A study released today from Stanford University claims the California wine industry will collapse due to global warming. The abstract is here. This is the key point in the abstract:
We find that the projected warmth over the this period [2000-2039] results in the loss of suitable winegrape areas throughout much of California, including most counties in the high-value North Coast and Central Coast regions.
This claim is made despite the marked increase in California grape production of approximately 400% along the North Coast, 2500% along the Central Coast, 1500% in the Central Valley, and 800% in the Southern Valley of California over the past 30 years of global warming.
What if the computer models used in the Stanford study are wrong? What if in fact the planet is cooling?
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 Daves have developed a systems for determing the number of degree days need 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 California climate cools by 2º to 4º C reducing the number of days when the temperature is above 10º C, thus reducting the number of degree days. Region III grapes could be now growing under Region II conditions. Region II grapes could be subjected to Region I conditions. Not ideal conditions for producing the best wine.
The earth has cooled over the past 15 year and there is a very good possibility that a Grand Minimum is in our future. During the last Grand Minimum, it was no longer possible to grow wine grapes in England, were grape are growing today in Southern England.
Over the next ten year we could experience the loss of Sierra vineyards, unless they adopt mitigations measure and adjust varities to deal with changes in the number of avilable degree days. The real problem will be if they adopt the mitigation recommended in the Stanford Study to deal with global warming.
H/T to The Hockey Schtick for the graphic.