Grape Harvest Dates from Burgundy demonstrate (once more) Global Warming since the End of the 20th Century

 

Organisation of the harvest in 1487; page from the accounting book of the Church of Notre-Dame of Beaune (Archives départementales de la Côte d’Or, B 2918/109)

Records of grape harvest dates (GHD) are the oldest and the longest continuous phenological data in Europe. They have been repeatedly used since the end of the 19th century to reconstruct past climate variations, and in the two last decades to reconstruct spring-summer temperature beyond the instrumental period. Newly, the GHD from the famous vine region of Beaune (Burgundy) between 1354 and 2018 have been entirely drawn from the archives and published in the European Geoscience Union journal Climate of the Past. It constitutes the worldwide longest GHD series in the literature and one of the longest phenological records ever. The 664-year-long Beaune series has been cross-checked with the April-to-August Paris temperature series comprising the 360 years from 1659 to 2018 (R = -0,76), as well as with tree-ring series, with documentary proxy evidence and with the Central European temperature series (from 1500). Statistical models show that the series is very reliable to reconstruct April-to-August temperature in the long run. Of major interest, the series is clearly subdivided into two parts. From 1354 to 1987 grapes were on average picked from 28 September on, whereby during the last 31-year long period of rapid warming from 1988 to 2018 harvests began 13 days earlier. The 33 earlier harvest dates of series are unevenly distributed over time. 26 of them occurred between 1393 and 2002, whereby since the hot summer 2003, 8 out of 16 spring-summer periods were outstanding according to the statistic of the last 664 years. In the Paris temperature measurements since 1659, April-to-July temperature reached the highest value ever in 2018. In sum, the 664-year-long Beaune GHD series demonstrates that outstanding hot and dry years in the past were outliers, whereby they became the norm since the transition to rapid warming in 1988.

Beaune GHD time-series, with indication of the 33 earlier dates (Labbe et al. 2019, p. 1496).

To know more: Labbé, T., Pfister, C., Brönnimann, S., Rousseau, D., Franke, J., Bois, B.: The longest homogeneous series of grape harvest dates, Beaune 1354-2018, and its significance for the understanding of past and present climate, Climate of the Past, 15, 1485-1501, https://doi.org/10.5194/cp-15-1485-2019, 2019.

Find here a podcast interview with Thomas Labbé (in German) by detektor.fm


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