In just a few years in the early 1200s, Genghis Khan united the fractious Mongol tribes into a conquering army. According to the new study of tree rings from a stand of stunted Siberian pines in the Khangai Mountains, his rise coincided with a period during which the normally cold, arid steppes of Central Asia saw their mildest, wettest weather in more than 1,000 years. Such conditions would likely have led to a boom in grass production, helping to fuel an increase in number of war horses and other livestock.
The tree rings, which span 1,112 years, from 900 to 2011, also suggest that recent droughts in the region were the most extreme during that period. Over the past 40 years, temperatures in parts of Mongolia have risen by as much as 2.5°C. And, since the 1990s, the country has suffered a series of devastating summer droughts. The tree rings show that the most recent, from 2002 to 2009, compares in length and paucity of rainfall only to those of the pre-empire 1120s and 1180s.
‘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 the study’s lead author, Neil Pederson of Columbia University in New York.
This story was published in the May 2014 edition of Geographical Magazine