Study Finds New Grape Varieties Pay Best Under Napa’s Most Extreme Heat

Winegrape growers facing more frequent extreme heat may have several ways to protect their vineyards, but new research suggests there is no single strategy that makes the most money in every climate scenario. The study, published this year in the American Journal of Enology and Viticulture, found that the best choice depends on how far temperatures rise and how often damaging heat hits.

Researchers from Cornell University and Pennsylvania State University used cabernet sauvignon production in Napa County, California, as a case study. They compared three responses to hotter conditions: keeping cabernet sauvignon in Napa and installing shade technology, replacing cabernet with a more heat-tolerant grape variety, or moving vineyard production to a cooler region. Their conclusion was straightforward: under mild warming, keeping existing vineyards and varieties can still be the most profitable path; under more intense heat, shade can make economic sense; and under the harshest conditions modeled, changing varieties produced the strongest returns.

The work focused on a problem that has become more urgent for California vineyards. Heat above 100 degrees Fahrenheit can push grape clusters in direct sun to even higher temperatures. That can damage berries, reduce yields and alter compounds that matter for wine quality. Because vineyards are perennial crops, growers cannot respond as quickly as producers of annual crops. A decision to replant, retrofit or relocate can shape costs and revenue for decades.

Kristen Barnhisel, winemaker for J. Lohr Vineyards & Wines and president of the American Society for Enology and Viticulture, said extreme heat is no longer a rare issue for winegrape growers. The society publishes the journal that carried the study. The research did not argue that growers should immediately switch grapes or cover vineyards with shade cloth. Instead, it tried to show when the likely financial benefit of each adaptation measure may be high enough to justify the cost.

To do that, the researchers built a financial model that included vineyard establishment costs, operating expenses, grape value and heat-related effects on production. In the first strategy, growers remained in Napa with cabernet sauvignon and used shade cloth to reduce direct sun exposure and limit heat damage. Shade can protect fruit, but it requires a large upfront investment and adds ongoing costs because materials wear out and need replacement.

In the second strategy, growers changed the cultivar. The study used carignan as an example of a grape better suited to hotter conditions. That option may improve resilience and help preserve output during hotter years, but it also comes with commercial risk. A vineyard owner may receive a different price for the grapes or the finished wine, and a switch can weaken the market identity built around a well-known variety grown in a famous place.

The third strategy was migration. In the model, that meant moving production from Napa County to the cooler conditions of Lake County. The study found that this path was the least attractive economically across all of the scenarios examined. Relocation requires land acquisition, new vines, trellising, irrigation systems and other infrastructure. It also means giving up part of the value tied to an established vineyard and a premium appellation.

The results shifted as heat became more severe. When the modeled climate change was relatively modest, continuing to grow cabernet sauvignon in Napa without major changes remained the most profitable choice. That reflected the value of existing vines, established buyers and Napa’s strong reputation. As heat stress increased, shade cloth became more attractive because it allowed growers to protect fruit while keeping the same vineyard and market position. In the most severe heat scenario, however, replacing cabernet with a more heat-tolerant variety delivered the best economic return.

The study also looked at something often discussed less in climate adaptation debates: whether consumers will pay more for wines made under those strategies. The research team surveyed more than 300 U.S. wine consumers in early 2024 using hypothetical labels that explained different climate adaptation approaches. On average, consumers said they would pay about 17% more for wine if they were told shade technology had been used to protect grapes from extreme heat. Wines made from a different, more heat-tolerant variety drew an average premium of about 12%, and wines tied to a move to another region drew about 11%.

Those premiums were not treated as permanent. The researchers assumed they could fade over time as consumers become more used to adaptation measures. Even so, the findings suggest wineries may have a financial reason to explain climate-related production decisions to buyers, at least while those practices still stand out in the market.

That has broader implications for the beverage business, where investment decisions are tied not only to farming costs but also to grape supply, wine style, regional identity and long-term branding. For wineries, the research points to a three-way decision involving technology, plant material and location. Each option can affect future production and profitability in different ways, and each carries consequences for how a bottle is marketed and priced.

The study said climate adaptation in vineyards should be judged in both agronomic and economic terms. Growers already make long-term choices about irrigation, canopy management, rootstocks, varieties and sites. Rising heat adds another layer to those decisions. For some premium vineyards in relatively favorable areas, staying with the current system may still make the most financial sense for years. For others facing repeated heat events, shade may become worth the added cost. In the most extreme cases, replanting to a different grape may offer the best long-term return even if it changes the product and the market story attached to it.

Markus Keller, science editor of the journal and a viticulture professor at Washington State University, said the value of the study is that it gives growers a way to compare those options in financial terms rather than judging them only by growing conditions. For vineyard owners in California, where grape variety, place and reputation are tightly linked, that comparison may become more important as warming continues and expensive decisions have to be made before the full scale of climate change is clear.