Evaluation of CMIP5 climate models for precipitation projections over the upper Blue Nile basin

Abstract:

Information on precipitation projection over a given basin is vital to determine the future climate and related water resources concerns. General Circulation Models (GCMs) are the primary tools that are used in climate change impact studies. In this study evaluation of the new generation models from the Coupled Model Intercomparison Project (CMIP5) was conducted for various characteristics of precipitation over the upper Blue Nile basin. This is based on over 20 GCMs and two emission scenarios from the Representative Concentration Pathways (RCP), RCP4.5 and RCP8.5. The daily precipitation for the current period 1971-2000 was compared with future projections for the period 2071-2100. The performance of GCMs to project mean and total precipitation at different time scales and the frequency of occurrence of extreme precipitation are thoroughly assessed. About one-third of the models produced acceptable performance in terms of minimum root mean squared error and mean error although there is no clear correlation with the spatial resolution or the type of climate models. Wide uncertainty range comprising both increasing (~100%) and decreasing precipitation (~-30%) change is expected towards the end of the 21^st century when considering all GCMs, indicating the need to carefully select models when conducting impact analysis studies.