Overview
Across the vineyards of the world there is a startling range of climates under which grapes are grown for the production of wine. The properties of climate have a pronounced effect on the process of wine production, and climate therefore sets the parameters for the selection of grape variety.
Climate (and weather) is made up of several factors: temperature; rainfall; humidity; evaporation; wind; sunshine and frost. If one was to focus on a single factor of paramount importance, it would be temperature, as this most closely regulates the production of aroma and flavour compounds in grapes.
The Big Picture - Climate - A Question of Scale
To make an analysis of climate and in order to draw conclusions about site suitability for viticulture, or decisions of vineyard management, climate is broken into three categories of scale: macro; meso and micro.
Regional Site and Micro Climate
From Macro to Micro
The largest is macro-climate and this refers to a large area of land. It covers many square kilometres and often equates to an entire sub-region or even a whole region. This is useful in determining climatic explanations of regional character.
Meso-climate is smaller and more localised. It breaks down topographic elements and can often be equated to a particular vineyard or section of vineyard. To use the example of a simple hillside, the top of the hill, the sloped section and the bottom of the hill will all be described in terms of their own separate meso-climates. Similarly, the western face of a hill will have a meso-climate distinct from the eastern face. Meso-climate is particularly useful in describing the climatic influence on the character of wines made from single vineyard plots or vineyard character.
The final, smallest scale is that of micro-climate. This is an often-misused term and frequently applied to descriptions of the meso-climate scale. Micro-climate in a vineyard sense is the area surrounding the vine, its canopy and its fruit. Differences can be made between the inner and outer canopy as two distinctly different micro-climates. This scale is particularly useful when discussing specific viticultural and vine management techniques.
The Defining Influence
The impact of climate on the character of wine grapes and ultimately, the finished wine cannot be overstated. The dual notions of vintage character and vintage variation are entirely related to the effect of climate. Whilst generalisations about climate are arrived at through a process of averaging and plotting variables, each year presents a unique set of challenges and conditions against which responses are made in the vineyard and winery.
The very best vineyards are those that have an affinity between the desired wine, the quality and character of grapes required to make that wine and grape variety. This balance is increasingly harder to define as weather patterns are becoming more irregular or atypical.
Beyond Temperature
The effects of other climatic elements should also be considered:
Sunshine: provides energy for photosynthesis and light for the initiation of colour and flavour development.
Humidity and Evaporation: sites that have high evaporation rates and low relative humidity have higher transpiration rates (evaporation of water off the leave surface) and may therefore require irrigation.
Rainfall: no water; no growth; no comment!
Wind: may be beneficial in terms of drying out vines and thereby preventing the onset of disease through damp conditions. Conversely it may also restrict vine growth and for this reason wind breaks are sometimes required.
Adelaide Hills Vineyard
A Case In Point - Changing Patterns of Climate - Bruce Tyrrell, Tyrrell’s Vineyards, Australia
The effects of global warming are currently much discussed in agriculture production, along with a gradual realisation that the already ‘unpredictable’ nature of climate and weather patterns is increasingly changeable and difficult to predict.
Bruce Tyrrell has noted a dramatic recent change of pattern in his beloved and native Hunter Valley: “The main challenge used to be that it gets wet at vintage, but we really haven’t had that for the last 4 years…Many regions have had to come to terms with climate change and it is ironic that one of the Hunter’s previous challenges – ‘humidity’ - has really now delivered it a natural advantage. If you consider that hot 45 degree days are really going to stress and perhaps ultimately shut down your vines, then 65% humidity at night keeps those vines going and suddenly the leaves – curled and parched at the end of the day - look great again in the morning.”
In 2006 the greatest challenge that the climate gave us was that pretty much all of the reds in South Australia and Victoria were ripe at the same time. The pressure on physical fermentation space – literally, where to put everything – was a direct result of an unusual and almost uniform growing season that suddenly all came together at the same time.”
Bruce Tyrrell – Tyrrell’s Vineyards, Hunter Valley NSW