Attribution of climate extreme events

Journal name:
Nature Climate Change
Year published:
Published online


There is a tremendous desire to attribute causes to weather and climate events that is often challenging from a physical standpoint. Headlines attributing an event solely to either human-induced climate change or natural variability can be misleading when both are invariably in play. The conventional attribution framework struggles with dynamically driven extremes because of the small signal-to-noise ratios and often uncertain nature of the forced changes. Here, we suggest that a different framing is desirable, which asks why such extremes unfold the way they do. Specifically, we suggest that it is more useful to regard the extreme circulation regime or weather event as being largely unaffected by climate change, and question whether known changes in the climate system's thermodynamic state affected the impact of the particular event. Some examples briefly illustrated include 'snowmaggedon' in February 2010, superstorm Sandy in October 2012 and supertyphoon Haiyan in November 2013, and, in more detail, the Boulder floods of September 2013, all of which were influenced by high sea surface temperatures that had a discernible human component.

At a glance


  1. Haiyan and sea level.
    Figure 1: Haiyan and sea level.

    Linear sea-level trends from August 1993 to July 2013 are shown. The global mean is 3.3 mm yr−1, and the track of supertyphoon Haiyan from 3 to 11 November 2013 is indicated in green, with the most intense phase when it was a category 5 (cat. 5) storm highlighted. Data from AVISO (

  2. August SSTs for 12-20[deg] N, 110-100[deg] W, just west of Mexico.
    Figure 2: August SSTs for 12–20° N, 110–100° W, just west of Mexico.

    The mean value is 28.92 °C for 1982–1999. The last value is for 2013.

  3. Water vapour channel imagery, GOES East 6.5 [mu]m and GOES West 6.7 [mu]m merged, for 18:45 GMT on 12 September 2013.
    Figure 3: Water vapour channel imagery, GOES East 6.5 μm and GOES West 6.7 μm merged, for 18:45 GMT on 12 September 2013.

    The image shows the extensive water vapour and associated activity both west of Mexico and in the Caribbean Sea and the river of moisture from south of Baja, Mexico to eastern Colorado. Colors are used to show more intense features. Image courtesy of

  4. Imagery from the 6.5-[mu]m water vapour channel of NOAA's GOES 13 satellite.
    Figure 4: Imagery from the 6.5-μm water vapour channel of NOAA's GOES 13 satellite.

    Images were taken at 05:45 GMT, on 11 (top) and 13 (bottom) September 2013. The water vapour is in the mid to upper troposphere; the brighter the imagery, the more saturated the air. Colorado is outlined in red. Images courtesy of Axel Graumann, NOAA/NESDIS/NCDC.

  5. Tropical storms Manuel and Ingrid.
    Figure 5: Tropical storms Manuel and Ingrid.

    Imagery on 15 September 2013 from Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. NASA image courtesy of Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team.


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  1. National Center for Atmospheric Research (NCAR), PO Box 3000, Boulder, Colorado 80307, USA

    • Kevin E. Trenberth &
    • John T. Fasullo
  2. Department of Meteorology, University of Reading, Reading RG6 6BB, UK

    • Theodore G. Shepherd


K.E.T. led the writing of the paper and conceived of the paper and figures. J.T.F analysed some data and contributed to two figures. All authors contributed to writing the manuscript.

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The authors declare no competing financial interests.

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