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Younger Dryas caused by a volcano after all?

One of the most abrupt climate change events in human existence was the Younger Dryas period about 13,000 years ago, and even though it was so sharp, and so severe, and so recent (geologically speaking) we still don’t know what caused it. A new paper argues that it is likely it was a volcano. But previously researchers have said “asteroid”.

The Earth was warming out of the last ice age, when it suddenly cooled, and stayed cold for twelve centuries, then warmed again, just as abruptly. This is what real climate change looks like, something we mere mortals are unprepared for and apparently have no way of predicting.

Spare a thought for the people alive at the time. They were subject to a fall of three degrees Celsius, apparently in the space of just one year, perhaps triggered by volcanic dust that darkened the sky.  What is still far from explained, whether it was by volcano or falling rock, was why the coldness continued so long then so suddenly ended. The snap  change wiped out some species, like possibly the last mammoths, and in some locations camels and horses.

The volcanic dust is thought to have fallen out within a few years. Presumably, the spreading reflective snow and ice locked in a cold era that would last 50 generations, but we don’t really know. If only we had scientific climate models that worked?

UPDATE: Coming soon, a better more likely explanation involving the sun. This volcano theory is really an excuse to remind us of what real climate change is like, and how little we know.

When is the next big volcano due, and is anyone prepared for that?

Younger Dryas, Climate Change

GISP

Cooling of Earth caused by eruptions, not meteors

Ancient sediment found in a central Texas cave appears to solve the mystery of why the Earth cooled suddenly about 13,000 years ago, according to a research study co-authored by a Texas A&M University professor.

Michael Waters, director of The Center for The Study of the First Americans and Distinguished Professor at Texas A&M University, and colleagues from Baylor University and the University of Houston have had their work published in Science Advances.

Some researchers believed the event – which cooled the Earth by about 3 degrees Centigrade, a huge amount – was caused by an extraterrestrial impact with the Earth, such as a meteor collision.

But Waters and the team found that the evidence left in layers of sediment in Hall’s Cave were almost certainly the result of volcanic eruptions.

Waters said that Hall’s Cave, located in the Texas hill country, has a sediment record extending over 20,000 years and he first began researching the cave in 2017.

“It is an exceptional record that offers a unique opportunity for interdisciplinary cooperation to investigate a number of important research questions,” he said.

“One big question was, did an extraterrestrial impact occur near the end of the last ice age, about 13,000 years ago as the ice sheets covering Canada were melting, and cause an abrupt cooling that thrust the northern hemisphere back into the ice age for an extra 1,200 years?”

Waters and the team found that within the cave are layers of sediment, first identified by Thomas Stafford (Stafford Research Laboratories, Colorado), that dated to the time of the proposed impact that could answer the question and perhaps even identify the trigger that started the ancient cold snap.

The event also likely helped cause the extinction of large mammals such as mammoth, horse and camel that once roamed North America.

“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, professor of geosciences at University of Houston and head of the research team.

“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.

“I was skeptical,” Brandon said. “We took every avenue we could to come up with an alternative explanation, or even avoid, this conclusion. A volcanic eruption had been considered one possible explanation but was generally dismissed because there was no associated geochemical fingerprint.”

After a volcano erupts, the global spread of aerosols reflects incoming solar radiation away from Earth and may lead to global cooling post eruption for one to five years, depending on the size and timescales of the eruption, the team said.

“The Younger Dryas, which occurred about 13,000 years ago, disrupted distinct warming at the end of the last ice age,” said co-author Steven Forman, professor of geosciences at Baylor.

The Earth’s climate may have been at a tipping point at the end of Younger Dryas, possibly from the ice sheet discharge into the North Atlantic Ocean, enhanced snow cover and powerful volcanic eruptions that may have in combination led to intense Northern Hemisphere cooling, Forman said.

“This period of rapid cooling coincides with the extinction of a number of species, including camels and horses, and the appearance of the Clovis archaeological tradition,” said Waters.

Brandon and fellow University of Houston scientist Nan Sun completed the isotopic analysis of sediments collected from Hall’s Cave. They found that elements such as iridium, ruthenium, platinum, palladium and rhenium were not present in the correct proportions, meaning that a meteor or asteroid could not have caused the event.

“The isotope analysis and the relative proportion of the elements matched those that were found in previous volcanic gases,” said Sun, lead author of the report.

Volcanic eruptions cause their most severe cooling near the source, usually in the year of the eruption, with substantially less cooling in the years after the eruption, the team said.

The Younger Dryas cooling lasted about 1,200 years, “so a sole volcanic eruptive cause is an important initiating factor, but other Earth system changes, such as cooling of the oceans and more snow cover were needed to sustain this colder period, “Forman said.

Waters added that the bottom line is that “the chemical anomalies found in sediments dating to the beginning of the Younger Dryas are the result of volcanism and not an extraterrestrial impact.”

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Younger Dryas caused by a volcano after all?, 9.0 out of 10 based on 68 ratings

118 comments to Younger Dryas caused by a volcano after all?

  • #
    Mal

    Volcanic activity leading to global cooling has always been the real risk to human beings and simply dwarfs any natural global warming
    We are so unprepared for this cooling

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  • #
    PeterS

    [Removed by request of PeterS.]AD

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    • #
      MCMXLIII

      Adult attention deficit disorder?

      [SNIP - Yes, too true, and now we've snipped. - Jo]

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    • #
      Peter Fitzroy

      [Snip about snipped]

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        • #
          Serp

          We should give credit where it’s due. My observation is that posts by Peter Fitzroy almost always open an extended chain of banter which can run for dozens of responses; moreover he has maintained this role without downright offensive acts such as those of that self styled invigilator who hasn’t posted for a while and whose name, blessedly, escapes me.

          33

          • #
            robert rosicka

            Serp because of Peter Fitzroy I have learnt so much more about CAGW and the con that it is .
            He might not realise it but his posts and links usually end up proving the opposite of what he is arguing thereby destroying the alarmist view that CO2 is bad and renewables are good .
            The many posts by commenters debunking his claims does confuse me though , is he working for the Ideologically brainwashed or is he working as a climate realist ?
            As an opponent to skeptics he seems to be helping us and moreso the newbies that come here undecided but looking for more info about CAGW , so from me thank you Peter for being a skeptics best resource.

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            • #
              AndyG55

              He certainly makes a HUGE target of himself and his comments.

              I often think he MUST be on the realist side to post so much anti-science comedy and satire of the AGW meme, continually pointing to facets of that meme which he must, by now, KNOW that he cannot back with any actual science.

              But he keeps doing it.

              As you say, the gift that just keeps on giving! :-)

              30

          • #
            Kalm Keith

            Wonderful.
            And we might add that he hasn’t been physically violent to anyone on the blog.
            Also he helps by reminding us that the blessings of Alessandra Occasio Cortez style activism and California style science are soon to be embedded in Australian culture.

            20

      • #
        R.B.

        Somebody has a ridiculously high opinion of himself.

        Since we are self designating as blog keepers, I think a warning should be added to Fitzroy’s posts. “Check his citations, because he doesn’t actually read them”.

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      • #
        R.B.

        [Duplicate]

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  • #
    DonS

    Hi Jo

    An interesting bit of research, hope they can repeat it at other sites. I was under the impression that a comet impact in Canada just north of the Great Lakes area had melted a lot of ice which had in turn flowed into the oceans and disrupted the warm currents and so plunged the world back into the glacial conditions.

    It may not be an either/or in this case. A big enough impact would result in a period of increased volcanic activity so some combination of the two may be at work. The length of time the cooling lasted seems to argue against a single volcanic event so it will be interesting to see how the research goes in future.

    Either way it makes all this wailing about a few degrees change over 300 years look a bit lame :)

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    • #

      I agree Don, the thing I found interesting about this was, as I said, it was so big, so recent, and so important and we still don’t know what caused it. Nor are we remotely prepared for a rapid cooling of any sort.

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      • #
        James Murphy

        Humans weren’t ready 13000 years ago. When it happens again, it won’t be remotely pleasant, and I imagine there will be a lot of victims everywhere, but over-all, the human species will do what it does well, adapt, innovate, and survive.

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      • #
        Javier

        The type of rapid warming and cooling that characterizes the Dansgaard-Oeschger cycle during glacial periods that produces the abrupt transitions between Greenland stadials and interstadials and back cannot take place during an interglacial as they require large changes in the input of fresh meltwater and sea-ice dynamics that depend on large extra-polar ice sheets. The closest thing was the 8.2 kyr event when proglacial Lake Agassiz had its final outburst.

        There is no danger of rapid cooling (or warming) on a global scale under present circumstances. You and your children are safe from that. It took three centuries for the Medieval Warm Period to turn into the Little Ice Age. It will take centuries for the present situation to turn into dangerous cooling.

        We will let Capt. Kirk and Mr. Spock deal with that situation.

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        • #

          Javier, even a one degree cooling would presumably reduce growing seasons and arable zones and affect food supply. And as you said, the 8200BC spike rather proves we are not at all protected from such events. And unless we understand the cause of the YD, I should think we don’t know whether we are protected from that either.

          It appears temps in Greenland reached modern levels briefly 12,500 years ago. Even despite that, those people weren’t protected from a major cooling force.

          11

          • #
            Javier

            The 8.2 kyr event cannot be repeated because the planet no longer has a big enough reservoir of cold fresh water to release to the ocean, since the extrapolar ice sheets finally melted around 7,000 years ago and polar ice sheets are very stable.

            The planet has a strong thermal homeostasis. One degree global cooling is huge. A large volcanic eruption could create problems but only for a short time, as the experience with the Krakatoa showed.

            What awaits us is probably what happened during the Eemian. Glacial inception is probably around 1500 years away. Our astronomical position is represented by the two dots in the first panel of the following figure:

            a) Obliquity configuration (continuous line; after Laskar et al. 2004). b) Summer energy at 70°N (dashed line; after Huybers 2006). Dots indicate current values. c) Methane levels (continuous line; after Loulergue et al. 2008). d) Carbon dioxide levels (dashed line; after Bereiter et al. 2015). e) Interglacial temperature profile (continuous line, no scale). f) Sea level (dashed line; after Spratt and Lisiecki 2016). g) Antarctic temperature anomaly (continuous line; after Jouzel et al. 2007). h) Greenland temperature anomaly (dashed line; after NEEM Community Members 2013). H11: Heinrich event 11. LEAP: Late Eemian aridity pulse. C25 and C26: North Atlantic cold events 25 and 26.

            The fun starts after glacial inception. The current climate situation does not provide support for alarmism, neither towards the warming side nor towards the cooling side. We are lucky to be living in a warm period this late in the interglacial. Let’s just enjoy it without panicking.

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      • #
        David Maddison

        We are possibly entering a cooling phase now. How will we survive that in Australia relying on some of the world’s most expensive electricity and a lack of dams and irrigation infrastructure, a denial of science, anti-development policies and no industry left to make things we can export apart from rocks?

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      • #
        TedM

        “Nor are we remotely prepared for a rapid cooling of any sort.”
        Correct to the point of being almost prophetic. Do WE believe that we can safely navigate such an event with wind and solar power. The deaths from cold related diseases could be, if I dare use the word, “UNPRECEDENTED”.

        A question for anyone with better meteorological knowledge than myself: would such an event reduce temperature gradients and result in generally lower wind speeds?

        If so, so much for our already unproductive wind farms.

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      • #
        Peter Fitzroy

        Rapid cooling and our capacity to survive it, equally apples to rapid warming.

        Also can you remove comment #2 – it is off topic

        27

        • #
          David Maddison

          Actually Peter, warming is not an issue at all, even if it were happening. Civilisation has made its greatest achievements during warming periods, e.g. the Minoan, Egyptian, Roman, Medieval warming periods.

          There has never been a period in human history when warming was a bad thing.

          Natural cooling such as the LIA, on the other hand, always results in famine, war and disease. The Chinese know this which is why they’re buying up agricultural land all over the world. China does very poorly during global cooling events as shown at the following link:

          https://c3headlines.typepad.com/.a/6a010536b58035970c01b8d0f76684970c-pi

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        • #
          AndyG55

          “equally apples to rapid warming”

          The world is in a COOL period in the current interglacial…

          …rapid warming is not an issue, even if it was occurring, which it isn’t.

          Another degree or two might bring the world up to the RWP, which was a very prosperous time for humanity..

          …. but not up to the higher temperatures of most of the first 3/4 of the Holocene when humans basically started to develop civilisations.

          Warming is not an issue.

          Even a little bit of cooling and could we head into an Ice Age, which would be a humanitarian disaster.

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      • #
        Graeme No.3

        Whatever the cause there is little doubt that there was a lot of cold water penned up in North America which fled into the ocean
        (see some of the Dakota badlands images) and I am told that similar sites are present along the Mackenzie river valley.
        When water has backed up 4,200 feet above sea level there is only one way it will go.

        https://www.britannica.com/place/Lake-Agassiz

        https://www.sciencedirect.com/science/article/abs/pii/S0033589413000756

        00

  • #
    Kalm Keith

    The full warming graph from the last Glacial Maximum about 20 to 25,000 years ago would have been interesting.

    At the maximum extent, the “Canadian” ice field mentioned was covering New York Central Park to a depth of almost a mile, say 1500 metres.

    It takes a lot of energy and a lot of time to melt that much ice and I suspect that a great deal of it was still there when the Younger Dryas event occurred.

    The Texas cave being explored is a long way from the proposed impact zone of the meteor up in Canada but most of any impact material might have been removed by the floods which eventually saw the ice cap taken further north.

    Was the source of the volcanic activity identified?

    Eighty thousand years of accumulated ice does take a while to melt.

    I’m a bit sceptical about the associated loss of species attached to this event YD.

    KK

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    • #
      sophocles

      I have a suspicion that Dr Michael Waters has some minor difficulties with orders of magnitude. I am not an expert in these matters so I can’t argue it. But I have a feeling that it would have to be a super-volcanic explosion to do what was done … and I haven’t found one of those in Texas this recently. And none of the standard ones (Phlegean Fields, Krakatau, Toba etc haven’t added their flavour to the mix at the right time.

      If you haven’t watched these videos (U-tube) you might want to. These are all pretty long,
      some up to three hours so you’ve been warned :-D

      There are missing things in Waters arguments.

      Joe Rogan Experience #606 – Randall Carlson
      Joe Rogan Experience #725 – Graham Hancock & Randall Carlson
      Joe Rogan Experience #872 – Graham Hancock & Randall Carlson
      Joe Rogan Experience #1124 – Robert Schoch
      Joe Rogan Experience #852 – John Anthony West
      Joe Rogan | The Strange History of the Denisovans w/Graham Hancock
      (the relevance of this one won’t be obvious yet)

      If you are interested, then when you’re ready, I’ll pass on more…

      Now, Mr Carlson and Mr Hancock are laymen, but Drs Schoch and West are not.
      Dr Waters misses the erosion of the Sphinx … that’s just one miss. Where did the rain come from?
      Was it pulverized ice sheet falling back down?

      I find `volcanic eruptions’ too convenient — to the point where I tend
      to regard them as a lazy man’s excuse. I didn’t find a volcano (or volcanoes) fingered by
      Dr Waters. Nor did my searching (admittedly brief) find any timely volcano. Or I missed the references.

      Consider too: There are two craters on the Hiawatha Glacier, not one.

      On Utube: NASA Finds Second Massive Greenland Crater

      Details for the first crater are easy to find.
      Point to remember: if it is impacts, the impactors
      are not meteorites but comet pieces. There are differences between the materials.

      And for a little background context:
      youtube: The Geography of the Ice Age.

      Just as a coincidence, there were two melt water pulses – one at the start
      of the YD 12900 YA and one at the end 10,600 YA.

      Enjoy and think about them

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  • #
    Contemptible Blackguard

    Forget about ADHD – Krudd has RDD or Relevance Deprivation Disorder. Check Brig General Robt Spalding Retired who wrote Stealth War. Gen Spalding might disagree with our so-called expert on China!

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  • #
    Peter Fitzroy

    Could the impact as described here cuase a volcanic eruption some where else?

    35

    • #
      el gordo

      I agree, if they can’t identify the volcano then the asteroid impact is more logical. We could look at the ice cores for confirmation, especially Greenland.

      The Younger Dryas put a damper on temperature rise, so unlike previous interglacials the Holocene wasn’t too hot and possibly as a consequence our descent into the next ice age has been more moderate. Enough time for humanity to get its act together.

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      • #
        Peter Fitzroy

        Someone with more skill them might be able to calculate the energy reduction required to lower the temperature as observed in the proxies, such a calculation could then be used to support the size of the volcano or the asteroid.

        As with warming, it ultimately becomes an energy calculation

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        • #
          David Maddison

          What warming?

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          • #
            AndyG55

            Much the same temp now as in the 1940s, maybe a bit cooler in a lot of the NH.

            Probably cooler than the MWP

            Definitely cooler than the RWP

            COOLER than most of the last 10,000 years

            Basically all we have had, very thankfully, is a slight rebound from the LIA, which was the coldest period in those 10,000 years.

            [typo fixed] ED

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        • #
          el gordo

          Its an energy calculation and the warm waters from Meltwater Pulse 1a circulated into the NH in very quick time, but the melting in the north was taking too long and the planet became unbalanced.

          The Antarctic Cold Reversal is a typical binge and purge phenomenon, length of day is altered.

          So I hypothesise that it took a thousand years for the cooler waters of the SH to reach the NH, causing the Younger Dryas, but i won’t discount the cosmic impact.

          01

          • #
            Peter Fitzroy

            It is a feature of the chaotic system, that it is impossible to model it even on the most broadest scales. The problem is that all we have are those models (including these reconstructions and attributions) for 99.99% of earth’s history.

            20

            • #
              el gordo

              True, but within the fog there is order, the planet is on autocorrect and looking for equilibrium. The YD was unavoidable, but after the jumpy start the Holocene finally settled down.

              The North American megafauna extinction is difficult to reconcile, along with the demise of the Clovis people.

              00

              • #
                Peter Fitzroy

                It is possible that the megafauna were a dead end, evolutionary speaking, and they were outcompeted by other genera. I don’t know enough to comment on the Clovis

                01

              • #

                A “disappearance” of a technology in a temporal record is not evidence of a demise.

                10

              • #

                there is no such a thing as an “evolutionary dead end” except in hindsight. You can never a priori make that statement about a species.

                10

              • #
                Peter Fitzroy

                Good point Gee Aye. I was not trying to suggest that they were doomed, more that interspecies competition was a factor

                00

              • #
                el gordo

                The Clovis may already have reached a genetic bottleneck at the Younger Dryas, but there was no need for the megafauna to disappear except for that warm spike before the YD.

                My reading suggests that warm interstadials have a tendency to do that, you can observe it in Australia much earlier. Flannery is wrong, humans were not responsible for the elimination of megafauna.

                00

              • #
                sophocles

                They were drowned and washed away by the massive floods caused by the rapid melting of the ice cap across Canada.

                Can you imagine a flood 250′ deep moving at 70mph?

                20

              • #
                el gordo

                A Biblical flood, its possible, I’ll follow that up.

                00

        • #
          sophocles

          The temperature in the YD dropped because so much of the north American ice caps were blown into LEO and to help it all along there were other smaller impacts.

          It goes cold when the sun is hidden. By the up-flung debris.

          The Northern forests burnt, so the Sun was also obscured by the smoke. Lots of “nuclear winter.”

          Look up the Taurid Meteor Stream. It hasn’t finished with us yet. The Earth passes through, not over nor around the Taurids twice a year: July and November. Fortunately for us Down Under it’s more a problem for the NH.

          Tunguska was a small Taurid, the airburst suffered in Russia a few years ago (as seen on all the dash cams)
          was an even smaller Taurid piece of cometary debris. If that one had come in on only a slightly more elevated path, it could have been 1500 killed rather than injured.

          There will be others. There are still plenty of Big Rocks in there.

          If you want to see a comet at work, search for Comet Shoemaker-Levy — you might be able to find some of the NASA videos of the lumps of that comet falling down on Jupiter. Without Jupiter, where it was in 1994, that could have been Earth.

          Comets have this nasty habit of falling to pieces. Their pieces also travel at higher speeds than your standard meteoroid. Kinetic Energy is 0.5mv²

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          • #
            sophocles

            bother: should have written it as: ½mv²

            10

            • #
              sophocles

              That’s better. Those bits of comet travel very fast and because they’re porous rock with lots of icy bits, they explode quite vigorously in atmosphere.

              Forcefully is a better word.

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  • #
    Strop

    But previously researchers have said “asteroid”.

    Wiki suggests a different reason and also that the Southern Hemisphere warmed.

    The Younger Dryas was the most recent and longest of several interruptions to the gradual warming of the Earth’s climate since the severe LGM, about 27,000 to 24,000 years BP. The change was relatively sudden, taking place in decades, and it resulted in a decline of temperatures in Greenland by 4 to 10°C (7.2 to 18°F) and advances of glaciers and drier conditions, over much of the temperate Northern Hemisphere. It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, in turn thought to have been caused by an influx of fresh, cold water from North America to the Atlantic.

    The Younger Dryas was a period of climatic change, but the effects were complex and variable. In the Southern Hemisphere and some areas of the Northern Hemisphere, such as southeastern North America, a slight warming occurred.

    20

    • #
      el gordo

      The Southern Hemisphere warmed naturally, which makes me think its not volcanic.

      ‘The North Atlantic region cooled during this interval with a weakening of Northern Hemisphere monsoon strength. The reduction in northward heat transport warmed the Southern Hemisphere due to a process commonly referred to as the bipolar-seesaw.’ Carlson 2010

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    • #
      Strop

      Wiki also refers to the eruption

      Currently available evidence suggests that the hypothesis that the Laacher See eruption triggered the Younger Dryas has considerable merit. Earlier, the hypothesis was dismissed based on the timing of the Laacher See Tephra relative to the clearest signs of climate change associated with the Younger Dryas Event within various Central European varved lake deposits. This set the scene for the development of the Younger Dryas Impact Hypothesis and the meltwater pulse hypothesis. However, more recent research places the very large eruption of the Laacher See volcano at 12,880 years BP, coinciding with the initiation of North Atlantic cooling into the Younger Dryas. Although the eruption was about twice size as the 1991 eruption of Mount Pinatubo, it contained considerably more sulfur, potentially rivalling the climatologically very significant 1815 eruption of Mount Tambora in terms of amount of sulfur introduced into the atmosphere. Evidence exists that an eruption of this magnitude and sulfur content occurring during deglaciation could trigger a long-term positive feedback involving sea ice and oceanic circulation, resulting in a cascade of climate shifts across the North Atlantic and the globe. Further support for this hypothesis appears as a large volcanogenic sulfur spike within Greenland ice, coincident with both the date of the Laacher See eruption and the beginning of cooling into the Younger Dryas as recorded in Greenland. The mid-latitude westerly winds may have tracked sea ice growth southward across the North Atlantic as the cooling became more pronounced, resulting in time transgressive climate shifts across northern Europe and explaining the lag between the Laacher See Tephra and the clearest (wind-derived) evidence for the Younger Dryas in central European lake sediments

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      • #
        el gordo

        ‘Laacher See volcano at 12,880 years BP, coinciding with the initiation of North Atlantic cooling into the Younger Dryas.’

        They are heavily reliant on positive feedback, because the effect from a large volcanic eruption would only be felt for around four years. I thought it might be a Bond Event but its fingerprint doesn’t show up in the Greenland ice cores.

        Our emergence from the depths of the YD is worth considering, temperatures increased 10 C degrees in ten years.

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      • #
        sophocles

        the operative word is slight.

        The Planet’s temperature when measured in Kelvins doesn’t change much. What the alarmists are doing is tromping around in the noise searching desperately for trends. One of the reasons things are not going how the warmists want is because noise is effectively random.

        10

    • #
      JCalvertN(UK)

      Re: ” It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole”. This nonsense was first proposed by Wally Broeker who postulated that world’s currents were part of a ‘global conveyor’ – driven by thermohaline downwelling in the polar regions. He further claimed that the Younger Dryas was triggered by an influx freshwater from the bursting of Glacial Lake Aggassiz – which stopped the thermohaline downwelling and in turn stopped the heat conveyor.
      In fact, in the Atlantic, warm water from the Equator is transported towards the arctic by the Gulfstream / North Atlantic Current. This is part of the North Atlantic Gyre (per Sverdrup) which is a solely WIND-DRIVEN system. Driven by the Hadley Cell – and nothing is going to stop that.

      40

      • #
        Phill

        Not nonsense. Extra salty water is concentrated when sea-ice forms as the salt is squeezed out of the forming ice-floes. The remaining water is heavier than normal sea water and sinks to the bottom of the sea. So in normal times there is a considerable northern pull from the Arctic to replace this sinking water, (which pops up a few millennia later off the coast of Chile). The Mediterranean is also a giant evaporation pan and clearly is part of the circulation problem as it creates a different easterly pull of water constantly refilling the basin and another outflow of cool dense salty bottom water that forms over the northern winters and mixes into the Gulf Stream flowing north. To state categorically that these systems cannot be disrupted by significant fresh water flows is wrong. Also have you considered the possibility that the sea currents drive the winds rather than the other way around.

        20

        • #
          JCalvertN(UK)

          RE: “there is a considerable northern pull from the Arctic to replace this sinking water”. ‘Pull’ is a physical impossibility without a significant surface gradient.
          Sure, there is such a thing as thermohaline downwelling. It contributes some of the driving force to the deep-water circulation – but it has no effect on the surface-water circulation – which is 100% wind-driven. The sinking water in the Arctic is more that adequately replaced by the wind-driven currents – without any need for “pull”.

          00

          • #
            sophocles

            Lake Aggassiz was just a puddle. It couldn’t possibly cope with the volume of water the icecap melting so rapidly produced. Ensure you view the Joe Rogan podcast on Youtube #606. It’s first on the list of the ones I posted further up. Pay attention to the numbers Randall Carson gives and see if you can imagine them.

            The megafauna were drowned and washed away … Can you imagine a flood 250feet deep and moving across the landscape at 70mph?

            Now think about what a freshwater pulse of that quantity of freshwater would do to the thermohaline current.
            What thermohaline?

            20

            • #
              JCalvertN(UK)

              But the wind would have kept blowing, and driving the North Atlantic Gyre which would have continued to transport heat from the equatorial regions towards the poles.
              Furthermore the currents system in the arctic is multi-tiered. The meltwater would have sat only on the top. Other processes could have continued to occur underneath.

              00

              • #
                sophocles

                But the wind would have kept blowing, and driving the North Atlantic Gyre which would have continued to transport heat from the equatorial regions towards the poles.

                Nope. We’re talking about a catastrophic disruption here. God knows how long it lasted and when I was last listening, He wasn’t talking. It might have taken several centuries for the weather to settle down after the first impact. If there was a second one towards the end of the YD, it would take another couple of hundred years.

                Go view the Joe Rogan podcast #606 with Randall Carson as his guest. Then view the others with Randall Carson and Graham Hancock. The YD was massively bad news. The mega fauna and Clovis man didn’t survive it. They were run over by 250ft deep floods moving as 70mph.

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      R.B.

      Not an interruption to gradual warming. The Bølling interstadial was extremely rapid warming and the cooling into the Older Dryas almost as fast and large as the start of the Younger Dryas.

      That we were peppered with large asteroids at the time is unlikely. A surge in volcanic activity as ice sheets melted is a possibility. Huge changes in ocean currents – much more likely.

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        sophocles

        Sorry: neither you nor I control the space traffic around this solar system.

        Go research the Origin of the Taurids and when you find a suitable rock to hide under, don’t tell me.

        As a spoiler:
        – a large (circa 100km in diameter) comet entered the Solar System sometime around 20,000 YA.
        – as comets tend to do when they approach the sun, it fell apart and formed two streams
        – we call those two streams today the Taurids
        – we pass through the Taurids twice a year.
        – according to Clube and Napier (look them up) there are bewteen 1 and 200 chunks of comet debris over a kilometer in diameter among the Taurids. If that doesn’t worry you, look up Tunguska on wikepedia and check it’s damage. It was only a little fella.

        the brighter a space object is, the bigger it is.
        While you’re looking stuff up, look up Comet Enke.

        Look up comet Atlas and what happened to it. It was supposed to put on a big show back in May. Did you see it?
        No? Neither did I.

        Those are all facts, not flights of fancy.

        If you can find a better rock to hide under, go to it.

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        el gordo

        The Bølling interstadial was most likely the cause of megafauna extinction.

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    tom0mason

    The problem with these kind of reports is the evidence and some questionable assumptions –
    “They found that elements such as iridium, ruthenium, platinum, palladium and rhenium were not present in the correct proportions, meaning that a meteor or asteroid could not have caused the event. “
    So do scientist really know so much about meteors (or asteroids) chemical signatures that they can be ruled out as the instigator of this event — especially considering that this happen about 13,000 years ago.
    Do meteors (or asteroids) have such a uniform chemical composition? Have meteors with an unusual iridium, ruthenium, platinum, palladium and rhenium chemical ratio never been identified, or is that scientists have only identified this type of evidence and have never looked any other?

    Sure there’s “evidence left in layers of sediment in Hall’s Cave were almost certainly the result of volcanic eruptions.” But that is an assumption, what volcano(es) and where?
    Was it just a super-volcano eruption, or was it many other (but still significant) lesser eruptions?
    Either way that still leaves the question of exactly where.

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      sophocles

      He’s wrong. There was a huge platinum spike. Which means one or more (large) comet fragments could have caused it.
      The deadly-to-dinosaurs meteor 66MYA was discovered because it left a big Iridium spike.

      I have neither heard of or know of any ratio of noble elements that characterizes such Extra Terrestrial hardware. As far as I knew, there were certain concentrations in the crust and anything which exceeded those supposedly typical crustal concentrations was/must be ET.

      I can’t find any volcanoes super or lesser which could have caused it. Time span is 12900 YA – 10,600 YA. If you can find any, please tell me.

      West Texas (where Water’s sediments are) are a long way south of where the action occured. (north west Greenland and across Canada.) Sediments are supposed to be difficult to deal with. I wouldn’t know as I’m not dealing with them. I’m also dubious about his claims for nano-diamonds and glass spherules. Aren’t they supposed to be
      atomic bomb (or equivalent) proxies? Aren’t they absent from volcanism?

      The collision positions are unknown. A few smaller ones are known but the biggy or biggies are not. The Hiawatha Glacier craters (there are two of them) are thought to be good candidates but we aren’t going to know until they are dated. In that detail, Waters is correct — dates for those are just estimates.

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        sophocles

        This is Dr Martin Sweatman’s criticism and suggestions on a similar paper also based on Hall Cave sediments.
        https://cosmictusk.com/befus-sun-sweatman-younger-dryas-comet-volcano/

        Sweatman has apparently posted a video so I’m off to look for it.
        This is science as it should be in action.

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        Eugenia

        I agree that this new conclusion is both 1) wildly exaggerated and 2) still only hypothetical, as it has yet to be replicated.

        Waters utterly fails to explain how his findings invalidate dozens of other studies done all around the world which have come to the same conclusion, e.g. that an asteroid was responsible for climate change at the start of the YD. Many of these findings are based on criteria other than the one he’s studying – for instance, the aforementioned increase in platinum.

        There is no reason why there could not have been a volcanic explosion AND an asteroid impact. The fact that Waters doesn’t mention any such possibilities makes him sound like more of a huckster who is desperate for funding, than a respectable researcher.

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    The Mauna Loa CO2 concentration time series graph shows distinct inflections at the time of the Mt Agung eruption, March 17 and May 16, 1963, and the Mount Pinatubo eruption, 12 June 1991. The CO2 series from Barrow Alaska shows inflections at the time of the Mount Pinatubo eruption and the earlier Tolbachik eruptions,6 July 1975 to 10 December 1976. In all cases the rate of increase in CO2 concentration decreased, presumably as a result of the ash clouds.
    Compare that with the most recent data from the Mauna Loa Observatory for June – July 2020. Not only has the world-wide shutdown in human activity not shown up in the weekly data series but the rate of increase in CO2 concentration has accelerated to the highest rate since measurements began at the Observatory, 62 years ago. The rate has steadily increased over that time from 0.55 ppm pa for the 3 years March 1958 to 1961, to 3.35 ppm pa for the latest 3 years July 2017 to 2020.
    Yet puny mankind goes on thinking that it can change the Earth’s climate and atmospheric CO2 concentration.

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      Kalm Keith

      As far as atmospheric CO2 goes, human origin CO2 is irrelevant.

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      Careful Bevan. Murry Salby has presented similar evidence, and also showed that the Bern model for CO2 residence time in the atmosphere used by the IPCC is completely false. And they sacked him.

      You may be next….

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        Thank you for the warning Aussie but I have been in retirement for the past decade so I can spend my time applying my experience and knowledge to analysing climate data. Perhaps one day when I am gone, the politicians might take some notice of my findings ??

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    Jojodogfacedboy

    Scientists tend to be hyper focused on only one or two theories and do not consider anything else.
    In the scale of the Universe, our planet is tiny.
    An object far greater then our planet could have past between our planet and Sun taking a day or two to which would have dropped the temperatures considerably.
    The second is that a massive object crashed into our Sun which could create a massive Sun spot.
    Just saying that their are other avenues to consider and not just the confined theories of our scientists.
    One thing has bothered me over the years was spectral analysis never took into consideration that each planet has different pressure when using this theory and would give a false reading using the same pressure as on our planet.

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      Jojodogfacedboy

      Or the object be partially orbiting and could partially cut our Sun’s rays for a few years or a combination…

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    Talking of volcanoes.
    Mount Sinabung in Sumatra has erupted, the plume is visible from space.

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      sophocles

      The smoke plumes from the NSW bush fires at the end of last year were also visible from space.

      How high has Sinabung’s plume reached?

      Has it beaten Pinatubo’s yet?

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    Gerald

    But, the volcano theory is on shaky ground :-

    “An extensively covered journal article by Sun et al. in Science Advances concludes that volcanoes — not a fragmenting comet — caused the Younger Dryas. Sun provides an invaluable trove of data, but less than 72 hours after the publication their interpretation is suffering.”

    https://cosmictusk.com/befus-sun-sweatman-younger-dryas-comet-volcano/

    &

    “Polymath professor takes down volcano paper; proper interpretation of data supports comet impact theory for Younger Dryas”

    https://cosmictusk.com/younger-dryas-volcanoes-or-comet-sun-befus-sweatman/

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    ralf ellis

    .
    I don’t buy this.
    The YD was unique because it not only caused cooling, but it was also coincident with a unique black-mat strata; it signified the end of all the megafauna; and it marked the end for Clovis Man. And Prof Vance Haynes said that their demise was instantaneous in geological terms – in less than a hundred years. Clearly this was more significant than a simple cool period.

    In addition we have the odd formations known as Carolina Bays – which have all the appearance of being low velocity impact craters, and all point towards a common radiant.

    https://www.ancient-origins.net/news-science-space/carolina-bays-and-destruction-north-america-004458

    RE

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    John F. Hultquist

    Oh dear. This idea is like a bad weed. It just keeps coming back.

    A very acceptable explanation is based on the large and continuous, for many many years, flooding of cold fresh water off of North America. Much of that went north into the Arctic Ocean (Mackenzie River) and then into the North Atlantic Ocean.

    One of the many problems with the impact hypothesis is the extended time of the cold period. Effects of volcanoes or asteroids do not last hundreds or even dozens of years. Unless, of course, there is a new one every year or two for a century.

    Read this and all the comments by John Tillman.
    WUWT: Aug 1; Younger Dryas Impact Hypothesis Takes Another Hit

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    Don Easterbrook

    This is total nonsense! The Younger Dryas was one of several late Pleistocene strong, abrupt, climate changes. About 15,000 years ago, the climate suddenly warmed from full glacial to full nonglacial in less than a century. Not long thereafter, the climate suddenly went from full nonglacial to full glacial. Volcanic eruptions can change global temps for a couple of years at most, so how could they cause a 1,300-year-long global cooling? Obviously, they can’t.

    On the other hand, there is a 100% correlation of solar magnetic strength, cosmic radiation, and production of beryllium-10 and radiocarbon in the upper atmosphere. Data can be found in “The solar magnetic cause of climate change and origin of the Ice Ages” at Amazon.com

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    Javier

    I agree with John Hultquist and Don Easterbrook that the volcano and cosmic impact theories don’t hold water. Younger Dryas was the last of a series of Heinrich events that are related to the Dansgaard-Oeschger (D-O) cycle of events taking place in the Arctic-North Atlantic region. It cannot be caused by a “one-off” event.

    When compared with other Greenland interstadial/stadial transitions the Younger Dryas (GI1/GS1 transition) is not particularly abrupt. It is less abrupt that GI/GS 4, 6, and 7 and more abrupt than GI/GS 8, 10, 11, 12.

    The solar theory of Heinrich events and Younger Dryas is not well supported by evidence. It is clear that Atlantic Meridional Ocean Circulation (AMOC) is central to the D-O cycle and that the forcing is most likely provided by fresh meltwater input and sea-ice dynamics in the Nordic Seas.

    Volcanoes don’t affect the climate (>30 years). They affect the weather over a few years. Pinatubo in 1991 is a very good example of this. It was the second eruption in terms of volcanic forcing since 1850, after the Krakatoa eruption, and its effects cannot be detected after just three years.

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      Javier

      By the way, during the Younger Dryas the Earth didn’t cool down, it kept warming. We know this for a fact because sea level continue rising during the Younger Dryas and that is incompatible with global cooling. The Younger Dryas cooling was essentially a Northern Hemisphere phenomenon, particularly in the Arctic/North Atlantic region, and was associated to simultaneous warming at the Southern Hemisphere, particularly at the Southern Ocean.

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        el gordo

        Antarctica and the Southern Ocean remained warm during the Younger Dryas because of the bipolar seesaw, but in looking for a trigger why not the Antarctic Cold Reversal? It appears to begin a thousand years prior to the YD cooling.

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          El G have you seen the latest Antarctic satellite study showing water flow into the southern ocean from the continent?

          Sort of supports your cooling idea. viz early 2000′s warmer conditions caused release of cold fresh water into the ocean which expanded the ice shelf to above average levels (yes warm means more ice due to drop in water temp plus higer freezing temp due to less salinity). Recently there has been less water flow and less ice (below average summer ice extents) therefore… is it cooling?

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            el gordo

            The recent paper which eluded to the fact that the Grand Canyon could be filled to the brim with Antarctic ice loss over 30 years. We already knew that some parts of the continent were showing more ice melt, like West Antarctica, but generally there is nothing new.

            I like the idea that warm salty water exists below frozen fresh water.

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              It is not true that we knew it already. The measurements are more than an incremental enhancement of previous data will enable a whole bunch of other studies that need baseline of this accuracy before getting off the ground. This is true of lots of research that gets labelled as “we already knew that”, or “why is this in such a high ranking journal”.

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        Don Easterbrook

        Javier,

        Take a look at any of the ice core data. They all show significant cooling to full glacial conditions during the YD.

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          Javier

          I am familiar with the ice core data. Antarctica and Greenland show completely opposite responses during BA and YD. Antarctica cooled during BA and warmed during YD.

          The response to YD by proxies varied depending on latitude. Shakun et al., 2012, had this figure (5b) showing how the planet responded to YD according to proxies:
          https://i.imgur.com/wQDPlN6.png

          You are too focused on Greenland records. Sea level continued increasing during YD and makes it IMPOSSIBLE that there was global cooling over the YD. There is no way around that. The cryosphere contracted during YD and that was due to the planet warming during YD.

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      Here is the problem Javier. Your comment says nothing about the paper in question. You merely state (and just state) another theory that you like. You then just arm wave that because some recent volcano had a certain effect that means it could not have been a volcano of a certain size, intensity and location operating in a completely different climatic period in the past.

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        Javier

        If you read the paper you will see that the authors are not defending or even proposing that a volcano was responsible for the Younger Dryas.

        The volcano hypothesis has few defendants because it has insurmountable problems including:
        - The Younger Dryas is the last in a series of similar events. According to Occam’s principle the explanation for the YD should be the same as for the previous similar events.
        - Volcanoes don’t affect climate, climate affects volcanoes:
        https://wattsupwiththat.com/2018/05/10/the-effect-of-volcanoes-on-climate-and-climate-on-volcanoes/

        The idea that volcanoes are capable of causing centennial or even millennial cooling is popular but contrary to evidence. The warm Holocene Climatic Optimum had a much higher level of volcanic activity than the cold Little Ice Age, according to GISP2 sulfate records.

        The evidence for other theories is in the scientific literature and too ample to discuss in a casual comment, but it is clear that the bipolar see-saw is involved because Greenland and Antarctic temperature records are doing the opposite during the Bølling-Allerød and Younger Dryas. There are dozens of studies that agree with the implication of AMOC showing changes in the strength of the currents or the formation of North Atlantic Deep Water. If you want to start reading about it I suggest:
        Lynch-Stieglitz, J., 2017. The Atlantic meridional overturning circulation and abrupt climate change. Annual review of marine science, 9, pp.83-104.

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          Don Easterbrook

          Javier,

          Read the papers by George Denton who published many, many 10Be dates on glacial erratics in New Zealand. They show that the YD and an earlier cooling were synchronous in both hemispheres.

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            Javier

            Instead of choosing the proxies that support your belief you have to give an adequate weight to proxies. LR04 is a global stack of benthic cores that records changes in sea levels through changes in δ18O. It is supported by sea level proxy records from multiple coral reefs in the tropics.

            The YD is almost invisible from the point of view of global sea level changes. It shows a slight decrease in the rate of sea level rise.

            https://i.imgur.com/Z0j6Uok.png
            https://i.imgur.com/aatCBMM.png

            Sea level is one of the best indicators of glacial conditions and quite consistent with Antarctic records over the past 800,000 years. Both indicate the BA/YD was a minor bump in the glacial termination, not the return to glacial conditions that you claim.

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    William Astley

    There has been too much time looking at temperature, ocean currents, CO2, and solar direct modulation of planetary cloud cover.

    Everything that is happening at the same time on the earth requires a physical explanation. Here are other observations which have been ignored which is odd, as the evidence is absolutely solid and multi source.

    There is a large region of the Northern hemisphere that recorded a sudden reversal of the geomagnetic field in that region, at the same time Younger Dryas abrupt cooling occurred. What caused the magnetic polarity on the surface of the earth to suddenly change, at the same time the planet abruptly cooled for 1200 years?

    It has been known for some time that super volcanoes occur at the same time that there are geomagnetic excursions.

    The geomagnetic field strength is 3 to 4 times stronger during the interglacial periods than the glacial periods. There is no physical explanation why that is true.

    The geomagnetic field is not ‘unstable’, as it changing periodically. Likewise, planetary climate is not unstable. Large planetary climate changes are periodic, not random large oscillations, driven by random forcing events such as super volcanic eruptions, which we have assumed, incorrectly, are occurring randomly. i.e. There is no forcing event that is causing super volcanoes.

    Also, the geomagnetic field changes are unexplainably abrupt.

    The geomagnetic field changes are being driven by something that can cause abrupt changes in the geomagnetic field in less than a decade.

    http://eprints.whiterose.ac.uk/416/1/gubbinsd4.pdf

    Is the geodynamo process intrinsically unstable?
    Recent palaeomagnetic studies suggest that excursions of the geomagnetic field, during which the intensity drops suddenly by a factor of 5 to 10 and the local direction changes dramatically, are more common than previously expected. The `normal’ state of the geomagnetic field, dominated by an axial dipole, seems to be interrupted every 30 to 100 kyr; it may not therefore be as stable as we thought.

    The largest change in atmospheric C14 in the last 20,000 years occurs, occurred at the same time as the occurrence of the Younger Dryas abrupt cooling.

    This is an excellent summary of summary of the observations concerning the Younger Dryas abrupt cooling.
    http://cio.eldoc.ub.rug.nl/FILES/root/2000/QuatIntRenssen/2000QuatIntRenssen.pdf

    Younger Dryas Abrupt Cooling Event
    …we argue that this is indeed supported by three observations: (1) the abrupt and strong increase in residual 14C at the start of the Younger Dryas that seems to be too sharp to be caused by ocean circulation changes alone, (2) the Younger Dryas being part of an approx. 2500 year quasi-cycle also found in the 14C record that is supposedly of solar origin, (3) the registration of the Younger Dryas in geological records in the tropics and the mid-latitudes of the Southern Hemisphere.
    Paleoclimatic context of geomagnetic dipole lows

    http://www.mendeley.com/research/paleoclimatic-context-geomagnetic-dipole-lows-excursions-brunhes-clue-orbital-influence-geodynamo/

    Paleoclimatic context of geomagnetic dipole lows and excursions in the Brunhes, clue
    for an orbital influence on the geodynamo?

    In the last 15 years, geophysicists have found the geomagnetic field is changing abruptly periodically correlating with climate change.
    http://geosci.uchicago.edu/~rtp1/BardPapers/responseCourtillotEPSL07.pdf

    The Gothenburg magnetic excursion is an unexplained large region of the earth’s surface where the geomagnetic field polarity reversed suddenly, reversed at the same time the planet abruptly cooled for 1200 years.
    http://www.sciencedirect.com/science/article/pii/003358947790031X

    The Gothenburg Magnetic Excursion
    http://link.springer.com/article/10.1134%2FS0016793212050076#

    Manifestation of the gothenburg geomagnetic field excursion in sediments on the northwestern Central Russian Upland
    http://onlinelibrary.wiley.com/doi/10.1029/2010EO510001/pdf
    What Caused Recent Acceleration of the North Magnetic Pole Drift?

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    Travis T. Jones

    Related numbers and words:

    July 2020: Ancient stone tools suggest first people arrived in America earlier than thought

    “Pieces of limestone from a cave in Mexico may be the oldest human tools ever found in the Americas, and suggest people first entered the continent up to 33,000 years ago – much earlier than previously thought.

    The findings, published Wednesday in two papers in the journal Nature, which include the discovery of the stone tools, challenge the idea that people first entered North America on a land bridge between Siberia and Alaska and an ice-free corridor to the interior of the continent.”

    https://www.nbcnews.com/science/science-news/ancient-stone-tools-suggest-first-people-arrived-america-earlier-thought-n1234578

    “Aug. 5 (UPI) — Archaeologists recently discovered 8,000-year-old stone fluted points on the Arabian Peninsula, the same technology developed by Native Americans 13,000 years ago, according to a study published Wednesday in the journal PLOS One.”

    https://www.upi.com/Science_News/2020/08/05/Native-American-stone-tool-technology-unearthed-in-Yemen-Oman/4961596654994/

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    Javier

    The scientific article at the source of this blog article does not defend that the Younger Dryas was caused by a volcano. A careful reading of the article at:
    https://advances.sciencemag.org/content/6/31/eaax8587
    shows that the authors just say that all the relevant geochemically and isotopically distinct layers around the start of the Younger Dryas have a volcanic origin. This means that there was no cosmic impacts at the time and thus it rules out the cosmic impact theory. But that does not mean that the authors defend the volcanic origin of the Younger Dryas. The authors are very careful in not even suggesting it. They even say that volcanoes have a very limited temporal impact and could not be responsible for the Younger Dryas. At most they could have contributed.

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    TdeF

    There is no man made Global Warming. The real temperature records show that the little tick at the end is insignificant. But those are just facts.

    However the Marxists and Fascists have moved on, taking over the BLM idea to riot throughout America and Europe. And government are pandering to sexual equality, black equality, identity politics, #METOO and could care less about safety, the Wuhan Flu or defence. Daniel Andrews signed an agreement with China when he had no legal right to do so. Those international rights were the reason the Commonwealth was formed.

    And the papers and media talk as if it is all real, carbon dioxide is pollution and now animals are the problem. And the police. And in America, any means of defending yourself. The promoters of revolution have not been as excited since 1918.

    No one talks about science any more. 30 years of indoctrination and a whole generation of people believes we are undergoing Climate Extinction, because they were told at school. And the censorship and book burning has already started.

    Of course it is all made up. Including the data. But Michael Mann and friends have done very well out of it. And that’s what matters. Although Tim Flannery wanted more and seems a bit p*ssed off. Good.

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    PeterS

    I am amused at all the various hypotheses. It is impossible to know how it all happened. No one was there to record a video of the event.

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      el gordo

      We have paleo climate history, from ice cores and shallow sea cores, corals, peat and tree rings.

      The main theory at the moment is the asteroid impact, so we can leave out the volcanic eruption. The other possibility is that the Bolling Allerod interstadial was running too hot and killed the megafauna, then the Antarctic Cold Reversal set in and a thousand years later the Younger Dryas began.

      Which one of these two theories is credible?

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    Stephen Richards

    The shape of that graph during the period from 12947 to 8630 does not suggest a straight forward explosive cooling and steady warming rather it suggests several stages of cooling, albeit that the initiation was sudden, and a more sudden warming. That doesn’t seem to me to be the profile one would expect from an asteroid but a series of very large volcanic eruptions might produce that profile. A series of eruptions would surely leave layers of ash, pumice etc of massive proportion if one could find it.

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    Stephen Richards

    The shape of that graph during the period from 12947 to 8630 does not suggest a straight forward explosive cooling and steady warming rather it suggests several stages of cooling, albeit that the initiation was sudden, and a more sudden warming. That doesn’t seem to me to be the profile one would expect from an asteroid but a series of very large volcanic eruptions might produce that profile. A series of eruptions would surely leave layers of ash, pumice etc of massive proportion if one could find it.

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    Bill Nichol

    Apologies if a commenter has already covered this, but the label on the x axis of the graph is incorrect. It is labelled “Years Before Present”. But the right had most number on the x axis is 1727, left hand most is -12947. It is simply years, where a negative number is BCE. If it really was “Years Before Present”, the smallest number could be on the right hand side, increasing to the left hand side. Odr the other way around, but no negative numbers.

    Call it a small detail, but when the small details that can be easily verified are wrong, it casts doubt on the accuracy of the big details.

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    Bill Nichol

    Apologies if a commenter has already covered this, but the label on the x axis of the graph is incorrect. It is labelled “Years Before Present”. But the right had most number on the x axis is 1727, left hand most is -12947. It is simply years, where a negative number is BCE. If it really was “Years Before Present”, the smallest number could be on the right hand side, increasing to the left hand side. Odr the other way around, but no negative numbers.

    Call it a small detail, but when the small details that can be easily verified are wrong, it casts doubt on the accuracy of the big details.

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    thingadonta

    Volcanos are always under estimated. They caused the biggest extinction at the end Permian, and had an input at the end Cretaceous. If big ones go off for thousands of years things start to go downhill. This can happen if somewhere in the crust becomes less stable and volatile. It doesn’t have to be a one off eruption, many extinctions relate to longer periods of volcanism.

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      el gordo

      The problem for the volcanologists is to prove the North American megafauna became extinct 12,700 years ago because of a large eruption. There is no evidence to support the proposition, but at the same time we could say the asteroid impact caused some volcanoes to go off.

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    I have been following the YD detective story for a long time. That volcanic activity took place at the time is no surprise.

    If you take a look at the stuff on the Mantle Plumes and LIP Commission sites, LIPs took place from time to time as far back as we can see. Volcanic activity overall has slowed down a bit as the planet has cooled, as has the temperature of what is erupted.

    I have wondered for a while if life on this planet is not accustomed to volcanic activity, as you rarely see a mass extinction unless something else is involved, usually an impact or other astronomical event.

    If the YD guys are right, you had a comet storm over North America, thousands of Tunguska sized airbursts over the period of an hour or so. Couple that with ongoing volcanic activity and you end up seeing evidence of both types of dust.

    The thing that is a bit scary about the YD hypothesis is that it posits a fragmented comet in the inner solar system. Today, we see 2 of those – the Kreutz Group and the Taurid Complex. I wonder if interaction with debris streams from fragmented comets has happened a LOT more often in geologic time than any of us have ever thought. Pretty difficult to see major global extinction events. Probably a LOT more difficult to see continental sized ones. Cheers -

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