In 1792, the Republican calendar named the month from September 22 to October 21 Vendémiaire, which translates as “grape harvester,” referencing the grape harvest. This time frame is well and truly over, as harvests are happening earlier in the season, influenced by climate change: Higher temperatures speed up grape ripening.
In Beaune, Burgundy, the average date for the start of the grape harvest is occurring earlier and earlier in the year, according to a study compiling grape harvest dates since 1354, published in the scientific journal Climate of the Past in 2019.
Its principal author, Thomas Labbé, co-founder of the PArHis historical study group and associate researcher at the University of Burgundy, has provided Le Monde with an updated version up to the date of the pinot noir harvest in Beaune, on September 13, 2024.
The graph below shows the grape variety harvest dates at the Hospices de Beaune since 1354, with a possible zoom on the recent period. Each dot represents one year, while the red line represents the rolling average over 11 years (five years before, five years after). This data shows that harvests have been brought forward by around two and a half weeks since the mid-1980s.
Reflecting on 670 years of harvesting
Covering a period of 670 years, this database was reconstructed from multiple archives. “The importance of the vineyard in economic terms means that we have traces that go back very far in the archives,” explained Labbé.
The “bans de vendanges,” by which local authorities authorize the start of harvests, provide very well-preserved information, particularly in the Middle Ages and under the Ancien Régime, when they represented an important seigneurial right. For the earliest vintages, in the 14th century, the date was established from the accounts of Notre-Dame de Beaune. For other periods, the registers of Notre-Dame de Beaune’s chapter deliberations and the deliberations of the town council were used by researchers, and, from 1966, regional press articles (for the pinot noir from the Hospices de Beaune estate).
The historical depth of the data collected shows a few vintages of rare earliness in the 16th century. But “these ‘exceptional’ years of the past have increasingly become the norm,” Labbé said. Since 1980, only two harvests have taken place in October and, of the 15 earliest years in the series, eight date from less than 25 years ago.
Wine indicator turned climate indicator
Like the dates marking Japan’s cherry blossom season, this database on the Burgundy grape harvest is a historical indicator of climate change, cited in the sixth report of the IPCC.
Earlier harvest dates have also been highlighted in other vineyards, in Alsace in northeastern France, or in Champagne, with less historical depth. There are, of course, margins of error and limits of interpretation to the links between climate and harvest dates. First of all, they are not a “thermometer”: “They remain first and foremost a viticultural indicator, which we have transformed into a climatic indicator because it is highly correlated with temperatures,” explained Labbé.
Other factors, such as changes in viticultural practices and tastes, may also have altered harvest dates. “Depending on the period, we don’t try to make the same wines; we can assume that in the older periods, we were looking for wines to drink very young, perhaps with more acidity. On the contrary, during the 20th century, people were looking for high sugar concentrations.” But, according to the historian’s research, rising summer temperatures remain the main factor influencing harvest dates.
Beyond the harvest date, climate disruption can have repercussions on the quality and taste of wines, including higher alcohol content and lower acidity. The industry is forced to adapt and consider, for example, changing grape varieties. Some producers also decided to move to more northerly regions, where wine-growing has historically been marginal, such as Brittany or Normandy.