Climatic patterns of cave mineral deposits associated with the collapse of Chinese dynasties

The history of Chinese dynasties spans 13 reigns from 2070 BC to the abdication of the last emperor in 1912. While the factors leading to inter-dynastic transitions are a complex mix of environmental, social and economic issues, the role of climate change is often cited as an issue. Key factors in these geopolitical changes. This is because China’s pre-industrial dependence on agriculture meant that the country was sensitive to rapid changes in climate, which could have various social and economic consequences. be.

A new study published in the journal Quaternary Science Reviews focuses on the role that changes in precipitation patterns may have played, particularly in relation to the variability of the Asian monsoon. These natural phenomena result in cold, dry winters leading to droughts, warm and wet summers with heavy rains from May to September, and tropical cyclones that make landfall and cause destruction.

To investigate this, Dr. Haowen Fan of the China University of Geosciences and colleagues analyzed 2,000 years of limestone cave records from the Heshang Cave in central China. These deposits form within caves, accumulate as calcium leaches from groundwater, and are commonly known as stalactites (growing from the ceiling of a cave) and stalagmites (growing from the floor of a cave).

Within these caves, annual growth zones exist as distinct layers from which oxygen isotopes (δ18O) were measured as a proxy for monsoon precipitation over time. For example, during the period 1–400 AD, stalactite δ18O was depleted and coincided with the Roman Warm Period, when precipitation increased, but in the following period, 400–800 AD, δ18O increased and precipitation decreased. It corresponds to the cold period of the Dark Ages.

The researchers found that these periods occur more frequently when the Asian monsoon is in positive phase (when sea surface temperatures are higher in the western Indian Ocean and lower in the eastern Indian Ocean, and therefore precipitation is higher in the west and lower in the east). discovered. It coincided with the evolution of Chinese dynasties on timescales of decades (peak periods of 13, 35, and 75 years). In particular, prolonged drought in eastern China reduced grain yields, raising issues of food sustainability and economic decline.

Importantly, Dr. Huang points out that the variation in climate patterns across China leading to social unrest, rather than universal changes across the country, is an important finding. More than 80% of China’s population has lived in eastern China since 221 B.C., forming the core region of dynasties such as the Han, Tang, Northern Song, Yuan, Ming, and Qing, and the region is at risk from climate change. This is an area that is highly susceptible to impacts. -economy.

For example, the Wei, Jin, and Northern and Southern Dynasties (181–540 AD) and the Tang Dynasty (618–907 AD) occurred during cold periods when the monsoon was weak, whereas the Ming and Qing dynasties (1321–1920 ) became popular during relatively cold seasons. Warm conditions where the monsoon was stronger. The weakest monsoon on record occurred between 1500 and 1650 AD, coinciding with the collapse of the Ming Dynasty. At this time, conditions worsened through the Little Ice Age, droughts reduced grain yields by 20% to 50% per capita, and rebellions occurred that overthrew dynasties.

Linking monsoon phases, drought, and water scarcity that affected ancient agriculture shows how reduced food supplies led to famine, economic depression, and ultimately civil wars that changed the course of China’s history. It gives an interesting insight into what’s going on.

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