Abstract: Boreal midlatitude extreme weather events are closely related to the circumglobal teleconnection (CGT) pattern. Using the ECHAM5.4 atmospheric general circulation model, we conduct a suite of sensitivity experiments forced by long-term sea surface temperature (SST) trends. By comparing a multibasin concurrent-warming experiment with single-basin and basin-removed forcing experiments, we quantify the impacts of SST warming trends in the Pacific, Indian, and Atlantic Oceans on the borealsummer circulation over the Northern Hemisphere and on surface air temperature changes over the Tibetan Plateau. The results show that tropical Pacific warming is one of the key drivers that excites mid-highlatitude teleconnection wave trains in boreal summer (e.g., the CGT), whereas Atlantic and Indian Ocean warming plays secondary roles mainly by modulating the intensity and location of the corresponding midlatitude anomaly centers. The basin-induced responses are not linearly additive: a simple superposition of the single-basin responses produces an overly strong wave-train amplitude and noticeable phase shifts, indicating nonlinear interactions among ocean basins that partly offset each other. Over the Tibetan Plateau, warming in all three basins leads to an increase in summer surface air temperature, with a pronounced positive nonlinear synergy, and the marginal contribution of Pacific warming is the largest. These findings highlight the nonlinear mechanisms through which multi-basin SST warming shapes tropical-extratropical interactions and influences the Tibetan Plateau climate, providing a basis for regional climate change attribution and prediction.