Science

Climate change is changing the chemistry of wine

Soon after a devastating glass fire broke out in California’s Napa Valley in September 2020, wine chemist Anita Oberholster’s inbox was filled with hundreds of emails from panicked vineyards. They wanted to know if they could harvest their grapes without the terrible effect on their wine: the stinky ashtray flavor known as smoke taint.

Oberholster of the University of California, Davis could only tell them “might”.

Industry labs were slammed with samples of grapes for testing, with waiting periods of up to six weeks. The growers didn’t know if it was worth harvesting their crops. Eight percent of California wine grapes were left to rot in 2020.

Winemakers are no strangers to the reversals caused by climate change. Warmer temperatures in colder regions have been a boon to some people who rejoice over riper berries—but disastrous to others. Severe heat waves, wildfires and other climate-driven disasters have ruined crops in Europe, North America, Australia and elsewhere.

And as 2020 showed, climate change can take its toll on grapes without directly destroying them. Wildfires and warmer temperatures can alter the taste of wine, the quality and much of its identity depending on the delicate chemistry of the grapes and the conditions in which they are grown. Many growers and winemakers are increasingly concerned that climate change is robbing wines of their defining flavors, even spoiling the vintage altogether.

“It’s a big concern,” says Karen McNeil, a wine expert and author who lives in Napa Valley. Wine Bible, “It’s the beat of wine—it’s attached to its place.”

McNeill says the biggest challenge that climate change brings to winemaking is the unpredictability. Growers knew which varieties to grow, how to grow them, when to harvest the berries and how to ferment them to produce a consistent, quality wine—but today, every step is up in the air. This growing recognition is driving researchers and winemakers to find ways to preserve beloved grape varieties and their unique qualities in the changing and appealing conditions of today’s warming world.

To learn about the dangers of our favorite drinks, we spoke with wine experts from two well-known wine regions—Bordeaux in France and California—to understand how climate change is uprooting their traditional vines and wines, and Visited the University of California, Davis. and in nearby Napa Valley to speak with scientists, growers and winemakers in late 2021.

We got an inside look at how each stage of winemaking was changing to preserve the desired flavor and aroma – and yes, there are plenty of wines to taste, from the finest Cabernet Sauvignons to specimens spoiled by smoke and scorching heat. Got for

taste of climate change

Extreme weather can kill even the hardiest vines, but most of the climate threat is an invisible one: chemical changes in the berries.

That’s because wine quality, at its most granular level, boils down to achieving a balance between three broad aspects of berries: sugar, acids, and secondary compounds. Sugar is made in the form of photosynthesis in the vines, and the acid is broken down as the grapes ripen. Secondary compounds—basically, chemicals beyond those necessary for a plant’s basic metabolism—accumulate over the course of the season. Grapes called anthocyanins give red grapes their color and protect the plant from UV rays. Others called tannins give wine bitterness and an astringent, drying mouthfeel; They protect the vines from grazing animals and other insects.

These three components, and therefore the taste of the wine, are influenced by a number of environmental factors, including soil type, precipitation levels, and fog, all of which are included in the French word “terroir”. Climate—the long-term pattern of temperature and precipitation—makes up the biggest part of terroir, says Oberholster.

When an area’s climate changes, that can disrupt the balance of sugars, acids and secondary compounds on which they develop during the growing season, says Megan Bartlett, a plant biologist who studies viticulture at UC Davis. There are. Grapes, like most fruits, break down acids and store sugar as they ripen. At warmer temperatures, ripening is supercharged, giving grapes a sweet, raisin-like flavor.

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