What are the cold periods in history and why?

The climate change in the history of China not only has obvious temporal and spatial differences, but also has a far-reaching impact on the social and historical development of China due to the interaction of the two differences. This paper attempts to outline this feature and its influence in order to teach local colleagues.

First, the time difference

Climate includes two basic elements: temperature and dry and wet conditions, and the study of historical climate must also start from these two aspects. The article "Preliminary Study on Climate Change in China in the Last Five Thousand Years" by the famous scientist Mr. Zhu Kezhen (①) systematically summarizes the basic laws of climate change in China, indicating that the temperature change in China in the last five thousand years has four warm periods and four cold periods.

1. The first warm period was from 3000 BC to 1 100 BC, that is, from Yangshao culture period to Yin and Shang dynasties. Oracle Bone Inscriptions recorded that Anyang rice was planted in February of the lunar calendar at that time, more than a month earlier than now. The analysis of the peat layer near Beijing shows that a large number of broad-leaved forests grew there five thousand years ago, which represents a fairly mild climate.

2. The first cold period was from 1000 BC to 850 BC, that is, the cold period of the Western Zhou Dynasty. The Chronicle of Bamboo Records records the freezing of the Yangtze River and Hanshui River in the Zhou Dynasty, indicating that the climate at that time was colder than it is now.

3. The second warm period is from 770 BC to the beginning of AD, that is, from the Eastern Zhou Dynasty to the Qin and Han Dynasties. Spring and Autumn Annals records that there is no ice in the first month of spring, no ice in February, no ice in spring and so on. According to Xunzi Guo Fu and Mencius Gaozi, agricultural cultivation in Qilu area is twice a year.

4. The second cold period lasted from 1 century to 600 AD, that is, the cold period of the Eastern Han Dynasty and the Southern and Northern Dynasties, and reached its peak in the first half of the 4th century AD. In the early years of the Jin Dynasty, the Bohai Bay was completely frozen from Changli to Yingkou for three consecutive years, and thousands of horses and chariots could drive on the ice, and the annual average temperature was 2-4℃ lower than now.

5. The third warm period is from 600 AD to 1000 AD, that is, the Sui and Tang Dynasties. During this period, there was no ice and snow in the winters of 650 AD, 689 AD and 678 AD, and the climate was warm and visible.

6. The third cold period is from 1000 to 1200, which is the Song Dynasty. During this period, Taihu Lake11was completely frozen and opened to traffic on ice, 1 165438.

7. The fourth warm period is 1200 ~ 1300, that is, the warm period in the late Song Dynasty and early Yuan Dynasty. 1225, Qiu Chuji, a Taoist, wrote a poem in Changchun Palace, Beijing, which said: "During the Qingming Festival, apricot blossoms bloom and thousands of families come and go." This shows that the climate in Beijing was warmer then than it is now.

8. The fourth cold period is from 1300 to 1900, that is, the cold period of Ming and Qing Dynasties. During this period, Taihu Lake froze for several feet at 1329, and oranges froze to death. During the period of 1493, heavy snow fell in the Huaihe River Basin, and Dongting Lake became an "ice sheet" from September of that year to February of the following year.

In the past five thousand years, the climate in China has changed alternately from four warm periods to four cold periods, and the time difference is very obvious.

Second, the spatial differences.

There are four factors affecting climate change in historical period: solar radiation, underlying surface, atmospheric circulation and human activities. The interaction of these factors determines the climate change. In addition, China's latitude position, land and sea position, vast area, complex terrain and circulation factors that dominate climate determine another feature of climate change in China-the emergence of spatial differences.

The climate fluctuation on the earth is first related to the intensity of solar radiation. The cycle of spring, summer, autumn and winter, the difference of cold, warm and hot areas are all due to the different intensity of solar radiation. China's territory starts from the middle reaches of Heilongjiang River in the north and reaches Zengmu shoal in the south, which spans 49 latitudes from north to south. From south to north, it includes six hot zones: equatorial belt, tropical zone, subtropical zone, warm temperate zone and cold temperate zone.

From the land and sea position, China is located between Asia-Europe continent, the largest continent in the world, and the largest ocean Pacific Ocean. Due to the different surface heat conditions, different temperature fields and pressure fields are formed, resulting in obvious monsoon circulation, which has a far-reaching impact on China's climate. Compared with the same latitude regions in the world, the Yellow River Basin in China is equivalent to the Mediterranean region, and the latitude south of the Yangtze River is equivalent to sub-Saharan Africa in North Africa. Jiangnan in China is a desert, but due to the subtropical monsoon climate, the eastern and southern parts of China have become unique areas with the richest subtropical natural resources in the world with high temperature and abundant precipitation.

From the east-west trend of the three mountain systems in China, they are the barriers of cold and warm air flow between the north and the south, and constitute an important climate dividing line. Among them, the Qinling Mountains with an altitude of 1500-2500m have the most obvious influence. The northern part of Qinling Mountains is warm temperate zone and the southern part is subtropical zone. The poem "Shan Mei opens in October, and the southern branch is warm in the north and cold in the south" just shows that Qinling Mountain is the climate dividing line between the north and the south of China. It is 5000 meters above sea level. The humid climate in the Pacific Ocean is not available, and the water vapor channel from the Indian Ocean is cut off by the Himalayas, which makes the northwest inland of China a desert arid climate. In addition, Siberian cold air suddenly invaded from the Mongolian Plateau, forming a strong cold wave that affected most parts of northern China in winter, which increased the spatial difference of climate change in the east, west, north and south.

In China, the climate is getting colder from south to north and from east to west, and forests, grasslands, barren sand and deserts also appear in turn, thus forming a completely different climate from east to west, north and south. The biggest feature is the natural differentiation of climate in the southeast and northwest. The spatial and temporal differences of climate change alternate, which has a great impact on the historical development of China in different periods.

Third, the influence of time and space differences.

The first is political influence.

The division between the southeast and northwest of China caused by the difference of climate in time and space has had a far-reaching impact on the social development of China. Modern geographers draw a diagonal line on the map of China, with the northwest of China to the west, accounting for 57. 1% of China's land area and 5.6% of the total population. Historically, it is generally the main activity area of nomadic people or ethnic minorities. To the east and south of the diagonal is the southeast of China, occupying 42% of the territory and 94% of the total population. It is basically the main activity area of agricultural nationalities (Han nationality) in history. (2) Among them, with the change of climate, the economy and culture in the southeast gradually surpass that in the north, and the population density is also increasing.

Between the northwest and southeast of China, the ancient Great Wall generally coincides with the natural dividing line between agricultural and pastoral areas. As early as 1 12 1 years ago, Taoist Qiu Chuji said when crossing Yehuling, the first pass in Zhangjiakou in the north, "Looking up and overlooking Taihang Mountain, it is sunny and lovely. Looking north, it is cold sand and cold grass, and it has been isolated from the wind of the Central Plains since then. " "Between the desert, it is freezing, windy, livestock and fish feed, fur is clothes, and people can change their disciples at any time, so horses and chariots are home. This geographical environment determines the confrontation between farming, animal husbandry and agricultural peoples and nomadic peoples in the history of China. Two economies, two nationalities, communicate peacefully with each other and wait for each other. Whenever the cold period replaces the warm period, there are always large-scale nomads going south to keep warm. The agricultural dynasty in the Central Plains is facing the challenge of nomadic people in the north. Among them, the "Five Wild Flowers" around 400 AD, the Khitan, the Nuzhen and the Mongols went south one after another around 1200 AD, and the Manchu entered the customs around 1700 AD, which is the most typical example of the military conflict between the farming and pastoral peoples. The war and relationship between the Central Plains Dynasty and the northern minority regimes have always influenced and restricted the social and historical development of China.

The most direct influence of the confrontation between farmers and herdsmen lies in politics. With several biggest military conflicts, there have been several typical political situations of confrontation between the Northern and Southern Dynasties. "Five Wild Flowers" accompanied the confrontation between the sixteen northern countries and the Northern Wei Dynasty, the Northern Qi Dynasty, the Northern Zhou Dynasty and the Southern Eastern Jin Dynasty, the Song Dynasty, the Qi Dynasty, the Liang Dynasty and Chen Dynasty. Along with the southward migration of Khitan, Nuzhen and Mongolia, it was the second confrontation between the Southern and Northern Dynasties and the Liao, Jin and Song regimes. In the Ming Dynasty, the regime in the early Ming Dynasty confronted the regime in the Northern Yuan Dynasty. Then there is the confrontation between the Nanming regime and the Qing regime in the late Ming Dynasty. Due to the long-term confrontation between the North and the South, the agricultural people have to rely on the authoritarian centralized government to organize scattered farmers to build the Great Wall of Wan Li, to defend their lives and live and work in peace and contentment, which is one of the important reasons for the long-term existence of China's authoritarian centralization of authority.

The second is the economic impact.

Five or six thousand years ago, it was a very humid climate at the same time as the warm period. At that time, the Heilongjiang River Basin was the wettest period for thousands of years, and the Beijing Plain was the hometown of rivers and ponds. About 2500 years ago, the climate became dry. During the archaeological excavation in Beijing, it was found that the mixed carbon swamp, which represents the humid climate, gradually disappeared. About 1000 years ago, the climate dried up again. According to a large number of local chronicles, since the beginning of A.D., with A.D. 1000 as the boundary, floods in southeast China have decreased relatively, while droughts have increased relatively. Prior to this, the drought period in 1000 was short and the wet period was long. Since then, the rainy period is short and the dry period is long. The chronology of drought and flood data in recent 500 years shows that drought is obviously more than flood.

The dry and wet change of climate has a great influence on agricultural production, and agricultural production in arid and cold areas is seriously restricted. Needless to say, in other areas, the development of agricultural production is also affected by cold, warm, dry and wet climate changes. Generally speaking, every time the temperature drops by 65,438 0℃, the position of the subtropical northern boundary moves south by about one latitude. The northern boundary position suitable for crop growth has also moved southward. In the past five thousand years, the general trend of climate fluctuation in China is that the warm period is short and the warmth is low, which determines the general trend that the economic center of gravity based on the agricultural economy as a whole moves southward. In the history of China, the economic center of gravity moved southward mainly in three periods: Wei, Jin, Southern and Northern Dynasties, economic stagnation and recession in the Yellow River basin, great development in the Yangtze River basin and economic rise in the south. During the Five Dynasties and the Song Dynasty, the southern economy rose and surpassed the northern economy, forming a new economic center of gravity, and the economic situation of "prosperity in the south and decline in the north" continued to develop; Since the Ming and Qing dynasties, the economic center of gravity has moved further south, the southeast coastal areas have developed abnormally, and the gap between the east and the west and the gap between the north and the south has further widened. Looking at the southward movement of these three economic centers, it coincides with the arrival of the second, third and fourth cold periods in history, and it is not difficult to see the relationship between geographical environment and economic development.

Thirdly, it is cultural influence.

Economy is the foundation, and its change determines the change of superstructure. With the shift of economic center of gravity to the south, it will inevitably lead to great changes in superstructure culture. The most obvious manifestations are: before Sui and Tang Dynasties, China's economic center of gravity was in the north, and its cultural center was also in the north; After the Sui and Tang Dynasties, the economic center of gravity moved south, and the cultural center moved south accordingly.

During the Qin and Han Dynasties, Guanzhong was the capital, and the economic and cultural center of gravity was in the Yellow River basin. There is a saying that "Shandong is the leader, Shanxi is the leader", "Kansai is the leader and Kanto is the leader". After the Sui and Tang Dynasties, food supply began to depend on the south, and the cultural center of gravity began to move south. In the Song Dynasty, there was a saying that "Su Changshu was the best in the world" and "Jiangsu and Zhejiang were the best in the world". In the Ming and Qing Dynasties, China's culture was based on the richest Yangtze River valley, forming a situation of "one in the southeast, one in Jiangsu and Zhejiang". Since modern times, with the development of coastal economy, Guangdong and Fujian have gradually occupied an important position in the economy, and China culture has a tendency to move further south.

As for the shift of China's cultural center of gravity to the south, predecessors mostly studied it from the aspect of "the geographical distribution of China's historical figures". Two families are introduced here to illustrate the relationship between culture and geographical environment. In the article "The Relationship between Historical Figures and Geography" (③), Ding Wenjiang listed the figures of the provinces according to the generations of Han, Tang, Song and Ming in the twenty-four histories:

Before Han Dynasty, after Han Dynasty, Tang Dynasty, Northern Song Dynasty, Southern Song Dynasty, Ming Dynasty

The provinces with the largest population are Shandong, Henan, Shaanxi, Henan, Zhejiang and Zhejiang.

Henan, Shaanxi, Hebei, Fujian and Jiangsu

In the article "Observing the North and South Cultures of China from History" (④), Japanese Sang Yuan took the imperial examination as an example and submitted the statistics of the number of people who passed the imperial examination in Ming and Qing Dynasties. From the fourth year of Hongwu in the Ming Dynasty to the forty-fourth year of Wanli, there were 244 people who won the top prize, ranked first, explored flowers and made friends in various subjects, including 2 15 in the south, accounting for 88%. 42 of them are from the south. In the first year of Qianlong, * * * takes sixty-five thousand four hundred and thirty-eight+zero five, and sixty-five thousand four hundred and thirty-eight+zero four in the south. In the Ming and Qing Dynasties, * * * took 203 students, and the South took 188 students.

Four. Discussion on related issues

1. By discussing the characteristics and impacts of climate change in China, we can further understand the role of geographical environment in historical development. How to treat the relationship between geographical environment and historical development is an old and often new topic. In the past, due to the one-sided criticism of "geographical environment determinism", the role of geographical environment in historical development was rarely discussed in detail. In recent years, through various studies and discussions, people realize that the geographical environment itself is a part of human society and its historical development. When transforming the natural environment, human beings should not violate the constraints of natural laws, otherwise they will be punished by natural laws. But what is the relationship between geographical environment and the development of human society? What influence does the geographical environment have on the development of social history? How great will the impact be? There are still different opinions on these issues. Through the analysis of this paper, we can first affirm that the influence of geographical environment on social history is a historical category. With the evolution of the times, its function mode and degree are constantly changing. Therefore, we should attach importance to the study and research of historical geography. Why is the feudal society in China particularly long in the study of China history? Why is the embryonic development of capitalism extremely slow? Many comrades believe that geographical conditions are the most fundamental factor. Specifically, the characteristics of geographical environment at home and abroad and the corresponding social production mode not only produced the demand for authoritarian regime, but also maintained the prosperity of feudal small agriculture, which made it difficult for China to have the objective conditions for the transition to capitalism, thus leading to the long-term continuation of feudal society in China. Are these views correct? We still need to make a thorough and detailed study of the historical geography of China before we can draw a conclusion.

Secondly, through the above analysis, we also realize that human history and geographical environment are a unity, they restrict and interact with each other, and this mutual restriction and interaction shows different forms in different times and regions. Generally speaking, the lower the level of productivity, the greater the restriction of human beings by geographical environment; The older the stage of social development, the greater the dependence of human beings on the geographical environment. In ancient China, the temporal and spatial differences of climate change influenced the development direction of politics, economy and culture, which showed that the geographical environment really promoted or delayed the history of China, especially the opposition between the minority regime and the Han regime in the history of China (Qin and Han Dynasty and Xiongnu, Eastern Jin and Southern Dynasties and "Five Lakes", Song and Liao Dynasties, Jin Dynasty, Ming Dynasty and Mongolia, Manchu Dynasty, etc.). ). They are all caused by the opposing environmental factors in agricultural and pastoral areas caused by the differences in climate time and space. With the development of social productive forces, especially the progress of science and technology, human society has increasingly restricted the geographical environment that can provide more material wealth for human beings. However, this does not mean that the role of geographical environment has decreased. Due to the role of human beings in the geographical environment, the geographical environment has changed and formed a new geographical environment system. In addition to the original natural environment, the economic environment and human environment system have been added, which has had a new impact on human society. In the modern climate change in China, we have to explore the new changes and new influences of human environmental pollution, which determines the guiding significance of studying historical geography to reality and practice.

2. By discussing the characteristics of climate change in China's history, we can further understand the disciplinary nature of historical geography. Historical geography is an ancient and young discipline, and there are different views on its nature in academic circles. At present, the history department and some geography departments of domestic universities have offered the course "Historical Geography of China". However, due to different views on its subject attributes, the teaching content, learning focus and research direction are quite different. Some people think it is a branch of history. Some people regard it as a branch of geography, emphasizing the discussion of natural phenomena and their laws in historical periods; Some people regard it as an interdisciplinary subject of history and geography, focusing on interdisciplinary research.

We believe that historical geography is not only an interdisciplinary subject between history and geography, but also an interdisciplinary and interrelated comprehensive subject in natural science and social science. Historical geography not only studies the natural process of natural environment change, but also studies the man-made process of transforming natural environment change. More importantly, it focuses on the changing law of the relationship between man and land in historical period. It cannot be simply summarized as a branch of history or geography, but a new interdisciplinary system. As Zhekulin, a historical geographer in the former Soviet Union, said, it is not only a marginal discipline formed by the combination of geography and history, but also "closely related to a series of scientific categories such as ethnography, toponymy and agricultural history in its own development process." Therefore, accurately speaking, it is "a comprehensive discipline on the edge of natural science and social science, and its main task is to study the regularity of social and natural's interaction." Based on this understanding, our vision of historical geography research will gradually broaden.

The nature of the discipline determines the research methods of the discipline. The world is a whole, and nature and human society are inseparable. Modern science and technology have reached the stage of mutual penetration and integration among disciplines, and historical geography has emerged to meet the requirements of this era. Therefore, it inevitably requires us to master the knowledge of different disciplines and carry out creative research on the basis of the cross-study of social science and natural science. If this analysis can play a role in attracting jade, the purpose will be achieved.