The Impact of Ozone-Depleting Substances on Tropical Upwelling, as Revealed by the Absence of Lower-Stratospheric Cooling since the Late 1990s

Polvani, Lorenzo M.; Wang, Lei; Aquila, Valentina; Waugh, Darryn W.

doi:10.1175/jcli-d-16-0532.1

Cited by 44 publications

(63 citation statements)

References 30 publications

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“…The role of ozone depletion in driving a decrease in AOA, shown by most of the models analysed here, has been found before (e.g. Polvani et al, 2017).…”

Section: Sensitivity Of Ozone To Ghgssupporting

confidence: 79%

Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI-1 simulations

et al. 2018

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Abstract. Ozone fields simulated for the first phase of the Chemistry-Climate Model Initiative (CCMI-1) will be used as forcing data in the 6th Coupled Model Intercomparison Project. Here we assess, using reference and sensitivity simulations produced for CCMI-1, the suitability of CCMI-1 model results for this process, investigating the degree of consistency amongst models regarding their responses to variations in individual forcings. We consider the influences of methane, nitrous oxide, a combination of chlorinated or brominated ozone-depleting substances, and a combination of carbon dioxide and other greenhouse gases. We find varying degrees of consistency in the models' responses in ozone to these individual forcings, including some considerable disagreement. In particular, the response of total-column ozone to these forcings is less consistent across the multi-model ensemble than profile comparisons. We analyse how stratospheric age of air, a commonly used diagnostic of stratospheric transport, responds to the forcings. For this diagnostic we find some salient differences in model behaviour, which may explain some of the findings for ozone. The findings imply that the ozone fields derived from CCMI-1 are subject to considerable uncertainties regarding the impacts of these anthropogenic forcings. We offer some thoughts on how to best approach the problem of generating a consensus ozone database from a multi-model ensemble such as CCMI-1.

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“…The role of ozone depletion in driving a decrease in AOA, shown by most of the models analysed here, has been found before (e.g. Polvani et al, 2017).…”

Section: Sensitivity Of Ozone To Ghgssupporting

confidence: 79%

Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI-1 simulations

et al. 2018

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“…Various observation‐based studies report that despite the leveling of ozone trends [ Harris et al ., ], the stratosphere continued to cool in the 21st century and this change is generally associated with the increase of greenhouse gases [ Stolarski et al , ; Seidel et al , ]. However, the cooling of the middle and upper stratosphere has slowed down after 1997 [ Randel et al , ], whereas the trends in the lower stratosphere have become insignificantly small [ Seidel et al , ] most likely due to reversal of the trends in ozone depleting substances [ Polvani et al , ]. Our analysis of two independent CDRs suggests that the middle stratosphere (AMSU channels 10–12) has cooled in the time period 2002–2016 at an average rate of −0.14 ± 0.12 to −0.36 ± 0.14 K/decade, whereas the statistically significant change in the LS temperature is restricted to certain seasons and latitudes.…”

Section: Discussion and Summarymentioning

confidence: 99%

Postmillennium changes in stratospheric temperature consistently resolved by GPS radio occultation and AMSU observations

Khaykin

Funatsu

Hauchecorne

et al. 2017

Geophysical Research Letters

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Temperature changes in the lower and middle stratosphere during 2001–2016 are evaluated using measurements from GPS Radio Occultation (RO) and Advanced Microwave Sounding Unit (AMSU) aboard the Aqua satellite. After downsampling of GPS‐RO profiles according to the AMSU weighting functions, the spatially and seasonally resolved trends from the two data sets are in excellent agreement. The observations indicate that the middle stratosphere has cooled in the time period 2002–2016 at an average rate of −0.14 ± 0.12 to −0.36 ± 0.14 K/decade, while no significant change was found in the lower stratosphere. The meridionally and vertically resolved trends from high‐resolution GPS‐RO data exhibit a marked interhemispheric asymmetry and highlight a distinct boundary between tropospheric and stratospheric temperature change regimes matching the tropical thermal tropopause. The seasonal pattern of trend reveals significant opposite‐sign structures at high and low latitudes, providing indication of seasonally varying change in stratospheric circulation.

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“…Previous studies have found that a strengthening of the BDC results in lower ozone concentrations in the tropical lower stratosphere and an increase in concentrations in the extratropics, and modeling studies have suggested that increases in GHG concentrations lead to a strengthening of the BDC Fleming et al, 2011;Garcia et al, 2008;Gillett et al, 2011;Oman et al, 2010). In contrast, a recent study by Polvani et al (2017) found that trends in ODSs, and not in GHG levels, have been the primary driver of trends in tropical upwelling. This complicates the problem of attributing ozone changes that are primarily BDC-related since both GHG and ODS forcing may be implicated in driving changes in the BDC.…”

Section: Introductionmentioning

confidence: 94%

Detectability of the impacts of ozone-depleting substances and greenhouse gases upon stratospheric ozone accounting for nonlinearities in historical forcings

et al. 2018

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Abstract. We perform a formal attribution study of upperand 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 . 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.

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The Impact of Ozone-Depleting Substances on Tropical Upwelling, as Revealed by the Absence of Lower-Stratospheric Cooling since the Late 1990s

Cited by 44 publications

References 30 publications

Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI-1 simulations

Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI-1 simulations

Postmillennium changes in stratospheric temperature consistently resolved by GPS radio occultation and AMSU observations

Detectability of the impacts of ozone-depleting substances and greenhouse gases upon stratospheric ozone accounting for nonlinearities in historical forcings

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