Strong pattern effect evident in Southern Ocean cloud feedback based on multiple lines of evidence

The Southern Ocean is known to be one of the cloudiest places on Earth, and the important contribution of Southern Ocean clouds to Earth’s energy budget is undisputed. By changing their composition in response to warming, clouds in this region currently limit the rate of warming, as they become brighter with increasing temperature and thus exert a stabilising feedback on the climate system. Here, based on multiple lines of evidence, we show that in the current state of the Southern Ocean climate, this negative feedback happens to be maximised. Moving away from the present climate state in either direction (cooling or warming) will thus reduce the feedback, such that the climate sensitivity to any perturbation can be expected to grow rapidly with each degree of temperature change. This finding adds urgency to the implementation of effective climate mitigation to limit warming and thus preserve the stabilising climate effect of Southern Ocean clouds.