"There is no Chang 'an City after the Tang Dynasty". Why do you say that?

After the Tang Dynasty, Chang 'an declined. Why can't Chang 'an rise again after the Tang Dynasty? In fact, Chang 'an can't rise, which is related to many reasons. In addition to historical reasons, there is also a very important reason, that is, climate. The decline of Chang 'an has much to do with the climate, and even plays a decisive role.

It can be said that the southward shift of climate zone directly led to the southward shift of China's economic and cultural center of gravity. This has nothing to do with human activities, it is God's decision, and it is global, and it is not the cause of deforestation, overgrazing and overgrazing.

From the 9th century to the10th century, the climate zone of the earth moved southward, and the northern hemisphere became cold and dry. This is global and has been confirmed by modern meteorology. This time happened at the turn of the Tang and Song Dynasties. There are a lot of records about this climate change in China historical materials, which confirmed the speculation of modern meteorology.

In the Tang dynasty, the annual precipitation in Guanzhong was 800~ 1000 mm, and now it has reached 600 mm, so it will not dry according to the weather. Now it is five droughts in ten years. At that time, the temperature in the north was generally 2~5 degrees higher than now. Chang 'an's climate is equivalent to the present Yangtze River valley, which is very livable and navigable. Oriental grain ships can enter Chang 'an through the canals of Yellow River and Weihe River. Now the Weihe River can't even float on the raft, and the water volume is too small.

Litchi can be produced in Bashu in Tang Dynasty. Have you seen litchi in Sichuan now? It will really freeze to death. The litchi that Yang Guifei eats comes from Sichuan. Su Dongpo was born in the south of Chengdu in Song Dynasty, but he had never eaten litchi since he was a child. Later, he became an official in Guangdong, learned about Weihe River and wrote poems.

In the Tang Dynasty, the climate in the south of the Yangtze River was equivalent to that in Guangdong now. It was hot and there were many mosquitoes. It is particularly prone to dysentery and has no antibiotics. Schistosomiasis was very serious at that time. In the Tang Dynasty, Guangdong had a swamp and tropical rain forest climate. Crocodiles are rampant, devouring people and animals. Han Yu spent eight months in this place and invented the technology of lime against crocodiles.

In contrast, the whole North China and the Central Plains have become dry, the whole Henan Plain has become ten years and nine droughts, and famine has continued year after year. However, every cloud in the south of the Yangtze River has a glimmer of hope that it will no longer be hot and humid. The Yangtze River Basin has become the national economic center, and Sichuan Basin, Taihu Basin, Jianghan Plain and Xiangjiang River Basin have all become land of plenty.