HI was introduced to describe how climate affects winemaking with a certain variety of grape [1]. To calculate this index, we take the daily mean and maximum temperatures relative to a baseline of 10° (negative values are made equal to zero) from 1 April to 30 September in the Northern Hemisphere (1 November to 30 April in the Southern Hemisphere) with a coefficient , related to the length of the day. The Huglin index is thereby given by:

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All temperature data was obtained from the Wolfram database.

Select a location to show temperature data and the variation of the HI index since 2000. The five locations considered either have an established tradition of winemaking or a developing industry (such as Yinchuan in China). Asti in Italy has over one hundred years of winemaking experience.

The HI index has been used here in a somewhat imprecise way. The values of the temperatures must actually refer to more localized areas, such as specific vineyards.

The results described in this Demonstration will be used by fourth-year students in the "MAD FOR SCIENCE" competition, a national award to find the best science project among high schools in Italy, to determine how climatic stress influences the chemical composition of wine, specifically polyphenols, sugars, etc. The objective is to choose, for a specific area, which vines are most resistant to the new climatic conditions and thereby to improve the quality of the final product.