In 31 German spring phases, temperature sensitivity did not decrease from 1952–1966 to 2012–2025, and the 1980–1994 to 1999–2013 decrease agrees with a forcing-only model
Question: did spring phenology in Germany become less sensitive to temperature (days per °C) with warming, and is a decrease larger than a forcing-only thermal-time model predicts? Data: Deutscher Wetterdienst annual-reporter wild-plant network, 31 spring phases of 27 taxa, 3.9 million station-years at 6,581 stations, 1952–2025, with HYRAS-DE 1 km daily temperature. Method: we fitted a forcing-only model for each phase on 1952–1985 data only and calculated within-station slopes of event day on fixed-window preseason temperature for observed and model dates. Intervals come from a year bootstrap shared by all phases. Results: mean observed sensitivity was 4.6, 4.6, 5.2, 4.3 and 4.4 days/°C in five 15-year windows. The 2012–2025 / 1952–1966 ratio was 0.95 (95% CI 0.78–1.15), and its CI was below 1 for no phase. Between 1980–1994 and 1999–2013, sensitivity decreased (0.81, 0.67–0.96). The model predicted 0.93 (0.80–1.05), and the difference was not significant (observed/model 0.87, 0.73–1.05). The observed ratio was lower than the model ratio in most phases, but the across-phase difference was within the CI in 11 of 12 contrasts (six variants: base temperature 0 or 5 °C, chilling-forcing model, common stations, re-anchored preseason). A chilling term did not improve the fit. After 1985, observed dates were 3.1 days (2.5–3.6) earlier than the forcing forecast (4.2 days in 2012–2025). This agrees with sci:sha256:5e63bb36c8ace247e7020a6acd9cf5d6e4f40feaffa50a9c8082d6ca2dff5bf3. The size depends on the model (0.9–3.4 days). It is similar in former East and West Germany, and winter warming does not explain it. Limitations: grid temperature error can attenuate early observed slopes more than later ones; the windows are short; the models are simple; observer and programme effects cannot be separated from biological change.
phenology · temperature sensitivity · thermal time · growing degree days · chilling · leaf unfolding · flowering · Germany · Deutscher Wetterdienst · HYRAS · climate change · out-of-sample forecast
References
6- supportsTemperature models fitted to 1952–1990 German leaf-out data predict 1991–2025 leaf-out 1.7 to 5.1 days too late for seven tree species sci:sha256:5e63bb36c8ace247e7020a6acd9cf5d6e4f40feaffa50a9c8082d6ca2dff5bf3
Independent replication with the same DWD and HYRAS sources but different code, 31 phases and a 1985 training cutoff: observed dates after the training years are earlier than forcing-model forecasts.
- supportsSpring phenology temperature sensitivity at Japanese weather stations did not decrease in 1953–2025 beyond a forcing-only model, which also explains lower cherry sensitivity at warmer stations sci:sha256:a30b18e0b9dbed22d7ae3539df648fe0cae472a7014dbd9770521051485120f2
Same question for Japanese stations; our German result also shows no decrease in sensitivity beyond a forcing-only model, and a peak in sensitivity near the mid-1990s.
- A fixed thermal-time model predicts lower spring temperature sensitivity at warm US lilac and honeysuckle sites in 1956–2009, but not the observed increase in sensitivity over time sci:sha256:c815add42242e8d2f8f213f08dbc384e8ad794e2578349ae8b7b145e55078c11
Related test with US lilac and honeysuckle data; no decrease in sensitivity over time beyond a thermal-time model.
- challengesdoi:10.1038/nature15402
We repeat the 1980–1994 vs 1999–2013 comparison with German data; the decrease (19%) agrees with a forcing-only model and is not present from the 1950s to the 2010s–2020s.
- supportsdoi:10.1111/gcb.15746
A forcing-only model predicts part of the apparent decrease in sensitivity; we test this out of sample.
- usesdoi:10.1007/s00704-020-03388-w
HYRAS gridded temperature dataset (v6-1 used).
Cited by
2 publicationsPublic catalog entries on Sciscape.
- usesGBIF record dates show a 3.4 times larger 1980–2020 flowering advance than the DWD network for 27 German plant species, and fern records also advance, so recording changes cause most of the trend
Its retained parsed DWD wild-plant phenology records (shared dataset sha256-a979680d...) give our DWD reference.
- German spring phenology kept its elevation gradient from 1952 to 2025 (2.75 and 2.76 days per 100 m), while thermal-time models with station temperatures predict a 10-12% decrease
Related test of temperature sensitivity in German spring phases against a forcing-only model.