title: Observational constraints on mixed-phase clouds imply higher climate sensitivity.
abstract: Global climate model (GCM) estimates of the equilibrium global mean surface temperature response to a doubling of atmospheric CO2, measured by the equilibrium climate sensitivity (ECS), range from 2.0° to 4.6°C. Clouds are among the leading causes of this uncertainty. Here we show that the ECS can be up to 1.3°C higher in simulations where mixed-phase clouds consisting of ice crystals and supercooled liquid droplets are constrained by global satellite observations. The higher ECS estimates are directly linked to a weakened cloud-phase feedback arising from a decreased cloud glaciation rate in a warmer climate. We point out the need for realistic representations of the supercooled liquid fraction in mixed-phase clouds in GCMs, given the sensitivity of the ECS to the cloud-phase feedback.
authors.affiliation: Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA. ivy.tan@yale.edu.
authors.forename: Ivy
authors.initials: I
authors.lastname: Tan
authors.affiliation: Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA.
authors.forename: Trude
authors.initials: T
authors.lastname: Storelvmo
authors.affiliation: Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Zelinka