The first part of this calculation is a pair of regressions to calculate the slope and intercept for two linear functions: one is the latitude to which there will be snow and ice on the surface (lower latitudes, closer to the equator, when it’s colder), and the second is the overall albedo from ice that you will get at that temperature. You are looking for functions Ice latitude = m1 * T + b1 and albedo = m2 * T + b2.