While research is ongoing to try to understand how the more than 1,000 aroma compounds identified in wine affect our flavor perception, many compounds appear to be sensitive to climate, particularly in the later stages of grape ripening. Some desirable compounds like rotundone, which gives Syrah its typical black pepper aroma, appear to accumulate more at cooler sites and in cooler years, so warmer-climate Syrahs have less of this character.
Winegrowers and winemakers have many options to adapt to warming climates. Growers are experimenting with new wine regions, cooler locations within existing regions (such as moving from warmer valleys to cooler hillsides), trying new varieties better suited to warmer conditions, and farming methods that provide more shade on the fruit. Winemakers can use approaches including alcohol removal and acid addition to improve wine balance. Steps like these can go a long way towards preserving great wines under climate change.
Ultimately, though, there are economic and biophysical limits to this adaptation. There are also cultural limitations: the know-how and sense of place that growers cultivate along with the land over generations of family farming is not easily moved, and consumers have come to expect a distinct flavor profile from wines from their preferred regions. Great wine is grown, not made; it reflects its place of origin. If the climate changes even a little bit, local knowledge and skills that have taken generations to hone can become less relevant, even in familiar territory.
But the changes we’re facing in climate are not small ones. Under our current trajectory of fossil fuel use, scientists project that the global average temperature will increase 4.7 to 8.6°F (2.6 to 4.8°C) over the next few generations. Even the low end of this range would be the difference in annual average temperatures between the winegrowing regions of Napa and Fresno today. Currently, Cabernet grapes from cooler Napa are worth more than 10 times as much as those from Fresno- a difference of over $3,000 a ton.
Wine illustrates our deep reliance on nature to provide us with everything we need to live, and many of the things that make life worth living. We are in a moment of critical climate choices. Choosing to limit climate change gives us more options for a more healthy, thriving, fair, and delicious world- including more of the traditional flavors of your favorite wines.
The end is drawing near for our first field season for the Vitis project, led by Lizzie Wolkovich at Harvard, where we're looking at the timing of development (phenology) for over 100 different varieties of grapevines at the teaching vineyard at the University of California- Davis. Sampling from a common garden like this lets us control for climate, soil, management, and other variables, so we can learn more about how the vines respond to the environment. Over 100 varieties of the world's most commercially important grapevines are planted side-by-side here in this one vineyard; my mom calls it the "Noah's Ark of grapevines." My collaborator Dylan Burge, from the California Academy of Sciences (above left), will be doing genomic analyses to search for the genetic basis of this environmental response. We hope that the results will help us identify relationships that could be useful for adapting viticulture to climate change, perhaps better matching the development and ripening of the vine with a changing environment.
We've already made observations on earlier phenological stages (budburst, where the vines first start growing in the spring; bloom, when the flowers that will develop into individual berries are visible; and veraison, when the berries start changing color and accumulating sugar). The last stage to monitor is ripening, which we're measuring now by taking berry samples in the field and analyzing them for their sugar content in the lab. Different varieties can ripen at very different rates, and achieve different sugar levels at ripeness; generally cool-climate grapes like Riesling ripen earlier and at lower sugar levels than warm-climate ones like Tempranillo. After Lizzie did a heroic singlehanded field campaign for the first sampling date a few weeks ago, it took three of us (Dylan, Teri Barry, and me) to match her for the second round! It was great to get out in the vineyard for a morning and make a small contribution on the ground to the fieldwork that Dylan and Lizzie have been running while I contribute from afar in Sweden.