From the late Quaternary Pleistocene about 1. 1 10,000 years ago, the earth entered the modern interglacial period from the latest interglacial period of the Quaternary Glaciation, also known as the post-glacial period. This period of time is roughly equivalent to the fact that mankind has entered a historical era with written records. With regard to the climate in this period, Norwegian glaciologists have made a snow line fluctuation map of nearly 10000 years, which shows that the snow line fluctuates greatly, indicating that the climate has changed obviously since the late glacial period. China has a long history. Zhu Kezhen sorted out and analyzed these records, and found that the climate in China for more than 5,000 years has four warm periods and four cold periods.

The first warm period was from 3000 BC to 1000 BC, that is, from Yangshao culture era to Anyang Yin Ruins era. In most of this period, the annual average temperature was about 2℃ higher than it is now, and the temperature in Leng Yue was about 3 ~ 5℃ higher than it is now.

From about 1000 BC to 850 BC (the beginning of the week), there was a short cold period, and the temperature was below 0℃.

From 770 BC to the early AD, that is, the Qin and Han Dynasties, it entered a new warm period.

From the early years of AD to AD 600, that is, from the Eastern Han Dynasty to the Six Dynasties, it entered the second cold period.

600 ~ 1000 A.D., namely the Sui and Tang Dynasties, was the third warm period.

From 1000 to 1200, that is, the Southern Song Dynasty was the third cold period, and the temperature was about 1℃ lower than that of modern times.

The fourth warm period is from 1200 to 1300, that is, the end of the Song Dynasty and the beginning of the Yuan Dynasty, but this time it is not as warm as it was in the Sui and Tang Dynasties, and it gradually shifts from the Huaihe River basin to the south of the Yangtze River basin, such as Zhejiang, Guangdong and Yunnan.

After 1300 years, that is, since the Ming and Qing dynasties, it was the fourth cold period, and the temperature was 1 ~ 2℃ lower than that of modern times.

In the past 5000 years, although cold periods and warm periods appeared alternately, the general trend was from warm to cold, and each cold period was longer and colder. During the second cold period, only the Huaihe River froze in 225 AD. 1670 During the fourth cold period, the Yangtze River was almost frozen.

Interestingly, Norwegian glaciologists use the height of the snow line to indicate the rise and fall of the temperature, while Zhu Kezhen uses historical documents to record the data, but the results are very consistent, indicating that the climate change since the post-glacial period is universal all over the world, which is definitely not a coincidence. Modern Climate Change Since the beginning of agricultural mechanization in 1850, the recent climate change in 100 is called modern climate change. The basic trend of climate change in the last hundred years is that the world climate after 196 1 is significantly different from that in the first half of the 20th century, but similar to that in the second half of the 9th century. /kloc-from the end of 0/9 to the 1940s, it was a period of global warming. The warming trend reached its peak in the 1940s, and then the temperature dropped, especially after 1960s. This change is probably a climate vibration in the past 10000 years.

This vibration can be explained by the change of atmospheric circulation. According to British climatologist Lamba, from 1895, the world circulation suddenly changed from a period dominated by meridional circulation to a period dominated by zonal circulation. Since then, the zonal circulation has been continuously strengthened. Reached the peak near 1940; Subsequently, the zonal circulation gradually weakened and the meridional circulation gradually strengthened. By 196 1, the zonal circulation weakened significantly and returned to the period when the meridional circulation was dominant.

During the strong zonal circulation, the cyclone activity is enhanced, the influence of planetary wind system is intensified, and the climatic zones in the northern and southern hemispheres move to the poles. In the period of weak zonal circulation, anticyclone activity is strengthened, monsoon develops, and high and low latitudinal airflow exchanges between the northern and southern hemispheres are frequent. The climate zone on the earth moves towards the equator. It can be seen that the change of world circulation pattern has great influence on global climate change.