Reconciling divergent trends and millennial variations in Holocene temperatures

  • Nature volume 554, pages 9296 (01 February 2018)
  • doi:10.1038/nature25464
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Cooling during most of the past two millennia has been widely recognized1,2 and has been inferred to be the dominant global temperature trend of the past 11,700 years (the Holocene epoch)3. However, long-term cooling has been difficult to reconcile with global forcing4, and climate models consistently simulate long-term warming4. The divergence between simulations and reconstructions emerges primarily for northern mid-latitudes, for which pronounced cooling has been inferred from marine and coastal records using multiple approaches3. Here we show that temperatures reconstructed from sub-fossil pollen from 642 sites across North America and Europe closely match simulations, and that long-term warming, not cooling, defined the Holocene until around 2,000 years ago. The reconstructions indicate that evidence of long-term cooling was limited to North Atlantic records. Early Holocene temperatures on the continents were more than two degrees Celsius below those of the past two millennia, consistent with the simulated effects of remnant ice sheets in the climate model Community Climate System Model 3 (CCSM3)5. CCSM3 simulates increases in ‘growing degree days’—a measure of the accumulated warmth above five degrees Celsius per year—of more than 300 kelvin days over the Holocene, consistent with inferences from the pollen data. It also simulates a decrease in mean summer temperatures of more than two degrees Celsius, which correlates with reconstructed marine trends and highlights the potential importance of the different subseasonal sensitivities of the records. Despite the differing trends, pollen- and marine-based reconstructions are correlated at millennial-to-centennial scales, probably in response to ice-sheet and meltwater dynamics, and to stochastic dynamics similar to the temperature variations produced by CCSM3. Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation, they reinforce the notion that climate models can adequately simulate climates for periods other than the present-day. They also demonstrate that amplified warming in recent decades increased temperatures above the mean of any century during the past 11,000 years.

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We thank T. Webb, S. Marcott, J. Shinker, T. Minckley, B. McElroy and E. Currano for comments. Data were obtained from the Neotoma and European Pollen Databases, and we acknowledge the work of the data contributors and the Neotoma and European Pollen Database communities. TraCE-21ka was made possible by the DOE INCITE computing programme, and supported by NCAR, the NSF P2C2 programme, and the DOE Abrupt Change and EaSM programmes. Funding was provided by Wyoming NASA Space Grant (#NNX10AO95H) and EPA STAR (FP-91763201-0) to J.M., and NSF support to B.N.S. (DEB-1146297), S.B. (EAR-1003848) and P.J.B. (ATM-06202409). S.L.S. was supported by the US Geological Survey Climate Research and Development Program.

Author information


  1. Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82072, USA

    • Jeremiah Marsicek
    •  & Bryan N. Shuman
  2. Department of Geography, University of Oregon, Eugene, Oregon 97403, USA

    • Patrick J. Bartlein
  3. US Geological Survey, Corvallis, Oregon 97331, USA

    • Sarah L. Shafer
  4. Department of Geography, University of Utah, Salt Lake City, Utah 84112, USA

    • Simon Brewer


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J.M. and B.N.S. oversaw and contributed to all aspects of the research and, with S.B., designed the project. P.J.B. and S.L.S. contributed analyses of the CCSM3 climate model simulation. J.M. and B.N.S. carried out the analyses and wrote the first version of the paper, and J.M., B.N.S., P.J.B. and S.L.S. contributed to the final version.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Jeremiah Marsicek.

Reviewer Information Nature thanks M. Haran and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Supplementary information

Excel files

  1. 1.

    Supplementary Table 1

    Taxa used in pollen-based climate reconstructions. Table comprising the specific taxa used in the pollen-based climate reconstructions for North America and Europe.

  2. 2.

    Supplementary Table 2

    Significant sites and sites used in modern analog technique analysis. Site table containing all of the details for sites deemed significant by our analysis, and the sites used in our analyses. These include the latitude, longitude, elevation, significance values for each variable for each site, the number of samples the site contains throughout the last 11,000 years, and the age model assigned to the core data.


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