A new study of tree rings revealed that Mongol horsemen were able to invade Asia about eight centuries ago through the help of rain.
Researchers from the Lamont-Doherty Earth Observatory in Columbia University concluded that the abundant rain showers and calm weather aided the Mongols in invading almost all parts of Asia sometime between 1211 and 1225.
In the study, they analyzed tree rings of Siberian pines in the Hangay Mountains of central Mongolia and made an accurate chronology of local climatic conditions that occurred from the 900 A.D. up to the present.
It was long believed that Mongols, during certain seasons, leave their mountainous homeland due to severe climate conditions. However, this new study revealed that the rise of Genghis Khan and the Mongol empire corresponds in the season of extensive good climate conditions in certain regions.
"What makes our new record distinctive is that we can see 15 straight years of above-average moisture," said lead study author, Neil Pedersen, a tree-ring scientist with the Lamond-Doherty Earth Observatory, to National Geographic. "It falls during an important period in Mongol history and is singular in terms of persistently wet conditions."
Extensive good climate conditions brought richer and greener pasture, and increased in herds of livestock and war horses, which Mongols took as an opportunity to carry out their plans.
"The transition from extreme drought to extreme moisture strongly suggests that climate played a role in human events," said study co-author Amy Hessl, a tree-ring scientist in the University of West Virginia in Morgantown, to National Geographic. "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. Where it's arid, unusual moisture creates unusual plant productivity, and that translates into horsepower-literally. Genghis was able ride that wave."
Further details of this study can be read on the March 10 issue of the Proceedings of the National Academy of Sciences.
