Monday, April 15, 2013
Napa Valley Vintners contest global warming data
Last week I wrote that I was surprised by the blasé reaction of the California wine industry to a National Academy of Sciences report that predicts doom for most wine here by 2050.
"The Napa Valley has been paying attention to this in great detail since 2006," Stults says. "I haven't heard anything about that from other regions, or the state as a whole looking at this."
Napa Valley Vintners hired the Scripps Institution of Oceanography in San Diego to run a project examining warming in the valley. They used 12,000 data collection points from all over Napa Valley. Some were individual temperature records kept by farmers for decades. Andy Beckstoffer, a major vineyard owner, had detailed information, as did Stony Hill owner Peter McCrea.
The study showed that over the last 50 years, "Napa Valley had experienced minor warming, 1 to 2 F, over nights, from January to August. There was no significant warming for daytime high."
Napa Valley has two sources of cool air: the San Francisco Bay to the south, and the Chalk Hill gap in Mayacamas. Stults argues that studies of global warming unfairly divide California essentially into two areas -- hot interior and cool coast -- while Napa Valley is uniquely between the two.
There seems to be some resentment in Napa Valley about the way temperature data has been officially collected. Stults says data used by Oregon climate specialist Greg Jones, which finds its way into most major studies, uses just two data collection points: one at Napa State Hospital, and the other on the roof of the Napa Valley Fire Station.
"We have photographs in the report of where (the Napa State Hospital thermometer) actually is," Stults says. "Right next to blacktop, and an air-conditioning unit. It's probably not synonymous with a vineyard in the valley or up on Howell Mountain."
I'm sure that's true; Howell Mountain is its own ecosystem. Also, it's worth noting that even if some valleys -- just speaking generically -- were to become too hot for viticulture, the mountains around them might not be. This is already the case in some hot parts of the Mediterranean.
That said, I wonder if this is the way temperature data is collected everywhere in the US, or indeed the world: from two points close to sea level per 1000 square miles. Maybe our grandchildren will all live in the mountains (cue bluegrass soundtrack).
I also wonder if every county where temperature data is collected feels the need to take pictures of the data collection point as evidence of its unworthiness. To be fair, not many counties have as much money riding on a couple degrees of temperature change as Napa.
Two things about that temperature change. First, while farmers most worry about daytime overheating, which can make some grapes unfit for table wines, nighttime temperature rise is also significant. Grapes can lose acidity more rapidly without nighttime cooling. Fortunately for Napa grapegrowers, Robert Parker is reviewing California wines again, so that's not a problem at the moment.
Second, past performance is no guarantee of future results. Scripps has done a lot of work documenting what has changed in Napa, but so far none in predicting what changes might be coming.
But, "We're paying attention to this, always," Stults says. "This (National Academy of Sciences report) came out just before a NVV board meeting. The board members saw this, and they're talking about it."
"There are steps people can take," Stults says. "Aspects, the way you plant your vines as it relates to the sun. Trellising. Irrigation. There are a lot of tools useful to these guys."
Some of these are short-term -- irrigation -- but planting aspects is a very longterm solution. I'd be interested to know what kind of future temperatures people planting now are planning for.
Posted by W. Blake Gray at 4:08 AM