Pollen-based continental climate reconstructions for the mid-Holocene and the Last Glacial Maximum
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.
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:
text csv files
Where the variables are…
mat: Mean Annual Temperature (°C)
map: Mean Annual Precipitation (mm)
mtco: Mean Temperature of the Coldest Month (°C)
mtwa: Mean Temperature of the Warmest Month (°C)
gdd5: Growing Degree Days above 5°C (°C days)
alpha: moisture index, defined as Mean Annual Actual Evaporation/Mean Annual Potential Evaporation (no units)
… and the periods are:
variable_delta_period_ALL_grid_2x2 data file contains the following variables:
| Variable || Column|
| lat || 1 ||
Latitude of grid-cell center (degrees North)
| lon || 2 ||
Longitude of grid-cell center (degrees East)
| variable_anm_mean || 3 ||
Grid-cell mean of reconstructed anomalies
| variable_se_mean || 4 ||
Grid-cell mean of standard errors of estimates
| variable_tstat || 5 ||
t-statistic = mean anomaly / mean standard error of estimate
= variable_anm_mean / variable_se_mean
| variable_sig || 6 ||
Significance of the t-statistic: -1, 0, 1
= sign(variable_tstat) if abs(variable_tstat) > 2
= 0 if abs(variable_tstat) < = 2
| variable_sig_value || 7 ||
Value of anm_mean if the t-statistic was significant
= variable_anm_mean if variable_sig <> 0
= 0 if variable_sig == 0
| variable_npts || 8 ||
Number of sites in the grid cell
The data files distributed on the PMIP3 site have been updated (from the files originally used in the Bartlein 2011 paper) in order to correct a few values
variable_delta_period_ALL_grid_2x2_ex extended files have the same data as the corresponding
variable_delta_period_ALL_grid_2x2 files, and include additional (unpublished) speleothem data and a few sites from the Shakun et al. (2012) appendix and from the Schmittner et al. (2011) Science paper. These have been used in the Harrison et al. (2013) benchmarking paper.
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
, 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