Climate change and ozone change are two major channels through which climate policies influence agricultural production, yet most studies assess climate or ozone in isolation, which can limit the accuracy of estimated climate policy effects. Here we use an integrated model to quantify how carbon neutrality policies pledged by 153 countries affect yields of maize, rice, soybean and wheat and the associated economic outcomes. We show that excluding ozone change may understate the benefits of existing carbon neutrality policies for the four main crops, by up to 38.7%. By including the combined effect of ozone and climate, carbon neutrality policies can prevent 0.5-41.5% in losses, and more than 70% of the crop area would experience crop gains compared with the no policy scenario. For countries that still experience agricultural losses, we discuss options to reduce food security risks in terms of mitigation policies, adaptation measures and agricultural trade agreements.

Abstract Ozone in the upper troposphere (UT) is critical for maintaining radiative balance at the top of the atmosphere (TOA). This study utilizes Aerosol and Chemistry Model Intercomparison Project (AeroChemMIP) simulations to investigate photochemical pathways influencing ozone production in the UT during the Asian summer monsoon (ASM). We analyze the impact of convectively transported ozone precursors like nitrogen oxides (NO x ), non‐methane volatile organic compounds (NMVOCs), and carbon monoxide (CO) on the sensitivity of ozone formation over the Asian region in the UT. Our results show an increase of ozone in the UT by ∼70% in the present‐day (2014) compared to the pre‐industrial era (1850). This excess ozone (∼35 ppb) is photochemically produced due to the elevated levels of NO x (∼152 ppt) and CO (∼21 ppb) in the UT along with its direct convective transport from the boundary layer. Changes in formaldehyde (HCHO), a proxy for VOCs, are negligible in the UT. Analysis of ozone in relation to its precursors (HCHO, CO, and NO 2 ) suggests that the UT is primarily NO x ‐limited, and ozone production follows the NO x ‐CO‐O 3 pathway. The UT ozone changes due to increasing ozone precursor emissions affect the radiative balance by exerting a positive ozone radiative effect of +0.9 Wm −2 at the TOA over the ASM anticyclone region. These findings indicate that suitable emission control strategies must be formulated to reduce NO x and CO emissions to limit ozone enhancement in the UT.

Abstract The acceleration of the Brewer-Dobson circulation is one of the most robust impacts on the atmospheric circulation of increasing levels of carbon dioxide (CO 2 ). However, a complete understanding of the mechanisms leading to that acceleration is as yet incomplete. Here, using a single-model framework, we separate and quantify three largely independent pathways that lead to BDC acceleration under an abrupt 4×CO 2 forcing: the warming of sea surface temperatures (SSTs), the cooling of the stratosphere from direct radiative forcing, and the composition feedbacks associated with changes of the ozone layer, each of which is caused by increased CO 2 . We accomplish this by contrasting NASA GISS Model E2.2 simulations in fully-coupled and atmosphere-only configurations. First, we validate our methodology, and demonstrate the response in the fully-coupled model can be simulated as the linear sum of contributions from warmer SSTs, direct radiative effects, and ozone changes. Second, we show that while surface warming induces ∼85% of the BDC acceleration, its impact is limited to the lower stratosphere. By comparison, in the upper-and-middle stratosphere, the BDC response is dominated by changes due to direct radiative forcing from CO 2 (80% of the acceleration at 10 hPa). Third, we find that changes in ozone lead to a deceleration of the BDC, nearly canceling the acceleration by the CO 2 direct radiative forcing in the mid-to-lower stratosphere (30–70 hPa).

Abstract. We calculate the global change in the production of tropospheric ozone (O3) and loss of methane (CH4) caused by 45 d of summertime South Korean anthropogenic emissions during the Korea-US Air Quality (KORUS-AQ) mission. Our modelling system consists of three stages: the boundary layer-residual layer (BL-RL) stage processes the emissions, photochemistry, deposition, aerosol reactivity, and transport over terrestrial South Korea at 0.1° × 0.1° with hourly resolution. The plume (PL) stage continues to integrate the chemistry of air masses from the BL-RL stage as they are transported offshore, simulating offshore pollution plumes observed by aircraft. After three days of chemical aging in non-diluting plumes, the pollution remnants are dispersed (DP stage) into the background atmosphere and integrated until the pollution disappears. Net O3 production is diagnosed in each stage using the integrated ozone change and our calculated perturbation lifetimes. In total, these 45 d of South Korean emissions create an excess CH4 sink of 4.3 Gmol and a net O3 source of 31.2 Gmol. A simplistic scaling of these values to annual global anthropogenic emissions suggests around 10 % of CH4 loss and 30 % of net O3 production is attributable to anthropogenic air pollution, but our Korean summertime case exaggerates these proportions. Reducing plume aging time to 2 d increases these terms by about 10 %, and immediate dispersion (no plume aging) more than doubles them. Our model supports the typical result that rapid dispersion of pollution, e.g. through coarse resolution, overestimates its impact on tropospheric O3 and CH4.

Abstract. Ozone (O3) contributes to global climate change and poses a direct threat to human health. This study investigates the historical variability, future projections, and associated present-day uncertainties of surface O3 concentrations over China using simulations from nine CMIP6 models and observational data from the Tracking Air Pollution in China (TAP) dataset. A multi-model ensemble mean (MME), constructed using an equal-weighted approach, is used to evaluate model uncertainties across different seasons, underlying surface types, total cloud cover, and PM2.5 concentrations, and assess model performance under future Shared Socioeconomic Pathway (SSP) scenarios. The results show that the MME captures the pronounced seasonal cycle of surface O3, with higher concentrations during June–August (JJA, ∼ 105 µg m−3) and lower values during December–February (DJF, ∼ 55 µg m−3), but underestimates O3 across most regions of China, particularly in East China. Model performance varies with environmental conditions, showing lower bias, MAE, and RMSE over natural land surfaces than over anthropogenic surfaces. The O3 bias is minimized under cloudy conditions, maximized under partly cloudy conditions, and generally increases with rising PM2.5 concentrations before declining beyond a certain threshold. Over the historical period, the MME simulates a substantial increase in annual mean surface O3 across China (∼ 39.3 µg m−3). Future projections indicate continued O3 increases under weak mitigation (SSP3-7.0), with East China rising by 26.9 %, and widespread decreases under strong mitigation (SSP1-2.6), particularly in Southwest and South China (> 30 µg m−3). Analysis of model spread and its drivers indicates that uncertainties in surface O3 projections arise from the combined effects of emissions (including precursors and PM2.5), climate conditions, and model representations of chemistry and circulation. Improving the understanding of these coupled influences is essential for enhancing the reliability of regional O3 projections and for informing effective air quality and climate mitigation strategies in China.

Abstract Stratosphere‐troposphere coupling (STC) in the Southern Hemisphere (SH) occurs primarily from austral spring to summer, and the dominant mode of variability in this vertical coupling (the “STC mode”) represents the timing of the seasonal transition of the polar vortex and its subsequent coupling to the Southern Annular Mode (SAM). Because it represents downward coupling over a season, stratospheric winds projected onto the STC mode are useful as a seasonal predictor of spring and summer SH surface climate. However, it is not clear how the STC mode and its connection to seasonal predictability will evolve in response to changes in stratospheric ozone and increases in greenhouse gases. Here, using four large ensemble simulations from 1950 to 2100, we apply a “snapshot EOF” technique in order to track the evolution of the mode in response to prescribed ozone and RCP8.5 greenhouse gas changes. We find that for all large ensembles, the STC mode in late spring strengthens (weakens) during the period of ozone depletion (recovery), and these responses are largest in the model that includes interactive ozone. A majority of the large ensembles further suggest a significant weakening of the mode by 2075 in an extreme RCP8.5 climate, including a decrease in the fraction of variance explained by the mode over time and a decrease in the correlation of the mode with the SAM. The key result is that as ozone recovers and greenhouse gases increase, there is a projected decline in the seasonal predictability of austral surface climate associated with the STC mode.

Four decades of climate-driven changes in Northern Hemisphere surface ozone.

Abstract. To predict the future state of the Earth system on multiyear timescales, it is crucial to understand the response to changing external radiative forcing (CO2 and Ozone). Analyzing the Northern Hemisphere (NH) winter stratospheric polar vortex temperature, we found a general temperature decrease in the reanalysis data (1982–2020), the expected trend with increasing CO2, except for a sharp warming during the period 1992–2000. Results from 1° GEOS-MITgcm coupled general circulation model simulations of past decades show a similar increase in the NH polar stratospheric temperature during 1992–2000 and a decrease during 2000–2020. To isolate the influence of external forcing, we conducted a series of 30-year-long “perpetual” time-slice experiments in which the external forcing for a particular year is held fixed at its values for 1992, 2000, and 2020. Each simulated year of these perpetual experiments is forced with the CO2, Ozone, anthropogenic aerosol emissions, and trace gases of that year, but none of the simulations include any explosive volcanic forcing. The increasing and then decreasing temperature trend is also manifest in the CMIP6 historical simulations performed with models that include a well-resolved stratosphere. The configuration of the perpetual experiments rules out a direct response to volcanic emissions or a change in the phase of decadal modes of variability as explanations for the warming rather than the expected cooling behavior. Analysis of the temperature budget showed (only significant terms are discussed) that the polar stratospheric temperature behavior is dictated by meridional eddy transport of heat resulting from changes in CO2 and Ozone over the past decades.

The depletion of Antarctic stratospheric ozone since the 1970s, and the resulting increase in UV radiation reaching the Earth's surface, have posed a well-recognized threat to polar aquatic and terrestrial ecosystems. Although this phenomenon is primarily driven by anthropogenic emissions, natural processes linked to volcanic activity and changes in solar irradiance can also influence ozone levels over time. Understanding past ozone changes over Antarctica is therefore essential for constraining the amplitude of its natural variability. Given the sensitivity of diatoms to different environmental conditions, we investigated the potential of these organisms as proxies for ozone variability by analyzing their relative abundance along a proglacial lake sediment profile dated using excess 210Pb. We found that a specific diatom assemblage dominated by Gomphonema sp., Nitzschia cf. kleinteichiana, Humidophila tabellariaeformis, and Pinnularia borealis shows significant responses to measured ozone data from Faraday/Vernadsky station, allowing the development of a quantitative reconstruction model for the modern epoch. Applying this model to a Holocene sediment core from the same ice-free area, we obtained a millennial-scale reconstruction of past ozone variability. Our results indicate that the magnitude of recent ozone depletion is unprecedented over the past 7,700 years. These findings demonstrate the value of lake-sediment diatom assemblages as proxies for reconstructing past stratospheric ozone dynamics in Antarctica and contribute to a deeper understanding of long-term atmosphere-biosphere interactions in polar regions.

Abstract. Recent studies suggest that emissions from large forest fires affect stratospheric chemistry, dynamics, and climate, similar to major volcanic eruptions. Using the chemistry-climate model EMAC, we demonstrate that organic carbon emitted from forest fires, injected into the stratosphere through pyro-cumulonimbi, enhances heterogeneous chlorine activation related to high solubility of HCl in particles containing organic acids and an augmented aerosol surface area, in agreement with existing literature. Following the 2019/2020 Australian megafires, the upward transport of the pollution plumes resulted in enhanced ozone depletion in the Southern Hemisphere lower stratosphere, as corroborated by satellite observations. It diminished column ozone in the following two years, accompanied by a dynamically induced reduction in 2020 due to the lofting of smoke-filled vortices, in total by up to 45 DU. The eruption of the submarine Hunga Tonga volcano in January 2022 caused a decline in total ozone across the entire Southern Hemisphere. The water vapour injection from the volcano altered only the vertical distribution of ozone loss. The sunlight-absorbing aerosol from the Australian and, to a smaller extent, the Canadian forest fire emissions in 2019/2020 induced the most significant perturbation in stratospheric optical depth since the major eruption of Pinatubo in 1991. It shifted the sign of instantaneous stratospheric aerosol forcing, derived at the top of the atmosphere, from −0.2 to +0.3 W m−2 in January 2020. The global aerosol radiative forcing resulting from the Hunga Tonga eruption was −0.16 W m−2, primarily driven by changes in stratospheric sulfate aerosols. The positive radiative forcing from the injected water vapour was minimal.

Abstract. Tropospheric ozone trends are important indicators of climate forcing and surface pollution, yet relevant satellite observations are too uncertain for assessments. The assessment project TOAR-II has used multi-instrument, ground-based data for global trends over 2000–2022 (Van Malderen et al., 2025a, b). For the tropics, trends are derived from SHADOZ ozonesonde profiles (Thompson et al., 2021, “T21”; Stauffer et al., 2024) or combinations of satellite, SHADOZ and IAGOS aircraft measurements (Gaudel et al., 2024). We extend T21 that covered 1998–2019, analyzing SHADOZ data at five sites with a Multiple Linear Regression (MLR) model for 1998–2023 and reporting trends for two free-tropospheric (FT) segments, the lowermost stratosphere and the total tropospheric column (TrCOsonde). Trends for the Aura period, 2005–2023, are computed from OMI/MLS TrCOsatellite. We find the following: Extending SHADOZ analyses 4 years shows little change from T21; TrCOsonde trends are small (0.5–1 DU/decade) except over SE Asia. Annual trends for TrCOsonde and OMI/MLS TrCOsatellite agree within uncertainties at four of five sites, with the largest differences at Samoa. Sensitivity tests show the following: (a) Adding thousands of FT IAGOS profiles to SHADOZ yields little change in trends; SHADOZ sampling is sufficient. (b) Quantile Regression (QR) and MLR median trends are both near zero, but QR captures extremes (5th percentile, 95th percentile) with changes up to ±1 DU/decade (p< 0.10). (c) Twelve-year analyses for trends lead to uncertainty changes too large for an assessment. This study and Van Malderen et al. (2025a, b) provide the most reliable TOAR-II trends to date: over the past ∼ 25 years, tropical FT ozone changes have been modest, ∼ (−3–+3) %/decade, except over SE Asia.

Future changes in ozone and oxidation capacity in China under the carbon peaking policy: The role of emissions and meteorology.

Abstract. Chemistry-climate models have developed significantly over the decades, yet they still exhibit substantial systematic biases in simulating atmospheric composition due to gaps in our understanding of underlying processes. Building on deep learning's success in different domains, we explore its application to correct surface ozone biases in the state-of-the-art chemistry-climate model UKESM1. Six statistical models have been developed, and the model Transformer outperforms others due to its advanced architecture. A simple weighted ensemble approach is further proved to enhance performance by 14 % over the best single model Transformer, reducing RMSE to 0.69 ppb. Applied to future scenarios (SSP3-7.0 and SSP3-7.0-lowNTCF), the UKESM1 shows a larger overestimation of ozone changes by up to 25 ppb compared to present-day conditions. Despite biases, UKESM1 captures the non-linear ozone sensitivity to precursors, with temperature-sensitive processes identified as a dominant contributor to biases. We highlight that simulations of future surface ozone are likely to become less accurate under a warmer climate. Therefore, the bias correction approaches introduced here have substantial potential to improve the accuracy of ozone impact assessments. These methods are also applicable to other chemistry-climate models, which is critical for informing air quality and climate policy decisions.

Abstract. The climates of the mid-Holocene (MH) and Last Interglacial (LIG) are characterised by warm periods caused by astronomical forcing and climate feedback. One potential feedback is variation in the stratospheric ozone, the influence of which would extend down to the troposphere, potentially affecting the climate. However, little is known about the role of changes in the stratospheric ozone during past warm interglacial periods. Here, we employ MRI-ESM2.0, an Earth system model with an interactive ozone model, and simulate the climate and atmospheric ozone during the MH and LIG. We show that the vertical and seasonal changes of stratospheric ozone in the LIG exhibited a stronger variation in the stratospheric ozone compared to that in the MH, indicating that both obliquity and precession forcings affect the stratospheric ozone distributions. We further show that ozone feedbacks decrease the surface air temperature by ∼ 0.35 and ∼ 0.25 K in the high-latitude regions of the northern hemisphere in MH and LIG, respectively, while the impact on the zonal mean surface air temperature around Antarctica is small. This is the opposite of the previous finding that implies the importance of ozone in southern hemisphere climates, indicating the need for further assessment of how dynamic ozone variations affect climate and atmospheric structures during past warm interglacial periods using multiple Earth system models.

Abstract In addition to posing threats to life and property, tropical cyclones (TCs) can influence the chemical composition of the upper troposphere and lower stratosphere (UTLS). The transport of air between the troposphere and stratosphere, known as stratosphere‐troposphere exchange (STE), involves greenhouse gases such as ozone and water vapor whose impact on Earth's radiation budget and climate is most sensitive to changes in UTLS composition. Therefore, we examine observations of STE in TCs and relate these changes to TC and environmental characteristics. We utilize 17 years of trace gas profiles from the Microwave Limb Sounder aboard the Aura satellite in conjunction with TC track information and environmental data to relate UTLS ozone and water vapor changes to TC intensity, distance from TC center, and environmental wind shear. We find that accounting for varying tropopause heights and basin‐specific background composition is important to accurate assessment of UTLS composition changes within a TC. We also find that TCs are associated with increased water vapor throughout most of the UTLS and dehydration at tropopause level, while ozone is reduced greatly in the upper troposphere. All diagnosed UTLS composition changes demonstrate significant sensitivity to distance from TC center and TC intensity. Additionally, we find that TC‐induced UTLS water vapor changes are sensitive to environmental shear magnitude, where weaker shear is associated with more pronounced tropospheric hydration and tropopause dehydration.

Abstract. We extended the Linearized ozone scheme – LINOZ in the ICON (ICOsahedral Nonhydrostatic) – ART (the extension for Aerosols and Reactive Trace gases) model system to include NOy formed by auroral and medium-energy electrons in the upper mesosphere and lower thermosphere, and the corresponding ozone loss, as well as changes in the rate of ozone formation due to the variability of the solar radiation in the ultraviolet wavelength range. This extension allows us to realistically represent variable solar and geomagnetic forcing in the middle atmosphere using a very simple ozone scheme. The LINOZ scheme is computationally very cheap compared to a full middle atmosphere chemistry scheme, yet provides realistic ozone fields consistent with the stratospheric circulation and temperatures, and can thus be used in climate models instead of prescribed ozone climatologies. To include the reactive nitrogen (NOy) produced by auroral and radiation belt electron precipitation in the upper mesosphere and lower thermosphere during polar winter, the so-called energetic particle precipitation indirect effect, an upper boundary condition for NOy has been implemented into the simplified parameterization scheme of the N2O/NOy reactions. This parameterization, which uses the geomagnetic Ap index, is also recommended for chemistry-climate models in the CMIP6 experiments. With this extension, the model simulates realistic “tongues” of NOy propagating downward in polar witner from the model top in the upper mesosphere into the mid-stratosphere with an amplitude that is modulated by geomagnetic activity. We then expanded the simplified ozone description used in the model by applying LINOZ version 3. The additional ozone tendency from NOy is included by applying the corresponding terms of the version 3 of LINOZ. This NOy, coupled as an additional term in the linearized ozone chemistry, led to significant ozone losses in the polar upper stratosphere in both hemispheres which is qualitatively in good agreement with ozone observations and model simulations with EPP-NOy and full stratospheric chemistry. In a subsequent step, the tabulated coefficients forming the basis of the LINOZ scheme were provided separately for solar maximum and solar minimum conditions. These coefficients were then interpolated to ICON-ART using the F10.7 index as a proxy for daily solar spectra (UV) variability to account for solar UV forcing. This solar UV forcing in the model led to changes in ozone in the tropical and mid-latitude stratosphere consistent with observed solar signals in stratospheric ozone.

Abstract Solar eclipse events (SEs) provide an excellent natural experiment for the response of the middle atmosphere to short‐term changes in solar radiation. For this study, we quantify radiation variations through obscuration, which is defined as the fraction of the solar disk obscured by the Moon during SEs. Using Aura Microwave Limb Sounder satellite observations, we analyze the changes in the average ozone mixing ratio at the upper stratosphere and the lower mesosphere during multiple SEs since July 2004. The results show that during SEs, ozone at the upper stratosphere and the lower mesosphere is sensitive to short‐term solar radiation changes and increases to about twice the normal daytime ozone mixing ratio. The ozone increase tends to level off with increasing obscuration during SEs, especially near the totality. We estimate that the effect of water vapor photolysis, the primary photochemical process of mesospheric ozone depletion, is greatly suppressed during SEs. Furthermore, we detect O 3 changes at 0.46 hPa, which cannot be explained solely by changes in temperature or solar radiation. However, CO observation, a long‐lived tracer, did not reveal any common characteristics in dynamical behavior related to O 3 changes near the stratopause.

This study analyses the stratospheric concentrations of ozone (O3) and nitrogen dioxide (NO2) over a 16-year period (2005 to 2020) over central Brazil using satellite data with the aim of determining the influence of NO2 on ozone distribution and the impact of fires and volcanic eruptions on these gases. The analysis shows that ozone and NO2 follow seasonal patterns, with the highest concentrations occurring in September and October and the lowest from January to June. A positive correlation was found between the concentrations of ozone and NO2, and the results of the Fourier analysis indicate semi-annual and annual cycles in the concentrations of these gases. Although there was an increase in the number of fires in the last 11 years of the study, this increase did not lead to significant changes in ozone or NO2 concentrations, indicating the stability of these parameters in the observed area. It is presumed that the reason for the lack of changes is lower intensity of fires despite their increased number. Regarding wind patterns, it is observed that they do not differ much either which is in accordance with the fact that the monitored area is fairly close to the equator.

Abstract. As part of the Quality Assurance (QA) plan of the In-service Aircraft for a Global Observation System (IAGOS), IAGOS-CORE and IAGOS-CARIBIC UV-photometer instruments have been compared with the dual-beam UV- Ozone (O3) PhotoMeter (OPM) of the World Calibration Center of Ozone Sondes (WCCOS) at the Forschungszentrum Jülich in an environmental simulation chamber. The WCCOS is established since about 30 years ago as part of the WMO-GAW measurement quality program of the global ozonesonde network, in which the OPM instrument serves as the ozone reference standard. In the simulation chamber, pressure, temperature, and ozone concentration can be controlled at quasi-realistic flight conditions between the Earth surface (∼ 1000 hPa) and ∼ 35 km altitude (5 hPa). During the intercomparison, different ascent/descent and cruise altitude profiles of ozone, pressure and temperature have been simulated between the surface and ∼ 12.5 km altitude (200 hPa). In general, the two O3 instruments P1-O3 (IAGOS-CORE) and CAR-O3 (IAGOS-CARIBIC) showed good agreement with the OPM reference standard within 5 %–6 %. At a pressure of 400–500 hPa the agreement was even within 2 %. The observed differences are small but systematic and reproducible during this experiment. CAR-O3 showed a small, pressure-independent deviation of −2 ± 1.5 % compared to the OPM. P1-O3 revealed O3 deviation to the OPM which changes with pressure of about +2 % at 1000 hPa to −3 % at 400 hPa, which might be an artefact on the experimental set-up and subject for further investigations. This intercomparison is a first step of the long-term goal to make the global ozone sonde data (GAW-NDACC-SHADOZ-GRUAN) and IAGOS-O3 (CORE: P1-O3, CARIBIC: CAR-O3) data traceable to one common reference, the OPM instrument of WCCOS. Recommendations are made for further regular (every two to three years) intercomparison of the operational instruments to ensure external consistency in general and specifically towards the synergy of IAGOS-O3 and ozonesonde data. An important gap in such intercomparison studies is the lack of a reference ozone instrument operated at reduced pressures at any National Metrological Institute in the world. For observation networks measuring vertical ozone profiles, it is essential to close this gap to enable the traceability of ozone measurements from different platforms to one reference standard. This is crucial to harmonize long-term ozone records to detect any changes of ozone in the free atmosphere.

Abstract. This study assesses three different measures of radiative forcing (instantaneous: IRF; stratospheric-temperature adjusted: SARF; effective: ERF) for future changes in ozone. These use a combination of online and offline methods. We separate the effects of changes in ozone precursors and ozone-depleting substances (ODSs) and configure model experiments such that only ozone changes (including consequent changes in humidity, clouds and surface albedo) affect the evolution of the model physics and dynamics. In the Shared Socioeconomic Pathway 3-7.0 (SSP3-7.0) we find robust increases in ozone due to future increases in ozone precursors and decreases in ODSs, leading to a radiative forcing increase from 2015 to 2050 of 0.268 ± 0.084 W m−2 ERF, 0.244 ± 0.057 W m−2 SARF and 0.288 ± 0.101 W m−2 IRF. This increase makes ozone the second largest contributor to future warming by 2050 in this scenario, approximately half of which is due to stratospheric ozone recovery and half due to tropospheric ozone precursors. Increases in ozone are found to decrease the cloud fraction, causing an overall negative adjustment to the radiative forcing (positive in the short wave but negative in the long wave). Non-cloud adjustments due to water vapour and albedo changes are positive. ERF is slightly larger than the offline SARF for the total ozone change but approximately double the SARF for the ODS-driven change (0.156 ± 0.071 W m−2 ERF, 0.076 ± 0.025 W m−2 SARF). Hence ERF is a more appropriate metric for diagnosing the climate effects of stratospheric ozone changes.