Observational constraints on mixed-phase clouds imply higher climate sensitivity

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…

• NS
  National Science Foundation

  Award: 1352417
• UD
  U.S. Department of Energy

  Award: DE-SC0012580
• NA
  National Aeronautics and Space Administration

  Award: NNX14AL07H
• LL
  Lawrence Livermore National Laboratory

  Award: DE-AC52-07NA27344