Impact of Stratospheric Aerosol Geoengineering on Extreme Precipitation and Temperature Indices in West Africa Using GLENS Simulations

Abstract

This study assesses changes in extremes precipitation and temperature in West Africa under a high greenhouse gas scenario, that is, a representative concentration pathway 8.5, and under a scenario of stratospheric aerosol geoengineering (SAG) deployment using the NCAR Community Earth System Model version 1. We use results from the Geoengineering Large Ensemble simulations (GLENS), where SAG is deployed to keep global surface temperatures at present day values. This impact study evaluates changes in some of the extreme climate indices recommended by the Expert Team Monitoring on Climate Change Detection and Indices. The results indicate that SAG would effectively keep surface temperatures at present day‐conditions across a range of indices compared to the control (CRTL) period, including Cold days, Cold nights and Cold Spell Duration Indicator which show no significant increase compared to the CRTL period. Regarding the extremes precipitation, GLENS shows mostly a statistically significant increase in annual precipitation and statistically significant decrease in the number of heavy and very heavy precipitation events relative to the CRTL period in some regions of Gulf of Guinea. In the Sahel, we notice a mix of statistically significant increase and decrease in Max 1‐day and Max 5‐days precipitation amount relative to the CRTL period at the end of the 21st century when large amounts of SAG has been applied. The changes in extreme precipitation indices are linked to changes in Atlantic Multidecadal Oscillation, NINO3.4 and Indian Ocean Dipole and these changes in extreme precipitation are driven by change in near surface specific humidty and atmospheric circulation.

Detecting Changes in Global Extremes Under the GLENS‐SAI Climate Intervention Strategy

“…For the 2040 maps under RCP8.5, these same regions are also the main contributors to the model's correct prediction (Figure 5c). Extreme precipitation under RCP8.5 exhibits large increases over Central Africa (Figure 1d), where the signal-to-noise ratio is also large (Figure 5d; Alamou et al, 2022), and this appears to translate to large contributions to the logistic regression model's predictions (Figures 5b and 5c). The same holds for Alaska and Greenland.…”

Hydrological Consequences of Solar Geoengineering

“…Simpson et al (2019) and Da-Allada et al (2020) find that SAI reduces precipitation over regions with climatologically high precipitation in Africa, including Southern Sahel and Western Africa. Drought frequency is expected to shift across basins (Abiodun et al 2021), with West Africa facing particularly increased drought stress (Alamou et al 2022) and the Western Cape experiencing decreased severe drought risk (Odoulami et al 2020). ET and soil moisture are also strongly reduced in the Congo (Dagon & Schrag 2019) and Northern Africa relative to high-CO 2 scenarios (Cheng et al 2019).…”