Impact of Stratospheric Aerosol Geoengineering on Meteorological Droughts in West Africa

Adéchina Eric Alamou,Casimir Y Da-Allada,Simone Tilmes,Eliézer Iboukoun Biao,Ezéchiel Obada,Ezinvi Baloïtcha,Esdras Babadjidé Josué Zandagba,Peter J Irvine,Frederic K Bonou

doi:10.3390/atmos13020234

Abstract

This study assesses changes in meteorological droughts in West Africa under a high greenhouse gas scenario, i.e., a representative concentration pathway 8.5 (RCP8.5), and under a scenario of stratospheric aerosol geoengineering (SAG) deployment. Using simulations from the Geoengineering Large Ensemble (GLENS) project that employed stratospheric sulfate aerosols injection to keep global mean surface temperature, as well as the interhemispheric and equator-to-pole temperature gradients at the 2020 level (present-day climate), we investigated the impact of SAG on meteorological droughts in West Africa. Analysis of the meteorological drought characteristics (number of drought events, drought duration, maximum length of drought events, severity of the greatest drought events and intensity of the greatest drought event) revealed that over the period from 2030–2049 and under GLENS simulations, these drought characteristics decrease in most regions in comparison to the RCP8.5 scenarios. On the contrary, over the period from 2070–2089 and under GLENS simulations, these drought characteristics increase in most regions compared to the results from the RCP8.5 scenarios. Under GLENS, the increase in drought characteristics is due to a decrease in precipitation. The decrease in precipitation is largely driven by weakened monsoon circulation due to the reduce of land–sea thermal contrast in the lower troposphere.

Highlights

Climate change and accelerated population growth have become the key limiting factors for sustainable human resources development and natural systems conservation [1]
We assess the performance of the CESM1 (WACCM) simulations to reproduce the observed precipitation in West Africa
Cause of Change in Drought Characteristic under RCP8.5 and Geoengineering Large Ensemble (GLENS) Scenarios In Section 3.2, we found that projected standardized precipitation index (SPI) from RCP8.5 scenario have an increasing trend while projected SPI from GLENS simulation have a decreasing trend

Summary

Introduction

Climate change and accelerated population growth have become the key limiting factors for sustainable human resources development and natural systems conservation [1]. The magnitude of climate change impacts on the environment and society increases [1,2], while the rapidly increasing population is challenging the food security of the world’s current population of 7.6 billion, which is projected to be 9.8 and 11.2 billion in 2050 and 2100, respectively [1,3]. Increasing temperature leads to an increase in specific humidity, wind speed and precipitation [4,5,6]. [5] shows that global-scale relative humidity is decreasing in the last decades with increasing temperature. Under the high anthropogenic greenhouse gas emission scenario (RCP8.5), increasing temperature can increase the rates of hydrologic system losses to evaporation and transpiration and, in turn, produce more rainfall [7]. The Intergovernmental Panel on Climate Change (IPCC) have noted a widespread point of view of climate scientists that events (e.g., droughts and floods) regarded as extremes are projected to become more frequent and widespread in the future [8]

Objectives

Methods

Results

Discussion

Conclusion