Meta-analysis of tropical surface temperatures during the Last Glacial Maximum

The magnitude of tropical cooling during the Last Glacial Maximum (LGM) has been the subject of uncertainty for over 25 years. We use principles of meta-analysis as an objective approach to reconcile estimates from different proxies. This approach treats each observation as a random estimate of the true mean and weights estimates by their reported precision. We assigned global uncertainties to proxies and derived a new regional standard deviation for temperatures calculated from the Sr/Ca ratio in tropical corals (sigma = 1.4 degrees C). Using a Bayesian spatial interpolation scheme, we estimate a mean cooling of LGM tropical sea surface temperatures of -2.7 +/- 0.5 degrees C (+/-sigma) and surface air temperatures of -5.4 +/- 0.3 degrees C (+/-sigma).