In the thirteenth-century a Mongol warrior named Genghis Khan took control of the nomadic tribes on the Great Stepee and launched a series of invasions that would see a vast empire being established from China to Eastern Europe. Now a team of researchers have shown that their success can be partly attributed to climate change.
The report, “Pluvials, Droughts, the Mongol Empire, and Modern Mongolia,” is co-authored by several scholars including Amy Hessl of West Virginia University, Nicola Di Cosmo of the Institute for Advanced Study, and Neil Pederson of Columbia University’s Lamont-Doherty Earth Observatory. It appears in the latest issue of the Proceedings of the National Academy of Sciences.
This paper is the first official academic record of the research based on amazing find by Hessl and Pederson in 2010. They came across a stand of ancient Siberian pines growing in an old lava field in the Khangai Mountains of Central Mongolia. Taking cross-sections of dead trees and samples from living ones, they have been able to use the tree-rings to determine weather going back 1,112 years.
Further research in Mongolia has led to discovery of trees that lived over 1700 years ago. The tree rings’ tale of ebbs and flows in water availability show that from 1180 to 1190 there was an intense drought, leading to political instability. By the end of that decade Genghis had taken control of the Mongol tribe, and in the following years conquered the other nomadic peoples
The researchers then found that starting in 1211, the Mongol steppe would see fifteen years of heavy rains, one of the wettest periods the region has ever seen. This produced a boom in the growth of wild grasses, which fed the Mongols horses and livestock. “The weather may literally have supplied the Mongols with the horsepower they needed to do what they did,” explained Pederson.
In 1215, Genghis Khan captured the capital city of China’s Jin Dynasty, and four years later the Mongols went to war with the Khwarezmian Empire in Central Asia, annihilating them within a few years. Over the following decades they also conquered Russia and parts of Eastern Europe, took control of most of China, and even toppled the Abbasid Caliphate in Baghdad.
The weather was not always favourable to the Mongols – there was a cold snap between 1260 and 1266, which coincided with the breakup of their empire into four regional powers.
Though political realities would have also featured into Genghis Khan’s power grab, the regional climate at the time appeared to support the empire’s expansion, according to the findings. The climate provided literal horsepower as his armies and their horses fed off the fertile land.
“The transition from extreme drought to extreme moisture right then strongly suggests that climate played a role in human events,” added Hessl. “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. Genghis was literally able to ride that wave.”
While the ramifications for history are significant, so are those for today. The report’s authors posit that human-caused warming has “exacerbated” the drought in central Mongolia, similar to a drought event that coincided with Genghis Khan’s rise to power.
“If future warming overwhelms increased precipitation, episodic ‘heat droughts’ and their social, economic, and political consequences will likely become more common in Mongolia and Inner Asia,” according to the report.
Sources: West Virginia University, Columbia University