Middle atmosphere chemical and dynamical effects in the CCMI-2022 stratospheric aerosol injection scenario

[Geoengineering News]

https://acp.copernicus.org/articles/26/11207/2026/

Authors: Andrin Jörimann, Timofei Sukhodolov, Simone Tilmes, David Plummer, Shingo Watanabe, Hideharu Akiyoshi, Gabriel Chiodo, Daniele Visioni, Sandro Vattioni, Eugene Rozanov, Ewa Monika Bednarz, Béatrice Josse, Yousuke Yamashita, and Thomas Peter

11 August 2026

Abstract

Stratospheric aerosol injection (SAI) could slow surface warming, however, potential side effects include changes in stratospheric ozone and changes in regional surface temperatures and precipitation resulting from tropical lower stratospheric warming. Previous multi-model studies have reported substantial discrepancies among models regarding these effects. Here we present results from the Chemistry-Climate Model Initiative Phase 2 (CCMI-2022), designed to constrain inter-model uncertainties by applying a common, transient stratospheric aerosol forcing to five chemistry-climate models that offsets surface warming after 2025 in a moderate greenhouse gas emission scenario. Simulations were analyzed between 2025–2099, and all models show a global total column ozone decrease in the first three decades of at most ∼ 10 DU relative to a no-SAI case. Tropical lower stratospheric heating differs by up to 4 K between models, but despite that, the models agree very well on the region of influence of key processes, like chlorine activation, nitrogen oxide passivation, and the strengthening of the deep branch Brewer-Dobson circulation. Therefore, the sign of the ozone anomalies due to SAI is consistent in all stratospheric regions except the lower polar stratosphere, although the contribution of different processes varies considerably. In three of the models, we separate pure chemical from dynamical (heating and nonlinear) contributions, and find that towards the end of the century, dynamical effects dominate ozone anomalies, except in the lower polar stratosphere, where heterogeneous chemistry plays a major role. Our findings highlight the need for sensitivity experiments on the absorptive heating and resulting dynamical effects under SAI.

Source: EGU