Agreement in late twentieth century Southern Hemisphere stratospheric temperature trends in observations and CCMVal-2, CMIP3, and CMIP5 models
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2013
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American Geophysical Union
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Abstract
We present a comparison of temperature trends using different satellite and radiosonde observations and climate (GCM) and chemistry-climate model (CCM) outputs, 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 to 1998 trends in the range of -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, 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 -3.8K/dec for the CCMs, -3.5K/dec for the CMIP5 GCMs, and -2.7K/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 each individual that makes up 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.
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© 2013 American Geophysical Union. We thank Greg Bodeker, Nathan Gillett, Susan Solomon, and Dave Thompson for discussion and useful input. We thank Steve Sherwood and the Met Office for the provision of the IUK (www.ccrc.unsw.edu.au/staff/profiles/sherwood/radproj/index.html) and HadAT2 (www.metoffice.gov.uk/hadobs) radiosonde data sets, respectively. We acknowledge the World Climate Research Programme's (WCRP) Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups (as listed in Tables S2 and S3 of this paper) for producing and making available their model output. For CMIP, the U.S. Department of Energy's Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led the development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. We acknowledge the Chemistry-Climate Model Validation Activity of WCRP's Stratospheric Processes and their Role in Climate project, and the participating model groups (as listed in Table S4 of this paper), for organizing and coordinating the CCMVal-2 activity, and the British Atmospheric Data Centre for collecting and archiving the model output. Natalia Calvo was partially supported by the Advanced Study Program from the National Center for Atmospheric Research. The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation. Leopold Haimberger was supported by the Austrian Science Funds (FWF) project P21772-N22. We thank Alexey Karpechko, Darryn Waugh, and an anonymous reviewer for their comments on an earlier version of the manuscript.