Climate

Climate factors

The climate characteristics result from many factors such as exposure (solar radiation), precipitation, temperature, humidity and wind as well as their sequence and interaction. In addition to the type of soil, the grape variety planted there and the individual method of winemaking, the climate is a decisive factor for the quality of the wine. But also the very special climatic conditions for a small area in which the vineyard is located (microclimate, site climate) and even smaller-scale conditions (microclimate) play an important role. The vine thrives best in warm, temperate zones of the northern and southern hemisphere, the so-called vine belts. These are the relatively narrow ranges between 40th and 50th latitude in the northern hemisphere and between 30th and 40th latitude in the southern hemisphere.

Conditions for the vine

The vine needs above all warmth and light. The optimal temperature for growth is between 25 and 28 °Celsius, according to studies by the Geisenheim Research Institute. This is mainly determined by the altitude. As a rule of thumb, it drops by 0.6° for every 100 metres of difference in altitude. A hillside location is ideal in terms of solar radiation. In addition, the thermals are favourable, because the cold air currents fall down the slope at night, where they warm up in the morning and move up again during the day. This cycle is especially important for white wines with regard to acidity.

The tops of hills are planted with trees to slow down the influx of cold air, which in Europe is mainly used in Germany, Austria and France. A positive climatic influence on viticulture is exerted by water bodies (rivers, lakes, seas), because light is reflected through them. It is no coincidence that many important wine-growing regions are located near water bodies.

The northernmost vineyards for quality wine cultivation are in Germany (51st latitude) and England (52nd latitude). The southernmost wine growing borders are on the Cape in South Africa (35th degree of latitude), in Argentina and Chile, and on the southern main island of New Zealand (40th degree of latitude). From the equator to 20 degrees north and south latitude, tropical conditions with heat and drought mean that there is no wine-growing, or only in higher areas at up to 2,000 metres above sea level, such as in Kenya. Outside these areas there is too little sunlight and precipitation or the danger of cold and frost. The suitability of a region or the criteria for quality viticulture is described under winegrowing suitability.

Influence on viticulture

The first scientific study concerning the Kima influence on viticulture was carried out by the Swiss botanist Augustin Pyrame de Candolle (1806-1893) in the middle of the 19th century. These findings were used by the two US researchers Albert Julius Winkler (1894-1989) Maynard A. Amerine (1911-1998) from the University of California. In 1944, they introduced the so-called Degree-Days system, which divides California into five climate zones. In the meantime, a number of different climate classification systems have been developed worldwide on this basis. These systems measure and evaluate different criteria during the annual vegetation cycle of the vine or for the entire year. These criteria include temperature values, number of hours of sunshine and rainfall. On this topic, see also Temperature Sums.

The optimal temperatures for viticulture are between 25 and 28 °C during the ripening period, provided there is sufficient supply of nutrients, good irrigation and sunlight. This is when photosynthesis reaches its optimum performance. The ideal annual average is 1,300 to 1,600 hours of sunshine, i.e. around 180 days with seven to nine hours a day. The wine-growing potential of an area is also measured by the average temperature of the entire growing season or that of the warmest month. With the so-called "MJT" (mean January temperature, in the northern hemisphere of course July) a now frequently used indicator for approximate comparisons has been created in Australia. Precipitation should amount to at least 300 millimetres in the months May to October (or November to April in the southern hemisphere), whereby spring precipitation is particularly important because of the growth of shoots. Higher amounts promote fungal diseases such as downy and powdery mildew and botrytis. The climate within a year may have an extensive effect on the quality, which is why one speaks of good or bad vintages.

Climate zones

A rough division into very large climate ranges is made on the basis of the annual average temperatures, among other things. These have risen at an alarming rate over the last 50 years. The calculated warming trend of 0.13 °C ± 0.03 °C per decade between 1956 and 2005 is almost twice as high as that of the last 100 years. This global warming and the associated climate change also has a major impact on viticulture.

Cool climate area
In Europe these include Germany, England, the north of France(Beaujolais, Burgundy, Champagne and Loire), Switzerland and Austria, and overseas Canada, the New England States on the east coast of the USA, the southernmost part of Chile, parts of California (Anderson Valley, Carneros), the Cape in South Africa, the Australian island of Tasmania and the southern tip of the main northern island of New Zealand. The average temperature is below 16 °Celsius. Aromatic white wines from early maturing grape varieties are typical for this area.

Interclimate area
These include Bordeaux and the northern Rhône Valley in France, Rioja in Spain, Tuscany and large areas in northern Italy, the Napa Valley in California and the south of Western Australia. The average temperature is between 16 and 18.5 °Celsius. Dark, alcohol-rich red wines are the main wines growing here.

Warm climate area
These include southern France, the Portuguese Douro Valley, the island of Madeira, southern Italy, large parts of Spain and parts of southern Australia. The average temperatures there are between 18.5 and 21 °Celsius. These areas are especially predestined for alcohol-enriched sweet wines.

Hot climate area
These include southern Greece, Turkey and southern Spain with average temperatures of 22 °Celsius and more. In addition to wine grapes, large quantities of table grapes and raisins are also produced here. Areas or zones with almost the same climate, which can also be located on different halves of the earth, are called homoclimates.

Climate Classification

Areas with the same climatic conditions are classified into climatic zones and thus classified. There are different models for this. A common classification is:

Continental climate (continental climate, land climate)
This climate is characterised by large seasonal variations in temperature, with a relatively large difference between the average temperature of the hottest and coldest months. It is characterised by hot summers, with mostly low cloudiness and humidity, and cold winters. The further inland from a continent, the less the balancing influence of the oceans, which is accompanied by a decreasing number of clouds and falling humidity. Compared to maritime (near sea level) areas, there is relatively little precipitation with peaks in summer due to heat storms. In autumn, temperatures fall rapidly.

The differences between vintages can be considerable. With high yields, there are significant quality-reducing effects. Continental climate occurs mainly in the Central and Eastern European inland areas, as well as in the interior of North America (USA and Canada). It is best suited for fruity, dry wines with (especially for white wines important) corresponding acidity.

Marginal climate
Climate in the climatic border area, in which viticulture is just about possible (marginal = something on the edge/on the border). It is characterised by relatively low average temperatures and a long vegetation cycle. See also under northernmost vineyard and southernmost vineyard and also under highest vineyard.

Maritime climate (maritime climate, oceanic climate, maritime climate)
This prevails near seas or large lakes, which act as a balancing temperature buffer. This is because the water temperature changes more slowly than the temperature on land due to the large heat capacity. This means that the land near the coast is cooled by the sea in summer and warmed in winter (positive lake effect). For this reason, there are also good conditions for viticulture in high northern latitudes such as in the northeastern USA and Canada due to the five "Great Lakes" Erie, Huron, Michigan, Superior and Ontario. However, the pure geographical location (coastal location) alone is no indication of a maritime climate, as the wind direction also has an influence.

The entire east coast of the United States of America has a continental climate because the wind blows from west (the huge interior) to east. Maritime climate is characterized by moderately warm summers and mild but rainy winters. There are evenly warm temperatures with high humidity. The temperatures in autumn fall fall only slowly. Compared to continental climates, there are much smaller differences between day and night and also summer and winter. Most of Europe is under the influence of maritime climate. It also prevails in many areas of the southern hemisphere such as Australia, New Zealand and South Africa, even if they are located inland.

Mediterranean climate (Mediterranean climate)
Typical for this climate are hot, dry summers and mild, humid winters. Due to lack of rainfall, it is not uncommon for artificial irrigation to be necessary in various forms. Due to low humidity there is usually a lower risk of fungal diseases. The best locations are at higher altitudes. The Mediterranean climate is characteristic of many coastal regions, which are located on the western sides of the continents. These are the entire Mediterranean basin, southwest and north Australia, the west coast of the USA, Chile, and the Cape Province in South Africa. The climate produces fully ripe, sugar-rich but sometimes low-acid grapes, which are ideal for sweet wines with a high alcohol content.

Pannonian climate
Area of influence of the Hungarian lowlands, which has a particular impact in northern Burgenland/Austria. Foothills can be seen as far as the borders of the Wachau, Kremstal and Kamptal wine-growing regions, which are characterised by the contrasting interaction of the Pannonian and western continental climates.

Dry climate
Destined for parts of Israel, Italy, Spain, South Australia, South Africa and Chile as well as the Central Valley in California. Due to the low rainfall and danger of drought, viticulture is not possible without regular artificial irrigation.

European wine growing zones

Within the framework of EU wine legislation, Europe has been divided into the three major wine-growing zones A, B and (with subzones) C, which have similar climatic conditions. For these zones, special wine law regulations apply, for example, regarding enrichment (alcohol increase), acidification and sweetening. Within these major climate zones, a distinction is made between smaller climate zones, although there are no 100% generally valid definitions. The hierarchy is based on the size of the vineyard area and is usually as follows (topdown):

Macroclimate
Larger area (also large climate) with at least 500 kilometres of horizontal extension. It refers to the climate of a wine-growing area or region. This is usually referred to as "climate". However, it is difficult to speak of a uniform climate within these large areas, since altitude, slope, direction and soil type have a great influence with different effects. This is expressed, for example, by different vegetation cycles in the vineyards.

Mesoclimate
Intermediate range between macro- and topoclimate in the extent of ten to several hundred meters. It is increasingly replacing the terms topoclimate or microclimate.

Topoclimate
Designation for a locally limited climate determined by the topography. This can, for example, concern a single hill, a slope or a valley.

Microclimate (site climate)
Frequently used term for small-scale conditions that give a vineyard a very typical and individual character, which can be different in a vineyard even in extreme cases. Components such as the proximity of a pond, river or forest, soil heat storage, solar radiation, mountains (which can protect against wind), but also the way the vines are trained can play a role. This term is related to the French terroir.

Microclimate
Specific climate at the smallest scale of a few metres within a vineyard, for example a vine, even on leaves and grapes.

Temperature Sums

The measured temperature totals (heat totals) are used to select suitable grape varieties and determine the optimal time for harvesting. In precision viticulture, highly scientific methods are used in vineyard management to try to take certain climatic conditions into account. From the 1980s onwards, climatic changes on earth have become visible and tangible on a large scale and have become a hotly debated topic. Although the fact of a (too rapid) climate change is still disputed and played down, some of the changes are dramatic. The division into wine-growing zones and the associated wine-growing worthiness will change as a result. Cool Climate Winegrowing became popular from the mid-1990s onwards, which refers to the planting of vines in higher areas with continental climatic conditions.

Medieval Warm Period

In the course of the earth's history, there have always been periods of time with serious changes in climate, but compared to today, these have by far not occurred so quickly within a few decades, but rather in enormously long periods of time. Between 900 and 1350, especially in Europe, there was a pronounced temperature high, which is called the Medieval Warm Period. At that time, the climate was so warm that even in the south of England it was possible to successfully grow wine. From 1450 the climate began to deteriorate again.

Little Ice Age

The term Little Ice Age is used to describe a climatic phenomenon that lasted for a relatively long time (400 years) in the period from 1450 to 1850, which occurred worldwide with regional and temporal focuses in Europe, North America, Russia and China. Particularly cold periods extended from 1570 to 1630 and from 1675 to 1715, which were associated with a worldwide expansion of glaciers. This developed dramatically in the opposite direction in a relatively short period of several decades. See in this respect under climate change.

Climate zones map: By LordToran - Self created, CC BY-SA 3.0, Link
edited by Norbert Tischelmayer Feber 2019
Vine belt: The winegrower 1 - Viticulture, Ulmer Verlag 2019, 4th edition
Climate Change: Pixabay
Main source: WIKIPEDIA climate and follow-up links