FARMERS MAY GENERALLY SKEW to the right politically, but few California grape growers champion a favorite conservative talking point: climate change is overblown. The shifting climate is a deep concern in Wine Country, and climbing temperatures are affecting how and where grapes are grown — most particularly in the Carneros Region, a coastal portion of Napa County long celebrated for its pinot noir wines.
Pinot noir is the constituent grape of France’s hallowed red Burgundy, and it has produced wines of comparable quality in some portions of California. Even more than other esteemed varieties such as cabernet sauvignon, pinot noir is challenging to cultivate. It is thin-skinned and delicate, requiring moderately warm days and cool nights to enhance the characteristics that ultimately result in complex, well-balanced and delicious wines.
The Russian River Valley in Sonoma County and the Anderson Valley in Mendocino County are celebrated for their pinot noirs, but Carneros is the historic cynosure for the grape. Long, balmy days under the Napa Valley sun combined with cool nights created by nearby San Pablo Bay have reliably yielded pinot noirs that rate with the world’s best.
But things are changing, and fast. A study by San Diego Scripps Institution of Oceanography researcher Daniel Cayan found that steadily climbing temperatures have advanced Napa’s grape-growing season by almost a month compared to the 1950s. That’s bad news for the region’s pinot noir, which must preserve a relative high ratio of acids in the fruit to produce optimal wines; high temperatures reduce acids and increase sugar content dramatically, resulting in heavy, high alcohol “hot” wines that maintain few of the spicy, complicated aromas and flavors traditionally associated with the grape.
As a result, growers are considering options beyond Carneros for the pinot noirs of the future: cooler zones such as the Sonoma Coast, the Anderson Valley and most notably the Petaluma Gap — a broad swale straddling northern Marin and southern Sonoma Counties that loosely connects San Pablo and Bodega Bays, allowing the constant passage of cooling marine fog and wind.
“Carneros was known as the prime cool weather region for pinot noir, but things are heating up there,” said Evan Pontoriero, the owner of Fogline Vineyards. Pontoriero specializes in small lots of pinot noir, zinfandel, syrah and chardonnay, with much of his fruit originating from the Petaluma Gap and adjacent Sonoma Mountain.
“We dependably get that 5 p.m. fog during the growing season, which cools things down dramatically and is ideal for the long, slow growing season you need for pinot noir,” Pontoriero said. “It’s so reliable that you don’t really plan on barbecuing after 5. It can get chilly.”
Pinot noir, said Pontoriero, “has always been about location, location, location, and for a long time that was Carneros. Some of the vineyards there — such as Winery Lake Vineyards — had global renown. But climate change has thrown everything into confusion. It’s still about location more than ever, but those locations are more limited in scope and certainty. You don’t hear Winery Lake cited much these days. And places like Sonoma Mountain, the Petaluma Gap and Sonoma Coast are generating more interest.”
Filling the production Gap
Ron Runnebaum, an associate professor of enology and viticulture at the University of California, Davis, said the Petaluma Gap’s emergence as a prime pinot noir area is relatively new.
“Historically, it seemed like there were significant challenges in getting fruit ripe in the Petaluma Gap,” Runnebaum said. “Getting the sugars, the titratable acidity and other ripeness qualities in balance were difficult. But we [Runnebaum and students working in his lab] researched five pinot noir vintages between 2015 and 2019 from both the Petaluma Gap and Carneros, and both were consistent for high quality.”
Runnebaum also observed that some Carneros growers have begun planting varieties more suited for warmer climates, such as merlot.
“It’s a reasonable assumption that they’re anticipating a warmer climate in Carneros, and they’re investigating other varieties that will still produce the high-quality fruit that wineries want to buy,” Runnebaum said. “Also, if they have (a mix) of varieties that ripen at different times they might be able to mitigate extreme weather events like heat waves, which can cause all the fruit to ripen at the same time and cause bottlenecks at the wineries.”
While concern over climate change is accelerating in Wine Country, growers have been aware of the potential impacts for some time said Kaan Kurtural, a Napa Valley grape grower and former viticultural professor with UC Davis.
“It was clear long ago that things were changing, with a particularly dramatic shift coming in the 1980s,” said Kurtural, “and Carneros isn’t alone in experiencing impacts. Actually, Carneros isn’t as affected as other portions of the Napa Valley due to the persistent influence of San Pablo Bay.”
In the mid-to-upper regions of the valley floor — better known for claret varieties such as cabernet sauvignon, cabernet franc and merlot than pinot noir — temperatures have risen significantly, said Kurtural. Growing grapes today in the upper valley, he said, is sometimes like growing grapes decades ago in Lodi — a viticultural region known for sweltering temperatures that are only slightly moderated by the Sacramento-San Joaquin Delta.
Kurtural said Carneros growers may ultimately have to transition away from pinot noir, but they could have a 15- to 20-year grace period.
“The good news is that they have lots of tools at their disposal to counter higher temperatures,” he said. “They can forgo certain traditional practices, such as removing leaves to allow more sun on the fruit to ensure ripening. They can spray shellac on the grapes or irrigate more aggressively to lower temperatures in the vineyards, and they can incorporate different trellis designs that provide more shade on the fruit.”
‘There’s a lot to juggle’
Benjamin Leachman, the director of viticulture at Walsh Vineyards Management in the Napa Valley, said climate change is enforcing new practices throughout Wine Country, with particular emphasis on alternative winegrape cultivars and new trellis designs.
“Everyone is trying to make decisions now that will take them through the next 30 years,” said Leachman. “There’s a lot to juggle. With most cultivars you want to have a long growing season and pick when it’s cooler, but now we often see late season wildfires [also driven by climate change] that can taint the fruit. So you have to take all those factors into consideration.”
Leachman cautioned that conventional wisdom on climate change impacts may not always be accurate. He cited Carneros as an example, noting the region isn’t necessarily warming uniformly.
“In the North Bay, we’ve just had the coolest summer since 1991,” he said. “Is it because the bayshore gets cooler as hot air in the interior valleys rises? In 2023, we were worried that temperatures were too cold during the growing season, not too hot. Some vineyards along the coast didn’t get picked because it was too cold, and we have similar concerns this year.”
Further, said Leachman, while the Carneros pinot noirs of tomorrow may differ from those of earlier decades, they won’t necessarily be inferior wines.
“Some people like acidic, austere pinot noirs,” Leachman said, “with Oregon pinots being a good example. But I’m a California boy, and I prefer rounder, lusher pinot noirs, and that may be what we’ll increasingly see in the Carneros in coming years. Pinot noir is a versatile grape. It’s been around for 2,000 years, and it has more mutations than any other (popular varietal). We deal with 54 different clones of pinot noir at Walsh Vineyards, each with its own characteristics. It’s really important to identify the best clone and rootstock for each vineyard site.”
While climate change may well dictate shifts in pinot noir vineyard planning, the fate of the varietal rests more with market dynamics than warming temperatures, said Pontoriero — at least for the foreseeable future.
“The demand for high-end pinot noir remains strong, and there will always be buyers who want that limited supply,” said Pontoriero. “We identified the Petaluma Gap early on as a prime area for pinot noir. It’s lived up to that promise, and we’re pretty optimistic going forward.”
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