The availability of a variety of Global Climate Models (GCMs) has increased the importance of the selection of suitable GCMs for impact assessment studies. In this study, we have used Bayesian Model Averaging (BMA) for GCM(s) selection and ensemble climate projection from the output of thirteen CMIP5 GCMs for the Upper Indus Basin (UIB), Pakistan. The results show that the ranking of the top best models among thirteen GCMs is not uniform regarding maximum, minimum temperature, and precipitation. However, some models showed the best performance for all three variables. The selected GCMs were used to produce ensemble projections via BMA for maximum, minimum temperature and precipitation under RCP4.5 and RCP8.5 scenarios for the duration of 2011–2040. The ensemble projections show a higher correlation with observed data than individual GCM’s output, and the BMA’s prediction well captured the trend of observed data. Furthermore, the 90% prediction intervals of BMA’s output closely captured the extreme values of observed data. The projected results of both RCPs were compared with the climatology of baseline duration (1981–2010) and it was noted that RCP8.5 show more changes in future temperature and precipitation compared to RCP4.5. For maximum temperature, there is more variation in monthly climatology for the duration of 2011–2040 in the first half of the year; however, under the RCP8.5, higher variation was noted during the winter season. A decrease in precipitation is projected during the months of January and August under the RCP4.5 while under RCP8.5, decrease in precipitation was noted during the months of March, May, July, August, September, and October; however, the changes (decrease/increase) are higher than under the RCP4.5.

各种全球气候模式（GCM）的可用性增加了为影响评估研究选择合适的GCM的重要性。在这项研究中，我们使用了贝叶斯模型平均（BMA）进行GCM的选择和来自巴基斯坦上印度河盆地（UIB）的13个CMIP5 GCM的输出的整体气候预测。结果表明，在最高，最低温度和降水量方面，十三个GCM中最佳模型的排名不一致。但是，某些模型显示了所有三个变量的最佳性能。所选的GCM用于通过BMA生成RCP4.5和RCP8.5情景下2011-2040年期间最高，最低温度和降水的集合预测。与单个GCM的输出相比，整体投影显示与观测数据的相关性更高，BMA的预测很好地反映了观测数据的趋势。此外，BMA输出的90％预测间隔紧密捕获了观测数据的极值。将这两个RCP的预测结果与基线持续时间（1981-2010年）的气候进行了比较，并注意到与RCP4.5相比，RCP8.5显示出未来温度和降水的更多变化。对于最高温度，在上半年的2011–2040年期间，每月的气候变化更大。但是，在RCP8.5下，冬季的变化更大。在RCP4.5下，预计1月和8月的降水量将减少，而在RCP8.5下，则将在3月，5月，7月，8月，9月和10月的月份减少。然而，