Climate Change and Severe Famines: Exploring the Relationship between Solar Radiation and the Dynamics of Historical Migration

Understanding the effects of past climate change on human societies and their adaptations is vital for both historical studies and modern resilience strategies. Our previous study examined the impacts of seasonal solar radiation variations, reconstructed from diary weather records across 18 locations in Japan, on rice prices and migration during the Tenpō famine (1833–1839). We found that severe weather, as reflected in these solar radiation estimates, led to high rice prices in Osaka. Consequently, higher temporal resolution data, compared to annual or limited-season data, can be more effective for studying the impacts of climate change on society.

This study further explores how climate change affects food and economics and how stresses such as famine and grain price fluctuations impact migration, using historical weather descriptions, rice prices, and migration data. The migration data were calculated based on individual-level panel data from local population registers of four communities (current Fukushima prefecture) from 1708 to 1870. The rice price series in the local market of Aizu in the same prefecture was used to measure the annual fluctuations in local agricultural output. The monthly solar radiation was reconstructed from historical weather descriptions for three locations in the target area of Moriyama, one to the north (Yamagata), and two to the south (Nikko). A comparison of the migration data with the reconstructed monthly solar radiation indicated that after the summer solar radiation decreased significantly, the number of migrations, abscondences, and deaths increased, particularly during the Tenmei (1782-1788) and Tenpo famines.