E = sigma x T^4,where sigma = 5.67×10^-8, and T is temperature in K
 At its most tightly coupled, T is the radiative temperature of the Earth, in the sense that a portion of the radiation emitted at the top of the atmosphere originates at the Earth’s surface. However, the outgoing longwave radiation is proportional to T4. A 1C increase in the polar latitudes in the winter, for example, would have much less of an effect on the change of longwave emission than a 1C increase in the tropics. The spatial distribution matters, whereas equation (1) ignores the consequences of this assumption. A more appropriate measure of radiatively significant surface
changes would be to evaluate the change of the global average of T4.