Climate change may be a political issue for candidates running for public office, but not for farmers, especially wine-grape growers. They examine both short term and long term weather data, anticipate and witness its effects on the plants, and make adjustments in trellising, irrigation, and picking among hundreds of decisions that ensure the health of the plants and quality of the fruit. In other words, farmers devote themselves to direct observation and practice, not theory.

Since the ancient Romans first planted vines on the Italian Peninsula and then everywhere else they colonized, the European climate has experienced cycles of warming and cooling of various durations, which have dramatically impacted vineyards. Long-term weather patterns of an area have always been crucial quality predictors for vineyards and vineyard planning and whether vineyards are even viable in a certain area at a given time.

Wine-grapes require a relatively narrow band of temperatures that at the cooler end of the spectrum will produce light and delicate wines and at the warmer end full-bodied sweet wines. Different grape varieties will thrive and ripen at various points on the spectrum. Apart from fruit flavor and aroma,temperatures influence the balance of acids,alcohol, and phenolics, including color, tannin,and flavor compounds. Heat totals particularly during the growing season are important, together with temperatures during the final month of ripening. Daily temperature variability and variability between night and daytime influence quality, with equitable temperatures being most desirable. Rainfall,humidity and evaporation, and wind also influence vineyards.

Twenty years ago in California, it was not unusual for late-ripening Cabernet Sauvignon to hang on vines until November. Now Cabernet ripens in mid August. According to the National Oceanic and Atmospheric Administration,last year was the warmest ever recorded up to then in California, Arizona, Southern Nevada, and parts of Southern and Coastal Oregon. This year, the entire West Coast and Nevada had even warmer temperatures January through June.

While different grape varieties require different temperatures, no California wine region is dependent upon any single grape.Even Napa, whose entire reputation is built on Cabernet Sauvignon, is home to other grape varietals, like Sangiovese and Syrah, among other varietals. If Cabernet is no longer viable there, other more suitable varietals can replace them, and they will have a history in that area. More and more grape varieties from hot and arid Spain are being planted throughout California. What a good idea.

Iconic Bordeaux, which depends on just Cabernet Sauvignon, Merlot, Cabernet Franc, Petite Verdot, Malbec, and Carmenere and the whites Sauvignon Blanc, Semillon, Muscadelle, Ugni Blanc, and Colombard, is in the midst of a research program, fermenting small batches of wines from an experimental vineyard, growing 52 grape varieties unknown in the region. Run by the French National Institute for Agricultural Research and supported by the Bordeaux Wine Council, Bordeaux winemakers are preparing themselves if, in20 years, traditional grape varieties areno longer viable. This research could potentially save a wine region and an industry that produces between 600to 800 million bottles of wine a year, shipped to over a hundred different counties.