Letter

Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data

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Accepted:
Published online:

Abstract

A number of reconstructions of millennial-scale climate variability have been carried out in order to understand patterns of natural climate variability, on decade to century timescales, and the role of anthropogenic forcing1,2,3,4,5,6,7,8. These reconstructions have mainly used tree-ring data and other data sets of annual to decadal resolution. Lake and ocean sediments have a lower time resolution, but provide climate information at multicentennial timescales that may not be captured by tree-ring data9,10. Here we reconstruct Northern Hemisphere temperatures for the past 2,000 years by combining low-resolution proxies with tree-ring data, using a wavelet transform technique11 to achieve timescale-dependent processing of the data. Our reconstruction shows larger multicentennial variability than most previous multi-proxy reconstructions1,2,3,4,7, but agrees well with temperatures reconstructed from borehole measurements12 and with temperatures obtained with a general circulation model13,14. According to our reconstruction, high temperatures—similar to those observed in the twentieth century before 1990—occurred around ad 1000 to 1100, and minimum temperatures that are about 0.7 K below the average of 1961–90 occurred around ad 1600. This large natural variability in the past suggests an important role of natural multicentennial variability that is likely to continue.

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Acknowledgements

We thank H. von Storch, E. Zorita and F. González-Rouco for the ECHO-G data, and H. Pollack and J. Smerdon for borehole data. All these persons and J. Esper, J. Luterbacher and M. Rummukainen are thanked for comments on early versions of the manuscript. We acknowledge financial support from the Royal Swedish Academy of Sciences, the Swedish Science Council and the Russian Foundation for Basic Research.

Author information

Affiliations

  1. Department of Meteorology, Stockholm University, SE-106 91 Stockholm, Sweden

    • Anders Moberg
  2. Dynamical-Stochastical Laboratory, Hydrometeorological Research Centre of Russia, Bolshoy Predtechensky Lane 11/13, Moscow 123 242, Russia

    • Dmitry M. Sonechkin
    •  & Nina M. Datsenko
  3. Department of Physical Geography and Quaternary Geology, Stockholm University, SE-106 91 Stockholm, Sweden

    • Karin Holmgren
    •  & Wibjörn Karlén

Authors

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Competing interests

The authors declare that they have no competing financial interests.

Corresponding author

Correspondence to Anders Moberg.

Supplementary information

Word documents

  1. 1.

    Supplementary Notes

    Details about proxy data series used, with reference list.

  2. 2.

    Supplementary Methods

    Description of the methods for estimation of the uncertainties in the reconstruction.

  3. 3.

    Supplementary Data

    Data for the NH temperature reconstruction.

PDF files

  1. 1.

    Supplementary Figure 1

    Time series plots of low-resolution proxy data series.

  2. 2.

    Supplementary Figure 2

    Time series plots of tree-ring series.

  3. 3.

    Supplementary Figure 3

    Time series plot of low-frequency component of the uncalibrated reconstruction, with jack-knifed estimates and associated 95% confidence intervals for the mean.

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