The influence of decision-making in tree ring-based climate reconstructions
Ulf Büntgen, Kathy Allen, Kevin J. Anchukaitis, Dominique Arseneault, Étienne Boucher, Achim Bräuning, Snigdhansu Chatterjee, Paolo Cherubini, Olga V. Churakova, Christophe Corona, Fabio Gennaretti, Jussi Grießinger, Sébastien Guillet, Joël Guiot, Björn E. Gunnarson, Samuli Helama, Philipp Hochreuther, Malcolm K. Hughes, Peter Huybers, Alexander V. Kirdyanov, Paul J. Krusic, Josef Ludescher, Wolfgang Jens-Henrik Meier, Vladimir S. Myglan, Kurt Nicolussi, Clive Oppenheimer, Frederick Reinig, Matthew W. Salzer, Kristina Seftigen, A. Stine, Markus Stoffel, Scott St. George, Ernesto Tejedor, A. M. Trevino, Valérie Trouet, Jianglin Wang, Rob Wilson, Bao Yang, Guobao Xu, Jan Esper
Abstract
Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature reconstructions from a common network of regional tree-ring width datasets. Taken together as an ensemble, the Common Era reconstruction mean correlates with instrumental temperatures from 1794-2016 CE at 0.79 (p < 0.001), reveals summer cooling in the years following large volcanic eruptions, and exhibits strong warming since the 1980s. Differing in their mean, variance, amplitude, sensitivity, and persistence, the ensemble members demonstrate the influence of subjectivity in the reconstruction process. We therefore recommend the routine use of ensemble reconstruction approaches to provide a more consensual picture of past climate variability.