A decline in global CFC-11 emissions during 2018−2019

Stephen A. Montzka*, Geoffrey S. Dutton, Robert W. Portmann, Martyn P. Chipperfield, Sean Davis, Wuhu Feng, Alistair J. Manning, Eric Ray, Matthew Rigby, Bradley D. Hall, Carolina Siso, J. David Nance, Paul B. Krummel, Jens Mühle, Dickon Young, Simon O'Doherty, Peter K. Salameh, Christina M. Harth, Ronald G. Prinn, Ray F. WeissJames W. Elkins, Helen Walter-Terrinoni, Christina Theodoridi

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

59 Citations (Scopus)
65 Downloads (Pure)


The atmospheric concentration of trichlorofluoromethane (CFC-11) has been in decline since the production of ozone-depleting substances was phased out under the Montreal Protocol1,2. Since 2013, the concentration decline of CFC-11 slowed unexpectedly owing to increasing emissions, probably from unreported production, which, if sustained, would delay the recovery of the stratospheric ozone layer1,2,3,4,5,6,7,8,9,10,11,12. Here we report an accelerated decline in the global mean CFC-11 concentration during 2019 and 2020, derived from atmospheric concentration measurements at remote sites around the world. We find that global CFC-11 emissions decreased by 18 ± 6 gigagrams per year (26 ± 9 per cent; one standard deviation) from 2018 to 2019, to a 2019 value (52 ± 10 gigagrams per year) that is similar to the 2008−2012 mean. The decline in global emissions suggests a substantial decrease in unreported CFC-11 production. If the sharp decline in unexpected global emissions and unreported production is sustained, any associated future ozone depletion is likely to be limited, despite an increase in the CFC-11 bank (the amount of CFC-11 produced, but not yet emitted) by 90 to 725 gigagrams by the beginning of 2020.
Original languageEnglish
Pages (from-to)428-432
Number of pages5
Issue number7846
Early online date10 Feb 2021
Publication statusPublished - 18 Feb 2021

Bibliographical note

Funding Information:
maintenance, and troubleshooting we are grateful to station personnel from NOAA and AGAGE. The operation of AGAGE stations was supported by the National Aeronautics and Space Administration (NASA, USA) (grants NAG5-12669, NNX07AE89G, NNX11AF17G and NNX16AC98G to the Massachusetts Institute of Technology; grants NAG5-4023, NNX07AE87G, NNX07AF09G, NNX11AF15G, NNX11AF16G, NNX16AC97G and NNX16AC96G to the Scripps Institution of Oceanography), the Department for Business, Energy & Industrial Strategy (BEIS, UK), the National Oceanic and Atmospheric Administration (NOAA, USA), and the Commonwealth Scientific and Industrial Research Organisation (CSIRO, Australia), Bureau of Meteorology (BoM, Australia). We also are indebted to personnel from cooperative institutions involved with flasks sampling in Australia (BoM/CSIRO), Canada (Environment and Climate Change Canada), Ireland (University of Bristol), Israel (Weizmann Inst.), Republic of Korea (Korean Meteorological Administration), the USA (University of Colorado, Harvard University, University of Wisconsin, Scripps Institution of Oceanography), and for logistics support from the US NSF at Summit Greenland, Palmer Antarctica, and South Pole Antarctica Stations. We thank R. Wang for algorithms for extracting background mole fractions from those influenced by recent emission input, and for calculating correlations between CFC-11 data from the American Samoa and Barbados stations and ENSO, and M. Lickley for discussions and results from Bayesian banks analysis. The Community Earth System Modeling project is supported by the National Science Foundation and the Office of Science (BER) of the US Department of Energy. We acknowledge the NOAA Research and Development High Performance Computing Program for computing and storage resources. The TOMCAT modelling work was supported by the NERC SISLAC project (NE/R001782/1) and simulations were performed on the UK Archer and Leeds Arc HPC machines. This work was funded in part by the NOAA Climate Program Office’s AC4 programme. Support was also received from The Met Office Hadley Centre Climate Programme, funded by the UK’s Department for Business, Energy and Industrial Strategy and Department for Environment, Food and Rural Affairs.

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature Limited.


  • Atmospheric chemistry
  • Atmospheric dynamics
  • Environmental impact


Dive into the research topics of 'A decline in global CFC-11 emissions during 2018−2019'. Together they form a unique fingerprint.

Cite this