Dependence of global radiative feedbacks on evolving patterns of surface heat fluxes

Abstract

In most climate models, after an abrupt increase in radiative forcing the climate feedback parameter magnitude decreases with time. We demonstrate how the evolution of the pattern of ocean heat uptake—moving from a more homogeneous toward a heterogeneous and high‐latitude‐enhanced pattern—influences not only regional but also global climate feedbacks. We force a slab ocean model with scaled patterns of ocean heat uptake derived from a coupled ocean‐atmosphere general circulation model. Steady state results from the slab ocean approximate transient results from the dynamic ocean configuration. Our results indicate that cloud radiative effects play an important role in decreasing the magnitude of the climate feedback parameter. The ocean strongly affects atmospheric temperatures through both heat uptake and through influencing atmospheric feedbacks. This highlights the challenges associated with reliably predicting transient or equilibrated climate system states from shorter‐term climate simulations and observed climate variability.

An Estimate of Equilibrium Climate Sensitivity From Interannual Variability

“…Recent work suggests that λ 4xCO2 is less negative (i.e., implying a higher ECS) than λ 2xCO2 (Armour, ; Proistosescu & Huybers, ). On the other hand, we use all 150 years of the 4xCO 2 runs to estimate λ 4xCO2 , which tends to produce values that are too negative (Andrews et al, ; Armour, ; Rose & Rayborn, ; Rugenstein et al, ). These two errors tend to cancel, but how much of a bias is left—and in which direction—remains an uncertainty in this analysis.…”

Observational Constraints on Cloud Feedbacks: The Role of Active Satellite Sensors

“…It is known that the SST change expected from rising CO 2 levels is more uniform than that from natural variability. Recent work shows that climate feedbacks are not constant but vary over the historical period (Armour et al 2013;Xie et al 2016;Gregory and Andrews 2016;Rugenstein et al 2016) and that this comes, in part, from the dependence of cloud feedbacks on patterns of surface temperature change. In particular, Zhou et al (2016) find the spatial patterns of surface warming have varied in a way that cloud feedbacks over recent decades are significantly more negative than longterm feedbacks.…”

Analyzing the dependence of global cloud feedback on the spatial pattern of sea surface temperature change with a Green's function approach

“…The dependence of cloud feedback on sea surface warming patterns is also important for CO 2 ‐induced global warming. Recent studies suggest that the magnitude of the climate feedback parameter changes over time after the CO 2 concentration increases abruptly [ Williams et al ., ; Held et al ., ; Armour et al ., ; Andrews et al ., ; Rugenstein et al ., ; Proistosescu and Huybers , ; Armour , ], which is at least in some models caused by an increase in the cloud feedback [ Andrews et al ., ]. Armour et al .…”