Observed Sc and Cu Cloud Variability and Feedback and Their Dependency to Environmental Factors

Abstract

Clouds play a critical role in shaping Earth's energy budget, yet cloud feedbacks, especially those from low‐level clouds, remain among the largest uncertainties in climate projections. Here, we extended an approach designed to discriminate stratocumulus (Sc) and cumulus (Cu) clouds in the tropics to a global scale to assess their contributions to low‐cloud feedback. To this end, we first use observations and reanalyses to characterize the sensitivities of Sc and Cu to key cloud‐controlling factors (CCFs). We then combine these sensitivities with CCF changes over an 12‐year period to infer a CCF‐based cloud change, which we validate against actual observations of the 12‐year cloud change. We further use this CCF‐based method to infer low cloud cover (LCC) and radiation changes under different warming scenarios: idealized warming, from climate model outputs, and historical trends, from reanalysis data sets. Our results show that near‐global low‐cloud feedback is primarily controlled by surface warming and the strength of lower‐tropospheric temperature inversions, and driven by Sc clouds. Finally, we find opposite signs of cloud feedback over the historical period (negative, ) or in response to an abrupt increase (positive, ).