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  • Insert cover image for Chapter 8 (p. 199).
  • Insert Figure 8.1a
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8 8 Presentation Transcript

  • Chapter 8: Global Climates and Climate Change Physical Geography Ninth Edition Robert E. Gabler James. F. Petersen L. Michael Trapasso Dorothy Sack
  • Climate What is the difference between weather and climate? Arctic Sea ice changes: 1977 (top) to 2007 (bottom)
  • 8.1 Classifying Climates
    • Early Greeks (Aristotle): Torrid, Temperate, and frigid
    • Two weather variables most often used today:
      • Temperature (minimum of 30 years of data)
      • Precipitation (minimum of 30 years of data)
    • Classify Climate
      • Atmospheric elements (statistics and math) = empirical
      • Based on the cause = genetic
  • 8.1 Classifying Climates
    • Thornthwaite System
      • Classifying based on moisture
      • Used often by soil and water resource scientists
      • Potential evapotranspiration
      • Actual evapotranspiration
  • 8.1 Classifying Climates What can you suggest are the causes for the major climate changes as you follow the 40 o latitude line from west to east?
  • 8.1 Classifying Climates What is the Thornthwaite climate type for coastal California?
  • 8.1 Classifying Climates
    • Köppen System
      • Most widely used
      • Based on regional temperature and precipitation
      • Advantages:
        • Easy to measure
        • Measured most often
        • Most important
      • Disadvantages:
        • Only average monthly temp and precip.
        • Ignored winds, clouds, intensity of precip.
  • 8.1 Classifying Climates
    • Simplified Köppen System
      • Divided into six major climate zones
        • A = Humid Tropical
        • C = humid mesothermal (mild winter)
        • D = humid microthermal (severe winter)
        • E = polar
        • BW and BS = arid and semiarid
        • H = Highland
  • 8.1 Classifying Climates Simplified Köppen System
  • 8.1 Classifying Climates
    • Tropical (A) Climate
      • High temp year round
      • Near equator
      • No winter season (average temp of coldest month above 18 o C (64.4 o F)
      • ITCZ
      • Af (tropical rainforest)
  • 8.1 Classifying Climates
    • Tropical (A) Climate
      • Aw (dry winter tropical savanna)
      • Am (along coast with tropical monsoon)
  • 8.1 Classifying Climates World Map of modified Köppen Classification System
  • 8.1 Classifying Climates World Map of modified Köppen Classification System
  • 8.1 Classifying Climates
    • Polar (E) Climate
      • No month has an average temp grater than 10 o C (50 o F)
      • EF (ice sheet): no month > 0 o C
      • ET (tundra): at least 1 month averages > 0 o C
  • 8.1 Classifying Climates
    • Mesothermal (C) Climate
      • 1 month below average temp grater than 18 o C (64.4 o F) and 1 month below 10 o C (50 o F)
      • Csa and Csb (Mediterranean)
        • Dry summer
        • Along west coasts between 30 o and 40 o latitude
      • Cfa (humid subtropical)
        • Wet year round
        • Southeast U.S.
  • 8.1 Classifying Climates
    • Mesothermal (C) Climate
      • Cfb and Cfc (marine west coast)
      • Wet year round
      • Summer’s cooler than Cfa
      • Along west coasts often extending up to 40 o latitude
  • 8.1 Classifying Climates
    • Microthermal (D) Climates
      • Usually year round precip.
      • Shorter summers and colder winters than “C”
      • Found only in N. hem.
      • Dfa and Dwa (humid continental, hot summer)
      • Dfb and Dwb (humid continental, mild summer)
      • Dfc, Dfd, Dwc, and Dwd (subarctic)
  • 8.1 Classifying Climates
    • Arid (B) Climates
      • Year round moisture deficiency
      • Precip received < potential ET
      • 15 o to 30 o latitude
      • BW (desert, annual precip. is less than half of annual potential ET)
      • BS (steppe; annual precip. is less than potential ET, but more than half)
  • 8.1 Classifying Climates
    • Highland (H) Climates
      • Mountain barriers can increase and decrease precipitation, cloud cover, and temperature.
      • Windward – wetter
      • Temperature decreases as you increase in elevation.
  • 8.1 Classifying Climates
    • Climate Regions
      • Region: similar internal characteristics distinct from other areas.
      • Transition
    • Scale of Climate
      • Microclimate
      • Topoclimates
      • Lake effect snow
      • Urban heat-island effect
  • 8.2 Climates of the Past
    • Ice Ages
      • Glaciation (cold period)
      • Interglacial (warmer period)
      • Pleistocene
      • Q: Why does the ice move in various directions in difference regions of the continent?
  • 8.2 Climates of the Past
    • Modern Research
      • Radiometric techniques
      • Ocean sediment
        • Calcium carbonate and shells
        • Oxygen-isotope record
      • Holocene
  • 8.2 Climates of the Past
      • Q: Has the general trend of temperature on Earth been warmer or colder during the Holocene?
  • 8.2 Climates of the Past
    • Methods for Revealing Climates of the Past
      • Paleoclimates
      • Oxygen-Isotope Ratio of Calcium carbonate and shells
      • Ice cores
      • Dendrochronology
      • Palynology
  • 8.2 Climates of the Past
    • Methods for Revealing Climates of the Past (con’t)
      • Palynology:
        • pollen-analysis
        • A core is drilled and removed to show the layers of the sediment.
        • Organic material can be radiocarbon dated.
    • Paleoclimatologists reconstruct the climate
  • 8.3 Rates of Climate Change
    • Altithermal
      • 7000 ya (years ago)
      • Warmer than today
    • What was the evidence?
      • Ice record from Antarctica and Greenland (oxygen-isotope.
      • Rapid change (few years or a decade)
      • Positive feedback system
  • 8.4 Causes of Climate Change
    • Orbital Variations (Milankovitch Cycles)
      • Eccentricity:
        • 100,000 years
        • Shape of Earth’s orbit
      • Obliquity
        • 41,000 years
        • Tilt of Earth’s axis 24.5 o - 22 o
      • Precession
        • 21,000 years
        • Distance to the sun
  • 8.4 Causes of Climate Change
    • Changes in Earth’s Atmosphere
      • Volcanic Activity
        • Tambora (1815, 1816)
        • Krakatoa (1883)
        • Mount Pinatubo (1991)
      • Greenhouse Gases
  • 8.4 Causes of Climate Change
    • Greenhouse Gases
      • Carbon Dioxide (CO 2 )
        • Blocks outgoing longwave radiation
        • CO 2 and ice sheets
        • Increasing trend (~ 380 ppm as of 2007).
      • Methane (CH 4 )
        • Very effective, however, currently very low.
      • CFC’s
      • Nitrous Oxides (N 2 O)
  • 8.4 Causes of Climate Change
    • Which greenhouse gas has the longest residence time?
  • 8.4 Causes of Climate Change
    • Changes in the Ocean
      • ENSO
      • Thermohaline Circulation
    • Changes in Landmasses
      • Shifting land masses (e.g. Continent over the poles)
      • New land blocking oceanic or atmospheric circulation
      • Change in albedo
  • 8.4 Causes of Climate Change
    • Impact Events
      • Asteroids
      • Comets
      • Tunguska Event
      • 65 mya
      • Near Earth Objects (NEO)
  • 8.5 Predicting Future Climates
    • Little Ice Age (1560-1850)
    • General Circulation Models (GCM’s)
    • Milankovitch Cycles
    • Greenhouse Gases
    • Global warming: most scientists believe that global warming is occurring.
  • 8.5 Predicting Future Climates
    • Global warming
      • most scientists believe that global warming is occurring.
      • Most mountain glaciers are retreating
  • 8.6 The Issue of Global Warming
    • The climate changes naturally
    • However, the vast majority of scientists content that humans are affecting our atmosphere.
    • IPCC (Intergovernmental Panel on Climate Change)
      • “ very likely that emissions of greenhouse gases from anthropogenic activities have caused” … most of the observed increase in globally-averaged temperature since the mid-20 th century.
  • 8.6 The Issue of Global Warming
    • On what continent has the observed temperature fluctuated the most during this time period, and which one the least?
  • 8.6 The Issue of Global Warming
    • Recommendations for the Future
      • Global Scale
      • Simple things we can do that will help reduce our negative impact on Earth’s fragile environment:
        • Use car pools and mass transit
        • Drive smaller cars
        • Use more energy-efficient lighting and appliances
        • Recycle
  • Physical Geography End of Chapter 8: Global Climates and Climate Change