Hot weather increases the sugar content of wines and alters their taste. How can the effects of climate change on winemaking be avoided?

Very high temperatures, not a drop of rain for a while and then non-stop rain again: climate change is a real challenge for winemaking – and many vineyards may have to fallow one after another in order to regain productivity . But apart from making production significantly more difficult, climate changes have another consequence: they also change the taste of wine.

“During the ripening period of the grapes, the quality of the wine is very sensitive to temperature,” writes a research team from the French school of Bordeaux Sciences Agro led by Cornelis van Leeuwen, in a study published in the scientific journal Nature Reviews Earth & Environment . And there are many reasons for this: high temperatures reduce, for example, the malic acid content of grapes as well as potassium levels – and therefore pH.

The taste of the fresh fruit is lost

According to the French research team, wine produced at high temperatures loses the aroma of fresh fruit and much more often exhibits notes of overripe fruit. The loss of the sense of freshness is due to the lower pH value while the lower acidity negatively affects the taste of the wine.

The more the heat, the more the sugar and alcohol content of the wine increases. This is also the reason why there are more wines with 13-15% alcohol content on the market. High temperatures also make red wines paler.

Forest fires also affect the taste

Forest and bush fires, which also occur more frequently due to climate change, also seem to affect wine quality. In Australia, for example, some wines have been criticized for having a burnt, ashy aftertaste.

The industry has long recognized this particular problem. “Production methods can allow us to correct these phenomena without calling into question the very definition of wine. This can be achieved through the selection of suitable microorganisms, by reducing the sugar and alcohol content and by acidifying the wines,” writes the French Wine Institute.

“The German consumer is conservative”

In Germany, too, efforts are being made to improve the quality of wines: “The winegrowers I know all tend to keep the way they make their wines because they have a market that enjoys them,” says Heiko Payet, an expert on climate impacts on winemaking from the University of Würzburg. “The German consumer is conservative,” he says.

Wines that are low in acidity and low in alcohol taste like brandy and almost no one likes them. “People want young, fruity, but also dry white wines – so does the new generation.”

In order to achieve the right taste there are various “ecological tricks”. “When, for example, I want to make a wine that’s not high in sugar, so it’s not too high in alcohol, but I still want the acidity, I just have to make sure that the grapes are less exposed to radiation of the sun,” says Paet.

Of course, due to climate change, one can also choose other varieties. Today, much more red wine is produced in Germany than was cultivated a few decades ago, but in Franconia the acreage is decreasing again, because there has not been the desired demand.

Paet is looking for alternative areas with the desired climate on behalf of the Bavarian State Institute of Viticulture and Horticulture. In other words, it investigates what the climate will be like in 50 or 70 years in the vineyards that produce the best Silvaner variety. Although the investigations have not yet been completed, the attention of the researchers is particularly drawn to the south-west of France. “This means that in about two generations the vines of Franconia will have the climate that now exists in Bergerac or Bordeaux.

When a suitable site is found, the Bavarian Institute will plant a highly heat-tolerant Sylvaner variety there to examine how such varieties should be grown in a warmer climate – but also how the wine should be kept in the cellar so that it has tastes like it was made in Würzburg.

Large arable lands could be lost

The research team from Bordeaux found that by the end of the century, 20% to 70% of Europe’s arable land in traditional wine-growing areas could disappear – depending on global warming.

Temperatures are becoming too hot for the vines of Central Europe and as a result wine producers are increasingly turning to other locations than where the vines were normally grown.

“Although this is not happening very intensively yet, I think that in the coming decades it will allow us to maintain the grape varieties and therefore the type of our wines, as well as being able to continue cultivating the same vineyards,” says Payet. .

Edited by: Giorgos Passas