Global Cooling Contributed to the Establishment of a Modern‐Like East Asian Monsoon Climate by the Early Miocene

The establishment of a modern‐like monsoon climate in East Asia by the early Miocene was a complex process forced by several factors, and previous studies paid less attention to global cooling. Here we investigate this process using climate modeling by considering changes in topography and global cooling under the early Miocene boundary conditions. Using early Miocene paleogeography and an atmospheric CO2 concentration of 560 ppmv, our model results indicate that a nonzonal climate pattern has appeared in East China but that this climate exhibits weak precipitation and wind seasonality. Such seasonality strengthens as the concentration of atmospheric CO2 decreases from 560 to 420 ppmv and resembles the modern‐like condition after the growth of the Antarctic ice sheet. Although the development of East Asian topography can further strengthen this seasonality, our results indicate that global cooling is also pivotal for the establishment of a modern‐like monsoon climate in East Asia. Plain Language Summary Up to now, there are still debates about what caused the formation of a modern‐like monsoon climate in East Asia by the early Miocene. In particular, it appears that the growth of the Tibetan Plateau markedly changed the atmospheric circulation and precipitation by intensifying the land‐sea thermal contrast and pressure gradient. While, some studies have emphasized that changes in the land‐sea distribution were also very important in this process. By comparison, previous studies pay less attention to global cooling. Here we investigate this process using climate modeling under the early Miocene boundary conditions. Our simulations indicate that the decrease in the atmospheric CO2 concentration and the growth of the Antarctic ice sheet can strengthen the precipitation and wind seasonality in East China and facilitate the establishment of a modern‐like East Asian monsoon climate. These results indicate that global cooling is also very important for the establishment of a modern‐like monsoon climate in East Asia, providing better understanding of climate effects of global cooling in this process. Key Points Global cooling was pivotal for the establishment of a modern‐like monsoon climate in East China Decrease in atmospheric CO2 concentration and growth of Antarctic ice sheet strengthened precipitation and wind seasonality in East China The development of East Asian topography further strengthened the precipitation and wind seasonality in East China