The climate terroirist — Gladstones’ new bag

By Gareth Renowden 08/01/2012

Regular listeners to The Climate Show will know that I often witter on about what I’ve been up to in my little vineyard. At Limestone Hills we grow pinot noir and syrah grapes and make small quantities of wine. It’s more than drinkable. One day it may even be very good. If we get that far, it will be because our back paddock has an interesting terroir (and because we will have worked hard). It will therefore come as no surprise that I follow how the wine business approaches climate change with more than passing interest. A few days ago a local winemaker blogged about a new book. Wine, Terroir and Climate Change by Aussie scientist Dr John Gladstones, noting that Gladstones was “sceptical about the degree of climate change that will occur and thus the degree of effect on terroir“. Unsurprisingly, the usual suspects have rushed to welcome a new member to their ranks. I decided to do a little digging…

First: Gladstones. He’s an Australian agronomist, now 79, who wrote a hugely influential book in 19921 on climate and vineyard site selection. Viticulture and Environment approached the idea of terroir (though he didn’t call it that) through a consideration of the climatic influences on grape growing. By putting the climatic requirements of different grape varieties into the context of local and regional climates, he provided a burgeoning Aussie wine business with a very handy site selection tool.

In his new book Gladstones takes an exhaustive look at all the elements that contribute to the concept of terroir, and then examines how climate change might have an impact. Not having read more than the few pages available on Google Books, I can’t provide a detailed assessment of his position, but this is how wine writer James Halliday describes Gladstones’ climate findings in an “appreciation” penned for the book’s publishers:

Almost 70 pages are devoted to a thorough examination of evidence on the subject, and its implications for viticulture. He carefully documents why he believes the analysis of the Intergovernmental Panel on Climate Change (IPCC) is fundamentally flawed, relying as it does on computer modelling unable to encompass the complexity of real climates, on uncertain data, dubious assumptions, and biased statistical procedures. In particular, it ignores the historical and geophysical record of past greater warmth and natural climate fluctuations, preferring instead a misinterpretation of the land-based thermometer record.

Fundamentally flawed? As I read that, alarm bells began to ring…

The IPCC model suggests that the last 150 years should have seen a global warming of 1°C or more caused purely by anthropogenic (man-caused) greenhouse gases. In fact the thermometer record showed an irregular increase of only about 0.6°C, of which half is well explained by natural fluctuations in the sun’s energy output and magnetic field.

Magnetic field? The bells were getting louder…

Of the rest, the evidence (including important new insights that Dr Gladstones draws from his studies of viticultural terroir) indicates that most is spuriously related to historical changes in thermometer placement and surroundings, together with real, if still unquantified, general warming due to widespread desertification from land clearing and over-grazing. From this he estimates that greenhouse gases can have produced no more than 0.2 °C of any genuine global warming over the period, which corresponds to a largely harmless 0.4−0.5 °C for any effective doubling of atmospheric concentration, as opposed to over 2 °C in the IPCC models.

…and I was reaching for my earplugs by this point.

Further complicating this is that plants, including vines, benefit from extra carbon dioxide but need higher night temperatures to do so fully. ’I conclude,’ writes Dr Gladstones, ’that the widely held expectation of a viticultural flight to existing cold areas is misplaced. Optimum locations for particular wine styles will probably change little over the coming half century.’ To further challenge climate change orthodoxy he adds: ’Thus the possibility cannot be ruled out that the best terroirs will continue their historical shift to warmer locations.’

In other words: a load of straw men demolished, facts misrepresented, and a eureka moment when his researches suggest climate sensitivity is much lower than the general view. I’m not going to provide a detailed rebuttal of Halliday’s parsing of Gladstones’ climate chapters, mainly because I can’t be sure that they’re true to the original2, but his rejection of the climate science mainstream on the basis of his own theorising puts him firmly into crank territory. There are multiple lines of evidence and a plentiful literature dealing with climate sensitivity that seem to have eluded him. This appears to be yet another case of an expert in one field being overconfident of his conclusions outside his area of expertise. Gladstones knows his stuff when talking about the relationship between vines and the climate they experience, but appears to have strayed well out of his depth when looking at the fundamental drivers of climate change.

From the perspective of the wine business around the world, Gladstones’ observations that “a viticultural flight to existing cold areas is misplaced“, and that “optimum locations for particular wine styles will probably change little over the coming half century” fly directly in the face of current experience in Australia and around the world. In my own limited purview, most of the winemakers I meet not only accept the mainstream view that climate change is a clear and present danger, but many can already see its effects in their vineyards and in their wines. The reasons are closely related to the way that winemakers work, and how the concept of terroir fits in to that.

So: a brief diversion. I first wrote about terroir a decade ago3, exploring the concept as it applies to wine and then extending it to other crops. The idea is French, and simple enough. A wine properly made is an expression of the place it is grown. You can think of it as a sense of place, or the “somewhereness” of the wine. The basic elements are the grape type, the vineyard soil and soil structure (which depends on the geology underlying the site), the shape of the land and its exposure to the sun and wind, the regional and local climates, and the specific microclimate and seasonal weather that the vines experience as they grow. On top of that you have to take into account the way that the grapes are grown and the wines are made — the human, cultural angle. All of these factors work together to create the finished product.

If you doubt that this sort of thing can be tasted in a wine, then I heartily recommend a visit to a friendly winemaker. Let’s take pinot noir — the grape of Burgundy — now widely grown in the new world (and at Limestone Hills). Except in the smallest producers (such as us), grapes from different parts of the vineyard and from different clones of the grape will be vinified separately, matured in oak barrels, and then blended to make the final wine for release to a (with luck) grateful public. The French call the blending process assemblage, and it’s a real skill.

A single clone of pinot4 can make wines that express different flavours depending on where in a vineyard the vine is growing. It can be the position on a slope, or because of variation in soil and drainage, or exposure to sun and wind, but skilled winemakers will identify the differences in flavour, pick accordingly, and then assemble the wine they want to release. The difference in taste in grapes grown only a few metres apart can be remarkable. In Burgundy, terroir accounts for all the difference between Grand Cru wines and the ordinary village appellation. The boundary between the most expensive wines in the world and the (relatively) bog standard can be as narrow as a road or stone wall.

This means that winemakers aiming to make fine wines must have a very finely tuned appreciation of the response of their grapes to the local terroir. Climate is a key factor. Seasonal differences — good years and bad years — are one thing. Long term change another. But winemakers can taste change as it happens. Their livelihood depends on it.

Back to Burgundy. Understanding the various terroirs of the Côte d’Or5 was not something quickly learned. Grapes have been grown there for a couple of thousand years or so. The value of the land has become intimately related to the quality of the wine it makes — and that depends on its terroir. And a key component of that is the regional and local climate. It follows that if the climate changes, then so does the wine — and the value of the vineyard.

Rapid climate warming is even more of a challenge. Grape/soil/climate/vineyard management relationships6 developed through long experience will no longer produce the optimum wine. If the Côte d’Or becomes too warm to produce great pinot noir — a grape variety best suited to warm slopes in cool climates — what will Burgundians do then? This is the challenge being faced by the global industry today.

In Australia, despite Gladstone’s opinion, the “flight to cool climates” has been underway for a long time, as the growth of Tasmania’s wine business demonstrates. Awareness of what warming might bring, and work on how to adapt to it is proceeding, as Leanne Webb described in a recent article at The Conversation:

Over the longer term, growers can change varieties to better fit with the warmer projected climate. Some ’hotter-adapted’ varieties, such as Vermintino and Fiano (whites) and Sagrantino and Nero d’Avola (reds), are already being trialled and introduced. Planting the right varieties will help grapes ripen at a time when they have the best chance of retaining their quality.

A small fly in that ointment: grapevines take time to mature. A newly planted vine may well produce a commercial crop in four or five years, but it won’t reach maturity — when its grapes will have the finest flavours — until well into its teens and twenties. Such is the rapid pace of climate change in the world’s wine regions that by the time a new vine is at its best it may already be unsuited to the climate it finds itself in.

John McQuaid provides an excellent overview of the global picture in What Rising Temperatures May Mean for World’s Wine Industry at Yale e360. He notes that rapid warming is well under way:

A 2005 study led by [Gregory] Jones found that the average growing-season temperature in 27 prime wine-producing regions around the world had risen 2.3 degrees Fahrenheit (1.3ºC) in the previous 50 years. In the vineyards of Spain, Portugal, southern France, and parts of California and Washington state, it rose a dramatic 4.5ºF (2.5ºC).

So far, this has not been all bad news. Extra heat brings more reliable ripening, more sugars and stronger wines. But too much heat, and finesse begins to disappear. For a while, adapting vineyard practices can compensate for warming, but eventually the warmth wins.

French wine maker Philippe Bardet who produces Merlot, Cabernet Sauvignon and Cabernet Franc grapes in the Bordeaux region, says that over the past 25 years his harvests have moved from late October to the beginning of September as grapes ripen ever faster. Concerned that this may be affecting the wine, Bardet has tried planting different, slower-ripening grape varieties to push it back. In fact, Jones, in his study, found that some warmer regions were already reaching a heat threshold beyond which quality began to decline.

McQuaid gives the last word to Richard Selley, who has just updated his magnum opus on winemaking in Britain, The Winelands Of Britain. In it he projects climate change in the UK out until 2080, and finds that parts of southern England may then only be suited to producing raisins, while pinot noir is confined to mountain slopes in the north:

’If by 2080 it’s too hot to make wine in southern England, what’s the rest of Europe going to look like?’ asked Selley, the British author. ’You’ll have to switch to making palm wine.’

McQuaid’s article is the single best examination of the issue I have read in a long while, and it provides a very stark contrast to Gladstones’ optimistic misreading of the gravity of the issue facing the world’s wine business. Meanwhile, I shall continue to plot expanding the number of syrah vines around the farm. They’ll do well as the Waipara climate warms…

[James Brown]

  1. Influential in Australia, at least.
  2. If someone would care to provide me with a review copy, I would be glad to dig a lot deeper.
  3. The article is available at my old farm blog, here.
  4. There are many different clones of pinot noir.
  5. I recommend Terroir: The Role of Geology, Climate, and Culture in the Making of French Wines by James E Wilson for a detailed discussion, rooted in geology, of the terroirs of Burgundy and all of France’s major wine regions.
  6. Written into the appellation rules in France.