It's common knowledge that the higher you are above sea level, the cooler the
temperature. Likewise, temperatures are colder the farther north and south you
travel from the equator. What is less well known is that there are some
general "rules" or guidelines that can be used to estimate the magnitude of
temperature changes that correspond to differences in latitude or elevation.
Generally, temperature decreases three (3) degrees Fahrenheit for every 1,000
foot increase in elevation above sea level. Of course, the reverse is also
true: temperature increases 3 degrees with every 1,000 foot decrease in
elevation. This means that if you were to travel from the desert where it was
90 degrees to a nearby mountain that was 5,000 feet higher, it would be 75
degrees at the top - a difference of 15 degrees. This certainly explains why
everyone likes the mountains so much in the summer.
Temperature also decreases as latitude becomes more northward in the Northern
Hemisphere and more southerly in the Southern Hemisphere. Latitude in this
sense simply refers to a measurement of movement north or south across the
surface of the earth. The general rule is that temperature changes three (3)
degrees Fahrenheit for every 300 mile change in latitude at an elevation of sea
level. If you are in the Northern Hemisphere, you can expect temperatures to
be 3 degrees cooler 300 miles north, 6 degrees cooler 600 miles north, and so
on, until you reach the North Pole. The same is true for the Southern
Hemisphere, except that temperatures cool the further you travel from the
equator toward the South Pole.
When you are calculating latitudinal temperature changes, remember to account
for differences in elevations. For example, you can expect a location that is
600 miles north and 2,000 feet lower in elevation to be about the same
temperature as your current location, because the elevational and latitudinal
temperature changes cancel each other out (6 degrees cooler + 6 degrees warmer
= no change). This rule of thumb, like all such rules, is general in nature
and obviously does not apply to all areas nor in all cases. It works best when
applied broadly, in increments of 1,000 feet (elevation) and 300 miles
(latitude). Temperature estimates are not as accurate when the rule is applied
over shorter distances.
In nature, differences in temperature due to elevation and latitude help to
create a diversity of plant and animal species within a relatively small area.
The numbers of plant and animal species that inhabit a certain area describe a
concept known as "biodiversity", one measure of a healthy, functioning
ecosystem. The greater the number of species, the greater the biodiversity and
often, the greater stability of an ecosystem. Minor variations in temperature
can profoundly affect the number and type of species in a given area.
Biodiversity and ecosystem health are thus very closely related to both
latitudinal and elevational temperature differences. Primary factors other
than temperature that influence biodiversity include soil properties,
topography, aspect (the direction a slope faces), and precipitation type,
timing, and intensity.