A new multivariable benchmark for Last Glacial Maximum climate simulations
File(s)
Author(s)
Cleator, Sean F
Harrison, Sandy P
Nichols, Nancy K
Prentice, I Colin
Roulstone, Ian
Type
Journal Article
Abstract
We present a new global reconstruction of seasonal climates at the Last Glacial Maximum (LGM, 21 000 years BP) made using 3-D variational data assimilation with pollen-based site reconstructions of six climate variables and the ensemble average of the PMIP3—CMIP5 simulations as a prior (initial estimate of LGM climate). We assume that the correlation matrix of the uncertainties in the prior is both spatially and temporally Gaussian, in order to produce a climate reconstruction that is smoothed both from month to month and from grid cell to grid cell. The pollen-based reconstructions include mean annual temperature (MAT), mean temperature of the coldest month (MTCO), mean temperature of the warmest month (MTWA), growing season warmth as measured by growing degree days above a baseline of 5 ∘C (GDD5), mean annual precipitation (MAP), and a moisture index (MI), which is the ratio of MAP to mean annual potential evapotranspiration. Different variables are reconstructed at different sites, but our approach both preserves seasonal relationships and allows a more complete set of seasonal climate variables to be derived at each location. We further account for the ecophysiological effects of low atmospheric carbon dioxide concentration on vegetation in making reconstructions of MAP and MI. This adjustment results in the reconstruction of wetter climates than might otherwise be inferred from the vegetation composition. Finally, by comparing the uncertainty contribution to the final reconstruction, we provide confidence intervals on these reconstructions and delimit geographical regions for which the palaeodata provide no information to constrain the climate reconstructions. The new reconstructions will provide a benchmark created using clear and defined mathematical procedures that can be used for evaluation of the PMIP4–CMIP6 entry-card LGM simulations and are available at https://doi.org/10.17864/1947.244 (Cleator et al., 2020b).
Date Issued
2020-04-06
Date Acceptance
2019-11-02
Citation
Climate of the Past, 2020, 16 (2), pp.699-712
ISSN
1814-9324
Publisher
Copernicus Publications
Start Page
699
End Page
712
Journal / Book Title
Climate of the Past
Volume
16
Issue
2
Copyright Statement
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
License URL
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000524489800002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Geosciences, Multidisciplinary
Meteorology & Atmospheric Sciences
Geology
MIDHOLOCENE CLIMATE
ATMOSPHERIC CO2
SYSTEM MODEL
POLLEN DATA
VEGETATION
RECONSTRUCTION
PALEOCLIMATE
PRECIPITATION
CONSTRAINTS
CIRCULATION
Publication Status
Published
Date Publish Online
2020-04-06