Temperature reconstructions from tree‐ring densities overestimate volcanic cooling

Martin P Tingley,Peter Huybers,Alexander R Stine

doi:10.1002/2014gl061268

Abstract

AbstractThe fidelity of inferences on volcanic cooling from tree‐ring density records has recently come into question, with competing claims that temperature reconstructions based on tree‐ring records underestimate cooling due to an increased likelihood of missing rings or overestimate cooling due to reduced light availability accentuating the response. Here we test these competing hypotheses in the latitudes poleward of 45°N, using the two eruptions occurring between 1850 and 1960 with large‐scale Northern Hemisphere climatic effects: Novarupta (1912) and Krakatau (1883). We find that tree‐ring densities overestimate postvolcanic cooling with respect to instrumental data (Probability≥0.99), with larger magnitudes of bias where growth is more limited by light availability (Prob.≥0.95). Using a methodology that allows for direct comparisons with instrumental data, our results confirm that high‐latitude tree‐ring densities record not only temperature but also variations in light availability.

Highlights

Tree-ring proxies are widely available at high northern latitudes and underpin many annually resolved reconstructions of climate over the Common Era [National Research Council, 2006; Jones et al, 2009; Masson-Delmotte et al, 2013]
The fidelity of inferences on volcanic cooling from tree-ring density records has recently come into question, with competing claims that temperature reconstructions based on tree-ring records underestimate cooling due to an increased likelihood of missing rings or overestimate cooling due to reduced light availability accentuating the response
Results support the SH14 hypothesis that reduction in light availability accentuates the maximum latewood density (MXD) response to volcanic events in regions that are most light limited

Summary

Introduction

Tree-ring proxies are widely available at high northern latitudes and underpin many annually resolved reconstructions of climate over the Common Era [National Research Council, 2006; Jones et al, 2009; Masson-Delmotte et al, 2013]. As they represent the response of dynamic and complex organisms to the ambient environment, some nuance in their interoperation is to be expected. We further investigate the fidelity of the maximum latewood density response to volcanic cooling in latitudes north of 45◦N and the roles played by climatological spatial patterns of the relative importance of light availability and temperature in limiting plant growth [Nemani et al, 2003]. The 1912 Alaskan eruption of Katmai, more accurately called Novarupta [Ohvril et al, 2009], and the 1883 Indonesian eruption of Krakatau are the two events that meet these criteria

Data and Methods

Results

Discussion and Conclusions