For anyone who feels they have finally mastered the concept of postmodernist books and architecture, there is a new intellectual and linguistic challenge, in the shape of "post-classic" wines. The term was coined by the world's leading viticulturist Dr Richard Smart, at the second World Conference on Global Warming and Wine in Barcelona last month before an audience of the great and good of the wine world and - via a carbon-saving video link - Al Gore. If even a few of the alarming predictions made by experts at that event prove accurate, many of the world's most famous wines may either simply cease to exist or be altered beyond recognition over the next 50 years. The effect of climate change will not be restricted to wine - but for Smart, wine may be "the canary in the coal mine of agriculture".
According to French tradition, the character of a classic wine - its DNA, if you like - is attributable to four factors that are collectively known as terroir. Three of these - the slope of the vineyard, its soil and subsoil and the climate were, it was believed, immune to human influence. The other ingredient - the choice of grape variety - was dictated by custom or law, so a burgundy producer, for example, has to make his red wine from pinot noir grapes; even the thought of his experimentally planting a few merlot or shiraz vines is as acceptable to the French wine establishment as birth control to the Vatican.
For true believers in terroir - a group that now includes a growing number of self-termed terroiristes in California - the part played by the winemaker is very similar to that of a musician performing a musical score. One vineyard should always produce the liquid equivalent of the Eroica while another will give you Clair de Lune. This is nowhere more evident than in the cellars of small burgundy estates, whose vignerons might produce small batches of wine using the same grape variety and methods from each of a number of plots situated often only yards apart. The variations in weather from one season to another and the winemaker's skills will all naturally affect the final result, but in theory at least, the meursault he makes from his chardonnay vines in the Perrières vineyard that was planted on the site of an ancient quarry should always taste recognisably stonier than the more immediately softer, more appealing wine from a plot called Les Charmes onthe other side of the road.
To a Gallic chauvinist, the subtleties of terroir are rarely if ever found outside France. Aimé Guibert of the Domaine Mas de Daumas Gassac in Languedoc-Roussillon has dismissed all New World wines as "industrial" and said that "every bottle of American and Australian wine that lands in Europe is a bomb targeted at the heart of our rich European culture". But unique combinations of grape, site and climate abound across the planet. Even a complete novice can spot the differences in flavour and style between the rieslings that top Australian winemaker Jeffrey Grosset produces in his Watervale and Polish Hill vineyards in the Clare Valley, which is just as well, because the Polish Hill can cost a fiver a bottle more. And the effects of those combinations transcend the climatic influences of particular years or winemakers. In other words, a 1955 Chateau Latour should be as recognisable in a lineup as the 2005, even though the cellarmaster and the weather of the two vintages were quite different.
Whether this will be as true of the 2055, however, is another question. According to research across 50 wine-growing regions by climatologist Gregory Jones of Southern Oregon University, Bordeaux will be 1.2C warmer in 50 years, while Chianti's vines might be baking in temperatures that are a full 2C hotter than they are today. Stated bluntly, both areas will be enjoying a similar climate to North Africa today. This warmer weather will give riper, sweeter grapes, which then become stronger, more alcoholic wines: "post classics" that lack the fine, complex subtle characteristics that are associated with the world's finest wines today. Red wines may be more immediately pleasing to drink, thanks to the lower levels of mouth-drying tannin that has historically been the hallmark of most young bordeaux and barolo, for example, but like the whites, they will lack the fresh bite of acidity that makes wine such a great accompaniment to food. Wine grapes, like people, tend to reveal their true character when they are subjected to stress, which is why most of Europe's most famous wine regions are in so-called climatically "marginal" areas where the vines often struggle to ripen. Wines produced in warmer weather, with adequate irrigated water, often lack the edge that separates the great from the simply adequate; drinking them can be a little like watching a top-class football team half-heartedly playing opponents from a lower division.
Many wine lovers will have already noticed the phenomenon. In the 1991 edition of his seminal book on bordeaux, David Peppercorn recalled that the great reds of the Medoc in the 1940s usually had alcoholic strengths of 11-11.5%. By the late 1980s, he regretted the trend towards 12.5% having become "the norm to be aimed at". In 2005, the norm was closer to 13.5% and critically well-received reds such as Chateau Balthus and Lynsolence weighed in at a whopping 14.5%. In California, where, in 1971, red wines averaged 12.5%, the Martinelli winery now makes a zinfandel with an alcohol content of 17.4%.
Whatever you might think of a red wine that is as strong as a gin-and-tonic, California's thick-skinned, sun-loving zinfandel grape, like the Rhone's and Australia's shiraz, is naturally suited to making wines with quite high alcohol. But Burgundy may become too hot for the pinot noir, the thinner-skinned, cooler-climate grape with which it has been associated for more than a thousand years. Jacques Lurton of Chateau la Louvière in Bordeaux expects the widely grown merlot in his region to be increasingly supplanted by the less heat-averse cabernet sauvignon and legal but currently unused grapes such as the petit verdot, and the malbec and carmenère that are respectively now more usually associated with wines from Chile and Argentina. So, it could be farewell to the classic aromas of cigar boxes and flavours of slightly unripe blackcurrants and green peppers that are the hallmarks of claret today, and hello to mouth-filling, rich, spicy, more peppery tastes that are rather more like Chateauneuf-du-Pape.
And what's true of these ancient French regions will be apply to areas such as Barolo in Italy, La Mancha and Rioja in Spain, Australia's Hunter Valley, all of which will effectively be rewriting the melodies and orchestration of their terroir. As global climate patterns change, we are already seeing greater variation between vintages, and, more worryingly for the men and women who grow the grapes, far greater unpredictability. For Ernst Loosen, one of Germany's most respected estate owners and winemakers, "Every year seems to be another challenge . . . a new problem. How do we handle these weather patterns? How am I to keep the style of my wine? It requires a lot of experimental stuff."
Among the solutions to Loosen's and hundreds of thousands of other winemaker's problems will be what his compatriate Hans Schultz of Geisenheim University calls "climate adjustment" or "shaping wines with technology". This will include new ways of growing and training vines and the introduction of irrigation to the classic regions of Europe. Watering vines is currently illegal in these areas because of fears of the overcropping it might facilitate, but if higher temperatures are not accompanied by rain, grapes can stop ripening completely.
The alternative to altering the way wine is made in traditional regions will be to shift production to places where the process is easier. Spain's leading winemaker Miguel Torres, who is spending millions of dollars on research into ways to counter climate change, is developing new vineyards high in the Pyrenees. Others, including owners of big-name bordeaux chateaux such as Mouton Rothschild and Cheval Blanc, are looking far beyond their own borders and investing in vineyards in South America. The challenge is to choose which countries offer the best prospects.
For Dr Smart, some areas that already produce wine will fare better than traditional parts of Europe. Tasmania, New Zealand and Argentina are all on a "lucky list" that is headed by Chile, thanks to the cold current that runs along its long coast. The southern hemisphere, Smart contends, will be less badly hit than the north because of its smaller land masses and larger areas of cooling ocean. He is working on a project in China, now the seventh largest wine producing country in the world. Most of China's existing vineyards are less than ideally situated, but there is a cool, new, unexploited region to the north-west of Beijing that shows real potential.
Another surprising possible beneficiary of post-classic wine may be England, though when English winemaker Stephen Skelton stood up at the conference wearing a union flag shirt he was, perhaps understandably, taken less than seriously. When he began to describe his experiences, however, the audience began to take more notice. "For the first seven years of my wine growing, I never saw a day with a temperature of over 29 degrees. Since 1994, there has only been one year when it did not rise above 29. Last year was actually the second warmest year ... in 356 years of record keeping, even though it was overcast in June and July." For the moment England's strongest suit lies in its sparkling wines which beat champagnes in blind tastings - and sell at champagne prices. One explanation for this is the price of the land on which the English grapes are grown. Skelton has apparently had interest from two major champagne houses but so far the costs of investment have proved too high. Another worry might be the thought that if, as has been suggested, global warming leads to a stoppage of the gulf stream, England will be a better place to develop ski slopes than vineyards.
The French national agronomic research institute, INRA, has pointed out that, with just two degrees of global warming, there will be places in Finland that enjoy a climate that is very similar to that of wine regions in northern France today.
Of course, there are those who dismiss global warming as being of little concern - or as being manageable. Bruno Prats, former owner of Chateau Cos d'Estournel in Bordeaux, said that he was very confident in the future of that region, provided the producers amended the blend of their grapes to suit the new conditions. In his view, the spicy petit verdot, traditionally a bit player in red bordeaux, where it rarely makes up as much as 5% of the final wine, may have a major role to play. But Prats is hedging his bets: today, the wine he makes comes from Chile. Another participant in the conference who seemed relaxed about climate change was the Bordeaux-based superstar winemaking consultant Michel Rolland, who has successfully helped to produce wine almost everywhere, including such unlikely countries as India and Uruguay. "So far," he said, "climate change has been very good for us." However, like Prats, Rolland has cannily invested some of his money in high-altitude vineyards in Argentina.
Climate change is not the only factor influencing the future of wine. Long before global warming became a mainstream concern, many of us had already begun to discover and enjoy wines that bear more than a passing resemblance to the ones that Old Europe is wrestling with today. In 1993, Oz Clarke's book New Classic Wines heaped justifed praise on regions such as Casablanca in Chile, Margaret River in Western Australia and Marlborough in New Zealand. All of these places were already delivering wines that offered a new spin on the traditional efforts of regions such as Bordeaux and Burgundy. Fifteen years ago, however, the idea that southern-hemisphere countries could be talked of in the same breath as those Gallic meccas was complete anathema. When Clarke launched his book at an international tasting event in New York, many of the French members of the audience ostentatiously left the hall. Today, some of those same Frenchmen and women are busily prospecting for vineyards on the other side of the world.
When lovers of classic wines that taste the way they did in the 1950s and 1960s have wanted to apportion blame for the fact that their modern counterparts have become bigger, richer and less "elegant" and "austere" - to use the old-fashioned winetaster's vocabulary - they have usually pointed their fingers at the US guru Robert Parker and his favourite winemaker Michel Rolland. Parker, the "emperor of wine" whose opinions shape the destinies and even the pricing policies of the most famous wines in the world, likes the big flavours that are associated with ripe grapes. His tasting notes rarely include words such as "elegant". The bottles that get the highest marks tend to be described as "opulent", "inky" "blockbusters" with "gobs of fruit". That 17.4% Zinfandel was, for example, a wine he particularly liked.
Parker owes his success to the fact that large numbers of people across the world agree with his tastes - or, at the very least, have lost their inclination for the way wines used to be. A glance at the shelves of Tesco or Thresher reveals that, far from being at the dawn of the age of the post-classic wine, we've been increasingly surrounded by it, and enjoying it, since the arrival of the first bottles of Cloudy Bay sauvignon and Rosemount chardonnay two decades ago. Today, it is an inconvenient truth that even given the richer style of French wines, most of us apparently still prefer to drink bottles from Australia and California. The only question is how long it will take us to shift our allegiance to the post-post-classics of China, Finland and, who knows, maybe even Yorkshire.
Classic v post-classic: The best of the old and new wines
Chardonnay
Originally, chardonnay came from Burgundy, with an alcoholic strength of around 12% and rarely more than the subtlest influence of new oak barrels. Today, that style of wine can still be found in Chablis, the coolest part of Burgundy. Elsewhere, richer more tropical flavours prevail (though excessive oak has been in decline for the past five years).
Classic Marks & Spencer Petit Chablis 2006 (£8.79)
Attractive, light, fresh wine with some of the "mineral" character that chablis gets from the chalky soil - and no oak. Great with oysters.
Post-classic Hendry Ranch Unoaked Chardonnay 2006 (£12.54, Vineyards Cellars, 01488 681313)
No barrels have been used in the making of this California effort either, but it's absolutely packed with almost every kind of sun-ripened fruit you can imagine.
Bordeaux
This is where the classic versus post-classic fight has arguably been most fierce, with US critics singing the praises of "blockbusters" that have been hated by classic lovers in Europe.
Classic 2004 Berrys' Margaux (£15.95, Berry Bros & Rudd, 0870 900 4300)
Made by arch-classicist Chateau Durforts Vivens in a moderate climate that produced wines applauded by bordeaux traditionalists, this is the kind of pure, medium-bodied, blackcurranty wine that even a novice might recognise as claret.
Post-classic Chateau Pavie 2003 (£133, everywine.co.uk)
The most controversial wine in Bordeaux - and arguably the world. US critic Robert M Parker said this "inky" wine from the hot 2003 vintage was a "brilliant effort ... a wine of sublime richness ... with extraordinary richness". In Britain, Jancis Robinson thought it "completely unappetising. Porty sweet. Ridiculous wine more reminiscent of a late-harvest zinfandel than a red bordeaux".
Spanish
Classic Spanish wine for most people was usually rioja: gentle stuff with a fairly light colour, that had often spent five years or more in big casks before it hit our shelves. Spain's post-classics are inky blockbusters from the region of Priorat, which once made cheap communion wine but now commands prices of up to £100 a bottle in New York.
Classic Muriel Rioja Crianza 2001 (£5.69, Sainsbury)
Typical of many people's notion of classic Rioja. Medium-bodied, with soft, strawberry and vanilla character from the barrels in which it has been aged.
Post-classic Alvaro Palacios Les Terrasses 2005 Priorat (£216.48 for a case of 12, equivalent to £18.04 each, Waitrose.com)
Great, intense wine with extraordinary richness of almost chocolatey flavour. Drink with an intensely flavoured plate of game.
· Robert Joseph is the author of the Complete Encyclopedia of Wine (Carlton). His book The Descent of Wine will be published later this year.
