The Medieval Warm(ish) Period In Pictures

Discussion in 'Environment' started by Matthew, Jul 9, 2011.

  1. Matthew
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    Matthew Blue dog all the way!

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    The Medieval Warm(ish) Period In Pictures
    Posted on 10 July 2011 by Rob Painting
    The Medieval Warm(ish) Period In Pictures
    The Medieval Warm Period (MWP) is a subject of "skeptic" focus, primarily because it was a time of natural warming. It took place from about 950-1250 AD, and, as opposed to today's warming which is global in extent and due to human activities, the MWP was mainly a northern hemisphere phenomenon and smaller in scale. Indeed, the advance of North American glaciers during the MWP is in stark contrast to what is happening in North America today.
    The MWP in global maps
    [​IMG]
    Mann (2009) was an analysis of a large set of climate/temperature proxies (ice cores, tree rings, cave mineral deposits, sediments, etc.) covering the MWP. See below:

    Figure 1: Reconstructed surface temperature anomaly for Medieval Warm Period (950 to 1250 A.D.), relative to the 1961–1990 reference period. Gray areas indicate regions where adequate temperature data are unavailable.

    It's clear from the map that only limited areas of the world were warmer during the MWP than the 1961–1990 reference period, Greenland in particular. Much of the rest of the planet, especially the oceans, were cooler. And take note of the cooler North American west coast, which is consistent with the glacier advance there during the MWP. Obviously, the Earth has continued to warm even further since the 1961–1990 period, so the difference in temperature between the MWP shown in the reconstruction and today is even greater.
    Climate Models and the MWP

    The climate proxies suggest a rather different distrubition of heat and rainfall than today. So the question arises: based on the current well-understood climate system, can ocean-atmosphere processes produce temperature patterns like the MWP? For answers we turn to climate models.

    The cool central and eastern Pacific suggested by Mann 2009 explain some of planet-wide climate features observed in the MWP, but they fail to explain other aspects, such as as a more positive North Atlantic Oscillation (NAO), and increased rainfall in parts of Asia.

    Graham (2010) used the NCAR climate model and, based on findings from other modelling studies and proxy evidence for a warmer Western Pacific Ocean, found that by forcing the simulation to have a slightly warmer Indian and Western Pacific Ocean relative to other ocean basins, the model results match the climate suggested by the proxies.

    Below are the comparisons between the climate model control runs (a pre-industrial baseline) and the simulations including a warmer Indian-Western Pacific Ocean, for the northern hemisphere (boreal) winter (figure 2 and 3)

    Figure 2: Differences in December–March temperature between the Indian Ocean Warm Pool (25) and control simulations (°C, color; values are Sea surface temperature over ocean and 2-m temperature over land).Lined contour interval is 0.5°C between 30°N and 30°S and 1°C elsewhere. From Graham 2010.

    Figure 3: Differences in December–March precipitation (expressed as fraction of Control simulation, color) and Sea level Pressure (difference, hPa) for the Indian Ocean Warm Pool simulation. SLP contour interval is 1.0 hPa except 0.25 hPa in the region 30°S–40°N and 25°E–100°E where the finer interval highlights temperature-driven low pressure around continental periphery of northern Indian Ocean. From Graham 2010.

    The warm Indian-Western Pacific Ocean, combined with the cool Central and Eastern tropical Pacific reveals a good match with the paleoclimate proxies shown in the Mann 2009 reconstruction, namely:

    The NAO becomes more positive (A in figure 2 and 3), matching proxies of Atlantic sea surface temperature and sea ice distribution. This due to an atmospheric teleconnection (two connected atmospheric processes separated by large distances) between the NAO and warming over the Indian Ocean.

    Seasonal dryness in northeast Africa (B in Figure 3 )

    And wetter conditions in India, Southeast Asia and China(C in figure 3)

    A mechanism for such warming of the Indian and western Pacific Oceans has not been found, nor do the climate model simulations resolve all the patterns suggested by the proxies (such as warming of the British Isles); however, these findings represent another small step forward in piecing together the puzzle of the MWP, and also support the interpretation of the proxy data in Mann 2009.
    Science marches on while skeptics don't

    The MWP was very unlike warming today; the growing North American glaciers during the MWP being somewhat of a giveaway. The MWP only affected warming in a handful of regions, with Greenland being especially warm (Figure 1), whereas much of the Earth was actually cooler than the late 20th century. By comparison; today virtually every glacier and ice sheet on the planet is in rapid retreat.

    Both the climate proxies and the climate models imply that the MWP was a re-organization of the Earth's climate, and that much of this re-organization can be explained by oceanic patterns of warming and cooling, although what started all this rolling in the first place is still unknown.

    So while some climate "skeptics" are stuck in a time loop, wilfully reliving their own version of Groundhog Day, science continues to move forward.

    ....
    Holy crap this shows that most of the world outside of europe/arcitc and some of the US was below the baseline for the period of 1961-1990 during the med evil warm period. They say that the glacial in north America were growing.

    I disagree because I believe the med evil was caused by the same thing that caused the little ice age. hehehe:lol:

    I believe most of the bigger short term 20-200 year movements within the climate are mostly caused by changes within the solar output. Of course not all as you know---another is the orbit around the sun that goes from more oval to circular in nature, which causes more solar energy to reach the earth when it is avged over the year with slightly more energy and another is the angle of the planet. Mostly longer term cycles.

    Of course if the different area's---were warmer at different times that would build support for a change within internal patterns like the nao, pdo, enso. We will see as more and more science is coming into support of such, but I will stick with a mixture of the solar output and maybe lean towards some internal patterns. Maybe the sun causes the internal changes?:eek:
     
    Last edited: Jul 9, 2011
  2. wirebender
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    wirebender Senior Member

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    Here is a map in which each temperature noted is supported by peer reviewed studies and the locations of the studies are marked on the map. The bulk of peer review (as opposed to mann's discredited hockey stick and associated studies) indicates that the MWP was both warmer than the present and global in nature. If you would like a link to a listing of the peer reviewed studies that support this map, look at the bottom of the graphic.

    It was interesting that the claim from mann is that during the MWP north american glaciers were still growing. Quite a few peer reviewed studies suggest that he couldn't be more wrong.

    [​IMG]
     
    Last edited: Jul 10, 2011
  3. sparky
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    sparky VIP Member

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    wondering what change would make a dif in the earth/sun relationship....

    .01 degree? .000001 degree?

    one would think there might be some hard science that could be pursued here...
     
  4. bigrebnc1775
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    bigrebnc1775 Diamond Member

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    global warming has nothing to do with temputure. It's all about the control of lifestyles. When the warmers get's that through their head, then we can talk. Until they stop lying their will be no discussion.
     
  5. sparky
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    sparky VIP Member

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    well that may be so bigreb, but i find the earth's inconsistent distance from the sun a hard science

    GW, at least so far, is a soft science

    one can be lied about easier than the other...

    ~S~

     
  6. bigrebnc1775
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    bigrebnc1775 Diamond Member

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    Global warming agenda is the lie Mother earth warms herself and cool herself when she wants to. Nothing we can do about that.
     
  7. skookerasbil
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    skookerasbil Gold Member

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    From the first post........."based upon the well understood climate system"............


    :rofl::rofl::rofl::blowup:



    semantics, propaganda and bullshit........the k00ks have it down to a 'Science"
     
    Last edited: Jul 10, 2011
  8. editec
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    editec Mr. Forgot-it-All

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    Clearly we know that the earth has undergone period of warming and cooling.

    That still does not in any way refute the argument that we are currently causing a warming trend.

    It merely posits that the trend toward a warming planet is underway and that it is a non-manmade event.

    That might be true.

    Then again it might not be true.

    The question is folks...do you feel lucky?


    Well do ya?
     
  9. bigrebnc1775
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    bigrebnc1775 Diamond Member

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    Your reply has a lot of flaws.

    If we already know the earth under goes changing temperatures and we know most of the warmers are liberal and we know liberals are control freaks, then we should also know whats behind their agenda.
     
  10. wirebender
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    wirebender Senior Member

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    To date, there is not a shred, of hard observed, repeatable evidence that we are causing any sort of change to the climate.


    Considering the fact that there is no evidence that proves that we are causing a warming in the climate, and the fact that the warming trend is now 14,000 years old, and the fact that there is absolutely nothing unprecedented or outside of natural variation going on now or in the forseeable future, and the fact that the "science" upon which the whole AGW scare is based is shakier than a bowl of jello in a 9.5 earthquake, I don't think feeling "lucky" has anything to do with it. The perponderance of the evidence says pretty clearly that there is nothing unusual going on.
     

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