1. Table of Contents What Causes Climate? Climate Regions
Long-Term Changes in Climate
Global Changes in the Atmosphere

2. World Temperature Zones
- What Causes Climate?
World Temperature Zones
Based on latitude, Earth’s surface can be divided into a tropical zone, two temperate zones, and two polar zones.

3. Ocean Currents - What Causes Climate?
Ocean currents have a significant effect on marine climates around the world.

4. Rain Shadow - What Causes Climate?
A mountain range can form a barrier to the movement of air masses and influence where precipitation falls.

5. Monsoons - What Causes Climate?
In a summer monsoon, wind blows from the ocean onto land. In the winter, the monsoon reverses and blows from land to the ocean.

6. Percentages - What Causes Climate?
Light from the sun strikes Earth’s surface at different angles. An angle is made up of two lines that meet at a point. Angles are measured in degrees. A full circle has 360 degrees.
When the sun is directly overhead near the equator, it is at an angle of 90º to Earth’s surface. A 90º angle is called a right angle. What percentage of a circle is it?
A 90º angle is 25% of a full circle.

7. Percentages - What Causes Climate? Practice Problem
Earth’s axis is tilted at an angle of 23.5º. About what percentage of a right angle is this?
It is about 26.1 percent of a right angle.

8. The Seasons - What Causes Climate?
The seasons are caused by the tilt of Earth’s axis as Earth travels around the sun.

9. Seasons Activity - What Causes Climate?
Click the Active Art button to open a browser window and access Active Art about the seasons.

10. Building Vocabulary - What Causes Climate?
After you read the section, reread the paragraphs that contain definitions of Key Terms. Use what you have learned to write a meaningful sentence using each Key Term.
Key Terms:
Examples:
leeward
monsoon
Key Terms:
Key Terms:
Examples:
temperate zone
marine climate
continental climate
windward
Examples:
climate
The land on the leeward side of the mountains—downwind—is in a rain shadow.
Climate refers to the average, year-after-year conditions of temperature, precipitation, winds, and clouds in an area.
Between the tropical zones and the polar zones are the temperate zones.
North America, South America, and Europe have mild marine climates, with relatively mild winters and cool summers.
Sea and land breezes over a large region that change direction with the seasons are called monsoons.
microclimate
A small area with climate conditions that differ from those around it may have its own microclimate.
tropical zone
The tropical zone is the area near the equator, between about 23.5º north latitude and 23.5º south latitude.
Continental climates have more extreme temperatures than marine climates.
Rain or snow falls on the windward side of the mountains, the side the wind hits.
polar zone
These polar zones extend from about 66.5º to 90º north and 66.5º to 90º south latitudes.

11. End of Section: What Causes Climate?

12. Climate Graphs - Climate Regions
A graph of average temperature (left) can be combined with a graph of average precipitation (middle) to form a climate graph. These graphs are for a tropical wet-and-dry region.

13. Climate Regions - Climate Regions
Climate regions are classified according to a combination of temperature and precipitation. Climates in highland regions change rapidly as altitude changes.

14. Climate Regions - Climate Regions
Climate regions are classified according to a combination of temperature and precipitation. Climates in highland regions change rapidly as altitude changes.

15. Dry Climates - Climate Regions
Dry climates include arid and semiarid climates. Albuquerque, New Mexico, has an arid climate.

16. Temperate Marine Climates
- Climate Regions
Temperate Marine Climates
There are three types of temperate marine climates: marine west coast, humid subtropical, and Mediterranean. Eugene, Oregon, has a marine west coast climate.

17. Temperate Marine Climates
- Climate Regions
Temperate Marine Climates
Santa Barbara, on the coast of southern California, has a Mediterranean climate. Mild temperatures throughout the year make the area ideal for growing olives and citrus fruits.

18. Temperate Continental Climates
- Climate Regions
Temperate Continental Climates
Temperate continental climates include humid continental and subarctic climates. Subarctic climates have cool summers and cold winters. Anchorage, Alaska, has a subarctic climate.

19. Polar Climates - Climate Regions
Polar climates include ice cap and tundra climates. The tundra climate region stretches across northern Alaska, Canada, and Russia.

20. Comparing and Contrasting
- Climate Regions
Comparing and Contrasting
As you read, compare and contrast the six main climate regions by completing a table like the one below.
Climate Region
Precipitation
Temperature
Tropical rainy
Heavy precipitation
Hot
Dry
Little rainfall
Hot or Cold
Dry to rainy, depending on season and location
Cool to hot, depending on season and location
Temperate marine
Temperate continental
Cold to hot, depending on season and location
Light to moderate rainfall
Polar
Dry
Cold
Wetter than nearby lowlands
Cooler than nearby lowlands
Highlands

21. Click the Video button to watch a movie about climate regions.

22. Links on Climates of the World
- Climate Regions
Links on Climates of the World
Click the SciLinks button for links on climates of the world.

23. End of Section: Climate Regions

24. Ice Ages - Long-Term Changes in Climate
The map shows the parts of North America that were covered by glaciers 18,000 years ago. On the steppe near the glaciers lived many mammals that are now extinct, including woolly mammoths.

25. Ice Ages and Temperature
- Long-Term Changes in Climate
Ice Ages and Temperature
The graph shows the estimated average worldwide temperature over the last 350,000 years. During this time, cold glacial periods (blue) alternated with warmer interglacial periods (pink).

26. Ice Ages and Temperature
- Long-Term Changes in Climate
Ice Ages and Temperature
Reading Graphs:
What does the x-axis of the graph represent? What does the y-axis represent?
Number of years ago, estimated average global temperature in degrees Celsius

27. Ice Ages and Temperature
- Long-Term Changes in Climate
Ice Ages and Temperature
Interpreting Data:
What pattern do you see in these data? How would you explain this pattern?
Periodic ups and down in average global temperature; the temperature changes represent ice ages and warmer times in between. These changes may have been caused by changes in Earth’s position in space.

28. Ice Ages and Temperature
- Long-Term Changes in Climate
Ice Ages and Temperature
Predicting:
Based on the pattern over the last 350,000 years, predict how global temperature will change in the future.
The pattern probably will continue. Global temperatures are relatively high now, so they may decrease in the future, all else equal. Earth eventually will have another ice age.

29. Moving Continents - Long-Term Changes in Climate
The continents have moved over millions of years. These movements have resulted in climate changes.

30. Continental Drift Activity
- Long-Term Changes in Climate
Continental Drift Activity
Click the Active Art button to open a browser window and access Active Art about continental drift.

31. Identifying Supporting Evidence
- Long-Term Changes in Climate
Identifying Supporting Evidence
As you read, identify the evidence that is used to show that climates change.
Evidence
Tree rings
Hypothesis
Climate change
Pollen
Evidence of past glaciers

32. End of Section: Long-Term Changes in Climate

33. Greenhouse Effect - Global Changes in the Atmosphere
Sunlight enters a greenhouse and is absorbed. The interior of the greenhouse radiates back energy in the form of infrared radiation, or heat. Much of the heat is trapped and held inside the greenhouse, warming it.

34. Global Warming - Global Changes in the Atmosphere
Scientists think that an increase in carbon dioxide in the air is a major factor in global warming.

35. The Ozone Hole - Global Changes in the Atmosphere
Chemicals produced by humans have damaged the ozone layer. A large are of reduced ozone, or ozone hole, has been created over Antarctica.

36. Asking Questions - Global Changes in the Atmosphere
Before you read, preview the red headings. Ask a what or how question for each heading. As you read, write answers to your questions.
Questions
Answers
What is the greenhouse effect?
The process by which gases in Earth’s atmosphere trap solar energy
Why is ozone depletion a concern?
A decrease in ozone in the stratosphere causes more ultraviolet light, which is harmful, to reach Earth’s surface.

37. Click the Video button to watch a movie about the greenhouse effect.
- Global Changes in the Atmosphere
The Greenhouse Effect
Click the Video button to watch a movie about the greenhouse effect.

38. More on the Greenhouse Effect
- Global Changes in the Atmosphere
More on the Greenhouse Effect
Click the Planet Diary button for an activity about the greenhouse effect.

39. End of Section: Global Changes in the Atmosphere

40. Graphic Organizer Climate Temperature Precipitation Latitude Altitude
is determined by
Temperature
Precipitation
is affected by
is affected by
Latitude
Altitude
Distance from water
Ocean currents
Prevailing winds
Mountain ranges

41. End of Section: Graphic Organizer