The Earth

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The Earths Climate System
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What natural forces affect the climate system?

• Natural fluctuations in the suns intensity
• The complex motion of the earth around the sun
• Believed to be the trigger for Ice AGES
• Volcanic eruptions
• Cool the climate by reflecting sunlight
• Shorter-term cycles like El Nino
• Interactions between components of the climate
  system
• These are called feedbacks

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Human Factors Affecting the Climate System

• Increases in greenhouse gases
• For instance Carbon Dioxide and Methane
• Deforestation
• Other land use changes
• Urbanization

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What Are Greenhouse Gases

• Gases that allow heat from the sun to pass
  through, but absorb heat emitted by Earth
• Natural part of the atmosphere
• Without them -20C vs 15C (-4F vs. 59F)
• Water vapor is a strong greenhouse gas
• Carbon dioxide occurs naturally in the
  atmosphere.
• Human activity increases Carbon dioxide,Methane,
  Nitrous Oxides, HFCs

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Alone GHG act as a Blanket
4. Remaining heat lost to space
3. GHG redirect some heat back to Earth
2. Earth absorbs sunlight and Radiates it
as heat
2.
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What causes these increases

• Fossil fuel burning release about 6 billion tons
  of carbon each year to the atmosphere
• Methane from agriculture, livestock, landfills
  and industry have increased by 133
• Nitrous oxide from agriculture and industry has
  increased by 15
• Change in land use and land cover release 1
  billion tons of carbon plus other gases

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Daily Rainfall gt 2 inches
Does 40 inches come in 100 events of 0.4 inches
or 10 4 storms?
Groisman et al BAMS 2001
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Does a Degree or Two Matter?
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Melting Glacier
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Rising Sea Level
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Looking to the Future

• What will happen to concentrations of climate
  altering gases such as carbon dioxide?
• What will happen to global temperature and
  precipitation?

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Typical climate model
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Model Validation
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Summary

• With VERY HIGH levels of certainty
• GHG concentrations have increased markedly
• In isolation these changes must result in
  warming
• With HIGH CERTAINTY
• Observed global temperatures have increased 1C
• Observed changes in precipitation character
• Observed impacts
• CO2 not this high for 100s of thousands of years
  
• Climate model projections show continued
  increases in temp
• With Limited Certainty
• Magnitude of Temperature Rise (1.5 - 5 C)
• Precise regional changes and impacts