Impacts of internal variability on winter temperature fluctuations over the Tibetan Plateau

The climate comprises an externally forced component and internal variability within the climate system. This variability arises from interactions among climate subsystems, significantly impacting climate change, particularly over the Tibetan Plateau (TP). Therefore, understanding the mechanisms governing TP temperature responses to internal variability is crucial. In this study, winter temperature components over the TP in response to internal variability and external forcing are distinguished using reconstructed monthly temperature data and large ensemble simulations from 11 CMIP6 coupled models spanning 1901 to 2014. Analysis reveals two cold periods (1901–1931, 1956–1999) and two warm periods (1932–1955, 2000–2014) within the internal-variability component from 1901 to 2014. These periods are significantly associated with the Atlantic Multi-decadal Oscillation (AMO) and Interdecadal Pacific Oscillation (IPO), explaining 38.9% of the winter temperature's internal-variability component over the TP. Manipulating AMO+ (AMO-) without IPO influence or IPO- (IPO+) without AMO impact intensifies the winter warm (cold) anomaly across the entire TP. This suggests that AMO and IPO contribute to the temperature's internal-variability component over the TP. Specifically, in winter, both AMO+ (AMO-) and IPO- (IPO+) induce a “− + −+” (+ − +−) Rossby wave train over Eurasia, influencing the East Asian trough, East Asian jet stream, Ural Blocking high, and the Siberian high, resulting in a warm (cold) anomaly over the TP. Moreover, our findings indicate that AMO and IPO collaboratively determine the cold or warm anomaly and its intensity over the TP in winter.