NOAA/WDS Paleoclimatology - East Asia 600 Year Seasonal Temperature Reconstructions using Tree-Ring Records

Seasonal differences of extra-tropical temperature are crucial components of the Earth's climate system. However, the relatively short observational record, especially for East Asia, has limited progress in understanding seasonal differences. In this study, we identify ten tree-ring chronologies separately correlated with local winter (December-February) temperatures and twelve different tree-ring chronologies separately correlated with summer (June-August) temperatures across East Asia. Using these discrete seasonal tree-ring chronologies, we develop two independent winter and summer temperature reconstructions covering the period 1376-1995 CE for East Asia, and compare them with model simulations. Our reconstructions show a more significant volcanic cooling and earlier onset of modern warming in summer than in winter. The reconstructed summer-minus-winter temperature difference decreased since as early as the late 19th century, which has driven the current state of seasonal difference to outside the natural variability range since the 1370s. Climate models could generally reproduce the variability and trends in seasonal reconstructions, but might largely underestimate seasonal differences due to the fact that seasonal expressions on external forcing and modes of internal variability are too small. Our study highlights the importance of using proxy-based seasonal reconstructions to evaluate the performance of climate models, and implies a substantial weakening of seasonal temperature differences in the future.