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  Chlorofluorocarbon – chlorine compounds that are the main cause of ozone depletion KEY TERMS

Scientists classify climates according to two major factors:  Temperature  Precipitation 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 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 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 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 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