Changes in climate have taken place and the average temperature of the surface of the earth have already ncreased by 6°C during the 20th century. According to climatic models and the hypothesis of the evolution of C02, global warming with develop between 1.4 and 5.8 C during the 21st century. Global warming will not only affect surface temperatures, but will also affect the difference between seasonal temperatures extreme phenomenons in climate, and water resources. These modifications will have an impéact on the quantity and the quality of farming production and on the environment (soils, water, biodiversity…) and will modify the zones of certain phenomena.
The northern hemisphere is heating up more than the southern hemisphere.

The greenhouse effect is a physico-chemical phenomene brought about by the presence in the atmosphere of gas absorbing the thermic infra-red rays generated by the earth's surface, and without which the average tempertaure of the earth would represent –18°C rather than +15°C. The observation, at the beginning of the 1970s, of an increase of a notable concentration of some of greenhouse gas, brought about man's intervention, have drawn attention to the problems linked to this evolution. The forecasts of climate specialists have since developed, becoming finetuned and more certain.

The history of the vine and winemaking is linked to out civilisation, to such an extent that it is possible to reconstruct France's climate 600 year's ago, whereas the first temperature measurements appeared back in 1850. Research scientists from INRA, the CNRS and the CEA decided to study the dates of the harvest in Burgundy the first written records of which date back to 1370. The development of Pinot Noir in Burgundyin relation to the temperature has been modelised by taking into account three key steps: flowering, fruit bearing and maturation. Research scientists have therefore managed to establish on a number of occasion between 1370 and 1850, Burgundy witnessed several years as hot as those we have experienced in recent years. However, 2003 is by far the hottest year that Burgundy has known in centuries, with a not at all normal increase in temperature of 5.86 degrees. This research is of interest as it can be applied to other regions where the vine was grown in Europe and in the Middle East. The work of these research scientists, carried out by the historian Emmanuel Le Roy Ladurie were published in the magazine "Nature" on the 18th of November 2004.

Thermic effects: Global warming, probably due to a period whereby the earth has become warmer, combined with human activity, will result in an increase in the number of very hot days (+30°), less very cold ones and more heat waves (2003 for example).
Hydric effects: Droughts will increase, wind gusts will be modified, the number of days with heavy rainfall will increase…

Warming noted since the middle of the 20th century has increased over the past 15 years everywhere in the world. The rhythm of warming is situated depending upon the hypothesis between +0.2° and 0.6° per decade.

Several indexs enable us to measure the effects of global warming:

- Drought index which takes into account available water supplies, soli evaporation, sunshine interception… This index allows for the classification of climates (moderate dryness, strong dryness…).
- Helio-thermic index ou Huglin index, finetuned for the vineyard… If this index is too low (<1500), vinegrowing isn't possible…
- Night temperatures equal to the average minimum temperatures during the ripening period.

These three indices allow for a multicriteria classification for the climates of vinegrowing zones. (refer to the published works of Alain Carbonneau ENSAM-INRA).

Adaptation of the vine to the changes in climate

Selection of grape varieties. The shortening of the vine's vegetative cycle influences the choice of grape varieties and growing techniques. For example Mourvedre is spreading throughout the Languedoc. This variety was previously only cultivated around the area of Bandol. As a result, Merlot can make its way to Germany and Syrah can even extend to Burgundy!

The shortening of the vegetative cycle is explained in this graph drawn up by Grégory Jones 5oregon University).

From 1950 to 2000, the start to the chief vegetative cycles of the vine have become earlier
- budbreak +6 days
- flowering +11days
- veraison +15 days
- harvest + 17 days

In the Rhone Valley, the harvest in Chateauneuf du Pape is currently kicking off three weeks earlier than it did 60 years ago.

Date of the start to the harvest in Châteauneuf du Pape since 1945 (Tittle of following image)





The period encompassing the most early ripening varieties through to the latest ones has become longer.
New vineyards could develop in the North of Germany and the South of England. For example a vineyard cultivated around Potsdam 800 years ago, when the weather conditions were suitable, has started to be cultivated again. Today vinegrowing is developing in England. As a result, the northern limits of white winegrowing is moving further north. In Germany, we are witnessing an increase in the production of red wine in relation to white.

Modification of the terroir? The changes in climate will automatically effect the notion of terroir. Climate influences a wines style. If the proximity to the ocean creates a certain blanc for Bordeaux wines, the climates of the South of France, Burgundy and Champagne affect the terroirs' makeup… In 40 or 50 years, the climate of Epernay will be the same as that of Montpellier today! A radical change will result in a difference in the choice of grape varities, vinegrowing practices and winemaking procedures…

The migration of vineyards towards the North is increasingly more certain. In addition, around the Mediterranean area, vintners or investors will look for vineyards at an altutude of 300 to 450 m.

The majors challenges associated with global warming will in the long run include: high degrees in alcohol, higher sugar, less acidity and less aromas. It is possible that that earlier harvest coupled with efficient cooling will help to preserve the balance between the sugar/acidity. However the aromatic complexity will be affected. Winemaking will probably help to lessen the effects of global warming, but at the price of new investments.

- Correcting the effects of droughts by irrigation. Difficult to imagine in France, a couple of years ago, this idea is becoming acceptable following in 2005 the INAO's decision of lightening the legislation concerning the irrigation of AOC vineyards.
- Precise irrigation in view of producing quality grapes, as part of sustainable viticulture, taking into account the soils' evolution (organic matter, fertilisation…
- Changes in climate equally include the modification of unltra-violet rays zand their effect on aromas. Vineyard management choices become all the more important…
- Increasing periods of drought could help to reduce phyto-sanitary treatments and will help to implement sustainable viticulture. In some French regions, treatments could be reduced to less than 4 a year…
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- Please Note: When it comes to most scenarios, the changes in climate result in bigger wine grape harvests both in the United States and Europe.

Viticulture is facing importance challenges linked to the new wine economy: globalisation of the market, new wineproducing countries, new WTO, the protection of GIs, knowledge of the market and the consumer…
In addition to all these challenges, vinegrowing and winemaking have to take into account the changes in climate with new scenarios destabilising the former order, creating at the same time new opportunities…