Stratospheric trends in IPCC model simulations

General circulation model experiments for the Intergovemental Panel on Climate Change (IPCC) Fourth Assessment Report are analyzed to evaluate the sensitivity of the lower stratosphere to CO2 forcing using both 20th and 21st century model output. Model simulations of the 20th century are compared with observed temperatures and winds to better understand model variability and assess the importance of stratospheric variability on tropospheric climate. A comparision of modeled and observed tropospheric and stratospheric temperature trends over the last three decades show similar general patterns, although there exists significant variability especially in the lower stratosphere. The relationship between these results and the model representation of trends in ozone, CO2, and water vapor will be discussed.