Exploring abrupt climate change induced by comets and asteroids during human history

Loose Goose: The Bos all over the map

goose gander

Long ago the Tusk noted a fascinating 2010 missive from The Bos concerning the virtue of everyone (else) remaining intellectually flexible. Or, as he put it, having a willingness to “change your mind.” Here is the link and I have copied the text at the bottom.

The Bos’ statement has not aged well. I attended his 2009 AGU Session and I shared his admiration of Wally Broecker’s willingness to change his mind regarding YD initiation via a St. Lawrence floodway. It was kinda of neat to be there in person when a major theory took a turn with the driver at the wheel. In retrospect, though, I doubt The Bos would make his current appeal using Broecker as his example.

Here is The Bos’ concluding remark where he recommends Broecker to the YDB team as an example of a nimble intellect following the data wherever it may lead:

The Younger Dryas impact proponents would do well to follow his example.

When Scientists Actually Change Their Minds, Mark Boslough, Skeptical Inquirer, May / June 2010

And here is Broecker himself this year concerning the Younger Dryas impact in NatGeo:

“Most people were trying to disprove this,” said Wallace Broecker, a geochemist and climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Now they’re going to have to realize there’s some truth to it”.

Did a Comet Really Kill the Mammoths 12,900 years Ago?, National Geographic online, September 10, 2013

So, The Bos makes a sanctimonious appeal to actively publishing research scientists to change their minds and drop their theory, using as his exemplar a scientific authority who later re-considers his own previously critical opinion of the same theory —  a theory to which The Bos himself remains implacably opposed?! How rich!

Perhaps The Bos should take his own advice in the New Year, personally follow Broecker’s example, and carefully re-consider the YDB impact as a legitimate subject deserving further study.

As a graduate student in 1980, I was interested in impact cratering. I had just finished reading the comet catastrophe novel Lucifer’s Hammer when Luis Alvarez, the famous physicist from Lawrence Berkeley, came to Caltech to present a colloquium on his group’s asteroid hypothesis. It made so much sense. What else but an impact could possibly cause a global climate catastrophe and mass extinction?

Many years later, I read an article that featured Wallace Broecker, the Columbia University scientist with revolutionary ideas about catastrophic climate change caused by abrupt slowdowns in ocean circulation. I was fascinated by his idea that the rapid onset of the Younger Dryas cold spell could have been caused by the collapse of an ice dam and a deluge of freshwater into the North Atlantic that shut off the Gulf Stream, stopping the flow of tropical heat to the northern continents and plunging them into ice-age conditions. He showed that there could be other causes of global catastrophes that don’t involve impacts.

I was delighted when Broecker agreed to give the opening presentation at the American Geophysical Union (AGU) session I helped organize, but I was surprised to learn that he had abandoned his famous hypothesis about the cause of the Younger Dryas. He started his presentation by reminding everyone that he used to argue that it was triggered by the flood from the ice-age Lake Agassiz, but when he flew over the route the floodwaters should have followed, he saw no geomorphic evidence for a flood. He had changed his mind!

His primary objections to the impact hypothesis were the same as his objections to the flood he had previously championed as the explanation: lack of evidence and lack of uniqueness of the Younger Dryas. Abrupt changes in climate, both warming and cooling, have happened many times, and Broecker argues that the climate system is inherently unstable. Why should only one of a long sequence of changes have such an improbable and catastrophic trigger event—whether impact or flood—when the climate system has repeatedly undergone such changes all by itself?

In his 1987 CSICOP address, Carl Sagan said, “In science it often happens that scientists say, ‘You know that’s a really good argument; my position is mistaken,’ and then they actually change their minds and you never hear that old view from them again… . I cannot recall the last time something like that has happened in politics or religion.”

Broecker’s esteem among scientists was not diminished when he changed his mind. The Younger Dryas impact proponents would do well to follow his example.

Mark Boslough was co-organizer of the AGU Younger Dryas session in December. He is a physicist at Sandia National Laboratories and an adjunct professor at the University of New Mexico.

Mark Boslough

Mark Boslough is a physicist at Sandia National Laboratories and adjunct professor at the University of New Mexico. His work on comet and asteroid impacts has been the subject of many recent TV documentaries and magazine articles. He believes that the impact risk—at its core—is primarily a climate-change risk, and he has turned his attention to climate change as a looming national security threat. The opinions expressed here are his own.

12 Responses

  1. Boslough:

    “Why should only one of a long sequence of changes have such an improbable and catastrophic trigger event—whether impact or flood — when the climate system has repeatedly undergone such changes all by itself?”

    This is illogical, actually.

    There is the widespread ASSUMPTION that all the other changes were the climate doing it “all by itself,” but that may not be the case at all.

    Just as all the other solar system planets and minor planets have scads of craters from impacts, we all know Earth should have them, too. Napier and Clube keep argunig for fairly frequent impacts, and their numbers are not so far off of what the GISP2 ice cores for 18O show. The Dansgaard-Oeschger record only shows that climate shfts are sudden and fairly often.

    NOTHING in any of these records argues for one cause over another. It is only in the assumption of climate never having external forcings that the “all by itself” idea has claimed a foothold.

    The “all by itself” thing is simply an assumption. From gradualism. Because gradualism DICTATES the default position as being “all by itself”, they declare every other hypothesis into an “extraordinary claim” that requires extraordinary proof.

    If the YDB was an impact, and if Napier and Clube and Duncan Steele (and others) are correct, it makes good sense to inquire whether the other, earlier, sudden large climate shifts are not also impact-related.

    To overlook such a corrollary seems to make no sense.

    The gradualists have had things their way for far too long, when they have been proven WRONG so many times.*** How many passes do they GET, anyway?

    *** Evolution is NOT a gradual process. It comes in fits and spurts. If it were gradual then paleontologist Stephen J Gould would not have had to come up with “Punctuated Equilibrium” in which he pointed out that the overwhelming number of “new species” came along at only a FEW points in time (the Cambrian Explosion being the biggest of the lot). Logic would suggest that if mutation comes sometimes from radiation and if ET events can create some kinds of radiation, then it would be worthwhile seeing if the two are somehow connected in the history of new species.

    If the YDB hypothesis turns out to be true, it should open up Pandora’s Box in terms of corollaries. If it can happen once, why not twice? Three times?

    And if the one time YDB caused a climate drop (of -14°C in Greenland), are we sure it could not have occurred other times? If we think so, is our certainty perhaps misplaced?

    These are questions that WILL come up, if the YDB becomes accepted science.

    Just as Darwinism had several corollaries in other fields than biology, the YDB should begin to have a ripple effect in all different directions, too.

  2. Sagan’s comment about scientists changing their opinions but not religious or political leaders: scientists’ opinions are (supposed to be) based on facts, things one adds to or corrects through further study or thought. Relgion and politics is belief or ideology based and not subject to the rules of experience, apparently: Communism, in the green/left way, was not falsified, but suffered a corrupted application. This is why we still have avowed, hardcore socialists (closet communists) today, as well as Harold Camping preachers of imminent doom.

  3. Scientist’s opinions are generally (but not always) based upon evidence, which is constantly changing. ‘Facts’ have little or nothing to do with science and are more appropriate for a court of law.

  4. Thomas –
    Interesting nuance. “Evidence” vs “facts”. One suspects that you are saying that evidence is not hard-wired into the universe, which is what facts are. So the scientist, recognizing his falibility, stays skeptical of his own consideration of what objective reality is, while the Courts, forced into a philosophy of black-and-white so-as to come to a legal conclusion, pushes skepticism to the side and acts as if we really can determine what is, i.e. the “objective” reality.

    It is an interesting twist of view. I must consider it more. However, I am a believer that there is an objective reality, difficult as it is for a human (or other limited intellect) to determine. Although we may get it wrong a lot, we get it right sometimes, too. So in this worldview, the scientist actually trys to find the “facts” and the Courts, the “evidence”. In this way, the Courts are persuaded not by a determination of what-is in a Godly way, but by what appears-likely-to-be, based on indirect information.

    Still, you have made me think more about facts vs evidence. Thanks.

  5. Doug –

    Not to take the parallel too far along, there always have been examples of scientists and groups of scientists who did what they could to not let the truth and the whole truth come out.

    The Clovis Barrier is one that comes to mind that is along our topic line…

    Global warming is one a little closer to our time. The Climategate emails showed precisely how a clique schemed and plotted to prevent papers disagreeable to them from being published, and how they planned to control what editors and peer reviewers were allowed to be used. It is all in the emails, of them taking among themselves.

    The Velikovsky Affair was another example of scientists playing office politics and threatening publishers – all when it would have been far easier to simply refute point by point Velikovsky’s mistake and then let the debate process work things out. But, no, they had to play hardball and take personal attacks – without ever having read the book “Worlds in Collision.”

    Then you have Galileo and Copernicus, stifled by the church – one actively and the other less so. You can say that those weren’t scientists doing the blocking, but they were the pretty much the closest thing to scientists of the church, which controlled the thinking on scientific matters, so for those days it is a rough equivalent…

    Then I will bring up the Dr Robert Gallo situation in AIDS research, where the world’s best expert on retroviruses vehemently disagreed about the HTLV-III retrovirus being the cause of AIDS, and the Nobel Prize winner in Medicine, Cary Mullis agreed with the other guy. Gallo also used his political pull to claim someone else’s work (Luc Montagnier) as his own in applying for a patent and then making a huge out-of-court settlement to block exposure of his crime. Billions have been spent on AIDS research in the directin of HTLV-III (later renamed the HIV Virus) with no solution, yet no other line of research has been allowed – for 25+ years now. Some people will claim I am wearing a tin foil hat o that one, but I assure you that Gallo was a criminal who got away with it and then made many millions while people died. And the world is no closer to an AIDS cure now than in 1982.

    Once again, I will recommend searching on YouTube for “Feynman scientific method” and also google “Feynman Cargo Cult Science.” Feynman talks about the responsibility of scientists to not fool themselves and various other aspects of evidence/experience/experiment.

  6. All evidence and facts, like letters and words and human speech, are man made artificial abstract concepts, that are assigned meaning by groups. Evidence is the raw data, bits and bytes and the rest of it, and the abstract structures that are constructed from that data, facts are assigned a binary true false meaning for your convenience only, to simplify conversation, such as in a court of law, where the end result is a true false assignment. Facts are generally very simple statements, and when you look at a fact closer they will become less true or false. With regards to the Younger Dryas bolide hypothesis, rocks hit the Earth all the time, some are big, some are small, and they comprise a flux, which can only be assessed by the evidence. The bigger ones only approach the true false criteria as in a limiting situation.

  7. Hi TLE –

    I think you are mistaking the existence of physical reality from you way of talking about it.

    That said, while language changes with time, and our perception, the physical reality does not.

    In the case of impact events, no changes to language are needed, in my opinion.

    None to physics either.

  8. Actually, no, Ed, at the quantum level physical reality does change depending on how close you look at it. That appears to be the case at the cosmological level as well. It’s called ‘duality’.

    I’m not arguing there is no objective reality. I’m merely pointing out flaws in how you look at it.


    A new paper is out, with the work done at Sandia on impacts on planetesimals at the end stage of planetary formation.

    Though it is on impacts and the work was done at Sandia Labs, not whose name is NOT on the authors list.

    What does this tell us about who at Sandia knows about impacts? Or who knows who knows about impacts?

    Impact vaporization of planetesimal cores in the late stages of planet formation Nature Geoscience (2015)

    Richard G. Kraus, Seth Root, Raymond W. Lemke, Sarah T. Stewart, Stein B. Jacobsen & Thomas R. Mattsson

    Differentiated planetesimals delivered iron-rich material to the Earth and Moon in high-velocity collisions at the end stages of accretion. The physical process of accreting this late material has implications for the geochemical evolution of the Earth–Moon system and the timing of Earth’s core formation1, 2, 3. However, the fraction of a planetesimal’s iron core that is vaporized by an impact is not well constrained as a result of iron’s poorly understood equation of state. Here we determine the entropy in the shock state of iron using a recently developed shock-and-release experimental technique implemented at the Sandia National Laboratory Z-Machine. We find that the shock pressure required to vaporize iron is 507 (+65, −85) GPa, which is lower than the previous theoretical estimate4 (887 GPa) and readily achieved by the high velocity impacts at the end stages of accretion. We suggest that impact vaporization of planetesimal cores dispersed iron over the surface of the growing Earth and enhanced chemical equilibration with the mantle. In addition, the comparatively low abundance of highly siderophile elements in the lunar mantle and crust5, 6, 7, 8 can be explained by the retention of a smaller fraction of vaporized planetesimal iron on the Moon, as compared with Earth, due to the Moon’s lower escape velocity.

    For those here who wonder what I think about this, given my POV about accretion, they are talking about late in the formation of planets, which I don’t have a bugaboo about at this time. It is the initial stages of the accretionary theory that I think are flawed. Once the planetesimals are larger, then things begin to make more sense, about compression of the planetesimal. At that stage, impacts may even help drive the compression, below the impact target, and with a greater gravity the ejecta would more likely return to help the compression process, or at least not lessen it. The net – impact compression versus impact losses – may be a positive. Early on in hte process, one thing I argue is that the gravity is insufficient to bring the material back as regolith. It all hinges on the escape velocity for the mass, versus the ejecta velocities.

    My interest is in how they got large in the first place, and accretion just doesn’t hold water (no pun intended), IMHO. Large is obvious, since hat is what exists. The problem is the process by which small became large. Certainly there was a growing stage, which by current thinking had to be billions of years. The universe is about 12.5 billion years old, and the Earth is 4.0 billion years old, leaving 8 billion years for the universe to expand, for solar systems to develop their general geometry, and for planets to grow.

    In our case, we ended up with a solar system with minor objects flying around. Orthodoxy says that the entire system was comprised of such minor objects, which is why they point at comets and asteroids and tell us with a straight face that those solid objects became solid early on and gathered together, with billions of years for this to all occur. I argue that the composition of the minor bodies, if they include metamorphic rock material, is impossible, making their theory untenable. You can’t have rocks which are the result of metamorphism, out in space; they have to form deep inside planets. And if so, how did they get from many hundreds of kms inside planets to their present locations out there in space? They put the cart before the horse – the end results are looked at as the progenitors.

    This is an absurdity. And when in science you run up against an absurdity (such as formulas that come up with infinite mass or infinite velocities, or infinite size), it means it is wrong, fundamentally wrong. Here the absurdity is that the materials inside the meteors need planets to form, but the meteors are said to precede the very planets that they needed to come from. Their logic is flawed, from where I sit.

  10. It sucks that we are in a shooting gallery star system. It boggles the mind to think how far along we would be scientifically and culturally if asteroids and comets weren’t sending us back to the stone age every few thousand years – and hampering us in between with smaller ones.

    Well, THIS time we got far enough along that we might be able to buy more time, by mitigating the next big one. Hopefully we are smart enough to actually be prepared. I am VERY glad that we have people like Bill Napier and Victor Clube beating people over the head and helping to wake us up to the threat. We don’t need to be alarmed in order to address the issue. And this is not the biggest nor most expensive thing we can be alarmed about. We should be able to mitigate this threat without disrupting our societies and knowledge accumulation, and without freaking out. If we get to the freaked out stage, it will be when we see one coming, and we aren’t ready.

    In the long run, this could be the most important endeavor in all of human existence – just to stay alive. The ancient accounts seem to show that we had gotten fairly far before. Maybe this time we can get farther. And if we can mitigate once, then we should be able to do it on into the future, giving humankind a continuous period for development. It would be nice to see what we can accomplish with, say, half a million years to develop.

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