Zhu Kezhen's "Preliminary Study of Climate Change in China Over the Past 5000 Years" has epoch-making significance, pioneering the field of historical climatology, advocating for observing social evolution by paying attention to environmental changes.
Mr. Zhu proposed phenology, which refers to the natural landscape changes throughout the year divided into 12 months, each month and each season, such as when flowers bloom and when rivers freeze; focusing on the dates when biological events appear in the annual cycle. Since biological phenomena are often sensitive to temperature changes, temperature-induced phenological changes have become an important indicator for observing historical climate records, especially in the study of climate change and global warming.
During the Warring States period, it was a warm period, about 2 degrees higher than today, and agricultural development reached the Warring States era, allowing winter wheat to be grown in the north. Plants and animals now found in the south were also seen in the north at that time, such as rhinoceroses and elephants. This warm period also laid the foundation for the high prosperity of the Warring States economy, and the wealth led to the development of literature by the Hundred Schools of Thought. All these were brought about by the warm period.
However, from the beginning of the Common Era until the first half of the fourth century (350 AD), the cold reached its peak, especially between the two Han dynasties, with a cold climate region, about 2 degrees lower than today. The 250mm and 500mm precipitation lines moved southward by hundreds of kilometers, and the 500mm precipitation line roughly coincided with the Great Wall. The Great Wall was established as a barrier to resist minority groups. The southward movement of the precipitation line indicates that north of the Great Wall, precipitation decreased, the grasslands became barren, and nomadic tribes could no longer graze in their original territories. Therefore, they migrated southward, leading to the later invasion of the Five Barbarians.
The study of climate change thus provides us with a new perspective. Traditional historians mainly consider moral factors when conducting historical research, believing that emperors and ministers influence the course of history, and that one person or this small group can dominate the history of a nation; however, they neglect the roles of environment, systems, and culture among other factors.
Starting a business is the same. Entrepreneurs and their teams are fragile in a large environment, and we can't control the market either. More importantly, we need to find the climate that can help the company develop better, which means the right direction, and find our own potential energy.