Future projections for chilling and heat forcing for European vineyards

Aims: The aims of this study were: (1) to compute recent-past thermal conditions over European vineyards, using state-of-the art bioclimatic indices: chilling portions and growing degree hours; (2) to compute future changes of these thermal conditions using a large ensemble of high-resolution climate models.

Methods and Results: To assess grapevine chilling and forcing conditions, chilling portions (CP) and growing degree-hours (GDH) indices were computed for the baseline period (1989–2005) and for the future RCP4.5 and RCP8.5 scenarios (2041–2060), using several regional-global climate model chains. These calculations also considered model uncertainties and biases. These indices were extracted to the current location of vineyards, in Europe and CP-GDH delimitations were assessed. For the baseline period, higher CP values were found in north-central European regions, while lower values tend to occur on opposed sides of Europe (east-west). Regarding forcing, southern European wine regions currently display the highest GDH values. Future projections depict lower CP in southwestern Europe (-45%) and higher CP (+30%) in Eastern Europe. For GDH, most of Europe is projected to have greater values (up to +30%). 

Conclusions: 

These changes may bring limitations to some of the world’s most important wine producers, such as Spain, Italy and Portugal. Nevertheless, a timely planning of appropriate adaptation measures may aid mitigating future yield/quality losses and improve the future sustainability of the winemaking sector. 

Significance and Impact of the Study: Temperature is a fundamental factor affecting plant growth and development rates. Grapevines have thermal thresholds for adequate growth, physiological development and phenology. Given the future projections for Europe, it is evident that grapevine productivity may be particularly vulnerable to climatic change.  As such, it become imperative to study how future temperature conditions will affect vineyards in Europe, namely the chilling and heat forcing conditions.