4. Relationships between Climate Change and Grain Harvest Fluctuations in China over the Past Two Millennia

The impact of climate change on agricultural production is integral to understanding the impacts of historical climate change on society and the economy of China. The semantic differential method was used to reconstruct the grain grade sequence with a 10-year resolution from 210 BCE to 1910 CE in China. A positive correlation between the winter half-year temperature departure and the grain yield was found. The bumper harvest stages corresponded to the warm periods, and poor harvest stages corresponded to the cold periods. In both warm and cold periods, the grain yield grades assumed a trend of convergence with the temperature increase. The sensitivity of grain yield to temperature change became weakened over the past 2000 years.