Assessment of temperature, trace species, and ozone in chemistry-climate model simulations of the recent past

Simulations of the stratosphere from thirteen coupled chemistry-climate models
(CCMs) are evaluated to provide guidance for the interpretation of ozone predictions made
by the same CCMs. The focus of the evaluation is on how well the fields and
processes that are important for determining the ozone distribution are represented in the
simulations of the recent past. The core period of the evaluation is from 1980 to 1999
but long-term trends are compared for an extended period (1960–2004). Comparisons of
polar high-latitude temperatures show that most CCMs have only small biases in the
Northern Hemisphere in winter and spring, but still have cold biases in the Southern
Hemisphere spring below 10 hPa. Most CCMs display the correct stratospheric response
of polar temperatures to wave forcing in the Northern, but not in the Southern
Hemisphere. Global long-term stratospheric temperature trends are in reasonable
agreement with satellite and radiosonde observations. Comparisons of simulations of
methane, mean age of air, and propagation of the annual cycle in water vapor show a wide
spread in the results, indicating differences in transport. However, for around half the
models there is reasonable agreement with observations. In these models the mean age of
air and the water vapor tape recorder signal are generally better than reported in previous
model intercomparisons. Comparisons of the water vapor and inorganic chlorine (Cly)
fields also show a large intermodel spread. Differences in tropical water vapor mixing
ratios in the lower stratosphere are primarily related to biases in the simulated tropical
tropopause temperatures and not transport. The spread in Cly, which is largest in the polar
lower stratosphere, appears to be primarily related to transport differences. In general the
amplitude and phase of the annual cycle in total ozone is well simulated apart from the
southern high latitudes. Most CCMs show reasonable agreement with observed total