Three Flavors of Radiative Feedbacks and Their Implications for Estimating Equilibrium Climate Sensitivity

The realization that atmospheric radiative feedbacks depend on the underlying patterns of surface warming and global temperature, and thus, change over time has lead to a proliferation of feedback definitions and methods to estimate equilibrium climate sensitivity (ECS). We contrast three flavors of radiative feedbacks - equilibrium, effective, and differential feedback - and discuss their physical interpretations and applications. We show that their values at any given time can differ more than 1 Wm-2K-1 and their implied equilibrium or effective climate sensitivity can differ several degrees. With ten (quasi) equilibrated climate models, we show that 400 years might be enough to estimate the true ECS within a 5% error using a simple regression method utilizing the differential feedback parameter. We argue that a community-wide agreement on the interpretation of the different feedback definitions would advance the quest to narrow the estimate of climate sensitivity.

Automated summary

The study highlights the importance of understanding different types of radiative feedbacks, which can vary significantly over time and impact the estimated climate sensitivity. By utilizing a simple regression method with differential feedback parameter, the true equilibrium climate sensitivity could potentially be estimated within a 5% error range in as little as 400 years.