evidence: The carbon cycle and other biogeochemical feedbacks, chemistry feedbacks, and slow feedback-like changes in vegetation types and ice sheets are deliberately not included in the concept of equilibrium climate sensitivity (Knutti and Hegerl, 2008; Knutti and Rugenstein, 2015), which was developed mainly to intercompare the performance of physical climate models consisting of an atmospheric general circulation model (GCM) and a simplified representation of the upper ocean only (for a recent discussion of the equilibrium climate sensitivity, see Stevens et al., 2016). For example, in an ESM, the ocean would be forced to continuously take up large amounts of CO2 from the atmosphere if the CO2 forcing were to be held constant at double present-day CO2 relative to the pre-industrial period. This would render an unrealistic ocean biogeochemical state after several hundred years leading also to unrealistic fluxes of DMS (dimethyl sulfide, (CH3)2S, a major contributor to cloud condensation nuclei). The ESM could never be run to a meaningful equilibrium.