 Many of today’s GCMs/ESMs have an ostensibly modular design: they consist of several component models corresponding to different parts of the climate system—atmosphere, ocean, land surface, etc.—as well as a “coupler” that passes information between them where the spatial boundaries of the component systems meet and that must account for any differences in the component models’ spatiotemporal resolution (Alexander &amp; Easterbrook 2015). Often these component models are modified versions of named, stand-alone models. For example, the Community Earth System Model version 1.2 (CESM1.2) housed at the U.S. National Center for Atmospheric Research incorporates the Community Atmosphere Model (CAM) and an extension of the Parallel Ocean Program (POP). Such modularity is intended to allow for easier reconfiguration of a GCM/ESM for different modeling studies, e.g., replacing the ocean model with a simpler version when this will suffice. Lenhard and Winsberg (2010), however, argue that complex climate models in fact exhibit only a “fuzzy” modularity: in order for the model as a whole to work well, some of the details of the component models will be adjusted to mesh with the particular features of other components and to try to compensate for their particular limitations.