Global Warming May Sour Wine Sales

July 10, 2006 — -- Extreme weather events triggered by global warming threaten to eliminate more than 80 percent of the best U.S. wine-producing regions by the end of this century, according to a new study published today.

The report's conclusions -- which appear online in the Proceedings of the National Academy of Sciences -- could have multibillion-dollar implications for the U.S. wine industry.

"Where things are headed now, we're likely to see some very dramatic changes in sectors that are not only economically important, but culturally and aesthetically very valuable," said Noah Diffenbaugh, a co-author of the study and atmospheric scientist at Purdue University.

Wine sales in the United States -- including imports -- total an estimated $26 billion a year, according to the Wine Institute, a California wine industry group.

California sales are $16.5 billion a year, and the United States is the world's fourth-largest grape producer.

In the last 50 years, the study says, average temperatures have warmed by about 1.6 degrees Fahrenheit in the main wine-producing regions of California, Oregon and Washington.

Virtually all climate scientists blame the rise on human-caused greenhouse gases -- like carbon dioxide -- released into the atmosphere from the burning of fossil fuels.

Looking at the average temperature increase doesn't tell the whole story, researchers say.

"What really hits the winegrape plants hard is the frequency of extremely hot days," Diffenbaugh said.

Using high resolution computer models and historical observations, the team has for the first time attempted to predict how well grape plants will be able to tolerate "extreme temperature days" that reach at least 95 degrees Fahrenheit. The conclusions predict the outlook isn't good.

The most tolerant winegrape plants are able to handle 14 days of 95 degree-plus weather in a season before they were ruined by the heat.

The models predicted that the number of those hot days would increase to anywhere from 30 per to 60 per season.

"Our minimum increase is more than double the maximum tolerance," Diffenbaugh said. "It's just too hot for the wine grapes too many days of the year."

The study's results show that areas "marginally suitable" for producing wine in today's climate would be nearly eliminated, and that the areas currently producing the most expensive, highest-quality wine would decline by more than half.