Document Type
Article
Publication Date
2026
DOI
10.1029/2025JD045176
Publication Title
Journal of Geophysical Research: Atmospheres
Volume
131
Issue
5
Pages
e2025JD045176
Abstract
We present atmospheric chlorine inventories over 21 years (2004-2024) and five latitude bands (82-60°N, 60-30°N, 30°N-30°S, 30-60°S, 60-82°S) across altitudes from the surface up to 61 km. These inventories were calculated using the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) version 5.3 retrievals of the volume mixing ratios (VMRs) of 13 chlorine-containing species. Of these, five are product gases: HCl, HOCl, ClONO₂, COClF, COCl₂, and eight are source gases: CCl₄, CH₃Cl, CFC-11 (CCl₃F), CFC-12 ( CCl₂F₂), CFC-113 (CClF₂CCl₂F}), HCFC-22 (CHF₂Cl), HCFC-141b ( C₂H₃Cl₂F), and HCFC-142b (C₂H₃}Cl₂F). Where necessary, ACE-FTS data were supplemented with data from the TOMCAT 3-D chemical transport model, the Aura Microwave Limb Sounder (MLS) instrument, and ground-based measurements from the National Oceanic and Atmospheric Administration (NOAA) and the Advanced Global Atmospheric Gases Experiment (AGAGE). Total chlorine (Cltot) profiles are dominated by source gas contributions in the troposphere and lower stratosphere. At lower altitudes, the primary contributors are chlorofluorocarbons (CFCs), chlorocarbons, and, increasingly in recent years, chlorine-containing very short-lived substances (Cl-VSLS). At higher altitudes, HCl becomes the dominant contributor comprising up to 99% of (Cltot) by 61 km. The relative contribution of individual species to Cltot showed that Cl-VSLS and HCFC-22 have partially slowed the reduction in atmospheric chlorine achieved by the phase-out of CFC production and consumption. Between 2004 and 2024, the global mean (Cltot) time series decreased by 9.56 ± 0.28 ppt/year (0.28 ± 0.01%/year), with values approaching 3.3 ppb in 2024. These findings demonstrate the significant impact of the Montreal Protocol in reducing emissions of substances that are both ozone-depleting and greenhouse gases.
Rights
© 2026 The Authors.
This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited.
Data Availability
Article states: "ACE-FTS version 5.3 retrieval results and ACE-imager extinction profiles are freely available from the ACE web portal: https://databace.scisat.ca/level2/ace_v5.3/display_data.php (ACE-SOC, 2025). Initial registration is required at: https://databace.scisat.ca/l2signup.php. TOMCAT model data, together with the calculated mean VMRs and corresponding uncertainties, are available at https://doi.org/10.5281/zenodo.17612886 (Raymond, 2025). NOAA data was obtained from their GML, publicly available online: https://gml.noaa.gov/dv/data/ (NOAA-GML, 2025), or https://gml.noaa.gov/hats/data.html (NOAA-LOGOS, 2025). Data for NOAA Chlorine Trends was obtained from https://gml.noaa.gov/aftp/data/hats/Total_Cl_Br/, with 2024 data provided by Stephen Montzka. Files for each species were downloaded individually, such as the CFC-11 HATS combined file at https://gml.noaa.gov/aftp/data/hats/cfcs/cfc11/combined/HATS_global_F11.txt (Dutton et al., 2025). The most recent AGAGE observations are available at (AGAGE-data, 2025; Prinn, Weiss, Arduini, Choi, et al., 2024). The data set employed in this study was retrieved from (AGAGE-data, 2024); however, that location is no longer accessible, so (Prinn, Weiss, Arduini, Arnold, et al., 2024) serves as an alternative source for similar AGAGE data. All measurements from AGAGE were obtained in a single tar file."
Original Publication Citation
Raymond, N., Bernath, P., Boone, C., & Chipperfield, M. P. (2026). Twenty-one years of global atmospheric chlorine inventories from Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements. Journal of Geophysical Research: Atmospheres, 131(5), Article e2025JD045176. https://doi.org/10.1029/2025JD045176
ORCID
/0000-0002-1255-396X (Bernath)
Repository Citation
Raymond, N.; Bernath, P.; Boone, C.; and Chipperfield, M. P., "Twenty-One Years of Global Atmospheric Chlorine Inventories from Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) Measurements" (2026). Chemistry & Biochemistry Faculty Publications. 386.
https://digitalcommons.odu.edu/chemistry_fac_pubs/386
Supporting Information S1
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