Modelling climate change and aridity for climate impact studies in semi-arid regions: The case of Giba basin, northern Ethiopia.

of long-term and future climate variability is crucial for impact assessment studies in drought-prone areas like the Giba basin in northern Ethiopia. This study has applied the statistical downscaling model (SDSM) and (De Martonne and Pinna combinative) aridity index methods to evaluate the climate system of the Giba basin. Historical data (1961-2019) from seven meteorological stations and global grided data were used for future climate projections (2020-2100) under the three emission scenarios (RCPs 2.6, 4.5, and 8.5) for the three-time horizons (2040s, 2060s, and 2080s). Analysis of results showed that rainfall and temperature projection on a monthly and/or seasonal basis has more significance than on an annual basis for impact studies particularly, in areas where irrigation practices are common like in the Giba basin. Seasonal projection of rainfall in the basin showed a slightly decreasing trend during the spring season (MAM), and a significant increment in the main rainy season (JJA) under all scenarios and for the whole projection year. On an annual basis, a maximum increase of rainfall, up to +285 mm/year and +298 mm/year was expected to increase at Abyi Adi and Mekelle Obs stations, respectively, under RCP 8.5 in the 2080s. Temperature projection showed a consistent rise throughout the basin that ranges from a minimum increase of Tmax by +0.29 °C in the 2040s (RCP 2.6) at Mekelle Obs station to a maximum increase of Tmin by +2.35 °C in the 2080s (RCP8.5) at Abyi Adi station. In general, it is observed that the rate of increment of projected Tmin was more than that of Tmax in all stations in the Giba basin, which showed a continuous contraction of the gap between Tmin and Tmax, hence, the prevalence of global warming. This has led to a considerable increment of aridity till the end of the 21st century. Hence, the implementation of locally-suited climate change resilient strategies is crucial to enhance the sustainability of the ecosystem and ensure food security in the basin.