The poor rhetoric of YDIH citics

Jim powell's new website documents the poor rhetoric of Younger Dryas impact hypothesis (YDIH) critics. Their approach is often pseduoskeptical. In many other cases their approach either lacks scientific rigour or is possibly fraudulent. Here I summarize the poor rhetoric of most of the key critical YDIH papers.

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1. Pinter and Ishman “Impacts, mega-tsunami, and other extraordinary claims.” GSA Today 18 (2008). doi: 10.1130/GSAT01801GW.1.

As shown by Powell, this initial rebuttal of Firestone et al. (2007), in wich the YDIH is presented for the first time, contains no new field data and is full of anti-science rhetoric.

2. Surovell et al. “An Independent Evaluation of the Younger Dryas Extraterrestrial Impact Hypothesis.” Proceedings of the National Academy of Sciences 106, 18155–58 (2009). doi.org/10.1073/pnas.0907857106.

Surrovell et al. (with Holliday and Claeys as co-authors) sampled the Younger Dryas Boundary (YDB) at 7 YDB sites but found no evidence of impact microspherules. However, their methods were flawed. LeCompte et al. "Independent evaluation of conflicting microspherule results from different investigations of theYounger Dryas impact hypothesis"  Proceedings of the National Academy of Sciences 109, E2960-2969 (2012). doi/10.1073/pnas.1208603109, later showed that, using Surrovell's et al.'s methods, their null result is expected. They also repeated measurements at 3 YDB sites, 2 the same as Surrovel et al., using similar methods to Firestone et al.,, finding abundant exotic microspherules at the YDB.

3. Gill et al. "Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America", Science 326,  1100-1103 (2009). DOI: 10.1126/science.1179504

In their abstract Gill et al. state "Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the Bølling Allerød warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago." But their age-depth model lacks any uncertainty analysis thus obviating their claims. Using more accurate radiocarbon dating methods, O'Keefe et al. "Pre-Younger Dryas megafaunal extirpation at Rancho La Brea linked to fire-driven state shift", Science 381, eabo3594 (2023). DOI: 10.1126/science.abo3594, contradicts Gill et al.'s conclusions and is consistent with the YDIH (at 2 sigma). In fact, the evidence in both Gill et al. (2009) and O'Keefe et al. (2023) strongly supports the YDIH claim that the impact dramatically affected the continent's megafauna.

4. Marlon et al. "Wildfire responses to abrupt climate change in North America", Proceedings of the National Academy of Sciences 106, 2519-2524 (2009). doi/10.1073/pnas.0808212106

Marlon et al. state (with Scott as co-author) in their abstract "We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indicated at any time during deglaciation." And yet their own data shows a peak in "z-scores of transformed charcoal influx" of YD impact age, within error bounds. Thus, their data actually supports the YDIH.

5. Paquay et al. "Absence of geochemical evidence for an impact event at the Bølling–Allerød/Younger Dryas transition", Proceedings of the National Academy of Sciences 106, 21505-21510 (2009). doi/10.1073/pnas.0908874106

Paquay et al. (with Surrovel, Holliday and Claeys as co-authors) find peaks in platinum group elements (PGEs) at the YDB at two of the sites they study. Their interpretation is that these are not strong enough to definitively claim an impact event. Fine, but they nevertheless find peaks in PGEs at the YDB which support theYDIH.

6. Daulton et al. "No evidence of nanodiamonds in Younger–Dryas sediments to support an impact event", Proceedings of the National Academy of Sciences 107, 16043-16047 (2010). doi/10.1073/pnas.1003904107

Daulton et al. (2010) (with Pinter and Scott as co-authors) claim their sample locations on Santa Rosa Island, California, correspond to the same YDB locations sampled by Kennet et al. in 2009 where nanodiamonds were reportedly found. In fact, their samples are either far too old or not from this location at all. This is shown by Wittke et al. (2013). Furthermore, their sample from Murray Springs is undated. So they have no evidence they actually sampled the YDB for nanodiamonds.YDIH critics (like Holliday et al. (2023) - see below) continue to deny these sampling errors.

7. Pinter et al. "The Younger Dryas impact hypothesis: a requiem", Earth Science Reviews 106, 247-264 (2011). doi:10.1016/j.earscirev.2011.02.005.

Regarding new fieldwork, Pinter et al. (2011) (with Scott, Daulton and Ishman as co-authors) looked for exotic microspherules at the YDB but they admit "No clear YDB “marker bed” was present in any of our sections, so unlike Firestone and Surovell, our results focus on the distribution (and nature; see below) of spherules through sediments pre-dating, dating to, and post-dating the onset of the YD". In fact, all their samples are actually far too young or old, except one sample form Santa Rosa Island which is known to be the wrong location (it's the same location as Daulton et al.'s (2010) above). So there is no evidence they actually sampled the YDB. Powell also shows their prose is full of rhetorical ploys and logical fallacies.

8. Boslough et al. "Arguments and Evidence Against a Younger Dryas Impact Event", a chapter in Geophysical Monograph Series (2012).

Boslough et al. (with Scott, Daulton and Surrovel as co-authors) present no new fieldwork. Powell shows this paper is loaded with rhetorical ploys and logical fallacies, i.e. pseudoskepticism.

9. van Hoesel et al. "Nanodiamonds and wildfire evidence in the Usselo horizon postdate the Allerød-Younger Dryas boundary", Proceedings of the National Academy of Sciences 109, 7648-7653 (2012). doi/10.1073/pnas.1120950109.

van Hoesel et al. confirm nanodiamonds at the YDB but despite having many radiocarbon measurements from within the YDB that are consistent with its date decide to date the YDB, without justification, using a single charcoal particle from 5 cm above the YD black mat. Actually, their data strongly supports the YDIH.

10. Meltzer et al. "Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago", Proceedings of the National Academy of Sciences E2163-2171 (2014). doi/10.1073/pnas.1401150111.

Meltzer et al. (2014) (with Holliday as co-author) claim the YDB is not synchronous across a wide range of sites. But their age-depth models lack any uncertainty analysis, thus obviating their conclusions. Kennett et al. "Bayesian chronological analyses consistent with synchronous age of 12,835–12,735 Cal B.P. for Younger Dryas boundary on four continents", Proceedings of the National Academy of Sciences 112, E4344-E4353, (2015), doi.org/10.1073/pnas.1507146112, using more advanced Bayesian statistical methods show that the dates of all known YDB sites are consistent with a synchronous event in the range 10,885 - 10,785 BC (now updated to 10,925 - 10,825 BC using the 2020 radiocarbon calibration curve).

11. Sun et al. "Volcanic origin for Younger Dryas geochemical anomalies ca. 12,900 cal B.P." , Science Advances 6, eaax8587 (2020).

As shown by Marc Young, Sun et al. failed to report their only measurement from the YDB, which also happens to exhibit a strong platinum signal. Marc analyses email correspondance between the authors to show this could be a deliberate omission.

12. Holliday et al. "Comprehensive refutation of the Younger Dryas impact hypothesis" Earth Science Reviews 247, 104502 (2023). doi.org/10.1016/j.earscirev.2023.104502.

Jim Powell argues that to refute a hypothesis it is necessary first to try to reproduce the key evidence using valid methods. Consistent negative results would show the hypothsis is likely to be flase. But Holliday et al. (with Daulton, Boslough, Scott, Marlon and Cleays) includes no new field data. Instead, as Jim Powell shows, their ~100,000 word article is loaded with pseudoskepticism. It has been rebutted multiple times. For example, see the image above.