Climate change and the quality of wine: a preliminary study on Collio whites

Italy is the biggest wine producer worldwide, followed by France and Spain (OIV, 2022). With a total value of about 3.8 billion euros in 2021, wine is also the most important agricultural vegetable production in Italy (CREA, 2022). Italian wines benefit from significant protection within the European Union (EU) quality schemes: out of the 3,069 registered product names classified as Geographical Indications (GIs), 526 pertain to Italian wines (Rosati and Del Bravo, 2022). The variety of terroirs across the Italian peninsula defines the quality and identity of its wines. The concept of terroir refers to the broad set of environmental conditions (soil, climate, topography, site-specific microbiome) whose interaction with human activities defines the sensory characteristics of agricultural products, most notably wine (van Leeuwen and Seguin, 2006). Consequently, similarly to any other agricultural product, the quality of wine closely depends on both controllable, or relatively stable over time, and uncontrollable factors. While oenological practices and processing technologies largely influence the quality and features of the final product and have the potential to limit defects, excellent grapes and musts are essential to produce high-quality wines (Reynolds, 2010; Reynolds, 2021). As a consequence of this peculiar combination of controllable or relatively stable variables (e.g. wine-making processes, soil composition, geomorphological features) and external factors outside the control of wine growers and winemakers, together with the time gap between grape production and release on the market, predicting quality of the final product is particularly challenging (Corsi and Ashenfelter, 2019). Furthermore, uncertainty has increased in recent years due to climate change, growing weather variability and extreme weather events (van Leeuwen and Darriet, 2016). Several scholars have addressed the issue of limited predictability of final outcomes, and proposed different econometric models to illustrate and assess the effect of meteorological variables on wine quality (Byron and Ashenfelter, 1995; Jones et al., 2005; Ashenfelter, 2010; Ashenfelter and Storchmann, 2016; Corsi and Ashenfelter, 2019), in an effort to concurrently support winemakers' formulation of pricing strategies and facilitate buyers' purchase and investment decisions. Nevertheless, “wine equations” have traditionally been based on red varieties, while it is well known that different effects are to be expected for white varieties, so much different that, in some extreme cases, they might even suggest the ones with the others. Therefore, it is interesting to focus on the difference between climatic effects on the quality of white and red varieties. As is usually the case, doing so in an otherwise homogeneous context can be of great help in isolating the effect of interest. The focus of our study is the analysis of meteorological variables as antecedents of white wine quality in the Collio region, Northeastern Italy. Located in close proximity to the mythical 45° Parallel North, which runs through the most important wine-producing regions in the Northern hemisphere (Patic et al., 2009), Collio is famous for the outstanding quality of its whites, within a country most famous for its reds. The research presented in this manuscript is the first to address the estimation of a Bordeaux equation à la Ashenfelter in a panel context, drawing on a large sample of varieties from the same region, including, crucially, both whites and reds. The results, in terms of the predicted consequences of global warming on the quality of Collio wines, are relevant to producers and policymakers of the region, whose economy relies on the production of its celebrated whites.