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Impact of Climate Change in East Asian History

Korean Minjok Leadership Academy
International Program
Choi, Jeong Hoon
Term Paper, AP World History Class, December 2009

Table of Contents

I. Introduction
II. History of Climatic Change in East Asia
II.1 Climatic characteristics of East Asia
II.2 Climatic periods in East Asia
II.2.1 The Roman Warm Period (RWP)
II.2.2 The Dark Age Cold Period (DACP)
II.2.3 The Medieval Warm Period (MWP)
II.2.4 Little Ice Age (LIA)
II.2.5 Current Warm Period(CWP)
III. Roman Warm Period (RWP) in East Asia
IV. Dark Age Cold Period (DACP) in East Asia
IV.1 Food shortage
IV.2 Migration of nomadic tribes
V. Medieval Warm Period (MWP) in East Asia
V.1 Increase in food production
V.1.1 China
V.1.1.1 Central China
V.1.1.2 Southern China
V.1.1.3 Northern China
V.1.1.4 Western China
V.1.2 Korea
V.1.3 Japan
V.2 Impact on politics
V.2.1 China
V.2.2 Korea
V.2.3 Japan
VI. Little Ice Age (LIA) in East Asia
VI.1 political and social impact of the LIA
VI.1.1 China
VI.1.1.1 Southern China
VI.1.1.2 Central and Northern China
VI.1.1.3 Western China
VI.1.1.4 Overall Impact of LIA
VI.1.2 Korea
VI.1.2.1 LIA and the Japanese Invasion of Korea
VI.1.3 Japan
VII. Current Warm Period (CWP) in East Asia
VII.1 Effects of the increase in food productivity
VII.1.1 China
VII.1.2 Korea
VII.1.3 Japan
VII.2 Catastrophes during the CWP
VIII. Conclusion

I. Introduction
            Climate is a very important factor in understanding history, especially history of agricultural society because it affects agriculture which is the basis of economy, culture, and even politics. In East Asia, it was even more influential because weather condition was believed to be a sign from heaven which shows the virtue of the ruler and his administration. However, it was not until technological advance allowed researchers to reconstruct ancient climate that its impact was acknowledged.
            This paper focuses on how the periodic climate change has affected East Asian history and society during the last two thousand years.

II. History of Climate Change in East Asia

II.1 Climatic characteristics of East Asia
            Most of East Asia has temperate climate, though Southern China belong to subtropic zone and Northern China to subarctic zone. Also, there are temperate coastal areas where the Pacific Ocean and its currents influence the climate such as most of Korean Peninsula, Japan, and some Chinese provinces including Shandong and its neighbors. Central and Western China exhibits highly continental climate. (1) As a result, any climate change in global scale happened at inland parts of China first, and after then, other parts of China, and then Korea and Japan.
            One of the most distinct features of East Asian climate is the East Asian Monsoon. East Asian Monsoon is caused by collision between the North Pacific Air Mass and the Siberian or the Okhotsk Air Mass. Usually, its magnitude depends on how 'strong' the North Pacific Air Mass is, or in other words, the temperature of the Pacific Ocean. Therefore, the magnitude of the East Asian Monsoon can be an indicator of climate. (2) The records of the ancient monsoon can be found in sediments in caves, such as that of Wangxiang cave (3)

II.2 Climatic periods of East Asia
            The climatic periods in last two thousand years can be divided into five periods, which are the Roman Warm Period, the Dark Age Cold Period, the Medieval Warm Period, the Little Ice Age, and the Current Warm period just like in the following graph (4), which shows the strength of East Asia monsoon over past two thousand year in China.

II.2.1 The Roman Warm Period
            It began at least about 700 B.C. and ended around 200 A.D. It is not shown well in the graph above. It was wet and warm period that was suitable for agriculture. (5) Many of paleoclimatic data from East Asia does not show any distinct sign of high temperature or high level of precipitation during the supposed period, but there are also some records which prove that there was a warm period before the DACP. (6) However, whether the RWP existed in significant degree or not is still in dispute and so is its precise date. Moreover, the impact of the RWP to the East Asian ancient history is not clear also because there were no notable political factions in all East Asia except in some parts of China.

II.2.2 The Dark Age Cold Period
            The DACP began at circa 200 A.D. and ended around 950 A.D. Unlike the RWP, there are many clear evidences that show significant drop in temperature, which makes its existence is certain, but its precise date is still questionable. Moreover, whether cold climate continued throughout the entire DACP is uncertain; in some parts of Asia, there were sporadic moderately- warm periods. (See the rise in the strength of monsoon about 600 A.D.) Climate of the DACP was often dry and cold, which was not proper for growing crops. (7)

II.2.3 The Medieval Warm Period
            After the DACP was another warm period that continued until c. 1350 A.D., and it was wet and warm again like the RWP. Although some scientists argue that actually there was no significant warm climate during the MWP in East Asia, it seems evident that at least the 12th century was warmer than any other periods - even warmer than today-discussed on this paper. (8)

II.2.4 The Little Ice Age
            The Little Ice Age was believed not to have existed in East Asia once and its exact date is still very dubious. However, it seems that there was a cold period in Asia which is parallel to the Little Ice Age in Europe. There are many theories about the beginning, the maximum point, and the end of the LIA, but none of them are currently gaining dominant support. (9) In this paper, I took the most reliable theory that is consistent with meteorological records during that time which suggests that the LIA was continued from the 14th century to the beginning of 19th century. (10) According to this theory, there was the maximum cold climate in middle of the 17th century, and the climate condition became better (that is, warmer) afterward. (11)

II.2.5 The Current Warm Period
            The CWP started from the 19th century, but as the graph above shows, the climate was already becoming warmer since the 18th century. Meteorological abnormalities related with cold weather continued to happen despite the rise of average temperature. The CWP is continuing until today; average temperature is still rising, and this phenomenon is commonly known as the global warming.

III. The Roman Warm Period (RWP) in East Asia
            It is impossible to figure out the exact impact of the RWP in East Asian history due to lack of historic records. During the RWP, agricultural civilization prospered in East Asia; in China, many countries were founded and fought for ascendancy, which ended in unification by Chin and Han; in Korea and Manchuria, several tribes established federations such as the Ancient Joseon; in Japan, the Yayoi culture flourished. All these phenomena may be attributed to rise of temperature and the following increase in agricultural prosperity, but there is no evidence that these were critical factors; there is no historical record about the climate of East Asia during the RWP, though there are many records that indicate climate abnormalities in parts of China near Hwang He and Korea. (Few meteorological events were recorded until the development of meteorology after the 15th century.) The following text from The History of the Three Kingdoms () can be an example.
            "In the January of the 21th year (of the reign of Adalla Isageum began, AD 174), it rained, and the raindrop contained soil." ( ('soil') was written as ('king' or 'great') in the old edition, but it is very likely to be an error. )
            The 'rain with soil' is now considered as a phenomenon caused by the shift of sand from Mongolian deserts, which can only happen during spring and/or autumn. (13) Therefore, such a rain in January is a proof that the weather was so warm that spring could begin at January (This January is roughly equal to February in modern Western calendar.)
            Some paleoclimatic researches even cast doubt to that RWP actually existed in East Asia, and it is true that not all regions of East Asia had significantly warm period. (14) Moreover, there are only a limited amount of historic records about this period., which are mostly ones of a comparatively small area including only temperate zones such as current Hebei region or Southern Korea. However, considering that hardly any political factions that can be called as 'nations' did exist during the RWP except in those areas, it can be said that the influence of the RWP on the history is substantial.

IV. The Dark Age Cold Period (DACP) in East Asia
            Although it seems certain that the DACP existed in East Asia, whether the entire time interval between the RWM and the MWP had continuously cold climate is still disputable. For example, it is recorded that in early Tang dynasty, climate was so appropriate for agriculture that it was possible to grow crops even in the arid borderland near Central Asia. (15) However, as many Chinese records of series of catastrophe in late Han period (late 2nd Century BC), the change of climate between the RWP and the DACP was somewhat noteworthy and did caused some significant effects to East Asian society. Korea and Japan, though it is not certain, seems to have been affected later. (Note that the following excerpt and the last excerpt discuss the same year but depict contradictory climates.)
            Some excerpts from the Book of Later Han () that proves the existence of low temperature in the beginning of the DACP are like the following :
            "In winter of the sixth year of the reign of Emperor Ling (174 A.D. ), it was very cold; in Beihai, Donglai, and Nangya provinces, ice on the wells was at least one zhi (30.3cm) thick."
            "In the June of the fourth year of the reign of Emperor Xian, (184 A.D.), it was windy and cold as winter."

IV.1 Food shortage
            The beginning of this period is marked by political disturbance in China. One of the factors involved in the collapse of the Han dynasty in the third century is low level of food production which can probably attributed to the DACP. For example, unlike any other time in the Chinese history, the warlords during late Han dynasty often suffered from lack of proper food supply.
            "In September (of 194 AD), (・) the Grand Founder (Cao Cao) lost Yi Zhou province, but because his food supply was not enough, he had to give up (any attempts to recapture it). (・) In this year, price for one 'tou' (180L) of grain was almost 500,000 qian, and people ate each other."
            Such situation resulted in great social instability. For example, unrecorded massive uprising (i.e. The Yellow Turban rebellion and The Five-Peck-of-Rice rebellion) of agricultural workers occurred, which continued for more than 20 years despite constant struggle of local warlords and the government to suppress them. (19) In addition, according to the Book of Later Han, there were at least four major riots of peasants due to food shortage during the reign of Emperor Xian (181~234 AD) which affected the entire Han China. (20) In other words, this food shortage was not limited in some provinces.
            Unfortunately, the impact of food shortage on Korea or Japan is uncertain. However, it is noticeable that the kingdom of Goguryo made several expeditions to acquire resources or agricultural land since the 3rd century A.D., which is about the beginning of the DACP in Korea. During the reign of King Dongcheon, Goguryo even attempted to occupy, not just to raid and loot, Northern provinces of Wei, though eventually her forces were bitterly defeated by Wei's fast response. (21) Many Chinese historians attributed the frequent attack and conquest of Goguryo was mainly caused by food shortage. (22)

IV.2 Migration of nomadic tribes
            After the food shortage shocked the established agricultural society, nomadic tribes that originally inhabited in northern Manchuria or inner Mongolia began to migrate to the south. Their migration-which was more like an invasion-was mostly successful, and caused a mayhem of the Sixteen Kingdoms period since 304 AD. For example, Xianbei even took over entire northern China and founded many 'barbaric' dynasties such as North Wei (founded in 386 A.D.), and remained as a dominant force in western Manchuria until the sixth century. (23)
            Due to lack of proper record, it is not certain why these Nomadic people migrated into China, but there are evidences which indicate that it was because of climate change. First of all, during the RWP, the nomadic tribes (Xiongnu) preferred not to conquer China but rather routinely loot towns and cities near the border; they had never attempted to settle down in China, unlike their next generations. (24) Therefore, it is possible that climate change had forced the nomads to migrate. In addition, this aggressive attitude of nomadic people in current Mongolia and Manchuria can also be explained by the fall of kingdom of Buyeo.
            Buyeo was located near the Songhua river, and her people lived on farming, though they also engaged in herding like nomadic people. Chinese historians record that the soil and climate of Buyeo was appropriate for raising most types of grains, which shows that the climate was much warmer than today (25). Even though its political influence dwindled as its rival, Goguryo was established, but Buyeo remained as an important social and economic entity until middle of the 3rd century; according to the History of the Three Kingdoms, Buyeo had an equal or even better socioeconomic status compared to Goguryo. However, when China was suffering from nomadic migration, Buyeo suddenly lost her power, and was practically fallen apart when the Murong tribe of Xianbei attacked her capital and forced king Uiryeo to commit suicide in 285 AD (26). Considering that no reason of this comparatively sudden collapse was mentioned in history, it can mean that climate became unfavorable for agriculture, which used to be the foundation of Buyeo economy.
            These evidences indicate that during the DACP, Manchuria and inner Mongolia had adverse climate condition which drove the nomadic tribes into China.

V. The Medieval Warm Period
            As the graph in II.2 shows, there was a drastic climate change in China and probably in Korea about the beginning of the MWP. Moreover, record of catastrophes also proves how extreme the climate change was; There were at least at least 650 massive floods and 220 hailstorms (Which tends to become frequent in a warm period (27)) during the entire reign of Song dynasty while there were only 99 recorded cases of drought. (28) It was big enough to bring or at least boost major changes in politics, society, and culture of the two countries. In Japan, it seems that such dramatic change was probably regulated by her neighboring ocean; the effect of the MWP was not obvious until the 11th century.

V.1 Increase in food production
            In contrast to the DACP in which food production level was low or at least not very stable, the MWP had a proper climate condition for agriculture: high climate and high precipitation. Consequently, population grew rapidly. For example, estimated Chinese population in the early 11th century was about 8.6 million households; at the beginning of the 13th century, it was 12.6 million households. (29)

V.1.1 China

V.1.1.1 Central China
            Central China, which means the area between Yangzi and Huang He in this paper, experienced a great agricultural-economic boom as the climate became more favorable for growing various types of crops.
            First of all, rice paddy cultivation was introduced. Although developed during Tang dynasty, it was not been widely adopted except in Southern China due to the possible danger of this method: if precipitation is not enough, rice paddy dries out, and the productivity goes down drastically. However, the warmer climate in the MWP allowed it to be spread. As a result, food production level rose up significantly. (30)
            Also, commercial agriculture became widespread. Rice paddy cultivation not only increased the production of rice, but also reduced the amount of time and labor required. As a result, farmers began commercial farming. The most common commercial crops included cotton and tea. (31)

V.1.1.2 Southern China
            Southern China became even more important in this period. During the MWP, the economic center of China had moved from Northern China to this area. The rice paddy cultivation was already prevalent even before the climate became warmer, so based on the high experience and driven by economic needs, the methods of agriculture became more and more sophisticated. For instance, better irrigation techniques such as using 'water wheels', which was a water pump that uses human or horse power to transfer water, was developed and soon widely adopted. (32) Moreover, new type of rice which was more appropriate for subtropic climate was introduced from Vietnam. (33) As a result, until the climax of the LIA, the food production level was kept high enough to maintain its population near the Malthusian balance even after the MWP was ended; 75% of Chinese population lived in Southern China by 1250. (34)
            Commercial farming, just like that in Central China, had become even more developed. (35) Some farmers even ran plantations in which they grow specialized crops such as herbs, sugar cane, or fruits, which provided high incentive for merchants.

V.1.1.3 Northern China
            Although the average temperature was constantly rising and so did the annual precipitation, Northern China was, just like it is today, still inappropriate for massive rice farming. Therefore, Northern Chinese farmers chose to grow other crops such as millet, wheat, and bean, and buy rice and other staples from merchants. During Song dynasty, government officials found that this is a very efficient system, and encouraged it throughout the entire provinces above Huang He. (36)
            However, after the Song dynasty retreated to Southern China due to Khitan and Jurchen invasion in middle of 12th century, agriculture in Northern China degenerated rapidly as many farmers migrated to other parts of China to avoid war and many farming areas were destroyed by the invaders. (37)

V.1.1.4 Western China
            Western China, which is current Sichuan and its neighboring provinces, consists of fertile basins and mountain ridges. Because of its terrible traffic condition, population in Western China had been not that high, but after the 12th century, it had changed. Massive immigration from Northern and parts of Central China gave the area a population boom. The productivity of the soil was not that low, but it was neither high enough to support all the immigrants. Therefore, immigrants built the famous terrace fields, also known as tituans. (38) Although it was not prosperous as that of Southern China, Western Chinese farmers also engaged in commercial farming, and some of their products, such as watermelon, were so successful that they are still being cultivated and exported in the area. (39)

V.1.2 Korea
            Although it is not directly mentioned, the Treatise on Wealth and Goods from the History of Goryeo () indicates that Korean agriculture was more highly developed compared to that of Shilla or other ancient nations because it was deeply influenced by that of China. (40)
            During the MWP, Korean farmers eagerly adopted the Chinese method of growing rice, though they accepted rice paddy cultivation relatively late due to lack of proper irrigation facility. Being neither subtropic like Southern China nor continental like Western or Northern China, however, Koreans developed their own way of growing crops which was very similar to European three-field system. It was widely adopted throughout the entire Goryeo provinces, and as a result, both the food production level and the diversity of nutrition were increased. (41) Considering that the method not appropriate for most parts of Korean peninsula nowadays, it can be concluded that it was the warm climate that enabled such an intensive innovation to take place.

V.1.3 Japan
            In Japan, agricultural development was mainly done by the attempts to increase the cultivatable area as much as possible rather than adopting new agricultural techniques, though some of the cultivation methods from Song dynasty did influenced Japanese agriculture.
            As the climate got warmer, food production increased, which resulted in increase of population, and as a result, demand for new farming areas became larger. Soon, farmers supported by local administrators or landlords began to explore new land for agriculture, and their attempt was quite fruitful. In addition, better climate condition increased the total amount of arable area, so difficulty of developing new farmland was insignificant during the MWP, and this also accelerated the process of cultivation. (42)

V.2 Impact on politics

V.2.1 China
            The rise in food production level probably aided the dynasty to sustain political stability in early MWP. Song dynasty had one of the weakest armies in the history of China, and therefore was always under peril of invasion of Khitans, and later, Jurchens. Unable to rely on military forces to get rid of the situation, emperors of Song dynasty decided to offer tribute to the nomadic tribes through the treaties such as the Oath of Shanyuan (), which was surely a shame, but also the most efficient way to solve the trouble. The increase of tax income due to the increased production of crop and economic growth caused by development of trade (both of them were the results of climate change.) made the tribute not burdensome for the government. (43)
            However, what gave stability to Song China ironically caused its downfall in the long run. Because the rise of market economy was so sudden and intense, the government could not take control of the market, so Song economy was basically laissez-faire. In the mid-11th century, Song economy was controlled by a number of rich merchants and landowners. They formed a cartel which ruined the economy and consequently reduced tax income of Song dynasty. (44) There were several attempts to regulate these Chinese-style bourgeois, but none of them were successful, and they only caused endless political feud in Song court, which made Song even more fragile to invasion. Eventually, Song collapsed, and the rest of the government fled to Southern China and established the South Song dynasty.

V.2.2 Korea
            In Korea, increased food production brought similar result. Of course, Goryeo economy was not that booming compared to that of Song China because trade was still under government control. It was the feudalistic system of Goryeo in which it offered some of its land to aristocrats as a type of reward for service to the country that became the source of trouble.
            Increased production of crops gave the landowner-aristocrats even more power. The influence of the aristocrats grew bigger and bigger, and about the 12th century, the government was almost controlled by a number of aristocrat families.
            This closed oligarchy system caused many troubles to Goryeo. First, there was endless struggle for ascendancy between the families. The scale of such struggle was beyond control of government; for instance, during the famous rebellion of Lee Ja-gyeom in which he tried to take over the control of Goryeo and take the throne using his influence, the rebel forces even attacked the palace and burned it down. (45)
            The second biggest problem was that Koryo had lost its social vigor as the aristocrat families continued their oligopoly of power. Any attempts to make changes were met with great resistance. For example, when a Buddhist monk Myocheong and his followers argued that the government should move the capital to Pyeongyang and should firmly stand against the Jin () dynasty in China which was demanding Goryeo to become its vassal, the families suppressed them with force through a two-year civil war. (46)
            Such problems caused social unrest in Goryeo, and this social unrest was eventually expressed in form of coup d'etat in 1270, in which a military junta took control of the government and massacred the aristocrats during the process.

V.2.3 Japan
            In Japan, the MWP was one of the reasons for rise of Kamakura Shogunate. As mentioned before, cultivation of new arable land was very frequent during the 11th century. Most of the new farmland were hardly under government control but rather under control of the local supporter, which gave birth to Japanese system of Shoen (), or manors. (47)
            Meanwhile, Japanese court was losing its influence over provinces because of power struggle between aristocrat families and the corruption of local administration. As Shoen system became dominant, the supporters of cultivation became somehow like the lords of European manors; they hired soldiers to protect their shoen and its semi-sovereignty. This was the beginning of the rise of samurais. (48)
            By the beginning of 12th century, Japan was almost a feudal state. Military power has become more important than civil administration, and this helped some upper-class samurais to gain even greater influence, both in politics and in military affairs. One of these successful samurai families was the Minamoto family, which, during the period of Minamoto no Yoshitomo, finally established the first shogunate in the history of Japan-The Kamakura Bakufu.

VI. The Little Ice Age(LIA) in East Asia
            Although the LIA may seem like another cold period like the DACP, it did not bring the same result to East Asia. The magnitude of the climate change was probably even bigger than that of the change between the RWP and the DACP, but there was a fundamental difference between East Asia during the DACP and the LIA; East Asian society had established system when the LIA began, which prevented any drastic changes from happening. Also, advanced agricultural techniques kept the food production level not too low except during major climatic abnormalities such as giant typhoons in Guangdong or extremely cold weather in central China. (49) As a result, among the meteoric events related with LIA, only a few caused any change in long term.

VI.1 Political and social impact of LIA

VI.1.1 China

VI.1.1.1 Southern China
            Southern China, which had been the economic center of China since Song period, was still holding its position. Because the effect of LIA was not that evident until the maximum point between late 16th century and mid 17th century (50), the food production level was still high until the late Ming period. Also, new crops from America such as potato, maize, and peanut helped Southern China agriculture to maintain its productivity. (51)
            However, as the climate continued to be worsened, Southern China inevitably lost its agricultural prosperity, and due to the huge population, this has brought a great disaster. First famine probably due to unfavorable weather in Southern China recorded in history happened in the reign of Emperor Chenghua (1464), and since then, food shortage became worse as time passed. For example, according to the History of Ming, in the third year of the reign of Emperor Jiajing (1523),
            "All southern provinces suffered from a great famine. Even parents and their sons ate each other, and skeletons were everywhere. The bad smell (of rotting corpses) was spread to even remote areas."
            Of course, cold weather itself damaged the local communities, just like in the following text.
            "From the winter of the fourth year of Emperor Jingtai¨s reign (1473) to the early spring of the next year, it snowed more than several zhi (30.3cm) in Shandong, Henan, Zhejiang, and Hui provinces. Seawater near Huidong was frozen over more than 40 li (16km) from the coast, and the death toll of people and stocks was near ten thousand"
            Moreover, there were frequent typhoons in the region probably caused by relative cooling of the sea. Typhoons always happen in East Asia, but they seldom affect Southern China unless the seawater near Ryukyu and Taiwan is cool and therefore creates a high air pressure that blocks the typhoons. This is why there were so many recorded typhoons in Southern China during the LIA.
            "In the July 6th of the first year of Emperor Jiajing's reign (1521), there was a great storm in Nanjing. Suburbs, downtown, tombs, and even palace and part of the city wall were destroyed. (・) More than ten thousand trees were rooted out (due to the storm)."
            The magnitude and the damage of the typhoon were like what were described in this excerpt. Between 1431 (the record of the first typhoon in South China) and 1638 (the record of the last significant typhoon during Ming period), there were at least 21 typhoons which had almost similar magnitude and impact. (55)
            Such a series of famine and disaster caused the collapse of Southern Chinese economy which was pivotal to the empire. Partially because of this, Ming dynasty was weakened and began to lose control of outer provinces.

VI.1.1.2 Central and Northern China
            This area suffered from famine even earlier than Southern China. However, for some times, this was not significant to Ming dynasty; even during the heyday of Ming dynasty (From Emperor Yongle to Emperor Xuande). Also, because commercial agriculture was even more widespread compared to that during Song period and the diversity of crops was also increased, until the 17th century the climate change was not that significant. However, just like in Southern China, economic collapse was inevitable.

VI.1.1.3 Western China
            Famine was inevitable in Western China, though it was not severe or frequent. However, because agricultural community in Western China had been largely destroyed by the beginning of the LIA (That is, about the collapse of Yuan dynasty) (56), series of meteorological abnormalities did not affect it that much; there was almost nothing left to be destroyed. The following excerpt shows an example of such situations.
            "(In 1525) there was a great storm in Shanxi province. It was so strong that it even seemed to blow up everything in the world. More than one hundred houses were destroyed."
            The description of this typhoon proves that it was a comparatively strong one. However, the damage it had done to the province was no more than destruction of 100~200 houses, which is contrary to the record about storm in Nanjing. This shows that Western China had already been devastated even before the LIA, and therefore was relatively less affected by the climate change.

VI.1.1.4 The overall impact of LIA
            Economic center of Ming dynasty was South China, and therefore, the LIA which caused great damage to Southern Chinese local communities was also very detrimental to the dynasty. Although development of agriculture helped Ming to sustain its economy for some time, the collapse was inevitable as the climate was getting worse for agriculture. As a result, Ming had fallen apart, and finally was conquered by Manchurians who established Qing dynasty.

VI.1.2 Korea
            Although many meteorological catastrophes possibly due to LIA are recorded in Korean history, it is less likely that any of them had significant meaning until the 17th century because they were concentrated on Northern Korea where population was not high. (58)
            However, as the average temperature went down significantly, many abnormalities induced by cold weather began to happen, like one described in the following excerpt.
            "(In April 27th ) In Gyeongi-do and Hwanghae-do, trees and crops were covered with frost."
            Such abnormalities also caused series of famine just like in China.
            "Heaven (Astronomic and meteorological signs) shows warnings and the earth is telling us about abnormalities; (..)In this year we are having a great drought. (・) Barley is not purchased in market anymore, and no seed is planted on earth."
            Despite these famines, Korean society remained relatively stable due to many reasons that are still controversial. Some widely accepted reasons are like the following : First, the disasters, unlike those in China, were less continuous, giving the damaged agricultural communities enough time to recover. Second, because Korean economy was relatively small, it was much easier for the government to control the economy and redistribute the products to the provinces with food shortage. (61)

VI.1.2.1 LIA and the Japanese Invasion of Korea
            During the Japanese invasion of Korea in 1592, many Japanese soldiers suffered from unexpected cold weather probably due to the LIA, which forced them to give up any further military actions and retreat. (62) Ryu Seong Ryong, a Joseon aristocrat who was in charge of most administration in wartime, mentions that
            "The enemy general (Kato Kiyomasa) had to lead his men back. When they were retreating, their moral was extremely low and so was their physical condition. (・) Some stragglers wandered around local farms (for food) and even begged for something to eat (to farmers)."
            Just like this, Japanese troops were almost forced out of Northern Korea, and after their first year in Korea, most of them retreated back to Southeast part of Korea where weather was warmer.
            Moreover, knowing that Japanese forces were not prepared enough for cold weather, Korean-Ming allied army launched massive counterattack on Japanese mostly during winter. For example, the Battle of Pyeongyang took place in January 2nd, 1593, and the Battle of Ulsan, December 16th, 1596. Both offensives were successful. (64)

VI.1.3 Japan
            Japan suffered from multiple cold-induced famines during the LIA. From the beginning of the 17th century to mid-19th century, there were 154 famines, of which 21 were widespread and serious. (65) Until the beginning of the 18th century, introduction of new agricultural techniques and social integrity under Tokugawa rule prevented the damage from colder climate to some degrees. However, as population grew and the increase in food production level decelerated, Japanese society was struck hard. Continuous famines kept the population growth rate in almost zero state from 1720 to 1820. Some of these famines were severe enough (Kyoho famine in 1732 was responsible for death of 1,000,000 people; so did Tenmei famine from 1782 to 1787) to dwindle the influence of the Bakufu and therefore make the Japanese society instable. (66)
            On the other hand, famine enabled the rise of new economy in Japan. (Tokugawa period, Encyclopaedia Britannica) Many peasants fled to urban areas because they could not pay for their tax due to decreased harvest. This inflow of cheap labor force made the economy flourish. In contrast, samurais of higher ranks who owned manor, daimyos, began to lose their influence. The source of their main income was the tax that peasants paid, and as many people began to abandon agriculture, economic stand of samurais began to be weakened. This financial crisis of the ruling class caused the fall of established Japanese social system. (67)

VII. The Current Warm Period
            Considering that we are still living in the CWP, it is impossible to fully assess the effect of the CWP. However, it is true that it did affect East Asia a lot. In most cases, the CWP helped East Asian countries to develop, but there were some cases of meteoric abnormalities that influenced history considerably.

VII.1 Effects of the increase in food productivity
            Just like any other warm periods, food production level rose as climate became more appropriate for agriculture. However, the result was quite different from that of the RWP or the MWP.

VII.1.1 China
            The CWP boosted both the population growth and political unrest in China. Since the late 18th century when the LIA was almost finished, China, especially southern China had explosively increasing population partially due to favorable climate. Because cultivation technique had already been refined during Ming period (68), when climate became warmer again, the food production level could, almost instantly, return to its original level before the LIA and soon, even higher than that. In other parts of China, the same thing happened, and the current system of growing crops according to different climate has been established. When the CWP just began, population growth was very rapid; in 1700, the Chinese population was estimated at 100,000,000, and this figure was trifled a hundred years later. (69) However, the population growth went too far and therefore caused food shortage by the middle of 19th century. (70) The unrest of late Qing dynasty was partly due to this.

VII.1.2 Korea
            The CWP brought many radical changes to once-stagnated Joseon society. First of all, better weather enabled new agricultural technologies such as rice plantation (which had been practiced in China a lot earlier) to be adopted, and productivity drastically increased. However, such sudden change caused demise of the traditional agriculture system. In addition, as amount of land required for production of rice decreased, commercial crops started to be produced, which accelerated the rise of monetary economy and progress to proto-capitalism in the late Joseon period. This was much more fundamental than change in China, because capitalism was contradictory to the established Confucian social order in which commerce was undesirable. As a result, traditional social system collapsed. (71)

VII.1.3 Japan
            In Japan, the effect of the CWP on its modern history is not sure. However, it is true that once stagnated population growth of Japan could have been re-accelerated because food production capacity was increased due to climate change.

VII.2 Catastrophes during the CWP
            The CWP has not been a merely warm period; it has been a period of recurring disasters, and antiquated governments of East Asian countries were not able to take care of them. For example, great floods and famine were continued throughout the early 19th century.
            "On 16th and 17th of July, it rained so much that the entire Gyeongsang province was almost submerged. Before then, it had not rained for three months, and we worried about possible famine; after the rain of two days, it became certain that our worry would become the reality."
            Also, the extreme cold weather of Japan in 1823-1829 claimed lives of hundreds of thousand people, but the government of both countries failed to implement any measures to deal with the catastrophe. Such disasters sometimes offset the positive effects of warmer climate, and even provoked social and political instability, which eventually drove all East Asian societies to mayhem.

VIII. Conclusion
            As discussed in this paper until now, fluctuations and irregularities of climate can be credited to determining, at least partially, East Asian history. In the RWP, warm climate played an important role in the development of agricultural society in East Asia. In the DACP, cold climate partly caused the Han dynasty to fall, and drove the nomads in Manchuria to invade Northern China. The MWP allowed Song, Koryo, and Japan in Heian age to flourish, but it also caused major power shifts within these countries. It made Song to retreat to Southern China, weakened the government in Goryeo, and gave rise to the feudalism in Japan. The following period, the LIA, damaged agriculture in China seriously, causing Ming dynasty to fall. Its impact on Joseon society was only temporary, but it did helped Joseon army fight against the Japanese. In Japan, it was one of critical factors that ended feudalism. The most recent period, the CWP, was warm again and boosted population growth in East Asia, but also had a number of climatic abnormalities which brought social and political unrest.
            Though often neglected, the environment has been one of the prime factors that determine not only our daily life but also the society and even history. Its importance was even greater in pre-industrial societies because agriculture, which is very susceptible to weather, was the base of almost every activity. Therefore, study of past environment would be important for understanding history more thoroughly.


1.      High-Top Earth Science I, Doosan-Donga, 2004
2.      The Co2 Science, East Asia and North Atlantic climate of the past two millennia
3.      The scienceblogs, Chinese climate history
4.      The source of the graph is
5.      The CO2 Science, Roman Warm Period-Summary
6.      Ibid.
7.      The Co2 Science, The Dark Ages Cold Period in China
8.      The Co2 Science, Medieval Warm Period(China)
9.      Little Ice Age, Wikipedia
10.      The CO2 Science, Little Ice Age (Regional-Asia:China)
11.      Ibid.
12.      The History of Three Kingdoms, the record of Shilla, volume #2
13.      High-Top Earth Science I, Doosan-Donga, 2004
14.      The CO2 Science, Roman Warm Period-Summary
15.      The New book of Tang, Treatise on industry, volume #55
16.      The Book of Later Han, Treatise on the Five Elements #15
17.      Ibid.
18.      The Record of Three Kingdoms, Biography of Emperor Wu #2
19.      Ibid.
20.      The Book of Later Han, Treatise on the Five Elements #15
21.      History of the Three Kingdoms, the record of Goguryeo, volume #20
22.      The Record of Three Kingdoms, The book of Wei, Treatise on the Eastern People, volume #30
23.      Xianbei, Wikipedia
24.      The record of the Historian, the biography of Xiongnu
25.      The record of the Three Kingdoms
26.      Ibid.
27.      High-Top Earth Science I, Doosan-Donga, 2004
28.      History of Song, volume #61 and 62
29.      Chinese History - Song Dynasty economy,
30.      Ibid.
31.      Ibid.
32.      Technological aspects of Song agriculture,
33.      Ibid.
34.      Song dynasty, Wikipedia
35.      Agriculture in China, Wikipedia
36.      Chinese History - Song Dynasty economy
37.      Ibid.
38.      Ibid.
39.      Ibid.
40.      The History of Goryeo, the Treatise on Wealth and Goods, volume #78
41.      Kim 2007, p. 497
42.      History of Japan, Wikipedia
43.      Song dynasty, Wikipedia
44.      Ibid.
45.      Kim 2007, p. 221
46.      Ibid.
47.      History of Japan, Wikipedia
48.      Ibid.
49.      The Co2 Science
50.      Agricultural Civilization in China,
51.      Ibid.
52.      History of Ming, Treatise on the Five Elements, volume #28
53.      History of Ming, Treatise on the Five Elements, volume #30
54.      Ibid.
55.      Ibid.
56.      Sichuan, Wikipedia
57.      History of Ming, Treatise on the Five Elements, volume #29
58.      Annals of Joseon Dynasty
59.      Annals of Joseon Dynasty, April 27th, 1653
60.      Annals of Joseon Dynasty, June 14th, 1644
62.      Ibid.
63.      Jingbirok, Chapter 8
64.      Jingbirok, chapter 15
65.      A Chronology of Japanese History,
66.      Little Ice Age famines in Japan, Co2 Science
67.      Wikipedia, History of Japan
68.      Agricultural Civilization in China,
69.      Demographic history of China, WHKMLA
70.      Little Ice Age famines in Japan, Co2 Science
71.      Kim 2007, p.351
72.      Annals of Joseon Dynasty, 1814, July 30th


Note : websites quoted below were visited in November 2009.
Primary Sources :
1.      Annals of Joseon Dynasty(Joseon Wangjo Sillok, )
2.      The History of Three Kingdoms (Samguk Sagi, )
3.      The New book of Tang (Xintangshu, )
4.      The Book of Later Han (Houhanshu, )
5.      The Record of Three Kingdoms )
6.      Ryu seong ryong; Jingbirok (), translated by Lee Jae-ho, Yeoksauiachim, 2007
7.      The record of the Historian (Shiji, )
8.      History of Song (Songshi, )
9.      The History of Goryeo (Goryeosa, )
10.      History of Ming (mingshi, )
Secondary Sources
11.      The MWP and the LIA in China, Co2 Science
12.      East Asia and North Atlantic climate of the past two millennia, Co2 Science
13.      Little Ice Age (Regional - Asia : China), CO2 Science
14.      Mid-Holocene and Medieval Warm Period Temperatures in China, Co2 Science
15.      Roman Warm Period (Asia) - summary, Co2 Science
16.      The Medieval Warm Period and Little Ice Age, Co2 Science
17.      Little Ice Age famines in Japan, Co2 Science
18.      Daniel Sarabis; Ecological Crises and their Systemic Origins: Historical East Asia in the Midst of a Dark Age, 2006
19.      Peter.B. de Menocal; Cultural response to Climate Change during the Last Holocene
20.      Stephen C. Porter, Zhou Weijian; Synchronism of Holocene East Asian monsoon variations and North Atlantic drift-ice tracers, University of Washington, 2006
21.      B.G. Hunt; The Medieval Warm Period, the Little Ice Age and simulated climatic variability, Springer Berlin/Heidelberg, 2006
22.      Kim Dae-Sik, Korean History, Sungmoondang, 2007
23.      MWP and LIA in IPCC reports, AbsoluteAstronomy (
24.      National Congress Library of Japan, Kindai (modern era) page.
25.      Database of 24 histories on Chinese Wikisource (
26.      The Annals of Joseon Dynasty Online Database,
27.      CO2 Science,
28.      Wikipedia
29.      Chinese history,
30.      ChinaCulture,
31.      AbsoluteaAstronomy,

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