GALILEO GALILEI, it is said, described wine as “sunlight, held together by water”. Today’s winemakers can only agree—at their own expense. Wine grapes are highly sensitive to climate. Too much heat and they accumulate excess sugar, producing overly alcoholic and flabby wines. Not enough and the fruit turns into tart, acidic liquor. That is why most wine regions are in areas where average temperatures fall between 12°C and 22°C during the growing season (April to October in the northern hemisphere; October to April in the south), These lie at latitudes of 30° to 50°. As the planet warms up, however, those bands are moving towards the poles (see map). A recent study reckons that the northern frontier of vine cultivation in Europe could advance by 20-60km each decade between now and 2050.

This has led some scientists to predict the extinction of wines that are nearly synonymous with the liquid itself, such as Burgundy’s pinot noirs or Bordeaux clarets. In contrast, those who tend to see glasses as half-full expect a new wave of grands crus to emerge from previously unlikely terroirs such as Sussex and Scandinavia. Many of today’s top estates are already under pressure. Vintners are harvesting their grapes three weeks earlier than they did the 1960s. More of them are forced to harvest at night, to ensure the heat of summer days does not cause grapes to oxidise. Canadian producers are planting vines farther and farther north. Argentina’s cellar masters are venturing as far south as Patagonia. And, in Chile, where wine regions are named after valleys, growers are heading for the country’s cooler hills.

A warmer climate is welcome news for northern European winemakers. But a warmer Denmark might also be a wetter one. Rain is helpful in winter and early in the season, but too much of it in the summer or early autumn results in watery grapes and a weak vintage. Excessive humidity can also bring disease, fungus and pests.

Climate change brings other risks too. Vineyards at higher latitudes may be more vulnerable. In 2014 the polar vortex—a huge area of cold air around the North Pole that drifted south—wiped out entire vineyards in Ontario and New York state. The weather will become harder to predict. In recent decades, a study released in July shows, extreme temperatures have become more frequent in wine regions (see chart). Vines are being more exposed to frost in spring and heat waves in summer. They are also seeing fewer days without rain, even in supposedly dry regions (see next chart). Both climate change and the industry’s efforts to adapt make it hard to guess which regions will be cultivated—or culled—by 2050. Insiders believe Bordeaux vintners have ways of mitigating climate change’s consequences if average global temperatures do not rise to more than 2°C above pre-industrial levels. These tend not to be particularly high-tech: shade netting helps protect grapes from fiercer sunshine; training vines higher puts them farther from rocky soils, which tend to radiate heat at night.