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Class #37: Friday, April 10 PowerPoint Presentation
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Class #37: Friday, April 10

Class #37: Friday, April 10

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Class #37: Friday, April 10

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  1. Class #37: Friday, April 10 Climate Types (D,E, and H) Past Climates: Proxy Data Class #37: Friday, April 10

  2. The 6 major climate groups • A: Tropical moist • B: Dry (can be subtropical or mid latitude) • C: Moist with mild winters (mid latitude) • D: Moist with severe winters (mid latitude) • E: Polar (high latitude) • H: Highland (rapid climate change with elevation) • 2nd letter: usually latitude (except B) • 3rd letter: differences in temperature Class #37: Friday, April 10

  3. Class #37: Friday, April 10

  4. Class #37: Friday, April 10

  5. Class #37: Friday, April 10

  6. D Climate typeSevere (winter) Midlatitude • Similar to C but severely cold winter • Average temperature of coldest month <27ºF • Snow on ground for extended periods • Average temperature of warmest month >50ºF • Overall, large change in temperature with season Class #37: Friday, April 10

  7. D climate subtypes • 2nd letter • “f” no dry season • “w” winter dry season • 3rd letter • “a” hot summer • “b” warm summer • “c” cool summer • “d” extremely severe winter Class #37: Friday, April 10

  8. D Climate Subtypes (continued) • Humid continental • Dfa, Dfb, Dwa, Dwb • Dfa, for example, Chicago • Subarctic • Dfc, Dfd, Dwc, Dwd • Long winter • Brief cool summer Class #37: Friday, April 10

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  10. Class #37: Friday, April 10

  11. E climate type • Polar climate, very dry and cold • Poleward of Arctic/Antarctic Circle, latitude 66.5º • E climate subtypes • ET Tundra: mosses, lichens, flowering plants, woody shrubs, small trees, permafrost • EF Ice caps: no vegetation; Greenland, Antarctic Plateau Class #37: Friday, April 10

  12. Class #37: Friday, April 10

  13. H climate type: Highland • Large variation of temperature and precipitation over small horizontal distances • Large diurnal temperature variation • Can be dry or moist, depending on orientation, humidity, and whether prevailing winds are upslope or downslope Class #37: Friday, April 10

  14. Have today’s climates always been the same? • This question leads to the study of past climates. • So do the questions: Can we predict future climates? What is the impact of humans on climate? • Two kinds of past climate: • Historical, past few thousand years • Paleoclimate, ancient, back billions of years Class #37: Friday, April 10

  15. Historical Climate • Humans have kept records • Instrumental record • Since about 1600 • Historical data: proxy data • Humans have kept some sort of record of climate conditions • Examples: dates of freezes of lakes and rivers, farmers’ logs, animals in cave paintings, other documents Class #37: Friday, April 10

  16. Another source of data for the historical period is trees • Tree rings are rings of growth in tree trunks in regions with distinct growing seasons. • A wider tree ring means more growth. • Growth varies with temperature and precipitation, depending on the species. • Information from various species is most helpful. • The study of tree rings is dendrochronology, and is done by dendrochronologists. • Figure shows dry periods in Iowa in 1700, 1740, 1820, 1820, 1890, and 1930 from tree rings. Class #37: Friday, April 10

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  19. Class #37: Friday, April 10

  20. Proxy measurements of precipitation from tree rings • Dry periods: 1930s, the “Dust Bowl” around 1700 1740 1820 1890 Class #37: Friday, April 10

  21. Pollen for proxy information • Pollen degrade slowly, distinctive shapes for each species • Oldest sediments are deepest • Spruce need a cool climate • Decline of spruce during warming • Pine need a warm and moist climate • Oak need it drier than pine Class #37: Friday, April 10