The surface temperature of a planet with a substantial atmosphere is determined by two principal processes; radiative balance in the largely isothermal tropopause, and adiabatic circulation in the troposphere. The tropopause gas temperature is given by the radiative temperature multiplied by the fourth root of one half. At pressures greater than 22kPa, gases cannot remain in stratified layers, but must circulate. As gases rise in the atmosphere, they gain gravitational potential energy. By the First Law of thermodynamics this energy is supplied by the thermal energy (the enthalpy) of the gas, which must cool as a consequence. Hence gases cool as they rise and warm up as they descend. The result is a temperature lapse rate, which is readily calculable from the equation of state of the gas and (in a moist atmosphere) the Clausius Clapyron Equation. This yields the correct temperature distribution for both Venus and the Earth. The 'greenhouse effect' is no more than folklore and thought habit; it is the modern equivalent of Piltdown Man and Canals on Mars.