Contrasting Changes in Rainfall Structure Between Monsoon and Adjacent Dry Regions Under Stratospheric Aerosol Injection

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2026JD046329

Authors: Jie Jiang, Tianjun Zhou, Wenmin Man, Meng Zuo

First published: 23 May 2026

https://doi.org/10.1029/2026JD046329Digital 

Abstract

Rainfall structure is projected to shift toward heavier precipitation under global warming due to increased atmospheric moisture. Such a shift can heighten the risks of both floods and droughts. Stratospheric aerosol injection (SAI) has been proposed to counteract continued warming, but its effects on rainfall structure and potential to introduce new hydrological risks remain unclear. Here, using simulations from two models (CESM2 and UKESM1) participating in ARISE-SAI-1.5, we show that restoring global mean temperature increase to 1.5°C through SAI produces contrasting responses between monsoon and adjacent dry regions. Specifically, the global monsoon region is expected to experience a reduction in heavy rainfall, while the global dry region exhibits increased precipitation across a broad range of intensities. Inter-model comparisons further reveal the sensitivity of rainfall structure to residual temperature anomalies over monsoon sub-regions. Monsoon regions exhibit reduced heavy rainfall but increased drought risk in the hemisphere experiencing stronger cooling. In contrast, dry regions consistently experience enhanced precipitation and fewer dry days across models. These responses are primarily driven by dynamic processes rather than thermodynamic effects. The emergence of potential new regional “hotspots” of precipitation extremes underscores the need for caution when deploying SAI.

Plain Language Summary

The continued increase in greenhouse gases is expected to change how rainfall is distributed, with more intense rainfall and fewer light events, increasing the risks of both floods and droughts. One proposed way to limit greenhouse-gas-driven warming is to inject sulfate aerosols into the upper atmosphere to cool the planet. Using climate model simulations, we examine how this approach affects rainfall structure when global temperature increase is restored to about 1.5°C. We find that stratospheric aerosol injection alters rainfall structure differently in wet monsoon regions and nearby dry regions. Monsoon areas generally experience less heavy rainfall, but some regions also face a higher risk of drought depending on differences in residual temperature anomalies between the hemispheres. In contrast, dry regions tend to receive more rainfall and have fewer dry days, regardless of the temperature profile. While this cooling strategy can reduce extreme rainfall at the global scale, it may also create new regional risks, especially in monsoon regions in the hemisphere that experiences stronger cooling. These results highlight the importance of carefully designing climate intervention strategies to avoid unintended impacts on regional water resources.

Source: AGU

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