Journal Article
Evaluation of CMIP6 GCM Performance in Simulating Historical Rainfall and Temperature Climatology of the Tana and North Gojjam Sub‐Basins in the Upper Blue Nile Basin, Northwestern Ethiopia
Abebe Shenkut; Getachew Alemayehu; Kindie Tesfaye; Mezgebu Getnet; Yibekal Alemayehu; Girma Mamo
International Journal of Climatology · Vol. 45, Issue 13 · 2025
Abstract
The Upper Blue Nile Basin, a vital water tower for northeastern Africa, faces growing climate risks that threaten its water resources and agricultural systems. While CMIP6 General Circulation Models (GCMs) represent the state‐of‐the‐art in climate projection, their performance in tropical highlands remains uncertain due to complex topography and localised climate processes. This study evaluates five CMIP6 models (ACCESS‐ESM1‐5, GFDL‐CM4, GFDL‐ESM4, INM‐CM4‐8, MRI‐ESM2‐0) against observed data (1990–2014) using a multi‐metric framework combining statistical indices (MR, KGE) and extreme climate indicators (RX1day, SU25, CSDI). Results reveal distinct model strengths: GFDL‐ESM4 and INM‐CM4‐8 showed superior rainfall simulation (KGE > 0.6 for daily scales), while ACCESS‐ESM1‐5 exhibited systematic wet biases (> 30% in main rainy season). Temperature simulations demonstrated strong elevation dependence, with GFDL‐ESM4 achieving the lowest errors (RMSE