Goosse et al 2006 and the MWP

Kevn UK writes in: "I’ve just been to the Climate in the Past and have just spotted the following report

“The origin of the European “Medieval Warm Period”
H. Goosse, O. Arzel, J. Luterbacher, M. E. Mann, H. Renssen, N. Riedwyl, A. Timmermann, E. Xoplaki, and H. Wanner”

“Abstract. Proxy records and results of a three dimensional climate model show that European summer temperatures roughly a millennium ago were comparable to those of the last 25 years of the 20th century, supporting the existence of a summer “Medieval Warm Period” in Europe. Those two relatively mild periods were separated by a rather cold era, often referred to as the “Little Ice Age”. Our modelling results suggest that the warm summer conditions during the early second millennium compared to the climate background state of the 13th–18th century are due to a large extent to the long term cooling induced by changes in land-use in Europe. During the last 200 years, the effect of increasing greenhouse gas concentrations, which was partly levelled off by that of sulphate aerosols, has dominated the climate history over Europe in summer. This induces a clear warming during the last 200 years, allowing summer temperature during the last 25 years to reach back the values simulated for the early second millennium. Volcanic and solar forcing plays a weaker role in this comparison between the last 25 years of the 20th century and the early second millennium. Our hypothesis appears consistent with proxy records but modelling results have to be weighted against the existing uncertainties in the external forcing factors, in particular related to land-use changes, and against the uncertainty of the regional climate sensitivity. Evidence for winter is more equivocal than for summer. The forced response in the model displays a clear temperature maximum at the end of the 20th century. However, the uncertainties are too large to state that this period is the warmest of the past millennium in Europe during winter.

The whole report in PDF format is given here


13 Comments

  1. Steve McIntyre
    Posted Oct 29, 2006 at 12:04 PM | Permalink

    Housekeeping Transfer to new post:

    So the HT continue to assert that the MWP only existed in the NH. So why did Mann refer to the IPCC 2AR figure that acknowledged the existence of the MWP and LIA as “the cartoon’ at the recent Congress hearing?

    KevinUK

    Comment by KevinUK “¢’‚¬? 29 October 2006 @ 9:36 am | Edit This
    #

    why did Mann refer to the IPCC 2AR figure that acknowledged the existence of the MWP and LIA as “the cartoon’

    The “cartoon” was initially Wegman’s phrase. He meant it honestly, as in “sketch”.

    Comment by bender “¢’‚¬? 29 October 2006 @ 10:01 am | Edit This
    #

    Nope I heard that phrase way before the Wegman report regarding graphs with MWP and LIA showing coming from climate modellers. It’s a to work the spin- “cartoon” makes it sound less then important then just calling it a graph.

    Comment by welikerocks “¢’‚¬? 29 October 2006 @ 10:11 am | Edit This
    #

    I think that the word “schematic” best describes the IPCC 2AR figure. The House hearing did not seem to understand the concept.

    Comment by Jason Lewis “¢’‚¬? 29 October 2006 @ 10:13 am | Edit This
    #

    7:

    However, the uncertainties are too large to state that this period is the warmest of the past millennium in Europe during winter.

    This says it all.

    Comment by jae “¢’‚¬? 29 October 2006 @ 10:16 am | Edit This
    #

    ..only existed in the NH. Yes where most of the land on earth is found. Not important to the science-because remember, they can’t read maps, and global only means global if they say it is global.

    We are bitter and mad aren’t we? Sheesh. :p

    Comment by welikerocks “¢’‚¬? 29 October 2006 @ 10:23 am | Edit This
    #

    Re #9
    Wegman’s utterance was spontaneous and independent of your source, and, I am sure, was the direct source of Mann’s words. Wegman chose it over the word “graph” because, mathematically and/or scientifically speaking, it is not a “graph”; it is a “schematic”, as stated in #10. When Wegman sputtered over the phrase “cartoon”, I was wishing he had said “schematic” because I knew someone would try twist that less suitable term to the utterer’s discredit. (Much as they try to twist usage of the phrase “team” to CA’s discredit.)

    Bottom line is #11.

    Comment by bender “¢’‚¬? 29 October 2006 @ 10:28 am | Edit This
    #

    #12 I thought the set of places where the MWP occurred was the set of places where people happend to be present and happend to leave records…

    Comment by Chris H “¢’‚¬? 29 October 2006 @ 11:45 am | Edit This

  2. welikerocks
    Posted Oct 29, 2006 at 1:07 PM | Permalink

    Chris H, Yes, those records do count too. The signal for the MWP has been found in biology , geology, glaciers,-lake sediments, stalagmites…, botany… Just google on it. I saw a paper that found the signal in the history of salamanders.

    Here I just went and found it: http://tinyurl.com/y5jj5f

    “Salamanders Record Climate Change
    By Rossella Lorenzi, Discovery News

    Sept. 22, 2005 “¢’‚¬? Fossil salamanders unearthed in Yellowstone National Park have kept a record of the effects of climate change over the past 3,000 years, according to a large-scale study of the amphibian remains.

    and is says further on:

    “We found a significant difference in the body size of the paedomorphic and terrestrial adults within the Medieval Warm Period (the warmest period of Yellowstone’s history, between 1,150 and 650 years ago). Terrestrial adults were much larger than the paedomorphic individuals,” Hadly told Discovery News.

  3. KevinUK
    Posted Oct 29, 2006 at 4:12 PM | Permalink

    Steve,

    Thanks for transferring my post to a thread on the blog so that hopefully it will spark off a discussion on what to me is the HT’s primary motive.

    From my own personal research into the evidence (lack of) for AGW (which has include my links on this blog so thank you to all those concerned), I came to the conclusion some time ago now that there are two key aspects that underpin the ‘warmers’ case for AGW. The first is proxy temperature reconstructions and the second is climate modelling. Despite what many ‘warmers’ may state to the contrary, in my opinion, the two are integrally dependent on one another for their continued funding. In short, the proxies provide the ‘record’ of temperature variation in the past which the climate models then claim to be able to re-produce thereby demonstrating their validity therby enabling the climate models to be ‘validly’ used predict temperature variations in the future.

    As has been discussed many times on various threads on this blog there have been some issues that have continued to trouble both the paleoclimatologist and the climate modellers, namely the documented (indisputable in my opinion) existence of the MWP and the LIA. It is vital to the ‘warmers’ case to reduce (even attempt to eliminate) any evidnce for the significant difference in temperature that occurred naturally between these two periods of recent history. This is why in my opinion Mann (I heard him use the phrase ‘cartoon’ before Wegman when I listened to the Congressional hearing testimony) referred to the IPCC 2AR figure as ‘the cartoon’. He is deliberately attempting to belittle any acknowledgement by the IPCC prior to the IPCC TAR of the existence of the MWP and LIA. The ‘warmers’ claim of ‘unprecedented’ warming in the 90s as illustared by the post-child HS curve is vital to their eco-theologically inspired call for action on curbing fossil-fuel use in the 21st century. If joe-public sees that there has been a large variation in the earth’s mean global surface temperature during the last millenium that was completely natural (i.e. between the MWP and the LIA) and that temperatures duringthe MWP were similar to those today, then they will not believe the claim that the current post 1970 warming cycle is due to CO2 emissions and is ‘unprecedented’ in the last thousand years. If joe-public cannot be persuaded that global warming is man-made and will have a dangerous impact on the planet then they will not stomp up the taxes that the ‘warmers’ know are needed inorder to fund a) their jobs b) the utopian renewable energy world that they so dearly believe in and expectthe rest of us to pay for.

    KevinUK

  4. welikerocks
    Posted Oct 29, 2006 at 4:36 PM | Permalink

    The discussion for this paper is online here:

    http://www.cosis.net/members/journals/df/article.php?a_id=3892

    some interesting comments:
    Anonymous Referee #2
    Received and published: 3 August 2006

    Introduction (p 2, first paragraph, lines 4-5): Cite some attribution studies instead.

    Introduction (p 2, first paragraph, line 8): Jones and Mann 2004 is a review paper. I suggest citing papers presenting reconstructions (e.g., Jones 1998, Mann et al. 1999, Esper et al. 2002, D’Arrigo et al. 2006, etc.).

    Introduction (p 2-3, second paragraph): I didn’t like this paragraph, and in fact believe that it is somewhat misleading. I suggest replacing “By contrast” with “Similarly” (first line), since most – if not all – large scale reconstructions indicate warmth during me- dieval times. The uncertainties in both the large scale and European scale reconstructions (Guiot et al.?) are too large for such a conclusion to be used in the introduction, and do not justify referring to “contrasting” trends. Also, referring to a “conundrum” certainly overlooks the current state of knowledge of past temperature variations in Europe and theNor thern Hemisphere.

    Model and forcing description (p 4-6): Detail potential weaknesses/uncer tainties of employing a global model while utilizing regional output (Europe and below). This should also be mentioned in the abstract.

  5. Demesure
    Posted Oct 29, 2006 at 5:07 PM | Permalink

    A model supporting the existence of MWP more than 500 years ago??? That’s ridiculous. And it links the MWP to land use? Oh God, this obsession with demonstrating man’s influence on climate !

    Even seasonal models (same type as climate models) fail miserably with 6 months forecasts on el Nino, a major event which can vent an enormous amout of ocean heat into the atmosphere as in 1998 for example. No one predicted this year’s huge el Nino even by August (see oct-nov-dec forecasts in graph). BTW, that’s why this year hurricane forescasts were also that bad (a strong el Nino means a weak hurricane season).
    So a model explaining what MAY happen during the MWP and what MIGHT cause it is just good for an IGNobel prize contest.

    Ref: http://iri.columbia.edu/climate/forecast/sst/pac_atl2006.html

  6. Follow the Money
    Posted Oct 29, 2006 at 7:00 PM | Permalink

    That gosh darn MWP. How many ways do they try to get around it?

    1. Deny it existed

    2. Adjust the hockey stick a little and say it was exaggerated.

    3. Call it a regional phenomenon

    4. Concoct a Gulf Stream theory

    5. Finally concede it, but say it was just as hot now than then!

    Still existing is the Vikings In Greenland Problem to explain. Maybe something can be whipped up a la the “scholarship” which explains AGW causes both retreating and advancing glaciers!

  7. Posted Oct 30, 2006 at 3:36 AM | Permalink

    There is evidence for the MWP in the Pacific. It was when the Polynesians discovered New Zealand and Easter Island. You need warm weather and gentle breezes to to travel great distances in an open canoe (or Viking longship) in foul and cold weather. For a while they made 2 way voyages to Easter island using Pitcairn as a staging post. Then it stopped as the LIA set in.

  8. MarkR
    Posted Oct 30, 2006 at 6:33 AM | Permalink

    “long term cooling induced by changes in land-use in Europe”

    Are these people mad. I thought the warmers theory was that forest clearance was causing increase in CO2 levels, and therefore, in their minds, an increase in temperature. But apparently it caused cooling instead.

  9. JPK
    Posted Oct 30, 2006 at 11:09 AM | Permalink

    #5

    Demesure,

    I’m not sure if ENSO is as big as a reason for the significant drop off in Atlantic Hurricanes for 2006. If you check NOAA’s link below and thier MEI numbers, 2006’s Multivariate Index (MEI) is about the same for 2005 (June-Sept):

    http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

    NOAA’s medium range forcasters are calling for a “mild” winter for most of the US (East Coast is the exception) due to a recent increase ENSO numbers. For those living in the middle US, where the late summer and autumn have been particularly cold and wet, this winter is forecasted to be warm and dry.

  10. JPK
    Posted Oct 30, 2006 at 11:28 AM | Permalink

    “Our modelling results suggest that the warm summer conditions during the early second millennium compared to the climate background state of the 13th–18th century are due to a large extent to the long term cooling induced by changes in land-use in Europe.”

    I’m not sure what changes in land-use they are referring to. Europe’s population circa 1000 was no more than 38 million. It doubled by 1350, but reduced to 55 million by disease, starvation and war. Most of the famous forests of Central Europe and the UK remained intact, and modern farming methods really didn’t hit Europe until the middle of the LIA. Are they blaming the MWP on human induced changes to the earth’s albedo in a small sections of Europe?

  11. Steve Sadlov
    Posted Oct 30, 2006 at 11:40 AM | Permalink

    RE: #9 – The NWS’ sequential 90 day outlooks are a travesty. Incidentally, there is the appearance that they tend to err on the side of abnormal warmth in most future 90 day periods. This has been the case now for a few years.

  12. Armin
    Posted Oct 31, 2006 at 3:21 AM | Permalink

    Just a quick question. Don’t you have the wrong PDF linked? The one that is linked says “Equatorial insolation: from precession harmonics to eccentricity frequencies”.

  13. Armin
    Posted Oct 31, 2006 at 3:23 AM | Permalink

    Update, yes you have the incorrect PDF. The correct one is

    http://www.clim-past.net/2/99/2006/cp-2-99-2006.pdf

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