“But can I train them [the US consumer] to drink wines with lower alcohol..."

Winemakers to blame for rising alcohols in California

Different viticulture techniques and later picking times – rather than climate change – have caused alcohol levels in Californian wines to rise, according to Christopher Howell, winemaker and general manager at Cain vineyard and winery.

Speaking at the Napa Valley Climate Seminar at Vinexpo in Bordeaux yesterday and referring to data collected since 1991 in Napa and Sonoma, Howell (left) said: “Temperatures have changed but nothing like as dramatically as the [grape] sugars… just over a period of two decades we have seen a huge increase in sugars and our claim is that most of this is due to fashion and winemaker choice.”

The overriding influence on the surge in sugar levels – and hence eventual abv – Howell ascribed to harvest times. “We are picking later than we used to, even if we have more warmth,” he stated.

He also explained that altered approaches to viticulture in the Napa Valley had affected alcohol levels, such as the use of different rootstocks, increasing the planting density and changing the trellising techniques. “Historically Napa looked like a big jungle, what was known as the Californian sprawl – visualise a teenager on the sofa – and so the fruit was buried in the leaves and it didn’t ripen properly,” he said.

Today however, more efficient training techniques such as the vertical trellis with shoot-positioning system (VSP) which, when combined with closely spaced vines, are producing grapes with a higher sugar content than 15 to 20 years ago.

As for climate change in the region, he pointed out that records over the last 15 years showed a slight average temperature increase but more dramatic changes when it came to nightime and morning temperatures.

“What we are finding in Napa is that the afternoon temperatures are going up but not as fast as the morning cold temperatures… it is the low temperature that is rising,” he explained.

He added: “Afternoon temperatures are not rising as much and this seems to be especially true as you go up the valley, and high up, summertime temperatures have not gone up at all.”

However, Cain stressed: “Reporting this is politically sensitive and we don’t want to be seen as climate change deniers.”

Turning the discussion towards future changes to mitigate the influence of rising nightime and morning temperatures, he said: “If we pick earlier you can get in trouble, you just get vegetables with lower alcohol, so we [Napa Valley] will always be picking at higher sugar levels than Bordeaux.”

He identified his concern surrounding the changing climate, saying: “Colder nights preserve the acidity but with warmer nights the acidity is metabolised in the grape berry and so warmer nights means there is less acidity – and so I would expect the pH to go up and the acidity to drop.”

Nevertheless, he suggested two possible solutions. “We want to train our fruit a little higher so it doesn’t get as much warmth from ground and we want to have a little bit more leaf area to provide some shade [for the grapes] – I think the best condition is dappled sunlight.”

Concluding, Howell turned his attention to the demands of the market and commented on the influence of consumer taste. “I don’t think the US market has reacted against the taste of the wines and in fact they like them.”

“If you look at harvest times from 1985 to 2005 in almost every case we are waiting longer to pick our grapes. We may not need to wait as long and we have been waiting dramatically longer, especially if we remember how our vineyard has changed.”

Then, he asked rhetorically: “But can I train them [the US consumer] to drink wines with lower alcohol, higher acidity, and perhaps a herbaceous note?”

Napa Vintners Release Findings of Climate Study
February 3, 2011
St Helena, CA-The Napa Valley Vintners (NVV) non-profit trade association announced today the release of the
Napa Valley-specific climate study titled Climate and Phenology in Napa Valley: A Compilation and Analysis of
Historical Data by Dr. Daniel R. Cayan, Dr. Kimberly Nicholas, Mary Tyree, and Dr. Michael Dettinger.
In 2006, a researcher garnered national media attention by predicting that Napa Valley would soon become too
warm to grow fine wine grapes. These reports noted signs of warming in California and the western United States
in recent decades, calling attention to several changing indicators in weather, hydrological and biological systems.
Evidence from other Mediterranean climate regions around the world indicated that climate warming may be
taking hold in these settings. However, the experience of Napa Valley growers has been contrary to the notion that
Napa Valley has warmed substantially.   A problem in applying this previous research to the Napa Valley is that it
has considered just a few weather station records in Napa Valley, which has long been known for very diverse
micro-climates and growing conditions.
This just-released Napa-specific study by Cayan and colleagues scrutinized weather and phenology (the growing
cycle of grapevines) records based on many more stations within Napa Valley, and arrived at a number of
important new conclusions. Over the four years of the study, more than 12,000 data points were collected from
measurements made at geographically diverse sites in the valley, using information ranging from hand-written
journals kept by long-time growers to digital data from current-day automated weather stations positioned valleywide. Most of the observations were from records taken since the late 1970s, but some of the hand-written
entries were from as early as the 1950s.  The Executive Summary of the study is attached; in brief, it finds that the
region has experienced some warming, approximately 1° to 2° Fahrenheit over the past several decades, but
considerably less warming than would be inferred from the standard cooperative observer weather stations in
Napa Valley.  The warming has been primarily in winter, spring and summer, and it has concentrated during
nighttime rather than daytime. Over the last several decades in growing season temperatures, there has been little
warming in the daytime and the available observations provide little evidence that the growing cycle of the
grapevines has changed substantially.
The results, overall, provide good short-term news that consumers are not "tasting" climate change in Napa Valley
wines. It reinforces the firmly held belief among growers and winemakers that the taste profile of Napa Valley's
wines is driven by its place of origin, as well as by the solid direction of the in-field practices related to viticulture
(clonal and rootstock selection, canopy management, irrigation, crop load and hang time, among others) along
with stylistic preferences in winemaking. 2
The Napa Valley-specific climate study began in 2006 when the NVV board of directors created a climate study task
force of vintner members who had both interest and knowledge of the issue. The task force identified Dr. Dan
Cayan of Scripps Institution of Oceanography at UC San Diego, one of the most experienced climate scientists in
the state, to lead a research team. A key member the team was Dr. Kimberly Nicholas, a North Coast native, who
at the time was in the midst of her doctoral degree program at Stanford University, studying the potential effects
of climate change on high-quality winegrowing in Napa and Sonoma. With this team in place, and working with
the vintners and growers in Napa Valley, a set of criteria was designed to collect and investigate as much historical,
in-field data as possible to determine climate patterns and trends specific to the Napa Valley appellation.
Vintner and climate study task force member Christopher Howell of Cain Vineyard & Winery said, "We winemakers
are farmers--as farmers, we live not by the climate, but much more by the weather, i.e.: day to day, week to week,
season to season, and year to year. In order to get clear evidence of climate change, we need to be able to
compare trends over decades--this is not a perspective on the usual human scale."   Indeed, this study and
previous research shows that Napa temperatures are correlated, to some extent, with changing ocean
temperatures along the Pacific coast;   for example, sea surface temperatures along the central California coast
have been unusually cool in recent years, associated with relatively cool air temperatures in the Napa Valley.      
Howell continued, "We love the quote attributed to Mark Twain who said, 'The coldest winter I ever spent was a
summer in San Francisco.' The Pacific Ocean is our region's greatest temperature control. From living here, we
know that the warmer the Central Valley becomes on a summer day, the more intensely the fog pours in from the
coast. This is the 'vacuum effect' of the warmer interior valley. We have been blessed to have the perfect mix of
warm days and fog/coastal cooling that allow us to grow some of the finest wines in the world.”
"Globally, the years 1998, 2005, 2006 and now 2010 were the warmest years on record, but they were some of the
coolest for the Napa Valley. There is a suggestion by some climate scientists that, as the interior areas warm in the
future, Napa temperatures may actually remain relatively moderate, or even cool as maritime air gets drawn
further up the Valley. Either way, warmer or cooler, it's different than what we're experiencing today--so as
prudent farmers we need to look at all of our possible scenarios and consider best practices to continue to grow
the best wine grapes," Howell concluded.
The new study emphasizes the need for maintaining regular observations at high-quality weather stations around
the Valley. Estimates of temperature changes in the Napa region are hampered by local changes in exposure,
buildings and paved areas around the longest existing weather stations.   For example, the commonly used
weather station at Napa State Hospital, with a record going back 100 years, is situated over an irrigated lawn next
to a black top driveway and a building with a large window air conditioning unit, and the St. Helena weather
station is mounted on the roof of the city fire station, but was moved three times in recent decades. Shorter
records collected by Napa weather observers indicate that these long-term stations are registering an artificial
warm bias which has likely increased over the last several decades. The study recommends that the Napa Valley
farming community should formally assess the adequacy of its current climate observations and establish a
protocol to maintain a high-quality, long-term climate monitoring network.
"I am proud of the leadership taken by the Napa Valley Vintners in this climate study. We have strong benchmarks
in place that will further allow us to track what changes may occur in our unique climate--really specific to the
Napa Valley. Though we are just 4% of California's wine grape harvest, we account for 34% of the value of the
California wine industry on the US economy. It's in all of our best interests to ensure a long and healthy future in
fine wine from the Napa Valley," said Kathleen Heitz Myers, president of the NVV board of directors.3
Additional research beyond this study continues on a number of fronts, looking at what in-field practices could be
employed should climate change take the form of regional warming, such as how canopies and cover crops are
managed as easy, short-term solutions.  Napa Valley growers and vintners are raising awareness of what can be
done locally while thinking globally with programs like Napa Green Certified Land and Winery, which are the most
comprehensive green initiatives in the wine industry and that have the well-earned reputation for going above and
beyond when it comes to environmental best practices.
The Napa Valley Vintners is the non-profit trade association responsible for promoting and protecting the Napa Valley appellation as the premier winegrowing region. From seven founding members in 1944, today the
association represents 400 Napa Valley wineries and collectively is a leader in the world-wide wine industry. To
learn more about our region and its legendary American wines, visit www.napavintners.com