DOI: 10.25921/njxd-hg08
title: NOAA/WDS Paleoclimatology - Globally Resolved Surface Temperatures Since the Last Glacial Maximum

description: Climate changes across the past 24,000 years provide key insights into Earth system responses to external forcing. Climate model simulations and proxy data have independently allowed for study of this crucial interval; however, they have at times yielded disparate conclusions. Here, we leverage both types of information using paleoclimate data assimilation to produce the first proxy-constrained, full-field reanalysis of surface temperature change spanning the Last Glacial Maximum to present at 200-year resolution. We demonstrate that temperature variability across the past 24 thousand years was linked to two primary climatic mechanisms: radiative forcing from ice sheets and greenhouse gases; and a superposition of changes in the ocean overturning circulation and seasonal insolation. In contrast with previous proxy-based reconstructions our results show that global mean temperature has slightly but steadily warmed, by ~0.5C, since the early Holocene (around 9 thousand years ago). When compared with recent temperature changes, our reanalysis indicates that both the rate and magnitude of modern warming are unusual relative to the changes of the past 24 thousand years.
description: This dataset contains gridded global climate reconstructions of annual mean surface air temperature (SAT), sea surface temperature (SST), d18O of precipitation (d18Op), and global mean surface temperature (GMST) from the Last Glacial Maximum Reanalysis (LGMR).  The LGMR spans the interval 24 to 0 ka BP at 200 year mean resolution, based on paleoclimate data assimilation of equilibrium "time-slice" simulations conducted at 0, 3, 6, 9, 12, 14, 16, 18, and 21 ka BP using the water isotope-enabled Community Earth System Model, versions 1.2 and 1.3 (iCESM1.2 and iCESM1.3; c.f., Methods section).   All LGMR files are provided in netCDF (.nc) format, with two files for each climate variable: an ensemble file (ens) containing all (n = 500) LGMR ensemble members, and a climatology file (climo) containing the ensemble mean and standard deviation.  Note that, due to the large size of the SST output, SST ensemble members are broken up into 10 different files each containing n = 50 ensemble members.  LGMR SAT and d18Op are provided at a horizontal resolution of 1.9deg x 2.5deg (latitude x longitude) and SST at a nominal resolution of 1deg near the equator (note both gridding schemes represent the native resolutions used by the iCESM's component atmosphere and ocean models).  In addition, all marine geochemical sea surface temperature proxy data (d18Oc, Mg/Ca, TEX86, and UK37) used in the LGMR are available in proxyDatabase.nc. Full file list: LGMR_d18Op_climo.nc, LGMR_d18Op_ens.nc, LGMR_GMST_climo.nc, LGMR_GMST_ens.nc, LGMR_SAT_climo.nc, LGMR_SAT_ens.nc, LGMR_SST_climo.nc, LGMR_SST_ens_101-150.nc, LGMR_SST_ens_1-50.nc, LGMR_SST_ens_151-200.nc, LGMR_SST_ens_201-250.nc, LGMR_SST_ens_251-300.nc, LGMR_SST_ens_301-350.nc, LGMR_SST_ens_351-400.nc, LGMR_SST_ens_401-450.nc, LGMR_SST_ens_451-500.nc, LGMR_SST_ens_51-100.nc, proxyDatabase.nc. All files available at: https://www.ncei.noaa.gov/pub/data/paleo/reconstructions/osman2021/. MATLAB code used to generate the LGMR reconstruction are available at https://github.com/JonKing93/DASH. The accompanying Bayesian proxy forward models (BAYSPAR, BAYSPLINE, BAYFOX, and BAYMAG) are at https://github.com/jesstierney. The iCESM model code is available at https://github.com/NCAR/iCESM1.2.