Kein Folientitel

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Long-term perspectives on the Earth
SystemLooking from the Past into the Future
Thomas Stocker
Climate and Environmental Physics University of
Bern, Switzerland www.climate.unibe.ch
Collaborators Bern Team, S. Johnsen
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UN Framework Convention on Climate Change
(in force since 21.3.1994, ratified by 186
countries)
Article 2 The ultimate objective ... is to
achieve stabilization of greenhouse gas
concentrations in the atmosphere at a level that
would prevent dangerous anthropogenic
interference with the climate system.
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Understand the past ...
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Phase 2 (2003 )
PANASH CLIVAR/PAGES IMAGES Polar
Programs Ecosystem Proc. Human Interactions
5 FOCI
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Vostok (Antarctica) 4 glacial cycles
(Petit et al., 1999)
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Rates of CO2 change from Antarctic ice cores
Paleorecords
Today gt150 ppm/cty
(Stocker Monnin, 2003)
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Millennial changes during the ice age
(Blunier Brook, 2001)
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Millennial changes during the ice age
Paleorecords
(Blunier Brook, 2001)
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The role of models in paleoclimate research
Paleorecords
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The role of models in paleoclimate research
Prediction
Processes
Paleorecords
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Hierarchy of Climate Models
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Millennial changes due to the ocean circulation ?
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A minimum model for the bipolar seesaw
South Memory(North)
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Thermal Bipolar Seesaw
GRIP (Greenland)
Byrd (Antarctica)
t 1120 yr
t 500 yr
t 2000 yr
t 4000 yr
(Stocker Johnsen 2003)
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the world aint so simple ... we need a model
hierarchy
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Coupled climate models show consistent NH cooling
HadCM3
NASA-GISS
(Schmidt, 2002)
(Vellinga, 2002)
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Not consistent changes in the southern hemisphere
HadCM3
NASA-GISS
(Schmidt, 2002)
(Vellinga, 2002)
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Dome Concordia (Antarctica) 800,000 yrs of
climate record
(EPICA, 2003, unpublished)
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• Summary 1
• high-resolution, well-dated paleorecords provide
  time and space information about Earth system
  dynamics
• models are required to identify and quantify
  processes and make predictions
• a model hierarchy is required to fully appreciate
  the paleoclimate records and extract information
  of combined records
• a model hierarchy is required to fully appreciate
  the possible limitations of reduced complexity
  models

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Understand the past ...
... to project the future
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Uncertainties in radiative forcing 1750 - 2000
(IPCC 2001)
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Ensemble simulation of future changes
Knutti et al. (2002)
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Ensemble-simulations of the Atlantic THC
(Knutti et al., 2003)
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Reduction of the Atlantic thermohaline circulation
Ensemble simulations with comprehensive models
show uncertainty, but not long-term evolution

• IGBP Synthesis (2003)

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Long-term Changes of the Atlantic thermohaline
circulation
Long-term simulations with reduced complexity
models suggest possibility of mode switches

• IGBP Synthesis (2003)

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• Conclusions
• understanding of the past and prediction of the
  future requires excellent paleorecords, combined
  with climate and process models
• one single model, or model simulation, ignores
  inherent gaps in our knowledge and inherent
  limits of predictability in the Earth system
• ensemble simulations are needed model
  complexity, initial conditions, model parameters
• use reduced complexity models to access long time
  scales and explore systematically parameter space