Analysis of the observed and projected changes in rainfall and temperature under climate change scenarios in Bale Mountains National Park, South Eastern Ethiopia

Abstract

This study examined historical trends and variability, as well as future projections of rainfall and temperature under different emission scenarios in Bale Mountains National Park (BMNP), southeastern Ethiopia. For the historical analysis, thirty years (1994-2023) of daily rainfall and temperature data from eight meteorological stations within and surrounding the park were obtained from the National Meteorology Institute of Ethiopia. Future climate conditions were projected using an ensemble of eight Global Climate Models (ACCESS-CM2, CMCC-ESM2, CNRM-CM6-1, INM-CM4-8, MIROC-ES2L, MPI-ESM1-2-LR, NorESM2-MM, and MRI-ESM2-0) from CMIP6 under three emission scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5), covering the near future (2021-2040), mid-century (2041-2070), and end of the century (2071-2099). Statistical methods, including descriptive statistics, spatial interpolation, the Mann-Kendall trend test, and Sen's slope estimator, were used to evaluate spatiotemporal patterns of historical climate variables. In addition, decadal deviations from long-term means were analyzed using the Inverse Distance Weighting (IDW) technique in ArcGIS 10.8 to identify climate shifts. The Delta method was applied to downscale Global Climate Model outputs for improved regional relevance. Results revealed strong spatial variability in rainfall influenced by elevation and orographic effects, with higher precipitation observed in elevated areas. Despite noticeable year-to-year fluctuations, most stations showed declining rainfall trends, particularly after 2000, indicating a shift toward drier conditions. Over the last three decades (1994-2023), the annual mean rainfall decreased by about 100 mm, while the maximum and minimum temperatures increased by approximately 1.6 °C and 1.7 °C, respectively, between the first decade (1994-2003) and the last decade (2014-2023). Future projections indicate increases in both rainfall and temperature relative to the 1985-2014 baseline period. The most pronounced changes are expected under the high-emission scenario (SSP5-8.5) by 2071-2099, with rainfall increasing by about 265 mm and temperatures rising by up to 3.9 °C. These findings highlight the urgency of sustained climate monitoring and adaptive conservation strategies.