Asymmetric warming over coastal California and its impact on the premium wine industry

Climatic changes over coastal California from 1951 to 1997 may have benefited the premium wine industry, as seen in higher quality wines and larger grape yields. Observed temperature warming trends were asymmetric, with greatest warming at night and during spring. Warming was associated with large increases in eastern Pacific sea surface temperatures (SST) and amounts of atmospheric water vapor. Although the average annual temperature warming trend was modest (1.13°C/47 yr), there was a 20 d reduction in frost occurence and a 65 d increase in frost-free growing season length. In the Napa and Sonoma valleys, warmer winter and spring temperatures advanced the start of the growing season by 18 to 24 d, and enhanced atmospheric water vapor resulted in a 7% reduction in evaporative demand. Given the strong coupling between Pacific SSTs and the coastal California climate, and because regional-scale SSTs persist for 6 to 12 mo, additional research may allow the possibility of predicting vintage quantity and quality from previous winter conditions.