What is Climate?
Weather is what is happening in the atmosphere at a particular location at the moment.
Climate is the average of weather in that location over a long period of time, usually for at
least 30 years. A location’s climate can be described by its air temperature, humidity, wind
speed and direction, and the type, quantity, and frequency of precipitation. The climate of
a location depends on it position relative to many things. Most important is latitude, but
other factors include global and local winds, closeness to an ocean or other large bodies of
water, nearness to mountains, and altitude. Climate can change, but only over long periods
of time.
The term climate also refers to Earth’s entire climate system. The climate system is influ-
enced by the movement of heat around the globe. Heat is carried by currents within the
atmosphere and oceans. The type and amount of vegetation also affects climate. Plants
absorb heat and retain water, which may increase or decrease rainfall. The composition of
the atmosphere also controls climate. If the concentration of greenhouse gases increase or
decrease, the heat-trapping abilities of the atmosphere rise or fall.
Latitude
The amount of solar energy a particular location receives is the most important factor in
determining that location’s temperature. The amount of sunlight that strikes the ground is
different at each latitude. The lower the latitude, the more sunlight an area will receive. At
the equator, days are equally long year-round and the sun is just about directly overhead at
midday. At the poles, during the winter, nights are long and the sun never rises very high
in the sky. Sunlight filters through a thick wedge of atmosphere, making the sunlight much
less intense. Ice and snow at high latitudes also reflect a good portion of the sun’s light,
giving these regions much greater albedo.