The Mongolian Plateau (MP) lies on the edge of the East Asian monsoon region. Due to the semiarid and arid climate, the ecosystem of the MP is highly vulnerable to climate change. Climate change in the MP has received considerable attention from the scientific community.
Based on multiple sets of observations and reanalyzed data, we found that the exceptionally strong warming was observed over the MP during the summer of 1986-2004 (Figs. 1a and 1b). In terms of spatial dimension, the MP is the fastest warming region in the Northern Hemisphere, with a rate of warming three times faster than the averaged land warming in the Northern Hemisphere. In terms of temporal dimension, the probability distributions of summer temperature over the MP have been adjacent to each other for the past 100 years. However, the distribution in the last two decades is outside the previous range of variability (Fig. 1c). In other words, the MP temperatures in the last two decades are unprecedented, due to unusually strong warming.
We found that the external forcing (such as anthropogenic emissions of greenhouse gases and sulfate aerosols) cannot fully explain this exceptionally strong warming over the MP (Fig. 2a), and the synchronous phase shift of the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO), the dominant SST decadal variability in the Pacific and Atlantic, respectively, contributed to this strong warming over the MP. Observations analyses, large ensemble simulations, pacemaker experiments, and AMIP experiments consistently show that the positive-to-negative phase shift of the IPO and the negative-to-positive phase shift of the AMO (Fig. 3) can trigger a mid-latitude atmospheric wave train that targets an anticyclonic circulation trend over the MP (Figs. 2d and 2e). This anticyclonic circulation boosted the MP surface warming through increased downward solar radiation and land-air feedbacks. Our results highlight the important role of internal climate variability in driving the rapid regional climate change over the MP.