French wine grapes show global warming acceleration

A report published on Thursday in the Climate of the Past scientific journal points to significantly hotter and drier conditions for grape harvests during the past 30 years.

The findings delve way back into the dates of annual harvests since 1354, specifically highlighting that wine grapes in the Burgundy area of eastern-central France are picked 13 days earlier – on average, since 1988 – than they were in the prior six centuries.

“We did not anticipate that the accelerated warming trend since the mid-1980s would stand out so clearly in the series,” said Christian Pfister, a professor at the Oeschger Centre for Climate Change Research at the University of Bern, Switzerland, who conducted the study along with other experts in France and Germany.

“We hope people start to realistically consider the climate situation in which the planet is at present,” he added.

The study strung together the dates of grape harvests in Beaune, the wine capital of Burgundy, going back 664 years – making it the longest-ever such reconstruction to gauge the changing climate.

‘Sensitive to temperature’

Thomas Labbe, co-author of the study and a researcher at the University of Burgundy, relied on archival sources to patch together the series of dates – including Beaune city council records, newspaper reports, and even wage payments made to grape pickers.

“The record is clearly divided in two parts,” said Labbe, referring to the periods before and after the onset of major global warming.

Until 1987, wine grapes were generally picked from September 28 onward, according to the study. Then there was a marked shift in the start of the harvest season.

The report shows that very hot and dry years were previously uncommon, but they have become the norm in the last three decades. When the spring-summer growing season is hotter and drier, the grapes tend to be ready for harvesting earlier in the autumn.

The press release announcing the report said that “grape harvest dates can be used as a proxy to study the climate because wine grapes are very sensitive to temperature and rainfall”.

The study made use of temperature records from Paris going back more than three centuries, allowing researchers to estimate temperatures in Beaune corresponding to dates listed on records that suggest exactly when harvests occurred.

Climate of the Past is an international publication that covers “all temporal scales of climate change and variability, from geological time through to multidecadal studies of the last century”. Studies concentrating solely on present and future climate details are not within its scope.

The journal is produced by the European Geosciences Union, a group focusing on Earth, planetary and space science research, with the goal of attaining a sustainable and just future for humanity and the planet.