1. Chapter 17
Climate

2. I. What is Climate?
A. Climate Vs. Weather
Weather is the condition of the atmosphere at a particular time
Climate is the average weather condition in an area over a long period of time

3. B. Latitude
Distance north or south from the equator
The higher the latitude is, the colder the climate tends to be
The amount of direct solar energy a particular area receives is determined by latitude

4. The sun’s rays hit the equator directly, at almost a 90° angle
The sun’s rays strike the poles at a lesser angle than they do the equator

5. C. Seasons
Seasons happen because the Earth is tilted on its axis at a 23.5° angle
The tilt affects how much solar energy an area receives as Earth moves round the sun

6. 1. Summer - Northern Hemisphere is tilted toward the sun and receives more direct sunlight and thus experiences warmer temperatures and longer days - Southern Hemisphere has colder temperatures and shorter days

8. 2. Winter - Northern Hemisphere is tilted away from the sun and receives less direct sunlight and thus experiences cooler temperatures and shorter days - Southern Hemisphere has warmer temperatures and shorter days

10. D. Prevailing Winds
Winds that blow from one direction
Affect the amount of precipitation that a region receives
If the prevailing winds form from warm air, the air cools and loses the ability to hold water vapor, bringing moisture
If the prevailing winds form from cool air, the air warms up and gains the ability to hold water vapor, bringing dry conditions

11. Winds that travel across large bodies of water absorb moisture
Winds that travel across land tend to be dry

12. E. Mountains
As elevation increases, temperature decreases
1. The Wet Side
Mountains force air to rise
As air rises it cools down, releasing moisture as snow or rain
The land on the windward side is usually green and lush

13. 2. The Dry Side
As dry air crosses the mountain, the air begins to sink
As air sinks, it warms up and gains the ability to hold water vapor
The land on the opposite side of the windward side is usually desert-like
This side of the mountain is in a rain shadow

14. F. Large Bodies of Water
Waters high specific heat causes it to absorb and release heat slower than land does
Large bodies of water help to moderate the temperatures of the land around it

15. G. Ocean Currents
Surface temperature of the water affects the temperature of the air above it
Warm currents heat the surrounding air and cause warmer temperatures
Cool currents cool the surrounding air and cause cooler temperatures

16. H. Climates of the World
Three major climate zones – tropical, temperate, and polar
Several types of climates in one zone due to differences in geography and the amount of precipitation

17. II. The Tropics
The tropical zone extends from about 23.5° north latitude to 23.5° south latitude
Receives the most direct solar radiation, causing hot temperatures
Three major biomes that differ in the amount of precipitation, soil characteristics, vegetation, and kinds of animals

18. A. Tropical Rain Forests
Warm and wet weather
Little difference between seasons
Greatest plant and animal diversity of any biome
Poor soil

19. B. Tropical Savannas
Very warm climate
Have a dry season that lasts four to eight months
Soils are nutrient poor
Plants include tall grasses, scattered trees, and thorny shrubs

20. C. Tropical Deserts
Receives less than 25 cm of rainfall per year
Hot deserts are caused by cool, sinking air masses

21. III. Temperate Zones
Experience seasonal change
Receive less solar energy than latitudes in the Tropics do

22. A. Temperate Forests
High amounts of rainfall and seasonal temperature differences
1. Evergreen Forests
Trees that keep their leaves year-round

23. 2. Deciduous Forests - Trees that lose their leaves at the end of the growing season - Soils are fertile because of the organic material in decaying leaves

24. B. Temperate Grasslands
Receive too little rain for trees to grow
Most-fertile soils of all biomes

25. C. Chaparrals
Vegetation is mainly evergreen shrubs
Rocky, nutrient-poor soil

26. D. Temperate Deserts
Cold deserts
Drastic change in temperature between day and night

27. IV. The Polar Zone
Located at the North and South Pole
Coldest average temperatures of all the climate zones

28. A. Tundra
Long, cold winters with almost 24 hours of night
Short, cool summers with almost 24 hours of daylight
Permafrost, or permanently frozen soil, lays underneath thawed soil

29. B. Taiga
Evergreen needle-leaved trees called conifers
- Flexible branches allow heavy snow to fall off without damaging the tree
- Contain acidic needles that drop and make the soil acidic

30. V. Changes in Climate
A. Ice Ages
The geologic record indicates that the Earth’s climate has been much colder than it is today
An ice age is a period during which ice collects in high latitudes and moves toward lower latitudes

31. 1. Glacial Periods
Enormous sheets of ice advance
Large amounts of water freeze, causing sea levels to drop

32. 2. Interglacial Periods
Warmer periods between glacial periods
Ice begins to melt and the sea level rises again
We are currently in an interglacial period that started 10,000 years ago

33. 3. Motions of the Earth
The Milankovitch theory proposed that changes in the Earth’s orbit and in the tilt of the Earth’s axis cause ice ages

34. 4. Plate Tectonics
One theory proposes that ice ages happen when the continents are positioned closer to the polar regions

35. B. Volcanic Eruptions
Send large amounts of dust, ash, and smoke into the atmosphere that act as a shield
The shield blocks some of the sun’s rays, which causes the Earth to cool

36. C. Asteroid Impact
When asteroids hit the Earth, they send up debris, blocking sunlight and thermal energy

37. D. The Sun’s Cycle
The sun follows an 11-year cycle, changing from a solar maximum to a solar minimum
When the sun is at its solar maximum, it produces a larger percentage of high-energy radiation

38. E. Global Warming
The Earth’s natural heating process, in which the atmosphere traps thermal energy is known as the greenhouse effect
An increase of carbon dioxide in the atmosphere increases absorption of thermal energy
An increase in temperature will cause polar ice caps to melt and cause flooding