Simulations of the Last Millennium

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Simulations of the Last Millennium

• Caspar M. Ammann, NCAR-Paleo
• Fortunat Joos, Univ. of Bern, Switzerland
• Bob Tomas, NCAR
• Collaborators
• D. Schimel, B. Otto-Bliesner, J.T. Kiehl, E.
  Wahl, C. Morrill, (NCAR)
• P. Naveau (CU-Applied Math), H.-S. Oh (U of
  Alberta, CA),
• N. Graham (Scipps/HRC), J. Luterbacher, C. Casty,
  H. Wanner (Univ. Bern)
• J. Bradbury, R.S Bradley (UMass)

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Overview

• Last Millennium Motivation
• What do we know about recent Climate Changes?
• Forcings
• Solar irradiance changes
• Explosive Volcanism
• GHG
• Last Millennium First Results
• Hemispheric Surface Climate Overall Climate
  Sensitivity?
• What can we learn from the recent past?
• What are the next steps?

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Ammann et al. 2003
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The Big Solar Minima (850-2000)
Wolf
Maunder
1900
Oort
Spörer
Dalton
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Low Frequency Solar Forcing?
Recently, doubt was raised about previous
estimates of solar irradiancechanges at low
frequency including spectral signatures at these
longtime scales Lean et al. 2002 (GRL)
Foukal 2002 (GRL) cosmogenic isotope
variations (from open magnetic flux) may not
necessarily signify concurrent changes in solar
irradiance (from suns total flux).
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Coral growth rates in the tropics vs 14C res.
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Volcanic Sulfate Signals in Ice Forcing Data
Antarctica Siple Dome
Greenland North GRIP
Tambora
Bigler et al.
Ammann Joos et al.
Cole-Dai et al.
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The Last Millennium
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Climate Reconstructions Past Millennium
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Method Oh et al. 2003
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Contributions from External Forcing over the
Millennium (850-1999)(explained variance)
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Contributions from External Forcing over the
Millennium (850-1999)(explained variance)
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The Ultimate Climate Indicator Glacier
Expansions and Retreats
The Medieval Warmperiod (850-1200)
Antique Optimum (300 BC- 300 AD)
Global Warming (1970-)
The Little Ice Age (1270-1850)
The Dark Ages (350-700)
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Extending into 21st Century