Winemaking: Cool Climate Viticulture

Newsletter Archives > Viticulture

Cool Climate Viticulture: a hot topic

Cool Climate responses to Global Warming must include mandatory drip irrigation for summer drought, cover crops for winter inundation, as here at Stoller Vineyards

We grow grapes in what is considered viticulturally a Cool Climate Region, one in which moderate temperatures and a gradual progression from budburst to harvest protects delicacy and nuance in the resulting fruit. We’re not so much concerned with number of sunshine hours as temperature accumulation during the growing season (including consideration of daily highs and lows since either too warm or too cool stops effective photosynthesis). Cool climate designation recognizes that wine quality from many of the best varieties is better where fruit gets fully ripe, but not too quickly and without temperature extremes.

There is a price to pay for the superior quality that can come from great vintages in areas like Oregon, or northern Europe’s Burgundy or Alsace or Germany, or New Zealand. The cost to grow grapes is greater in both planting and cultivation; the yield necessarily smaller to obtain metabolic balance, develop intensity and assure ripening; and the risk of lacklustre fruit greater from poor vintages with early Fall rains or cold and disease.

There are many idealists, traditionalists or perfectionists who keep Cool Climate grapegrowing going. Many of us buy each others’ wines exclusively because we’re nuance and complexity driven. To many of us there is always more to be learned farming on-the-edge, and we eagerly seek out other zealots. We even have a conference every four years. The Cool Climate Viticulture and Oenology Symposium began in 1984 in Oregon and continues to move around, welcoming us to Melbourne, Australia in January 2000. In addition to ongoing topics such as yeast, deacidification, clonal research, ML, computer modelling, trellising, harvest prediction and others, a very hot topic this year was Global Warming and its implications.

Global warming. It's not a question of IF or even WHEN, since it has already begun, it's a question of HOW BAD IT WILL BE!

No one doubts that we are warming due to the greenhouse effect and greater solar intensity from ozone depletion— just consider anecdotal examples such as the loss of glacier mass sufficient to unearth long-buried animals and humans, the reduction over the last century of frost days in October in Germany from 6 to fewer than one, or the statistically undeniable high temperature records over the last two decades on all continents. predictions are that over the next half century in cool climate areas average temperatures of 11.5 degrees C will rise 1.8-2.5 degrees (3-4.5 degrees F), that CO2 levels will double leading to 20% or greater increase in humidity and 30-50% reduction in soil moisture, and that precipitation will drop to half of normal in summers and twice normal in winter. Weather events will become even more extreme, as our planet tries to reestablish equilibrium.

Benefits? Let me count the few. Increased CO2 improves water efficiency of plants, fruitfulness and color. Plus you’ll be able to plant Merlot in Germany.

The overall climate change not only affects temperature and rainfall but Ultraviolet-B levels. UV-B radiation level can significantly affect plant constituents important in fruit and wine flavors and possibly even fruit set and photosynthesis itself, since the high energy radiation is absorbed by DNA. In Australia, the intensity has increased 10-15% in the last 20 years. A small positive—it inhibits powdery mildew.

In Oregon, these climate changes will require irrigation in the drier summers and good erosion control during the wetter winters, plus might allow marginal, cooler sites greater success with current varietals and existing, successful warm sites the opportunity to play with California and Bordelais varietals. Rain abbreviated vintages should become the rare exception, but as soon as the harvest is over expect half of Oregon’s population to head for dry refuge as the winter deluge descends.

Cassandran warnings? Perhaps, but to pretend we don’t have to react, by attacking the causes globally, and be prepared to respond to inevitable local changes will be foolhardy. Cool climate grapegrowing will always exist, because the wines are most refined and complex and food worthy. It’s just that we’ll get them from new places. And most people will have to satisfy themselves with Meditteranean varieties. Marsanne anyone?