Reading the article below about a cold snap in New Zealand and the devastating impact on the local vineyards started me thinking about the challenge of wine grape growing during the next grand minimum.
Some Central Otago vineyards lost as much as 50% of their crop after devastating frosts hit the region over the weekend.
Temperatures plummeted to as low as -5.5 degrees Celsius in some areas, rendering frost-fighting techniques next to useless.
Gibbston Valley and Central Otago viticulturist and consultant Timbo Morrison-Deaker described the damage as “particularly ugly” and the worst he could recall. “Gibbston as a sub-region looks 40% gone and Lowburn is about 25% gone. Those are significant figures.”
The severe weekend frosts follow a disastrous Northern Hemisphere season, reportedly the worst in 50 years, and had already led to predictions of a worldwide shortage of grapes, said Mr Morrison-Deaker.
More details HERE on the damaging frost.
In an old blog I wrote about about the impact a PDO switch from a warm phase to cool phase could have on wine grapes growing in the Sierra foothills. During my research I discovered this study.
Influence of climate variability on wine regions in the western USA and on wine quality in the Napa Valley by Gregory V. Jones* and Gregory B. Goodrich
ABSTRACT: Trends in climate variables important to winegrape production in the western United States include fewer frost days, longer growing seasons and higher spring and growing season temperatures. These trends have been related to a steady increase in wine quality and a decrease in year to year variability. While the trends in climate have been linked to increasing sea surface temperatures (SSTs) in the eastern Pacific, it is unknown whether this is caused by climate change or may be part of natural oscillations in the Pacific. In this study, fifteen climate variables important to winegrape production were analyzed for ten wine regions over the western USA. The variables were stratified by phases of the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) both separately and then in combination (modulation effect) to determine if there are any significant differences between teleconnections. Wine Spectator vintage ratings for Cabernet Sauvignon wines from the Napa Valley were also stratified in the same method and multivariate statistics were used to determine which variables are most important to wine quality. ENSO phase by itself was not found to be important to either climate variability in wine regions in the western USA or wine quality in Napa Valley, but the cold phase of the PDO was found to be associated with increased spring frosts and a shorter growing season that results in lower ratings relative to warm PDO. The combination of neutral ENSO conditions during the cold phase of the PDO was nearly always associated with low quality wine in the Napa Valley, which is a function of cold springs with increased frost risk, cool growing seasons, and ripening period rainfall (cold PDO) and above average bloom and summer rainfall (neutral ENSO). While climate trends to generally warmer growing seasons with less frost risk have occurred, this research highlights the impact of climate variability on wine quality where, should the PDO return to a multi-decadal cold phase, wine growers in the Napa Valley and across the western USA will likely experience greater variability in wine quality.
We are now in a cold phase our local vineyards have experiences some significant damage from late spring frosts and cool summers, according a discussion I had with a local Sierra Foothills wine maker recently.
I have highlighted some areas in the study that pertain to this discussion. If a cold phase PDO will have an impact on wine grapes, then a temperature decline associated with a grand minimum could have a more significant impact over a potentially longer period than a PDO switch.
Wine grapes, depending on the variety, require a range of degree days for the berries to mature with enough sugar to make great wine. The scientist at UC Davis have developed a systems for determining the number of degree days needed by grapes in California by region. According to Wikipedia:
The system is based on the hypothesis that grapevines do not grow if the temperature is below 50 °F (10 °C). Days in the growing region (assumed under the system to be April 1 through October 31 in the Northern Hemisphere; October 1 through April 30 in the Southern Hemisphere) are assigned degree days according to the amount that the day’s average temperature exceeds this threshold; one degree day per degree Fahrenheit over 50 °F. In places where SI units are preferred, degrees Celsius over 10 °C may be used, but should be multiplied by 1.8 to convert to Fahrenheit degree days for the following list. All days in the locale are then added up, with the sum used to determine the region’s classification as follows:
▪ 2,500 degree days or less: Region I
▪ 2,501–3,000 degree days: Region II
▪ 3,001–3,500 degree days: Region III
▪ 3,501–4,000 degree days: Region IV
▪ Greater than 4,000 degree days: Region V
The system is used officially in California, and other United States growing regions.
Most of the grapes in California are grown in Region II and Region III to take advantage of local conditions. Now suppose that the climate cools by 2º to 4º C reducing the number of days when the temperature is above 10º C, thus reducing the number of degree days.
The earth has cooled over the past 16 year and we may be on the cusp of the Next Grand Minimum. During the last Grand Minimum, it was no longer possible to grow wine grapes in England, were grapes are growing today in Southern England.
The Maunder Minimum and the Little Ice Age extended from 1400 to 1850, but it is essentially still too cold to grow wine grapes successfully in most of England. However, in 1068 AD, 938 years before today, Britain’s tax officials reported in the Domesday Book that nearly 50 British vineyards were growing wine grapes. Romans were also reported to have grown wine grapes in Britain when they occupied the island. German wine grapes are not grown as high on the hillsides today as during the Medieval Warm Period.
Wine grapes are one of humanity’s most accurate and sensitive indications of temperature in the pre-thermometer era. Please pay attention to how the wine grapes are growing and surviving in your neighborhood. If you have some details please share them in the comments.