Climate change projections using CMIP6 GCMs and downscaling approaches in the Upper Wabe Shebele Basin, Ethiopia.

Climate change presents considerable challenges, particularly for agrarian countries like Ethiopia. This study employed modeling and scenario-based methodologies to examine anticipated changes in precipitation and temperature in the Upper Wabe-Shebele River Basin. The study compared baseline data from 1986 to 2022 with two future projection periods: 2023 to 2053 and 2054 to 2086. Various bias correction techniques were applied to the precipitation and temperature datasets. For precipitation, the methods utilized include linear scaling, distribution mapping, empirical quantile mapping, and power transformation were utilized. Conversely, for temperature, power transformation was substituted with variance scaling, while the other three methods were employed for both datasets. The statistical downscaling model and climate model data for hydrologic modeling were calibrated and validated. The findings show a 35.89% reduction in precipitation and a 2.03 °C increase in temperature compared to the baseline. Future projections suggest that under the high emissions scenario SSP5-8.5, mean annual rainfall is expected to decline by 41.76% in the 2040s by 50.33% in the 2070s. Even under the lowest emissions scenario SSP1-2.6, rainfall is anticipated to decrease by 21.19% in the 2040s and by 30.25% in the 2070s. Temperature is projected to increase by 0.89-3.6 °C depending on the emissions scenario and time period. Additionally, both precipitation and temperature are also expected to show variations in their monthly distributions throughout the year. These climatic changes are expected to significantly reduce water availability and agricultural productivity.