It seems that climate change can topple empires.

According to an article in Nature, the Tang dynasty ended the same time as Mayan civilization because the monsoon rains were not strong enough in winter. The tropical rain belt migrated.

Widespread drought (causing poor harvests and starvation) brought both of these brilliant societies to an end.

Why you should be concerned

This is the same monsoon system that affects Southeast Asia today. Researchers wonder whether global warming could cause current governments to face the same problems as the last emperor of the Tang, and the last king of the Maya.

Asia is already running beyond its ecological means, and water is one of the most symbolic cases of this deficit.

— Rae Kwon Chung, director of the environment and sustainable development division of the United Nations Economic and Social Commission for Asia and the Pacific

Reference
Gergana Yancheva, Norbert R. Nowaczyk, Jens Mingram, Peter Dulski, Georg Schettler, Jörg F. W. Negendank, Jiaqi Liu, Daniel M. Sigman, Larry C. Peterson and Gerald H. Haug. “Influence of the intertropical convergence zone on the East Asian monsoon.” Nature 445, 74-77. January 4, 2007.