In the 21st century, political leaders respond to climate change by debating carbon caps and sending delegates to international conferences. In the 13th century, Genghis Khan responded by creating an empire.
That's the conclusion of Amy Hessl, a scientist from West Virginia University who studies tree rings. While doing research in Mongolia, she and colleagues discovered evidence of a severe drought in the 1100s, followed by an unusually wet period in the early 1200s. The period corresponds to Genghis Khan's conquest of Asia.
That wet spell would have created an abundance of plant life, causing "the ideal conditions for a charismatic leader to emerge out of the chaos, develop an army and concentrate power," she told the AFP, as quoted by the BBC.
"Where it's arid, unusual moisture creates unusual plant productivity, and that translates into horsepower. Genghis was literally able to ride that wave."
The wave took the Mongol empire across Asia, from the Korean Peninsula to the Middle East, covering much of China and Russia and parts of Europe.
Hessl joins this week's Climate Cast to discuss her findings.