A centuries-old record tracking the blooming of cherry blossoms in Japan—one of the world’s longest continuous climate datasets—is set to continue despite the death of the scientist who dedicated his life to preserving it. The dataset, spanning over 1,200 years, has been instrumental in revealing the growing impact of climate change on seasonal patterns.
Professor Yasuyuki Aono of Osaka Metropolitan University meticulously compiled historical and modern records of cherry blossom flowering dates, focusing on the mountain cherry species in Kyoto. By examining archival material dating back to as early as the ninth century, Aono was able to reconstruct bloom timings as far back as the year 812.
His research showed a clear and consistent trend: cherry blossoms have been flowering progressively earlier in recent decades, providing tangible evidence of rising temperatures linked to climate change. Notably, the years 2021 and 2023 recorded the earliest peak bloom dates in the entire 1,200-year dataset.
Aono continued his work until shortly before his death in August 2025. In one of his final entries, he recorded the 2025 peak bloom date as April 4. However, the row for 2026 remained blank, raising concerns among researchers about whether the historic dataset would come to an abrupt end.
The uncertainty prompted action from the global scientific community. Tuna Acisu, a data scientist associated with an online research platform, launched a search to find someone capable of continuing Aono’s work. The challenge was not merely to observe cherry blossoms, but to maintain consistency by tracking the same species in the same location—Arashiyama in Kyoto—and using comparable methods.
Following the appeal, a researcher in Japan has stepped forward to take on the responsibility, ensuring that the dataset will not be lost. The individual, who has chosen to remain anonymous for now, is working to confirm the 2026 bloom date using the same historical and observational techniques employed by Aono.
Scientists have emphasized the unique importance of Aono’s work. While cherry blossom monitoring is widespread in Japan due to its cultural and economic significance, most observations focus on different species, such as the Somei-yoshino variety. Aono’s focus on the mountain cherry, combined with the extraordinary historical depth of his data, makes the record particularly valuable for climate research.
Experts say such long-term datasets are rare and crucial for understanding environmental changes over centuries. Aono’s work has joined other unconventional climate indicators—such as tree rings and historical weather records—in helping scientists reconstruct past climates and assess current trends.
The continuation of this dataset not only preserves a vital scientific resource but also honors Aono’s legacy. His decades-long dedication bridged history, culture, and science, turning Japan’s iconic cherry blossoms into a powerful symbol of a warming world.
