Potential impacts of stratospheric aerosol injection on drought risk managements over major river basins in Africa

Babatunde J Abiodun,Windmanagda Sawadogo,Abayomi A Abatan,Olumuyiwa A Oloniyo,Douglas G Macmartin,Temitope S Egbebiyi,Mark New,Christopher Lennard,Romaric C Odoulami,Pinto Izidine

doi:10.1007/s10584-021-03268-w

Abstract

Most socio-economic activities in Africa depend on the continent’s river basins, but effectively managing drought risks over the basins in response to climate change remains a big challenge. While studies have shown that the stratospheric aerosol injection (SAI) intervention could mitigate temperature-related climate change impacts over Africa, there is a dearth of information on how the SAI intervention could influence drought characteristics and drought risk managements over the river basins. The present study thus examines the potential impacts of climate change and the SAI intervention on droughts and drought management over the major river basins in Africa. Multi-ensemble climate simulation datasets from the Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) Project were analysed for the study. The Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI) were used to characterize the upper and lower limits of future drought severity, respectively, over the basins. The SPEI is a function of rainfall and potential evapotranspiration, whereas the SPI is only a function of rainfall, so the difference between the two indices is influenced by atmospheric evaporative demand. The results of the study show that, while the SAI intervention, as simulated in GLENS, may offset the impacts of climate change on temperature and atmospheric evaporative demand, the level of SAI that compensates for temperature change would overcompensate for the impacts on precipitation and therefore impose a climate water balance deficit in the tropics. SAI would narrow the gaps between SPEI and SPI projections over the basins by reducing SPEI drought frequency through reduced temperature and atmospheric evaporative demand while increasing SPI drought frequency through reduced rainfall. The narrowing of this gap lowers the level of uncertainty regarding future changes in drought frequency, but nonetheless has implications for future drought management in the basins, because while SAI lowers the upper limit of the future drought stress, it also raises the lower limit of the drought stress.

Highlights

Drought poses a significant threat in Africa, especially over the river basins, where it usually stresses water resources and disrupts the socio-economic activities of the riparian countries
In contrast to the potential evapotranspiration (PET) projection, precipitation is projected to increase in the tropics but to decrease in the sub-tropics with the maximum decrease in Southern Africa (Fig. 2j)
This study has investigated the extent to which the stratospheric aerosol injection (SAI) intervention can mitigate the impacts of RCP8.5 warming on drought characteristics over Africa, by focusing on the 12 biggest and most transboundary river basins that support a wide range of socio-economic activities across the continent

Summary

Introduction

Drought poses a significant threat in Africa, especially over the river basins, where it usually stresses water resources and disrupts the socio-economic activities of the riparian countries. Several studies have reported an increasing trend in drought characteristics (severity, frequency, and persistence) over the last decades (Masih et al 2014; Omar and Abiodun 2020; Spinoni et al 2019; Padrón et al 2020) and attributed this trend to global warming (e.g. Uhe et al 2017; Funk et al 2018; Bellprat et al 2015; Pascale et al 2020; Otto et al 2018). These trends may well continue into the future (Cook et al 2020; Spinoni et al 2020; Abiodun et al 2019)

Methods

Results

Conclusion