Aims: The impact of water deficit stress on vine shoot growth, berry weight, grape composition and overall vintage quality was investigated in Bordeaux vineyards. Methods for assessing water deficit stress were compared.Methods and results: Vine water status was assessed on three soil types during four vintages by means of stem water potential and carbon isotope discrimination measured on grape sugar. Regional water deficit was compared for a range of over 30 vintages by means of water balance modelling. It was shown that water deficit stress anticipated shoot growth slackening, limited berry weight and enhanced berry anthocyanin content. Berry sugar content was greatest when water deficit was mild. It was shown that stem water potential measurements and carbon isotope discrimination are accurate tools for assessing vine water status at plot scale. Seasonal water deficit at a regional scale can be correctly estimated by water balance models. Vintage quality in Bordeaux is determined by the intensity of water deficit stress rather than by the level of the temperatures.Conclusions: Vine phenology and grape ripening are highly dependent on water uptake conditions. Mild water deficit stress enhances grape quality for the production of red wines. Vine water status can accurately be assessed by means of stem water potential or carbon isotope discrimination measured on grape sugars. Quality losses through severe water stress can be avoided through the use of drought-adapted plant material, appropriate canopy management, yield reduction or the implementation of deficit irrigation.Significance and impact of the study: This study shows the key role of water deficits in the production of quality grapes for red wine production. Methods for assessing vine water status are compared and discussed. Among many existing methods, the accuracy of stem water potential, carbon isotope discrimination measured on grape sugar and water balance modelling are emphasized.

Climate change is affecting grape yield, composition and wine quality. As a result, the geography of wine production is changing. In this Review, we discuss the consequences of changing temperature, precipitation, humidity, radiation and CO₂ on global wine production and explore adaptation strategies. Current winegrowing regions are primarily located at mid-latitudes (California, USA; southern France; northern Spain and Italy; Barossa, Australia; Stellenbosch, South Africa; and Mendoza, Argentina, among others), where the climate is warm enough to allow grape ripening, but without excessive heat, and relatively dry to avoid strong disease pressure. About 90% of traditional wine regions in coastal and lowland regions of Spain, Italy, Greece and southern California could be at risk of disappearing by the end of the century because of excessive drought and more frequent heatwaves with climate change. Warmer temperatures might increase suitability for other regions (Washington State, Oregon, Tasmania, northern France) and are driving the emergence of new wine regions, like the southern United Kingdom. The degree of these changes in suitability strongly depends on the level of temperature rise. Existing producers can adapt to a certain level of warming by changing plant material (varieties and rootstocks), training systems and vineyard management. However, these adaptations might not be enough to maintain economically viable wine production in all areas. Future research should aim to assess the economic impact of climate change adaptation strategies applied at large scale.

Records of grape harvest dates (GHDs) are the oldest and the longest continuous phenological data in Europe. However, many available series, including the well-known (Dijon) Burgundy series, are error prone because scholars so far have uncritically drawn the data from 19th century publications instead of going back to the archives. The GHDs from the famous vine region of Beaune (Burgundy) were entirely drawn from the archives and critically cross-checked with narrative evidence. In order to reconstruct temperature, the series was calibrated against the long Paris temperature series comprising the 360 years from 1659 to 2018. The 664-year-long Beaune series from 1354 to 2018 is also significantly correlated with tree-ring and documentary proxy evidence as well as with the central European temperature series (from 1500). The series is clearly subdivided into two parts. From 1354 to 1987 grapes were on average picked from 28 September on, whereby during the last 31-year-long period of rapid warming from 1988 to 2018 harvests began 13 d earlier. Early harvest dates are shown to be accompanied by high pressure over western–central Europe and atmospheric blocking over Denmark. The 33 extremely early harvests comprising the fifth percentile bracket of GHDs are unevenly distributed over time; 21 of them occurred between 1393 and 1719, while this is the case for just 5 years between 1720 and 2002. Since the hot summer of 2003, 8 out of 16 spring–summer periods were outstanding according to the statistics of the last 664 years, no less than 5 among them within the last 8 years. In the Paris temperature measurements since 1659, April-to-July temperature reached the highest value ever in 2018. In sum, the 664-year-long Beaune GHD series demonstrates that outstanding hot and dry years in the past were outliers, while they have become the norm since the transition to rapid warming in 1988.