Please give me an email at mepolhill@yahoo.com, it would be great to catch up with you.

Best Regards,

Mark

Thank you for the update. It is much appreciated.

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The update explains that the model of Chuine et al. is essentially just a cubic polynomial, despite initially appearing much fancier.

Also, I was contacted about Chuine et al. last year by an American TV producer, who was going to do a documentary on climate change. It seems, though, that the producer had misunderstood my paper: he thought that my paper argued against substantial correlation between temperatures and grape harvest dates. A recent post on ClimateAudit suggested a similar misunderstanding.

In fact, the data of Chuine et al. make it clear that temperature explains over half the variance in the Burgundy harvest dates. There is no dispute about that, and the figure on my site (at the above link) illustrates the correlation.

The primary problem with the publication of Chuine et al. is that the authors’ model is inadequate for estimating the temperature in unusually warm years (as detailed in my paper and on my site). An important additional problem is that the model was designed to give results on average, and does not necessarily work for individual years (this is clear and it is also treated on my site). Following is a partial illustration of the latter problem, which I sent to the producer.

]]>The criticism that my paper had concerns the claims Chuine et al. made about a particular year (2003) being extremely warm. My paper did not criticize using vineyard date for averages. Here is an example….

Suppose that you measure the heights of all children in Grades 1-9 in Philadelphia. Now suppose you were interested in the heights of children in Grades 1-9 in Chicago. The average heights from Philadelphia will give good estimates for the average heights in Chicago. For instance, the average height of Grade 4 children in Philadelphia is a good estimate of the average height of Grade 4 children in Chicago.

Suppose that I told you about a certain John Smith who was in Grade 4 in Chicago. What is his height? Any estimate is going to be just a very rough guess, because an individual child might be far from average. This is obvious, but that is what Chuine et al. did, essentially, for estimating individual years.

Vineyard data can sometimes be used to estimate the temperature for averages of years, but not for individual years. (I do not know how many years you would need to include in an average; 30 should be enough, possibly much less.) For example, the Burgundy vineyard data indicate that 1800-1830 was substantially cooler than 1670-1700, and this is very probably true. The work of Chuine et al. demonstrates that this works, ….

Note that in 2006 for the first time since records began in Holland the boundary between Ca and Cb (hottest month 22 degrees) was passed. The thirty year moving average ( Kàƒ⵰pens definition of climate !), however, is still well within the limits of a Cb climate.

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Some excerpts:

-It is unrefutable that Normandy was a production site of excellent wines and its hills, now covered with apple trees were once the place of abundant vineyards.

-The evidences of this once prosperous activity are numerous, be it written testimonies, architecture, monuments, traditions, chronicles, objects, town names…

-Testimonies go back to 12th century but “recent” events are also plenty, for example the Battle of Arques on 21th september 1589, recorded by the duke of Angouleme where the cavalery had difficulties to move because of the vigourous vineyard.

-In the 13th century, the first harvests were obtained on the 6th of AUGUST!

To give an idea, the feast of the Beaujolais Nouveau (fine wine… for the Japanese) officially starts at 0:00h the 15th of November.

-Around the end of the 17h century, long and harsh winters began to set in. 1684 winter was “horrible” and lasted 5 months. Even the ocean was freezed from Tréport to the Havre and the port of Fecamp was totally blocked by ice. 1709 was even worse.

Apparently, there are plenty historical elements describing mediaval wine activities in the North of France. Maybe the next publication of Dr Chuine would be about Normandy’s grappes harvest dates as a temperature proxy?

]]>I used the daily Dijon temperatures for the years 2002 and 2003 to calculate the flowering, cell elongation completion and photosynthate completion dates using the Chuine pinot noir grape maturation equations published in Nature. These are the equations that use daily average temperatures and then on inverse regression use the AMJJA mean temperature to predict a harvest date. Remember that 2003 was the year of the very hot summer in Dijon, and Europe generally, and was emphasized in the Chuine et al. Nature article.

The calculated flowering, elongation completion, photosynthate completion and harvest dates for the years 2002 vs 2003 were June 19 vs June 9; July 5 vs June 25; August 11 vs August 1 and September 12 vs September 2, respectively.

The harvest dates predicted, using the Chuine et al. inverse regression model and the AMJJA mean temperature, for 2002 vs 2003 were September 18 vs August 18, respectively.

The AMJJA mean temperatures for 2002 vs 2003 were 22.0 degrees C vs 25.0 degrees C, respectively. The mean temperatures for the entire year for 2002 vs 2003 were 17.2 degrees C vs 18.1 degrees C, respectively. The monthly mean temperatures in degrees C for the grape growing season of AMJJA for 2002 were 16.7, 18.9, 25.6, 25.6 23.3, respectively and for 2003 were 17.8, 21.7, 27.8 26.7 31.1, respectively.

It turns out that the Chuine equations (not the inverse regression) differentiate between 2002 and 2003 only in the flowering period and the differences depended on the temperatures in only a 2 months time period, i.e. the latter part of April, May and the first part of June. Although the accumulation of the flowering factor started in early April for 2002 and 2003, it really does not contribute significantly until the middle of that month. On closer examination with actual temperatures, it turns out, as Willis E noted earlier, the photosynthate process is relatively insensitive to the normal temperatures at which it operates in Dijon and even slows when an optimum temperature is exceeded. I had earlier noted that the cell elongation process had a steeper slope with temperature than that of the photosynthate process and suggested that because of this one might expect cell elongation period temperatures to correlate better with the harvest dates than the photosynthate period. For the years 2002 and 2003, the time period for cell elongation had mean daily temperatures that all exceeded the sloping portion of the curve and put them into a temperature independent range. Both years had a calculated 16 days for this process to complete. I would expect that only a significantly cooler period than normal would have an effect on the length of the cell elongation process.

If one makes correlations with 2 month periods of mean temperatures (1951-2003) to harvest dates, the best correlation is for the 2 months of May and June which gives a linear regression fit with R^2 = 0.54 versus the second best 2 month combination of June and July which yields R^2 = 0.48. This would be in agreement with what I found for the years 2002 and 2003 using the Chuine equations, but the Chuine equations do not appear, at last from a precursory analysis, to explain why the combinations of MJJ with R^2 = 0.61 and MJJA with R^2 = 0.72 and AMJJA with R^2 = 0.73. These results lead me to suspect (from the 2002 and 2003 data) that while the Chuine equations/processes play a role in the pinot grape maturation process, and thus the harvest dates, there are other considerations which put the latter part of the growing season temperatures back in play in determining the harvest timing.

Since I consider my analysis as more “playing around with the data” then anything of a serious nature, I did not bother with tabling my calculations. But I do have a question to John A on whether I can copy tables and graphs directly from my computer (Excel/Word) or must they first be transferred to an online site?

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