I’m sorry, I meant ‘Medieval Climatic Anomaly’

Temparature reconstruction plot from the IPCC's 2007 report

It took me a little while of thinking to work out why I don’t like the term ‘medieval climatic anomaly’, which I stumbled across following this notice at News for Medievalists (before that furore broke) about a new book, Herb Maschner, Owen Mason and Robert McGhee (edd.), The Northern World, AD 900-1400 (Salt Lake City 2009). It’s not that I’m immediately down on the book; firstly it looks quite important in its way (though why do so many of our climate proxies have to come from Greenland, which we already have reason to suspect may have been different? This has caused to me to wonder if there was sediment core work done on, say, Lake Geneva, and it turns out that such work is older than I am, so really, I ought to read more before sounding off. Anyway!) and secondly I haven’t read it yet and can’t tell exactly where between science and anthropology it falls and how much of either I might be able to follow. But there is this term, for what I know as the Medieval Warm Period, and it bothers me.

After a short while pondering it seems to me that it defuses the controversy of the term ‘Medieval Warm Period‘, of which after all we have seen enough just round these parts lately, but not necessarily in helpful directions. To call the warm peak an ‘anomaly’ suggests that it’s odd, ignorable, not significant, whereas what little I understand of these things suggests that these changes of graph are either cyclical or caused, what they aren’t is random. On the other hand, one of the battles over this (for all the wrong reason, it seems to me, but you know this) is whether any current change in our climate is ‘anomalous’, so maybe this is actually a stronger term. I’m just not sure it reads that way. Then the other thing is the abandonment of the descriptive adjective ‘warm’. The result is that someone who hadn’t met the term before wouldn’t easily see why it might matter. Now is that a crazy-filter, or a strange attempt to avoid courting persecution by activist sceptics by not ‘prejudging’ the issue? I hope not the latter, because that leads to Bad Science (as does that link) but the former is a bit objectionable too. Surely what needs to happen with this debate is that it reaches more people, not fewer? On the other hand, only a few months ago I was arguing that the material of this book shouldn’t be allowed to be influenced by that debate or be part of it…

As you can tell, I am a bit conflicted about how to discuss this whole issue. Not least because, if it should turn out on investigation that, actually, this here ‘medieval climatic anomaly’ wasn’t as important in Western Europe in the tenth century as has sometimes been preached, I lose my principal handle on social change in that period. And dammit, I like that handle.


15 responses to “I’m sorry, I meant ‘Medieval Climatic Anomaly’

  1. As someone who tries to keep up with this period for a different part of the globe (although one that is also supposed to have gotten warmer, and the resulting argument is thus: Warm and dry? Or warm and wet? Good for crops or bad?), there could be another reason to drop the “warm.” Which is that, if the coral evidence that is mentioned in The Great Warming for the Pacific Islands is correct, that it the temperature didn’t in crease everywhere, but dropped in at least one place.

    Which, again, just goes to show that local variation cannot be ignored.

    • Good points both, and thankyou for the perspective. I am also now realising that I cannot remember where it was that I first read someone suggesting how much an insignificant-sounding degree or two upwards might have eased off extreme rainfall and thus raised crop yields…

      Basically, my experience with the medieval climate kind of mirrors the global population’s with the current one: I didn’t realise when I was first made aware of the possibilities how significant they might be, and now I have rather a lot invested in an idea about it that looks more fragile every time I read something on it. What is currently letting me stay with my thinking is exactly this idea of regional variation, but I really do have to get at the state of the literature for Western Europe some time soon because if it doesn’t work there, I have no theory…

      Sorry, still thinking out loud here.

  2. I touched on why I chose the term I did in my post -to which you kindly linked- and I think I still agree with your points. It would be disingenuous to speak in a manner to avoid climate change deniers; and one should speak to reach as many as possible.

    That said, the MWP/MCA strikes me as anomalous rather than a ‘period’. It appears to be only limited to parts of the Northern Hemisphere, and is only over a very short (however crucial for us) time period. ‘Anomaly’ seems to address this facet of the thing better than ‘period’ which would imply a broader sweep.

    I also prefer to drop ‘warm’ from both MCA/MWP and from ‘global warming’ simply because of the positive connotations of the word. Warm is not always good. Increased warmth is not the only result of alterations in temperature. Other climate patterns are altered- rainfall, winds, currents, &c. Yet the term ‘warm’, particularly in areas prone to snow, sounds like balmy spring days suitable for swimming.

    Placing the emphasis on the climactic shifts which occur as a result of the temperature change helps keep one focused on the not-always-pleasant results of these events.

    I feel like I am rambling, so I shall leave it at that.

    • ‘Tis no more of a ramble than my post was, if not in fact rather less. Your points are also good, but I’m glad you saw mine as I wasn’t at all sure if I had any when I clicked ‘publish’.

  3. You’re discussing a phenomenon which likely won’t need a label under most circumstances. I think generally in a book, journal article, or even most discussions, you can define what you mean within the context of the discussion fairly simply without sounding too wordy. It’s not a real problem in most contexts to explain about a mid-latitude (I don’t recall any evidence of warming in the lower latitudes) N Hemisphere period of warming as opposed to a Medieval Warm Period.

    Where that comes into play is for the generalist or someone who wants just the broadest brushstrokes – someone who would like to talk about the Roman Warm Period, the Medieval Warm Period along with the Little Ice Age.

    I like labels but only if they’re explicitly clear in their meaning. Medieval Warm Period isn’t horrible as labels go but I just don’t see the need for it. But I also don’t see the need for “anomaly” either.

    I don’t know if you’ve read Michael Jones’ The End of Romain Britain. As a book overall it has its flaws but I like the way he handles a 50-page discussion of climate. He opens with, “The Roman era in Britain (AD 43-410) coincided with a generally favorable period, conditions being warmer, drier, and less stormy than in the preceding “Belgic” Iron Age.” p. 187 I don’t believe (have to re-read it to be sure) that he ever used a label for this period.

    • I’m more concerned about the phenomenon having its explanatory force nuanced out of it by actual data, but yes, you’re right, the label isn’t crucial at all.

      • I missed that – what I get for reading at midnight. Data does have this habit of screwing with the most wonderful theories.

        I’m sure what you’ll find is that you can postulate the weather in your area – but it might not be as “tight” as you want it. And I’m pretty sure you know that. And then you get into all kinds of things like if warm weather 200km away can create a rain shadow, thermals, upslope snow showers, etc in your area.

        You have an atmospheric sciences/meteorology person to work with who can help you with modeling when you get to that point?

        • Not yet, but who knows where I’ll be when the time becomes available? I hadn’t thought that far ahead but you’re quite right, of course, the correct answer to my worries is ‘let’s go interdisciplinary’!

          • Yeah – we have a guy in our Earth and Atmospheric Sciences Dept whose research interests reads: “Regional Climate Modeling and Numerical Weather Prediction, Synoptic Dynamic Meteorology, Coupled Atmosphere-Land-Ocean Studies, Global to Regional Scale Water Cycle”

            Of course there’s the old “show me the money” issue plus too many research needs, too little time. I’ve been trying to find someone who’ll do some rain shadow modeling for a project I’m involved with in my real job and, while I can get people’s eyes to light up when I talk about it, getting someone to commit to the time hasn’t happened yet. There may be some grant opportunities though.

            I’m too old to have to re-learn all the flow dynamics stuff I forgot the day after the final.

  4. rogerthesurf

    Here are some references about the medieval warm period which show it was not local.
    You could also check out the links on my blog http://www.rogerfromnewzealand.wordpress.com about Greenland, Switzerland, Greenland ice cores and the US on my blog. Well here is an anecdotal one about Spain.

    Of course the medieval warm period shows up in other literature as well, such as a New Zealnd study


    or if you want to read “Grove, J.M. 988:The little ice age.by methuen.

    Warm periods are well documented by other cultures eg

    http://www.springerlink.com/content/gh98230822m7g01l/ etc

    where the historical history of China’s climate is examined.

    Medieval warming and earlier periods are even suggested in the Antarctic Ice core project.

    and the Pacific warm pool.

    I could go on.

    Oops did someone say localised?

    Of course the MWP is only one of a number of warming (warmer than the present) which have occured in historical times.

    Lets not forget that during the Holocene period, the Sahara was lush and fertile. Do some reading on that maybe? http://www.jstor.org/pss/2997337 is a good start.

    Its a little irrelevant but I like this video clip where Obama is laughed at when mentioning climate change in speech http://www.hootervillegazette.com/climatejoke.html



    • Thankyou for the links, especially the one to, er, me. I think that whether or not we argue for a global phenomenon we are, the world being what it is and full of micro-climates, going to have to accept a certain amount of regional variation. My concern at the moment is with the granularity of that and whether in fact the temperature series that exist, even from relatively close like Switzerland, are enough to tell me what the weather was like in my subject area. I’m trying to use this phenomenon to explain something quite broad and so regional variation, while realistic and interesting, is problematic and I don’t know if I can find out how problematic.

      None of this is urgent, I should say: I am snowed under with more immediate requirements than this article.

  5. Pingback: Linkage is Good for You: Had to Get Away Edition

  6. I thought the “Medieval Warm Period” was the bit where everyone gathered around the fire-pit in the hall and drank mulled ale until the sun came back … :)

  7. Pingback: Seminars XL & XLI: two takes on really big changes « A Corner of Tenth-Century Europe

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