Younger Dryas climate event solved via nanodiamonds – it was a planetary impact event

From the University of California at Santa Barbara -By Julie Cohen |

Most of North America’s megafauna — mastodons, short-faced bears, giant ground sloths, saber-toothed cats and American camels and horses — disappeared close to 13,000 years ago at the end of the Pleistocene period. The cause of this massive extinction has long been debated by scientists who, until recently, could only speculate as to why.


This graphic is used to illustrate the Younger Dryas event – it is not part of the paper discussed below – Anthony

A group of scientists, including UC Santa Barbara’s James Kennett, professor emeritus in the Department of Earth Science, posited that a comet collision with Earth played a major role in the extinction. Their hypothesis suggests that a cosmic-impact event precipitated the Younger Dryas period of global cooling close to 12,800 years ago. This cosmic impact caused abrupt environmental stress and degradation that contributed to the extinction of most large animal species then inhabiting the Americas. According to Kennett, the catastrophic impact and the subsequent climate change also led to the disappearance of the prehistoric Clovis culture, known for its big game hunting, and to human population decline.

In a new study published this week in the Journal of Geology, Kennett and an international group of scientists have focused on the character and distribution of nanodiamonds, one type of material produced during such an extraterrestrial collision. The researchers found an abundance of these tiny diamonds distributed over 50 million square kilometers across the Northern Hemisphere at the Younger Dryas boundary (YDB). This thin, carbon-rich layer is often visible as a thin black line a few meters below the surface.


Kennett and investigators from 21 universities in six countries investigated nanodiamonds at 32 sites in 11 countries across North America, Europe and the Middle East. Two of the sites are just across the Santa Barbara Channel from UCSB: one at Arlington Canyon on Santa Rosa Island, the other at Daisy Cave on San Miguel Island.

“We conclusively have identified a thin layer over three continents, particularly in North America and Western Europe, that contain a rich assemblage of nanodiamonds, the production of which can be explained only by cosmic impact,” Kennett said. “We have also found YDB glassy and metallic materials formed at temperatures in excess of 2200 degrees Celsius, which could not have resulted from wildfires, volcanism or meteoritic flux, but only from cosmic impact.”


The solid line defines the current known limits of the Younger Dryas Boundary field of cosmic-impact proxies, spanning 50 million square kilometers.

The team found that the YDB layer also contained larger than normal amounts of cosmic impact spherules, high-temperature melt-glass, grapelike soot clusters, charcoal, carbon spherules, osmium, platinum and other materials. But in this paper the researchers focused their multi-analytical approach exclusively on nanodiamonds, which were found in several forms, including cubic (the form of diamonds used in jewelry) and hexagonal crystals.

“Different types of diamonds are found in the YDB assemblages because they are produced as a result of large variations in temperature, pressure and oxygen levels associated with the chaos of an impact,” Kennett explained. “These are exotic conditions that came together to produce the diamonds from terrestrial carbon; the diamonds did not arrive with the incoming meteorite or comet.”

Based on multiple analytical procedures, the researchers determined that the majority of the materials in the YDB samples are nanodiamonds and not some other kinds of minerals. The analysis showed that the nanodiamonds consistently occur in the YDB layer over broad areas.

“There is no known limit to the YDB strewnfield which currently covers more than 10 percent of the planet, indicating that the YDB event was a major cosmic impact,” Kennett said. “The nanodiamond datum recognized in this study gives scientists a snapshot of a moment in time called an isochron.”

To date, scientists know of only two layers in which more than one identification of nanodiamonds has been found: the YDB 12,800 years ago and the well-known Cretaceous-Tertiary boundary 65 million years ago, which is marked by the mass extinction of the dinosaurs, ammonites and many other groups.

“The evidence we present settles the debate about the existence of abundant YDB nanodiamonds,” Kennett said. “Our hypothesis challenges some existing paradigms within several disciplines, including impact dynamics, archaeology, paleontology and paleoceanography/paleoclimatology, all affected by this relatively recent cosmic impact.”

– See more at:

h/t to David Hagen.


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Interesting science. Love the new presentation of WUWT!


There’s always going to be arguments about. Hopefully research & time will provide a reasonably solid answer.
The prospect of a devastating hemispheric blast so recent is a bit chilling.

beng –
You haven’t heard it all yet. Google “8.2 kya event”. That is 4,600 years even MORE recent. And then if you dare, start googling different ancient people’s accounts of serious stuff going on in the sky and raining down stuff – not only in the time of man, but also in the time when the accounts are still around. Those accounts aren’t useful battling against entrenched scientific thinking, but they all seem to say that their people saw something happen.
So you’ve got reason to be chilled by the idea. That’s why some people are working hard to get NASA to do some space defending – at least begin to prepare.


“You haven’t heard it all yet. Google “8.2 kya event””
That’s BTW exactly the time Plato gave for the sinking of Atlantis.


From wikipedia:
“The 8.2 kiloyear cooling event may have been caused by a large meltwater pulse from the final collapse of the Laurentide ice sheet of northeastern North America—most likely when the glacial lakes Ojibway and Agassiz suddenly drained into the North Atlantic Ocean.[10][11][12] The same type of action produced the Missoula floods that created the Channeled scablands of the Columbia River basin. The meltwater pulse may have affected the North Atlantic thermohaline circulation, reducing northward heat transport in the Atlantic and causing significant circum-North Atlantic cooling.”

YD was caused by a large comet impact. Please see
Nearly 200 years ago, geologists at The Royal Society ‘proved’ that the lands presently occupied were not inundated by a global flood. True. But that conclusion assumed that the Earth has has its present amount of water since its beginning. That is demonstrably false; presently occupied landscapes were not flooded in this event.
I will present material similar to that found at the link, above, at the upcoming Geological Society of America conference in Vancouver. (The link is to slides from a recent Esri user conference.)
In the words of Plato, this massive comet caused an “extraordinary inundation” – a nearly incomprehensible amount of water….

Richard G

Interesting read from that link Michael Jaye.


From what I saw in a documentary about the YD extinctions, they believe it was a comet air burst, thus no crater, sort of a mega-Tunguska Event.

Steve Keohane

Thanks for the interesting link


Submerged canyons on the continental shelf were carved by now submerged rivers flowing on land when sea level was 400 feet lower during glaciations. Those deeper than that are caused by outwash floods, plus submarine earthquakes. among other terrestrial sources. No need to posit a giant comet impact.

Richard G

While I was skeptical of a 2500 km comet containing 25% ice impacting in such a recent geological period, I found the underwater geological formations interesting. I was aware of the features down to 400 ft. depth from the last glacial sea level, but not the features below that.
I find it interesting that they all seem to terminate near the same depth below sea level. We really don’t know anywhere near as much below the ocean surface as we do for what’s above it. I find it hard to understand how flood outflows could affect the topography to such a depth and then suddenly terminate sharply near the same depth throughout the globe.
Is it because we don’t have detailed imagery below that depth, so we don’t see the details further down?Could it be that sea levels were once at that level? You would think that flood outflows throughout the earth wouldn’t so uniform in volume to terminate at uniform depths.
While I haven’t read much of the literature on this, I’m aware of plate tectonics, undersea currents, flood outflows and landslides being proposed as having shaped the landscape of the seafloor. I’m sure someone well read in undersea geology could provide some knowledge or data.

Gentle Tramp

These are interesting new ideas. BUT: Whereto has all the water gone which must have been on earth during e.g. the jurassic era when great areas of the continents were submerged under sea water???


If I am correct, the deepest canyon from a river draining into the ocean is the Congo. You can clearly see its canyon on Google Earth. You might add it to your list. While your thesis is interesting, it seems like a giant comet producing the volume of water you claim, would create such a huge difference in our understanding of the planet, that someone would have come up with the idea a long time ago. And I think that would have been an extinction event of nearly everything on the planet, far greater than any of the other impact extinction events.
I could see a small comet adding to the present volume of water and a combination of ice melt and comet water raising sea levels a few hundred feet, but to have the earth as dry as you indicate in one of your pictures seems very extreme. Especially since you think it was that dry a mere 6kya.

James the Elder

Judging by the map, somewhere in or around NA there should be an impact site. I does fit nicely with the findings on the East Coast of a sterile sand layer from around that time period indicating a disaster that forced the Clovis survivors westward. There is an impact crater in the Hampton Roads/Norfolk area of VA, but it’s not a candidate, missing by some 35 million years.

M Courtney

This has appealed to me for years.
But I know it has been controversial for years too.
In The Younger Dryas impact hypothesis: A requiem previous such hypotheses were found wanting.
I quote,

In summary, none of the original YD impact signatures have been subsequently corroborated by independent tests. Of the 12 original lines of evidence, seven have so far proven to be non-reproducible. The remaining signatures instead seem to represent either (1) non-catastrophic mechanisms, and/or (2) terrestrial rather than extraterrestrial or impact-related sources. In all of these cases, sparse but ubiquitous materials seem to have been misreported and misinterpreted as singular peaks at the onset of the YD.

Maybe this time it’s different.


The research publication goes to great lengths addressing this and other criticisms. James Kennett is an accomplished, careful, and thorough research scientist.

I agree. If you read all of the YD impact team’s papers, the “forensics” of it all will overwhelm you. He does his homework, and so do the others.
On the other hand, the field work is either sloppy in taking samples from the correct layer, or they take too wide of a sample, which waters down the sample in the lab – which then flattens out the spikes in the data. For several of their papers, the skeptics actually didn’t even DO any field work of their own – making those papers little more than opinion pieces. (I am not making this up.)


It always was different. There was a (2012??) reanalysis of the work which found that the investigators with the negative findings had apparently not found what they did not want to find – confirmation bias. Reanalysis showed the very samples that were found negative for impact markers were loaded with them. The reanalysis work had a very critical discussion of the methods employed.

Confirmation bias is exactly what it seems to me, too.
James Wittke was the one with the rebuttal paper, and it basically shredded all the supposed falsifying evidence. But the skeptics were too dense to recognize that they had been body slammed.
The thing is now even some people that thought this was a possible real thing now think that the skeptics have been successful in tearing the idea down. But basically all the YD team can do is keep testing other evidence. The world seems to simply not get it.
They have probably more evidence for this YD event than Luis Alvarez and his supporters had for the dinosaur killer of 65 million years ago. Sites on 4 continents, more than half dozen materials normally associated with impacts (but, oh no, not in this case…). All that is needed is a crater.
But Peter Schultz working at NASA Ames convincingly showed that a hyper velocity impact onto an ice sheet will likely NOT leave a crater underneath. The crater WAS in the ice itself – which got shattered, melted, vaporized, and blown away. And with it went the crater.
Be aware that the ice sheet was deeper than Barringer Crater. In fact, it was about as deep as Barringer Crater is in diameter. With the ice attenuating the impact, any crater under that spot will likely be FAR differenrt from what is currently allowed as “good craters”.

Wouldn’t that make it “infirmation bias” instead ? 😉

Actually, one of Kennett’s cohorts rebutted that supposed requiem quite thoroughly. I was just re-reading some of that this week. The samples taken were done as if by amateurs – because they sampled the wrong layers. They also did not have an impact specialist on their skeptical team, though they did have a good nanodiamond guy (Tyrne Daulton – who may be heard from again in the near future.
But as Ted Bunch communicated to a friend,

“…not to worry, Dalton is a competent scientist and did what he could do with the materials given to him. The problem lies with [Andrew] Scott and Pinter.”

That was back in 2010, about the “Requiem” paper.
You also have to understand that Andrew Scott is a forest fire guy. That is what he studies. But IMHO he also wants forest fires to be important – in much the same way, that Michael Mann and Phil Jones want climatology to be important. If someone comes up with a scenario that aces forest fires, especially if it is a catastrophic hypothesis, that would mean he has to fit his forest fires in as second fiddle.
I just looked them up the other day, and none of their “requiem” team was an archaeologist, with experience taking careful samples from the side of a pit.
In addition, that black layer with the nanodiamonds – spread over 50 million square kms makes it kind of more than just your evreyday, garden variety brush fire.

Well, I’m happy to read it was not CO2!

Alberta Slim

Andres .. Please give the spin doctors a little more time ;^D


A dry ice comet?


Oh, that could be sublime!

“Well, I’m happy to read it was not CO2!”
Of course not… it’s CO2 that was responsible for the near-vertical temperature readjustment (7) though, as well as (1)… what else could explain it?
or… the proxies of 1/2, 5/6/7 are messed up for some reason. Without those anomalies it looks like a relatively smooth rise.

M Courtney

One of the past theories was that the impact was from a radioactive comet.
This led to the disproportionate killing off of large animals (radioactivity built up in the fat cells).
Also, it was hypothesised that it led to the Carbon dating being messed up causing the recovery to appear like it happened overnight.
I can’t find the paper… I think it was by Firestone.
I remain sceptical but I do like the way “it is consistent” with the evidence

M Courtney

It may have been this that I just found linked on Wikipedia.


Firestone is the originator of the YD impact hypothesis. I heard him give the original presentation at the Clovis in the Southeast conference in 2005. The conference was hosted by an archaeologist, Al Goodyear – which made for some tiresome confusion ;-). The YD marked by an apparent radio-carbon anomaly that correlates with other environmental signatures that mark the YD. However, even if the anomaly is real, it doesn’t seriously change just how abrupt the onset and progression of the YD was.
The radioactive comet idea really is humbug though. Radiocarbon is caused by cosmic rays and not even a comet that glowed in the dark would be that radioactive to begin with. It could not under any circumstances be radioactive enough to generate a global anomaly. Besides, objects coming in from the Oort Cloud or the Kuiper Belt have been in deep space for very long periods, possibly since before the solar system formed. That means that only very long-lived radioisotopes would have survived, and the longer-lived the isotope, the less radioactive it is. No amount of biological amplification is likely to significantly increase the radiation hazard from such isotopes to the point that large mammals would be seriously affected.


Even if the comet was pure plutonium, after impact the remains would be scattered over half of the globe. The total radiation at any location would be too low to kill anything.
Regardless, as the KT impact showed, these things are most stressful on the largest animals anyway, even without postulating a radiation affect.

Jeff Alberts

Firestone and Goodyear? Really? ROTFL.


Or, could it be related to the thunderbolts project?

Steve Keohane

Very interesting. Didn’t Velocovsky covern an ancient SW American Indian myth of something in the sky to the northeast prior to devastation?

Thanks for that. I will have to try to see about that. I read it like 40 years ago…

Where was the impact? Shouldn’t that crater be evident?

M Courtney

Thought to be over the N American Ice sheet.
It melted.



That makes the stratigraphic reconstructions really difficult. That’s probably why they’re having such a hard time tying all the evidence together for the event, much less the location. Identifying the plume would be difficult as advancing/receding ices containing ejecta move around and then deposit after melt and runoff. I don’t envy them that task.

tteclod –
No, it is not “convenient.” With expanded glaciers covering down to 40° latitude it is ENTIRELY likely that it hit on the kilometer thick ice sheet. Just as it is likely (more so) for an object to impact the ocean instead of the land. And yet, Tunguska and Chelyabinsk air burst over LAND, which is only 29% of the Earth. Amazing, isn’t it?

Anthony –
I’ve got some interesting stuff on thadebris fieldt. At least A debris field. Not good enough to do anything with yet, though. But amazing and tantalyzing.

NielsZoo –
There are at least three lines of evidence that point to the Great Lakes – but dating on one of them is haywire, so it isn’t quite possible to tie it to the time of the YD onset.
I wish I was an OSL man right now…

Anthony – please see my comment and link, above. It was an extraordinary event – planet changing. Impact is evident at Google Earth/Maps(satellite view).


the 1908 Siberian Tunguska event completely flattened ~2000km^2. air bursting comet or meteorite less than 200meters in size. the YDB would have been substantially larger but it too could have been an airburst. or most heavier impacts over the ocean.

Even Tunguska has craters. For a global event to produce the proposed evidence, carbon nano diamonds, either the air burst would be the source of the carbon, which requires still more complex explanation of the celestial body with adequate carbon to spark the event, or there is an impact site with abundant carbon. One may reasonably estimate a center of impact, then go hunting for the crater. Even glacial concealment should be easy to consider.


Or a swarm of icy Tunguska-sized objects. All air-blasts w/no craters & little stone or metals. The wide area of charcoal/nano-diamond layer supports that postulate.

How about a very large object that broke up in the atmosphere, impacting at a number of places across the NH?
/Mr Lynn


There was a paper out in 2007 which said much as the above and mentions nanodiamonds.

Abstract – 2007
Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling
A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

KImbo –
Yeah, that is the paper that started it all.


Tunguska created no craters.

Check again.


Was the temperature graph part of the paper? I didn’t see it in the press release and was unable to view the whole paper.


I’d like to know that too.


No it was not. It appears to be something Anthony had on hand to help show what the Younger Dryas cooling period was.

Chris Schoneveld

Could you give us the reference of that other paper?

John Boles

Yes, BTW, I like the new format, it flows better and is easier to read. Good work Anthony!


I like the larger figures, and being able to address someone’s comment directly, instead of posting a reference to it waaaaay at the bottom.

Tom O

“Situation solved. No need to look here again. We’ve done this, now move on to something else.” It’s a nice theory, has some supporting evidence, but is it “solved?” Nothing that deals with the past through proxies is every solved, but it does present a possibility. When did scientists start saying “we solved this” anyway? I always understood that there was no solutions, just theories and possible explanations. How much better these new scientists are than they were, say 50 years ago, because whenever they take on a situation for study, they always “solve it.”


Tom, this is basically climatology. Expect outrageous and unwarranted claims of certainty.

Tom O –
I laughed at that. A little bit of absolutism going back and forth between their papers. One side names theirs a “Requiem” for the YD impact hypothesis. So Kennett has to come back with an in-your-face, too.
Personally, the amount of “forensics” on this impact are quite strong and unassailable. The skeptics tried – and failed. They can only nibble around at the corners, like wolves trying to work a caribou pup out of the herd. They can’t do a thing to the core of it. Especially as there is a “suite” – several different lines of evidence, all pointing to the same thing – an impact. But if all of you think defending CO2 against warmists is a bear, try selling geloogists and astronomers on catastrophism only 170 years after they thought they’d buried The FLood forever.
I am telling you: They will fight this until they are blue in the face. You’ll have to claw Gradualism out of their cold, dead hands. Because if this is right, then during times of catastrophe Gradualism wasn’t working anymore, and that means they’ve lost control of geological history. Even comet Shoemaker-Levy hitting Jupiter 20 good whacks in 1994 (20 years ago now!) didn’t let some of them let loose of their “comets don’t hit planets in our lifetimes” mantra.
The Catastrophe Barrier will make the Clovis Barrier look like child’s play. ESPECIALLY if the darned thing hit on the ice sheet and there isn’t a pristine Barringer-type crater.

Doug Proctor

Geologists -I are one – recognize catastrophes as numerically insignificant but representationally dominant in the geologic record. The one in a thousand year flood wipes out all evidence of lesser floods AND creates a changs of such great character that it withstands the modifications of everyday processes.
The principle that has survived the Biblical fight re The Deluge, is that the processes we see today are the processes that existed yesterday. With local necessary modifications, they are universal processes, applicable to the surface of Mars and Titan today as much as the Earth of 350 million years ago. That being said, catastophism must be viewed skeptically. Like CAGW, the idea is that the period of concern is or was “special”; normal patterns or expectations are irrevevant. This is a dangerously simple and useful concept, especially if one has a career to consider (Michael Mann), a legacy to create (b. Obama) or a fortune to create for oneself or others (Al Gore).
Still … Comets …
There was a lot going on 12,900 years ago. It strikes me that while disasters generally results from a connected series of small problems, including an extraterrestrial coup-de-gras is a trifle melodramatic. Ain’t saying it’s untrue, just sayin’ the story is a little CNN to warrant grabbing and running with if you don’t like the taste of crow.


Well said, Doug Proctor, below.


the KT boundary was recently revised to 66.038 ± 0.025/0.049 Mya.
Science 8 February 2013:
Vol. 339 no. 6120 pp. 684-687
DOI: 10.1126/science.1230492

Hahahahaha –
I freaking LOVE how they talk about things millions of years in the past as if they really bloody know it was 65 vs 66 – or 66 vs 67. Yep, the Miocene started at dawn on the 1st of January, 12.7000000000000 mya.
When the new Carbon14 calibration curves (IntCal13) came out the YDIH was no longer at 12.9kya; it was at 12.8kya. Literally, there was Analiese van Hoesel bitching and moaning a few weeks later that the whole YDIH is full of crap because some of the layers didn’t match up with the new 12.8kya date. She said they were off by 100 years. Which James Wittke took her to task about.
AS IF! As if they really, REALLY know it is 12.8kya now.
But they will run around the very next day after one of these shifts like the Out-Of-Town Experts that they all claim to be, spouting exact, ROCK SOLID dates – dates that are almost as certain to change in the next 25 years as I am to take another breath in 3, 2, 1.. . . YEP, still here, folks!
(And the FUNNIEST thing is that they pronounce REALLY tight C14 uncertainty ranges – like +/- 35 years at 13,000 years ago. I TOTALLY respect the guys doing it, but the uncertainty bars are just too tight – IMHO. I mean, they just adjusted the calibration curve by THEE TIMES THAT.)
But then people like van Hoesel take the damned things literally. If you are off 40 years, well, to her that is not a match. (Forehead slap time…)

And then there are the dates on the climate reconstructions. They all have error bars for the AMPLITUDE, but they never show error bars for the time element. And that DOE make a difference – especially when homogenizing multiple proxies and many different data sets – all of which DO have error bars on the ages of the samples. It shows up on every C14 test and is there for ice cores, too. But every age of every sample, every tree, is treated as if it, too, is accurate to 7 zeros.
What it does in homogenization of data is that if several close dates have their peaks or valleys shifted in time, that tends to flatten out the rolling averages even MORE. I’ve said before that that is ONE of the reasons Mann’s Hockey Stick has a straight shaft.
End of rant.


What’s the source of the Greenland temp graph in this article?comment image
Showing current temperatures almost as low as LIA 😕


The Data looks like it came from a 1997 paper by Cuffey and Clow reported in the J. of Geophysical Research. The right side of the graph is incorrectly labeled. What is labeled as the MWP is actually the Roman warm period 2,000 YBP with a sharp Dark Ages cooling followed by the MWP 1,000 YBP. The arrow for the present global warming shows the LIA with the tiny blip at 0 BP. The scale of the graph makes the modern warming hard to discern.


It’s not the Roman Warm Period. It’s the Sui-Tang WP, which occurred during the Dark Ages Cool Period. The Roman is to the left.


It’s the GISP2 ice core data from Greenland, Alley et al. (2004):
The data start at 0.0951409, which is 95 years “before present”, where “present” is, by convention, 1950. So the point at which the data end, inexplicably marked “Present global warming”, is actually 1854.


The graph is somewhat misleading without it being clearly pointed out that ‘present global warming’ actually means 1854. To give proper context it needs to be brought up to date. The modern warming should be at least within touching distance of the MWP no matter what the scale of the graph


See post below for link to Kobashi et al. (2011). The measured average temperature at the GISP2 site for the decade 2001-2010 was -29.9C, which is almost exactly the maximum on the vertical scale on the above chart. However, note also that Kobashi et al. found higher temperatures in the MWP than Alley et al. using a different method. See figure 1 in the paper (it’s Open Access).

BTW, for those who don’t know, with a resolution of greater than 200 years, ice cores cannot be used for high-res dating. The reason for this poor resolution is that the gases migrate up and down within the ice – giving a kind of a fuzzy view of what the gasses could possibly tell us.


It was just a picture of the paper’s figure 1, which you can access from the first link. For some reason the system here didn’t like the format.


The second link says ‘Forbidden’ so I cant see Figure 1

I think the missing salient point here is how did CO2 cause the Younger Dryas and the subsequent rebound? And maybe more importantly how did CO2 maintain the subsequent stable temperatures?
Could it be that maybe, just maybe CO2 is an inconsequential trace gas?


So if it hadn’t have been for the impact event the warming period would have been another ~4,000 years, pushing the interglacial out to over 14,000 years. Great to know that with this info we really could be on the cusp of a new ice age.

The dates are 18,000ya, 12,800ya, and 11,500ya, for the end of the Last Glacial Maximum, the Younger Dryas onset, and the Younger Dryas termination. The YD only lasted 1300 years. (Some say 1,000.)
Seeing as the vast majority of the Pleistocene – which we are still in – was ice ages, these last 11,500 years are distinctly an anomaly. If we head back into one there is SOME chance that it could “take” and we could be SOL.

D. Cohen

The pattern of the past interglacial-glacial cycles is that the descent into a colder climate from the previous interglacial is, overall, a relatively gradual process, with the coldest temperatures occurring just before the next interglacial starts with a bang (that is, a rapid climb into a warmer climate). That is one of the reasons why the abrupt cooling back into icy conditions that occurred during the Younger Dryas stands out as something worth investigating. Another reason is that some specialists in human prehistory say that the rapidly deteriorating climate in areas which had enjoyed substantial population growth during the immediately preceding warm period may have led to the invention of agriculture to create a more reliable source of food.

There could have been an impact at the older YDB but we don’t need it to cause whatever the Younger Dryas was. The only proxy that cleary shows large deviations is water/ice isotopes, d18O, d2H and deuterium excess in the ice cores and speleothems of the northern hemisphere. There is not any other record or proxy that supports the conclusions we have drawn from that, on the contrary, nothing fits, for instance this one:
But it’s essentail to note that these three isotope excursions are exactly the same during the Dansgaard Oeschger events. Consequently, if you need an extraterrestrial event to explain the Younger Dryas, you’d need to find some 25 more extraterrestrial events during the late Pleistocene to explain the other Dansgaard Oeschger events as well.
More over many of the megafauna did not go extinct at the Younger Dryas boundary. Most species perished much earier world wide, but the iconical Woolly Mammoth thrived during the Yonger Dryas in Siberia and disappeared only well after the start of the Preboreal/Holocene. Moreover we keep witnessing the dismissal of young Mastodon carbon dates in America (and only mastodons), because that’s obviously impossible because the Mastodon died out at the Younger Dryas boundary, so that evidence must be false (what fallacy is that?)
But also youngest date of the extinct giant deer/ Irish Elk from Siberia is 7700 radio carbon years. So why do we think that the megafauna extinction is limited to the Younger Dryas boundary?
Comic impact, sure, why not, but you can’t blame it for all the things we see changing at the end of the Pleistocene.

exactly where are the 25 other events

Yes, people often point out that the Younger Dryas isn’t unique. (But don’t tell the biologists that! – THEY are the ones who made a big deal out of it, LONG before Richard Firestone et al came along with the YDIH.
And that is supposed to shut up YD impact people. None of the others actually says squat about the Dansgaard-Oeschger events. (BTW, don’t forget the Bond events – also at 1470-1500 year intervals, for what it is worth). But I’ve tentatively suspected that the D-O events and the YD impact ARE connected. How so? Well there is something called the “8.2 kya event” (google it), and THAT is one of the Bond events. And THAT one is also suspected of being an impact – by people FAR removed from Firestone and Kennett.
My thinking is very rudimentary, but basically it is to consider that all of the D-O events may possibly be impacts.
As you can tell from the GISP2 graph, those are SERIOUS temperature excursions – 10 or 20 or 30 times as big as what warmists are worried about. And they all come on so damned quickly. That is not Gradualism doing that. Internal system forcings I just don’t think can do that.
Crazy idea? Yeah, that is what everybody tells me. But ten years ago asserting ANY impacts connected with ONE D-O warming would have gotten one an invite to the straight jacket store… We now have TWO. As we here all know, correlation is not necessarily causation. But with two of them matching to Bond events and at least on of the two matching with a D-O event, it seems possible, if not probable.

“But it’s essentail to note that these three isotope excursions are exactly the same during the Dansgaard Oeschger events. Consequently, if you need an extraterrestrial event to explain the Younger Dryas, you’d need to find some 25 more extraterrestrial events during the late Pleistocene to explain the other Dansgaard Oeschger events as well.”
Multiple fragments of the same object. IMO this repeated isotope deviation is evidence for impact, not against.

There is much evidence that the Younger Dryas resulted from ‘sudden’ diversion of Lake Agassiz drainage (meltwater as the southern terminus of the Lauentide ice sheet) from the Mississippi valley hence the Gulf to the St Laurence hence the North Atlantic. This disrupted the thermohaline circulation until the fresh water pulse dissipated.
It is of course possible that a cosmic impact was responsible for the diversion rather than the theorized melting of ice dams.
It is not possible that the Younger Dryas itself was responsible for the North American megafauna extinction event at around this time. Those fauna were adapted to the ice age that was receding, and a return to those conditions per we would not have mattered. Clovis over hunting has always seemed a bit of a stretch. Too many animals, not enough hunters. This does provide a testible alternative. All the megafauna species would have disappeared from the fossil record at the time of the event. Worth researching whether that is true, for example at the La Brea tar pits or other known megafauna deposits like the recent cave (prior waterhole) discovery in Utah IIRC.
Refreshing to read about real science rather than climate ‘science’.

Those hunters had a nuclear weapon in the form of what would later be called a buffalo jump. Stampeding herd animals in the direction of a cliff could wipe out the whole heard. Thus they ended up killing far more than they had too but it was the easiest way to feed and provide animal skins to a tribe. The excess would, of course, rot.

Paul In Boston

Buffalo jumps were used by the Indians in historic times. Here’s a description from the Lewis and Clark expedition.


And more importantly much safer for the hunters

“Buffalo jumps were used by the Indians in historic times.”
And yet they never managed to make species extinct again. Figures…
Oh wait, what if something caused both the extinction AND the human migration ? We already know from both Triassic-Jurassic and Cretaceous-Paleogene extinctions that when something BAD happens, big animals suffer first and foremost while the most adaptable species strive and benefit from the destruction.

Actually, Wallace Broeker – the man responsible for the Lake Agassiz meltwater hypothesis – a couple of years ago admitted that that idea was a no go.
Check out this WUWT post from June 16, 2012:
Some people have been trying to resurrect the idea by invoking a Mackenzie River meltwater pulse instead – but that one comes out about 4,000 km away, on the farthest side of Canada you can go to from the mouth of the St Lawrence.

David L. Hagen

At Climate Etc, Rud Istvan refers to an opposing review disputing the cosmic impact evidence by Holliday et al., The Younger Dryas impact hypothesis: a cosmic catastrophe from J. Quaternary Sciences 29: 525-530 (2014).

Mike Smith

What, no models!
What kind of climate work is this?

johann wundersamer

Oh Ja, a planetary impact.
Extinctet mastodonts 13.000 years ago:we’ve got nanodiamonds ’50 million
square kilometers across the
Northern Hemisphere’:what so impactet planet earth:a SUV?
Or maybee:13.000 years ago 13.000 SUV’s impactet planet earth to produce some nanodiamonds colleterating mastotonts.
Time sharing with them other yellow pages all over the planet earth.
Astounded. Hans


I guess the theory that the extreme warming by the Bolling Oscillation which melted so much of the continental ice sheets so quickly thus changing the thermohaline circulation causing a re-glaciation, can be put aside into the corner … for now. So much science; so many theories; when will it all become settled?

Alberta Slim

Jim… Ask al Gore. He knows everything…. ….;^D


Perhaps the comet caused the sudden warming

It will never be settled sa long as they keep putting patches on to SOMEHOW make the science explain what the previous idea couldn’t. Not without patches upon patches upon patches – ala MicroSoft and Windows. NOT a good model to follow.
I call the patches “crowbars”, because they pull them out ANY time the have a falsification, and they just pull speculations out of their BUTTS and try to force the new thing to make the old idea fit the inconvenient facts. But piling speculations on top of falsified hypotheses is not science. It’s just hip-shooting and hard heads.
The thing is, that they just need to throw OUT the falsified ideas and stop long enough to derive BETTER ideas from the bottom UP. But they identify too much with one idea, and they don’t seem to let it go. So, what e have is several falsified things still in the mix, cluttering up not only the overall, but the brains of those who stubbornly refuse to let it go.


YDB is rapid but not exceptionally so. Other changes around that period were as great in magnitude and not that much slower.
There was already a huge general cooling since the initial false start to the deglaciation.
The end of YD was more remarkable and this time it stuck.
CO2 levels were low enough at the glacial maximum that the increase would have had a GW effect acting as a positive feedback to whatever was driving warming. A positive feedback would also cause snap changes like YDB and YD end, it works both ways. Methane could also be a cause of GW +ve feedback.
That kind of latching behaviour is typical of +ve feedbacks ( which have to be bounded by stronger negative f/b ).

Bruce Cobb

Maybe. Or, it could be the heat was simply hiding in the deep oceans, like it is doing now. Heat is sneaky that way.


The temperature graph is mislabeled & misdrawn. The supposed Medieval Warm Period is actually the Sui-Tang WP, a warm interval during the Dark Ages Cold Period. The following peak is the Medieval & should be at least as high as the S-T but lower than the Roman. The stretch labeled “Little Ice Age” is the latter DACP. The real LIA comes after the Medieval Warm Period.

Bill Illis

Greenland and Antarctica temperatures over the last ice age for reference. How many Younger-Dryas-type cooling events can you count here.


Interesting graph, Bill.
Upto about 40ka BP the large events seems fairly well synchronised. I’d guess that phase shift before that are more likely time-scale calibration errors than bipolar disorder, though the main warming leading to deglaciation seems to have started a good 10ka earlier in SH.

As I mentioned earlier those alleged cooling events are the Dansgaard Oeschger events. But what you actually see is the oxygen and hydrogen isotope ratios in the ice cores, which are supposed to be proxies for temperature. However this is a logical fallacy. Affirming the Consequent. If it rains, the streets are wet. The streets are wet, hence it rains. Consequently: when it’s cold the isotopes are low. The isotopes are low, hence it was cold. Not necesarily. How about for instance arid versus moist?


There are plenty of paleontological records that shows that the D-O events really were temperature shifts. Or at least that animals and plants (including humans) reacted as if they were climate shifts.

One thing that we need to be aware of with the Greenland and Antarctic ice cores is that, being high latitude locations the cores may OR may not represent the rest of the world.
Especially if the YD impact idea is true, then Greenland was directly downwind of the event near the Great Lakes (as I see it, anyway). And if the burning in N America was from Alberta to the Carolinas, then that was a broad front of smoke headed toward Greenland, one that could hardly miss the place.
THAT could have had a very quick and very heavy effect on the ice in central Greenland. It would likely have been the most seriously affected place outside mainland N America.


“A new stomatal proxy-based record of CO2 concentrations ([CO2]), based on Betula nana (dwarf birch) leaves from the Hässeldala Port sedimentary sequence in south-eastern Sweden, is presented. The record is of high chronological resolution and spans most of Greenland Interstadial 1 (GI-1a to 1c, Allerød pollen zone), Greenland Stadial 1 (GS-1, Younger Dryas pollen zone) and the very beginning of the Holocene (Preboreal pollen zone). The record clearly demonstrates that i) [CO2] were significantly higher than usually reported for the Last Termination and ii) the overall pattern of CO2 evolution through the studied time period is fairly dynamic, with significant abrupt fluctuations in [CO2] when the climate moved from interstadial to stadial state and vice versa. A new loss-on-ignition chemical record (used here as a proxy for temperature) lends independent support to the Hässeldala Port [CO2] record. The large-amplitude fluctuations around the climate change transitions may indicate unstable climates and that “tipping-point” situations were involved in Last Termination climate evolution. The scenario presented here is in contrast to [CO2] records reconstructed from air bubbles trapped in ice, which indicate lower concentrations and a gradual, linear increase of [CO2] through time. The prevalent explanation for the main climate forcer during the Last Termination being ocean circulation patterns needs to re-examined, and a larger role for atmospheric [CO2] considered.”


A drop from >400ppm to 200ppm around YDB for a drop of about 8 degrees C, that’s about 25 ppm/K getting sucked back into sinks on a multi centennial scale. Presumably mainly oceanic absorption.
Considerably larger than figures like 8-10 ppm/K I’ve seen coming from ice cores.
If the calibration is accurate here, it suggests that there is significant physical blurring going in ice samples.

Jimbo and Greg, one need to take the absolute CO2 levels of stomata data with a grain of salt. Stomata data have a much better resolution than ice core data, but they are a proxy for local CO2 levels over land, not background levels as the ice core CO2 data are.
Local CO2 over land in general is higher than background, as a lot of organic debris decays over the year(s). In cases of abrupt climate change like the Younger Dryas was, the amount of debris can change a lot, as plant growth (and this its debris) is a lot less at colder temperatures. With as result a change in local CO2 bias. The main wind direction also can have changed and the plant growth/plant types in the main wind direction…
Anyway, while the ice cores resolution is worse, that doesn’t change the average CO2 level of the ice core over the time of resolution, as there is no measurable diffusion in ice cores. Thus if the average of the stomata data differs from the ice cores over the period of the latter’s resolution, then the stomata average is certainly wrong.


The complete paper is avalable here:
It contains data from several öther stomatal studies that supports the results. There apparently really were rises and drawdowns of 100 ppm or more in just a century or so.


Bill Illis
August 29, 2014 at 10:06 am
The same D/O Cycles & Heinrich Events are evident in previous glaciations & transitions to interglacials, along with Bond Cycles within the interglacials.
If there were an impact around the time of the YD (which I doubt on the flimsy basis of the evidence), there’s no reason to imagine that the putative event caused the YD.
Does only Kennett’s team find support for their hypothesis? Is no one else looking?

None of the other rapid changes in the D-O, the Heinrich events, nor the Bond events are coincident with a black layer with the nanodiamonds and other impact markers. (The only other layer with any similarities is the K-T boundary. And we know what that one did (we think).
The black layer shows up across N America from Alberta to the Carolinas and down to Blackwater Draw and other places, as well as in BELGIUM, and SYRIA, and in S America at the northern end of the Andes.
Like it says above, the black layer is found in an area that spans some 50 million square kms, so it was not small. It was not even medium nor Goldilocks-sized. This was the mother of all firestorms on one of the three biggest continents. And it reached across the Atlantic AND the Mediterranean, as well as the Gulf of Mexico and Caribbean. Obviously it sent monumental amounts of soot and smoke into the air, which if it laid down a layer in Syria stronly suggests that the smoke went around the world. We are talking of a smoke cloud that was
. That the impact “forensics” lie at the very bottom of that black layer at its interface with the next lower soils, indicates that the impact markers and the black layer occurred together. And that the black layer was added to, to make a thickness that averages about 10 cm (4″).
50 million km^2 is basically 10% of the Earth’s surface. That is far bigger than any natural event in the known history of mankind.


Greg sez: “Tom, this is basically climatology. Expect outrageous and unwarranted claims of certainty.”
Not at all. Multiple samples of the relevant strata–no magic single tree in Yamal. No tree rings, speleothems, or bat guano strata. No ad hominem arguments. No use of the terms “robust,” “consistent with,” “rigorous,” “transparent,” “open,” or “peer reviewed.” As near as I can tell, sufficient methodology is included to permit replication. But most of all, there is no de rigueur shibboleth/ecco la fica in the closing paragraphs stating that this study confirms CO2 as the source of all global warming.


Yes, it seems the unwarranted uncertainty was some editorial enthusiasm at WUWT. “Younger Dryas climate event solved via nanodiamonds – it was a planetary impact event”
Neither the press release nor the quotations from Kennet are making such claims. He always seems clear that it’s their hypothesis, not that it’s “solved”.
My criticism was misplaced.

Hahaha – “As near as I can tell, sufficient methodology is included to permit replication.” Yet the skeptics of this couldn’t follow simple protocols and screwed up their effort at replication – and then they ran with their bogus results, bad-mouthing the YDB scientists.
Am I the only one here who thinks some scientists got their degrees out of Cracker Jacks boxes?
ROFL – I didn’t think so. 🙂


August 29, 2014 at 10:13 am
CO2 over 400 ppm in the late Allerød. Who knew that there were so many SUVs at the end of the Paleolithic?

Germany had about 10,000 CO2 samplings in the early 1900s (up into the 1930s). It didn’t affect jack. Their weather was as crappy as it often is. And lest anyone thinks “Oh, what did they know way back then?” the sampling of CO2 was well refined by about 1850. Or so I’ve read.

gary gulrud

Not an expert but 13,000 years is like geologic yesterday. Point me to the crater, please?


The Laurentide Ice Sheet was over 3km thick in places. Depending on the impact site, angle, energy etc. there may not have been a significant amount of crustal damage done and the melt alone could have erased it. There could have been no crustal damage done if it hit a thick area of ice. A bunch of unknowns here as the nanodiamonds would require the impactor be one of the more carbon rich meteorite types if terrestrial carbon was not the original source. Not enough data here to make that call but a missing impact site is not a falsification criteria here.

Peter Schultz did hyper velocity impacts experiments at NASA Ames. He got speeds of like 4 km/sec or so, and used super high-speed cameras. You are right – hitting dead center on about a 1 inch slab of ice. The loose sand underneath was still flat and basically unmarked. The ice? All OVER the place. It’s on a NOVA episode about the YD impact from about 5 years ago. One interesting aspect is that the highest velocity of ice was straight up, even with a 45° impact.
My best info is that the thickest ice at the Last Glacial Maximum was 2 km thick at its center – near the eastern edge of Hudson Bay. I assume that it tapered to the edges. But I have no idea how high at the edges. I don’t think anyone does. But certainly less than 2 km. If the calving ice at the edge of the Antarctic is any guide, the edge was maybe 100-200 meters, and maybe tapered sharply up to 500-1000 meters. (My guess.)
The hypothesis has the impact in the Great Lakes area. One guy – MIchael Davias – thinks that it was Saginaw Bay. And that the impactor was so big it made it THROUGH the ice sheet there and carved out the bay. With the ice being ejected along with bedrock, the rock probably ended up on the ice sheet not so far away. His idea has a lot of merit, but most scientists pretty much ignore it. After all, he’s talking about a catastrophe.
There’s no catastrophes in Gradualism!

It’s in the Southern Ocean, southeast of Madagascar. Open Google Maps (satellite view) or Google Earth.

I believe that was Shiva – an entirely different time and a really big one in its own right. The tsunami must have been prodigious.


Or maybe Mesolithic. More advanced than the Paleolithic, but still, how did they produce so much CO2? They hunted in the forests. They didn’t burn them down.

johann wundersamer

why just let them collaborated ‘mastodons’ stay away and talk ’bout
Asking. Hans

That is not the explanation because many events similar to the Younger Dryas have happened through out the historical climatic record as Don Easterbrook so clearly shows.
If this was a one time isolated occurrence the theory they advance might of had some merit but the Younger Dryas event is not an isolated unique climatic event when one reviews the data.
My question is why is it only in climate science that data is some how ignored?
A much better explanation is these abrupt climate changes had to do with sea ice dynamics when the initial state of the climate was not to far from boarder line threshold values for glacial versus non glacial conditions moderated by solar variability and all the associated primary and secondary effects.
Don Easterbrook says:
August 21, 2014 at 8:41 am
A big problem with computer models is that the results depend not only on what assumptions you put into the model, but also what you don’t put in.
Some major problems with this particular model include:
1. “The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before present. The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciation 20,000 years ago, nor at high sea levels such as those prevailing today – they occurred during periods of intermediate ice volume and intermediate sea levels.”
This statement is dead wrong–both the oxygen isotope ratios and temperature curves from the GISP2 ice core show that the most sudden warming that brought the last Ice Age to a close occurred abruptly 15,000 years ago when ice sheets were at their maximum extent and sea level was at its lowest. The ice sheets had been at their late glacial maximums for several thousand years when, out of the blue, temperatures suddenly soared 13 C (23 F) in something like 100 years, causing wholesale melting of the ice sheets. Then, just as abruptly, temperatures turned around and cooled 10 C (18 F) by 14,000 years ago. Temperatures then fluctuated up and down( but not so intensely) at intermediate levels for about 1,000 years. 12,700 years ago, temperatures took another nosedive into the Younger Dryas cold period and remained at full glacial conditions for 1,000 years. During the Younger Dryas, temperatures repeatedly changed abruptly from cool to warm (the Dansgard-Oeschger events). 11,500 years ago, another great warming spike caused temperatures to soar 12 C (21 F) in about 100 years (at one point, around 20 degrees in 40 years), then continued warming at slower rates for a total warming of 17 C (30 F) from 11,700 to 10,000 years ago. (Keep in mind that these temperatures are for Greenland, not global, but they correlate very well with temperature conditions in the rest of the world). These abrupt, multiple, intense changes (back and forth) at full glacial conditions (not ‘intermediate’) hardly sound like changes caused by gradual changes in ocean/atmospheric conditions.
2. All of the five most significant colder temperature changes that occurred during the past 500 years (the Little Ice Age) coincided with low sunspot intervals, lower total solar irradiance, lower solar magnetic flux, and increases in the production rates of beryllium-10 and carbon-14 (isotopes created in the upper atmosphere by increase in cosmic ray flux rates). These are not mere coincidences–such good correlation is not random chance, but must be due to cause-and-effect circumstances. None of this, of course, made it into the computer model simulations.
There are other serious problems with the methodology in this paper, but the bottom line is that (1) their initial premise of changes occurring only during ‘intermediate’ glacial conditions is dead wrong, and (2) sunspot intervals, lower total solar irradiance, lower solar magnetic flux, and increases in the production rates of beryllium-10 and carbon-14 argue strongly for other factors not included in their models. Thus, their conclusions cannot be considered

“This statement is dead wrong–both the oxygen isotope ratios and temperature curves from the GISP2 ice core show that the most sudden warming that brought the last Ice Age to a close occurred abruptly 15,000 years ago when ice sheets were at their maximum extent and sea level was at its lowest.”
The standard model says that the Last Glacial maximum was between 22kya and 18kya, and that from 18kya to 12.8kya was the Allerod interstadial, when the ice sheets retreated. There is nothing about 15kya except it is in the middle of the Allerod. Nothing I’ve ever seen says the ice was at maximum at 15kya. And I’ve read scores upon scores of papers on this era. Glacial Max was at 18kya. THAT was when the big melt-off was.
The D-O events were spaced at an average of 1470-1500 years. You say that they happened repeatedly during the 1300-year-long Younger Dryas. That does not compute.
I agree that the abruptness and the magnitude of temperature changes are incredibly unlikely from internal forcings. For internal forcings, only when processes self-organize, like with the ENSO, can they cause changes, but the changes only amount to a few tenths of a degree C. Extrapolating 13°C or 10°C or more out of internal forcings is asking micro-forcings to do what need super macro forcings. So, yeah, you are thinking rationally there.
But I am befuddled as to where you got your dates.
I think there is a connection between D-O events, Bond events, and the YF onset. Some say that the D-O events prove that the YD was not an impact. But the “8.2 kya event” (google it) is considered both a Bond event and a probable impact, too (depending on who you ask). If one, maybe no connection. If TWO, then one has to think about it – what would THAT tell us?

Paul Hooks

When I read this 3 years ago I found it interesting
“Candle flames contain millions of nanodiamonds”
Just food for thought.

Dude, not all nanodiamonds are equal. Cubic ones are in fires. Hex ones are the ones that come from off Earth. It has to do with pressures and temps.


The arrow identifying the Little Ice Age is misplaced on the graph.


So is the Medieval Warming Period.

Don Easterbrook

This appears to be a rerun of several earlier articles making the same claim–a cosmic impact caused the Younger Dryas. Four 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).
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.


Exactly. The question should be what made the temperatures rise so suddenly 14,500 BP (nr 1) and 11,900 BP (nr 7). It are these two moments in time responsible for the abundance of these tiny diamonds.

CC Squid

Dr. Easterbrook,
You are trying to to take a scalpel to a gun fight! Trying to replace the “CO2” meme with the knowledge of “it’s the sun stupid” will take many more years. Remember the movies where the witch doctor points to an eclipse of the sun and everyone starts to dance and sing to the gods? IMHO this is currently how the “deniers” are being depicted.
My prediction is that it will take another 15 more years for the “climate science” departments and many others to be condensed and or elimated. This will only happen after the “old” scientists die or retire and when the newer scientists can publish without the obligatory bow to CO2. “It’s the sun stupid” is threatening to take food off of too many people’s plates! Follow the money!


I agree. It appears to this old geologist that two unrelated events are being conflated. The extinction event is much more likely due to impact of extraterrestrial material with the atmosphere – perhaps the Carolina Bays and other apparently time-equivalent impacts are related – think about 500+ concurrent Chelyabinsk events – and the resulting disruption in the atmosphere and on the ground below.
The climate shift was quite probably associated with other completely independent influences. That they appear at about the same time is purely coincidence.

Don Easterbrook, after each sizable cosmic impact on Earth always follow 3 phases: 1. A sharp downdip of temps, followed by 2. a temp rebound to a level substantially HIGHER than at the cosmic impact date and finally, the last phase, 3,. a temp regress back to the lower temp level of the impact date — this mechanics produces a Z-shaped or high-voltage sign e.g. in the Greenland GISP2 temp time series. More on relation on effects of cosmic impacts and Z-type temp evolution at,
there is no point of wild speculating around with volcanoes, dust, time span without first doing some reading on the empirical relation and the effects of a cosmic impact on climate change…regards JS

Don –
“the preceding late Allerod cold period. ” Actually, the Allerod was not a cold period. It was the interstadial, when temps reached close to today’s.
NO, they have not addressed the question of the length of the YD. Yes, of course 1300 years is too long to have dust up in the air. By a factor of 100 or more. The YD researchers have been bogged down dealing with the carping of their skeptics on the impact materials – which are very real. As this paper shows. Saying that materials that MUST be heated above 2200C are not indicative of an impact (and not possible with any Earth processes on the surface), and all the different ones are all spiking right there – what does it take for you to even look at their data? It ain’t ONE material that convinces – it is the suite of materials. Right now the focus is on making the case for the impact materials. The other questions can’t be dealt with just yet. It’s not an excuse; it’s reality.
The black layer being on 3 continents and with some evidence of it in northern S America, too, indicates a natural event larger than any in known human history. With essentially the same suite of markers in Syria and Belgium, something happened that was big. Super big.
I myself think that the single biggest question is that 1300 years – and then the even more abrupt RISE in temps.
At the same time, I do not take Greenland ice now or 13,000 years ago as a valid proxy for the state of the climate. The D-O events may simply be an artifact of the location. The GISP2 core suggests very big changes in temps, over seemingly impossible time periods. Nothing within the climate can do changes that big. They are all micro-forcings, with no capacity to do much more than a few tenths of a degree. Either something (perhaps at multiple times?) from outside the system intruded or we should consider that we are getting a false picture from the ice cores. At least as it pertains to global climate.
At the same time, it was not Firestone and the other YDIH researchers who first made a big hoopla about the YD. It was biologists and climate guys. And they have been at it for DECADES, with no resolution on the horizon. Firestone and all of them can’t help it if their C14 numbers kept coming back with 12.9 kya written all over them. If the dates came back with 37 kya on them some other scenario would have had to be dealt with.
And when they found mammoth bones immediately UNDER the black layer – with the black layer draped ON the surface of the bones and staining them – what were they to think? No connection at all? Not even. There they are, at 12.9 kya (now 12.8 with IntCal13), black layer, mammoth bones, spikes in nanodiamonds, spikes in several other markers for impacts. ONE marker is one thing. A suite of them is a whole other ballgame.
The 1300 year conundrum will still be out there. First things first.

Don Easterbrrok is 100% correct. This is the wrong explanation.

Exactly Mr. Easterbrook.

I thought my first comment did not go through. Sorry for the duplicate.

I’m skeptical. The event was more likely caused by electrical interaction between the planets that scarred them all in a solar system upheaval.

DD More

Can someone please vacuum off the frozen mastodon, the frozen one with food in the stomach, and find the dust and micro diamond.

Charles Brecknell

One of the most interesting talks on catastrophies I’ve seen.


Based upon what I have learned about extinction of mammoths and other mega fauna, I find the comet hypothesis woefully inadequate. It is hardly settled science at this point.


Correct. The pattern & timing of extinctions doesn’t support the impact hypothesis.


Dinosaures were killed by a comet; Mammoths were killed by a comet ; humans will be killed by CO2


Not a comet in either case. A meteor contributed to demise on the non-avian dinosaurs. The meteor hypothesis for the demise of the Pleistocene megafauna is thin at best. The same & similar species also went extinct outside the region allegedly affected by an ET impact.

Read Otto Muck’s work for a full explanation. This is old news


Megafauna extinctions in North America do not correspond closely with the YD, although C14 & calendar year comparisons make for difficulty. In any case, different species & populations went extinct at different times, as nearly as evidence can be resolved.
For instance, island populations of ground sloths survived for thousands of years longer than on the continent.

Actually, at Blackwater Draw there were mammoth bones immediately under the black layer – which has been dated to 12.8 ya on many occasions. Not only was the mammoth there, but the black layer lay over and conformed to the bone. Not only that, but the black material was in intimate contact with the bone and stained the bone.
Outside the pygmy mammoths, no mammoth in the world dates past that 12.8 kya.
C14 vs calendar dating is a simple matter of looking the carbon14 (calendar) date on the IntCal13 graphs. Or, if you are lazy, there is software to do the comparing. It’s not difficult at all.
As to the claims of different times, people say that. So far in all my reading of papers on that, no one has shown any that lived past 12.8 kya. That mammoths died earlier? If the LIVED earlier, then of course they DIED earlier.
Pleas can you point me to the ground sloths? I’d be quite interested.


1.) How is a North American event supposed to have caused South American extinctions but not, apparently, Eurasian or African?
2. How is an event which caused a blip in temperature indistinguishable from a great many others supposed to have caused extinctions even in areas in NA which were west of the supposed fallout area? (But not outside of NA.)
3.) Why does UofC@SB think ‘science is magic’/’science is settled’ reporting appeals to the public? “..until recently, could only speculate as to why.”

1.) and 2.) both good and very valid questions. And ones that the researchers are well aware of. I’ve been on this for about 7 years or so, and I can tell you that the researchers on it are bogged down just trying to get people to accept their “forensic” results. There is a small group of hacks that the researchers think they have to please, so they are spending all their time on that. They do not have unlimited manpower. Give it time.
There are considerably more PRO papers and researchers than there are CONs. Some of them came out of the blue. Like last year some researchers at Harvard and Princeton found supporting evidence.
If you go into the voluminous lab tests in the Appendices to the different papers, you will see that this is serious stuff, very real. Some of the materials are impossible to create without the super-high pressure and temps in a hyper-velocity impact. So, if not an impact, then what? If it looks like a duck, quacks like a duck, and has duck feet. . .
There are multiple lines of evidence.


At least in those days they had climate change you could believe in. I wonder if they too had high priest predicting the end of the world. When exactly did they have their tipping point.

I’ll tell you what:
If you ever get around to reading the accounts of some of the indigenous peoples, it is not hard to start thinking that something actually DID come out of the sky, with a tail like a dragon, blah blah blah and killed a whole lot of people and shook the earth and caused all kinds of havoc.

David L.

So humans didn’t hunt everything to extinction?


Evidence still suggests that we did indeed have a big impact among the naive megafauna of the New World.

Hahaha –
Yeah, the idea of a few thousand guys on foot scouring the entire N American continent – in 200 years – and were able to FIND all of them, much less kill them. That soudnds plausible to me.
Especially when they were killing something bigger than elephants and curing and hauling the 5 tons of meat back – still on foot.
And THEN consider this:
There are only 14 kill sites on the whole continent, and those are where? Basically, like 95% of the Clovis sites are in the SE of the USA. (A site comprises ANY Clovis point, even one – even a broken one.) Google “clovis sites map” THERE ARE A LOT OF SITES. And hardly ANY out west. Where the mammoth kill sites are.
But how many kill sites are in the SE of the USA?
Their families were back east, and they were out in Texas and NM and Arizona, killing mammoths and butchering them. To take the food WHERE? Back to Alabama? From New Mexico?

And BTW, they came up with that Clovis, Extinctor of Mammoths thing when they assumed that the only hunting Clovis man did was for Mammoths.
And you know what they are only now beginning to find out? They hunted rabbits and deer and raccoons and foxes – stuff you can sling over your shoulder and take back to camp to cook for dinner tonight – just like all hunting societies did.
So, with 95% of Clovis in the SE and lots of deer and such to hunt there, what were they doing out west, 1500 mile away?

Jim Reekes

Global effects of comet impacts and volcanoes (which can be triggered by comet impacts) has been a topic I’ve followed with great interest. I’m convinced they are effecting things on this planet much more so than we realize. Not only effecting the weather, but civilizations.
The last major impact coincides with the time of the Pleistocene–Holocene, and the Holocene extinction event. It’s the 6th great extension event on the planet.
Wooly Mammoths, Saber Tooth Tigers, Giant Sloths, and so many other animals, were pushed into extinction. Or, in the case of the early human inhabitants, were nearly made extinct. Humans then re-populated the N America with a second wave of migration. That’s the one you were probably told about in your high school history books, but humans were here for much longer.
Also coinciding with the time of the impact was the end of the last ice age, when much of N America was covered by a glacier. As the ice melted it created a huge fresh water lake covering cover of Manitoba, northwestern Ontario, northern Minnesota, eastern North Dakota, and Saskatchewan. It made all the “great” lakes added together seem like ponds in comparison. It was approximately the size of the Black Sea, about 170,000 sq miles.
As the lake filled, it eventually broke through draining through the Mackenzie River and then into the Arctic Ocean. That’s a MASSIVE amount of fresh water pouring into the salt water in the Arctic. So much so it would be a likely source of flood myths. This water was even flowing south through the Mississippi River.
This must have altered the global climate, and it would have altered the Thermohaline Circulation (aka Atlantic Conveyor Belt). Then there was another great draining around 8,200 years ago (or 6200 BCE), after more ice had melted. This last great melt happens to coincide with the the 8,200 yr climate event. Evidence for this event can be found in Greenland ice cores.
These melts were so large they would have increased global sea levels (~6ft).
The disruption to the Thermohaline Circulation would have likely triggered global cooling. Possibly by as much as 10 deg F. The total duration of the cooling was ~150 years, with sudden cold periods of ~60 years. Even more curious, global CO2 levels dropped ~25ppm.
Such a dramatic impact on the Atlantic’s thermohaline circulation would likely cause a shift in the latitude of the jet stream. This is like the current Polar Vortext, which is when the jet stream has shifted south and pushes the colder air from the Arctic over warmer lands. It would also effect global precipitation. Some ares become much wetter, while others become much drier.
Africa went through ~500 years of drought. The event likely given Mesopotamia the support for their irrigation, which gave rise to agriculture and the surprise of food. This in turn gave rise to the advancements of civilization. But then very suddenly (~100 years) the global climate seems to have corrected itself, and ended this unique weather phenomena.
The Burckle Crater may be the result of comet impact around 2900BCE. It’s about 18 miles in diameter, and it’s under the Indian Ocean at 12,500 feet below sea level. If this does turn out to be an impact crater, it would have caused a mega-tsunami of biblical proportion (e.g. mythical flood event that would have wiped out civilizations along the coasts).
It’s another example of how natural causes come along every few thousand year and dramatically change the global climate. There are a number of comet impacts that has effected civilization. I wish the historians were talking with the paleo-climatologists, and comparing their timelines.
The end of the Medieval Warm Period (MWP) created the Great Famine of 1315. The rise to the population explosion as a result of the good climate during MWP. It all came to an abrupt end with the shift to cold weather. The end of the MWP saw millions died after as crops failed for several years. The following few decades were some of the worst weather on record.
Along with the cooler temperatures were heavy rains throughout Europe. So much so crops failed and people starved. Without the hay to feed livestock, the animals also died. People were more concerned with survival than enlightenment. It wasn’t until the global climate recovered that we enter the Renaissance.
Meat preservation during this period became difficult and unaffordable since it was based on the use of salt, which was produced by evaporation but became nearly impossible due to high humidity.
Natural forces effected civilization was the Dark Ages. It was actually “dark.” There was hundreds of years of vocalic eruptions triggering global cooling. Hekla blew its top in 1300 and continued to spew its guts for one full year! It was called the “Gateway of Hell” by the Europeans.
There’s a scale for measuring eruptions, the Volcanic Explosivity Index (VEI). When you get a VEI 4 you’re at the point where it will effect climate. Not only was Hekla a VEI 4, but it was spewing its guts throughout the Dark Ages. That’s just one volcano. Then in 1362 Iceland’s another monster blows it’s top and is bigger than the famous Mount Vesuvius that buried Pompeii. You can find a history of volcano eruptions throughout the Dark Ages.
The destruction of the very advanced Minoan civilization was caused by the Santorini eruption in 1645 BC. This monster was a mega-eruption at VEI 7. It was an island, and when it blew its top the island was gone. This left a crater below sea level, causing the ocean to rush into the gaping hole causing an even bigger explosion. All that water (~20 TRILLION gallons) was instantly vaporized, and thrown high into the atmosphere. Some of it froze and remained floating around the world as tiny particles of ice (mirrors). This reflected solar radiation for several years, causing an even longer and colder volcanic winter.
The Santorini eruption was seen in ancient Egypt. They even had a tsunami wave reach their coast. That eruption also triggered the expected famine and diseases. In fact, the story of the Exodus and the ten plagues of Egypt can be explained as a result of a volcano.
The Huaynaputina eruption in 1600 triggered a couple years of volcanic winter, causing the Russian famine of 1601-1603 when more than half a million people died.
I’m amazed by the irony of how Briffa’s work on tree ring and climate is so focused on CO2 levels and temperatures. That same data can be used to show the effect of volcanoes, which should be correlated to events in civilization.


The warm & cold centennial-scale climatic cycles observed during the Holocene & prior interglacials & glacials are not caused by volcanic eruptions.
Hekla for example was more active during the Medieval Warm Period (c. AD 900-1400) than it was during the Little Ice Age (c. 1400-1860) or so far in the Modern Warm Period (c. 1860 to present). Here are its VEI 3, 4 & 5 eruptions for each cycle. The year given is for when the activity began, but six lasted more than one year or included back to back annual eruptions.
Medieval WP Eruptions of Hekla (~500 years):
1104: 5
1158: 4
1206: 3
1300: 4
1341: 3
1389: 3
Little Ice Age (~460 years):
1510: 4
1597: 3
1636: 3
1766: 4
1845: 4
Modern WP (~154 years to date):
1947: 4
1970: 3
1980: 3
1991: 3 (same year as Pinatubo)
2000: 3
If there be any correlation at all, it’s that great activity warms rather than cools the climate, which is indeed what researchers have generally concluded, despite short-term cooling of weather for a year or two, possibly a few years for the very biggest, tropical eruptions.

Jim Reekes

The warm & cold centennial-scale climatic cycles observed during the Holocene & prior interglacials & glacials are not caused by volcanic eruptions.

Just to be clear, I’m not claiming volcanoes are driving climate. I was talking about how comets and volcanoes can disrupt civilizations. They also effect weather, in a number of ways.
As for the large time scale changes in climate, my understanding is that it’s driven by the Milankovitch cycles.

Jim –
Good stuff. Keep at it.
But dump the Lake Agassiz thing. It didn’t happen. The ice was still too far south at the Holocene start. The ice was not retreated enough in time to do any of that. Wallace Broeker was the guy who came up with that idea, and he admitted a few years ago that he had to abandon the idea.
But he didn’t come out very very vocal admitting his mistake, and so many people don’t even know that he dumped the idea.
OTHERS, though, think that an outflow down the Mackenzie River and exiting into the Arctic Ocean up near Alaska is just as good. But that is like 4,000 miles and at the other far corner of Canada. Even f fresh water went that way, it had to make it past the Canadian Archipelago and Greenland in order to end up east of Iceland and screwing with the Gulf Stream.
Anyway, that is a dead horse.