Future changes in seasonal-mean precipitation over West Africa under the representative concentration pathways

Abstract

This study analysed the future changes in seasonal - mean precipitation over West Africa during the mid (2040 - 2065) twenty first century using the Norwegian Earth System Model version 1 (NorESM1 - M). The NorESM1 - M has ~1.89° x 2.5° horizontal atmospheric resolution and 26 vertical levels. The skill of the model in reproducing the observed seasonal - m ean precipitation distribution was evaluated for the historical period (1980 - 2005) using satellite derived precipitation data from the Global Precipitation Climatology Project. Using three possible future levels of atmospheric greenhouse gas concentrations - the Representative Concentration Pathways (RCPs) of 2.6Wm - 2 , 4.5Wm - 2 and 8.5 Wm - 2 , we calculated the projected changes in seasonal - mean precipitation over West Africa for the mid - twenty first c e n t u r y. The projected changes show that the transition to dry season (September-October-November)will experience the highest amounts of increase. Overall, RCP 4.5 projects higher levels of precipitation change compared to the other two RCPs. This points to a non - linear effect of intensified greenhouse forcing on precipitation over West Africa; suggesting that after a particular level of greenhouse gas concentrations further increase may have little or no effect on the regions precipitation. Keywords : West Africa, Precipitation, Climate Change Projections, NorESM 1 - M, RCPs