Which of the following is classified as a Region I area on the Winkler scale?

The Winkler scale is a system used to classify grape-growing regions based on temperature and climate. A Region I area on the Winkler scale is characterized by a cooler climate, suitable for growing grapes that thrive in moderate temperatures, such as Pinot Noir and Chardonnay.

Carneros AVA is recognized for its cool climate, heavily influenced by the nearby San Pablo Bay, which leads to fog and cooler temperatures. This makes it an ideal environment for the cultivation of grape varieties that prefer a cooler climate, aligning it with the characteristics of Region I.

In contrast, the other options—Santa Barbara AVA, North Coast AVA, and Central Coast AVA—encompass a wider range of climates, including warmer areas, which allows for the production of varietals that are better suited to warmer conditions, placing them in higher regions on the Winkler scale.

Thus, Carneros AVA stands out as the correct answer because it is distinctly classified as a Region I area, renowned for its suitability for cool-climate grape varieties.