The relationship between drought and temperature, previously so crucial in determining the timing of French wine grape harvests, has weakened in recent decades due to climate change, reports a paper published online this week in Nature Climate Change. The study shows that enhanced warming is generating the high temperatures needed for early wine grape harvests in France, in the absence of drought, with possible implications for vineyard management and wine quality.

Warmer temperatures tend to accelerate wine grape maturation, whereas increased precipitation tends to delay it. High-quality French wines are typically associated with early harvest dates.

Benjamin Cook and Elizabeth Wolkovich use historical harvest and climate data to show that, from 1600 to 2007, early grape harvests in France and Switzerland occurred with higher temperatures during spring and summer, but were delayed by wet conditions. However, they find that the relationship between harvest timing and drought - previously needed to generate the high summer temperatures required for grape maturation in Western Europe - has broken down since 1980. Extreme heat now occurs more frequently due to enhanced warming from anthropogenic greenhouse gas emissions, without drought conditions. Using wine quality ratings of vintages from the Bordeaux and Burgundy regions over the past 100 years, the authors also find that the relationship between wine quality and drought has weakened since 1980.