Specific mediterranean characteristics. Mediterranean climate

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1 Effect of global warming in mediterranean conditions Climate change - Average temperatures increase and efficient rainfalls decrease Consequences for vines and grapes - Shortening of phenologic stages - Water stress - Consequence on vineyards implantation Effect of global warming on vine grape and winemaking in mediterranean conditions Jacques Rousseau, Daniel Granès, Laurent Duret, Institut Coopératif du Vin Consequences for wines - Another way of planning the picking period - Changes in chemical contents of wines - A necessary adaptation of winemaking processes Mediterranean climate Specific mediterranean characteristics Rainfall (mm) Climatic diagram of perpignan (23 years of average datas) Rainfall (mm) Temperatures ( C) January February March April May June July August September ctober November December High autumn and spring rainfall <> Low summer rainfall Mild winter temperature <> High summer temperature > 27 h sunshine/year Temperature ( C) High number of days of strong and dry winds High ETP even with moderate temperatures An extreme variability according to: Altitude: from to 6 m! Sea proximity Local rainfall.. Extremely local From chambre d Agriculture 66

2 What are mediterranean conditions? (1) A climate adapted to wine growing : - High level of sunshine period : > 27 hours per year (in Montpellier) - Cool average temperature in winter : 6 C in Montpellier in January - Average hot temperature and few rainfall in summer : 23 C in july and august in Montpellier with less than 5 mm per month Specific characteristics High number of days of strong and dry winds - High ETP even with moderate temperatures An extreme variability according to: altitude: from to 6 m! Sea proximity Local rainfalls Recent changes: temperatures increase during vegetative cycle of grape wine 1968 Evolution of sum of température in Nîmes (France) since year Main conséquence : evapotranspiration increases as well! Transpiration Evaporation Increase of very warm days Rainfall decrease during vegetative cycle of grape vine Source: CIRAME

3 What happens to mediterranean climate? As a consequence, grape vine is subject to dryer and dryer conditions The global warming affects the mediterranean climate : - Increase of temperature during the full year but specially winter; - Decrease of rainfall during winter and summer, but higher number of heavy rains; - A higher frequency of abnormal climatic events : - Heavy rainfalls in 1999, 22; - Higher numbers of days with hard winds - Hail is more frequent Sum of temperature Spring and summer rains => Mediterranean climate changes to sub-desertic conditions, with bad consequences for grapevine. 4 % Efficient rains Example: 27 in Perpignan Consequences on the grape vine cycle Bursting out: not always very early Perpignan rainfall Average 23 years 27 3 Perpignan temperature Average 23 years 27 High precocity of flowering 26: earliest ever 3 years 27: earliest since. 26 Rainfall (mm) January February March April May June July August September ctober November December Rainfall (mm) Less rainfall in summer Higher temperatures in spring Frequent high rainfall (> mm/day) - in autumn: 1988, 1999, 22, 23, 24, 25, 26 - and during harvest: 22, 25, January February March April May June July August September ctober November December Very high Huglin s Index (sum of temperatures) at the end of May Diseases are more frequent, specially powdery mildew in spring : several damages in june and beginning of july Early veraison First harvests earliest ever Fortunately fresh temperatures in August slow ripening Fresh nights favourable to anthocyans synthesis Brutal concentrations in september (23, 26, 27): Berries with thin skins Effect of wind No summer rainfalls From chambre d Agriculture 66

4 Increase of precocity and grouping of maturity Beginning and end of grape picking (in red color) and total length of picking period (in white color) at experimental ICV winery for chardonnay, sauvignon, shiraz, merlot and cabernet sauvignon variety, picked at same sugar content /8 5/8 9/8 13/8 17/8 21/8 25/8 29/8 2/9 6/9 1/9 14/9 18/9 22/9 26/9 3/9 Date de réception (raisin à 12,5 % vol alc) Date of picking (grape at 12,5 % alc. Vol) 21/8 19/8 17/8 15/8 13/8 11/8 9/8 7/ Early harvesting is a heavy trend since year 2 19/8 16/8 2 13/ / /8 16/ /8 25 1/8 26 7/ days Evolution of date of harvesting at experimental ICV winery (Chardonnay variety plots harvested at equal level of sugar level) Water stress is more and more frequent Water stress enhances : Loss of harvest Change in grapes content Mortality of vine plants Heterogeneity in plots => Varieties like shiraz, merlot or chardonnay are very sensitive to this stress Typical wines made with water stressed grapes - concentrated wines with unriped tanins and strong alcoholic feeling, without fruity taste - Less and less required by the market and consumer ApH1 (mg/l) Heat after veraison = less colour Rainfalls Total anthocyans Temperature 4/8 8/8 12/8 16/8 2/8 24/8 28/8 1/9 5/9 9/9 13/9 17/9 21/9 25/9 Cabernet 392 Cabernet 3491 Cabernet : anthocyan synthesis increases after reduction of temperatures, not after rainfalls

5 Consequences on vineyard implantation Interest for late varieties Ripening in better temperatures conditions More likely to meet autumn rainfall Vineyard adaptation: canopy management Vertical trelis Interest for altitude vineyards More rains Less excessive temperatures Interest for deeper soils More water resources in summer Overyield risk reduced under dry conditions Sauvignon : sunburn damages 4 July 26 Increased transpiration on narrow canopy Vineyard adaptation: canopy management A necessary adaptation of vine management - Irrigation and management of water ressources - Soil tillage : no weed competition and optimization of deep root system - Vineyard benchmarking: - upgrading of traditionally basic vineyards - Excessive stress on traditionally premium vineyards Cordon Mechanized harvesting possible Transpiration reduced Protection against sunburn Umbrella Excellent for grape protection against sun and for soil shading

6 What are mediterranean conditions? (2) Under standard maturation conditions i.e. sun + moderate water stress : High sugar concentration (generally > 22 g / L) Low available nitrogen supply (generally < 25 mg / L) Low malic acid concentration, generally < 2 g / L High ph, generally > 3.6 before alcoholic fermentation These 2 parameters are also closely dependent upon grape variety Early harvesting: Heavy consequences on winery management kg 17 aout Planning of picking time for a winery in aout 25 aout 29 aout 1-sept Exemple of a winery (cave coopérative) : Picking planning - Heavy cooling requirement at the beginning (white and rosé wines); - Modification in picking organisation : - Harvest at night ; - Staggering of picking over the full week and the full day 5-sept 8-sept 12-sept 15-sept Change in chemical contents of wines Wines with more sugar concentration but with less available nitrogen - Problems of fermentation - Wines with high alcoholic level : TAV > 15% Wines generally with higher ph but depending of conditions! - Increase color instability and ageing - More risks of microbiological damages - Problems to realize MLF (low level of malic acid) More problems to reach phenolic maturity - Wines with hard tanins - Color instability Nitrogen (mg/l) Increasing fermentation risks Fermentation risk according to must composition Alcohol potential % vol Risk medium High risk Very high risk

7 Increasing fermentation risks Where is the risk of contaminations? Standard evolution of microorganisms during winemaking Assimilable N, mg/l millions 1 millions 1 million 1 AF Maceration MLF Saccharomyces cerevisiae Lactic Acid Bacterias Spoilage yeasts %vol potential When alcohol potential is > 13%, more than 9 % of the grapes have less than 25 mg / L of assimilable nitrogen and 5 % less than 15 mg / L Weeks after yeasts inoculation Risk of contamination Two maturities reached at different moments Exemple of a experimental plot of OM Pyrénées Roussillon in 22 - Grenache ODM Technological Phenolic maturity = pulp maturity 2 maturity = skin 1 maturity 8 23/8 3/8 6/9 13/9 2/9 27/9 4/ A full maturity difficult to reach same experimental plot OMPR in 27 Evolution de la maturité 27 - Grenache Maury ODM 3 - Technological maturity = pulp maturity 6/8 14/8 21/8 28/8 4/9 11/9 18/9 25/9 Poids 2 baies (g) DO 52 x Degré pot Gap of 15 days III Not only the phenolic maturity is difficult to reach (with bigger gap) but the level of extractible polyphenols is less III

8 A necessary adaptation of winemaking processes Conducting the alcoholic fermentation - Addition of complex organic nutrients and oxygen; - Management of temperatures (T max ) - Choice of yeast strain, rehydratation process Managing the MLF, (delay to finish it) - Lactic bacterias additions - Hygien (rackings) - Temperature Managing ageing and storage of wines - Optimal active SO 2 - Temperature and hygien of storage Conclusions Global warming is a reality. It changes under mediterranean conditions : - vineyard plantation - vineyard management - winemaking process - wine ageing technics Care anytime is necessary with better knowledge of global warming consequences. Thank you for your attention Laurent DURET lduret@icv.fr