Abstract

According to current climate models, the Paris threshold of 2 degrees warming above pre-industrial levels may already be crossed within the next 20 years, or not within the next 50 years even if CO2 emission continue to increase rapidly. This large spread in the time span until the Paris threshold is crossed can almost entirely attributed to the spread in equilibrium climate sensitivities (ECS) across climate models. The ECS spread across climate models, in turn, can primarily be traced to uncertainties in the representation of low clouds in climate models. The representation of clouds and especially of low clouds in climate models has been a recalcitrant problem for decades. This talk argues that the time is ripe now for rapid advances in the representation of clouds in climate models and discusses ways in which this can be achieved, to obtain more accurate climate projections.