Climate

Earth Science Chapter 18

Climate

• Average, year-after-year conditions• Temperature• Precipitation• Wind• Clouds

Microclimate

• Small area with a climate different from its surroundings• Example: grove of trees

Factors affecting temperature• Latitude

• Warmer near equator where sun is more direct

• Altitude• Cooler higher in atmosphere

• Distance from large bodies of water• Oceans make temperatures less extreme

• Ocean currents• Warm currents warm air above them, cool

currents cool air above them

Tropical zone

• Near equator• Between 23.5°N and 23.5°S latitude• Direct or near-direct sun all year

• Warm climates

Polar zone

• Near poles• 66.5° to 90° N and 66.5° to 90° S

latitude• Sun’s rays always at a lower angle

• Cold climates

Temperate zones

• Between tropical and polar zones• In summer, more direct sun

• Warm weather• In winter, less direct sun

• Cool weather

Marine climates

• Near oceans, especially on west coasts• Relatively mild winters and cool

summers• Ocean winds

Continental climates

• Too far inland to be affected by ocean• More extreme temperatures

• Cold winters and hot summers

Factors determining precipitation

• Prevailing winds• Areas downwind from large bodies of water

receive more precipitation

• Presence of mountains• More precipitation on windward side, less on

leeward side• Air cools as it rises

• Seasonal winds• Like wide area land and sea breezes

Monsoons

• Sea and land breezes over a large region that change direction with the seasons

• Can produce heavy rains in summer, little rain in winter

Seasons• Caused by tilt of Earth’s axis

• NOT distance from Sun• End (N or S) of Earth pointed toward

sun has summer• End (N or S) pointed away from sun has

winter• When neither is pointed towards it, it is

fall or spring• Seasons website

Discuss• Name four factors that affect temperature.• List three factors that affect precipitation.• Two locations are at the same latitude in the

temperate zone. One is in the middle of a continent. The other is on a coast affected by a warm ocean current. How will their climates differ?

• How does a mountain range in the path of prevailing winds affect precipitation on either side of the mountains?

Six main climate regions

• Classified by temperature and precipitation

• Tropical rainy• Dry• Temperate marine• Temperate continental• Polar• Highlands

Tropical Rainy

• Tropical wet• Many rainy days with thunderstorms all year long• Only windward side of Hawaiian Islands in US

• Tropical wet-and-dry• Slightly less rain that tropical wet• Have distinct dry and rainy seasons• Have tropical grasslands called savannas

• Grass with small clumps of trees

• Only on the southern tip of Florida in the US

Dry• Precipitation that falls is less than what could

evaporate• Not just low rainfall

• Arid• Deserts

• Hot and sandy or cold or rocky• Average less than 25 cm of rain per year• Southwest US

• Semiarid• Steppes - edges of deserts

• AKA prairie or grassland• Enough rain for grasses and low bushes

Temperate Marine

• Marine west coast• Coolest marine climate• Mild, rainy winters• between 40° latitude and pole• Heavy precipitation – thick forests• Northern California to southern Alaska

Temperate Marine

• Mediterranean• Drier and warmer than west coast marine• Mostly around Mediterranean sea• Mild climate with two seasons

• Cool rainy winter• Warmer, drier summer

• Southern California coast in US

Temperate Marine

• Humid subtropical• Warmest marine climate• Wet and warm, but not as consistently hot

as tropics• Cool to mild winters with more rain than

snow• SE US

Temperate Continental• Extremes of temperature• Only in northern hemisphere• Humid Continental

• Constantly changing weather• Bitter cold winters and hot humid summers

• Subarctic• Farther north• Short cool summers and long, bitterly cold

winters• Pine trees

Polar• Coldest• Ice cap

• Always below freezing• Land covered with ice and snow• Dry air• Little vegetation

• Tundra• Short, cool summers and bitterly cold winters• Some layers of the soil are always frozen

(permafrost)• Wet and boggy in summer

Highlands

• Colder than regions around them• Precipitation increases with altitude• Tree line – any higher, and too cold for

trees

Discuss• What two major factors are used to identify

climates?• What are the six main climate regions?• Which place would have more sever winters

– central Russia or the west coast of France? Why?

• How could a forest grow on a mountain that is surrounded by desert?

• Place the following climates in order from coldest to warmest: tundra, subarctic, humid continental, ice cap

Climate-studying principle

• If plants or animals today need certain conditions to live, then similar plants and animals in the past also required those conditions

Ancient climate information

• Pollen• What types of plants used to live in an area• What type of climate it used to have

• Tree Rings• Thickness depends on temperature in cool

climates and amount of precipitation in dry climates

Ice Ages

• AKA glacial episodes• Glaciers covered large parts of Earth’s

surface• Carve grooves in rock, deposit sediment

• Most recent was 10,500 years ago• So much water in ice that the sea level was much

lower• When melted, coastal areas flooded and Great

Lakes formed

Climate change causes

• Earth’s position• Time Earth is closest to sun shifts over

23,000 years• Angle of axis tilt also shifts slightly over

thousands of years• Solar energy

• Sunspots – cool areas on the sun• Sun produces more energy when there are

more sunspots – Earth warms

Climate change causes

• Volcanic Activity• Gases and ash may filter solar radiation,

making it cooler• Movement of continents

• Different locations on Earth• Changed locations of land and sea• Changed wind and ocean currents

Discuss

• What types of evidence do scientists gather to study changes in climate?

• If you are studying tree rings, what do several narrow rings in a row indicate?

• What occurs during an ice age?

Short-term climate changes

• El Niño• Warm surface water from western Pacific

moves towards South American coast• Can cause unusual and severe conditions

around the world• Heavy rains or droughts

• Every two to seven years

Short-term climate changes

• La Niña• Colder than normal waters in eastern

Pacific• Can cause unusual and severe conditions

around the world• Colder winters in Pacific NW• Greater hurricane activity

Global Warming

• Gradual increase in temperature of Earth’s atmosphere

• 0.5 °C in last 120 years

Greenhouse hypothesis

• Greenhouse gases trap in heat like the glass in a greenhouse• Carbon dioxide, water vapor, and methane

• Human activities may add greenhouse gases to the air

Changing CO2 levels

• Increase in carbon dioxide might be a major factor in global warming

• Increase might be from increased burning of wood and fossil fuels

• Carbon dioxide level could double by year 2100.• Global temperature could rise by 1.5 to

3.5 °C

Climate variation hypothesis

• 0.5 °C rise in last 120 years might be from natural climate variation

• Could be due to solar energy variations• Could be a combination of increased

CO2 and solar energy variations

Possible Global Warming effects

• Farmers in some areas could plant two crops per year

• Cold places could become farmland• Fertile fields might become dust bowls• Warmer ocean water could mean

stronger hurricanes• Sea level could rise, causing flooding

• Already 10 – 20 cm rise over last 100 years

Ozone depletion

• CFCs damage ozone layer• Over Antarctica because of winds in the

atmosphere• Increase in skin cancer and eye

damage

CFC bans

• US and many other countries banned from aerosols in late 1970s

• 1990 – many nations agreed to phase out entirely• Should be eliminated from US use next

year• Should gradually shrink ozone hole

Discuss

• What are two events that can lead to short-term climate change?

• What are two things that might contribute to global warming?

• What effect have human activities had on the ozone layer?