Climate predictions using recent and high-resolution climate models are becoming important for effective decision-making and for designing appropriate climate change adaptation and mitigation strategies. Due to highly variable climate and data scarcity of the upper Blue Nile Basin, previous studies did not detect specific unified trends. This study discusses, the past and future climate projections under CMIP6-SSPs scenarios for the basin. For the models’ validation and selection, reanalysis data were used after comparing with area-averaged ground observational data. Quantile mapping systematic bias correction and Mann–Kendall trend test were applied to evaluate the trends of selected CMIP6 models during the 21st century. Results revealed that, ERA5 for temperature and GPCC for precipitation have best agreement with the basin observational data, MRI-ESM2-0 for temperature and BCC-CSM-2MR for precipitation were selected based on their highest performance. The MRI-ESM2-0 mean annual maximum temperature for the near (long)-term period shows an increase of 1.1 (1.5) °C, 1.3 (2.2) °C, 1.2 (2.8) °C, and 1.5 (3.8) °C under the four SSPs. On the other hand, the BCC-CSM-2MR precipitation projections show slightly (statistically insignificant) increasing trend for the near (long)-term periods by 5.9 (6.1)%, 12.8 (13.7)%, 9.5 (9.1)%, and 17.1(17.7)% under four SSPs scenarios.

中文翻译：

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埃塞俄比亚 UBNB (Abay) CMIP6 情景下过去和未来气候趋势的评估

使用最新的高分辨率气候模型进行气候预测对于有效决策和设计适当的气候变化适应和减缓战略变得越来越重要。由于青尼罗河流域上游气候多变且数据稀缺，之前的研究没有发现具体的统一趋势。本研究讨论了该流域在 CMIP6-SSP 情景下的过去和未来气候预测。对于模型的验证和选择，在与面积平均的地面观测数据进行比较后，使用了再分析数据。应用分位数映射系统偏差校正和 Mann-Kendall 趋势检验来评估所选 CMIP6 模型在 21 世纪的趋势。结果表明，温度的ERA5和降水的GPCC与流域观测数据的一致性最好，选择用于温度的 MRI-ESM2-0 和用于降水的 BCC-CSM-2MR 是基于它们的最高性能。MRI-ESM2-0 近期（长期）年平均最高气温显示增加 1.1 (1.5) °C、1.3 (2.2) °C、1.2 (2.8) °C 和 1.5 (3.8) °C C 在四个 SSP 下。另一方面，BCC-CSM-2MR 降水预测在近期（长期）期间显示出轻微（统计上不显着）增加的趋势，分别为 5.9 (6.1)%、12.8 (13.7)%、9.5 (9.1)% 和在四种 SSP 情景下为 17.1(17.7)%。