by wind, reflection of the sun, snow, and humidity level. These factors can cause the isotherm to change rapidly and sometimes constantly over several kilometres, in both winter and summer all year round. Also, atmospheric subsidence and ascendence can contribute to variations in the isotherm. These conditions imply that the 0 °C isotherm varies globally and more so locally. See also Temperature inversion Lapse rate References The Mountain Manual, Seuil, 2000 Mountains Montane ecology Meteorological phenomena