Climate change is altering the chemistry of wine

Winemakers aren’t immune to the changes brought on by the climate change. The warmer temperatures are a blessing to certain regions in cooler climates that are enjoying riper berries; however, they are devastating for other areas. The scorching heat, wildfires, and other climate-driven disasters have destroyed the harvests of Europe, North America, Australia, and around the world.

As 2020 demonstrated clim, ate change could cause harm to the grapes but not directly destroy their nutritional value. Wildfires and higher temperatures could alter the taste of wines. Their flavor and character are based on the delicate nature of the grapes and the environment in which they’re grown. Numerous winemakers and growers are becoming more worried that climate change could be destroying wine’s distinct taste or even ruining the vintages completely.

“That’s the big worry,” says Karen MacNeil, a wine expert who lives in Napa Valley and author of The Wine Bible. “That’s the heartbeat of wine — it’s connected to its place.”

The most significant challenge changes in the weather create for winemaking is uncertainty, MacNeil says. The winemakers were able to determine what grape varieties to plant and how to cultivate them, as well as when to harvest the berries and how to process them into the same quality wine. But today, each step is in the open. The increasing recognition of this is causing winemakers and researchers to seek ways to protect the most beloved grape varieties as well as their distinct properties in the ever-changing and unpredictable conditions of our changing climate.

To find out about the threats to our beloved beverage, we spoke to the wine industry experts of two well-known wine regions -the wine regions of Bordeaux and Napa Valley in France and California to learn how climate change is taking away their old vines and wineries as well as a trip into Napa Valley, the University of California, Davis as well as the close to Napa Valley in late 2021 to meet with growers, scientists, and winemakers.

We were given an insider’s view of how each stage of winemaking changes to keep the desired flavor and aromas. And did we get to sample lots of wines, including the best Cabernet Sauvignon, to samples spoiled by heat and smoke?

From evaluating new grape varieties to changing winemaking, winemakers and growers are looking for ways to reduce climate-related impacts.

The flavor of climate change

Extreme weather can kill the toughest vines. However, the majority of the threat from climate is invisible chemical alteration within the fruit.

The reason is that the wine’s quality when at its most fine, is about achieving equilibrium between three major factors of fruit: sugar, acid, and secondary compounds. Sugar accumulates in the berries when vines photosynthesize, and acid degrades when the grapes begin to ripen. Secondary compounds- essentially substances that aren’t essential to the plant’s metabolism — build up throughout the season. Anthocyanins, also known as anthocyanins, make red grapes more vibrant and help protect plants from UV radiation. The tannins, in turn, give wine bitterness, as well as an astringent and dry mouthfeel. For grapes, they safeguard against predators like grazing animals as well as other insects.

These three elements that makeup wine’s flavor are influenced by many environmental variables, which include the types of soil, the amount of rainfall, and fog. All of these are incorporated into the French term “terroir.” Climate -which is the pattern of precipitation and temperature, the largest component of terroir Oberholster states.

When the climate in a particular area changes, it can alter the balance of acid, sugar, and secondary compounds by adjusting the speed at which they grow during the growing season, according to Megan Bartlett, a plant biologist at UC Davis studying viticulture. UC Davis. Like all fruits, they are able to break down acids and build up sugar when they begin to ripen; when temperatures are warmer, the ripening process is accelerated and results in a sweet, raisin-like taste of grapes.

Yeasts consume sugars during fermentation and excrete alcohol. So, the fermentation of sweeter berries results in greater levels of alcohol in wine -and, indeed, the wines from warm regions like south France are getting boozier. This isn’t a good thing for consumers in the area, particularly since it’s being coupled with a decline in acidity, claims Cecile Ha, representative of the Bordeaux Wine Council. Edge provides freshness and makes sure that wines last for a long time within the wine cellar.

Temperatures rise and alter the delicate chemical composition of wine grapes.

In certain wines, more alcohol levels can cause a burning sensation and obscure subtle aromas, claims Carolyn Ross, a food scientist at Washington State University who cataloged wine aroma compounds in the Annual Review of Food Science and Technology. Wines with higher alcohol levels also tend to be more sour. As temperatures rise, “you’re getting pushed more and more towards that Zinfandel style,” Bartlett states. “Which is fantastic when Zinfandel is the style you’re looking for. However, If there’s been a planting of Pinot or Cab it’s not truly expressing the most desirable version of this variety.”

If the tale were merely about acid and sugar, the answer would be straightforward: Pick the grapes earlier, before they become too sweet, and when they still have their tartness. However, winemakers also want a mixture made of second compounds developed to provide the rich aromas that are essential to top-quality wines. This could force winemakers to decide between harvesting earlier with no fully developed tannins and anthocyanins or harvesting later when the berries are laden with those substances, yet they are also too sweet.

Everything being equal, The changes in the wine grapes due to warmer growth temperatures can bring out more flavorful and, in other words, “cooked” flavors in wine. MacNeil describes the process as follows: “an unripe cherry, to an almost-ripe cherry, to a ripe cherry, to cherry juice, to cherries that have been cooked down on the top of a stove like if you’re going to make a pie, to dried cherries that are almost like raisins.” For wines that hail from warmer regions it’s a concern since they’re in danger of losing their identity as increasing numbers of wines turn”raisiny. (“All raisins taste alike,” says MacNeil.)

A blurring between wine has already affected the industry due to warmer temperatures or unpredictable weather and the increased exchange of new techniques. This has made the certification for master Sommeliers- which is a challenging exam that involves guessing a wine’s type or year of production, as well as its region, even more difficult.

“There are a lot of people who are older masters of wine and master sommeliers who will tell you that if they had to take that exam now, especially the tasting exam, they would never pass it,” MacNeil declares.

The taste of fire

The changes in the wine’s flavor aren’t as obvious in comparison to another most feared climate change smoking impairs the taste of wine. A little smoke by, for instance, barrel-aging could enhance the wine; it’s a “very characteristic ashtray character at the back of your throat,” as Oberholster describes it, using some notes like “Band-Aid” and “medicinal.”

Volatile phenols, which are compounds generated when wood is burnt through grapes, are mainly found within the skins. The phenols are bonded with sugars to form odorless glycosides -until they are fermented, after which some of them disintegrate, giving a distinctive, strong taste. (The break-up continues in the bottle or barrels and mouth.) The flavor is the most prominent in the case of berries bathed with fresh smoke instead of older smoke.

The sensation will be “retro-nasal,” meaning the scent is released into your sinuses when the wine hits your tongue. It’s estimated that 20 to 25 percent of people are unable to smell it, possibly due to the lack of enzymes that break bonds and release smokey notes. This is primarily a danger to red wines because red wines are made by fermenting grape skins.

UC Davis wine chemist Anita Oberholster examines the effects of smoke.


The recent flurry of massive wildfires, exacerbated by climate change, has left Napa growers nervous each year as the grape harvest draws near. Since 2017, a thick layer of smoke has hung over Napa vineyards on a regular basis. The worried grape growers have sought advice from Oberholster to seek advice, and the chemist has made several test batches that were exposed to different degrees of smoking.

On the day that we meet with her, Oberholster takes us to a 24,000-bottle-capacity library of wine at the UC Davis Robert Mondavi Institute. She locates two red wines from the shelves and then hands out the wines of 2020. One is a mildly stained wine from grapes that were exposed to a week of fumes from Glass Fire; the other is a highly tainted ferment due to grapes exposed to smoke from a massive number of lightning-triggered fires that extended right to the vineyard that year.

Then, we have an informal tasting test at Ula’s dining room tables in Reno. In comparison to a Kirkland Signature Cabernet and a Kirkland Signature Cabernet Sauvignon, the tainted wines exhibit the smokiness of a campfire that Katya feels mostly as a scent, and Ula is also feeling a burning sensation in her throat.

“Drinking burnt wood,” Ula writes in her notebook from the smokey vintage.

Planting more durable vines

Smoke taint can be a sour taste and can be heard screaming its presence to people who aren’t experts. However, many winemakers are concerned about the more subtle ways climate change could affect the flavor and character of their wines. To be ready, producers and researchers from warmer regions are learning to adjust to the changing climate, their vineyards, and even the vines themselves.

In Bordeaux In Bordeaux, for instance, the style that is traditional for wine from red is traditionally full-bodied and has distinct fruity aromas and the characteristic “pencil lead” earthiness. However, earlier springs mean that the conventional grapes maturate during the height of summer instead of the fall, creating many sugars but fewer acids and unintentional changes in the aromas. To find grape varieties that are more suited to warmer climates but still produce wines with Bordeaux aromas, Agronomist Agnes Destrac-Irvine of the French National Institute for Agriculture, Food and Environment and her colleagues have recently completed an extensive study over a decade of 52 different varieties from different regions.

With wine producers and winemakers, they came up with four white and two red varieties that would meet the requirements. It’s a major step for French authorities, who had previously permitted only six traditional red varieties and eight white varieties of traditional grapes to be grown. In 2021, they officially authorized Bordeaux wine producers to test out the new varieties in the case that they do not comprise over 10 percent or more of the final blend of wine.

The newcomers are adding new tools to winemakers’ palates to help balance the impact of climate change on Bordeaux blends, according to Destrac-Irvine. One of these is that the French variety Arinarnoa can increase the level of tannins and acidity. Another is that the Portuguese Touriga Nacional can boost powerful aromas of black fruits that the types with a high heat tolerance could be unable to retain. “If you have more colors,” Ha says Ha at the Bordeaux Wine Council, “maybe it will give you more possibilities to paint.”

However, the decision to approve the six varieties is based only on a trial period. The reason is that in Bordeaux, the region where farmers have been cultivating vines for more than two millennia, the notion of creating new varieties is frightening, according to Gregory Gambetta, a plant physiologist at Bordeaux Sciences Agro and the Institute of Vine and Wine Science. The classic types are deeply entwined with the history and culture of the region that “frankly,” he says, “it would be much better if we could adapt the system using other levers.”

So Gambetta and other researchers are trying to research ways to protect vines from climate change by using different rootstocks that are typically of a different variety. Rootstocks determine the overall vigor of a plant as well as the use of water. If they are chosen to withstand climate change, the aboveground array that defines the distinctive chemical and flavor of grapes — will still be used and grow.


Leave a Reply

Your email address will not be published. Required fields are marked *