Monday, April 15, 2013

Napa Valley Vintners contest global warming data

Wine drinkers will be happy to know that Napa Valley is taking global warming seriously, according to Napa Valley Vintners spokesman Rex Stults. Plus, they don't believe that current studies are accurate -- and say they have photographs to prove it.

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.

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winterspeak said...


Interesting story. I've seen other pictures of data collection points showing them next to heat exhausts and blacktop, so I don't think Napa is unique in this regard. Data collection is hard, and a remote weather station in a field can become surrounded by parking lot. This probably impacts it's reading.

John M. Kelly said...

Blake I've stayed out of this mostly. But Saturday Rob McMillan posted an excellent piece on his blog ( where he points out something in the PNAS report that seems to have been overlooked by both professional and amateur journalists in their hyperbolic rush to trumpet that the world as we know it is ending.

The report suggest that there will be little change in the coastal appellations.

So - probably - fine wines will continue to be fine. Inland appellations are likely to be impacted by changing weather patterns that result in less water for irrigation long before things heat up. Given the agricultural diversity of the Central Valley that will likely result in some very difficult water wars.

Unknown said...

We are a Montana based company and we have seen data that suggests there will be no more snow skiing in the Rockies by 2050. What a tragedy it would be to lose Napa Wines and skiing....

W. Blake Gray said...

John: I hope I haven't suggested otherwise. You can see from the nifty color-coded map I posted Thursday that the coasts should be fine.

Napa is an interesting topic because the wines are so iconic and there's so much money at stake.

But the real issue is the San Joaquin Valley, where about half of all the wine currently sold in the US comes from.

For this post, I just had to give NVV its say. Could have asked them to do it in comments on Thursday's post, but it seemed to warrant a new post.

John Taylor said...

Hey Blake, First off I want to thank you for keeping a light shining on this subject. It's incredibly important in the Napa microcosm and the world macro as well.

So let's just assume for a moment that the data specific to Napa Valley is faulty, yet we know that global warming in general is a scientific fact. It would seem to me that the obvious next step would be to have the NVV in conjunction with winery and vineyard owners do their own study using data collection devices placed in areas appropriate for agricultural study. The data could then be analyzed by experts who've done research specifically for global warming effects on farmland.

We can argue this specific study until we're all out of a job and drinking wine from Newfoundland, or we can come together to find a real solution. I choose the latter.


For 30 years we have grown Cabernet, Franc, Merlot, Malbec and Pte Verdot on our 45 acre property on the southern flanks of Mt. Veeder, overlooking Northern Carneros. The BIG difference here has been in rainfall - when and how much. We are consistently seeing less rainfall in the middle of winter, and heavier storms at the beginning and end of the season. This is a clear pattern in our part of Napa. As for temps, speaking generally, if anything, winters are getting colder/drier and summers getting foggier - but with the the middle of the day summer heat being hot as ever.

I think it's fair to say that climate change doesn't automatically mean hotter / drier everywhere necessarily. It may mean increasingly powerful weather events and greater activity in the atmosphere generally.

All those who are worried about dried out wine regions and desiccated ski resorts may want to rethink their assumptions. Certainly global warming is real. Yet, tHe net effect of all this heat may well mean MORE precipitation in mountain areas - with perhaps a shorter ski season. For wine regions it will most likely force all of us in California viticulture to adjust and tweak and evolve along with the weather.