The addition of a quadratic term, to account for potential optimum growing season temperatures, significantly refined the results of the linear specification and indicated that many regions may be at or near their ideal climates (Table IV). First, for most wine regions the quadratic estimates of (Equation 2) increased R2 values by a mean of 35% over the linear specification (median increase of 13%). For instance, the explained variance for the Rhine Valley improved from 0.60 to 0.72; andforSaint-E ́milionandPomeroltheincreasewasfrom0.39to0.54.Figure3 shows examples of predicted optimum growing season average temperatures for the Alsace region, the Loire Valley (sweet white wines), Bordeaux, and Barolo. For the four regions depicted, the predicted optimum growing season temperatures for the best wine quality (Equation 3), ranged from 13.7 ◦C for the Alsace region, 16.7 ◦C for the Loire Valley, 17.3 ◦C for Bordeaux, to 18.6 ◦C for Barolo (explained variances range from 0.48–0.72). Therefore, it appears that the general rule of thumb “the warmer the better” does not necessarily apply for even cool climate wine regions. The variation about the prediction lines indicates that, even when