In this study, we analyse the climatic impacts on the grape harvest date(GHD) in Burgundy (France) on interannual and decadal time scales. We affirmthat the GHD is mainly influenced by the local April-to-August temperature(AAT) and provide the spatial expansion of this relationship. The spatialcorrelation pattern yields similar results for the instrumental andpre-instrumental period, indicating the consistency of the pre-instrumentalfield data with the instrumental GHD-spring/summer relationship. We find apreviously undocumented second climate impact on the GHD. The wintertemperature is significantly correlated with the GHD ondecadal-to-multidecadal time scales and affects the GHD independently of theAAT. A multiple linear regression model, with AAT and decadal wintertemperature as predictors, was found to be the best model to describe the GHDtime series for the instrumental period. Stability tests of the correlationsover time yield that both impacts on the GHD, AAT and decadal wintertemperature, strengthen during the instrumental period. Using partialcorrelation analysis, we demonstrate that this is partly caused by a changein the winter–spring/summer temperature relationship. Summarising, the GHD iswell suited to reconstruct interannual variations of the spring/summertemperature over large parts of Europe, even if the changingwinter–spring/summer relation might affect the reconstruction in a secondorder. For decadal time scales, the December-to-August temperature shows thestrongest relationship to the GHD and, therefore, proposes that the GHD can beused for European temperature reconstructions beyond the spring/summerseason. Finally, we argue that our findings regarding the changedwinter–spring/summer relation are relevant for physical and biologicalsystems in several ways and should be analysed by other long-term proxy dataand available model simulations.
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