(CN) – Research published Thursday may finally answer the important question of how climate change is expected to disrupt the wine market.
Winemakers in the Burgundy region of France have long recorded harvest data, providing a centuries-long picture into the past. But data usually used from Dijon contains errors and is skewed by urbanization encroaching on vineyards.
That flawed data inspired half a dozen researchers led by Thomas Labbé of the Liebniz Institute for the History and Culture of Eastern Europe to compile a new dataset based on unedited records from the wine capital of Burgundy, published in the open access journal Climate of the Past.
Beaune has long been known for its fine red and claret wines produced from varieties of pinot noir and Gamay. However, the Gamay was once considered so inferior the duke of Burgundy attempted to outlaw its cultivation in 1395, though it continued to be grown. Today the vineyards also produce Chardonnay grapes.
Grapes are extremely sensitive to temperature and precipitation and therefore make ideal canaries for climate change – grapes can be harvested earlier after a hot, dry spring than in colder years. After flowering, grapes go through veraison and ripen before they are ready to be picked. While grapes ripen more easily in warm weather, extreme heat and drought slows fruit growth and can stop it altogether.
Spanning from 1354 to 2018, the Beaune data correlates with Parisian temperature logs, tree rings and wheat harvest data.
For 633 years, the average harvest occurred on or around Sept. 28. Since 1988 onward however, harvests have shifted to nearly two weeks earlier, a phenomenon associated not just with warming temperatures but also with “high pressure over western–central Europe and atmospheric blocking over Denmark.”
“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 in a statement.
Researchers totaled 33 extremely warm events, about 5% of harvests, scattered throughout the centuries but more concentrated in more recent years. Written records – newspapers, church meetings, and even payroll accounts – offered a deeper understanding of the impact of warm harvests, which lasted up to 27 days longer in 1540 and 1556.
During the heatwave of 1540, the church held eight processions praying for rain as grapes turned to raisins on the vine, eventually producing “a sweet sherry-like wine which made people more rapidly drunk than usual.”
Another significant shift occurred between the 18th and 19th century, when grapes began being harvested one week later and which researchers hypothesize wasn’t driven by season so much as a desire to harvest more mature grapes for longer lasting wines.
The data set also reflects the impacts of the Little Ice Age and documented volcanic eruptions on vintages.
“The transition to a rapid global warming period after 1988 stands out very clearly. The exceptional character of the last 30 years becomes apparent to everybody,” Pfister said. “We hope people start to realistically consider the climate situation in which the planet is at present.”
Consequently, winemakers today are selecting different strains, researchers pointed out, and “winemaker choices depend on both cultivar and the style of wine. For instance, the number of days between veraison and harvest for CV Cabernet–Sauvignon has nearly been doubled in a famous Château in the appellation Margaux near Bordeaux.”