In FT, Map>>World Settings brings up a property sheet with multiple pages. On the Temperature page, there are two groups of settings and another three settings: the two groups specify the world's base temperature and the last two specify the amount of fBm randomness added to the equator-to-pole temperature variance. The first setting (axial tilt) controls the distribution of the variance. If you make a flat world (set land roughness edit to 0) and set the temperature random and variance to 0, the world will have the same temperature everywhere. Increasing the variance to 100 will give a difference in temperature between the equator and poles of 100 degrees. Increasing the Random factor to 20 will add an fBm randomness of 20, giving an overall world variance of up to 120 degrees from the base value.

The rainfall page lacks the variance parameter, but has the base value and random amounts that operate in the same way.