EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A recent slowdown in the decline of CFC-11 concentrations in the upper troposphere

Patrick Sheese1, Kaley Walker1, Chris Boone2, Laura Saunders1, Sandip Dhomse3,4, Wuhu Feng3,5, and Martyn Chipperfield3,5
Patrick Sheese et al.
  • 1Department of Physics, University of Toronto, Toronto, Canada
  • 2Department of Chemistry, University of Waterloo, Waterloo, Canada
  • 3School of Earth and Environment, University of Leeds, Leeds, UK
  • 4National Centre for Earth Observation, University of Leeds, Leeds, UK
  • 5National Centre for Atmospheric Science, University of Leeds, Leeds, UK

Since 2004, the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) instrument has been measuring concentrations of chlorofluorocarbons (CFCs) in the stratosphere and upper troposphere and is currently the only satellite instrument that measures vertically resolved profiles of CFC‑11. Since CFCs are major ozone depleting substances, monitoring their atmospheric abundances is critical for understanding ozone layer recovery. Recent studies based solely on surface-level measurements have shown strong evidence for new CFC‑11 production, leading to an increase in CFC‑11 emissions over the past decade. In this study, the TOMCAT/SLIMCAT 3-D chemical transport model is used in order to bridge the altitude/geolocation gap between ACE-FTS measurements in the UTLS and surface level measurements. Trends in two different time periods over the ACE-FTS mission, 2004-2012 and 2013-2018, are examined to determine if the recent change in surface level CFC-11 trends is influencing UTLS concentrations. The ACE-FTS measurements show that, below ~10 km, the rate of decrease of global CFC-11 concentrations was slower during 2013-2018 (-1.2 pptv/year) than during 2004-2012 (‑2.0 pptv/year). Similar trends are observed in the model data for the same spatial/temporal regions.

How to cite: Sheese, P., Walker, K., Boone, C., Saunders, L., Dhomse, S., Feng, W., and Chipperfield, M.: A recent slowdown in the decline of CFC-11 concentrations in the upper troposphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11308,, 2020


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