On the attribution of stratospheric ozone and temperature changes to changes in ozone-depleting substances and well-mixed greenhouse gases

Abstract. The vertical profile of global-mean stratospheric temperature changes has traditionally represented an important diagnostic for the attribution of the cooling effects of stratospheric ozone depletion and CO2 increases. However, CO2-induced cooling alters ozone abundance by perturbing ozone chemistry, thereby coupling the stratospheric ozone-temperature response to changes in CO2 and ozone-depleting substances (ODSs). Here we untangle the ozone-temperature coupling and show that the attribution of global-mean stratospheric temperature changes to CO2 and ODS changes (which are the true anthropogenic forcing agents) can be quite different from the traditional attribution to CO2 and ozone changes. The significance of these effects is quantified empirically using simulations from a three-dimensional chemistry-climate model. The results confirm the essential validity of the traditional approach in attributing changes during the past period of rapid ODS increases, although we find that about 10% of the upper stratospheric ozone decrease from ODS increases over the period 1975–1995 was offset by the increase in CO2, and the CO2-induced cooling in the upper stratosphere has been somewhat overestimated. When considering ozone recovery, however, the ozone-temperature coupling is a first-order effect; fully 2/5 of the upper stratospheric ozone increase projected to occur from 2010–2040 is attributable to CO2 increases. Thus, it has now become necessary to base attribution of global-mean stratospheric temperature changes on CO2 and ODS changes rather than on CO2 and ozone changes.

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On the attribution of stratospheric ozone and temperature changes to changes in ozone-depleting substances and well-mixed greenhouse gases

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-1435-2008 ◽

2008 ◽

Vol 8 (5) ◽

pp. 1435-1444 ◽

Cited By ~ 49

Author(s):

T. G. Shepherd ◽

A. I. Jonsson

Keyword(s):

Climate Model ◽

Traditional Approach ◽

Stratospheric Ozone ◽

Three Dimensional ◽

Order Effect ◽

Temperature Changes ◽

Stratospheric Temperature ◽

Cooling Effects ◽

Ozone Depleting Substances ◽

Global Mean

Abstract. The vertical profile of global-mean stratospheric temperature changes has traditionally represented an important diagnostic for the attribution of the cooling effects of stratospheric ozone depletion and CO2 increases. However, CO2-induced cooling alters ozone abundance by perturbing ozone chemistry, thereby coupling the stratospheric ozone and temperature responses to changes in CO2 and ozone-depleting substances (ODSs). Here we untangle the ozone-temperature coupling and show that the attribution of global-mean stratospheric temperature changes to CO2 and ODS changes (which are the true anthropogenic forcing agents) can be quite different from the traditional attribution to CO2 and ozone changes. The significance of these effects is quantified empirically using simulations from a three-dimensional chemistry-climate model. The results confirm the essential validity of the traditional approach in attributing changes during the past period of rapid ODS increases, although we find that about 10% of the upper stratospheric ozone decrease from ODS increases over the period 1975–1995 was offset by the increase in CO2, and the CO2-induced cooling in the upper stratosphere has been somewhat overestimated. When considering ozone recovery, however, the ozone-temperature coupling is a first-order effect; fully 2/5 of the upper stratospheric ozone increase projected to occur from 2010–2040 is attributable to CO2 increases. Thus, it has now become necessary to base attribution of global-mean stratospheric temperature changes on CO2 and ODS changes rather than on CO2 and ozone changes.

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The representation of solar cycle signals in stratospheric ozone. Part II: Analysis of global models

10.5194/acp-2017-477 ◽

2017 ◽

Cited By ~ 3

Author(s):

Amanda C. Maycock ◽

Katja Matthes ◽

Susann Tegtmeier ◽

Hauke Schmidt ◽

Rémi Thiéblemont ◽

...

Keyword(s):

Solar Cycle ◽

Solar Irradiance ◽

Climate Models ◽

Climate Model ◽

Stratospheric Ozone ◽

Temperature Response ◽

Solar Variability ◽

High Latitudes ◽

Stratospheric Temperature ◽

The Impact

Abstract. The impact of changes in incoming solar irradiance on stratospheric ozone abundances should be included in climate model simulations to fully capture the atmospheric response to solar variability. This study presents the first systematic comparison of the solar-ozone response (SOR) during the 11 year solar cycle amongst different chemistry-climate models (CCMs) and ozone databases specified in climate models that do not include chemistry. We analyse the SOR in eight CCMs from the WCRP/SPARC Chemistry-Climate Model Initiative (CCMI-1) and compare these with three ozone databases: the Bodeker Scientific database, the SPARC/AC&C database for CMIP5, and the SPARC/CCMI database for CMIP6. The results reveal substantial differences in the representation of the SOR between the CMIP5 and CMIP6 ozone databases. The peak amplitude of theSOR in the upper stratosphere (1–5 hPa) decreases from 5 % to 2 % between the CMIP5 and CMIP6 databases. This difference is because the CMIP5 database was constructed from a regression model fit to satellite observations, whereas the CMIP6 database is constructed from CCM simulations, which use a spectral solar irradiance (SSI) dataset with relatively weak UV forcing. The SOR in the CMIP6 ozone database is therefore implicitly more similar to the SOR in the CCMI-1 models than to the CMIP5 ozone database, which shows a greater resemblance in amplitude and structure to the SOR in the Bodeker database. The latitudinal structure of the annual mean SOR in the CMIP6 ozone database and CCMI-1 models is considerably smoother than in the CMIP5 database, which shows strong gradients in the SOR across the midlatitudes owing to the paucity of observations at high latitudes. The SORs in the CMIP6 ozone database and in the CCMI-1 models show a strong seasonal dependence, including large meridional gradients at mid to high latitudes during winter; such seasonal variations in the SOR are not included in the CMIP5 ozone database. Sensitivity experiments with a global atmospheric model without chemistry (ECHAM6.3) are performed to assess the impact of changes in the representation of the SOR and SSI forcing between CMIP5 and CMIP6. The experiments show that the smaller amplitude of the SOR in the CMIP6 ozone database compared to CMIP5 causes a decrease in the modelled tropical stratospheric temperature response over the solar cycle of up to 0.6 K, or around 50 % of the total amplitude. The changes in the SOR explain most of the difference in the amplitude of the tropical stratospheric temperature response in the case with combined changes in SOR and SSI between CMIP5 and CMIP6. The results emphasise the importance of adequately representing the SOR in climate models to capture the impact of solar variability on the atmosphere. Since a number of limitations in the representation of the SOR in the CMIP5 ozone database have been identified, CMIP6 models without chemistry are encouraged to use the CMIP6 ozone database to capture the climate impacts of solar variability.

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The Response of the Ozone Layer to Quadrupled CO2 Concentrations: Implications for Climate

Journal of Climate ◽

10.1175/jcli-d-19-0086.1 ◽

2019 ◽

Vol 32 (22) ◽

pp. 7629-7642 ◽

Cited By ~ 2

Author(s):

Gabriel Chiodo ◽

Lorenzo M. Polvani

Keyword(s):

Climate Model ◽

Stratospheric Ozone ◽

Temperature Response ◽

Ozone Layer ◽

Climate Impacts ◽

Boreal Winter ◽

Tropospheric Circulation ◽

Radiative Perturbation ◽

Global Mean ◽

Co2 Forcing

Abstract The quantification of the climate impacts exerted by stratospheric ozone changes in abrupt 4 × CO2 forcing experiments is an important step in assessing the role of the ozone layer in the climate system. Here, we build on our previous work on the change of the ozone layer under 4 × CO2 and examine the effects of ozone changes on the climate response to 4 × CO2, using the Whole Atmosphere Community Climate Model. We show that the global-mean radiative perturbation induced by the ozone changes under 4 × CO2 is small, due to nearly total cancellation between high and low latitudes, and between longwave and shortwave fluxes. Consistent with the small global-mean radiative perturbation, the effect of ozone changes on the global-mean surface temperature response to 4 × CO2 is negligible. However, changes in the ozone layer due to 4 × CO2 have a considerable impact on the tropospheric circulation. During boreal winter, we find significant ozone-induced tropospheric circulation responses in both hemispheres. In particular, ozone changes cause an equatorward shift of the North Atlantic jet, cooling over Eurasia, and drying over northern Europe. The ozone signals generally oppose the direct effects of increased CO2 levels and are robust across the range of ozone changes imposed in this study. Our results demonstrate that stratospheric ozone changes play a considerable role in shaping the atmospheric circulation response to CO2 forcing in both hemispheres and should be accounted for in climate sensitivity studies.

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Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011)

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-2533-2012 ◽

2012 ◽

Vol 12 (5) ◽

pp. 2533-2540 ◽

Cited By ~ 8

Author(s):

C. McLandress ◽

J. Perlwitz ◽

T. G. Shepherd

Keyword(s):

Northern Hemisphere ◽

Climate Models ◽

Climate Model ◽

Stratospheric Ozone ◽

Three Dimensional ◽

Temperature Response ◽

Ocean Model ◽

Tropospheric Temperature ◽

Cmip3 Model ◽

Incomplete Removal

Abstract. In a recent paper Hu et al. (2011) suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of CMIP3 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We suggest that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.

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Contributions to stratospheric ozone changes from ozone depleting substances and greenhouse gases

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-9647-2010 ◽

2010 ◽

Vol 10 (4) ◽

pp. 9647-9694 ◽

Cited By ~ 3

Author(s):

D. A. Plummer ◽

J. F. Scinocca ◽

T. G. Shepherd ◽

M. C. Reader ◽

A. I. Jonsson

Keyword(s):

Greenhouse Gases ◽

21St Century ◽

Climate Model ◽

Stratospheric Ozone ◽

Three Dimensional ◽

Ocean Model ◽

Residual Circulation ◽

Chemical Effects ◽

Ozone Depleting Substances ◽

Year 2000

Abstract. A state-of-the-art chemistry climate model coupled to a three-dimensional ocean model is used to produce three experiments, all seamlessly covering the period 1950–2100, forced by different combinations of long-lived Greenhouse Gases (GHGs) and Ozone Depleting Substances (ODSs). The experiments are designed to investigate the mechanisms by which GHGs and ODSs affect the evolution of ozone, including changes in the Brewer-Dobson circulation of the stratosphere and cooling of the upper stratosphere by CO2. Separating the effects of GHGs and ODSs on ozone, we find the decrease in upper stratospheric ozone from ODSs up to the year 2000 is approximately 30% larger than the actual decrease in ozone due to the offsetting effects of cooling by increased CO2. Over the 21st century, as ODSs decrease, continued cooling from CO2 is projected to account for more than 50% of the projected increase in upper stratospheric ozone. Changes below 20 hPa show a redistribution of ozone from tropical to extra-tropical latitudes with an increase in the Brewer-Dobson circulation, while globally averaged the amount of ozone below 20 hPa decreases over the 21st century. Further analysis by linear regression shows that changes associated with GHGs do not appreciably alter the recovery of stratospheric ozone from the effects of ODSs; over much of the stratosphere ozone recovery follows the decline of halogen concentrations within statistical uncertainty, though the lower polar stratosphere of the Southern Hemisphere is an exception with ozone concentrations recovering more slowly than indicated by the halogen concentrations. These results also reveal the degree to which climate change, and stratospheric CO2 cooling in particular, mutes the chemical effects of N2O on ozone in the standard future scenario used for the WMO Ozone Assessment. Increases in the residual circulation of the atmosphere and chemical effects from CO2 cooling more than halve the increase in reactive nitrogen in the mid to upper stratosphere that results from the specified increase in N2O between 1950 and 2100.

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An updated analysis of the attribution of stratospheric ozone and temperature changes to changes in ozone-depleting substances and well-mixed greenhouse gases

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-14857-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 14857-14872 ◽

Cited By ~ 1

Author(s):

A. I. Jonsson ◽

V. I. Fomichev ◽

T. G. Shepherd

Keyword(s):

Greenhouse Gases ◽

Middle Atmosphere ◽

Stratospheric Ozone ◽

Linear Regression Analysis ◽

Multiple Linear Regression Analysis ◽

Temperature Changes ◽

Stratospheric Temperature ◽

Temperature Feedback ◽

Stratospheric Cooling ◽

Ozone Depleting Substances

Abstract. This paper presents an analysis of the attribution of past and future changes in stratospheric ozone and temperature to anthropogenic forcings. Recently, Shepherd and Jonsson (2008) argued that such an analysis needs to account for the ozone-temperature feedback, and that the failure to do so could potentially lead to very large errors. This point was illustrated by analyzing chemistry-climate simulations from the Canadian Middle Atmosphere Model (CMAM) and attributing both past and future changes to changes in the abundances of ozone-depleting substances (ODS) and well-mixed greenhouse gases. In the current paper, we have expanded the analysis to account for the nonlinear radiative response to changes in CO2. It is shown that over centennial time scales the relationship between CO2 abundance and radiative cooling in the upper stratosphere is significantly nonlinear. Failure to account for this effect in multiple linear regression analysis would lead to misleading results. In our attribution analysis the nonlinearity is taken into account by using CO2 heating rate, rather than CO2 abundance, as the explanatory variable. In addition, an error in the way the CO2 forcing changes are implemented in the CMAM has been corrected, which significantly affects the results for the recent past. As the radiation scheme, based on Fomichev et al. (1998), is used in several other models we provide some description of the problem and how it was fixed. The updated results are as follows. From 1975–1995, during the period of rapid ozone decline, ODS and CO2 increases contributed roughly equally to upper stratospheric cooling, while the CO2-induced cooling (which increases ozone) masked about 20% of the ODS-induced ozone depletion. From 2010–2040, during the period of most rapid ozone recovery, CO2-induced cooling will dominate the upper stratospheric temperature trend and will contribute roughly equally with the ODS decline to ozone increases, effectively doubling the rate of ozone recovery.

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Comment on "Tropospheric temperature response to stratospheric ozone recovery in the 21st century" by Hu et al. (2011)

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-32993-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 32993-33012 ◽

Cited By ~ 1

Author(s):

C. McLandress ◽

J. Perlwitz ◽

T. G. Shepherd

Keyword(s):

Northern Hemisphere ◽

Climate Models ◽

Climate Model ◽

Stratospheric Ozone ◽

Three Dimensional ◽

Temperature Response ◽

Ocean Model ◽

Tropospheric Temperature ◽

Surface Warming ◽

Incomplete Removal

Abstract. In a recent paper Hu et al. (2011) suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of IPCC AR4 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We argue that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.

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Quantifying the contributions to stratospheric ozone changes from ozone depleting substances and greenhouse gases

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-8803-2010 ◽

2010 ◽

Vol 10 (18) ◽

pp. 8803-8820 ◽

Cited By ~ 29

Author(s):

D. A. Plummer ◽

J. F. Scinocca ◽

T. G. Shepherd ◽

M. C. Reader ◽

A. I. Jonsson

Keyword(s):

Greenhouse Gases ◽

21St Century ◽

Climate Model ◽

Stratospheric Ozone ◽

Three Dimensional ◽

Ocean Model ◽

Residual Circulation ◽

Total Column Ozone ◽

Chemical Effects ◽

Ozone Depleting Substances

Abstract. A state-of-the-art chemistry climate model coupled to a three-dimensional ocean model is used to produce three experiments, all seamlessly covering the period 1950–2100, forced by different combinations of long-lived Greenhouse Gases (GHGs) and Ozone Depleting Substances (ODSs). The experiments are designed to quantify the separate effects of GHGs and ODSs on the evolution of ozone, as well as the extent to which these effects are independent of each other, by alternately holding one set of these two forcings constant in combination with a third experiment where both ODSs and GHGs vary. We estimate that up to the year 2000 the net decrease in the column amount of ozone above 20 hPa is approximately 75% of the decrease that can be attributed to ODSs due to the offsetting effects of cooling by increased CO2. Over the 21st century, as ODSs decrease, continued cooling from CO2 is projected to account for more than 50% of the projected increase in ozone above 20 hPa. Changes in ozone below 20 hPa show a redistribution of ozone from tropical to extra-tropical latitudes with an increase in the Brewer-Dobson circulation. In addition to a latitudinal redistribution of ozone, we find that the globally averaged column amount of ozone below 20 hPa decreases over the 21st century, which significantly mitigates the effect of upper stratospheric cooling on total column ozone. Analysis by linear regression shows that the recovery of ozone from the effects of ODSs generally follows the decline in reactive chlorine and bromine levels, with the exception of the lower polar stratosphere where recovery of ozone in the second half of the 21st century is slower than would be indicated by the decline in reactive chlorine and bromine concentrations. These results also reveal the degree to which GHG-related effects mute the chemical effects of N2O on ozone in the standard future scenario used for the WMO Ozone Assessment. Increases in the residual circulation of the atmosphere and chemical effects from CO2 cooling more than halve the increase in reactive nitrogen in the mid to upper stratosphere that results from the specified increase in N2O between 1950 and 2100.

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Polar Middle Atmospheric Responses to Medium Energy Electron (MEE) Precipitation Using Numerical Model Simulations

Atmosphere ◽

10.3390/atmos12020133 ◽

2021 ◽

Vol 12 (2) ◽

pp. 133

Author(s):

Ji-Hee Lee ◽

Geonhwa Jee ◽

Young-Sil Kwak ◽

Heejin Hwang ◽

Annika Seppälä ◽

...

Keyword(s):

Climate Model ◽

Middle Atmosphere ◽

Meridional Circulation ◽

Stratospheric Ozone ◽

High Energy ◽

Chemical Changes ◽

Temperature Changes ◽

Mesospheric Temperature ◽

High Energy Electrons ◽

Circulation Changes

Energetic particle precipitation (EPP) is known to be an important source of chemical changes in the polar middle atmosphere in winter. Recent modeling studies further suggest that chemical changes induced by EPP can also cause dynamic changes in the middle atmosphere. In this study, we investigated the atmospheric responses to the precipitation of medium-to-high energy electrons (MEEs) over the period 2005–2013 using the Specific Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). Our results show that the MEE precipitation significantly increases the amounts of NOx and HOx, resulting in mesospheric and stratospheric ozone losses by up to 60% and 25% respectively during polar winter. The MEE-induced ozone loss generally increases the temperature in the lower mesosphere but decreases the temperature in the upper mesosphere with large year-to-year variability, not only by radiative effects but also by adiabatic effects. The adiabatic effects by meridional circulation changes may be dominant for the mesospheric temperature changes. In particular, the meridional circulation changes occasionally act in opposite ways to vary the temperature in terms of height variations, especially at around the solar minimum period with low geomagnetic activity, which cancels out the temperature changes to make the average small in the polar mesosphere for the 9-year period.

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Chemical and climatic drivers of radiative forcing due to changes in stratospheric and tropospheric ozone over the 21<sup>st</sup> century

10.5194/acp-2017-741 ◽

2017 ◽

Author(s):

Antara Banerjee ◽

Amanda C. Maycock ◽

John A. Pyle

Keyword(s):

Greenhouse Gas ◽

Tropospheric Ozone ◽

Radiative Forcing ◽

Climate Model ◽

Stratospheric Ozone ◽

Radiative Forcings ◽

Climatic Drivers ◽

Ozone Precursor ◽

Ozone Depleting Substances ◽

Projected Changes

Abstract. The ozone radiative forcings (RFs) resulting from projected changes in climate, ozone-depleting substances (ODSs), non-methane ozone precursor emissions and methane between the years 2000 and 2100 are calculated using simulations from the UM-UKCA chemistry-climate model. Projected measures to improve air-quality through reductions in tropospheric ozone precursor emissions present a co-benefit for climate, with a net global mean ozone RF of −0.09 Wm−2. This is opposed by a positive ozone RF of 0.07 Wm−2 due to future decreases in ODSs, which is mainly driven by an increase in tropospheric ozone through stratosphere-to-troposphere exchange. An increase in methane abundance by more than a factor of two (as projected by the RCP8.5 scenario) is found to drive an ozone RF of 0.19 Wm−2, which would greatly outweigh the climate benefits of tropospheric non-methane ozone precursor reductions. A third of the ozone RF due to the projected increase in methane results from increases in stratospheric ozone. The sign of the ozone RF due to future changes in climate (including the radiative effects of greenhouse gas concentrations, sea surface temperatures and sea ice changes) is shown to be dependent on the greenhouse gas emissions pathway, with a positive RF (0.06 Wm−2) for RCP4.5 and a negative RF (−0.07 Wm−2) for the RCP8.5 scenario. This dependence arises from differences in the contribution to RF from stratospheric ozone changes.

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