(i) the radiative forcings of past eruptions and the microphysical, chemical and dynamical processes which affect the evolution of stratospheric aerosol properties and
(ii) the response mechanisms governing post-eruption climate variability and their dependency on the climate state at the time of the eruption.
This can only be achieved by combining information from satellite and in-situ observations of recent eruptions, stratospheric aerosol and climate modelling activities, and reconstructions of past volcanic histories and post-eruption climate state from proxies.
In recent years the smoke from intense wildfires in North America and Australia has also been an important component of the stratospheric aerosol layer, the presence of organic aerosol and meteoric particles in background conditions now also firmly established.
This session seeks presentations from research aimed at better understanding the stratospheric aerosol layer, its volcanic perturbations and the associated impacts on climate through the post-industrial period (1750-present) and also those further back in the historical record.
Observational and model studies on the stratosphere and climate impacts from the 2022 eruption of Hunga Tonga are also especially welcomed.
We also welcome contributions to understand the societal impacts of volcanic eruptions and the human responses to them. Contributions addressing volcanic influences on atmospheric composition, such as changes in stratospheric water vapour, ozone and other trace gases are also encouraged.
The session aims to bring together research contributing to several current international co-ordinated activities: SPARC-SSiRC, CMIP7-VolMIP, CMIP7-PMIP, and PAGES-VICS.
Stratospheric aerosol forcing, which primarily represents aerosols from explosive volcanic sulfur emissions, is a key natural forcing dataset for Phase 7 of the Coupled Model Intercomparison Project (CMIP7) climate modelling experiments. The CMIP7 stratospheric aerosol forcing datasets for the historical period (1750-2023) include (1) stratospheric sulfate aerosol optical properties, and (2) upper tropospheric-stratospheric volcanic sulfur dioxide emissions. Understanding how historical volcanic forcing has changed from CMIP6 to CMIP7 is essential for interpreting differences in simulation results across CMIP phases and assessing model performance. A key methodological advance in CMIP7 is the emission-driven approach for pre-satellite era stratospheric aerosol optical properties, which incorporates additional ice-core-based volcanic sulfur emission data compared to CMIP6. In this study, we present a systematic evaluation comparing the CMIP6 and CMIP7 stratospheric aerosol forcing datasets against observations, including aerosol optical depth estimates from lunar eclipses, stellar extinction, and satellite retrievals. The comparison provides an in-depth analysis of spatial and temporal patterns in stratospheric aerosol optical depth across CMIP6 and CMIP7, examining both background climatology and selected large-magnitude eruptions in the pre-satellite and satellite eras. This evaluation highlights the key differences between CMIP6 and CMIP7 datasets, improvements achieved through updated methodologies, their potential implications for climate simulations, and directions for future forcing dataset development.
How to cite: Chim, M., Stiller, D., Ziegler, E., and Aubry, T. J. and the CMIP7 Stratospheric Aerosol Forcing Evaluation Team: Evaluation of the CMIP7 historical stratospheric aerosol forcing dataset, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7896, https://doi.org/10.5194/egusphere-egu26-7896, 2026.
How to cite: Añel, J. A., Antuña-Marrero, J. C., Calle, A., Cachorro, V., de la Torre, L., Barriopedro, D., García-Herrera, R., van den Bosch, J., and Pacheco, J.: Extending the late 1963 to 1964 Mt Agung rescued searchlight aerosol profiles dataset, from early 1963 to 1976., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19794, https://doi.org/10.5194/egusphere-egu26-19794, 2026.
This study provides a comprehensive analysis of the climate response in Northern Hemisphere winter to major volcanic eruptions of the past, using multi-member ensembles of historical experiments of 15 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) and three reanalysis data sets. Focusing on the two largest historical eruptions of Krakatoa and Pinatubo, the results highlight a large model consensus on the strengthening of the polar vortex and an associated increase in surface temperatures over parts of Northern Eurasia in the CMIP6 multi-model mean in the first winter following the eruptions. This finding is consistent with models simulating a positive phase of the North Atlantic Oscillation. The responses of the surface temperatures and winds show hardly any dependence on the phase of the El Nino-Southern Oscillation. Our results further underline a strong influence of internal variability on the simulated near-surface responses to volcanic forcing, even in the case of these strong eruptions. Thus, separating the influence of internal variability from the forced response requires output from large ensembles of historical simulations.
Reference
Weber, L., Krüger, K., and Fiedler, S.: On CMIP6 model consensus for the climate response in Eurasian winter to historical volcanic eruptions, in revision.
How to cite: Fiedler, S., Krüger, K., and Weber, L.: Do CMIP6 models agree on the climate response in Eurasian winter to major volcanic eruptions since 1850?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13126, https://doi.org/10.5194/egusphere-egu26-13126, 2026.
Rapid adjustments are a key component of effective radiative forcing, influencing both short- and long-term climate responses and prediction uncertainty. Volcanic eruptions act as “natural laboratories” for studying these adjustments, providing insights into the atmospheric and surface mechanisms that occur in response to sudden stratospheric aerosol perturbations.
To disentangle these responses from internal variability and anthropogenic trends, we adopt a stepwise approach, analysing six model and observational datasets that capture rapid adjustments to imposed negative shortwave forcing. These include idealized reduced-solar-constant datasets (abrupt-solm4p from CFMIP), idealized stratospheric aerosol layer simulations with non-absorbing and absorbing aerosols (provided by Moritz Günther), and fixed as well as fully coupled sea surface temperatures. Furthermore, the volc-pinatubo-full simulations from VolMIP, CMIP6 historical simulations, ERA5 reanalysis, and CLARA satellite observations were analysed.
Across these datasets, we identify characteristic adjustment patterns of radiative fluxes, temperature, circulation, and cloud properties on timescales of months to a year after peak forcing. In volcanic eruptions, stratospheric temperature and dynamical adjustments play a key role and are often closely coupled to tropospheric responses. Comparing idealized solar and aerosol forcing with realistic Pinatubo simulations and observations allows us to assess the extent to which simplified experiments capture essential adjustment patterns typical for volcanic eruptions.
Results reveal consistent vertical and regional adjustment fingerprints across datasets, while also highlighting model limitations. For example, due to low stratospheric resolution and simplified QBO parametrizations, models fail to reproduce the full stratospheric temperature response observed in ERA5, whereas observations are more strongly influenced by internal variability than ensemble-mean model results.
These findings demonstrate the value of volcanic eruptions as a useful tool for constraining rapid adjustments to shortwave forcing and for improving their representation in climate models.
How to cite: Lange, C. and Quaas, J.: Understanding rapid adjustments to shortwave forcing: from idealized solar perturbations to model and observational analysis of the 1991 Pinatubo eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14962, https://doi.org/10.5194/egusphere-egu26-14962, 2026.
ESA’s EarthCARE satellite mission launched in May 2024 and carrying Atmospheric LIDar (ATLID) provides high-resolution vertical profiling of aerosols and clouds at 355 nm. Fully operational since August 2024, ATLID has been witness to a significant perturbation of stratospheric aerosol budget following the eruptions of Ruang volcano (Indonesia) in late April 2024 as well as to a major panboreal outbreak of wildfire-generated pyrocumulonimbus (pyroCb) events in Canada and Siberia in late May 2025 that had a hemisphere-scale impact on stratospheric aerosol loading and composition. Using ATLID L1B data together with limb-viewing satellite observations (OMPS-LP and SAGE III), we quantify the stratospheric aerosol perturbations generated by these events, characterize the long-range transport of volcanic and smoke aerosols and contrast their optical properties and dynamical evolution.
To evaluate the ATLID performance in the stratosphere, its data are compared with collocated lidar observations at various locations in both hemispheres and overpass-coordinated balloon flights in France carrying in situ aerosol sensors. The intercomparison with suborbital observations suggests excellent performance of ATLID in the stratosphere and proves its capacity to accurately resolve fine structures in the vertical distribution of stratospheric aerosols.
ATLID observations of the global progression of volcanic and wildfire aerosols align closely with those from OMPS-LP and SAGE III, while uniquely providing continuous coverage through polar night. We show that Ruang aerosols were subject to an unusually massive isentropic transport into the southern extratropics and were most probably entrained by the 2025 Antarctic polar vortex, potentially enhancing the polar stratospheric cloud occurrence and Antarctic ozone hole.
The stratospheric aftermath of the 2025 panboreal wildfire outbreak (POW) was characterized through a synergy of ATLID and ground-based lidar observations within ACTRIS and NDACC networks. The lidar measurements consistently report record-breaking values of stratospheric aerosol backscatter and AOD during the passage of the most intense Canadian pyroCb plume. This plume displayed a pronounced warm anomaly, linked to strong solar absorption by black carbon, and underwent diabatic self-lofting from ~13 km to 20 km altitude. ATLID further indicates that smoke aerosols dispersed across the northern extratropical stratosphere and may have penetrated into the tropics.
How to cite: Khaykin, S., Soares, O., Kadygrov, N., Sicard, M., Leblanc, T., Berthet, G., Balugin, N., Sakai, T., Jin, Y., and Liley, B.: Global Transport and Composition of Volcanic and PyroCb Stratospheric Aerosols Observed by EarthCARE/ATLID and ground-based lidars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14031, https://doi.org/10.5194/egusphere-egu26-14031, 2026.
This talk presents the highlights of the third chapter of the APARC Hunga Volcanic Eruption Atmospheric Impacts Report. The study focuses on the global meridional and vertical evolution of the Hunga sulphate aerosols and water vapour after the full zonal dispersion of the plume, which occurred about one month after the eruption. Measurements from satellites, balloon, and ground-based stations are used to track the dispersion of water vapour and aerosol, and to document the evolution of the aerosol size distribution. The uncertainties in the satellite observations are assessed using detailed intercomparisons. Finally, results from dedicated climate model simulations of the global transport and evolution of Hunga aerosol and water vapour in comparison to the observations are summarized.
How to cite: Bourassa, A., Khaykin, S., Aquila, V., Baron, A., Rieger, L., Rozanov, A., and Ueyama, R.: Atmospheric transport and evolution of Hunga water vapour and aerosols , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14830, https://doi.org/10.5194/egusphere-egu26-14830, 2026.
The eruption of the Hunga volcano on January 15, 2022, was unprecedented in the satellite record because of the ~150 Tg of water injected in the stratosphere, paired to a relatively low (~0.5 Tg) sulfur dioxide injection. The uniqueness of this eruption provides an opportunity to evaluate chemistry-climate models over a new range of conditions, different from the sulfur rich eruptions on which they have generally been tested. We describe coordinated Hunga simulations from ten chemistry climate models with prognostic aerosol modules and show how the presence of the volcanic water vapor led to larger particles than would occur in a water-poor eruption. This has the effect of rapidly increasing the stratospheric aerosol optical depth in the first month and accelerating the settling of the volcanic aerosols in the following months. While the models are able to reproduce the observed evolution of the water vapor eruption plume and the distribution of volcanic aerosols. they fail to simulate the aerosol optical depth. Most of the difference between models and observations, and among models themselves, can be traced to the aerosol microphysics, which is highly dependent on the parameterizations made by each model.
How to cite: Aquila, V., Ueyama, R., Bourassa, A., Khaykin, S., Baron, A., Rieger, L., and Rozanov, A. and the Hunga Tonga–Hunga Ha′apai Volcano Impact Model Observation Comparison (HTHH-MOC) Team: Multi-model simulations of the evolution of aerosols and water vapor from the Hunga eruption., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4069, https://doi.org/10.5194/egusphere-egu26-4069, 2026.
We have developed a new set of radiative kernels to facilitate the quantification of the stratospheric aerosol direct radiative effect. The multi-dimensional kernel dataset quantifies the radiative sensitivity, which varies with latitude, longitude, time, and wavelength, to stratospheric aerosol optical depth (AOD), distinguishing absorptive and scattering aerosol types. Besides the geographical varying band-by-band kernels, we also introduce an analytical method that emulates the kernel values as a function of environmental control factors, including top-of-atmosphere insolation and reflectance. Applying these kernels, we estimate the stratosphere aerosol radiative effects of the 2022 Hunga volcanic eruption and the 2020 Australian wildfire. The Hunga eruption resulted in a global mean cooling effect of approximately -0.4 W/m² throughout 2022. In contrast, the Australian wildfire induced a global mean instantaneous ARE of +0.3 W/m² and a stratosphere-adjusted ARE of -0.04 W/m². Validation against radiative transfer model calculations confirms the accuracy of the kernel-based estimates. Our findings underscore the significance of spectral dependencies in stratospheric aerosol radiative effect and highlight the distinct radiative sensitivities of stratospheric aerosols compared to their tropospheric counterparts. The radiative kernels afford an efficient and versatile tool for assessing the climatic impacts of stratospheric aerosols.
How to cite: Huang, Y. and Yu, Q.: Estimation of the radiative effect of stratospheric aerosols using a new set of radiative kernels , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3194, https://doi.org/10.5194/egusphere-egu26-3194, 2026.
The Hunga Tonga-Hunga Ha'apai underwater volcanic eruption in January 2022 injected 150 Tg of water vapour (H2O) into the stratosphere, increasing the total stratospheric H2O mass by 10%. The goal of this study is to investigate the transport of the Hunga H2O within, and out of, the stratosphere in the four years since the eruption, using H2O observations from the Microwave Limb Sounder (MLS) and model simulations from WACCM and FLEXPART. The Hunga H2O is isolated by using the tropical cold point temperature to account for H2O that entered the stratosphere through the tropical tropopause, rather than via the eruption. The resulting residual H2O shows that the Hunga water vapor has moved to higher latitudes and lower altitudes over time. There is excess H2O in the tropics in 2023 and 2024, providing evidence of mixing from mid-latitude back to the tropics. As of mid-2025, approximately half of the 150 Tg of H2O that was injected by Hunga has either been removed or transported to the lowermost stratosphere.
How to cite: Dubé, K., Randel, W., Bourassa, A., Tegtmeier, S., Wang, X., Hlady, E., and Brehon, M.: The evolution of stratospheric water vapour in the years since the Hunga Tonga eruption , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15123, https://doi.org/10.5194/egusphere-egu26-15123, 2026.
The January 2022 eruption of the Hunga volcano (20°S) injected 150 Tg of water vapour into the middle atmosphere, leading to an increase in the stratospheric water burden of 10%, unprecedented in the observational record. In the first two years post-eruption, the stratospheric burden hardly changed (Millán et al., 2024), except for a small decay due to Antarctic polar stratospheric cloud dehydration in 2023 (Zhou et al., 2024), leaving the residence time of volcanically injected water vapour—a key control on its climate impact—uncertain. Here we use satellite observations from the Microwave Limb Sounder (MLS) and an off-line 3-D chemical transport model (CTM), TOMCAT/SLIMCAT, with ERA5 meteorology to study the residence time of this excess H2O.
Using MLS observations, we show a substantial decline from 2024 to early 2025, the largest drop since the eruption. Simulations with the TOMCAT/SLIMCAT CTM reproduce the observed global spread and decline of the injected H2O through early 2025. Together, observations and model simulations indicate that the long-term removal of the Hunga water has now entered a new phase, with stratosphere-troposphere exchange playing an increasingly important role, exceeding Antarctic dehydration in 2024. We estimate that the additional stratospheric water vapour is now decaying steadily with an e-folding time of 3 years and will reach the observed pre-Hunga range of variability around 2030.
The presentation will provide an up-to-date status of observations and discuss whether the decay of the Hunga excess water is proceeding as expected.
How to cite: Zhou, X., Chen, Q., Feng, W., Heddell, S., Dhomse, S., Mann, G., Pumphrey, H., and Santee, M.: Residence time of Hunga stratospheric water vapour perturbation quantified at 9 years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22524, https://doi.org/10.5194/egusphere-egu26-22524, 2026.
Volcanic eruptions in the tropics inject aerosols into the stratosphere, altering radiative fluxes and perturbing climate patterns, including the El Niño–Southern Oscillation (ENSO). Using a set of 40-member ensemble simulations with the NorESM1-M model, we investigate how the season and hemisphere of tropical eruptions influence ENSO responses. Our results demonstrate that the eruption season significantly modulates aerosol distribution and radiative forcing, with summer eruptions producing up to 50% stronger forcing than fall or winter events. ENSO responses exhibit a pronounced phase-locking behavior: tropical Northern Hemisphere eruptions in spring or summer trigger El Niño-like anomalies in the first post-eruption winter, followed by La Niña-like conditions in the second year, whereas fall and winter eruptions produce weaker, delayed anomalies. Southern Hemisphere eruptions generally induce muted ENSO signals, emphasizing the role of hemispheric location in modulating response amplitude. These findings reveal a two-tiered control on volcanic impacts: eruption timing sets the ENSO “anomaly clock,” while injection hemisphere modulates its strength, highlighting the importance of seasonality in predicting climate responses to tropical volcanic events.
How to cite: Pausata, F. S. R. and Zanchettin, D.: Seasonal Timing Controls ENSO Responses to Tropical Volcanic Eruptions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6092, https://doi.org/10.5194/egusphere-egu26-6092, 2026.
Stratospheric volcanic aerosols can induce global cooling and other climatic effects on annual to multi-decadal timescales. Future global warming is projected to affect atmospheric processes governing volcanic plume dynamics and stratospheric aerosol transport. For instance, tropospheric warming driven by anthropogenic emissions leads to increased tropopause height and reduced tropical temperature lapse rate, resulting in enhanced atmospheric stratification. In addition, the Brewer-Dobson circulation is expected to accelerate under climate warming. These atmospheric changes can significantly influence volcanic plume rise dynamics, sulfate aerosol lifecycle, and the magnitude of radiative forcing. Despite growing recognition of climate-volcano feedbacks, few studies have examined their effects within fully-coupled Earth System Models.
In this study, we investigated the climate effects of future volcanic eruptions under different background climate states, including pre-industrial, low-end (SSP1-2.6) and high-end (SSP3-7.0) future anthropogenic emission scenarios. We first generated stochastic future eruption scenarios based on an array of bipolar ice cores, satellite measurements, and geological records spanning the past 11,500 years. We then simulated climate projections from 2015 to 2100 using three selected stochastic scenarios representing low-end, median, and high-end future volcanic activity within a plume-aerosol-chemistry-climate modelling framework (UKESM-VPLUME) with interactive volcanic aerosols. The UKESM-VPLUME framework couples a 1-D eruptive plume model (Plumeria) with the UK Earth System Model, enabling the simulation of injection height changes under different background climate states. Our results show that volcanic effects on stratospheric aerosol optical depth, effective radiative forcing, and global mean surface temperature are greater under climate warming for both tropical and extratropical eruptions. Our findings demonstrate the importance of accounting for climate-volcano feedbacks to understand long-term volcanic radiative forcing in future climates.
How to cite: Chim, M., Aubry, T., and Schmidt, A.: Climate-volcano feedbacks under global warming, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7286, https://doi.org/10.5194/egusphere-egu26-7286, 2026.
Much previous modeling work on the climate response to volcanic eruptions has focused on specific past events. Here, we explore the climate response over a whole range of amplitudes covering (and exceeding) all events of the last six millennia, by simulating eruptions with 5, 10, 20, 40, 80, and 160 Tg of stratospheric injected sulfur. Our simulations show a strongly non-linear relationship between eruption magnitude and climate response, with temperature and precipitation responding differently. Global mean surface cooling saturates at 40 TgS, whereas precipitation decreases all the way to 160 TgS. We also find that the precipitation responds and recovers faster than the temperature, especially for the larger events. Our findings imply that a severe reduction in precipitation, rather than a dramatic surface cooling, might be the most important climatic impact associated with very large eruptions.
How to cite: Raiter, D., McGraw, Z., and Polvani, L.: Non‐linear and distinct responses of temperature and precipitation to volcanic eruptions with stratospheric sulfur injection from 5 to 160 Tg, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2844, https://doi.org/10.5194/egusphere-egu26-2844, 2026.
Radiative forcing from stratospheric aerosols produced by major volcanic eruptions is likely to be the primary forcing agent of preindustrial climate variability, and will have a significant impact on climate when the next strong eruption occurs. The radiative forcing from volcanic eruptions is relatively short-lived, and the surface cooling is controlled by various factors including the magnitude of the forcing, its duration, the climate feedback parameter and other aspects like effective ocean heat capacity and ocean mixing. Here, we explore analytical solutions to simple energy balance models using idealized forms of volcanic aerosol forcing, and estimate model parameters based on comprehensive Earth-System Model simulations of volcanic forcing from VolMIP and LESFMIP experiments. We use the analytical solutions to explore relationships between forcing and response, for example, between the magnitude of forcing and the peak temperature anomaly, and the sensitivity of these relationships to the model parameters.
How to cite: Toohey, M. and Morovati, M.: Using simple models to understand the global mean temperature response to volcanic aerosol forcing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14229, https://doi.org/10.5194/egusphere-egu26-14229, 2026.
Some major volcanic eruptions, such as the one of Mt. Pinatubo in 1991, can inject large amounts of sulfur dioxide (SO2) into the stratosphere, leading to the formation of a volcanic aerosol cloud. This dense aerosol cloud induces radiative heating of the stratosphere, causing ozone and water vapour changes, thereby altering middle atmospheric dynamics and chemistry. The scale of these impacts on stratospheric temperature anomalies is still highly uncertain.
In this study we analyse data from the Historical Eruptions SO2 Emission Assessment Protocol (HErSEA) under the Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP). The results from eight global interactive-aerosol models confirm our general understanding of the stratospheric aerosol forcing due to SO2 injection following a volcanic eruption. As direct observations are sparse we compare models to three widely used reanalyses (ERA5, MERRA2, and JRA55). This analysis shows that while the multi-model mean temperature anomalies agree well with reanalyses, differences among individual models can be large. Our study shows that agreement in the median occurs through error compensation when averaging across models. The analysis and the sensitivity tests for model selection presented here highlight that by far the most important factor driving both magnitude and spread of the multi-model distribution in temperature response to volcanic aerosol forcing is model choice. Differences in transport, radiative transfer, and microphysics as well as the characterization of aerosol size distributions play a crucial role for the simulated spread in the temperature response.
Another candidate to explain the spread in the ISA-MIP models, is the use of interactive aerosol schemes. To test this hypothesis, we compared the ISA-MIP multi-model distribution with those obtained from CCMI-2022 and CMIP6-AMIP model intercomparisons, which use prescribed SADs. If indeed interactive aerosol treatment would be a key contributor, one would expect smaller multi-model temperature anomaly distributions from CCMI-2022 and CMIP6-AMIP. Interestingly, this hypothesis has to be rejected, as no reduction in the multi-model spread is found. Hence, we argue for caution in attribution studies and the interpretation of stratospheric aerosol injection experiments relying on individual or few models.
How to cite: Perny, K., Sukhodolov, T., Kuchar, A., Arsenovic, P., Rosati, B., Brühl, C., Dhomse, S. S., Jörimann, A., Laakso, A., Mann, G., Niemeier, U., Pitari, G., Quaglia, I., Sekiya, T., Sudo, K., Timmreck, C., Tilmes, S., Visioni, D., and Rieder, H. E.: An assessment of the stratospheric temperature response to volcanic sulfate injections from recent Model Intercomparison Projects, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17112, https://doi.org/10.5194/egusphere-egu26-17112, 2026.
The submarine eruption of the Hunga Tonga-Hunga Ha’apai (HTHH) in January 2022 represents a novel geophysical event due to the injection of large amounts of water vapor (WV) into the stratosphere. Following the eruption, the injected WV was transported from the tropics to higher latitudes via stratospheric circulation. Approximately one year after the eruption, the WV anomalies were spread throughout the global stratosphere, including both polar regions.
Previous studies have shown that the excess stratospheric WV was associated with significant anomalies in atmospheric circulation, particularly a weakening of the Northern Hemisphere (NH) stratospheric polar vortex (SPV). However, the observed 2024/2025 winter with an exceptionally strong NH SPV may represent a plausible manifestation of HTHH-induced modulation of vortex variability.
Here we diagnose the chain of processes linking the HTHH eruption to the exceptional behavior of the SPV observed in recent years using satellite observations, reanalyses data, and ensemble model simulations with the SOCOLv4 Earth system model, as well as model data from the HTHH Impact Model Observation Comparison project.
Our preliminary multi-model results show a seasonally recurring transport of WV in the stratosphere and lower mesosphere, accompanied by changes in composition, radiation, and dynamics. We propose mechanisms whereby excess WV from HTHH and associated ozone changes induce radiative perturbations that precondition the SPV. Furthermore, we examine how the underlying mechanisms depend on the model-projected WV forcing and how this relates to known biases of chemistry-climate models.
How to cite: Lehner, B., Kuchar, A., and Rieder, H.: Simulated modulation of stratospheric polar vortices by the Hunga Tonga-Hunga Ha’apai eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17957, https://doi.org/10.5194/egusphere-egu26-17957, 2026.
In contrast to the near-quiescent decades of the 1920s-1950s, the 1960s stratospheric aerosol layer had continued volcanic enhancement, with the major eruption of 1963 Agung and the subsequent VEI4 eruptions of 1965 Taal, 1966 Awu and 1968 Fernandina.
The first in-situ measurements of a volcanic enhancement to the stratosphere aerosol layer were made from high-altitude balloon in 1963 and 1964, from Minneapolis. A continuing program of these dust-sondes were launched approximately quarterly from Minneapolis, and a short series of launches from Panama in September 1966 (Rosen, 1968) measured strong volcanic enhancement just weeks after the Aug 1966 Awu eruption.
A different series of balloon measurements were made from Minneapolis in 1965-1968, and within coincident soundings in Panama in Sep 1966. This instrument was a rotating 4-telescope sun photometer designed to measure the vertical profile of solar extinction at 4 wavelengths and provided the foundations for the SAGE and SAM satellite instruments launched in 1979. A 2021 MRes project at Leeds University has recovered the vertical profile datasets of the 910nm channel of these 22 balloon solar extinction soundings from Figures within the University of Wyoming PhD thesis of Ted Pepin.
This poster presentation will present the 1965-1968 solar extinction measurements, analysed within an 2024/25 undergraduate dissertation project, comparing to CMIP stratospheric aerosol forcing datasets and showing the clear signal of volcanic enhancement apparent during NH winter 1966/67. We are preparing the dataset for inclusion in the archive of the Network for Detection of Atmospheric Composition and Change (NDACC), alongside the 1963-1967 dust-sonde measurements provided in 2017 to the NDACC archive by the instrument PI (James Rosen (University of Wyoming).
We will analyse 1963-67 simulations with the UM-UKCA interactive stratospheric aerosol model, from continuing from runs already validated for the Agung period (Dhomse et al. 2020). The Minneapolis balloon measurements will be used to assess potential SO2 emissions from 1965 Taal (September) and 1966 Awu (August), the 3D model shown to represent well variations in the transport to mid-latitudes of volcanic aerosol from similar tropical eruptions.
How to cite: Mann, G., Xu, J., Tate, C., Dhomse, S., Feng, W., Rap, A., and Li, Z.: Measurements and interactive modeling of the 1960s stratospheric aerosol layer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21627, https://doi.org/10.5194/egusphere-egu26-21627, 2026.
The 1912 eruption of Katmai/Novarupta injected an estimated 7 Tg SO2 into the atmosphere leading to Northern Hemisphere cooling. The eruption has been an important case study for deriving the relationship between ice-sheet sulfate deposition and stratospheric SO2 emission, the so-called ‘transfer function’, which has been subsequently used to estimate the SO2 emissions for other historical extratropical eruptions. However, new ice core data and sulfate isotope analyses demonstrate that a portion of the SO2 was injected below the stratospheric ozone layer, suggesting a lower injection altitude for the plume bottom than previously assumed, with implications for the transfer function. Here, using the UK Earth System Model and an interactive aerosol scheme, we investigate the role of injection altitude and magnitude and revisit the transfer function and climate response considering both tropospheric and stratospheric SO2 emissions.
How to cite: Marshall, L., Burke, A., Yu, Y., and Krüger, K.: Exploring the role of SO2 emission altitude in the 1912 eruption of Katmai/Novarupta, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9868, https://doi.org/10.5194/egusphere-egu26-9868, 2026.
The 2019 Raikoke eruption injected material directly into the stratosphere and had major impact on climate. The particle composition of the volcanic aerosols still remains debated today. The eruption generated usual hemispherically-dispersed plumes, but also a long-lived, compact and vorticized volcanic plume (VVP). While this type of plume is usually observed for biomass burning aerosol smoke plumes, it is identified for the first time after a volcanic eruption. A synergistic analysis of S5P/TROPOMI, MetOp/IASI, CALIPSO/CALIOP and AERONET data is conducted to retrieve particle size in the VVP and in the dispersed plumes. In the VVP, fine particle peak radii increased to a record size within three months after the eruption. It is three times greater than the particle radius retrieved in the dispersed plumes, and even greater than the one reached by the strongest eruption of the last decades, i.e., the 1993 Mt Pinatubo eruption. The growth coincides with the decrease in SO2 concentration, suggesting the growth of sulfate aerosols. However, dynamical, optical and radiative signatures point to a more complex composition, where submicronic ash become coated by sulfates. This phenomenon is enhanced in the VVP where SO2 concentration is initially one order of magnitude higher than in the dispersed plumes, because of its vorticized nature. It means that the local SO2 concentration is the critical factor limiting sulfate aerosols growth, and not the total eruption SO2 emission budget. Finally, this unprecedented particle size observed in the VVP with persisting submicronic ash calls for a re-evaluation of the current approach for modeling impacts of stratospheric eruptions on climate.
How to cite: Ruyneau de Saint-George, P., Boichu, M., Bonnat, J., Grandin, R., Goloub, P., Mathurin, T., and Pascal, N.: Record growth of stratospheric aerosols from 2019 Raikoke eruption with sulfate-coating of submicronic ash, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1797, https://doi.org/10.5194/egusphere-egu26-1797, 2026.
Reconstructions of past volcanic forcing and the associated climate response are currently limited to volcanic stratospheric sulfur injections (VSSI) by explosive eruptions. Transfer functions that link volcanic SO4 depositions in polar ice cores with VSSI are estimated based on observations and climate modeling. Tropospheric sulfur emissions from effusive and explosive eruptions are climate-relevant, yet historical volcanic sulfur fluxes to the troposphere are poorly quantified before the satellite era. Reconstructing volcanic contributions to tropospheric aerosol concentrations is, however, essential to understanding past, present, and future climate, and to correctly assessing anthropogenic versus natural tropospheric aerosol contributions.
Using the Community Earth System Model with the Community Atmosphere Model set-up (CESM2-CAM6), we simulate SO2 and SO4 dispersal and deposition during an effusive volcanic eruption with continuous emissions. The case study is based on the 2014-2015 Holuhraun eruption in Iceland, which released up to 9.6 Tg SO2 between 31 August 2014 and 27 February 2015. We vary the meteorological conditions during the time of the eruption by performing ten free-running simulations as well as one simulation that is nudged towards MERRA reanalysis winds.
From the modeled SO4 deposition in Greenland, we calculate transfer functions between deposition and total (prescribed) sulfur emissions for three different domains: the Greenland ice sheet, central Greenland, and the location of the EastGRIP ice coring project. This interpretation of a transfer function differs from that used for explosive stratospheric eruptions, which assumes that all emitted SO2 is converted into SO4 before deposition. We find, however, that only about half of the total sulfur deposition is in the form of SO4 in the simulated scenario, and half as SO2. Owing to Greenland's proximity to the emission source in Iceland, combined with a deposition region limited to the North Atlantic and adjacent areas, the relative local SO4 deposition is higher than for previously investigated statospheric eruptions with global deposition. Thus, the resulting transfer function values are lower than in previous studies of stratospheric volcanic sulfur.
The presented tropospheric transfer function provides an approach to reconstructing tropospheric sulfur loading from past volcanic eruptions in the northern extratropics based on local SO4 signals in Greenland ice.
How to cite: Gottschalk, M., Zoëga, T., and Krüger, K.: Towards a transfer function for tropospheric volcanic sulfur emissions: The Holuhraun 2014-2015 eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11343, https://doi.org/10.5194/egusphere-egu26-11343, 2026.
The 2022 Hunga eruption significantly perturbed the stratosphere by injecting substantial water vapor and SO2, drastically changing the aerosol optical depth and particle size. Post-eruption, satellite limb-scattering retrievals of aerosol extinction from Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) and Optical Spectrograph and InfraRed Imager System (OSIRIS) diverged from Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) solar occultation measurements. We demonstrate that this discrepancy stems from the fixed aerosol particle size assumptions inherent to the limb sensor's retrieval algorithms, which are different than the large particle sizes observed following the eruption.
Using particle size distribution parameters derived from SAGE III/ISS measurements as input to the OMPS-LP and OSIRIS retrievals, we effectively eliminated the bias in retrieved extinction and Aerosol Optical Depth (AOD) compared to SAGE III/ISS. This consistency across the three datasets provides an improved understanding of aerosol distributions in the highly perturbed stratosphere.
How to cite: Remai, C., Zawada, D., Bourassa, A., Dube, K., Baron, A., Smith, K., Rieger, L., and Degenstein, D.: Stratospheric Aerosol Particle Size Explains Divergent Limb and Solar Occultation Measurements After the Hunga Eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8219, https://doi.org/10.5194/egusphere-egu26-8219, 2026.
The January 2022 Hunga Tonga–Hunga Ha’apai eruption caused an unprecedented injection of water vapor into the stratosphere. The excess water vapor from this event stayed in the stratosphere for several years, but whether it influenced surface climate conditions remains unclear. Here, we aim to investigate the impacts of the anomalous water vapor on the variability of the Arctic stratospheric polar vortex and its downward influence on extratropical surface climate. Using the coupled high-top Community Earth System Model Version 2 (CESM2/WACCM6), we conduct a 12-member ensemble of 3-year-long idealized water vapor perturbation simulations that mimic the eruption. Our ensemble simulations demonstrate that water vapor-induced upper-stratospheric cooling weakens the Arctic stratospheric polar vortex in the first post-eruption winter of 2022/2023, with a weaker influence in the second post-eruption winter. The weakening of the polar vortex is driven by the reduced equator-to-pole temperature gradient in the winter stratosphere and is accompanied by pronounced polar stratospheric warming episodes that propagate into the troposphere. We identify more frequent occurrences of the negative Arctic Oscillation and colder-than-normal winters over the northern Eurasian continent in individual perturbation simulations. Our simulations suggest that the Hunga water vapor forcing increases the frequency of a weakened Arctic stratospheric polar vortex and slightly increases the chance for Eurasian winter cooling, although with a weak signal-to-noise ratio.
How to cite: Dai, L., Timmermann, A., Semmler, T., Chen, Y., and Wright, J. S.: Water vapor impacts from the 2022 Hunga eruption on the Arctic stratospheric polar vortex and surface temperatures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9285, https://doi.org/10.5194/egusphere-egu26-9285, 2026.
Our simulations with the chemistry climate model EMAC show an extreme sensitivity of aerosol properties and radiative and chemical implications to
the spatial distribution of the injections of Hunga SO2 and water vapour. The main effects are modification of particle size and sedimentation by water
uptake and lofting of aerosol by radiative heating with consequences for horizontal tranport and residence time of aerosol and water vapour. For Hunga we got an instantaneous radiative forcing by aerosol of -0.12 to -0.17 W/m2 at the top of the atmosphere in the first 6 months after the eruption depending on injection patterns like the vertical distribution and the horizontal extent of the plume. How much water vapour is retained in the stratosphere strongly depends on the altitude and the horizontal size of the box into which water vapour is injected because of ice formation in case of supersaturation. Observations indicate that the vertical distributions of SO2 and H2O injections differ. We will present an extension of the published results and further sensitivity studies to optimize the agreement in the temporal and spatial development of aerosol extinction and water vapour with observations by OSIRIS, SAGE III and MLS, including the effects of the Ruang eruption in April 2024. The study will contribute to the APARC-HTHH-MOC model comparison project.
How to cite: Brühl, C. and Kohl, M.: Sensitivity of radiative forcing by volcanic aerosol to the injection patterns for SO2 and H2O, studies with the CCM EMAC for 2022 to 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10125, https://doi.org/10.5194/egusphere-egu26-10125, 2026.
Volcanic eruptions and extreme wildfires produce stratospheric aerosol plumes with distinct optical properties and lifetimes. Here we analyze the evolution of volcanic and wildfire aerosols using Level-2 aerosol layer products from the CALIOP (CALIPSO) and ATLID (EarthCARE) spaceborne lidars.
The analysis is based on a layer approach, in which aerosol properties are binned and analyzed at the Level-2 aerosol layer scale rather than along individual vertical profiles, allowing a consistent comparison between events and throughout plume ageing. Aerosol layers are characterized using observations at 532 and 1064 nm (CALIOP) and 355 nm (ATLID) in terms of scattering ratio, depolarization ratios (volume depolarization, VDR, and particulate linear depolarization, PLDR), and color ratio. The scattering ratio constrains aerosol concentration, depolarization ratios provide insight into particle shape and type, whereas the color ratio scales with particle size, with coarse particles preferentially removed by gravitational sedimentation.
Distinct optical fingerprints are found for volcanic and wildfire aerosols. Volcanic eruptions such as Puyehue–Cordón Caulle (2011), Calbuco (2015) and Raikoke (2019) eruptions exhibit strong ash signatures at early stages, characterized by high PLDR and elevated color ratios, indicative of coarse, non-spherical particles. In contrast, Kasatochi (2008) and Sarychev (2009) eruptions shows intermediate PLDR values, consistent with a mixed aerosol composition combining volcanic ash and sulfate particles. Hunga eruption (2022) is dominated by sulfate aerosols and shows low depolarization but relatively high color ratios in the young plume, which rapidly decrease as the largest ash particles are efficiently removed by gravitational sedimentation.
ATLID Level-2 product is used to document the temporal, vertical, and zonal evolution of stratospheric smoke after the Panboreal wildfire outbreak in May 2025. Very high value of scattering ratio and aerosol optical depth (AOD) are observed shortly after the largest pyroCb injection on 29 May, followed by a progressive decrease associated with plume dilution and redistribution during vertical ascent and long-range transport. PLDR values remain moderate throughout the plume evolution, indicating the presence of non-spherical particle components in stratospheric smoke. A slight increase in PLDR with plume ageing is observed for most events, possibly related to particle aggregation or microphysical processing. These consistent PLDR patterns across different events provide insight into the ageing processes of stratospheric smoke.
The lidar ratio exhibits coherent values within individual layers throughout plume evolution, providing a stable constraint on aerosol optical properties despite decreasing aerosol loading.
First ATLID observations of the Canadian wildfires in May 2025 demonstrate the added value of the HSRL (High Spectral Resolution LiDAR) technique. ATLID exploits Rayleigh and Mie backscatter separation to provide direct measurements of aerosol extinction and lidar ratio. These observations offer new constraints on aerosol type and ageing of smoke aerosols in the stratosphere while extending the CALIOP-based statistics of stratospheric aerosol optical properties.
How to cite: Soares, O., Khaykin, S., Godin-Beekmann, S., and Kadygrov, N.: Evolution of optical parameters of volcanic and wildfire plumes in the stratosphere from CALIOP and ATLID observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13104, https://doi.org/10.5194/egusphere-egu26-13104, 2026.
The University of Saskatchewan (USask) routinely derives stratospheric aerosol extinction from limb radiance measurements by the Ozone Mapping and Profiler Suite Limb Profile (OMPS-LP). Recently a new version of the data product (v2.1) has been publicly released with several improvements. Most notably aerosol extinction is reported at multiple wavelengths using a novel bias correction scheme that reduces wavelength dependent errors present in limb scatter derived aerosol by training a gradient boost regression scheme on coincidences with SAGE III-ISS occultation measurements. The algorithm has also been extended to routinely process data from both the NPP (launched in 2011) and N21 (launched in 2021) versions of OMPS-LP. Here we describe the algorithm, it's improvements, and validate the data product against correlative measurements.
How to cite: Zawada, D., Dube, K., Bourassa, A., and Degenstein, D.: The USask OMPS-LP v2.1 Stratospheric Aerosol Data Product, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14064, https://doi.org/10.5194/egusphere-egu26-14064, 2026.
Trajectory hunting is a Lagrangian, transport-based technique that links atmospheric observations along calculated air-parcel pathways to enable consistency checks and to contribute to validation and data comparison studies. By connecting independent observations across space and time, trajectory hunting increases the number of coincidences available for comparison and thus reduces uncertainty in studies limited by sparse availability of direct matches. In this study, we assess the use of trajectory hunting for stratospheric aerosol extinction measurements based on observations from the Optical Spectrograph and InfraRed Imaging System (OSIRIS). Trajectories computed with HYSPLIT and FLEXPART are used to connect independent OSIRIS aerosol extinction profiles along transport pathways, enabling self-consistency tests under various stratospheric conditions. In addition, using the 2022 Hunga Tonga eruption as a case study, we apply trajectory hunting to assess volcanic plume transport by mapping plume evolution and age along simulated dispersion pathways, and to compare these against spaceborne observations to evaluate the consistency of trajectory hunting during periods of strong stratospheric perturbation. These results will demonstrate the potential of using trajectory hunting to support validation of stratospheric aerosol products and to provide observationally constrained insights into aerosol transport and evolution, with implications for future applications to the High-Altitude Aerosols, Water Vapour, and Clouds (HAWC) mission and multi-sensor stratospheric aerosol datasets.
How to cite: Wu, Y., Walker, K., and Bloxam, K.: Trajectory hunting for linking stratospheric aerosol extinction measurements: validation with OSIRIS and application to the 2022 Hunga Tonga eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14419, https://doi.org/10.5194/egusphere-egu26-14419, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 5
EGU26-14645 | ECS | Posters virtual | VPS3
Climate Response to Tambora-Scale Volcanic Eruptions Under Present and Future Climate ConditionsTue, 05 May, 14:42–14:45 (CEST) vPoster spot 5
We quantify climate effects of Tambora-scale eruptions under current and future warming using the SOCOL-MPIOM coupled atmosphere-chemistry-ocean model for 2020, SSP2-4.5, and SSP3-7.0 (2080) scenarios.
Global cooling amplifies counterintuitively with background warming: SSP3-7.0 shows 44% stronger cooling than present-day due to polar vortex intensification increasing from 5.5% to 44.5%. Regional responses reveal complex patterns: winter exhibits Arctic warming (+0.4-0.6°C) simultaneous with tropical cooling (up to -8°C) and continental extremes (up to +15°C). Summer brings widespread continental cooling (-2 to -4°C). Monsoon systems weaken by 20-35% while mid-latitude winter precipitation intensifies by 20-40%.
Results demonstrate that volcanic impacts under anthropogenic warming generate spatially heterogeneous extremes rather than uniform cooling, critical for agricultural and water resource risk assessment.
How to cite: Tkachenko, M. and Eugene, R.: Climate Response to Tambora-Scale Volcanic Eruptions Under Present and Future Climate Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14645, https://doi.org/10.5194/egusphere-egu26-14645, 2026.
