What makes a good or bad wine year? The question concerns not only producers, but also scientists, who have long been trying to answer it by closely observing weather conditions.
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A new study published Wednesday in the journal iScience examined the question in a new level of detail and throws a wrench in the works by arguing that climate change could partly and to some extent help improve wine quality.
By analyzing critics’ reviews of Bordeaux wines over several decades, the study shows that good years are characterized by large temperature swings, a higher average temperature, and an early and short season.
However, due to climate change, these diseases are likely to become more and more common. The study therefore concludes that as the planet warms, the quality of wine could continue to increase up to a certain limit.
“I don’t think climate change is a good thing,” warns Andrew Wood, lead author of the study.
In fact, warming is simultaneously bringing numerous problems for the vines, in particular the increase in “extreme events,” he told AFP.
For example, the increased risk of fire is obviously a threat. Early budding also makes the vines more susceptible to hail or frost in spring.
And even when good years are characterized by a dry and hot summer, too severe a drought can have devastating consequences. At a certain threshold, it can even get to the point where the grapes “fall off the vines,” he emphasizes.
But if the vines survive, the chances of favorable weather for good wine all year round should increase – at least for now.
“It could be that we are very close to the moment” when wine “stops getting better and becomes much worse,” the Oxford University researcher adds. “We just don’t know where the threshold is.”
“Stronger” wines
Analyzing the ratings attributed to Bordeaux vineyards between 1950 and 2020, researchers have observed a current trend toward improvement in wine quality.
These are in particular the grades that wine merchants assign each year at regional level for the entire Bordeaux vineyard.
The observed improvement is linked to an increase in the number of years in which these favorable conditions have existed more recently, according to the authors, who acknowledge that technological advances may also have played a role.
Rising temperatures lead to increased photosynthesis and therefore more sugar, resulting in higher alcohol content or “stronger” wines.
These wines “age longer, giving you richer, more intense flavors, more sugar and less acidity,” comments Andrew Wood.
Previous studies have long identified the positive effects of rainy winters and high summer temperatures.
But the other seasons also play an important role, as the researchers showed here: a warm, humid spring and a cool, dry autumn are also associated with better-rated wines.
To achieve this level of precision, they examined critics’ ratings after individual tastings of controlled designation of origin (AOC) wines and compared them to the local weather.
According to the researcher, this weather “recipe” could be transferred to other regions of the world. But he points out that this is not an excuse to give in to drunkenness.
“The problem in scenarios where it gets really hot is the water. If the plants don’t have enough, they die,” he explains. “The consensus is that the wines will continue to improve until they decline.”