Climate

A mountain in Carbon County, Utah

Climate on mountains become colder at high elevations, due to the way that the sun heats the surface of the Earth. The sun warms the ground directly, while the greenhouse effect acts as a blanket, reflecting heat back towards the Earth that would otherwise be lost to space. The greenhouse effect thus keeps the air at low elevations warm. As elevation increases, there is less greenhouse effect, so the ambient temperature goes down.

Valley of the Ten Peaks, Canadian Rockies

The rate at which the temperature drops with elevation, called the environmental lapse rate, is not constant (it can fluctuate throughout the day or seasonally and also regionally), but a typical lapse rate is 5.5°C per 1,000 m (3.57°F per 1,000 ft).
Therefore, moving up 100 meters on a mountain is roughly equivalent to moving 80 kilometers (45 miles or 0.75° of latitude) towards the nearest pole. This relationship is only approximate, however, since local factors such as proximity to oceans (such as the Arctic Ocean) can drastically modify the climate. As the altitude increases, the main form of precipitation becomes snow and the winds increase.

The effect of the climate on the ecology at an elevation can be largely captured through a combination of amount of precipitation, and the biotemperature, as described by Leslie Holdridge in 1947. Biotemperature is the mean temperature; all temperatures below 0 °C (32 °F) are considered to be 0 °C. When the temperature is below 0 °C, plants are dormant, so the exact temperature is unimportant. The peaks of mountains with permanent snow can have a biotemperature below 1.5 °C