Winegrowing in a Warming Climate

Winegrowers all over the world are seeing the effects of a warming climate with earlier bud break and harvest dates, higher levels of sugar and lower levels of acidity. Many are already working to adapt their cultural practices to higher temperatures and considering more heat tolerant varieties when they replant. Over time, as temperatures continue to rise, some varieties will no longer be suitable in regions where they have been grown for centuries, while new wine regions farther north (farther south in the Southern Hemisphere) will blossom.

We provide our growing list of winegrower clients with the insights they need to make good decisions about how to deal with the changing climate. Our projections are localized to their vineyards and variety specific. They include key bioclimatic indices, in addition to temperature and rainfall, that help them understand how changing climatic conditions will affect the grapes they are growing.

For example, the graph below shows the projected decadal mean number of days with temperatures of 95° F or greater during the 45 days prior to maturity for Cabernet Sauvignon in a vineyard in Rutherford in the Napa Valley. Since the rate of climate change is uncertain, we use an ensemble of downscaled climate projections to represent the range of possible outcomes. The ensemble mean, the average of all of the projections, can be thought of as the “middle of the road” scenario, while the 10th and 90th percentile values illustrate the range of possibilities represented by the projections within the ensemble.

The ensemble mean is projected to increase by sixty percent over the next several decades while the 90th percentile will increase at a more rapid pace by a factor of 2.5. In the decade from 1996 to 2005, the highest temperature on 1 day in 4 of the 45 days before maturity equaled or exceeded 95° F. In the decade from 2036 to 2045, 1 in 3 will at the ensemble mean and more than 1 day in 2 will at the 90th percentile. In addition, the corresponding number of days for the warmest years of each decade will be greater than those for the decadal mean for both the ensemble mean and the 90th percentile.

For more information about the climate your vineyards will experience over the next several decades, contact Argos Analytics at

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