Climate change is improving French wine quality

NASA study finds climate change shifting wine grape harvests in France and Switzerland- higher-quality wines are typically associated with earlier harvest dates


French vineyards like the one in the photograph are experiencing earlier harvests in recent years as the region's climate has warmed. CREDIT Credits: Elizabeth Wolkovich/Harvard University
French vineyards like the one in the photograph are experiencing earlier harvests in recent years as the region’s climate has warmed.CREDIT Credits: Elizabeth Wolkovich/Harvard University

A new study from NASA and Harvard University finds that climate change is diminishing an important link between droughts and the timing of wine grape harvests in France and Switzerland.

During a study of wine grape harvest dates from 1600 to 2007, researchers discovered harvests began shifting dramatically earlier during the latter half of the 20th century. These shifts were caused by changes in the connection between climate and harvest timing. While earlier harvests from 1600 to 1980 occurred in years with warmer and drier conditions during spring and summer, from 1981 to 2007 warming attributed to climate change resulted in earlier harvests even in years without drought.

The finding is important because higher-quality wines are typically associated with earlier harvest dates in cooler wine-growing regions, such as France and Switzerland.

“Wine grapes are one of the world’s most valuable horticultural crops and there is increasing evidence that climate change has caused earlier harvest days in this region in recent decades,” said Ben Cook, lead author and climate scientist at NASA’s Goddard Institute for Space Studies and the Lamont Doherty Earth Observatory at Columbia University in New York. “Our research suggests that the climate drivers of these early harvests have changed.”

Indicators of wine quality, such as wine ratings, show the best years for grape harvest typically include warm summers with above-average rainfall early in the growing season and late-season drought.

“This gives vines plenty of heat and moisture to grow early in the season, while drier conditions later in the season shift them away from vegetative growth and toward greater fruit production” said the study’s co-author, ecologist Elizabeth Wolkovich of Arnold Arboretum and the Department of Organismic and Evolutionary Biology at Harvard University, Cambridge, Mass.

Researchers conducted an analysis using 400 years of harvest data from Western Europe. The study considered variability and trends in harvest dates, climate data from instruments during the 20th century, and reconstructions from historical documents and tree rings of temperature, precipitation and soil moisture dating back to 1600.

That analysis was compared with shifts in wine quality in the Bordeaux and Burgundy regions of France based on the ratings of vintages during the past 100 years. Detailed quality information was available for those two regions in addition to the broader harvest data available throughout France and Switzerland.

The results indicate a fundamental shift in the role of drought and moisture as large-scale drivers of harvest time and wine quality. While warm temperatures have consistently led to earlier harvests and higher-quality wines, in recent decades the impact of drought has largely disappeared as a result of large-scale shifts in climate.

“Wine quality also depends on a number of factors beyond climate, including grape varieties, soils, vineyard management and winemaker practices,” Cook said. “However, our research suggests the large-scale climate drivers these local factors operate under has shifted. And that information may prove critical to wine producers as climate change intensifies during the coming decades in France, Switzerland and other wine-growing regions.”


The paper was published March 21 in the journal Nature Climate Change.

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March 22, 2016 1:03 am

Be assured, someone is going to come along and say this is bad, even worse then we thought!

Reply to  Aussiebear
March 22, 2016 1:29 am

This IS bad news –
Better wines = more drinking = more drunken debauchery & an end of civilization as we know it.
( I’m looking forward to the debauchery bit )
So it is worse then we thought – but better than we hoped for !

Reply to  1saveenergy
March 22, 2016 3:01 am

Unlike the researchers, I live in the south of France, I often participate in the vindange ( grape harvest );I know professional wine producers; I make wine. I also work outside in construction and I know when it is a hot summer: it smacks me on the head.
It has not been hot like it was in 2003 since then. The last 5 years or so have been notably cooler with winter dragging on for months. This winter has been exceptionally mild.
There has been a dramatic revolution in the wine industry in the last 20-25 years in the south of France with much of cheep poor quality wines being unable to compete with foreign wines which have taken a large share of the market.
What survives is more careful, often hand picked or organic label wines. Collective wine producers that survived have upped their game. There is very little of the 11degree plonk that was common 25y ago. All this is a determining factor in the CHOICE of when grapes are harvested. This is not like japanese cherry blossom, it is a deliberate choice, not just the annual weather.
Trends in harvest dates are just as much a function of changes in the wine market as they are any change in climate. It does not seem that the authors had any controls in place to assess this.
Sure warmer summer, more sun makes better wine. So does better wine production strategies.

And that information may prove critical to wine producers as climate change intensifies during the coming decades in France, Switzerland and other wine-growing regions.”

No sign of it “intensifying” in the last 15 years, so they may have problems with that false assertion which is presumably driven by broken model predictions.
Mind you, I’m sure is Tom Karl can adjust the climate data for us the wine will become much better in the near PAST ” as climate warms”.

Reply to  1saveenergy
March 22, 2016 10:22 am

.I live in Barcelona (Catalunya) and summer temperatures have been normal or colder since 2003. Great wines here too.

Reply to  1saveenergy
March 23, 2016 2:53 pm

“organic wine” is codename for “poisoning the earth with non-organic non-radioactive (or infinite half life) toxic Cu”.

Reply to  Aussiebear
March 22, 2016 5:30 pm

“Suprisingly” worse than we thought!

george e. smith
Reply to  Aussiebear
March 23, 2016 1:52 pm

Give us a shout when French wines get up to the level (quality productivity) of California wines.
Every year is a great vintage year for California wines.

Reply to  george e. smith
March 23, 2016 10:31 pm

Many vineyards in the Napa Valley have their own weather stations. Anecdotally the consensus is no trend in temperature, but until this current year a noticeable earlier bud break. Valley floor white varietals got an early start this year, but the reds more coy.
I farm at 9-1700 feet in the Mayacamas on the Sonoma side (barely). All cabernet. Hints of early break but they ducked back under the covers through the last rain iteration. Pushing hard now, but right on our “normal” schedule as best we know it from 25 years of data.
You can’t believe the media wailing. Lewis Perdue:
• Obama Seeks More Coordination on Dealing With Drought
• Tunnels don’t add up, now we know why
• Practical plus high-tech solutions can ease California’s water crisis
• Why some reservoirs don’t fill as quickly
• Why We Should Pay What Water Is Worth
• Five Important Facts on World Water Day
This is the latest edition sobered by the reality of normalcy. Before this, if I may take some license,
Wine growing regions will all move north.
Napa will become a desert.
It will soon no longer be possible to grow wine in the current premium regions.
My best answer to Larry Kummer is that we should ALL answer the foolishness every chance we get at the grassroots level. At the level of the dips who write this stuff. They don’t expect an answer. They are preaching gospel. They need to hear us.

Reply to  george e. smith
March 24, 2016 2:34 am

Likewise Cape wines. Here every season is different but in a similar way. A bit warmer, a bit colder, a bit wetter, a bit drier. Great climate and never boring.
May I take this opportunity to plug Eagle’s Nest wines in Constantia. They are great and the winemaker, Stuart Botha, is as good as they get.

george e. smith
Reply to  george e. smith
March 24, 2016 5:25 pm

Don’t like Cabernet. Pinot Noir’s were great until some idiot made a movie, then they just got good and expensive But keep up the good work Gymno, we need all the exports we can muster.

Reply to  george e. smith
March 31, 2016 10:28 pm

George, that movie was about Merot.

March 22, 2016 1:14 am

Lots of nuts out there will wait till one has a go , until then might open a bottle .

March 22, 2016 1:15 am

Good to see one upside.

Patrick MJD
Reply to  Seth
March 22, 2016 1:20 am

Spoken by someone who clearly has no clue about growing stuff! Well done Seth!

Reply to  Seth
March 22, 2016 3:53 am

Open Both eyes, take the blinkers off, and learn how to pay attention- then you will find you can see quite a bit of positives, some of which can be easily be found in the scientific literature- the above is just ONE example of many over the past 15 years.

Reply to  Seth
March 22, 2016 4:37 am

Seth: Good to see one upside.
Yes Seth, we are thankful for small mercies, like the greeneing of the Sahel; it must be absolute hell for the people living there.

Patrick MJD
March 22, 2016 1:16 am

“Wine quality also depends on a number of factors beyond climate, including grape varieties, soils, vineyard management and winemaker practices,” Cook said.”
I am glad soil was mentioned, soil composition that is. It’s a significant factor in wine varieties. Whites grow well in places like the Wairarapa in New Zealand (NZ). Reds grow well in Marlborough and Hawkes Bay. (Wines and olives grow VERY VERY well in NZ anyway due to the rich volcanic soils, sun and water. Not terribly affected by climate unless its a grape grown in a frost prone area).

Tom in Texas
Reply to  Patrick MJD
March 22, 2016 11:39 am

Absolutely soil matters, unfortunately here in Galveston county, Texas clay does not make great grapes. But the wild muscadine grapes are on a huge come back. These are producing a nice Chardonnay. My best bet is Honey Mead with fresh pick blackberries from the back. I also love this plant feeding frenzy, My tomatoes went from 6″ to 18″ in about 10 days and the potatoes are not far away. YE HA or for those that see things another way HA YE

george e. smith
Reply to  Patrick MJD
March 24, 2016 5:33 pm

So why can’t I get Marlborough Reds in California ??
But I can get plenty of Marlborough green shell mussels so thanx for those Patrick. But some dopes over here still order those fish bait Prince Edward Island excuse for a mussel. But I fix that by giving them a taste of the real thing. The GS mussels we get here are as big (the meat) as the whole damn shell of those black Canadian wimps.
I’ve even been known to drink white wines just to have some zedders.

March 22, 2016 1:16 am

Yet more evidence that warming is really happening and it’s not someone fiddling with the temps…

Reply to  spaatch
March 22, 2016 1:20 am

Yes, the planet is warming NATURALLY as we come out of the Little Ice Age !…Did you expect it to get colder ?? ….

Reply to  Marcus
March 22, 2016 2:26 am

Yes, the planet is warming NATURALLY
Most of the forcing is, in fact, anthropogenic greenhouse gasses.
as we come out of the Little Ice Age!
Just because it was colder before doesn’t mean that it will get warmer. “Coming out” of the little ice age can’t cause warming. You need some forcing, without which it would stay cold.
Did you expect it to get colder ?? ….
That’s what it would be doing without anthropogenic forcing.

Reply to  Marcus
March 22, 2016 2:35 am


That’s what it would be doing without anthropogenic forcing.

NO. That is what a climate model, tuned to follow a small section of the climate record, does. The fact that the model does not follow climate record at all well either before or after the period that it was tuned to fit is a sure fire indications that the fiddle factors are not quite right yet.

Reply to  Marcus
March 22, 2016 3:00 am


The fact that the model does not follow climate record at all well either before or after the period that it was tuned to fit is a sure fire indications that the fiddle factors are not quite right yet.
Do you have a link to the DOE PCM outside the period it was tuned to fit?

Reply to  Marcus
March 22, 2016 4:28 pm

Seth: “Most of the forcing is, in fact, anthropogenic greenhouse gasses.”
No it isn’t.
Stop making stuff up.

Reply to  Marcus
March 22, 2016 7:17 pm

seth March 22, 2016 at 2:26 am
“… You need some forcing, without which it would stay cold. …”

Can you please explain the, er, ‘forcing’, that cooled it off from the medieval warm period into the ‘little ice age’, i.e. from a NATURALLY sustained warmer and much longer epoch than we currently have?
Until you unambiguously can your ‘logic’ fails at the first hurdle, so is easily set-aside as meaningless position-taking, that reflects a biased interpretation, that is not possible to adequately test let alone declare substantiated or ‘settled’ science.
No credible testing = not a matter for science.
If not even science, then it sure can’t be “settled science”.
It’s not even science, so I file that sort of thinking under ‘obnoxious theology’.
And in case you didn’t notice in your mistaken haste to assert global CO2 ‘forcing’, as a thermal crisis, notice the following now, before you waffle more of your line of ‘reasoning’.
Water Vapor and Temperature plots are almost a perfect mirror-image of each other:comment imagecomment image
In other words, the recent thermal ‘forcing’ was performed ~99% by the H2O water molecule greenhouse gas effects, first as the liquid phase source, then as the evaporated gaseous phase, which then created the thermal-blanket pulse transient signal, in parallel to the water’s evaporated release and +/- 60 degree latitude band atmospheric water vapor rise.
The thermal pulse was NOT produced by a global CO2 concentration – at all!
Please indicate you now comprehend this observed relationship, and that the actual “greenhouse gas” involved in this event was almost, but not quite entirely 100% due to H2O vapor for the observed thermal G/H gas pulse of Feb 2016.
However, if you want to continue with the silly CO2 ‘forcing’ BS story from here, you’re remarks can only be considered scientifically irrelevant, irrational and time wasting.

Patrick MJD
Reply to  spaatch
March 22, 2016 1:20 am

“Wine quality also depends on a number of factors beyond climate, including grape varieties, soils, vineyard management and winemaker practices,” Cook said.”

Reply to  Patrick MJD
March 22, 2016 9:31 am

Since wine quality is somewhat subjective, how did they determine what the wine quality was back in 1600-1900? I know, they used a model!

Reply to  spaatch
March 22, 2016 3:15 am

You’ve just shown most of it , although you graph does not state what it actually uses as “observations”.
Look at you graph. It matches fairly well from 1975-2000 then cuts off ( handy ). If you look just before 1975 the models are notably cooler and fail to follow the temp records. Going back to 1915 they fail to match the colder period. In fact they totally fail to capture the late 19th c. cooling ( conveniently left off ) and early 20th c. warming that was as strong as the late 20th c. warming.
When a model can produce both the early and that late 20th c. warming in equal parts we may be able to take it more seriously. So far, not one of the dozens of models to that since they are all based on the ASSUMPTION the CO2 is the main driver but no one can actually make it work.
They balance exaggerated warming with exaggerated volcanic cooling and it works quite well for about 25-25y of the record. What you see in the blue line is exaggerated volcanic cooling of the models, not anything to do with what climate may or may not do.
Now if you are prepared to close one and not look critically at that graph you may be fooled into thinking the models are about right. Science is based on detailed crtical analysis, not ignoring the bit that don’t fit.

Reply to  spaatch
March 22, 2016 3:55 am

Who said it hadn’t been warming? And what is the reason claimed for ‘adjusting’ temps upward, which has been clearly shown to be happening? Can you answer the first one with the actual words of the people involved? And of course, the people involved MUST be people who actually have an influence, not someone living deep in Appalachia who never went to school.

March 22, 2016 1:17 am

Why is NASA even studying European wine grapes ? What does that have to do with Muslim outreach ? LOL

Patrick MJD
March 22, 2016 1:25 am

And remember, wine WAS grown in Northern England in Roman times. It wasn’t terribly good quality according to history, maybe good for cooking is all, but it was grown all the same. Varieties of wine that suit a cooler climate are being grown in more southerly areas in the UK (I forget now what varieties). The success of which is more to do with choice of variety and plant management than any risk from “climate change”.

Reply to  Patrick MJD
March 22, 2016 5:38 pm

Wine grapes were also grown in England during the Middle Ages. One comment from an individual during the reign of Henry II (r. 1154 – 1189) was that you had to grit your teeth to drink it.

March 22, 2016 1:36 am

“The finding is important because higher-quality wines are typically associated with earlier harvest dates in cooler wine-growing regions, such as France and Switzerland”.
BS!!! Harvests are based on a balance between many factors, sugar/PH/acids and many others, then add the good old taste tests. Many growers hope for a long slow ripening and with most varieties actually cooler temps are much preferred. And there is absolutely no mention made of soils, micro climates on smaller vineyards, improved growing methods such as nutrients/micro irrigation (computer controlled), and millions of dollars spend in hi-tech labs to influence the end result. In the 1600’s and maybe as little as 60 years ago I doubt a grape grower had any idea what his hooch was going to taste like 6 months after harvest. Today they can can tell within weeks after fermentation what the end product will be. (and for champagne lovers? that was a total accident). The only reason I can see that 400 years ago farmers liked early harvests was because they ran out of last years supply.

Reply to  asybot
March 22, 2016 10:04 am

And don’t forget choice of style to match market demands.
Want a crisp German style wine, high in acid and low alcohol? Harvest early and cold with low sugar high acids. Want a mellow mild flavor high alcohol Italian style table wine, perhaps from the same grape variety? Higher heat later harvest with high sugars and lower acids.
California makes wines from German style whites to Italin style Chianti from the same Northern California valleys.
It is a choice when to harvest tied as much to the vintner’s goals and plant varieties planted, as to climate or weather.
Then figure in that two microclimates 80 mile apart may have dramatic variation in harvest times even for the same goal of wine type, and even different sides of the same hill have different harvest times and their whole thesis goes pear shaped. Napa is about that far from Modesto, but one has 80 F summers and the other 105+F. One overcast and humid, the other clear and dry. Then you must figure in valley floor vs mountain top vineyards. Oh, and harvest may be delayed if the crusher is already in use…

Reply to  E.M.Smith
March 22, 2016 11:21 am

Em @ 10.04, Thanks you are spot on, I just didn’t want to keep on going. Thanks for adding all of those points. I saw your post below as well would have loved to have gone there.

george e. smith
Reply to  E.M.Smith
March 24, 2016 5:38 pm

Dang EM you have to go all the way to 80 miles to get a climate change ?? I only have to go 18.52 km down here in Sunnyvale. That’s 10 nm for the noncognoscenti.

March 22, 2016 2:04 am

Reblogged this on Climatism and commented:
Welcome news for the winemakers of Northern England whose livelihoods were wiped out around 1,000 years ago as the Medieval Warm Period or Medieval Climate Optimum, came to a chilling end, as the Little Ice Age ensued.

March 22, 2016 2:07 am

“Climate change is improving French wine quality”
Maybe , in a couple of decades, they will catch up to Australia. 🙂

Patrick MJD
Reply to  AndyG55
March 22, 2016 2:25 am

IIRC, many red vines originated from countries like France and are a good few years old here in Aus. Aussie reds are great. If you want whites, go New Zealand, in my, tried and tested, opinion *ahem*.

Reply to  Patrick MJD
March 22, 2016 2:29 am

The exception being Pinot Noir, which is better in NZ than anywhere in Australia.
Some Tasmanian ones approach.

Patrick MJD
Reply to  Patrick MJD
March 22, 2016 2:41 am

A cooler climate variety, no surprise there! But temperature (Climate) isn’t what makes them good. It’s the soil!

george e. smith
Reply to  Patrick MJD
March 24, 2016 5:40 pm

Please send us some good Marlborough Pinot Noir.

March 22, 2016 2:08 am

“Ben Cook”
A very unfortunate last name… 🙁
no-one will take him seriously.

Dr. S. Jeevananda Reddy
March 22, 2016 3:41 am

The shift in the planting and harvesting times after the introduction of new cultivars in different crops over the globe have been changed drastically. With high yielding new varieties under irrigation, the whole system of crop production changes. All these you can not attribute to climate change.
Dr. S. Jeevananda Reddy

Tom Halla
March 22, 2016 8:44 am

One should also consider the effects of programs like the UC Davis oenologogy studies, and the reactions to the practices of UC Davis graduates. The effect of what are esentially engineering in wine production as opposed to traditional artisan production has improved wine quality generally over the last fifty or so years.

Reply to  Tom Halla
March 22, 2016 10:28 am

I attended there and took Vit. & Eno. Intro class. The program is very impressive. Even as a non-major, we had to learn all the basics. Those in the major were busy changing the world and making new varieties. They had a couple of story tall, 4 inch, glass brandy still running in the entry of the V&E building, but only those in the major could use it…
There was great attention put on grape varieties for different climate types and various growth season lengths. One was developing grapes that could be grown in colder places, like Oregon and Washington. Then, it was almost unheard of, now they make great wines. NOT from climate change, but from plant breeding and growing practices. (One topic was about laying vines down and covering to get them through cold winters as a new practice to be rolled out up north.)
Though it looks like U. of Minnesota has taken the lead now in cold hardy cultivars
Look for a LOT more hype about Global Warming and wine with Minnesota making wine… (the State with “Little Sweden” in it…)

Reply to  E.M.Smith
March 22, 2016 11:33 am

There are now very good cool climate viticulture programs in SA, NZ and also Canada, @ Pam Grey up here in BC we are now growing grapes in the Kamloops ( ~ 200 miles north of the 49th) area and the Okanagan valley has had a wine industry since the 30’s. There are now over 300 licensed wineries in BC ( from mom and pop to very large out fits)

Reply to  E.M.Smith
March 22, 2016 5:46 pm

Go way back to the Norman invasion on England and look where still wine was successfully produced. Further north than today. Cheers…

Pamela Gray
March 22, 2016 9:26 am

I would expect wine production to increase and advance northward during a warm interstadial period. We are in the peak of just such a period. Make lots of wine and store it somewhere south of the 45th parallel. Why? Earth does not spend much time at the peak of an interstadial. Most of Pleistocene Earth-time is either on the way down to a glacial stadial period, or rising out of one. Much of our fuel in terms of coal stores are usually covered by ice fields and much of our rivers used for power generation are frozen solid, as will the water behind dams used to run the turbines.
It would be way cool to move South and open up a bottle of 500 year old wine from vineyards in the northern part of France. Or Montana for that matter.

March 22, 2016 10:30 am

I agree strategies are changing faster than the climate. We live in Washington State wine country and this is a very competitive industry as you are as profitable as wine reviewing snobs will allow. Your wine must please a vocal few to be considered by the great unwashed masses, and everyone is constantly examining their methods, responding to the current and forecast weather, incorporating new technologies, and availability of labor for the harvest. This last is not a trivial problem. And suitable oak isn’t getting any cheaper or more available.

March 22, 2016 10:45 am

How do they know that the wines are getting better ?
Have they be personally checking them ?

Reply to  Neo
March 22, 2016 11:35 am

@ Neo, that is the fun part of working with wines, you are constantly “checking” them 🙂

Bruce Cobb
March 22, 2016 1:52 pm

Every so often, the climate campaigners like to throw in a positive “result” from “climate change”. Makes it look like they are being honest. But there are a host of reasons why wine quality could be improving, including the increased CO2, which plants love.

John F. Hultquist
March 22, 2016 1:54 pm

During the past 40-50 years there has been intensive research regarding grapes, vineyards, and wine (viticulture & oenology). Scientific advances did not pass by these activities. Countries have supported such activities – one example is Washington State University’s “Prosser Irrigated Research & Extension Center” (IAREC). I won’t bother to mention others because they are well known.
Further, countries have invested to improve their grapes (and wine quality), in part, because of international trade agreements that introduced competition; France and Canada are prime examples.
[Five of us just finished pruning 17 acres of grapes and celebrated with a bit of sparkling wine {usa-champagne – sorry France}.]

March 22, 2016 3:50 pm
That chart shows the 1930’s as being cooler than 1998. Hansen said 1934 was hotter than 1998, so how do you get a chart that looks like that, if that is the case?

March 22, 2016 3:53 pm

This is not the sort of thing that the pro-CAGW crowd want to hear. It will be enough to drive them to drink. However not to drink French Wine. Articles like this could lead to a boycott of French Wine consumption by pro-CAGW wine drinkers.

Reply to  ntesdorf
March 23, 2016 4:13 am

oh dont worry
the prowarmist ABC radio in Aus ran this today
a disaster for french winemakers who will need to look for cooler climate land elsewhere as the wines will be ruined.
I kid you not.

Adrian Good
March 22, 2016 10:14 pm

What is the effect of rising CO2 on grape, fruit and edible plants maturing. Plants grows faster but does CO2 affect timing of fruiting?

David Blake
March 22, 2016 10:33 pm

I’m a wine professional working in Northern Burgundy and I can tell you that you just can’t make this harvest date comparison between the centuries. The study is worthless.
There are so many other factors to be considered, for instance:
* Disease control is so much better now. In ye olde times growers picked before the grapes went rotten. Or, if they went rotten the previous year, they made pretty sure that they picked early the next year. I guess the temptation was always to pick early, seeing as the alternative was the possibility of not putting bread on the table. Nowadays we can reduce disease pressure so that the winemaker has more choice of when to pick.
* Consumer tastes have changed. They demand riper, fruitier wines so growers pick later. « onze degré » just doesn’t cut it anymore.
* Markets have changed. In the past buyers had no choice buy to buy the local, thin, wine. Now with the internationalisation of markets growers must compete more.
* Regulation has changed. In the past it was easy to blend in a bit of wine from down south. It’s not a co-incidence that in the ’60’s and ’70’s the largest importer of Algerian wines was in Nuits-St-Georges, and that in those years much more burgundy was sold than was actually produced! So one could pick early (and safe) and “boost” the wine with a good old drop of « pied noir ». Nowadays the paperwork prevents (well 99.9% of) this.
* Harvest date is as much a function of flowering date than it is of weather. Flowering date is a function of pruning date. Pruning date is down to many factors like man power and frost risk. In the old days without any frost protection (no smudge pots in the distant past), and without electric secateurs the tendency may have been to finish pruning later than today.
I don’t see that this study took any of this into account.

J Calvert N(UK)
Reply to  David Blake
March 25, 2016 6:35 am

Ah, you can be sure they would have made ALL the necessary ‘adjustments’. And that after the data had been ‘adjusted’, the climate change signal was found to be eevun stronger than it was before.

March 23, 2016 2:39 pm

Harvest dates are very rough proxies for growing season temperature at best. Crop size, grape variety, presence or absence of vine disease, cultural practices, soil moisture, wind, winemaker’s preferences, and regulatory agencies can affect when harvest takes place. If all these factors were held constant over the examined time period, then harvest date would be better as a proxy. Unfortunately they have not. Over the last 50 years average crop size has fallen, earlier maturing grape varieties have been favored, virus free plant stock with great photosynthetic capacity is widespread, and new cultural practices have advanced ripening. To make it even more complicated vines have an internal clock that begins to tick the day the buds push.. You can approximate when a vineyard will have ripe fruit by the date of bud break, given crop size is constant. Bud break was early this year, in the Napa Valley. Benefitting from soils kept warm by winter rains. (thank you El Nino) We all know it will be an early year even if we have an unseasonably cool summer.
Obviously, neither Nasa or Harvard know s__t about grape growing.

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