In light of the Paris 2015 UN Climate Change Conference taking place from November 30 to December 11, and its goal of reaching a universal agreement on climate from all nations, we’re taking a look back at climate-focused articles from the pages of the magazine.
Gregory V. Jones is a professor, research climatologist and author of numerous book chapters, reports and articles on wine economics, grapevine phenology, site and climatological assessments of viticultural potential and climate change.
Overall, wine quality results from the balance of four ripeness clocks running simultaneously but at different rates: sugar accumulation, acid respiration, phenolic ripeness and fruit character. The balanced “sweet spot” timing for these clocks occurs when a variety is grown in its ideal climate and ripens at the tail end of the growing season during warm, dry days and cool nights. Each vintage’s weather presents challenges that affect the degree to which these ripeness clocks are in tune. Every year, grape growers and winemakers must choose when to harvest to achieve their preferred balance in these ripeness clocks. Unbalanced
wines typically result from yields that are too high for the vine to fully ripen the fruit, or vintages that were too cool or too hot. If balance is way out of sync on a regular basis, then we can conclude that the variety is not suited to that climate.
Higher alcohol levels are often regarded as evidence of unbalanced wines, and changes in viticultural practices have made it easier to achieve higher sugar levels and thus, higher alcohol levels. Now we have better plant material, including clones and rootstocks with greater disease resistance; they also produce smaller vines with more exposed fruit and are better matched to soil characteristics. This has clearly made it easier for growers to ripen fruit to higher levels. An example of this is in the Napa Valley where, prior to 1980, much of the area was planted to vines with leaf roll virus, which delayed ripening and made it very difficult to produce wines that reached 12% alcohol or more (Vierra, 2004). Further advances in viticultural practices such as well-timed and-tuned irrigation, better management of vine nutrition, trellising changes allowing for more leaf and fruit exposure and better pest and disease control also play a role in producing riper fruit. Add to all this better winemaking techniques, including more efficient yeast strains, and there is no doubt of nurture’s contribution to rising alcohol levels.
Yet nature shares some responsibility. Of all the environmental factors influencing grape and wine production, soil and climate are the two most prominent. While soil is an important factor, it clearly does not change appreciably over short time scales. Climate, on the other hand, has changed: Over the last 50 years, growing seasons in wine regions globally have warmed 1.3°C on average (Jones, 2007). These changes have lengthened the growth period, accelerated vine growth cycles and directly influenced fruit and wine composition (Jones and Davis, 2000; Schultz, 2000;] Jones et al., 2005; Duchêne and Schneider, 2005; Webb et al., 2008). Given the importance of these trends and relationships, there is a substantive amount of other research occurring in both academia and the industry that will further substantiate the strong connections among climates, grape varieties and balance in wine.
So let’s go back to the four ripeness clocks and think of the situation 30 to 50 years ago, when growers were cultivating varieties in climates based upon how they performed then, which arguably worked to varying degrees. All of the changes in plant material and vine management essentially fine-tuned the system, but in many cases there was no longer an ideal match to the climate. The sugar accumulation and acid respiration clocks started to come into balance earlier, while fruit character and phenolic ripeness would happen later. Throw in a warming environment with longer growing seasons and the result is a complex moving window with an even earlier sugar/acid balance causing a greater disconnection from fruit character and phenolic ripeness. To deal with this climate-variety mismatch, longer hang time in many regions was necessary to achieve the desired fruit character and phenolic ripeness. But, as Richard Smart has said, “the need for hang time is being overstated and uncritically accepted…if grapes need hang time, they are not being grown properly in the first place.” (Smart, 2003/2005). While growers first used hang time to deal with climate-variety mismatches, they’ve since extended it to play to higher and higher fruit character and phenolic ripeness.
And no wonder. Much of the market has embraced these riper, higher-alcohol wines. An average rating increase of ten points on a 100-point scale from a powerful wine critic or publication can translate into a 200 to 300 percent price increase per bottle (Nemani et al., 2001). In response, a whole industry has developed that attempts to reverse-engineer high scores. Many growers and winemakers have extended hang time even further to achieve higher fruit character and phenolic ripeness, hoping to “dial-in” a high score.
If climates continue to change as projected (1.5 to 2.5°C by 2050), then further changes in vine growth and climate-variety suitability will occur. These changes will only increase the gap between the timing of phenolic ripeness, sugar/acid balance and fruit character. While there are technologies to “fix” unbalanced wines, it’s not clear how far these technologies can go before some tipping point is reached. In order to deal with a changing climate, in my opinion, changes in variety and vineyard management will have to occur.
In the end consumers are the key…if they keep buying bigger, bolder wines with higher alcohol, then that style will persist. However, many are clamoring for wines with lower alcohol and more finesse that age better and are more harmonious with food. This has led to a counter culture of consumers and winemakers who are essentially saying that they want balanced wines—or, in other words, wines produced from fruit grown in its ideal climate.
Sources:
Duchêne, E. and C. Schneider (2005). Grapevine and climatic changes: a glance at the situation in Alsace. Agron. Sustain. Dev., 24: 93-99.
Godden, P. and M. Gishen (2005). Trends in the composition of Australian Wine. Wine Industry Journal, Vol. 20, No. 5, September/October 2005.
Jones, G. V. and R. E. Davis (2000). Climate Influences on Grapevine Phenology, Grape Composition, and Wine Production and Quality for Bordeaux, France. Am. J. Viti. Enol., 51: 249-261.
Jones, G. V., Duchêne, E., Tomasi, D., Yuste, J., Braslavksa, 0., Schultz, H., Martinez, C., Boso, S., Langellier, F., Perruchot, C., and G. Guimberteau (2005b). Changes in European Winegrape Phenology and Relationships with Climate, GESCO 2005.
Jones, G. V. (2007). Climate Change and the global wine industry. Proceedings from the 13th Australian Wine Industry Technical Conference, Adelaide, Australia.
Nemani, R. R., White, M.A., Cayan, D. R., Jones, G. V., Running, S. W., and J. C. Coughlan (2001). Asymmetric climatic warming improves California vintages. Climate Research, Nov. 22, 19(1): 25-34.
Schultz, H. R. (2000). Climate change and viticulture: a European perspective on climatology, carbon dioxide, and UV-B effects. Aust. J. Grape and Wine Res., 6: 2-12.
Smart, R. E. (2003). Hang the Hang Time. Practical Winery & Vineyard, January/February 2003.
Smart, R. E. (2005). Scrutinizing the Hang Time Trend. Practical Winery & Vineyard, March/April 2005.
Vierra, G. (2004). Pretenders at the Table-Are table wines no longer food friendly? Wine Business Monthly, 11(7), July 2004.
Webb, L. B., Whetton, P. H., and E. W. R. Barlow (2007). Modelled impact of future climate change on the phenology of winegrapes in Australia. Aust. J. Grape and Wine Res., 13: 165-175.
This story was featured in W&S Fall 2010.
This story appears in the print issue of fal 2010.
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