Climate Change and Wine

Jane Masters MW is Opimian’s Master of Wine


For centuries wine growers in classic regions have painstakingly kept empirical records in order to understand the impact of soil and climate on wine quality and to classify vineyard sites. Over many years grape varieties were matched to specific growing conditions, and viticultural practices evolved to produce the style and quality of wines specific to a given region. As new areas were pioneered, these were most often identified and developed due to cumulative knowledge gained in traditional regions. Now that the climate is changing, should we as wine consumers be concerned?


There is no doubt climate change is having an effect. Some northern European winemakers may feel a positive effect for the time being. Warmer summer temperatures mean their grapes ripen more easily than they used to, although certain critics would argue that wine styles have changed. Certainly, German wines have become higher in alcohol, drier in style, more fruity and less acidic. Depending on your point of view, this could be seen as a positive or a negative. And the UK sparkling wine industry has flourished in recent years, even though English summers remain erratic for ripening grapes. But many other regions are seeing higher temperatures, heat spikes and drought.


Grape varieties have different tolerances to temperature, and the band within which they produce quality grapes can be more or less narrow. A given grape variety will produce very different flavours in warm vs. cool climates. Sauvignon Blanc delivers grassy mineral wines in Sancerre in the Loire, gooseberries and passionfruit in New Zealand, and ripe, fatter, heavier styles in California. Warmer temperatures result in faster sugar accumulation in grapes, potentially leading to higher alcohol wines. Tartaric and malic acid naturally present in grapes also drop as temperatures rise. The combination of high alcohol and low acidity can result in a dull, flabby wine.


From a winemaker’s point of view, what we call phenolic maturation—the development of skin pigments and tannins in black grapes—should ideally occur at the same time as target sugar and acidity levels are achieved. But as temperatures increase, the synchronisation becomes harder. And if the temperature gets too high, a vine’s metabolism closes down altogether; so really hot conditions can result in wines that are both high in alcohol and reveal unripe, green flavours.


To produce quality grapes, vines need dormancy in winter, which is stimulated by the cold. Warmer winters lead to earlier bud break, making vines more susceptible to late-spring frosts, affecting yields. Warmer winters also have an impact on fungal diseases, insects (which are vectors for disease)and other pests.


Climate change also causes drought. Vines need water, either through rainfall or through irrigation where permitted. And the higher the temperature, the more water needed to produce quality grapes. Even where irrigation is allowed, water reserves are finite. On top of this, running a winery consumes a large quantity of water. Governments and local municipalities may have to restrict allocations and be forced to choose between supporting agriculture, businesses and their residents. During the severe water shortage in the Cape in South Africa in 2018, the population was restricted to a total of 50L a day.


Long periods of drought in Australia, California and Spain no doubt contributed to the severity of wildfires, with some loss of vineyards, and potential issues of smoke taint affecting wine quality. Extreme natural events including freak storms, hail and flash floods can wipe out a crop and the livelihood of growers. Climate change makes these more frequent—growing grapes and making wine is becoming a riskier business.


Vineyards are usually planted a minimum of 20 years for the long term and many for much longer. These are often small holdings owned and farmed by families for whom wine is part of their culture and way of life. Wine growers see themselves as custodians of the land they farm for future generations—the very definition of sustainability. Wine growers are adapting to mitigate the impact of climate change. Researchers are developing more drought- and heat-resistant grape varieties. The wine trade has started to work more collectively with associations such as the Porto Protocol on addressing the challenges of climate change and minimizing the wine trade’s contribution to it. We as wine drinkers can support them by continuing to enjoy wine—I, for one, am doing my bit!