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The Greenhouse Effect and Global Warming

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Title: The Greenhouse Effect and Global Warming


1
The Greenhouse Effect and Global Warming
2
Diffuse Radiation
Diffuse Radiation - Clear skies 80 of
insolation reaches the surface - Cloudy skies
10-45 of insolation may reach the surface
3
The Greenhouse Effect
  • Popular name for process whereby greenhouse gases
    in atmosphere absorb longwave radiation from
    Earth and then emit or counterradiate it back to
    the surface providing additional heating

4
The Greenhouse Effect (contd)
  • Process acts to warm lower atmosphere by keeping
    longwave radiation from escaping to space (like
    insulation holding in heat in a house)
  • With no atmospheric greenhouse effect, Earth
    would be much colder current mean global temp is
    15C (59F) w/o greenhouse effect, temps would
    be about -18C (0F), which is a difference of
    33C (59F)...

5
Greenhouse Gases
  • Gases involved in this process are called
    greenhouse gases
  • All are considered trace gases, meaning they only
    constitute a small percentage of atmospheric
    content, but they play a very important role
  • Include CO2, H2O, CH4, and Water vapor

6
How Do Greenhouse Gases Get into the Atmosphere?
  • CO2 burning of fossil fuels (coal, oil, natural
    gas) and vegetation, during plant decomposition,
    during volcanic eruptions
  • H20 evaporation, evapotranspiration, airplane
    exhaust, volcanic eruptions
  • CH4 decay of organic matter, human activity
    (rice cultivation, farm animal wastes, bacterial
    decay in sewage and landfills, fossil fuel
    extraction and transportation, and biomass
    burning)

7
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8
Quick Focus on Carbon Dioxide
  • Charles Keeling started taking CO2 observations
    at Mauna Loa, HI, in 1958
  • Now 45 years of observations what do we see?

9
A Bit More about CO2
10
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11
Industrial Revolution
  • 1750-Europe, early-mid 1800s in US

12
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13
A Few More Facts
  • CO2 and H2O vapor considered most important
    greenhouse gases
  • CFC-12 absorbs 10,000 times more longwave
    radiation than CO2 (adding one CFC-12 molecule is
    equivalent to adding 10,000 CO2 molecules)
  • CFCs widely used in refrigeration process,
    formerly major component in aerosol spray cans
    (banned in 1976 by U.S. EPA)
  • Liquid water droplet and ice particles in clouds
    also very important in atmospheric greenhouse
    effect

14
NOAAs Viewpoint
15
Global Warming Debate
  • Its happeningand that is not the debate.
  • Although scientists agree that Earth is getting
    warmer, there is debate about the impact of human
    activities
  • Many think human activity is a major cause, while
    others claim its part of a natural cycle
  • Data sources and beliefs

16
What Natural Processes Lead to Climate Change?
  • Changes in solar radiation solar constant
    variations, 11-year sunspot cycle
  • Astronomical changes 23,000-year precession
    cycle (wobbling of axis), 41,000-year cycle in
    axial tilt, 100,000-year cycle in orbital
    eccentricity (revolution path not always
    elliptical)
  • Volcanic activity (Mt. Pinatubo, Philippine
    Islands, April 1994 Fig. 3.25, p. 112)
  • Cloudiness

17
Warming vs. Cooling
  • Natural cycles can lead to warming or cooling,
    depending on phase of cycle (solar radiation
    changes and astronomical changes) or
    location/time of day in atmosphere (dust from
    volcanic activity and cloudiness)
  • All greenhouse gases tend to cause warming
    (exception is when CFCs destroy O3)

18
Greenhouse Gases and Global Warming
19
What Do the Records Show?
  • Problem with observations organized, continuous
    recording of weather only goes back 140 years
  • Have other sources to determine temperature and
    atmospheric composition
  • 1. Tree rings 1 ring 1 yr wider rings
    more tree growth warmer temperatures, more
    precipitation
  • 2. Ice cores drill ice and sample gases in
    bubbles
  • 3. Oceanic sediment cores drill ocean floor
    and look at whats there (including plankton)
  • 4. Reef cores similar to 3
  • 5. Pollen in soil and packrat middens

20
Temperature Records
21
Temperature Records
22
How could global warming affect us?
  • Rising sea levels flooding of coastal/low-lying
    areas, harm water supply, shift in crop patterns
  • Change in growing seasons
  • Warmer temps more evaporation ? drier soils
  • Animal/plant habitat expands or contracts
  • More cloud cover
  • Stronger hurricanes farther north/south due to
    warmer ocean temps
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