Speaker: Haozhe He, University of Miami

Title: State-dependence of CO2 Forcing and its Implications for Climate Sensitivity

Abstract: When evaluating the effect of CO2 changes on the earth’s climate, it is widely assumed that instantaneous radiative forcing from a doubling of a given CO2 concentration (IRF2×CO2) is constant and that variances in climate sensitivity arise from differences in radiative feedbacks, or a dependence of these feedbacks on the climatological base-state. In this paper, we show that the IRF2×CO2 is not constant, but also depends on the climatological base-state, increasing by ~25% for every doubling of CO2, and has increased by ~10% since the pre-industrial era primarily due to stratospheric cooling, implying a proportionate increase in climate sensitivity. This base-state dependence also explains about half of the intermodel spread in IRF2×CO2, a problem that has persisted among climate models for nearly three decades. 

Brief bio: Haozhe He is a fifth-year PhD student at the University of Miami, working with Dr. Brian Soden. His research focuses on radiative forcing, feedback and climate sensitivity. He received his B.S. in Atmospheric Sciences from Nanjing University of Information Science & Technology, and obtained his M.Sc. in Global Environment Change at Beijing Normal University.