Using historical climate data, model simulations of future climates, and vintage rat- ings, four central conclusions were reached regarding climate change implications for quality global wine production. First, from 1950–1999, growing season average temperatures have increased in the world’s high-quality wine producing regions by 1.26 ◦C. Second, while some of the trend in better quality can undoubtedly be at- tributed to better viticultural and enological (the science of the making of wines) practices, in the majority of regions, climate variations and trends were found to influence year-to-year variations and trends in vintage quality ratings: from 10–60% of vintage ratings were explained by growing season temperature variations with the greatest effects in the cool climate regions of the Mosel and Rhine Valleys of Germany. Third, based on a quadratic econometric modeling approach, 12 of the wine regions were found to have an optimum growing season temperature above which vintage ratings tended to decline, suggesting that the rule of thumb “the warmer the better” is not globally applicable. In addition, many of the wine regions for which the quadratic specification is significant have trended to their optimum, while some are already beyond the predicted optimums.