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Physical Geography: Climate and Vegetation
Section 2
Climate
Terms and Names
convection the transfer of heat in the atmosphere by upward motion of the air
El Niño the warming of waters off the west coast of South America
greenhouse effect the theory that gases released by burning coal and petroleum trap
solar energy, causing higher temperatures
Before You Read
In the last section, you learned how the earth’s rotation creates weather
and seasons. In this section, you will read about the factors that create
and change climate.
As You Read
Use a chart to take notes on factors that affect climate.
Factors Affecting Climate
a coastal region chill the air. Sometimes
they prevent warm air and the moisture it
holds from falling to earth.
WIND CURRENTS/OCEAN
CURRENTS (Pages 54–55)
What is convection?
1. How do wind and ocean currents
affect the climate?
Wind and ocean currents help distribute
the sun’s heat from one part of the world to
another. This is done through convection.
Convection is the transfer of heat in the
atmosphere by upward motion of the air.
Convection occurs when the sunlight
heats the atmosphere. The heated air
expands. A region of low air pressure is
created by this expansion. Cooler denser
air in a nearby high-pressure region rushes
into the low-pressure area.
Ocean currents are like rivers flowing in
the ocean. Warm water flows away from
the equator toward the poles, and cold
water flows back toward the equator.
Winds blowing over the ocean currents are
heated or cooled by the currents. The
winds then affect the lands that the winds
blow across.
Currents also affect the precipitation in
an area. Cold ocean currents flowing along
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ZONES OF LATITUDE (Pages 55–56)
How does latitude location affect
climate?
Geographers divide the earth into three
general regions of latitude: low or tropical,
middle or temperate, and high or polar.
Tropical regions are found on either side
of the equator.
Lands in tropical regions are hot all year
long. In some areas, a shift in wind patterns
causes variations in climate. The high
latitude or polar regions circle the North
Pole and South Pole. They are cold all year.
During summer in the polar regions, the
temperature reaches a high of only 50° F.
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Guided Reading Workbook
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Section 2, continued
An example of a natural change is El
Niño. This is warming of the waters off
the west coast of South America. About
every two to seven years, the eastern
winds that blow over the central Pacific
Ocean slow or reverse direction. This
changes the ocean temperature and affects
the weather worldwide.
Usually, these easterly winds bring
seasonal rains and push warm ocean water
toward Asia and Australia. In El Niño years,
however, the winds push warm water and
heavy rains toward the Americas. This can
cause floods and mudslides there. At the
same time Australia and Asia experience
drought conditions.
When the winds blow in the opposite
direction, to the west, the warmer waters
are pushed to the lands on the western
Pacific rim. This is called La Niña. La
Niña causes increased precipitation in
places such as India and increased dryness
on the eastern side of the Pacific.
The earth’s two temperate regions lie at
the middle latitudes. They are between the
tropics and the polar regions. Within the
temperate regions, climates can vary
greatly. The variations range from
relatively hot to relatively cold. These
variations occur because solar heating is
greater in the summer than in the winter.
2. What are the three general regions of
latitude?
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ELEVATION/TOPOGRAPHY (Page 56)
How does elevation affect climate?
Another factor in determining a
region’s climate is elevation, or distance
above sea level. The air temperature drops
as elevation increases. Climates above
12,000 feet become like those in Arctic
areas.
Landforms also affect climate. This is
especially true of mountain areas.
Remember that as winds move up the side
of a mountain they cool. They also lose
their ability to hold moisture and release
rain or snow. By the time the winds reach
the other side of the mountain, they are
dry and become warmer as they flow
down the mountain.
4. What happens in the Americas during
El Niño?
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GLOBAL CLIMATE CHANGE
(Page 58)
What is global warming?
3. What happens to winds as they move
up the side of a mountain?
Evidence shows that climates are
changing around the world. Since the late
1800s, the temperature of the earth has
increased by one degree Fahrenheit.
Estimates suggest that temperature will
increase from 3.2 to 7.2 degrees in the
next century.
Some argue that this warming is part of
the earth's natural cycle.
However, most climate scientists argue
that global temperature increases are
caused by the greenhouse effect. The
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Changes in Climate
EL NIÑO (Pages 56–57)
How does El Niño affect the weather?
Climates change over time. Changes in
climate are natural and the result of human
activities.
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Guided Reading Workbook
Name _____________________________ Class _________________ Date __________________
Section 2, continued
greenhouse effect occurs when the layer of
gases released by the burning of coal and
petroleum traps solar energy. This causes
higher temperatures in the same way that a
greenhouse traps solar energy.
The greenhouse effect and global
warming will probably increase as more
nations industrialize. If this trend
continues, ice caps will melt, flooding
some coastal areas and covering some
islands. Weather patterns could also
become more erratic.
5. What are some of the predicted results
of the greenhouse effect?
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Guided Reading Workbook
Name _____________________________ Class _________________ Date __________________
Section 2, continued
Use the chart below to take notes on how each of the following affects
climate.
Factors Affecting Climate
1. wind currents
2. ocean currents
3. zones of latitude
4. altitude
5. topography
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Guided Reading Workbook