Could climate shifts improve wine vintages?

Wine quality is known to vary from year to year, but what makes for a good year?  In a paper published on 11 October in the journal iScience, researchers show that weather plays an important role in determining wine quality.

By analysing 50 years’ worth of wine critic scores from the Bordeaux wine region in relation to that year’s weather, the researchers found that higher-quality wine is made in years with warmer temperatures, higher winter rainfall and earlier, shorter growing seasons — conditions that are predicted to be made more frequent through climate change.

Lead author Andrew Wood, from the University of Oxford, said wine quality and wine taste are driven by weather.

The same vineyard can produce different vintage qualities in different years, despite coming from grapes grown on the same vines, same land and produced by the same methods.

“We found evidence that temperature and precipitation effects occur throughout the year — from bud break, while the grapes are growing and maturing, during harvesting and even over winter when the plant is dormant,” Wood said.

 While weather and climate are expected to impact crops, the link between climate change and agricultural produce quality has not been widely explored.

To investigate how wine quality is impacted by yearly weather fluctuations and climate change, the researchers paired high-resolution climate data with annual wine critic scores from the Bordeaux wine region in South West France from 1950 to 2020. Wine quality was analysed both at the regional scale and on a more local one, focusing on yearly variation for individual “appellations d’origine contrôlée” (AOCs) within Bordeaux — ie, defined geographical regions with defined methods of grape cultivation and wine production. Then, the researchers used models to test whether wine quality was impacted by weather factors such as season length, and ranges and shifts in temperature and precipitation.

Unlike previous studies that focused on weather during the growing season, the study also investigated the impact of weather during the non-growing winter season, when grape vines are usually dormant. According to Wood, perennial crops like grapes are there all the time, so things that happen outside of the growing season can impact the wine.

The researchers focused on Bordeaux because it is a region that relies on rainfall for irrigation and because it has long-term records of wine scores which could be used. Though wine judging is subjective, most critics agree on what is a ‘good’ vs ‘bad’ wine, so quality is a “non-subjective property of perennial crops”, according to the authors.

The researchers found that Bordeaux wine quality scores tended to improve between 1950 and 2020. This could be because Bordeaux’s climate warmed over that period, but it could also be because of the increased use of technology in winemaking over this period or because wine makers are increasingly matching techniques to consumer preferences.

According to Wood, the trend is that people generally prefer stronger wines that age for longer and carry richer, more intense flavours, higher sweetness and lower acidity. He also said that wines are generally getting stronger due to greater warming associated with climate change.

In general, high-quality wines were associated with cooler, wetter winters; warmer, wetter springs; hot, dry summers and cool, dry autumns.

The researchers believe wine in the Bordeaux region is likely to continue increasing in quality as climate change progresses with warmer weather and less rainfall during the summer and more rainfall during the winter.

However, this is only true up until the point at which water becomes limited. If plants don’t have enough water, they eventually fail.

According to Wood, the general consensus is that wines will continue to get better up to the point where they fail.

Though the study focused on Bordeaux wines, the researchers believe their results could also apply to other wine regions. The methods could also be extended to examine the impact of yearly weather variation and climate change on other perennial crops, such as cocoa and coffee, if long-term quality records are available.

Image credit: iStock.com/JuliaLototskaya