National Oceanic and Atmospheric AdministrationGeophysical Fluid Dynamics Laboratory

Princeton, NJ 08542http://www.gfdl.noaa.gov

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 1960-2050 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 ~ 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.

AMTRAC: Description and runs

Mean Ozone trend 1980-1999

Observed ozone trends 1980-1999 (Randel pers. comm., 2005)

Observed ozone trend

Temperature solar cycle

Ozone solar cycle

AMTRAC polar spring lower stratosphere temperature evolution 1960-1999

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 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.