Revising midlatitude summer temperatures back to A.D. 600 based on a wood density network

Annually resolved and millennium‐long reconstructions of large‐scale temperature variability are primarily composed of tree ring width (TRW) chronologies. Changes in ring width, however, have recently been shown to bias the ratio between low‐ and high‐frequency signals. To overcome limitations in capturing the full spectrum of past temperature variability, we present a network of 15 maximum latewood density (MXD) chronologies distributed across the Northern Hemisphere extratropics. Independent subsets of continental‐scale records consistently reveal high MXD before 1580 and after 1910, with below average values between these periods. Reconstructed extratropical summer temperatures reflect not only these long‐term trends but also distinct cooling pulses after large volcanic eruptions. In contrast to TRW‐dominated reconstructions, this MXD‐based record indicates a delayed onset of the Little Ice Age by almost two centuries. The reduced memory inherent in MXD is likely responsible for the rapid recovery from volcanic‐induced cooling in the fourteenth century and the continuation of warmer temperatures until ~1600. Key Points First millennial climate reconstruction based on extratropical tree ring density network Improved ratio between low‐ and high‐frequency temperature variability New insights into postvolcanic cooling and the onset of the Little Ice Age