Comparison and Calibration of Climate Proxy Data in Medieval Europe

Abstract

Two major sources of information on paleoclimate are historical documentary and scientific paleo proxy data. Recently, interdisciplinary research groups have sought to mesh historical and scientific data to gain a transformative understanding of paleoclimate, but the consilient study of climate history has generally lacked a statistical framework. This study develops a statistically robust methodology which considers anomalously extreme years within a database of documentary reports originally gathered from Medieval European manuscripts by the historian Pierre Alexandre. After spatially and temporally calibrating relevant paleo proxy temperature and precipitation reconstructions available through the National Oceanic and Atmospheric Administration with modern instrumental data from the Climatic Research Unit at the University of East Anglia, we sought to determine whether the historically anomalous years also stood out in the scientific record. We considered paleoclimate proxies from tree rings, speleothems, and varved lake cores. Results indicate that the year 1137 C.E., an extremely hot and dry year in the historical record, is statistically anomalous in both suites of temperature and precipitation reconstructions. Instances of extreme heat event years in the documentary record stand out in both temperature and precipitation reconstructions, while extreme precipitation event years do not, potentially due to a disconnect between the types of precipitation events emphasized by historical and scientific climate proxies. This result adds to the growing evidence of the ability to statistically identify climate events in both natural and written records. It also suggests that future studies should use statistical methods rather than corroboration when comparing scientific and historical data sets.