Download 8.5 Natural Factors That Affect Climate

8.5
Earth’s climate is powered by energy from the Sun.
The interactions between the Sun and Earth’s air, land,
liquid water, ice, and living things play a role in producing
Earth’s climate.
Solar Energy
▶▶ solar energy: energy from
the Sun
▶▶ radiation: any energy
that travels in the form
of waves
Solar energy is energy that comes from the Sun. Almost all
processes on Earth are ultimately powered by solar energy. Solar
energy is a type of radiation. Radiation is energy that is emitted
or transmitted in the form of waves. Solar energy has a range of
energy levels, which can be divided into visible light, ultraviolet light,
and infrared radiation (Figure 1). These different types of radiation
have different energy levels.
dig deeper
Ultraviolet Light
The high energy of
ultraviolet (UV) light enables
it to penetrate skin, which is
why it can cause sunburn.
Energy output
Did You Know?
Ultraviolet
(short wavelength, high
energy)
Visible
Infrared
(long wavelength, low energy)
Wavelength
Figure 1 Solar energy is made up of waves that have different energy levels.
Different Regions on Earth Receive Different
Amounts of Solar Energy
An important natural factor in determining climate is how much
solar energy a region receives, and how that amount of solar energy
changes over time. The next subsections will describe some factors
that affect the amount of solar energy received by regions on Earth.
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TRY This spreading out
Skills: Performing, Observing, Analyzing
3.A., 3.B.
3.Have one person hold the cardboard at a
45º angle to the light beam. Have a second person
use a different-coloured pen to trace the shadow
on the graph paper.
In this activity, the flashlight beam represents a beam
of sunlight. The cardboard represents a 1 km2 area
on Earth’s surface.
Equipment and Materials: 15 cm  15 cm piece of
cardboard; graph paper; transparent tape; flashlight;
two different-coloured pens
A.Compare the two shadows produced in
Steps 2 and 3. T/I
1.Tape the graph paper to a wall. Then, shine the
flashlight on the paper and change your position
until the light beam forms a clear circle.
B.In which position did the cardboard block the
most light? T/I
C.Remember that the size of the cardboard
represented the same area of land. In which
position (at the equator or the poles) would the
land be warmer? T/I 2.Have one person hold the cardboard at a 90º
angle to the light beam. Have a second person
trace the shadow that appears on the graph paper.
Latitude
Latitude is the distance north or south of Earth’s equator, measured
as an angle. Figure 2 shows how latitude affects the amount of
solar radiation that different places on Earth’s surface receive.
▶▶ latitude: the angular
distance north or south
of Earth’s equator,
measured in degrees
• At lower latitudes (closer to the equator), solar radiation
hits Earth’s surface almost straight on. This solar energy is
concentrated in a smaller area. (See the red lines in Figure 2(a).)
• At higher latitudes (farther from the equator), solar radiation
hits Earth’s surface at a larger angle. This solar energy is
spread across a larger area. (See the red lines in Figure 2(b).)
(a)
energy
from
the Sun
r
ato
equ
(b)
North
Pole
energy from the Sun
r
ato
equ
South Pole
Figure 2 (a) At lower latitudes, incoming solar energy does not spread out very much.
(b) At higher latitudes, incoming solar energy spreads out.
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8.5 Natural Factors That Affect Climate 309
Earth’s Tilt and Orbit
Figure 3 shows Earth’s orbit around the Sun. Earth is drawn so that
the poles are not straight up and down, because our planet is tilted.
As Earth moves around the Sun, this tilt dramatically affects the
amount of solar energy that different regions receive.
For example, during our summer, the North Pole is tilted toward
the Sun. Canada, therefore, receives more solar energy in summer,
when we have warmer weather (Figure 4(a)). During our winter, the
North Pole is tilted away from the Sun. Canada then receives less
solar energy, so our winters are colder (Figure 4(b)). The tilt has
more of an effect on seasonal changes in climate than the distance
of Earth from the Sun.
(a)
(b)
Figure 3 Earth’s tilt has a greater effect on climate than its orbit.
Climate Change and Earth’s Motion
Figure 4 Earth’s tilt
affects our seasons. We
can enjoy (a) canoeing in
the summer months, and
(b) tobogganing in the
cold winter months.
In 1941, scientist Milutin Milankovitch developed a theory to explain
the ice ages in Earth’s history (Figure 5). He suggested that the cycles
of ice ages are caused by three factors:
•Shape of Orbit: Earth’s orbit changes shape from more circular
to less circular over a period of about 400 000 years. Earth gets
up to 23 % more solar energy at the closest distance compared
to the farthest distance.
• Tilt: Earth’s tilt varies over about 41 000 years from 22.1° to
24.5°. As the tilt changes, the seasons also change.
• Wobble: As Earth spins, it slowly wobbles around on its axis.
The wobble causes Earth’s axis to change the direction it
points to. One complete wobble takes about 26 000 years.
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Together, these changes cause the regular patterns of ice ages
and warmer periods. Climate scientists think that these patterns are
the main cause of the 100 000-year cycles in Earth’s climate.
However, these take place too slowly to be responsible for recent
global warming.
wobbling of the axis
Earth’s orbit
Sun
tilt
changing shape
of orbit
changing
tilt
Figure 5 Natural causes of Earth’s ice ages and warming periods
8.5 Wrap Up
• Earth’s climate is powered by solar energy.
• Latitude affects how intense the sunlight is at a particular location.
• The seasons are the result of Earth’s tilt and orbit.
• Long-term cycles in Earth’s climate are caused by changes in the shape of
Earth’s orbit and tilt, and Earth’s wobble.
Check Your Learning
1.Describe the range of energy levels given off by
the Sun. K/U
5.What do you think Earth’s climate would be like if
it had a circular orbit and no tilt? A
2.List three possible causes of long-term climate
change. K/U
6.(a) Why are the seasons important to you?
(b) Using a method of your choosing, describe
how your life would be different if you lived
somewhere with dry and rainy seasons. You
may be able to answer this question from your
own life story. C A
3.Explain why a city in Canada experiences winter
at the same time as a city in South America
experiences summer. K /U
4.Compare the Sun’s energy that reaches the
equator to the Sun’s energy that reaches the areas
nearer the poles. Draw diagrams to support your
answer. K/U C
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7.Which has a greater effect on Canada’s seasonal
climate changes—Earth’s tilt or Earth’s orbit? K/ U
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