Abstract:
The impacts of global warming on rainfall in West Africa were examined using a
numerical framework for 5 monsoon years (2001, 2007, 2008, 2010, and 2011).
Rainfall characteristics over the three climatic zones, Guinea coast, Savannah,
and Sahel, were analyzed. The potential changes associated with global warming
were assessed by the pseudo-global warming (PGW) downscaling method.
Multiple PGW runs were conducted using climate perturbation from the 40-
member ensemble of the Community Earth System Model version 1 (CESM1)
coupled with Community Atmospheric Model version 5.2 (CAM5.2) component
large ensemble project. The model output was compared with Tropical Rainfall
Measuring Mission and Global Precipitation Climatology Project rainfall alongside
surface temperature from the European Center for Medium-Range Weather
Forecast Reanalysis. Results show that the estimated rainfall amount from the
future climate in the 2070s increases slightly compared with the current climate.
The total rainfall amount simulated for the current climate is 16% and 63% less
than that of the PGW runs and observations, respectively. Also found is an
increase (decrease) in heavy (light and moderate) rainfall amount in the PGW
runs. These results are, however, contingent on the global circulation model
(GCM), which provides the boundary conditions of the regional climate model.
CESM1.0-CAM5.2, the GCM employed in this study, tends to provide a greater
surface temperature change of about 4 C. This projected temperature change
consequently caused the increase in the simulated precipitation in the PGW
experiments, thus highlighting the advantage of using the PGW method to
estimate the likely difference between the present and future climate with reduced
large-scale model differences and computational resources. The findings of this
study are, however, useful to inform decision-making in climate-related activities
and guide the design of climate change adaptation projects for the West African
region.
