The goal is to numerically simulate how the planetary temperature of a naked planet would change through time as it approaches equilibrium (the state at which it stops changing, which we calculated before). The planet starts with some initial temperature. The “heat capacity” (units of Joules / m2 K) of the planet is set by a layer of water that absorbs heat and changes its temperature. If the layer is very thick, it takes a lot more heat (Joules) to change the temperature. Another numerical method takes time steps, extrapolating the heat content from one step to the next using the incoming and outgoing heat fluxes to balance a bank account by adding all the income and subtracting all the expenditures over some time interval like a month. The heat content "jumps" from the value at the beginning of the time step, to the value at the end.