The Bordeaux barometer: Cool vs hot vintages

As technological advances make it easier to deal with variable weather conditions, Jane Anson assesses the impact of hot and cool vintages in Bordeaux and offers advice on what to buy – whatever the weather...

The Bordeaux barometer: Cool vs hot vintages

When you first learn about Bordeaux, you are told one very simple rule: this may be southwest France but it’s also a port city close to the Atlantic, and so has an oceanic climate. This fact governs the next rule, which is: because of the climate, Hot Years are good, and Cool Years are challenging.

But what does that actually mean in terms of how the wines taste – and is the maxim even true any more given both climate change and new techniques in both the vineyard and cellar?Looking back, it was the hot years that were always the most acclaimed: 1870, 1921, 1929, 1947, 1949 (the hottest summer since 1929), 1961, 1982, 1989 (hottest summer since 1949), 1990 – and more recently 2005, 2009 and 2015. The cooler years, such as 1963, 1968, 1974, and more recently 1992 and 2013, have been dismissed.Perhaps it was 2003 that made everyone reconsider the simple formula, although I could also point to 2001, which was relatively cool but dry, and produced exceptionally elegant wines that often beat the more foursquare 2000 today – even though that was the hotter vintage.‘Dry versus wet is almost certainly a more accurate indication of quality today,’ says Guillaume Pouthier at Les Carmes Haut-Brion – although he admits that having a vineyard which ripens early due to its warm location was extremely helpful in 2017. That year he had finished harvesting by the time the rains arrived in mid-September (and he hadn’t been affected by frost earlier in the season, giving him a double advantage).

Axel Marchal at the University of Bordeaux’s Institute of Wine and Vine Science agrees. ‘The idea of hot and cold is definitely important, but mainly at key moments rather than an accumulation of temperature across the whole growing season – essentially this means at budding, flowering, colour change and harvest. You also want a good swing of day and night temperatures during ripening to allow the grapes to build up to harvest slowly and develop complexity,’ he expains.

‘But more than temperature, it’s the amount of sunshine and rain that is absolutely key – so we can learn a lot about the quality of a vintage by assessing how much rain falls at key moments,’ adds Marchal.

So what does all this mean in the glass?

Hot and/or dry years

In a hot year, everything ends up more concentrated – so higher alcohol levels, lower acidity, a rich, round mouthfeel and riper flavours. A classic hot year in Bordeaux will see notes of liquorice, chocolate, black cherry, exotic spices on the palate, even prune and fig if things are really extreme.

Even in very hot years, if there is enough of a night-time drop in temperatures, the grapes will retain freshness and so cellaring potential. If that acidity drops too low, the wine may taste good (if big) when young, but it is less likely to age well beyond the first five or 10 years.

‘For refinement and finesse, the grape must be able to rest, and slow down the ripening process,’ says Marchal. ‘So when we look at vintages such as 2003, clearly they were very hot, but that doesn’t mean that they were great, as the temperature remained constantly high day and night.’

2005 is a good example of why heat isn’t everything. It was extremely dry but not overly hot, which is why its wines show such amazing balance. 2010 could fall into the same category, as again it was very dry from August onwards, but without excessive temperatures and with impressive day-night swings. In fact, overall 2010 was not as sunny as 2015 or 2005. Temperatures through the summer dropped lower in the evening than 2015 or 2005, and yet the dry weather persisted and – particularly on the Left Bank – gave the grapes plenty of time to ripen, which is why you see such huge concentration and ageing potential in the final bottles, and why the best display a menthol freshness on the finish.

There are now plenty of technical options that a vine-grower can take to mitigate the worst effects of heat. Perhaps most importantly, leaf-thinning is best kept to a minimum to allow for shading of the grapes. The use of cover crops or growing grass between the rows is less useful in very hot years, because you want any allowable water supply to be able to get to the vines.

‘In 2011, we had a very dry summer, and I pulled up the grass growing between half of the rows,’ says Annabelle Cruse-Bardinet at Château Corbin in St-Emilion. ‘It was very successful and looking back I wish I had done it across the whole vineyard. But I know that the Corbin vineyard responds extremely well in dry years because we have reserves of water naturally and our clay-gravel soils have a good retention capacity.’

Another consideration is choice of grape variety. There’s a good reason that in recent years vineyards such as Château Dauzac and Château Branaire-Ducru (and in fact pretty much every big Médoc name) have been increasing plantings of Cabernet Sauvignon at the expense of Merlot – as have estates such as Châteaux Ausone, L’Eglise Clinet and Angélus with Cabernet Franc. It’s because these grapes retain freshness and structure better in hot years.

Selecting wines in hot years

When things are hot, you want to look for the coolest spots with well-regulated water supplies, often clay or limestone.

So, in the Médoc, St-Estèphe can do exceptionally well in these years, as it has more clay and limestone than the other big appellations – making Montrose a particular success in 2003, for example. Listrac-Médoc will produce extremely fragrant wines in hot years, as it has several spots of limestone and sand. The limestones of St-Emilion are also extremely forgiving in hot years, as this type of soil is near perfect for its regulation of water – think Clos Fourtet, Château Canon and Château Belair-Monange.

Cool and/or wet years

Cool and dry years are relatively rare in Bordeaux, although they tend to be very good when they come along, as long as the growing season is long enough and sunny enough for the grapes to fully ripen. More common – and clearly more difficult – are cool, wet years. Over the past decade or so, 2013 and 2007 are the most obvious examples. 1999 was another, particularly over on the Right Bank, where the harvest was cool and damp, while 1998 saw a similar problem on the Left Bank, but was excellent in St-Emilion and Pomerol.

In terms of flavour profile, a cool year will see fresher fruit flavours, higher acidities and lower alcohol. If conditions are also rainy, there are also likely to be green pepper or pyrazine flavours, as the grapes will not have ripened sufficiently to burn this molecule down to non-detectable levels.

There can also be issues with yield. This can be reduced if the temperature is too low during flowering, as the grapes will not set evenly or abundantly (temperature is more important than avoiding rain at this point). However rain in the summer can mean yields are high but the juice is not fully concentrated, because a vine will keep pushing out its green shoots as long as it has enough water to do so, and what we want during ripening is for all of that energy to go on the grapes, not the leaves.

To combat cool weather later in the season, growers can prune back the canopy cover, at least on the side of the afternoon sunshine, to ensure that the grapes receive the maximum amount of heat and light. In a wet year, allowing grass to grow between the rows can also mop up that extra moisture.

Selecting wines in cool years

In cooler years the importance of soils that restrict water and maintain heat is key. Sand, for example, can make great wines in hot years, but cool years are very difficult because sand just won’t get warm enough to ripen the grapes. Gravels are less challenging because they offer good drainage and may retain enough heat to allow the grapes to ripen.

In years when you see a cool or wet summer but a warm and dry late season, you almost always want to look to Pauillac, St-Julien and Margaux, because in those regions the gravel soils will retain any late-season sun and give the Cabernet Sauvignon time to reach its long, slow maturation. Just look at 2016 for an example of this effect in action. If this switches around, and the summer was good but rains came in late September or October, those same Médoc areas might not have had enough time to ripen, whereas the gravels over in Pomerol should have ripened up the Merlot grape perfectly.

Playing the odds

Take all of this, and throw in a little common-sense geography, and you suddenly have a pretty good road map to choosing wines. Benjamin Bois, a researcher and lecturer at the University of Burgundy-Franche-Comté, has divided Bordeaux into five temperature zones, and has found that the same grape variety sees a three- to four-day difference between one zone and the next. This means that the exact same grape variety can see a difference in reaching maturity of up to 20 days from the warmest to the coldest spot, something that clearly has an impact when assessing which areas have done well in particular vintages.

The vineyards that are almost systematically cooler than others are those found closest to the Landes forest in the Médoc (so parts of Listrac, Moulis, Médoc and western Graves), plus the northern reaches of Blaye, and the furthest eastern sections of Entre-Deux-Mers. At the opposite end the warmest parts of the region are found in Sauternes, the corridor along the river and estuary in the Médoc, Bourg, Pomerol, the plateau of St-Emilion and Pessac-Léognan.

The estuary clearly has a big impact, meaning that vineyards within a 15km radius of this body of water (which is 10km across as its widest point) feel the benefit of warmer temperatures. And then there’s the impact of urban centres, specifically that of Bordeaux itself, that ensures earlier ripening for the nearby grapes. Pessac-Léognan, for example, tends to ripen its grapes on average one week earlier than the rest of Bordeaux, and so in years where rains come in mid-September, it can have an advantage in that its grapes are already at a good ripeness – though conversely in extremely hot years growers have to be careful of keeping freshness.

‘Each vintage has its challenges,’ comments Jean-Claude Berrouet, who has been the winemaker for JP Moueix for over 40 years. ‘But sometimes the most rewarding to work on, and to drink, are the ones where the winemaker has to overcome the limitations of a specific plot of land. This is just as true in hot as in cool years.’

What to buy

Hot or dry years: 2000, 2003, 2005, 2009, 2010, 2015, 2016. These are the years when you have a good choice of terroirs; but the hotter the year, the more you want to look for limestone or clay soils that can ensure water supply to the vines, or for châteaux located next to the estuary, where the nights can help to retain freshness. Think Montrose, Canon, Clos Fourtet, Petrus and Latour.

Cool or rainy years: 1997, 2007, 2013. The best suggestion in these years is to focus on first, not second wines, as they will have benefited from the best selection. Also look at how and when the rain fell. If the vintage had a dry enough harvest period to allow a long and slow ripening, look for well-drained gravel soils; so Ducru Beaucaillou, Lagrange and most of the big Médoc classifieds. If the period during harvest was extremely rainy, then Cabernet Sauvignon may never have reached ripeness, and instead the warmest parts of Bordeaux should have fared better. So think Pomerol particularly, or Pessac-Léognan estates such as Brown or Les Carmes Haut-Brion.

Jane Anson is a Decanter contributing editor, Bordeaux correspondent and author of the book Bordeaux Legends.