Just read an article about climate change. It was written by Mr Coching Chu(1890-1974), a prominent Chinese meteorologist, geologist and educator. He was the president of my university from 1936 to 1949.
In this long article, Mr Chu introduced the climate change records of East Asia during the last 5000 years.
It used to be a lot warmer than now. From 3000 BC to 1000 BC, the winter temperature was three to five Celsius degree higher. A lot of tropical and sub-tropical plants, such as bamboo, orange tree and plum tree, was common in Northern China. Now it's impossible for them to survive the harsh winter there.
From 1000 BC to now, the climate has been waving up and down. The major cycle is 400-800 years, with the temperature changing up and down by one Celsius degree.
This brings an interesting question. Is the current global warming really a result of human activities, or just part of a natural cycle?
If you can read Chinese, here's the link of this article:
The Wiki page of Mr Coching Chu: