Did the Mongol Invasions Trigger a Little Ice Age?

Debunking the “Genghis Khan the Green” theory

The idea that our planet cooled because of the Mongol invasions has been a hot topic of discussion for more than a decade.

Genghis Khan was dubbed “the Green Conqueror” because he slaughtered so many people that total carbon emissions fell, lowering the earth’s temperature.

Some have even claimed Mongol conquests caused the Little Ice Age in the 14th century.

This isn’t just some random conspiracy theory. There is some science behind the claim.

Julia Pongratz and her colleagues published an article in the journal Holocene in 2011 that examined the effects of epidemics and wars on global carbon dioxide emissions between 850 and 1850.

She discovered that the Mongol Invasions, which killed 40 million people, significantly cut world carbon dioxide emissions.

Though the Black Death killed 75 million people in a shorter period, the researchers concluded the Mongol conquests were the primary cause of global cooling.

The Daily Mail popularized Pongratz’s research with their famously titled tabloid “Genghis Khan the Green.” The Guardian also published her findings, sparking a debate on the subject.

After being mentioned on the Joe Rogan Experience podcast, the study received a lot more attention.

We’ll not be looking at the science behind the claims. I am confident in Pongratz’s research methodologies.

Closer historical inspection, however, debunks the idea that the Mongol invasions lowered global temperatures. The researchers have made several broad assumptions with little basis in events that occurred.

Carbon Emissions and the Mongol Conquests

Let us examine the claims made by Pongratz and her colleagues.

• Mongol invasions from 1200 to 1380, as shown in the table below, had a significant impact on carbon emissions.

• The Mongol invasions killed 40 million people. Though the numbers are significantly lower than the Black Death (75 million people), the impact was greater since there was enough time for forest recovery. As a result, trees could absorb carbon dioxide.
• Human depopulation and forest regeneration absorbed 700 million tonnes of carbon.
• As the agricultural area was abandoned, and forests rose, the planet cooled, triggering the Little Ice Age.
• The Black Death and the fall of the Ming dynasty occurred in too short a time span to affect the Earth’s temperature and carbon emissions.

Pongratz’s reasoning makes logical sense. Fewer humans should cause lower emissions. Reduced cultivable land and woodland regeneration would help cool the planet.

But there are major historical flaws in her argument.

Let’s start with the most glaring one: the timeline of the Mongol invasions, which is the foundation of her study.

A case of good science bad history

Pongratz dates Mongol invasions from 1200 to 1380, a 180-year period.

Temujin was elected Khan of the Mongols after unifying the tribes of Inner Asia in 1206, taking the title Chinggis Khan (Genghis Khan).

In 1209, the Mongol invasions began with a campaign in Xi Xia (also known as the Tangut Kingdom). The Tanguts were a Sino-Tibetan people who ruled Northern China, Northern Tibet, and Southern Mongolia.

There were no “Mongol invasions” before 1209.

I’m puzzled why Pongratz chose 1200 as the start of the Mongol invasions before there was anyone known as Genghis Khan.

Her proposed end date for the Mongol “Invasions” is 1380.

After the death of Mönkhe Khan in 1260, the last great Khan of the united Mongols, the Mongol Empire, was partitioned.

Kublai Khan, the Yuan dynasty’s founder, governed China, parts of Southeast Asia, Tibet, and Mongolia.

Batu Khan and his descendants governed much of modern-day Russia, the Caucuses, and Western Siberia. Historians call this territory the Golden Horde.

Hulagu Khan and his successors ruled over Persia and the Middle East. We call this region the Ilkhante.

The Chagatai Khanate ruled over a large swath of Central Asia, from what is now Xinjiang and northern Afghanistan, to Transoxiana (modern-day Uzbekistan).

The Yuan Dynasty lasted until 1368, the Ilkhante until 1335, and the Chagatai Khanate until 1363.

Apart from a battle at Kulikovo between Moscow (headed by Prince Dmitry Donskoi) and Mamai (the kingmaker of the Golden Horde), the year 1380 is largely ignored in the history of the Mongol Empire.

To Russian nationalists, this battle symbolizes the “end of the Tartar yoke.” But the Horde was far from finished. Following the Kulikovo, the Khans of the Golden Horde sacked Moscow multiple times.

The Horde would not fall until 1502.

What is the reasoning for the choice of the year 1380?

There is none.

The researchers chose both the beginning and ending dates for Mongol invasions at random.

Invasions don’t last for the entire life of an empire. Once an empire is established, imperial soldiers maintain law and order, quell rebellions, and deal with external threats.

Except for Song China, most of the territory under the Mongol Empire was captured by 1260. With Kublai’s defeat of the Southern Song kingdom and his failed invasion of Japan, we can say that the Mongol invasions stopped in 1279.

Mongol conquests lasted 70 years, from 1209 to 1279. Pongratz claims that 63 years of the Black Death was inadequate time for forests to grow on abandoned farmlands, leaving little time for the ground to cool.

Shouldn’t the same rationale apply to Mongol invasions?

Examining the death tolls during Mongol conquests

We’ll get to the death toll.

But first, let’s look at the researchers’ data. Table 1 shows a 33-year overlap between the Mongol invasions and the Black Death.

How did Pongratz and her team determine the cause of death during this time? There are no historical documents that show whether someone died because of a Mongol raid or the epidemic during this period.

This is a major red flag.

Further, scholars have cast doubts on the death tolls during the Mongol invasions. Historical sources have inconsistencies.

According to Juvayni, a Persian historian at the court of Hulagu Khan, Genghis Khan sacked Herat and slaughtered every single citizen. The same historian later says Herat rebelled shortly after the massacre, and Mongol soldiers had to subdue the rebellion.

The two don’t add up.

Who revolted if everyone was dead?

The historical death estimates also fail to account for the Mongol propaganda machine, which worked around the clock to exaggerate the numbers to ensure the easy capitulation of cities. This is not to deny that the Mongol conquests were horrific. They most emphatically were. But they were as violent as any medieval conquest.

We have romanticized ancient and medieval times. We envision never-ending conflicts and conquests. But back then, conquerors wanted to take over as much territory as they could without actually fighting.

Genghis imported paper from Korea to conduct a strong propaganda campaign. He engaged the best writers to describe his atrocities in graphic detail. He’d then send these reports to enemy cities, causing local leaders to surrender without a fight.

Were cities and villages depopulated because of Mongol attacks? Without a doubt.

Was it enough to bring the Earth’s temperature down?

For the sake of argument, if we agree that widespread depopulation reduces carbon emissions significantly, shouldn’t similar destructive conflicts have the same effect?

The An-Lushan Rebellion in the 8th century might have wiped off up to one-sixth of the world’s population. We have no evidence it caused a decline in Earth’s temperature.

The theory that the 14th-century Little Ice Age was caused by Mongol invasions needs to be taken with a large pinch of salt.

Here are the key takeaways from our discussion:

• The Mongol invasions didn’t last for 180 years, as claimed by Pongratz. They lasted for 70 years. The dates assumed by the researchers are incorrect.
• The invasions lasted for 70 years. According to the researchers’ argument, the estimated duration is insufficient for forests to recover over abandoned farmlands. Hence, it is impossible that carbon dioxide emissions were reduced because of the Mongols.
• There is a 33-year overlap between Mongol invasions and the Black Death, based on the timelines proposed by the researchers. There is no way to distinguish who died from the plague and from a raid during this period.
• A conflict-induced population decline does not always reduce the Earth’s temperature. There was no global cooling following the An-Lushan rebellion, which may have killed as many people as the First World War.
• Historical death tolls are questionable. It is important to critique them before using numbers from ancient sources in scientific research.

The myth that Genghis Khan and the Mongols were eco-friendly conquerors who contributed to global cooling can be laid to rest for the time being.

The Mongol invasions were one of the defining events in human history. Powerful kingdoms of China, Persia, and Russia fell under the might of the Mongols, who forged the largest land empire the world has ever seen.

But not everyone surrendered to the world conquerors. If you enjoyed this story, check out the following write-up on three lesser-known kingdoms that stopped the Mongol juggernaut.

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References

• Thomas T. Allsen (2004) Culture and Conquest in Mongol Eurasia, Cambridge Studies in Islamic Civilization Cambridge University Press
• John Man (2014) Mongol Empire: Genghis Khan, his heirs, and the founding of modern China.
• Peter Jackson (2017) The Mongols and the Islamic World: From Conquest to Conversion, Oxford University Press.
• Pongratz et al (2011) Coupled climate-carbon simulations indicate minor global effects of wars and epidemics on atmospheric CO2 between ad 800 and 1850, Holocene.
• https://www.dailymail.co.uk/sciencetech/article-1350272/Genghis-Khan-killed-people-forests-grew-carbon-levels-dropped.html
• https://www.theguardian.com/theguardian/2011/jan/26/genghis-khan-eco-warrior