How does climate change affect French wines?

I have written in the past about climate change and viticulture, but 2026 is the year in which the news channels seem to be talking about it every day. We have had wildfires in Languedoc, Roussillon and, notably, Bordeaux. We have had heatwaves, with daytime temperatures reaching 40°C and not falling below 24°C during the night. 

Almost every wine region started its harvest earlier than ever. Some as early as July. Traditionally, the grape harvest in France was in September and October.

Climate change means hotter and longer heatwaves, increased humidity in mid-summer, more intense storms, prolonged heavy rain resulting in flooding and long periods of very little rain, leading to drought conditions. It is the extremes and the length of abnormal periods that cause problems for agriculture. 

Plants generally fare best when seasons change in a regular manner. They don’t cope well with varying conditions and extremes. There is only so much that farmers can do to moderate the impact of a rapidly changing climate. Vignerons in the Languedoc-Roussillon have suffered drought since 2021. This year we rejoiced to see heavy rains refilling the water table over winter, but since the end of May temperatures have been higher than in previous years and predicted summer rains did not materialise. Similar stories have been repeated across all wine regions. What are the consequences for wine in these extreme conditions?

Drought causes vines to produce fewer and smaller grapes. It can also cause them to stop ripening, as they slow down photosynthesis to retain water, making it difficult to predict when to harvest. Grapes don’t ripen once picked, unlike other fruits, so getting the harvest date correct is very important. While vines do produce better wines when their access to water is restricted, prolonged, extreme drought will reduce the quality along with the quantity and eventually kill vines, even old ones. Heavy storms, particularly hail, can damage the grapes. If hit by hail close to harvest, the vintage can be ruined. Even during the growing season, they can lead to waterlogged soils, too much shoot growth and make it difficult to drive tractors down the rows.

Successive heatwaves and elevated temperatures throughout the growing season will, in the absence of drought, cause grapes to ripen more quickly. Ripening is a combination of increasing sugar content, decreasing acidity and the development of flavour. With black grapes for red wine, the ripening of tannins in the skins and the pips is very important for texture, aroma and longevity of the wine. This is known as phenolic ripeness. 

Traditional red wines, especially those capable of improving over time, are produced by soaking the skins during and after fermentation for weeks. Grapes which lack phenolic ripeness will produce astringent flavours in the wine if they are soaked in the usual way. Winemakers may choose to remove the skins early, by pressing the red wine after just a few days, to avoid this and make a lighter-bodied red wine, similar to a strongly coloured rosé. 

Alternatively, they may add a range of fining agents which can reduce astringent and bitter tannins. Gelatine is the most common fining agent, but casein (from milk), egg white, isinglass and several vegetable protein powders are also used. But they can strip flavour and body.

When grapes ripen more quickly due to higher temperatures, they gain sugar before developing flavour and reach the normal sugar-acid levels without reaching phenolic ripeness. The vigneron is faced with the choice of picking early and dealing with unripe tannins and flavours, or picking at the normal time and dealing with increased sugar levels (and therefore higher alcohol) and a lack of acidity, with a heavier, more flabby structure. Long, slow ripening produces the best wines.

The wildfires close to Bordeaux have raised the question of whether the smoke will affect flavour. Smoke taint is a complex problem. The grapes may not taste smoky, nor the fermenting juice show signs of taint. But phenolic chemicals in wood smoke can combine with sugars in the grapes in a process called glycosylation to produce molecules that transform during and after fermentation to develop aromas of smoke, ash or burnt wood many months later. This glycosylation process can be several weeks before harvest. As far as I know, there are no methods of removing smoke taint from wine once it is present.

Wine labs provide analytical services to test grapes for these chemicals, alerting vignerons to the level of risk. This allows a producer to eliminate grapes from the harvest or keep those wines separate to see if taint develops. It’s a balancing act that depends on how much the estate values reputation by eliminating the risk of taint versus producing enough wine to meet demand or balance books. The analysis isn’t free and takes time. Lower-quality estates may decide not to bother.

One would assume that the top châteaux would not take the risk. They may decide to take the hit and simply not harvest affected parcels, produce a separate wine from the doubtful vineyards and see how it turns out, or sell off those grapes to less quality-focused producers and négociants. 

On the other hand, an estate without much reputation will be faced with how much risk to take by harvesting and combining grapes that may taint the wine versus producing less wine and therefore reducing revenue or losing contracts, which depend on certain volumes. 

Although Bordeaux may be famous for its top châteaux, like Mouton-Rothschild, Lafite and Margaux, the vast majority of consumers drink Bordeaux wines that cost under €5 and come from either little-known estates or are blended by négociants from grapes and wines of many growers. I can only hope that those consumers quite like a little smoky character or the taste of charred wood.

Effects of climate change don’t necessarily mean wines produced in those areas will be worse. Vignerons and winemakers have tools at their disposal and choices to make to mitigate effects. However, only producers sufficiently focused on quality and with enough financial resources to make sacrifices will be able to avoid the negative impacts. 

Consumers must be more conscious of reputation when buying from regions affected. They can’t assume lower-priced wines will be of the usual standard, nor should they write off a vintage from a reputable producer. What we can’t expect is that wines from such a year will have the characteristics of a normal vintage.

Jonathan Hesford has a Postgraduate Diploma in Viticulture and Oenology from Lincoln University, New Zealand and is the owner, vigneron and winemaker of
Domaine Treloar in the Roussillon.
If you have questions on this wine column, email info@domainetreloar.com