I. Introduction

• A. Climate scale
  
  • 1. 1 day - diurnal cycle
    
    • a. Weather occurs on an hourly or daily basis
      
      • 1) Primary cause: Rotation of the Earth on it's axis
        
    • b. Yesterday's weather was:
      
  • 2. 1 year - yearly cycles
    
    • a. Equinoxes and solstices.
      
      • 1) 23.5 degree tilt of the Earth's axis
        
    • b. Last year:
      
  • 3. 10 years - decadal scale
    
    • a. Longer-term variabilities begin to appear
      
      • 1) El Niño & La Niña
        
      • 2) Rapid climatic shifts can occur
        
    • b. Last 10 years:
      
      • 1) El Niño & La Niña
        
  • 4. 100 years - Centennial scale
    
    • a. Paleoclimatic data to track solar and ocean variability
      
      • 1) Large scale climatic changes and variability
        
      • 2) Pacific Decadal Oscillation (PDO) & North Atlantic Oscillation (NAO)
        
    • b. Last 100 years:
      
      • 1) Human population and CO2 levels rose exponentially
        
      • 2) Climate related events severely impacts human populations
        
    • c. What is El Niño?
      
      • 1) Basically, it's a giant puddle (or pod) of heated water that sloshes across the Pacific Ocean
        
        • a) Similar to an iceberg
          
        • b) Bulge on the surface
          
        • c) Most of "pod" beneath the surface
          
        • d) Due to difference in density
          
        • e) National Geographic's Model (http://www.nationalgeographic.com/elnino/mainpage.html)
          
      • 2) Normal conditions in the tropical Pacific Ocean
        
        • a) Surface winds move from east to west
          
        • b) From high pressure in S. America to low pressure in Australia
          
        • c) Drags water westward
          
        • d) Warm water pools in the western Pacific
          
      • 3) Every 3 - 8 years, system reverses
        
        • a) Called the Southern Oscillation
          
        • b) Trade winds weaken or reverse
          
        • c) Warm water migrates from Australia to S. America
          
        • d) Arrives in time for Christmas - Corriente del Niño
          
      • 4) ENSO - El Niño-Southern Oscillation
        
        • a) Typically lasts 1 year
          
        • b) May last up to 3
          
        • c) In multi-year events, first year not as affected
          
        • d) Affects both hemispheres
          
      • 5) Recognizing an El Niño
        
        • a) Sea Surface Temperatures (SST)
          
        • b) Normal: 6-8° C warmer in the western tropical Pacific than in the eastern tropical Pacific
          
        • c) Check SST to see if in "normal" range
          
      • 6) La Niña
        
        • a) Return to "normal" conditions from an El Niño strong
          
        • b) Produces:
          
          • i. Strong currents
            
          • ii. Powerful upwelling
            
          • iii. Chilly and stormy conditions along S. American coast
            
        • c) Eastern Pacific cools rapidly, Western Pacific warms rapidly
          
        • d) Renewed Trade Wind activity spreads the cooler eastern Pacific waters westward
          
  • 5. 1,000 years
    
    • a. Variability in
      
      • 1) Carbon cycles on land and sea
        
      • 2) Thermohaline current
        
    • b. Last 1,000 years
      
      • 1) Europe's "Little Ice Age"
        
      • 2) Large Volcanic Eruptions
        
      • 3) Multi-decadal droughts
        
  • 6. 10,000 years
    
    • a. Natural cycles begin to appear
      
      • 1) Those not influenced by humans
        
      • 2) Use Paleoclimatic data
        
        • a) Ice cores
          
        • b) Palynology
          
        • c) Tree Rings
          
    • b. Last 10,000 years
      
      • 1) End of last Ice Age
        
        • a) Melting of polar ice caps and glaciers
          
        • b) Rising sea level
          
        • c) Formation of the Black Sea, Pleistocene Lakes in Western U.S.
          
  • 7. 100,000 years
    
    • a. Extreme long term trends
      
      • 1) Milankovitch cycles
        
    • b. Last 100,000 years
      
      • 1) Last Ice Age cycle 60,000 to 20,000 ybp
        
        • a) Ice Age Cycles began ~2.6 myo to present
          
      • 2) Decline of the Neanderthal, rise of Homo sapiens
        

II. Causes of Global Climate Change

• A. Global Cooling
  
  • 1. Volcanic Eruptions
    
    • a. Tambora, Indonesia - 1815 "year without a summer"
      
    • b. Mount Toba, present day Sumatra - 73,000 years ago accelerated glaciation
      
  • 2. Milankovitch cycles
    
    • a. Processional of equinoxes - every 23,000 years
      
      • 1) A measure of the slow clockwise motion of the equinoxes along the ecliptic due to the motion of the earth's axis of rotation around the pole of the ecliptic; the angular movement of the spin axis of an object around an axis fixed in space.
        
    • b. Obliquity - every 41,000 years
      
      • 1) Tilt of the Earth's axis
        
        • a) Currently 23.5º
          
      • 2) Affects insolation - the amount of sunlight an area receives
        
    • c. Eccentricity - 100,000 to 400,000 year periods
      
      • 1) The amount that the earth's revolution deviates from a circular path.
        
      • 2) More circular path, all points on it are perihelia
        
      • 3) More elliptical path, more pronounced perihelion and aphelion
        
  • 3. Changes in ocean circulation
    
    • a. Changes in deep ocean circulation patterns
      
      • 1) Thermohaline current - brings cold, nutrient rich water from the poles to the equator
        
      • 2) Moderates temperatures
        
      • 3) Influx of fresh water from melting ice caps dilutes salinity, therefore decreasing density, and current shuts off
        
    • b. Position of the continents
      
      • 1) Currents circulate around ocean basins
        
      • 2) Changes in continent position can restrict current flow
        
• B. Global Warming
  
  • 1. Sunlight received by the Earth may be reflected by either the atmosphere or the surface.
    
    • a. Some of the light is absorbed by the Earth and re-emitted as infrared energy (heat).
      
    • b. Gases, both natural and artificial in origin, prevent some of this heat from escaping to space thereby causing the Earth to grow warmer.
      
    • c. Global temperatures are 0.6ºC higher than 100 years ago
      
  • 2. Gases that cause the global warming (greenhouse effect)
    
    • a. Carbon dioxide (CO2)
      
      • 1) Carbon dioxide from burning of coal, oil, natural gas, and wood
        
      • 2) CO2 content of the atmosphere is 25% higher than pre-industrial levels
        
    • b. Methane
      
      • 1) Atmospheric methane is 100% higher than pre-industrial levels
        
    • c. Chlorofluorocarbons
      
      • 1) This gas is widely used in refrigerators and air conditioners
        
      • 2) At causes both global warming and destruction of the ozone layer
        

I. Introduction | II. Causes of Global Climate Change | III. Effects of Global Climate Change | Links | top | Geol 357 Lecture Home

III. Effects of Global Climate Change

• A. Global Cooling
  
  • 1. Temperatures
    
    • a. Europe and North America ~20°C colder than present
      
    • b. Tropical regions ~ 2°C colder than present
      
  • 2. Development of ice caps
    
    • a. Lowers sea levels
      
    • b. Causes land bridges to form
      • cool animation from NSF's Arctic Natural Sciences Program (requires Quicktime)
        
    • c. Changes to flora and fauna
      
• B. Global Warming
  
  • 1. The Impact of Global Warming on the Earth is Uncertain
    
    • a. Scientists are unable to precisely model the nature of this process
      
    • b. General atmospheric warming due to human pollution is highly probable
      
    • c. Polar ice caps may partially melt raising sea level
      
      • 1) The impact on coast areas could be enormous
        
    • d. Some parts of the land may receive less rain while others receive more
      
  • 2. Some Solutions To The Global Warming Problem
    
    • a. Use Energy More Efficiently
      
      • 1) Practice conservation in every way possible
        
    • b. Develop Alternate Energy Sources
      
      • 1) Solar energy is ideal in this regard
        
      • 2) Hydroelectric, wind, and geothermal power would also help
        
      • 3) Increased reliance on nuclear power is a possibility
        
        • a) Disposal of nuclear waste and other dangers create considerable concern
          
    • c. Other Strategies
      
      • 1) Improve public transit to reduce automobile use
        
      • 2) Create market incentives to use other energy sources by taxing the use of carbon products
        
      • 3) Reverse the world-wide trend toward deforestation
        
      • 4) Rapidly terminate the world-wide use of chlorofluorocarbons
        
      • 5) Modify your life style so as to minimize impact on the environment
        
    • d. Serious Concerns
      
      • 1) The developed countries achieved their wealth on fossil fuels. How can we deny developing nations these same benefits?
        
      • 2) Deforestation is a short-term benefit to the logging industry and farmers around the world. How can we prevent them from making a living?
        
      • 3) China has huge coal deposits that will be used to support a huge population. How can they be encouraged to develop other energy sources?
        
      • 4) Many poor coastal countries will suffer greatly from a sea level rise and yet they produce very little carbon pollution. What obligations do the rich countries have to those who will suffer because of the pollution of others?
        

I. Introduction | II. Causes of Global Climate Change | III. Effects of Global Climate Change | IV. Topic #4 | V. Topic #5 | VI. Topic #6 | Links | top | Geol 357 Lecture Home