Can we continue to enjoy Pinot Noir wine? / Kimberly A. Nicholas

Changes in the chemical compounds in grapes resulting from climatic changes force winegrowers to take different actions to preserve the familiar taste of wines

It was a hot day in the vineyard, and I was covered in dust, sweat, and the sticky juice produced by the grapes I picked for my research on the effect of light and temperature on the biochemistry of grapes. Suddenly I noticed something that made me stop: in the corner of the plot - 26 acres of Carneros County land in California's legendary Sonoma Valley planted with rows upon rows of Pinot Noir vines - there were hidden a handful of vines of a different variety. Since as a master's student in viticulture I had learned the ruse of ampelography, the art of identifying and classifying vines based on the shape of their leaves and clusters of grapes, I tried my hand at an educated guess. I estimated that these were varieties of the red wine grapes Cabernet Franc, Petit Verdot, Syrah and Malbec as well as the white wine variety Sauvignon Blanc.

Some time later I met Ned Hill, a friend from high school who these days manages some of the finest vineyards in the area, including the one where I encountered these strange vines, and I asked him about the matter. "It's an experiment I'm conducting," Ned replied. "The area is getting a little too hot for growing Pinot grapes. Right now their price is good, so I prefer not to make any changes. But it may soon be worthwhile for us to switch to growing vines of a different variety, so I'm trying some varieties suitable for a warmer climate."

Cabernet in the province of Carneros? It sounds like heresy mostly. The higher region, the one up in the hills of the Napa Valley, is known for its Cabernet grapes, but this region, where the Sonoma Valley and Napa Valley widen and blend together into one valley that stretches to the San Francisco Bay, is the cooler territory of the Pinot grape. The mild weather during the day, the cool nights, the fresh gusts of wind from the sea and the clay soil yield Pinot grapes that taste like fresh strawberries spiced with cardamom and cinnamon. This is the typical taste of the region where I grew up, and it is this fingerprint that gives the wine produced here its uniqueness and value.

But if the temperatures continue to rise, the wine produced from these Pinot grapes will not be the same familiar Pinot wine. In such a case, the growers in the area may be forced to switch to growing Syrah or even Cabernet grapes and will call into question the continuation of the tradition of the Carneros district, and this may also harm sales. My friend Ned may be able to move his activity north, to an area where the climate is cooler, but the Pinot grapes grown elsewhere will be affected by the soil conditions, humidity and precipitation there, and thus will lose the characteristic Pinot grape flavor of the Carneros region. Alternatively, my friend could apply innovative technologies and try to adapt his cultivation methods to the changing conditions in order to preserve the unique flavor signature of Carneros, a task that is not easy at all.

Climate change is beginning to affect the unique flavors of various wines around the world, and hence also the experience we, the wine consumers, have come to know and expect to receive from our favorite wines. In the face of these changes, winegrowers and winemakers are already required to make difficult, but also fascinating, decisions regarding ways of responding. Will they be able to adapt to climate change and ensure, for example, that Pinot grapes from the Carneros region and Burgundy grapes from the Burgundy region of France retain their characteristic taste? Will famous wine regions decline in size and give way to new wine growing regions? The answers to these questions depend on both the pace of climate change and the pace of innovation.

Fine wine is grown, not produced

Scientists fear the effect of rising temperatures on the amount of crops in basic crops such as wheat, corn and rice. But as far as grapes are concerned, it is not the quantity that may be affected by the warming, but mainly the quality.

In some vineyards in hot areas, the goal today is indeed to grow large quantities of grapes, not necessarily of high quality, and sell them at a low price. For example, winegrowers in Fresno in the Central Valley of California are trying to obtain a harvest of 3 tons of grapes per acre. In 2013, these grapes were sold at an average price of $340 per ton and were mostly used to make cheap wine that sold for less than seven dollars per bottle.

The more romantic version of viticulture can be found in cooler places: on the fringes of the areas that hug the Californian coast. In the Napa Valley, only about 300 km north of Fresno, skilled winegrowers grow vines by hand and literally touch each vine many times during the growing season. They also deliberately limit the yield of the vineyard: in the winter season, they thin the vines so that each vine grows only a few clusters, and in the summer they go repeatedly along the rows of vines and prune any cluster that has not reached optimal size.
They hope to compensate for the financial loss caused by the reduction of the crop through its quality. The hope is that each vine will direct all its resources to the few clusters on it and thus give the grapes deeper and more complex flavors and aromas. Their yield target is a ton per acre. In 2013, each such ton was sold for $3,680. There is no doubt that this price, which is ten times higher than that received by the growers in Fresno, was achieved in no small part due to the careful management of the vineyard. But it is the cooler climate in the region that contributes most to the high quality. This is an impressive result of a seemingly negligible difference of about 2.5 degrees Celsius between the average annual temperatures of the two growing areas. And as one of the winegrowers told me, "Even a genius wouldn't be able to grow quality Pinot Noir grapes in Fresno. It's too hot there."

A climate that is "too hot" is indeed problematic, since the temperature regulates the course of life of all types of plants, and wine grapes are particularly sensitive to it. Wine is greatly influenced by the environment where the grapes are grown, and the French even have a special word for this growing environment: terroir. Like coffee and other products that are geographically unique, wine reflects the environment it came from. The vine produces sugar in the process of photosynthesis, and then extracts from this initial component a variety of compounds that give the wine a special taste and aroma, of raspberries, for example, or of recently mowed grass. The temperature, the humidity, the light and the soil itself influence the way the vine orchestrates this piece of dance. Since more than 80% of the wine's content is water, and the alcohol content in the wine is between 12% and 15%, only about 5% remains for all the other ingredients. But it is this small proportion of the other ingredients that creates the unique taste of each wine. And changes in the climate could damage this unique taste.

Although wine production requires a high level of skill, almost all the winemakers I interviewed for my research admitted, in response to the question of how the industry responds to environmental challenges, that the potential quality of the wine is almost completely determined before the grapes reach the winery. Although some of the potential flavors of the wine derive from the production process (for example, the yeast used during the fermentation stage or the aging method in oak barrels), but as a well-known wine production expert told me, "If everything in the vineyard is done correctly, my job is simply not to destroy it." Fine wine is grown, not produced.

Different climate, different taste
The climate largely affects the cultivation of wine grapes. Vintners distinguish between three levels of climate: the macroclimate of a particular geographic area; the mesoclimate of the vineyard plot; And the microclimate that the canopy of leaves within which it grows creates for each cluster.

The macroclimate is influenced by broad geographic factors that determine the growing season and the temperature patterns and the amount of precipitation. But it is the temperature that determines most of all which of the thousands of varieties of wine grapes will be able to grow optimally in a certain place: starting with the varieties that produce clear white wine and are suitable for the short growing season and the cool climate of Germany, and ending with the varieties that have a bright red color that are able to retain their flavors during the dry, hot summer and the longest of Spain. The temperature also determines when the vines will wake up in the spring after winter dormancy and drives the growth and ripening processes. With global warming, new areas, southern England for example, are becoming more suitable for growing grapes, while some of the warmer wine regions, especially some areas in Australia, have to deal with high temperatures and repeated forms that cause crop fluctuations, excessively high alcohol levels and unbalanced flavors.

Changes in the amount of precipitation in a certain area and the timing of its fall may affect the quality of the grapes in different ways. Excessive moisture can accelerate fungal rot, while drought can cause a plant to become stunted. In many of the wine regions of the New World, including California, extensive irrigation is practiced, but a study I conducted with a group of colleagues from Stanford University shows that even in such regions the natural precipitation has an effect on the yield.

The influence of the mesoclimate of a vineyard on the taste of the wine is less clear, but it is known that the taste is determined first and foremost by the balance of sugar and acid in the grapes, the two components that build the basis of the wine's taste. Fruits accumulate sugar as they ripen, a process directly controlled by temperature. The sugar content in ripe wine grapes is extremely high, about a quarter of their weight. For comparison, this content is twice as much as the sugar content of a juicy and sweet peach. The heat increases the sugar content at a predetermined rate: a percent or two every week during ripening. The sugar turns into alcohol during the fermentation process, so the sweeter the grapes are, the higher the alcohol concentration in the wines produced from them. Global warming in recent decades has been reflected in a worldwide trend of producing wines with a higher alcohol concentration. Often a high alcohol concentration is experienced as "hotter" and more bitter and may change the sensations given by the more delicate flavors, and even overshadow them altogether.

The acids are the 'yin' (yin), which complements and balances the 'yang' (yang) of the sugar. They are found in large quantities in unripe grapes and are partially decomposed as the grapes ripen. The acids in the wine give it a sharp and refreshing taste. In cooler wine regions, varieties are grown that can ripen quickly in the short growing season, but are also characterized by pleasant, not too high, levels of acidity. Wines originating from cold climate regions, such as the German Riesling, may lose their freshness due to the increase in temperatures since the refreshing taste of the acids dissipates in the heat.

The role that sugar and acids play in wine has been known to winemakers for a long time, but in recent years they have become more and more aware of the critical impact of less common ingredients in wine on our drinking experience. For example, phenolic compounds are important when it comes to wine color. Even before we sip the wine, we see it in the glass, and its color affects our overall experience. In one of the experiments conducted on the subject, even experienced wine tasters described white wine dyed red as having the taste characteristics of red wine. In the juice produced from classic varieties of wine grapes (varieties originating from the old world) there are no colorants (pigments). The origin of the wine color is phenolic compounds called anthocyanins, found in the skin of the grape. These compounds are common in nature; They give blueberries their blue color and eggplants their purple color. When the grapes are crushed after the harvest, the red varieties are left in contact with the skins throughout the fermentation process, i.e. for weeks, so that they transfer their color to the juice. In contrast, the concentration of phenolic compounds in white wine grape varieties is low to begin with, and they are usually separated immediately from their skins.

Although the phenolic compounds in the grape are formed under the influence of exposure to the sun, wines originating from warmer climates often do not excel in the desired intense red color. Studies conducted on the subject indicate that not only differences in the average temperature affect the color of the wine. In fact, the increase in temperature beyond certain limits may have non-linear effects that will actually cause a decrease in the concentration of anthocyanins.

The microclimate of the vineyard also affects the tannins, which give the wine its texture (such as "viscous" or "smooth"). Tannins are phenolic compounds of a different type, and their name (tannins) is derived from their use in the past to tan leather. The taste of the tannins is quite repulsive, and thus they protect unripe fruits from animals and pests. When we sip wine, the tannins bind to the proteins in the saliva in our mouth and dry out the tongue and gums, and this sensation affects the way we experience the taste of the wine. Tannins have a bitter taste and in the right balance they help the wine to enrich the taste of the food. They also clean, literally, the palate and remove fat from the taste receptors, and this allows us to feel the taste more fully with each bite. Excessive exposure to heat or light may reduce the amount of tannins and damage the balance of flavors in the wine.

ripe for sniffing
It is the trace compounds, found in tiny concentrations, that give the wine most of its unique character. These compounds play an essential role, especially when it comes to the aroma of the wine. When we taste wine, we often mix it first to savor its aroma. The stirring evaporates the compounds in the wine, and thus they bind to the receptors in our nose, and these send signals to our brain that are interpreted as taste, which means that a unification of sensory input from different channels takes place here. In fact, what we normally perceive as taste is mainly provided by our refined sense of smell. This is why food is so bland to us when we have a cold: a blocked nose does not allow the aroma compounds to reach the inner part at the back of the mouth, where the smell receptors are located. Try to plug your nose and eat a piece of unpeeled apple and a piece of uncooked potato; Amazingly, you'll be hard-pressed to tell the difference. It therefore seems appropriate to replace the term wine tasting with the term wine smelling, although it must be admitted that the latter term sounds much less appealing.

Winemakers and researchers are still studying the subject of trace compounds that are formed in different ways. They accumulate in grapes usually in the late stages of ripening, and we know that their formation is sensitive to temperature in these stages. The ripening of the taste, as this process is called, can occur at a different rate than the ripening of the sugar, which occurs at a predetermined rate and according to which it has always been customary to determine the harvest date. Today, many winemakers determine the harvest date based on tasting the grapes in the vineyard. They are looking for the flavors that, in their estimation, will lead to the creation of fine wines. Usually these flavors develop along a continuum: first they remind the taste of green fruits and vegetables; Then, the taste of dark berries, such as raspberries; And finally, the jammy taste of raisins and similar fruits.

In some areas where this approach is applied, they tend to postpone the harvest and leave the grapes on the vine for a longer "hanging time", which allows optimal flavor maturation. Not all winegrowers are in favor of this approach because the water content in the grapes decreases over time, and this may result in a lower weight and therefore also a smaller profit. Longer hanging time also increases the sugar levels in the grapes and may force the winemakers to add water to the juice extracted from the grapes to reach the correct alcohol level.

Researchers are trying to understand exactly how the more than a thousand aroma compounds found in wine affect our sense of taste. It is difficult to predict their effect, because the concentrations of some of them in wine are extremely low, and the sensory sensitivity to them can be very different between different people. For example, more than 200 compounds can give a wine a strawberry aroma, and the factor that evokes a feeling of "strawberry" in one person will not necessarily evoke a similar sensation in another. (So ​​if you're still looking for the "correct" answer when you taste wine, well, there is no such answer!)

Sometimes one "critical" compound is the main cause of a characteristic smell, and understanding how it affects our senses may help winegrowers produce a better product. In the 80s, Hildegrad Hyman of the University of California, Davis, acted on a gut feeling and discovered that a compound called methoxypyrazine, which causes the unwanted pepper aroma in Cabernet Sauvignon, is destroyed by exposure to light. Following the discovery, the winegrowers in the area changed the way the vines were planted (that is, the way they support the vines) so that the shade on the fruit would decrease. Indeed, the taste of California Cabernet wines has improved considerably. A more recent study conducted by Claudia Wood with her colleagues in Australia, Chile and Germany revealed that it is a single compound called rotundone that produces the aroma of black pepper in wine produced from Syrah grapes, where this aroma is highly desirable. Other studies show that in cooler regions and in colder years the proportion of this compound in grapes is greater.

The vine-growers fight back a hair
Understanding all the factors that affect the taste of wine will help winegrowers assess how they can adapt to the changing climate. The most extreme option open to them is to move to another area, for example from California to Oregon. A less extreme step would be to move the vineyard to a more suitable location in the same area, for example from warm depths to cool hills. A few studies have looked at these possibilities, but they are mainly based on the predicted changes in temperature and do not take into account other important environmental factors. Articles published in the popular press based on these limited studies went so far as to declare certain wine regions endangered and predicted a decline in crop quantity and quality.

The idea of ​​relocating the vineyard is not easy to implement, and its successful implementation is conditional on the existence of several essential conditions. For example, suitable soil, which will provide the right nutrients, and water supply are necessary to obtain high quality wine, but there is no certainty that they will be found elsewhere. There may not even be suitable unused land. Uprooting an entire industry, including its infrastructure, is a complex and expensive task. Moreover, a new vineyard reaches full yield only after five or six years, and to achieve profitability it may take even 20 years. Vintners whose family worked the land in a certain place for generations feel a deep sense of belonging to the place and will not willingly give it up. Often consumers also have a strong connection to a well-known wine region. In new areas where the climate has become warm enough to grow wine grapes, it will take time to acquire cultural knowledge that will enable dealing with the challenges involved in planting a yielding vineyard, dealing with pests and diseases, and developing a local style and a unique identity that buyers will appreciate and cherish.

What about the selection and improvement of other vine varieties to suit the changing conditions? Only one species of vine, the wine vine (Vitis vinifera), is the source of all the thousands of grape varieties used to make wine. Vintners selected certain varieties for their good adaptation to a particular environment, just as dog breeders selected certain breeds of dogs to pull sleds in Alaska and other breeds to attract attention on the streets of Los Angeles.

But if we simply take a grape variety with characteristics that are suitable for growing in a certain region and try to grow it in another region, we will usually not achieve the same taste. For example, cuttings (that is, branches from the genetically identical mother plant) of Pinot Noir vines from the Burgundy region of France, an area with a cool climate, were found to ripen quickly and produce high quality grapes. Indeed, the wines produced from vines propagated from these cuttings got the name of fine wines. Recently, these cuttings have also been widely planted in warmer California, but the different environment has resulted in faster ripening and has not always been able to reproduce the prestigious flavor profile of the French wine. Planting varieties from warm regions, such as Spain, in new areas where the climate is warming may yield delicious wines, but by trial and error the process may take years.

There is very active research on creating new varieties of basic foods that will be more resistant to global warming. But when it comes to wine grapes, the potential inherent in the creation of such varieties is limited, also because the creation of new varieties of wine grapes can take a decade or more, but mainly because of cultural reasons. For example, the French law that regulates the designations given to wines states that only certain varieties, unique to certain regions, can carry the protected name of the region, such as Bordeaux. (However, in the 90s, a relatively new variety called Marcellin, a hybrid of Cabernet Sauvignon and Grenache, was allowed to bear the designation given to wines from the Rhône region of southern France: Côtes du Rhône.) Consumers around the world tend to remain loyal to their favorite varieties. on them, therefore introducing new varieties to the market may encounter real difficulties.
In an attempt to combat climate change, winegrowers can make different decisions about planting and growing methods in an existing vineyard. They can change, for example, the direction of growth of the rows of vines or the way a few vines are thinned so that they shade more of the fruit as the temperatures rise. Vintners can also install a new vine variety that is less vulnerable to heat on an existing vine. But such crucial decisions are usually made only once, at the beginning of the vineyard's long life cycle.

Even less dramatic decisions can greatly affect adaptation to climate change. The winegrowers have no influence on the air temperature at the macro level of their region, and they have only a limited possibility to influence the temperature at the meso level of the vineyard, for example through overhead sprinklers or shading sheets, but they can determine what will be the number of leaves that shade the ripening cluster and what will be their location, and so cool the microclimate. Such cooling can allow the grapes to retain their flavor and aroma compounds.

For example, in the measurements I made in the vineyards in Carneros County, California, I discovered very high levels of solar radiation (three times the previously reported levels) on the grape clusters hanging from more than 500 Pinot Noir vines. The stems and leaves were all held high above the grape clusters by a mesh of iron wires to allow for optimal air circulation and reduce the spread of disease. In the data analysis that I conducted with my colleagues from Stanford University and the University of California at Davis, we found that each percent increase in the level of radiation results in a decrease of more than two percent in the desired concentrations of tannins and anthocyanins. Arranging the vertical halyard struts in such a way as to provide more shade to the fruit can help preserve these compounds.

Although most of the flavor of wine comes from the grape itself, winemakers can take various measures during the processing stage of the grapes to try to preserve the flavor characteristic of a wine from a certain region. For example, if the grapes lose their acidity too quickly as the temperatures rise in the area, the addition of acid during the processing process in the winery can provide a solution to the problem. Another example: as mentioned, if the grapes accumulate too much sugar, the high concentration of alcohol that will be created during the fermentation process may overshadow the delicate flavors in the wine. The winemakers can get rid of the excess alcohol through reverse osmosis or other methods. However, it should be noted that such methods are relatively crude and cannot completely change the original flavors that the grapes carry from the vineyard.

Coaxing the soil to yield the best flavor is an art that takes years of hard work. Some of the industry experts believe that New World wine regions, such as Napa and Sonoma, are still groping for their best terroir. Jason Kesner told me a few years ago, when he was managing a vineyard of elite grapes on the border of Carneros County and Napa Valley, that even the most prominent vineyards in the region are still generations away from their destination. According to him, it takes a generation to grow a vineyard, "and then your children are forced to try to understand how the vines really should have been planted, and only in their children's generation does the token really fall. This is why the French have such wonderful vineyards - they simply had more time to learn. "However, since the quality of the grapes depends so much on the climate, even a small change in the climate can cause local knowledge and skills acquired and developed over generations to become less relevant, even when it comes to familiar territory."

Change places
Despite their relatively young age, Napa Valley Cabernets and Carneros County Pinots have a unique profile and loyal following of their own. "I opened a bottle of wine and it smelled like Carneros," said Debbie Ziegelbaum of Robert Sinsky Vineyards in Napa Valley. Climate change, if it does change the aroma and taste of grapes from these regions, could damage their status as wine regions. Although climate warming may improve the quality of wine originating in certain cool regions, in Tasmania for example, it is likely that these changes will harm the large wine regions whose activity is adapted to the current conditions. For example, according to my research, a warming of more than XNUMX degree Celsius in the spring season could reduce California's wine grape yields. And another example: the price of California Pinot Noir grapes drops dramatically when the ripening of the grapes takes place at a temperature that is higher than the optimal temperature threshold.

As we have seen, vine growers and winemakers have several methods to adapt to climate change. Time will tell if these methods will stand the test. But the question arises, from what point in the process does the application of these methods lead to the production of wine of an industrial nature instead of the wine with the unique taste of its place of origin? And in the end, despite all the efforts of the growers, there are biophysical and economic limits to adapting to climate change.

The latest scientific reports predict that if the world continues to use fossil fuels at its current rate, the global average temperature will rise in the coming generations by about 2.6 to 4.8 degrees Celsius. Such an increase may not seem very high, but note that the lower end of the range is, approximately, the current temperature difference between Napa Valley and Fresno, and its upper end is the temperature difference between the wine city of Lodi, located in the Central Valley of California, and the city of Houston, Texas. Despite the resourcefulness and creativity employed by the winegrowers, it is hard to imagine Houston becoming the next Napa Valley.

Wine is, quite literally, a message in a bottle. It allows us to visit lands that our feet may never set foot on. It reflects the wonderful environmental and cultural diversity of our planet, and also our deep dependence on nature, which is the source of everything we need to live and many of the things that give flavor to our lives. We are currently on a path that leads to the complete destruction of life on earth. If we do not reconsider our course very soon, the lost taste of the wines of my hometown will probably be among the less serious victims.

in brief
Climate change is increasing the air temperature in many of the wine regions. Since the temperature affects the accumulation of the chemical compounds in the grapes, temperature changes can cause wines originating from a certain region to lose their special flavors.

A higher temperature increases the sugar content in the grape. Therefore the concentration of alcohol obtained in fermentation is higher. The temperature also affects the concentrations of other compounds that give the wine its special aroma, which has a decisive effect on our sense of taste.

Winegrowers are taking a variety of steps in an attempt to adapt to climate change, starting with changing the direction of growth of the rows of vines and ending with rearranging the leaves in such a way as to provide more shade. Moving a vineyard to the north or to a higher area in order to reduce its exposure to heat involves high costs, and does not even guarantee the restoration of the taste due to the different humidity and soil conditions in the new area.

on the notebook
Kimberly A. Nicholas (Nicholas) serves as an associate professor of sustainability sciences at Lund University in Sweden and serves as a consultant to winegrowers and winemakers worldwide. She grew up in a family of winegrowers who cultivated a vineyard of Cabernet Sauvignon grapes in Sonoma County, California. Follow her on Twitter: @KA_Nicholas.
Do it yourself
Home wine tasting test (over 18 years old)
Each of us can learn to taste wine more analytically without needing the opinion of professional tasters. All we have to do is learn to identify ingredients in wine and associate them with the appropriate descriptive terms. Since different people can attach different verbal adjectives to the same flavor, the participants in wine tasting tests first smell physical samples of different flavors, for example blueberries, in order to reach a general agreement about what is meant by the term "blueberries". Then the members of the tasting panel go into separate booths, which are lit with a dim red light that gives all the wines the same color. The test administrator slides trays with numbered wine glasses through the cell partitions, and the panelists rate the wines on a computer screen.
At home you can simplify the process and make it more enjoyable. First, invite a group of friends and ask them to bring bottles of a certain type of wine, let's say a boat. As hosts, you have to find samples of the typical flavors of the boat: black pepper, Osana, cloves. Place each of the samples in a glass and cover the glasses with paper cups so that the aroma compounds retain their scents. When the guests were seated, pass the glasses with samples of the "standard scents" between them. After that, taste each of the wines and try to identify the flavors and evaluate their strength.

If you find you need help, you can use the aroma wheel developed by Anne Noble. In the center of the wheel are defined general categories of aroma, such as fruity or spicy. As you move away from the center towards the rim of the wheel, the fragrances become more and more subtle in each category. For example, a fruity aroma can in the first step sharpen into an aroma of berries and in the next step into a raspberry aroma. The more we learn to experience the sensory world in more detail, the more enjoyable the hours of food preparation and the food itself will be.

More on the subject
Farm-Scale Adaptation and Vulnerability to Environmental Stresses: Insights from Winegrowing in Northern California. Kimberly A. Nicholas and William H. Durham in Global Environmental Change, Vol. 22, no. 2, pages 483-494; 2012.
Climate Change, Wine, and Conservation. Lee Hannah et al. in Proceedings of the National Academy of Sciences USA, Vol. 110, no. 17, pages 6907-6912; April 23, 2013.
Save the Coffee, Hilary Rosner, Scientific American Israel, February-March 2014.
www.sciam.co.il/archives/8551