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Wine, the Weather and Butterflies

The quality and quantities of wines produced in any region of the world are always at the mercy of the weather. There is, however, a distinction between weather and climate. The type of climate (hot, cool, maritime or continental) will determine the variety of wine making grapes that can be grown consistently and successfully over a long period of years. The climate, that is weather as it occurs over a long period of time in any one region, also has a pronounced and obvious effect on grape constituents and consequently the flavours of the wines made from them. For instance, in hot climate grapes ripen well and accumulate lots of sugar and intense fruit flavours, whereas in cool climates there is a slow build-up of sugar in the grapes and at a lower level with accompanying high levels of acidity and lower intensity of fruit flavours.

In any particular year, when the grapes are harvested, this is designated as ‘the vintage’ year and is often stated on the wine bottle label. When the vintage is described as good, it means that the weather conditions were perfect in that region for producing grapes to make good wine for that year. In the northern hemisphere the harvest occurs in September to October, while in the southern hemisphere it is April to May, so a bottle of wine from countries below the equator with the same vintage year date on the label will in fact be six months older than that from the north. Wine producers in the prestigious wine regions such as in Bordeaux, will ‘declare’ a vintage; that is, when the wine is tasted in the April following the year of its production it will be assessed for its quality and potential to improve with age and this will be recorded and publicised. This vintage assessment will influence and ultimately determine the price at auction and whether wine investors will purchase a particular vintage in order to reap the financial rewards at a later date.

The annual growth cycle of grapevines begins with bud break in the spring followed by shoot growth and flowering, and in summer flower set with berry formation and ripening occurs until late autumn, culminating in leaf fall in early winter and vine dormancy. Each stage is sensitive to the weather conditions, but it is the overall weather experienced by the vineyard over the whole year which will ultimately determine the quality of the grapes and the wine made from them. Vineyard managers have no control and are at the mercy of the weather. They only have control of vine development and final grape quality by the use of viticultural practices like canopy management, irrigation, vine training and the use of agrochemicals to affect the grape quality. Spring frosts can destroy nascent vine buds, heavy rain in summer can strip flowers off a vine and autumn rain may cause the grapes to swell and dilute pulp flavour content. So inclement weather at any time of the year can adversely affect the quality of the grapes and wine made from them.

In the Baden wine region in Germany and Alsace in France, which are only thirty miles apart and facing each other across the broad Rhine valley, it is very apparent that wines are distinctly different from each of these regions, even when made from the same grape variety. For instance, the Riesling wine from Germany is light bodied and acidic whereas the Alsatian version from France is higher in alcohol and more intensely flavoured. This situation occurs for other grape varieties too which make wines in different locations.

How can the same grape produce such different wines from locations which are very close to one another? The French have a word to account for this, ‘terroir,’ which literally translated into English means ‘soil’ but in France the word accounts for much more. It describes the total environment in which grape vines are grown; it encompasses the climate, weather, inclination of slope of the vineyard and the direction in which it faces and altitude and the soil and soil constituents and last but by no means least, the grape variety! In Burgundy, plots of vineyards which are adjacent to each other, growing the same Pinot Noir or Chardonnay grape varieties can produce completely different wines, one far superior to the other.

In a BBC documentary about the weather (Storm Troopers: The Fight to Forecast the Weather), ‘Chaos Theory’ was given as the explanation why very small differences in the start of a process or initial conditions in a complex system, the weather in this case, can lead to widely different unpredictable outcomes with time. The proponent of this theory was Edward Lorenz, a professor in mathematics and meteorology at the Massachusetts Institute of Technology, who was trying to predict the weather from mathematical equations that took into consideration temperature, air pressure and humidity. His observations ultimately led him to formulate ‘Chaos Theory’ and what also became more popularly known as the ‘butterfly effect’ - a term that grew out of an academic paper he presented in 1972 entitled: "Predictability: Does the Flap of a Butterfly's Wings in Brazil Set Off a Tornado in Texas?" The principle is that a butterfly fluttering its wings on one side of the planet could lead to storms on the other side. A small initial alteration of the environment can lead to big and significant differences in the outcome later in time.

With extremes of weather predicted for the future because of climate change it seems inevitable that we will see fluctuations in the weather affecting not only the quantity but also potentially the composition and quality of our wine grapes with predictability becoming less certain. This, combined with the other small initially different conditions of terroir, will make wine composition more unpredictable.

So next time you see a butterfly watch its wings flap and think they may be influencing the quality and flavours of the wine you will be drinking in the next vintage year!

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