Jottings from the Granite Studio

Via CDT, an interesting piece that argues the Tang dynasty may have been done in by climate change. (The full report can be found in the journal Nature, but is available to subscribers only.)

According to a collaborative effort between scientists from Germany and China, between 700 and 900 CE the climate changed, the winter monsoon was strong but the summer monsoons weakened. This period was also marked by cooler temperatures and shorter growing seasons.

What eventually brought down the dynasty were the prolonged droughts, which caused significant crops failures and subsequent peasant uprisings. This ultimately led to the collapse of the dynasty in 907.

The team led by Gerald Haug of the Geoforschungszentrum (GFZ) in Potsdam, eastern Germany, suggests that this shift in tropical precipitation occurred on both sides of the Pacific, and not just in coastal East Asia.

The same migration of the rainband occurred in Central America and doomed the so-called classic period of the Mayan civilisation, at almost exactly the same time as the Tang era, they state in this week’s Nature.

Comparisons of the titanium records from the Huguangyan Lake, in Guangdong province, and from the Cariaco basin, in Venezuela, have thrown up remarkable similarities.

Both suggest a general shift towards a drier climate at around 750 and then, during this generally drier period, three-year cycles in which rainfall was very low would ensue.

And here I was thinking the fall of the Tang was all Yang Guifei and An Lushan’s fault.

Climate change has also been cited as a factor in both the medieval economic revolution of the Song and the downfall of the Ming, corresponding to patterns some historians and climatologists have dubbed the “Medieval Warm Period” of the 11th and 12th centuries and the “Little Ice Age” of the early 17th century.”

There is also, of course, Mark Elvin’s theory in The Retreat of the Elephants that the expansion of Chinese civilization has radically changed the environment and ecology of China in a process that dates back millennia.

The truth is, as the authors of the report note, there is very rarely any single cause that can bring about the fall of a civilization or a dynasty. While climatic shifts could affect agricultural production, this would likely be a contributing factor rather than a “smoking gun.”

But that said, in recorded human history, the Earth has never been as warm as it is right now nor has it warmed so rapidly. We are testing the limits of the Earth’s ability to heal, and while I would not attribute the fall of past civilizations solely to climate change, I can’t be so sure about present ones.
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Update: The exceptional Chinese history group blog Frog in a Well is also following this story and raises some good points about just how important the monsoon would or would not have been to Tang agriculture.