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Abstract

In the twentieth century, high summer temperatures were beneficial to grape and wine quality in Bordeaux. However, owing to global warming gradually raising temperature closer to the optimum needed by the regional grape varieties, the positive effect of higher-than-usual summer temperatures has vanished over the last decades. Therefore, it is unknown whether any weather variable is still impactful enough to quantify future wine quality. Here we provide a predictive model of wine prices, based only on weather data. We establish that it predicts more accurately a vintage’s long-term quality than a world-class expert rating this same vintage in the year following its production. We first design a corpus of features suited to the grapevine lifecycle, so as to distinguish the grapevine’s contrasting needs across the different stages of its growth. Using Bayesian inference with a Hamiltonian Monte Carlo (HMC) algorithm, we then select the most powerful drivers of wine quality. Finally, we build a predictive model that leverages Local Least Squares kernel regression (LLS) to allow model coefficients to change over the vintages, thus factoring in the time-varying nature of climate impact on the grapevine. Using the phenology-adapted features, and letting coefficients vary through time with LLS, both significantly improve performance. The proposed model thus achieves state-of-the-art predictive accuracy, and it even provides a better predictive ranking of successive vintages than the grades given by world-famous wine critic Robert Parker. This demonstrates that weather is still a very efficient predictor of wine quality in Bordeaux. This study provides strong support for the usage of weather-based models as auxiliaries in the pricing of premium agricultural products. The HMC algorithm, both flexible and robust to noise, can be used in the feature selection step of many modelling problems. Finally, the novel usage of a LLS architecture, allowing the input-output relationship to smoothly vary over time, would have exciting development in the modelling of other agricultural systems, in face of the changes introduced by global warming and adaptation of production methods.

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The assessment of regional climate change requires the development of reference long-term retrospective meteorological datasets. This article presents an 8-km-resolution atmospheric reanalysis over France performed with the the Safran-gauge-based analysis system for the period 1958–2008. Climatological features of the Safran 50-year analysis—long-term mean values, inter-annual and seasonal variability—are first presented for all computed variables: rainfall, snowfall, mean air temperature, specific humidity, wind speed and solar and infrared radiation. The spatial patterns of precipitation, minimum and maximum temperature are compared with another spatialization method, and the temporal consistency of the reanalysis is assessed through various validation experiments with both dependent and independent data. These experiments demonstrate the overall robustness of the Safran reanalysis and the improvement of its quality with time, in connection with the sharp increase in the observation network density that occurred in the 1990s. They also show the differentiated sensitivity of variables to the number of available ground observations, with precipitation and air temperature being the more robust ones. The comparison of trends from the reanalysis with those from homogenized series finally shows that if spatial patterns are globally consistent with both approaches, care must be taken when using literal values from the reanalysis and corresponding statistical significance in climate change detection studies. The Safran 50-year atmospheric reanalysis constitutes a long-term forcing datasets for land surface schemes and thus enables the simulation of the past 50 years of water resources over France. Copyright © 2009 Royal Meteorological Society
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Gas-exchange, water relations, vegetative growth and berry sugar concentration of the Kékfrankos grapevine were studied at two growing sites in Eger Wine district, Hungary (Eger-Kőlyuktető – non-stressed, flat vineyard and Eger-Nagyeged hill – water stressed, steep slope vineyard). At the hilly site predawn water potentials and stomatal conductance indicated mild to moderate water stress. As a result, stomatal regulation caused restricted carbon assimilation per unit leaf area. Interestingly, comparing the two sites, lower assimilation rate was accompanied by higher fruit sugar concentration. Water deficit also reduced the yield and the relative proportion of larger berries within bunches. However, in each berry weight category (I: 2.01g) there was a higher sugar concentration at the water stressed vineyard irrespective of berry size. Therefore, berry size was not the only factor that could influence berry sugar concentration. Water deficit also resulted in decreased leaf area per shoot and thus, modification in canopy architecture. Although, there was a higher leaf area for 1kg fruit at the flat vineyard compared to the hilly site, differences in “sink-source” relations and light interception of the canopy between the sites resulted in different yield sugar concentration.
Article
When interdependence of disturbances is present in a regression model, the pattern of sample residuals contains information which is useful in prediction of post-sample drawings. This information, which is often overlooked, is exploited in the best linear unbiased predictor derived here. The gain in efficiency associated with using this predictor instead of the usual expected value estimator may be substantial.
Article
Notwithstanding the observed positive correlations between critics' quality ratings and wine prices, the range of these correlations is quite high. In light of this, researchers must consider the factors that either strengthen or weaken the association between quality ratings and prices. In this paper, we propose that the slope of the relationship between quality ratings and wine prices is moderated by the amount of attention that producers receive. Because attention increases with a producer's critical exposure (i.e., its history of critical coverage), price-quality relationships will be steeper for producers with more critical exposure. This prediction is confirmed in an analysis of New World wines selling into the U.S. market over the 1987 to 2001 period. While a wine's price is a positive function of its own quality rating, the strength of the price-quality relationship increases with a producer's critical exposure (JEL classifications: L11, L13, L15). "A signal hitherto unheard is useless by itself." (Arrow, 1974: 40)
Article
Local least squares kernel regression provides an appealing solution to the nonparametric regression, or "scatterplot smoothing," problem, as demonstrated by Fan, for example. The practical implementation of any scatterplot smoother is greatly enhanced by the availability of a reliable rule for automatic selection of the smoothing parameter. In this article we apply the ideas of plug-in bandwidth selection to develop strategies for choosing the smoothing parameter of local linear squares kernel estimators. Our results are applicable to odd-degree local polynomial fits and can be extended to other settings, such as derivative estimation and multiple nonparametric regression. An implementation in the important case of local linear fits with univariate predictors is shown to perform well in practice. A by-product of our work is the development of a class of nonparametric variance estimators, based on local least squares ideas, and plug-in rules for their implementation.
Article
This study concerns firstly the methodology to describe the climate of vineyards, on a macroclimate scale of viticultural regions worldwide. Three synthetic and complementary viticultural climatic indices (potential water balance of the soil over the growing cycle, heliothermal conditions over the growing cycle and night temperature during maturation), validated as descriptors, are used: (1) dryness index (DI) which corresponds to the potential water balance of the soil of Riou’s index, here adapted using precise conditions to calculate it, as an indicator of the level of presence-absence of dryness; (2) heliothermal index (HI) which corresponds to Huglin’s heliothermal index; (3) cool night index (CI) an index developed as an indicator of night temperature conditions during maturation. These indices are representative of the variability of the viticultural climate worldwide, related to the requirements of varieties, vintage quality (sugar, colour, aroma), and typeness of the wines. A Multicriteria Climatic Classification System (Géoviticulture MCC System) for the grape-growing regions worldwide is formulated based on classes for each of the three climate indices, with elements to explain the results. Three formulated concepts provide the system base: viticultural climate, climatic group and viticultural climate with intra-annual variability (for warm regions with more than one harvest a year in natural climate conditions). The application of the Géoviticulture Multicriteria Climatic Classification System is presented for 97 grape-growing regions in 29 countries. The system is a research tool for grape-growing and wine-making zoning. It also enables work at different levels on the scale, on a world-wide scale or larger – the large grape-growing region, the small grape-growing region, as shown by the studies performed. It allows relating the viticultural climate to the elements of grape quality and the typeness of the wines considering the climatic zone.
Article
A hedonic price function, relating the price of Australian wine to its attributes, is estimated. Six attribute groups are found to be statistically important in explaining deviations from average wine prices, i.e., quality, cellaring potential, grape variety/style, grape region, grape vintage and producer size. Various interaction terms between these variables and the impact of the year of marketing are also modelled. The consequent marketing implications for producers and consumers are discussed.
Article
In this paper, the quality of the wine from the Dão (Viseu) region of Portugal is examined and relationships between wine quality and climatic variability are obtained using spectral and correlation analysis to determine the structure of the temporal variations. The spectra of the series of quality of wine values show statistically significant oscillations coherent with those found in the series of teleconnection indices. The series cover a period of 33 years. A significant correlation was obtained between wine quality and minimum air temperature in May, December and total precipitation in April. The teleconnection circulation indices are used to provide some physical insight into the most significant oscillating components of the climatic and the wine quality series. We found significant and positive correlations between the quality of the wine and the Southern Oscillation Index (SOI) of August and negative with the SOI of January and with the North Atlantic Oscillation of April. Wine quality and climatic series can be predicted using statistical models depending on significant oscillations.
Article
Overfitting problem in model fitting for quantitative measurements is discussed. Two types of overfitting can be distinguished, which include using a model that is more flexible than it needs to be and using a model that includes irrelevant components or predictors. Adding predictors that perform no useful function means that in future use of the regression to make predictions it will be needed to measure and record the predictors so that their values can be substituted in the model. Adding irrelevant predictors can also make predictions worse because the coefficients fitted to them add random variation to the subsequent predictions.
Article
We estimate hedonic price functions for premium wine from Australia and New Zealand, differentiating implicit prices for sensory quality ratings, wine varieties and regional as well as winery brand reputations over the vintages 1992-2000. The results show regional reputations have become increasingly differentiated through time (although less so for New Zealand). In particular, cool-climate regions are becoming increasingly preferred over other regions in Australia. In each country, price premia associated with both James Halliday's and Winestate magazine's sensory quality ratings, and with Halliday's winery ratings and classic wine designations, are highly significant. Copyright 2003. The Economic Society of Australia.
Article
Bordeaux wines have been made in much the same way for centuries. This article shows that the variability in the quality and prices of Bordeaux vintages is predicted by the weather that created the grapes. The price equation provides a measure of the real rate of return to holding wines (about 2-3% per annum) and implies far greater variability in the early or 'en primeur' wine prices than is observed. The analysis provides a useful basis for assessing market inefficiency, the effect of climate change on the wine industry and the role of expert opinion in determining wine prices. Copyright © The Author(s). Journal compilation © Royal Economic Society 2008.
Article
This paper describes an econometric assessment of wine market prices for 21 of the Crus Classés châteaux in the Bordeaux region of France. The model developed in the analysis attempts to define the relationship between factors that influence wine quality and those that influence wine prices. Characteristics of the models are: (1) climate influences on grape composition (acid and sugar levels), (2) grape composition influences on market prices, (3) subjective quality evaluations (Parker‐points) on market prices, and (4) the effects of age of the wine on market prices. The results indicate that composition levels of Merlot‐dominated wines are more climate sensitive than those from Cabernet Sauvignon‐dominated wines. Overall, warm, dry summers result in high sugar and low acid levels at harvest which in turn lead to higher quality wines. Wine market price sensitivity to Parker‐point ratings indicates that properties with high Cabernet Sauvignon‐dominated wines are highly dependent on the external ratings while Merlot‐dominated wines have a decreased rating sensitivity. Smaller properties tend to gain over proportionally from high ratings indicating great jumps in price from year to year. Additionally, châteaux that have experienced high ratings for past vintages exhibit great sensitivity to point steps in ratings for current vintages. Aging has a positive effect on Bordeaux wine pricing. This is due to the increasing maturity as well as the increasing absolute scarcity. Absolute scarcity of product is expressed by the size of the property, with small properties producing less per vintage and therefore having less in the market. Additionally, Merlot‐dominated wines exhibit more maturing potential and profit more from aging than Cabernet Sauvignon‐dominated wines. Average per château real annual profit ranges from 1 to 10%. High levels of grape ripeness, absolute scarcity, and smaller properties that are dominated by Merlot in their blend lead to the highest profits. Forecasts for a vintage not yet on the market indicates that 1995 is better than 1994 for both Cabernet Sauvignon and Merlot‐dominated wines, but that 1996 and 1997 are not as good as 1995, especially for Merlot‐dominated wines.
Article
In a recent paper, O. Ashenfelter, D. Ashmore, and R. Lalonde (1993) found they could explain the variation in the price (and quality) of Bordeaux vintages by a combination of age, temperature, and rainfall. The same ideas are applied here to Grange hermitage, Australia's premier wine. Weather variation is less important than in Bordeaux. However, some remarkably robust results are obtained: a 'quality index' for Grange is derived, predictions about still unreleased vintages are made, the Australian regression coefficients work well in the Bordeaux equation, and issues relating to market efficiency in the pricing of young wines are examined. Copyright 1995 by The Economic Society of Australia.
Article
this paper, we produced the curves fi 0 (E) and
Future scenarios for viticultural zoning in Europe: ensemble projections and 560 uncertainties
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Fraga, H. et al. (2013) 'Future scenarios for viticultural zoning in Europe: ensemble projections and 560 uncertainties', International Journal of Biometeorology, 57(6), pp. 909-925. doi:10.1007/s00484-
Prices of American Pinot Noir wines: Climate, 573 craftsmanship, critics
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A Review and Comparison of Bandwidth
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Gradient-based learning applied to document recognition
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