around the world, including the Strait of Gibraltar, the Turkish Straits, and the Strait
of Malacca. Waterways built by humans can be considered choke points as well—
the Panama Canal and Suez Canal are both prime examples of such stretches of
water that serve vital strategic and economic functions.
Climate
Climate is the characteristic state of theatmosphereat alocationor in aregion.It
is the entirety of weather conditions over the long term. It is composed of aver-
ages, extremes, and variability. The World Meteorological Organization specifies
climate-length weather records to be 30 years and more. Climate is derived from
the Greek wordklima, signifying the angle of the sun above the horizon. The input
of solar energy is the prime driver of climate. Solar angles vary by latitude with
lower latitudes having the highest solar angles and the most solar radiation at the
top of the atmosphere.
From the times of the classical Greeks it was known thatEarthwas spherical
and that varying solar angles caused varying climates. So, two-and-a-half millen-
nia ago climate was classified into torrid, temperate, and frigid zones. Although
the Greek classification was largely correct, they had never traveled to the Equator
to discover temperatures are not as hot as in other parts of the tropics where the sun
is not as high in the sky. The erroneous Greek conclusion points to the existence of
non-solar influences on climate. In this case, the presence of the clouds in the
Intertropical Convergence Zone (seeWinds and pressure systems) moderates
equatorial temperatures.
Latitude is clearly a key factor, but there are a number of factors that, when inte-
grated together, determine the climatic nature of Earth’s regions. Six other factors
are generally given as climatic controls. (1) The distribution of land and water is
quite uneven over the planet and land heats and cools so much more rapidly than
oceans that annual temperature ranges are significantly impacted. (2) The circula-
tion of the atmosphere circulates large amounts of air. For example, in the middle
latitudes, the surface and upper westerlies bring oceanic air to the western parts of
continents thus moderating their temperatures. (3) There are pronouncedocean
currents, and these are capable of modifying climate. For instance, the cold Ben-
guela Current off of southwestern Africa stabilizes air passing over it to help cre-
ate the exceptional dryness of the Namib Desert. (4) Storminess and lack of
storminess play a considerable climatic role. Places prone to storminess are sub-
ject to much more cloudiness and precipitation than places lacking storminess.
In that the various types of storms are mechanisms by which the atmosphere’s
Climate 59