Exploring the influence of environmental variables on the quality ratings of four Californian wine varieties

Details

Supervisors

Iania, Leonardo

Faculty

Louvain School of Management

Degree label

Master [120] : ingénieur de gestion, à finalité spécialisée

Abstract

This paper examines the relationship between weather variables and the quality ratings of four wine varieties: The Californian North Coast Cabernet Sauvignon, Chardonnay, Zinfandel and Pinot Noir. The aim of this research is to identify weather variables that can explain a great proportion of the variance in the quality ratings, despite a limited impact on wines from regions with stable climates, such as California. To achieve this objective, rating qualities (Robert Parker Wine Advocate, 2023b) and weather variables (NCEI National Centers for Environmental Information, 2023d) were downloaded. The quality ratings were transformed to account for the fact that they are bounded between 50 and 100, and the weather variables were averaged over two counties (Sonoma and Napa) for greater precision. The weather variables used were the average temperature, the average temperature squared, the maximum and minimum temperature, the difference between the maximum and minimum temperature, the precipitation, and the Southern Oscillation Index (SOI). In this paper, a yearly and seasonal analysis is done to test whether by splitting the variables by season, the data fit the regression models better. The main finding of this research is that these weather variables do play a role in explaining the variations in wine quality. However, their role is quite limited. The adjusted R-squared of the models are highly influenced by a positive trend, that accounts for the improvement of qualities, not related to the climate variables. The difference between the maximum and minimum temperature and the SOI are the variables that are the most often statistically significant, apart from the trend, indicating they probably have a significant influence on the quality of the wine. Climate change will likely impact wine quality, and therefore vineyard production and profitability. It is thus crucial to assess the influence of weather on the quality of the different wine varieties, allowing winemakers to adapt accordingly.