Could Climate Warming Sour Grapes?

Growing winegrapes is a game of chance. A good vintage is determined while the fruit is still on the vine. Timing, moisture and temperature produce just the right balance of sugar and acid for a full-bodied Cabernet Sauvignon or a softly fruity Chardonnay.

The United States’ hard-won respectability as a premium wine producer attests to the climatic suitability of the country’s venerated winegrape-growing regions, but could increasing numbers of hot days upset the grape cart? Yes, says USU researcher Michael White who, along with colleagues, developed a comprehensive model that forecasts human-driven climate changes and applied it across the nation for various winegrape-growing scenarios.

 

In a paper published in the July 11 issue of Proceedings of the National Academy of Sciences, White and fellow researchers predict that nearly 81 percent of U.S. winegrape-growing regions could be lost to climate warming by the close of the century, including about half of the areas producing high quality wines.

 

The model, which provides detailed projections based on fine-scale processes and extreme weather events, involved five months of supercomputer calculations. “This is the first assessment at this detail for the full continental United States,” says Noah Diffenbaugh of Purdue University, who worked with White on the study.

 

White, associate professor in the USU College of Natural Resources’ Watershed Sciences Department, says the model captures critical details overlooked by conventional climate models.

 

“If you just look at average monthly temperatures in large areas, you completely miss the point about the way the climate is changing,” he says. “This model allows us to look at smaller regions and observe daily time scales.”

 

Diffenbaugh likens the impact of climate change to the stock market. Looking at averages, he says, extreme market dips and peaks are hardly noticeable. “(But) on a given day stocks could have gone down in value dramatically, and certain stocks and investors could have lost everything. The outcome for those investors is far worse than the yearly average would suggest.”

 

Like the unfortunate investors, winegrowers in areas that experience increasing numbers of extremely hot days could see their livelihoods die on the vine.

 

“We anticipate that premium winegrape production will shift to higher elevations,” says White. “The question is – will increased moisture in these areas make them unsuitable for optimal grape production?”

 

Diffenbaugh says the team’s research is applicable to other crops and even human health.

 

“This is a snapshot of where things are headed for now, but decisions we make as a group and as individuals can alter the course,” he says.

 

The study, which was funded by the National Science Foundation, NASA and Purdue University, included researchers from Southern Oregon University and Trieste, Italy’s Abdus Salam International Centre for Theoretical Physics. 

 

Contact: Michael White, 435-797-3794, mikew@cc.usu.edu