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    Separating signal and noise in atmospheric temperature changes: The importance of timescale

    Santer, Benjamin D. and Mears, Carl A. and Doutriaux, C. and Caldwell, Peter and Gleckler, Peter J. and Wigley, Tom M. and Solomon, Susan and Gillett, N.P. and Ivanova, D. and Karl, Thomas R. and Lanzante, John and Meehl, G.A. and Stott, Peter A. and Taylor, Karl E. and Thorne, Peter and Wehner, Michael F. and Wentz, Frank J. (2011) Separating signal and noise in atmospheric temperature changes: The importance of timescale. Journal of Geophysical Research, 116 (D22105). ISSN 0148-0227

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    We compare global‐scale changes in satellite estimates of the temperature of the lower troposphere (TLT) with model simulations of forced and unforced TLT changes. While previous work has focused on a single period of record, we select analysis timescales ranging from 10 to 32 years, and then compare all possible observed TLT trends on each timescale with corresponding multi‐model distributions of forced and unforced trends. We use observed estimates of the signal component of TLT changes and model estimates of climate noise to calculate timescale‐dependent signal‐to‐noise ratios (S/N). These ratios are small (less than 1) on the 10‐year timescale, increasing to more than 3.9 for 32‐year trends. This large change in S/N is primarily due to a decrease in the amplitude of internally generated variability with increasing trend length. Because of the pronounced effect of interannual noise on decadal trends, a multi‐model ensemble of anthropogenically‐forced simulations displays many 10‐year periods with little warming. A single decade of observational TLT data is therefore inadequate for identifying a slowly evolving anthropogenic warming signal. Our results show that temperature records of at least 17 years in length are required for identifying human effects on global‐mean tropospheric temperature.

    Item Type: Article
    Keywords: signal; noise; atmospheric temperature changes; timescale;
    Academic Unit: Faculty of Social Sciences > Geography
    Faculty of Social Sciences > Research Institutes > Irish Climate Analysis and Research Units, ICARUS
    Item ID: 6534
    Identification Number:
    Depositing User: Peter Thorne
    Date Deposited: 04 Nov 2015 17:05
    Journal or Publication Title: Journal of Geophysical Research
    Publisher: American Geophysical Union (AGU)
    Refereed: Yes
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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