Climate and China’s Dynastic Cycles:  Did Climate Cause Rises and Falls?

Image result for flooding of the yellow river

Yellow River Flood

E. N. Anderson

Dept. of Anthropology

University of California, Riverside

 To be presented at the annual meeting of the Social Science History Association session on East Asian Climate History, Phoenix, November 9, 2018.  V. 10/17/2018, 4344 words

This is IROWS Working Paper #132 available at


Recently, several authors have attributed the rise and fall of Chinese dynasties to climate change.  This has been done by finding loose correlations between the timing of dynastic rise and fall and major changes in Eurasian climate.  Dynastic fall is often considered to be affected by climate.  A detailed survey of China’s dynastic cycles shows no overall close correlation.  The only dramatic correlation is that of the Medieval Climatic Anomaly (Medieval Warm Period) with the rise of Central and North Asian states, especially the Mongols.  Other correlations often run against expectations, as when conquest and consolidation from the north occurs during especially cold times.  One reason for lack of correlation is that climatic improvement was apt to help both China and its enemies, as when warmer and moister climate at the start of Han helped both Han and the Xiongnu.

            I’m very glad to be present in spirit at this gathering.  My greetings to all of you.  Hello to Nicola, and I certainly hope to meet the others of you soon.  I wish I were there, but I must run a session for the California Sociological Association, which is meeting in Riverside at this same time.  I eagerly seek comments on this work—it’s still in progress and would benefit greatly from your help.

            I am working on a book evaluating the role of climate in Chinese history.  Recently, several books of world history (notably Brooke 2014; Campbell 2016) have argued that climate has a determinative and causal effect on history.  Writers on China have not been far behind.  As early as 1988, Bret Hinsch argued for this, and more recently Qiang Chen (2015) has given climate history a determinative role.  A formidably bright and data-rich team at the University of Hong Kong, led by Harry Lee and David Zhang (e.g. Lee 2018; Lee and Zhang 2010; Lee et al. 2017; Pei, Lee, and Zhang 2018; D. Zhang et al. 2007, 2011, 2014), has contributed several papers on climate as determinant.

            The present paper will introduce the problem by dealing directly with Qiang Chen’s model, which is simple: dynasties may be expected to rise on good climatic times and fall in bad ones. 

            China’s climate is fortunately simple compared to most of the world.  It is dominated by the East Asian monsoon.  In summer, hot wet air blows up from the South China Sea, causing rainfall; the rain totals decrease from southeast to northwest, subject to modification by orographic factors.  In winter, cold dry air blows down from Siberia.

            Over centuries, the monsoon weakens or strengthens, depending on global warmth or cooling.  Warmer climates worldwide lead to a stronger monsoon and thus more rain.  Cooler periods have the opposite effect. 

            China has always been subject to droughts and floods.  Droughts are worse during cool periods, which are usually dry.  On the other hand, some cool summers are accompanied by massive flooding.  Flooding naturally tends to track warmer centuries.  The cool wet summers remain to be adequately explained.  Over the centuries, China experienced local hunger almost every year, and major famines associated with flood or drought almost every second year (Mallory 1926).  To be exact, there were 4180 famines noteworthy enough to get into the histories in 826 of the 2117 years of dynastic China (Su et al. 2018).  The Lee and Zhang group has correlated these disasters with internal wars, and found a fair correlation, but not close to 100%.  In related work, Yun Su and colleagues have found that cool periods are correlated with famines, and improving weather with good economic times, but the correlation is far from perfect, thanks to dynastic rise and fall and other political events (Su et al. 2018), and that dynastic cycles loosely correlate with climate (Wei et al. 2015; Yin et al. 2016).

            A problem with intepretation is caused by the fact that these disasters are as much man-made as natural.  The Chinese realized from earliest times that flood control, farming practices, famine relief institutions, and similar infrastructure could avert or alleviate such disasters.  Their belief that the moral qualities of the emperor have much to do with droughts and floods has been ridiculed as mere superstition by ignorant westerners, but it is the literal truth.  From Frank King (1911) and Walter Mallory (1926) to Mark Elvin (2004) and Robert Marks (2012), more informed westerners have pointed out that China’s floods and droughts were devastating in proportion to how badly the infrastructure was managed.  This finding implies that the correlation between wars and catastrophes is a two-way street.  Not only do droughts and floods create tensions that may cause wars; wars and other political problems cause or exacerbate the disasters.

            A case study is Ling Zhang’s brilliant new book, The River, the Plain, and the State (2016).  She shows how unusual weather—the intermittently cold but wet years of the early 1100s—combined with factionalism and dissention in the Song Dynasty court, to bring about a situation in which the Jurchen conquerors from the north could successfully invade and take over northern China.

            Let us turn to a quick review of the major dynasties and associated major climate changes.  The early dynasties are too poorly known for much comment, with the striking exception of recent findings that major climate change including floods on the Yellow River coincide with the currently accepted dates for the rise of the Erlitou culture, which is almost certainly the historic Xia Dynasty.  The Great Yu supposedly controlled the Yellow River floods and established the dynasty, and he is now seen by many Chinese historians as a collective image of early chieftains or kings who put in flood works and consolidated the Xia regime.

            The light of history gets brighter as we come to the Qin Dynasty.  It soon fell, but was replaced after civil war by the Han Dynasty, founded by a Qin general.  (From here on, I am summarizing my book, which gives all the references for what follows; I will send the ms to anyone interested.  For history I rely on the Cambridge History of China, the Harvard series, and above all—when in doubt—on the seasoned interpretations of Frederick Mote in Imperial China 900-1800, 1999.)  Its rise coincides with the rise of what in Europe is called the Roman Empire Optimum, a warm, pleasant period that was predictably moist in eastern Asia.  The optimum surely helped Han to consolidate and flourish.  Successful farming led to the rise of agricultural experimentation and agricultural extension projects.  The only trouble was that a warmer, moister climate benefited Han’s arch-rival, the Xiongnu.  In fact, since they lived in cold and dry Mongolia before extending southward to conquer northwest China, they benefited relatively more than China itself. 

            The Chinese histories credit the decline and fall of Han to the weakness of the last emperors and the Yellow Scarves rebellion in the 180s CE.  In its last years the de facto ruler was the general Cao Cao, and in 220 he pulled the plug on the miserable young emperor and founded his own kingdom. But by this time there were already two kingdoms asserting militant independence in Sichuan and central China, and their battles gave us the epics that are China’s equivalent of the Iliad and Odyssey as foundational texts.

            The following three centuries were characterized by disunion and strife, and by climate similar to that of the 20th century.  But the final reuniting of China could not be farther from Chen’s model. The period from 550 to 650 CE was extremely cold, thanks to volcanic action in several areas; the sun was darkened by volcanic ash for a century.  Yet in 580 and again in 620, China was unified, first under Sui and then—when Sui went down—under Tang.  And these dynasties came from the north; their founders were northern warlords.  They both followed a pattern of conquering the cold, dry northwest and striking out from there.  The Chinese histories say that the founders were part Turkic and were hardened frontier fighters leading other hardened frontier fighters.  Perhaps cold weather stimulates striking for the warm south. 

            Tang waxed great in a favorable climatic period (Su et al. 2018).  The fall of Tang coincides with unsettled and fluctuating weather at the onset of the Medieval Warm Period (aka Medieval Climatic Anomaly), but again the Chinese historians agree that Tang had been declining for decades.  It never quite recovered from the rebellion of 754, led by An Lushan.  (Since my Chinese surname is An, I claim kinship.)  The last emperors of Tang were a dismal lot; five died from what is suspected to be overdoses of poisonous “longevity” drugs.  The Huangchao Rebellion of 880 fatally weakened the dynasty.  It fell in 907.

            After a period of disunion, the Song Dynasty rose in the north and conquered China in 960.  At this point the Medieval Warm Period (MWP, Medieval Climatic Anomaly) comes into its own.  Temperatures rose until by the late 1100s and 1200s they were about what human-caused global warming is giving us now or will soon.  (Unlike present warming, the MWP was almost entirely natural; claims that rice agriculture was a major contributor are based on a misunderstanding of traditional rice production.)  This was accompanied by wetter weather in China.  Vietnam, however, had an uneven time of it, since the rain’s northward shift often left southern Vietnam and Cambodia dry.  Benefits to Chinese agriculture were somewhat offset by increased flooding. 

            The most significant effect of the MWP on China may have been its warming of Mongolia and northeast China.  They became warmer and wetter.  This did not cause local people to arise and become military, but it certainly allowed them to.  They could build up higher populations of men and horses.  Horses were especially important.  Large numbers of horses were necessary for war, and the MWP saved them from the dread dzud, the late ice-storm conditions that iced the grass and starved the herds. 

            The first to take advantage of better conditions were the Khitan, speakers of a language now known to be related to Mongolian.  They conquered what it now northeast China and 16 provinces at the northern fringe of Song.  The Jurchen soon rose, threw off Khitan rule, chased the Khitans into Central Asia, and conquered not only the Khitan realm but all northern China.  Song was reduced to paying what amounted to tribute.  Then in the early 1200s, the Mongols under Genghis Khan rose and conquered most of Central Asia.  Under his son they conquered the Jurchen Jin dynasty, and under his grandson Khubilai they conquered all China in 1279.  Of course you all know the details—the point I am making is that this all coincides with the Medieval Warm Period.  Liao and Jin rose with it.  Northern Song fell to Jin during an unsettled period with several cold wet years.  The Mongols rose during a particularly warm spell, and conquered China in another.  The Mongol Yuan dynasty then fell to resurgent Chinese power in 1368, when the Little Ice Age (LIA) was beginning.  It is probably too neat to say the LIA explains the fall of Yuan, but there is no denying that colder and more erratic weather, with attendant droughts and floods, had more than a little to do with Yuan’s fall.  Yuan in the early 1300s succeeded in the incredible task of taming the Yellow River, but the river was out of control again well before 1368.

            The Ming Dynasty then comes in with what almost seems like the express purpose of blowing up every theory about imperial cycling.  It rose and flourished during the worst of the Little Ice Age (Brook 2010, 2016).  It survived 276 years of erratic rule; some of the Ming emperors appear to have been mentally ill.  It survived corruption, eunuch rule, powerful women—all the things that traditional Chinese historians considered fatal to the Mandate of Heaven.  And when it did fall, it fell during a particularly cold period, but fell to a northern power—the Manchu Qing dynasty—that should never have been able to come to power and prevail during such an appallingly frigid and hostile time.  All our comfortable generalizations about Chinese empires and cycles are put in jeopardy.  This anomaly has been noted and discussed by Wei et al. (2015), who point out that Ming almost fell during succession conflicts in the early 1400s.

            Finally, Qing rose during one of the coldest periods since the Pleistocene Ice Ages, and fell during a genial, warm, pleasant period.  This defies all theory and common sense, as far as climatic influences go.  It is, however, reasonable given the political realities of those times.  Among other things, Qing never quite recovered from the Taiping Rebellion, just as Han had failed to recover from the Yellow Scarves and Tang failed to recover from An Lushan’s and then Huang Chao’s rebellions. 

            Evaluating the above in the light of Chen’s idea, Han, Jin, and Yuan fit well: they rose in good times and fell in bad ones.  Sui, Tang, Ming, and Qing fit very badly: they rose in terrible climatic times, and fell in bad to average times.  Song rose with warming climate, but then lost to groups made even more successful by that warmth.  Short-term fluctuations that produced unsettled weather over a few decades appear to have contributed to the fall of Northern Song and Yuan.  An interesting observation, not often pointed out, is that while Han was clearly helped by good weather, their enemies the Xiongnu were also helped, making them formidable foes.

            All this suggests, at least to my mind, that climate is one part of the back story, along with demography, diseases, agricultural progress, and other broad environmental factors.  The mid story and front story are clearly matters of human agency.  Only humans act.  They are the ones that decide, fight, eat or starve, farm or flee disasters, kill and save.  They can react to climatic disasters by a potentially infinite range of actions, from flight to civil war to bearing it.  The Chinese proverb says:  “Freezing to death, stand straight and face the wind; starving to death, never bend.”  (Rohsenow 2000, #D183.) 

            Were Chinese historians right, then, to blame the loss of the mandate on heavy taxes, corruption, unfair government, women, and eunuchs?  The first three certainly mattered a great deal.  More to the point, the cycles fit less well with climate change than with the theory of cycles devised by the great Arab historian Ibn Khaldun in the 1300s (Ibn Khaldun 1958) and recently revised and updated by Peter Turchin (2003, 2006, 2015, 2016; Turchin and Zefedov 2009).  Ibn Khaldun’s development of this theory is detailed and brilliant, and does not do well with summaries, but I will summarize as best I can.

            He begins with the observation that “God put good and evil into the nature of man” (Ibn Khaldun 1958:261).  This is deeper than it looks; his theory depends on cyclic alternations between prosocial and antisocial behavior.

            His idea was that a dynasty is created when an earlier one collapses or when some other opening is created.  At this point, “barbarians”—we would now call them semiperipheral marcher polities—unite behind a charismatic leader, and take over the realm.  The leader has to be a master at creating what Ibn Khaldun called ‘asabiyah, basically the loyalty and commitment of his followers.  ‘Asabiyah has been mistranslated as simple loyalty or social solidarity behind a charismatic figure, but Ibn Khaldun emphasized that it is created by the leader’s history of successful fighting, adjudicating problems, being generous with resources (especially loot), serving loyally and bravely with his troops, and otherwise taking care of his people.  Another mistake is thinking Ibn Khaldun’s “barbarians” were nomadic herders.  They were not; his examples were either settled agricultural polities or professional soldier bands.  In China, one notes the mistaken use of “nomads” (e.g. in Chen 2015) to describe peoples like the Jurchen and Manchu, who were largely settled farmers. 

            The dynasty formed by the founding leader holds together due to the fierce loyalty and bonding of the first generation.  The second generation enjoys a golden age, based on steady economic progress in this happy and harmonious political situation.  The third generation begins to erode, because the dynastic family and the court have grown remote and out of touch with ordinary people.  They become corrupt, spend on court luxuries and military adventuring, and fail to take care of bread-and-butter issues.  The fourth generation is entirely palace-bred and disconnected from the populace. Meanwhile, population has grown, land and food are scarce, and sharp landlords are monopolizing what there is.  The heavy taxes, corruption, and unfair governance of the Chinese historians is also in Khaldun’s model (though not the women and eunuchs). 

            All this leads to rebellion, which weakens the dynasty such that barbarians can sweep in again from the marchlands.  In China, about half the dynasties started exactly that way; the other half started with a general or warlord serving the previous dynasty, a contingency easily accommodated by Ibn Khaldun’s theory. 

            The key moment in a Khaldunian cycle comes when more people see it as in their interests to go against the regime than to work with it.  Ordinary corruption and banditry are tolerable, but when the elites actively plot coups and the people’s constant low-level banditry turns to organized rebellion, the regime is doomed.

            China’s dynastic cycles were usually longer than three or four generations, but Turchin’s reworking of Ibn Khaldun’s theory allows and even predicts this.  Also, in China, almost every dynasty had periodic crises, coups or rebellions that renewed the dynasty and re-set the clock.  In Tang, for instance, the Empress Wu episode and the An Lushan rebellion came at critical points, allowing the dynasty to renew itself under new leadership.

            To make a long story short, the Turchin reworking of Ibn Khaldun’s theory is quite predictive, or retrodictive, of China’s cycles.  It operates without climate as a variable.  However, it does not rule climate change out as a precipitating factor for change.  Climate, however, would be predicted to be only one among many environmental factors that could stress a dynastic regime and help the “barbarians” bring in a new one.

            The cases in which climate change coincides with the fall and rise of dynasties do not seem to be marked as more dramatic, or quicker, or more violent than other changes, again with the striking exception of the Medieval Warm Period, when three powerful northern polities in a row attacked China with increasingly violent and successful military action.  I personally have no doubt that climate change enabled this.  However, I also have no doubt that climate change by itself did not cause this.  Genghis Khan would surely have found a way to succeed, somehow, somewhere, climate change or no.  Still, warmth allowed him to build up in a short time a huge army, mounted on tough horses.

            All this is, of course, relevant, because of current climate change, and because Ibn Khaldun’s cycling still goes on today.  Indeed, Turchin presciently predicted a political breakdown in the United States just before the 2016 elections (Turchin 2016); his prediction has so far been entirely correct, showing that Tunisian thinker writing in the 14th century understood politics better than most Americans do.  However, the climate change we will be seeing in the next 100 years is far greater than anything since the last major glacial advance and retreat. 

            A more general cyclic theory, C. S. Holling’s resilience cycle, is also applicable, and has indeed been applied to dynastic cycling by Wei Zhuding, Yun Su, and their group (Wei et al. 2015).  This theory merely states that cycles will occur in any natural population, such that a population crash or low point will allow rapid growth of population, which will level out, then decline as density-dependent factors build up (Gunderson et al. 2010). 

            Less obvious, but also interesting, is the question raised for causal thinking in history.  If we are to follow Marx’ call for a “science of history,” we will have to come up with a theory of causation that gives individuals the central role.  Marx himself saw history as determined by economic forces, but contingently by individuals acting in accord with those overwhelming forces.  As he put it in an oft-quoted line: “People make history, but they do not make it as they please; they do not make it under self-selected circumstances, but under circumstances existing already, given and transmitted from the past” (from The Eighteenth Brumaire of Louis Bonaparte).  Consider the incredible importance of the bubonic plague in Europe in 1346-50, or the potato blight in 1846-48.  The potato blight made history quite directly, driving millions of Irish and German refugees to North America, profoundly changing its cultures.

            The “circumstances given already” include more than class struggle and development of the means of production.  They include climate, disease, demographics, and many other factors.  The responses of people to all these contingent events cannot be easily predicted, if only because there are so many things to take into account.  Famine can make people migrate, fight, work harder, eat famine foods like tree bark, eat each other, or rebel—all those responses are amply attested in the Chinese historical sources.  The government can react by providing relief, sending soldiers to suppress rebellion, or doing nothing—again all amply attested, along with complaints about local bureaucrats and landlords misappropriating the relief materials.  Hence the poor, though clear and real, coupling of climate to famine and strife in dynastic China, as found by Yun Su, Wei Zhudeng and their group (see above).  Harry Lee’s list of wars also fails to correlate anywhere close to 100% with climate, but shows enough correlation to prove that climate was one background factor.

            Ibn Khaldun’s model fits every dynasty very well, but it does not specify exactly when and how such events will occur.  It merely specifies that the cycle will run as described, leading to collapse sooner or later.  Ibn Khaldun himself stressed the role of contingent factors: a charismatic leader may not arise at exactly the right time, good governance can delay collapse, excessive war can make it come more rapidly, and so on. 

            In this model, climate may be one of the contingent factors that precipitate decline and fall.  This seems to have been the case in Han, Tang, Northern Song, Yuan, and to an extent Ming.  It may also be one factor in a dynastic rise, as in the case of Han (possibly), Liao, Jin, and Yuan.  Or, as in the other cases, it may simply not be a relevant or clearly explanatory factor.

            History is the result of people’s choices.  As Marx said, they do not choose in a vacuum.  But the long-term cyclic factors and immediate contingent factors affecting their choices leave them a great deal of room to make mistakes or to choose wisely.  This is a hopeful thought as we move into the most rapid and dramatic warming phase in recorded history.





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