Recently, I came across this paper, which after "hartem öffentlichen und anonymen" review has been published by Clim. Past, 9, 41–56, 2013 (see www.clim-past.net/9/41/2013/ - open access! - doi:10.5194/cp-9-41-2013)
O. Wetter and C. Pfister: An underestimated record breaking event – why summer 1540 was likely warmer than 2003
Christian Pfister from U Bern is one of the leading environmental historians, with a profound knowledge about historical accounts of climate in particular in Switzerland, southern Germany and other Central European areas. he works with, among many others, Jürg Luterbacher, Heinz Wanner, and I am proud to also be among his coauthors.Among his work, which I personally value very highly, is the analysis of the genesis of the Schweizer Waldpolizeigesetz in the 19th century - see Pfister, C., and D. Brändli,1999: Rodungen im Gebirge - Überschwemmungen im Vorland: Ein Deutungsmuster macht Karriere. In R.P. Sieferle and H. Greunigener (Hrsg.) Natur-Bilder. Wahrnehmungen von Natur und Umwelt in der Geschichte Campus Verlag Frankfurt/ New York, ISBN 3-593-36327-5, 371 pp, 9-1. I read this as a partial parable of the role of science in designing contemporary climate policy.
Now, the abstract of his article reprinted with Christian's permission:
The heat of summer 2003 in Western and Central Europe was claimed to be unprecedented since the Middle Ages on the basis of grape harvest data (GHD) and late wood maximum density (MXD) data from trees in the Alps. This paper shows that the authors of these studies overlooked the fact that the heat and drought in Switzerland in 1540 likely exceeded the amplitude of the previous hottest summer of 2003, because the persistent temperature and precipitation anomaly in that year, described in an abundant and coherent body of documentary evidence, severely affected the reliability of GHD and tree-rings as proxy-indicators for temperature estimates. Spring–summer (AMJJ) temperature anomalies of 4.7 C to 6.8 C being significantly higher than in 2003 were assessed for 1540 from a new long Swiss GHD series (1444 to 2011). During the climax of the heat wave in early August the grapes desiccated on the vine, which caused many vine-growers to interrupt or postpone the harvest despite full grape maturity until after the next spell of rain. Likewise, the leaves of many trees withered and fell to the ground under extreme drought stress as would usually be expected in late autumn. It remains to be determined by further research whether and how far this result obtained from local analyses can be spatially extrapolated. Based on the temperature estimates for Switzerland it is assumed from a great number of coherent qualitative documentary evidence about the outstanding heat drought in 1540 that AMJJ temperatures were likely more extreme in neighbouring regions of Western and Central Europe than in 2003. Considering the significance of soil moisture deficits for record breaking heat waves, these results still need to be validated with estimated seasonal precipitation. It is concluded that biological proxy data may not properly reveal record breaking heat and drought events. Such assessments thus need to be complemented with the critical study of contemporary evidence from documentary sources which provide coherent and detailed data about weather extremes and related impacts on human, ecological and social systems.
O. Wetter and C. Pfister: An underestimated record breaking event – why summer 1540 was likely warmer than 2003
Christian Pfister from U Bern is one of the leading environmental historians, with a profound knowledge about historical accounts of climate in particular in Switzerland, southern Germany and other Central European areas. he works with, among many others, Jürg Luterbacher, Heinz Wanner, and I am proud to also be among his coauthors.Among his work, which I personally value very highly, is the analysis of the genesis of the Schweizer Waldpolizeigesetz in the 19th century - see Pfister, C., and D. Brändli,1999: Rodungen im Gebirge - Überschwemmungen im Vorland: Ein Deutungsmuster macht Karriere. In R.P. Sieferle and H. Greunigener (Hrsg.) Natur-Bilder. Wahrnehmungen von Natur und Umwelt in der Geschichte Campus Verlag Frankfurt/ New York, ISBN 3-593-36327-5, 371 pp, 9-1. I read this as a partial parable of the role of science in designing contemporary climate policy.
Now, the abstract of his article reprinted with Christian's permission:
The heat of summer 2003 in Western and Central Europe was claimed to be unprecedented since the Middle Ages on the basis of grape harvest data (GHD) and late wood maximum density (MXD) data from trees in the Alps. This paper shows that the authors of these studies overlooked the fact that the heat and drought in Switzerland in 1540 likely exceeded the amplitude of the previous hottest summer of 2003, because the persistent temperature and precipitation anomaly in that year, described in an abundant and coherent body of documentary evidence, severely affected the reliability of GHD and tree-rings as proxy-indicators for temperature estimates. Spring–summer (AMJJ) temperature anomalies of 4.7 C to 6.8 C being significantly higher than in 2003 were assessed for 1540 from a new long Swiss GHD series (1444 to 2011). During the climax of the heat wave in early August the grapes desiccated on the vine, which caused many vine-growers to interrupt or postpone the harvest despite full grape maturity until after the next spell of rain. Likewise, the leaves of many trees withered and fell to the ground under extreme drought stress as would usually be expected in late autumn. It remains to be determined by further research whether and how far this result obtained from local analyses can be spatially extrapolated. Based on the temperature estimates for Switzerland it is assumed from a great number of coherent qualitative documentary evidence about the outstanding heat drought in 1540 that AMJJ temperatures were likely more extreme in neighbouring regions of Western and Central Europe than in 2003. Considering the significance of soil moisture deficits for record breaking heat waves, these results still need to be validated with estimated seasonal precipitation. It is concluded that biological proxy data may not properly reveal record breaking heat and drought events. Such assessments thus need to be complemented with the critical study of contemporary evidence from documentary sources which provide coherent and detailed data about weather extremes and related impacts on human, ecological and social systems.
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21 comments:
Interesting post, thank you.
The results fit well with plant stomata proxies (Kouwenberg et al. 2005) wich show a higher resolution than ice cores.
http://i90.photobucket.com/albums/k247/dhm1353/Climate%20Change/LawDomeMLOKouwenberg800.png
The big question: does the temperature lag atmospheric CO2 concentration or is the CO2 concentration rather following changes in temperatures?
V. Lenzer
Pfister and Wetter are a remarkable team. First they are the only historians, even social scientists, who directly contribute to environmental science, from the top of my head. Pfister even doesn't hesitate to metaphorically push aside a bunch of engineers and CFD modellers to intervene in recent politics, based on their research.
I also highly recommend their work about floods in the river Rhine basin.
But even they can't resist the pressure to hype in climate science.
Who the humpf cares which of the summers 1540 and 2003 was warmer? There is hardly a more uninteresting question imaginable. Their achievement lies of course in the improved understanding (or realization of lack thereof) of biological proxies and documentary evidence. But hey, we need a catchy title!
hvw,
I don't understand: the summer of 2003 plays in climate discourse an outstanding role; of course, it is interesting that the summer of 1540 was warmer.
Some more information (in German) on our favorite environmental historian, Christian Pfister, here in this review of "Nachhaltige Geschichte":
http://www.sehepunkte.de/2010/04/16331.html
hvw -
I am also a bit surprised that you find the question, if 1540 was comparable or surpassing the 2003 heat wave in Switzerland and parts of central Europe.
For me there are two issues, why this analysis of relevance
- purely scientific interest; old claims are re-examined, attempts made for falsification - and seemingly successfully so; but maybe another paper shows up in some future, again finding the present analysis of limited validity/plausibility. An interesting example of how science is functioning well.
- the dynamics of accepting knowledge claims in science and the public. Was the claim of unprecedented warmth (this claim was out in the public, maybe also in the scientific assessment of the event?) prematurely accepted because it fitted so nicely in what we all "know" to be true? Was this a case, where culturally constructed knowledge influenced scientific conclusions by cutting skepticism short?
I would appreciate if you could explain your position in some more detail.
@ Hans von Storch and Werner
First, I really shouldn't have criticised their choice of title; it's perfectly fine, I'd have chosen it myself. I was carried away by the need to be polemic, you know.
The paper is not really about a comparison of 2003 with 1540. Its substance is a re-assessment of 1540 temperatures.
old claims are re-examined, attempts made for falsification
I would like to believe that their motivation was not an attempt to find a summer warmer than that of 2003. I would like believe that their motivation was to add with their methods and new data to the body of knowledge and see what happens. It happend that they came up with T_2003 < T_1540, but if that would not have been the case, their main point, imho, the falsification of the hypothesis that latewood density and not thouroughly analyzed grape harvesting dates as proxies capture extremely hot summers, could still have persisted. Even if they had corrobated the opposite, that would have been an equally valuable contribution.
There are very many opportunities for interesting studies motivated by this paper, e.g. improve proxy analysis, find new proxies, apply their methods to other periods/years, etc... But the most misguided motivation would be a study that tries to dig out evidence that 1540 was cooler, in my opinion. But given the current climate here, discussion of the paper will most likely focus on that point and consequently suffer in quality and relevance.
On a personal note, and maybe interesting for Werner, I value this paper even more for its style, the wealth of knowledge it transmits, a whiff of the more narrative style of historians and an idea about the interconnectedness of many things that go into their work. Who would have guessed the religious denomination of Swiss cantons would influence climate reconstructions? I think this kind of work, including the place where it was published, is a prime example about how true transdisciplinarity can be achieved.
In that light, I find it sad, shallow and wasteful to reduce this to 1540 vs. 2003.
Werner:
the summer of 2003 plays in climate discourse an outstanding role; of course, it is interesting that the summer of 1540 was warmer.
Do you also think it should play that role? Do you think answering the question whether it was hotter than 1540 or not advances the climate debate in a positive way? Do you think that a potentially ensueing blog debate about whether it was or not would be a symptom of mature problem solving or rather a sign that we sit in der Klimafalle (like I do)?
Hans:
Maybe I miss something. Could you please explain how exactly the knowledge whether 1540 or 2003 was warmer contributes in any meaningful way to our understanding of climate and climate change? Of course I see great value in how we know it, but isn't the end result irrelevant?
The discussion of a scientific issue and rather inconvenient results of research get's difficult when the CAGW supporters try to turn the debate into a case of opinion: "we sit in der Klimafalle"
Do we, indeed?!
What kind of a trap?
While the battle of opinions continues, we learn that there is nothing, really nothing unprecetented to discover in climate history - not even the dogmatic or religious views on climate change. The romans already shared them, the Mayans, the church and many others.
The climate never got impressed by any of these attempts and did what it does best: it changed like it always did.
Here is some more interesting news about historical peaks. This one is about atmospheric CO2 concentrations up to 425 ppm (!) when the last ice age came to an end, more than 12'000 years before our time ...
http://www.sciencedirect.com/science/article/pii/S0277379113000553
V. Lenzer
In general I'm sceptical about using proxy data to estimate or rank extremeness of events.
Since extremes are rare by definition they escape reliable proxy calibration. Attempts to extrapolate from regular to extreme are further spoiled by underlying concepts of 'everything else being equal/random'. Dependencies and main drivers might well change in case of extremes, thresholds unaccounted for might become relevant or change. It all boils down to the need for reliable multi proxy models taylored to extreme events which are impossible to calibrate properly.
I also feel some reservations against obtaining CIs that are based upon the idea of 'regression to the mean' for extreme events.
PS: The critique of Douglas Keenan (2005) re. the claims of Chuine (2004) deserve recognition IMO:
Grape harvest dates are poor indicators of summer warmth, D. J. Keenan, 2005
hvw,
thanks for your thoughtful comment. I had to think about what "mature problem solving" might be. Of course, a blog debate is not problem solving, but it can incite something like a "mature debate" without only reproducing the usual pathological reflexes. Hard to tell. Maybe maturity is not a problem of the authors of the article, who just contribute to a well-established debate in climate science. Maturity is maybe more a problem of or to be expected by the readers, fellow-researchers and other audiences.
If I read your response correctly, you are torn between understanding that the authors make a reference to 2003 ("I'd have chosen it myself") and simultaneously being critical of it. Not a bad position, I guess. Working with ambivalences and ambiguities is indeed a sign of a mature debate. This maybe reflects best a mature attitude; to switch into a more reflective mode instead of repeating the ever same arguments. In my reading, Wetter (what a name!) and Pfister offer this option, even though they position themselves in the debate
(almost in a confessional mode - which is a characteristic of the climate debate: it forces you to confess which side you are on).
AMJJ season is not summer and the 2003 anomaly was by far largest during the summer months (JJA).
Werner,
I had to think about what "mature problem solving" might be ..
I guess what I have in mind is a constructive agenda. Taking about matters that are important. Which most of the time are not the typical us vs. them topics.
Look at Anonymous' comment #10 here: It looks like he or she has a good point: June and August anomalies in 2003 were responsible for the "record". April was even below average, May and July not terribly extreme. So maybe Wetter & Pfister did not "falsify" the 2003 "hottest summer since middle ages" because they just looked at a different season?
But is that of any importance? Does that invalidate anything remotely interesting we can learn from their work? I'd say no.
almost in a confessional mode - which is a characteristic of the climate debate: it forces you to confess which side you are on
That is the sickness of it all. It is almost a necessary ritual these days to confirm that you do not doubt AGW if you publish anything that could give the "skeptics" even a remote chance to mis-represent your work. We all know that, we all live with the resulting cruft.
In my mind, anybody who starts his/her scientific work or comment with a frame of mind that contains two conflicting sides necessarily produces cargo science at best. Because nature (and also society I guess) just doesn't fit into these drawers. But I understand that it is not very easy not to fall into that trap these days.
hvw,
well argued. Maybe there is even no outside to this trap; the confessional mode is part of the DNA of climate science. It's the prize it had to pay for its spectacular rise as a Leitwissenschaft and its close relationship with power. Without it, it would be something else. But what?
Wetter and Pfister use combined information from proxies and historic documents for their study, an excellent idea indeed. In a series of five extensive volumes a Dutch meteorologist Jan Buisman has collected such documentary information on weather and climate in the Netherlands (and surroundings) for the past thousand years. Buisman uses only information from sources under condition that such information can be confirmed by other independent sources. His reference lists are quite impressive. And he describes the year 1540 as “one of the hottest and driest of the past thousand years”. Though he is not mentioned within the reference list, Wetter and Pfister assured me that they are familiar with Buisman’s volumes. A pity, that Buisman wrote in Dutch, but his work is highly esteemed, as even Le Roy Ladurie once said: ”I advice everyone to study Dutch, to be able to read Buisman's works".
Werner,
Maybe there is even no outside to this trap; the confessional mode is part of the DNA of climate science.
I think the vast majority of climate scientists are well aware of the problem and actively try to avoid it. Simply because scientists in general have been trained to do that. That is enough to function as good or bad as any other science that yields policy relevant results. The "confessional mode" is a recent ritual to fend of possession by "skeptics" (the Banishing Ritual of the Pentagram would likely be more efficient, but looks even weirder).
It's the prize it had to pay for its spectacular rise as a Leitwissenschaft and its close relationship with power
A Faustian bargain, isn't it? The soul (scientific integrity) for power and fame. At least climate science did not sell its laughter, judging from the reaction to this by those affected.
Serious question: Can you please point me to a definition of "Leitwissenschaft"? Google fails me here. Thanks.
hvw,
Leitwissenschaft, da musste ich auch erst mal kurz nachdenken woher ich den Begriff habe. Dann fiels mir wieder ein: in den achtziger Jahren setzte die Umweltbewegung ihre Hoffnungen auf die Ökologie als einer "Leitwissenschaft", die auf der eine Seite mit modernsten wissenschaftlichen Mitteln arbeitet (Ökosystemtheorie), und auf der anderen aber auch die Naturdinge bezeichnet und katalogisiert - sozusagen der Schmetterlingssammler mit der Botanisiertrommel. Aus diesem hybriden Gebilde erhoffte man sich einen Wegweiser (Leitwissenschaft) in eine ökologischere Zukunft - Ökologie wurde zu einem Begriff für das richtige Leben etc (in Anspruch, den die Wissenschaft der Ökologie natürlich gar nie einhalten konnte. (Der Landschaftsforscher Ludwig Trepl kritisierte das damals schon in einem Aufsatz mit dem Titel "Ökologie - eine grüne Leitwissenschaft?").
Das erinnert in vielem an die Klimaforschung heute, die zum einen ebenfalls hochwissenschaftlich - computerisiert daherkommt (Achtung: science!) und zum anderen aber auch von Eisbergen, Eisbären, Baumringen, Wetterereignissen usw handelt, die die Alltagserfahrung und deren Ikonographie ansprechen. Die Klimawissenschaft bedient diese Erwartungen ja auch in schöner Regelmäßigkeit - man lese die Beschreibungen von keynote speeches etc in der Klimafalle - und weckt so auch Erwartungen an Hinweise für das richtige, klimaschonende Leben aus der Klimawissenschaft als einer Leitwissenschaft. (Und sie bringt ja auch lauter wegweisende "Gurus" hervor, die z.B. "große Transformationen" beschwören oder vor ihnen warnen usw.)
Ich gebe zu, das ist sehr allgemein. Aber stimmt sicher in vielerlei Hinsicht: die Klimaforschung hat in der Umweltbewegung die Rolle der Ökologie übernommen und damit auch die Erwartungen, die an sie geknüpft werden. Die Utopie für das richtige Leben ist heute "klimatologisch" (so wie sie vorher ökologisch war - oder auch noch ist).
(Ist das zu weit interpretiert, dass die Lüdecke Diskussion oben sowohl eine wissenschaftliche als auch eine ideologische Debatte ist - und beides ist geradezu vehext ineinander verwoben. Das ist nach Trepl, soweit ich mich erinnere, ein ennzeichen von Leitwissenschaften. Die Ökologie kann manches Lied davon singen, glaube ich).
Ludwig Trepl hat ein sehr lesenswertes Blog: Landschaft & Ökologie
Oh, prima Tip, dankeschön!
Werner,
da erwartet man maximal einen Suchstring, und stattdessen gibts richtig Text um die Ohren. Vielen Dank! Das Thema ist zu unbekannt und reichhaltig, dass ich jetzt etwas schlaues sagen könnte. "Leitwissenschaft" hat in dieser Lesart also damit zu tun, dass von ideologisch motivierten Laien viel hineinprojeziert wird? Also eher die Pest am A., als etwas wünschenswertes.
Ja, die Klimawissenschaften haben offensichtlich so ein Problem. Ich denke aber nicht,, dass ich "die Klimaforschung hat in der Umweltbewegung die Rolle der Ökologie übernommen und damit auch die Erwartungen, die an sie geknüpft werden. Die Utopie für das richtige Leben ist heute "klimatologisch"" so ohne weiters zustimmen kann. Ökologie scheint mir im Wurzelbereich weit intensiver und tiefer mit weltanschaulichen, ethischen, ideologischen, ja spirituellen und esoterischen Vorstellungen verflochten zu sein, als das für die Atmosphärenphysiker und Ozeanographen möglich scheint.
Quentin Quencher, von mir auch vielen Dank für den Tipp! Der aktuelle Kommentar dort passt ja auch sehr gut!
hvw inquiried:
Maybe I miss something. Could you please explain how exactly the knowledge whether 1540 or 2003 was warmer contributes in any meaningful way to our understanding of climate and climate change? Of course I see great value in how we know it, but isn't the end result irrelevant?
i was a bit perplexed, and then had other business, so it took a while for responding. I do not think that the question if 2003 was unprecedented for the specific part of the world, gives answers about the understanding about the mechanics (if you allow the term) of climate variability and change. In the same way, as scenario simulations do not provide such understanding. After having compared the proxy data, we know - if the analysis was correct and the result accurate! - that the 2003 event was not unprecedented but very, very rare. We do not know why; in the same way, we do not why the precipitation change in the mediterranean region is negative in fall in all scenarios, while the recent change is positive.
What I am at is, that some results are just interesting, thought inspiring, are pointing out that simple assertions, which are aired in the public, are often false, or at least contested.
A major positive element in the news "summer 2003 possibly not warmer than 1540" is that the healthy reflexes of science (cf Merton) of questioning and contesting all assertions, if they are used in a politically charged discourse or not, are still in place. Analyses, such as the one we discuss here, need to be contested themselves, but if surviving the finding represents a point of reference which our understanding, changing in time, must be able to cope with.
When you, hvw, ask for relevance - relevance for whom, for what? Has science to be relevant? I guess, our difference is mainly rooted in this word (and a halo of other conceptual issues).
Hans von Storch,
thanks for your detailed reply. Obviously I completely agree with your first paragraph.
What I am at is, that some results are just interesting, thought inspiring, are pointing out that simple assertions, which are aired in the public, are often false, or at least contested.
Sure, and the assertions don't even need to be simple. But that is a general characteristic of natural science, in any field, and one of reasons for the fun to be had.
A major positive element in the news "summer 2003 possibly not warmer than 1540" is that the healthy reflexes of science ... are still in place
Herein might lie the cause for our little difference. I don't share your perception that the healthy reflexes of science (cf Merton) of questioning and contesting all assertions ever were endangered or suppressed in climate science. Therefore, challenging a previous result doesn't make a paper particularly newsworthy by itself.
When you, hvw, ask for relevance - relevance for whom, for what? Has science to be relevant? I guess, our difference is mainly rooted in this word (and a halo of other conceptual issues).
Yes. I was using the word in the common, narrowly defined sense, i.e. relevance for the research community ("Whom?") and for answering interesting questions ("What?"), where "interesting" is defined by the researchers. I see you apply a broader meaning of "relevance", the definition of which becomes quickly a matter of philosophical and political discussion.
If we listen to media and blogosphere, Marcott et al seems to have more relevance. It seems, iconic graphs and symbols have a great potential of relevance.
I share hvw's point of view. For me it's a minor issue, of course relevant in a special field, but it didn't fit to my interests.
PS:
Scientists are not nice people all the time. I found this in Pacal Yiou's interactive comment in CPD:
"The axes of the graphics are hard to read. There are a few basic rules in textbooks on
“how to write scientific articles” (e.g. Day and Gastel, 2006, chapter 17)"
Andreas
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