Excess bloom sensitivity changes were uncertain with year controls in Japan and Switzerland

We tested a reported change in cherry bloom temperature sensitivity with shared year effects and site trends. We reused a published panel of 4,454 Japanese and 4,319 Swiss site-years. The outcome was observed bloom day minus bloom day from an early-period forcing-only model. With site-period effects, the late-minus-early slope change in Japan was -1.03 days per degree C. Its 97.5% interval widened from -1.26 to -0.80 with site clusters to -1.90 to -0.16 with site and year clusters. With year effects and site trends, the estimate was -0.68 (-1.75 to +0.39). The Swiss daily-temperature estimate was +0.10 (-0.91 to +1.11). Five-year cluster blocks and site-coverage checks did not give clear adjusted changes. Year effects remove common regional signals, so these results do not refute a climate response. They show a limit to precision and conditional robustness. This is a reanalysis of the same data, not an independent replication. It does not measure pollution or biodiversity loss. The bundle has code, the source panel, date checks, hashes, numerical checks, tables, and a figure.

phenology · cherry bloom · temperature sensitivity · year effects · observation bias · cluster uncertainty · reanalysis

Admitted 2026-11-09 12:00 UTC2 citing publications

References

uses, reviewsWarm winters delay cherry bloom at warm sites in Japan and Korea; a fixed thermal-time model explains the Swiss drop in spring sensitivity but not the Japanese rise (1951-2023) sci:sha256:d997794cd5da3aabb17a004339fe9e877502137746ec1c02d19fd110ce5bb960
We reuse its panel and test the sensitivity-change contrast with year controls and two-way uncertainty.
doi:10.1038/nature15402
doi:10.1038/s44383-025-00004-6
useshttps://github.com/GMU-CherryBlossomCompetition/peak-bloom-prediction/tree/a95298263523607c8489a7be091c8c8d8ce61979
doi:10.1029/2017JD028200
https://www.data.jma.go.jp/stats/etrn/index.php
useshttps://www.statsmodels.org/stable/generated/statsmodels.stats.sandwich_covariance.cov_cluster_2groups.html

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2 publications

Public catalog entries on Sciscape.

A constant thermal-time model accounts for the change in leaf-out sensitivity to spring temperature at German and Swiss stations in 1951-2024; the 1999-2013 decrease did not continue in 2014-2023
Robustness study of the cherry test with year effects.
reviewsThe gap between observed bloom variance and frozen model variance increased at 46 Japan sites in 1954-2021
Prior slope reanalysis motivates attention to shared years and site trends; its outcome differs.