For a Kinder, Gentler Society
Natural Science

Global Warming ? Climate Change ? Man Made ?

A stalagmite in a Chinese cave has provided a remarkable record of the Asian monsoon over the past 1,810 years. An analysis, published on Friday in the journal Science, suggests that a weakening of the monsoon – leading to drought and crop failures – contributed to the fall of three dynasties: the Tang, Yuan and Ming.

The 1.2-metre-long stalagmite, a column of calcium carbonate built up as mineral-rich water dripped from the cave roof, showed annual growth rings when cut open, like an ancient tree.

Scientists from Lanzhou University and the University of Minnesota analysed the shape and composition of the rings to draw up a record of rainfall and temperature over the years.

The results from Wanxiang Cave in northern China provide the most detailed evidence so far of a link between solar activity, climate and culture. For example, the fall of the Tang in the year 907 coincided with a temporary weakening of the sun, which the researchers believe led to a cooler and dryer climate.

They think that the same underlying factors were responsible for the collapse of the Maya civilisation under severe drought stress at the same time on the other side of the world.

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