Avertir le modérateur

jeudi, 26 novembre 2015





 Claude Gilois

An article published in the Journal ‘Proceedings of the National Academy of Sciences’ in early 2013(1), concluded that the climatic change could lead to a catastrophic scenario for most of the world’s viticulture. An article was published in this blog in May 2013(2)


They used 17 climatic models developed by climatologists to evaluate the impact of climate change on the world’s major viticultural areas. They worked on two of the four scenarios[1] proposed by the IPCC[2]. Firstly, they used the intermediate scenario (also called RCP 4.5)[3], which evaluates the concentration of the major greenhouse gases (expressed in C02) to be 530 ppm in 2050. We are now just about to cross the 400-ppm barrier, the highest concentration since the Pliocene epoch, 3.2 to 5 million years ago. They also use the most pessimistic scenario (RCP 8.5), which estimates the concentration of C02 gas to be 630 ppm in 2050. Today, the concentration of C02 is in excess of the most pessimistic scenario.


The scientists have concluded that the areas suitable for viticulture would be reduced by 19% to 62% with the intermediate scenario (RCP 4.5) and by 25% to 73% with the most pessimistic scenario (RPC 8.5) as vine varieties have a very narrow window of temperature to grow as shown in the following graph.


temperature d'acceptabilite de la culture de la vigne.jpg


At a time where negotiations for COP21 are reaching their last stages to try to limit CO2 emissions, and most countries have announced their programs of reduction, scientists have concluded that on that basis we would be on a scenario of a temperature increase of 3.5o provided that all countries abide by their commitments, which is far from being a certainty as John Kerry, Secretary of State, speaking for the USA has already indicated that they would refuse a binding treaty.


However, the report from the scientists contains a bias that, they themselves acknowledged in the publication. Their report does not take into consideration the strategies that could be deployed to limit the impact of the climatic changes, apart perhaps for the relocation of vineyards to the north in the northern hemisphere, and to the south in the southern hemisphere. Before we look at the various strategies of adaptation, we can already make some observations, the consequences of which appear to be inevitable.


  1. Vineyards located near the sea will suffer less stress and disruption as oceans act as thermal regulators to limit spikes of temperature, and the temperature variation of oceans is much slower than the temperature of land.


  1. Consequently, the viticulture on islands will be less affected. This is why the consequences of climatic changes will be far less intense in a country such as New Zealand where no vineyard is located more than 100 kms from the sea.


  1. Vineyards located in high altitudes will be less affected than vineyards on the flat as high altitude is also an important thermal regulator especially on nocturnal temperatures and it allows the photosynthesis of plants to be facilitated.


  1. Vineyards located on northern slopes in the northern hemisphere and on southern slopes in the southern hemisphere will have a better capacity for adaptation as they will be less exposed to the sun.


  1. Viticulture on slopes will cope better as they will be less exposed to extreme factors associated with climate change such as torrential rain and flooding (better drainage).


  1. The New World, less regulated, will have greater capacities for adaptation than the Old World where regulation is more stringent and sometimes excessive.


  1. Old, non-irrigated vines, which have the ability to control their vigor, will have a greater potential for adaptation even if their yields might become even smaller.


  1. Vineyards located on the best terroirs, that consistently produce great wines will be less affected by the changes. We know the capacity of great terroirs to sublimate adverse conditions.


  1. Regions producing blends will be less affected than those producing single varietal wines as it is easier to play with the composition of blends. It would be possible to increase the proportion of petit verdot or even reintroduce carmenere in Bordeaux at the expense of merlot, which is very sensitive to temperature increases.
  2. Countries less populated in relation to the available land for culture will have a greater capacity in their adaptation by being able to relocate their vineyards more easily.


  1. Viticulture will decrease in regions where vines were planted to produce wine in response to a demand at certain times in history to face increased consumption (South of France, Spain, South of Italy).


  1. Countries that possess a greater varietal diversity will flair better than those dominated by a handful of international varieties markedly reduced after the phylloxera. Varietals that have become marginal could see resurgence in their usage.


  1. New producing countries will emerge and old producing countries where viticulture has disappeared will re-emerge.


  1. Domains that have a lot of vineyard surfaces will have to be more pro-active and show a greater creativity to contain the problem.  



 Naked in the vines to protest against climatic changes 

(1) Lee Hannaha,b,1, Patrick R. Roehrdanzb , Makihiko Ikegamib, Anderson V. Shepardb,2, M. Rebecca Shaw, Gary Tabord Lu Zhie , Pablo A. Marquetf,g,h,i, and Robert J. Hijmans. Climate change, wine, and conservation (2013)

Proceedings of the National Academy of Sciences.

(2) http://voyagesvinsdumonde.20minutes-blogs.fr/archive/2013/05/04/rechauffement-climatique-et-viticulture.html#more

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