Decadal East Asian monsoon anomalies and implications for societal conflicts

The East Asian summer monsoon anomalies, responsible for floods and droughts across China, pose great challenges to the climate resilience of human society. However, mechanisms and impacts of decadal-scale monsoon variability remain poorly understood, due to limited instrumental data. Our annual-resolution speleothem record (1787–2007 A.D.) from China, along with simulation results, reveals a persistent monsoon weakening since the end of the Little Ice Age, superimposed by decadal oscillations. Five monsoon extremes, triggered by diminished solar output and further amplified by ocean-atmosphere processes in the Atlantic and Pacific oceans, caused widespread megadroughts in China. One dramatic flood-drought abrupt alternation in the 1850s substantially contributed to the Taiping Rebellion (1851–1864 A.D.). Our findings demonstrate that monsoon anomalies can cause crop failure and exacerbate overpopulation, ultimately leading to social unrest, particularly in regions experiencing rapid demographic expansion.

造成中国境内洪涝与干旱灾害的东亚夏季风异常，对人类社会的气候韧性构成了严峻挑战。然而，由于器测资料有限，年代际尺度季风变率的机制与影响迄今仍未得到充分阐释。本研究基于中国区域公元1787–2007年的年分辨率洞穴碳酸盐沉积（speleothem）记录，并结合数值模拟结果，发现自小冰期末期以来，东亚夏季风呈现持续减弱趋势，且叠加有年代际振荡信号。由太阳活动减弱触发、并经大西洋与太平洋海气过程进一步放大的五次季风极端事件，曾引发中国大范围的特大干旱。19世纪50年代发生的一次剧烈洪涝-干旱突变型转换，极大地推动了太平天国运动（公元1851–1864年）的爆发。本研究结果表明，季风异常可引发作物歉收，加剧人口过剩问题，最终导致社会动荡，在人口快速增长的区域尤为突出。