The SOMM Journal

June / July 2015

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Page 89 of 100

{ }  89 PHOTO: THINKSTOCK Climate change is not going to affect every region the same way. Specifically, current models predict greater warming over land and higher northern latitudes. Temperatures themselves are not predicted to change uniformly either. While daytime tem- peratures on average will increase, it's the increase in nighttime low temperatures that is of particular note. For grapes specifically, current models predict that growing and ripening seasons are likely to change in some places, while some find that temperatures will increase so much that varieties of grapes traditionally grown in certain region will no longer survive there. Viticultural regions are defined by a relatively narrow geo- graphical strip in the middle latitudes between 12 o C and 22 o C average daytime temperatures. While other plants and agricultural products may be grown and produced in nearly every corner of the world, wine grapes are very fussy and can only be grown in certain niches or microclimates in order to produce the quality wine accepted today. Vitis vinifera grapes are known to grown anywhere from 13 o C– 15 o C, as we see in cool -climate grapes such as Müller-Thurgau or Pinot Gris, to 17 o C–24 o C, as we see in hot-climate grapes such as Zinfandel and Nebbiolo. Most wine grapes are grown within a 10 o C range, between 12 o C and 22 o C, while other variet- ies are more sensitive and can only grow within a much smaller temperature range in order to produce quality wines. Due to the sensitivity of a lot of V. vinifera grapes, increases in local tempera- tures could spell disaster. Take Pinot Noir for example: Unlike some more temperature- hardy grapes, Pinot Noir can only grow in a very narrow 2 o C range, between 14 o C and 16 o C, as we see in Burgundy or in northern Oregon. Of course, the plant itself can grow in a wider temperature range; however, in terms of wine quality, any devia- tion from this 14 o C to 16 o C range will result in lower quality wines and thus a negative influence on the local wine industry. If global temperatures rise higher than the predicted 2 o C increase in the best case scenario, we'll likely see that regions like Burgundy and Oregon may no longer be able to produce quality Pinot Noir wines due to the fact that temperatures in that region are no longer in the ideal range. On the other hand, climate change does not spell doom and gloom for every wine region. In fact, newer wine regions in locations that were historically too cold will likely see temperatures increase to a point where they are now in the "longitudinal sweet spot" for grape growing. Rising global temperatures will ultimately lead to an upward shift of the ideal grape-growing zone throughout the world, markedly changing local wine industries either for the worse in the case of those already teetering on being too hot for grapes, or for the better for those that were historically too cold but now are within that 10 o C range for quality wine grape growth. Models also predict that brand new areas could be suitable for wine grape growing that had not been considered in the past, like Yellowstone or the Yukon. If nothing changes in terms of mitigation of climate change and the models play out as they are currently showing, by 2100 the United States will likely see an 81% reduction in suitable wine grape acreage (White et al, 2006), with upwards of half of the current acreage in Napa and Santa Barbara counties lost by 2040 (Diffenbaugh et al, 2011). Sea Levels and Precipitation Not only are rising temperatures themselves a direct problem, but these increases also result in the melting of the polar icecaps and high-altitude snow packs, thus raising sea levels and changing ocean currents. Since ocean currents are a major driver of weather throughout the globe, any change in this current may change weather patterns and spell disaster for industries relying on the weather for maximizing product quality—like grapes and wine. Current models predict that global sea levels may rise any- where from 0.2m to 4m. At 5m, models show lower-lying grape growing regions such as Bordeaux, Portugal, New Zealand, parts of Australia and parts of California will see increases in flooding by sea water, resulting in increased salinity in the soil and ham- pered vine growth. In terms of precipitation, current models project decreases in precipitation in sub-tropical regions, while at the same time increases in precipitation in higher northern latitudes and near the equator. Drought pressures will continue to be seen in certain regions, as we've seen already in Australia and in much of California and now Washington State and throughout the Pacific Northwest. Increased precipitation events could lead to increased erosion in the vineyards, as well as decreased nutrient availability in the vineyard soil, ultimately hampering vine growth. Climate change—be it brought on by anthropomorphic sources, the natural cycle of the earth, or a combination thereof—is and will continue to have a significant influence on global ecosystems, including agricultural and viticultural systems. Since the beginning of the 20th century, we have already seen increases in atmospheric CO 2 levels and a global temperature increase of 1.4˚C, with two- thirds of that increase occurring since 1960, and models predict even further increases even in the best-case scenarios.

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