Abstract/Summary

The responses of the Earth’s climate system to positive and negative CO2 emissions are not identical in magnitude, resulting in hysteresis. In particular, the degree of global precipitation hysteresis varies markedly among Earth system models. Based on analysis of Earth’s energy budget, here we show that climate sensitivity controls the degree of global precipitation hysteresis. Using an idealized CO2 removal scenario, we find that the surface available energy for precipitation continues to increase during the initial negative CO2 emission period following a positive CO2 emission period, leading to a hysteresis of global precipitation. This feature is more pronounced in Earth System Models with a high climate sensitivity. Our results indicate that climate sensitivity is a key factor controlling the hysteresis behavior of global precipitation in a changing CO2 pathway. Therefore, narrowing the uncertainty of climate sensitivity helps improve the projections of the global hydrological cycle.