Coffin tree-ring δ¹⁸O reveals prolonged drought contributing to the collapse of the Northern Song Dynasty

The Northern Song Dynasty (960–1127 CE) was one of the most prosperous dynasties in Chinese history. In its final years, the Fang La Rebellion (1120–1122 CE), the most severe peasant rebellion of the period, erupted in the lower Yangtze River basin (LYRB) and contributed to the dynasty’s collapse. However, the role of climate in the rise of this rebellion remains unclear due to the lack of high-resolution paleoclimate records in the LYRB over this critical epoch. In this study, we constructed a tree-ring oxygen isotope (δ¹⁸O) chronology based on 954 measurements from five coffin timbers excavated in the LYRB to reflect longer-term hydroclimate variability. The chronology was cross-dated to 805–1150 CE against a tree-ring δ¹⁸O chronology from central Japan. Our tree-ring δ¹⁸O record indicates that the LYRB began to dry around the 1080s, which may have contributed to declining social resilience, as reflected in reduced cropland area, rising rice prices, and the decline of the dynastic economy. After 1101 CE, worsening drought and intensified court exploitation further heightened social tensions, contributing to the Fang La Rebellion in 1120 CE and, to some extent, the collapse of the Northern Song Dynasty.