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A modern Mongolian man on a horse.

Some 800 years ago, ancestors of modern Mongolians conquered the world on horseback. A period of unusually mild weather may have helped propel them by making them rich in livestock.

  PHOTOGRAPH BY KEVIN KRAJICK/THE EARTH INSTITUTE, COLUMBIA UNIVERSITY

Roff Smith

National Geographic

Published March 10, 2014

For unsuspecting herdsmen in the 13th century, April showers didn't bring May flowers—they brought Mongol hordes.

New research by tree-ring scientists from Columbia University's Lamont-Doherty Earth Observatory and West Virginia University may have uncovered the reason why an obscure band of nomadic Mongol horsemen were able to sweep through much of Asia in a few meteoric decades 800 years ago, conquering everything in their path: They enjoyed an unprecedented, and yet-to-be-repeated, 15-year run of bountiful rains and mild weather on the normally cold and arid steppes.

By sampling tree rings in the gnarled and twisted Siberian pines in the Hangay Mountains in central Mongolia, the team pieced together a remarkably precise chronology of local climatic conditions stretching from the year 900 A.D. to the present. The study, published in this week's Proceedings of the National Academy of Sciences, offers a new interpretation of why the Mongols suddenly went on the move.

A photo of a gnarled tree in a lava field in Mongolia.
To create the climatic chronology, the researchers sampled tree rings in ancient Siberian pines (like the one above) in the Hangay Mountains in central Mongolia.
PHOTOGRAPH BY KEVIN KRAJICK/THE EARTH INSTITUTE, COLUMBIA UNIVERSITY

The traditional view has been that the Mongols were desperately fleeing harsh conditions in their craggy, mountainous homeland. The Lamont-Doherty team, however, found just the opposite: Between 1211 and 1225—a period that neatly coincides with the rise of Genghis Khan and the Mongol empire—central Mongolia enjoyed a spell of sustained benign weather unlike anything the region has experienced during at least the past 1,100 years and probably much longer.

"What makes our new record distinctive is that we can see 15 straight years of above-average moisture," says the study's lead author, Neil Pedersen, a tree-ring scientist with the Lamond-Doherty Earth Observatory. "It falls during an important period in Mongol history and is singular in terms of persistently wet conditions."

A photo of a gnarled tree in a lava field in Mongolia.

More Grass, More Horses, More Power

The long run of unusually good conditions meant abundant grasses and a huge increase in herds of livestock and war horses that became the basis of Mongol power—a marked contrast to the long and exceptionally severe droughts that gripped the region during the 1180s and 1190s, causing unrest and division.

The Mongols saw their opportunity and seized it—and were fortunate enough that this great tide in their affairs happened to coincide with the rise to power of a vigorous chieftain who would go on to unite them: Genghis Khan.

"The transition from extreme drought to extreme moisture strongly suggests that climate played a role in human events," said tree-ring scientist Amy Hessl of West Virginia University in Morgantown, a co-author of the study, whose research was funded in part by the National Geographic Society's Committee for Research and Exploration. "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."

A photo of the rings of a tree.
Tree rings, which can be dated year by year, are clearly visible in well-preserved specimens.
PHOTOGRAPH BY KEVIN KRAJICK/THE EARTH INSTITUTE, COLUMBIA UNIVERSITY

And ride it he did. By the time he died in 1227, he and his followers had founded an empire that would ultimately cover Korea, China, Russia, the Middle East, Eastern Europe, Persia, India, and Southeast Asia. Although the Mongol empire would break up over the centuries, some of Genghis Khan's direct descendants were still ruling pockets of central Asia into the 1920s.

The timely change in climatic conditions that helped to launch the Mongol empire "doesn't appear to have been associated with any change in volcanic eruptions or solar irradiance," says Kevin Anchukaitis, a paleo-climatologist at the Woods Hole Oceanographic Institute. The task that lies ahead: determining if weather influencers like El Niño and the North Atlantic Oscillation might have brought the beneficial rains in Central Asia.

A photo of a person standing on a shrunken lake.
High on a landlocked plateau, Mongolia is generally cold and arid, with tenuous supplies of grass and water. This huge lake is salty and shrunken from drought.
PHOTOGRAPH BY KEVIN KRAJICK/EARTH INSTITUTE, COLUMBIA UNIVERSITY

Mongol Invasion: Modern Version

The climate chronology compiled by the Lamont-Doherty team reveals that the dawn of the 21st century has seen some of the hottest weather and most severe droughts in centuries—hotter and drier than even the severe drought years of the 1180s and 1190s. It also suggests that climate may play a role in a modern Mongol invasion—from the arid steppes to the crowded cities.

The recent drought years have followed a string of fairly wet years toward the end of the 20th century. That's a double whammy, says Pedersen, since the relative abundance of rainfall in the 1990s could have made herdsmen less prepared for the harsh conditions of a severe drought.

The hard years, coupled with sweeping changes in Mongolia's post-communist society, have sparked a mass exodus from the steppes into the country's capital, Ulaanbataar, where roughly half of Mongolia's three-million-strong population now lives.

Correction: An earlier version of this story incorrectly identified West Virginia University as the University of West Virginia. It also stated that the population of Mongolia was "six-million-strong." The population of Mongolia in 2013 was 3.2 milion people.

23 comments
TuThanh Ngo
TuThanh Ngo

very wonderful, a great empire after all. He one of the greatest strategists of all time !!!!

Dean Branscum
Dean Branscum

Everything in life is cyclical.....even a foolhardy comment will come around. I've been to Ulaanbaatar, and floated the very river that Ghengis Khan bathed in as a boy. The climate changes every year.

Madeline Ryan
Madeline Ryan

Very intresting! I am doing a report on him! thank you

long john
long john

The mongols were a disastrous civilization which only brought death and misery. They created nothing but more efficient  ways of killing. I think there is not a single monument in all the country or some proof of local culture. Absolutely nothing!

This is happening when you don´t like to work, you have to steal from the others. 

BTW for the Soviet Union was impossible to impose collectivization in Mongolia  because the mongols don´t have the slightest concept of working and having a stable home. Truely free men...

Can Benli
Can Benli

I AM THE GENGIS KHAN PURE BLOOD 100/100.

Rahul Daimari
Rahul Daimari

might be..but no climate can bring out the loyalty , brains and bravery of Genghis and Tamerlane.. all the wars were won by their sheer ingenuity 

Alex Macha
Alex Macha

I love learning about the mongols, and this is just an awesome article. What an interesting fact that climate had such huge influence to the mongols success. 

Agrani Mahajan
Agrani Mahajan

Hey Lauren nice insight!!. Have been wondering for quite sometime that how come all forecasts are only restricted to 100 yrs data. What happened before that. There is some proof to the confusions I had in mind

Bruce Parsons
Bruce Parsons

Lauren, I suggest you come clean with the proof this is a conspiracy.   Unfortunately as you well know there is no conspiracy, the science is there to state unambiguously it is in fact warmer than it was in 1200, NOW!   And worse yet, your ill informed opinions have been planted either by you or in you at the behest of the richest people on the planet.   I did not expect this sort of foolishness on the NG web site but I guess the trolls think this as good a place as any to sell their foolishness.   Did you read the article - this is hotter an drier than it was then.   This is a well established scientific fact regardless of your trolling.   What I always wonder is, what are you going to tell your grandchildren to explain your blindness to the facts?   What are you going to say to them when they ask you, why did you do nothing about this when you had a chance?

Rachel Link
Rachel Link

This is such an awesome intersection of history and science!

Lauren R
Lauren R

This is science reporting in a semi-Orwellian world.

The warming being discussed is part of the Medieval Warm Period -- which was a well-known historical event before being erased from mention by the Manmade Global Warming propaganda operation.

It was one of the series of natural warming-cooling cycles over the last 5000 years, each a little cooler overall than the previous one -- because the Earth has been slowly wobbling back down into the next ice age. Here's a tree ring study from Finland showing the last 2000 years:

http://www.sciencedaily.com/releases/2012/07/120709092606.htm

20th century warming occurs where expected, and as of 2014 is still cooler than the last warm phase as expected.

The Vikings were able to settle and farm in Greenland in the Middle Ages because it was WARMER than today.

Hiding this from the public is the central propaganda work of Manmade Global Warming -- which tries to limit all climate discussion to the last 150 years so it can show charts of only upward temperatures, declare the "warmest year on record", and claim Earth is being struck by a never-before-seen manmade disaster.

Here the Middle Ages have to be discussed, so the warming is presented as a brief local fluke in Mongolia, and nothing like today's severe manmade warming -- though a stark reminder of the threat to humanity of climate change.

Where's the giant portrait of the Great Leader for us to be hailing.

James Mwaura
James Mwaura

I always love their environment and prowess to face it as it is. They should have ventured more across the Great Rift Valley into Africa and Kenya. Maybe our history would be different

Munkhtur E.
Munkhtur E.

Wow, how did Mongolia get 6 million people? I believe it is 3 million. There is more to it of course for herdsmen moving from the countryside to the city( most schools are in the city, more jobs) and of course communists forced many herdsmen to give up their livestock and made them move to cities. My grandpa was forcefully gave away all his horses, sheep etc to the communist party and was forced to move to Ulaanbaatar and was given free 3 bedroom apartment. But of course that was not what he wanted. Most people moved to cities from countryside forcefully and miss their pasture land ; most go into depression and drinking more vodka. But yes, harsh winters like Zud can make some herdsmen lose all or most of their flock and make them want to move to cities for easier(questionable) life.

Tom Campbell
Tom Campbell

The cited institution in Morgantown, WV is "West Virginia University," not "U of WV."  U of WV was a governance system for universities in WV that was abolished in 2000.

Steve Borysiak
Steve Borysiak

You mean to tell me there was "climate change" 800 years ago? This changes everything.

Steve Borysiak
Steve Borysiak

You mean there was "climate change" way back 800 years ago? This changes everything.

J K
J K

Interesting.  But re-check that last fact: The country of Mongolia has only about 3 million people, not 6 million.

Jay Bird
Jay Bird

It is striking, Lauren R., that the article you cite does nothing to support your claims your conclusion. Work on the reading comprehension before you try to converse seriously with the grown-ups.

Sean Hollingsworth
Sean Hollingsworth

@Lauren R  I am 100% with you on this one!!  The problem that I have faced is that current contemporary school of thought does actively choose to ignore any paleo-climatological information.  They comfortably ignore facts about how the woolly mammoths died, or the climate that they enjoyed before being instantly through-frozen. 

jim adams
jim adams


@Steve Borysiak check out a small book by climate scientist, Dr William Ruddiman: Plows, Plagues, and Petroleum, How Humans took Control of Climate.

During his researches into the 55 or so glacial cycles of the last 2.5 million years, he found that they all had similar climate features which coincided with Earth's orbital and axial tilt and axial wobble features -- until our cycle. About 8000 years ago, our cycle started deviating from the pattern of the other cycles.

He checked a wide variety of sources, from archeology, satellite photos, climate records, census data, historical records,  relevant geology, palynology, glacial ice cores, etc  -- and found that 8000 years ago, humans agriculture started making a slight difference in planetary temperatures/CO2,  which in turn made incremental differences in the temperature/CO2 up to about 1750, the start of the industrial revolution. 

At this point, the global temperatures no longer increased incrementally, but significantly. This made the changes/differences look like what one climate scientist called "a hockey stick". Then, 3 to 5 decades ago we started increasing the temperature.CO2 shifts even more significantly and that's where we are today.

It's a race between us humans and the Chicxulub asteroid about which will be more destructive to our planet. I know how driven we in the United States are to win competitions, so i'm not betting on the asteroid.

So you know: I hate being a Cassandra (Wikipedia it) and i'm just finishing a week with my 2 and 4 year old grand kids. I'm devastated that we are creating a world in which they have a very low probability of having a future -- unless we -- as a Nation and a World -- create A War on Global Warming before the end of this year.


Chris Crawford
Chris Crawford

@Steve Borysiak  Yes, climate has changed throughout history. There were also forest fires 800 years ago. Does that mean that modern forest fires are all natural in cause?

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