A Brave New Wine World
By Richard Olsen
During the past year, discussions about the potential impact of “global warming” have dominated the mass media. Although the exact outcomes and causes are in dispute, few now doubt the existence of the phenomenon. What does it mean for the wine industry? As wine is all about long-term agriculture and entirely dependant on the weather, I’d say a great deal.
The eventual consequences of climate change on the wine industry are unclear, as are the possible effects on the rest of the planet. The real question is: Are the changes something we will only see in the distant future or are they something we’re living and breathing right at this moment?
When I was a graduate student in science education at Stony Brook in the late 1980’s, I did my masters thesis on the subject of climate change and the potential effects onLong Island. The concept was at the time, little more than a derided footnote in the public consciousness. However, even back then the research was clear that climate change was real. I particularly remember conversations I had with Dr. Anthony D. Del Genio at the NASA Goddard Institute for Space Studies (GISS) atColumbiaUniversity. Dr. Del Genio is a planetary physicist who has been studying climate models since the 1970’s. He is also a wine buff and had done some investigation of his own into the effects of climate change on the wine industry. Most importantly, I remember when he told me, “all of us will begin to feel the effects of climate change by the end of the 1990’s.” He not only was prescient – he also had some really good data.
One of the main tools used to track climate in agriculture is Growing Degree Days or GDD. This is a system that cumulatively calculates the average daily temperature of the growing season using a base of 50 degrees F. Winegrowers have used this system for many years to determine the boundaries of local climate as well as helping predict the quality and timing of the vintage. Cooler regions have fewer GDD and warmer regions have higher GDD. I’ve listed some examples of GDD as described in the seminal textbook General Viticulture by A.J. Winkler, published in 1974:
I < 2500 (Geisenheim,Germany,Geneva,NY)
II 2501-3000 (Napa,CA, Bridgehampton, L.I.)
III 3001-3500 (Oakville,CA, Riverhead, L.I.)
IV 3501-4000 (Lodi,CA,Sidney, AU)
V 4001 (Fresno,CA,Tehran,Iran)
I decided to look at some more recent data from the past 20 years and see if anything new turned up. For one,Northern Californiais becoming much warmer. The city of Napa, which used to be classified as a Region II back in the 1970’s, is now averaging seasons that are well into Region III and often as high as Region IV. Other areas withinNapaValleyandSonomahave reached well over 4000 GDD in past 5 years – approaching conditions that might make it difficult to produce quality wines in the near future.
Back East, things get a little more complicated. Data obtained for theFinger Lakesregion since the 1970’s show no statistically significant increase in GDD. It is surprisingly consistent, with average GDD hovering around 2600 for most areas around the lakes.
Long Islandpresents an entirely different story. When I first wrote and applied for the 2 local AVA’s – The Hampton’s, L.I. in 1984 and The North Fork of Long Island in 1985, I used data that went back to the 1940’s. According to that information, theNorth Fork(represented by Riverhead data) had an average of 2932 GDD while theHampton’s, (represented by Bridgehampton data) averaged 2531 GDD. Over the past 11 years, the numbers look quite different. Since 1996, the average GDD for Riverhead is 3331 days, while the average for Bridgehampton is 2805 – an increase of 399 and 274 respectively for these two regions. Although it is not a long enough period of time to draw a definitive conclusion, one can definitely see the trend; onLong Islandas well as inCalifornia, an average increase of 300-500 GDD has been recorded since the 1970’s.
This summer I contacted Dr. Del Genio again and mentioned to him I was going to write a piece revisiting this topic. I also wanted to get his thoughts on what has changed in his understanding since 1990 and what he sees in the future. Interestingly, he mentioned that he and his staff have begun to draw some new conclusions from the models used to predict climate change. He stated that since the onset of Clean Air Legislation that began in the 1960’s, the levels of particulates (i.e. dust, soot, etc.) in the air have decreased, which ironically, has lead to higher recorded temperatures in the densely populated areas of the Northeast, Midwest and California. These particles in the air known as aerosols scatter sunlight and make the light less concentrated – in essence, masking the warming effects of elevated CO2 levels. The areas showing the greatest response to clean air legislation are showing the greatest rise in temperature today – as much as 2-3 degrees F. on average. This effect is seen onLong Islandsince we are close to NYC – but he also mentioned our maritime influence, so important for moderating winter temperatures. Our reduced aerosols along with slight increases in water temperature are more than likely responsible for the increase in GDD. It also explains why a region like theFinger Lakes, further removed from air quality issues and with more of a continental climate, is presently showing less of a warming effect. This is one good example of just how complex a system our climate is and why it is so hard to accurately determine future outcomes.
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