‘Growing Degree Days’ up 18% locally in last 100 years — which can be good, or bad, depending on the varietal
By Jim Flint for Ashland.news
Climate change is a double-edged sword for the wine industry.
On the one hand, it can present weather events, variability, and long-term structural change, resulting in crop risks, production and quality issues, and suitability challenges.
On the other hand, it can explain why Britain could be your next favorite wine region.
Such was the gist of remarks by Dr. Greg Jones, CEO of Roseburg’s Abacela Winery, who spoke on Thursday, April 13, about climate’s influence on sustainable wine production at Southern Oregon University’s Hannon Library. The talk was part of Friends of the Hannon Library Speaker Series, free and open to the public. It was also livestreamed.
“Wine regions have developed worldwide where the weather and climate were most conducive,” Jones said. “But the weather and climates of wine regions vary greatly.”
Some areas are at climate margins, he noted. Others have warmer days or warmer nights, they’re drier or wetter, have reliable growing season rain or none, and some are more prone to risk from weather extremes.
“The topic can be depressing at times,” he said.
Jones is an atmospheric scientist and wine climatologist who grew up in the wine business. He has taught and conducted research at the University of Virginia, Linfield University, and SOU.
He described the climate trends for Oregon from 1948 to 2016.
“Growing season temperatures are warmer overall,” he said, “and the number of days below freezing has increased.”
Across all locations, minimum, maximum and average growing season temperatures are up from 2.0 to 3.1 degrees Fahrenheit. Ripening period temps are up and the number of growing season days with highs greater than 95 degrees (5-15 more) has increased.
On the other hand, across all Oregon regions there are 18-28 more days below freezing annually, 7-15 more in the spring, and three to eight more in the fall.
Jones said these changes can affect vine growth and how vines harden and become stronger.
“Low variability is best,” he said. “It helps avoid stress. We like low risk of frost. And for high quality fruit, we don’t want to harvest during the summer.”
When the climate changes and the grapes don’t like it, growers are limited in their ability to overcome the challenges. They can try to “trick” the vines genetically or add irrigation when the climate becomes drier. Eventually, they might have to plant different varieties.
“All varieties have inherent climatic thresholds for optimum quality and production characteristics,” Jones said.
“And all varieties are grown across a range of temperatures, with wine style differences across the range. Varieties can be found grown outside these bounds, but are often under- or over-ripe. They’re also very limited in production, or focused on bulk markets,” he said.
Pinot noir does best in a cool to intermediate environment, or with temps in the range of the high 50s to low 60s in degrees Fahrenheit. Tempranillo thrives in an intermediate to warm environment, ranging from the low- to mid-60s.
Wines produced in areas on the low end of the range have lighter body, lower alcohol, higher acidity and brighter fruit; on the higher end of the range, fuller body, higher alcohol, softer acidity and darker fruit.
“Pinot noir exhibits one of the narrowest climatic niches for premium quality production,” Jones said.
Once a region’s climate moves firmly into another range, the only alternative may be to switch to more suitable wine grape varieties.
Jones explained how a warming climate disrupts the nature of the grape and wine chemistry.
“Berries ripen faster at warmer temperatures,” he said, “building up more sugars, which raises alcohol content in the wine. Acid, which adds freshness and zest to wine, declines in warmer temperatures.
Pigments, called anthocyanins, break down under heat. And tannins, important for wine mouthfeel, may not develop enough if grapes are harvested early to curb rising sugars.”
How many wine varieties can you name? A half-dozen? Twenty?
There are about 5,000 unique varieties grown worldwide. Fewer than 1,400 are grown commercially as “prime” varieties.
Jones said 50% of the world’s planting is now done with 16 varieties, and in new world wine regions, seven varieties make up 50% of the plantings.
“Climate change is just one of many factors putting pressure on the wine industry,” he said. “Other factors include economics, growing demand but changing demographics, challenges from other beverages, new markets, new consumers, new styles, and changes in the tastes of wine writers and raters.”
In the wine growing industry, “growing degree days” (GGDs), a measure of heat accumulation, are often cited as a way of estimating the growth and development of plants and insects during the growing season. The basic concept is that development will occur only if the temperatures exceed a base (50F this case) for a minimum time period.
In Medford, GGDs have increased nearly 18% in the last 100 years. That means the grapes are ripening sooner. Whether that’s good or bad for the grape depends on the variety. At some point, a particular variety will suffer in quality from more GGDs and it will no longer be viable.
Jones said research and development will help provide more tools for wine growers, as will better and more information.
“We need to be better stewards of the land,” Jones said. “Don’t continue to make problems worse. We can’t do enough mitigation, so we’ll also have to adapt.”
As warming continues to be likely in the future, economics and greed will influence response times, Jones said.
“Building resiliency in our agricultural systems is a must.”
Meanwhile, Southern Oregon continues to garner attention for its wide range of outstanding wines — cabernet sauvignon, syrah, merlot, tempranillo, pinot noir, viognier and more.
And yet, if the U.K.’s burgeoning wine industry is any indication, your great-great-grandchildren living some day in Anchorage, may be touting their own favorite local vintages.
Reach writer Jim Flint at email@example.com.