Evolution of Stratospheric Temperature in Climate Model Simulations

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Evolution of Stratospheric Temperature in
Climate Model Simulations

• John Austin

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CCMval Description and runs

• Coupled chemistry-climate model simulations
• Uniform, observed forcings (solar, GHGs,
  aerosols, SSTs/sea ice).
• 12 different models complete climate models
  with reasonably complete stratospheric chemistry.
• Some runs have simplified tropospheric chemistry
• Some runs include several ensembles
• Period covered 1960-2050 mostly.
• Eyring et al. JGR, submitted.

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Climatology of the final warming (S)
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Monthly mean 50 hPa T
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100 hPa seasonal variation
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AMTRAC Description and runs

• GFDL climate model, coupled chemistry
• 48L model, upper boundary 0.002 hPa
• Horizontal resolution 2 x 2.5 deg.
• Finite Volume dynamical core
• Comprehensive stratospheric chemistry
  simplified tropospheric chemistry
• 3 member ensemble
• (1) 1960-2005 with observed forcings
• (2) 1990-2100 with A1B etc. forcings and SSTs
  from GFDL IPCC runs.

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Observed ozone trend
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Temperature solar cycle
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Ozone solar cycle
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SOCOL MSU-4 equivalent temperature(25 months
running mean) courtesy Schnadt et al.
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Conclusions

• Past T trends are in reasonable agreement with
  observations for the period 1980-2000 in the
  lower and upper stratosphere.
• A solar cycle in T occurs in model results, but
  is smaller than the SSU solar cycle.
• In the global average, the lower stratosphere
  temperature evolution agrees well with
  observations.
• Tropopause T decreases 1960-2005 (0.16 K/decade)
  and increases thereafter (not shown) at 0.23
  K/decade.
• Much work is yet to be done within CCMval and on
  individual models.