systems for measuring ODSs in newly manufactured products and in ambient air throughout China. Here we update our atmospheric measurements from 12 globally distributed sites to understand how the CFC-11 concentration decline has changed since publication of these papers and China's initial mitigation efforts. In response to the question "has the decline rate changed recently," we assess three different, quasi-independent aspects of our measurement results: global and hemispheric mean rates of change, the hemispheric mean concentration difference, and the variability of concentrations in the Pacific Basin. These results provide an initial assessment of early mitigation efforts by China and other countries, although a rapid atmospheric response would be diminished if there has been a substantial increase in the CFC-11 bank owing to use of the newly produced CFC-11 in closed-cell foams.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A33T2900M
- Keywords:
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- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 6699 General or miscellaneous;
- PUBLIC ISSUES