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 600 years. 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 600 years 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.
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- Supplementary Information (8.3 MB)
This file contains Supplementary Figures 1-53 with legends, Supplementary Tables 1-6, Supplementary Discussion and additional references.
- 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.
- 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.
- 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.
- 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.