Probabilistic quantification of chlorofluorocarbons banked in equipment and their contributions to emissions: results from a Bayesian assessment
Abstract
Chlorofluorocarbon (CFC) banks in equipment such as air conditioning and foams worldwide continue to emit ozone depleting substances after global production stops, so understanding banks and their emissions is critical for evaluating the success of the Montreal Protocol. Recent reports of unexpectedly large emissions of CFC-11 heighten the need to improve the understanding of the size of the banks and quantify their contributions to current releases. Past studies have assessed banks using a bottom-up method that inventories sales and equipment, and a top-down method based on emissions inferred from concentrations along with reported production. Large differences have been reported between these two approaches. Here we develop a new Bayesian probabilistic approach that incorporates a broader range of constraints than either of the earlier approaches individually. We show how the three approaches taken together provide a fuller understanding of key factors and uncertainties, reconciling some long-standing discrepancies. We apply the Bayesian approach to CFC-11, 12, and 113 to evaluate bank sizes and emission rates and their consistency with emissions inferred from observations. The implied banks of CFC-11 and CFC-12 are much larger than suggested in recent international scientific assessments. Bank emissions account for much of the CFC-11 and 12 emissions inferred from global concentration data, with the important exception of increases in CFC-11 emission reported after 2013. This finding is consistent with work by others suggesting recent unreported production of CFC-11. Current banks could delay polar ozone hole recovery by about six years. Inferred emissions of CFC-113 are subject to large uncertainty, but are much too large to explain from banks, raising questions about sources of this gas as well.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A33T2897L
- 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