E&E News – “Climate change may endanger Napa Valley's posh wine industry"

Jul 1, 2011
In The News

Washington, D.C., Jul 1, 2011 -

Northern California's status as the country's cultural and economic center of high-value wines is likely in jeopardy by mid-century as global warming cuts into the amount of land suitable for growing premium grapes, a study has found.

A research team led by Stanford University found that top-notch grapes in California's Napa Valley could be cut in half by 2040 if temperatures rise 1 degree Celsius over the next 30 years.

The study, published yesterday in the journal Environmental Research Letters, found that vines associated with premium grapes prized in Napa especially -- where Pinot noir and Cabernet Sauvignon are king -- would have trouble coping with the temperature shift.

The same research team penned a study in 2006 that projected as much as 81 percent of premium wine grape acreage in the United States could become unsuitable for some varietals by the end of the century. Their latest work attempts to build upon those findings with a shorter time horizon, in an attempt to inform a California industry said to be valued at just under $20 billion annually.

The scientists involved expected dire predictions for Napa but were caught off guard by the results, a co-author said.

"I was surprised that local temperature changes could have such a big impact on an important industry with only 1 degree Celsius of global warming," said Noah Diffenbaugh, a fellow at the Woods Institute for the Environment at Stanford.

Diffenbaugh added that the latest study might be viewed as more relevant than the 2006 version because three decades is a time frame "over which people are actually considering the costs and benefits of making decisions on the ground."

"One of our motivations for the study was to identify the potential impact of those changes," he said, "and also to identify the opportunities for growers to take action and adapt."

An industry moving north?

The study narrowly looked at four counties in California, Oregon and Washington responsible for the 25 most expensive wines on the market.

Three of the counties -- Napa and Santa Barbara in California and Walla Walla County in Washington's Columbia Valley -- would likely see their high-quality grape crops drop, while a fourth, Yamhill County in Oregon's Willamette Valley, could effectively become the new Napa.

If temperatures rise as by 1 degree Celsius, which researchers called a conservative estimate, then all four regions studied are likely to see higher average temperatures during growing seasons and a substantial increase in "very hot days" in the summer months.

For Napa, that scenario spells trouble, while the Willamette Valley would see an increase in high-value acreage as warm weather inches north. Growers could simply switch to more resilient vines that can withstand up to 45 very hot days above 95 degrees Fahrenheit, but those varieties tend to produce lower wine value, the study said.

So what should growers do about it? Diffenbaugh admitted the research presents difficult problems.

"It's risky for a grower to make decisions that consider climate change, because those decisions could be expensive and the climate may not change exactly as we expect," he said. "But there's also risk in decisions that ignore global warming, because we're finding that there are likely to be significant localized changes in the near term."

The study was based on the assumption that there will be a 23 percent increase in atmospheric greenhouse gases by 2040, which could raise the average global temperature by about 1.8 degrees Fahrenheit, or 1 degree Celsius.

Other co-authors were Michael White of Utah State University, Gregory Jones of Southern Oregon University and Moetasim Ashfaq of Oak Ridge National Laboratory, a former postdoctoral researcher at Stanford. The study was funded in part by a National Science Foundation grant.