A Review of the CMIP5 21st Century Climate Change Projection in the Niger Basin

Climate simulations in West Africa have been a challenge for climate models due to the complexity and the diversity of processes to be represented. No coherent trend for either decreasing or increasing precipitation emerges from the Coupled Model Intercomparison Project Phase 3 (CMIP3) Global Climate Model (GCM) products. The Coordinated Regional Downscaling Experiment (CORDEX) is a program sponsored by World Climate Research Program (WCRP) to develop an improved framework for generating regional-scale climate projections for impact assessments using recent CMIP5 GCM projections. This paper compares patterns of climate projections in the Niger basin with the most recent and improved CORDEX-CMIP5 climate projections. It presents a comparative evaluation of projected rainfall, temperature, and potential evapotranspiration (PET) trends in the Niger basin using 8 GCMs and two emission scenarios (RCP 4.5 and RCP 8.5) available within the CORDEX-Africa framework. Rainfall and temperature data from a set of 8 CMIP5 GCMs under the mild (RCP 4.5) and high (RCP 8.5) emission scenarios were analyzed. The GCMs were dynamically downscaled to about 50 km resolution with the RCM SMHI-RCA (Sveriges Meteorologiskaoch Hydrologiska Institute) within the CORDEX-Africa regional downscaling experiments. Potential evapotranspiration (PET) was computed from temperature based on the Hamon model. Spatio-temporal patterns of ensemble median of changes of the eight GCMs relative to the present-day reference period of 1970–1999 were evaluated in two future 30 years periods: the near term (2030–2059) and far-term (2070-2099). Results show that climate change will drive an increase in precipitation, temperature, and PET in the Niger basin. This analysis will enhance the deployment of suitable coping strategies to impending climate trends; especially for food and energy production schemes which are prerequisites to sustainable regional developments.