# A Review of the Potential Climate Change Impacts and Adaptation Options for European Viticulture
## 4 Potential Climate Change Impacts
### Climate Change Projections and Impacts on Grapevines
Although some studies suggest that the last frost events will move to earlier dates at a faster rate than budburst and, hence, reduce spring frost risk in the future [39], other studies were inconsistent or predicted increased risks for spring frost damage [37; 38; 40; 128; 129], indicating a high degree of uncertainty [80]. Although winter, spring, and fall frosts may threaten the economic sustainability of viticulture in a specific region/location and, hence, warming is considered as mostly positive, the production of ice wines is jeopardized. Ice wines are traditional premium wines of many cool climate regions that are produced when grape berries are exposed in fall or early winter to a frost event of \(-7\)\({}^{\circ}\)C, or below, and are pressed in the frozen status. In this case, water in the berries is in the form of ice crystals and the juice is then concentrated, leading to the production of these unique dessert wines. However, these conditions are expected to become increasingly rare in the future. This is mostly due to the combination of two effects: higher temperatures leading to earlier maturity, and the date of first relevant frost events (minimum temperature of \(-7\)\({}^{\circ}\)C or below) being delayed, or such events not even occurring in the future. Hence, ripe grapes have to sustain a much longer period until the freezing event occurs and the risk of severe berry decay and complete yield loss will thus increase [130]. In a comprehensive modelling effort, where a process-based crop model was coupled with climate, soil, and terrain databases, taking into account physiological effects of water supply and CO\({}_{2}\) concentration, European grapevine yields, phenology, water, and nitrogen stresses, both for present (1980-2005) and future (2041-2070) climate scenarios (Representative Concentration Pathway (RCP), RCP4.5 and RCP8.5), were analysed [98]. For current climates, the simulated components (e.g., yield and phenology) were validated against multi-site observations. For the future climates, the projected changes suggested an extension of the climatic suitability for grapevine cultivation up north to the 55\({}^{\circ}\) N parallel, thus creating the necessary conditions for the emergence of new winemaking regions at higher latitudes in Europe. The main phenological stages (budburst, flowering, veraison, and maturation) are projected to undergo significant advancements (\(>2\) weeks earlier), with implications for phenophase lengths between these stages [98]. Increased dryness throughout Europe was also projected, but with severe water stress over several regions in southern Europe (e.g., southern Spain, Portugal, and Italy), locally reduced yield and leaf area. Future biomass changes may lead to modifications in nitrogen (N) demands. Under future climate conditions, vineyards in Southern Europe may experience a reduction in biomass growth, owing to severe water stress. This will result in a high propensity of N deficit in Northern/Central Europe, under warmer and moist conditions [98]. In this context, increased atmospheric CO\({}_{2}\) may partially offset the dryness effects, promoting yield and leaf area index increases in Central/Northern Europe. The higher concentrations of CO\({}_{2}\) in the future are expected to have positive impacts on the grapevine development cycle and yield attributes [131; 132; 133; 134; 135; 136], although many uncertainties remain. Experiments conducted in free air carbon dioxide enrichment (FACE) systems have shown significant impacts of elevated CO\({}_{2}\) on, for instance, several vegetative growth parameters, primary productivity, grapevine bud fertility, and yield potential [135; 136]. Higher CO\({}_{2}\) concentrations may contribute to a decrease in plant transpiration rates, which may tend to compensate for increased soil evaporation [137], thus mitigating the evapotranspiration increase under future conditions [138]. Changes in UV-B radiation have been of concern in the past, due to alterations of the protective ozone layer.