Yan Zhao, Feng Qin, Quan Li, Qiaoyu Cui, Polychronis C Tzedakis, Chen Liang, Chenglong Deng, Yifan Cui, Wenwei Zhao, Weihe Ren, Junyi Ge, Qiuzhen Yin, Zhipeng Wu, Mingqiang Liang, Yaoliang Liu, Zhiyong Zhang, Maotang Cai, Haicheng Wei, Yanfen Kong, Huan Li, Hongyi Qiu, Haitao Xu, Hanfei Yang, Haoshuang Han, David A Hodell, H John B Birks, Zhengtang Guo
Earth's climate has experienced abrupt millennial-scale climate variability (MCV) at least since the early Pleistocene, yet their evolution and drivers remain elusive. A 3.5-million-year decadal-to-centennial-resolved lake sediment sequence from the monsoonal Tibetan Plateau reveals a stepped evolution of MCV that differs in detail from that of North Atlantic records. Lithological and pollen changes show precursor millennial events during the interval ~ 3.5-2.7 million years ago (Ma), with the onset of multiple events at ~ 2.8 Ma. From ~ 2.7 Ma, MCV became a permanent feature of glacial periods, intensifying after ~ 1.5 Ma and extending over both glacial and interglacial periods. The embedded astronomical frequencies of MCV and their persistent linkage with precession indicate a tropical insolation origin, driven by changes in the latitudinal temperature gradient and propagated to the Tibetan Plateau via monsoonal circulation. These findings highlight that both tropical forcing and high-latitude ice-dynamic mechanisms should be considered as "dual engines" of MCV.