Younger Dryas Impact Hypothesis Takes Another Hit

Guest “whatever” by David Middleton

Texas cave sediment upends meteorite explanation for global cooling
7 hours ago
Baylor University

Texas researchers from the University of Houston, Baylor University and Texas A&M University have discovered evidence for why the earth cooled dramatically 13,000 years ago, dropping temperatures by about 3 degrees Centigrade.

The evidence is buried in a Central Texas cave, where horizons of sediment have preserved unique geochemical signatures from ancient volcanic eruptions—signatures previously mistaken for extraterrestrial impacts, researchers say.

The resolution to this case of mistaken identity recently was reported in the journal Science Advances.

“This work shows that the geochemical signature associated with the cooling event is not unique but occurred four times between 9,000 and 15,000 years ago,” said Alan Brandon, Ph.D., professor of geosciences at University of Houston. “Thus, the trigger for this cooling event didn’t come from space. Prior geochemical evidence for a large meteor exploding in the atmosphere instead reflects a period of major volcanic eruptions.


One unnecessary hypothesis upends another… So what? In terms of Late Pleistocene Greenland stadials, the Younger Dryas isn’t even particularly anomalous. The real anomaly, to the extent there is one, is the preceding Bølling–Allerød interstadial.

Phys Dot Org
Central Greenland temperature reconstruction (Alley, 2000)

The Bølling–Allerød interstadial featured a sharp rise in atmospheric carbon dioxide (possibly >400 ppm according to at least one plant stomata study) and Central Greenland temperatures as warm as the Little Ice Age.

While impact events and/or volcanic eruptions certainly could have played a role in Late Pleistocene to Early Holocene extinctions and may have even had transient effects on Younger Dryas climate change, the Dansgaard–Oeschger Events occurred with clock-like regularity during the final Pleistocene glacial stage. These episodes of rapid warming to nearly interglacial conditions occurred approximately every 3,000 years from 90 ka to 12 ka, indicating a periodic drive mechanism.

Dansgaard–Oeschger and Heinrich Events (NOAA)

No one really knows what drove the Dansgaard–Oeschger and Heinrich cycles… But neither impact events nor volcanic eruptions can explain such a clearly quasi-periodic climate change signal.

250 thoughts on “Younger Dryas Impact Hypothesis Takes Another Hit

  1. The problem with the asteroid impact theory is that it required widespread forest fires to generate the soot required to blot out the sun. We have the recent example of the Tunguska event where hundreds of square miles of forest were knocked down but there was no fire.

        • Knowing how pet theories keep sustaining themselves, I think we can predict that this one will do a Lazarus and will rise from its grave (again and again).

          For some reason, theories of extra-terrestrial impact events that are supposed to have caused climate change and/or mass extinctions have a visceral appeal to many who dabble in paleoclimatology. Probably because they describe dramatic, even disastrous events.

          A good uniformitarian should always look for the footprint of processes that we can observe in action today, before invoking paleo-catastrophes.

          • Catastrophes are part of the uniformitarian background, but just less obvious on shoter time scales, as are weathering, sedimentation and earthquakes.

            The success of the Alvarez hypothesis set up a new paradigm. Never mind that the odds against a mass-extinction capable impact in the past 13,000 years are about 2000 to one.

            But you’re right, cataclysmic scenarios do appeal to armchair paleoclimatologists. But they shouldn’t attract the number of supposed scientists sucked in by the YDIH.

          • For some reason, theories of extra-terrestrial impact events that are supposed to have caused climate change and/or mass extinctions have a visceral appeal to many who dabble in paleoclimatology. Probably because they describe dramatic, even disastrous events.

            Right you are, Smart Rock, …… and here is a prime example, to wit:

            Dinosaurs and up to 75% of all other life went extinct 65 million years ago because of a massive asteroid that hit the Earth in the Yucatán Peninsula in Mexico, now known as the Chicxulub crater.

          • Samuel,

            Do you have a better supported explanation for the extinction of the nonavian dinosaurs and so many other organisms at the K/Pg boundary?

          • John:

            Do you have a better supported explanation . . .

            I hear this appeal to authority/black and white fallacy from climate believalists as well, “Do you have a better explanation other than CO2 for the increase in temperature over the last 50 years?”

            I’m not saying you’re wrong, but it’s a non sequitur to argue that if I don’t have an alternative explanation yours is the correct one.

          • Sy,


            Samuel claims that the Yucatan impact didn’t wipe out the dinos, etc. Without stating reasons for doubting the reality of that fact and without proposing an alternative, what does he have? Nothing.

          • sycomputing

            If one has a hypothesis that explains most of the events, but not all of them, the logical question is “Why not everything?”

            That is, ALL animals classified as dinosaurs — big and small — became extinct. However, other similar animals that fill similar ecological niches, such as alligators, crocodiles, monitor lizards, herbivorous iguanas, and sharks, survived the extinction event. Some dinosaurs apparently survived long enough to evolve into true birds. Why did dinosaurs get wiped out while some animals with similar body constructions, sizes, and diets survived? If food disappeared for ocean-going mosasaurs and icthyosaurs, why did fish and turtles survive? If you say that the big mosasaurs and icthyosaurs were big and needed more food, my response would be that young ones had different diets and needed less food and should have survived along with all the fish. The extinction explanation leaves some things to be desired for its role as a comprehensive explanation.

          • Clyde,

            You’ve got it all wrong.

            It wasn’t body plan, but size, diet and where you lived that mattered. The smallest dinosaurs, ie birds, and especially those which fed on seeds, and lived in or near water and farthest away from the impact which survived.

            Larger land animals which did survive were similarly aquatic. In the oceans, again, your size, in what level you lived, what you ate, what your shell was made of, etc. determined your odds of survival.

            Every single datum backs the overwhemingly supported conclusion that the Yucatan impact caused the mass extinction event, with none against it.

          • Clyde,

            Ichthyosaurs died out long before the K/Pg mass extinction event.

            Please state specifically which extinctions you find incompatible with the Alvarez hypothesis, and why.


          • John:

            Samuel claims that the Yucatan impact didn’t wipe out the dinos . . . Without stating reasons for doubting the reality of that fact and without proposing an alternative, what does he have? Nothing.

            Let’s grant your proposition and look at the logical implications. So, in your argument Sam has nothing in the way of an hypothesis. You have the Yucatan impact.

            Does the mere fact that you have an hypothesis make it true? It sure sounds like that’s what you’ve just said.

            I think that’s pretty much the Black and White fallacy, a.k.a., the False Dilemma: You presented two alternative states as the only possibilities, when in fact more possibilities exist. Maybe it WAS the Yucatan impact and maybe it wasn’t. Just because the Yucatan impact may be the best hypothesis at present doesn’t make it true.

            Remember bacteriology before germ theory was verified? Yep, there was none. There were alternative hypotheses of disease, but all of them were wrong.

            Sam’s doubt and/or lack of an alternative to any particular hypothesis can’t SOLELY be evidence that yours is true. All it is evidence of is Sam not having an hypothesis.

            Again, I’m not saying you’re wrong.

          • Clyde:

            If one has a hypothesis that explains most of the events, but not all of them, the logical question is “Why not everything?”

            I think that’s reasonable, however, it doesn’t follow that from any hypothesis’s failure to explain EVERYTHING that the hypothesis is necessarily wrong either.

            We don’t want to say that do we?

          • Sy,

            You are so wrong in every possible way.

            If Sam wants to challenge the fact of mass extinction via Yucatan impact, he has to offer some reason for doing so. He can’t because no such reasons exist.

            Since there are no such reasons, then he next has to offer an alternative hypothesis for the mass extinctions. He can’t do that, either.

            The mere fact of the Yucatan hypothesis doesn’t make it “true”. What shows it to be real is the mass of incontrovertible evidence in its favor.

            If you or Sam imagine that you can show the fact of the Yucatan impact and its consequent die off false, please, have at it!

            But I’m sure you can’t, since all the evidence in the world shows it real.

          • You are so wrong in every possible way.

            In every possible way? Are you REALLY sure about that John?

            If Sam wants to challenge the fact of mass extinction via Yucatan impact, he has to offer some reason for doing so. He can’t because no such reasons exist.

            Since there are no such reasons, then he next has to offer an alternative hypothesis for the mass extinctions. He can’t do that, either.

            So, you would argue that Sam can’t challenge the fact that the Yucatan impact explains a mass extinction because no such reasons exist, but at the same time, he needs to offer an alternative hypothesis for the mass extinctions?

            Hmmm . . . 🙂

            Emphasis added:

            The mere fact of the Yucatan hypothesis doesn’t make it “true”. What shows it to be real is the mass of incontrovertible evidence in its favor.

            So the “fact of the Yucatan hypothesis” is the “incontrovertible evidence in its favor”? Sounds suspiciously like you’ve already assumed the conclusion in your premise:


            If you or Sam imagine that you can show the fact of the Yucatan impact and its consequent die off false, please, have at it!

            Not really my purview. I’m only interested in how people utilize logical fallacies in their thinking. I mean, after all, George Washington was killed because the best evidence at the time suggested he ought to be blood-letted for what ailed him.


            Again, not saying your wrong, unless of course we discover later that there’s a 3rd explanation. You know, NOT bloodletting, if you get my drift.

          • John Tillman August 1, 2020 at 3:29 pm


            Do you have a better supported explanation for the extinction of the nonavian dinosaurs and so many other organisms at the K/Pg boundary?

            John T,

            If I didn’t truly believe that “I have a better supported explanation for said extinction” then I would be asking questions rather than ….. mimicking, plagiarizing or paraphrasing the commentary of other authors ….. who think, …. no, … who actually believe the junk science they have been forced to believe in order to get a “passing grade” in their field of study.

            John T, ….. common sense thinking, logical reasoning and/or intelligent deduction provides the best explanation …… if one can believe the proxy records of paleoclimate are reasonably correct.


            John, please note the “rise and fall” of atmospheric CO2 ppm on the above graph ……. with the designated “Age of the Dinosaurs”, …… the period, which spans from about 252 million years ago to about 66 million years ago.

            The rise in CO2 sparked the evolution of large dinosaurs ….. and the decrease in CO2 caused the demise of large dinosaurs.

          • Sam,

            Large dinosaurs died all of a sudden, at the same time as sea creatures. Their demise could not possibly have been from lack of CO2.

            Even during the Cretaceous, CO2 was above the level needed by C3 plants. Indeed, that’s when flowering plants first flourished.

            Gigantic land mammals evolved under even lower CO2 in the Cenozoic, and the largest sea animals of all time live now.

            Sorry, but yet another of your crackpot notions is busted by reality.

            BTW, dinosaurs didn’t evolve immediately after the Permian extinction, but in the Middle Triassic.

          • Samuel claims that the Yucatan impact didn’t wipe out the dinos, etc. Without stating reasons for doubting the reality of that fact and without proposing an alternative, what does he have? Nothing.

            Large dinosaurs died all of a sudden, at the same time …….

            Such stupidity could only be taught post-1970 in the US public schools,

            John T, ….. GETTA CLUE, …… a dinosaur fossil is/was the result of an accident …… and “dating” it only tells you when that particular accident occurred, ……NOT when all the dinosaurs perished.

            The large dinosaurs began dying off when atmospheric CO2 started its decline around 144mya as denoted on the above cited graph.

            I’ve been posting my reason for doubting the Yucatan theory for several years now, and here is a re-post of one of said, to wit:

            The removal of all that CO2 from the atmosphere a few million years ago ….. and sequestering it into what is now “fossil fuels”, …… sure as hell made a difference in the survival of the dinosaurs …… because, IMLO, it was the primary reason for the dinosaur extinction(s).

            “DUH”, just like now days, atmospheric CO2 is at the “tippity top” of the biological “food chain”.

            The greater the quantity of atmospheric CO2 ppm = the greater the growth in size and numbers of “green-growing” plant biomass.

            And the greater the growth in size and numbers of “green-growing” plant biomass = the greater the growth in size and numbers of reproducing species of animal biomass.

            And those large dinosaurs, both plant eaters and meat eaters, evolved because the “eatin” was plentiful and the “livin” was easy.

            But the “plant-eating” animals could not keep up with the “growth-rate” of the plants, ….. and thus the CO2 laden “un-eaten” plants were being sequestered in swamps and under water ….. whereas the “meat-eating” animals could keep up with the “growth-rate” of the “plant-eating” animals ……. and thus the “eatin” was plentiful and the “livin” was easy for all the animal carnivores.

            And shur nuff, ….. the “eatin” was plentiful and the “livin” was easy for all the animal carnivores ….. until such time that atmospheric CO2 ppm quantities started a drastic decline because too much of the available CO2 had been and still was being sequestered in the dead plant biomass (fossil fuels) as well as in the calcium carbonate (CaCO3) exoskeletons of long dead marine invertebrates..

            And when the atmospheric CO2 ppm quantities started a drastic decline, so did the decline in the “growth-rate” and quantities of the green plants. And when the green plant quantities started a drastic decline, so did the decline in the “growth-rate” and quantities of herbivores that depended upon said green plants. And when the “plant-eating” animal herbivore quantities started a drastic decline, so did the decline in the “growth-rate” and quantities of “meat-eating” animal carnivores. And it was the “biggest” and ”largest” of the “plant-eating” animal herbivore ….. and the “biggest” and ”largest” of the “meat-eating” animal carnivores ….. that died-off and became extinct the quickest.

            There is not enough atmospheric CO2 quantities now days, to support the growth rate of “green growing” biomass that would be necessary to support the growth rate and reproduction of extremely large “plant eating” herbivores or “meat-eating” carnivores.

            When one gets too “big” and too “hungry”, they will eventually “eat their way out of house n’ home”.

            John, …. GETTANOTHER CLUE, …… iffen current CO2 ppm decreases back to pre-industrial levels ….. then people will start dying off in mass numbers.

          • John Tillman – August 2, 2020 at 7:07 am

            BTW, dinosaurs didn’t evolve immediately after the Permian extinction, but in the Middle Triassic.

            John T, …… please cite actual, factual scientific evidence that justifies your above claim.

            GETTA CLUE, that was an intentionally posted “stupid question” because there is NWIH you can provide said. You are basing your claim on “fossil evidence” ….. and “fossil evidence” only tells you when the animal was alive, ….. not when the species evolved …… nor when the species perished.

          • Samuel,

            There are no dinosaur fossils before the Middle Triassic, and fossils from the Early Triassic show their relatives, which haven’t yet evolved charateristic dinosaur traits.

            Molecular clock studies reinforce the lesson of the rocks.

            Your evidence-free assertion that falling CO2 doomed the dinos is easily shown false. Nonavian dinos abounded in the latest Cretaceous; in the earliest Paleogene, nada, zip, zero. Same goes for a host of other groups numerous and successful right up to the period and era boundary.

            As noted, there was no shortage of CO2 in the Cretaceous. There was more than enough for all plant groups to survive and thrive.

            The catastrophic effects of the Yucatan impact are clear in the geologic as well as biologic record. Why are you so averse to reality?

            A seismically induced onshore surge deposit at the KPg boundary, North Dakota


          • John

            You are correct, the ichthyosaurs died out before K/Pg event. Paleo’ is not my strong suit. However, the mosasaurs did apparently become extinct at the same time as land dinosaurs.

            You said, “It wasn’t body plan, but size, diet and where you lived that mattered. The smallest dinosaurs, ie birds, and especially those which fed on seeds, and lived in or near water and farthest away from the impact which survived.” You said that size mattered, yet ALL dinosaurs — with the probable exception of the bird lineage — abruptly disappeared, regardless of size and diet. Small mammals survived. And sharks and many fish survived. We know that the foraging habits and diet of sharks change as they grow larger, so it is reasonable that young mosasaurs would be impacted in a manner similar to sharks and fish of their juvenile size. Neither of us were around at the time, so I’m not as confident as you that anyone knows the details of why animals in the same ecological niches as dinosaurs survived while the dinosaurs didn’t. Why is it we still have chambered nautiluses but no ammonites? How did lingula and sharks make it through all the extinction events?

          • Clyde Spencer – August 2, 2020 at 8:48 pm

            Neither of us were around at the time, so I’m not as confident as you that anyone knows the details of why animals in the same ecological niches as dinosaurs survived while the dinosaurs didn’t. Why is it we still have chambered nautiluses but no ammonites? How did lingula and sharks make it through all the extinction events?

            Clyde, the per se “experts” are not going to answer your logical questions ……. because iffen they do then you will be SMARTER than they are ….. and they couldn’t survive the thought of that.

            Logical reasoning tells me that IFFEN the Yucatan event wiped out all the large dinosaurs in one fell swoop, ……… then dinosaur fossils should be numerous and “easily found” in all locales where dinosaurs were living and breeding. Meaning most anywhere and everywhere in North and South America. And not just “bunched up” in the badland of the upper Midwest.

            “YUP”, how in ell did the avian dinosaurs (birds) and all the other surface living animals survive the “Chicxulub impactor” event, …. given the following “facts” that everyone but me believes?

            Chicxulub crater — The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. Production of carbon dioxide caused by the destruction of carbonate rocks would have led to a sudden greenhouse effect. Over a decade or longer, sunlight would have been blocked from reaching the surface of the Earth by the dust particles in the atmosphere, …..

            Everything living in “the dark”, a freezing their arses off and hungry, …. for over a decade or longer, …….. GIMME A BREAK.

          • Clyde,

            It wasn’t just size. Most birds, ie small dinos, died out with the big, non-avian ones. Those which survived weren’t just small, but seed-eaters or living far from the impact, ie on Antarctica, and sea or shore waterbirds.

            The larger land animals which survived in the Arctic were also aquatic or semi-, like croc relatives.

            No matter what group you look at, the signature of the impact is there, on land, sea and in the air. To imagine otherwise is simply perverse, so overwhelming is the evidence.

          • Samuel,

            So much error, it’s hard to know where to begin. The short version is, absolutely everything you spout is not just wrong, but laughably so.

            Dinosaurs didn’t evolve because of high CO2, but low O2. CO2 fell during the Cretaceous because of the demands of flowering plants, which in turn allowed land animals to reach the largest sizes ever.

            You’re not just wrong, but a$$backwards wrong, ie 180 degrees out, than which it isn’t possible to be more wrong. CO2 trended down during the Cretaceous because flowering plants, ie food for new, big dino groups flourished, drawing down the plant food level in the air.

            Please, before presuming to comment on paleontology, geology or any other topic, study the subject first.


            Everyone who knows anything about Mesozoic life laughs at you.

          • Dinosaurs didn’t evolve because of high CO2, but low O2. CO2 fell during the Cretaceous because of the demands of flowering plants, which in turn allowed land animals to reach the largest sizes ever.

            Brilliant, Tillman, …… utterly BRILLIANT.

            So, low ppm atmospheric O2 produced gigantic reptiles whereas high ppm atmospheric O2 produced gigantic insects. ……. I BELIEVE, …… I BELIEVE.

            And the flowering plants were sucking up the atmospheric CO2 far, far, faster than the ocean ‘outgassing’ could replenish it. ……. I BELIEVE, ……Tillman, …… I BELIEVE.

            I think I dun fergetted that flowering plants outgas O2 as a waste product of their metabolism. Inhaling CO2, …… exhaling O2, ….. a miracle of science, no less.

            Tillman, its obvious to me that you actually believe that anthropogenic activities are the root cause of the current increases in atmospheric CO2 ppm.

            “A mind is a terrible thing to waste.”

          • John Tillman – August 3, 2020 at 3:59 pm

            CO2 trended down during the Cretaceous because flowering plants, …. ie food for new, big dino groups flourished, ….. drawing down the plant food (CO2) level in the air.

            David Middleton, in that you chimed in with a scientific video to assist John Tillman in explaining to us uneducated how fast the current CO2 ppm is decreasing because of all the increased food production, I say “Thank You”.

            YUP, what was good for the dinosaur’s survival (more food growth) is also good for human survival …… and it gets that nasty ole CO2 out of the air and back down to preindustrial levels..

          • John Tillman – August 3, 2020 at 3:59 pm

            CO2 fell during the Cretaceous because of the demands of flowering plants,

            Sorry, Johnny boy, ….. about your “100 million year error”, to wit:

            An uninterrupted sequence of fossilized pollen from flowers begins in the Early Cretaceous, approximately 140 million years ago, and it is generally assumed that flowering plants first evolved around that time.But the present study documents flowering plant-like pollen that is 100 million years older, implying that flowering plants may have originated in the Early Triassic (between 252 to 247 million years ago) or even earlier.

            “HA”, …… may have originated in the Early Triassic, HUH?

            And when did the “Age of the Dinosaurs” commence, ……. Johnny boy Tillman?

      • Picky, picky, picky!

        Please get with the post-modern science program. We don’ need no stinkin’ evidence!

      • To account for supposed extinctions, an airburst comet would need to be a million times more massive than the Tugnuska bolide.

        The necessary chemical signature of such an event does not exist. It’s pure fantasy, without a shred of real physical evidence.

    • The idea that warming might occur with a meteor impact on the ice shield makes sense and would indicate that the meteor hit first, warmed the climate, and finally the Earth went back to the normal business of a Glacial period. It then came out of it on its own as the normal move into an Interglacial period. This makes much more sense, as if the meteor threw us back into glacial conditions and the world wanted to be warmer, it would have done so faster. Things can heat up much faster than they cool down, mostly just by radiation.

    • It was the outflow of ice sheet meltwater and icebergs into the Arctic Ocean for 700 years after the onset of the YD, followed by the knock-on effects of this sustained cold, fresh water input on the AMOC.

      Please see below. Search for “MacKenzie”. Thanks!

      BTW, my dad in the 1930s traversed the MacKenzie region by Ford Tri-Motor. I grew up on tales of the Great White North. So self-serving Commie academics can’t pull the musk ox wool over my near-sighted eyes!

      • BTW, my dad in the 1930s traversed the MacKenzie region by Ford Tri-Motor. I grew up on tales of the Great White North. So self-serving Commie academics can’t pull the musk ox wool over my near-sighted eyes!

        Don’t be talking trash, John T, ……… because all of those self-serving Commie academics are great fans of Jack London and have read all of his novels about ….. the Great White North.

        And we both know that Jack knew more than your father did. 😊

        • Jack cicn’t know jack when it came to politics. He was a racist socialist, who didn’t even spend much time in the North, ie late 1897 to early 1898.

          My dad preferred Robert Service.

          • The Cremation of Sam McGee
            Robert W. Service – 1874-1958
            There are strange things done in the midnight sun
            By the men who moil for gold;
            The Arctic trails have their secret tales
            That would make your blood run cold;
            The Northern Lights have seen queer sights,
            But the queerest they ever did see
            Was that night on the marge of Lake Lebarge
            I cremated Sam McGee

            Now Sam McGee was from Tennessee,
            where the cotton blooms and blows
            Why he left his home in the South to roam
            ’round the Pole, God only knows.
            He was always cold but the land of gold
            seemed to hold him like a spell;
            Though he’d often say in his homely way
            that he’d sooner live in Hell.

            On a Christmas Day we were mushing our way
            over the Dawson trail.
            Talk of your cold! through the parka’s fold
            it stabbed like a driven nail.
            If our eyes we’d close, then the lashes froze
            till sometimes we couldn’t see,
            It wasn’t much fun, but the only one
            to whimper was Sam McGee.

            And that very night, as we lay packed tight
            in our robes beneath the snow,
            And the dogs were fed, and the stars o’erhead
            were dancing heel and toe,
            He turned to me, and “Cap”, says he
            “I’ll cash in this trip, I guess;
            And if I do, I’m asking that you
            won’t refuse my last request.”

            Well, he seemed so low that I couldn’t say no;
            then he says with a sort of moan,
            “It’s the cursed cold, and it’s got right hold
            till I’m chilled clean through to the bone
            Yet ‘taint being dead-it’s my awful dread
            of the icy grave that pains;
            So I want you to swear that, foul or fair,
            you’ll cremate my last remains.

            A pal’s last need is a thing to heed,
            so I swore I would not fail;
            And we started on at the streak of dawn
            but God! he looked ghastly pale.
            He crouched on the sleigh, and he raved all day
            of his home in Tennessee;
            And before nightfall a corpse was all
            that was left of Sam McGee.

            There wasn’t a breath in that land of death,
            and I hurried, horror-driven
            With a corpse half hid that I couldn’t get rid,
            because of a promise given;
            It was lashed to the sleigh, and it seemed to say.
            “You may tax your brawn and brains,
            But you promised true, and it’s up to you
            to cremate these last remains”.

            Now a promise made is a debt unpaid,
            and the trail has its own stern code,
            In the days to come, though my lips were dumb
            in my heart how I cursed that load!
            In the long, long night, by the lone firelight,
            while the huskies, round in a ring,
            Howled out their woes to the homeless snows–
            Oh God, how I loathed the thing!

            And every day that quiet clay
            seemed to heavy and heavier grow;
            And on I went, though the dogs were spent
            and the grub was getting low.
            The trail was bad, and I felt half mad,
            but I swore I would not give in;
            And I’d often sing to the hateful thing,
            and it hearkened with a grin.

            Till I came to the marge of Lake Lebarge,
            and a derelict there lay;
            It was jammed in the ice, but I saw in a trice
            it was called the Alice May,
            And I looked at it, and I thought a bit,
            and I looked at my frozen chum;
            Then “Here”, said I, with a sudden cry, “is my

            Some planks I tore from the cabin floor
            and I lit the boiler fire;
            Some coal I found that was lying around,
            and I heaped the fuel higher;
            The flames just soared, and the furnace roared
            such a blaze you seldom see,
            And I burrowed a hole in the glowing coal,
            and I stuffed in Sam McGee.

            Then I made a hike, for I didn’t like
            to hear him sizzle so;
            And the heavens scowled, and the huskies howled,
            and the wind began to blow,
            It was icy cold, but the hot sweat rolled
            down my cheeks, and I don’t know why;
            And the greasy smoke in an inky cloak
            went streaking down the sky.

            I do not know how long in the snow
            I wrestled with grisly fear;
            But the stars came out and they danced about
            ere again I ventured near;
            I was sick with dread, but I bravely said,
            “I’ll just take a peep inside.
            I guess he’s cooked, and it’s time I looked”.
            Then the door I opened wide.

            And there sat Sam, looking cool and calm,
            in the heart of the furnace roar;
            And he wore a smile you could see a mile,
            and he said, “Please close that door.
            It’s fine in here, but I greatly fear
            you’ll let in the cold and storm–
            Since I left Plumtree, down in Tennessee,
            it’s the first time I’ve been warm”.

            There are strange things done in the midnight sun
            By the men who moil for gold;
            The Arctic trails have their secret tales
            That would make your blood run cold;
            The Northern Lights have seen queer sights,
            But the queerest they ever did see
            Was that night on the marge of Lake Lebarge
            I cremated Sam McGee.

          • Sorry again about the typos. Should never post on my phone. Dad’s favorite:

            The Shooting of Dan McGrew
            BY ROBERT W. SERVICE
            A bunch of the boys were whooping it up in the Malamute saloon;
            The kid that handles the music-box was hitting a jag-time tune;
            Back of the bar, in a solo game, sat Dangerous Dan McGrew,
            And watching his luck was his light-o’-love, the lady that’s known as Lou.

            When out of the night, which was fifty below, and into the din and the glare,
            There stumbled a miner fresh from the creeks, dog-dirty, and loaded for bear.
            He looked like a man with a foot in the grave and scarcely the strength of a louse,
            Yet he tilted a poke of dust on the bar, and he called for drinks for the house.
            There was none could place the stranger’s face, though we searched ourselves for a clue;
            But we drank his health, and the last to drink was Dangerous Dan McGrew.

            There’s men that somehow just grip your eyes, and hold them hard like a spell;
            And such was he, and he looked to me like a man who had lived in hell;
            With a face most hair, and the dreary stare of a dog whose day is done,
            As he watered the green stuff in his glass, and the drops fell one by one.
            Then I got to figgering who he was, and wondering what he’d do,
            And I turned my head — and there watching him was the lady that’s known as Lou.

            His eyes went rubbering round the room, and he seemed in a kind of daze,
            Till at last that old piano fell in the way of his wandering gaze.
            The rag-time kid was having a drink; there was no one else on the stool,
            So the stranger stumbles across the room, and flops down there like a fool.
            In a buckskin shirt that was glazed with dirt he sat, and I saw him sway;
            Then he clutched the keys with his talon hands — my God! but that man could play.

            Were you ever out in the Great Alone, when the moon was awful clear,
            And the icy mountains hemmed you in with a silence you most could hear;
            With only the howl of a timber wolf, and you camped there in the cold,
            A half-dead thing in a stark, dead world, clean mad for the muck called gold;
            While high overhead, green, yellow and red, the North Lights swept in bars? —
            Then you’ve a hunch what the music meant. . . hunger and night and the stars.

            And hunger not of the belly kind, that’s banished with bacon and beans,
            But the gnawing hunger of lonely men for a home and all that it means;
            For a fireside far from the cares that are, four walls and a roof above;
            But oh! so cramful of cosy joy, and crowned with a woman’s love —
            A woman dearer than all the world, and true as Heaven is true —
            (God! how ghastly she looks through her rouge, — the lady that’s known as Lou.)

            Then on a sudden the music changed, so soft that you scarce could hear;
            But you felt that your life had been looted clean of all that it once held dear;
            That someone had stolen the woman you loved; that her love was a devil’s lie;
            That your guts were gone, and the best for you was to crawl away and die.
            ‘Twas the crowning cry of a heart’s despair, and it thrilled you through and through —
            “I guess I’ll make it a spread misere”, said Dangerous Dan McGrew.

            The music almost died away … then it burst like a pent-up flood;
            And it seemed to say, “Repay, repay,” and my eyes were blind with blood.
            The thought came back of an ancient wrong, and it stung like a frozen lash,
            And the lust awoke to kill, to kill … then the music stopped with a crash,
            And the stranger turned, and his eyes they burned in a most peculiar way;
            In a buckskin shirt that was glazed with dirt he sat, and I saw him sway;
            Then his lips went in in a kind of grin, and he spoke, and his voice was calm,
            And “Boys,” says he, “you don’t know me, and none of you care a damn;
            But I want to state, and my words are straight, and I’ll bet my poke they’re true,
            That one of you is a hound of hell. . .and that one is Dan McGrew.”

            Then I ducked my head, and the lights went out, and two guns blazed in the dark,
            And a woman screamed, and the lights went up, and two men lay stiff and stark.
            Pitched on his head, and pumped full of lead, was Dangerous Dan McGrew,
            While the man from the creeks lay clutched to the breast of the lady that’s known as Lou.

            These are the simple facts of the case, and I guess I ought to know.
            They say that the stranger was crazed with “hooch,” and I’m not denying it’s so.
            I’m not so wise as the lawyer guys, but strictly between us two —
            The woman that kissed him and — pinched his poke — was the lady that’s known as Lou.

  2. In reply to:

    “No one really knows what drove the Dansgaard–Oeschger and Heinrich cycles… ”

    The verb tense used for the word ‘drove’ implies that a Heinrich event would not happen again. For some unexplained reason Heinrich events come after the warmest Dansgaard-Oeschger ‘events’

    Got like that these guys named the abrupt planetary changes after themselves…. So it looks like we are currently experience a Dansgaard-Oeschger warming.

    Drove as opposed to what drives… Cyclic events are cyclic because they are driven/caused by something that is powerful and cyclic.

    We know that the largest increase atmospheric C14 atmosphere, in the last 13,000 years occurred at the same time of the Younger Dryas YD (see linked to YD summary paper below).

    The physical cause of the abrupt increase in C14 at the time of the Younger Dryas is “The Gothenburg Magnetic Excursion” which is a very, large, abrupt unexplained change in the North Polar region of the magnetic field.

    The magnetic field shields the planet from high speed cosmic particles. When the geomagnetic field is weaker there is more C14 produced by the cosmic particles striking Nitrogen.

    The YD event is abrupt cooling of the northern hemisphere and some cooling the Southern hemisphere, interglacial warm to cold with 70% of the cooling occuring in a decade and then the planet remains cold for 1200 years and then warms.

    The continental ice sheets returned to cover large portions of the UK and Northern Europe and Canada for example. If I remember correctly the UK had average temperature of -3C during the YD and had an average temperature before the YD cooling similar today.

    These abrupt changes to the geomagnetic in the North Region occur periodically and come in a small, medium, and large abrupt changes to the geomagnetic field.

    The Gothenburg Magnetic Excursion is a large geomagnetic field excursion that happened for no explanation.

    The sudden abrupt weaking ot the magnetic field in a region increases the amount of cosmic particles that strike that region.

    And there are large very, hot burn marks ….

    at 18 different locations in the Northern Hemisphere on different continents and at different latitudes on the continents ….the burn marks correlate in time with occurrence of the YD, abrupt cooling for 1200 years.

    And the geomagnetic field abruptly changed at the same time the planet abruptly cooled for 1200 years.

    The Gothenburg Magnetic Excursion
    The Gothenburg Magnetic Excursion in a broad sense ranges from 13,750 to 12,350 years BP and ends with the Gothenburg Magnetic Flip at 12,400−12,350 years BP (= the Fjärås Stadial in southern Scandinavia) with an equatorial VGP position in the central Pacific.

    The Gothenburg Magnetic Flip is recorded in five closely dated and mutually correlated cores in Sweden.

    In all five cores, the inclination is completely reversed in the layer representing the Fjärås Stadial dated at 12,400−12,350 years BP.

    The cores were taken 160 km apart and represent both marine and lacustrine environments.

    The Gothenburg Magnetic Flip represents the shortest excursion and the most rapid polar change known at present. It is also hitherto the far best-dated paleomagnetic event. The Gothenburg Magnetic Excursion and Flip are proposed as a standard magnetostatigraphic unit.

    This is a good review paper of the Younger Dryas cooling event. The dead theory to explain the YD event is the fresh water melt water pulse. The largest melt water pulse occurred a 1000 years before the YD cooling which proved that the YD cooling and other cyclic ‘Heinrich’ Events are not caused by melt water pulses as there as no cooling then in the paleo record.

    And come on. A melt water pulse could not cause cooling for 1200 years, burn marks, and abrupt changes to the geomagnetic field.

    Reduced solar activity as a trigger for the start of the Younger Dryas?

    This paper is a good review of the data concerning the Younger Dryas. It is interesting to look at the development of the different hypotheses and mechanisms from a scientific historical standpoint as well as pure science. The authors postulated TSI variance mechanism is not correct.

    • Re William Astley
      August 1, 2020

      Many thanks. I’ve been wondering about the YD for a long time. Although I could understand how any of the proposed mechanisms could cause the temperature to drop suddenly, I could see no way the temperature would stay lower for 1300 years and then suddenly rise again.

      All is now clear: the day has not been wasted. I have learned something!

      • It happens in every glaciation and deglaciation. During the latter however (terminations), the cold snaps in the melting trend don’t always last that long. Depends upon the ice mass and insolation, controlled by Milankovitch cycles.

        • John,

          The YD abrupt cooling event, interglacial warm to glacial cold, with 70% of the cooling occuring in a decade and the cooling lasting for 1200 years, …..

          Occurred 13,900 years ago, at a time when summer solar insolation at 65N was maximum. This was during the interglacial period. And these Heinrich events are cyclic.

          The YD event has zero do with summer solar insolation at 65N…..

          The YD paradox is only one of a dozen paradoxes for Milankovitch’s dead theory. Dead theories are not part of the solution.

          This is a link to one of the new observations in the last 5 years, that prove that both hemispheres are warming and cooling in phase, at the same time, rather than out of phase warming and cooling….

          Where one hemisphere warms while the other cools.

          The orbital changes cause insolation changes that warm one hemisphere and cool the other in the summer, cause out of phase forcing in summer, so summer solar insolation at 65N is not the mechanism that is causing the glacial/interglacial cycle.

          There are more than a dozen paradoxes (observations that cannot be explained by Milankovitch’s theory.)

          The following is a partial list of some of the problems with the theory.

          1) The observational effects that are found in the paleo record is physically impossible for changes in solar insolation at 65N to explain. The paleo record shows cyclic temperature changes that correlate with cosmogenic and geomagnetic excursions, such as the YD abrupt cooling correlating with the Gothenburg Magnetic Excursion.

          The effect in the climate record is an order of magnitude too high and there is evidence of abrupt change, both hemispheres (same periodicity) not gradual change.

          Glacial records depict ice age climate in synch worldwide

          “Because the Earth is oriented in space in such a way that the hemispheres are out of phase in terms of the amount of solar radiation they receive, it is surprising to find that the climate in the Southern Hemisphere cooled off repeatedly during a period when it received its largest dose of solar radiation,” says Singer. “Moreover, this rapid synchronization of atmospheric temperature between the polar hemispheres appears to have occurred during both of the last major ice ages that gripped the Earth.”

          2) Unexplained change from a 41,000 year cycle to 100,000 year cycle. How does one explain the observation that the glacial/interglacial cycles started with a cycle periodicity of 41,000 years in duration and then 1.6 millions ago the cycle time changed to a cycle of 100,000 years (90,000 years glacial and 10,000 years interglacial.)

          2) Orbital eccentricity is the weakest of the orbital cycle modulation on insolation. Why does it dominate for the last 1.6 million years?

          3) The stage 5 glacial was terminated 10,000 years before the insolation change. There is no cause for that change. There is no back up forcing mechanism to terminate glacial periods.

          4) There is evidence in the paleo climate data of cyclic abrupt climate change. (Heinrich events, such as the 12,900 years BP Younger Dryas abrupt cooling event.) There is no forcing mechanism that explains the cyclic abrupt climate changes. The Younger Dryas abrupt cooling event occurred when summer solar insolation at 65N was maximum.

          5) The glacial and interglacial periods end abruptly. The paleo record supports the assertion that the mysterious cyclic abrupt climate forcing function terminates both the glacial and interglacial period.

          6) The cycle abrupt climate change cools both the Southern Hemisphere and the Northern hemisphere synchronously. This does not make sense at the Southern Hemisphere has maximum insolation in the summer when the Northern Hemisphere has minimum insolation in the summer.

          • Of course deglaciation cooling events occur when insolation is high. That’s what causes the ice sheets to melt. Then the meltwater and icebergs interrupt the AMOC, causing abrupt cooling. The sun still shines the ice, melting it, but the oceans are cooled off. Lower SSTs lead to colder temperatures, and a feedback loop with atmospheric circulation, despite continued high insolation.

            Heinrich Events during glacial intervals are caused by surges of icebergs, caused by growth of the ice sheets.

          • The AMOC changes also explain the polar seesaw effect. There’s a lot of recent literature on the subject.

          • William Astley posted: “The YD paradox is only one of a dozen paradoxes for Milankovitch’s dead theory. Dead theories are not part of the solution.”

            Correct me if I’m wrong on this, but I do not believe that at any time Milutin Milkovitch stated, or even implied, that other cosmic (e.g., massive asteroid impacts) or geological events (e.g., plate tectonics) could not create climate perturbations equal to or greater than any of his proposed long-term orbital parameters that he asserted drive of Earth’s climate over eons.

          • Gordon,


            But few climatological hypotheses are better supported than the Milankovitch parameter control of glacial cycles. Maybe none.

            As “theories” go, it’s alive and kicking. No one has laid a glove on it fundamentally, but it just keeps getting more and more confirmation and clarification. As with all good science, it’s always subject to refinement and improvement.

          • The YD paradox is only one of a dozen paradoxes for Milankovitch’s dead theory.

            You got it all wrong. There is no YD mystery. It is just the last of a chain of frequent temperature reversals during glacial periods. And Milankovitch theory is very much alive and kicking. Misunderstood and bastardized by lesser minds the original theory of Milankovitch has no problem explaining the timing of interglacials.

            2) Unexplained change from a 41,000 year cycle to 100,000 year cycle.

            Should be number one. It is not unexplained. Interglacials still occur at the 41,000 year beating. It is just that the planet got too cold, the northern ice sheets got out of the Arctic into mid-latitudes and it became so hard to melt them in the time allowed by obliquity that it required the help from precession that does depend on eccentricity, and interglacials started skipping one or even two obliquity oscillations giving the appearance of a 100-kyr cycle when it is still a 41, 82 or 123 kyr occurrence. To see it you just have to shift the temperature data by 6500 years with respect to the astronomical data, which is the time that it takes the oceans to equilibrate to the astronomical forcing and presto:

            5) The glacial and interglacial periods end abruptly.

            Interglacials end progressively over about 5-7,000 years while glacial periods end in 3-4,000 years. Abrupt is just a word so it depends how you define it.

            The orbital changes cause insolation changes that warm one hemisphere and cool the other in the summer, cause out of phase forcing in summer, so summer solar insolation at 65N is not the mechanism that is causing the glacial/interglacial cycle.

            Of course not, because as I said the heavy work is done by obliquity that is symmetrical over the planet. Precession, responsible for summer solar insolation, does secondary work. Almost everybody has this wrong. It is a deeply ingrained mistake of the kind that delays science for decades. One really needs to think out of the box to understand the glacial cycle. Some authors are doing that, notably Peter Huybers.

          • Javier,

            I’m of your tilt school as the most important Milankovitch parameter.

            I agree that the Mid-Pleistocene Transition didn’t abolish the 41 Ka tilt cycle. Rather, glaciations after it survived the first tilt cycle with an interstadial, to continue on to a second or third such cycle. Hence the apparent ~100 K year glacial duration, an average of 82 and 123 K years.

            This pattern shows up pretty clearly in GISP and other cores and proxies.

          • In reply to John Tillman’s comment: The AMOC changes also explain the polar seesaw effect. There’s a lot of recent literature on the subject.

            You just make stuff up. There is no discrete world ocean conveyor. Wally drew a picture and then when measurements where made it was found there is no discrete conveyor.

            And a complete stoppage of the North Atlantic drift current is not sufficient to cause the YD abrupt cooling.

            This paper explains and runs a atmospheric ocean model that disproves the melt pulse theory based on the maximum change that event could cause.


            Is the Gulf Stream responsible for Europe’s mild winters?

            Most of the winter warming of Europe is from solar heating the Atlantic ocean at the same latitude. The summer heating of the Atlantic is released in the winter and is carried by the west to east winds.

            The Polar See Saw cannot be explained by ocean currents because Greenland Ice sheet temperatures are changing in sync but out of phase with the Antarctic ice sheet for the small temperature changes and in phase for the large temperature changes.

            Svensmark shows in the attached paper that a mechanism that modulates (increases and decreases) planetary cloud cover (high latitude regions) will cause warming in the Arctic and cooling on the Antarctic ice sheet….

            … because the albedo of the surface of the Antarctic ice sheet, is higher (more reflective) than the top of white clouds. He got data from satellites to prove that.

            Comment: The reason why this is true, is the very high speed winds over the Antarctic ice sheet, breaks the ice crystals, which creates an ice like reflective surface.

            Svensmark explains the mechanism that explains the polar see-saw in the attached paper and provides data …

            Which proves the sun is modulating planetary cloud cover (sun) high latitudes both poles.

            And a reduction in cloud cover causes warming in the Northern hemisphere and cooling over the Antarctic ice sheet.


            The Antarctic climate anomaly and galactic cosmic rays

            …If changes in cloudiness play a part in climate change, their effect changes sign in Antarctica. Satellite data from the Earth Radiation Budget Experiment (ERBE) are here used to calculate the changes in surface temperatures at all latitudes, due to small percentage changes in cloudiness. The results match the observed contrasts in temperature changes, globally and in Antarctica. Evidently clouds do not just respond passively to climate changes but take an active part in the forcing, in accordance with changes in the …

            Borehole temperatures in the ice sheets spanning the past 6000 years show Antarctica repeatedly warming when Greenland cooled, and vice versa (Fig. 1) [13, 14]. North-south oscillations of greater amplitude associated with Dansgaard-Oeschger events are evident in oxygenisotope data from the Wurm-Wisconsin glaciation[15]. The phenomenon has been called the polar see-saw[15, 16], but that implies a north-south symmetry that is absent. Greenland is better coupled to global temperatures than Antarctica is, and the fulcrum of the temperature swings is near the Antarctic Circle. A more apt term for the effect is the Antarctic climate anomaly.

            Attempts to account for it have included the hypothesis of a south-flowing warm ocean current crossing the Equator[17] with a built-in time lag supposedly intended to match paleoclimatic data. That there is no significant delay in the Antarctic climate anomaly is already apparent at the high-frequency end of Fig. (1). While mechanisms involving ocean currents might help to intensify or reverse the effects of climate changes, they are too slow to explain the almost instantaneous operation of the Antarctic climate anomaly.

            Figure (2a) also shows that the polar warming effect of clouds is not symmetrical, being most pronounced beyond 75◦S.

            In the Arctic it does no more than offset the cooling effect, despite the fact that the Arctic is much cloudier than the Antarctic (Fig. (2b)). The main reason for the difference seems to be the exceptionally high albedo of Antarctica in the absence of clouds.

          • There is no single forcing that abruptly shifts between glacial/interglacial, it’s stochastic resonance.

          • William,

            If you seriosuly believe that I’ve just made up the ocean conveyor, then there is nothing I can say to you, but please, take your meds.

          • William,

            I made nothing up. Please read the papers I cited.

            The meltwater which caused the YD didn’t stop the Gulf Stream. You clearly don’t understand the AMOC and how meltwater affects it.

            The YD is just another cold snap, like Heinrich events, but in a deglaciation.

    • “Burn marks” don’t correlate in time with the YD. They occur throughout time. No correlation.

      There is no valid evidence in support of the YDIH.

      The meltwater and iceberg floods from the MacKenzie drainage into the Arctic Ocean lasted 700 years. Its effect on the AMOC endured for another 500 years.

      The double flooding of the Bering Strait is just further evidence for the reality of this uninterrupted flow of cold, fresh water, not just a pulse.

      • Should have said “no correlation with just the YD”, although the correlation isn’t very good. Cold spells are drier, and have more fires.

        • That icebergs and meltwater cause Heinrich Events and deglaciation stadials like the Dryases can be considered settled, but there is always more to figure out. Even after astronomers accepted the reality of the Copernican heliocentric model, some persisted with Aristotelean perfectly circular orbits, until and even after Kepler showed them elliptical.

          • That icebergs and meltwater cause Heinrich Events and deglaciation stadials like the Dryases can be considered settled

            That is not what the bibliography reflects. There is a lot of controversy over these issues. Personally I find the meltwater explanation the typical arm-waving explanation, as the evidence that meltwater events took place when they are required by the hypothesis is very weak. Regarding the icebergs, it is clear that they are the cause of the ice-rafted debris, but it is not clear if they are the cause or the consequence of the Heinrich events.

            In fact meltwater pulses 1a and 1b take place at the wrong time to explain the YD. The evidence seems to indicate that Meltwater pulse 1b is a lagged response to the warming that put an end to the YD.
            Abdul et al., 2016. Younger Dryas sea level and meltwater pulse 1B recorded in Barbados reef crest coral Acropora palmata.

          • As far from arm-waving as can possibly be.

            The effects on the AMOC of meltwater delivered to the Fram Strait is as explicit and testable as it gets. Why concentrate on the bibliography, when the data provided in the paper is the point?

            The IRD is deposited by the Heinrich Events. The IRD is how they were discovered.

            The meltwater pulses aren’t responsible for the YD. That’s the point. Some even doubt there was a 1b. It doesn’t matter. The YD was caused by a continuous stream of meltwater and icebergs from the MacKenzie, not by the one or two pulses.

            Please read the paper. Then please read those which cite it. The discovery of this outflow expains the previously mysterious apparent double inundation of the Bering Strait.

          • The effects on the AMOC of meltwater delivered to the Fram Strait is as explicit and testable as it gets. Why concentrate on the bibliography, when the data provided in the paper is the point?

            Do you mean the Tarasov & Peltier, 2005 paper? You’ve got to be kidding me. That paper is based on computer simulations, not data.
            “Here we analyse an ensemble of simulations of the drainage chronology of the North American ice sheet in order to identify the geographical release points of freshwater forcing during deglaciation.”
            Is this your settled science? Computer simulations?

            The YD was caused by a continuous stream of meltwater and icebergs from the MacKenzie

            Where is the evidence for that? And if it was a continuous stream and not a pulse why the YD had a more or less abrupt start and not a progressive cooling, and why did the YD stop when there was meltwater all the way to several millennia within the Holocene from the melting ice sheets.

            The huge problem with the meltwater hypothesis is that to cause a cooling that lasted 1200 years the amount of freshwater that should have been added to the sea should be sufficient to elevate the sea level by 32 meters. In sharp contrast sea level rise during the YD actually decreased to about half of its previous rate probably due to the cooling. Sea level rise during YD was minimal.

            You should read Carlson & Clark, 2012, Ice sheet sources of sea level rise and freshwater discharge during the last deglaciation. Their chapter 9 is dedicated to North American freshwater discharge and the YD cold event. They don’t appear to be particularly keen on your MacKenzie hypothesis, so settled science it is not.

            Yes, Meltwater pulse 1 was before the YD.

            MWP 1A was about 1000 years before the YD and MWP 1B was about 200 years after the YD. You have them represented in figure 2 of the Tarasov & Peltier, 2005, paper.

          • Javier,

            I refer to the 2018 paper by Keigwin, et al. Tarasov and Peltier, 2005, just came up with the idea. Keigwin provides the evidence.

            Please read it.

    • There are long cycles in ocean circulation which should have some effect on the climate. On the other hand there are really long convection cycles in the Earth’s mantle.

      Speeds can be faster for small-scale convection occurring in low-viscosity regions beneath the lithosphere, and slower in the lowermost mantle where viscosities are larger. A single shallow convection cycle takes on the order of 50 million years, though deeper convection can be closer to 200 million years. link

      I think the probability of something with a tens of thousands of years cycle somewhere in the Earth system is rather high.

    • Hi William
      How does the galactic current sheet as part of the galactic magnetic field interact with the earth’s magnetic field? Since the current sheet “passes” through the earth every 12K years or so and coincides with the Gothenberg and other excursions, this iinversion of the magnetic poles, coupled with solar emissions could explain a lot of the paradoxes. Earth’s position in the cosmos obliges it to undergo all kinds of changes.

      • The “inversion of the magnetic poles” last occurred about 773,000 years ago.

        Gulf of Mexico Neogene Astronomically
        Tuned Time Scale 2018 with Ceara
        Rise-Western Equatorial Atlantic, ODP
        Leg 154, Shackelton and Crowhurst
        (1997) emended

        The Younger Dryas and other 24-25 Greenland stadials occurred between ~90,000 and ~12,000 years ago.

  3. I researched this as a possible example for ebook The Arts of Truth. Ultimately did not make the book. Neither the volcano nor the impact hypothesis are viable explanations for the ~1300 year long Younger Drias.
    Stratospheric Volcanic aerosols wash out after about 18 months-2 years (e.g. Pinatubo). Ifvthey don’t reach the stratosphere they was out in less than 4 weeks. Zero evidence For a sequence of more than 500 >VEI5 eruptions in that time interval. (Need a VEI5 or 6 to reach the stratosphere.)

    The alternative bolide impact theory fails for a different reason. The claimed soot and other stuff from an impact have radiocarbon dates varying by about 800 years depending on where the sample came from. Fail.

    The probable explanation is that vast Lake Agassiz (formed from meltwater from the Laurentide Ice Sheet over Canada) eventually burst thru the ice in what is now the St.Laurence Seaway and drained over decades into the Atlantic. We know this happened from scour in the seaway geology and from the very large debris fan outside its mouth on the sea floor. The remnants of vast Lake Agassiz are the Great Lakes. It is thought the massive pulse of cold freshwater disrupted the Atlantic current and the Gulf Stream, both of which move warm salt water north. It took the North Atlantic about a thousand years to start circulating ‘normally’ again.

    • Not the St. Lawrence Seaway. Please see my comment when it appears.

      MacKenzie River into the Arctic Ocean.

      • Lake Agassiz also drained via the Mississippi and Hudson Bay at different times during the melt, depending on the state of the lake level and local isostatic rebound, which would have different outlets at different times, some simultaneous in some circumstance when conditions were right including to the Arctic as you say via the Mackenzie River. So we have at least 4 different outlets to Lake Agassiz, probably over different times at the start of the latest melt and numerous glaciations the last 2.6 million years. The big ones would have been via the St. Lawrence to the Atlantic IMHO, as that seems to have the largest geological cut with a lot of water moving at once. And would have had the biggest impact on the Gulf Stream, as compared to to cold Lake Agassiz fresh water dumping into a colder Arctic Ocean. This seems too be the only credible explanation for the rather recent YD event and possibly earlier events. As the scablands show in eastern Wa State, these flood releases happen regularly when the conditions are ripe to develop.

        If there had been an impact event of the scale required to cause the YD, you would think there would be scads of evidence to indicate that. I used to believe that, until all you convinced me the last 7 years that there is no major evidence for a bolide impactor.

        • Nor any need for such an impact to explain the YD.

          Scientific of you to change your mind, based upon evidence! Too bad not all “scientists” do the same.

          Glaciations, deglaciations and interglacials are all different, but share certain traits, especially since the Mid-Pleistocene Transition.

          • Of course the pseudoscientists’ professional rice bowl depends upon maintaining their blatantly false narrative until retirement.

  4. This is unmitigated horst schist…

    The verb tense used for the word ‘drove’ implies that a Heinrich event would not happen again…

    We have no way to know if Dansgaard-Oeshger and Heinrich events occurred during previous glacial stages or if they will occur in future glacial stages. The periodicity simply indicates that the underlying driver was periodic. It implies nothing about prior or future glacial stages. The fact that the current interglacial stage exhibits its own roughly 1,000 yr periodicity suggests that some version of that periodic driver may still be operating.

    • They did. Since they’re beyond 14C age range, other proxies must be employed, like stalagmites, marine and lacustrine sediment cores, foram ratios, alkenones, varves, raised beaches, etc.

      There is a lot of literature on D/O events as well as Heinrich events in previous glaciations and deglaciations (terminations).

    • The warming and cooling cycle is occurring in both hemispheres and using the Antarctic ice sheet and Antarctic peninsula ice cores data has been shown to have occurred over two and half glacial cycles, for 250,000 years.

      Antarctic Survey ( Nature , 2012, doi:10.1038/nature11391),reports two recent natural warming cycles, one around 1500 AD and another around 400 AD, measured from isotope (deuterium) concentrations in ice cores bored adjacent to recent breaks in the ice shelf in northeast Antarctica. …

      And the periodicity of warming and cooling in the southern hemisphere is the same periodicity as the northern hemisphere.

      The Antarctic peninsula juts out of the Antarctic Polar vortex, so its temperature matches the rest of the high latitude Southern hemisphere temperatures.

      The paper quoted below notes there has been 342 natural warming periods in the Southern Hemisphere, all of which were followed by cooling periods, in the last 250,000 years in the Antarctic Peninsula ice sheet data.

      The periodicity of the southern hemisphere warming and cooling is the same as the periodicity of the northern hemisphere which points to same forcing function (it is the sun).

      Davis and Taylor: “Does the current global warming signal reflect a natural cycle”

      …We found 342 natural warming events (NWEs) corresponding to this definition, distributed over the past 250,000 years …. …. The 342 NWEs contained in the Vostok ice core record are divided into low-rate warming events (LRWEs; < 0.74oC/century) and high rate warming events (HRWEs; ≥ 0.74oC /century) (Figure). … …. "Recent Antarctic Peninsula warming relative to Holocene climate and ice – shelf history" and authored by Robert Mulvaney and colleagues of the British Antarctic Survey ( Nature , 2012, doi:10.1038/nature11391),reports two recent natural warming cycles, one around 1500 AD and another around 400 AD, measured from isotope (deuterium) concentrations in ice cores bored adjacent to recent breaks in the ice shelf in northeast Antarctica. ….

      And there is proxy method to get very accurate temperature data from measuring the temperature of ice at depth insulated so the temperature measured is the ice temperature at depth. The ice temperature retains is correlation to the temperature when the ice formed for around 10,000 years.

      Svensmark used ice core temperature measure from the Greenland and Antarctic ice sheets to prove that changes in cloud cover are the direct cause of the Greenland and Antarctic ice sheets.

      A change in the solar cycle could explain duration temperature changes 60 to 100 year cycles.

      That mechanism cannot explain the 1200 year YD abrupt cooling. An abrupt change to the geomagnetic field can explain long term changes to cloud cover and…

      There was a very large geomagnetic field excursion, when the YD occurred.

      A large sudden forcing of the geomagnetic field initially will produce a resisting EMF generated current that absolutely tries to resists the forcing field change. The forcing field change stops.

      Overtime currents are generated that enables the total disturbed geomagnetic field to integrate the sudden change. After integration the geomagnetic field gets either stronger or weaker depending on the location and hemisphere where the majority of the forcing is occurring.

      This must be so as the geomagnetic field is roughly three times stronger in intensity during the interglacial than in the glacial period and the geomagnetic field is also changing at a 41 year cycle.

  5. I am now more confused than my daily average. The various events chronologically associated with the Younger Dryas don’t seem to be themselves correlated. Having said that I am a firm believer that life during a magnetic reversal, while the deflection mechanism is weak, will be precarious for humans and other mammals. We’ll see.

    • More and more we are learning that animals, for example honeybees, navigate by build-in magnetic compasses. A pole reversal must to quite a biological disturbance.

  6. I find it fascinating that Dansgaard–Oeschger events basically STOPPED after the Younger-Dryas. The plots sort of look like the 8.2 KYA Cooling event was ‘an attempt’ (so to speak) of renewing the cooling, yet didn’t make it; and ever since, Greenland temperatures have been fairly stable. Wonder why . . .

    And what were temperatures like at lower latitudes, say around 40-50 degrees? Were they going through similar temperature changes during the D-O events, though may be not quite as great temperature changes in Greenland? (I might suspect lower latitudes and the tropics were less affected . . . ).

    All very interesting reading, regardless of causes . . .

    • There is a roughly 1,000 yr Holocene climate cycle, with a much lower amplitude than the Dansgaard–Oeschger.

      • Bond Cycles, usually considered 1500-year intervals, are the interglacial equivalent of D/O Cycles in glacials. There is debate over their period, but the peaks of Holocene warm periods do seem to be around a millenium apart.

        HCO: ~5.2 Ka
        Egyptian WP: ~4 Ka
        Minoan WP: ~3 Ka
        Roman WP: ~2 Ka
        Medieval WP: ~1 Ka
        Modern WP: Now.

        A little more than a millennium is a better fit.

        Due to warmer baseline, the amplitude of Bond Cycles is much lower than for D/Os.

        • I think the period is closer to 1,000 than 1,500 years. But it is variable and the amplitude is sometimes low enough to nearly exceed background.

          • Reference:
            GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 10, 1510, doi:10.1029/2003GL017115, 2003
            “Timing of abrupt climate change: A precise clock”
            Stefan Rahmstorf
            Potsdam Institute for Climate Impact Research, Potsdam, Germany

            Rahmstorf establishes the average timing between D-O events (including Bond events) events to be 1470 years, stating:
            “. . . with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period.”

          • Bond events aren’t D-O events. They are equivalent to Heinrich events (the opposite of D-O). The Holocene version of Bond events were initially thought to have a roughly 1,500 yr period. More recent estimates put it closer to 1,000 yrs.

          • The Bond cycle is a myth. Bond events are real but they were numbered in an unacceptable way to support a nonexistent 1500-yr Bond cycle. Debret et al., 2007 The origin of the 1500-year climate cycles in Holocene North-Atlantic records, demonstrated that the periodicity of the Bond events is mixed. 1000-yr in the first half of the Holocene and 1500-yr in the second half.

            There is a 1500-yr climatic cycle in the Holocene, but it is subtle and difficult to spot, reflected only in a few selected proxies during the Holocene Climatic Optimum. It becomes stronger during the Neoglacial, affecting Bond events as Debret et al. show. I wrote about it in my Nature Unbound series at judithcurry. It was chapter V – The elusive 1500-year Holocene cycle.

          • “Timing of abrupt climate change: A precise clock”

            That article has been falsified. The 1470-yr cycle in D-O events was based on an incorrect date model for GISP2. Using tephras and other markers the Greenland chronology was remade by GICC05 chronology and the 1470-yr frequency peak dissolved.

            That is the problem of basing your entire hypothesis on a single evidence (GISP2 chronology), as NGRIP chronology did not show that periodicity. If your hypothesis is not supported by a lot of evidence you are on shaky ground.

            Besides nearly everything Stephan Rahmstorf says or writes is either wrong or false.

          • David and Javier,

            Bond cycles clearly must differ from D/O cycles because during interglacials like the Holocene we no longer have NH continental ice sheets (except for GIS) and North Atlantic shelves.

            Nevertheless the underlying solar fluctuations, plus oceanic and atmospheric circulations driven thereby, still obtain.

          • Bond events/cycles are not well defined. Initially they were the timing from D-O peaks to Heinrich troughs during the last Pleistocene glacial stage. This was estimated to be ~1,470 yrs. I think Bond’s paper on this was around 1992.

            Then, in 1995-1997 he identified a Holocene version of Heinrich events. My recollection is that he initially put the timing of these at ~1,583 yrs. This discovery actually caused Wally Broecker to walk back his thermohaline circulation catastrophe hypothesis a bit. More recent work puts the Holocene Bond events timing closer to 1,000 yrs.

            However, the Pleistocene Bond cycle is a peak-trough timing, while the Holocene Bond cycle is trough-peak-trough. The peak-trough would be 500-750 yrs.

    • The 8.2 Ka event was the last meltwater pulse from the LIS (or Innutian Ice Sheet, if you regard them as separate), as it shrank to its approximate present size on Baffin Island.

    • Ungava Peninsula; (Wiki) “The peninsula was not deglaciated until 6,500 years ago (11,500 years after the Last Glacial Maximum) and is believed to have been the prehistoric centre from which the vast Laurentide Ice Sheet spread over most of North America during the last glacial epoch.

      The “most of North America” is a stretch, but otherwise that “centre” is approximately shown on Google Earth with a search of Ungava Peninsula.

      Of interest would be when deglaciation of the Ungava area and south in Eastern Canada had progressed sufficiently much that the remaining ice was melting, rather than moving.

    • They did? Look at the rise and fall of early “civilizations” for some evidence of some kind of periodicity that should need some sort of scientific explanation. Might they be somewhat different in an inter-glacial?

      I remember E.M. Smith had a discussion of these “changes” some years ago, and the rise and fall of civilizations, going way back in time. From archaeology we know so much more today.

      I am loving this vigorous, to say the least, discussion. This is real science – using the scientific method to look for truths — but it can be hard on friendships and/or colleague-ships.

  7. Actually, geologists, paleoclimatologists, oceanographers and atmospheric scientists do have a very good grasp of what caused the YD and the alternating stadials and interstadials during glaciations and deglaciations (terminations). Cold, fresh water released into the oceans by armadas of icebergs (Heinrich events) or by meltwater from the ice sheets.

    The YDIH and other gods on machines “explanations” are not only wrong, having been repeatedly shown false in detail, but totally unnecessary. They’re time-wasting exercises akin to looking for evidence of phlogiston after the isolation of oxygen or for the humors theory of disease after the discovery of germs.

    The only problem with the meltwater hypothesis before 2005 was ascertaining by which route the flood entered the ocean. It had been shown by 1989 that the usual drainage of the Laurentide Ice Sheet (LIS) via the Mississippi didn’t flow during the YD. Broecker (please forgive him for being the “Father of Global Warming”) in that year suggested the St. Lawrence, which seemed a natural given Niagara’s date of c. 12,000 BP. But analysis of its channels and sediments didn’t really show any clear sign of such an ice-dammed outwash flood. And in any case, proglacial meltwater Lake Agassiz was SW of the LIS. An arm of it could have hooked around the southern face of the retreating LIS, but the lay of the land was against this possibility.

    And there the situation stood until 2005, when Tarasov and Peltier proposed that the meltwater discharge was not into the Gulf of Mexico or North Atlantic, but into the Arctic Ocean, via the MacKenzie River drainage.,%20Arctic%20Freshwater%20Forcing%20of%20the%20Younger-Dryas%20Cold%20Reversal,%20Nature,%20435,%20662-665,%202005.pdf

    The last deglaciation was abruptly interrupted by a millennialscale reversal to glacial conditions, the Younger Dryas cold event. This cold interval has been connected to a decrease in the rate of North Atlantic Deep Water formation and to a resulting weakening of the meridional overturning circulation owing to surface water freshening. In contrast, an earlier input of fresh water (meltwater pulse 1a), whose origin is disputed, apparently did not lead to a reduction of the meridional overturning circulation. Here we analyse an ensemble of simulations of the drainage chronology of the North American ice sheet in order to identify
    the geographical release points of freshwater forcing during deglaciation. According to the simulations with our calibrated glacial systems model, the North American ice sheet contributed about half the fresh water of meltwater pulse 1a. During the onset of the Younger Dryas, we find that the largest combined meltwater/iceberg discharge was directed into the Arctic Ocean. Given that the only drainage outlet from the Arctic Ocean was via the Fram Strait into the Greenland–Iceland–Norwegian seas, where North Atlantic Deep Water is formed today, we hypothesize that it was this Arctic freshwater flux that triggered the Younger Dryas
    cold reversal.

    Perhaps their paper didn’t get the respect it deserved because the North Atlantic paradigm ruled so strongly. The chain of lakes from Manitoba across the NW Territories, marking the retreating LIS edge stared everyone in the face, but like geographers since AD 1500 looking at South America and Africa before Wegener, had eyes but couldn’t see.

    In any case, two years later Firestone and unindicted coauthors perpetrated their ET impact hypothesis, if the wild conjecture may be so designated. It was promptly shown false, and has been repeatedly since then, but its easy career-making potential meant that it took on a zombie-like existence, with a voodooist cult following. It lurches along, from one new lame excuse to another.

    Even loopier “hypotheses” have been floated, in this debased age when just about anything but reality gets published readily. Broecker’s former coauthor Kennett even deserted to the Dark Side of the farce.

    But a few real scientists over the years have investigated the MacKenzie River hypothesis, and repeatedly confirmed it. Both observations and simulations of drainage and the effect on the Atlantic meridional overturning circulation (AMOC, the zonally-integrated component of Atlantic surface and deep currents). and atmospheric circulation supported it.

    After this 2018 paper, the case is effectively closed, as it long ago should have been, had the scientific method ruled. Science is never settled, of course, but no present alternative hypothesis can compete with this ice-rafted deluge of valid evidence. The iceebergs and meltwater deliver cold, fresh water to where it will have the most effect, and the flow lasts hundreds of years, solving the issues of duration and amplitude of YD cooling.

    A period of cooling about 13,000 years ago interrupted about 2,000 years of deglacial warming. Known as the Younger Dryas (YD), the event is thought to have resulted from a slowdown of the Atlantic meridional overturning circulation in response to a sudden flood of Laurentide Ice Sheet meltwater that reached the Nordic Seas. Oxygen isotope evidence for a local source of meltwater to the open western North Atlantic from the Gulf of St Lawrence has been lacking. Here we report that the eastern Beaufort Sea contains the long-sought signal of 18O-depleted water. Beginning at ~12.94 ± 0.15 thousand years ago, oxygen isotopes in the planktonic foraminifera from two sediment cores as well as sediment and seismic data indicate a flood of meltwater, ice and sediment to the Arctic via the Mackenzie River that lasted about 700 years. The minimum in the oxygen isotope ratios lasted ~130 years. We suggest that the floodwater travelled north along the Canadian Archipelago and then through the Fram Strait to the Nordic Seas, where freshening and freezing near sites of deep-water formation would have suppressed convection and caused the YD cooling by reducing the meridional overturning.

    The scientific method still survives in a few refugia.

    Comparing the last termination with the previous six going back to the Mid-Pleistocene Transition (the switch from ~40,000-year glacial cycles to those averaging ~100,000 years) is instructive, but beyond the scope of a comment. The four before Termination VII occurred during the transition, ie ~700 Ka to 1.2 Ma. Suffice it to say, that stadials (coolings) caused by meltwater and iceberg armadas are evident in all of them, although not all have coolings as pronounced and long-lasting as the YD. Those that do reflect similar Milankovitch cycle alignments, hence summer solar insolation regimes. Those which don’t experienced higher insolation.

    • The last deglaciation was abruptly interrupted by a millennialscale reversal to glacial conditions, the Younger Dryas cold event.

      This is a common misconception from focusing too much on Greenland proxies. The world kept deglaciating at a slower pace during the Younger Dryas and there was no reversal. That’s what proxies from China, Antarctica and other parts of the world show, and more importantly that is what sea level proxies show. The best proxy for the deglaciation is sea level change, and just looking at LR04 shows that YD is barely noticeable in sea level:

      I’m sorry to say this, but D-O events and the YD are big events in the Northern Hemisphere, particularly in the North Atlantic region, and affect the Antarctic and Southern Atlantic through teleconnections. The rest of the planet is much less affected by them.

  8. The Bolling Allerod is simply the last of the 20 or so DO events during the last glaciation.

    The “Younger Dryas” is just a name given to the interval between the last DO event and glacial termination.

    Does anyone know the names given to the other 19 intervals between DO events.

    Every day several volcanoes are erupting somewhere on earth. Then can be and are used to explain everything, both warming and cooling.

    • Heinrich Event cold snaps are numbered from 1, going back in time during the last glaciation. H1 is also the Oldest Dryas (or close), followed by the Older Dryas and Middle Dryas, before the B/A warm spell during Temination I.

        • I do, too, although what then to make of the two Dryases between the Oldest and Younger?

          Minor fluctuations not worthy of numbers, just names?

          The YD ouflow into the Arctic Ocean contained both icebergs and meltwater, so it’s a hybrid Heinrich Event.

          • D-O events are identified by changes in global methane registered in Antarctic cores. No methane abrupt change no D-O. Heinrich events in addition show changes in CO2 of 10-15 ppm. The Older Dryas and the Intra-Allerød Cold Period do not show the CH4 or CO2 signatures. They are just your John Doe cooling for who knows what reason. Within the Holocene we have the Pre-Boreal Oscillation at 11.4 and the two Boreal Oscillations at 10.3 and 9.3 that look similar. All the evidence points that they were caused by low solar activity. Those “short” cooling periods are very common, about one every millenia.

          • Can’t provide links right now, but methane clathrates figure prominently in fluctuations.

          • Javier,

            Thanks for turning a random question into a learning experience,

            I’m reluctant to embrace clathrates, because CACA, but that doesn’t mean I won’t accept an element with evidence. Quite the contrary.

    • John
      Thanks for your illuminating post about the MacKenzie river deluge, I didn’t see it when writing my above post. Deglaciation must always cause a number of massive floods, from glacial dam bursts to rising sea level overtopping land bridges as in the Black Sea (the one that probably gave us Noah’s flood and other ancient flood myths. When I say “myth” I employ CS Lewis’ definition of the word which doesn’t preclude it being true.)

      • Noah’s Flood is a myth in both senses of the term. The Black Sea flood may have stimulated some myths, but also actually happened.

        The MacKenzie outflow was unusual in being more or less continuous for 700 years, and hitting the North Atlantic Deep Water at it most vulnerable point, hence the length and depth of the YD cold snap.

      • You’re welcome. It’s a pleasure and privilege to be able to share good science with readers interested in same.

    • The Bolling Allerod is simply the last of the 20 or so DO events during the last glaciation.

      I would say that the last D-O was the one at 11,700 BP that kick-started the Holocene. It has all the same features and magnitude except it hasn’t ended yet.

      • Yes it’s the same jump between attractors. A valid alternative name for the DO events is “micro-interglacials”.

        • In geology, they’re called interstadials.

          An interglacial occurs when the ice sheets have largely disappeared, and generally last longer than interstadials.

        • Yes, exactly. You noticed it too. They have the same structure. They are excited from a stable glacial/stadial state into a quasi-stable interglacial/interstadial state that degrades until it reaches a relaxation phase after going through an unstable point. The comparison of MIS9e interglacial and D-O8 shows it:

          Within an ice age only the glacial/stadial state is truly stable. I predict a lot of fun for humankind when the end of the interglacial is reached. It could be a couple of millennia still, though no guarantees.

  9. My thoughts on D-O events is the oceans start to stratify and develop a warm deep upper layer when the poles are covered with heavy ice and the open water of the Arctic ends. Antartica and Arctic flow to the bottom ocean slows down and the conveyor slows down. Warming ocean retains heat and stratification deepens increasing the energy retention. Warms enough to cause Antarctic to melt it’s insulating blanket and the conveyor starts up and pushes the warm water up and releases the energy warming the planet for a few centuries/thousand years and as the cold water replaces the warm water and the stratification decreases it becomes cold again finishing the cycle. The previous long long cold period without interruption probably allowed the energy to grow to the many thousands of years of todays interglacial.

    • Forgot to add the insolation and changes to the wobble that increased the solar radiance to the northern and souther hemispheres that also helped kick the conveyor into motion. YD was the meltwater slowing down the conveyor again and adding a cold top layer for parts of the NH that took a while to overcome.

  10. Explanation for Dansgaard-Oeschger (DO) events?
    Between alternate attractors.

    Flickering is a signal of an impending alternate attractor

    Flickering as an early warning signal

    Dakos V, van Nes EH, Scheffer M. Flickering as an early warning signal. Theoretical Ecology. 2013 Aug 1;6(3):309-17.


    Most work on generic early warning signals for critical transitions focuses on indicators of the phenomenon of critical slowing down that precedes a range of catastrophic bifurcation points. However, in highly stochastic environments, systems will tend to shift to alternative basins of attraction already far from such bifurcation points. In fact, strong perturbations (noise) may cause the system to “flicker” between the basins of attraction of the system’s alternative states. As a result, under such noisy conditions, critical slowing down is not relevant, and one would expect its related generic leading indicators to fail, signaling an impending transition. Here, we systematically explore how flickering may be detected and interpreted as a signal of an emerging alternative attractor. We show that—although the two mechanisms differ—flickering may often be reflected in rising variance, lag-1 autocorrelation and skewness in ways that resemble the effects of critical slowing down. In particular, we demonstrate how the probability distribution of a flickering system can be used to map potential alternative attractors and their resilience. Thus, while flickering systems differ in many ways from the classical image of critical transitions, changes in their dynamics may carry valuable information about upcoming major changes.

  11. I’m waiting for a study that concludes the Younger Dryas was not a cold period but a period of rapid warming following an ice age.

    • It was indubitably frigid, for ~1200 years. It followed the warm B/A phase of the last termination, just as in previous such deglaciations during the Late Pleistocene.

        • For sure. But, as above, the warmth starts the deglaciation process, but meltwater and icebergs from the shrinking ice sheets periodically interfere with the AMOC, chilling the oceans. Southern oceans later warm as a result, hence the polar seesaw.

          Despite high insolation, the climate can and does cool during terminations, which last around 10,000 years, but duration depends on how much ice accumulated in the previous ~100,000 years, and how much insolation there is, which depends upon Milankovitch cycles.

          • Thanks for your reply. Here’s another explanation. The dO18 of the ice sheet represents the water it was evaporated from, fractionated to leave the heavier O18 molecules behind. With rapid melting this meltwater, already depleted in O18, blanketed the north atlantic and then was further fractionated by evaporation, until it finally snowed out on Greenland and formed ice doubly depleted in O18, yielding the anomalously low temperatures attributed to the Younger Dryas, actually a time of rapid warming and massive melting. I’ve held this idea for some time. Any thoughts?

          • Pochas,

            That’s obviously not what happened, either locally in the Beaufort Sea or in the Arctic or Atlantic. But nice try.

          • Yup. Glacial intervals are dry and windy. More insolation and attendant deglaciation increase precip, both rain and snow, which is another reason for the virtually constant runoff into the Arctic Ocean during the YD.

  12. Good grief guys. Get with the science. Don’t you know that CO2 is responsible for everything?

    More seriously, thanks for the post and thanks for the great replies.

  13. The fact that there was four separate signals of the supposed events from 13000 BP to 9000 BP, as caused by volcanic eruptions is not at all likely. For one thing, there was not that much significant volcanic activity through this interval, for another, ordinary volcanic eruptions the nature of those assumed here are far too small to cause climate downturns having three degree Celsius temperature decreases, nor extending more than two or three years. The only way vulcanism can cause large long lasting climate perturbations, is if there were from supervolcanos, none of which has taken place in the last more than 20,000 years, Much earlier in Earth’s history, features known as the Deccan and Siberian Traps, that occurred many millions of years ago would have been candidates for very large changes in the climate.

    Furthermore, on the topic of the four climate downturns cited, there were several climate cold intervals that took place 13000 to about 9000 BP, 1) the Younger Dryas around 13,000 BP, 2) another at approximately 11450 BP, 3) a third near 10,300 BP and 4) another somewhere in the vicinity of 8500 to 8200 BP, admittedly slightly later than the 9,000 BP date cited.

  14. When I read ‘melt water pulse’ and ‘ burn marks’, I couldn’t but think of some aliens with ray guns…

  15. Wiki:
    “The Tunguska event was a large explosion that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908 …
    It is estimated that the shock wave from the air burst would have measured 5.0 on the Richter magnitude scale, and estimates of its energy have ranged from 3–30 megatons of TNT (13–126 petajoules).”

    The significance of Tunguska event is not this one which occurred 112 years ago, but rather such events occur clocklike on the order a century time period.
    And can we ignore ten megaton explosion occurring randomly anywhere in world. And when you change time period from century to say thousand year you get clocklike, explosions of even larger impactors, which repeats when talking about time periods of tens of thousands of year, and hundreds of thousands of year, millions, tens million and hundred of millions where get dinosaur extinction size space rock, occuring clocklike. Or other way, where smaller space rocks, which break windows and cause sunburns in which explosions size of small nuclear bomb, ie:
    “The Chelyabinsk meteor was a superbolide that entered Earth’s atmosphere over Russia on 15 February 2013 …
    The light from the meteor was brighter than the Sun, visible up to 100 km (62 mi) away. …
    to be equivalent to the blast yield of 400–500 kilotons of TNT (about 1.4–1.8 PJ) range – 26 to 33 times as much energy as that released from the atomic bomb detonated at Hiroshima.”
    Which are time scale per decade. And chances are they impact no where near human settlements which occupy a small fraction of earth surface.
    Now, this not saying volcanic eruption are not important, but sort of similar thing because because about 75% of all volcanic eruption occur in deep water of ocean which are likewise are undetectable as we also don’t have human settlements on the ocean floor. The volcanic eruption globally occur clocklike and perhaps involve more explosive power when talking about time period less than 100,000 years.
    BUT this climate stuff, is concerned almost entirely about weather, rather than actual global climate.
    When talking about weather, what is major aspect is the surface temperature of earth ocean. The average surface temperature of 40% of ocean surface, the tropical ocean surface, it’s average temperature is 26 C, and average of 60% of remaining ocean is about 11 C, giving average global surface temperature of 17 C.
    {{And average global land surface air temperature is about 10 C, which due to large land areas which are below 10 C, like Europe which is 9 C {which is excluding Russia which has average of about -5 C} and China averages about 9 C. And also note that Europe is warmed by about 10 K due to ocean warming and/or the Gulf Stream, otherwise it would similar to Canada which has average temperature of about -4 C]}}
    So tropical ocean has thick slab of warm water near the surface, and 60% of rest of ocean doesn’t have such thick layer of warm water. But 60% of ocean is having large effect upon weather {global weather}. Or tropical ocean is the world’s heat engine {or that thick slab of warm water is the heat engine]. Anyway the thick slab or thinner layer of warmer water of 60% of ocean, sits on our cold ocean which has average temperature of about 3.5 C.
    This cold ocean is global climate, it’s cold, and therefore we are in an Ice Age, and has been for millions of years. If instead the was say 10 C, Earth climate is more normal- or we are not in an Ice Age. During our Ice Age the ocean temperature varies within the range of 1 to 5 C. If it’s +4 C we in the warmer part of interglacial period and anywhere near 1 C, the deepest parts of a glaciation period.
    Anyhow, a relative very thin layer of warm water controls weather, and that could be disrupted by nuclear bomb type forces- impactors or volcanic eruptions, though even weather all by itself can have various kinds of weather patterns which generally are related oceanic patterns/cycles.

    • Or replace butterfly effects with megatons explosion effects, and anything over 1000 megaton explosion, is a big butterfly effect.
      “The Chicxulub impact event was an ~100 million megaton blast”
      Anything over say, a million megaton blast, isn’t a butterfly or megaton effect- it’s kiss butt goodbye effect.
      With volcanic eruption, measurement seems to be how many billions of tons of “ash, rock, pumice and gas” it throw into the atmosphere and more than trillion tons {or 1000 cubic km of rock} is getting pretty close to the “kiss butt goodbye effect” Ie:
      “The “Toba Supereruption” that occurred between 69,000 and 77,000 years ago at Lake Towba, Sumatra, Indonesia, has been identified as one of the earth’s largest eruptions. The ensuing catastrophe included a global volcanic winter lasting a decade and 1,000 years of atmospheric cooling.

      Scientists have determined Toba erupted three times in the past 1 million years. ”
      Or Yellowstone or other Super volcanoes.
      I tend to think super volcanoes in tropics and all the “ash” messes with the tropical heat engine. And there the biological effect of adding all that “fertilizer” to the vast ocean sterile regions of the ocean- the fish might be quite happy.

  16. No one really knows what drove the Dansgaard–Oeschger and Heinrich cycles…

    That is true for everything that happened before there was somebody observing and recording what happened, nevertheless we have theories and hypotheses about what happened in the past and what could have caused it, and Dansgaard–Oeschger and Heinrich cycles are no different.

    The modern understanding of D-O events comes after
    -Petersen SV, Schrag DP and Clark PU (2013) A new mechanism for Dansgaard‐Oeschger cycles. Paleoceanography 28 (1) 24-30.
    that was further elaborated by
    -Dokken TM, Nisancioglu KH, Li C et al (2013) Dansgaard‐Oeschger cycles: Interactions between ocean and sea ice intrinsic to the Nordic seas. Paleoceanography and Paleoclimatology 28 (3) 491-502
    -Ezat MM, Rasmussen TL and Groeneveld J (2014) Persistent intermediate water warming during cold stadials in the southeastern Nordic seas during the past 65 ky. Geology 42 (8) 663-666
    -Sadatzki H, Dokken TM, Berben SM et al (2019) Sea ice variability in the southern Norwegian Sea during glacial Dansgaard-Oeschger climate cycles. Science Advances 5 (3) eaau6174

    Essentially the modern interpretation is that the bipolar see-saw that alternates warming and cooling between the Arctic and the Antarctic is driven by the strength of the AMOC. At the Nordic Seas Greenland stadials (cold periods) there is a build up of an inherently unstable stratification with sea ice on top over a very cold fresh water layer while the warmer water brought from the south by a strengthened AMOC gets layered below at the subsurface levelbelow the halocline, its buoyancy checked by the stratification. This stratification is known from the presence of warm loving foraminifera at the subsurface level. The increase in warm water weakens the stratification and when the meltwater input decreases at the end of the stadial there is an abrupt collapse of the unstable stratification and all the warm water accumulated over centuries rises to the surface melting the ice and producing the abrupt warming initiating the interstadial. The AMOC keeps bringing warm water now at the surface level keeping the interstadial going for a few centuries until the sea ice starts growing again initiating a new cycle.

    Regarding the trigger of D-O events, I am convinced that a lunisolar tidal cycle is responsible. During glacial periods there are monster tides in the North Atlantic and the biggest ones are produced at certain intervals when (1) there is a Sun-Earth-Moon syzygy (alignment), (2) when the Moon is closest to the Earth, at perigee, (3) when the Moon is located at one of the nodes of the Earth’s ecliptic, and (4) when the Earth is closest to the Sun, at perihelion. When these mega-monster tides take place at a time when the stratification has been sufficiently weakened they give the inherently unstable system the coup de grace.

    Heinrich events appear to be D-O events on steroids that take place at ~ 6000 years intervals when the Greenland stadial lasts longer, and the ice build-up is larger, and the temperature difference between the Arctic and the Antarctic is larger, and the AMOC gets stronger.

    There is a very sound reason D-O events stopped after the last one 11,700 years ago. The world got too warm for the sea ice build-up and sea level increased a lot and the tides got weaker. However the lunisolar tidal cycle continued acting, only it reversed its effect since on a warm world the surface cooling from water mixing is its main noticeable effect, so it became the 1500-yr Holocene cooling cycle.

    • And then there are the studies showing the DO events to be unforced internal oscillations of the Northern Seas coupled system:

      I think it’s a hybrid of both. Excitable media with internal oscillatory dynamic can be forced by external periodic forcing.

      BTW the DO events (microinterglacials) are not at regular intervals, but sporadic.

      • During glacial intervals, they’re called interstadials.

        The coolings, like the YD, are called stadials. The YD was the last stadial of the last glaciation and its deglaciation.

      • And then there are the studies showing the DO events to be unforced internal oscillations of the Northern Seas coupled system

        There are all sort of studies about D-O events and most of them are wrong. There are studies even assigning them to solar forcing, like Muscheler and Beer, 2006 “Solar forced Dansgaard/Oeschger events?”
        One could really choose the forcing of his liking and support it in the bibliography.

        However D-O events have a (quite) precise timing that indicates an external trigger. As usual the climate system sets the stage and the external forcing just provides the push that sets things in motion. And no, I am not talking about the much published 1450-year cycle that even Rahmstorf defended and turned out to be an artifact from an incorrect chronology. The timing I am talking about is on GICC05 chronology.

      • Javier

        The wiki article on DO events–Oeschger_event

        says this under the heading “timing”:

        However the older parts of the GISP2 core do not show this regularity, nor do the same events in the GRIP core. This may be because the first 50 kyr of the GISP2 core are most accurately dated, by layer counting. The climate system response to the trigger is varying within 8% of the period. Oscillations within the Earth system can be expected to be far more irregular in period. Rahmstorf suggests that the highly regular pattern would point more to an orbital cycle. Such a source has not been identified. The closest orbital cycle, a Lunar cycle of 1,800 years, cannot be reconciled with this pattern.[13] The dating between the European GRIP ice core, and the American GISP2 ice core differs by about 5000 years at 50,000 years BP. It was noted by Ditlevsen et al. (2005)[14] that the spectral peak found in the GISP2 ice core was not present in the GRIP core, and thus depended critically on the accuracy of the dating. The dating issue was largely solved by the accurate dating of the NGRIP core.[15] Using this dating the recurrence of Dansgaard–Oeschger events is random consistent with a noise induced Poisson process.[16]

        The author considers that the latest most precise dating of the NGRIP core supports random rather than regular events citing this reference:

        Now as I’ve said many times in discussions with you, and Ulrich Lyons and William Astley and others convinced of strong astrophysical forcing of all climate events, it doesn’t have to be either-or in an exclusive way between astro forcing and internal oscillation. It can be both and. You can have external periodic forcing interacting with internal nonlinear oscillatory dynamics. It has a name – the “periodically forced nonlinear oscillator”.

        There are well established experimental models in the literature of the periodically forced nonlinear oscillator. The BZ reaction (Belousov-Zhabotinsky) thin film chemical oscillator can be periodically forced with external light flashes. The same is true of the catalysed CO oxidation on a platinum surface. Even ocean tides can fall into this category when the coastal or estuarine geography is complex with a narrow neck. The heart beat is also generated from a network of cardiac muscle fibres acting as nonlinear oscillators and adding a pacemaker is an example of external periodic forcing of the system to try to get the beat regular.

        Periodic forcing of a nonlinear oscillatory system can be either weak or strong. When it’s strong, then the system’s oscillation is the same as the external forcing oscillation. But when it’s weak the emergent system oscillation can be complex and differ considerably from the forcing oscillation. Then it becomes hard to link the system’s oscillation to its external forcing. But it still is externally forced. I suspect such scenarios of weakly periodically forced nonlinear oscillation are common in the ocean-climate system. There are hints at astrophysical periodicity but they are elusive and they come and go from the climate time record.

        The advantage of the periodically forced nonlinear oscillator model in climate is that it does not require the astrophysical forcing to have all the energy needed to change the oceans for instance. The forcing can provide a pacing role only and the energy for the periodic transitions comes from the internal dynamics.

        Milankovitch obliquity forcing of interglacial timing and duration is an example of strong periodic forcing. The cycles are slow enough for obliquity’s variation of solar input alone to change the ocean’s temperature, with the 6500 year thermal lag that you have pointed out previously.

        However the DO events are much too rapid for external astrophysical forcing to provide all the energy. Here the internal dynamics and excitability caused by ocean-cryosphere interactions provides the energy, but there is still the possibility of weak external periodic forcing. How to prove that could be a challenge though.

        • The dating between the European GRIP ice core, and the American GISP2 ice core differs by about 5000 years at 50,000 years BP.

          The Europeans were far more careful with the dating of GRIP and NGRIP cores than the Americans with GISP2 core. In 2005 the Greenland Ice Core Chronology 2005 (GICC05) time scale was published by the Centre for Ice and Climate at the Danish Niels Bohr Institute using NGRIP, GRIP, and DYE-3 cores and reaching back to 60,202 b2k.

          The GISP2 timescale was corrected to the GICC05 scale a few years later by Rasmussen et al., 2014 that also extended GICC05 back to 104,000 b2k. I only use NGRIP or GISP2 on GICC05 scale.

          The author considers that the latest most precise dating of the NGRIP core supports random rather than regular events

          Wikipedia, Ditlevsen, Obrochta and others that defend that D-O events are random are WRONG. GISP2 on GICC05 shows a different and much more interesting distribution of the D-O events than the original 1470-yr spacing that was an artifact of the bad timescale of GISP2. Obviously being on GICC05 it means this non-random distribution of D-O events is present in both NGRIP and GISP2.

          However the DO events are much too rapid for external astrophysical forcing to provide all the energy. Here the internal dynamics and excitability caused by ocean-cryosphere interactions provides the energy

          Absolutely. The energy is provided by the accumulation of warm subsurface water below the halocline brought by AMOC over centuries to millennia. That sandwiched thermal energy has nowhere to go as there is very little vertical mixing, and accumulates until it fills the allowed space in the oceanic basin (Nordic Seas primarily). That’s why despite their diversity all D-O events produce essentially the same magnitude of warming, a feature that nobody has ever highlighted to my knowledge. The maximum amount of energy they accumulate is essentially fixed.

          The rapid development of a D-O warming is due to the rapid ascent of that warm water due to its natural buoyancy once the stratification that kept it in place gets disrupted. The heat quickly melts the sea ice and is released to the atmosphere producing the warming in a few decades. Once the heat storage is exhausted a new meta-stable interstadial has been produced that will return back to stadial conditions depending on the amount of heat it receives through the AMOC (now at surface level) and the growth of sea-ice as the cooling progresses.

          but there is still the possibility of weak external periodic forcing. How to prove that could be a challenge though.

          Exactly. According to my analysis nearly all, but perhaps not all, D-O events are astronomically triggered by lunisolar tidal forces following a periodic distribution. I think that the fact that the distribution is not random, and that the astronomical forcing provides a mechanism for the disruption of the stratification strongly supports it and makes it a better hypothesis than competing ones. After all saying that something is random doesn’t explain much and doesn’t produce any predictions.

        • Indeed “random noise” is an inappropriate and even ignorant term to invoke in climate systems. There is always some coupling or feedback which will cause some emergent pattern and departure from pure stochastic noise; at the very least some autocorrelation or autocovariance.

    • Nothing mysterious about “black mats”.

      They have nothing. Never had anything.

      They’re more antiscientific than the CACA Team.

        • You’re looking at fake science.

          “Nanodiamonds” are hardly unique to the YD. As in, not at all.

          Nanodiamonds do not provide unique evidence for a Younger Dryas impact

          Nanodiamonds and wildfire evidence in the Usselo horizon postdate the Allerød-Younger Dryas boundary

          Please read and study real science, not antiscientific fantasy. Please exercise real scientific skepticism over preposterous, baseless assertions.

          The antiscientific zombies are still lurching brainlessly toward the humans waiting, chainsaws at the ready.

          You have been taken in by scammers.

        • There is no real science. There is real evidence and there is false evidence (i.e. the Piltdown fossil). Then there is interpretation of the evidence that can be correct or incorrect. The nano diamonds are just a piece of evidence that can be interpreted one way or the other, exactly as the Pt spike. A hypothesis is weak when it is supported by very little equivocal evidence and is strong when it rests on a huge amount of evidence that admits no other reasonable interpretation, particularly when it comes from different fields of science. For example the molecular genetics developed after the 1970s fully supports the evolution of living organisms, and it is just one of several fields providing a huge amount of evidence on support of evolution.

          A hypothesis with so little evidence support as the YDIH is not even worth of consideration. They should stop lucubrating and go to work to obtain more solid evidence.

          The YDIH is the typical hypothesis that is favored by non-scientists that like talking about real science, and that is very telling.

          • IMO, “so little” should read “no” evidence to support it, and all the evidence in the world against it.

        • PS: Your link says “63” scientists.

          It could be 666. Wouldn’t matter. All that matters is the evidence, ie observations of nature.

          They’re all wrong. Not just a little bit, but completely, totally and utterly. To such an extent that they should be, but, like Mann, et al, aren’t. Because the facts don’t matter any more in post-modern science.

          I’ll bet that most of them, like their CACA-spewing comrades, know they’re lying, but don’t care. Indeed they laugh at how many gullible peons in the public who pay their salaries they’ve fooled.

          Swine. Except not as honest or smart as trough-feeding pigs.

        • Perhaps you’re unaware that the IUGS has over a million members. If science were based upon voting, your fantasy would be voted down by more than 1,000,000 to 63.

          But that’s not how science works. Had you a single piece of evidence not easily shown false, then real scientists would pay attention and not subject you to the ridicule which your delusion so richly deserves.

    • Actual science rather than pseudoscientific fantasy:

      2008, re “mats”:

      2010, re “comet”:

      2011, re “nanodiamonds, glass spherules and tektites”:

      2018, re “iridium, shocked quartz, platinum”:

      As I said, they’ve got nothing, but at least they’re not jabbering about the Carolina Bays anymore. Apparently only reitrement will stop their zombie lurching.

      • Darn!
        We almost made it through this thread without mention of the Carolina Bays.
        Negative sense, so progress.

      • It will lurch on as long as its snake oil salesmen proponents keep paying to get their “research” published, that they should not perish.

        After they retire, the zombie attacks will cease.

        It’s a stinking splat of wet excrement, but at least less destructive than CACA.

      • There may well have been a bolide around that time. As there continually are bolides following the natural fractal log-log plot of size with frequency. (Every August 12 I go out with my daughters at night to watch the Perseid bolides.)

        But neither bolide nor anything else is needed to explain why the Bolling-Alerod interstadial ended the same way that all 19 preceding interstadials also ended. As Javier says, “nothing to see here”.

  17. “No one really knows what drove the Dansgaard–Oeschger and Heinrich cycles… But neither impact events nor volcanic eruptions can explain such a clearly quasi-periodic climate change signal.”

    In the 2nd graph the H1, H2, H3 etc peaks both the warming and cooling phase was about the same length of time. As it gets closer to the final cooling period (YD) the peaks are higher.

    If we assume the sun was constant in activity +- 1% deviation then there would have to be a cause on Earth which has either stalled or gone away. The melting of ice which cool the oceans which then reverse the warming into a cooling….. which then abruptly stop cooling and warming starts…… all comes to an end @ 10,000 BP.

    Then it all stops altogether. Are there any other correlations for that period that also stop?

    • The cause could just be muted during interglacial stages. The Bond cycle could be a muted variation of the D-O.

      • IMO, it is, but lacking ice sheets, and with a warmer baseline temperature, its amplitude is an order of magnitude less.

  18. Is this a case of “can’t see the forest for the trees”?

    It’s good to focus on the cause of the “cooling” period associated with the Younger Dryas global temperature minima—whether caused by volcano(es) or extraterrestrial object “impact”—but of much more significance to me is the period of extremely rapid warming following this minima (see the first graph in the above article). The indication from the GISP2 ice core temperature reconstruction is that temperatures in the area of Greenland (therefore most of Earth?) rose by 12 C over about 200 YEARS, or a warming rate of 6 C per century.

    And the IPCC would have us all believe a global warming rate of 2-3 C per century is both “unprecedented” and “catastrophic” for the planet. If GISP2 YD data is truly represented a global temperature change, I cannot understand how the whole Earth could warm so rapidly in such a short period of time, unless Earth received almost no solar energy input up to TD minimum, and then suddenly (remarkably?) Earth’s skies cleared and allowed almost 100% insolation onto Earth’s surface. And is it possible that Earth’s oceans have so little effective thermal inertia?

    And even still, something doesn’t smell right.

    Oh . . .and lest I forget to note it . . . there were not a lot of fossil fuel plants, power generation plants, ICE vehicles and atmospheric CO2 in the period of 12,000 to 11, 600 years ago.

    • The YD was not caused by volcanoes or ET impact, anymore than were its hundreds of predecessors in the Pleistocene.

      The area of Greenland would have warmed much more than the rest of Earth.

      • Ok, John, fine. What’s the best scientific (or your own) explanation for the cause of the rapid warming rate in Greenland during recovery from YD or from any of the other preceding stadial recoveries?

        • Should be obvious.

          Terminations are obviously warming intervals, with high summer insolation if polar latitudes. The default trend is warming. This trend is interrupted by cold, fresh water outbreaks, themselves caused by the warming. Once the effects of the Heinrich/stadial excursions are over, it’s back to the warming.

          • John, if “the default trend is warming” and that is your explanation for the rapid recovery from the YD temperature minimum, the why are we not now globally, or at least in the area around Greenland—well into the Holocene interglacial— experiencing warming rates of around 6 C per century?

            Your explanation would seem to require that there is actually some change since the YD recovery that is damping down the “trend of warming” from 6 C per century to our present (measured) global warming rate of 1-2 C per century.

            Perhaps the damping is due to increased levels of CO2 since the time of YD . . . imagine that! 😉

          • Again, I’d have thought the answer obvious.

            We’re in a very different point in the Milankovitch Cycles now than 11,400 years ago.

          • Sorry, John, I’m not aware of any Milankovitch cycle, or combination of fundamental Milkankovith cycles, that could “turn on” and then “turn off” global warming over an interval as short as 200 years, the time interval of abrupt warming in Earth’s recovery from the YD minimum.

            To state that “We’re in a very different point in the Milankovitch Cycles now than 11,400 years ago” sidesteps the question I asked.

            Your “obvious answer” leaves much to be desired.

        • Gordon,

          I don’t know why it takes so long for my comments to be approved. Many go completely missing. If my reply doesn’t soon appear, I’ll try again.

          I’m ready to give up on WUWT. It was just as bad at the previous hosting site.

        • John
          I don’t think WUWT moved host in the end – too big and complex and operation for the platforms to cope with. We all experience posting delays from time to time. Stay with us!

    • By “dogma”, apparently you mean, “facts”. If I’m mistaken, please show me where.


      Not that I have anything against Lyell. I wonder if you’ve read him. He explicitly mentions catastrophes as a component of uniformitarianism.

    • Perhaps you’ve been lied to as to what “uniformitarianism” means. Contrary to what perhaps you’ve been falsely told, it simply means that geologic processes in the past are those which we see at work today, or find evidence of in fairly recent rocks,

      Hence, ET impacts, outwash floods, seafloor spreading leading to “continental drift”, you name it are uniformitarian, not just the gradual rising up and wearing down or mountains or the depositing of sediment at a stately rate over time.

      Young Earth creationists and their ilk set up a cartoonish straw man of modern geology. They are blasphemous liars against God.

      • Yep. 99.9% of the criticism of Uniformitarianism comes from people who are clueless about the concept.

        Technically, Uniformitarianism says that the past can generally only be explained by geological processes we observe today. There are a few exceptions, particularly in the Proterozoic, because some of those processes can’t be observed today.

        We observe the formation of oölites around places like Andros Island. When we find Cretaceous oölitic limestone, Uniformitarianism tells us that it formed in a depositional environment like Andros Island.

        This is why I wrote an entire series of WUWT posts on Uniformitarian impact craters.

        • Thanks for that series!

          Yes, there were times in Earth’s past when some geologic processes were at work which no longer seem to be.

          And there was a time before tectonics.

  19. A little remarked fact is that sea level continued to rise at about the same fast rate during the YD, despite sea and air temperatures cooling dramatically. High summer insolation at high latitudes explains this perhaps counterintuitive observation.

    But this fact is consistent with continuous outflow via the MacKenzie drainage, maintaining the long cold spell of the YD stadial.

    • I agree that sea level continued rising and that is a very important point that indicates there was no global cooling during the YD. However the Arctic and North Atlantic cooling did reduce the rate of sea level rise during the YD.

      This figure is from the Tarasov & Peltier 2005 paper that you linked in one of your comments:

      “Ice recession [at the Laurentide Ice Sheet] during the YD was generally slow, particularly at the northern and eastern margins of the ice sheet, where deglaciation mostly occurred after this period (Andrews, 1973; Dyke, 2004).

      the Younger Dryas (YD) cold event is now known (cf. Dyke, 2004) to have been characterised by a period of moraine construction and, in several places, major readvances of the ice margin and ice marginal lobes (e.g. Dyke and Savelle, 2000). Such readvances have been well-documented along several parts of the ice sheet margin and include the large Gold Cove readvance from Labrador across Hudson Strait (Miller and Kaufman, 1990) and major readvances at the north-western margin of the ice sheet in the Canadian Arctic Archipelago (Dyke and Savelle, 2000). In many places, such readvances were associated with major ice lobes/ice streams, such as the Cumberland Sound Ice Stream on Baffin Island (Jennings et al., 1996; Andrews et al., 1998) and the M’Clintock Channel ice stream on Victoria Island (Hodgson, 1994; Stokes et al., 2009).”

      From Stokes 2017. Deglaciation of the Laurentide Ice Sheet from the Last Glacial Maximum.

      So we have a long (1200 yr) cold period that reduced the melting at the Northern ice sheets and therefore reduced the meltwater flux to the North Atlantic that is supposed to be its cause. That is why the meltwater hypothesis morphed to say that the important thing is not the amount or the existence of big pulses that matters, but the location of the flux that is supposed to have changed. I don’t like hypotheses that morph when they find themselves unsupported by evidence. It indicates they are based on narrative more than on hard evidence.

      The 8.2 kyr event indicates that proglacial lake outbreaks only cause a short-lived cooling and no strong reduction of the AMOC.

      I know I tend to reach conclusions very far from scientific consensuses and my own Younger Dryas hypothesis is massively heretical. I don’t think the Younger Dryas requires an explanation. After every D-O interstadial the climate of the North Atlantic cools by default at its own pace and in many cases it reaches a point when sea ice quickly extends southward producing a very fast cooling phase:

      Since the Bølling-Allerød period is just a D-O, the cooling afterwards (Younger Dryas) doesn’t require an explanation. The North Atlantic just went back to its stadial default state and the cooling became abrupt when the sea ice extended southwards shutting the temperature exchange between the ocean and the atmosphere producing a feedback that accelerates the regional cooling.

      NO IMPACT, NO MELTWATER, NO ANYTHING. Just business as usual after an interstadial. Lyell and Occam would be proud of me. We just like to name things and produce fancy explanations for phenomena that don’t require them.

      • It is the unwarranted assumption that the North Atlantic should be warmer at the time of the Younger Dryas what makes an explanation for that cold period necessary. If we remove that assumption the Younger Dryas does not require an explanation. The North Atlantic was at the temperature and conditions it was supposed to be at that time, and the warm period before the YD, the Bølling-Allerød was the anomaly, but an anomaly that has repeated over 20 times during the Last Glacial Period, so unique explanations are disavowed.

      • Javier
        Very nicely explained!
        The Bollling-Allerod is simply DO event number 19 or 20 on the last glacial interval. The last one before Holocene inception. So the YD indeed doesn’t really exist at all, just the interval between the final DO event and interglacial inception.

        Or maybe, the DO events are “failed interglacials” and the Holocene is the successful one that held at the warmer level instead of falling back.

        • Or maybe, the DO events are “failed interglacials”

          No, they are not. The last deglaciation is a good model for how interglacials are born. Obliquity was increasing from about 29 ka to about 10 ka, so at about 20 ka went through its mid-point and started to be above average. It is not coincidence that was the coldest point. Also at 20.5 ka Dec-Jan-Feb (summer) insolation at the Southern Hemisphere was at its peak. This is what makes the deglaciation start at Antarctica. The mid-northern latitudes remain in glacial state until the combination of high obliquity and high northern summer insolation are capable of pushing back the overgrown ice sheets. This is why the North Atlantic lags to the rest of the planet in coming out of the glacial state and why this glacial state was still the default state during the Younger Dryas period. Only after 8000 years of deglaciation did the North Atlantic finally join in when it got rid of a great deal of summer sea ice for good through the last D-O warming at 11,700 BP.

          The interglacial usually peaks a couple of millennia after obliquity and norther summer insolation peak and then it is usually downhill from there in an irregular fashion, first slowly and then faster. Since 8000 BP every millennium has been colder than the previous one, and that includes the millennium that ended 20 years ago. No reason to think this millennium just started will break the pattern and be warmer than last.

      • Support for what I said comes from Nye & Condron 2020, Assessing the Statistical Uniqueness of the Younger Dryas: A Robust Multivariate Analysis

        “During the last glacial period (c. 120-11 kyr BP), dramatic temperature swings, known as Dansgaard-Oeschger (D-O) events, are clearly manifest in high resolution oxygen isotope records from the Greenland ice sheet. Although variability in the Atlantic Meridional Overturning Circulation (AMOC) is often invoked, a unified explanation for what caused these ‘sawtooth shaped’ climate patterns has yet to be accepted. Of particular interest is the most recent D-O shaped climate pattern that occurred from ∼14,600 to 11,500 years ago – the Bølling/Allerød (BA) warm interstadial and the subsequent Younger Dryas (YD) cold stadial. Unlike earlier D-O stadials, the YD is frequently considered a unique event, potentially resulting from a rerouting and/or flood of glacial meltwater into the North Atlantic, a meteorite impact, or a volcanic eruption. Yet, these mechanisms are seldom considered as the cause of the earlier stadials. Using a robust multivariate outlier detection scheme – a novel approach for traditional paleoclimate research – we show that the pattern of climate change during the BA/YD is not statistically different from the other D-O events in the Greenland record, and that it should not be considered unique when investigating the drivers of abrupt climate change. Our results thus raise important questions about the ability of glacial meltwater input and other ‘one off’ events to trigger abrupt, centennial-to-millennial length, changes in climate.”

        That’s bound to be very controversial with so many unique explanations for the Younger Dryas out there. Move along, folks, nothing to see here.

        • But the other stadials are caused by meltwater or icebergs (Heinrich Events). So the study is right that the YD doesn’t differ, but wrong as to causation. So you’re right to urge moving along from volcanoes, impacts of other catastrophic ET explanations, although not from meltwwater and the AMOC, although those proximate causes might themselves be under ET or at least orbital and rotational mechanical control.

      • The 8.2 Ka event was briefer than the YD because there was so little ice left to melt.

        The YD was long and deep because it was the main meltwater outflow of the last termination.

        The B/A warm interval provided the meltwater lake dammed by ice in the NE Territories.

        Heinrich Events during glacials are IMO a little different. I don’t know if they follow relatively warmer intervals in such cold periods or not. They’re caused by icebergs from the ice sheets. A surge could come from warmth breaking them lose or the growth of a shelf to its natural limits.

        There has been a lot of speculation and study on causation since Hartmut Heinrich discovered periodic IRD.

      • The 8.2 Ka event was briefer than the YD because there was so little ice left to melt.

        The YD was long and deep because it was the main meltwater outflow of the last termination.

        The B/A warm interval provided the meltwater lake dammed by ice in the NE Territories.

        Heinrich Events during glacials are IMO a little different. I don’t know if they follow relatively warmer intervals in such cold periods or not. They’re caused by icebergs from the ice sheets. A surge could come from warmth breaking them lose or the growth of a shelf to its natural limits.

        There has been a lot of speculation and study on causation since Hartmut Heinrich discovered periodic IRD.

        I got a 409 Conflict message while trying to post this comment.

        • Sorry for the double. I didn’t know if the first post registered.


          IMO, the YD was a global event. Its effects were delayed about 500 years in Asia and the Pacific.

          Initially the Southern Hemisphere warmed, but that too was an effect of the 700 year long flow of meltwater into the Arctic Ocean. Please read Keigwin.

          I don’t disagree that warm and cold cycles are related, but am convinced that Heinrich Events and YD-like intervals in terminations are caused by meltwater in the Arctic, Atlantic and possibly Pacific Oceans and adjacent seas. Maybe Indian and Southern Oceans ad well, despite polar seesaw.

          • I’ve read Keigwin et al., 2018 and remain unconvinced. All they show is that there was deglacial flood at the Beaufort Sea at 14.5 and between 13 and 12 ka. This is very unsurprising as the planet was deglaciating since around 18 ka and sea levels were increasing and that water had to come from somewhere.

            All the rest are assumptions. The 14.5 ka flood must have caused warming or no effect while the 13-12 ka flood must have shut down the AMOC (no evidence for that) causing the YD (no evidence for that, sorry, I don’t admit computer models as evidence for anything but computer skills). I am sure that if you look elsewhere you will find deglacial floods at many places at different times during the deglaciation. Why is this one so special? Because we have assumed that the YD requires a cause so we need something that took place at that particular time that we can blame.

            The problem is that from the point of view of long climate records the YD is not special. The YD is Greenland stadial 1 (GS1) lasting 1200 years and it is not different from many other GS like for example GS6 (900 years) or GS8 (1100 years). See:

            And it is a tough problem because Greenland stadials represent the basal state of the glaciation, for example GS18 lasted 4,400 years and GS19.1 lasted 5,200 years. Combined, stadials represent like two thirds of the last glacial time from 78 ka. So essentially the hypothesis is that glacial floods at a specific point in the Beauford Sea for thousands of years are required to maintain the basal glacial state. Either that or the particular flood at a particular GI-GS transition (BA/YD) is just a coincidence and the answer lies elsewhere. Considering that the GI-GS transition at 12.9 Ka took place during the deglaciation while previous GI-GS transitions did not, the odds are that the Beauford Sea flood is just a coincidence, and a sign that the ice sheets were melting due to the deglaciation. If you need a flood for your hypothesis during the deglaciation and you look hard enough you are likely to find it, and then you can blame that particular flood and no others for the required effect. Hypothesis-driven science, a.k.a. science on demand. If you need evidence for an impact and look hard enough you are also likely to find something that can be interpreted that way, like some charcoal, or spherules, or nanodiamonds, or a heavy metal spike.

            The sad truth is that during an ice age interstadials and interglacials are bound to end and their ending doesn’t require an explanation because the record clearly shows that their duration is linked to orbital conditions. Looking for an explanation for something that doesn’t require one is a definition of futility.

          • The YD happened to occur as a result of flow into the Arctic, but Heinrich Events primarily result from iceberg calving off the Labrador Ice Shelf, maybe with some Fenno-Scandian or British input as well.

            Stadials need not result from just Arctic inflow but also into the Atlantic, and possibly even Pacific as well.

            Keigwin isn’t just modeling, but includes observational data, not that all modeling is necessarily as nad as GIGO GCMs.

            Please see this 2020 Bering Strait inundation study, confirming the MacKenzie delta origin of YD meltwater.

            Sea level fingerprinting of the Bering Strait flooding history detects the source of the Younger Dryas climate event


          • The YD happened to occur as a result of flow into the Arctic

            Your faith is touching, but it is just one of several hypotheses and as I have shown with several articles a controversial one. The causality is far from being supported by evidence. Science is not about faith but about uncertainties and one can never be sure about things that happened in the distant past. Same with Heinrich events. Icebergs are part of the events but there is no evidence that they are the cause. There is no point in discussing with people who believe they already have the answers.

            Which orbital conditions do you think ended the YD?

            That is not what I said, I said their duration is linked to orbital variations. The evidence supports that interglacials and Greenland interstadials are favored by high 65N summer insolation and high obliquity and disfavored when they are low. So GIs like the BA tend to be more frequent and last longer and GSs like the YD tend to be shorter when 65N summer insolation and obliquity are high. It can be seen in the data very clearly:

            GIs are inherently unstable in the Pleistocene and their instability is affected by orbital conditions. They are bound to end sooner or later. Under these conditions a specific trigger to end them is not required. The search for the cause of the YD appears to me misguided. Maybe it was a glacial flood what tipped the end of the BA, or maybe a solar induced cooling, or maybe a combination of factors.

            What is interesting is the timing of the BA GI. It happened a little bit too early to become part of the interglacial. The LGM was very cold and the planet was still too cold and the BA ended. This is not observed in other glacial terminations so it must be an infrequent event. The YD is not unique, we have registered about 20 of those. The BA is unique because of its timing.

          • You said that their “duration is linked to orbital conditions”. Isn’t duration determined by when the warm cycle ends, ie how long it lasts?

            The BA ended precisely when the MacKenzie outwash flood began. It’s not a coincidence because the causative mechanism is understood. No faith required, just the scientific method.

            That was also the time at which drainage via the Mississippi stopped.

            Prior deglaciations all show warmer and cooler fluctuations as in Termination I, but differ in detail, based upon orbital and rotational parameters. For instance, Terminations II and IV don’t have good analogies to the YD, but Termination III does. Also analogues for Heinrich Events 1 and 2:

            Abrupt climate changes during Termination III in Southern Europe


            Deglaciations and glaciations are ruled by Milankovitch Cycles, and so are their temperature ups (interstadials and interglacials) and downs (stadials). But all available evidence confirms the proximate cause of the YD as the 700 year-long flow of ice sheet meltwater and icebergs into the Arctic Ocean from 12.9 Ka. Just as Heinrich Events are caused by iceberg armadas in the Atlantic, whatever the ultimate source of their timing might be.

            You reject those conclusions, but to me the inferences look unavoidable.

            As for the earlier (c. 14.6 Ka) Meltwater Pulse 1a, this simulation found that the abrupt Bølling warming produced 3-4 m of global MSL rise from the North American ice sheet in 340 years, but that “this response (was) amplified to 5–6 m when (triggered by) the ice sheet saddle (between the LIS and CIS) collapse”.

            Abrupt Bølling warming and ice saddle collapse contributions to the Meltwater Pulse 1a rapid sea level rise


            Much the same thing happened 12.9 Ka, but the outflow continued longer and into the Arctic rather than directly into the Atlantic, causing the YD.

          • As I said there is no point in continuing this discussion as you are so convince that the hypothesis you support is the cause of the YD that you don’t admit even the slightest possibility that it might be a wrong one. One has to be aware that the vast majority of hypotheses ever proposed have turned out to be wrong or flawed, so most scientists are careful when they talk about the hypotheses they propose.

            The BA ended precisely when the MacKenzie outwash flood began.

            Precisely is an incorrect term. We are talking about imprecise datings. The YD is dated at 12,900 ± 50 years BP and the dating of glacial floods has a lot more uncertainty than ice cores so it cannot be ruled out that they took place a century or more apart.

            It’s not a coincidence because the causative mechanism is understood. No faith required, just the scientific method.

            No. The causative mechanism has been proposed. Nobody has ever demonstrated that a large glacial flood is capable of shutting down the AMOC and cause a millennia of cold climate.

            It is important to distinguish between what constitutes proof, what is just supportive, and what is based on assumptions. The MacKenzie flood is supportive but its effect on climate is based on assumptions. You don’t seem to be able to see this.

            Terminations II and IV don’t have good analogies to the YD, but Termination III does.

            Well, not really. At least not from the point of view of EPICA core.

            am convinced that Heinrich Events and YD-like intervals in terminations are caused by meltwater in the Arctic, Atlantic

            Now we are making progress. It is a conviction of yours. Convictions are dangerous in science.

            You should read JW Rheinlænder, 2020 thesis (and papers). The role of ocean circulation and sea ice in abrupt climate change. He says this:

            “In summary, the results presented in this thesis confirm that ocean circulation has played a persistent and central role in abrupt climate change in the past, but emphasizes that variations in AMOC strength might not be the main trigger. In addition, the thesis highlights changes in sea ice as a necessary condition to drive large and rapid changes in high latitude climate. Such changes may occur in response to unforced and self- sustained oscillations of the coupled atmosphere-ocean-sea ice system, demonstrating that abrupt climate change can occur without being subject to large external forcing.”

            It is clear that when considering all the evidence scientists are supporting different hypotheses. Recent research seems to support that changes in sea-ice might play a central role in abrupt climate change and are capable of triggering rapid changes through strong feedback effects. The MacKenzie flood is clearly not the only viable hypothesis at this point.

  20. I think massive eruptions of lava that last a long time are indications of volcanic impacts, like the Siberian Traps or the Deccan Traps, which formed the Indian Subcontinent. These are caused by impacts that generate shockwaves that cause the crust to rupture at the antipode. They also can cause extinction events.

    • The Yucatan impact had nothing to do with the Deccan Traps eruptions, which began before it.

      They had everything to do with the passage of the Indian Plate over the Reunion Island hot spot.

  21. “The evidence is buried in a Central Texas cave, where horizons of sediment have preserved unique geochemical signatures from ancient volcanic eruptions—signatures previously mistaken for extraterrestrial impacts, researchers say.”

    That is a clear as mud.

    Mud that is deposited in a cave as secondary, tertiary, quaternary, quinary, senary… levels of erosion.

    Expecting heavy and rare Earth metals to be found as distant isolated deposits in a cave is absurd.

    Nor are the volcanic episodes identified and verified by the volcanic craters and fallout.

    Competing theories are still competing theories without a clear conclusion.

    “No one really knows what drove the Dansgaard–Oeschger and Heinrich cycles… But neither impact events nor volcanic eruptions can explain such a clearly quasi-periodic climate change signal.”

    • Please read the paper:

      Volcanic origin for Younger Dryas geochemical anomalies ca. 12,900 cal B.P.

      Timing of volcano eruptions with Hall’s Cave sediment deposition

      Distant volcanic eruptions may provide both the compositional control and physical mechanism to produce the HSE-enriched cryptotephra horizons in Hall’s Cave. The multidecadal to century scale time resolution for sedimentation in Hall’s Cave obviate correlation with specific volcanic eruptions. However, this section documents significant eruptions within the time frame of the cryptotephra horizons fingerprinted by 187Os/188Os ratios and HSE systematics. These times indicate active volcanism in regions in the Northern Hemisphere that could have contributed cryptotephra to Hall’s Cave sediments. The cryptotephra horizon at 151 cm at the YD basal boundary layer at 13.11 to 12.90 ka was likely sourced from the 13.10 ± 0.10 ka eruption of Laacher See. The Laacher See eruption ejected 6.3 km3 (DRE) of sulfur-rich magma far into the stratosphere and likely dispersed volcanic aerosols throughout the Northern Hemisphere (8, 9). Laacher See released from 2 to 150 Mt of sulfur. Although under debate, this may have triggered the temperature decline associated with YD climate change in the Northern Hemisphere (10).

      To identify possible volcanic sources for the other horizons in Hall’s Cave that have 187Os/188Os ratios and HSE signatures consistent with cryptotephra, the 14C ages of large-magnitude volcanic eruptions during the late Pleistocene to Holocene are compared to the 14C ages of the five HSE-enriched unradiogenic horizons (UR1 to UR5) in Hall’s Cave (Fig. 1 and table S5). The five interpreted cryptotephra horizons can be grouped into three volcanic mixing events that correlate well with known eruptions. The couplet of UR1 and UR2 horizons at 176 and 171 cm BDT [below datum by Toomey in 1986; (23)], with a depositional age of 13.33 ± 0.19 ka, is similar to the Glacier Peak volcano in Washington, USA erupted at 13.71 to 13.41 ka and/or the J Swift tephra from Mount Saint Helens erupted at 13.75 to 13.45 ka (table S5). These eruptions demonstrate that the Cascade volcanic arc was highly active at these times and would likely have dispersed volcanic aerosols and cryptotephra widely across the Northern Hemisphere.

      There are possibly two eruptive candidates for Horizon UR5 at 140 cm BDT, which dates to 10.98 ka. Both the Fisher Tuff eruption from the Aleutian Arc and the Lvinaya Past eruption from the Kuril Arc occurred during the appropriate time interval (table S5). Each of these large-volume arc volcano eruptions produced a Plinian eruption column that reached the stratosphere and distributed volcanic aerosols across North America (46).

  22. I like it when these things go back and forth. Engages the mind.

    “But neither impact events nor volcanic eruptions can explain such a clearly quasi-periodic climate change signal.”

    I wouldn’t hang my hat on that. A periodic stream of meteor debris orbiting may have a large amount hit on one pass then not much or more on the next etc.

    Another possibility I’ve read about is that the sun has quasi-periodic Super-Carrington events.

    More interesting brain food to let digest. Love it.

    • None of the putative impact detritis is of ET origin, so there’s no evidence for a meteor or comet collision, hence no basis for imagining that such a thing caused the YD.

  23. Dear John T,

    Please don’t give up on WUWT. I thoroughly enjoy and have learned a lot from your contributions. Yes, the moderation may be slow at times, but there is not an army of paid staff here. Patience is a virtue…

    • Thanks!

      I know that everyone suffers delays.

      Do you also get 409 messages and lose comments entirely. I don’t always remember to save them, if worth saving.

  24. Who was it who said

    “They’ll kill us if it turns out to be natural variability”?

    Anyway, they are right…

  25. Wow!
    That was a big comment thread!
    I think what I got out of all that is that mankind better prepare for the consequences of a sudden glaciation event. I’d vote for a consistent development of nuclear power plants.
    It wouldn’t “cost” much, as we need the power anyways, and it would be resilient to cold climate change.

    • The precautionary principle would break the bank, probably for naught. We simply have to wait for objective evidence of an impending event and deal with it as best we can. And as of now there is no evidence that CO2 controls anything but the income of certain “scientists.”

      • True.

        But it wouldn’t break the bank to set up an asteroid detection and defense system, on the model of integrated air and missile defenses.

        Humanity might be able to interrupt the next glaciation, still probably thousands of years away. Fusion power would help.

  26. Perhaps I am too late for this party, but I would not have been invited anyway. I feel like a voice in the wilderness. I take exception with most of what is being said here. The first thing is, Charles Lyell was not at all accepting of catastrophic events on the large scale. Just read or see Richard Huggett’s book on the subject. Huggett clearly indicates an overwhelming opposition to catastrophes in Pleistocene and Holocene times. Lyell and James Hutton and others believed that most all the Earth’s geological processes were gradual. Secondly, I really take exception to some of the comments being made that comets and and / or asteroids have not been involved in initiating the Younger Dryas and some of the lesser but still cold and dry Holocene events. Well respected astronomers like William Napier, Duncan Steel, Asher, Victor Clube and John Lewis and more, have developed the theory of impacts as extremely important factors going back into at least the late Pleistocene. I as a climatologist for all my working life am following that theory and attempting to prove from a climate standpoint that many factors confirm their theory. One of the items I have found, is that meltwater could not have caused the Younger Dryas. There are so many reasons for this and oceanographer Carl Wunsch highlights this thought by saying, ocean water such as the North Atlantic are not driven by temperature and salinity change (thermohaline circulation). Instead, the mechanism involves winds and to some extent tidal forces. There is in addition,no proof that the North Atlantic circulation was slowed or stopped during the Younger Dryas as the few marine cores that supposedly supported the hypotheses have been proven as flawed. Also a marine core off the coast of Portugal indicates that the ocean waters were very saline during the Younger Dryas. Finally, the fact that events such as the Younger Dryas and other events like that near 8200 BP were so sudden, in perhaps in as little time as few years, or so excludes such ideas as the very slow, orbital, axis changes etc. of the Earth, as they are far too slow to cause climate shifts that are being addressed here.

    • You just don’t know what Uniformitarianism means…

      Uniformitarianism generally means:

      • Laws of nature (physics and chemistry) same today as in the past
      • Rates of processes may change (e.g. more heat in the very early Archaen from radioactive isotopes that have now completely decayed, so plate tectonics might have operated more rapidly)
      • Some processes very rare (e.g. large meteor impacts), but we can estimate their frequency and try to scale up the effects.  We might have to draw on observations from other planets, which suffer less erosion and recycling, to help understand such events on earth.

      Uniformitariansim is sometimes abbreviated as “the present is the key to the past”.  We observe processes operating on earth at present, and try to use them to interpret the record we see in the rocks.

      Meteor and comet impacts are covered. Noah’s flood isn’t.

    • Please read Lyell’s “Principles of Geology”. All editions are available on line. Lyell continually writes about the role of catastrophes–floods, volcanoes, earthquakes, etc.–in shaping Earth. A single sample from the first edition:

      “In speculating on catastrophes by water, we may certainly anticipate great floods in future, and we may therefore presume that they have happened again and again in past times. The existence of enormous seas of fresh-water, such as the North American lakes, the largest of which is elevated more than six hundred feet above the level of the ocean, and is in parts twelve hundred feet deep, is alone sufficient to assure us, that the time will come, however distant, when a deluge will lay waste a considerable part of the American continent. No hypothetical agency is required to cause the sudden escape of the confined waters. Such changes of level, and opening of fissures, as have accompanied earthquakes since the commencement of the present century, or such excavation of ravines as the receding cataract of Niagara is now effecting, might breach the barriers. Notwithstanding, therefore, that we have not witnessed within the last three thousand years the devastation by deluge of a large continent, yet, as we may predict the future occurrence of such catastrophes, we are authorized to regard them as part of the present order of Nature, and they may be introduced into geological speculations respecting the past, provided we do not imagine them to have been more frequent or general than we expect them to be in time to come.”

      Lyell defined uniformitarianism as the view that the geological processes observable now operated in the past. Today catastrophes occur, so they must have done so during the whole history of our planet. He contrasts uniformitarianism with catastrophism not because he believed that cataclysms don’t happen, but because he could see that Earth was not shaped by a single global flood.

      That the onset of the YD happened quickly is no surprise. Same goes for the beginning and end of the previous B/A warm spike. As the sources I’ve provided show, cold snaps like the YD during glaciations, deglaciations, and to a lesser extent during interglacials, as now, are associated with infusions of fresh cold water into oceans, affecting sea level, submarine and surface currents and atmospheric circulation.

    • You confuse Wunsch’s view of surface currents with deep circulation:

      Please cite the salinity studies you mention. Without knowing to which you refer, I can’t comment. But the Gulf Stream still functions during deglaciations, if farther south, so Portugal might well have been washed by salty water during the YD. I know that IRD from Heinrich Events indiates that icebergs from across the Atlantic off Labrador made it to off the Portuguese coast.

  27. Dave: Although I appreciate where you are coming from, not all agree with your conclusions in regard to catastrophic events as being a part of the Uniformitarianism doctrine as espoused by Charles Lyle and others . I have relied heavily for my information upon Richard Huggett and his book, “Catastrophism: Asteroids, Comets, and other Dynamic Events in Earth History, 1997, and also Michael Benton’s Book where he spells out Lyell’s thesis in detail, and his book is “When Live Nearly Died, The Greatest Mass Extinction of all Time” 2003. Thank you for your response Dave, regards, Rod Chilton

  28. John: Point taken re: Lyle, yes you are correct at least to some extent, but I am still not convinced he really appreciated the full range of where the catastrophes originate. Richard Huggett and Michael Benton do not nor did French scientist in Lyell’s time, Georges Cuvier. So I see a dilemma here, and I think it best we just disagree on this point. The other issue concerns me much more as and that is freshwater presence as acting to slow or shut down ocean circulation, in this case the North Atlantic. if you care to read what if you can hold of my earlier book “Sudden Cold: An Examination of the Younger Dryas Cold Reversal,2009, you will see some of the reasons that this did not happen. I am building on this with my new manuscript that I have been working on over the last nine or ten years as well. I also believe there is a synthesis of the views expressed as in the book on the Internet, if you type my name, it should come up. Finally, climate modelling failed to satisfy one of the main criteria, that of meltwater being able to initiate the North Atlantic shutdown rapidly. Regards, Rod Chilton.

  29. Thank-you John, I am aware of the influxes going into the Northern Oceans, but as you should know by now, I do not believe they disrupt ocean circulation, the nature we are talking about here. I certainly do respect your diligence in reading and writing John about this topic. It is just that again, we simply are not convinced by each others ideas. So be it, but like you I do find this time very fascinating and it is good to have intelligent debate, so missing from many other important topics. Kind regards, Rod.

    • And to you.

      I just go with the evidence, all of which that I’ve found points to weakening by cold, fresh water infusion of the AMOC during the Younger Dryas, to include predicted knock-on effects thereof. Some of the latter are even counter-intuitive, like Greenland Ice Sheet mass loss.

  30. In less than 48 hours Dr. Sweatman popped this bubble. Wait until the YDI authors respond, it will become even more clear Sun et al. fudged it. Conclusions start at 15:00 mins:

    The folks on this blog should understand the overwhelming compulsion for the mainstream to hide, fudge and “re-explain” the truth. Earth and paleo-climate are not a closed system. Mysterious “tipping points” are best explained by impacts and have zero relevance to our current situation, unless CO2 somehow attracts comet fragments. Comets are not nearly as fun politically.

    • George,

      You missed the whole point of this post.

      It doesn’t argue that volcanoes caused the YD. It uses volcanic geochemical deposits to show the YD impact “hypothesis” false.

      Explaining the YD by the Laacher See eruption (LSE) is just as preposterous as the YDIH, but volcanic eruptions do account for the supposed “evidence” of an impact.

      As you also must know Sweatman is only a little better educated for commenting on paleoclimatology than are you, a sociology undergrad. althoug your university does have good geologists, some of whom have even studied the Eifel Hot Spot, source of the 12.9 Ka LSE. They’ve, no surprise, discovered that the Greenland Pt signature doesn’t match any meteoritic source, nor for that matter LSE tephra.

      Thus all that geology can say about the putative Pt fingerprint near the start of the YD is that it definitely didn’t come from outer space.

      But I for one am glad to welcome the Crackpot in Chief to commenting here.

      • But now, on reflection, I find it ironic that your university is home to the three academics, ie two profs and a doctoral student, promoting the ludicrous LSE hypothesis for the YD, ie that attacked in the YouTube video you cite.

        But at least PhD candidate Charlotte Green shows that the Greenland Pt signature can’t be of ET origin.

        Investigating the origin of a Greenland ice core geochemical anomaly near the Bølling-Allerød/Younger Dryas boundary

  31. George Howard: Thank-you for your contribution. I have been attempting to defend the Comet hypothesis here, but I have not made much headway. I even cited well respected astronomers including William Napier, Victor Clube, D. J. Asher, Duncan Steel, John Lewis and must not forget scientists in other disciplines such as Firestone and of course yourself, who hold that the Younger Dryas was the result of impacts. Many including Firestone remained convinced that an impact event likely derived from the Taurid Meteor Complex is the origin. Also, it is absolutely ridiculous that volcanic eruptions, the nature of those cited in the paper referred to are able to cause more than a few years, to perhaps slightly more years of climate change, only the extremely ancient Deccan and Siberian traps would be able to accomplish this. And on the topic of freshwater being able to cause slowing of the THC, this has been proven to many, that it just not plausible. This I am attempting to spell out in my new book, that expands on what I wrote in the 2009 book ” Sudden Cold”.

    • Napier, et al, argue for a large, disintegrating comet, for which there is zero evidence.

      Clube argues for a meteor, for which there is zero evidence. But also, with fellow fantasists, for an escapee from the Taurid stream, ie Clube, Napier, Asher & Steel, from the last century. for which there is zero evidence.

      Lewis is a ChiCom shill. Please be careful as to whom you chose as friends.

      They’re all really old guys who have been shown wildly wrong repeatedly.

    • You’re right about volcanoes not being able to cause the YD, but the same applies to impacts, even if they did occur, which all evidence shows they didn’t.

      However the 700 year-long flow of meltwater into the Arctic Ocean not only could but did weaken the AMOC.

      The odds against an extinction event causing bolide impact within the past 13,000 years are 2000 to one, so, no surprise, there is no evidence whatsoever of such and event. Science requires evidence, unlike the fantasy of an impact on or above the Laurentide Ice Sheet, for which there is none, with all the evidence in the world against it.

      No matter how many fantasists you cite, argument from fantasists is a logical fallacy.

  32. If the odds are 1/2000 against , then the odds for would be1999/2000. I’ll take the latter.

    • The odds that an impact capable of mass extinctions occurred 12,900 years ago are one in 2000.

      We know that an impact did not cause extinctions during the YD because megafauna on Caribbean islands survived thousands of years after the YD until humans arrived there, but related animals were wiped out in distant Patagonia earlier.

      Also, many extinctions happened before and after the YD.

      The YDIH is complete, total and utter nonsense.

  33. John: Sorry but you are wrong on all counts, except that volcanoes, perhaps except the supervolcanos are not capable of long-term climate shifts the nature of the ones being considered here, and none of these has erupted big time within the past twenty thousand years plus.

    And John, I believe you have overstepped the bounds of good taste when you call scientists that I respect highly as fanatics. I have corresponded with William Napier many times over the past number of years and he is anything but, what you have said. I must take leave of this exchange with you, as you are never going to see the light and I will never except your line of thinking. Take care, Rod.

    • I don’t think that volcanoes can control the climate, just weather for a few years at most.

      It appears that you’ve misunderstood the point of this post as well.

      The volcanic signatures show the YDIH false, yet again. They don’t suggest that repeated eruptions caused the YD, as in the LES hypothesis.

      Dr. Napier’s supposedly scientific papers are as fictional as his novels. His cometary hypothesis is just as whacky and evidence-free as Firestone’s meteor impact delusion. People can make contributions outside their area of specialization, but Napier would have benefitted from studying oceanography, atmospheric sceince, paleoclimatology and geology before presuming to publish on these disciplines.

      • Napier’s cometary speculation fails even by his own discipline, astronomy. To qualify as a scientific hypothesis his WAG must make testable predictions capable of being confirmed or shown false.

        Where in the inner solar system is the parent body from which he claims cometary debris showered Earth, igniting fires? After just 12,900 years, it should still be there.

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