World Geography Chapter Overview
Chapter 3: Climates of the Earth
Climate refers to weather patterns that occur in a place over time. Although the earth's
climates are influenced by many factors, the most important is the earth's position in
relation to the sun. Other influences relate to the specific location of a place and the
features that exist there. World climate regions vary greatly, and each supports
characteristic vegetation. Human activity may be contributing to the cycle of climate
change.
Earth-Sun Relationships The amount of sunlight that reaches the earth varies depending
on Earth's tilt and rotation. Earth's revolution, or yearly orbit around the sun, also affects
the amount of sunlight each area receives, resulting in seasonal changes. In the northern
hemisphere, the solstice marks the beginning of summer and the equinox, winter.
Because of the earth's tilt and rotation, sunlight at the Poles varies dramatically through
the seasons, ranging from continuous sunlight to long periods of darkness. The
greenhouse effect, which normally regulates heat in the atmosphere to support life, may
be changing due to increased carbon dioxide released into the atmosphere by human
activities.
Factors Affecting Climate Latitude, elevation, wind and ocean currents, and landforms
all influence climate individually or in combination. The zone of low latitudes, near the
equator, receives more direct rays of the sun year round than the zones of high latitudes
near the Poles. Mid-latitudes experience variable weather. High elevations have colder
temperatures due to thinner atmosphere that retains less heat. Wind currents carry warm
and cool air around the earth in fairly constant patterns. Warm and cold ocean currents
affect the temperature along coastal lands. The combination of water vapor and wind
currents can form patterns of precipitation. Landforms such as large bodies of water and
mountain ranges can also influence temperatures and precipitation.
World Climate Patterns Geographers divide the world into climate regions, each with
its characteristic vegetation. Hot, wet tropical climates feature tropical rain forests; dry
climates include desert, with little vegetation, and steppe, with scattered scrub and cactus.
The mid-latitude climates include four temperate climate regions of various weather
patterns and seasonal changes that support vegetation ranging from thick forests to
grasslands. Highlands and high latitude climates have much colder temperatures with
mixed forests or only mosses and lichens. Scientists are working to better understand the
evidence of past climate changes as well as the effects of human activities on climate.