Seasonal temperature adjustment gave no clear common reduction in cherry bloom interval synchrony at 48 Japan stations in 1970-2024

We tested whether local seasonal temperature accounts for shared annual changes in the time from first flower to full cherry bloom. We used 2,639 station-years at 48 Japanese stations in 1970-2024 from a verified public campaign panel. Four tests split stations at 36 N and years at 1997. Each station model removed a local linear trend, then added March-April and prior December-February temperature. The change in mean station-pair correlation ranged from +0.028 to +0.054. 0 of four lower limits were above zero after correction for four tests. These descriptive fits do not identify a climate cause. Selected sample trees, shared observation rules, monthly weather after bloom, and short time series limit inference.

cherry · phenology · spatial synchrony · temperature · observation bias · Japan