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Subject: Climate model uncorks concerns for U.S. wine industry

The most detailed climate model to date projects U.S. wine production could decline by 81 percent by the end of this century due to human-driven climate warming.

A research team used a high-resolution climate model, requiring five months of computation time, to project daily temperatures for specific regions of the United States and determine the effects on premium wine production.

"This is another piece of evidence that climate change is likely to affect our daily lives," said co-author Noah Diffenbaugh, an assistant professor of earth and atmospheric sciences and member of the Purdue Climate Change Research Center. "It goes well beyond the global mean temperature.

"Premium wine has economic and aesthetic value in the U.S. and globally. It is an important part of our culture and is very vulnerable to changes in temperature. The impact of the projected climate change is potentially dramatic."

The United States is the fourth largest grape producer in the world, and its wine production has an economic value of $2.9 billion annually, according to the U.S. Department of Agriculture.

Premium wine grapes require a well-balanced climate that gets neither too hot nor too cold. There must be a low risk of frost and an absence of extreme heat.

The model projects that the frequency of extremely hot days, days 95 F or higher, could increase during the growing season anywhere from 30-50 days in what are currently the most highly productive regions. Winegrape plants would be unable to tolerate this, and production would be eliminated in many areas. Grape and wine production would be shifted to much smaller regions in the Northeast and Northwest, and premium wine production would be reduced by half while total wine production would be reduced by 81 percent, Diffenbaugh said.

The results of the research will be published in the July 10 issue of the Proceedings of the National Academy of Sciences.

The team, led by Michael White, of Utah State University, highlighted the importance of incorporating fine-scale processes in climate change impact studies.

Earlier climate models using average monthly temperatures and focusing on much broader areas would have been unable to see these affects. Changes in the average temperature due to climate warming would only be enough to cause minor reductions in the total area available for winegrape production, Diffenbaugh said.

"Had we continued to look only at mean, or average, temperature, we would have underestimated the impact on wine production. It doesn't show the extremes, which are what had the greatest impact in this study," he said.

Diffenbaugh explained the significance of looking at a smaller time scale.

"It is similar to the stock market," he said. "When one looks at the average for the year, it could show that stocks are down 7 percent. That alone won't cause anyone to lose his or her shirt. But we know that the stock market dips and peaks during the year; it fluctuates. On a given day, stocks could have gone down in value by much more, and certain stocks and investors could have lost everything. The outcome for those investors is far worse than the yearly average would suggest."

The climate model relied on the powerful computer system at Purdue's Rosen Center for Advanced Computing to perform the five months of computation required for such high resolution.

"When we run a climate model experiment such as this, we do our best to include all the details and factors that affect our environment and the climate, including changes in greenhouse gases over time," Diffenbaugh said. "It is a very complicated system. Sophisticated climate models include hundreds of thousands, even millions, of line of computer code and require massive computing power to run detailed experiments such as this."

This research is applicable to other crops and even human health.

"Investigations into the potential effects on soybean production, corn pests, timber production and infectious diseases and heat-related illness are already under way," he said.

Diffenbaugh said the future is not set and many factors will influence the real outcome.

"Our research is a detailed projection of where we might be headed over the next century. How things turn out will be a function of a lot of choices made over the coming decades. As people respond, the trajectory changes. This is a snapshot of where things are headed now, but decisions we make as a group and as individuals can alter the course. By pushing the envelope scientifically, we have much more information available to us; what is done with that information is what will determine the outcome."

The Rosen Center for Advanced Computing is a research computing center named in memory of Saul Rosen, who served as director of Purdue's Computing Center from 1968-87 and who helped to establish Purdue as a pioneering academic institution in high-performance computing. The Rosen Center is a part of Information Technology at Purdue, which is responsible for planning and coordinating the central computing and telecommunications systems on the West Lafayette campus. The Rosen Center provides advanced computing resources and services to support the computationally intensive research of Purdue faculty and staff. It also conducts its own research and development to enhance the capabilities of these resources.

The Purdue Climate Change Research Center promotes and organizes research and education on global climate change and studies its impact on agriculture, natural ecosystems and society. It was established in 2004 to support Purdue in research and education on regional scale climate change, its impacts and mitigation and adaptation strategies. The center serves as a hub for a range of activities beyond scientific research, including teaching, public education and the development of public-policy recommendations.

CONTACT: Michael White, mikew@cc.usu.edu; Noah Diffenbaugh, (765) 490-7288, diffenbaugh@purdue.edu; Mary-Ann Muffoletto, (435) 797-1429, maryann.muffoletto@usu.edu; Elizabeth Gardner, (755) 494-2081, ekgardner@purdue.edu

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