 Each component model in a GCM/ESM in turn incorporates representations of a number of important processes operating within that part of the climate system. For atmosphere models, for example, it is common to distinguish the “dynamics” and the “physics” (see, e.g., Neale et al. 2010). The dynamics (or “dynamical core”) is a set of fluid dynamical and thermodynamic equations reflecting conservation of momentum, mass and energy, as well as an equation of state. These equations are used to simulate large-scale atmospheric motions, which transport heat, mass and moisture; the scale of the motions that can be resolved depends on the grid mesh of the model. The “physics” encompasses representations of sub-grid processes that impact grid-scale conditions in a significant way: radiative transfer, cloud formation, precipitation and more. These processes are parameterized, i.e., represented as a function of the grid-scale variables that are calculated explicitly in the dynamical core (e.g., temperature, pressure, winds, humidity). Parameterization is necessary in other components of climate models as well, whenever sub-grid processes significantly influence resolved-scale variables.