Tree-ring-based winter temperature reconstruction for East Asia over the past 700 years

Almost all proxy-based temperature reconstructions for East Asia have hitherto been designed to resolve summer or annual temperature variability. Reconstruction for the winter temperature is still lacking. Here, we report an annually resolved, winter-season (December-February, DJF) temperature field reconstruction for East Asia covering the period 1300-2000 CE, based on 260 temperature-sensitive tree-ring records. The most striking feature of our new reconstruction is a significant long-term warming trend since the 14th century, which is associated with winter solar insolation at mid-latitudes of the Northern Hemisphere and the global anthropogenic impact. The amplitude of reconstructed winter temperature change over the study period was similar to 4.7 times greater than that for summer temperature, and the rate of winter temperature increase was similar to 6 times as much as that of summer temperature. The results from climate model simulations were consistent with the reconstruction, showing that the amplitude and rate of temperature change in winter were greater than that in summer. The reconstruction also suggests the possible influence of volcanic eruptions, anthropogenic activities and winter solar insolation on the winter temperature variations. Our result also suggests a long-term decrease in summer-to-winter temperature difference occurred in 1625 (+/- 24 years) CE.