The Spring-Autumn and Warring States period coldness (400–350 BCE) contributed to the social unrest evidenced from coffin tree rings in southeastern China

Abstract

China's Spring and Autumn and Warring States period (SAWS, 770–221 BCE) marked the transition from feudal fragmentation to centralized imperial rule. The southeastern region of China, a crucial area for early civilization and socio-economic development, has generally yielded tree-ring paleoclimate records with precise dating shorter than 400 years, thereby limiting research on climatic influences during this epoch. Here, we analyzed coffins unearthed from four archaeological sites dating to the SAWS period in northern Jiangsu, southeastern China. We identified the species as Phoebe spp. wood of Lauraceae based on its wood anatomical features. We established four floating chronologies spanning 200–400 years, with radiocarbon dating constraining the temporal ranges to the SAWS period. Our floating chronology represents large-scale temperature variability as indicated by a significantly positive correlation with Northern Hemisphere temperature (NHT) reconstruction. Given the close matches between the floating chronology and NHT, we thus dated the chronology to 492–63 BCE. An anomalous cooling event occurred around 400–350 BCE for the overall warm 492–63 BCE period, coinciding with reduced solar activity. Our study reveals that this cold event may have indirectly triggered frequent large-scale wars and reforms in China's SAWS period. It also coincided with the social unrest in contemporaneous Europe and had widespread impacts. This study provides critical archaeological tree-ring data from a typical monsoon region in China, revealing the significant influence of abrupt climatic events on early society in monsoon regions.