How the hydrological cycle affects the global cloud feedback

Cloud feedback remains the largest source of uncertainty in projections of Earth’s climate sensitivity and future warming. Recent generations of Earth System Models (ESMs) show a trend toward more positive cloud feedback, contributing to higher estimates of effective climate sensitivity (ECS). This raises an important question: can observational constraints help rule out or support these higher values? Our work focuses on the hydrological processes that drive cloud feedback, particularly the role of large-scale moisture transport and precipitation efficiency. Both observations and models show a consistent global moisture flux pattern: moisture convergence in the tropics and extratropics, and divergence in the subtropics, maintaining a near-zero global moisture balance. As the climate warms, this pattern strengthens due to the Clausius-Clapeyron relationship, enhancing the moisture flux and driving cloud responses. These cloud responses are further shaped by how efficiently atmospheric moisture is converted into precipitation, linking hydrological and radiative processes in a warming world. Using a framework that relates cloud feedback to features of the hydrological cycle, precipitation efficiency and radiative efficiency, we constrain cloud feedback globally using satellite observations. Observations of precipitation efficiency and radiative efficiency narrow the spread of cloud feedback across the Community Atmosphere Model version 6 (CAM6) perturbed parameter.