Identifying human influences on atmospheric temperature


Santer, Benjamin D. and Painter, Jeffrey F. and Mears, Carl A. and Doutrauix, Charles and Caldwell, Peter and Arblaster, Julie M. and Cameron-Smith, Philip J. and Gillett, Nathan P. and Gleckler, Peter J. and Lanzante, John and Perlwitz, J. and Solomon, Susan and Stott, Peter A. and Taylor, Karl E. and Terray, Laurent and Thorne, Peter and Wehner, Michael F. and Wentz, Frank J. and Wigley, Tom M. and Wilcox, Laura J. and Zou, Cheng-Zhi (2013) Identifying human influences on atmospheric temperature. Proceedings of the National Academy of Sciences, 110 (1). pp. 26-33. ISSN 1091-6490

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Abstract

We perform a multimodel detection and attribution study with climate model simulation output and satellite-based measurements of tropospheric and stratospheric temperature change. We use simulation output from 20 climate models participating in phase 5 of the Coupled Model Intercomparison Project. This multimodel archive provides estimates of the signal pattern in response to combined anthropogenic and natural external forcing (the fingerprint) and the noise of internally generated variability. Using these estimates, we calculate signal-to-noise (S/N) ratios to quantify the strength of the fingerprint in the observations relative to fingerprint strength in natural climate noise. For changes in lower stratospheric temperature between 1979 and 2011, S/N ratios vary from 26 to 36, depending on the choice of observational dataset. In the lower troposphere, the fingerprint strength in observations is smaller, but S/N ratios are still significant at the 1% level or better, and range from three to eight. We find no evidence that these ratios are spuriously inflated by model variability errors. After removing all global mean signals, model fingerprints remain identifiable in 70% of the tests involving tropospheric temperature changes. Despite such agreement in the large-scale features of model and observed geographical patterns of atmospheric temperature change, most models do not replicate the size of the observed changes. On average, the models analyzed underestimate the observed cooling of the lower stratosphere and overestimate the warming of the troposphere. Although the precise causes of such differences are unclear, model biases in lower stratospheric temperature trends are likely to be reduced by more realistic treatment of stratospheric ozone depletion and volcanic aerosol forcing.

Item Type: Article
Keywords: climate change; detection; attribution; climate modeling; multimodel analysis;
Academic Unit: Faculty of Social Sciences > Geography
Item ID: 6487
Identification Number: 10.1073/pnas.1210514109
Depositing User: Peter Thorne
Date Deposited: 20 Oct 2015 15:32
Journal or Publication Title: Proceedings of the National Academy of Sciences
Publisher: National Academy of Sciences
Refereed: Yes
URI:

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