Stratospheric cOmposition in a changing CLIMate: drivers and mechanisms (SOCLIM)

"Harness the value of stratospheric composition as a source of predictability"

SOCLIM, an ERC Starting Grant, funded by European Commission (2024-2029)

See official announcement on IGEO-CSIC-UCM website (in Spanish):

See list of funded ERC-StG projects:

Involved entities: IGEO-CSIC (lead), G. Chiodo (lead PI)

Partners: Universidad Complutense de Madrid (Madrid, Spain - STREAM group), Universite de Lausanne (Lausanne, Switzerland - S2S group), Swiss Federal Institute of Technology (Zurich, Switzerland - S2S group), World Radiation Center (Davos, Switzerland), Forschungszentrum Juelich (Juelich, Germany), ECMWF (Bonn, Germany and Reading, UK), National Center for Atmospheric Research (Boulder, USA)

Synopsis: Predicting weather and climate on sub-seasonal to multi-decadal time scales is notoriously difficult. This is due to the fact that at these time-scales (beyond 10 days), forecasts are highly dependent on the initial conditions, but also suffer from imperfections in the model. One valuable avenue to improve forecasts is the identification of predictability sources, that is, slowly varying components of the climate system and/or regularly varying phenomena which can potentially provide basis for climate predictability. On multi-decadal time scales, predictions are also highly uncertain, due to the large uncertainty in the large-scale circulation response to climate change. While the stratosphere plays a key role in these aspects, efforts have largely focused on dynamical aspects, disregarding its chemical composition. Stratospheric ozone (O3) and water vapour (SWV) largely determine the stratospheric chemical composition, which determines the protection of the biosphere against harmful UV radiation and contribute to the Greenhouse Effect. Despite advances in understanding the effects of Antarctic ozone depletion and recovery, impacts on Arctic and global stratosphere are not well understood. This is due to limited understanding of the complex interactions between stratospheric composition and circulation and their insufficient representation in models. Here is where the ERC project SOCLIM comes into play!

SOCLIM will provide new understanding of the role of stratospheric ozone and water vapour as (1) source of predictability on sub-seasonal to seasonal (S2S) time-scales, (2) drivers of atmospheric circulation changes on decadal to multi-decadal time-scales and (3) radiative effects on global climate by using theory, observations and models.

We aim to develop a chemistry-weather prediction system to assess impacts on predictability. Then, we will use chemistry-climate models to quantify impacts on climate change, via the influence of stratospheric composition on the atmospheric circulation. Lastly, we will determine its contribution to global warming in a range of scenarios from unabated emissions to mitigation via climate intervention techniques such as stratospheric aerosol injections (SAI). SOCLIM will contribute towards reducing uncertainty in weather and climate predictions, providing better constraints on the climatic impacts of anthropogenic emissions and delivering crucial information for future emission policies.

Schematic of the main objectives of SOCLIM: explore the role of stratospheric ozone and water vapor (1) as sources of predictability on S2S time-scales, (2) as drivers of atmospheric circulation changes over the 21st century via their effects on the stratospheric polar vortex (SPV), and (3) as radiative feedbacks on regional and global climate change. The project is divided into 3 Work Packages (WPs), corresponding to each of these 3 objectives. The corresponding WPs are: WP1 (SOCLIM-S2S), WP2 (SOCLIM-CIRC), and WP3 (SOCLIM-FEEDBACKS)

Work Package 1: assess and quantify the impact of stratospheric composition on predictability (SOCLIM-S2S)

Total Column ozone anomaly in March 2020, a major "Arctic depletion event". During the same spring, record warm and dry anomalies were also observed over wide spread portions of the Northern Hemisphere. A key question in this WP is whether disruptions in the Arctic ozone affect surface climate and its predictability on S2S time-scales. Image credit:

Presently, the coupling between stratospheric composition and the atmospheric circulation is not fully resolved in forecasting systems. There is evidence that this coupling may be important for surface climate in the aftermath of Arctic ozone depletion events (Friedel et al., 2022a, 2022b), but this evidence is limited to coarse-resolution climate models. In this WP, we will explore the role of stratospheric composition (ozone and water vapor) as a source of predictability for S2S time scales.

More specifically, we will:

1. Diagnose the capability of state-of-the-art existing prediction systems (IFS from ECMWF) in representing observed variability of the ozone layer and in particular extreme variations, with focus on the Arctic. 

2. Improve the representation of stratospheric composition in S2S prediction systems and the related dynamical and radiative feedbacks.

3. Explore the physical mechanisms whereby stratospheric composition affects predictability of tropospheric and surface climate.

Work Package 2: assess and quantify the impact of stratospheric composition on long-term projections of the atmospheric circulation (SOCLIM-CIRC)

The Stratospheric Polar Vortex (SPV) has wide implications for tropospheric and surface climate. Presently, model projections of the SPV are very uncertain (Karpechko et al., 2022), and Arctic ozone may be one of the drivers (Chiodo et al., 2023). In this WP, we will explore the role of stratospheric  composition, including the coupling between ozone and water vapor. Image credit: Waugh et al., 2017

Presently, future projections of how the atmospheric circulation will be affected by global warming are very uncertain (Shepherd et al., 2014). This especially concerns the SPV, stratosphere-troposphere coupling and how they will change (Ayarzaguena et al., 2020; Karpechko et al., 2022), which has implications for surface climate at the regional level (e.g. Simpson et al., 2018). In this WP, we will explore the role of future changes in stratospheric composition (ozone and water vapor; Keeble et al., 2021) as drivers of the SPV, and coupling to surface climate. In particular, we will explore the role of composition as a source of uncertainty, and how it can be constrained.

More specifically, we will:

1. Explore the impact of stratospheric ozone and water vapor on the dynamical coupling between the stratosphere and troposphere, with emphasis on the impacts on surface climate.

2. Assess the role of ozone and water vapor (among other drivers) as sources of uncertainty in future projections, via mechanistic modeling experiments (e.g. nudging).

3. Constrain these sources of uncertainty by using statistical methods, possibly including machine learning methods

Work Package 3: assess and quantify the impact of stratospheric composition as a feedback in climate projections and climate intervention scenarios (SOCLIM-FEEDBACKS)

Stratospheric composition can exert a radiative and dynamical feedback, thereby altering regional and global climate. In this WP, we will explore the role of composition in the context of externally forced climate change, including including SRM via e.g. Stratospheric Aerosol Injections and non-CO2 emissions (e.g. N2O and CH4).

Presently, the magnitude of stratospheric composition feedbacks is widely uncertain: this concerns both the ozone (Chiodo et al., 2019) and water vapor (Banerjee et al., 2019; Nowack et al., 2023) feedbacks. In this WP, we will explore the role of these feedbacks, following future IPCC emission scenarios, including interventions via Solar Radiation Modification (SRM). 

More specifically, we will:

1. Identify the sources of the existing uncertainty in the magnitude of stratospheric composition feedbacks, in particular involving stratospheric water vapor.

2. Assess and quantify the impact of stratospheric composition in the context of climate change from non-CO2 forcing agents (N2O and CH4).

3. Assess and quantify the impact of ozone and water vapor feedbacks in the context of climate intervention strategies, involving SO2 as well as direct aerosol injections (Weisenstein et al., 2022; Vattioni et al., 2023)

Relevant literature

Vattioni, S., et al. (including G. Chiodo) (2023): Chemical impact of stratospheric alumina particle injection for solar radiation modification and related uncertainties, Geophysical Research Letters, DOI:10.1029/2023GL105889

Friedel, M., G. Chiodo, A. Stenke, D. Domeisen, S. Fueglistaler, J. Anet, and T. Peter (2022a): Springtime Arctic ozone depletion forces Northern Hemisphere climate anomalies, Nature Geoscience, DOI:10.1038/s41561-022-00974-7 supplementary material, Nature Research Briefing

Friedel, M., G. Chiodo, A. Stenke, D. Domeisen, and T. Peter (2022b): Effects of Arctic ozone on the stratospheric spring onset and its surface impact, Atmospheric Chemistry and Physics, DOI:10.5194/acp-22-13997-2022

Weisenstein, D., et al. (including G. Chiodo) (2022): A Model Intercomparison of Stratospheric Solar Geoengineering by Accumulation-Mode Sulfate Aerosols, Atmospheric Chemistry and Physics, DOI:10.5194/acp-22-2955-2022

Friedel, M., G. Chiodo, et al. (2023): Weakening of springtime Arctic ozone depletion with climate change, Atmospheric Chemistry and Physics, DOI:10.5194/acp-23-10235-2023

Chiodo, G., M. Friedel, S. Seeber, A. Domeisen, A. Stenke, T. Sukhodolov and F. Zilker (2023): The influence of future changes in springtime Arctic ozone on stratospheric and surface climate, Atmospheric Chemistry and Physics, DOI:10.5194/acp-23-10451-2023

Chiodo, G., and L.M.Polvani (2019): The response of the ozone layer to quadrupled CO2concentrations: implications for climate, Journal of Climate, DOI:10.1175/JCLI-D-19-0086.1

Banerjee, T., G.Chiodo, M.Previdi, M.Ponater, A.Conley and L.M.Polvani (2019): Stratospheric water vapor: an important climate feedback, Climate Dynamics, DOI:10.1007/s00382-019-04721-4 supplementary material

Chiodo, G., and L.M. Polvani (2017):Reduced Southern Hemispheric circulation response to quadrupled CO2due to stratospheric ozone feedback, Geophysical Research Letters, 44, 465–474, DOI:10.1002/2016GL071011supplementary material

Job openings within ERC project

- PhD position on "stratospheric composition and impacts on predictability" - see full description here

- Post-doc position on "stratospheric composition and impacts on predictability" - see full description here

- Scientific programmer