How is a warming climate changing where and when wine grapes grow?

It is pushing the wine map and the wine calendar around. Wine grapes grow mainly between 30 and 50 degrees latitude north and south, but climate change and advances in viticulture are increasing the area under vine elsewhere. Global warming has also shifted the harvest season in some countries. Some vineyards may pass a climatic threshold that makes it harder to keep current wine quality, while some regions could be pushed into more optimal conditions.

Why does heat matter so much? Of all environmental factors, temperature seems to have the most profound effect on viticulture. Prolonged high temperature can harm the development of the components that give grapes colour, aroma, sugar accumulation, acid levels and flavour compounds. Hotter temperatures and an earlier growing season can push berries towards more sugar, less acid and different aroma compounds. Temperatures around or above 35 degrees Celsius stall anthocyanin production, the pigments that colour red wine, and degrade those already made.

The vines are also a thermometer. Records of grape harvests in Europe have been used to reconstruct summer growing-season temperatures going back more than 500 years.

Growers are adapting. In 2021, controversially, growers in Bordeaux were authorised to trial four red and two white vine types from elsewhere in France, up to 10% of the final blend. Others are experimenting with rootstocks that use water more efficiently under stress, or adapting practices from warmer regions.

There are winners as well. English viticulture revived from the 1970s, possibly helped by rising local temperatures, and in 2004 a panel judging European sparkling wines gave most of the top ten places to English wines, with French Champagnes taking the rest.