Climate
P. Lobosco
Chapter 17-1
What is climate?
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Objectives:
To describe what determines climate.
To explain how latitude, oceans and other
factors affect the climate of a region.
What Causes Climate?
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Climate is the name for the general conditions
of temperature and precipitation for an area
over a long period of time.
It determines the types of plants or animals
that can survive and it influences how people
live.
Factors that Affect Climate
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Latitude
Large Bodies of Water
Ocean Currents
Mountains
Rain Shadows
Cities
Latitude
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Latitude is the measure of the distance north
and south of the equator. Latitude is measured
in degrees. Areas close to the equator, or 0
degrees latitude, receive the direct rays of the
sun. These direct rays provide the most
radiant energy. Areas near the equator have a
warm climate. Polar regions have a cold
climate.
Latitude Zones
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The tropics extend from the
equator to 23.5º north and
south. They receive the
most direct solar radiation.
The temperate zones extend
from 23.5º to 66.5. These
areas receive moderate
amounts of solar radiation.
The polar zones from 66.5 º
to the Poles receive very
little solar radiation.
Tropical Zones
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The tropical zones, which extend from 23.5º
north and south latitude to the equator, have
high temperatures and high humidity. Tropical
zones are also known as low-latitude climates.
The average temperature during the coldest
month of the year does not fall below 18
degrees C. Many deserts are located on the
western coasts of the continents. This is
because the prevailing winds, the trades, blow
from east to west.
Temperate Zones
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In each hemisphere, the temperate zone is
found between 66.5ºand 23.5º latitude. In the
areas of the temperate zones farther from the
equator, snow is common in the winter.
In the areas of the temperate zones closer to
the equator, rain normally falls all year round.
The average amount of precipitation is about
the same throughout. The average
temperatures range from 5 º C to 20 ºC.
Deserts in the Temperate Zone
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Deserts in the temperate zones are usually
located in land, far away from the oceans. The
winds that blow across these inland deserts
carry little moisture.
Although very hot during the day,
temperatures at night can drop to below
freezing. Inland deserts are found in Australia
(the Great Sandy Desert) and Central Asia (
the Gobi Desert).
Polar Zones
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In each hemisphere, the polar zone extends
from the pole to about 60 degrees latitude. In
polar zones, the average yearly temperature is
below freezing. There are some areas in the
polar zones, such as the northern coasts of
Canada and Alaska and the southern tip of
South America, where the snow melts during
the warmest part of the year.
Large Bodies of Water
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The surface temperature
of water affects the
temperature of the water
above it. Warm water
warms the air and cold
water tends to cool it.
Marine and Continental Climates
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Within each of the three major climate zones, there
are marine and continental climates. Areas near an
ocean or other large body of water have a marine
climate. Areas located within a large landmass have
a continental climate.
Areas with a marine climate receive more
precipitation and have more moderate temperatures.
A continental climate has less precipitation and a
greater range in temperature.
Ocean Currents
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Land areas near warm ocean
currents have warm
temperatures.
The Gulf Stream is an ocean
current that carries warm
water along the eastern
coast of the United States.
The California Current
travels toward the equator
carrying cold water along
the west coast of the United
States.
Elevation
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Elevation, or altitude, is the distance above sea
level. As elevation increases, the air becomes
less dense. This means there are fewer gas
molecules in the air and they are spread far
apart. Less- dense air cannot hold as much
heat as denser air. So as elevation increases,
temperature decreases.
Rain Shadows
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Mountains also affect
regional climates.
On the windward side of a
mountain range air rises and
cold, and drops its moisture.
On the leeward side the dry
air descends and dries the
land.
Deserts are common on the
leeward side of the
mountain ranges.
Cities
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Large cities affect local
climate.
Streets, parking lots and
building heat up and in turn,
heat the air.
Air pollution heats up traps
the heat, creating the heatisland effect.
Temperatures are at least 5º
higher than the surrounding
areas.
Chapter 17-2
Climate Types
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Objectives:
To describe a climate classification system.
To explain how organisms adapt to a particular
climate.
Koppen Classification
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Koppen classified world climates by using the
annual and monthly averages of temperature
and precipitation.
He then related the types and distribution of
native vegetation to the various climates.
It separates into six groups, tropical, mild, dry,
continental, polar and high elevation.
Classifying Climate
Adaptations
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The climate determines the vegetation in the
area.
Organisms adapt to their environment.
An adaptation is any structure or behavior that
helps an organism survive its environment.
Structural adaptations are inherited and
develop in a population over a long period of
time.
Structural Adaptation
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Some organisms have body
structures that help them
certain in climates.
The fur of mammals is
really hair that insulates
against the cold.
Cacti have a thick, fleshy
stem that hold water,
Cacti also have spiny
needles that also reduce
water loss.
Behavioral Adaptations
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Some behaviors help
organisms survive in certain
climates.
Rodents and certain
mammals undergo a period
of decreased activity called
hibernation.
They have a lower body
temperature and lowered
body processes.
Other Behavioral Adaptations
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Bees huddle together
during cold weather.
On hot days, snakes
hide under rocks.
Desert turtles and
lizards obtain water
from their food.
Estivation
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Lungfish survive
periods of intense heat
by entering an inactive
state called estivation.
As the weather gets hot
and water evaporates,
the fish will burrow into
mud and cover itseld in
mucus and mud and
wait until the weather
improves.
Human Behavioral Adaptations
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Humans also exhibit
behavioral adaptations.
We shiver when we are
cold because the rapid
muscle movement
produces heat.
We sweat when we a re
hot because as the water
evaporates, it takes
some heat with it.
Chapter 17-3
Climatic Changes
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Objectives:
Explain what causes seasons
Describe how EL Nino affects climate
Explore the possible causes of climatic
change.
Seasons
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Seasons are short
periods of climatic
change.
Because the Earth is
tilted, certain areas of
Earth receive changing
amounts of radiation
throughout the year.
High Latitudes
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During the year, the
high latitudes near the
poles have great
differences in
temperature and
daylight hours.
Short Term Changes in Climate
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Some short-term changes may be the result of
changes in ocean currents and global winds.
Ocean currents help transfer heat to the
atmosphere. This process generates global
winds. The global winds help move ocean
currents.
Any major change in an ocean current can
cause a change in climate. El Nino is an
example.
Peru Current
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A cold current that
flows from west to east
across the southern part
of the Pacific Ocean
turns toward the equator
along the coast of South
America and flows
north along the coast of
Chile and Peru. It is
known as the Peru
Current.
El Nino
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Occasionally the Peru
Current is covered by a
thin sheet of warm
water. Every 2 to 10
years, strong winds
spread the warm water
over a large area
resulting in droughts in
some areas and flooding
in others.
La Nina
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The opposite of el Nino is
La Nina.
During La Nina, the winds
blowing across the Pacific
are stronger than normal and
warm water accumulates in
the western Pacific. The
water near Peru is colder.
This causes droughts in the
southern United states and
excess rainfall in the
northwestern Untied States.
Changes in Climate
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The natural factors responsible for long term
climate changes are the slow drifting of the
continents, changes in the sun’s energy output
, natural catastrophic events and variations in
the position of the Earth relative to the sun.
These natural factors are not related to human
activity. The results of the human activity of
the burning of fossil fuels may also lead to
changes in climate.
Variations in Radiant Energy
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During periods of high
energy output, the Earth’s
temperature would rise. The
temperature would drop
during periods of low
energy output.
Scientists have found a link
between sunspots activity
and climate change. During
very cold periods there are
very few sunspots.
Catastrophic Events
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Catastrophic events such as
meteorite collisions and
volcanic eruptions can put
tremendous amount of dust
ash and other particles into
the atmosphere.
This in turn blocks sunlight
and cools the planet.
Cities can also put up
pollution that increases
cloud cover downwind from
the city. It also reduces
rainfall in these areas.
Changes in Earth Movement in
Space
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The shape of the Earth’s
orbit can change.
Sometimes it is more
circular, sometimes more
elliptical.
The Earth’s tilt has varied
from 21.5º to 24.5º. The tilt
changes about every 41,000
years.
The Earth’s axis also
wobbles like a top.
Ice Ages
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Periods when much of the Earth’s surface has
been covered with enormous sheets of ice are
called ice ages or major glaciations.
Scientists have found evidence of four major
ice ages during the last 2 million years each
lasting between 60,000-100,000 years. The
average temperature was 10-15ºC.
The causes are not known but they are
probably associated with variations in the tilt
of the Earth’s axis and/or the shape of the
Earth’s orbit around the sun.
Interglacials
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Interglacials are the time periods between
major glaciations. Interglacials are warm
periods. During an interglacial, the average
temperature was about 4 to 6 degrees higher
than the average temperature during a major
glaciation. A cold period called the Little Ice
Age lasted from 1500 to 1900.
Drifting Continents
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About 230 million years
ago, all the Earth’s
landmasses were joined in
one super continent,
Pangaea. As the continents
moved toward their presentday locations, the sea level
dropped, volcanoes erupted,
and much of the Earth’s
surface was pushed upward.
The combined effect was a
drop in temperature and
precipitation all over the
Earth. These changes were
gradual.
Extinction of the Dinosaurs
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The climate change caused by the drifting of
the continents may have resulted in the
extinction of the dinosaur. Many types of
plants also became extinct. Dinosaurs that
depended on these plants died. Meat-eating
dinosaurs that depended on plant-eating
dinosaurs died. Other scientists believe that
dinosaurs became extinct as the result of a
giant asteroid striking the Earth 65 million
years ago.
Greenhouse
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The greenhouse effect is a natural process that
occurs when certain gases in Earth’s
atmosphere trap heat and serve to warm the
earth.
When the Earth’s climate changes, the amount
of carbon dioxide that cycles among the
atmosphere, ocean and land can also change.
Greenhouse gases include water vapor, carbon
dioxide and methane.
Global Warming
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In the mid-nineteenth century industrialization led to
the increased burning of fossil fuels, including coal,
oil and natural gas. Then these fuels are burned they
release carbon dioxide that traps heat. Carbon dioxide
has increased by 20% in the last 100 years. As a
result, the atmosphere becomes warmer, increasing
0.6º C in the last 100 years.
Deforestation may also contributes to global
warming.
Carbon Cycle