Miss Nelson
SCIENCE ~ CHAPTER 9
CLIMATE
Climate Change
SECTION 4
What do you already know about climate change?
ANTICIPATORY SET
S 6.4.e –Students know differences in pressure, heat, air movement, and humidity result in change in weather
STANDARDS
How might human activities be affecting the temperature of Earth’s atmosphere?
How have human activities affected the ozone layer?
THE BIG IDEA
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
Chlorofl uorocarbon – chlorine compounds that are the main cause of ozone depletion
KEY TERMS
Scientists classify climates according to two major factors:
TemperaturePrecipitation
CLIMATE REGIONS
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
CLIMATE CHANGE
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
GLOBAL WARMING
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 gasesCarbon dioxideWater vapormethane
THE GREENHOUSE HYPOTHESIS
Many scientists have hypothesized that human activities that add greenhouse gases to the atmosphere are warming Earth’s atmosphere
THE GREENHOUSE HYPOTHESIS
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
CHANGING LEVELS OF CARBON DIOXIDE
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
CLIMATE VARIATION HYPOTHESIS
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
POSSIBLE EFFECTS
Read Global Warming on pages 375 – 377 of your textbook
GLOBAL WARMING
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
OZONE DEPLETION
(Chloro – floro –carbons)
A major cause of ozone depletion is a group of compounds called chlorofluorocarbonsAlso known as CFCs
Found in:Air conditionersRefrigeratorsAerosol 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
CHLOROFLUOROCARBONS
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
RESULTS OF OZONE DEPLETION
Read Ozone Depletion on page 378 of your textbook
OZONE DEPLETION
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.
CHECK FOR UNDERSTANDING
Complete the Modeling, Guided Practice, and Independent Practice
Sections of your Climate 9-4 Worksheet.
MODELING / GUIDED / INDEPENDENT