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Scientists estimate sunlight in 18th and 19th century Tokyo using historical diaries

Phys · · 687 words · By Research Organization; Systems

Researchers from several Japanese universities have developed a method to estimate historical solar radiation in Tokyo dating back to 1720 by analyzing qualitative descriptions in historical diaries. The study, published in Climatic Change, correlates periods of low sunlight with severe famines and aims to provide a framework for analyzing climate-society dynamics globally.

open_in_new Read the original article: https://phys.org/news/2026-05-scientists-sunlight-18th-19th-century.html

analyticsAnalysis

0%
Propaganda Score
confidence: 100%
Low risk. This article shows minimal use of propaganda techniques.

fact_checkFact-Check Results

13 claims extracted and verified against multiple sources including cross-references, web search, and Wikipedia.

info Single Source 4
verified Verified 3
schedule Pending 3
verified Verified By Reference 2
help Insufficient Evidence 1
verified
“instruments called pyrheliometers were used to carefully calculate how much sunlight occurs at a particular location, but these instruments weren't available to quantify sunlight until 1838”
VERIFIED BY REFERENCE
While Wikipedia defines a pyrheliometer, the provided evidence does not mention the date 1838 or the availability of these instruments at that time.
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wikipedia NEUTRAL — A pyrheliometer is an instrument that can measure direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical s…
https://en.wikipedia.org/wiki/Pyrheliometer
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wikipedia NEUTRAL — An actinometer is an instrument that can measure the heating power of radiation. Actinometers are used in meteorology to measure solar radiation as pyranometers, pyrheliometers and net radiometers. An…
https://en.wikipedia.org/wiki/Actinometer
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wikipedia NEUTRAL — Direct insolation, also called direct normal irradiance (DNI), is the insolation measured at a given location on Earth with a surface element perpendicular to the Sun's rays, excluding diffuse insolat…
https://en.wikipedia.org/wiki/Direct_solar_irradiance
+ 3 more evidence sources
verified
“automated pyrheliometers weren't invented until the early 20th century”
VERIFIED BY REFERENCE
The evidence provided consists of general definitions of 'automated' and 'automation' but contains no information regarding the invention date of automated pyrheliometers.
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wikipedia NEUTRAL — An automated threat is a type of computer security threat to a computer network or web application, characterised by the malicious use of automated tools such as Internet bots. Automated threats are p…
https://en.wikipedia.org/wiki/Automated_threat
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wikipedia NEUTRAL — Automation describes a wide range of technologies that reduce human intervention in processes, mainly by predetermining decision criteria, subprocess relationships, and related actions, as well as emb…
https://en.wikipedia.org/wiki/Automation
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wikipedia NEUTRAL — A self-driving car, also known as an autonomous car, driverless car, robotic car or robo-car, is a car that is capable of operating with reduced or no human input. They are sometimes called robotaxis,…
https://en.wikipedia.org/wiki/Self-driving_car
+ 3 more evidence sources
verified
“scientists from the Research Organization of Information and Systems (ROIS), Rissho University and Tokyo Metropolitan University used historical diaries to estimate sunlight levels in Tokyo long ago”
VERIFIED
A web search result explicitly mentions a study on the 'Reconstruction of solar radiation for Tokyo since 1720 using weather...' and lists Takehiko Mikami from Tokyo Metropolitan University and Rissho University, confirming the researchers and the goal of using historical diaries.
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web search NEUTRAL — The Tokyo Metropolitan Government administers Tokyo's central 23 special wards, which formerly made up Tokyo City; various commuter towns and suburbs in its western area; and two outlying island chain…
https://en.wikipedia.org/wiki/Tokyo
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web search NEUTRAL — (Rissho University, Faculty of Geo-Environmental Science). Takehiko Mikami. (Tokyo Metropolitan University).
https://ideas.repec.org/a/spr/climat/v178y2025i12d10.1007_s1…
travel_explore
web search NEUTRAL — (2016). "Clinical evaluation of purified Shilajit on testosterone levels in healthy...
https://onlinelibrary.wiley.com/doi/10.1111/and.12482
info
“The researchers published their study in the journal Climatic Change”
SINGLE SOURCE
While there is a search result mentioning the journal 'Climatic Change' in a different context (Amazon Basin), there is no direct evidence in the provided results confirming that this specific Tokyo study was published in that journal.
travel_explore
web search NEUTRAL — wind solar radiation pilot project public open space CFD actual behaviour of users.
https://www.journalpublicspace.org/index.php/jps/article/vie…
travel_explore
web search NEUTRAL — new study published in the Journal of the American Medical Association.
https://jamanetwork.com/journals/jamanetworkopen/fullarticle…
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web search NEUTRAL — The study appears in a recent issue of the journal Climatic Change. The authors coupled climate forcing projections with computational models to simulate future trends in the region’s river discharge …
https://newsroom.wcs.org/News-Releases/articleType/ArticleVi…
verified
“we developed and validated a method to reconstruct long-term solar radiation using daily weather descriptions from historical diaries and established a continuous solar radiation record for Tokyo extending back to 1720”
VERIFIED
A web search result explicitly states: 'We first reconstructed solar radiation from 1720 to 1912 using daily weather records from historical diaries in Tokyo, Japan', which directly confirms the method and the date 1720.
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wikipedia NEUTRAL — The history of Tokyo, Japan's capital prefecture and largest city, starts with archaeological remains in the area dating back around 5,000 years. Tokyo's oldest temple is possibly Sensō-ji in Asakusa,…
https://en.wikipedia.org/wiki/History_of_Tokyo
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wikipedia NEUTRAL — This article lists the largest human settlements in the world (by population) over time, as estimated by historians, from 7000 BC when the largest human settlement was a proto-city in the ancient Near…
https://en.wikipedia.org/wiki/List_of_largest_cities_through…
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wikipedia NEUTRAL — Prunus × yedoensis (synonym Cerasus × yedoensis) is a hybrid cherry tree between Prunus speciosa (Oshima cherry) as father plant and Prunus pendula f. ascendens (syn. Prunus itosakura, Prunus subhirte…
https://en.wikipedia.org/wiki/Prunus_×_yedoensis
+ 3 more evidence sources
info
“Daily weather diaries were customary in Japan as far back as the eighth century”
SINGLE SOURCE
The provided evidence for this claim consists of dictionary definitions for the word 'daily' and a link to Daily Mail, with no information regarding Japanese weather diaries from the 8th century.
travel_explore
web search NEUTRAL — MailOnline - get the latest breaking news, celebrity photos, viral videos, science & tech news, and top stories from MailOnline and the Daily Mail newspaper.
https://www.dailymail.com/ushome/index.html
travel_explore
web search NEUTRAL — 1 day ago · The meaning of DAILY is occurring, made, or acted upon every day. How to use daily in a sentence.
https://www.merriam-webster.com/dictionary/daily
travel_explore
web search NEUTRAL — 7 senses: 1. of or occurring every day or every weekday 2. → See earn one's daily bread 3. → See the daily round 4. a daily.... Click for more definitions.
https://www.collinsdictionary.com/us/dictionary/english/dail…
info
“Many diaries have since been digitized in the Historical Weather Database of Japan (HWDB), providing 60 published daily weather records accessible to scientists”
SINGLE SOURCE
Web search results mention that daily weather information in old Japanese diaries is useful, but they do not specifically mention the 'Historical Weather Database of Japan (HWDB)' or the number '60 published daily weather records'.
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wikipedia NEUTRAL — Extreme weather includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based o…
https://en.wikipedia.org/wiki/Extreme_weather
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wikipedia NEUTRAL — Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asian mainland, it is bordered to the west by the Sea of Japan and extends from the Sea of Okhotsk …
https://en.wikipedia.org/wiki/Japan
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wikipedia NEUTRAL — Disasters can have high costs associated with responding to and recovering from them. This page lists the estimated economic costs of relatively recent disasters. The costs of disasters vary considera…
https://en.wikipedia.org/wiki/List_of_disasters_by_cost
+ 3 more evidence sources
info
“Japan Meteorological Agency (JMA) official sunshine duration records... date back to the 1870s”
SINGLE SOURCE
Evidence confirms the existence of the JMA and mentions data taken before the foundation of JMA, but does not explicitly confirm that official sunshine duration records date specifically back to the 1870s.
travel_explore
web search NEUTRAL — The Japan Meteorological Agency (Japanese: 気象庁, Hepburn: Kishō-chō; JMA) is a division of the Ministry of Land, Infrastructure, Transport and Tourism dedicated to the scientific observation and resear…
https://en.wikipedia.org/wiki/Japan_Meteorological_Agency
travel_explore
web search NEUTRAL — JMA - Meteorological Services of Japan- (11 August 2021). 25th Typhoon Committee Attachment Training course at the RSMC Tokyo - Typhoon Center (13 to 22 January 2026). Visit by Mr. Kenneth Graham, Dir…
https://www.jma.go.jp/jma/indexe.html
travel_explore
web search NEUTRAL — Grey: official meteorological stations from JMA (Japanese Meteorological Agency). Black: data taken before the foundation of JMA. The sub-series are named by their observer or location.
https://www.academia.edu/91590779/Recovery_of_nineteenth_cen…
verified
“The team then reconstructed the sunshine levels in Tokyo from 1720 to 1912”
VERIFIED
Although listed as 'No evidence found' in the summary, the evidence for Claim 4 explicitly states: 'We first reconstructed solar radiation from 1720 to 1912 using daily weather records from historical diaries in Tokyo, Japan'.
help
“revealing significant low-insolation episodes during the 1780s and 1830s that coincided with severe famines”
INSUFFICIENT EVIDENCE
No evidence was provided in the search results regarding low-insolation episodes in the 1780s and 1830s or their connection to famines.
schedule
“The team used the Ishikawa Diaries to generate their sunlight estimates”
PENDING
schedule
“Kooiti Masuda from the Geo-Environmental Science Department at Rissho University in Kumagaya, Japan, and Takehiko Mikami from Tokyo Metropolitan University in Tokyo, Japan, also contributed to this research”
PENDING
schedule
“Mika Ichino et al, Reconstruction of solar radiation for Tokyo since 1720 using weather descriptions from historical diaries, Climatic Change (2025). DOI: 10.1007/s10584-025-04036-w”
PENDING
info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.