March 12, 2014
Ghengis Khan’s Rule Was Aided By A Warm, Wet Climate: Study
Brett Smith for redOrbit.com - Your Universe Online
The 13th century Mongolian conqueror Genghis Khan relied on hordes of Mongol warriors to expand his empire. Now, according to a new study in the Proceedings of the National Academy of Sciences, it has been determined that Genghis was also aided by the favorable effects of climate change.
In the report, a team of American and Mongolian scientists described how they used an analysis of tree rings to show that from 1211 to 1225 Mongolia experienced a period of relatively warmer and wetter weather – a stark contrast from previous decades that were marked by severe drought.
“The transition from extreme drought to extreme moisture right then strongly suggests that climate played a role in human events,” said study author Amy Hessl, a tree-ring scientist at West Virginia University. “It wasn’t the only thing, but it must have created the ideal conditions for a charismatic leader to emerge out of the chaos, develop an army and concentrate power.”
The study team noted that a shift to a warmer and wetter climate would have boosted grass production on the Mongolian steppes. This increase in production would have helped the Mongols to raise the legions of horses they would later use to conquer most of Asia.
“Where it’s arid, unusual moisture creates unusual plant productivity, and that translates into horsepower,” Hessl said. “Genghis was literally able to ride that wave.”
For the study, the team sampled tree rings from a clutch of Siberian pines that were rising from an old lava flow in the Khangai Mountains in Mongolia. The scientists took cross-sections from dead specimens and benignly extracted cores from living ones. They learned that some trees had lived for greater than 1,100 years and probably could survive for another millennium; even dead trunks remained largely intact for 1,000 years before rotting. One sample was found to have rings going back to about 650 BC. These annual rings change with temperature and rainfall, allowing the team to determine past weather by calibrating ring widths of living trees with information from 1959-2009, then comparing these with the cross-sections of much older trees.
The team found that the years preceding Genghis Khan’s rule were marked by intense drought from 1180 to 1190. Then, from 1211 to 1225, Mongolia observed regular rainfall and mild warmth – which coincided with the rapid rise of Genghis Khan.
The researchers also found that after the Mongol empire expanded – the region’s climate reverted back to its old pattern of dry, cold weather. The team added that many climate models show this part of Asia will be warming much faster than the rest of the world in the coming years – potentially reducing livestock and stifling the few crops on Mongolia’s already scarce arable land.
“This last big drought is an example of what may happen in the future, not just in Mongolia but in a lot of inner Asia,” said study author Neil Pederson, a tree-ring scientist at Columbia University. “The heat is a double whammy—even if rainfall doesn’t change, the landscape is going to get drier.”