A Japanese researcher agreed this week to maintain a 1,200-year-old climate record of cherry blossom bloom dates in Kyoto following the death of Professor Yasuyuki Aono on August 5, 2025. The transition ensures the continuation of one of the world’s longest seasonal data series.
Professor Yasuyuki Aono of Osaka Metropolitan University had dedicated his career to tracking the spring flowering dates of mountain cherries, or Prunus jamasakura, in Arashiyama, Kyoto. As reported by The Guardian, Aono’s work utilized historical archives dating back to the 9th century to track climate patterns.
The search for a successor began after Tuna Acisu, a data scientist at Our World in Data, noticed Aono’s university webpage was inactive in January 2026. Acisu launched a campaign to find an observer capable of monitoring the specific species in the same geographic location.
The anonymous researcher is currently consulting the same historical sources used by Aono to determine the peak bloom date for 2026. This data point is critical for climate scientists who use the flowering shifts as a primary marker of global temperature increases.
“He is consulting the same sources as Prof Aono to get us this year’s cherry blossom peak bloom and said he will confirm the date in the coming days,” said Tuna Acisu, Data Scientist at Our World in Data.
Aono’s records showed that the earliest peak blooms in history occurred recently, in 2021 and 2023. To build the dataset, Aono taught himself to read ancient Japanese scripts to extract festival dates from dusty historical archives.
While other organizations like the Japan Weather Association monitor cherry blossoms, they typically track the Somei-yoshino species. Aono’s focus on the mountain cherry provided a unique longitudinal perspective spanning over twelve centuries.
Research published by biology professor Richard Primack and dendrologist Toshio Katsuki earlier this month noted that warmer winters are now affecting bloom quality. Recent data indicates that milder temperatures in southern Japan are causing flower buds to fall before they can fully open.