Comparing stratospheric aerosol injection strategy optimization in CESM and UKESM

[Geoengineering News]

https://iopscience.iop.org/article/10.1088/2752-5295/ae9e63/meta

Authors: Ezra Brody, Douglas G MacMartin, Daniele Visioni, Ben Kravitz, Ewa M Bednarz and Matthew Henry

25 August 2026

Abstract

Greenhouse gas (GHG) induced global warming is an ongoing problem, and stratospheric aerosol injection (SAI) is being studied as a potential supplement to GHG reduction. Since the latitude at which SAI is deployed determines its effect on the climate, the combination of latitudes used and the amount of material injected at each latitude can be tailored to best meet certain objectives. This is referred to as SAI strategy. Prior research has analyzed various SAI strategies as well as searched for optimal strategies in one climate model, the Community Earth System Model (CESM). This study adds a second climate model, the United Kingdom Earth System Model (UKESM), and compares the results of optimization. The optimized strategies are substantially different between the two models; CESM requires injection focused on lower latitudes whereas UKESM requires injection focused on high latitudes. This is mainly due to the differences in model climate sensitivity patterns to increasing GHG forcing, and not how the models respond to SAI. This means there is large uncertainty in what SAI strategy would be needed to achieve a certain set of climate objectives in the real world, although this would be reduced during a deployment. Next, we searched for a subset of latitudes that can be used in both models without much deviation from optimal performance. The combination of injections at 15°N, 15°S, 60°N, and 60°S was found to perform reasonably well, suggesting that this set of four latitudes may be well-suited for inter-model comparisons of three-degree-of-freedom strategies.

Source: IOP SCIENCE