Researchers report that climate conditions in northern China since 270 BCE may have enabled agricultural boom and societal prosperity. 

The Qin and Western Han dynasties (221 BCE–24 CE) marked a prosperous era in China. However, It remains unclear if the agricultural boost during this period was associated with more favorable climatic conditions due to a lack of high-resolution paleoclimate records. 

Qin et al. compared tree-ring records from modern Chinese pines (Pinus tabulaeformis Carr.) in northern China with archaeological Chinese pine samples in Huangwan tomb in Han dynasty. 

Analysis of the tree ring width and stable isotope composition of the samples facilitated estimation of annual precipitation during the Qin and Western Han dynasties. 

The results suggest that between 270 BCE and 77 BCE, the climate of northern China was stable and consistently wetter than during the recent period (1951–2015 CE). 

Regional precipitation amounts from the Asian summer monsoon may have been 18% to 34% higher during the ancient dynasties than during the recent period (1951–2015 CE). 

Such increased precipitation would have shifted the boundary for rainfed agriculture around 60 to up to 200 kilometers northwest of its current position.

According to the authors, a similar wetting trend in the northwest China since the 1980s resembles the historical climate analogue, suggesting that similar benefits for regional environmental and agricultural systems may re-occur under current climate change, at least in the near term.

This work was published in PNAS on Dec. 23.