Winners and Losers: How Stratospheric Aerosol Injection Reshapes Hydroclimate Whiplash Risk - Preprint

[Geoengineering News]

https://essopenarchive.org/doi/abs/10.22541/essoar.15009302/v1

Authors: Dr. Leyuan Zhang and Dr. Danielle Touma 

22 September 2026

https://doi.org/10.22541/essoar.15009302/v1

Abstract

Hydroclimate whiplash, defined as rapid transitions between extreme wet and dry conditions, is expected to increase under continued greenhouse gas warming with impacts on agriculture, ecosystems, and infrastructure. Here, we assess whether stratospheric aerosol injection (SAI) can offset this increase using three 10-member ensembles from the Assessing Responses and Impacts of Solar intervention on the Earth system with Stratospheric Aerosol Injection (ARISE-SAI) framework across three deployment strategies: ARISE-SAI-1.5 (1.5°C target, deployment from 2035), ARISE-SAI-1.0 (1.0°C target, deployment from 2035), and ARISE-SAI-2045 (~1.5°C target, deployment from 2045). Whiplash events are defined as months in which the absolute month-to-month change in the 3-month Standardized Precipitation Evapotranspiration Index (SPEI-3) exceeds two standard deviations. Under the baseline warming scenario, global mean whiplash frequency increases by 1.87 percentage points. ARISE-SAI-1.5 offsets ~77% of this increase, ARISE-SAI-1.0 exceeds full compensation (~121%), and delayed deployment achieves a comparable offset (~75%). Suppression of dry-to-wet and wet-to-dry transitions is nearly symmetric, indicating that SAI acts primarily through reduced hydroclimate variability rather than shifts in mean moisture. In all regions, SAI reduces whiplash frequency substantially more than intensity, although the changes in frequency are highly heterogeneous: the Mediterranean, northeastern Brazil, and northern Australia, and western North America show pronounced suppression across all SAI scenarios, while western Central Africa shows increases in whiplash frequency. Seasonally, suppression is strongest in boreal fall over the Mediterranean and in austral summer over northeastern Brazil. Overall, SAI can substantially reduce hydroclimate whiplash in most regions, with stronger forcing generally producing greater suppression.

Source: ESS OPEN ARCHIVE