Continental climate reconstructions for mid-Holocene and Last Glacial Maximum

Pollen-based continental climate reconstructions for the mid-Holocene and the Last Glacial Maximum

Main reference: Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis Bartlein, P. J., S. P. Harrison, S. Brewer, S. Connor, B. A. S. Davis, K. Gajewski, J. Guiot, T. I. Harrison-Prentice, A. Henderson, O. Peyron, I. C. Prentice, M. Scholze, H. Seppä, B. Shuman, S. Sugita, R. S. Thompson, A. E. Viau, J. Williams, H. Wu, 2011. , Climate Dynamics, 37, 775-802. DOI 10.1007/s00382-010-0904-1

These data are a synthesis of existing and available quantitative reconstructions of six bioclimatic variables based on fossil pollen for the mid-Holocene and the Last Glacial Maximum. The reconstructions are expressed as anomalies and associated uncertainties on a 2×2-degree grid. The data were gridded by simple averaging of the reconstructions in individual grid cells, and the uncertainties were obtained by pooling the prediction error estimates of individual reconstructions. No attempt was made to interpolate or fill in empty grid points.

Click on the pictures below to download the HIGH resolution pdf
mid- Holocene	Last Glacial Maximum

Please see the original paper for exact definitions of the time slices used here, the specific approaches used in synthesizing data from multiple sources, and recommendations for the use of the data in data-model comparisons.

The gridded reconstructions are available in two formats (binary and text), with one file per variable and per period:

netCDF binary files: variable_delta_period_ALL_grid_2x2.nc

text (.csv) files: variable_delta_period_ALL_grid_2x2.csv

Where the variables are...

mat: Mean Annual Temperature

map: Mean Annual Precipitation

mtco: Mean Temperature of the Coldest Month

mtwa: Mean Temperature of the Warmest Month

gdd5: Growing Degree Days above 5°C

alpha: moisture index, defined as Mean Annual Actual Evaporation/Mean Annual Potential Evaporation

... and the periods are:

06ka: mid Holocene

21ka: Last Glacial Maximum

Each file contains the latitudes and longitudes of the grid, along with 7 variables:

variable_anm_mean: grid-cell mean of reconstructed anomalies

variable_se_mean: grid-cell mean of standard errors of estimates

variable_tstat: mean anomaly / mean standard error of estimate (anm_mean/se_mean

variable_sig: = sign(t) if abs(t) > 2 (same for all variables?)

variable_sig_val: =anm_mean if sig.ne.0

variable_npts: number of sites in grid box

< Jean-Yves, là, il faut mettre les derniers fichiers de Bart, et mettre à jour la paragraphe ci-dessus pour les formats disponibles >

Click here to access the data

Extension of the Bartlein et al (2011) reconstructions

Main reference: Harrison et al?

The following files are “extended” files with additional (unpublished) speleothem data and a few sites from the Shakun et al. appendix from the Schmittner et al. (2011) Science paper. These have been used in the Harrison et al. “benchmarking” paper.

map_delta_06ka_ALL_grid_2x2_ex.csv

mat_delta_06ka_ALL_grid_2x2_ex.csv

mat_delta_21ka_ALL_grid_2x2_ex.csv

map_delta_06ka_ALL_grid_2x2_ex.nc

mat_delta_06ka_ALL_grid_2x2_ex.nc

mat_delta_21ka_ALL_grid_2x2_ex.nc

The additions consist of:

Last Glacial Maximum, Mean Annual Temperatures: 1 speleothem record and 2 terrestrial records from Shakun et al.

Mid-Holocene, Mean Annual Temperatures: 3 speleothem records

Mid-Holocene, Mean Annual Precipitation: 4 speleothem records

The organisation of the files are the same as described in section 1 above.

References:

Schmittner, A., N. M. Urban, J. D. Shakun, N. M. Mahowald, P. U. Clark, P. J. Bartlein, A. C. Mix, A. Rosell-Melé, 2011. Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum. Science, 334, 1385-1388, DOI: 10.1126/science.1203513

Shakun, J. D., P. U. Clark, F. He, S. A. Marcott, A. C. Mix, Z. Liu, B. Otto-Bliesner, A. Schmittner and E. Bard, 2012. Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation, Nature, 484, 49-55, DOI:10.1038/nature10915

Harrison, S. P., P. J. Bartlein, S. Brewer, I. C. Prentice, M. Boyd, I. Hessler, K. Holmgren, K. Izumi, K. Willis, 2013. Climate model benchmarking with glacial and mid-Holocene climates. Climate Dynamics, DOI 10.1007/s00382-013-1922-6

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