Temperature plays a crucial role in shaping wine style both before and during fermentation, but overall climatic conditions become an additional key consideration when wines undergo barrel maturation. Over the years, enology literature has offered a wide range of recommendations regarding the ideal climatic conditions for aging wine in wooden barrels, highlighting how different temperatures—from as low as four degrees Celsius to as high as 20 degrees Celsius—can either accelerate or decelerate the wine’s aging process.
“Barrel aging mainly means subjecting the wine to an oxidative process,” says Nicolas Vivas, a wine consultant and researcher at the University of Bordeaux’s Demptos Research Center. “Today, the trend is towards obtaining fresher wines that focus on fruit expression. To achieve that, barrel rooms need to be maintained at temperatures lower than 18 degrees Celsius, around 14 to 15 degrees Celsius.”
According to Vivas, higher temperatures may lead to loss of freshness and fruit expression, and to the development of heavier aromas such as jam, honey, or cooked and overripe fruit. Warmer conditions can also negatively affect the color of the wine and limit its aging potential. Crucially, heat increases the risk of off-flavors and bacterial infections—for instance from Brettanomyces bruxellensis—potentially leading to spoilage.
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Here, experts weigh in on the myriad ways that climatic conditions like temperature, humidity, and drought can affect the barrel-aging process during winemaking.
A Matter of Style
“Maturing at higher temperatures can be a stylistic choice,” says Vivas. “In Bordeaux, people would age at higher temperatures in the first six to 12 months, and drop them in the second year. This way you make an easier, fruitier wine but you also have faster oxidation in the bottle, that’s why now many are adopting a different approach.”
India’s Sula Vineyards has been betting on cooler temperatures over the past five years, an approach that winemaker Karan Vasani claims has had noticeable beneficial effects on the wine’s aromatic qualities and ageability.
“We used to mature wines at around 17 to 18 degrees Celsius,” says Vasani. “Then, in 2018, we decided to bring it down to 14 degrees Celsius because our evolution in the barrel was too fast. Now we feel that we get better maturation, better wine quality, and better protection from microbial spoilage. The profile of the wine has increased significantly.”
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Argentine winemaker Juan Pablo Murgia of Otronia and Argento has been maturing wines at cooler temperatures—between 14 to 16 degrees Celsius—for at least a decade. “I’ve been working in the direction of obtaining fresher and primary aromas, so the best options are lower temperatures and, above all, larger oak containers such as 5,000-liter foudres,” says Murgia. “Higher temperatures increase oak extraction and develop heavier flavors [rather than] fresher ones.”
While fortified wines face fewer concerns related to microbial infections and oxidation, leading Marsala producer Cantine Florio is also looking at the cooler areas of its labyrinthine two-hectare cellar to freshen up its premium Marsala Vergine.
“We always thought that a Vergine had to be characterized by tertiary aromas more akin to rum and whisky,” says director Roberto Magnisi, “but recently we’ve been looking at a new style of Marsala Vergine, a more delicate, elegant one … with even floral and marine aromas.”
The Importance of Humidity
In order to create these innovative styles, Florio is not only blending wines from the cooler sections of its cellar, but also from the more humid areas as moisture, too, plays a critical role in wine’s oxidative process. Higher humidity levels saturate the barrel’s staves with water, limiting the wine’s overall oxygen intake and slowing the oxidation process. Drier conditions, on the other hand, cause the wood to shrink, letting more oxygen interact with the liquid. This speeds up the maturation process and increases the loss of liquid through evaporation.
“We make wine in a very hot and humid climate,” says Vasani. “Both our facilities (one in Maharashtra in Nasik and one just outside of Bangalore) have air conditioning. This dries the air out a lot so we also have misters which release very fine water droplets into the air and manage to keep the humidity at about 70 percent.”
For Vivas, humidity levels of around 80 percent are ideal for a slow and gradual development of wine in barrels. In some regions, however, the rising occurrence of droughts poses significant obstacles for winemakers to maintain these conditions.
Historic Veneto producer Masi, for instance, has an artificially controlled cellar but has been “increasingly struggling to maintain the right humidity levels [of 80 percent] during prolonged periods of drought,” as enologist Andrea Tella puts it, a problem they might have to address in the near future.
A Warming Indoor Climate
Alongside drier conditions, warming temperatures are becoming a concern too, particularly in wineries with no artificial control over indoor climate.
Leonardo Bellaccini, the enologist for Tuscany’s San Felice winery, claims that climate change has resulted in a substantial increase in indoor temperatures within one of his barrel rooms that lacks air conditioning. “That’s where we used to make our white wines in temperature-controlled tanks,” he explains. “In that part of the cellar I don’t keep my premium wines because in the summer, temperatures are a lot higher and the wines evolve faster.”
A recently published study by a research team from the Universidad Politécnica de Madrid (UPM), highlights the potentially catastrophic consequences of the warming climate for sherry’s biologically aged wines such as fino and manzanilla.
The region’s bodegas have traditionally provided the necessary environmental conditions for flor—the yeast responsible for their distinctive character—to develop and thrive. Lustau, for instance, manages to maintain an ideal indoor temperature of 20 to 22 degrees Celsius without modern cooling systems. Yet, with temperatures expected to increase by an average of 2.3 degrees Celsius by 2050—and up to an astonishing four degrees Celsius in the summers of hot years—the study argues that some facilities would struggle to absorb this shift, eventually failing to provide the necessary conditions for the production of biologically aged sherries.
Architecture and design research is actively exploring innovative solutions to address the challenges faced by winemakers in maintaining appropriate indoor temperatures. The UPM team is currently working on designing new, energy-efficient buildings known as nearly zero-emissions-buildings (NZEB) that can effectively counteract the anticipated temperature increase in the Marco de Jerez region by incorporating intelligent construction materials and innovative cooling systems. Meanwhile, Vins de Provence is proactively encouraging the development of new cellars, either underground or in hillsides, in response to the two to six degree Celsius rise in temperature expected to hit Provence by the end of the century.
By implementing new winery designs, as well as new strategies and technologies, winemakers can preserve desired temperature and humidity levels. Whether driven by stylistic preferences or by the need to adapt to climate change, indoor conditions are of fundamental importance in supporting the quality and consistency of wines throughout the maturation process, ultimately shaping their style in harmony with the winemaker’s vision and esthetic.
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Dr. Jacopo Mazzeo is a U.K.-based freelance drinks journalist, consultant, and photographer. He contributes to leading trade and consumer publications including Decanter, Wine Enthusiast, Whisky Magazine, and Good Beer Hunting. Jacopo consults on consumer trends and marketing strategies, is a former sommelier, and judges international wine, beer, and spirits competitions. Before he embraced full-time journalism, he studied musicology at the University of Bologna and took a PhD at the University of Southampton. Follow Jacopo on Instagram @jacopomazzeophoto
