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Medieval warmth and English wine

Filed under: — gavin @ 12 July 2006

Never let it be said that we at RealClimate don’t work for our readers. Since a commenter mentioned the medieval vineyards in England, I’ve been engaged on a quixotic quest to discover the truth about the oft-cited, but seldom thought through, claim that the existence of said vineyards a thousand years ago implies that a ‘Medieval Warm Period‘ was obviously warmer than the current climate (and by implication that human-caused global warming is not occuring). This claim comes up pretty frequently, and examples come from many of the usual suspects e.g. Singer (2005), and Baliunas (in 2003). The basic idea is that i) vineyards are a good proxy for temperature, ii) there were vineyards in England in medieval times, iii) everyone knows you don’t get English wine these days, iv) therefore England was warmer back then, and v) therefore increasing greenhouse gases have no radiative effect. I’ll examine each of these propositions in turn (but I’ll admit the logic of the last step escapes me). I’ll use two principle sources, the excellent (and cheap) “Winelands of Britain” by geologist Richard C. Selley and the website of the English Wine Producers.

Are vineyards a good temperature proxy? While climate clearly does impact viticulture through the the amount of sunshine, rainfall amounts, the number of frost free days in the spring and fall, etc., there a number of confounding factors that make it less than ideal as a long term proxy. These range from changing agricultural practices, changing grape varieties, changing social factors and the wider trade environment. For instance, much early winemaking in England was conducted in Benedictine monasteries for religious purposes – changing rites and the treatment of the monasteries by the crown (Henry VIII in particular) clearly impacted wine production there. Societal factors range from the devastating (the Black Death) to the trivial (working class preferences for beer over wine). The wider trade environment is also a big factor i.e. how easy was it to get better, cheaper wine from the continent? The marriage of Eleanor of Aquitaine and the English King in 1152 apparently allowed better access to the vineyards of Bordeaux, and however good medieval English wine was, it probably wasn’t a match for that!

However, for the sake of argument, let’s assume that climate is actually the dominant control – so what does the history of English vineyards show?

The earliest documentation that is better than anecdotal is from the Domesday Book (1087) – an early census that the new Norman king commissioned to assess his new English dominions, including the size of farms, population etc. Being relatively ‘frenchified’, the Normans (who had originally come from Viking stock) were quite keen on wine drinking (rather than mead or ale) and so made special note of existing vineyards and where the many new vines were being planted. Sources differ a little on how many vineyards are included in the book: Selley quotes Unwin (J. Wine Research, 1990 (subscription)) who records 46 vineyards across Southern England (42 unambiguous sites, 4 less direct), but other claims (unsourced) range up to 52. Lamb’s 1977 book has a few more from other various sources and anecdotally there are more still, and so clearly this is a minimum number.

Of the Domesday vineyards, all appear to lie below a line from Ely (Cambridgeshire) to Gloucestershire. Since the Book covers all of England up to the river Tees (north of Yorkshire), there is therefore reason to think that there weren’t many vineyards north of that line. Lamb reports two vineyards to the north (Lincoln and Leeds, Yorkshire) at some point between 1000 and 1300 AD, and Selley even reports a Scottish vineyard operating in the 12th Century. However, it’s probably not sensible to rely too much on these single reports since they don’t necessarily come with evidence for successful or sustained wine production. Indeed, there is one lone vineyard reported in Derbyshire (further north than any Domesday vineyard) in the 16th Century when all other reports were restricted to the South-east of England.

Wine making never completely died out in England, there were always a few die-hard viticulturists willing to give it a go, but production clearly declined after the 13th Century, had a brief resurgence in the 17th and 18th Centuries, only to decline to historic lows in the 19th Century when only 8 vineyards are recorded. Contemporary popular sentiment towards English (and Welsh) wine can be well judged by a comment in ‘Punch’ (a satirical magazine) that the wine would require 4 people to drink it – one victim, two to hold him down, and one other to pour the wine down his throat.

Unremarked by most oenophiles though, English and Welsh wine production started to have a renaissance in the 1950s. By 1977, there were 124 reasonable-sized vineyards in production – more than at any other time over the previous millennium. This resurgence was also unremarked upon by Lamb, who wrote in that same year that the English climate (the average of 1921-1950 to be precise) remained about a degree too cold for wine production. Thus the myth of the non-existant English wine industry was born and thrust headlong into the climate change debate…

Since 1977, a further 200 or so vineyards have opened (currently 400 and counting) and they cover a much more extensive area than the recorded medieval vineyards, extending out to Cornwall, and up to Lancashire and Yorkshire where the (currently) most northerly commercial vineyard sits. So with the sole exception of one ‘rather improbably’ located 12th Century Scottish vineyard (and strictly speaking that doesn’t count, it not being in England ‘n’ all…), English vineyards have almost certainly exceeded the extent of medieval cultivation. And I hear (from normally reliable sources) they are actually producing a pretty decent selection of white wines.

So what should one conclude from this? Well, one shouldn’t be too dogmatic that English temperatures are now obviously above a medieval peak – the impact of confounding factors in wine production precludes such a clear conclusion (and I am pretty agnostic with regards to the rest of the evidence of whether northern Europe was warmer 1000 years than today). However, one can conclude that those who are using the medieval English vineyards as a ‘counter-proof’ to the idea of present day global warming are just blowing smoke (or possibly drinking too much Californian). If they are a good proxy, then England is warmer now, and if they are not…. well, why talk about them in this context at all?

There is a bigger issue of course. For the sake of argument, let’s accept that medieval times were as warm in England as they are today, and even that global temperatures were similar (that’s a much bigger leap, but no mind). What would that imply for our attribution of current climate changes to human causes? ……. Nothing. Nowt. Zero. Zip.

Why? Well, warm periods have occured in the past, and if not the medieval period, then probably the last interglacial (120,000 years ago), certainly the Pliocene (3 million years ago), without question the (Eocene 50 million years), and in particular the Paleocene-Eocene Thermal Maximum (55 million years ago), and so on. Current theories of climate change do not rely on whether today’s temperatures are ‘unprecedented’. Instead they examine the physical causes of climate change and match up what we know about their physical effects and time history and see which of the multiple drivers or combination can best explain the observations. For the last few decades, that is quite clearly the rise in greenhouse gases, punctuated by the occasional volcano and mitigated slightly by the concomittant rise in particulate pollution.

Understanding past climate changes are of course also very interesting – they provide test cases for climate models and can have profound implications for the history of human society. However, uncertainties (as recently outlined in the NAS report) increase as you go back in time, and that applies to our knowledge of the climate drivers as well as to temperatures. So much so that even a medieval period a couple of tenths of a degree warmer than today would still be consistent with what we know about solar forcing and climate sensitivity within the commonly accepted uncertainties.

My oenological research project has not then lead me to any profound insights into climate change in the past, but it has given me a little more respect for the dedication of my winemaking compatriots. So next time I’m in the area, I’ll drink to that!

81 Responses to “Medieval warmth and English wine”

  1. 51
    PHEaston says:

    I am rather surprised reading the article and some comments here. My understanding is that one of the principle reasons for the existence of this site was to put the case for the hockey stick. The reason why the hockey stick was so important is that while it was difficult to demonstrate with certainty that the current rising trend is manmade, at least it is unprecedented (in the past 1000 to 2000 yrs) – and therefore probably manmade. This case was fundamental in IPCC TAR and a major driver in the political support for Kyoto. You now seem to be saying that while we cannot be sure the current temperatures are unprecedented, we can at least be certain they are manmade! Well, what is the evidence for this? Even the hockey stick indicates that the current rate of temperature rise is not unusual when compared to a similar one during the first half of 20th century (up to 1945) when no-one claims man was not the cause.

    [Response: Your understanding is incorrect. RC was set up to talk generally about climate science in all its aspects since there is a clear desire among the public and journalists to have more context and depth on the subject. Read some of the posts, for instance: ‘What if … the Hockey Stick was wrong’ to see why that little sub-field, interesting though it is, is only a minor part of the climate change story. After all, IPCC was set up in 1989, and Kyoto negotiated in 1997 – years before these reconstructions were done. One further misconception: temperature rises in the early part of the century did have an anthropogenic component, only it was not as dominant as it is currently. – gavin]

  2. 52
    Steve Bloom says:

    Gavin, you mention the “brief resurgence in the 17th and 18th Centuries, only to decline to historic lows in the 19th Century when only 8 vineyards are recorded.” I vaguely recall reading that at approximately the same time cheap hard liquor (mainly gin — “the scourge of the working class” as I believe it was known) became widely available for the first time, and it seems plausible that this would have displaced much of the market for domestic wine.

  3. 53
    Dave B says:

    51 response:

    did the well documented global cooling between 1940 and 1975 have an anthropogenic component as well, or is only WARMING anthropogenic?

    [Response: Yes. There was an anthropogenic component to the mid-century cooling as well – namely sulphate aerosols. But like the earlier period, natural forcings also played a role. It is only in the last few decades that the GHG signal has asserted it’s dominance, but that doesn’t mean it was zero before that. – gavin]

  4. 54
    Dave B says:

    53 response:

    has the sulphate aerosols component remained flat, or has it decreased? (or increased slower than CO2?)
    also, how large of a negative forcing (or cooling forcing) did the sulphate aerosols make? are there measured atmospheric sulphate aerosol concentrations available, to support your claim?

    [Response: Look at and references therein for the estimated time history of trop. aerosols and reasons why it’s thought a reasonable (though not perfect) estimate. -gavin]

  5. 55
    PHEaston says:

    RE 53
    Warming is anthropogenic. Cooling is called Global Dimming. This is caused by aerosols in the air from general air pollution, and particularly that from aeroplanes. For example, when planes were grounded in the USA afer 9/11, there was an observable cleaner air. In the (unlikely?) event that global temperatures should stabilise or reduce within the next few years, this will be due to the fact that climate modellers have underestimated the impact of man made pollution. It will be our lucky escape – that our aerosol polluting activities will have outweighed our greenhouse gas pollution. The result is that we may head towards global cooling instead of warming. You may as well aceept that whatever we do, we can’t win. Our only consolation is that life expectancy and quality of life for the vast majority of Earth’s human inhabitants is better than its ever been in human history.

  6. 56
    S Molnar says:

    Speaking of why this site exists, I believe a lot of the readers (certainly I am one) have some combination of ignorance and lack of time/resources/inclination to go to original sources in order to learn what’s presented here, which makes this a valuable resource. On the other hand (and not to pick on Dave B in particular, since it’s a recurring theme), some readers seem disinclined (or maybe just unaware of the option?) to look at the index or use the search engine at the top of the page to find out what has already been covered. It seems to me that a cursory check of previous posts is required by basic etiquette; not an exhaustive survey, mind you – some things are buried deeper than others – but it isn’t too hard to search on, say, “aerosol”, and come up with this posting (which may not answer all the questions, but at least establishes the framework for the discussion):

    Would a big banner that says “Please use the index and search engine before asking” help the discussion or just intimidate the meek? I’m not sure.

  7. 57
    Jim Baerg says:

    Re: #43

    However, some advance that drasticly cuts the cost of getting into orbit, eg: the space elevator, would allow the solar power satellite idea to help solve the problem by reducing fossil fuel use.

    Eventually the space habitat idea is likely to work, but it will take a while to learn how to make closed cycle ecosystems work on a much smaller than planetary scale.

  8. 58
    jayster says:

    maybe your anwser is quite right,but nobody knows what would happened next second.
    I’m 38

  9. 59
    Dan says:

    re: 56. I doubt it will make any difference. There appear to be quite a few “drive by” posters who ignore the peer-reviewed science, think that they know more than the many thousands of climate scientists and science organizations around the world, who, after the essence of their posts have been essentially shot down, disappear, only to reappear under a different name a little later with another cherry-picked comment. Yet no evidence is given that they were here to learn anything. Or that they learned from the evidence provided in response to their first comment. Or that they can admit they were wrong. They just go off into the ether and come back in the form of another poster name. As someone already posted, “That a layman cannot fathom the significant gap in knowledge between themselves and scientists on the cutting edge of their field has got to be the height of arrogance.”

  10. 60

    Re #54 — is there an annual time series for aerosols anywhere? Please let me know.


  11. 61
    Hank Roberts says:

    Google finds a few; here are the first 2 hits:

    about 324,000 for +aerosol +”time series”

    IDEA – Site Specific Time-series and Correlations of MODIS Aerosol Optical Depth and Surface PM2.5 Concentration. Sample site-specific time series of MODIS AOD …

    NOAA Paleoclimatology Program – Robertson et al. 2001 Hypothesized …
    A new compilation of annually resolved time series of atmospheric trace gas concentrations, solar irradiance, tropospheric aerosol optical depth, …

  12. 62
    Gar Lipow says:

    RE: 56 – in many ways the index is more helpful that the search for non-experts – because it is useful even if you don’t know which key word to search under.

    BTW, it is nice to occassionally have a topic like this one with a bit of a lighthearted spin to it – even as it forms the basis for more serious discussion.

  13. 63
    R. Rowland says:

    Don’t forget Roman Britian, when the climate was warmer than it would be in the “Dark Ages.” Googling “roman britain”, “wine production” yielded 88 hits, the first of which takes one to

  14. 64
    Steve Short says:

    Similar comments re warming can be made about both Tasmania and the South Island of New Zealand. For some years now the northern end of the South Island of New Zealand has been growing excellent white wines (maybe stunning if you are a sauvignon blanc or fumee blanc fan ;-) and now red wines, in particular pinot noir are beginning to be grown successfully in Central Otago in the South Island. This was an area where, in the 1950s and 1960s, little pots of burning sump oil used to be slung under apple and pear tree orchards in the winter to stop sudden deep frosts killing the trees! Similarly Tasmania is also now producing excellent white wines and there are also recent plantings of reds. As someone who lived in the South Island 1971 through 1974 and in Tasmania 1975 through 1978 I can assure readers that they were both much colder places than today and there was no wine industry to speak of in either place. Presumably this effect is due to the warming of the Tasman Sea.

  15. 65
    chris says:

    Re: 22, 27, 32,34

    Perhaps this is actually quite well accepted, but I’ve had a go at hunting it down anyway.

    The ice core data right through the Medieval Warm Period (MWP) and the Little Ice Age (LIA) etc. tends to support the notion that the small variations in atmospheric CO2 are at best responses to temperature variations as a result of other local or global effects, rather than being responsible for temperature changes.

    So in addition to the fine-grained CO2 data from Ethridge et al (cited in comment #27) covering the last 1000 years, the less detailed record does have some data points covering the preceding 1000 years (i.e. 1000 AD back to 0 AD and further into the past). This from:

    Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica
    Indermuhle A, Stocker TF, Joos F, Fischer H, Smith HJ, Wahlen M, Deck B, Mastroianni D, Tschumi J, Blunier T, Meyer R, Stauffer B
    NATURE 398 (6723): 121-126 MAR 11 1999
    Abstract: A high-resolution ice-core record of atmospheric CO2 concentration over the Holocene epoch shows that the global carbon cycle has not been in steady state during the past 11,000 years. Analysis of the CO2 concentration and carbon stable-isotope records, using a one-dimensional carbon-cycle model, suggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial-scale changes of atmospheric CO2 concentrations.

    …in which the CO2 in the Taylor Dome core CO2 data falls easily within the range 275-285 ppm for the entire period from about 3000 years before now until a couple of hundred years before now.

    That doesn’t rule out the possibility that land clearances may have affected climate events locally that may have impacted on the ability to grow vines at various periods during the last thousand years.

    Another important question with respect to the ice core data is the extent to which diffusional effects might have smoothed some of the short timescale variability. For example the use of stromatal frequency as a proxy for CO2 levels indicates lower lows and higher highs in atmospheric CO2 levels:

    see, for example:

    Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles
    Kouwenberg L, Wagner R, Kurschner W, Visscher H
    GEOLOGY 33 (1): 33-36 JAN 2005
    Abstract: A stomatal frequency record based on buried Tsuga hetero-phylla needles reveals significant centennial-scale atmospheric CO2 fluctuations during the last millennium. The record includes four CO2 minima of 260-275 ppmv (ca. A.D. 860 and A.D. 1150, and less prominently, ca. A.D. 1600 and 1800). Alternating CO2 maxima of 300-320 ppmv are present at A.D. 1000, A.D. 1300, and ca. A.D. 1700. These CO2 fluctuations parallel global terrestrial air temperature changes, as well as oceanic surface temperature fluctuations in the North Atlantic. The results obtained in this study corroborate the notion of a continuous coupling of the preindustrial atmospheric CO2 regime and climate.

    Does that mean the question is still open? I’ve been a good boy and checked the index on this site for discussions of the stomatal frequency as a proxy for atmospheric CO2 levels, but there seems to be little on this at all. I’m curious to know what the general consensus is, as to the reliability of stomatal frequency as a CO2 proxy. Obviously it’s easy to imagine all sorts of problems with this proxy, the question of calibration in particular, being prominant. Is it pants? Is it generally thought to be qualitatively useful but quantitatively suspect etc. etc.?

  16. 66
    Gareth says:

    Re: #64

    The development of the wine business in New Zealand’s South Island has little to do with climate change over the last 30 years. It has much more to do with growers experimenting with grape growing in areas where other crops (like sheep) used to be more important. In my own region (Waipara Valley in Canterbury), the first grapes were planted in the 80s when an irrigation scheme was constructed. Other pioneers demonstrated the valley’s potential for fine wines in the 90s, and in the last five years major commercial growers have moved in. Much the same pattern has been followed in other SI regions.

    And I can assure Steve that Central Otago still gets very cold in winter (just been skiing there), but many of the orchards have been replaced by vineyards.

  17. 67
    S Molnar says:

    Re #59: This inability to recognize superior ability in professionals has been documented in other fields. For instance, it is well known (i.e., I read it a long time ago and won’t bother to try to find the reference) that many sports fans genuinely believe they can do better than the professionals, provided the sport is one in which the athletes are of normal dimensions (such as pre-steroidal baseball, as opposed to, say, basketball). It seems to me that this criterion of looking more or less the same is important no matter the field: consider that Albert Einstein and Stephen Hawking are both viewed by the general public as great geniuses, but Niels Bohr and Steven Weinberg are essentially unknown. The difference? Well, Einstein and Hawking may have been marginally better, but that distinction, if true, is insignificant for practical purposes. My belief is that the real reason for the apotheosis of Einstein and Hawking is their oddities of speech, appearance and actions. Bohr and Weinberg could pass for businessmen, but not Einstein and Hawking.

    Which brings me to my idea to save civilization and viniculture as we know it, which I would only dare express on a thread devoted to Bacchus: We need a climate scientist to affect mannerisms that will enable him to capture the public’s imagination, and use this platform to bring about major policy changes. I suggest Gavin as the sacrificial scientist (Hansen may be a great man, but he looks like he could be the manager of a convenience store). Gavin should dress eccentrically, speak with a heavy European accent (either Einstein or Teller will work as a reference), and have some sort of prop, like a wheelchair (Note: I’m not making light of ALS/Motor Neurone Disease). In case Gavin lacks natural thespianic talent, he can always model himself after a certain character in a certain Kubrick film. Come on, Gavin, we need you.

  18. 68
    Phillip Shaw says:

    Re #67: I second the nomination. But I feel that a charismatic spokesperson, such as Carl Sagan, can be as effective as an eccentric one. I also think that a slogan or motto would valuable (particularly for the American audience since we seem to have the attention span of chipmunks). Two possible slogans I just toss out for consideration are “Hot enough for you?” and “Is it just me or does it seem warm in here?”

  19. 69
    Brian Gordon says:

    Re: Etiquette and know-it-alls:

    “It seems to me that a cursory check of previous posts is required by basic etiquette…”

    Many of us come to this ‘climate change’ thing thinking we know FAR more than we do about the basics, and programmed to think any conflicting response is a sign of ideological bias. I think this leads to the ‘look-down-your-nose-while-attacking-then-run’ approach. You think you have a good grasp on an issue, some clearly biased person (scientist or not) posits something that contradicts your view, so you attack. I’ve done it. [Sorry…I’ve grown more secure since then. :-) ]

  20. 70
    Brian Gordon says:

    Regarding charismatic leaders: isn’t that what we have now? ‘Leaders’ devoid of integrity or wisdom, but they sure are popular…they’re like diet books that tell us we can eat all we want and still lose weight. Those types of books continue to sell very well, after many years of ‘debunking.’

    We need someone(s) who become charismatic *because* of his/her/their integrity, a la Gandhi or Jesus.

  21. 71
    Steve Sadlov says:

    RE: #37 – that may well be true in your microclimate of the Inland Empire. However, in No Cal, the opposite has been true for the past several years – almost no spring at all (extended winter, essentially) and weak, overall, summers. For example, this year was one of the coldest springs on record (as documented by me, real time, here, including reports of some amazing late season low altitide snow events – for example Calistoga had sticking snow in March, a once every 50 year event). As a result – there is a low yield this year, simply in terms of the sheer numbers of grapes on the vines. The grapes also started out stunted (thankfully, a couple of mid summer hot spells have helped them to catch up in terms of size). Now, the big question is, when will the fall cooling and real rains set in. If it happens in October (un like last year’s more normal scenario but like the previous year’s scenario) then growers may be in a world of hurt – for exactly the opposite reasons prophecied in the report.

  22. 72

    Can anybody point me to a good source on the Viking colonization of Greenland? I keep hearing from AGW denialists that Greenland was warm and comfortable during the middle ages, which was how it got its name, and therefore climate change is swift and happens all the time and we shouldn’t worry about it. The way I heard it, Greenland was deliberately misnamed to steer competing colonizers away from the equally misnamed Iceland. But I’d like to be able to cite a source.


  23. 73

    Barton, there is a popular paperback by Brian Fagan called “The Little Ice Age” and published by Basic books in 2002. ISBN 0-465-02272-3 See

    It begins with a description of the colonisation of Greenland, and has a list of references for each chapter at the end of the book.


  24. 74

    Thanks, Alastair.


  25. 75
    Steve Sadlov says:

    Another interesting datapoint regarding the impacts of the West Coast’s nearly non existent spring is the fact that the berry crops while prolific are ripening late. Even the recent heat has not been enough to overcome this. I am a small grower but struggle a bit due to an ENE facing exposure on a hill. So, I really need to have my fruit already well along during the Solstice. Unfortunately, this year the fruit is only now at that point. The sun angle is already getting low enough that I am seeing uneven rippening, which is sad, because, even though I have a record number of (Olala) berries on the vines, many of them will be poor in quality. There are still even a few blossoms in evidence, those berries will probably be affected by the fall rains. I have to imagine other growers are experiencing problems as well this year.

  26. 76
    JohnLopresti says:

    I think Gavin has recognized an indicator species, but uncovering the useful data could be time consuming. I have contacted a professor, recently retired, who investigated grape rDNA, identifying parentage of modern vines such as some members of the cabernet family, and others. Cabs are the base grape in Bordeaux. I think perhaps the diffuseness of the discussion and the voluminousness of the literature which would have to be searched add to the complexity of pursuing Gavin’s conjecture to a useful conclusion, though some of the linked webpages demonstrate others are developing the theme already in England proper. If the Diffenbaugh NAS study is borne out in climate change, we will see grape growing zones progressing northward.

    In the research using viticulture as an indicator species, I think there is an important niche for rDNA as a research tool. But for now, that is the most I could suggest; the emeritus professor whom I contacted, has reviewed this thread and echoed as much, as well. It would be a wonderful project worth developing by UC Davis in conjunction perhaps with some companion entity on the other side of the Atlantic.

  27. 77
    Stephen Bloch says:

    Re #22: the MWP appears to have ended (or “started ending”) around 1300. Next to Fagan’s The Little Ice Age on my bookshelf is William Chester Jordan’s The Great Famine, which concentrates on the years 1315-1322, when all of Europe experienced unusually cold, wet weather. This pattern (Jordan claims) continued intermittently in subsequent decades, so that by the time the Black Plague arrived in 1348-1349, the population was weakened by a generation of frequent famines and thus more susceptible to infection.

    Re #72: Also on the same bookshelf is Jared Diamond’s Collapse, which includes several chapters about the Greenland colonies. He’s a popularizer, and I gather there is some disagreement among experts about e.g. his claim that the Norse colonists in Greenland refused to eat fish (preferring pork, beef, mutton, goat, and seal in that order — exactly the opposite of their order of suitability for the climate!) Anyway, a fascinating read for anyone interested in (anthropogenic or not) climate change, and (climatogenic or not) cultural collapse.

  28. 78
    Paul Williams says:

    Re response to #54

    Looking at the forcing for aerosols, it’s hard to see how they could have been responsible for cooling from 1940 to 1975, then lost influence so abruptly that global temperature then started reacting to GHGs, resulting in the step in temperature that occurred in 1975/6. Aerosols seem to be increasing along a relatively smooth curve according to the GISS link, so what is the explanation for the step change in temperature in 1975/6?

    I’ve tried looking at the aerosol link, and searched on 1975 and 1976, but couldn’t find that specific question addressed.

  29. 79
    Richard Tol says:

    I find this debate about past wine production in England baffling. Wine is not a plant, it is a crop, that is, it is not the plant that decides whether it grows in England, but the farmer. The upshot of this is that you do not only need to understand the natural conditions, but also the social and economic circumstances.

    The decline of English viniculture had probably little to do with climate change, and a lot to do with the falling costs of transport of wine from Bordeaux to England. English wine used to be bad but much cheaper than French wine. As the price of imports fell, English vineyards were outcompeted and gave up.

  30. 80
    Podchef says:

    Seems to me in the annals of mediaeval history there was a man-made climactic change–different from and separate of the krakatoa-like volcanic explosion which plunged the world into a dark winter and heralded the “dark ages”. If I recall correctly, an abundance of logging throughout Europe altered the temperatures for a decade or so around the time of the plauge. Can’t recall where such info popped into my head, but all this talk of English butts and their contents reminded me of the link to the trees. . . .

  31. 81
    JohnLopresti says:

    If anyone wants to pursue the DNA tracing method, I thought I would supply a few links to articles. The geneticists among you likely have subscriptions, but many scholarly writings are behind the paywalls of bioscience. Here is a very long abstract of a paper dated 1998 presented by a Cornell Univ. expert; the follow through references to view include the basic research by Meredith and Bowers in papers cited at the bibliography. Here is the website of a small ranch growing syrah, which like the Bordeaux varietals, has its origins in regions traced to the eastern Mediterranean and beyond. The commenter above who described Vitis vinifera as a cropping choice is accurate within bounds, but in its highly cultivated and genetically fostered form in which we have known it in modern centuries it is very climate sensitive. It is interesting reading to study the scientists’ work selecting natural streamcourse grapes from all over the world in developing European modern grapevines. An especially intense epoch in the grape plant’s history occurred at the end of century XIX when a US wingless aphid pest was exported to Europe acidentally, where it obliterated nearly all viticulture in the best European regions. Grapevine breeders quickly developed rootstock and scions for replacement vines in Europe; much work along these lines was done in the US at Cornell U, however, Cornell is situated in a zone with snow, humidity, and gross heat peaks, all of which limited the natural capabilities of Cornell U to perform onsite plant breeding science. UC Davis, however, although in a quite torrid area of CA, is sufficiently close to modern vinifera ranches for access to a large corps of growers to test experimental conditions scientifically. Only the most recent science has great accuracy, as even in CA it was only very recently that the beverage product could approach the best European practices both in field and within winery.
    Because the vine is a woody plant and cares little about soil fertility it may be cultivated in a variety of locations. Perhaps there are some paleo beer makers reading this website; as I recall in the archeologic and anthropologic literatures, beer fabrication was effected in very ancient times. I am not sure whether its existence preceded that of wine. I hope this provides some supplemental information and guidelines for further research. I think the outcome might serve as yet another stencil through which to view modern civilization’s evolving weather in a sensitive way.