the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Apr 2023
Atmospheric impacts of chlorinated very short-lived substances over the recent past – Part 2: Impacts on ozone
Ryan Hossaini
Martyn P. Chipperfield
Abstract. Depletion of the stratospheric ozone layer remains an ongoing environmental issue, with increasing stratospheric chlorine from Very Short-Lived Substances (VSLS) recently emerging as a potential but uncertain threat to its future recovery. Here the impact of chlorinated VSLS on past ozone is quantified, for the first time. using the UM-UKCA chemistry-climate model. Model simulations show that between 2010–2019 Cl-VSLS reduced total column ozone by, on average, ~2–3 DU in the springtime high latitudes and by ~0.5–1 DU in the tropics, with up to 5–6 DU monthly and zonal mean Arctic ozone reductions simulated in the springs of 2011, 2014 and 2020. Cl-VSLS impacts during the recent cold Arctic winter of 2019/2020 are also quantified to have resulted in up to 6 % reduction of lower stratospheric ozone and ~6 DU ozone in total by the end of March. On the other hand, the simulations show that the inclusion of Cl-VSLS does not considerably modify the magnitude of the diagnosed recent ozone trends. We also estimate the ozone depletion potential of dichloromethane, the most abundant Cl-VSLS, at 0.0107. Our results thus illustrate a so-far modest but nonetheless non-negligible role of Cl-VSLS in contributing to stratospheric ozone budget over the recent past that if to continue could offset some of the gains achieved by the Montreal Protocol.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2218 KB) - Metadata XML
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Supplement
(1108 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Ewa M. Bednarz et al.
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-496', Rafael Pedro Fernandez, 30 May 2023
Please see my comments in the attached file.
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AC1: 'Reply on RC1', Ewa Bednarz, 30 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-496/egusphere-2023-496-AC1-supplement.pdf
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AC1: 'Reply on RC1', Ewa Bednarz, 30 Aug 2023
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RC2: 'Comment on egusphere-2023-496', Anonymous Referee #2, 31 May 2023
Authors: Ewa M. Bednarz, Ryan Hossaini, Martyn P. Chipperfield
Title: Atmospheric impacts of chlorinated very short-lived substances over the recent past – Part 2: Impact on ozone
Scientific Significance: The scientific questions addressed in this paper are appropriate for ACP. This work addresses for the first time the recent (2010-2019) impact of chlorinated Very Short-Lived Substances (VSLS) on ozone. The authors state they found “modest and non-negligible role of Cl-VSLS” to the stratospheric ozone budget. They also emphasized that continued Cl-VSLS emissions “could offset some gains by the Montreal Protocol”. They were the second group to “estimated” the ODP of dichloromethane. I highly recommend this work for publication. Below are a few comments that may add to the impact of this work.
Scientific Quality: This work is of high scientific quality. The authors use a state-of-the-art CCM (UM-UKCA) nudged to ERA-Interim and ERA-5 meteorology. They also show results from an ensemble mean from the UM-UKCA CCM. The Cl-VSLS chemistry is also represented in a detailed manner.
Presentation Quality: Generally, in good shape. However, I would increase the font size of Figures 3 and 4.
Specific Comment.
Abstract, line 16. Typo “for the first time. Using the”
Abstract, lines 19. I found it confusing in the abstract when the authors highlight the 2011, 2014, and 2020 years and state that up to 5-6DU monthly and zonal mean Arctic ozone reductions are simulated. Then in line 20 they highlight year 2020 with “~6DU ozone in total by the end of March”. They state 2020 was a recent cold winter. I would suggest reworking sentences here being more specific why you picked 2011 and 2014 relative to 2020?
Abstract, lines 21-23. The authors state that Cl-VSLS “do not considerably modify the magnitude of the recent ozone trends”. Please be more specific, is this is tropical, polar, global, everywhere, etc? Also, why would one expect the trend to be significant over a short period (i.e., 2010-2019), especially in the Arctic? I would suggest adding more detail in the abstract if you want to mention ozone trend results.
Abstract, line 22. The ODP of Cl-VSLS is quantified. The paper mentioned this was the second ODP derivation. What do you mean that it was “estimated” – is that a typical way to discuss the derivation of an ODP? This topic deserves a couple sentences to clarify why you feel it is important to put this discussion in the abstract. See my comment on lines146-147 below.
Lines 46-49. “We showed that the contribution from these Cl-VSLS to stratospheric chlorine had increased from 70 ppt Cl in 2000 to 130 ppt Cl in 2019, i.e. almost doubling over the first two decades of the 21st century.” One could make an argument that this information was taken from Bednarz et al., 2022, Part 1 – but it would be nice have this information brought to the abstract level when summarizing the trend results.
Lines 53-54. In addition to Chipperfield et al. 2018, Wargan et al., 2018, and Orbe et al., 2020, Stone et al. also came to this conclusion (that dynamical variability is driving the O3 trend) using a chemistry climate model similar to UM-UKCA. Stone, K. A., Solomon, S., & Kinnison, D. E. (2018). On the identification of ozone recovery. Geophysical Research Letters, 45. https://doi.org/10.1029/2018GL077955.
Line 85-86. “Furthermore, no significant Cl- VSLS-induced Arctic ozone loss can be diagnosed from the model ERA-Interim nudged monthly and zonal mean data for the spring 2011; this might be related to the small size of the polar vortex in that year and thus difficulties in reproducing its dynamical properties in a nudged model setup.” This sentence is a bit disconcerting in that the reader is meant to figure why there are difference in the choice of reanalysis products. The main question in my mind is why even show ERA-Interim in this study? Presumably ERA-5 is the best ECMWF product to look at nudged ozone trends?
Figure 3 and 4. Please increase the font size of the titles and x-axis.
Lines 114-118. This is a very interesting discussion, i.e., “the impact of curbing emissions of long-lived ODSs achieved by the Montreal Protocol was estimated to reduce the magnitude of the Arctic ozone depletion in that spring by up to ~35 DU in mid-March compared to peak halogen levels in early 2000 (Feng et al., 2021).” It might be useful to bring this comparison of curbing the emissions of long-lived ODSs achieved by the Montreal Protocol up to the abstract level (i.e., versus 6 DU from Cl-VSLS)?
Lines 146-147. “The calculated stratospheric ODP of 0.0102 (confidence interval of 0.0062-0.0163) is similar to the whole atmosphere ODP metric, implying that CH2Cl2 has a relatively small effect on ozone below the tropopause in UM-UKCA.” This is an interesting result. Is there anything more you can say about this result? Is this due to where CH2Cl2 is emitted (e.g., China)?
Citation: https://doi.org/10.5194/egusphere-2023-496-RC2 -
AC2: 'Reply on RC2', Ewa Bednarz, 30 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-496/egusphere-2023-496-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Ewa Bednarz, 30 Aug 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-496', Rafael Pedro Fernandez, 30 May 2023
Please see my comments in the attached file.
-
AC1: 'Reply on RC1', Ewa Bednarz, 30 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-496/egusphere-2023-496-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Ewa Bednarz, 30 Aug 2023
-
RC2: 'Comment on egusphere-2023-496', Anonymous Referee #2, 31 May 2023
Authors: Ewa M. Bednarz, Ryan Hossaini, Martyn P. Chipperfield
Title: Atmospheric impacts of chlorinated very short-lived substances over the recent past – Part 2: Impact on ozone
Scientific Significance: The scientific questions addressed in this paper are appropriate for ACP. This work addresses for the first time the recent (2010-2019) impact of chlorinated Very Short-Lived Substances (VSLS) on ozone. The authors state they found “modest and non-negligible role of Cl-VSLS” to the stratospheric ozone budget. They also emphasized that continued Cl-VSLS emissions “could offset some gains by the Montreal Protocol”. They were the second group to “estimated” the ODP of dichloromethane. I highly recommend this work for publication. Below are a few comments that may add to the impact of this work.
Scientific Quality: This work is of high scientific quality. The authors use a state-of-the-art CCM (UM-UKCA) nudged to ERA-Interim and ERA-5 meteorology. They also show results from an ensemble mean from the UM-UKCA CCM. The Cl-VSLS chemistry is also represented in a detailed manner.
Presentation Quality: Generally, in good shape. However, I would increase the font size of Figures 3 and 4.
Specific Comment.
Abstract, line 16. Typo “for the first time. Using the”
Abstract, lines 19. I found it confusing in the abstract when the authors highlight the 2011, 2014, and 2020 years and state that up to 5-6DU monthly and zonal mean Arctic ozone reductions are simulated. Then in line 20 they highlight year 2020 with “~6DU ozone in total by the end of March”. They state 2020 was a recent cold winter. I would suggest reworking sentences here being more specific why you picked 2011 and 2014 relative to 2020?
Abstract, lines 21-23. The authors state that Cl-VSLS “do not considerably modify the magnitude of the recent ozone trends”. Please be more specific, is this is tropical, polar, global, everywhere, etc? Also, why would one expect the trend to be significant over a short period (i.e., 2010-2019), especially in the Arctic? I would suggest adding more detail in the abstract if you want to mention ozone trend results.
Abstract, line 22. The ODP of Cl-VSLS is quantified. The paper mentioned this was the second ODP derivation. What do you mean that it was “estimated” – is that a typical way to discuss the derivation of an ODP? This topic deserves a couple sentences to clarify why you feel it is important to put this discussion in the abstract. See my comment on lines146-147 below.
Lines 46-49. “We showed that the contribution from these Cl-VSLS to stratospheric chlorine had increased from 70 ppt Cl in 2000 to 130 ppt Cl in 2019, i.e. almost doubling over the first two decades of the 21st century.” One could make an argument that this information was taken from Bednarz et al., 2022, Part 1 – but it would be nice have this information brought to the abstract level when summarizing the trend results.
Lines 53-54. In addition to Chipperfield et al. 2018, Wargan et al., 2018, and Orbe et al., 2020, Stone et al. also came to this conclusion (that dynamical variability is driving the O3 trend) using a chemistry climate model similar to UM-UKCA. Stone, K. A., Solomon, S., & Kinnison, D. E. (2018). On the identification of ozone recovery. Geophysical Research Letters, 45. https://doi.org/10.1029/2018GL077955.
Line 85-86. “Furthermore, no significant Cl- VSLS-induced Arctic ozone loss can be diagnosed from the model ERA-Interim nudged monthly and zonal mean data for the spring 2011; this might be related to the small size of the polar vortex in that year and thus difficulties in reproducing its dynamical properties in a nudged model setup.” This sentence is a bit disconcerting in that the reader is meant to figure why there are difference in the choice of reanalysis products. The main question in my mind is why even show ERA-Interim in this study? Presumably ERA-5 is the best ECMWF product to look at nudged ozone trends?
Figure 3 and 4. Please increase the font size of the titles and x-axis.
Lines 114-118. This is a very interesting discussion, i.e., “the impact of curbing emissions of long-lived ODSs achieved by the Montreal Protocol was estimated to reduce the magnitude of the Arctic ozone depletion in that spring by up to ~35 DU in mid-March compared to peak halogen levels in early 2000 (Feng et al., 2021).” It might be useful to bring this comparison of curbing the emissions of long-lived ODSs achieved by the Montreal Protocol up to the abstract level (i.e., versus 6 DU from Cl-VSLS)?
Lines 146-147. “The calculated stratospheric ODP of 0.0102 (confidence interval of 0.0062-0.0163) is similar to the whole atmosphere ODP metric, implying that CH2Cl2 has a relatively small effect on ozone below the tropopause in UM-UKCA.” This is an interesting result. Is there anything more you can say about this result? Is this due to where CH2Cl2 is emitted (e.g., China)?
Citation: https://doi.org/10.5194/egusphere-2023-496-RC2 -
AC2: 'Reply on RC2', Ewa Bednarz, 30 Aug 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-496/egusphere-2023-496-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Ewa Bednarz, 30 Aug 2023
Peer review completion
Journal article(s) based on this preprint
Ewa M. Bednarz et al.
Ewa M. Bednarz et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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