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

The impact of ozone-depleting substances on global lower-stratospheric temperature trends is widely recognized. In the tropics, however, understanding lower-stratospheric temperature trends has proven more challenging. While the tropical lower-stratospheric cooling observed from 1979 to 1997 has been linked to tropical ozone decreases, those ozone trends cannot be of chemical origin, as active chlorine is not abundant in the tropical lower stratosphere. The 1979–97 tropical ozone trends are believed to originate from enhanced upwelling, which, it is often stated, would be driven by increasing concentrations of well-mixed greenhouse gases. This study, using simple arguments based on observational evidence after 1997, combined with model integrations with incrementally added single forcings, argues that trends in ozone-depleting substances, not well-mixed greenhouse gases, have been the primary driver of temperature and ozone trends in the tropical lower stratosphere until 1997, and this has occurred because ozone-depleting substances are key drivers of tropical upwelling and, more generally, of the entire Brewer–Dobson circulation.

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Ozone and temperature decadal trends in the stratosphere, mesosphere and lower thermosphere, based on measurements from SABER on TIMED

Annales Geophysicae ◽

10.5194/angeo-32-935-2014 ◽

2014 ◽

Vol 32 (8) ◽

pp. 935-949 ◽

Cited By ~ 19

Author(s):

F. T. Huang ◽

H. G. Mayr ◽

J. M. Russell ◽

M. G. Mlynczak

Keyword(s):

Stratospheric Ozone ◽

Lower Thermosphere ◽

Definitive Evidence ◽

Broadband Emission ◽

Stratospheric Temperature ◽

Temperature Trends ◽

Time Period ◽

Ozone Trends ◽

Ozone Trend ◽

The Tropics

Abstract. We have derived ozone and temperature trends from years 2002 through 2012, from 20 to 100 km altitude, and 48° S to 48° N latitude, based on measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. For the first time, trends of ozone and temperature measured at the same times and locations are obtained, and their correlations should provide useful information about the relative importance of photochemistry versus dynamics over the longer term. We are not aware of comparable results covering this time period and spatial extent. For stratospheric ozone, until the late 1990s, previous studies found negative trends (decreasing amounts). In recent years, some empirical and modeling studies have shown the occurrence of a turnaround in the decreasing ozone, possibly beginning in the late 1990s, suggesting that the stratospheric ozone trend is leveling off or even turning positive. Our global results add more definitive evidence, expand the coverage, and show that at mid-latitudes (north and south) in the stratosphere, the ozone trends are indeed positive, with ozone having increased by a few percent from 2002 through 2012. However, in the tropics, we find negative ozone trends between 25 and 50 km. For stratospheric temperatures, the trends are mostly negatively correlated to the ozone trends. The temperature trends are positive in the tropics between 30 and 40 km, and between 20 and 25 km, at approximately 24° N and at 24° S latitude. The stratospheric temperature trends are otherwise mostly negative. In the mesosphere, the ozone trends are mostly flat, with suggestions of small positive trends at lower latitudes. The temperature trends in this region are mostly negative, showing decreases of up to ~ −3 K decade−1. In the lower thermosphere (between ~ 85 and 100 km), ozone and temperature trends are both negative. The ozone trend can approach ~ −10% decade−1, and the temperature trend can approach ~ −3 K decade−1. Aside from trends, these patterns of ozone–temperature correlations are consistent with previous studies of ozone and temperature perturbations such as the quasi-biennial (QBO) and semiannual (SAO) oscillations, and add confidence to the results.

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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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An update on ozone profile trends for the period 2000 to 2016

10.5194/acp-2017-391 ◽

2017 ◽

Cited By ~ 1

Author(s):

Wolfgang Steinbrecht ◽

Lucien Froidevaux ◽

Ryan Fuller ◽

Ray Wang ◽

John Anderson ◽

...

Keyword(s):

Climate Model ◽

Stratospheric Ozone ◽

Atmospheric Composition ◽

Data Sets ◽

Ozone Profile ◽

Ozone Trends ◽

Climate Model Simulations ◽

Stratospheric Cooling ◽

Ozone Depleting Substances ◽

The Tropics

Abstract. Ozone profile trends over the period 2000 to 2016 from several merged satellite ozone data sets and from ground-based data by four techniques at stations of the Network for the Detection of Atmospheric Composition Change indicate significant ozone increases in the upper stratosphere, between 35 and 48 km altitude (5 and 1 hPa). Near 2 hPa (42 km), ozone has been increasing by about 1.5 % per decade in the tropics (20° S to 20° N), and by 2 to 2.5 % per decade in the 35° to 60° latitude bands of both hemispheres. At levels below 35 km (5 hPa), 2000 to 2016 ozone trends are smaller and not statistically significant. The observed trend profiles are consistent with expectations from chemistry climate model simulations. Using three to four more years of observations and updated data sets, this study confirms positive trends of upper stratospheric ozone already reported, e.g., in the WMO/UNEP Ozone Assessment 2014, or by Harris et al. (2015). The additional years, and the fact that nearly all individual data sets indicate these increases, give enhanced confidence. Nevertheless, a thorough analysis of possible drifts and differences between various data sources is still required, as is a detailed attribution of the observed increases to declining ozone depleting substances and to stratospheric cooling. Ongoing quality observations from multiple independent platforms are key for verifying that recovery of the ozone layer continues as expected.

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Stratospheric Temperature Trends over 1979–2015 Derived from Combined SSU, MLS, and SABER Satellite Observations

Journal of Climate ◽

10.1175/jcli-d-15-0629.1 ◽

2016 ◽

Vol 29 (13) ◽

pp. 4843-4859 ◽

Cited By ~ 29

Author(s):

William J. Randel ◽

Anne K. Smith ◽

Fei Wu ◽

Cheng-Zhi Zou ◽

Haifeng Qian

Keyword(s):

Solar Cycle ◽

Lower Stratosphere ◽

Stratospheric Ozone ◽

Volcanic Eruptions ◽

Weighting Functions ◽

Stratospheric Temperature ◽

Temperature Trends ◽

Decadal Scale ◽

Data Record ◽

The Tropics

Abstract Temperature trends in the middle and upper stratosphere are evaluated using measurements from the Stratospheric Sounding Unit (SSU), combined with data from the Aura Microwave Limb Sounder (MLS) and Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) instruments. Data from MLS and SABER are vertically integrated to approximate the SSU weighting functions and combined with SSU to provide a data record spanning 1979–2015. Vertical integrals are calculated using empirically derived Gaussian weighting functions, which provide improved agreement with high-latitude SSU measurements compared to previously derived weighting functions. These merged SSU data are used to evaluate decadal-scale trends, solar cycle variations, and volcanic effects from the lower to the upper stratosphere. Episodic warming is observed following the volcanic eruptions of El Chichón (1982) and Mt. Pinatubo (1991), focused in the tropics in the lower stratosphere and in high latitudes in the middle and upper stratosphere. Solar cycle variations are centered in the tropics, increasing in amplitude from the lower to the upper stratosphere. Linear trends over 1979–2015 show that cooling increases with altitude from the lower stratosphere (from ~−0.1 to −0.2 K decade−1) to the middle and upper stratosphere (from ~−0.5 to −0.6 K decade−1). Cooling in the middle and upper stratosphere is relatively uniform in latitudes north of about 30°S, but trends decrease to near zero over the Antarctic. Mid- and upper-stratospheric temperatures show larger cooling over the first half of the data record (1979–97) compared to the second half (1998–2015), reflecting differences in upper-stratospheric ozone trends between these periods.

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An update on ozone profile trends for the period 2000 to 2016

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-10675-2017 ◽

2017 ◽

Vol 17 (17) ◽

pp. 10675-10690 ◽

Cited By ~ 55

Author(s):

Wolfgang Steinbrecht ◽

Lucien Froidevaux ◽

Ryan Fuller ◽

Ray Wang ◽

John Anderson ◽

...

Keyword(s):

Climate Model ◽

Stratospheric Ozone ◽

Atmospheric Composition ◽

Data Sets ◽

Ozone Profile ◽

Ozone Trends ◽

Climate Model Simulations ◽

Stratospheric Cooling ◽

Ozone Depleting Substances ◽

The Tropics

Abstract. Ozone profile trends over the period 2000 to 2016 from several merged satellite ozone data sets and from ground-based data measured by four techniques at stations of the Network for the Detection of Atmospheric Composition Change indicate significant ozone increases in the upper stratosphere, between 35 and 48 km altitude (5 and 1 hPa). Near 2 hPa (42 km), ozone has been increasing by about 1.5 % per decade in the tropics (20° S to 20° N), and by 2 to 2.5 % per decade in the 35 to 60° latitude bands of both hemispheres. At levels below 35 km (5 hPa), 2000 to 2016 ozone trends are smaller and not statistically significant. The observed trend profiles are consistent with expectations from chemistry climate model simulations. This study confirms positive trends of upper stratospheric ozone already reported, e.g., in the WMO/UNEP Ozone Assessment 2014 or by Harris et al. (2015). Compared to those studies, three to four additional years of observations, updated and improved data sets with reduced drift, and the fact that nearly all individual data sets indicate ozone increase in the upper stratosphere, all give enhanced confidence. Uncertainties have been reduced, for example for the trend near 2 hPa in the 35 to 60° latitude bands from about ±5 % (2σ) in Harris et al. (2015) to less than ±2 % (2σ). Nevertheless, a thorough analysis of possible drifts and differences between various data sources is still required, as is a detailed attribution of the observed increases to declining ozone-depleting substances and to stratospheric cooling. Ongoing quality observations from multiple independent platforms are key for verifying that recovery of the ozone layer continues as expected.

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Tropical troposphere to stratosphere transport of carbon monoxide and long-lived trace species in the Chemical Lagrangian Model of the Stratosphere (CLaMS)

Geoscientific Model Development Discussions ◽

10.5194/gmdd-7-5087-2014 ◽

2014 ◽

Vol 7 (4) ◽

pp. 5087-5139 ◽

Cited By ~ 6

Author(s):

R. Pommrich ◽

R. Müller ◽

J.-U. Grooß ◽

P. Konopka ◽

F. Ploeger ◽

...

Keyword(s):

Carbon Monoxide ◽

Large Scale ◽

Lower Stratosphere ◽

Lagrangian Model ◽

Quasi Biennial Oscillation ◽

Data Set ◽

Model Version ◽

The Tropics ◽

The Impact ◽

Good Agreement

Abstract. Variations in the mixing ratio of trace gases of tropospheric origin entering the stratosphere in the tropics are of interest for assessing both troposphere to stratosphere transport fluxes in the tropics and the impact of these transport fluxes on the composition of the tropical lower stratosphere. Anomaly patterns of carbon monoxide (CO) and long-lived tracers in the lower tropical stratosphere allow conclusions about the rate and the variability of tropical upwelling to be drawn. Here, we present a simplified chemistry scheme for the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the simulation, at comparatively low numerical cost, of CO, ozone, and long-lived trace substances (CH4, N2O, CCl3F (CFC-11), CCl2F2 (CFC-12), and CO2) in the lower tropical stratosphere. For the long-lived trace substances, the boundary conditions at the surface are prescribed based on ground-based measurements in the lowest model level. The boundary condition for CO in the free troposphere is deduced from MOPITT measurements (at &approx; 700–200 hPa). Due to the lack of a specific representation of mixing and convective uplift in the troposphere in this model version, enhanced CO values, in particular those resulting from convective outflow are underestimated. However, in the tropical tropopause layer and the lower tropical stratosphere, there is relatively good agreement of simulated CO with in-situ measurements (with the exception of the TROCCINOX campaign, where CO in the simulation is biased low &approx; 10–20 ppbv). Further, the model results are of sufficient quality to describe large scale anomaly patterns of CO in the lower stratosphere. In particular, the zonally averaged tropical CO anomaly patterns (the so called "tape recorder" patterns) simulated by this model version of CLaMS are in good agreement with observations. The simulations show a too rapid upwelling compared to observations as a consequence of the overestimated vertical velocities in the ERA-interim reanalysis data set. Moreover, the simulated tropical anomaly patterns of N2O are in good agreement with observations. In the simulations, anomaly patterns for CH4 and CFC-11 were found to be consistent with those of N2O; for all long-lived tracers, positive anomalies are simulated because of the enhanced tropical upwelling in the easterly phase of the quasi-biennial oscillation.

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Seasonal stratospheric ozone trends over 2000–2018 derived from several merged data sets

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-7035-2020 ◽

2020 ◽

Vol 20 (11) ◽

pp. 7035-7047 ◽

Cited By ~ 1

Author(s):

Monika E. Szeląg ◽

Viktoria F. Sofieva ◽

Doug Degenstein ◽

Chris Roth ◽

Sean Davis ◽

...

Keyword(s):

Stratospheric Ozone ◽

Equatorial Region ◽

Data Sets ◽

Opposite Pattern ◽

The North ◽

Stratospheric Temperature ◽

Temperature Trends ◽

Ozone Trends ◽

Seasonal Dependence

Abstract. In this work, we analyze the seasonal dependence of ozone trends in the stratosphere using four long-term merged data sets, SAGE-CCI-OMPS, SAGE-OSIRIS-OMPS, GOZCARDS, and SWOOSH, which provide more than 30 years of monthly zonal mean ozone profiles in the stratosphere. We focus here on trends between 2000 and 2018. All data sets show similar results, although some discrepancies are observed. In the upper stratosphere, the trends are positive throughout all seasons and the majority of latitudes. The largest upper-stratospheric ozone trends are observed during local winter (up to 6 % per decade) and equinox (up to 3 % per decade) at mid-latitudes. In the equatorial region, we find a very strong seasonal dependence of ozone trends at all altitudes: the trends vary from positive to negative, with the sign of transition depending on altitude and season. The trends are negative in the upper-stratospheric winter (−1 % per decade to −2 % per decade) and in the lower-stratospheric spring (−2 % per decade to −4 % per decade), but positive (2 % per decade to 3 % per decade) at 30–35 km in spring, while the opposite pattern is observed in summer. The tropical trends below 25 km are negative and maximize during summer (up to −2 % per decade) and spring (up to −3 % per decade). In the lower mid-latitude stratosphere, our analysis points to a hemispheric asymmetry: during local summers and equinoxes, positive trends are observed in the south (+1 % per decade to +2 % per decade), while negative trends are observed in the north (−1 % per decade to −2 % per decade). We compare the seasonal dependence of ozone trends with available analyses of the seasonal dependence of stratospheric temperature trends. We find that ozone and temperature trends show positive correlation in the dynamically controlled lower stratosphere and negative correlation above 30 km, where photochemistry dominates. Seasonal trend analysis gives information beyond that contained in annual mean trends, which can be helpful in order to better understand the role of dynamical variability in short-term trends and future ozone recovery predictions.

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Intercomparison of temperature trends in IPCC CMIP5 simulations with observations, reanalyses and CMIP3 models

Geoscientific Model Development ◽

10.5194/gmd-6-1705-2013 ◽

2013 ◽

Vol 6 (5) ◽

pp. 1705-1714 ◽

Cited By ~ 11

Author(s):

J. Xu ◽

L. Zhao ◽

Keyword(s):

Coupled Model ◽

Temperature Trend ◽

The Arctic ◽

Cmip5 Models ◽

Model Intercomparison ◽

Model Simulations ◽

Temperature Trends ◽

Intercomparison Project ◽

Stratospheric Cooling ◽

The Tropics

Abstract. On the basis of the fifth Coupled Model Intercomparison Project (CMIP5) and the climate model simulations covering 1979 through 2005, the temperature trends and their uncertainties have been examined to note the similarities or differences compared to the radiosonde observations, reanalyses and the third Coupled Model Intercomparison Project (CMIP3) simulations. The results show noticeable discrepancies for the estimated temperature trends in the four data groups (radiosonde, reanalysis, CMIP3 and CMIP5), although similarities can be observed. Compared to the CMIP3 model simulations, the simulations in some of the CMIP5 models were improved. The CMIP5 models displayed a negative temperature trend in the stratosphere closer to the strong negative trend seen in the observations. However, the positive tropospheric trend in the tropics is overestimated by the CMIP5 models relative to CMIP3 models. While some of the models produce temperature trend patterns more highly correlated with the observed patterns in CMIP5, the other models (such as CCSM4 and IPSL_CM5A-LR) exhibit the reverse tendency. The CMIP5 temperature trend uncertainty was significantly reduced in most areas, especially in the Arctic and Antarctic stratosphere, compared to the CMIP3 simulations. Similar to the CMIP3, the CMIP5 simulations overestimated the tropospheric warming in the tropics and Southern Hemisphere and underestimated the stratospheric cooling. The crossover point where tropospheric warming changes into stratospheric cooling occurred near 100 hPa in the tropics, which is higher than in the radiosonde and reanalysis data. The result is likely related to the overestimation of convective activity over the tropical areas in both the CMIP3 and CMIP5 models. Generally, for the temperature trend estimates associated with the numerical models including the reanalyses and global climate models, the uncertainty in the stratosphere is much larger than that in the troposphere, and the uncertainty in the Antarctic is the largest. In addition, note that the reanalyses show the largest uncertainty in the lower tropical stratosphere, and the CMIP3 simulations show the largest uncertainty in both the south and north polar regions.

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Effect of Exclusion of Anomalous Tropical Stations on Temperature Trends from a 63-Station Radiosonde Network, and Comparison with Other Analyses

Journal of Climate ◽

10.1175/2763.1 ◽

2003 ◽

Vol 16 (13) ◽

pp. 2288-2295 ◽

Cited By ~ 19

Author(s):

James K. Angell

Keyword(s):

Global Changes ◽

Station Network ◽

Temperature Trends ◽

A Value ◽

Microwave Sounding Unit ◽

Microwave Sounding ◽

Stratospheric Cooling ◽

The Tropics ◽

Large Standard Error

Abstract A 63-station radiosonde network has been used for many years to estimate temperature variations and trends at the surface and in the 850–300-, 300–100-, and 100–50-mb layers of climate zones, both hemispheres, and the globe, but with little regard for the quality of individual station data. In this paper, nine tropical radiosonde stations in this network are identified as anomalous based on unrepresentatively large standard-error-of-regression values for 300–100-mb trends for the period 1958–2000. In the Tropics the exclusion of the 9 anomalous stations from the 63-station network for 1958–2000 results in a warming of the 300–100-mb layer rather than a cooling, a doubling of the warming of the 850–300-mb layer to a value of 0.13 K decade−1, and a greater warming at 850–300-mb than at the surface. The global changes in trend are smaller, but include a change to the same warming of the surface and the 850–300-mb layer during 1958–2000. The effect of the station exclusions is much less for 1979–2000, suggesting that most of the data problems are before this time. Temperature trends based on the 63-station network are compared with the Microwave Sounding Unit (MSU) and other radiosonde trends, and agreement is better after the exclusion of the anomalous stations. There is consensus that in the Tropics the troposphere has warmed slightly more than the surface during 1958–2000, but that there has been a warming of the surface relative to the troposphere during 1979–2000. Globally, the warming of the surface and the troposphere are essentially the same during 1958–2000, but during 1979–2000 the surface warms more than the troposphere. During the latter period the radiosondes indicate considerably more low-stratospheric cooling in the Tropics than does the MSU.

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The impact of iodine on ozone trends in the lower stratosphere

10.5194/egusphere-egu2020-12955 ◽

2020 ◽

Author(s):

Martyn Chipperfield ◽

Wuhu Feng ◽

Sandip Dhomse ◽

Yajuan Li ◽

Ryan Hossaini ◽

...

Keyword(s):

Lower Stratosphere ◽

Transport Model ◽

Stratospheric Ozone ◽

Ozone Layer ◽

Small Contribution ◽

Chemical Transport Model ◽

Heterogeneous Processes ◽

Ozone Trends ◽

Phase Chemistry ◽

The Impact

Depletion of the stratospheric ozone layer by chlorine and bromine species has been a major environmental issue since the early 1970s. Following controls on the production of the long-lived halocarbons which transport chlorine and bromine to the stratosphere, the ozone layer is expected to recover over the course of this century. Decreases in the stratospheric loading of chlorine and bromine have been observed and there are signs of this resulting in an increase in ozone in the upper stratosphere and the Antarctic lower stratosphere. However, in contrast to this expectation of increasing stratospheric ozone, Ball et al. (ACP doi:10.5194/acp-18-1379-2018, 2018, ACP doi:10.5194/acp-19-12731-2019, 2019) have reported evidence for an ongoing decline in lower stratospheric ozone at extrapolar latitudes between 60&#176;S and 60&#176;N. Chipperfield et al. (GRL, doi:10.1029/2018GL078071, 2018) analysed these results using the TOMCAT 3-D chemical transport model (CTM). They reported that much of the observed ozone decrease could be explained by dynamical variability. Furthermore, they investigated the potential role for bromine and chlorine from very short-lived species (VSLS) but found only a small contribution.Very recently, Koenig et al. (PNAS, doi:10.1073/pnas.1916828117, 2020) have reported quantitative observations of almost 1 pptv iodine in the lower stratosphere. They show that this iodine is an important contribution to the local iodine loss budget and speculate that a trend in iodine could therefore explain the observed downward trend in ozone.Here we use an updated version of the TOMCAT CTM to investigate the impact of iodine on lower stratospheric ozone trends. We repeat the simulations of Chipperfield et al. (2018), using both ERA-Interim and ERA5 reanalyses (to compare the quantification of the dynamical contribution). We use assume trends in the stratospheric injection of iodine to quantify the possible impact of this on global ozone trends through both gas-phase chemistry and novel heterogeneous processes.&#160;

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