More solar linkages to climate variations

From Pierre Gosselin’s No Tricks Zone:

Oases of the Chinese Taklamakan Desert Greened Up In Sync With Solar Millenial Cycles
by Sebastian Lüning and Fritz Vahrenholt

The Taklamakan Desert is the 2nd world’s largest sand desert after the Rub el-Khali Desert in Saudi Arabia. A Chinese-Australian team of scientists lead by Keliang Zhao of the Chinese Academy of Sciences in Peking studied the sediment-profiles from an oasis at the edge of the Taklamakan where they reconstructed the climate of the last 4000 years based on pollen. The scientists published their results in March, 2012.

The study is yet another beautiful example of the global climatic impact of the solar millenial cycles (also see our recent article “New Study in PNAS Confirms Solar Impact Over the Last 9000 Years“ and “Solar Millennium Cycles Regulated the Wet and Dry Periods of the Mediteranean During the Roman Times“, also see pages 68-75 of our book “Die kalte Sonne“.

Figure 2: Reconstruction of the moisture development in the region of study using pollen for the last 4000 years. The shaded gray areas depict wet periods in the Tarim Basin. These coincide with the cold phases in the North Atlantic (numbered 1, 2, 3) and solar weak phases, as described by Bond et al. (2001). Chart from Zhao et al. (2012).

Read the full story here

Climatic variations over the last 4000 cal yr BP in the western margin of the Tarim Basin, Xinjiang, reconstructed from pollen data

Keliang Zhao, Xiaoqiang Li, John Dodson, Pia Atahan, Xinying Zhou, Fiona Bertuch

Abstract

The nature of Holocene climate patterns and mechanisms in central Asia are open areas of inquiry. In this study, regional vegetation and climate dynamics over the last ca. 4000 years are reconstructed using a high resolution pollen record from the Kashgar oasis, on the western margin of the Tarim Basin, central Asia. Ephedra, Chenopodiaceae and Cannabaceae dominate the pollen assemblages, and Chenopodiaceae/Ephedra ratios and percentages of long-distance transported pollen taxa are used to infer regional variations in moisture and vegetation density. Three periods of increased humidity are identified, from ca. 4000–2620 cal yr BP, ca. 1750–1260 cal yr BP and ca. 550–390 cal yr BP and these periods coincide with the respective Holocene Bond Events 2, 1 and 0, which are reported in the North Atlantic. Any increase in strength, or southward migration, of the mid-latitude westerlies would result in more precipitation and meltwater on mountains surrounding the study site. Warm and dry conditions are detected between ca.1260 and 840 cal yr BP (AD 690–1110), and cool and wet conditions are detected between ca. 840 and 680 cal yr BP (AD 1110–1270), during the Medieval Warm Period (ca. AD 800–1200). The climate variations in the Kashgar region over the last 4000 years appear to have been dominated by changes to the westerly circulation system and glacier dynamics on surrounding mountains. However, the question of whether the Asian monsoon delivers precipitation to the western Tarim Basin, a region that is influenced by several climate systems, is still open to debate.


Highlights

► New pollen records for the last 4000 cal yr BP in the western Tarim Basin.
► Four humid and three dry periods were identified in the study region.
► Increase in the strength of the westerlies resulted in the three humid periods.
► The climate was warm and dry during the early Medieval Warm Period (AD 690–1110).

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40 Responses to More solar linkages to climate variations

  1. Don Keiller says:

    This will never get into AR5

  2. cui bono says:

    We’ve seen this several times before – when work is done by scientists outside the US/Europe nexus of CAGW belief, it seems to be more centered on the evidence and less in a message.

    What’s the Chinese for “Just the facts, ma’am”?

  3. vukcevic says:

    Most convincing link between the solar activity and climate is to be found in the Arctic and the North Atlantic
    http://www.vukcevic.talktalk.net/CET-NAP-SSN.htm
    Most convincing link between the solar activity and any Earth’s measurable property is to be found in the Antarctic and the Southern Ocean
    http://www.vukcevic.talktalk.net/SSN-dBzA1.htm
    Solar and climate scientist presented by the evidence contained in the widely available data files, instead to research and investigate opt for easy way out, declaring the above findings as ‘spurious correlations’ and the science as ‘settled’ and therefore no new discoveries are possible.

  4. Edward Morgan says:

    Is anyone honest still surprised?

  5. Evil Denier says:

    I hope someone is recording the S(k)S rationale for Sol having no (zero; nada) influence on the climate. RC will attempt to weasel out of it – we’ll remember.

  6. DesertYote says:

    Kind of funny that Ephedra and Cannabaceae are two of the three top pollen sources.

  7. Gail Combs says:

    If you go to the link for Pierre Gosselin’s No Tricks Zone: there is a graph of precipitation vs year based on tree cores (rolls eyes). Note that the years around 1970ish were dry, we are now in a “wet” time period and on the slide down towards another “dry” period.

    As a farmer this scares me.

  8. Tim Ball says:

    None of this is new or surprising. The concept of wet and dry cycles in the middle latitude deserts is well documented. It was the underpinning of Ellsworth Huntington’s work on “The Pulse of Asia” that was shuffled aside because of his views on environmental and climatic determinism. He focussed on the wet and dry patterns of both the Tarim and Dzungaria basins.

    The wet and dry patterns are connected with shorter solar cycles by Douglas, David (1971) Landscheidt among others. The error is assuming that a solar cycle must show up in all records and only applies to temperature.

  9. Stephen Wilde says:

    Like I’ve been saying.

    As far as I know no one else has yet set out a plausible mechanism and until someone does I’ll keep publicising mine.

    http://climaterealists.com/index.php?id=6645

  10. Tom in Worcester says:

    That’s how it looks now ….. how will it look after the “adjustments”?

  11. Hu McCulloch says:

    DesertYote says:
    May 14, 2012 at 2:06 pm
    Kind of funny that Ephedra and Cannabaceae are two of the three top pollen sources.

    Ephedra (that which pseudoephedrine mimics) was among the supplies for the afterlife commonly found in some central Asian equestrian burials excavated a while back. I think the burials were about 5000 years old. So maybe it was being cultivated?

  12. Hu McCulloch says:

    There is no mention in the Abstract of solar linkages. Is that entirely Gosselin’s interpretation?

  13. SteveSadlov says:

    A long cold dry period in the usual will send the barbarians on the warpath … again.

  14. DirkH says:

    Hu McCulloch says:
    May 14, 2012 at 3:12 pm
    “There is no mention in the Abstract of solar linkages. Is that entirely Gosselin’s interpretation?”

    Pierre has translated a writeup by Vahrenholt/Lüning in German. So it’s probably their interpretation.

  15. berniel says:

    Tim Ball says:
    May 14, 2012 at 2:10 pm
    None of this is new or surprising. The concept of wet and dry cycles in the middle latitude deserts is well documented. It was the underpinning of Ellsworth Huntington’s work on “The Pulse of Asia” that was shuffled aside because of his views on environmental and climatic determinism. He focussed on the wet and dry patterns of both the Tarim and Dzungaria basins.

    Precisely right. This account of Huntington’s expedition to the Tarim Basin is a recommended read if you are interested in the early explorations for archeological evidence of climatic change and of its influence on civilisation. And note that Huntington was also shuffled aside for two other reasons: for working outside the academy and for his promotion later in life of eugenics. This is perpetuated in Fleming’s Historical Perspectives on Climate Change. Huntington could not be ignored, indeed a whole chapter is dedicated to him, but only to sling mud at him for his views on things other what Fleming’s book is supposed to be about. More here:
    http://enthusiasmscepticismscience.wordpress.com/2010/09/23/civilisation-and-climate/

  16. etudiant says:

    The original article does indeed directly link the results to fluctuations in solar activity.
    Specifically, it notes the moist periods coincide with periods of cold North Atlantic, which are derived from low solar activity, according to the papers by Bond cited in the abstract.

  17. Legatus says:

    Stephen Wilde, is this a good summery of your idea?
    More active sun means more solar wind, protons from the solar wind destroy more ozone in the mesosphere, especially near the poles where the earths magnetic field tends to pull the protons in. Less ozone in the mesosphere means less warming of the mesosphere by solar UV radiation, the mesosphere cools, and that cools the stratosphere. This causes the troposphere to rise, which will tend to push the jet streams poleward, which will tend to result in less cloudiness over a greater portion of the earth and thus there will be more incoming solar radiation (especially into the oceans). The greater incoming solar radiation at lower latitudes will also tend to warm that area which will further push the jet streams poleward, however that will be modulated by the oceans which may tend to delay, offset, enhance, or move that effect around.

    Some ideas based on this:
    Destroying ozone may mean that the whole CFC and ozone hole idea was false, the ozone hole was caused by the suns activity, not CFC’s. This is further shown by the ozone hole first being discovered by the small rockets of the day used by NASA in, I believe, 1938, and I have heard were in their magazine that year (I have been unable to confirm this). CFC’s where first used in the early 60’s.

    Destroying ozone will let in more UV to down here. This may stimulated the production of DMS from ocean life (a chemical), which tends to mean more clouds. This may mean more clouds especially near the poles if the destruction of UV mean an ozone difference between the poles and the rest of the mesosphere. If the lessening of ozone is more widespread, then there may be more DMS over worldwide oceans and more tenancy to cloudiness. The DMS induced cloudiness will tend to offset the less cloudiness caused by poleward movement of jet streams. This may be different in different places since it depends on DMS producing microorganisms which may be greater or lesser at different places and times.

    If lower solar activity means jet streams move toward the equator and there are more clouds and less sun, if lower solar activity also means more cosmic rays, and if cosmic rays do indeed produce more clouds. then we will have two things tending to produce more clouds. However, a cooler ocean will tend for less evaporation and less clouds, less UV may mean less DMS for less clouds (over oceans), and the effect may be different at lower latitudes since those areas will only be effected by the cosmic rays but not by the jet streams which are at higher latitudes. A greater temperature differential, cooler at higher latitudes, may change ocean currents, moving warmth and coolness around at different speeds, which may cool some lower latitudes, warm some upper latitudes, and change precipitation and other weather patterns.

    About the above, it appears some are reporting a correlation between solar activity and “ice rafted debris”. This appears to match pretty well (assuming that the methods used are sound to track them). However, some ice cores from Greenland do not show temperatures changing much there to match that solar activity. Thus it may be that jet streams moving equator-ward may in some areas merely mean a change in wind patterns and especially ocean currents which make for more ice rafted debris arriving in some areas without necessarily producing much change in temperature in other areas, such as inner Greenland.

    Since this idea is based on jet streams, places like higher latitude Eurasia may see fairly sudden changes in climate, lower latitude areas will depend on changes in ocean currents that reach higher latitudes and may not see changes for some time, some lower latitude areas that are less effected by currents may not see changes unless the lower solar activity lasts so long that the coolness becomes worldwide.

    If sudden changes of jet stream position are possible from solar activity alone, one would expect that there would be a temporary change every 11 years or so, at solar minimum, is there? If there is not, then either this idea is false, or it needs a fairly long period of change of solar activity to activate, probably due to the presence of the oceans which tend to slow everything down, plus the presence of counter-agents like DMS which may tend to offset things, thermostat effects that kick in and tend to reduce change.

  18. Sam Barber says:

    “…these periods coincide with the respective Holocene Bond Events 2, 1 and 0.”
    So, what’s the big deal? These events are already well documented.

  19. Mac the Knife says:

    DesertYote says:
    May 14, 2012 at 2:06 pm
    “Kind of funny that Ephedra and Cannabaceae are two of the three top pollen sources.”

    It does seem surprising, from our ‘modern’ perspective, doesn’t it? Perhaps they are useful proxies for the Stoned Age? Regardless, it WAS a stimulating paper! Now, if you’ll excuse me, I feel an overwhelming need for some munchies…… and a cold brew to wash ‘em down.

  20. Latitude says:

    Hu McCulloch says:
    May 14, 2012 at 2:31 pm

    DesertYote says:
    May 14, 2012 at 2:06 pm
    Kind of funny that Ephedra and Cannabaceae are two of the three top pollen sources.

    Ephedra (that which pseudoephedrine mimics) was among the supplies for the afterlife commonly found in some central Asian equestrian burials excavated a while back. I think the burials were about 5000 years old. So maybe it was being cultivated?
    ===============

    good catch Hu!

  21. Steven Mosher says:

    The moisture variations in the northeastern Tibetan Plateau are synchronous over a large spatial and temporal range in multidecadal scale for the last millennium, especially during dry periods. Wavelet analyses and comparisons with the minimal solar activity show that the precipitation variations for the last millennium may have some association with the solar activity on multidecadal to centennial scales.

    And opps looks like there might be a problem for GCR theory here.

  22. Paul Vaughan says:

    Legatus (May 14, 2012 at 5:28 pm) asked:
    “If sudden changes of jet stream position are possible from solar activity alone, one would expect that there would be a temporary change every 11 years or so, at solar minimum, is there?”

    Yes:

    Solar-Terrestrial-Climate Weave
    http://i49.tinypic.com/219q848.png

    The earliest public documentation of this pattern I can find so far:

    Figure 3a & 3b (pdf p.24 & p.25) from:
    Dickey, J.O.; & Keppenne, C.L. (1997). Interannual length-of-day variations and the ENSO phenomenon: insights via singular spectral analysis.
    http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/22759/1/97-1286.pdf

    Science Historians & other interested parties:
    Please let us know of ANY & ALL reports of the pattern prior to Le Mouël, Blanter, Shnirman, & Courtillot (2010), the first authors to write of the pattern in addition to illustrating it, to the best of my current knowledge. Note that at the time of Dickey & Keppenne (1997) there was more than a full cycle less data and that additionally the time series ended at a point where end effect might have further undermined researcher confidence.

    Capable Data Explorers:
    1. ENSO intersignal interference (ISI) will blind you to the pattern if your window extent isn’t pegged to solar cycle length.
    2. The pattern is a summary of lunisolar-integrated variations.

    So far I’ve found over 30 ways to isolate the pattern.

  23. Pamela Gray says:

    I don’t think intrinsic ENSO factors on multidecadel oscillation and overturning scales have been ruled out yet as the source of global temperature trends. Until someone comes up with something else that is more powerful than these intrinsic oceanic atmospheric drivers, ENSO remains as King and Queen of this court.

  24. Brian H says:

    DesertYote says:
    May 14, 2012 at 2:06 pm

    Kind of funny that Ephedra and Cannabaceae are two of the three top pollen sources.

    Yet another dope-y comment! High thar, DY. How’s the view from up there?

    ;)
    >;-p
    /tease

  25. Mac the Knife says:

    Gail Combs says:
    May 14, 2012 at 2:08 pm
    “If you go to the link for Pierre Gosselin’s No Tricks Zone: there is a graph of precipitation vs year based on tree cores (rolls eyes). Note that the years around 1970ish were dry, we are now in a “wet” time period and on the slide down towards another “dry” period.
    As a farmer this scares me.”

    Gail,
    I had a look at the graph you referenced above. The right hand axis is labeled # of Cores and the blue shaded area in the graph I assume indicates the number of cores used to construct each data point in the the precipitation curve over the 1000 year period. Is that correct?

    Within the text of the translation by Sebastian Lüning and Fritz Vahrenholt, it states “Junyan Sun and Yu Liu of the Chinese Academy of Sciences studied tree rings in the northwest (Tibetan) plateau edge from two living 1000 year old trees.” It doesn’t tell us how many cores were taken from each tree, but it does state “Both scientists were able to reconstruct the distinct precipitation fluctuations occurring over the last 1000 years. The corresponding wet and dry periods each lasted some decades.” It further states “A comparison to the other climate reconstructions coming from the same region shows great similarities in moisture development and that we are dealing with a representative regional climate signal.” Sun and Lui independently created precipitation curves from the cores from the 2 trees and then verified they were comparable to the precipitation curve generated from a bunch of other tree cores taken from around the plateau. Is that correct?

    I’m trying to make sure I understand the constructions here and, if I have not, please tell me where I’ve gone wrong.

  26. ferd berple says:

    Legatus says:
    May 14, 2012 at 5:28 pm
    This may stimulated the production of DMS from ocean life (a chemical), which tends to mean more clouds.
    =======
    It is the arrogance of human beings to assume that only they have the power to change the climate. Life has existed on this planet for as long as it has because it long ago developed the ability to regulate the climate long-term, keeping average temperatures within about 3% of current temperatures (degrees K) over the past 500 million years.

    It is humans, with their short term view that misunderstand their role, overestimating their importance. Having only learned to measure temperature withing the past few hundred years, we now believe that we are the ones controlling the earth’s thermostat. The alternative, that the situation is outside our control, is too fearful to consider.

    Yet, each human being is simply a host, transporting the microbes that provide it with life. The vast majority of the cells in a human body are not even human. We live in an infinite universe. No matter how much we learn, there is still infinitely more to learn.

    It is our ignorance that leads us to believe we know a high percentage of what there left to learn. If we take all the knowledge of every human and add it together, it forms exactly 0% of what is still left to learn. The unknown is so large that it defies even our ability to imagine its size.

  27. gymnosperm says:

    Legatus,

    Luv the way you’re thinking. We all need to stretch that way. Humans were not selected to understand climate change, but rather to deal with it. Our numbers have grown. We have harnessed powers that may make us a force in climate. We really need to understand it now in order to deal with it. Unfortunately, I must suggest that you need to add another dimension and factor in longitude (ie Rossby Waves in the jet streams and the THC in the oceans). You go.

  28. Stephen Wilde says:

    Legatus,

    That is a fair summary.

    However I think that pinning the solar effect down to protons alone is probably unduly restrictive. Rather, I now think it is the net result of a whole suite of solar effects on the temperature of the upper atmosphere caused by varying wavelength and particle proportions from the sun but the ozone response does appear to dominate on the basis of the evidence available.

    Lots of implications follow from that and I’m pleased to see you exploring some of them.

  29. alex says:

    Hi?

    The Chinese authors of the peer-reviewed paper do not talk about any solar relation whatsoever.

    It is the two Germans who ‘interprete” the Chinese results at their blog.
    This is not serious.

    Alex.

  30. “Having only learned to measure temperature withing the past few hundred years”
    Erm, really? Perhaps go and do some reading before spouting nonsense like that?

  31. vukcevic says:

    Steven Mosher says: May 14, 2012 at 8:25 pm
    And opps looks like there might be a problem for GCR theory here.

    GCR is only a hypothesis.
    See text update to the sun-Earth electric & magnetic link, including a quote from Dr. L. Svalgaard, as an initial introduction into possible theoretical explanation for this potentially primary factor in synchronizing the observed climate change with the solar magnetic activity.
    http://www.vukcevic.talktalk.net/SSN-dBzA1.htm

  32. redneck says:

    Highlights
    ► New pollen records for the last 4000 cal yr BP in the western Tarim Basin.
    ► “Four humid” and three dry periods were identified in the study region.
    ► Increase in the strength of the westerlies resulted in the “three humid” periods.
    ► The climate was warm and dry during the early Medieval Warm Period (AD 690–1110).

    Ahhm so which was it four or three humid periods.

  33. Paul Vaughan says:

    @Pamela Gray (May 14, 2012 at 9:11 pm)

    What seems to go horribly wrong conceptually is that “temperature anomalies” severely corrupt many (most?) climate enthusiasts’ sense of the relative magnitudes of variations as a function of timescale.

    In order of decreasing magnitude:
    1. annual.
    2. interannual (including ENSO).
    3. multidecadal.

  34. Paul Vaughan says:

    vukcevic, is it really the case that you can find no reference to the coherence in the literature? I remember hearing of this coherence long ago, but I’ve never done a literature survey of the topic and to my knowledge the data you plot are not available publicly, so it has not been convenient to take a look. Have you suggested to the proprietors of the data that they consider putting it up on plain-text webpages? Also, as I understand, the historical data is modeled. We need info on the models. For example, what inputs do they take? This is key. Thanks.

  35. Paul Vaughan says:

    @Pamela Gray (May 14, 2012 at 9:11 pm)

    Just about anyone here could estimate screw thread lead [ http://upload.wikimedia.org/wikipedia/commons/0/00/Lead_and_pitch.png ] using “rise over run” from grade 9 math.

    I have an elementary question for you:

    What metric would quantify the changing “rise over run” in this summary of decadal earth rotation & westerly wind anomalies?
    http://i49.tinypic.com/219q848.png

    Once you and everyone else reading here have consumed all of a few seconds figuring that out (rate of change of solar cycle length), here’s the next question:

    What terrestrial variables show coherence with that metric?

    Here are a few examples:
    http://i40.tinypic.com/16a368w.png

    More examples are illustrated on p.4 here:
    http://wattsupwiththat.files.wordpress.com/2011/10/vaughn-sun-earth-moon-harmonies-beats-biases.pdf

    Assumptions of uniform modulus of continuity (whether made explicitly or implicitly) are NOT supported by earth rotation & atmospheric angular momentum data. In simpler terms: Mother Earth’s subtle responsiveness to Father Sun’s advances varies according to Mother Earth’s own cycles.

  36. Ulric Lyons says:

    Pamela Gray says:
    May 14, 2012 at 9:11 pm
    “I don’t think intrinsic ENSO factors on multidecadel oscillation and overturning scales have been ruled out yet as the source of global temperature trends. Until someone comes up with something else that is more powerful than these intrinsic oceanic atmospheric drivers, ENSO remains as King and Queen of this court.”

    Glassman had a go: http://rocketscientistsjournal.com/2007/07/solar_wind.html

    An El Nino episode is a response to a drop in what is driving temperatures, look at 96/97 and 08/09;
    http://omniweb.gsfc.nasa.gov/tmp/images/ret_19222.gif
    A stratospheric volcanic eruption can have the same result and bring on El Nino conditions.
    The LIA had higher El Nino frequency, and full glacial conditions are likely to have a continuous El Nino state.

  37. vukcevic says:

    Paul Vaughan says: May 15, 2012 at 7:42 am
    ………
    Hi Paul
    Historically early start is the ‘magnetotellurics’ (MT), known to geophysists since 1860s.
    Telluric currents are geomagnetically induced and flow in the surface layers of the Earth’s crust. The MT currents are induced by interactions between the solar wind and the magnetosphere and or possibly by solar radiation effects in the ionosphere.
    MT monitoring systems are installed by Geographical Survey Institute of Japan in number of locations to measure fluctuations in the intensity of surface electromagnetic field that may relate to seismic activity.
    NOAA website has an easy to use geomagnetic calculator for 1900 onwards epoch. The ETH Zurich (1590-1995) and Potsdam GM Institute’s (5000 BC -1950AD), data files are more difficult to handle, some time ago I developed number of Fortran patches (linking into my old F7) for rapid calculations.
    When I come up with some new data plot, Dr.S tends to do a quick check, and declares whole thing spurious or cherry picking, thus of no value to the science.

  38. Paul Vaughan says:

    I suggest everyone take a careful look at the Dickey & Keppenne (1997) article to which I linked above. They give insight into NASA’s inclination 15 years ago. In hindsight, their vision was 20/20 (while their voice was mute).

    What they illustrated (even though they didn’t write about it explicitly):
    For an ENSO-overarching summary tuned to semi-annual or annual grain and Schwabe extent, ENSO’s amplitude varies in synch with the solar cycle.

    That’s a rather key bit of insight.

    Keep in mind this is NOT abstract speculation; this is OBSERVED. You can’t even avoid finding ENSO in annual & semi-annual LOD. You’ll either find it in the modulus or in the argument as you vary extent. The solar-terrestrial-climate weave IS ROBUST and once you’ve isolated it you’ll find ENSO in the phase residuals – complementary sides of the same coin.

    Equator-pole gradients and consequent westerly pumping accumulates subtle variations into climatologies via north-south zonal-land-ocean-heat-capacity-contrast asymmetry. Tisdale’s Steps and steps more generally, whether up or down, synch loosely with the solar cycle since there’s an asymmetric cyclic amplitude boost.

    ==
    Vukcevic: The graphs you bring to the discussion are valuable, some much more so than others. A few have been VERY informative. Please keep contributing. You are a volunteer and should NOT be subject to abuse from anyone. Thank you sincerely for your contributions. Best Regards.

  39. David Ball says:

    Paul Vaughan says:
    May 15, 2012 at 9:53 pm
    I have said the same to Vuckevic on several occasions.

  40. We discuss geochemical and sedimentological characteristics of 12 tephra layers, intercalated within the finely laminated sediments of Lake Van. Within the about 15 kyr long sediment record studied, volcanic activity concentrated in the periods 2.6-7.2 and 11.9-12.9 kyr B.P. Concentrations of 25 elements provide the geochemical fingerprint of each tephra layer and allow comparison to literature values of potential source volcanoes such as Mts. Nemrut and Suephan. The youngest two tephra layers (and probably also the other three ashes from the 2.6-7.2 kyr B.P. eruptions) originate from the Nemrut volcano. The source of the older tephra (11.9-12.9 kyr B.P.), however, remains unidentified.

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