Multiple equilibria in a minimal climate model

A two cell energy balance model includes long and shortwave radiation, heat transfer from warm places to cool places, greenhouse effect, and an albedo that depends on temperature. For a range of parameters, it has four stable equilibria, including one solution that is cool at low latitudes and warm at high latitudes. Discontinuous jumps between equilibrium states occur as parameters are varied. Conditions for these transitions to occur are found for the case of a single control parameter that models the strength of the greenhouse effect, and for the case of two controls that model the solar heating of each cell.