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