Climate change could reduce wine production in iconic California wine regions including Napa and Sonoma, while counties like Mendocino and Monterey could become more suitable for vineyards by the end of the century, researchers warn.
(CN) – Napa and Sonoma counties have defined American wine since the 19th century, but the delicate environment that helped create those world-famous regions could be under threat.
According to researchers in a study published on Tuesday in Frontiers in Climate, the impacts of climate change could reduce the suitability of grape growing and winemaking in California’s historic wine country this century and redraw the wine map of the Golden State.
Although researchers found that California’s most famous wine regions may struggle to maintain wine production, parts of Northern California and coastal California, particularly Mendocino and Monterey counties, could become new wine powerhouses.
“Our findings indicate that the outlook for Mendocino and Monterey is uniquely promising because of a dual trend,” study co-author. Yusuke Hiraga of Tohoku University in Sendai, Japan, said in a statement. “They are predicted to experience increased climatic suitability for summer cultivation and a decrease in extreme fire weather days. This combination makes these areas stand out as relatively favorable expansion zones, distinct from many other regions with either increasing suitability along with increasing fire weather or decreasing suitability.”
In the study, Hiraga and other researchers modeled California’s current and future climate suitability for growing grapes at nearly 400 sites in the state, mostly on the North Coast and Central Coast.
They found that suitability for growing grapes in the state’s historic wine-growing regions, such as Napa, Sonoma, San Luis Obispo and Santa Barbara, is likely to decline under severe climate change conditions in a worst-case scenario.
They say winemakers and grape growers will have to rethink how they grow vineyards as the climate changes.
“On the ground, as a viticulturist, it’s important to consider climate change adaptation strategies sooner rather than later,” Hiraga said in an email interview.
“Switching to a different variety is one of the most effective adaptation strategies as the impacts of climate change on different varieties are completely different from each other. Another possible adaptation strategy is shifting the harvest time. This should be effective in adapting to climate change without drastic changes in varieties or anything else,” he said. “Even in relatively hot regions like Temecula, those adaptation strategies are still expected to be beneficial.”
The suitability of wine production, the researchers found, depended mostly on annual rainfall, temperatures during the growing season, temperatures during the coldest month and vapor pressure deficit – a measure of how much moisture the air can absorb before it becomes saturated.
To conduct the study, the authors plotted projections from global climate change models with a 4-kilometer-by-4-kilometer grid across the United States based on two alternative carbon emission scenarios. The first scenario assumes that climate change mitigation policies are implemented gradually, while the second is a worst-case scenario.
The researchers modeled three periods for both scenarios: 1976-2005, the baseline; 2040-2069, mid-century; and 2070-2099, the end of the century. The suitability of each grid square for grape cultivation was predicted using a machine learning algorithm.
The researchers found that conditions were better in scenarios with lower greenhouse gas emissions, suggesting that higher emissions could reduce wine quality by the end of the century. But it’s not all bad news for California oenophiles.
“Sonoma Chardonnay showed potential to be of better quality in the changing climate in the future,” Hiraga said.
The researchers also modeled the changing weather conditions associated with fire hazard and the expected severity according to each grid square.
While the number of days with extreme fire conditions increased in large parts of the state, particularly in northern and high-elevation regions, these days also decreased in large parts of Mendocino and Monterey counties, the researchers found.
“While our study highlights long-term changes in climate and fire weather suitability through the end of the century, it does not attempt to predict a specific timeline for when developing areas will surpass currently established regions in summer growth potential,” Hiraga said in the statement. “Such accurate forecasting is complex, as the future of viticulture is shaped not only by climate change and fire weather, but also by a variety of anthropogenic factors.”
The researchers used an algorithm trained on wine ratings from professional tasters published between 1996 and 2023 in Wine Spectator magazine to predict future wine quality by year.
California is responsible for about 80% of total wine production in the United States and is the fourth largest producer of wine in the world. according to the Summer Institute. The United States is only behind Spain, France and Italy in wine production.
In a similar study published in 2025, Hiraga and his team found a similar pattern for Japan’s wine map, with current wine regions such as the Kofu Basin, roughly two hours west of Tokyo, likely to decline, while northern prefectures may begin to become more hospitable to viticulture.
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