Based on a study of the longest comparable series of grape harvest dates recorded in Beaune, the wine capital of France, climate change researchers were able to gather a new line of evidence that shows how climate trends have changed in the past 30 years. Results of the study were published by the European Geosciences Union in the Climate of the Past journal 2019 edition, showing how warming trends sped up starting from mid 1980s up to the present.
Christian Pfister, professor at the Oeschger Centre for Climate Change Research of the University of Bern, Switzerland, conducted the study with Thomas Labbé, Stefan Brönnimann, Benjamin Bois, Jörg Franke and Daniel Rousseau, scientists and historians from Switzerland, France, and Germany, Professor Pfister commented that they did not expect the accelerated warming trend would stand out so clearly in the series of grape harvest dates,
What the Study of the Beaune Grape Harvest Dates Revealed
According to the study, grape harvest dates can be used as basis in analyzing climate changes since wine grapes are quite sensitive to rainfall and temperature.
As cited by an article in the French tourism website, Mother Nature decides when grapes are ripe enough for picking. During years when the growing season (spring, summer) is hot and dry, the grapes are ready for picking earlier than in years when spring summer is colder.
Thomas Labbé, lead author of the study and a researcher at the universities of Leipzig and Burgundy said he meticulously reconstructed the grape harvest dates in Beaune, going as far back as1354, and spanning 664 years.
Gathering data from a large number of unedited archives of records and newspaper reports from the Beaune city council, including information on wages paid to grape pickers, Labbé was able to reconstruct the longest ever continuous record of grape harvest dates in the wine capital of France.
The record was divided into two parts, one prior to 1987, when wine grapes were typically harvested from September 28 onward; the other part, from 1988 onward when harvest dates begun at an average of 13 days before September 28. The division of records clearly indicated that from 1988 the region’s climate was hotter and drier compared to the climate conditions during the past six (6) centuries.
The team’s analysis of the grape harvest date series indicated that very hot and dry years were not common in the past, but in the past 30 years, such climate conditions have become the norm. .
To validate the results of their analysis, the team matched their findings to Paris’ detailed records of temperatures covering the past 360 years. They then used the information to estimate Beaune region’s April-to-July temperatures for the entire 664-year coverage of Beaune’s series of grape harvest dates.
Professor Pfister remarked that the rapid transition to global warming period after 1988, stands out with utmost clarity, since the extraordinary characteristics of the last 30 years have become apparent. The climate change professor concluded by saying
“We hope people start to realistically consider the climate situation in which the planet is at present.”