Differences Between Present-Day and Cretaceous Hydrological Cycle Responses to Rising CO2 Concentration

Climate model simulations have suggested that, in East Asia, the mean precipitation increases with global warming, leading to more humid conditions. In contrast, Cretaceous proxy data show an aridification in the low latitudes of East Asia during the mid-Cretaceous when CO2 levels were higher and the climate was relatively warmer compared to the early and late Cretaceous. We conducted simulations of the Present-day and Cretaceous climates with different CO2 levels using an atmosphere-ocean general circulation model, MIROC4m, to investigate the hydrological cycle changes as CO2 is increased. The results show that the responses of the hydrological cycle in East Asia for the Present-day and Cretaceous experiments are the exact opposite; an increase in the Present-day, and a decrease in the Cretaceous, as geological evidence shows. Overall, the opposite response in the Cretaceous is attributed to a weaker summer atmospheric circulation, associated with the absence of the Tibetan Plateau.