The Tenpō Famine of the 1830s was one of the worst in Japanese history, with the poor weather causing escalating rice prices as a major cause. To better understand how historical weather anomalies affected crop prices in Japan and ultimately led to the famine, researchers developed a new framework to analyze historical weather data. The results were published in Scientific Reports on February 18.
Historical climatologists often rely on proxy data, such as variations in tree ring formation and lake sediment, to map historical weather patterns and their influence. But this proxy data has limitations. It’s often a single data point that covers an entire year, and the data doesn’t factor in regional differences or fluctuations throughout the seasons.
“We aimed to better understand how climatic anomalies were related to rice price fluctuations in early modern Japan, focusing on the Tenpō Famine of the 1830s. Previous studies relied mainly on annual data, making it difficult to examine how seasonal climate variation corresponded with changes in rice prices. In this study, we reconstructed monthly solar radiation from 18 historical diaries (1821-1850) and compared it with monthly rice price data in Osaka. This approach allowed us to examine the relationship between climate and rice prices at finer temporal resolution,” said Mika Ichino, a then-project assistant professor at the Research Organization of Information and Systems in Tokyo, Japan.
Researchers used the Historical Weather Database, one of the most extensive collections of historical weather observations for Japan in this time period. Using this database, the researchers could look at large-scale climate patterns over the entire country to understand variation from region to region. They developed a baseline of typical solar patterns at the same locations from 1981 to 2010. To reconstruct the historical solar radiation patterns, researchers developed a framework to estimate solar radiation based on weather descriptions in diary entries and observational logbooks.
“In 1836, solar radiation in July and August was about 10% below normal in central Japan, and rice prices rose rapidly, eventually to three to four times their typical level in the next summer. The timing suggests that rice prices were influenced by seasonal climate conditions before the harvest. Examining monthly climate and rice price data reveals intra-annual dynamics that are not visible in annual statistics,” said Ichino.
Rice prices are a common data point used in historical climatology studies, but it is an imperfect method when used on its own. Trade, riots, typhoons, and government interference can also impact historical rice prices. When taken together, climate data using actual solar radiation estimates instead of typical proxy data and rice prices, can help paint a full picture of how climate impacts society. The detailed data can also help researchers understand regional differences and nuances.
Researchers found a significant reduction in solar radiation in the summer of 1836, especially in central Japan. The poor summer weather conditions lasted through August of 1838. From August 1836 until September 1837, rice prices were significantly higher than in a typical year. There is also historical evidence showing that the officials expected a poor harvest, with one proclamation from the time period cautioning against overbuying before a poor harvest was confirmed to keep prices stable. Prices continued to fluctuate even during the famine, with some months showing much higher prices than others. The new framework allows researchers to look more closely at climate fluctuations and how it impacted prices from month to month, not just once a year.
Looking ahead, researchers hope to look at other regions and time periods. “The next step is to extend the reconstruction of monthly solar radiation to broader regions and longer periods, and to integrate these data with additional historical records related to agriculture and prices. Expanding both spatial and temporal coverage will help clarify the relationship between climatic anomalies and rice price fluctuations in more detail. Our broader aim is to understand how societies have responded to unusual climate conditions by examining historical evidence at a seasonal resolution,” said Ichino.
Other contributors include Kooiti Masuda at Rissho University, Takehiko Mikami at Tokyo Metropolitan Unversity, and Yasuo Takatsuki at Kobe University.
The JSPS KAKENHI, Joint Support-Center for Data Science Research, and Ishi Memorial Securities Research and Promotion Foundation supported this research.
###
About the Research Organization of Information and Systems (ROIS)
ROIS is a parent organization of four national institutes (National Institute of Polar Research, National Institute of Informatics, the Institute of Statistical Mathematics and National Institute of Genetics) and the Joint Support-Center for Data Science Research. It is ROIS's mission to promote integrated, cutting-edge research that goes beyond the barriers of these institutions, in addition to facilitating their research activities, as members of inter-university research institutes.
Scientific Reports
Unusual solar radiation and its impact on the Japanese rice market during the 1830s famine
18-Feb-2026