How can we learn about temperatures and climate change from before thermometers even existed?
One remarkable window into this is the peak bloom date of cherry trees in Kyoto, Japan, a record stretching back over 1,200 years. Because the trees bloom earlier in warmer springs, those dates act as a proxy for how the climate has changed. The “heat island” effect of urbanization has also played a role.
For decades, the record was kept by Professor Yasuyuki Aono of Osaka Metropolitan University, who meticulously reconstructed the dates by reading centuries of diaries and chronicles from Kyoto. You can see this data in the chart here.
Earlier this year, when our data scientist Tuna Acisu went to update our chart with the latest bloom date, she learned that Professor Aono had sadly passed away — and that no one was set to continue his work.
After several leads went nowhere, Tuna made one last appeal to our audience on social media (see her posts on X/Twitter and Bluesky). We were looking for someone with botanical expertise who could identify the peak bloom from photos, or a local in Kyoto with access to bloom-specific reporting.
The response was overwhelming, with over a thousand comments and shares from people trying to help. Soon after, a successor stepped forward: Dr. Genki Katata, a researcher in Japan, who will carry the dataset forward!
Tuna’s appeal caught the attention of major media, with The New York Times and The Guardian interviewing her about her role in the story.
The success of Tuna’s quest to continue this important dataset is a great example of what we can achieve collectively. Thanks to everyone who helped make it happen!
Explore the interactive version of this chart
