WUWT previously covered this story on August 29th, and also on September 20th, 2012. This is a new press release from the University of Chicago today. A new study published in The Journal of Geology provides support for the theory that a cosmic impact event over North America some 13,000 years ago caused a major period of climate change known as the Younger Dryas stadial, or “Big Freeze.”
Around 12,800 years ago, a sudden, catastrophic event plunged much of the Earth into a period of cold climatic conditions and drought. This drastic climate change—the Younger Dryas—coincided with the extinction of Pleistocene megafauna, such as the saber-tooth cats and the mastodon, and resulted in major declines in prehistoric human populations, including the termination of the Clovis culture.
With limited evidence, several rival theories have been proposed about the event that sparked this period, such as a collapse of the North American ice sheets, a major volcanic eruption, or a solar flare.
However, in a study published in The Journal of Geology, an international group of scientists analyzing existing and new evidence have determined a cosmic impact event, such as a comet or meteorite, to be the only plausible hypothesis to explain all the unusual occurrences at the onset of the Younger Dryas period.
Researchers from 21 universities in 6 countries believe the key to the mystery of the Big Freeze lies in nanodiamonds scattered across Europe, North America, and portions of South America, in a 50-million-square-kilometer area known as the Younger Dryas Boundary (YDB) field.
Microscopic nanodiamonds, melt-glass, carbon spherules, and other high-temperature materials are found in abundance throughout the YDB field, in a thin layer located only meters from the Earth’s surface. Because these materials formed at temperatures in excess of 2200 degrees Celsius, the fact they are present together so near to the surface suggests they were likely created by a major extraterrestrial impact event.
In addition to providing support for the cosmic impact event hypothesis, the study also offers evidence to reject alternate hypotheses for the formation of the YDB nanodiamonds, such as by wildfires, volcanism, or meteoric flux.
The team’s findings serve to settle the debate about the presence of nanodiamonds in the YDB field and challenge existing paradigms across multiple disciplines, including impact dynamics, archaeology, paleontology, limnology, and palynology.
C. R. Kinzie, et al., “Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP,” The Journal of Geology 2014, 122(5). http://www.jstor.org/stable/10.1086/677046
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The interesting thing is to draw a continuous warming from before the Younger Dryas as though it never occurred, and then connect it about horizontally to the post YD peak warming, and the curve you get looks a whole lot like the Eemian.
And all the interglacials have pointy heads, while the Holocene has the appearance of a plateau. Fascinating to speculate whether civilisation got a leg-up because of the YD, which appeared to put a damper on the Holocene and give homo sapiens a chance to make something of themselves.
The resolution of the ice core data decreases the farther back we go. If we were able to examine the previous Pleistocene interglacials in as much detail I’m sure we’d find them equally ‘up/down’ temperature-wise as the Holocene. For example, take the Eemian (130-115ka):
http://en.wikipedia.org/wiki/Eemian#mediaviewer/File:EPICA_delta_D_plot.svg
Are you suggesting that had the YD not occurred the Holocene would have come and gone more quickly and thus civilization would not have had sufficient time to develop before the onset of the next glacial max? I don’t see much evidence for that. It has taken humanity about 12k years to get from stone-age hunter gatherers to where we are now. Previous interglacials lasted as long or longer. If anything, the YD almost stopped the Holocene in its infancy. Now that would have been a real climate catastrophe!
I think you could make a much stronger case for humans being evolutionarilly more advanced and thus more able to take advantage of the Holocene interglacial climate than previous interglacials. You might even make the case that the Eemian was the ‘garden of eden’: a species memory of a distant past when the land was warm and fruitful, and filled with abundance. 😉
In the absence of evidence of an extraterrestrial impact, all manner of theories attempting to explain simultaneous extinctions could be considered.
Now, we have evidence of one or more continents burning about the time these extinctions are thought to have occurred. Judging from the geologic record, entire continents don’t burn often. Or multiple continents at burning at the same time, not often either.
So did the circumstances that created a 50,000,000 sq. km. burn layer have anything to do with the extinctions? Doesn’t seem an unreasonable possibility.
Nanodiamonds? Maybe. Meteor? Maybe. But a climate changing meteor? A meteor that wipes out big game while stirring not a mouse? Or climate that does the same? Or disease? The comet theory and the overkill theory are best kept separate. –AGF
Where did you ever read that mice weren’t also killed? You didn’t.
As to the comet theory and the overkill theory not being kept separate, you are either misstating the state of affairs or misinterpreting. The two hypotheses (not theories) are mutually pretty much exclusive.
It is quite ironic that at least two of the skeptics to the YD impact hypothesis (YDIH) – Surovell and Melzer – are researchers who seriously seem to question the exclusive hunting of megafauna. Surovell even has a paper entitled, “How many elephant kills are 14?: Clovis mammoth and mastodon kills in context” (Surovell and Waguespack 2008) http://uwacadweb.uwyo.edu/nmwhomepage/pdfs/QI%202008.pdf. Melzer also authors papers counting the number of Clovis-mammoth/mastodon sites, and there are only those 14.
Mr. Garcia, have you ever seen a list of Pleistocone extinctions–species by weight? Did mice go extinct? The K/T extinctions were pretty much size-didn’t-matter, unless you were small enough to live in burrows. The Pleistocen extinctions are typically labeled “Pleistocen Megafauna Extictions.” Now of course the “overkill” theory is opposed to all other explanations, including comet/climate. The distinction I am attempting to make is that between the possibility of a meteor event which is not blamed for Pleistocene extinctions and one that is. See, you could conceivable have ET nanodiamonds and still have overkill.
Now one poster links some papers that show the nano-diamond evidence is bunk: some three of some 40 supposed sites have anything close to reliable dating. Strike one.
It would take an enormous ET object to cool the climate for more than a year or two. That would do more than wipe out a few large species. Strike two.
Megafauna disappear everywhere humans show–beginning with Australia and continuing with New Zealand, Madagascar, Mauritius, and every other island with animal land lubbers, big and small. North America was no different. Strike three.
Mr. Garcia, have you ever seen a list of Pleistocone extinctions–species by weight? Did mice go extinct? The K/T extinctions were pretty much size-didn’t-matter, unless you were small enough to live in burrows. The Pleistocen extinctions are typically labeled “Pleistocen Megafauna Extictions.” Now of course the “overkill” theory is opposed to all other explanations, including comet/climate. The distinction I am attempting to make is that between the possibility of a meteor event which is not blamed for Pleistocene extinctions and one that is. See, you could conceivable have ET nanodiamonds and still have overkill.
Now one poster links some papers that show the nano-diamond evidence is bunk: some three of some 40 supposed sites have anything close to reliable dating. Strike one.
It would take an enormous ET object to cool the climate for more than a year or two. That would do more than wipe out a few large species. Strike two.
Megafauna disappear everywhere humans show–beginning with Australia and continuing with New Zealand, Madagascar, Mauritius, and every other island with animal land lubbers, big and small. North America was no different. Strike three.
[Hmm, posted double and wasn’t even done–using an old browser.] Continued:
And of course there are all those pesky problems with the meteor/climate theory, like why did mammoths persist on Wrangel Island and elsewhere–far to the north where climate was coldest. And of course the scientific answer is that humans were late arriving there (4.7kya). In fact why did all the most northern species survive? Because they were safe from humans, not climate change.
So, multiplying improbabilities: nanodiamond evidence? 1% maybe.
Comet caused climate change? Ditto.
Climate caused extinctions? Highly unlikely.
Product (comet killed mammoths)? This whole theory is on the order of creationism and CACC. Very, very bad science. –AGF
agfosterjr says @September 12, 2014 at 8:22 am
Although it is not currently a popular explanation, disease hasn’t really disappeared as a potential cause of population & even species-losses. And it would ‘cover’ why island-populations etc persisted after continental eradication.
Disease-problems can also be more difficult for larger animals to withstand.
Like the formerly laughable idea that Modern humans are connected to Neanderthals, questions about ancient diseases may soon become more answerable than we have heretofore thought.
The terminal Pleistocene extinctions are likely a camel-straw situation where no single “cause” can or should be singled out. The most obvious primary issue is a changing climate. The YD punctuates a period of rapid change with another period of extremely rapid change in an opposite direction. With a “predictable” shift in life zones plants and animals can adapt through population redistribution or other means. But two such shifts would be a profound stress. Another point is that if you take a graph of the Late Pleistocene that shows the YD, the late YD warming rate is a very close match to that of the Bolling-Allerod immediately prior to the YD. That implies that whatever processes were set in motion to warm the planet at the end of the LGM continued to act throughout the YD, implying that the cause of the YD literally overpowered the climate system. Life would have been very difficult.
The LP extinctions were not universal nor are all the “extinctions” true extinctions. Elephants survived quite well in Africa and southern Asia, as did rhino. Horses vanished from the Americas but not from anywhere else on the planet. Bison seem to have changed by fairly minor biological adaptations to body size and body conformation. They aren’t extinct. They just look different. Musk Ox survived just fine as did caribou. They simply moved northward.
It is important to remember also that the perigalcial environments south of the great ice sheets have no modern analogs. It is a profound mistake to consider modern tundra and taiga as equivalents since they are not, and can not be. Insolation for instance was much higher. While the “climate” might have been colder, the incoming light was more intense in the lower latitudes than can be found in tundra or taiga today, meaning the primary productivity was much higher in these periglacial zones during the Pleistocene. The primary extinctions are almost all among animals that were occupants of those environments and they evidently vanished along with the environments. In North America the situation may have been complicated as the Bering land bridge opened allowing diseases to move somewhat more freely between the major land masses.
Since a human population was present in the Americas by as early as 17,000 BP, it seems unlikely that “overhunting” was a serious problem. It is important to remember too that there are immensely many more elephants, dire wolves, sabertooths and Alaskan lion in the la Brea Tar Pits than there are known to be victims of human predation.
agfostrjr –
Just because ALL mice didn’t die doesn’t mean at all that MOST mice could have died. Did you ever take allogic course? An event that kills 100% of one or more species but only 80% of others can leave those 80% species still around, enough to repopulate. It’s called a bottleneck. The event, whatever it was – climate or impact (or some OTHER cause no one has thought of) – that caused the YD onset killed ALL of some. Because SOME of the others made it though the bottleneck you can’t read that as a “selective”.
Because SOME survived in no way means that every individual in that species was spared.
SOME small animals – including small mammals – made it through the K-T. You said it yourself.
It doesn’t matter that we LABEL the event the “Pleistocene megafauna extinction.” Labels don’t mean anything.. Warmists call the current climate “global warming”. That label doesn’t make it so.
As to your strike one… Are you going to conclude that because someone presented THEIR one side of the case, that the issue is over without hearing the rebuttals? If so, holy crap! If you judge before hearing both sides, you would make a terrible jury member. Look at my post of 6:10 pm yesterday (reply to ob at 1:14 pm) that includes rebuttals of the earlier assertions of “bunk”. You can see that just because the skeptics state something that that is not the end of the discussion. Scratch strike one.
As to your strike three, have you noticed that every place you mentioned is an ISLAND? read up on extinctions, and you will find that islands are specifically easy places to make a species go extinct. It’s part of the reality of extinctions and WELL discussed in the literature. You can’t equate an 8 million square mile continent to an island. Different realities exist and must be considered. Try cornering the last 1,000 mammoths in one corner of N America with a few thousand hunters – without the mammoths doing an end run and escaping back out into the other 7.9 million square miles. Scratch strike three.
As to strike three, what do YOU consider “an enormous ET object”? Have you read any of the literature, or do we get to just pick our own nebulous number range – say 100 feet to 7000 miles? “Enormous” is so vague it means nothing.
You got nothing.
Duster –
All good points.
“It is important to remember too that there are immensely many more elephants, dire wolves, sabertooths and Alaskan lion in the la Brea Tar Pits than there are known to be victims of human predation.”
Along those lines, are you aware that there are only 12 Clovis-mammoth kill sites and 2 Clovis-Mastodon kill sites? That’s it. That’s all the evidence for overkill. 14 sites. Surovell himself wrote a paper entitled, “How many elephant kills are 14?: Clovis mammoth and mastodon kills in context”. http://uwacadweb.uwyo.edu/nmwhomepage/pdfs/QI%202008.pdf
Steve:
I took a quick look at the Surovell/Melzer paper (I skipped the math stuff…way above my pay grade). The paper attempted to analyze the known Clovis-mammoth/mastodon sites in the context of similar known sites in the “Old World”. The authors of the paper, rather refreshingly, are blunt about the fact that they are making a range of assumptions (identifying them as they go along), that there is much that is not known and that the way the evidence has been preserved may bias the results (factors like time span between the different comparators, geology/climate, etc.). However, based on the examination that they conducted, they feel that the better view is that (p. 94 of the article):
“[…] we suspect that a strong behavioral signal is coming through our sample, biased or not. In other words, the abundance of mammoth and mastodon kills known from Clovis contexts relative to Old World contexts is largely a product of past human behavior. Does this mean that mammoth meat was served on the dinner table every night in the latest Pleistocene of North America? Absolutely not. From our analysis, we cannot estimate an absolute frequency of elephant hunting. All we can say is that in comparison to the Old World record, Clovis peoples seem to have exploited elephants with much greater frequency than in any other time and place.”
Now, they are not claiming (in this paper, at least) to link this possibly greater predilection for hunting of big game with the extinction of those animals – rather, they merely are noting that, based on their assessment of the available evidence, it was a greater part of Clovis culture than elsewhere, in the older comparator cultures that were analyzed. However, it seems to me that this paper does not itself undercut the “hunting to extinction” thesis, and potentially could be used to support it.
(I’m taking no view on the hunted-to-extinction hypothesis: merely noting that the paper itself does not contradict it, and potentially could support it.)
I found that the way you’ve stated the issue is perhaps a bit different what is actually being considered. You note that they are “researchers who seriously seem to question the exclusive hunting of megafauna”. I’m not sure what you mean by “exclusive” and certainly Surovell/Melzer expressly seem to note that they are not suggesting that the Clovis ran a Flintstones’ style drive-in for mammoth ribs. As noted above, however, they do appear to conclude that such hunting was more frequent in Clovis than comparable cultures in the Old World (though they are not positing the absolute extent of such hunting).
ian005 –
Amazing – someone who actually DOES go and read papers linked. . .LOL
Yeah, that is not the only paper they’ve done on this general angle. In another paper Meltzer goes into depth on other types of game that Clovis likely killed. This paper as I read it at LEAST considers that it WASN’T mammoth meat drive through – which is more than I can say for many. And this thinking they’ve done for about 20 years now.
I am actually giving them credit for objectivity, even though they are on the opposite side of the impact fence.
To me, it is an open question of their dietary choices. But if you go to the maps on the PIDBA-org site, you will see that where most Clovis sites are there are no mammoth kill sites, except way up in Wisconsin and Michigan, in the northern reaches. Not many Clovis sites exist out west. Most are east of the Mississippi River. This is one of the points Dennis Stanford makes in his Solutrean-Clovis hypothesis. Considering the amount of plant matter elephants eat (and mammoths, by inference), it is amazing that no mammoth kill sites are where most Clovis points have been found – where the forests were densest. (Especially when one considers that the most reasonable place for points to be lost is at kill sites.) In Africa elephant ranges are mixed, but in India and SE Asia their main range has been forests, so one would tend to think that mammoths also would prefer forests. So if we have Clovis in forests mainly and proboscideans preferring forests, why do we find Clovis points at mammoth kill sites almost exclusively in regions that were not forested?
I am beginning to think that Clovis point sites are not necessarily Clovis PEOPLE sites. I am beginning to think that Clovis knappers traded their points and the points got used by all sorts of people. I think that is a thought Melzer had in one of his papers, too. If so, that would mean that Clovis points are not necessarily a good proxy for Clovis people.
Time will tell on that. As to the overkill, it’s a tough sell for me, because N America is REALLY big, and tracking down all those megafauna to every corner of the continent, by a few thousand hunters in a few hundred years – that seems illogical to me, to even START down that logical path.
If 14 kill sites doesn’t refute – and I agree it doesn’t – it also lends VERY little support to the overkill hypothesis.
Ian005 –
One more response, if I may…
You said “However, based on the examination that they conducted, they [Surovell and Meltzer] feel that the better view is that (p. 94 of the article):
‘[…] we suspect that a strong behavioral signal is coming through our sample, biased or not. In other words, the abundance of mammoth and mastodon kills known from Clovis contexts relative to Old World contexts is largely a product of past human behavior. Does this mean that mammoth meat was served on the dinner table every night in the latest Pleistocene of North America? Absolutely not. From our analysis, we cannot estimate an absolute frequency of elephant hunting. All we can say is that in comparison to the Old World record, Clovis peoples seem to have exploited elephants with much greater frequency than in any other time and place.’ ”
While I can probably respond on every one of those points that they made, I would rather make a different point.
I often remind people that science is NOT the accumulation of evidence, but the INTERPRETATION of the evidence. To whit, science has often been described as the attempt to understand and explain the natural world. Such understanding and explanation is what they are paid to do – not to just assemble data and walk away. There is always the attempt to put the evidence in some context, and that is where interpretation comes in.
As those authors phrased it (very honestly, I will credit), “…we suspect that…” and “…From our analysis we cannot estimate an absolute…” and “…All we can say is that . . . Clovis peoples seem to have exploited…”
All of this is their interpretation. I don’t say that to demean them. I say it to shine a light on the element of interpretation. THESE scientist weigh the evidence in their particular way. And each other researcher into this area has interpretations weighed in various other ways. This happens in other areas of inquiry, too, not just this one – that different weighings of mostly the same body of evidence yields several (if not many) different interpretations.
As I’ve noted in these comments already, there are FOUR scenarios for megafauna extinctions out in the academic world right now – climate change, overkill, plague/illness, and impact. You and I both know that all of them can’t be correct, not as the main forcing. Yet each one each year or so has papers weighing evidence preferentially toward ONE of these four, and these aer done in all seriousness. The authors of each paper sincerely think that their interpretation should be favored above the other three. Are three of the four groups of scientists simple-minded? Of course not. But the way they select which evidence to include and which to exclude, PLUS the relative weight given to the particular bits of evidence, gives an almost unlimited panoply of overall interpretations.
It appears that “science” gives these variously interpreting authors very broad authority to weigh evidence, I would say. To me, this only serves to obfuscate the entire field of study (this and perhaps many others), by not having sufficiently tight standards that are applied to evidence and treatment of evidence. And by not even having HIERARCHIES of evidence as courts do. (In courts, forensics are #1, documents #2, and on down to eye witness evidence, which is last on the totem pole.)
As mr lorax said at 12:24 pm yesterday:
“…The researchers leading the “impact skeptics” are anthropologists. In their field of anthropology, truth is somewhat subjective, as in whatever you can convince the other anthropologists of, without a lot of actual definitive physical evidence. They are hoping by making a lot of nice sounding arguments they can establish their theory of “something not an impact” being responsible for the black mat layer. Unfortunately for them, this is a topic with substantial physical evidence.”
In science, empirical (measured physical) evidence should be #1, the equivalent of forensics in court – which forensics are, in fact, actually empirical and physical and measured. Mr lorax’s “convinc[ing] of others” arguments sans physical evidence should be put much farther down the totem pole. “Reasonableness” or reason itself, should never be put ahead of physical evidence, measured and organized. Reason is, when you come down to it, one of two things – a guess, or an interpretation. And one could argue that all interpretations are themselves guesses, so perhaps reason needs to be piled down at the bottom of the evidence hierarchy with eyewitness evidence.
Perhaps 70-95% of the comments here on this thread are wrapped up in pretty-sounding “reasonable” ideas. But supposedly science replaced that Aristotlean approach long ago, replaced by quantified physical evidence. As mr lorax calls it here, “substantial physical evidence.”
Mr lorax understands the hierarchy that SHOULD exist in this debate about a hypothesis in the Earth Sciences. Surovell, Pinter, and Holliday, etc, somehow don’t. The amount of interpretation should be as SMALL as possible. (In that sense, Occam’s razor perhaps should be ruling here.) But since Surovell, et al, do not seem to understand the hierarchy of evidence in science, they don’t know when they’ve been bested. They think that more talk will win the day.
But when physical evidence says that temps over 2200°C are required, and 2200°C is far above what forest fires and the fermentation of insect poop can produce, they just don’t get it. And if they DO NOT, how in the world can they ever be convinced that they are wrong? So, Wittke, and Kinsie, and Kennett, and Le Compte, and Israde keep on putting the highest evidence in front of them, and what is the reaction? Surovell keeps having his eyes glaze over.
Steve Garcia
September 12, 2014 at 3:20 pm
….
Along those lines, are you aware that there are only 12 Clovis-mammoth kill sites and 2 Clovis-Mastodon kill sites?
Actually, I believe there have been another couple of kill sites identified within the last two years. Another problem with the “overkill” concept is the vanishing of other mega predators. The short faced bear, sabertooth, Alaskan lion and direwolf all vanished from America along with mammoth. Other herbivores also vanished including mastodon, horse, camel, and ground sloth, though the latter may have hung around several millennia. No overkill account handles these collective extinctions well. The argument is silly at best.
When you discuss Clovis one thing most people are unaware of is that there are only a handful of Clovis occupation sites, of which the best is probably the Gault site in Texas. That site yielded lots of smaller mammals, birds and even evidence of pond turtles in the Clovis diet. The site was evidently placed to take advantage of a good water supply and abundant Edwards Plateau chert. I believe it may be the only long-term, Clovis occupation site known. The archaeological debate about Clovis is far louder than the evidence justifies.
Mammoths did not go extinct during the YD either in North America or Siberia.
Mastodon populations show clear evidence of human hunting pressure and its effects before going extinct.
The YD was no different climatically than the onset of other interglacials and other cold events during the transition and the Holocene. The null hypothesis has not been rejected, and there is in any case no clear evidence of an impact.
Ted and Duster, see noon posts. This thread business doesn’t work for me. –AGF
As for the possibility of a Younger Dryas magnetic reversal, core/mantle coupling should not be ruled out. Probably no event incurs as much core/mantle torque as rapid polar ice sheet melting. That is to say, magnetic reversal does not affect climate, but the reverse. –AGF
Except maybe precession–constantly?
ok smart guy I’ll bite would like your thoughts on mine ten thousand years ago enough ice pressed down on the core through the Hudson bay to make Florida rise above what the ocean had dropped from ice displacement with Hawie as my example and a couple of miles of ice pressing down on the crust my magma core would wear the crust thin at which time the ice would melt from the heat at the bottom melting the ice from center out giving us a huge lake thousands of feet above ocean level just like now with mankind having 95% of its population living within 50 feet of ocean level the ice dam would eventually collapse and I would suggest to you that the crust would rebound dumping all of the displaced water back into the ocean lifting that level one to two hundred feet in as little as 24 hours the loss would be as huge as to the speed in which the ocean rose and the flood would spread outward depending on which ocean the water got dumped into your thoughts sir
There is an immense amount of data collected on geomagnetic reversals now spanning about 250 MY, IIRC my Historical Geology properly. There is no regularity of spacing or clear periodicity to chrons, some have lasted more than 10 MY many others are as short as several tens of thousands of years. Frequency does appear to increase toward the present and many, many more reversals have occurred in the Cenozoic than have been found in the Mesozoic. There is no correlation that I can see between reversals and “climate.” Also, since climate appears to be an emergent property of weather, and possibly only real in the minds of climatologists, I am dubious that there would be real correlations.
I have been avidly watching the development of this theory since it was first proposed in 2006 and have seen many counter studies, and counter-counter studies. As a biologist mass extinction events are bread and butter of punctuated equilibrium that helps define our understanding of speciation. Some of the challenge to the theory are from the vocal environmental “Man is the cause of the extinction” crowd, who, much like their warmist cohorts crow about protecting the planet from humanity because of the “ongoing” extinction event by pointing to it.
Here’s a prediction, in a month to six months, yet another counter study will say there is insufficient evidence for the impact event, and yes those dastardly Paleo-Indians ate their way all the way to Patagonia.
Ah, but those Paleo-Indians would have crossed the continent the same way that … Lewis and Clarke did: By walking across mountains, and valleys, and hills and dales. (True, they started from the east coast with horses using well-established roads as least as far as Pittsburgh (Ohio River) but even the settlers leaving the Mississippi from St Louis got all the way to the Wilmette Valley in less than 6 months. Washington DC to Washington state’s Pacific Coast took two years, then least than two years to get back.)
So, from the Bering Strait to Patagonia? Less than 10 years … If they wanted to. To settle? Look at the Mongol hordes sweeping across the steppes with entire tribe in arms.
Well, according to the people in the know, those Paleo-Indians didn’t ride horses. Obviously they had voracious appetites and set fires to the grasslands to stampede hundred of animals over cliffs (so the reasoning goes). Hey, all that CO2 they produced not only destroys the noble savage myth, but implies they should have stupided themselves into extinction. Biologists make no such assumptions, anthropologists seem to. Of course I am paraphrasing the eco-enviro-anthropologists I’ve run into in my many years of getting degrees, and now with me working in an educational position now.
One of the very curious facts about Clovis sites is that the vast majority of them are in the EAST, not the west. It is amazing how many Clovis finds are mapped in the east on PIDBA.org – and how FEW were out west. And yet, there are ZERO Clovis-mammoth/mastodon kill sites in the east.
In addition, the “point technology” up and over the Bering Strait has absolutely NOTHING in common with the Clovis points. Instead of one long and graceful blade, like Clovis, the Siberian spear points are serrated – mainly wood or ivory with many small flakes embedded in them. In addition, no Clovis sites exist up at the northern end of the “ice-free corridor). The tech there matches Siberia. But not Clovis.
Yes, SOME people came to America via Beringia. No one argues that. The real question is: Was Clovis part of that?
Steve Garcia
September 11, 2014 at 5:42 pm
…
Yes, SOME people came to America via Beringia. No one argues that. The real question is: Was Clovis part of that?
Since we really don’t know when or how humans first colonized the Americas, we can’t say. The best archaeological evidence is that it happened before 17,000 years ago. In fact what we do know now is that Clovis (as in the classical, early percussion-fluted technology) is an American development made by populations already resident. Archaeology like all science is subject to the hazard presented by Occam’s Razor. The simplest explanation is usually the best (but,it is also the easiest to remember, to think about, to imagine, and presents the greatest temptation to disregard contradictory or complicating data). The idea that CO2 is the “control knob” for climate is a good example of over-simple explanatory hypotheses.
Duster –
We see more or less the same things about the peopling of the Americas, as far as we’ve opened that door.
On Occam’s razor and the “simplest is usually right” meme, yeah, you caught some of its failings there. My experience in science and engineering is that you START with the simplest explanation/approach, and then all sorts of complications DO come in. I am virtually certain that some form of the impact hypothesis will win out here, but I think it will have numerous complications added in. Right now, it is simple and straightforward. But as the need comes in (probably fairly quickly) to cover things like the other spikes in the D-O record, and the duration of the YD at 1300 years, the hypothesis will get more complex. Hey, the topic covers about 5 or 10 areas of inquiry, so it needs to address things all over the map, so it would be amazing if its simplest version is the final one.
People here bring up good points – but I know for a fact that the scientists involved have thought of all of those and many more. It kind of amazes me that people will assume scientists overlooked the obvious candidates (and most of the ideas here are the obvious ones – no offense to anyone intended). That doesn’t mean “Trust the scientists blindly”, though. People here SHOULD be asking those questions. But the ridicule on some comments is silly, and for the most part uninformed, or – like warmists – .informed of only one side of the story.
This is a VERY complex hypothesis. That is why all those scientists’ names are listed (I count 26). Each one or two is covering his/her area of expertise. That is a lot of disciplines.
The human cause for the obliteration of the New Zealand moas is well-established. The major facilitator of that extinction was that the moas had no evolutionary experience of humans, didn’t fear them, and didn’t know to avoid encounters. Paleo-Maoris could just walk up to a moa and club it death. And they apparently did so. Bone yards show they often killed more moa than they needed for food.
It’s likely that the large fauna of Australia were likewise killed off by the paleo-Aborigines. Mega-fauna disappeared from Australia, after the arrival of the Aborigines, at the same time as they thrived on New Zealand.
The evidence does not support the extinction of Australian fauna due to climate change, or to a sudden impact.
A similar case can be made for North American mega-fauna, in that they had no evolutionary experience of humans. In analogy with the New Zealand moas, it is likely true that they had no response to avoid humans and that humans could kill them after almost trivially easy stalking. There’s no reason to think that paleo-Americans were reticent about mass-killing prey animals or that they were conscious stewards of their environment.
Buffalo jumps all across the US and Canadian midwest show that native Americans killed far more bison than they could eat or use. Two larger species of bison had already been driven to extinction in pre-Columbian times. So, there is good circumstantial evidence at least, that north American mega fauna were driven to extinction by predatory competition from humans. The hunting hypothesis is made stronger by the fact that virtually all mega-fauna disappeared during this time. A climate extinction event might be expected to make extinct some suite of non-adaptive species. Not all species.
Also, why shouldn’t an impact that obliterated animals obliterate humans, as well? But humans weren’t obliterated. David Meltzer and Vance Holliday say (pdf) that, “conditions during the Younger Dryas interval may not have measurably added to the challenge routinely faced by Paleoindian groups who, during this interval, successfully (and perhaps rapidly) dispersed across the diverse habitats of Late Glacial North America.” J. World Prehist. (2010) 23, 1–41.
You are not ever going to hear one thing from Melzer or Holliday in harmony with the impact hypothesis. They are firmly entrenched in the small skeptics group. So, no matter how many papers or how many other scientists find support for it, Holliday and Melzer will be among the last to agree. So, you will always find some paper of theirs kibitzing negatively. Right now they are basically doing Op-Eds, with almost NO actual science, just commentary.
Notice that while the TONE of that passage is negative, they waffle on it with “may not have”. So, they have their “may not haves”, while the YDIH scientists keep putting out paper after paper with all sorts of empirical evidence at the “forensic” level. Lab tests of actual physical samples taken carefully in the field.
In other words, one side is doing physical science and the other side is doing play-by-play with a negative twist.
Paleo-Maoris ? Paleo-English ?
We are talking about around 1000 years ago.
However there is no doubt that Maoris killed off the moa.
And killed more than they could eat ?
Certainly, because they used the feathers for cloaks.
Fur trappers in 18th-19th century North America killed more animals than they needed for food as well.
Your comment reads to me as confirmation bias. Decide the outcome, decide the events to the outome, decide the perpetrators which is of course always man…
The moa extinction event is a very long way away from causing the extinction of the megafauna.
Or are you going to argue that the short faced bear didn’t know to fear man? Ditto for the saber tooth and the poor innocent lamb loving dire wolf.
Very few small field finds are stretched far beyond their evidence to fault man as the cause.
Did mankind drive animals over a cliff when possible for enough food for a tribe over a very long winter? Quite likely.
Now explain how mankind drove the largest most dangerous creatures of the age miles and miles till they found a convenient cliff? Or did they dig pit traps for the mastodons? Perhaps they rode the backs of the dire wolf and saber tooth till they found a tall enough hill? Maybe they ran them up and down manmade mounds till the beasts died of exhaustion?
The blunt truth is that the concept for man caused the mega fauna extinctions is based on little real evidence and has major holes in the whole premise. Much like the climate crowd, when their concept is questioned they scream louder and point to research echoes, identical including the lack of proof.
“The major facilitator of that extinction was that the moas had no evolutionary experience of humans, didn’t fear them, and didn’t know to avoid encounters.”
Most prey animals learn very quickly to avoid predators and how and where to avoid them. Perhaps small island populations might be seriuosly depleted but the concept of lack of “evolutionary experience of humans” would seem to be very unlikely as a reason for poor adaptability to predators, at least to this hunter.
Steve G, notice the citation at the end of the quote: (2010) Journal of World Prehistory.
Meltzer and Holliday published their data and conclusions in a bona-fide science journal. You mischaracterized their venue as an op-ed, and your general criticism is fact-free.
A Google Scholar search turned up a 2012 book chapter criticizing the impact hypothesis, in which Meltzer is joined by 15 co-authors: “Arguments and Evidence Against a Younger Dryas Impact Event,” in Climates, Landscapes, and Civilizations (eds L. Giosan, D. Q. Fuller, K. Nicoll, R. K. Flad and P. D. Clift), American Geophysical Union, Washington, D. C.. doi: 10.1029/2012GM001209.
It may be he’s wrong, but his criticisms deserve to be heard without personal dismissals merely because he may be in a minority position and insists on arguing his case. After all, he may be right. The rational debate, in any case, is only to the betterment of science because it forces everyone’s investigation to be most thorough.
For myself, I don’t see any necessary contradiction between climate change following a Younger Dryas impact, but most mega-faunal extinctions due to other causes such as human competition.
ATheoK, early humans didn’t have to ride dire wolves. They only had to out-compete them for prey.
And yes, without direct evolutionary experience, dire wolves, mastodons, saber-tooths, and all the rest would not have had an avoidance response for humans. Predators might have seen humans as a new sort of prey. Humans do not take kindly to members of their family (or tribe) being attacked and eaten. When predated, humans generally respond by hunting down the predators.
The population of predators is generally fairly thin in any case. It wouldn’t take an overlong period of strong human competition, plus direct predation for fur and self-defense, to drive an animal predator population into extinction.
Jim G, when they inhabit the same geography predators and prey generally co-evolve.
They first evolve into that relationship, and they then evolve within that relationship. All of that occurs over tens of thousands of years.
The capacity to catch prey evolutionarily improves in response to an evolutionary improvement of prey to escape — a kind of co-evolutionary arms race. Predator and prey start naive and jointly move towards sophistication.
Your experience as a hunter is with animals that have a long evolutionary experience of humans. In North America, it’s now been at least 14,000 years of experience. Their avoidance of humans (you) has been bred into their genome by systematic culling (predation).
The introduction of rats into island populations exemplifies a sophisticated predator encountering naive prey. This has been well-investigated. Rats can walk up to ground-nesting birds and start chewing on a bird’s legs, while the bird evidences no alarm at all.
Pat Frank –
“Meltzer and Holliday published their data and conclusions in a bona-fide science journal. You mischaracterized their venue as an op-ed, and your general criticism is fact-free.”
NO, you misunderstood, so I must have misstated myself. What I MEANT to say was that the CONTENT of Holliday’s and Melzer’s work is the Op-Ed. Basically, they have published about half as many papers as the YD proponents. And their papers tend to have a lot of comment and editorializing and very little empirical science in them. Seriously, not much. I refer to them as “the Kibitzers” sometimes. Monday morning quarterbacks. Surovell’s oft-quoted 2009 paper is loaded with errors that their team made in failing to replicate the work of the YD proponents.
See my comment of 6:10 pm last night, in reply to ob at 1:14 pm. I pasted in Israde’s shredding of Surovell’s genuinely sloppy work.
As to calling certain journals nasty things, Surovell and Melzer and Holliday actually tried to make debate points by saying that the PNAS editors were giving the YD proponents an easy pass, and that the YD proponents were taking advantage of that. This in spite of the fact that the skeptics themselves have used PNAS for several of their own papers. The skeptics have gotten really immature at times, actually.
Sorry about all that bold at the end of that comment. I mis-typed the closing brackets after the word “editorializing.”
[Fixed. Remember to tip the mods. 8<) .mod]
Steve G. the link to Meltzer’s book chapter summary is here. Note the section headings: Introduction; Fundamental Flaws (in the impact hypothesis); Evidence-Based Arguments (concerning the YD); Conclusions.
They appear to deploy a large amount of empirical science throughout.
I’m not saying I agree with them. I’m saying they have an argument and they should be allowed to make it so long as they stick to scientific arguments.
From what I have seen of their papers — I’ve not made a close study — they seem to be contextually valid and to argue their point by reference to data.
As to the PNAS editors, given the easy pass they’ve given to pretty fatuous papers promoting AGW, I wouldn’t put other sorts of bias beyond them.
A blog post on the reliability of their data
http://quantpalaeo.wordpress.com/2014/08/30/yet-another-younger-dryas-impact-paper/
A paper on the general evidence for the hypothesis
http://onlinelibrary.wiley.com/doi/10.1002/jqs.2724/abstract
From the Supplemental materials in Israde’s 2010 paper “”, she shreds the Surovell inability to follow well-spelled out sampling and testing protocols laid out by Firestone 1007:
So, just like in junior high science lab, if you don’t follow the protocol, you results are meaningless. Surovell couldn’t follow protocol, but he and his group expect the world to weigh their evidence equally with the properly taken samples and the properly tested samples.
If the above is over your head (some of it is over mine, certainly), the more you learn about what it says, the more you realize that this evidence of Surovell’s is pretty bad.
Then, since then, they’ve done little besides snipe and run to their favorite science editors around the country and scream bloody murder.
Above, you say “small skeptics group”. That would include the AGU, which published a devastating analysis of this evidence-free, cockamamie conjecture. Had its proponents any evidence, there would be a basis for debate, but there isn’t. Its advocates just keep changing their scenarios and presenting over and over again the same thoroughly debunked junk science.
The drop in temperature was very fast. When the period was over the temperature rise was very fast too but not as fast as the drop to start the Younger Dryas. A drop this fast suggests something truly out of the ordinary happened.
This story seems to have more lives than a cat! As Anthony points out, it has been in earlier articles making the same claim–a cosmic impact caused the Younger Dryas. Five of these have appeared on WUWT (some with comments from me) at the dates listed below: You can read the articles in the WUWT archives by searching for ‘cosmic Younger Dryas.’
May 21, 2013 — (my comment) There are several compelling lines of evidence showing that the Younger Dryas (YD) was NOT caused by a cosmic impact or other single event. Aside from the fact that cosmic material in YD sediments doesn’t prove a cause-and-effect relationship (correlation isn’t proof of causation), the YD lasted for about 1,300 years, which is far too long for atmospheric dust not to have fallen to the ground. Even more compelling evidence is that the YD is not a simple, single climatic event–it was a series of repeated oscillations of climate each lasting several hundred years. In Scotland, Washington state, and various other places, glaciers advanced and retreated not only during the YD, but also during the preceding late Allerod cold period. The glaciers advanced and retreated as many as 8-12 times during Allerod/YD period and is thus not explainable by a single cosmic event. There were also a number of similar glacial oscillations during the preceding several thousand years. A cosmic event cannot explain the long duration (1,300 years) of the YD nor the multiple oscillations.
June 13, 2012 — (my comment) Before jumping on the comet bandwagon, a number of dots need to be connected and some critical questions need to be addressed. For example, how could a single event, even with multiple projectiles, cause an ice age that lasted for more than 1,000 years? Surely not from atmospheric dust and if not that, then what? The Younger Dryas is not the only climatic event during the post glacial maximum period—there are also a number of others spanning the time from 14,500 radiocarbon years (about 17,500 calendar years) to 10,000 14C years (about 11,500 calendar years). These are well known, well dated, and well documented in ice cores and in the global glacial record. So the question is, how could an impact event cause both multiple warming and cooling events over a 3,000 year period? Doesn’t seem logical at all for either impact or volcanic events.
Some other questions pertain to the evidence for the proposed cosmic event. Geologists are used to studying micro-images of rocks and looking at the two samples shown in the paper, it is obvious that both show definite flow structures that closely resemble glass flows from volcanic lava. The statement “Morphological and geochemical evidence of the melt-glass confirms that the material is not cosmic, volcanic, or of human-made origin. “The very high temperature melt-glass appears identical to that produced in known cosmic impact events such as Meteor Crater in Arizona, and the Australasian tektite field,” is very vague. What morphological and geochemical evidence? As for these specimens being identical to trinitite from atomic blasts, there is surely no flow structure in the photos shown so how can they be identical?
The bottom line here is—a lot more dots need to be connected and these critical questions (as well as a number of others) need to be addressed before concluding that the Younger Dryas was caused by a cosmic impact.
March 12, 2012 –(my comment) Before jumping on this bandwagon, consider the following:
1. There may well have been a meteorite impact near the beginning of the Younger Dryas (YD), but that doesn’t prove it was the CAUSE of the YDs. It’s the same logic as saying the cause of the 1978-1998 warming coincided with rise in CO2 so the cause must be CO2. Bad logic.
2. The YD is just the most prominent of many Dansgard-Oerscher abrupt climatic events.
3. The YD ended just as abruptly as it began a little over 1000 years later.
4. The YD corresponds with changes in 10Be and 14C production rates, suggesting changes in incoming radiation and pointing toward a Svensmark type cause.
5. The problem with single event causes (e.g., volcanic eruption) is that they cannot be sustained for the length of time of the climate change. If the idea is that the cooling was caused by ejection of dust into the atmosphere, that wouldn’t last for more than 1000 years.
6. If the YD was caused by dust in the atmosphere, it should show up in the Greenland ice cores (where even very small, annual accumulations of dust from summer ablation are well preserved). There is no such evidence of dust from an impact event throughout any of the well preserved YD ice core record.
7. The list goes on and on–too many to include them all here. Perhaps a longer response later. The bottom line is that a single event, meteorite impact event doesn’t prove the origin of the YD.
I also wrote two articles explaining the issues (posted on WUWT).
http://wattsupwiththat.com/2013/06/02/multiple-intense-abrupt-late-pleisitocene-warming-and-cooling-implications-for-understanding-the-cause-of-global-climate-change/
http://wattsupwiththat.com/2012/06/19/the-intriguing-problem-of-the-younger-dryaswhat-does-it-mean-and-what-caused-it/
The issues are clear cut and spelled out in these comments and articles. In a nutshell, the Younger Dryas includes so many very sudden, intense climate changes over a period of several thousand years that it couldn’t be related to a single cosmic event. Even if there was a cosmic event as the authors postulate, it certainly didn’t cause the Younger Dryas.
September 1, 2014 at 8:47 am
Three issues seem apparent here:
1. Is evidence of a cosmic impact about the time of the Younger Dryas (YD) conclusive?
2. What caused the extinction of mammoths, saber-toothed tigers, sloths, etc. in the late Pleistocene?
3. What caused the Younger Dryas.
Each of these is an independent question that may or may not bear on the other issues. If there was indeed a cosmic event near the YD, that doesn’t prove that it was the cause of the YD nor the cause of extinctions. Many of the discussions above mix these issues. In order for the impact hypothesis to be a credible cause of the YD, it must account for all of the distinctive features of the YD. (Remember Richard Feynman’s and Albert Einstein’s caution that it only takes one negative piece of evidence to kill a hypothesis). Well, take a look at the number and magnitude of well documented YD temperature changes and the duration of the YD (1000 years), which cannot be explained by any single or even multiple cosmic events (there are too many climatic fluctuations over too long a time). These effectively kill the cosmic event hypothesis as a cause of the YD.
A comment on the temperature fluctuations and the validity of the Greenland ice cores. Be aware that the abrupt warming and cooling of the late Pleistocene was not confined to the YD but began about two thousand years before the YD and well before the postulated cosmic impact event. These earlier temperature fluctuations were as large or larger than those of the YD. These large, abrupt temp fluctuations do not depend only on the ice core evidence. The ice core data is confirmed by well documented advances and retreats of glaciers on a global scale, the CET temp records, and a host of other temp proxies.
The bottom line remains that you cannot explain the multiple, intense temp fluctuations of the late Pleistocene (YD and older) by cosmic impact.
Right. We would first need a mechanism to connect the two.
Yep, fully with Don on this one. There were some outstanding comments on this topic 2 weeks ago:
http://wattsupwiththat.com/2014/08/29/younger-dryas-climate-event-solved-via-nanodiamonds-it-was-a-planetary-impact-event/ by “milodonharlani” in particular, and my own modest contribution was the idea that the YD represented the time it took to melt out a frozen-solid 5 mile thick arctic ice cap — like a Greenland on steroids. However, Anthony seems to favor the impact hypothesis and it’s his blog, so there you go.
Why couldn’t the impact induce a precipitous descent into cold, followed by a thousand years of oscillation between relatively warmer and colder climates? These followed by a final return to the pre-impact climate attractor.
One might expect to see rapid oscillations in a dynamically coupled system following a sudden energetic perturbation away from a quasi-equilibrium state.
There have been other meteor impacts documented, and yet those meteors didn’t bring about anything like YD. What’s so special about this particular meteor that triggered the YD cooling?
Maybe the impact, coupled with solar changes, coupled with some human caused extinctions?? It does not have to be all of one or the other.
That’s my guess. Only slight changes in regional isolation precipitated massive glacier growth/recession w/the help of Gulf-stream-current, albedo and ice-shelf changes amplifying the effects. Seems quite plausible a comet-strike causing a decades-long “nuclear winter” could change the above-mentioned conditions back to glacial for a thousand yrs.
Whether this caused mega fauna extinctions is another question — much harder to determine. But the evidence for a catastrophic comet strike seems pretty conclusive IMO. I really don’t understand why there is so much vitriol about the possibility of a comet-strike, given the ample evidence. Only thing that comes to mind is defending the “humans did it” meme?
“4. The YD corresponds with changes in 10Be and 14C production rates, suggesting changes in incoming radiation and pointing toward a Svensmark type cause”
http://youtu.be/zS7Adv3DFXg
http://www.squatterman.com/images/squatter-man-petroglyphs.jpg
Don “Each of these is an independent question that may or may not bear on the other issues. If there was indeed a cosmic event near the YD, that doesn’t prove that it was the cause of the YD nor the cause of extinctions. Many of the discussions above mix these issues.”
Yes, they do, but SO ARE YOU.
Right now, the involved researchers are focusing on ONE time period and on the “forensic” evidence – in order to even ascertain that, yes, an impact occurred – or no, it didn’t. The full suite of impact materials they’ve studied argue that, yes, it appears that one happened. They are LOOKING for that one piece of evidence to falsify it – as Einstein and Feynman argue should be done. IN specific areas where they have found something doesn’t FIT, they’ve abandoned that line of inquiry (e.g., the Carolina bays), as they SHOULD. But removing the Carolina bays hasn’t left the rest of it wanting for evidence.
The researchers are focusing on THAT time period and THAT evidence. So they are not working on the corollary parts of the bigger picture. THAT would be “mixing the issues.” Actually, the points you bring up ARE in themselves mixing the issues, because they are not in position to answer the 1,000 length of the YD until long after they have determined for certain that the impact even happened. First they have to determine if the microscopic evidence shows positive. And it certainly does – which you would know id you go reading the actual papers instead of Survell’s and Melzer’s and Holliday’s sniping op-ed papers. Se for yourself if there are holes in their evidence – as far as they have taken the evidence.
Just like the evidence for evolution had to have many, many naturalists go out and find butterfly samples and birds and shrew,, etc., in order to establish a foundation of BASIC evidence, these researchers are trying to lay the groundwork at the micro level, before moving on to the macro level.
Are they going to have some big conundrums when they GET to the macro lecvel? Yes, of course – on just those points you make. But if the micro evidence tells them that a big event happened which spewed impact materials over a 50 million square km area, are they to NOT try to see what it actually MEANS? Of course not. Are they going to stop looking because the conflagrations on 3 continents made it hard to find out which materials are terrestrial and which are not, and which are impact-related and which are not? Of course not. If an impact occurred, it would have a complex suite of evidence, in many disciplines. They have to go where the evidence leads them. There are some questions that can’t be answered with today’s level of evidence. So they have to go ADD to today’s evidence, so that the picture can become clearer. And if that evidence is THERE, and if it is microscopic, they sure as hell aren’t going to find it by starting at the (inappropriate) macro level.
“In order for the impact hypothesis to be a credible cause of the YD, it must account for all of the distinctive features of the YD. (Remember Richard Feynman’s and Albert Einstein’s caution that it only takes one negative piece of evidence to kill a hypothesis).”
Don, it doesn’t matter one whit whether YOU think the evidence is credible or not. YOU are not in there, in the labs and in the field with them. They are all competent scientists and they are doing the science that they have in front of them. What you think is credible – WHO CARES? Have you agreed with every scientist out there, on every topic ever studied? And lets’ look at the mammoth extinction for a moment. WIUth FOUR – count ’em, FOUR – current hypotheses out there, and only ONE of them can be correct, can YOU tell all of us which one is correct? Each one of them has competent scientists arguing that HIS hypothesis is correct. At least three of them must be wrong, but that doesn’t mean that they should stop their research, does it?
“Well, take a look at the number and magnitude of well documented YD temperature changes and the duration of the YD (1000 years), which cannot be explained by any single or even multiple cosmic events (there are too many climatic fluctuations over too long a time).”
THIS POINT I agree with you on, 100%. If there was an impact at one point, but not at the others, that poses a big problem, doesn’t it? OR there is something we all aren’t seeing right now.
If the late paleontologist Stephen J Gould had come out with his “Punctuated Equilibrium” in, say, 1785, everyone would have thought he was crazy. Science had to grow into the point where he could see that extinctions and species explosions are the reality, not the gradual mutational story of Darwin. If Gould had come out with it in 1885, he would have been laughed out of town, too. But in 1985, the science was well enough along to have his idea make SOME sense to some people.
Don’t forget that when Agassiz was finding evidence in the Jura Alps about ice ages, no one else was up with him. And when Darwin was hiking around near the coasts of S America and having ideas that didn’t include a Creator, there were a LOT of people who wouldn’t agree with him in a million years. In fact, he was so intimidated by them that it took him over 20 years – and Alfrred Russel Wallace – to publish “On the Origin of Sepeices”.
MUCH of the science of that year 1885 has gone by the boards, replaced with newer ideas, and – we hope – more correct ideas. In 2085 or 2114, will today’s science all still be around? OF COURSE NOT.
So, just because we can’t see an answer to those spikes in the Greenland ice core evidence doesn’t mean that THAT idea is the wrong one. (For example: Is there ANY chance at all that they are actually artifacts of the methodology of studying ice cores? We KNOW, from the animal and plant record that at the YDB, that THAT was a real climate change – but how about the others? Do we have that solid, or do the ice cores stand out as the only – or almost only – evidence that those are real?) Do YOU have an explanation for those spikes, within gradualist climatology, with its micro-forcings that have trouble raising the temperature by 1°C? Is there ANYTHING in that to explain rises and falls of 13°C? 14°C?
And if 14°C cooling at one point didn’t kill off the mammoths, why did the YDB?
So, so WHAT, if you don’t see that this has legs? Some people do.
Or do we have to toe a line of consensus on this, even before all the evidence is in?
Are folks like you going to go up and tell them, “STOP! You aren’t real scientists if you believe in this evidence” – are you?
beng
September 12, 2014 at 7:13 am
The evidence for a YD impact is so far from ample as to be nonexistent. There is not a single shred of incontrovertible evidence in favor of this hypothesis. All its proponents are left with is supposed hexagonal nanodiamonds (lonsdaleite), which have repeatedly been shown by independent investigators to be graphene, and the same material has been found at other sites going back at least to 40,000 years ago.
No less an expert that the father of impact theories, Walter Alvarez, thoroughly debunked this evidence-free conjecture.
http://www.usgs.gov/newsroom/article.asp?ID=3180&from=rss#.VBedRVcqlPk
Technical Announcement:
New Evidence Argues Against Prehistoric Extraterrestrial Impact Event
Younger Dryas “Impact Markers” are the Result of Natural Processes
Released: 4/23/2012 3:00:00 PM
Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communications and Publishing
12201 Sunrise Valley Dr, MS 119
Reston, VA 20192
It’s not just the USGS. Please read this AGU monograph on the YDIH in full. It’s more devastating than its bland abstract suggests:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CC8QFjAC&url=http%3A%2F%2Fwww.agu.org%2Fbooks%2Fgm%2Fv198%2F2012gm001209%2F2012gm001209.pdf&ei=7ZsXVOuyGeKrigL11YH4BA&usg=AFQjCNERJCPDRNT01nhPsMC2B8Sf36JVQg&sig2=cnF60Eoe5X-gRM8piLEI5g&bvm=bv.75097201,d.cGE
Climates, Landscapes, and Civilizations
Geophysical Monograph Series 198
© 2012. American Geophysical Union. All Rights Reserved.
10.1029/2012GM001209
Arguments and Evidence Against a Younger Dryas Impact Event
M. Boslough,1 K. Nicoll,2 V. Holliday,3 T. L. Daulton,4 D. Meltzer,5 N. Pinter,6 A. C. Scott,7 T. Surovell,8 P. Claeys,9 J. Gill,10 F. Paquay,11 J. Marlon,10 P. Bartlein,12 C. Whitlock,13 D. Grayson,14 and A. J. T. Jull15
1Sandia National Laboratories, Albuquerque, New Mexico, USA.
2Department of Geography, University of Utah, Salt Lake City,
Utah, USA.
3School of Anthropology and Department of Geosciences, University
of Arizona, Tucson, Arizona, USA.
4Department of Physics and Center for Materials Innovation,
Washington University, St. Louis, Missouri, USA.
5Department of Anthropology, Southern Methodist University,
Dallas, Texas, USA.
6Department of Geology, Southern Illinois University, Carbondale,
Illinois, USA.
7Department of Earth Sciences, Royal Holloway University of
London, Egham, UK.
8Department of Anthropology, University of Wyoming, Laramie,
Wyoming, USA.
9Earth System Science, Vrije Universiteit Brussel, Brussels,
Belgium.
10Department of Geography, University of Wisconsin-Madison,
Madison, Wisconsin, USA.
11Department of Geology and Geophysics, University of Hawai‘i
at Mānoa, Honolulu, Hawaii, USA.
12Department of Geography, University of Oregon, Eugene, Oregon,
USA.
13Department of Earth Sciences, Montana State University, Bozeman,
Montana, USA.
14Department of Anthropology, University of Washington, Seattle,
Washington, USA.
15AMS Radiocarbon Facility, University of Arizona, Tucson,
Arizona, USA.
We present arguments and evidence against the hypothesis that a large impact or airburst caused a significant abrupt climate change, extinction event, and termination of the Clovis culture at 12.9 ka. It should be noted that there is not one single Younger Dryas (YD) impact hypothesis but several that conflict with one another regarding many significant details. Fragmentation and explosion mechanisms proposed for some of the versions do not conserve energy or momentum, no physics-based model has been presented to support the various concepts, and existing physical models contradict them. In addition, the a priori odds of the impact of a >4 km comet in the prescribed configuration on the Laurentide Ice Sheet during the specified time period are infinitesimal, about one in 1015. There are three broad classes of counterarguments. First, evidence for an impact is lacking. No impact craters of the appropriate size and age are known, and no unambiguously
shocked material or other features diagnostic of impact have been found in
YD sediments. Second, the climatological, paleontological, and archeological
events that the YD impact proponents are attempting to explain are not unique, are arguably misinterpreted by the proponents, have large chronological uncertainties, are not necessarily coupled, and do not require an impact. Third, we believe that proponents have misinterpreted some of the evidence used to argue for an impact, and several independent researchers have been unable to reproduce reported results. This is compounded by the observation of contamination in a purported YD sample with modern carbon.
Oops.
Journal of Glaciology Volume 56, Number 199, December 2010
DOI: http://dx.doi.org/10.3189/002214310794457191
Discovery of a nanodiamond-rich layer in the Greenland ice sheet
Kurbatov, Andrei V.; Mayewski, Paul A.; Steffensen, Jorgen P.; West, Allen; Kennett, Douglas J.; Kennett, James P.; Bunch, Ted E.; Handley, Mike; Introne, Douglas S.; Que Hee, Shane S.; Mercer, Christopher; Sellers, Marilee; Shen, Feng; Sneed, Sharon B.; Weaver, James C.; Wittke, James H.; Stafford, Thomas W.; Donovan, John J.; Xie, Sujing; Razink, Joshua J.; Stich, Adrienne; Kinzie, Charles R.; Wolbach, Wendy S.
I won’t get drawn into this fight, but will point out that the Kurbatov 2010 paper was a preliminary finding to be followed by a full paper which however has never appeared. Critics have re-analyzed their “nanodiamonds” and found them to be (1) industrial soot from the 1700s, and (2) insect dander (trying not to trigger the moderation bot here). So who’s right? Beats me, but for me it’s clear that an impact event isn’t needed. The big extinctions were very obviously caused by human hunting, so who needs a meteor?
You missed Don’s point BP…. He was indicating that there would be 1300 years of dust in an ice core…. not just a single layer deposited over a couple of years…. Once the dust settled there would be an end to its cooling effect on the climate…… He wasn’t denying a dust layer, just that the dust was not in the atmosphere long enough to cause a 1300 year cooling.
If there was continued cooling then it must be from another mechanism…. and probably separate from the impact event….. I would posit that the impact probably put paid to the Clovis culture… but had little impact on the global climate of YD period.
Well, suppose NDs they’ve found are in fact soot or insect product or whatever. Still, it is a narrow peak, with concentrations some 5 million times above background, never occurring at any other depth in ice cores. Anything that abundant and only once demands explanation. And yes, there is much dust right above that thin layer. It is obviously not a direct consequence of an impact, just the usual high dust level of glacial times. So much so, that “dust age” is a more accurate term than “ice age”, because in cold epochs there was a hundred times more airborne dust while continental ice volume was only several times above its current level.
J.H. –
No, Berenyi didn’t miss Don’s point. Don didn’t MAKE the point you say he did. Don said, “If the YD was caused by dust in the atmosphere, it should show up in the Greenland ice cores”. As written, Don was wrong. There IS dust in Greenland – and right at the 12,800 year mark. Beréyni’s reply is correct and a direct rebuttal.
Don makes a point based on what we know now about dust in the atmosphere. But is what we know now actually correct? Probably, but not necessarily. If I had a dime for every time a scientist admits that, “Well, THAT was a surprise. Now we will have to rethink what we thought we knew about this phenomenon.” Scientists make such admissions several times a year, usually. (I point to Shoemaker-Levy 9 as a nice example…)
Don likes to quote Einstein. I will go with Arthur C. Clarke and #1 of his laws:
“When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.”
Berényi Péter –
This is a very perceptive comment. There IS all that un-consolidated loess deposited on top of that black layer in so many places, and yes, though loess is usually seen to be wind-blown, it COULD be seen as you say.
Do I myself have an answer for that 1300 years? No. But I am keeping an open mind about it. That loess so common on top of the black layer has not been paid enough attention to – especially when it was evidently laid down in EXACTLY the time period when so may point to the 1300 years and argue that dust doesn’t stay up for 1300 years. As I recall, the loess in at least some places is just about 1300 years deep. Is there a connection? Are we missing anything?
Based on so many comments here, hardly anyone here seems to have actually read the paper at all. Those spikes are VERY important. The spikes mean something, and the scientists involved are trying to ascertain what. And the answer keeps coming back: impact. Everything else at this time is secondary to that.
We could well be looking at a highly improbable concatenation of events. The improbability does not make it impossible. In fact, every impact event is precisely that unlikely all by itself. But consider the planet is also pulling out of glacial epoch, which happens once about every 100 ky during the Pleistocene. So now there are to rare, but profound, events on the table happening simultaneously in geological terms. If the YD was in fact a Daansgard-Oeschger event, they happen at irregular intervals but are usually seperated by millennia, that piles a third unlikely event on. The YD may have been a rather tight knot hole that terrestrial life dragged itself through. Also, as I mentioned in an early note, the actual environments around the periphery of the great ice sheets have no modern ecological analogs and that definitely includes both tundra and taiga. They ceased to exist with the ice sheets. So did the faunal associations.
Perhaps some might be interested in this talk scheduled for the October Geological Society of America conference in Vancouver: https://gsa.confex.com/gsa/2014AM/webprogram/Paper241481.html
I posted this a while back in a similar thread:
http://cometstorm.wordpress.com/2011/04/27/a-different-kind-of-climate-catastrophe-2/
This guy did a good job of laying out the comet impact theory. Though I still having trouble with his theory on how the Carolina bays formed.
Anyway.. it is a good read if you can spare the time.
I’ve read that link before, but it’s still rather astonishing and sobering. Recommend that link to anyone who is interested in this question:
http://cometstorm.wordpress.com/2011/04/27/a-different-kind-of-climate-catastrophe-2/
My explanation is first of all the state of the climate at that time was near boarder line threshold values of glacial versus non glacial conditions. This would then lend itself to given changes in items that exert influence on the climate to have a much greater influence. I think the ice dynamic plays a big part in all of this.
That said I think much smaller changes were needed in given items that control the climate to set a cascade of things in motion which could then shift the climate from one regime to another. Today it can still happen but the changes will probably have to be more substancial and last longer in duration.
My candidates are solar variability and associated primary and secondary effects, changes in the earth’s magnetic field which can either enhance or moderate solar variability , the initial state of the climate( which I just explained), and Milankovitch Cycles . However in regards to Milankovitch Cycles they were less favorable for glaciation then today’s parameters which include the tilt of the earth’s axis(less today then 12000 years ago ), eccentricity of the earth’s orbit(more eccentricity)more favorable if N.H. aphelion back then occurred in summer instead of winter(not favorable), and precession of the equinoxes(aphelion today now in N.H. summer) all favorable for cooling.
This leads me to conclude it is the initial state of the climate (the ice dynamic) moderated by solar variability (primary and secondary effects) further moderated by the weak earth magnetic field at that time. Gothenburg reversal or at least excursion taking place 11500 years ago. This then could bring the climate to threshold values both for rapid warming and rapid cooling.
It had nothing to do with co2 concentrations which are a by-product of the climate not a cause.
It had absolutely nothing to do with some cosmic impact due to the simple but compelling fact that the YD event was by no means unique . Similar events took place many times before. Also the climate within the YD was also very variable.
Impacts can have huge and immediate, to an unlimited degree, effects on a planet. Magnetic fields changes, etc., not so much.
The other apparent temperature changes in the millennia preceding the proposed YD event do indeed suggest a non-impact explanation, since the YD event is of similar, if larger, magnitude. Otherwise, you need multiple impacts, which obviously would be unlikely.
However the mere existence of a 50M sq. km. soot layer demands explanation, irregardless of all else.
Do the circumstances that created a 50M sq. km. soot layer have anything to do with the extinctions and temperature change? Doesn’t seem an unreasonable possibility.
I agree with all that you say here. I have myself considered the possibility of all of those down-spikes as being impactors, and, of course, that seems a VERY unlikely scenario – but a reasonable one to at least consider before tossing it out. (Sometimes the crazy sounding idea is the one that turns out to be true. Witness the Scablands of Harlan Bretz and the tectonic plates of Wegener. The YD seems to be the only one of them with the “soot layer”, as you call it. (The very lowest part of that soot layer is where the impact markers are being found – so don’t forget to include the impact markers in your thinking, too.) That unique soot layer kind of rules that multiple impacts idea out.
However, FYI someone here commented that some NEW Greenland ice cores now exist, and that those show that the spikes in the GISP2 ice cores evidence some extremes that maybe are not so extreme. That seems to me to be an important development.
In addition, researchers are beginning to become aware that impacts do occur quite a bit more frequently than was thought not so very long ago. The thinking about the frequency of big impacts has come down from tens of millions of years to about 5,000 to 10,000 year intervals. There is nothing precise about the numbers, but the more evidence we’ve acquired over the decades, the clearer it has become that big impact intervals are considerably less than once thought. One of the big events, later even than the YD onset, is one called the “8.2 kya event”. It even has it’s own Wiki page. Was it an impact? Some say yes. Some say no. But they’ve barely scratched the surface as far as evidence goes, so who knows?
For those interested in this topic, here is a detailed paper not behind a paywall:
http://www.pnas.org/content/104/41/16016.long
I am not endorsing Firestone et al, but you can learn a lot from the paper.
Real men burn down a forest to make a breakfast fire and wipe out an endangered species for lunch. Clovis man qualifies. –AGF
Can I quote you at the website “The Art of Manliness?” To quote the commercial “Priceless.”
Give credit to the author: Bruce Feirstein (“Real Men Don’t Eat Quiche”).
http://www.clim-past.net/8/1473/2012/cp-8-1473-2012.pdf
I suppose all these climatic events according to them were the result of cosmic impacts to.
Who knows?
FYI, the suspected duration between big impacts isn’t what it used to be. In his 1999 book “Impact!: The Threat of Comets and Asteroids”, astronomer Gerrit Verschuur has this to say about that:
Today’s figures are not the final ones in this. The more we learn, the more we think the intervals are smaller, rather than larger. As of 15 years ago the number was 5,000 to 10,000 between whacks. If that shortens by another 50-75% what are we talking about? And would that tell us anything about those spikes in the ice cores? ANY connection at all? Not even possible?
We’ve lived in a very tame portion of human history. We don’t have an ice age, for one. For another, there are lots of tales from early human societies that speak of things that sound an awfully lot like impacts. Is our Comfy Chair mentality any kind of protection?
I am not saying let’s take the several trillion dollars from global warming in the next 85 years and turn it over to space lasers and such? NO. But looking into the matter may not be a stupid thing to do. And part of that is to look in the past to determine what risk we are under. And that is certainly the cheap part.
I’d say ‘yes’ to taking the several trillion dollars from global warming in the next 85 years, and turning it over to space lasers and such.
With that sort of investment, by 2100 we’d have an industrial ring in near space, another on the moon, and hotels going up on Mars.
We’d capture any comet or asteroid that approached Earth and turn it into raw materials. Productive industry: the ultimate protection against terrestrial bolide impact.
Let’s see. The Earth just came out of a 80K year cold period with temperatures a lot colder but somehow the megafauna had been able to survive.
http://c3headlines.typepad.com/.a/6a010536b58035970c0134849d3fd9970c-pi
Around 12,800 years ago, a sudden, catastrophic event plunged much of the Earth into a period of cold climatic conditions and drought again and the megafauna used to 80K years of cold did not survive.
They could well have been choking on clouds of nanodiamonds….
Ironically, you have hit on something pretty close to one of the now discarded parts of the YD hypothesis – that there were a LOT of small iron balls embedded in mammoth tusks. It is one of the first things that drew Firestone’s attention to this event/period. But eventually they had to drop that aspect, while pursuing other, less sexy, lines of evidence.
Robertvd – Yes, you understand EXACTLY what biologists have been wondering about for a LONG time, enough to give the period beginning right then a name – the Younger Dryas. The biologists still after several decades are scratching their heads – nothing in gradualism so far has been able to explain it. But WOE unto those who conjure up ideas of catastrophes!…LOL
Obviously, since those other 13-14°C ups and downs didn’t kill off the mammoths and giant sloths, etc. – plus the Clovis points stopped appearing in the fossil record, there was something unique about the YD onset.
Amazingly, this microscopic evidence keeps on pointing at 12,800 years ago, too.
So, the REAL question is how to connect the dots. That is what the YD scientists are trying to do. There are a lot of folks here hip-shooting and second-guessing the scientists – and mostly without ever having even read the paper.
Slow change is adapted to. Fast change is not. What matters is not the magnitude of the event, but the magnitude of its first differential.
If you dont have time to walk to a better feeding ground, you are dead.
A slowly rising sea level is far less of an issue than a tsunami.
These deposits are always buried.
Buried under what ?
Where does the top-cover come from ?
I’m sure there is a simple explanation, such as: wind drift, erosion, plants decaying, etc.
But, why does everything become buried, all else being equal ?
They don’t in general, but it is only where they do that we can find them today. Same with cave men who did not live in caves, but we can only find their traces in caves because their wooden and thatched dwellings are gone gone gone…
I hear you, but most the dreaded fossil fuels are pretty deep too.
uk(us) September 11, 2014 at 4:08 pm
The ‘fossil fuels’ are deep because their initial biological components are buried by orogenic processes. Due to heat and pressure, gases and liquids tend to rise after formation unless/until they encounter an impermeable layer that stops the upwards migration. The Alberta oil sands are a good example of oil that has migrated all the way to the surface.
The earth is still accreting material from space.
Vogons flush their bilges as they fly over.
You might think they’d be more eco-friendly, then again, why not fertilize the beasts.
uk(us), Stuff gets buried to a large extent from plants catalyzing a slow “rain” of converted carbon dioxide into dead plant material. I suppose dust also gets accumulated. That also assumes the location is not dominated by sedimentation. I think it is a very interesting area to study, and I’m sure lots of folks have, but not me.
Indeed. my back garden featured about 50 years of scrub – thorn and tree – and very little grew under it. When I cleared that there as a couple of inches of highly fertile topsoil composed of mainly leaf litter, overlying the glacial moraine clay, which is what lies underneath, and under that is chalk.
So many processes deposit solids on top of stuff – erosion of mountains and hills, and organic sediments.
I have actually seen derelict houses less than 100 years old in the process of being overlaid with plant growth and soil.
I’d say an inch every 20 years is probably about the way it goes. Round here. YMMV.
Fist there is the YDB layer.
That is immediately – as in part of and touching – the black layer. That has several names, such as “The Black Mat” and the “Bradley soils” in the USA. THAT layer is varying thicknesses. In Belgium/Holland it is about 10 cm thick.
What some here may not realize is that the black layer is acknowledged by all to be from some major, MAJOR conflagration, and it is made up pretty much entirely of burned plants. Over an area stretching from Syria to Belgium, to Holland, to Alberta, to Arizona, to Michigan, and to South Carolina, and then into the northern reaches of the Andes. And there is a layer in the glaciers of Greenland, too.
So, whatever happened, it was bigger than your back yard barbecue.
Above the black layer, it varies, depending on the location. In Belgium and Holland it is sand – mostly un-stratified, but not always. It is also sand below – also un-stratified – and called the “Usselo horizon”. In Nebraska the Bradley soils have mostly loess above – which is also un-stratified.
In case you aren’t aware, at at least one of the YD sites, there was found a mammoth skeleton with the YD layer AND the black lying right ON the bone, and staining it. So in at least one location the last mammoth known and the YD were right at the same time.
Of course the temperatures over the glaciers during the Younger Dryas had to be warm enough to melt them rapidly and generate the copious flows of meltwater that blanketed the North Atlantic, meltwater that was depleted in O18 from the freezing process and then further depleted by evaporation before being deposited as snow on Greenland. I think the purported cooling during the YD probably never happened.
pochas – Not right. First of all, the YD was a real period, noted first of all by the biologists, who noticed that the plants had all changed, and around the world it all happened at the same time.
Also, the YD was not warmer, as you are thinking. The melting of the last glacial period before the YD cold was the Wisconsinan glacial period, and between the two were two warm periods (the Bolling and the Allerod) separated by the Older Dryas, a short cool period.
Yes, these things really happened. The biologists have never been able to explain the sudden cold. And they’ve been on this for several decades, scratching their heads. The impact hypothesizers didn’t make it up.
http://en.wikipedia.org/wiki/Timeline_of_environmental_history#Pre-Holocene_.281.5_Mya.29
Those scientist who support the cosmic impact theory for the cause of the YD need to address all these climate variations in in the context of their cosmic impact theory for the cause of the YD to be taken seriously.
.
Of course they do. They are not idiots. They made a conscious choice about where to start. They chose to make sure they had the microscopic stuff well in hand before they try to tackle the macro issues.
It is called “doing due diligence”, and it is a BIG part of good science. They are, in fact, trying to falsify the hypothesis. Don’t blame them if the evidence keeps telling them that there was an impact, and that there was a BIG planetary reaction to it.
“the only plausible hypothesis”
Argumentum ad Ignorantiam.
Ah, and you haven’t hard the certainty on the OTHER side, about “Requiems” and such.
At least one side – the authors of this paper – is actually doing SCIENCE, collecting empirical samples and lab testing them with every test known to man.
If YOU had 7 years of lab results coming back positive, what would YOU be saying?
For a rebuttal of this theory having to do with the radiocarbon dating of the supposed YD impact layer–a fundamental problem for the hypothesis and a lot more date certain than the KT iridium layer dating from the Chixilub impact that helped wipe out dinosaurs and eventually resulted in this blog and all of its commentators–see Meltzer from SMU, published in PNAS. Easy multiple Google finds using comet Meltzer Younger Dryas.
Nano diamonds are also produced in candle flames. Just the way nano stuff works, when surface properties dominate over bulk properties. Think lightning sparked forest fires spread out in time. No comet needed.
Yes, forest fires making a ONE time layer 4″ think and more on 4 continents – all at the same time.
And did you even bother reading the paper?
If you should be made aware that there are at least four kinds of nano-diamonds. Which ones are YOU talking about? If you don’t know, you are hardly in a position to cast aspersions. As to the quality of work done by Melzer and Surovell and Holliday, see my comment above at 6:10 pm in response to Ob at 1:14 pm. If you can’t understand it, it points out how they didn’t even understand how to follow proper protocols.
The new high resolution NEEM ice core has temperatures in Greenland increasing by 16C in just 240 years from 15,737 bp to 15,494 bp.
And then temperatures fell again by 12C in the next 300 years.
There were significant swings in the climate well before the Younger Dryas. It was tough going for any non-technological non-adaptive animal in those times.
Yes, and the YD people will address that in time. Right now they are doing due diligence, making sure the evidence is correct at the microscopic level, the most fundamental level. As they should. If that is not done, they aren’t scientists, but hip shooters.
Cosmic impact and the resulting cold/freezing conditions: After each meteor impact,
the global temps go steeply down, rebounce at the same velocity to higher than at
impact date and stabilize again at the previous level ….this is a multicentennial
event. The temp evolution forms a GISP2 Z-syimbol or high voltage-symbol. This is
evidenced EMPIRICALLY for all (more than 10) Holocene meteor impacts over the:
entire Holocene…..
Literature: http://www.knowledgeminer.eu/climate_papers.html
The argument:””ME know nothing” — therefore “for ME not true” is constantly repeated by
the worst ignorant types…..JS…
“In a nutshell, the Younger Dryas includes so many very sudden, intense climate changes over a period of several thousand years that it couldn’t be related to a single cosmic event. ”
that’s funny.
now one could argue multiple causes.
but the presence of rapid change cant PRECLUDE a cosmic event.
keep up the fight against plate tectonics.
somebodies gotta do it.
Steven –
Very humorous.
But correct.
The climate folks have a really hard time with causes for such huge swings. Even with global warming, there doesn’t seem to be any capacity for the internal system to account for such huge swings – only perhaps a degree or two. (Never mind the models.).
If this one pans out, what does that imply for some of the others – ones for which there is no black layer? They are in the ice cores, those spikes. If this spike means an impactor, there is a LOT that will have to be re-thought out.
“…Fight against plate tectonics.”?
I must’ve missed that comment; though the hypothesis for plate tectonics has as little proof as the other hypotheses for ice ages.
Lots of freeze/thaw hypotheses, little proof; but the evidence of impacts is interesting. There is enough evidence to a very dramatic event, but it does lack evidence for all of the Younger Dryas fluctuations.
One thing is certain, those climate models are not proof; even when coupled to plate tectonics models.
This press release makes the same errors as UCSB’s. Mastodons did not go extinct at the YD, for starters.
So it wasn’t the mastodonian SUV?
Like others I’ve kept an eye on this idea but it keeps hitting the same evidence wall. Time. An impact event is quite a reasonable explanation for the entry into the YD era but not for its continuation or exit.
Meteoric ash, like volcanic ash doesn’t hang around in the atmosphere for 1,000 years and then suddenly vanish.
JohnB – Your points are well made. Yes, those conundrums exist. The researchers on this are primarily working on the microscopic evidence so far, doing due diligence, getting their feet on the ground with the impact materials. That is the first step, as they see it. The rest they will have to deal with later.
Right now it is certain that there are impact markers that are almost always accepted as such. But this time there is a group arguing that the markers are not impact related, even though there is a suite of them, all pointing at an impact. The point they make about the extent of the effects is important – 50 million sq km with conflagrations on 4 continents – obviously something out of the ordinary happened and it was big. And all the dates come back right around 12,800 years ago. The skeptical group is quibbling about the dates being off on some. Their other quibbles have been rebutted, over and over, and those will be, too. See my comment at 6:10 pm above, in response to ob (1:14 pm).
A recent study at Oregon State may indicate that the Younger Dryas temperature variations did not occur, or at least were much less intense. The study used N2 diffusion from gas bubbles in three new Greenland ice cores to determine temperature and obtained a much more steady increase through this time period. The authors suggest that the older temperature variations, obtained using 18O/16O, were artificially produced by changes in the moisture source of snow fall on GL over this time. To a large degree, this O isotopic ratio reflects the temperature of the water source, and any ice temperature profile must be calibrated to a known entity.
I am going to agree with you, Don, and I am GLAD that the new ice cores are coming into play.
I have never been satisfied that the GISP2 and GRIP ice cores are telling the story quite right. I DO think that it is logical that the swings were less than the O18 proxies show in the previous ice cores. And my thinking has been that the high temps and low temps were artifacts of something in the processing of the ice cores and data.
It is kind of funny. Someone above argued that there were “only” 6 carbon-14 dates from Lake Cuitzeo – but there were only TWO ice cores, and basically only one sample from each ice core, at that particular 12,800 ya level. With a resolution of 200 years, do ice cores weigh more heavily than carbon-14?