the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Oct 2025
Observationally-derived Fractional Release Factors, Ozone Depletion Potentials, and Stratospheric Lifetimes of Four Long-Lived CFCs: CFC-13 (CClF3), CFC-114 (C2Cl2F4), CFC-114a (CF3CCl2F), and CFC-115 (C2ClF5)
Abstract. The longer an Ozone Depleting Substance (ODS) remains in the stratosphere, the longer it will be available for the process of ozone depletion. We present improved policy-relevant parameters: Fractional Release Factors (FRFs), Ozone Depletion Potentials (ODPs), and stratospheric lifetimes, for four understudied long-lived chlorofluorocarbons (CFCs): CFC-13 (CClF3), CFC-114 (CClF2CCClF2), CFC-114a (CCl2FCF3), and CFC-115 (C2ClF5). Previous estimates for the stratospheric lifetimes of these compounds were derived using model and laboratory-based kinetic studies. This study instead uses stratospheric observational data, and correlations between FRFs and lifetimes, to semi-empirically and independently determine the steady-state stratospheric lifetimes of these compounds.
Our newly derived stratospheric lifetime estimates are 315 (287–331) yr for CFC-13 (300+ years shorter than previous estimates), 190 (176–201) yr for CFC-114 (1 year shorter than previous estimates), 81 (7687) yr for CFC-114a (25.7 years shorter), and 369 (328–435) yr for CFC-115 (295 years shorter). For CFC-13 and CFC-115 this is outside the uncertainty ranges of previously published estimates. This suggests that these two compounds may have had greater emissions than previously thought, in order to account for their abundance. We calculated FRFs and ODSs for the four CFCs of interest: CFC-13 (FRF = 0.07, ODP = 0.4), CFC-114 (FRF = 0.12, ODP = 0.5), CFC-114a (FRF = 0.31, ODP = 0.52), and CFC-115 (FRF = 0.06, ODP = 0.27). Providing new and updated lifetimes, FRFs and ODPs for these compounds, will help improve future estimates of their tropospheric emissions and their potential resulting damage to the stratospheric ozone layer.
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Status: open (until 27 Nov 2025)
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RC1: 'Comment on egusphere-2025-4941', Anonymous Referee #1, 04 Nov 2025
reply
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AC1: 'Reply on RC1', Elinor Tuffnell, 05 Nov 2025
reply
RC “This manuscript presents new estimates for the stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials (ODPs) for CFC-13, CFC-114, CFC-114a and CFC-115. The new estimates are based on stratospheric measurements rather than a combination of modelling and laboratory studies. They thus provide valuable complementary evidence regarding the current measurements and would be of direct interest for use in the Scientific Assessment of Ozone Depletion.
The analysis is good and the uncertainties are described so that it is certainly publishable material.”
Author Reply:
We thank the reviewer for this positive assessment of our work and its relevance to the Scientific Assessment of Ozone Depletion.
RC: “However the structure of the manuscript makes it hard to read and understand. More thought on how the material is ordered and presented would make the paper stronger as well as more accessible. I do not think that more analysis is required.
The main problem is that there is no description on how the manuscript is structured as part of the introduction. Rather, it ends with a somewhat technical discussion of the difficulties of getting separate measurements of the two isomers CFC-114 and CFC-114a. Previous estimates of lifetimes, ODPs and FRFs are presented in Table 1. This could be presented more as a state of knowledge, a description of what new information this manuscript will provide (perhaps the current discussion section) and end with a summary of the sections that will follow. A clear discussion of the broader significance of the work is also lacking. Why should I care about FLFs, etc?
The manuscript would also benefit from similar ‘heads up’ material at the beginning of each main section (Methods, Results, etc.).”
Author reply:
We thank the reviewer for these helpful suggestions to improve the structure and readability of the manuscript. We have added the suggested ‘heads-up’ material to better sign-post the content for the reader.
RC: “It is important to make clear the distinction between what information or data already exists in the literature and what new information is presented. For example, it was not clear to me on first reading that all the material in Table 1 is published and that it represents the current knowledge on which this manuscript builds. It is important that this is made clear in the accompanying text and in the caption.”
Author reply:
Thank you for catching this oversight, we have now added the necessary clarification to the text and caption.
RC: “The Discussion and Conclusion sections are both on the short side. Most of the material in the Discussion section could go in the Introduction as it is not really discussing the implications of the results. Can the paper do without a Discussion section by bolstering the material about implications in the Results section and ending with a stronger summary? “
Author reply:
There was a lively discussion amongst the co-authors of this paper regarding the discussion section of the manuscript; what should go there, what should be removed, and whether a discussion section was necessary in this case. In light of this and your comment, some restructuring along the lines you suggest, has been completed.
Citation: https://doi.org/10.5194/egusphere-2025-4941-AC1
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AC1: 'Reply on RC1', Elinor Tuffnell, 05 Nov 2025
reply
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This manuscript presents new estimates for the stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials (ODPs) for CFC-13, CFC-114, CFC-114a and CFC-115. The new estimates are based on stratospheric measurements rather than a combination of modelling and laboratory studies. They thus provide valuable complementary evidence regarding the current measurements and would be of direct interest for use in the Scientific Assessment of Ozone Depletion.
The analysis is good and the uncertainties are described so that it is certainly publishable material. However the structure of the manuscript makes it hard to read and understand. More thought on how the material is ordered and presented would make the paper stronger as well as more accessible. I do not think that more analysis is required.
The main problem is that there is no description on how the manuscript is structured as part of the introduction. Rather, it ends with a somewhat technical discussion of the difficulties of getting separate measurements of the two isomers CFC-114 and CFC-114a. Previous estimates of lifetimes, ODPs and FRFs are presented in Table 1. This could be presented more as a state of knowledge, a description of what new information this manuscript will provide (perhaps the current discussion section) and end with a summary of the sections that will follow. A clear discussion of the broader significance of the work is also lacking. Why should I care about FLFs, etc?
The manuscript would also benefit from similar ‘heads up’ material at the beginning of each main section (Methods, Results, etc.).
It is important to make clear the distinction between what information or data already exists in the literature and what new information is presented. For example, it was not clear to me on first reading that all the material in Table 1 is published and that it represents the current knowledge on which this manuscript builds. It is important that this is made clear in the accompanying text and in the caption.
The Discussion and Conclusion sections are both on the short side. Most of the material in the Discussion section could go in the Introduction as it is not really discussing the implications of the results. Can the paper do without a Discussion section by bolstering the material about implications in the Results section and ending with a stronger summary?
Minor comments
50/51 ‘…respectively, while the…’
Tab 1 caption Something wrong with formatting. More importantly, I think there should be a clear statement that these values are published elsewhere.
Introduction I don’t think it is enough to
174/175 something gone wrong here – ‘..which is not a mathematical..’?
176 ‘..showed that the atmospheric ratio..’
208 ‘independent’
213 ‘dissociated’ more common
232 ‘..because of the non-linearities…’
243 ‘estimate’ rather than ‘prediction’
331 State what the Lickley simulation period is
364 How will the new metrics help understand the sources of these compounds?
365on This is the first time that this material has been presented. It should also be covered in the Introduction and the Discussion (if the authors decide to keep one). It is the type of broader discussion which I find lacking in the rest of the paper.
General Check correct format for references with date in brackets - ‘Laube et al, (2016)’. Is the comma needed?