The Rise of Genghis Khan: The world’s greatest land empire was probably encouraged by climate change
IN THE second half of the 20th century, Mongolia warmed by 2°C—an increase few, if any, other countries can match. Recent change has brought droughts and zuds (winter storms) which complicate the lives of the country’s herders of sheep, cattle and goats as they adjust to a market economy after decades of communism. This year’s meeting of the American Geophysical Union, in San Francisco, however, heard of an earlier change in the Mongolian climate that may have been responsible for complicating the lives of rather more than just a few herdsmen. For if Amy Hessl of West Virginia University and Neil Pederson of Columbia University are correct, it was an alteration in the climate that allowed Genghis Khan and his horde to conquer half of Eurasia.
The great Khan rose to power in 1206, the year he united Mongolia’s tribes behind him, and died in 1227. Dr Hessl and Dr Pederson have tree-ring data which seem to show that from 1208 to 1231 Mongolia enjoyed a string of wetter-than-usual years which was longer than any other such period in the past millennium. Previous tree-ring studies show the same period was also unusually warm.
A clement climate lasting a generation would have provided richer grazing than normal. More fodder means more horses, and thus more of the wherewithal of empire—for if an army marches on its stomach, a horde surely gallops on its grazing. No one thinks that the Great Khan himself had nothing to do with it. But his strategic genius might have been for naught if the climate had provided him only with broken-down na