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17.3: Climate Change

Difficulty Level: At Grade Created by: CK-12
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Lesson 17.3: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. It takes large changes in Earth’s climate to affect living things.

_____ 2. Only one ice age occurred over the past billion years.

_____ 3. In the Pleistocene ice age, Earth’s temperature was 5 °C cooler than it is today.

_____ 4. During the last ice age, glaciers covered much of North America.

_____ 5. Temperatures were higher during the Medieval warm period than they have been over the past decade.

_____ 6. Plate tectonics may cause ocean currents to shift.

_____ 7. An enormous volcanic eruption would increase Earth’s temperature.

_____ 8. Solar storms are the main cause of recent global warming.

_____ 9. Greenhouse gases block sunlight and cool the planet.

_____ 10. The amount of carbon dioxide in the air has been increasing for many decades.

Lesson 17.3: Critical Reading

Name___________________ Class______________ Date________

Read this passage based on the text and answer the questions that follow.

El Niño and La Niña

El Niño and La Niña refer to certain short-term changes in climate. The changes are natural, and they occur in cycles. To understand the changes, you first need to know what happens in years when El Niño and La Niña do not occur. In these years, the trade winds blow from northeast to southwest across the Pacific Ocean. The winds blow warm surface water away from South America. This allows deeper, colder water to flow up to the surface near the coast. This is called upwelling.

El Niño occurs when the Pacific Ocean is warmer than usual. This causes the trade winds to change direction. The winds blow from northwest to southeast. They blow warm surface water toward South America. This prevents upwelling. These changes affect climates worldwide for a year or two. For example, some places may get more rain than normal. Other places may get less. Overall, the weather is more severe.

La Niña generally follows El Niño. It occurs when the Pacific Ocean is cooler than usual. The trade winds blow in their normal direction from northeast to southwest, but they are stronger than normal. They blow cool water across the Pacific Ocean toward Asia. These changes also affect climates worldwide.

Scientists think that global warming is affecting El Niño and La Niña. They seem to be cycling faster now than in the past. They are also more extreme.


  1. What is El Niño? Why does El Niño occur? How does El Niño affect Earth’s climate?
  2. How does La Niña differ from El Niño?
  3. How does global warming seem to be affecting El Niño and La Niña?

Lesson 17.3: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Which of the following statements about climate change is false?
    1. Earth’s climate has changed many times in the past.
    2. Earth’s climate has been hotter than it is today.
    3. Earth’s climate has been colder than it is today.
    4. Earth’s climate has never changed before now.
  2. The 14 hottest years on record have all occurred since
    1. 1900.
    2. 1990.
    3. 1995.
    4. 1998.
  3. Natural processes that may have affected Earth’s temperature in the past include a ##change in the tilt of Earth’s axis.
    1. large asteroid striking Earth.
    2. huge volcanic eruption.
    3. all of the above
  4. Recent global warming is due mainly to
    1. plate tectonics.
    2. sunspot activity.
    3. human actions.
    4. none of the above
  5. Effects of global warming include all of the following except
    1. sea ice melting.
    2. coral reefs dying out.
    3. more extreme weather.
    4. fewer short-term climate changes.
  6. What happens during El Niño?
    1. The trade winds change direction.
    2. The Pacific Ocean cools off more than usual.
    3. Upwelling occurs off the west coast of South America.
    4. Warm water travels from northeast to southwest across the Pacific Ocean.
  7. La Niña occurs
    1. when the Pacific Ocean is warmer than normal.
    2. because the trade winds change direction.
    3. only in the Atlantic Ocean.
    4. following El Niño.

Lesson 17.3: Matching

Name___________________ Class______________ Date________

Match each definition with the correct term.


_____ 1. dramatic increase in Earth’s temperature since the middle of the 1800s

_____ 2. short-term climate change in which the Pacific Ocean is warmer than usual

_____ 3. slight increase in Earth’s temperature that occurred about 1000 years ago

_____ 4. period in Earth’s history when temperatures were cooler than normal

_____ 5. movement of cold water from the bottom to the surface of the ocean

_____ 6. difference from average temperature

_____ 7. short-term climate change in which the Pacific Ocean is cooler than usual


a. medieval warm period

b. La Niña

c. ice age

d. global warming

e. El Niño

f. upwelling

g. temperature anomaly

Lesson 17.3: Fill in the Blank

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

  1. Over much of Earth’s history, the planet’s average temperature was __________ than it is today.
  2. During an ice age, __________ spread to lower latitudes.
  3. The last major ice age occurred during the __________ epoch.
  4. The burning of fossil fuels adds the greenhouse gas __________ to the atmosphere.
  5. Global warming is causing sea levels to __________.
  6. During El Niño, the northern trade winds blow from the __________.
  7. If global warming predictions are correct, the Amazon basin and the __________ will experience the greatest temperature increases.

Lesson 17.3: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Describe how Earth’s temperature has changed since the mid-1800s. Identify causes and effects of the temperature change.

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