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Old 5th August 2015, 04:52 PM   #81
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Which has nothing to do whatsover with this thread or the anthro release of GHG gases on a large scale.

We can look at the Deccan traps and others for similar spikes in CO2 and fancy that, the earth was warmer..... amazing how physics works....

Quote:
Carbon dioxide emissions from Deccan volcanism and a K/T ...
www.ncbi.nlm.nih.gov/...
National Center for Biotechnology Information
by K Caldeira - ‎1990 - ‎Cited by 62 - ‎Related articles
A greenhouse warming caused by increased emissions of carbon dioxide from the Deccan Traps volcanism has been suggested as the cause of the terminal ...
http://www.ncbi.nlm.nih.gov/pubmed/11538480

A greenhouse warming caused by increased emissions of carbon dioxide from human burning of fossil fuels is the current state of affairs.
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Old 5th August 2015, 04:55 PM   #82
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I don't see why creationists would doubt climate change. God jacked the humidity all out of control that one time.
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Old 5th August 2015, 05:03 PM   #83
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Originally Posted by macdoc View Post
Which has nothing to do whatsover with this thread
Pretty sure natural variability in climate change is pretty fundamental to the topic of this thread, unless you are denying climate change ever happens except by one narrow cause. Perhaps you are the type of person Pixel42 could have been referring to? (I suspect unwittingly, on their part)

As for the rest of what you wrote, my earlier comment applies.
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Old 5th August 2015, 05:34 PM   #84
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You know perfectly well who the phrase 'climate change denier' commonly refers to. You (I suspect unwittingly) described them perfectly.
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Old 5th August 2015, 11:55 PM   #85
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CS - you'll take any opportunity to slip your pathetic anti-AGW proselyizing mantra in. Gets completely tiresome. Peddling "natural variation" ... Trying to gain some adherents are you??

You talk about "reasoning"!!!!!!???? ......
Reasoning does not trump evidence. You can chain logic all you like - without evidence it's idle speculation which you like to dress up in bafflegab to impress the unwitting reader and promote your "agenda" at every turn.

If there is "pet theories" clinging, its those that think a handful of humans did in the North American megafauna.

The topic is centred around NORTH AMERICAN mega-fauna - not Australia, not Madagascar

The evidence for a cosmic trigger for YD has been growing clearer over time. This last paper adds substantive detail and support for that thesis.

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Old 6th August 2015, 04:34 AM   #86
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Originally Posted by macdoc View Post
Reasoning does not trump evidence. You can chain logic all you like - without evidence it's idle speculation which you like to dress up in bafflegab to impress the unwitting reader and promote your "agenda" at every turn.

If there is "pet theories" clinging, its those that think a handful of humans did in the North American megafauna.

The topic is centred around NORTH AMERICAN mega-fauna - not Australia, not Madagascar

The evidence for a cosmic trigger for YD has been growing clearer over time. This last paper adds substantive detail and support for that thesis.
So I presume since Reasoning does not trump Evidence, you have an explanation of the Sporormiella spores evidence, and why that dropped long before the controversial black charcoal layers? Because by your own argument, no matter how unreasonable it may sound, it can't, on reasoning alone, trump the actual Sporormiella spores evidence.

PS You claim there were only a "handful of humans". Please tell me the population, including your evidence for that.
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Old 6th August 2015, 06:16 AM   #87
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Originally Posted by CoolSceptic View Post
Pretty sure natural variability in climate change is pretty fundamental to the topic of this thread, unless you are denying climate change ever happens except by one narrow cause. Perhaps you are the type of person Pixel42 could have been referring to? (I suspect unwittingly, on their part)
The fact that the Quaternary megafauna endured repeated climate changes, often on a scale few non-paleontologists/paleoclimatologists realize, is something that the "climate change did it" crowd tends to ignore. For climate change to be the cause, they must explain why it didn't cause mass extinctions any other time in the Quaternary, and they never do.

Originally Posted by macdoc
The evidence for a cosmic trigger for YD has been growing clearer over time.
All you have is weak evidence that can support multiple conclusions, as I've demonstrated.

Where is the crator? Where are the extraterrestrial isotopes? Where is the DIRECT evidence for an impact? What were the shallow marine fauna doing, or the plants? (We have absolutely astounding plant data, thanks to Neotoma middens; any discussion of North American climate change that doesn't include that data can be dismissed on that basis alone, as the authors clearly did not do adequate research.) Look at what it took to establish the Alvarez Hypothesis; THAT is what you need to provide.

Thus far I have seen no direct or unambiguous evidence for an impact--and believe me, this thread the least of my sources. I study this time period for a living and I have yet to see ANYTHING that directly relates to an impact. All ANYONE has provided is evidence that things went extinct, and the petulent demand (yes, your behavior in this thread has been petulent) that we accept that as proof of an impact.

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We can look at the Deccan traps and others for similar spikes in CO2 and fancy that, the earth was warmer..... amazing how physics works....
Please explain why during OIS 11 and the Late Cretaceous Ocean Anoxic Events there was no mass extinction associated with climate changes.
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Old 6th August 2015, 08:03 AM   #88
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The problem with what you've provided to disprove your interpretation, RBF, is that most of them are impossible to determine from the geologic record. I am impressed that you've put that much thought into it (macdoc clearly hasn't), but you also haven't examined the limits of what you can look for.

Personally, I'd have said similar testing with other cores, using additional proxies. The issue is that local conditions dictate what you see in core logs, not regional conditions. One needs to take a number of cores, across the region in question, to generate a coherent view of what happened back then. And one proxy isn't very robust; there's ALWAYS an alternative explanation. When using proxies, it's best to have multiple proxies that can be compared against one another. If we fail to see the same results in different cores and/or with different proxies, we can start building a case against your interpretation. I'd also call for a finer-scale sampling, though that'd jack the price up several orders of magnitude; it requires a highly skilled expert to sort through grains of sand for a few weeks, not cheap! Fun, though. Librivox.org has "The Hour of the Dragon" on audiobook, which is a fantastic way to sort this stuff (you want to distract your brain just a bit, to allow your eyes to sort through the stuff, as it's all pattern recognition).

I've got the equipment.....I really need to find an excuse to spend a week or two doing that again....It's a very good way to be productive, but still rest your body after field work.

The fact is, you've got a reduction in a proxy of a proxy for an actual value. You're looking for herbivore population density, and are using dung to estimate that, and are using spores in dung to estimate that. There are a myriad of alternative explanations besides the one that you favor for why that is--including alternatives you haven't identified, such as migration, disease (fungus get sick too), shifts in ecosystem composition that don't affect herbivore density (turnovers), shifts in hydraulic sorting, and the like. Someone more well-versed in microfossils can think of more, including issues with sample prep (always a fun discussion...). It's not that your argument isn't logically sound, it's just that it's not substantial enough to support the weight of the story you're building on it. Add in more cores, and we start to have something.
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Old 6th August 2015, 08:10 AM   #89
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Originally Posted by Dinwar View Post
The K/Pg impact is thought to have kicked up dust that reduced incidental radiation for 1k years.
Apples to bananas. The K/P impact was vastly larger than anything being discussed here. The K/P ~100X more energetic that the Toba eruption. The Toba eruption in turn was hundreds or thousands of times more powerful than any potential impact 12K years ago, it was the largest volcanic eruption in the 25 million years.

Despite its size the Toba eruption only impacted the Earths climate for about a decade and didn’t cause any large scale extinctions. Even for something as large as the K/P impact the dust and aerosols wouldn’t have stayed in the atmosphere for more than a couple decades. What it would have done is break the biological and chemical systems that keep the Earth’s climate at equilibrium. It would have taken at least 1000 years to re-organize and even then, in most cases it would be something completely new.




Originally Posted by Dinwar View Post

The real problem is we don't HAVE a good profile for impact-caused mass extinctions. We have precisely one to work with, so saying we have a profile is very drastically over-stating things. We have a fairly good idea of what happened at the K/Pg boundary (Gerta Keller's nonsense not withstanding), but again, Chixilub was a particularly bad place for something to strike
I disagree. I think we now have a pretty good idea of how mass extinctions happen. The details may change from extinction to extinction, but they occur when enough of the chemical, biological and physical systems that hold the earth’s climate and ecology at a semblance of equilibrium get disrupted simultaneous. When this happens these systems and all the other biological systems that depend on them collapse. Since most of these systems are global, the signature for this type of extinction is also global.

Originally Posted by Dinwar View Post
With the equitorial current in operation, I can see the northern and southern hemispheres reacting differently to a global forcing mechanism.
For ocean currents, yes but the stratospheric dust an aerosols that cause climate changes end up distributed in both hemispheres (just like CO2 ends up mixing though both hemispheres rather than being confined to the one where it was released.) Climate models show this and there is plenty of evidence from volcanic eruptions to show it’s true.

There are some teleconnections for ocean systems as well, but this difference between air and water currents creates a signature that can help identify the cause of a cooling event. An impact would be global in nature, while changes in ocean currents is mostly contained to the hemisphere the disruption occurred and tend to be very different between specific locations. E.G. while YD cooling was only ~ 0.6 deg C globally the cooling was almost all in specific places in North America and Europe where cooling was very large 10+ deg C in some places. This signature isn’t consistent with cooling from an impact or volcano.
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Old 6th August 2015, 08:31 AM   #90
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Quote:
The details may change from extinction to extinction, but they occur when enough of the chemical, biological and physical systems that hold the earth’s climate and ecology at a semblance of equilibrium get disrupted simultaneous. When this happens these systems and all the other biological systems that depend on them collapse.
Uh.....huh. And Romeo and Julliet can be summarized by "Teen lovers commit suicide."

There are a number of gaps in your model. First, the specific chemical, biological, and physical systems involved in each of the mass extinctions we know about are different. For that matter, we don't know what some of the systems involved were--we know what they could be, but what was doing what when is a notoriously difficult problem in paleontology. Paleothermometers are hard enough to come by; productivity and atmospheric composition are tricky at best; and EVERYTHING needs to be processed to remove local from regional from global signals. Second, the differences in biological responses clearly show that mass extinctions fall into two categories: mass die-offs (where origination rates remain reduced for a significant period of time) and mass turn-overs (where origination rates elevate relatively quickly, within the period of elevated extinction rates). What you've described cannot be said to account for that. Then you have the obvious stuff, the biases in the fossil record and so forth. Then you have the weird stuff--for example, was there a mass extinction between the Ediacaran and the Cambrian? These are not trivial questions.

As I said before, anything looks easy at the 1:1,000,000 scale. But when you get to the 1:24,000 scale, it becomes nightmarishly difficult. (For those who don't get the reference, these are scales used by USGS topographic maps, which serve as the basis for geologic maps. 1:24,000 is the standard quadrangle map, while 1:1,000,000 are state-wide maps that are of little value to anyone.)

Quote:
Apples to bananas. The K/P impact was vastly larger than anything being discussed here.
I never said that we were looking for an impact of the same size. I was pointing out the effects of such a large impact.

Quote:
Even for something as large as the K/P impact the dust and aerosols wouldn’t have stayed in the atmosphere for more than a couple decades.
Every study I've read disagrees with you. It nearly put the dust into orbit; it was well above the level where rain could wash it away, or where most other processes could strip it from the atmosphere.

Quote:
For ocean currents, yes but the stratospheric dust an aerosols that cause climate changes end up distributed in both hemispheres (just like CO2 ends up mixing though both hemispheres rather than being confined to the one where it was released.)
To a certain extent yes, but while there are connections between them they are separated to some extent while the equitorial currents are in place. The reason Antarctica is as the way it is is, in large part, because there's a current going around the continent, isolating it. The marine current has implications for atmospheric processes as well as marine ones, keeping it--to a certain extent--isolated from the rest of the world. The equitorial current would have similar effects when it is in operation.

I don't know of any studies of volcanism prior to the closing of the Isthmus of Panama (and therefore the shutdown of the equitorial current), so I'm not sure how you can make such a statement. Any modern volcanism occurs within a paradigm where there is no equitorial current, and therefore cannot be used to support your argument.

Quote:
An impact would be global in nature,
The signatures of global forcing mechanisms are necessarily filtered by regional and local conditions. It cannot be otherwise--the stuff has to be deposited somehow, and regional and local conditions determine that "somehow".

Quote:
E.G. while YD cooling was only ~ 0.6 deg C globally the cooling was almost all in specific places in North America and Europe where cooling was very large 10+ deg C in some places. This signature isn’t consistent with cooling from an impact or volcano.
No argument here.
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Old 6th August 2015, 08:35 AM   #91
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Good post lomiller

The YD bolide in no way compares to the K/T plus there is no known impact - just clear evidence of a cosmic event. Knock on from that leads to climate and biome changes.

This
Quote:
The details may change from extinction to extinction, but they occur when enough of the chemical, biological and physical systems that hold the earth’s climate and ecology at a semblance of equilibrium get disrupted simultaneous.
....it gets into semantics as to the exact mechanism(s) that led to the various extinctions once the initial event occurs. In Australia 60% of the mega-fauna were extinct before man arrived and the most likely culprit over that very long time frame is gradual climate change due to natural variability....the time frame is long enough.

The Clovis/North America situation is bounded by human arrival ( not 100% clear but anything earlier would have been miniscule ). The Younger Dryas onset and it's duration.
The YD is an anomaly, the cosmic event is a very solid explanation for that anomaly and the resulting climate change/biome changes a good explanation for the die off.

Humans may have played a small role.....but they were not the primary driver of extinction ....unlike now.

BTW two excellent science books - Song of the Dodo which deals with crashing populations and fascinating island bio-geograhy
and the KT Event - TRex and Crater of Doom ( don't be put off by the title - it's very tongue in cheek and exceptionally good science by the people involved at Berkley ).

Enjoyable reading you learn a lot and are entertained. Great combination.
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Old 6th August 2015, 08:44 AM   #92
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Originally Posted by Dinwar View Post
The fact that the Quaternary megafauna endured repeated climate changes, often on a scale few non-paleontologists/paleoclimatologists realize, is something that the "climate change did it" crowd tends to ignore. For climate change to be the cause, they must explain why it didn't cause mass extinctions any other time in the Quaternary, and they never do.
Climate changes are actually quite slow normally, with the fastest observed global changes since the K/T extinction being on the order of 0.1 Deg C /Century. Current climate change is on a whole different scale, it’s ~10X faster than other observed changes and its global not local so it impacts all regions not just selected ones and humans have sharply limited species ability to migrate.


Anyway regarding the impact theory, this isn’t “climate did it” vs “something else did it”. Realclimate has been covering this for a almost a decade and the mood among climate scientists certainly seems to be that an climate change caused by an impact doesn’t fit the climate data,
http://www.realclimate.org/index.php...ust/?wpmp_tp=1
http://www.realclimate.org/index.php...or-fools-gold/
http://www.realclimate.org/index.php...younger-dryas/
http://www.realclimate.org/index.php...ct-hypothesis/
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Old 6th August 2015, 09:13 AM   #93
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Originally Posted by Dinwar View Post
I never said that we were looking for an impact of the same size. I was pointing out the effects of such a large impact.
This doesn’t make sense...

Originally Posted by Dinwar View Post
Every study I've read disagrees with you. It nearly put the dust into orbit; it was well above the level where rain could wash it away, or where most other processes could strip it from the atmosphere.
Can you point to one that shows enough dust to cause significant climate impact put into a high enough orbit to stay there for centuries? You’d also need to consider the chemical behaviour would be different for orbiting dust than for Aerosols in the atmosphere which have the strongest cooling impact.
Originally Posted by Dinwar View Post
The signatures of global forcing mechanisms are necessarily filtered by regional and local conditions. It cannot be otherwise--the stuff has to be deposited somehow, and regional and local conditions determine that "somehow".
Incorrect. There are local, regional and global climate proxies and signatures. For a global proxy it doesn’t matter where you take it so long as you can date it.

Originally Posted by Dinwar View Post
I don't know of any studies of volcanism prior to the closing of the Isthmus of Panama (and therefore the shutdown of the equitorial current), so I'm not sure how you can make such a statement. Any modern volcanism occurs within a paradigm where there is no equitorial current, and therefore cannot be used to support your argument.
This seems like hand waving. While it;s not impossible that this did something to wind flow that would prevent dust and gasses from crossing hemispheres there is no evidence for it. We can’t really consider “possibilities” that have no known mechanism and no evidence that they occurred.

If the atmosphere were isolated by hemisphere it would show up in atmospheric chemistry, oxygen concentrations, CO2 concentrations, etc would differ between hemispheres . there is no evidence to support the notion that these were ever anything but well mixed.
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Old 6th August 2015, 10:49 AM   #94
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Originally Posted by lomiller
Can you point to one that shows enough dust to cause significant climate impact put into a high enough orbit to stay there for centuries? You’d also need to consider the chemical behaviour would be different for orbiting dust than for Aerosols in the atmosphere which have the strongest cooling impact.
Not offhand. It was for my graduate work, plus keeping a general eye on things since then (my current work doesn't let me play with the K/Pg very often).

Quote:
Incorrect. There are local, regional and global climate proxies and signatures.
NO. Emphatically and categorically NO. The are signatures, yes; HOWEVER, sediment is deposited in LOCAL settings. Organisms live in their LOCAL changing environment. This means that our understanding of global forcing mechanisms is always, always, always from sources that filter the global forcing through LOCAL conditions. ALL information from the fossil record is affected by taphonomy, and the fossil record is the only one we have.

Quote:
For a global proxy it doesn’t matter where you take it so long as you can date it.
Let's take this out of the abstract: What factors can affect the delta-C13 of a sample taken? (See "Isotopes: Principles and Applications" for a full discussion; Zachos et al., 2001 [Google it and you can find a free copy] has a decent overview, as I recall.)

Please note that I am in no way saying that we can ignore the statements made about global climate based on available sample sites. I'm not trying to dismiss global warming here. The issue is that you are grossly oversimplifying the issue, in ways that undermine the credibility of the entire enterprise, and are committing errors that I'm am more or less obliged to combat. I'm saying nothing about your conclusions here--it's your methodology that has deep flaws that any competant paleoclimatologist would not allow. In answering the above question, you'll see some of those issues and, hopefully, start to understand just how complex an issue paleoclimatology really is.

Quote:
This seems like hand waving.
What you are saying is that you don't care about the climactic paradigm of the time period we are discussing while you are discussing paleoclimatology. This is no different from an anti-vaxer refusing to read the ingredient list on vaccines while arguing against chemicals not in modern vaccines. There is no rational justification for it.

Quote:
While it;s not impossible that this did something to wind flow that would prevent dust and gasses from crossing hemispheres there is no evidence for it.
The presence of the equatorial current had profound implications for climate, including wind and weather regimes. This would have very strong affects on dust distribution.

As for no evidence, I assume you have either the experience in paleoclimatology to support this, or references that argue such? What would constitute evidence?

Quote:
If the atmosphere were isolated by hemisphere it would show up in atmospheric chemistry, oxygen concentrations, CO2 concentrations, etc would differ between hemispheres .
Right on! And humidity would be identical everywhere too! Just like it is today!!!

The reality is that we see variations in atmospheric concentrations of nearly everything we can test for, based on regional and local conditions. Oxygen levels vary, just ask anyone who's had to calibrate a YSI DO probe (you do that in air). CO2 values do too; there are mechanisms for local die-offs involving this. Humidity--let's just say I'd rather work in the Mojave at 100F than in Alabama at 100F. The real issue in this conversation, however, is weather--jet streams, storm patterns, and the like. Volcanoes do not spew their ash all over the world evenly; even the largest deposit more ash in some areas and less in others (ash is a good proxy for fine-grained particles as while the fine grained stuff extends further, the ash shows where it's going and is composed of mostly the same stuff). Where these areas are depends on regional and local weather patterns, things like prevailing winds, jet streams, sevarity of storms, and the like. If you have an equitorial current, the weather patterns for the northen and southern hemispher become increasingly isolated from one another--just like we see with Antarcitca today (so your line about there being no evidence for it is categorically false). All of this combined could easily keep a large scale volcanic eruption confined to a single hemisphere. Because our weather patterns are different--due to the failure of the equitorial current after the closing of the Isthmus of Panama--we cannot use modern weather patterns to understand the effects of ancient volcanism. Paleoclimatologists know this, which is why the models I've seen for that time period do not simply plug an impact or other factor into modern climate paradigms, but rather attempt to model past climate paradigms--including ocean currents--in order to understand what was actually going on.

Global forcing mechanisms are ALWAYS ALWAYS ALWAYS filtered by regional and local events. And sometimes by other global forcing mechanisms.

Quote:
Climate changes are actually quite slow normally, with the fastest observed global changes since the K/T extinction being on the order of 0.1 Deg C /Century.
Given that we have nothing that crosses the K/Pg boundary that can provide such data, I'm well within my rights to dismiss such statements. It's not necessarily that you're wrong; however, you're dealing with an average, and the average may be masking significant jumps and drops in temperature. (What we have is things before and after the K/Pg, and not nearly as many as people think because the Paleocene was not a particularly good time period for life.)

We can't say much at all prior to the Late Cretaceous. It's hard to get good data over long periods of time for that length of time, and it's even more difficult to find unaltered shell that can be dated with any semblance of this degree of accuracy. You can't use recrystalized critters as paleothermometers, as there's no way to prove that the isotopic ratios stayed the same during the recrystalization (and VERY good reasons to assume it didn't).

Quote:
Current climate change is on a whole different scale, it’s ~10X faster than other observed changes and its global not local so it impacts all regions not just selected ones and humans have sharply limited species ability to migrate.
None of which has any bearing on this conversation unless you wish to argue that large-scale industrialization occurred at ~12ka.

Quote:
...and the mood among climate scientists...
While they are not completely irrelevant to this discussion, I'm curious as to why you choose to focus on climatologists and not PALEOclimatologists. These are very different fields, requiring very different skillsets. For example, I would never expect a climatologist to understand the nuances of delta-O18 sampling or the like.

The rule of thumb is, when dealing with deep time the folks you work with should have "paleo" in their job title. Taphonomy and other considerations make teasing out data from the past too different from looking at modern data for folks doing the latter to be very good at the former.
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Old 6th August 2015, 02:07 PM   #95
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To clarify what I mean a bit:

We cannot directly measure paleoclimatological factors, such as temperature or rainfall. What we do is examine proxies. The two most common (Zachos et al., 2001, Figure 2) are stable isotopic ratios for oxygen and carbon. These allow a number of factors, including temperature, to be determined for a fairly long stretch of time, because organisms absorb these stable isotopes from the environment and integrate them into their bodies. For more recent stuff, ice cores can be used as well, though the utility of this methodology falls off pretty quickly by my standards (you don't have ice cores from the Tertiary).

This presents several problems. First and foremost, you must find unaltered biological material in order to sample--and that material must be extremely well dated. This means you need to find shells, corals, or other materials that have not been recrystalized, replaced, or otherwise altered, because any alteration could shift the isotopic ratios. The presence of such material decreases as you move backwards in time--more time means more chances for something to alter the composition. And even if you find an unaltered shell, if you cannot precisely date it it's essentially worthless. If you have a shell from a formation that can only be dated to "the late Eocene", there's not much utility to that datum; the late Eocene is a broad period of time. And the trouble there is that these are all dictated by local factors. Sedimentation rates are not globally driven, and volcanic ash layers are not cosmopolitan.

This is why I distrust rates of temperature change across the K/Pg: there's literally nothing that crosses that boundary continuously AND which can provide accurate temperature data. The stuff that crosses that line tends to be sediments, which cannot be used in paleothermometry. What we actually have are data points before and after the event, and we interpolate the rate of change by dividing the change between those points by the time between them--which assumes that the rate of change was constant, which may or may not be true. Look at Zachos et al.'s figure and you'll see the concentration of sample points. The further back you get, the less dense that concentration becomes. And when we're talking about geologically instantanious events such as bolide impacts, this becomes a real issue. You can cover a lot of change if you have a long enough time period.

The problem here is that local conditions dictate what gets preserved. You can have all the shifts in temperature, productivity, evaporation, and precipitation you want, but if nothing is preserved you don't get a sample. If the preservation is in a style not ammenable to precise dating, your sample isn't worth taking.

All of this holds true for any paleothermometer. It has to be unaltered, and it has to be able to be assigned a very precise date.

It gets even worse than this. There are known ways for global climate shifts to have paradoxical local effects. Global warming, for example, may actually COOL some areas, due to shifts in marine currents. So while the majority of the world will show a warming trend, that area may show a distinct cooling trend in various paleothermometers.

It's actually even worse for stable isotopic paleothermometers, though. THey work via thermodynamics--heavier isotopes take more energy to move around or to stop than lighter ones, so processes tend to favor one over the other. Problem is, multiple processes are at work. Any paleothermometer must be preserved--and the best way to do that is via organic material, specifically shells. The problem there is that organic processes can affect the outcome. Temperature can affect carbon isotopic ratios, but so can things like productivity. Oxygen isotopic ratios are affected by temperature, but also productivity and precipitation/evaporation. These are local affects, which can mask the global signatures. Teasing out the global from the local is a non-trivial process. I'm sure the statisticians are comfortable with it, but it's always seemed a bit voodoo to me, and it's VERY easy to trick yourself into thinking the data supports your conclusion when in fact you've biased your analysis. "Isotopes: Principles and Applications" discusses these issues in depth; in particular, Figure 26.4 illustrates the effects of regional variations in delta-O18 due to precipitation, for example (from -2 to -24, with the northern hemisphere being MUCH more variable). The discussion of carbon isotopic ratios is more focused on economic geology (makes sense, given the context of the rest of the book).

For the purposes of this discussion, there are a few take-aways:

1) Anything known must have been deposited, and deposition is always dictated by local conditions.
2) While global signatures do exist, so do regional and even local signatures, and teasing those out from the data is very tricky.
3) There are known complicating factors to the best paleothermometers we have (oxygen and carbon stable isotopic ratios), and those often involve local and regional issues.
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Old 6th August 2015, 02:11 PM   #96
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Originally Posted by Dinwar View Post
NO. Emphatically and categorically NO. The are signatures, yes; HOWEVER, sediment is deposited in LOCAL settings. Organisms live in their LOCAL changing environment. This means that our understanding of global forcing mechanisms is always, always, always from sources that filter the global forcing through LOCAL conditions. ALL information from the fossil record is affected by taphonomy, and the fossil record is the only one we have.
While the sediment layers may be local they still contain global signals like atmospheric conditions that existed when they formed. E.G. because high latitude ice sheets preferentially lock up O16, global reductions in atmospheric O16 are a proxy for larger ice sheets and colder global temperatures.
Originally Posted by Dinwar View Post
While they are not completely irrelevant to this discussion, I'm curious as to why you choose to focus on climatologists and not PALEOclimatologists. These are very different fields, requiring very different skillsets.
These are not nearly as different as you seem to think. Climatologists study a system and how it reacts. Doing so requires understanding the system itself and how it works. Because the laws of physics don’t change over time even if the initial state and forcing are different the system itself doesn’t fundamental change. When a climatologist is studying how the closing of Panama changes the earths climate they don’t develop a whole new model to describe it, they use the same models used to study other aspects if global climate.
Originally Posted by Dinwar View Post
The reality is that we see variations in atmospheric concentrations of nearly everything we can test for, based on regional and local conditions. Oxygen levels vary, just ask anyone who's had to calibrate a YSI DO probe (you do that in air). CO2 values do too; there are mechanisms for local die-offs involving this. Humidity--let's just say I'd rather work in the Mojave at 100F than in Alabama at 100
Sure there can be slight differences in concentrations even for well mixed gases, the fact that small variations exist doesn’t make them relevant and it certainly. Comparing them to a gas that is not well mixed simply shows us you don’t understand the distinction between a gas that is well mixed and one that is not.
Originally Posted by Dinwar View Post
Global forcing mechanisms are ALWAYS ALWAYS ALWAYS filtered by regional and local events. And sometimes by other global forcing mechanisms.
Global climate forcing is a function of energy flux at the top of the atmosphere. Even where it can be measured locally it’s only the aggregate that matters. The only “local or regional” events that matter are those large enough to show up in the aggregate. ENSO does, slightly, though not in the obvious way. La Nina cooling actually shows up as an increase in rate of energy entering the atmosphere, El Nino warming shows up as a decrease.

Originally Posted by Dinwar View Post
Given that we have nothing that crosses the K/Pg boundary that can provide such data, I'm well within my rights to dismiss such statements.
Why would we need data crossing the K/Pg boundary to make statements about what’s happened since?
http://www.sciencemag.org/content/341/6145/486
Finds that the current rate of climate change (of ~0.15 Deg C per decade) is at least 10X faster than any similar change in the last 65 million years.
Originally Posted by Dinwar View Post
What you are saying is that you don't care about the climactic paradigm of the time period we are discussing while you are discussing paleoclimatology. This is no different from an anti-vaxer refusing to read the ingredient list on vaccines while arguing against chemicals not in modern vaccines.
I’m saying you can’t just invent your own paradigm with no supporting evidence. There are no models that allow for atmospheric isolation between the two hemispheres nor any physical evidence to support it ever happened so “but what if it did” isn’t something useful to worry about. If anything the apt analogy here is that you are like the homeopath arguing that water has memory even though there is no physical basis or evidence to suggest it’s actually the case.

BTW, the most current research suggests the closing of Panama doesn’t explain climate conditions and changes occurring at the time.

http://www.nature.com/nature/journal...ture13597.html
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Old 6th August 2015, 02:22 PM   #97
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Originally Posted by Dinwar View Post
To clarify what I mean a bit:

We cannot directly measure paleoclimatological factors, such as temperature or rainfall. What we do is examine proxies.
We don’t actually measure very many things directly. For example to measure temperature “directly” we really measure things like height of mercury in a tube or electrical resistance in a wire. This doesn’t mean we are not ultimately measuring temperate.

What’s relevant is whether there is a signal present in the data and if that signal can be extracted from the data. Oxygen isotopes are actually are pretty good example because depending on how they collected and used there are local, regional and global temperature signals that can be and are extracted from them.
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Old 6th August 2015, 02:30 PM   #98
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Ice cores and places like Lake Baikal can give indications, location specific of the climate.

The team assessing the bolide got a geographically wide spread trace of that event. Good science....they think they have it within 100 years of the YD.

That is an excellent place marker to evaluate changes in other paleo biome data before and after that anchor point to build a better picture. Proxies from multiple areas geographically and temporally all help to build both at least a hemispheric picture and timeline ....and hopefully outliers are muted.

Good example where multiple approaches are synthesized on a hemispheric basis.



Courtesy realclimate
http://www.realclimate.org/index.php.../paleoclimate/

http://www.realclimate.org/index.php...constructions/

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Old 6th August 2015, 04:37 PM   #99
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Originally Posted by Pixel42 View Post
You know perfectly well who the phrase 'climate change denier' commonly refers to.
Oh, don't worry, I'm quite familiar with how the term "climate change denier" is used. Let me explain.

It is a poorly constructed, loaded term used by political activists to exploit the logical fallacy of guilt-by-association. It is used by the scientifically inept activist to smear those who have valid, coherent criticism of the climate science community (e.g. Freeman Dyson, John Christy, Steve McIntyre, Tim Cohn) by associating them with those whose criticism of climatology does not rise above junk science (and there is no shortage of those - e.g. Claes Johnson, Monckton of Brenchley, Piers Corbyn et cetera)

Indeed, it is my familiarity with the term that caused me to treat it with the derision it deserved when you used it earlier.
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Old 6th August 2015, 05:06 PM   #100
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Originally Posted by macdoc View Post
CS - you'll take any opportunity to slip your pathetic anti-AGW proselyizing mantra in. Gets completely tiresome. Peddling "natural variation" ... Trying to gain some adherents are you??
It's okay macdoc. There are some things you will never understand.

Such as the elegance and beauty of a simple mathematical formula that fully encompasses the spectrum of climate variability - cosmic impacts included - by describing the natural dispersion of energy through the system. No other simple formula comes close to describing the behaviour of the climate system across nine orders of magnitude of scale.

But if you don't understand the mathematics behind it, you cannot see the elegance or the beauty of the solution. I wouldn't say the maths is terribly difficult - probably grad level physics would be sufficient, with an intuitive grasp of statistics - but it simply isn't something you can pick up just by reading the papers, you need more than that to get a real understanding.

I feel a little sorry for the way you flail around trying to find fault with something you don't understand, much like watching a creationist trying to find fault with evolution. But trying to educate you is about as likely to succeed as trying to educate a creationist.

If I really cared about converting others, I would have written a layman's guide to this some time ago. But as someone who finds beauty and elegance in mathematics, it pains me to describe it in crude analogies. Ho hum. Maybe one day.
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Old 7th August 2015, 02:54 AM   #101
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Originally Posted by CoolSceptic View Post
it is my familiarity with the term that caused me to treat it with the derision it deserved when you used it earlier.
I save my derision for people who deny well established scientific facts because they are emotionally invested in beliefs which require them not to be true. People like creationists, woo slingers and climate change deniers.
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Old 7th August 2015, 05:09 AM   #102
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or financially invested perhaps ...in the case of some, even financially rewarded for purposed obfuscation delivered pedantically.
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Old 9th August 2015, 06:27 AM   #103
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Bones of elephant ancestor unearthed: Meet the gomphothere

Quote:
the bones that Holliday and his colleagues uncovered date back 13,400 years, making them the last known gomphotheres in North America.
...
Radiocarbon dating, done at the UA, puts the El Fin del Mundo site at about 13,400 years old, making it one of the two oldest known Clovis sites in North America; the other is the Aubrey Clovis site in north Texas.

The position and proximity of Clovis weapon fragments relative to the gomphothere bones at the site suggest that humans did in fact kill the two animals there. Of the seven Clovis points found at the site, four were in place among the bones, including one with bone and teeth fragments above and below.

Finding Would Reveal Contact between Humans and Gomphotheres in North America

Quote:
This finding completes a scene in which archaeologists visualized how Clovis groups hunted this elephant ancestor. “This is an unprecedented finding in Mexico since it is the first time that projectile heads are found associated to a bone bed of this kind of proboscides.
It's evidence.
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Old 13th January 2017, 05:42 AM   #104
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snip
Quote:
This single fossil has changed the nature of the megafauna extinction debate. We can now abandon the rapid/over kill hypothesis and start to untangle how climate may have played a role, or how changes in Aboriginal population numbers may have impacted on the ecology of the megafauna?
Becoming clearer in Australia that overkill is not the main factor..

Quote:
Aboriginal Australians co-existed with the megafauna for at least 17,000 years
January 11, 2017 7.56pm GMT

Australia was once home to giant reptiles, marsupials and birds (and some not so giant), but the extinction of this megafauna has been the subject of a debate that has persisted since the 19th century.

Despite great advances in the available scientific techniques for investigating the problem, answering the key question of how they became extinct has remained elusive.

Indeed, the same questions as those asked in the 19th century by scientists, such as the British comparative anatomist Sir Richard Owen and the Prussian scientist and explorer Ludwig Leichhardt, remain: were people responsible for their demise or was it climate change?

Our new research, published in the latest Quaternary Science Reviews journal, shows that early humans to Australian lived alongside some of the megafauna for many thousands of years before the animals became extinct.
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Old 13th January 2017, 06:31 AM   #105
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Originally Posted by macdoc View Post
Was there not some talk previously about a ton of small comets hitting the atmosphere daily - supplying much of the water?
I recall reading an article about that years ago in OMNI magazine. The notion was that there was a relatively constant infall of small comets into the upper atmosphere, resulting in a fairly large accumulation of water over years.
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Old 13th January 2017, 12:50 PM   #106
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I think that has been discounted and the discover of water so deep in the crust leads to the conclusion the water was part of the planetary formation in the first place.
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Old 27th January 2017, 06:59 PM   #107
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Back and forth it goes...seems I saw one support human overkill...

Quote:
Climate change helped kill off super-sized Ice Age animals in Australia
During the last Ice Age, Australia, Tasmania and New Guinea formed a single landmass, called Sahul. It was a strange and often hostile place populated by a bizarre cast of giant animals.
Date:
January 26, 2017
more
https://www.sciencedaily.com/release...0126163025.htm
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Old 10th March 2017, 12:36 PM   #108
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and back in North America

Quote:
Discovery of widespread platinum may help solve Clovis people mystery
Date:
March 9, 2017
Source:
University of South Carolina
Summary:
No one knows for certain why the Clovis people and iconic beasts -- mastodon, mammoth and saber-toothed tiger -- living some 12,800 years ago suddenly disappeared. However, a discovery of widespread platinum at archaeological sites across the US has provided an important clue in solving this enduring mystery.
https://www.sciencedaily.com/release...0309120656.htm
but looking more and more like an impact/climate change extinction even than human overkill
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Old 8th April 2017, 05:13 PM   #109
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Nice overview from NOVA on impact and other hypothesis.

https://www.youtube.com/watch?v=MGbwzpQUtXk

and newer material points to impact..

Quote:
Heavy Metal: Comet-driven megafauna extinction?
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Posted March 13, 2017
Roughly 13,000 years ago, large ice-age mammals known as megafauna — horses, camels, mammoths, mastodons and many others — suddenly disappeared in North America. At the same time, a widespread human culture vanished. Mounting scientific evidence suggests this happened in dramatic fashion by a comet or an asteroid slamming into the Earth.


This cliff profile at Arlington Canyon on Santa Rosa Island shows platinium abundance.

New research by UC Santa Barbara geologist James Kennett and colleagues bolsters the argument for indications of such an event, which ushered in a cool period known as the Younger Dryas.

The team had previously identified, from a thin layer at the Younger Dryas Boundary (YDB) dated to 12,800 years ago, a rich assemblage of high-temperature spherules, melt glass, nanodiamonds and other exotic materials, which can be explained only by cosmic impact. Now they can add platinum to the list.
http://www.technology.org/2017/03/13/heavy-metal/

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Old 13th April 2017, 04:14 AM   #110
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Meanwhile, from another perspective, there is this (among others):

Comprehensive analysis of nanodiamond evidence relating to the Younger Dryas Impact Hypothesis

Daulton, T. L. et al (2016)
http://onlinelibrary.wiley.com/doi/1.../jqs.2892/full

Which pours a lot of cold water on the impact hypothesis evidence presented up until then. To quote part of the conclusions:

Quote:
The YDB nanodiamond data are considered by some as the strongest physical evidence for a YD impact/bolide event. We have analyzed the nanodiamond data used to provide evidence for the YD Impact Hypothesis and have identified critical problems with the collection of those data and/or the data interpretation.
And;
Quote:
To perform the highly challenging measurement of nanodiamond abundance in sediments/ice, methods other than TEM will need to be explored and developed. Any method must be tested/calibrated against control specimens (sediments/ice initially devoid of nanodiamonds, that are spiked with measured p.p.b. amounts of nanodiamonds). Furthermore, unlike previous abundance measurements, future measurements must be conducted as blind studies to preclude unconscious bias.
In other words, some researchers might be seeing what they want to see. Therefore I would take the platinum abundance data with a pinch of salt, until such time as it has been independently verified. Kennett is one of the researchers mentioned numerous times in the paper I linked, whose work is questioned therein. The paper is sadly paywalled, however, pm me if you want a copy.
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Old 13th April 2017, 10:27 PM   #111
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Did you see the diamond quantity only in the one layer and one of the types is only created by impact.

If they are not present above and below ....bit obvious isn't it.

Eh sorry - that was a NOVA presentation.

https://www.youtube.com/watch?v=MGbwzpQUtXk

http://www.pbs.org/wgbh/nova/clovis/debate.html

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Old 14th April 2017, 03:34 AM   #112
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Originally Posted by macdoc View Post
Did you see the diamond quantity only in the one layer and one of the types is only created by impact.

If they are not present above and below ....bit obvious isn't it.

Eh sorry - that was a NOVA presentation.

https://www.youtube.com/watch?v=MGbwzpQUtXk

http://www.pbs.org/wgbh/nova/clovis/debate.html
Obviously, I didn't want to copy paste the whole paper, but here is a little more:



Quote:
3. Most of the reported YDB ‘nanodiamonds’ are not diamond, but rather are the controversial ‘n-diamond’. The use of ‘n-diamond’ as an impact marker, is problematic due to the presence of native Cu nanocrystals in sediments that can be easily confused for ‘n-diamond’, should that C phase exist. Furthermore, ‘n-diamond’ is reported in sediments that do not date to the YD onset, and more importantly, formation of these nanocrystals has not been linked exclusively to shock formation processes.

4. The presence of a single spike in nanodiamond concentration within Pleistocene to Holocene sediments at the YDB layer would strongly suggest that a unique event - but not necessarily an impact - occurred at the YD onset. Nanodiamond abundances from bulk sediments processed by acid dissolution, for crushed carbon spherules, and for ice by Kinzie et al. (2014) and those previously published by several of its coauthors in other studies (e.g. Kennett et al., 2009a,b; Kurbatov et al., 2010; Israde-Alcantara et al., 2012a), as well as by a coauthor of Kennett et al. (2009a) (Bement et al., 2014) are all based on TEM studies. However, the TEM measurements by Kinzie et al. (2014) and others using similar methodologies are not of nanodiamonds, but are of ‘rounded particles’. More importantly, the many experimental difficulties inherent in using TEM to measure nanodiamond abundances have led to large unconstrained error, rendering this approach infeasible. We find there is no evidence to suggest a unique spike in the ‘nanodiamond’ concentration at the YDB layer. The distribution of nanodiamonds in Pleistocene to Holocene sediments (and in ice, if present, which has yet to be confirmed by independent groups, see Boslough, 2013b) remains unclear. Therefore, considering conclusions 1–4, the reports of nanodiamonds in Late Pleistocene sediments cannot provide evidence for a YD impact.
It might be worth adding that I have seen one author (Firestone, from memory) claim that pits in mammoth tusks were due to micrometeorite impacts! Failing to realise that such micrometeorites would not reach the Earth's surface at the velocity necessary to penetrate a material as tough as mammoth tusk. They would float to the ground. And we should be thankful that they do. I'll have to try and dig up the original paper, and the rebuttal, if I can find it again.
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Old 1st February 2018, 09:45 PM   #113
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More massive evidence ...no impact site....yet...and far wider spread

Quote:
Toward end of Ice Age, human beings witnessed fires larger than dinosaur killers
Date:
February 1, 2018
Source:
University of Kansas
Summary:
About 12,800 years ago, thanks to fragments of a comet, humans saw an astonishing 10 percent of the Earth's land surface, or about 10 million square kilometers, consumed by fires.
Share:

FULL STORY

New research shows that some 12,800 years ago, an astonishing 10 percent of the Earth's land surface, or about 10 million square kilometers, was consumed by fires.
Credit: © Oran Tantapakul / Fotolia

On a ho-hum day some 12,800 years ago, the Earth had emerged from another ice age. Things were warming up, and the glaciers had retreated.

Out of nowhere, the sky was lit with fireballs. This was followed by shock waves.

Fires rushed across the landscape, and dust clogged the sky, cutting off the sunlight. As the climate rapidly cooled, plants died, food sources were snuffed out, and the glaciers advanced again. Ocean currents shifted, setting the climate into a colder, almost "ice age" state that lasted an additional thousand years.

Finally, the climate began to warm again, and people again emerged into a world with fewer large animals and a human culture in North America that left behind completely different kinds of spear points.

This is the story supported by a massive study of geochemical and isotopic markers just published in the Journal of Geology.

The results are so massive that the study had to be split into two papers.

"Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ~12,800 Years Ago" is divided into "Part I: Ice Cores and Glaciers" and "Part 2: Lake, Marine, and Terrestrial Sediments."

The paper's 24 authors include KU Emeritus Professor of Physics & Astronomy Adrian Melott and Professor Brian Thomas, a 2005 doctoral graduate from KU, now at Washburn University.

"The work includes measurements made at more than 170 different sites across the world," Melott said.
more
https://www.sciencedaily.com/release...0201173251.htm

Fox in the hen house for a variety of theses in including Younger Dryas cause and megafauna extinction in North America amongst others.
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Old 1st February 2018, 10:10 PM   #114
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Originally Posted by macdoc View Post
More massive evidence ...no impact site....yet...and far wider spread



more
https://www.sciencedaily.com/release...0201173251.htm

Fox in the hen house for a variety of theses in including Younger Dryas cause and megafauna extinction in North America amongst others.

The theory remains distinctly at odds with the climate data. Such an even would have caused global cooling while the cooling it's attempting to explain was confined to the Northern Hemisphere.
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Old 1st February 2018, 10:20 PM   #115
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I think the sense is that the Northern region was primed for a mini-ice age to develop as it was emerging....and it did.
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Old 1st February 2018, 10:56 PM   #116
Skeptic Ginger
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Originally Posted by Damien Evans View Post
If you managed to blow it up into sufficiently small pieces it could burn up in the atmosphere. Just sayin'.
And if the pieces were spread out enough a fair number would hit the oceans and we could deal with the tidal waves of the big ones.
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Old 1st February 2018, 11:02 PM   #117
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Originally Posted by macdoc View Post
Mass and kinetic energy do not change under that scenario - only impact crater and there is some evidence that an airburst energy release may be more devastating than a crater event.

Remember all that energy will still go into the atmosphere .
Uh, I'm calling you on this one.

As an example, hypothetically: are you claiming an atomic bomb, spread out over the American continent would have the same damage profile as it would should it hit LA?

Because that makes no sense.

Not that I'm questioning anything else you've posted in this devolved into BS thread.
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Old 1st February 2018, 11:15 PM   #118
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I haven't read the papers related to the article linked by macdoc, but I'm not sure it would help if I did. These claims have been made before, and other researchers failed to replicate their results. So I would tend to hang fire, until such time as others have looked at their latest claims.
An interesting article here about the previous claims:
https://psmag.com/environment/comet-...to-earth-31180

Firestone, Kennett and 'West' are all co-authors on the latest papers. I shall remain skeptical in the meantime.
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Old 4th February 2018, 06:33 PM   #119
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The two papers are:
Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago. 1. Ice Cores and Glaciers
and
Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago. 2. Lake, Marine, and Terrestrial Sediments
The full papers are behind a paywall.

The part 1 paper has a perplexing history of "RECEIVED: Sept 11, 2017 ACCEPTED: Sept 14, 2017" suggesting only 3 days for peer review. I hope that it was actually received earlier, for example with part 2 (RECEIVED: Feb 02, 2017 ACCEPTED: Sept 14, 2017).

The abstract for Part 1 has a "The cosmic impact deposited anomalously high concentrations of platinum" claim. However both asteroids and comets have high levels of platinum.
Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas (2013) concludes that the evidence
Quote:
...hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis
The rest of the abstract seems to hint that the only considered source for an increase in dust, ammonium, nitrate, oxalate, acetate, and formate is biomass-burning from fires caused by impacts with comet fragments. Ammonium, nitrate, oxalate, acetate, and formate are combustion aerosols but ammonium at least has other sources. A 1996 paper High-resolution ammonium ice core record covering a complete glacial-interglacial cycle has
Quote:
Biomass burning is estimated to be a major source for ammonia emissions for preindustrial times. It contributes between 10% to 40% to the total ammonium deposited on the central Greenland ice sheet during the Holocene. ...
Variations in the ammonium concentration during the glacial age are discussed in terms of changes in transport and deposition mechanisms and changes in source strength, which can be related to the extent of the Laurentide ice sheet.
That paper suggests that we cannot rule out an abrupt climate change unrelated to an impact causing a spike in ammonium and perhaps other combustion aerosols. Retreating glaciers might give a spike in dust as more land is exposed.
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Old 6th February 2018, 01:19 AM   #120
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Excessive biomass which then burns can also be the result of an ecological cascade due to overhunting the herbivores who typically cycle biomass. A smaller scale but similar massive increase of fire was seen when the bison were extirpated from their former range. Throughout the western great plains regions were seen a 30x increase in frequency and magnitude of fire. One would think a similar increase could have happened when the clovis peoples started hunting out the megafauna.

I don't know how you would test the hypothesis vs an asteroid/comet source for the increase in fire, but I suspect finding a widely ranging time period area to area vs a single date for all N America would tend toward ecological cascade event rather than bolide as the source for fire. Firestick farming is another possible source.
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