It was Labor Day 2017, and the remote thermometer at McIntyre Estate Vineyard in Monterey County’s Santa Lucia Highlands was registering a noontime temperature Steve McIntyre couldn’t quite believe: 104 degrees.
McIntyre jumped in his car, hoping the sensor was broken. Twenty miles later he stepped out into the searing air at his vineyard and knew there was no mistake. It would hit 116 before the day was over, the hottest since he first planted the site in 1973.
“It felt like a gut punch,” he said.
The U.S. is the largest wine-producing country outside Europe, and 80% of that output comes from California. For an industry in which even subtle shifts in temperature or humidity can transform a harvest’s value, increasing extremes and unpredictability pose an existential threat.
Grape leaves change colors with the season at a vineyard in the Santa Cruz Mountains in November 2024.
(Tomas Ovalle / For The Times)
Extreme heat can kill a vine just as it can a human. As temperatures rise, so does the speed at which vines pull water from the soil. Once a plant starts losing water faster than it can rehydrate, it mounts a perilous last-ditch effort to save itself.
The stomates — the parts of the leaf that control gas and water exchange — close up in an attempt to reduce water loss. Photosynthesis slows to a crawl. That can kick off further complications that, without emergency intervention, can be fatal.
“It’s just like a cascade of things that start happening,” said McIntyre, who also runs the vineyard management company Monterey Pacific. “I really do compare it to a human with heat stroke.”
This month, researchers from Japan’s Tohoku University published a granular investigation of California viticulture in a changing climate. After mapping a roughly 16-square-kilometer grid of the state, the team ran each cell through multiple climate models to generate data on current and future weather conditions. They then fed that information into an algorithm to analyze wine cultivation suitability over time.
What they found was a redrawn map of California’s prime wine regions.
The team based its definition of suitability primarily on total annual precipitation, cumulative temperature across the growing season, minimum temperature of the coldest month and vapor pressure deficit, meaning the difference between the amount of moisture in the air at a given point and the amount it could hold when saturated.
For decades, viticulturists and researchers have sounded the alarm how climate change could upend a signature industry in California. Above, vineyards dot the hillsides in Watsonville.
(Tomas Ovalle / For The Times)
Under their model, suitability for grape cultivation may decline over the next 70 years in Napa and Sonoma counties, which currently dominate the state’s premium wine market. Expected climate changes like increased precipitation, lower relative temperature increases and a decrease in extreme fire-weather days in Monterey and Mendocino counties, in contrast, would significantly increase the area’s suitability for wine production.
Viticulturists and researchers have been sounding the alarm about a changing climate’s potential to upend this signature state industry for decades. In 2011, a Stanford University study projected that land suitable for cultivating premium wine grapes in California’s North Coast region, which includes Napa and Sonoma, could halve by 2040. Winegrape-bearing acreage in California has shrunk steadily since 2013.
Yet these outcomes aren’t inscribed in stone. The model didn’t account for climate adaptations, which virtually all of California’s winemakers are already implementing.
McIntyre’s Chardonnay and Pinot Noir vines survived the 2017 heat wave, in part because the vineyard was already experimenting with shade canopies and could roll them out across the site quickly.
Elsewhere, winemakers are adopting misters and low-water irrigation systems, replanting their rows in directions that avoid the peak of the afternoon sun and even experimenting with heat-tolerant grape varietals.
“By changing when the grapes are picked or how they are managed in the field, growers can adapt to global warming without completely replacing their crops,” said Yusuke Hiraga, an assistant professor of engineering at Tohoku University and the lead author of the study. “These flexible management techniques are expected to be highly useful in protecting wine quality.”
More climate news
The Times’ water reporter Ian James has the alarming news that Lake Mead and Lake Powell, the nation’s two largest reservoirs, have fallen to their lowest combined levels on record.
Lake Mead, the country’s largest reservoir, is 27% full. Lake Powell, the second-largest, is at just 23% of capacity and is just 33 feet away from no longer being able to generate hydroelectric power.
For the 35 million people and 5 million acres of farmland that depend on the Colorado River for water, this is a big deal.
“It’s a hell of a milestone,” said Jack Schmidt, director of Utah State University’s Center for Colorado River Studies. “If you need any more evidence that we have a five-alarm fire, here it is.”
On Tuesday, the U.S. Department of the Interior Secretary Doug Burgum met with governors of the seven states that rely on the Colorado River for water, including California. The agency will release a plan to deal with water shortages next week, Burgum said afterward.
Most of California’s water allotment goes to agriculture, and many growers are already preparing for a drier future. My colleague Blanca Begert recently traveled to California’s Central Valley, where some farmers are leasing their acres to solar companies.
California is legally mandated to reach 100% clean electricity by 2045, an effort that will require an additional 10 gigawatts of clean energy a year and between 0.5 and 1.3 million acres of in-state solar development, Blanca and Ian reported. According to the Public Policy Institute of California, solar on retired farmland in the Central Valley could contribute up to 30 gigawatts of solar capacity.
Switching from crops to solar isn’t like experimenting with a new grape varietal. It’s a total shift of a farm or region’s identity, and the story notes that some of the largest arrays are planned for places that have historically been strongly anti-solar.
“Growers are feeling pinched,” Caitlin Peterson, associate director of the PPIC Water Policy Center, told them. “Solar is one of the potential options for folks that are having to take land out of production that has the potential to be fairly lucrative.”
One more thing
As Sunday’s World Cup final between Argentina and Spain approached, a perfect storm of heat, humidity and smoke from Canada’s wildfires appeared poised to overshadow the game in East Rutherford, N.J. FIFA officials discussed an emergency change of venue.
The day before the final, thunderstorms blew away the worst of the smoke. Spain claimed victory in temperatures in the low 80s, with relatively low humidity.
But nearly 20% of this year’s World Cup matches took place in heat and humidity conditions that the players’ union has deemed hazardous, an analysis by the Guardian found.
The morning after the U.S. loss to Belgium in the World Cup’s Round of 16, I spoke to Dr. Bert Mandelbaum, chief medical officer for U.S. men’s soccer and vice chair of Cedars-Sinai Medical Center’s orthopedic surgery department.
He pointed out that virtually every aspect of the game degrades in the heat. Performance, recovery ability and decision-making erode. Artificial turf becomes intolerably hot, and the soil in natural grass can harden until it’s like playing on concrete. Air molecules inside the ball expand, making it a harder and faster object whose trajectory is harder to predict.
Even though the new mandatory hydration breaks got a lot of fans hot under the collar, they’re a necessary part of player safety, Mandelbaum said.
“Difficult weather environments bring on dehydration and can create severe exhaustion, heat exhaustion, and those [conditions] have tremendous and dire consequences,” Mandelbaum said.
