by Sally Colby
Climatologist Dr. Gregory Jones, of Southern Oregon University, has studied many of the major wine grape regions of the world. He has found that no matter where he goes, people tend to view weather and climate similarly.
“If I travel somewhere in the world and it’s just been the hottest day or week or month of the year, I’m brilliant,” he said. “But if I go somewhere and it’s just been the coldest day, or week or winter, I’m kind of an idiot.”
Jones says that whether the planet is warming, cooling or stable might be somewhat debatable, but the certainty is that the global climate is in a constant state of flux. Weather and climate can present single, localized short term weather events like hail, frost, freezes and heavy rain. Growers are all familiar with dry periods, wet periods, warm periods, cold periods; all of which are based on aspects of how the atmosphere works.
“Climate structure/climate change issues are about suitability,” said Jones. “How we do things relative to a given cultivar in a given environment and whether it can produce the way we want it to?”
Consider the basics of growing grapes. The temperature threshold among individual varieties, regions or vintages can be too cold. “You end up with low sugar levels, unripe flavor or unbalanced wines at harvest,” said Jones. “We also know that too warm a threshold, or in a given region or with a certain variety you can have overripe flavor, lower retention of acid and unbalanced wine. What we all shoot for is planting a variety in a given climate such that it’s in its optimum zone and tends to be consistent in terms of productivity and quality. We know that variations in weather events present challenges, but zones are what we’re looking for.”
Jones has conducted extensive research in wine-grape regions around the world.
He’s interested in discovering whether temperature thresholds are fixed or if there is a measure of adaptability relative to management; and how the varietal performs over time and adapts to changes in climate.
In the 1980s, Jones collected data on grape-growing throughout the world and created a simple way to look at how varieties ripened within a given climate. “We know that all varieties have inherent climatic thresholds for the kind of productivity and quality we’re looking for,” he said. “Pinot noir has one of the most narrow climatic tolerances. The pinot noir regions are typically 57 and 61 degrees F. That’s roughly a four degree climate niche, which means that there’s a stylistic difference. If you ripen pinot noir in cooler regions, it’s lighter and more elegant. If you ripen it in warmer regions, it’s more bold and bigger bodied.”
Can pinot noir be grown in climates that are warmer than the upper temperature threshold? Jones says yes, but typically not for the familiar premium quality pinot noir wines. “If varieties are grown outside the boundaries, it’s typically for bulk wine production,” he said. “It can be done, but for a different market.”
What’s the state of the climate today? Jones says that with the exception of the eastern United States, 2013 was the fourth warmest year since the start of modern record keeping in 1880. But why haven’t temperatures continued to climb at the rate they once did?
“Through observations and modeling, we’ve been able to figure out where this is happening,” said Jones. “The Pacific, which has been relatively cold, has been absorbing the majority of excess heat and has muted the warming. Much of our modeling tells us that if the Pacific absorbs enough and comes to equilibrium, we’re going to ramp up really fast relative to warming.”
What drives variability? The most significant is the tropical Pacific ENSO, or el Nino southern oscillation. Jones says that when ENSO shifts, there are consequential effects in many different regions, even into Europe and Australia.
Other climate influences include the Pacific Decadal Oscillation (PDO), the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). “All of these things interact,” said Jones, “and they produce situations in which we have strong winter/spring variability within our wine regions. It can influence vintages. There’s a lot of interaction between these influences in areas – no single climate variability mode is responsible for climatic differences.”
Jones explains there is a temperature gradient between the poles and the equator that creates a westerly jet stream structure that wiggles across the mid-latitudes. The wiggles associated with the jet stream are tied to the temperature gradient between the poles and the equator. If the temperature gradient changes, so does the nature of the jet stream.
Observations and modeling both show that when there’s a change between temperature gradient between the poles and the equator, the westerly wind flow changes. This artic amplification slows the jet stream and creates a much greater north-south wiggle, or meander, in the jet stream. “The ‘meanders’ can become slower and more pronounced, and can become stuck in place,” said Jones. “The record dry conditions in the west are a result of this effect.”
Records show that over the last 10 years, there have been more extremes in temperature and precipitation. A 15- year drought in Australia broke in the 2010-11 vintage with extreme rainfall, which resulted in heavy disease pressure.
“In western United States, 2010 and 2011 were years of extremes,” said Jones. “It was extremely difficult to ripen fruit there. We had frost in fall with fruit still on the vines, and late frosts in spring in places that hadn’t seen spring frost in over 50 years. Then 2013 saw record September rainfall from a typhoon out of the South Pacific that slammed into northern California, southern Oregon and Washington just as a beautiful vintage was coming to a close.” Jones noted that eastern United States experienced strong variability from year to year, with relatively mild winters until 2014.
“Some places are seeing warming in nighttime temperatures, and others are seeing warmer daytime temperatures,” said Jones. “We also know that dormant periods are typically warmer worldwide.” However, some areas have experienced less freeze and/or frost damage. Jones says that climate has driven some altered ripening profiles, which can be good or bad, and can result in opportunity for stylistic wines.
,Another consequence of climate change is the prolonged drought in Australia that resulted in high saline soil. On the too-much rain side of that coin, steep slope viticulture regions throughout have seen heavy rain that leads to erosion. “It’s become commonplace in steep slope viticulture for soil to be moved from the bottom of the slope to the top and redistributed every year,” said Jones.
In general, warmer growing seasons produces lower acidity. “Total acidity is down in many places in the world,” said Jones. “In Burgundy, low acid is much more of an issue than low sugar. Throughout Germany, some of the acids that give Rieslings their characteristics have gone away, and they’ve had to deal with it through acidification.”
What should growers do? Talk to anyone who has been growing grapes for 40 years, and it’s clear that they’ve made changes. Techniques are different, but rates of change allow for adaption strategies.
Jones says growers should take advantage of the genetic potential of varieties and keep up with research efforts. “This industry is in place because of plant breeding and the ability to produce a vine that we know can deal with differing climate structure,” he said. “In Greece or Portugal, there are varieties that grow in extremely warm climates, yet they became acidic. We need to understand why so we can genetically manage that.”
Adaptation to current growing areas is going to become more common. “People are planting on north-facing slopes because south-facing slopes are too warm,” said Jones. “That’s a challenge, but also allows for more adaptations. There are also changes in training systems. There may have been some over-tuning for a while with extremely tight VSP.”
Jones believes we are aware of the cool limits, but not the warm limits. “There’s more variability in wine regions – everyone is seeing it and it will increase in the future,” he said. There’s continued warming going on, but at a slower rate. However, variability issues will be more of a concern than changes in average temperatures. Wide swings between seasons could be more problematic.
Growing grapes in a changing climate
by Sally Colby