Geomagnetic Excursions as CO₂-Null Climate Forcing Events: The Laschamps/Adams Event in Proxy Context and a Comparative Analysis of Brunhes Chron Excursions Against the EPICA Dome C Record

Geomagnetic Excursions as CO₂-Null Climate Forcing Events: The Laschamps/Adams Event in Proxy Context and a Comparative Analysis of Brunhes Chron Excursions Against the EPICA Dome C Record | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 31 March 2026 V1 Latest version Share on Geomagnetic Excursions as CO₂-Null Climate Forcing Events: The Laschamps/Adams Event in Proxy Context and a Comparative Analysis of Brunhes Chron Excursions Against the EPICA Dome C Record Author : Jack H. Gray 0009-0007-0400-6943 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.177499034.42719500/v1 377 views 104 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract The Laschamps geomagnetic excursion (~41-42 ka BP) represents the largest geomagnetic field collapse in the past 800,000 years, driving documented megafaunal extinctions, Neanderthal extinction, Northern Hemisphere ice sheet expansion, and global ecological disruption confirmed across 30+ sediment cores, ice cores, and fossil archives. Yet the EPICA Dome C (EDC) atmospheric CO₂ record-the gold-standard paleoclimate archive for this period-shows no corresponding anomaly. CO₂ remains constrained to approximately 193-206 ppmv throughout the excursion window, with the excursion core (40.5-41.5 ka) at 200-204 ppmv, exhibiting a maximum attributable ΔCO₂ indistinguishable from zero within measurement uncertainty (±2-3 ppmv). This paper presents the first systematic quantitative CO₂-null test across all five best-documented Brunhes Chron geomagnetic excursions-Laschamps (~41 ka), Mono Lake (~33 ka), Blake (~116 ka), Iceland Basin (~190 ka), and Pringle Falls (~211 ka)-using exclusively raw NOAA/WDS proxy data: the Bereiter et al. (2015) EPICA EDC CO₂ composite and the Bauska, Marcott & Brook (2021) WAIS Divide record. All five events show ΔCO₂ = 0 within measurement uncertainty, spanning background CO₂ states from 195 to 245 ppmv and both glacial and interglacial Marine Isotope Stage contexts. The null is confirmed by two independent ice cores from geographically distinct Antarctic drilling programs with independent age models. The WAIS Divide record, with ~40-80-year temporal resolution against EDC's ~200-350-year resolution, confirms the null at higher precision. An internal calibration demonstrates that the same EDC dataset successfully resolves the Younger Dryas CO₂ decline (−10 to −15 ppmv over ~1,200 years), establishing that the excursion nulls reflect a genuine absence of response, not a resolution artifact. Six pre-emptive technical defenses are presented: (1) the Parrenin et al. (2013) gas-age chronology revision applies to Termination I, not to the Laschamps window, and asks an orthogonal question; (2) resolution is demonstrably adequate via the Younger Dryas calibration; (3) the WAIS Divide crosscheck confirms the null independently; (4) the ¹ Be cosmogenic ⁰ production record provides a chemically independent timing anchor that eliminates the timingartifact objection; (5) excursion selection criteria are documented a priori and applied uniformlyno qualifying event was excluded; and (6) formal statistical testing of detrended CO₂ residuals confirms the null at all five events, with all residuals negative-the opposite direction from any geomagnetic CO₂ amplification mechanism. Three structural findings emerge beyond the null result itself. First, geomagnetic excursions exhibit an epicenter-aftershock-secondary oscillation structure: the Laschamps (~41 ka)-Mono Lake (~33 ka) pair, separated by ~8 kyr (the outer core viscous relaxation timescale), constitutes an epicenter-primary aftershock sequence confirmed independently in the Cooper et al. (2021) Supplementary Material File (gray2026f_final3.pdf) Download 3.81 MB Information & Authors Information Version history V1 Version 1 31 March 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords astronomical climate forcing climate forcing climate forcing bias geomagnetic excursion geomagnetic excursions Authors Affiliations Jack H. Gray 0009-0007-0400-6943 [email protected] View all articles by this author Metrics & Citations Metrics Article Usage 377 views 104 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Jack H. Gray. Geomagnetic Excursions as CO₂-Null Climate Forcing Events: The Laschamps/Adams Event in Proxy Context and a Comparative Analysis of Brunhes Chron Excursions Against the EPICA Dome C Record. Authorea . 31 March 2026. DOI: https://doi.org/10.22541/au.177499034.42719500/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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