Warm, wet weather may have helped Genghis Khan rule

Source: Sciencenews.org

Wet, mild weather — not drought — may have helped Genghis Khan expand the Mongolian empire to the largest in human history.

Rings in trees in the mountains of central Mongolia show that at the same time the empire began to grow in the 13th century, the weather of central Asia became uncommonly wet. The moist climate could have boosted the region’s grasslands, giving Khan and his people more food for raising livestock and horses and a better ability to focus on building political and military power, researchers suggest March 10 in theProceedings of the National Academy of Sciences.

Tree-ring and weather data also suggest that central Mongolia's drought from 2000 to 2009 was the hottest in the last 1,000 years. If warming continues, it could disrupt how modern Mongolians live, the scientists say.

Pluvials, droughts, the Mongol Empire, and modern Mongolia

Source: pnas.org

1. Neil Pedersona,1,2, 
2. Amy E. Hesslb,1,2, 
3. Nachin Baatarbilegc, 
4. Kevin J. Anchukaitisd, and 
5. Nicola Di Cosmoe

Author Affiliations

1. Edited by Karl W. Butzer, The University of Texas at Austin, Austin, Texas, and approved February 11, 2014 (received for review October 2, 2013)

1. Abstract
2. Authors & Info
3. SI
4. Metrics
5. PDF
6. PDF + SI

Significance

A 1,112-y tree-ring record of moisture shows that in opposition to conventional wisdom, the climate during the rise of the 13th-century Mongol Empire was a period of persistent moisture, unprecedented in the last 1,000 y. This 15-y episode of persistent moisture likely led to a period of high grassland productivity, contributing fuel to the Mongol Empire. We also present evidence that anthropogenic warming exacerbated the 21st-century drought in central Mongolia. These results indicate that ecosystems and societies in semiarid regions can be significantly affected by unusual climatic events at the decadal time scale.

Abstract

Although many studies have associated the demise of complex societies with deteriorating climate, few have investigated the connection between an ameliorating environment, surplus resources, energy, and the rise of empires. The 13th-century Mongol Empire was the largest contiguous land empire in world history. Although drought has been proposed as one factor that spurred these conquests, no high-resolution moisture data are available during the rapid development of the Mongol Empire. Here we present a 1,112-y tree-ring reconstruction of warm-season water balance derived from Siberian pine (Pinus sibirica) trees in central Mongolia. Our reconstruction accounts for 56% of the variability in the regional water balance and is significantly correlated with steppe productivity across central Mongolia. In combination with a gridded temperature reconstruction, our results indicate that the regional climate during the conquests of Chinggis Khan’s (Genghis Khan’s) 13th-century Mongol Empire was warm and persistently wet. This period, characterized by 15 consecutive years of above-average moisture in central Mongolia and coinciding with the rise of Chinggis Khan, is unprecedented over the last 1,112 y. We propose that these climate conditions promoted high grassland productivity and favored the formation of Mongol political and military power. Tree-ring and meteorological data also suggest that the early 21st-century drought in central Mongolia was the hottest drought in the last 1,112 y, consistent with projections of warming over Inner Asia. Future warming may overwhelm increases in precipitation leading to similar heat droughts, with potentially severe consequences for modern Mongolia.

• paleoclimate
 
• dendrochronology
 
• human ecology
 
• Anthropocene
 
• coupled human natural systems

Footnotes

• 1N.P. and A.E.H. contributed equally to this work.
• 2To whom correspondence may be addressed. E-mail: adk@ldeo.columbia.edu or Amy.Hessl@mail.wvu.edu.

• Author contributions: N.P. and A.E.H. designed research; N.P., A.E.H., and N.D.C. performed research; N.P., A.E.H., and K.J.A. analyzed data; and N.P., A.E.H., N.B., K.J.A., and N.D.C. wrote the paper.
• The authors declare no conflict of interest.
• This article is a PNAS Direct Submission.
• Data deposition: All tree ring data have been deposited in the International Tree Ring Databank,www.ncdc.noaa.gov/paleo/treering.html.
• This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1318677111/-/DCSupplemental.
  
  
  
  
  

  Genghis Khan rode climate change to take over Asia

  Doyle Rice, USA TODAY3:24 p.m. EDT March 10, 2014

  
  

  
  

  

  (Photo: NG HAN GUAN AP)

  SHARE 11CONNECT 29TWEET 1COMMENTEMAILMORE

  Throughout human history, natural climate change has played a role in the rise and fall of civilizations around the world, from the Mayans to the Romans.

  The empire of Genghis Khan of Mongolia, one of the most notorious characters in world history, was helped by a dramatic rise in rainfall and mild temperatures in central Asia in the early 13th century, according to a study released Monday in the Proceedings of the National Academy of Sciences.

  Led by Genghis Khan and his sons and grandsons, the Mongols ruled most of modern-day Russia, China, Korea, southeast Asia, Persia, India, the Middle East and eastern Europe, forming the largest land empire in world history.

  Previous research had speculated that the Mongols were escaping extreme drought, but this research takes the opposite tack.

  Scientists led by physical geographer Amy Hessl of West Virginia University and Neil Pederson of Columbia University's Lamont-Doherty Earth Observatory believe that the rise of Genghis Khan and the start of his sprawling empire was propelled by a temporary run of nice weather.

  How did the additional rain and unusually mild weather help Khan? Horsepower, Hessl said. The abundant grasses provided the fuel for the horses that helped the Mongols and their superb cavalry conquer vast lands. It also helped provide food in the way of livestock fed by the bounty.

  "Where it's arid, unusual moisture creates unusual plant productivity, and that translates into horsepower," she said. "Genghis was literally able to ride that wave."

  Khan's rise to power was in 1211 to 1225 A.D. During that time, scientists found that Mongolia saw sustained rainfall and mild warmth never seen before or since.

  
  

  

  At its height, Genghis Khan's empire stretched all the way from eastern Europe to Korea.(Photo: Columbia University Earth Institute)

  
  

  Khan and his crew didn't carry rain gauges or thermometers as they marauded over the steppes, so scientists used paleoclimatic "proxy" data -- in this case rings from dead pine trees -- to reconstruct the climate of that era.

  The tree rings from those years were "persistently wide," said Pederson which he said "suggest that period, climatically-speaking, was persistently wet."

  Since the mid-20th century, the region has warmed rapidly, and the rings show that recent drought years were the most extreme in more than 1,000-years — possibly a side effect of global warming.

  "Future warming may overwhelm increases in precipitation, leading to similar heat droughts, with potentially severe consequences for modern Mongolia," the authors wrote.

  "Though we cannot attribute a single event to climate change, warming temperatures have stacked the deck toward (more evaporation), so even if the amount of precipitation remains the same, high temperatures will generate a more intense drought," Hessl said.

  "That's what we observed in the early 21st century, and based on past moisture variation in Mongolia and future predictions of warming, we would expect to see similar events in the future."

  
  

  

  Genghis Khan, his sons and grandsons created the largest empire in world history, thanks in part to good weather.(Photo: Columbia University Earth Institute)
  
  
  
  

  From: Past Horizons

  RISE OF GHENGIS KHAN LINKED TO MONGOLIAN CLIMATE CHANGE

  Article created on Tuesday, March 11, 2014

  
  

  Eight hundred years ago, relatively small armies of mounted warriors suddenly exploded outward from the cold, arid high-elevation grasslands of Mongolia, and conquered the largest contiguous empire in history.

  Led by Genghis Khan and his sons and grandsons, the Mongols briefly ruled most of modern-day Russia, China, Korea, southeast Asia, Persia, India, the Middle East and eastern Europe. They reshaped world geography, culture and history in ways that still resound today. How did they do it? Among the forces at work: the Mongols’ fast horses and brilliant cavalry tactics; their openness to new technologies; and the political genius of Genghis himself. Now, a research group is looking into a possible other factor: climate change.

  Ancient trees

  Tree-ring scientists at Columbia University’s Lamont-Doherty Earth Observatory have worked in Mongolia since 1995. In 2010, Lamont researcher Neil Pederson and Amy Hessl of West Virginia University were seeking old trees for a study of wildfire history. High in the Khangai Mountains, north of the steppe where the long-disappeared Mongol capital of Karakorum once lay, they explored a nearly solid-rock plain of hardened lava left by a volcanic eruption some 8,000 years ago. Growing out of fissures and thin soils were thousands of gnarled, stunted larches and Siberian pines–a tree-ring scientist’s treasure. Annual rings of many species reflect rainfall or temperature in predictable ways. These can be read like books; and trees in the driest, harshest sites like this are exquisitely sensitive to rain, live to extraordinary ages, and leave trunks that may stand for centuries after they die. They are truly ancient manuscripts, writ with a fine hand.

  

  Rings of ancient trees provide key insights into past climate. In Mongolia’s rocky Khangai Mountains, ecologist Byambasuren Oyunsanaa and biophysicist Damdin Suren Sodov cross-section a dead trunk that easily could have grown 1,000 years ago. Image: Columbia University

  Grass production boom

  Pederson and Hessl analysed 17 trees to chart a yearly record of rainfall back to 658 AD. They saw that from 1211-1230—the exact time of the Mongols’ rise—central Mongolia saw one of its wettest periods ever. That time also was unusually warm, as shown by a  2001 paper from other Lamont researchers. Pederson and Hessl reasoned that the clement weather could have brought an unusual boom in grass production—and thus a boom in camels, yaks, cattle, sheep and other livestock that have always comprised the country’s main wealth. A glut of war horses–each Mongol cavalryman was said to have five or more—could have enabled fighters to travel like never before, along with a mobile meat supply. “The weather may literally have supplied the Mongols with the horsepower they needed to do what they did,” says Pederson. He stresses that the idea is still based on only a small sample, and more data is needed to draw firm conclusions. Pederson, Hessl and an interdisciplinary team including Mongolian scientists are now exploring the hypothesis, with a $1.4 million grants from the National Geographic Society and the U.S. National Science Foundation. The work will include not only further analyses of tree rings, but lake sediments, historical documents and other sources.

  In summer 2012, Pederson, Hessl and several Mongolian colleagues spent a week gathering more tree-ring samples. Hiking over the jagged Khorgo lava field hauling chainsaws (used for cross-sectioning dead wood) and corkscrew-like tree-corers (for harmless straw-like samples from live trees), they sampled hundreds of trees. Analysis this time—still in progress–found trees as old as 1,700 years, recording roughly the same arc of weather. The team also scouted lakes in the grasslands below, where herders for centuries have driven livestock and horses. Like tree rings, lake-bottom sediments build up year by year. Avery Cook Shinneman, a biologist at the University of Washington, plans to analyse sediments at selected lakes in order to estimate abundances of livestock over time. This will be done using varying levels of fungal spores that live in the dung of grazing animals, and algae fertilized by the dung. The data will be fed into a model developed by Hanqin Tian, an ecologist at Auburn University in Alabama, who studies the weather of modern Mongolia and its relation to grassland productivity. The Mongols left few written records, but Nicola di Cosmo, a historian at the Institute for Advanced Study in Princeton, N.J., will look into contemporary accounts from China, Persia and Europe for clues to climate and military events. From all this, the researchers hope to develop a picture of how sun, water, soil and animals might have created an energy system that the Mongols could have tapped into.

  

  Layers of sediment in lakes where herders have watered animals for centuries may contain clues to past numbers of livestock. Here, a grad student scoops mud as cattle move in. Image: Columbia University

  Shifting climate can influence civilisations

  The idea that shifting climate can influence civilisations has gained traction in recent years. For instance, in 2010 a team from Australia, Vietnam, Thailand and Japan led by Lamont tree-ring specialists showed that the 14th-century Angkor civilisation of Cambodia and later kingdoms rose and fell based on rainfall, although other factors were almost certainly involved. The Mongols could have suffered a climatic setback, too: a cold snap in 1260-1266 and subsequent return to more normal weather in Mongolia appears to coincide with the decline of Karakorum, whose heyday lasted only 30 years. The empire soon fragmented. Today, barely anything of Karakorum remains but a giant stone turtle that once marked one of its corners.

  Though the centre gave way fast, the Mongols’ influence runs deep. In the West, they are stereotyped as ruthless invaders; but in fact by unifying huge territories (including what is now modern China) they brought peace and economic stability to the people of many long-warring smaller fiefdoms. Rival rulers who joined them were left in place (although they had to pay taxes), and the Mongols made it a policy to leave common people alone to follow their own regional customs and cultures. There is a case to be made that the Mongols in fact originated many modern governmental concepts: religious freedom; state-sponsored agricultural research; an international postal system; and civil-service appointments based on merit, not aristocratic pedigree. The last ruling line of Genghis Khan’s descendants survived in central Asia’s Bukhara region until the 1920s, when they were unseated by the Soviets.

  

  Pastoral traditions remain strong, but Mongolians are now rapidly gaining access to roads, vehicles, cell phones and other modern trappings. This shift could exert increasing pressure on a land where grass and animals have up to now been the main source of wealth. Image: Columbia University

  Mongolian weather today

  The research may have ramifications for a rapidly modernising Mongolia and beyond. Temperatures near today’s capital of Ulan Bator have gone up 4.5 degrees F in the last 40 years—well beyond the global mean. But it is not clear whether warmer weather will help the nation, or hurt it. Still generally cold and arid, Mongolia is the world’s most sparsely populated nation (3 million people in 600,000 square miles) but population is growing. It is still powered by livestock—now up to 40 million head, possibly beyond its sustainable carrying capacity. There is a drive to raise more crops, but only 1 percent of the land is arable. A huge copper mine opening soon has brought the first long-distance paved roads, but also growing competition for water. The country has suffered a series of devastating droughts since the 1990s, often followed by a dzud—an unusually long, cruel winter. The last, in 2009-2010, killed 8 million livestock and drove many herders to Ulan Bator. There is some evidence that these cycles are becoming more frequent and intense–but whether stemming from warming climate, or signalling a return to conditions of previous centuries, is not yet clear. It is believed that Mongolian weather may be driven to some degree by the El Niño Southern Oscillation–a pattern that definitely influences the monsoon rains, and crops, of far wider regions. The new data may yield insights about such weather patterns and their relation to the future, as part of an ongoing study of seasonal monsoon rains.

  In a sense, livestock have up to now served as the “fossil fuel” of Mongolia. Are there limits? Says Hessl: “We’re living in a pretty interesting time, when some of our own major sources of energy appear to be pretty tenuous. I think we can look to prior civilisations to see how they dealt with changes in energy availability. At any one time, there were winners, and there were losers.”

  Source: Colombia University

  
  

  More Information
  Roots of Empire – Science Mongolian climate, ecology and culture – project blog Cite this article Colombia University. Rise of Ghengis Khan linked to Mongolian climate change. Past Horizons. March 11, 2014, from http://www.pasthorizonspr.com/index.php/archives/03/2014/rise-of-ghengis-khan-linked-to-mongolian-climate-change