Forced response and internal variability changes in the hydrological cycle and general circulation in a hot world beyond 2100 in the Community Earth System Model

Abstract Climate change affects both the mean state and its variability. Hence, the decomposition of climate variability into a forced response and internal variability is essential to understand climate change. Especially how the hydrological cycle will change is still uncertain. Here, we use ensemble simulations to elucidate the forced response and internal variability changes in a hot world beyond 2100 in the Community Earth System Model version 2. We extract the dominant modes of the forced response and of internal variability. The dominant mode of the forced response of the hydrological cycle changes sign in the early 22nd century, even though greenhouse gas emissions are decreasing. We find that pronounced atmospheric circulation changes are largely responsible for the hydrological cycle shift. The dominant modes of internal variability exhibit significant reduced amplitude of the variability after the forced response mode changes its sign, suggesting that the forced response has significant impact on internal variability. These results have implications for anthropogenic climate change beyond 2100.