Recent temperature extremes at high northern latitudes unprecedented in the past 600 years

Journal name:
Nature
Volume:
496,
Pages:
201–205
Date published:
DOI:
doi:10.1038/nature11969
Received
Accepted
Published online

Recently observed extreme temperatures at high northern latitudes1, 2, 3, 4, 5, 6, 7 are rare by definition, making the longer time span afforded by climate proxies important for assessing how the frequency of such extremes may be changing. Previous reconstructions of past temperature variability have demonstrated that recent warmth is anomalous relative to preceding centuries2, 8, 9 or millennia10, but extreme events can be more thoroughly evaluated using a spatially resolved approach that provides an ensemble of possible temperature histories11, 12. Here, using a hierarchical Bayesian analysis13, 14 of instrumental, tree-ring, ice-core and lake-sediment records, we show that the magnitude and frequency of recent warm temperature extremes at high northern latitudes are unprecedented in the past 600years. The summers of 2005, 2007, 2010 and 2011 were warmer than those of all prior years back to 1400 (probability P>0.95), in terms of the spatial average. The summer of 2010 was the warmest in the previous 600years in western Russia (P>0.99) and probably the warmest in western Greenland and the Canadian Arctic as well (P>0.90). These and other recent extremes greatly exceed those expected from a stationary climate, but can be understood as resulting from constant space–time variability about an increased mean temperature.

At a glance

Figures

  1. Time series of temperature anomalies and centennial slopes.
    Figure 1: Time series of temperature anomalies and centennial slopes.

    a, Average land temperature between 45°N and 85°N (black), 90% pointwise (blue shading) and pathwise (grey) credible intervals20 (see Methods); the unweighted average of all available instrumental observations (magenta); and the ten largest volcanic eruptions in the 1400–2011 interval according to ice-core sulphate concentrations30 (vertical red). b, As in a, but individual ensemble members are first smoothed with a nine-year Hanning window, along with a separate reconstruction10 (dashed red). c, As in a, but for linear trends calculated for overlapping 100-year intervals. To facilitate comparison between the recent rate of warming and earlier rates of cooling, the median and 90% pointwise uncertainty for the cooling centred at 1596 is also inverted in sign and extended across to the modern period (red lines and shading).

  2. Warm and cold extremes.
    Figure 2: Warm and cold extremes.

    a, The proportion of draws (see Methods) for which 2003 and 2010 were warmest, and for which the warmest year fell in the 1990s and 2000s. White shading indicates zero. b, The fraction of all locations for which years were warmest or coolest, averaged across all ensemble members. Results are binned by decade, except for the last interval, which contains only 2010–2011. c, As in b, but for a reconstruction that uses only the ice-core and lake-varve series and covers the interval 1400–1994.

  3. Histograms of temperature anomalies and instrumental maxima for the period 1992-2011.
    Figure 3: Histograms of temperature anomalies and instrumental maxima for the period 1992–2011.

    a, Histogram of temperature anomalies across locations, ensemble members and years for the interval 1992–2011 (blue); the simulated distribution of temperature anomalies, using median parameter values fitted over 1400–2011 (black) and after shifting its mean to that of the 1992–2011 anomalies (dashed red). Vertical lines are repeated in each panel and correspond to the 3.8°C anomaly near Moscow in 2010 and the four other even more extreme values in the 1992–2011 interval which, from lowest to highest, are from Siberia in 2007, Svalbard in 2006 and two locations in northern Canada in 1998. b, Histogram of the maximum value of the instrumental observations at each location over the 1992–2011 interval (blue), and the distribution of the maximum values according to 10,000 realizations (black) and a single (magenta) realization based on the simulations with the mean shifted as in a. c, Distributions of the five largest simulated instrumental observations across space and time in the 1992–2011 interval, with the mean shifted as in a.

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Author information

Affiliations

  1. Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA

    • Martin P. Tingley &
    • Peter Huybers

Contributions

M.P.T. performed the analysis. Both authors contributed to the design of the analysis, the interpretation of results, and preparation of the manuscript.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to:

Data and code are available from NOAA Paleoclimatology at ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/tingley2013/.

Author details

Supplementary information

PDF files

  1. Supplementary Information (8.3 MB)

    This file contains Supplementary Figures 1-53 with legends, Supplementary Tables 1-6, Supplementary Discussion and additional references.

Zip files

  1. Supplementary Data 1 (630 KB)

    This file contains the instrumental data sets used in the analysis, in both original form and standardized as described in the Methods, in Matlab and .txt formats. Also included is a short ReadMe document that describes the data files.

  2. Supplementary Data 2 (716 KB)

    This file contains the tree ring density data sets used in the analysis, in both original form and standardized as described in the Methods, in Matlab and .txt formats. Also included is a short ReadMe document that describes the data files.

  3. Supplementary Data 3 (218 KB)

    This file contains the varve data sets used in the analysis, in both original form and standardized as described in the Methods, in Matlab and .txt formats. Also included is a short ReadMe document that describes the data files.

  4. Supplementary Data 4 (262 KB)

    This file contains the ice core data sets used in the analysis, in both original form and standardized as described in the Methods, in Matlab and .txt formats. Also included is a short ReadMe document that describes the data files.

    We are unable to host the Supplementary Code and Model output files and these can be found at the following link:- ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/tingley2013/tingley2013.zip

    These files contain a number of model outputs, available, where possible, in both Matlab and .txt formats. Also included are a number of Matlab scripts that manipulate the model output to reproduce the main features of the analysis, and a short ReadMe document that describes the data and files.

Additional data