Man Made Climate Change vs' Natural Variability

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Man Made Climate Changevs.Natural Variability
Presented By Mark Seaman Sam Atwood
EESC W4400
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Natural Variability in the Climate System

• Long-Term
• Glacial / Interglacial Periods
• Variability over 10s to 100s of thousands of
  years
• Max 4C to 6C change over a Glacial /
  Interglacial cycle
• Variations in Orbit, and Ice Sheet Cover and
  other Feedbacks
• Short-Term
• Last several Millennia
• Max /- 0.2C change over a century
• Solar Irradiance and Volcanism
• Not constant on all time or spatial scales
• Little Ice Age and Medieval Warm Period

Benin
Source Jones, P.D., and M.E. Mann (2004)
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Anthropogenic Impact on Climate System

• Typical natural range of variability exceeded in
  20th Century
• 0.6 to 0.9C change
• Man Made Forcings
• Physically understood mechanisms
• Greenhouse Gas Levels
• Climate Sensitivity 1.5C to 4.5C with doubling
  of CO2
• Sulfate Aerosols
• Land Use Changes
• Last half of 20th Century
• Anthropogenic impacts dominate over Natural
  Variability

Source Jones, P.D., and M.E. Mann (2004)
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Temperature Variations in Last Millennium
Source IPCC Climate change 2001 - Synthesis
report
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Primary Take Home Points

• Man Made Climate Change is different from Natural
  Variability in the Climate System
• This difference
• Timescale The time of the change is quicker
• Spatial scale Mean trends for the entire planet
• Magnitude The direction and amount of change

Questions?