Selection of multiple ensemble representative CMIP5 climate models for climate change study in developing river basin: the case of Awash River Basin, Ethiopia

The aim of this investigation is to identify a representative set of climate model projections for the Awash Basin using accessible general circulation model (GCM) predictors from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive. Various approaches were employed to systematically shortlist and select suitable climate models under two representative concentration pathways (RCPs). For RCP4.5, 105 GCMs were used and for RCP8.5, 78 GCMs were used to select the best performance models for a climate change impact study in this basin. These approaches are combined in the current study to create a three-step sequential procedure for choosing climate models: (1) initial selection of climate models based on the range of projected changes in climatic means, (2) refined selection based on the range of projected changes in climatic extremes, and (3) final selection based on the ability of the climate models to simulate historical climate changes between 1971–2000 and 2071–2100 were analyzed. Five corners of possible extreme future scenarios (wet-warm, wet-cold, dry-warm, dry-cold, and the 50th percentile of the temperatures) were used. A total of 25 GCMs were selected for RCP4.5 and RCP8.5 based on the range of expected mean temperature and rainfall change. Based on the range of extreme changes, 10 GCMs were chosen. Five GCMs were ultimately selected for each RCP4.5 and RCP8.5 by merging all three stages. The findings of this study will contribute valuable insights to better understand and adapt to the impacts of climate change in the Awash River Basin and similar regions.