Utah State University

July 10, 2006

"Extreme heat reduces and shifts United States premium wine production in the 21st century," by M.A. White, N.S. Diffenbaugh, G.V. Jones, J. Pal, and F. Giorgi, Article #03230, Proceedings of the National Academy of Sciences

Sour grapes: Researchers say climate warming could impact U.S. wine industry

LOGAN, Utah — 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.

In a paper published in the July 11 issue of Proceedings of the National Academy of Sciences, 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.

America's 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, say researchers who developed the model that forecasts human-driven climate changes and applied it across the nation for various winegrape-growing scenarios.

Utah State University researcher Michael White and Noah Diffenbaugh of Purdue University who, along with colleagues Gregory V. Jones of Southern Oregon University and Jeremy Pal and Filippo Giorgi of Trieste, Italy's Abdus Salam International Centre for Theoretical Physics, developed the model, which provides detailed projections based on fine-scale processes and extreme weather events.

"This is the first assessment at this detail for the full continental United States," said Diffenbaugh, assistant professor of earth and atmospheric sciences in Purdue's College of Science, who added that the comprehensive model required massive computing power.

White, assistant professor of aquatic, watershed and earth resources in USU’s College of Natural Resources, said 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 said. "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.

"When one looks at the average for the year, one does not see the dips and peaks," he said. "We know the market fluctuates, and 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," said White. "The question is will increased moisture in these areas make them unsuitable for optimal grape production?"

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

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

CONTACTS: Michael White, 435-797-3794, eve 435-760-7452, mikew@cc.usu.edu; Noah Diffenbaugh, 765-490-7288, diffenbaugh@purdue.edu; Elizabeth Gardner, 765-494-2081; ekgardner@purdue.edu; Gregory V. Jones, 541-552-6758, gjones@sou.edu; Jeremy Pal, jpal@ictp.it; Filippo Giorgi, giorgi@ictp.trieste.it