A Less Cloudy Future: The Role of Subtropical Subsidence in Climate Sensitivity

Abstract

Sensitivity Training: Equilibrium climate sensitivity—the increase in global mean surface air temperature caused by the doubling of the concentration of atmospheric CO ₂ —is needed to predict anthropogenic climate change. For decades, models have estimated its value to be between 1.5° and 4.5°C, but with too high an uncertainty to have strong predictive value. Fasullo and Trenberth (p. 792 ; see the Perspective by Shell ) show that the seasonal variation of tropospheric relative humidity is related to climate sensitivity and could be used to constrain models and narrow the range of equilibrium climate sensitivity estimates, thereby allowing more accurate predictions of future warming.