Consistent rainy season changes predicted from Regional Climate Models ensembles indicate threats to crop production in West Africa

Abstract:

Agricultural production in West Africa is extremely vulnerable to precipitation change and variability. Designing adaptation options to anticipate these changes in precipitation requires robust predicting future climate conditions. Output from Global Circulation Models (GCMs) is too coarse to be used directly to assess regional and high order statistics changes. We use output from a set of Regional Climate Models that dynamically downscale CMIP5 GCMs and analyze mid-century changes in the characteristics of precipitation in West Africa over cropland areas. For each RCM/GCM combinations, we compared predicted precipitation for the period 2035-2065 under the RCP 8.5 scenario with its historical reconstruction of 1975-2005. The mean changes emerging from an analysis of the ensemble of 15 RCM/GCM combinations suggest moderate (~3%) increases in annual precipitation,a very consistent delay in the onset of the rainy season (1 to 4 days from South to North) and no consistent change in the ending of the rainy season. This illustrates a general shortening of the rainy season. An analysis of dry spells (periods of consecutive days with less than 5 mm) for a durations of between 5 and 15 days revealed an increased probability of experiencing longer dry spells during the rainy season in the future climate, coupled with a general intensification of precipitation. This finding was consistent across all models. Our analysis promotes regional prioritization of adaptation measures to the changes in precipitation characteristics that could potentially have detrimental effects on crop yields while also affecting water resources management, species distribution, and others sectors. Increased storage of water, in combination with supplemental irrigation can be an important mechanism for adapting to the effects for regional precipitation changes on crop yield.