Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings
We perform a formal attribution study of upper- and lower-stratospheric ozone changes using observations together with simulations from the Whole Atmosphere Community Climate Model. Historical model simulations were used to estimate the zonal-mean response patterns ("fingerprints") to comb...
| Main Authors: | , , , , |
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| Format: | Article |
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Copernicus Publications
2018
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| Online Access: | http://hdl.handle.net/1721.1/115415 https://orcid.org/0000-0003-0740-0528 https://orcid.org/0000-0002-2020-7581 |
| _version_ | 1826194629558534144 |
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| author | Santer, Benajmin D. Kinnison, Douglas E. Mills, Michael J. Bandoro, Justin Solomon, Susan |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Santer, Benajmin D. Kinnison, Douglas E. Mills, Michael J. Bandoro, Justin Solomon, Susan |
| author_sort | Santer, Benajmin D. |
| collection | MIT |
| description | We perform a formal attribution study of upper- and lower-stratospheric ozone changes using observations together with simulations from the Whole Atmosphere Community Climate Model. Historical model simulations were used to estimate the zonal-mean response patterns ("fingerprints") to combined forcing by ozone-depleting substances (ODSs) and well-mixed greenhouse gases (GHGs), as well as to the individual forcing by each factor. Trends in the similarity between the searched-for fingerprints and homogenized observations of stratospheric ozone were compared to trends in pattern similarity between the fingerprints and the internally and naturally generated variability inferred from long control runs. This yields estimated signal-to-noise (S∕N) ratios for each of the three fingerprints (ODS, GHG, and ODS + GHG). In both the upper stratosphere (defined in this paper as 1 to 10 hPa) and lower stratosphere (40 to 100 hPa), the spatial fingerprints of the ODS + GHG and ODS-only patterns were consistently detectable not only during the era of maximum ozone depletion but also throughout the observational record (1984–2016). We also develop a fingerprint attribution method to account for forcings whose time evolutions are markedly nonlinear over the observational record. When the nonlinearity of the time evolution of the ODS and ODS + GHG signals is accounted for, we find that the S∕N ratios obtained with the stratospheric ODS and ODS + GHG fingerprints are enhanced relative to standard linear trend analysis. Use of the nonlinear signal detection method also reduces the detection time – the estimate of the date at which ODS and GHG impacts on ozone can be formally identified. Furthermore, by explicitly considering nonlinear signal evolution, the complete observational record can be used in the S∕N analysis, without applying piecewise linear regression and introducing arbitrary break points. The GHG-driven fingerprint of ozone changes was not statistically identifiable in either the upper- or lower-stratospheric SWOOSH data, irrespective of the signal detection method used. In the WACCM simulations of future climate change, the GHG signal is statistically identifiable between 2020 and 2030. Our findings demonstrate the importance of continued stratospheric ozone monitoring to improve estimates of the contributions of ODS and GHG forcing to global changes in stratospheric ozone. |
| first_indexed | 2024-09-23T09:59:17Z |
| format | Article |
| id | mit-1721.1/115415 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T09:59:17Z |
| publishDate | 2018 |
| publisher | Copernicus Publications |
| record_format | dspace |
| spelling | mit-1721.1/1154152022-09-26T15:00:46Z Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings Santer, Benajmin D. Kinnison, Douglas E. Mills, Michael J. Bandoro, Justin Solomon, Susan Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Bandoro, Justin Solomon, Susan We perform a formal attribution study of upper- and lower-stratospheric ozone changes using observations together with simulations from the Whole Atmosphere Community Climate Model. Historical model simulations were used to estimate the zonal-mean response patterns ("fingerprints") to combined forcing by ozone-depleting substances (ODSs) and well-mixed greenhouse gases (GHGs), as well as to the individual forcing by each factor. Trends in the similarity between the searched-for fingerprints and homogenized observations of stratospheric ozone were compared to trends in pattern similarity between the fingerprints and the internally and naturally generated variability inferred from long control runs. This yields estimated signal-to-noise (S∕N) ratios for each of the three fingerprints (ODS, GHG, and ODS + GHG). In both the upper stratosphere (defined in this paper as 1 to 10 hPa) and lower stratosphere (40 to 100 hPa), the spatial fingerprints of the ODS + GHG and ODS-only patterns were consistently detectable not only during the era of maximum ozone depletion but also throughout the observational record (1984–2016). We also develop a fingerprint attribution method to account for forcings whose time evolutions are markedly nonlinear over the observational record. When the nonlinearity of the time evolution of the ODS and ODS + GHG signals is accounted for, we find that the S∕N ratios obtained with the stratospheric ODS and ODS + GHG fingerprints are enhanced relative to standard linear trend analysis. Use of the nonlinear signal detection method also reduces the detection time – the estimate of the date at which ODS and GHG impacts on ozone can be formally identified. Furthermore, by explicitly considering nonlinear signal evolution, the complete observational record can be used in the S∕N analysis, without applying piecewise linear regression and introducing arbitrary break points. The GHG-driven fingerprint of ozone changes was not statistically identifiable in either the upper- or lower-stratospheric SWOOSH data, irrespective of the signal detection method used. In the WACCM simulations of future climate change, the GHG signal is statistically identifiable between 2020 and 2030. Our findings demonstrate the importance of continued stratospheric ozone monitoring to improve estimates of the contributions of ODS and GHG forcing to global changes in stratospheric ozone. 2018-05-16T19:23:29Z 2018-05-16T19:23:29Z 2018-01 2017-11 2018-05-04T17:28:20Z Article http://purl.org/eprint/type/JournalArticle 1680-7375 1680-7367 http://hdl.handle.net/1721.1/115415 Bandoro, Justin et al. “Detectability of the Impacts of Ozone Depleting Substances and Greenhouse Gases Upon Stratospheric Ozone Accounting for Nonlinearities in Historical Forcings.” Atmospheric Chemistry and Physics Discussions (July 2017): 1–42 © 2018 Author(s) https://orcid.org/0000-0003-0740-0528 https://orcid.org/0000-0002-2020-7581 http://dx.doi.org/10.5194/ACP-2017-585 Atmospheric Chemistry and Physics Discussions Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/ application/pdf Copernicus Publications Copernicus Publications |
| spellingShingle | Santer, Benajmin D. Kinnison, Douglas E. Mills, Michael J. Bandoro, Justin Solomon, Susan Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings |
| title | Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings |
| title_full | Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings |
| title_fullStr | Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings |
| title_full_unstemmed | Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings |
| title_short | Detectability of the Impacts of Ozone Depleting Substances andGreenhouse Gases upon Stratospheric Ozone Accounting forNonlinearities in Historical Forcings |
| title_sort | detectability of the impacts of ozone depleting substances andgreenhouse gases upon stratospheric ozone accounting fornonlinearities in historical forcings |
| url | http://hdl.handle.net/1721.1/115415 https://orcid.org/0000-0003-0740-0528 https://orcid.org/0000-0002-2020-7581 |
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