Redistributing Risk: Air-Quality Mortality under Two Stratospheric Aerosol Injection Strategies - Preprint

[Geoengineering News]

https://essopenarchive.org/doi/full/10.22541/essoar.15009636/v1

Authors: Dr. Alice Florence Wells , James Wilson Hurrell, Dr. Jeffrey R. Pierce, Dr. Temitope S. Egbebiyi, and G. Brooke Anderson

29 September 2026

Abstract

Stratospheric aerosol injection (SAI) could affect human health through multiple pathways, including changes to surface air quality, and the magnitude and sign of these impacts may depend on the injection strategy. This study compares the air-quality-related mortality effects of two SAI strategies, G6-1.5K-SAI (30°N and 30°S at ~21.5 km) and G6-1.5K-HiLLA (60°N and 60°S at ~15 km), in CESM2(WACCM6), both targeting a global mean temperature of 1.5°C above preindustrial levels under an SSP2-4.5 baseline. We use bias-corrected surface ozone and PM2.5 concentrations alongside Global Burden of Disease exposure-response functions to estimate excess mortality from one ozone-related and seven PM2.5-related health outcomes under each strategy. Both strategies produce a hemispheric asymmetry in surface ozone, which increases across much of the Northern Hemisphere and decreases in the Southern Hemisphere, consistent with changes in stratosphere-troposphere exchange, UV-driven photochemistry, and reduced water vapor. Ozone-related mortality changes are latitudinally dependent but small and similar across strategies (~5,000-6,000 fewer deaths per year globally). PM2.5-related mortality responses, however, differ substantially between strategies. In the ensemble mean, G6-1.5K-SAI produces approximately 28,000 fewer deaths in global PM2.5 mortality per year, while G6-1.5K-HiLLA produces approximately 74,000 additional deaths per year, with the difference associated primarily with enhanced dust production from changes in precipitation and wind patterns and greater exposure to sulfate aerosol under G6-1.5K-HiLLA. While SAI-driven changes in air-quality-related mortality are small in the context of the total projected burden under SSP2-4.5, these results demonstrate that, in CESM2(WACCM6), SAI strategies targeting the same global temperature can produce markedly different regional and global air-quality health outcomes.

Source: ESS Open Archive