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Climate

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  1. Climate Earth Science Chapter 18

  2. Climate • Average, year-after-year conditions • Temperature • Precipitation • Wind • Clouds

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

  4. 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

  5. Tropical zone • Near equator • Between 23.5°N and 23.5°S latitude • Direct or near-direct sun all year • Warm climates

  6. 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

  7. Temperate zones • Between tropical and polar zones • In summer, more direct sun • Warm weather • In winter, less direct sun • Cool weather

  8. Marine climates • Near oceans, especially on west coasts • Relatively mild winters and cool summers • Ocean winds

  9. Continental climates • Too far inland to be affected by ocean • More extreme temperatures • Cold winters and hot summers

  10. 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

  11. 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

  12. 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

  13. 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?

  14. Six main climate regions • Classified by temperature and precipitation • Tropical rainy • Dry • Temperate marine • Temperate continental • Polar • Highlands

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. 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?

  30. 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

  31. 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

  32. Global Warming • Gradual increase in temperature of Earth’s atmosphere • 0.5 °C in last 120 years

  33. 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

  34. 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

  35. 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

  36. 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

  37. Ozone depletion • CFCs damage ozone layer • Over Antarctica because of winds in the atmosphere • Increase in skin cancer and eye damage

  38. 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

  39. 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?