What caused a 1300 year deep freeze 12,800 years ago? New PNAS paper says it wasn’t an impact

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Temperature fluctuations over the past 17,000 years showing the abrupt cooling during the Younger Dryas. The late Pleistocene cold glacial climate that built immense ice sheets terminated suddenly about 14,500 years ago (1), causing glaciers to melt dramatically. About 12,800 years ago, after about 2000 years of fluctuating climate (2-4), temperatures plunged suddenly (5) and remained cool for 1300 years (6). About 11,500 years ago, the climate again warmed suddenly and the Younger Dryas ended (7). Graph by Don Easterbrook.

About 12,800 years ago, the last Ice Age was coming to an end, the planet was warming up. Then, inexplicably, the planet plunged into a deep freeze, returning to near-glacial temperatures for more than a millennium before getting warm again. The mammoths disappeared at about the same time, as did some Native American cultures that thrived on hunting them. That climatic event is known as The Younger Dryas.

Many explanations for the event point to the impact of a comet or an asteroid, but now there is a new study suggests the driver/trigger was all from terrestrial based events.”

According to the article in Science Magazine, they find no evidence for an impact:

The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.”

The notion was popularized in television documentaries and other coverage on the National Geographic Channel, History Channel, and the PBS program NOVA.

Now comes what some researchers consider the strongest attack yet on the Younger Dryas impact hypothesis. In a paper published online this week in the Proceedings of the National Academy of Sciences, a team led by David Meltzer, an archaeologist at Southern Methodist University, Dallas, in Texas, looks at the dating of 29 different sites in the Americas, Europe, and the Middle East in which impact advocates have reported evidence for a cosmic collision.

Only three of the 29 sites actually fall within the time frame of the Younger Dryas onset

http://news.sciencemag.org/archaeology/2014/05/what-caused-1300-year-deep-freeze

From the publication:

A key element underpinning the controversial hypothesis of a widely destructive extraterrestrial impact at the onset of the Younger Dryas is the claim that 29 sites across four continents yield impact indicators all dated to 12,800 ± 150 years ago. This claim can be rejected: only three of those sites are dated to this window of time. At the remainder, the supposed impact markers are undated or significantly older or younger than 12,800 years ago. Either there were many more impacts than supposed, including one as recently as 5 centuries ago, or, far more likely, these are not extraterrestrial impact markers.

Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago

David J. Meltzer, doi: 10.1073/pnas.1401150111

David J. Meltzera, Vance T. Holliday, Michael D. Cannon, and D. Shane Miller

Abstract

According to the Younger Dryas Impact Hypothesis (YDIH), ∼12,800 calendar years before present, North America experienced an extraterrestrial impact that triggered the Younger Dryas and devastated human populations and biotic communities on this continent and elsewhere. This supposed event is reportedly marked by multiple impact indicators, but critics have challenged this evidence, and considerable controversy now surrounds the YDIH. Proponents of the YDIH state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the Younger Dryas onset. They are not. We have examined the age basis of the supposed Younger Dryas boundary layer at the 29 sites and regions in North and South America, Europe, and the Middle East in which proponents report its occurrence. Several of the sites lack any age control, others have radiometric ages that are chronologically irrelevant, nearly a dozen have ages inferred by statistically and chronologically flawed age–depth interpolations, and in several the ages directly on the supposed impact layer are older or younger than ∼12,800 calendar years ago. Only 3 of the 29 sites fall within the temporal window of the YD onset as defined by YDIH proponents. The YDIH fails the critical chronological test of an isochronous event at the YD onset, which, coupled with the many published concerns about the extraterrestrial origin of the purported impact markers, renders the YDIH unsupported. There is no reason or compelling evidence to accept the claim that a cosmic impact occurred ∼12,800 y ago and caused the Younger Dryas.

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135 Responses to What caused a 1300 year deep freeze 12,800 years ago? New PNAS paper says it wasn’t an impact

  1. JR says:

    MWP and LIA annotations can’t be right in the picture?

  2. Bloke down the pub says:

    In a paper published online this week in the Proceedings of the National Academy of Sciences, a team led by David Meltzer.

    Appropriate for a paper about the end of an ice age.

    I don’t see any alternative suggestion for the cause being mentioned .

  3. Lewis P Buckingham says:

    JR says:
    May 13, 2014 at 3:34 am
    They are talking about central Greenland alone, so it could be right.
    The Roman warming, preceding the Medieval warming, was warmer than the Medieval which on this trace is warmer than the present warming in Greenland, so the relationship is right.

  4. wfrumkin says:

    Everyone knows the mammoths were driving SUVs and caused their own extinction

  5. P J Brennan says:

    They were mammoths, they made mammoth farts…

  6. higley7 says:

    [SNIP electric universe bullshit has no place here - Anthony]

  7. joel says:

    I go with the mammoth fart theory. It explains everything.

  8. vukcevic says:

    The 3 million years of the Earth’s history has 30 or so glaciation epochs each about 100,000 years, inter-spaced with about 10,000 years of warm epochs between them.
    Our 10K years is up.
    In geological terms it appears that climate is a bi-stable affair, and those familiar with the bi-stable oscillators will know that once you approach critical period even a small input excitation will tip it over into the alternative state.
    If the AGWs are correct, then the northern latitudes civilization’s only hope is to pump as much CO2 as possible and at same time build as many as possible nuclear power stations, might need one for each major city.
    AGWs keep telling us “it is worse than expected”, but even they do not realize how much worse may get.

  9. Steve C says:

    It was the cavemen. They heeded all the warnings about “global warming” and put their campfires out.

  10. Michele says:

    The geomagnetic field changes and heliospheric field changes are correlate with abrupt drops in planetary temperature and great vulcanic eruptions.

    http://michelecasati.altervista.org/index.html

  11. johnmarshall says:

    It wasn’t an impact(s) so what was it? What are the conclusions? If any. If not this is not a proper science research paper.

  12. Nick Stokes says:

    The AR4 didn’t mention any impact theory 6.4-2-2:
    “Freshwater influx is the likely cause for the cold events at the end of the last ice age (i.e., the Younger Dryas and the 8.2 ka event). Rather than sliding ice, it is the inflow of melt water from melting ice due to the climatic warming at this time that could have interfered with the MOC and heat transport in the Atlantic – a discharge into the Arctic Ocean of the order 0.1 Sv may have triggered the Younger Dryas (Tarasov and Peltier, 2005), while the 8.2 ka event was probably linked to one or more floods equal to 11 to 42 cm of sea level rise within a few years (Clarke et al., 2004; see Section 6.5.2).”

  13. Bill Marsh says:

    I don’t have a subscription to PNAS so I can’t read the paper, but, my question is:
    If they found that three impact sites did fall in the chronological time frame, did they examine those sites to determine if the impact could have been big enough to spark the Younger Dryas temp drop?

  14. richard says:

    what caused the rapid warming?

    take that away and you get the rapid cooling.

  15. The Ghost Of Big Jim Cooley says:

    From the Guardian (BBC will publish it online later):
    ‘Scientists believe they have found the cause of a cooling period 13,000 years ago. Excavating in a secret location, scientists think they have come across an early hybrid farm vehicle. Professor Ed Case says that the vehicle had an Ox front but clearly had a piston-engined rear drive. “We believe that vehicles of this type clearly were the cause, as they would have emitted large amounts of soot due to a lack of understanding about catalytic converters.” Professor Case told the Guardian that it was Man what was to blame. “It surely was.” said Professor Case. A new BBC series showing the excavations and these remarkable vehicles is planned.’
    http://humanpast.net/images/preshistory0001.jpg

    [/sarchasm That gaping whole between reality and the CAGW religion .. Mod]

  16. Dave says:

    Mammoth farts is a possibility, but I bet those bad ol’ Neanderthals caused it by burning tons upon tons of mammoth chips.

  17. Bill Marsh says:

    Mr Stokes,

    Doesn’t seem like the IPCC was all that certain about the ‘freshwater influx’ hypothesis. Do they present any evidence to support what appears to be conjectural ‘floods’ and ‘fresh water influx’?

  18. vukcevic says:

    Nick Stokes says:
    May 13, 2014 at 4:25 am
    a discharge into the Arctic Ocean of the order 0.1 Sv may have triggered the Younger Dryas (AR4).
    ……
    Are you sure about that?
    Arctic overflow is about 10Sv, so AGW caused melting of the Greenland glaciers with another excessive Arctic ice melt, may produce the required 0.1 Sv of fresh water, creating a tipping point into a new Ice Age.

  19. The Ghost Of Big Jim Cooley says:

    I’m telling you all, if we upload enough of these nonsense articles, Google will pick them up and they’ll get stored as genuine Guardian articles that are every bit as absurd as their general stuff! Write your own right now.

  20. Stephen Richards says:

    There are huge problems with all the theories about the YD cooling. Mamoths have been found frozen with their last meal well preserved in their stomachs. This can only happen when freezing is extremely fast. In our current climate there is nowhere on earth, where vegetarian animals live, where this fast freeze can happen. The temperature drop must have been massive and very fast. Remember, bodies decompose from the inside out !!

  21. If you study all of the records at the Younger Dryas boundary, there is certainly a lot more to say to it. It may or may not have been one or more impactor. One of these records for instance is the so called radiocarbon reservoir age in the ocean. For ust about every period this is well controlled and understood except for the beginning of the Younger Dryas. See Reimer et al 2009. (Radiocarbon, Vol 51, Nr 4, 2009, p 1111–1150) Why would that be? It could point to extreme overturning of the ocean layers. Can that be attributed to impactors?

  22. gaelansclark says:

    Nick Stokes…in quoting AR4 and my paraphrasing……
    The warming caused all of that cooling!!!!

    WOW

  23. klem says:

    My understanding is that there was no precipitous drop in atmospherics CO2 concentrations prior to the Younger Dryas. I believe CO2 concentrations continued to rise throughout the YD event.

  24. Steven said:
    There are huge problems with all the theories about the YD cooling.

    No there are no mammoth mummies dated to the Younger Dryas. Most are much older. It’s a totally different story. It would pay to read the real scientific literature about this. Not the sensational fairy tales.

    Recommended:

    http://epic.awi.de/9052/1/Hub2004a.pdf
    http://cio.eldoc.ub.rug.nl/FILES/root/2006/QuatIntMol2/2006QuatIntMol2.pdf?q=jarkov

    Read that first, before believing anything about the ‘flash frozen’ tales.

  25. MikeB says:

    Did no one else think it strange that, according to the labelling on the headline graph, present day global warming appears to be colder than the little ice age?
    The labelling is misleading and. in my opinion, this sort of thing undermines sceptic credibility.
    The graph seems to be derived from the GISP2 ice core (Richard Alley Quaternary Science Reviews Volume 19, Issues 1-5, 1 January 2000, Pages 213-226).

    The GISP ice-core records do not go up to the present time. They estimate up to about 100 years ago and so do not include ‘present global warming’. What is labelled as ‘present global warming’ is in fact the ‘little ice age’. Also note that the labelling of medieval warm period is incorrect. It should be the final little blip coloured red on the upslope.
    You can see the original here (before Mr. Easterbrook got at it)
    http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.html

  26. sleeping bear dunes says:

    The graph by Easterbrook shows MWP warmer than present. What was the source of his graph and how widely accepted is it?

  27. Astronaut :) says:

    What about theory that solar system travels through densier dustarea in milkyway?

  28. Ed Reid says:

    Looks like an upside down and backwards hockey stick to me.

  29. John M says:

    The LIA and MWP are mislabelled. If you look at the timescale below you can work out the issue. He has the LIA sitting between the RWP and MWP at 1500 YBP.

  30. Col Mosby says:

    Get the feeling not much advancement of knowledge here.

  31. LevelGaze says:

    @ Bloke down pub and JohnMarshall
    You are both making the same category error, I think.
    Because no alternative explanation is suggested does not nullify the findings of a report like this or in any way degrade its reliability.

  32. hell_is_like_newark says:

    Some things that happened during the Younger-Dryas:
    1. It got colder yet sea level continued to rise dramatically.
    2. Melt-water from the Laurentide ice sheet switched from flowing South into the Gulf of Mexico suddenly shifted to dumping into the North Atlantic.
    3. The Clovis culture and large land mammals pretty much disappeared in the fossil record. There is a mysterious black mat above which mega-fauna and the Clovis no longer exist.

    As more evidence comes out, personally I am becoming convinced that earth got slammed by a fragmented comet that blasted a good portion of North America Tunguska-style, taking a good portion of the ice sheet with it (which explains why sea levels continued to rise). A man named Dennis Cox put a really good overview of the impact theory. http://cometstorm.wordpress.com/2011/04/06/a-different-kind-of-climate-catastrophe/

    Though I am having trouble accepting his theory on the formation of the Carolina bays, I think he is on the right track with everything else.

  33. JP says:

    “Many explanations for the event point to the impact of a comet or an asteroid, but now there is a new study suggests the driver/trigger was all from terrestrial based events.” ”

    So, what were the terrestrial events? Exactly what did the new study “suggest.”

    It sounds like the paper was nothing more than a massive correction to the proxy dating. Which is good, if it turns out their math and methodology are correct. However, to assume that the Younger Dryas Period therefore was created solely by terrestrial events is going a bridge too far.

  34. JP says:

    @Nick Stokes,

    The Anthropologist, Brian Fagan, uses the same theory in one of his books on Climate and Civilization. I checked Wiki when I read the book about 5 years ago. I went back looking for it a few months ago I couldn’t find it. Interesting.

  35. Sparks says:

    I never liked the idea of an asteroid or comet impact occurring at regular intervals correlating with ice-ages.

    MikeB says:
    May 13, 2014 at 4:46 am

    “Did no one else think it strange that, according to the labelling on the headline graph, present day global warming appears to be colder than the little ice age?

    You’re right MikeB that’s because it’s a typical climatological graph… ;)

  36. Latitude says:

    richard says:
    May 13, 2014 at 4:29 am
    what caused the rapid warming?
    ====
    That’s the question I would be asking too…
    because temps went back down to the same base line
    There’s two step ups in warming…..and now we’re on a slow trend down again

  37. emsnews says:

    Comet strikes are totally different from asteroid strikes. Yes, the Siberian Tunguska strike shows how devastating a comet explosion can be and if an ice ball hits the Atlantic Ocean, this can cause an ocean rise (tsunamis).

    The Younger Dryas could also be caused by the comet striking the Southeast US plus Yellowstone and other continental volcanic events happening in quick succession. If this coincides with a cooler irradiation from the sun…tip into severe Ice Age conditions are quite possible.

  38. Berényi Péter says:

    A requiem to the Younger Dyras Impact Hypothesis was already announced three years ago.

  39. NotAGolfer says:

    But there was a consensus! Impact! It was settled science! Is this paper written by DENIERS?

  40. Pamela Gray says:

    I rather like the premis of this article. Take someone else’s “[name]mometer” data or “[name] driver” data and beat the crap out of it to see if it stands up to close scrutiny. Do I care they do not propose a replacement theory? Nope. This is called replication and I love it.

  41. Steve Keohane says:

    hell_is_like_newark says:May 13, 2014 at 5:10 am
    Thanks for the Dennis Cox Link, a good read.

  42. LevelGaze says:

    @Pamela Gray
    You said it much better than I did.

  43. Sparks says:

    In my opinion it was the sun that causes glacial periods such the Younger Dryas and interglacial periods like the present.

    I’ve been working on a mechanism (which fits current solar theory) of how this can work, and its very interesting! (just a heads up).

  44. Steve from Rockwood says:

    Depending on what you read you can make pretty much anything up. Such as “The mammoths disappeared about the same time [12,800 years ago]“. Nick Stokes also adds in the usual “Fresh water influx is the likely cause for the cold events [of 12,800 years ago]“.

    Problem is mammoths did not go extinct until about 3,750 BCE. Hunters were camped alongside the Great Lakes about 9,000 years ago when water levels were only 40 feet lower than today, Alaskan hunters were hunting mammoth about 12,000 years ago, and so on.

    So how could the planet be plunged into a deep-freeze while the Alaskan hunters went merrily about hunting mammoth and the mammoth went merrily about being non-extinct for another 8,000 years (in Siberia no less)? And how could the ice sheets of North America grow so quickly and melt so fast? The low water levels were blamed on a continental scale dry period, not a massive discharge into the ocean.

    Contradictory conclusions are one thing. But evidence that flies in the face of your theory is something else. Yuka, the incredibly preserved baby mammoth, was living almost 3,000 years after mammoths went extinct. WUWT?

    http://www.dailymail.co.uk/sciencetech/article-2124991/Siberian-mammoth-Yuka-Ice-Age-creatur-perfectly-preserved-10-000-years.html

  45. Bruce Cobb says:

    There were several Dryas periods, the first being some 15-18K years BP. Also, there is evidence of previous Dryas-like events at the end of previous glacial periods. Thus, an extraordinary event such as a comet or asteroid strike as the cause doesn’t seem logical. We may never know, but some sort of shutdown of the thermohaline or similar terrestrial reaction seems the most likely cause.

  46. jauntycyclist says:

    its a mystery?…..so they don’t understand how climate processes work? i thought we knew with 95% certainty how it all worked?

  47. Paul says:

    “those bad ol’ Neanderthals caused it by burning tons upon tons of mammoth chips”
    I’m no expert, but wouldn’t those be carbon neutral?

  48. agfosterjr says:

    Steve from Rockwood says:
    May 13, 2014 at 5:46 am

    Right on. In fact there is a trend: the more northerly the species’ habitat, the more likely it was to survive; e.g., arctic fox, musk ox, polar bear. All the evidence points to human predation.
    –AGF

  49. richard says:

    The great thing about being a skeptic is the fun to be had from reading the comments and bashing the alarmist nonsense . Having read a few of the alarmist ones everyone has to remain ” oh so serious”

  50. JohnWho says:

    Whoa!

    According to that graphic, we are cooler now then we were in the LIA!

    That can’t be right.

  51. John Slayton says:

    I’m sitting here this morning reading this in Sierra Vista, with the Murray Springs Clovis site about 10 miles out of town. Both the Science article and the journal abstract refer to 3 sites that are appropriately dated to the Younger Dryas. Unfortunately, they don’t name them. My impression is that Murray Springs is well dated, including with Clovis artifacts, and I would guess it is one of the three. If I remember correctly, the Murray Springs black mat layer (with alleged nano-diamonds) was correlated with other sites some distance away–like thousands of miles. One suggestion was that there may have never been an actual impact, only a disintegration causing huge damage along the object’s trajectory. Seems to this layman that 3 well-dated sites that far apart showing (if true) identical geological anomalies, is significant evidence for impact, even if all the others are irrelevant.

    PS. Could someone with access, bring back the names of those three sites?
    : > )

  52. JimS says:

    Listen to vukcevic , above.

  53. JimS says:

    The warming at number 7 on the chart, “Warming at end of Younger Dryas” looks unprecendented to me – the mother of all hockey sticks, for sure.

  54. John Whitman says:

    From the AAAS article ‘What Caused a 1300-Year Deep Freeze?’ (12 May 2014 3:00 pm) by Michael Balter,

    “The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.” “

    - – - – - – - – - -

    Science in very blunt self-correction mode with that assessment of “conjured up “out of thin air” “.

    I am also starting to enjoy the blunt scientific self-correction mode increasingly applied to the observation contradicting theory of significant AGW by fossil fuel.

    John

  55. Don Easterbrook says:

    The most telling evidence against the impact theory of the cause of the Younger Dryas (YD) is not the dating of impact craters–that just shows that a particular crater didn’t happen during the YD. Far more significant is that (1) we now know that the YD was a multiple event (I’ve mapped 9 YD separate moraines) not a single unique event, (2) the YD lasted 1000 years and you can’t keep dust in the air that long, (3) the YD ended just as suddenly as it began, and (4) the abrupt warm/cool climate changes near the end of the last Ice Age are not restricted to the YD (it’s the biggest one, but there are many others). You would need to have a lot of impacts for a long time.
    If you want to see the geologic evidence for these, see “Multiple, intense, abrupt, late Pleistocene warming and cooling: Implications for understanding the cause of climate change” posted June 2, 2013 on WUWT and “The intriguing problem of the YD–what does it mean and what caused it?” posted June 19, 2012 on WUWT.

    The abrupt and intense climate changes that occurred 10-15,000 years ago near the end of the last Ice Age are called Dansgaard-Oeschger Events, named after the scientists who discovered them in the first Antarctic ice cores and since found in the Greenland ice cores and in the glacial record. Dansgaard and Oeschger referred to them as ‘flickering’ of climate. No one has come up with really convincing evidence for their cause, but they are well documented. Broecker suggested changes in global ocean circulation, but that doesn’t work because climate changes in the Southern Hemisphere should lag the Northern Hemisphere by hundreds of years and we now know that these climate changes were simultaneous in both hemispheres. Understanding the cause is really important because if we knew that, we would be in a much better position to understand what causes major ice ages.

  56. MikeUK says:

    There is some similarity between the politics of the CO2 and asteroid impact debates, with the asteroids being the “consensus”, defended almost to the death by zealots against what are seen as attacks by a few souls brave enough to suggest problems with it.

    I believe that careers have been ended by the asteroid zealots, but now it appears that that particular consensus was wrong, and volcanism may have been more significant.

    Some commenters here asked for the alternative explanation for the cooling. Seems likely to me to have been just a rerun of the main ice age cooling event.

  57. Bill Illis says:

    richard says:
    May 13, 2014 at 4:29 am
    what caused the rapid warming?
    take that away and you get the rapid cooling.
    ——————————–

    Exactly.

    There are 28 of these rapid warming and rapid cooling events during the last ice age in the Greenland ice cores. Older, Younger and Oldest Dryas events were just one of these 28 phases.

    The megafauna were adapted to live in an environment which had 2 km high glaciers covering the Earth down to 50N. The glaciers melted away, the environment changed, the grass turned into bushland, humans arrived on the scene and the megafauna died out at different intervals. Not a nice tidy story but its not hard to imagine how it all happened.

  58. pochas says:

    Any experts here? What happens when you freeze water? Does the O18 go with the ice or stay in the liquid water. If it stays behind (in the liquid), what happens when you melt the ice, lots of it? Would you get an anomalous dO18 as the melt water blankets the surface and would this anomaly be picked up in the ice cores?

  59. herkimer says:

    My best estimate is that warming of the post glaciation period around 14300 BP was interrupted by a series( 4 to 5 separate major periods as shown by the blue lines) of global volcanic activity which put a lot of gas and particulate matter into our atmosphere. It took until 12000 BP for the atmosphere to clear and the warming to resume. People had to flee to caves and underground places for safe air in many regions

  60. evanmjones says:

    what caused the rapid warming? take that away and you get the rapid cooling.

    Milankovitch cycles will have caused the warming. And that certainly can’t have caused the cooling.

  61. Bill Illis says:

    Speaking of 2 km high glaciers melting in a short few thousand years, can you imagine how big the floods were and how wide the rivers flowing south got in the summer melt season. The Mississippi would have been impossible to ford unless your species could build good boats.

  62. Steve from Rockwood says:

    Don Easterbrook says:
    May 13, 2014 at 7:06 am

    “The most telling evidence against the impact theory of the cause of the Younger Dryas (YD) is not the dating of impact craters–that just shows that a particular crater didn’t happen during the YD. Far more significant is that (1) we now know that the YD was a multiple event (I’ve mapped 9 YD separate moraines) not a single unique event, (2) the YD lasted 1000 years and you can’t keep dust in the air that long…”
    ————————————————-
    It seems unlikely (as Don mentions above) that an impact could have such a long term effect in such a discontinuous way. Same for volcanoes. Both would have immediate effect from which the Earth would recover quickly (maybe not so much the life forms). But to switch the Earth from warm to cold for 1,000 years and then quickly back to warm (from an asteroid or volcano) doesn’t seem logical.

    Also these events are described as being world-wide and yet life flourished in Siberia and Alaska throughout this time period. Such as the Alaskan wolf (45,000 to 10,000 years ago) which survived the ice age, then the YD, but then disappeared. Their extinction is blamed on rapid global warming, which also makes no sense to me. At a time when humans were hunting caribou in record numbers the wolves went hungry?

  63. The above pictured graph is not exactly to scale because it is intended to be a “reference diagram” for the author’s commentary. Here is the .jpg link to it:
    http://wattsupwiththat.files.wordpress.com/2012/06/clip_image0021.jpg

    If you want to see the above referenced central Greenland temperature proxy “to scale” …… then click on this .png link to this “Holocene Temperature Variations” graph ….. http://commons.wikimedia.org/wiki/File:Holocene_Temperature_Variations.png …. and observe the “light blue” line on said graph, which is the Greenland proxy data as per, to wit:

    (light blue) GISP2 ice core, interpreted paleotemperature, Greenland: Alley, R. B.. Quaternary Science Reviews. doi:10.1016/S0277-3791(99)00062-1

    And if you are interested in the relationship between the Holocene Temperature Variations proxies and the Post Glacial Sea Level Rise proxies ….. then click this link:
    http://i1019.photobucket.com/albums/af315/SamC_40/HoloceneInterglacialmeltwatertemperatureMediumWebview.jpg

  64. ffohnad says:

    This very obviously is not a scientific study. It is speculation fronted by scare tactics just as the majority of CAGW articles are. Here in the states this whole exercise beginning with the creation of this study is a transparent attempt by the administration to divert attention from the colossal mistakes and misuse of power practiced by modern American politics. I not only disbelieve in this tactic but am appalled by the ignorance of those who take it seriously.
    If this portrays contempt of the IPCC and it’s supporters in your mind…..congratulation you got it right.
    Doug

  65. Chris4692 says:

    johnmarshall says:
    May 13, 2014 at 4:25 am

    It wasn’t an impact(s) so what was it? What are the conclusions? If any. If not this is not a proper science research paper.

    The conclusion was it wasn’t an impact. Beyond what the data and any given analysis shows, science has to leave room for “I don’t know”.

  66. Mandobob says:

    All things being equal :), as water freezes, O18 tends to concentrate in the remaining “liquid” water resulting in a relative increase in the ratio between O18/O16. Conversely, the O16 tends to concentrate in the “ice”. This process is readability observable as precipitation from sea level to higher altitudes (and latitudes {both high and low]) show strong fractionation between O16 and O18. As such large volumes of high (or very low) latitude ice, if rapidly melted and flooded the oceans may result in anomalous O16/O18 ratios for a limited time, but likely under a residence time unrecordable in the sediment record. For ice cores, I would believe that any significant melt would be discernible as a anomalous “missing” section mostly based on other distinguishing features besides stable oxygen isotope rations.

  67. Sandi says:

    A bit annoying when reading a study raises more questions than it answers.

  68. ffohnad says:

    Don E
    It seems to me the most likely influence on the YD would be a sudden change in the heating source. Has there been studies that show any solar factor in convincing ways? Being a geologist I have, of course some familiarity with proxy evidence, but do not recall such studies concerning the YD. I am quite sure however, it has nothing to do with carbon, or man, so in essence this issue being used to promote AGW, is pure obfuscation. A growing trend in the face of hypothesis failure.

    My justification for considering this topic fraudulent rests primarily on the fact that I have never seen a hypothesis supported after such obvious lack of correlation to observed reality.
    Many sketchy attempts to prop up this idea, including adjustment to the past records, ignoring evidence, and general anger from those who don’t appreciate our resistance to using pre-modern science to show that the emperor has no clothes, goes beyond science and towards religion.
    In religion everything must be based on faith, thus providing wealth and power tp adherents, and pesky facts are considered heresy.
    The climate issue is far closer to the religious system than the scientific one, and unlike many true believers I am still a scientist not an alchemist.
    Doug
    ,

  69. Whenever astrophysicists,geologists, warmists or some other body of ‘science’ does not know anything, they always invoke a rogue rock as the culprit. Lame. Maybe blame Hawking’s phantom spacemen from the ‘multiverse’. At least this paper tries to delve into some other reasons as to why an ice age occurred so quickly.

  70. Peter Jones says:

    I’m going with too many mammoth BBQ pits causing soot in sky and blocking the sun – - Yup, man-made climate change!!

  71. gymnosperm says:

    “pochas says:

    May 13, 2014 at 7:24 am

    Any experts here? What happens when you freeze water? Does the O18 go with the ice or stay in the liquid water. If it stays behind (in the liquid), what happens when you melt the ice, lots of it? Would you get an anomalous dO18 as the melt water blankets the surface and would this anomaly be picked up in the ice cores?”

    Glacial melt water is depleted in 18O not because it froze but because the water had to EVAPORATE to be transported from the ocean to land. Evaporation rejects heavy isotopes similarly (and probably for the same reasons) as biological processes. Evaporative rejection is the basis for using 18O as a temperature proxy. It measures the amount of water stored as ice with higher concentrations of 18O being colder periods when more 16 is stored in ice.

    The concept works well for periods when there is ice on the planet as there has been for the last 20 million years or so. The approach gets dicey when it is applied to the majority of the last half billion years when there has been no ice. During ice free times biological rejection may be seriously skewing the results, especially during extinction events.

  72. Dennis Cox says:

    Bottom line: They didn’t really “study” anything. Re-hashing existing data does not come under theheading of doing science. It’s just an excercize in statistics. If you give the same data set to ten different statisticians, you’ll get ten different results. And anyone who claims they can resolve a date thirteen thousand years ago to a resolution better than +/-100 years is living in a fantasy world anyway. So what the paper really illustrates is the sad state of the science of radiometric dating.

  73. Steve from Rockwood says:

    I’m not familiar with radiometric dating but I have heard that geochronologists can “do it for ages”.

  74. Retired Engineer John says:

    There was a period of extreme instability in the Earth’s climate starting about 11,500 years ago and extending back some 3,000 years. Those are extreme temperature changes that require big changes in the Earth’s balance of energy for an extended period of time. Singular events such as volcanos or comet impacts could not produce lasting effects sufficient to make these changes. Any explanation should be accompanied by calculations of the changes in accumulated energy required to make the temperature changes along how much change a proposed event could possibly make. I suspect that only an instability in the Sun could cause such large variations.

  75. Patrick (the other one) says:

    The name of the three sites:
    Big Eddy, Missouri
    Daisy Cave, California
    Sheriden Cave, Ohio

    These are listed in Figure 1 of the paper as “Sites with supposed YDB layer dated to 12.8 +/- 0.15 k cal BP”.

  76. jim2 says:

    Maybe it could have been the Vela supernova, a relatively close explosion at 800 lightyears.
    The resulting cosmic rays could have enhanced clouds and cooled the Earth.

    Vela Supernova Remnant.jpg Vela Supernova 11th–9th millennium BCE ? 800 ? Vela Supernova Remnant

    http://en.wikipedia.org/wiki/List_of_supernova_remnants

  77. Steve P says:

    Sandi says:
    May 13, 2014 at 8:26 am

    A bit annoying when reading a study raises more questions than it answers.

    Yes, it would be nice if we had all the answers, but we don’t. See Arthur Conan Doyle:

    How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?

    Beyond impacts and volcanism, what remains to account for the relatively rapid ups and downs of the YD?

    Variation in solar output?

    Close passage, sans impact, of a large extraterrestrial body, perhaps causing Earth to wobble on its axis for a bit?

  78. Stephen Richards says:

    leftturnandre says:

    May 13, 2014 at 4:46 am

    Sopme of the mamooths found in alaska were from about the 15000 to 18000years ago. A supposed YD period but not the most recent. We have not found a mummy we date to precisely the last YD.

  79. GeoLurking says:

    Probably unrelated…. but if you place a line along the long axis of the Carolina Bays, they tend to focus somewhere over the Pacific Northwest. They are dismissed as not being from an exploding impactor as vociferously as those that lightly dismiss the “black mat” research.

    http://en.wikipedia.org/wiki/Carolina_bays

  80. milodonharlani says:

    Steve from Rockwood says:
    May 13, 2014 at 5:46 am

    IMO Yuka’s age is not yet well constrained, or if so, a more precise date hasn’t been published. Usual reference is to “at least” or “over” 10,000 years ago.

    But clearly, some mammoths did survive past the glacial/interglacial transition, as shown by the finds from Wrangel Island.

    Yuka showed signs of having survived lion attack & of being scavenged by humans after death.

    http://news.discovery.com/animals/endangered-species/woolly-mammoth-yuka-120404.htm

  81. arthur4563 says:

    How about a transient response from the nuclear reaction within the Earth’s core?

  82. milodonharlani says:

    vukcevic says:
    May 13, 2014 at 4:08 am

    Milankovitch cycles aren’t quite that regular, at least as to interglacials. Also, for over half of the past 2.6 million years, the 40,000 year cycle dominated, not the 100,000 year, as lately. The timing & causes of the switch are controversial.

    Since the switch in dominant cycle period, interglacials have varied in length from thousands to tens of thousands of years. As has often been discussed on WUWT, the likely duration of the Holocene cannot yet be foretold with any confidence.

    The previous interglacial, the Eemian lasted 16,000 years by the most common way of dating its onset & demise. It was also warmer than the Holocene, which, by the same dating system, is about 11,400 years old. The Eemian was preceded by two shorter interglacials, although one had a YD-like interval between two warm spikes. The interglacial before those two shorter ones, MIS 11, was a monster, both warmer & much longer than the subsequent three (MIS 9, 7 & the Eemian). Going farther back in time, before three intervening interglacials, you come to MIS 19, which resembled MIS 11. So based upon only 800,000 years, there appears to be an approximately 400,000 year pattern in interglacial cycles in which orbital mechanical parameters roughly repeat.

    If the Holocene proves to last as long as MIS 11 & 19, which showed similar Milankovitch orbital mechanical positions, then “catastrophic” natural global warming could result. There would however be plenty of time to adapt to any sea level rise from melting of the southern dome of the Greenland Ice Sheet (& possibly part of the West Antarctic IS). This might not happen however, even given tens of thousands more years, because the Holocene has been cooler than MIS 11 (& the Eemian) & is liable to remain so. (This dome partially melted during the Eemian, such that Scandinavia became an island.) In any case, the site of NYC under a few meters of water would be preferable to under a kilometer of ice.

    Humanity will be lucky if the Holocene lasts tens of thousands of years more, based upon orbital mechanics, rather than the few thousand it appears headed for, based upon the longer-term global cooling trend of the past 3000 years observable in paleoclimatic proxy data. The jury is still out & may remain so for a long time.

  83. Steve Garcia says:

    Never never never stop asking “QUO BENE?” “Who benefits?”

    Think in terms of the Jones/Briffa/Mann “Team”.

    Look at the sceince writer on this one. HAHAHAHAHAHA – THE Richard Kerr who still has not acknowledged the pro-impact evidence from YEARS ago.

    At http://www.CosmicTusk.com, there is even a widget showing Kerr’s indolence:

    KERR WATCH<
    Number of days writer Richard Kerr has failed to inform his Science readers of the confirmation of nanodiamonds at the YDB: 3 years, 4 months, and 22 days

    HAHAHAHAHAHA, what a JOKE!

    Now look at the first name on the paper. MELTZER. Meltzer has spent his career on the mammoth overkill hypothesis, and is totally invested in it. If the impact hypothesis wins, Meltzer loses.

    So, with Meltzer, his career is on the line, THREATENED by the YDB impact hypothesis.

    Look at the second name on the paper. HOLLIDAY. Holliday is ALSO massively inverted in the Clovs Man DID IT hypothesis. If the impact hypothesis wins, Holliday also loses.

    Holliday and Meltzer have been carping on the YDB impact hypothesis since it came out, they and a very small cadre of gradualists who basically do not do any original work themselves regarding the impact evidence but just run around and try to poke holes in the pro-impact papers, which are loaded with ORIGINAL research and TONS AND TONS of forensic data on several fronts.

    Do you think I am kidding? EVEN THIS PAPER – look at the Abstract. It’s a JOKE. All they do is KIBITZ:

    Proponents’ evidence “is not internally consistent, not reproducible, and certainly not consistent with being produced by impact,” says a geochemist who has been publishing on impacts for 27 years.

    Do you SEE? All it is is a COMMENTARY paper.

    WHERE IS THEIR ORIGINAL SCIENCE, folks?

    There ISN’T any.

    This crowd – being mainstream (meaning uniformitarian-gradualist) – has the ear of similarly gradualist science editors. Richard Kerr is only one. ThePro-impct people have a tough time getting published – and every time they do, one of the Meltzer crowd is interviewed to “give balance”.

    But where is the

    So, every LITTLE PUNY point in refutation they can make is heralded from the rooftops – even if it doesn’t amount to anything. Names on the YDB skeptical “Team” are Daulton, Pinter, van Hoesel, Boslough, and Surovell. Their work is SHODDY and proven to be shoddy.

    At the same time, Surovell, though a died-in-the-wool gradualist, pokes big holes in the Mammoth Overkill hypothesis with some of his papers. I point to Surovell’s 2007 paper, “How Many Mammoth Kills Are 14?…” (http://www.uwyo.edu/nmwhomepage/pdfs/qi%202008.pdf) Which craps all over the PUNY amount of evidence that Clovis Man was the “extinction event” for Meltzer’s Overkill hypothesis.

    I ALSO point to my blog entry of two days ago: “Mapping Clovis Man vs Mammoths – Just Asking” at http://feet2thefire.wordpress.com/2014/05/10/mapping-clovis-man-vs-mammoths-just-asking/ The theme of that blog entry is that whenever we here of CLovis Man did this sand CLovis Man did that, they talk about CLovis out WEST.

    You wanna know something? Google Image “Clovis Sites Map”. You will SEE where Clovis Man REALLY was – and, Baby, it wasn’t out WEST! Clovis Man was primarily – VASTLY SO – east of the Misssissippi River.

    And here is the kicker:

    In the region where Clovis was greatly populated, THERE WERE NO MAMMOTHS.

    So, the great Mammoth devourers, Clovis Man, was eating OTHER animals!

    You won’t hear Meltzer or Holliday

    The skeptics always get the science journalists to state something like the one here: “Now comes what some researchers consider the strongest attack yet on the Younger Dryas impact hypothesis.” They have counted it dead and buried (if you listen to THEM tell it) several times over. AND ALWAYS PREMATURELY AND AMATEURISHLY.

    They are fighting to save their careers. They have a VESTED INTEREST in the impact hypothesis failing, and they are doing everything – EXCEPT ORIGINAL SCIENCE – to shoot it down.

    This so-called “paper” and its contents are – as usual – WEAK and adding nothing to the discussion but WORDS. WHERE IS THEIR ORIGINAL SCIENCE? NEW ORIGINAL LAB DATA?

    As one last blast at them, I will agree with Richard Fireston’s comment, ““Radiocarbon dating is a perilous process.” And it IS. Only recently did the Carbon14 IntCal calibration curves get changed – FOR THE THIRD TIME IN NINE YEARS. In one of the changes, the of the YDB impact radiocarbon dates moved by 100 years – from 12,900 years ago down to 12,800 years ago. And that will not be the last such change. So the skeptics picking nits about a few scores of years is a tempest in a teapot. The pro-impact realize this uncertainty in dating, and put down the best dates they can – but realize that those may change down the road.

    Melzer and Holliday act like all that dating is written in stone (no pun intended), and jump on any 5-year anomaly.

    Like I said, amateurish.

  84. Steve Garcia says:

    Sorry about that editing. The sloppiest comment I’ve ever posted here.

    At lest 2 sentences started and not finished. BAD. Typos galore.

    Mea culpa.

  85. DesertYote says:

    Pleistocene climate seems to be a bi-stable affair. All, as in 100%, bi-stable systems experience ringing upon state change. If one understands what causes the state changes, one will understand what causes the ringing. The Younger Dryas sure looks like the ringing of a bi-stable systems state change. It is best to try to understand what causes the ice age state changes first before invoking magic meteors

  86. Billy Liar says:

    Berényi Péter says:
    May 13, 2014 at 5:36 am

    A requiem to the Younger Dyras Impact Hypothesis was already announced three years ago.

    http://www.sciencedirect.com/science/article/pii/S0012825211000262

    Great paper! … from the conclusions of which I extracted this absolute gem of a quote:

    Some insight is gained by adding a historical perspective here. Scientific hypotheses are constantly being proposed, tested, confirmed, or cleanly rejected, but a small minority of these stray from this time-proven path. Many scientists are unaware of the surprising number of hypotheses that have gone badly astray, often after widespread initial interest and support (Langmuir and Hall, 1989; Gratzer, 2000; Park, 2000).

    Widely applicable!

  87. milodonharlani says:

    DesertYote says:
    May 13, 2014 at 11:30 am

    Some argue there are three Pleistocene states: interglacial, glacial & glacial maximum.

    Heinrich Events (iceberg armadas in the North Atlantic) during glacial phases & Dryas Events during deglaciation appear to arise from waxing & waning of ice sheets. The latter events coincide with fresh meltwater pulses.

    http://onlinelibrary.wiley.com/doi/10.1029/94PA00032/abstract;jsessionid=292E4DCFA02F926DE23E675A14A6AEB0.f03t03?deniedAccessCustomisedMessage=&userIsAuthenticated=false

  88. Jimbo says:

    Next time someone tells you that any change in glacier melt in Greenland is unprecedented, show them this from the IPCC.

    IPCC – TAR – 2001
    …..The warming phase, that took place about 11,500 years ago, at the end of the Younger Dryas was also very abrupt and central Greenland temperatures increased by 7°C or more in a few decades (Johnsen et al., 1992; Grootes et al., 1993; Severinghaus et al., 1998)……
    http://www.ipcc.ch/ipccreports/tar/wg1/074.htm
    blockquote>
    Temperature?

    Abstract
    Richard B. Alley
    Ice-core evidence of abrupt climate changes

    …..As the world slid into and out of the last ice age, the general cooling and warming trends were punctuated by abrupt changes. Climate shifts up to half as large as the entire difference between ice age and modern conditions occurred over hemispheric or broader regions in mere years to decades…….
    http://www.pnas.org/content/97/4/1331.full

  89. Mac the Knife says:

    The repetitive mega-floods from glacial Lake Missoula (~ 12,000ya, Montana USA) fall into the Younger Dryas time period. Are there any similar occurence of massive ice dammed glacial lakes from northern europe bursting forth in this time period ?

  90. Steve Garcia says:

    @Nick Stokes at 4:25 am:
    “The AR4 didn’t mention any impact theory 6.4-2-2:
    ‘Freshwater influx is the likely cause for the cold events at the end of the last ice age (i.e., the Younger Dryas and the 8.2 ka event). Rather than sliding ice, it is the inflow of melt water from melting ice due to the climatic warming at this time that could have interfered with the MOC and heat transport in the Atlantic – a discharge into the Arctic Ocean of the order 0.1 Sv may have triggered the Younger Dryas (Tarasov and Peltier, 2005)’ ”

    If you want to see a floundering hypothesis, the “freshwater influx>oceanic conveyor shutdown” is as bad as it gets. Wally Broeker came up with the idead long ago, and it was supposed to have come out of the St Lawrence, a Scablands-like flood from an ice dam failure at the southern end of glacial Lake Agassiz.

    THE FLOUNDER BEGINS… Unfortunately, it was found out more than 10 years ago that the ice sheet had not retreated north far enough at 12,800 years ago, so THAT idea had to get dumped. Broeker hismelf admitted it was a lost cause. But then someone came up with the BRILLIANT (/snarc) idea of having the ice dam fail to the NORTH, out via the MacKensie River and north to the western Arctic Ocean north of the Yukon.

    Which is THE dumbest idea EVER. That fresh water entering the WESTERN Arctic was going to cause the Gulf Stream to fail? That the fresh water and the fresh water was going to find its way to the east of Iceland, around all those islands north of Canada – and THEN not be diluted as hell? It is amazing how illogical and physics-challenged you can be and still have ANYONE call you a scientist.

    It is so dumb that I award them eternal ownership of the Pointed Dunce Cap Award.

  91. Steve Garcia says:

    leftturnandre at 4:46 am:
    “Steven said:
    There are huge problems with all the theories about the YD cooling.

    No there are no mammoth mummies dated to the Younger Dryas. Most are much older.”

    Sorry, lefturnandre, but you are wrong. At Murray Springs, for one, there were found mammoth bones with the “black mat” lying right on the surface of the bones, draped over them. The bones are even permanently STAINED from the black mat.

    And what does the black mat have to do with the YD? The underside of the black mat IS the YD.

    As to “most” of the mammoths being “much older,” that couldn’t possibly be because MOST mammoths lived in earlier times, could it? And what do their earlier deaths have to do with the extinction of the LAST of the full-sized mammoths? Absolutely nothing. That is like saying that your great-grandparents died before you will have died. So what?

  92. Steve Garcia says:

    Oh, and lefturnandre, they are not “mammoth mummies.” Sheesh! The ones that aren’t just bones actually have had meat still on them, edible by sled dogs. Frozen? Yes. Desiccated? I’ve been looking into these for decades and can’t recall one account mentioning desiccation, though I could be wrong. Most of the carcasses are quite intact.

  93. James at 48 says:

    During an overall ice age (which we are in) inter-glacial periods are innately unstable states. We are on borrowed time.

  94. Duster says:

    As much as I dislike Firestone’s impact hypothesis, he has a point about the hazards of 14-C dating. The 14-C production rates are far too variable to rely on without an alternate method to use as a check, especially as you deal with greater time depths. Otherwise, you are using a rubber ruler and need to handle any measurements with great care. One suggestion that Firestone was not interested in pursuing was the possibility that the nanodiamonds and other “cosmogenic” debris might be due to the passage of the solar system through a small dark nebular body. Common estimates of the planetary accumulation of normal meteor dust range from around five to more than 300 metric tons per day! Entry into a nebular cloud could raise that rate considerably, and, thinking about it, the increased interplanetary haze caused by the nebula would reduce insolation triggering cooling (see Sir Fred Hoyle’s “Black Cloud” for a fictional consideration of such an event). That could mean that there was no impact, but there was an increase cosmogenic materials, and that the time span of the onset was also greater.

  95. milodonharlani says:

    Mac the Knife says:
    May 13, 2014 at 12:11 pm

    The Bretz Floods occurred roughly between 15,000 & 13,000 years ago, so, within dating precision, a little too early for the YD. Other mega-jökulhlaups or Glacial Lake Outburst Floods (GLOFs) are evident from around the world from various times, however.

    The Strait of Dover & English Channel are thought to have been formed by erosion from two major floods. The first was about 425,000 years ago (onset of interglacial MIS 11), when an ice-dammed lake in the southern North Sea overflowed to break the Weald-Artois (SE England to NW France) chalk range in a catastrophic flood erosion event. After this, the Thames & Scheldt emptied through this gap into the English Channel, but the Meuse & Rhine still flowed northwards. In a second flood about 225,000 years ago (interglacial MIS 7) the ice-dammed Meuse & Rhine formed a lake which broke catastrophically through a high weak barrier (perhaps chalk, or an end-moraine left by the ice sheet). Both floods cut massive flood channels in the dry bed of the English Channel, somewhat like the Channeled Scablands of the Pacific NW or the Wabash River of the Midwest.

    It has also been suggested that gigantic jökulhlaups from a Hudson Bay area lake dammed by Laurentide IS ice at the mouth of Hudson Strait could have caused Heinrich events (armadas of icebergs leaving ice-rated debris on the floor of the North Atlantic) during the last glaciation.

  96. E.M.Smith says:

    IMHO the Cosmic Tusk folks have it most right. String of impactors mostly onto the ice sheet. LOTS of detail at their site.

    Folks are mixing several different things in comments:

    1) What causes glacial / interglacial cycles.
    2) What causes instability / wide swings in glacial temperatures
    3) What causes period of Ice Age Glacials
    4) What caused extinctions / reductions of animals

    and a few more….

    For most of these there are relatively simple answers IF you keep them separated from each other. For example, the Ice Age Glacial periods. Milankovitch pretty much worked this out. Precession, obliquity and eccentricity. The transition from 41,000 year to 100,000 years, IMHO indicates a continued lower temperature on earth.

    The key is realizing that we are only in an interglacial when the north pole melts. During the 40,000 ish thousand year time it was warm enough that that happened when the tilt was changed on the 41,000 year cycle. N.Pole at the sun, ice melted. Once we got even colder, that alone was not enough and we needed it to happen when the eccentricity was enough that summers were a few days longer than the average. (Yes, that still ‘has issues’…)

    BTW, we are IN an “Ice Age”, just in an interglacial during it. There are also stadials and interstadials that are not quite as warm / cold as the glacial / interglacial swaps. Ice Ages (not just the glacial / interglacial swapping) seem driven by placement in the galactic arms.

    During a glacial, temperatures are more metastable. Swaps of ocean currents cause a switch of the Thermohaline Circulation fairly easily ( there’s a paper that shows the heat backing up in Florida then and summer like rains even in winter here). That ocean current swapping is the biggest trigger of the various swaps. (D.O. and such look tied to Lunar tides and their 1470 -1800 year cycles of extremes).

    The extinctions of animals are largely in sync with impact events and occasionally with sudden introductions of other species (continents collide / connect). The idea that humans hunted ALL the megafauna of North America to extinction at exactly the same time is simply stupid. There just were not enough humans to do that.

    So, on the thread of this posting, IMHO the impact into the ice theory accounts for all the known facts. Including sending a wall of icy slush over the pole to explain the land form of mixed stuff in Siberia (including the plant and animal inclusions).

    BTW, Comet Encke is the likely culprit. Entered about 20,000 years ago and began to break up. LOTS of big chunks “lost”, and likely impacted Earth in many cases. We have regular meteor showers to this day based on the left overs. (Taurids). That pretty much proves we are in the shooting gallery for the break up.

    So this paper found some craters that have mildly divergent dates, and the event spans some time. Since we’ve had about 20,000 years of Encke Bits whacking us, I say “So what?”…

  97. mikewaite says:

    Just by coincidence, at middday today I was reading a book ,published about 1975 on AngloSaxon England and the possible effect the prevailing rainfall and temperature had on the successive invasions by Anglo Saxons, Viking and Danes on south East England following the end of Roman occupation.(Our little band of amateur archaeologists had been driven off the excavation site by downpours of freezing rain – which is odd given that we are in early summer and Britain is in the savage grip of unstoppable global warming according to the BBC and the Guardian).
    Anyway , with one petrified hand clasping a life giving cup of triple strength espresso , I was leafing through the book and came upon a 2000 year chart of Greenland temperatures from oxygen isotope ratios measurements by a Danish scientist.
    The usual variations , the mediaeval “optimum” as the author called it( regarding it as a global effect ) , and the following minimum were there , but the final temperature , ca 1975 was exactly on the longterm mean . No mention of CO2, or hockey sticks and the variations were treated as a natural fluctuation , not related necessarily to human activity or lack of it .
    I am sure that later studies are more detailed and accurate but it was such a relief to read a calm and matter – of- fact presentation of scientific data without the shrill screams of imminent doom.
    What happened to those happy innocent days of ( largely) impartial , objective and scholarly science .
    All gone , gone with the wind? .

  98. Steve Garcia says:

    @Col Mosby at 5:02 am:
    “Get the feeling not much advancement of knowledge here.”

    Exactly. This is what I call a “kibitzing paper” – though you COULD call it an Op-Ed paper. It doesn’t DO any new science. All it does is point at REAL work others did and give opinions, with NO new forensics of their own, just trying to pick holes in the work of others.

    I am ALWAYS amazed that journals allow Op-Eds. Opinions are not science.

    If you look at my long comment here, this small team – I call them “The Daulton Gang” does nothing on the YD except try to undo the work of the pro-impact people. The Daulton Gang only ONCE has gone out in the field (that I know of so far) to get their OWN evidence, and when Surovell did that, he completely FAILED to follow sampling protocol. He diluted the samples by not taking narrow (2 cm or so)samples. So HIS lab results showed WAAAAY too low of impact material levels. His failure has duly been noted. And THEN the bigger didn’t even come back with a response! He just let it lie! What the heck kind of scientist doesn’t even DEFEND his own work?

    And HE was the only one who went out in the field and got his own samples. PATHETIC.

    So, as you say – no “advancement of knowledge”. The Daulton Gang, in fact, doesn’t WANT any new development – because if the eivdence for an impact at the YDB holds up (and it looks like it will), then their entire careers are garbage.

    ["bigger" ? Mod]

  99. J Martin says:

    What could possibly flash freeze mammoths ? Surely nothing within nature on Earth, the only thing cold enough woud be a ball of ice from outer space. The black mat could be other consequences of the impact.

    Or is ice from the arctic or Greenland cold enough to flash freeze an animal well adapted to arctic, or at any rate, Siberian temperatures ? seems unlikely so I can only give credence to the icey comet impact theory.

  100. milodonharlani says:

    E.M.Smith says:
    May 13, 2014 at 12:38 pm

    The Overkill Hypothesis doesn’t maintain that all megafauna were hunted to extinction at the same time. It does however attribute the extirpation or extinction of about 15 genera wholly or in part, directly or indirectly to the Clovis people.

    But advocates of the hypothesis also cite genera which survived the alleged Clovis Blitzkrieg as supporting evidence, since most of them were of relatively recent Asian origin, thus adapted to human predation. Among the exceptions is the indigenous American pronghorn, the second fastest land animal on earth.

  101. Steve Garcia says:

    @Em SMkith -
    “The idea that humans hunted ALL the megafauna of North America to extinction at exactly the same time is simply stupid. There just were not enough humans to do that.”

    DUH.

    You might be interested in my Sunday blog post at http://feet2thefire.wordpress.com/2014/05/10/mapping-clovis-man-vs-mammoths-just-asking/

    Discussing the fact that most Clovis points are NOT found out west. The VAST majority are in the EAST. And the highest concentrations are where NO mammoths have ever been found. Obviously the Clovis people were eating something THERE other than mammoths.

    It Boggles my mind that anyone could think such a stupid thing – that Clovis would hunt a 5,000 lb mammoth, which has about 3,000 lbs of meat AS THEIR MAIN SOURCE OF MEAT. HOW in the wworld could they keep it from spoiling? Drying racks? Do they have any IDEA how many drying racks it would take? And how could they haul that much meat back to their families? And WHY? When there are many kinds of smaller game to hunt, that are much less dangerous and do not take a factory-sized effort to cure and then pack up and haul?

    Add to that that the great number od Clovis people were east of the MIssissippi, and what are we talking here – hunting expeditions 1,000 to 2,000 miles away? And hauling that much meat back THAT far?

    Whatever those arkies and paleos are smoking, I don’t want any of it. Let them Bogart that joint, my friend.

    One site has over 12 mammoth skeletons. That is about 40,000 lbs of meat. At 1/2 lb of meat per serving, that is 80,000 meals.

  102. milodonharlani says:

    mikewaite says:
    May 13, 2014 at 12:42 pm

    Gone with onset of CACA grant money.

    Many consider it no accident that the Dark Ages folk migrations, aka barbarian invasions, coincide with the deterioration of climate from the Roman Warm Period to colder prevailing conditions. Then during the Medieval Warm Period, the barbarians settled down, becoming Christian farmers rather than pagan pirates & raiders.

    During the High Middle Ages, population grew, horses were bred larger thanks to abundant fodder & armor got heavier on both knights & their mounts. Then from around AD 1250, things started deteriorating again, but worsened in the early 1300s. Then from the 1340s came famine, war & pestilence, carrying off perhaps 60% of Europe’s population. Maybe more. The Little Ice Age bottomed out around 1700, but persisted in reduced form until about 1850.

  103. Steve Garcia says:

    @hell_is_like_newark at 5:10 am:
    “Some things that happened during the Younger-Dryas:
    1. It got colder yet sea level continued to rise dramatically.
    2. Melt-water from the Laurentide ice sheet switched from flowing South into the Gulf of Mexico suddenly shifted to dumping into the North Atlantic.
    3. The Clovis culture and large land mammals pretty much disappeared in the fossil record. There is a mysterious black mat above which mega-fauna and the Clovis no longer exist.”

    1. Yes, correct.
    3. Yes, correct.

    As to 2. No. Yes, the outflow to the Gulf of Mexico changed. NO, to the shift to the Atlantic. The originator of that idea, Wally Broeker, even gave up on that idea. The timing of the retreat of the Laurentide simply was too late. The serachd for outlet for the ice dam failure on Lake Agassiz had to be aborted. The timing killed the idea, and Wally accepts that.

    Since that became patently clear, the idea floundered, but then the proponents have shifted to an outlet via the Mackenzie River north, across the Yukon, to the western Arctic – about as FAR away from the Atlantic as you can get in Canada – like 4,000 miles away, and past many islands, including the big one, Greenland. On a DUMBEST IDEA OF THE 21st CENTURY scale, that one is about a 12 on a 10-point scale. But they are running with it.

    Seriously stupid idea. Why not have it flow WEST, over the Rockies? It is just about that dumb. Or through some imaginary underground river to come up right by Iceland?

    In any event, the St Lawrence outlet for Lake Agassiz failed. Oh, it might have succeeded if it didn’t have to be right THEN. (But no Scablands-like scour has ever been found south of Lake Agassiz, so no, it still fails.)

  104. milodonharlani says:

    Steve Garcia says:
    May 13, 2014 at 12:57 pm

    There were mammoths in the US SE (such as Florida) & indeed Mexico. North America was home to other mammoths besides woollies, like the giant Imperial & Columbian species or subspecies. Plus of course North & South American mastodons & gomphotheres, proboscideans not members of the elephant family.

    http://news.discovery.com/human/evolution/early-man-florida-120509.htm

    But the Overkill Hypothesis doesn’t argue that Clovis hunters killed only mammoths. Quite the contrary. And surely a lot of meat was wasted. That’s sort of the point.

  105. Steve Garcia says:

    @John Slayton at 6:35 am:
    “Could someone with access, bring back the names of those three sites?”

    How about this:
    From Wiki:
    “The San Pedro River Valley is rich in discovered Clovis culture sites. Within a 50-mile radius are nearly a dozen Clovis sites including the Lehrner Mammoth Kill Site, the Naco Mammoth Kill Site, the Escapule Clovis Site and the Leikem Clovis Site.”

    “If I remember correctly, the Murray Springs black mat layer (with alleged nano-diamonds) was correlated with other sites some distance away–like thousands of miles. One suggestion was that there may have never been an actual impact, only a disintegration causing huge damage along the object’s trajectory. Seems to this layman that 3 well-dated sites that far apart showing (if true) identical geological anomalies, is significant evidence for impact, even if all the others are irrelevant.”

    Exactly.

    As I’ve pointed out here (and elsewhere), there is a small cadre of YDB skeptics that I call “The Daulton Gang” – mainstreamers all, which means they have invested their careers in other mammoth extinction hypotheses, and have a vested interest in poking holes in the evidence you have read about. That cadre does NOT do any original work – no field work, no sampling, no NOTHING. All they do is write up “Op-Ed” pieces that the journals keep on publishing. Because the journals themselves are fully vested in a non-catastrophic naturla history of Earth.

    Actually, one of them DID go out to get samples (Surovell 2009). But he was out of his element and he screwed it up – totally did not sample correctly. He mixed in samples of FAR too wide a time range, which resulted in watered-down samples. HE didn’t follow the sampling protocol. And he also didn’t even ask someone else what to do, so he did it wrong. THEN he published. And THEN the pro-YDB folks ripped him a new anus. He hasn’t been back to either rebut or to do new sampling. He didn’t even DEFEND his work.

    BTW, the pro-impact evidence now extends to FOUR continents.

  106. talldave2 says:

    I keep telling the CAGWers that if they really want to worry about something climate-related, they should focus on the overdue transition out of the current interglacial, which is far more likely to end human civilization than any putative future warming.

    But you can’t blame the evils of modern industry, so no go.

  107. talldave2 says:

    Re the Overkill hypothesis — this has way too much explanatory power to be dismissed on those grounds. It’s entirely possible for bands of early humans to hunt everything in an area to extinction within months of their arrival — that’s why you don’t see settlement remains in the fossil record next to large animal extinctions, they never had a chance to settle!

  108. talldave2 says:

    It Boggles my mind that anyone could think such a stupid thing – that Clovis would hunt a 5,000 lb mammoth, which has about 3,000 lbs of meat AS THEIR MAIN SOURCE OF MEAT.HOW in the wworld could they keep it from spoiling?

    Clovis Hunter 1: “Hey, look at that thing. It has so much meat on it, we have no idea how to preserve it!”

    Clovis Hunter 2: “Yeah, good point. Let’s continue to nearly starve instead.”

    And WHY? When there are many kinds of smaller game to hunt, that are much less dangerous and do not take a factory-sized effort to cure and then pack up and haul?

    Could not be more wrong. Humans can set gravity traps for large prey. Big dumb animals have a much better reward/effort ratio than little clever animals.

  109. milodonharlani says:

    talldave2 says:
    May 13, 2014 at 1:24 pm

    End of the Holocene isn’t overdue, although temperature trend has been down for at least 3000 years. The Eemian lasted about 5000 years longer than the Holocene has to date, while MIS 11 lasted tens of thousands of years longer. Interglacials vary a lot in duration.

    Depending upon which orbital parameter dominates, the Holocene could last a lot longer. Or not. Interglacials are all different in details, but there does appear to be a ~400,000 year pattern, ie a super interglacial every fourth glacial/interglacial cycle.

    The issue of when the Holocene might end & whether its demise is overdue has been discussed a lot on this blog.

    http://www.clim-past.net/8/1473/2012/cp-8-1473-2012.html

    Forgive the authors’ mention of CO2, which in this case is a proxy for temperature, since higher T means higher T, not necessarily the other way around.

  110. milodonharlani says:

    talldave2 says:
    May 13, 2014 at 1:28 pm

    You’re right, IMO. Humans have repeatedly been shown capable of hunting naive species to extinction, even on continental scales, not just islands.

    The Overkill Hypothesis isn’t mutually exclusive with an impact hypothesis, however, IMO. But fluctuations in deglaciation similar to the Dryas Events have been observed in previous Pleistocene glacial/interglacial transitions. Maybe Earth enters cometary or asteroidal debris zones periodically, but IMO there are better explanations. However if convincing physical evidence emerges for a YD impact or series of hits, then I’m willing to entertain that possibility.

  111. I thought the prevailing theory for the Younger Dryas was the opening of the outlet from the Great Lakes to the North Atlantic releasing a lot of dammed up meltwater barely above freezing disrupting the Gulf Stream.

  112. vukcevic says:

    milodonharlani says:
    May 13, 2014 at 10:45 am
    ………..
    Thanks, I was speaking in more general terms, I am aware of the periodic variability in the Ice ages cycles. I suspect there may be more to the Milankovic cycles than just the earth’s axis inclination.
    Milankovic cycles may have something with the SSN, the Arctic tectonics and the N. Atlantic temperatures. My limited collection of integrated tectonics data for the region, compares ‘well’ with the sunspot cycles, considering what two sets of data represent.
    When I chop the data and compare to the NA SST (AMO), an even ‘better’ agreement is reached.
    http://www.vukcevic.talktalk.net/SNAt.htm
    pseudo-science at its best (or its worst according to Dr. S); perhaps more next time.

  113. milodonharlani says:

    The Monster (@SumErgoMonstro) says:
    May 13, 2014 at 1:52 pm

    That is the prevailing theory, but geological evidence for it is weak. I find it plausible, however alternative hypotheses, besides the impact theory, compete with it.

    One suggests that the jet stream shifted northward in response to the changing topography of a melting Laurentide Ice Sheet, bringing more rain to the North Atlantic, freshening the ocean surface enough to slow thermohaline circulation.

    Some evidence also exists that a solar flare might have caused or contributed to extinction of the megafauna, although this can’t explain apparent variability in the extinctions among continents.

    The freshwater lid from glacial melting hypothesis is IMO supported by similar observations in at least the prior deglaciation, if not previous ones.

  114. John Archer says:

    Dennis Cox, [May 13, 2014 at 8:52 am]

    First of all, I thoroughly enjoyed reading your ideas (A Different Kind of Climate Catastrophe [2011/04/06]) usefully linked to above by hell_is_like_newark, for which, both of you: thank you very much indeed. It would thrill me no end to have it established that you are on the right track.

    By the way, I subsequently discovered that you have what seems to be another (updated/revised?) version which I haven’t had time to look at yet: A Different Kind of Climate Catastrophe (2) [2011/04/27]. Could you briefly outline its status, please?

    I’m a complete layman as far as geology is concerned but the way you put all that together looked eminently convincing to me. Your openness shone through too — you score big brownie points on that one. :)

    Could you kindly outline the subsequent reception of your ideas? You alluded to upcoming or in-progress studies by others. Have these seen fruit yet? Your paper is now three years old, so I’m hoping some progress has been made.

    I like your style very much. :)

    Best wishes,
    John Archer

    P.S. I’m posting this before having read all the comments here—of which there are quite a few—so I may have missed some relevant responses. Put it down to my ungovernable urge for immediate gratification. :)

  115. James the Elder says:

    talldave2 says:
    May 13, 2014 at 1:34 pm
    Could not be more wrong. Humans can set gravity traps for large prey. Big dumb animals have a much better reward/effort ratio than little clever animals.
    ==========================================================

    20 hunters carrying 100 lbs each back to camp to smoke and make jerky. The left behinds wouldn’t matter. If camp was close by, they go back and get it. As Yuka looked, the hunter(s) took the choice cuts and let the wolves have the rest. Smaller hunting bands would leave more, but no big deal; go kill another one. I doubt the Plains Indians had a preset limit on how many Bison they took.

  116. milodonharlani says:

    James the Elder says:
    May 13, 2014 at 3:36 pm

    Archaic (or possibly Paleo-Indian, who might not have been “Indians”) people, possibly ancestors of some present American Indian groups, stampeded Bison antiquus over cliffs c. 8000 BC, as historical Plains Indians did with Bison bison.

  117. Carla says:

    jim2 says:

    May 13, 2014 at 9:31 am

    Maybe it could have been the Vela supernova, a relatively close explosion at 800 lightyears.
    The resulting cosmic rays could have enhanced clouds and cooled the Earth.

    Vela Supernova Remnant.jpg Vela Supernova 11th–9th millennium BCE ? 800 ? Vela Supernova Remnant
    http://en.wikipedia.org/wiki/List_of_supernova_remnants
    ————————————————————————–
    My thoughts too..a nova wave..
    http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.html
    The graph above looks like the foreshock wave was dense cloud, main shockwave piece hot and the aftershock wave dense cloud.

  118. milodonharlani says:

    vukcevic says:
    May 13, 2014 at 2:10 pm

    Of course Milankovitch cycles have to do with more than just the earth’s axial tilt, which is of lesser importance than some other orbital mechanical variations.

    The parameters studied by Milankovitch included obliquity (axial tilt) & the precession index (which two factors control the seasonal cycle of insolation), plus eccentricity & longitude of perihelion.

  119. milodonharlani says:

    vukcevic says:
    May 13, 2014 at 2:10 pm

    Good discussion on implications of Milankovitch cycles for possible fate of the Holocene:

    http://wattsupwiththat.com/2012/03/16/the-end-holocene-or-how-to-make-out-like-a-madoff-climate-change-insurer/

    No one can say if the Holocene will last half a precession cycle, a full one or more.

  120. Carla says:

    Or..
    maybe it was the transition period to or entry into the S1 magnetic shell. Turbulence in the interstellar regions.
    Figure 1 of,
    “Time-variability in the Interstellar Boundary Conditions of the Heliosphere:
    Effect of the Solar Journey on the Galactic Cosmic Ray Flux at Earth”
    Priscilla C. Frisch · Hans-Reinhard Mueller
    2011
    http://arxiv.org/pdf/1010.4507.pdf

  121. Brian H says:

    [/sarchasm That gaping whole between reality and the CAGW religion .. Mod]

    Why would woo want wots of ws? You don’t know your arm from a hole in the gwowd.

  122. RoHa says:

    @Sandi
    “A bit annoying when reading a study raises more questions than it answers.”

    Not at all! Without those questions, how would you apply for more grants?

  123. Steve Garcia says:

    @John Whitman 6:56 am:
    “The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.” “
    - – – – – – – – – -
    Science in very blunt self-correction mode with that assessment of “conjured up “out of thin air” “.

    Hardly, John. This small group of self-appointed guardians of the sacred trust (meaning their academic careers) has done NO work on this subjecct othre than to snipe at things that are mostly incosequential and trying to convince people through “Science by news release” that their opponents are wrong. But this group does NO original work, NO field sampling that isn’t done wrong, and rankly they got NUTTIN’.

    The “conjured up out of thin air” is a snarc-y ad hoc attack on the pro-impact people. They have nothing else but snide comments. DO you see any professional respect in that? I don’t.

    Snarc-y doesn’t make it self-correction.

    Trust me: Meltzer is 100% invested in the Clovis Overkill hypothesis – the current mainstream consensus, which has holes in it big enough to drive a Mac truck through. If you think the CO2 CAGW hypothesis is weak, you should look into that one. But Meltzer If the impact hypothesis wins the day, Meltzer’s entire career is mammoth poop. Holliday does nothing but kibitz on the impact hypothesis. He is out of his league, but his career is caca, too if it flies. And the man hasn’t done ONE bit of science on this – just Op-Eds masked as science. It is all behind the desk pontificating.

    The VAST bulk of the pro-impact scientists is forensics – samples, lab tests in about 12 different ways, quantified and collated. Holliday lets them do the work and then sits back and says, “But you forgot to put in that semi-colon! It’s bad science! And you are 10 years too early!” yep, like the C14 dating is that precise that anyone would know…

    As Firestone says about their picayune points: ““Radiocarbon dating is a perilous process.”

  124. Steve Garcia says:

    @Bill Illis at 7:27 am:
    “Speaking of 2 km high glaciers melting in a short few thousand years, can you imagine how big the floods were and how wide the rivers flowing south got in the summer melt season. The Mississippi would have been impossible to ford unless your species could build good boats.”

    Bill – The 2km was not an average, nor was it 2km at the edges, as many people believe. The 2km was at the highest point,which was east of Hudson Bay – 600 km from the edge in Michigan. You can basically blame all the science writers who’ve ever written on this, for not clarifying it for the public. I had to go look high and low to find it out. At the southern edges the ice was “only” 1-3 hundred meters, though no one knows for sure. It might have actually been only a 20-30 feet high right at the edge in many places.

    Remember, for the ice to retreat, it had to melt back at the edges. Glaciers today in Greenland are kms thick far from their bottom ends, but look at most of them at the leading edges and they are usually not 100 meters. The southern zone of the ice sheets was partially exposed to the warmth south of the edge, so it would have logically lost ice thickness the closer you got to the edge. As the ice sheets retreated, this thinning at the southern edge would have probably continued, until at one point all of the ice sheet was gone.

    Your last sentence doesn’t really make sense. To ford a river is to WALK across it.

  125. milodonharlani says:

    Steve Garcia says:
    May 13, 2014 at 9:38 pm

    The glacial meltwater lakes & seas formed during the retreat of the Laurentide Ice Sheet on the last glaciation have been pretty well studied:

    http://dspace.usc.es/bitstream/10347/3757/1/pg_049-074_xeografica7.pdf

    It’s from a Spanish language journal, so its English is a little rough in places, but the graphics reflect state of the art understanding of the geology & geography of the melting process. Two graphics bracket the YD.

  126. Steve Garcia says:

    @Retired Engineer John at 9:17 am:
    “There was a period of extreme instability in the Earth’s climate starting about 11,500 years ago and extending back some 3,000 years. Those are extreme temperature changes that require big changes in the Earth’s balance of energy for an extended period of time. Singular events such as volcanos or comet impacts could not produce lasting effects sufficient to make these changes. Any explanation should be accompanied by calculations of the changes in accumulated energy required to make the temperature changes along how much change a proposed event could possibly make. I suspect that only an instability in the Sun could cause such large variations.”

    It is hard to draw solid conclusions, because the Greenland ice cores show NUMEROUS monumentally huge changes – Down AND up – called Dansgaard-Oeschger events. The YD onset apears to dovetail with ONE of those. 1300 years later a reversal of that occurred, and that one no one knows enough about yet to tackle it. The YD onset has been noted in various sciences – biology, climatology especially – and MANY people have been REALLY wanting to get to the bottom of it. The climate really DID shift -a LOT. After several thousand years of temps not far from ours today (and which was the first real warm period in a very LONG time), the YD put the planet right back in the cooler. Not just in Greenland, but everywhere. But Greenland, being Arctic, is, like most arctic regions, more sever in the ups and downs that happen when the climate changes. So the ice cores may be representing the most severe changes at the YD onset (as well as those other D-O downturns).

    YES, you are correct about the energy losses – they DO need to be explained. The duration of the YD of 1300 years – it DOES need to be explained. The equally sudden rebound from the YD glacial/stadial DOES also need to be explained.

    Be aware that nothing so far within the closed system of the Earth that has been suggested as the cause has come anywhere NEAR being feasible as an explanation. They invoke gradualism, and all its know internal mechanisms simply are inadequate in the extreme.

    Firestone himself did not set out to look for the YD cause. He ran across some weird numbers in radiocarbon dating. As he kept turning up other weird stuff – iron balls imbedded in mammoth tusks and other megafauna tusks, magnetic grains in certain layers that kept on showing up at different sites (now extended to four continents), mammoth bones lying with the mysterious “black mat” literally ON the bones, staining them and imparting radioactivity and magnetism to the bones. He orignally thought it was from a supernova somewhere nearby, because he ruled out (based on the evidence he was uncovering) any terrestrial causes. By the time he got into it a bit, others were joining in trying to figure out WTF was going on – or had GONE on. The impact scenario was not the first idea in their heads, but it was always a possibility, once they found out how FAST those iron balls had to be traveling. The bottom SURFACE of that black mat turned out to be consistently carbon dated to 12,900 years ago (calibrated – and then not long ago adjusted down to 12,800). THAT put the mammoth extinction not only AT the YD onset by date, but also PHYSICALLY.

    The Holliday-Melzer tandem have addressed all of these points in a 2010 paper that didn’t get NEARLY this much attention. They don’t have any answers, either. And they don’t DO any original work on this – all theydo is snipe at those doing the work. “Those who can, DO; those who CAN’T teach.” With Melzer and Holliday if could finish with “..; those who CAN’T, snipe.”

    IMHO, there IS sufficient evidence of a forensic type – properly taken samples, tested in labs, providing much quantitative data, pointing at X, Y, or Z possible causes, and of sufficient BREADTH of evidence types (impact materials, ammonium spikes in the atmosphere (e.g.), to collectively point at an impact as the most likely suspect. It is possible to point at individual data and snipe at that one – while ignoring ALL the other types of data – and then turn around and tell the world, “NOPE. That one thing is kind of weak, so the whole thing is crap.” That is what is done here. The Holliday-Melzer group (including Boslough, Daulton, Pinter, van Hoesel and few others) conveniently pretend that the other line of evidence do not exist – and they hope that no one will ask them about it all.

    It would actually not be laughable if any of them actually did any field work themselves. But they are like Monday morning quarterbacks – you know, really someone we should all listen to (snarc).

  127. milodonharlani says:
    May 13, 2014 at 10:45 am

    The previous interglacial, the Eemian lasted 16,000 years by the most common way of dating its onset & demise. It was also warmer than the Holocene, which, by the same dating system, is about 11,400 years old.
    ——————–

    My personal opinion is, ….. if one is calling the current period the “Holocene Interglacial” then one has to date it at being about 21,000 years old as defined by the “start” of the post-ice age melting of the glacial ice.

    To wit, proxy graph of Post-Glacial Sea Level Rise
    http://withfriendship.com/images/e/22018/another-graph-of-the-holocene.gif

    Sea levels had already risen by 70 meters (230 feet) by 12,000 years ago, …. stalling at the start of the Younger Dryas, ….. and then re-starting their rise 1,000 years later at 11,000 years ago at the end of the YD. Glacial ice melting also stalled at about the 14,000 year date and re-started 1,000 years later.

    Thus, the question is, …. why two (2) identical “1,000 year periods” of non-melting ….. right in the middle of a 15,000 year period of extremely quick melting of glacial ice? Could not the “freshwater” influx into the North Atlantic be a likely culprit for causing both?

    Anyway, global temperatures had to have started rising long time before sufficient melt water could have been detected via said Sea Level Rise proxies.

  128. a reader says:

    If you have never seen the Illinois surface topography map produced by the Illinois State Geological Survey, go to their website and check out their online version. I don’t know of many other maps which so clearly show the power of melting glaciers. Much of the topography of NE Illinois (and really much of the state) was produced by the Kankakee Torrent–a sudden release of a vast amount of glacial melt water released about 15,000 years ago–which pushed the Mississippi river to its current position from the present Illinois River valley. It is so stunningly beautiful that it graces my office wall.

  129. Dr. Strangelove says:

    Steve Garcia

    “The timing of the retreat of the Laurentide simply was too late. The serachd for outlet for the ice dam failure on Lake Agassiz had to be aborted. The timing killed the idea, and Wally accepts that.”

    The timing was not so bad. Geological evidence of major outbreak of Lake Agassiz 13,000 yrs ago. Younger Dryas began 12,800 yrs ago. Off by 200 years. You need time for fresh water to travel from Beaufort sea to North Atlantic.

    “the proponents have shifted to an outlet via the Mackenzie River north, across the Yukon, to the western Arctic – about as FAR away from the Atlantic as you can get in Canada”

    Yes but the Bering Strait had a land bridge 12,000 yrs ago. Fresh water cannot flow to Pacific Ocean. It went under the frozen Arctic Ocean to Greenland Sea to North Atlantic. That took 200 years.

  130. Dr. Strangelove says:
    May 15, 2014 at 1:57 am

    Yes but the Bering Strait had a land bridge 12,000 yrs ago. Fresh water cannot flow to Pacific Ocean. It went under the frozen Arctic Ocean to Greenland Sea to North Atlantic. That took 200 years.
    ——————

    Great point about the land bridge but …… I have to question whether the Arctic Ocean was frozen over at that time and I’m inclined to believe that it wasn’t, as per, to wit:
    =====================

    Holocene Treeline History and Climate Change Across Northern Eurasia

    Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P.

    Forest establishment and retreat was roughly synchronous across most of northern Russia. Treeline advance on the Kola Peninsula, however, appears to have occurred later than in other regions. During the period of maximum forest extension, the mean July temperatures along the northern coastline of Russia may have been 2.5° to 7.0°C warmer than modern.

    The development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions, including heightened summer insolation, the demise of Eurasian ice sheets, reduced sea-ice cover, greater continentality with eustatically lower sea level, and extreme Arctic penetration of warm North Atlantic waters. The late Holocene retreat of Eurasian treeline coincides with declining summer insolation, cooling arctic waters, and neoglaciation.

    http://www.sciencedirect.com/science/article/pii/S0033589499921233

  131. Thanks, Dr. Easterbrook.
    I have a new article my climate pages showing an older version your “Temperature fluctuations over the past 17,000 years” graphic.

  132. milodonharlani says:

    Samuel C Cogar says:
    May 14, 2014 at 10:06 am

    I’m with you on meltwater as the likeliest explanation for Dryas Events.

    Dating the onset of not just the Holocene but previous interglacials is always open to discussion. The beginning of Holocene has most recently (JOURNAL OF QUATERNARY SCIENCE, 2009) been dated to ~11,700 calendar years BP (where “present” means AD 1950), rather than some other point, based upon Greenland ice core & “selected auxiliary records”.

    http://www.stratigraphy.org/GSSP/Holocene.pdf

  133. milodonharlani says:

    Upon reading my own source, I see that the definition of BP its authors used has been moved up to AD 2000 from 1950.

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