Napa Wineries Face Global Warming

As revelers uncorked wine bottles to celebrate the holidays and ring in the New Year, more of them were celebrating with a glass of California-grown Pinot Noir than a decade ago. But the growing market for this complex, subtle wine could soon run up against climate conditions that make it increasingly difficult to grow top-quality wines in the state, especially ones that do best in cool climates, like Pinot Noir.

“Pinot Noir is being grown in hot areas of California where it doesn’t grow so well,” said Andrew Walker, professor of viticulture at the University of California, Davis. He examines a Listán Prieto vine on the UC Davis campus. This wine grape was brought to California by Spaniards and was the first to be planted in the state. (Photo by Joan Johnson Miller/KQED, 2007).

It just goes to show, scientists say, that which wines become popular has more to do with personal taste and marketing than with warming temperatures and water availability.

“Pinot Noir is being grown in hot areas of California where it doesn’t grow so well,” said Andrew Walker, a professor of viticulture at the University of California, Davis. “The public wants it, and so we’re making it, even if it’s not that great.”

Nearly 260,000 tons of Pinot Noir grapes were crushed in California in 2013. That’s four times the 58,000 tons crushed in 2003, according to the California Department of Food and Agriculture.

In recent years, Pinot Noir has been extensively planted in coastal Sonoma County, where the grapes produce top-quality wines. But the grape has also spread to warmer parts of California. In 2013, some 23,000 tons of Pinot Noir were crushed in the hot Central Valley, in the area between Madera and Kern counties.

Pinot Noir is a particularly finicky grape, said David Graves, the co-owner of Saintsbury Winery, in Napa Valley’s Carneros region, which produces renowned Pinot Noir wines. The marine fog that enters San Francisco Bay blankets Carneros and makes it an ideal place to grow good Pinot Noir.

David Graves, co-owner of Saintsbury Winery, in the Carneros region of the Napa Valley, an area known for the quality of its Pinot Noir wines. Graves stands next to a weather station that monitors conditions in his vineyards. (Photo by Joan Johnson Miller/KQED, 2007).

“It doesn’t flourish in a lot of climates. It’s not a very forgiving grape,” said Graves. “It tends to like cooler spots.”

Scientists at Stanford, Purdue, Utah State University and two other research institutes estimate that by 2040 global warming is likely to cut in half the area in Napa and Sonoma valleys where temperatures are suitable to grow top-quality wine grapes. To come up with their calculations, researchers estimated that global temperature would climb one degree Celsius (about two degrees Fahrenheit), which is on the lower end of global warming estimates, said Stanford’s Noah Diffenbaugh.

Temperatures above 95 degrees Fahrenheit, for long periods of time, can hurt wine quality. To produce good wines, grapes need heat, but it has to be followed by a cooling-off period. Heat produces the sugars that will become alcohol, while cooling slows this process long enough for the compounds that produce the flavors in wine to develop. Temperatures above 95 degrees, without subsequent cooling, degrade compounds called anthocyanins, which give red wines their deep color and contribute to their complex flavors.

Pinot Noir is a variety that does well in cool climates and is particularly vulnerable to warming temperatures. These vines were planted at Saintsbury Winery, in Napa Valley. (Photo by Joan Johnson Miller/KQED, 2007).

The boom in Pinot Noir is part of the consolidation of a handful of well-known, popular wines in the state – Chardonnay, Merlot, Sauvignon Blanc, Cabernet Sauvignon and Zinfandel. Scientists say that more effort should be put into testing wine varieties new to California that might do well as temperatures climb.

“In a warming climate we need more diversity,” said Walker.

One of the world’s largest wine and beer companies, Constellation Brands, is collaborating with UC Davis on research into warm-climate varieties. They’re testing grapes like Petite Sirah and Petit Verdot, which are somewhat known in California already, and some more obscure varieties like white wine grapes Fiano and Petit Manseng, said UC Davis’ Matthew Fidelibus, in charge of the trials at the university’s Kearney Agricultural Research and Extension Center, in Parlier.

But whether or not wines made from these grapes catch on depends not just on whether researchers can produce good-quality grapes and abundant yields. Marketing and economics are key, said Walker. And for now, wines like Pinot Noir, which are fetching a good price for growers and are popular at the store, reign supreme, climate predictions aside.

This video, originally posted on July 31, 2007, was updated on Jan. 6, 2015.

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