Climate and Pinot Noir

Vitis vinifera is the Latin name of the plant species used to make most of the world’s wine. Although many thousands of varieties of this species exist only a few dozen are important. These varieties grow in temperate climates, ranging in latitude from 32-51 degrees north and 28–45 degrees south; with lower latitudes (closer to the equator) typically associated with more heat accumulated over the growing season.

The distribution of heat over the growing season is influenced by a regions proximity to the ocean. Continental climates have more heat accumulated peak season (with less early and late season) while maritime climates tend to have heat more evenly distributed over the season. Retention of Pinot Noir’s delicate fruit aromas tends to be associated with cool late season temperatures.

The topography of a region also plays a major role in climate, with regions exposed to prevailing weather systems tending to be cooler and wetter than those tucked behind mountain ranges. As rainfall requires cloud, wetter areas tend to have less sunlight hours, lower heat accumulations and more rainfall.

Pinot Noir is an early ripening variety that is susceptible to moisture (causing bunch rot) over the ripening period. When grown in warmer regions, wines tend to lose the desirable fresh fruit and fungal aromas characteristic of this variety and in cooler and wetter areas herbal characters prevail, with wines tending towards the thin and acidic. These factors combined with the need for desirable soil types limit the number of areas suitable for the production of great Pinot Noir.


Development of sugars, flavour and colour in Pinot Noir

Pinot Noir wines are around 98% water, alcohol, acids and unfermented sugars; however it’s the last 2% that ultimately determines wine quality. Included in this 2% are flavour and colour compounds that are derived from the grapes and during the fermentation process.

Over the growing season grape vines go through a series of phenological (developmental) stages where secondary metabolites, important to the flavour and colour of wine, are synthesised, degraded or lost to the environment. One such phenological stage is veraison and marks the beginning of the grape ripening process. Acids synthesised prior to veraison begin to be diluted and degraded and sugars now begin to be accumulated. At this stage, grapes turn from green to red due to the production of red colour pigments (anthocyanins), triggered by the accumulation of Phenylalanine ammonia lyase (PAL), an enzyme used to catalyse reactions in the shikimic acid pathway. This pathway is also important in the formation of catechins, the building blocks of tannins.

Another important pathway is the mevalonic acid pathway used in the synthesis of terpenoids, important aroma components of grapes. The triggering of these pathways and the biosynthesis of their metabolites is strongly influenced by environmental factors including temperature and light and the nutritional status and water relations within the vine. Like flavour and colour development, berry sugar is too influenced by climatic factors (through the process of photosynthesis) and although linked, is not always synchronized with flavour and colour development.

This fact has led to the concept of analytical and physiological ripeness, where analytical ripeness is achieved when the sugars, acids and pH are within a range suitable for wine making and physiological ripeness refers to when the desired flavour and colour compounds are at their peak. When both the sugars and acids, and the development of colour and flavours, are optimized at harvest, many believe this to be the key to great wines. When they are not, the wines will lack character at best, and at worst, be undrinkable.

Climatic factors play a critical role in a vines expression of its location and environment and of all the grape varieties this expression is most pronounced in Pinot Noir. Central Otago is one of the few areas where both flavour and sugars are at their optimal at harvest.


Central Otago and Pinot Noir

Central Otago, situated in the South Island of New Zealand, has a semi-continental climate with hot summers and cold winters, however being an island nation, extremes in temperature are moderated by the influence of Tasman and Pacific Oceans. Heat accumulated over the growing season ranges between 900 – 1200 growing degree days with cooler sub regions tending towards the former and warmer, the later. Prevailing weather systems from the Tasman Ocean dispatch most of their moisture as they rise over the Southern Alps. Central Otago, being tucked in the rain shadow of this range boasts a dry climate (400 -700 mm per year), spread almost evenly thought out the year.

Central Otago is located on the 45th parallel, similar in the southern hemisphere to what Burgundy and Oregon are in the northern hemispheres (47th and 45th respectively). Both these regions are predominantly planted to Pinot Noir and are recognised as producing the world’s finest Pinot noir. However, unlike these regions Central Otago is blessed with a lower rainfall over the ripening period reducing the incidence of bunch rot and allowing the grapes to be left on the vines longer. This benefits the ripening process as heat accumulation over the growing season is slightly less than both Burgundy and Oregon. This results in wines that are not only world class but also have a quality and distinctiveness of their own.