Cloud Susceptibility and Climate Sensitivity to Midlatitude Marine Cloud Brightening

[Geoengineering News]

https://essopenarchive.org/doi/pdf/10.22541/essoar.175130099.96612620

Authors

Haruki Hirasawa, Matthew Henry, Alex M Mason, Philip J Rasch, Sarah J Doherty, Robert Wood, James Haywood, Knut Von Salzen

30 June 2025

Abstract

The climate intervention approach Marine Cloud Brightening (MCB) would aim to reduce climate warming by injecting sea salt aerosol (iSSA) into the lower troposphere to increase cloud albedo. Due to the short atmospheric lifetime of tropospheric aerosol, MCB iSSA emissions and their resulting radiative forcing are regional by nature. This presents a significant challenge and opportunity, as there are many potential patterns of MCB implementation that could produce substantially varying climate responses. Simulations of MCB implementation in the subtropical oceans show global cooling, but may also show strong, though potentially undesirable, regional temperature and precipitation responses. Here, we use three Earth System Models (ESMs) to estimate the impact of MCB implementation in fourteen different ocean regions, assessing MCB forcing and cooling efficiency in each region and examining the patterns of temperature response from each case. We find that iSSA emissions in the midlatitude oceans produce stronger cloud forcing, greater cooling efficiency, and more spatially uniform cooling. With this information, we evaluate a novel MCB emission strategy that places emissions in the midlatitude oceans. The ESMs show this iSSA emission pattern produces temperature and precipitation responses across all three ESMs that are quite similar in pattern (but of opposite sign) to the greenhouse gas (GHG) response. Thus, compared to previously tested iSSA injection patterns, midlatitude MCB implementations may be more suitable when intending to maintain climates close to present day conditions.

Source: ESS Open Archive