London, July 15 (ANI): Climate change, especially periods of cooling, led to wars, disasters and upheaval in ancient China, new research reveals.
Zhibin Zhang of the Chinese Academy of Sciences and colleagues used historical records and paleoclimatic reconstructions covering about 2,000 years.
The team found the frequency of wars, droughts, floods, the price of rice, locust plagues and temperatures in China were strongly associated within time bands of around 160 and 320 years.
"Our study suggests that the food production during the last two millennia has been more unstable during cooler periods," The Scotsman quoted the authors, as saying.
Consequently, social conflict increased due to rebellions within dynasties and/or aggression from northern pastoral nomadic societies in ancient China, they said.
The collapses of the agricultural dynasties of the Han (206BC-AD220), Tang (681-906), Song (960-1279) and Ming (1368-1643) were more closely linked to low temperature, according to the researchers.
They said: "It is very probable that cool temperatures may be the driving force in causing high frequencies of meteorological, agricultural disasters and then manmade disasters (wars] in ancient China."
In particular, the results indicate that periodic low temperatures could have made internal wars more frequent, largely indirectly through increasing drought and locust plague frequencies, between AD950 and the 1900s.
The team believes external aggression wars mostly occurred between Chinese dynasties and the pastoral nomadic societies to their north, such as the Manchus who overthrew the Ming dynasty.
A dip in mercury by a few degrees Celsius can shorten the northern growing season of grass by 40 days, adversely affecting grasslands and causing huge losses of domestic livestock. This pushed northern tribes south.
The researchers found two predominant periodic bands of around 160 and 320 years during the past two millennia.
"These periods may be related to cyclic variations of solar activity, or cyclic changes of orbit position of the Earth," they said, pointing to 87 and 210-year cycles of solar activity based on observations of sunspots.
"It is generally believed that global warming is a threat to human societies in many ways. However, some countries or regions might also benefit from increasing temperatures in some ways," the authors added. (ANI)