There has been an overall increase of precipitation intensity in southern China since the late 1970s, and a corresponding drying trend in north China. Previous studies demonstrated the impacts of surface climate conditions such as the Tibetan Plateau snow cover and tropical sea surface temperatures on interdecadal variations of the East Asian summer monsoon. DOE scientists at Pacific Northwest National Laboratory assessed the ability of the Coupled Model Intercomparison Project phase 5 (CMIP5) to simulate the observed interdecadal precipitation enhancement over the Yangtze River valley, and also investigated the contributions of Arctic and mid- to high-latitude warming in the recent decades to the interdecadal variability of the East Asian summer monsoon rainfall. The team used historical simulations from six CMIP5 models for their analysis. The team found that only one of the models could reasonably simulate the observed interdecadal surface warming over the boreal mid- to high-latitudes in winter, spring, and summer. That model also simulated the observed summer monsoon rainfall trends in northern and southern China and the various relationships between atmospheric large-scale circulation and rainfall patterns in the reanalysis and observation data. Models that failed to capture one or more of the relationships also failed to simulate the observed rainfall trends. This points to the importance of Arctic and mid- to high-latitude processes on the interdecadal variability of the East Asian summer monsoon. Analyses of the various relationships also points to the positive anomalies of the Baikal blocking high as the bridge that links the warmer winter and spring surface temperature in the Arctic and mid- to high-latitudes to the interdecadal increase of summer precipitation over the Yangtze River valley.