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SCIENCE ~ CHAPTER 9
CLIMATE
Miss Nelson
SECTION 4
Climate Change
ANTICIPATORY SET
What do you already know about climate
change?
STANDARDS
S 6.4.e –
Students know differences in pressure, heat, air
movement, and humidity result in change in
weather
THE BIG IDEA
How might human activities
be affecting the temperature
of Earth’s atmosphere?
How have human activities
affected the ozone layer?
KEY TERMS
 Ice age – time in the past when continental
glaciers covered large parts of Earth’s surface
 Global warming – a gradual increase in the
temperature of Earth’s atmosphere
 Greenhouse gas – Gases in the atmosphere,
such as carbon dioxide, that trap solar energy
 Ozone hole – a large area of reduced ozone
concentration in the stratosphere, found over
Antarctica
 Chlorofluorocarbon – chlorine compounds that
are the main cause of ozone depletion
CLIMATE REGIONS
Scientists classify climates
according to two major factors:
Temperature
Precipitation
CLIMATE CHANGE
 The last ice age ended only about 10,500 years ago
 Ice sheets covered most of Europe and North
America
 So much of Earth’s water was frozen, that the level
of the oceans was much lower than today
 When the ice melted, and the water returned to the
oceans, some got trapped on land
 Great lakes
CLIMATE CHANGE
Read Climate Change on page 374 of your
textbook
GLOBAL WARMING
Most past changes in world climates were
caused by natural factors
Volcanic activity
Motion of the continents
Recently scientists have observed climate
changes that are the result of HUMAN
ACTIVITIES
GLOBAL WARMING
The gradual increase in the
temperature of Earth’s atmosphere
is called global warming
THE GREENHOUSE HYPOTHESIS
Gases in Earth’s atmosphere hold in
heat from the sun
Keeps the atmosphere at a comfortable
temperature for living things
THE GREENHOUSE HYPOTHESIS
Gases in Earth’s atmosphere trap
energy and form a “blanket” around
Earth
This process is called the
greenhouse effect
THE GREENHOUSE HYPOTHESIS
Gases in the atmosphere that trap
energy are called greenhouse gases
Carbon dioxide
Water vapor
methane
THE GREENHOUSE HYPOTHESIS
Many scientists have hypothesized
that human activities that add
greenhouse gases to the
atmosphere are warming Earth’s
atmosphere
CHANGING LEVELS OF CARBON DIOXIDE
Scientists that think that an increase in
carbon dioxide is a major factor in global
warming
Until the late 1800s carbon dioxide in the
atmosphere remained about the same
Measured carbon dioxide levels in bubbles
trapped in Antarctic ice
CHANGING LEVELS OF CARBON DIOXIDE
Human activities that increase carbon dioxide:
Burning wood, coal, oil, natural gas
CLIMATE VARIATION HYPOTHESIS
Not all scientists agree on the causes of
global warming
Some believe that the raise in global
temperatures may be due in part to
natural variations in climate
POSSIBLE EFFECTS
 While there may be some potential benefits to an
increased global temperature…
Most are not positive:
 Higher temperatures evaporate water, and expose
soil
 Leads to “dustbowls” when dry soil blows away
 Warmer ocean water could lead to stronger
hurricanes
 Warm water expands… which would increase sea
level around the world
GLOBAL WARMING
Read Global Warming on pages 375 – 377 of
your textbook
OZONE DEPLETION
Another global
change in the
atmosphere
involves the
ozone layer
OZONE DEPLETION
Ozone in the stratosphere filters out much
of the harmful ultraviolet radiation from
the sun
View Figure 25 on page 379 of your textbook
In the 1970s scientists noticed that the
ozone layer over Antarctica was growing
thinner
OZONE DEPLETION
Chemicals produced by
humans have been damaging
the ozone layer
CHLOROFLUOROCARBONS
(Chloro – floro –carbons)
A major cause of ozone depletion is a group of
compounds called chlorofluorocarbons
 Also known as CFCs
Found in:
 Air conditioners
 Refrigerators
 Aerosol sprays
CHLOROFLUOROCARBONS
Most chemical compounds released
into the air eventually break down
CFCs can last for decades and rise
all the way to the atmosphere
RESULTS OF OZONE DEPLETION
If the ozone blocks ultraviolet radiation…
… then a decrease in ozone means and
increase in the amount of ultraviolet
radiation that reaches Earth’s surface
RESULTS OF OZONE DEPLETION
In the late 1970s, the United States and many
other countries banned most uses of CFCs in
aerosol sprays
In 1990, many nations agreed to phase out
the production and use of CFCs
The size of the ozone layer is expected to
gradually shrink over time as these decreases
take effect
OZONE DEPLETION
Read Ozone Depletion on page 378 of
your textbook
CHECK FOR UNDERSTANDING
What is a greenhouse gas?
How do greenhouse gases cause the
greenhouse effect?
CHECK FOR UNDERSTANDING
What is a greenhouse gas?
A greenhouse gas is a gas in the
atmosphere that traps energy.
What is global warming?
Global warming is the gradual increase
in the temperature of Earth’s
atmosphere.
MODELING / GUIDED / INDEPENDENT
Complete the Modeling, Guided Practice,
and Independent Practice Sections of your
Climate 9-4 Worksheet.