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    Consistency of modelled and observed temperature trends in the tropical troposphere


    Santer, Benjamin D. and Thorne, Peter and Haimberger, L. and Taylor, Karl E. and Wigley, Tom M. and Lanzante, John and Solomon, Susan and Free, M. and Gleckler, Peter J. and Jones, P.D. and Karl, Thomas R. and Klein, T. and Mears, C. and Nychka, D. and Schmidt, A. and Sherwood, Steve C. and Wentz, Frank J. (2008) Consistency of modelled and observed temperature trends in the tropical troposphere. International Journal of Climatology, 28 (13). pp. 1703-1722. ISSN 1097-0088

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    Abstract

    A recent report of the U.S. Climate Change Science Program (CCSP) identified a ‘potentially serious inconsistency’ between modelled and observed trends in tropical lapse rates (Karl et al., 2006). Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to human-caused increases in well-mixed greenhouse gases (GHGs). We revisit such comparisons here using new observational estimates of surface and tropospheric temperature changes. We find that there is no longer a serious discrepancy between modelled and observed trends in tropical lapse rates. This emerging reconciliation of models and observations has two primary explanations. First, because of changes in the treatment of buoy and satellite information, new surface temperature datasets yield slightly reduced tropical warming relative to earlier versions. Second, recently developed satellite and radiosonde datasets show larger warming of the tropical lower troposphere. In the case of a new satellite dataset from Remote Sensing Systems (RSS), enhanced warming is due to an improved procedure of adjusting for inter-satellite biases. When the RSS-derived tropospheric temperature trend is compared with four different observed estimates of surface temperature change, the surface warming is invariably amplified in the tropical troposphere, consistent with model results. Even if we use data from a second satellite dataset with smaller tropospheric warming than in RSS, observed tropical lapse rate trends are not significantly different from those in all other model simulations. Our results contradict a recent claim that all simulated temperature trends in the tropical troposphere and in tropical lapse rates are inconsistent with observations. This claim was based on use of older radiosonde and satellite datasets, and on two methodological errors: the neglect of observational trend uncertainties introduced by interannual climate variability, and application of an inappropriate statistical ‘consistency test’.

    Item Type: Article
    Keywords: tropospheric temperature changes; climate model evaluation; statistical significance of trend differences; tropical lapse rates; differential warming of surface and temperature;
    Academic Unit: Faculty of Social Sciences > Geography
    Faculty of Social Sciences > Research Institutes > Irish Climate Analysis and Research Units, ICARUS
    Item ID: 6558
    Identification Number: https://doi.org/10.1002/joc.1756
    Depositing User: Peter Thorne
    Date Deposited: 11 Nov 2015 11:24
    Journal or Publication Title: International Journal of Climatology
    Publisher: Royal Meteorological Society
    Refereed: Yes
    URI:

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