the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
600 years of wine must quality and April to August temperatures in Western Europe 1420–2019
Christian Pfister
Stefan Brönnimann
Andres Altwegg
Rudolf Brázdil
Laurent Litzenburger
Daniele Lorusso
Thomas Pliemon
Abstract. This study investigates the validity of wine must quality as a summer (JJA) temperature proxy between 1420 and 2019 based on expert ratings and quality measurements from Germany, Luxembourg, Eastern France and the Swiss Plateau. The evidence was reviewed according to the best practice of historical climatology. Expert ratings tended to agree with Oechsle density measurements that gradually replaced them from the 1840s. A statistical model calibrated to predict wine must quality from climate data explains 75 % of the variance, underlining the potential value of wine must quality as a climate proxy. Premium crops were collected in years of early harvest involving high insolation during maturation while poor crops resulted from very late harvests in cold and wet summers. An analysis of daily weather types for high and low-quality years after 1763 shows marked differences. On a decadal timescale, average quality was highest from 1470 to 1479, from 1536 to 1545 and from 1945 to 1954. Poor crops were collected in prevailing cold and wet summers such as 1453 to 1466, 1485 to 1494, 1585 to 1614, 1685 to 1703, 1812 to 1821 and 1876 to 1936. In the period of enhanced warming after 1990, high qualities became the rule.
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Christian Pfister et al.
Status: open (until 24 Nov 2023)
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RC1: 'Comment on cp-2023-66', Anonymous Referee #1, 15 Sep 2023
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The goal of the study is to determine if wine must quality can be used to obtain useful information on summer temperature in Europe over the past centuries. This is highly relevant as uncertainties remain on past climate variations during this period and new high-quality reconstructions are welcome. The paper describes well the basis of the link between must quality and climate, the available long series and make a strong case on the interest of wine must quality as a proxy of past summer conditions. I thus recommend the publication of this study after some minor changes as detailed below.
General point
1/ In the majority of studies devoted to new records covering the past centuries, a reconstruction of a physical variable (like for instance here summer temperature) is proposed and validated against modern observations. This is not explicitly the case here. The dependence of the must quality on temperature and precipitation is discussed (e.g. Table 7) but this is not used to provide a reconstruction. I think the authors should justify this choice and explain why they decide not to show such a reconstruction.
Specific points
1/ Table 4 provides the correlation of must quality and GHD +, tree ring MXD and GHD+ but surprisingly to me not Tree Ring MXD and must quality. Is there a reason for this choice? As must quality is the topic of this paper, this would have been instructive to see how the series compares to the one of tree ring MXD and if this agreement is higher or lower than between Tree Ring MXD and GHD+.
2/ Line 217 and 225. I have not understood to what refer the ‘small number of cases per year’ and the ‘low case numbers’. If the series are annual, each year has just one number for me. Is this due to missing years? Is it related to the small number of sources for this period (table 1)?
3/ Title of section 4: I would not use ‘The climate model’ because it is a statistical model of wine quality that is presented, not a climate model, even if it uses meteorological variables.
4/ Line 272. Is there a reason why precipitation in April and August are important and not the other months? Were the other months well below the selection criteria or were they close to be accepted by the backward selection?
5/ Line 287. When the ‘same regression model’ is mentioned for GHD, I guess it means the same meteorological variables but it has been recalibrated for GHD. The much higher explained variance for the verification period suggests that the behavior of this record is more stable in time than the one of must quality. This would be nice to include a discussion of this aspect in the final section of the manuscript.
6/ For figure 5, 5 years of high must quality and 5 years of low quality seems a small sample to me. Are the conclusions robust if a larger number of years is selected?
7/ Line 298. I guess 19 and 20 refers to the number of days. I would add the information explicitly.
8/ Figure 6 presents the same series as figure 4 if I am right but with a different caption. This could introduce confusion. I would include all the information for figure 4 and then explain in figure 6 that the same time series is shown.
9/ Lines 321-322. Is there a source or reference for those nicknames?
10/ Line 343. The information on the size of grape harvest seems a bit out of context here. It is required to have a longer discussion, including ideally references so that the reader could have an idea of the potential of this variable for climate reconstructions.
Citation: https://doi.org/10.5194/cp-2023-66-RC1
Christian Pfister et al.
Data sets
Wine must qualities DE, LU, FR, CH 1420-2019 Christian Pfister and Stefan Brönnimann https://doi.org/10.48620/317
Christian Pfister et al.
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