Young, Paul and Butler, Amy and Calvo, Natalia and Haimberger, Leopold and Kushner, Paul and Marsh, Dan and Randel, William and Rosenlof, Karen (2013) Agreement in late twentieth century Southern Hemisphere stratospheric temperature trends in observations and CCMVal-2, CMIP3 and CMIP5 models. Journal of Geophysical Research: Atmospheres, 118 (2). pp. 605-613. ISSN 0747-7309
Abstract
We present a comparison of temperature trends using different satellite and radiosonde observations and climate (GCM) and chemistry-climate model (CCM) output, focusing on the role of photochemical ozone depletion in the Antarctic lower stratosphere during the second half of the twentieth century. Ozone-induced stratospheric cooling peaks during November at an altitude of approximately 100 hPa in radiosonde observations, with 1969-1998 trends in the range -3.8 to -4.7 K / dec. This stratospheric cooling trend is more than 50% greater than the previously estimated value of -2.4 K / dec [Thompson and Solomon, 2002], which suggested that the CCMs were overestimating the stratospheric cooling, and that the less complex GCMs forced by prescribed ozone were matching observations better. Corresponding ensemble mean model trends are -3.8 K / dec for the CCMs, -3.5 K / dec for the CMIP5 GCMs, and -2.7 K / dec for the CMIP3 GCMs. Accounting for various sources of uncertainty – including sampling uncertainty, measurement error, model spread, and trend confidence intervals – observations, and CCM and GCM ensembles are consistent in this new analysis. This consistency does not apply to every individual that comprises the GCM and CCM ensembles, and some do not show significant ozone-induced cooling. Nonetheless, analysis of the joint ozone and temperature trends in the CCMs suggests that the modeled cooling/ozone-depletion relationship is within the range of observations. Overall, this study emphasizes the need to use a wide range of observations for model validation, as well as sufficient accounting of uncertainty in both models and measurements.