National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics Laboratory Princeton, NJ Evolution of Stratospheric Temperature in Climate Model Simulations John Austin

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 mostly. Eyring et al. JGR, submitted. CCMval: Description and runs

Climatology of the final warming (S)

Monthly mean 50 hPa T

100 hPa seasonal variation

GFDL climate model, coupled chemistry 48L model, upper boundary ~ hPa Horizontal resolution 2 x 2.5 deg. Finite Volume dynamical core Comprehensive stratospheric chemistry; simplified tropospheric chemistry 3 member ensemble (1) with observed forcings (2) with A1B etc. forcings and SSTs from GFDL IPCC runs. AMTRAC: Description and runs

Mean Ozone trend

Observed ozone trends (Randel pers. comm., 2005) Observed ozone trend

Temperature solar cycle

Ozone solar cycle

AMTRAC polar spring lower stratosphere temperature evolution

AMTRAC polar lower stratospheric temperature evolution, 12-month running mean

AMTRAC (colored lines) and observed (black line) global average temperature for 1960 to 2005 weighted in the vertical by the MSU4 weighting function.

SOCOL MSU-4 equivalent temperature (25 months running mean) courtesy Schnadt et al.

Conclusions Past T trends are in reasonable agreement with observations for the period 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 (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.