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.
