{"id":383743,"date":"2025-06-19T16:29:14","date_gmt":"2025-06-19T14:29:14","guid":{"rendered":"https:\/\/climatescience.press\/?p=383743"},"modified":"2025-06-19T16:29:16","modified_gmt":"2025-06-19T14:29:16","slug":"the-carbon-isotope-fingerprint-just-got-smudged-and-i-owe-some-of-you-an-apology","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=383743","title":{"rendered":"The Carbon Isotope Fingerprint Just Got Smudged \u2013 and I Owe Some of You an Apology"},"content":{"rendered":"\n
\"\"
ChatGPT<\/figcaption><\/figure>\n\n\n\n

<\/p>\n\n\n\n

From Watts Up With That?<\/a><\/p>\n\n\n\n

By Charles Rotter<\/a><\/p>\n\n\n\n

In light of the recent\u00a0Nature<\/em>\u00a0study, I discussed yesterday in\u00a0Settled Science Springs a Leak<\/a><\/em>, it\u2019s time to revisit a position I\u2019ve long held\u2014and, it turns out, one that now requires correction. Specifically, the long-standing assumption that carbon isotope ratios (\u03b4\u00b9\u00b3C and \u0394\u00b9\u2074C) provide unambiguous proof that the rise in atmospheric CO2 is almost entirely anthropogenic.<\/p>\n\n\n\n

For years, I\u2019ve maintained that anyone challenging the anthropogenic origin of the CO2 increase had to address the isotope fingerprint argument before their work could be taken seriously. Submissions that didn\u2019t engage with the \u0394\u00b9\u2074C or \u03b4\u00b9\u00b3C evidence were declined, often with little further discussion. That confidence, I now recognize, was misplaced.<\/p>\n\n\n\n

The recent study, Old carbon routed from land to the atmosphere by global river systems<\/em>, has fundamentally altered the context in which the isotopic attribution arguments operate. According to the authors, 59% of global riverine CO2 emissions are sourced from old carbon<\/strong>, meaning millennial-aged carbon from deep soils, sediments, or rock weathering<\/strong>\u2014not recently photosynthesized biomass.<\/p>\n\n\n\n

These emissions are radiocarbon-dead<\/strong>, lacking the \u0394\u00b9\u2074C signal, and are often depleted in \u03b4\u00b9\u00b3C\u2014precisely the isotopic traits long attributed to fossil fuel combustion. Until now, these natural contributions were omitted from carbon cycle models and largely absent from attribution logic.<\/p>\n\n\n\n

\n

\u201cThis previously unrecognized release\u2026equates to 1.2<\/em>\u2009<\/em>\u00b1<\/em>\u20090.3 Pg C year<\/em>\u207b<\/em>\u00b9\u2026 and 41<\/em>\u2009<\/em>\u00b1<\/em>\u200916% of river CO2 emissions<\/em>\u2026could contain recent anthropogenic-derived carbon.<\/em>\u201d<\/em><\/p>\n<\/blockquote>\n\n\n\n

The implication is unambiguous: the very isotopic signatures used to claim anthropogenic dominance in atmospheric CO2 are now also emerging from newly recognized natural processes at global scale<\/strong>. These rivers are essentially exhaling ghosts\u2014carbon that predates the industrial era by centuries or even millennia\u2014and doing so in quantities on par with major biospheric fluxes.<\/p>\n\n\n\n

The Isotope Argument Just Got Muddy<\/strong><\/p>\n\n\n\n

The confidence behind isotopic attribution rested on the idea that only fossil fuels could be responsible for the observed depletion in \u03b4\u00b9\u00b3C and \u0394\u00b9\u2074C. This paper shatters that by showing that the Earth has its own large, continuous natural source of isotopically similar carbon.<\/p>\n\n\n\n

Previously, isotope-based attribution was treated like a fingerprint match: the crime scene carbon looked like fossil fuel carbon, and fossil fuel emissions matched the rising levels in the air. Case closed.<\/p>\n\n\n\n

But now we know there\u2019s another suspect. And he\u2019s been walking around in the open the whole time\u2014we just didn\u2019t test the rivers.<\/p>\n\n\n\n

A Second Look, Long Overdue<\/strong><\/p>\n\n\n\n

To be clear, this doesn\u2019t prove the rise in atmospheric CO2 is not anthropogenic. But it does mean that the evidentiary strength of isotopic data as a sole or dominant indicator of that origin is now substantially weaker<\/strong>.<\/p>\n\n\n\n

Climate science has always leaned heavily on isotope ratios because they offered a veneer of mathematical certainty. With the carbon mass balance deeply uncertain, and the models riddled with arbitrary assumptions, the isotopes offered something that looked solid.<\/p>\n\n\n\n

Now that, too, is compromised.<\/p>\n\n\n\n

To those contributors whose submissions I rejected on the basis that they did not sufficiently address the isotope argument: I owe you an apology.<\/strong><\/p>\n\n\n\n

You raised objections in good faith. Many of you suspected that natural processes were more complex and underappreciated than the models allowed. This paper has proven that instinct correct. You didn\u2019t need to disprove the \u0394\u00b9\u2074C narrative outright; you simply needed the science to catch up to the question.<\/p>\n\n\n\n

It just did.<\/p>\n\n\n\n

Confidence Requires Humility<\/strong><\/p>\n\n\n\n

This study is a stark reminder that confidence in science is no substitute for humility in the face of uncertainty<\/strong>. That applies as much to editorial policy as it does to modelers, activists, or policymakers. In this case, the error was not in demanding rigor\u2014but in assuming it had already been achieved.<\/p>\n\n\n\n

Carbon isotope ratios remain valuable tools, but they are no longer unimpeachable witnesses. They are part of a broader, far more uncertain picture of how carbon moves through the Earth system\u2014a picture we now know was missing a major river-fed chapter.<\/p>\n\n\n\n

A Final Word<\/strong><\/p>\n\n\n\n

The takeaway is simple: no one gets to claim the science is settled when it just got rewritten<\/strong>.<\/p>\n\n\n\n

And so, to every researcher, independent thinker, or persistent submitter who brought forth alternative views and was met with the standard rebuttal\u2014\u201cCome back when you\u2019ve dealt with the isotope ratios\u201d<\/em>\u2014you were due more openness than you received.<\/p>\n\n\n\n

For that, I offer a strong, clear, and unreserved apology.<\/strong><\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

In light of the recent\u00a0Nature\u00a0study, I discussed yesterday in\u00a0Settled Science Springs a Leak, it\u2019s time to revisit a position I\u2019ve long held\u2014and, it turns out, one that now requires correction. Specifically, the long-standing assumption that carbon isotope ratios (\u03b4\u00b9\u00b3C and \u0394\u00b9\u2074C) provide unambiguous proof that the rise in atmospheric CO2 is almost entirely anthropogenic.<\/p>\n","protected":false},"author":121246920,"featured_media":383746,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","_crdt_document":"","advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691823091,691835917,691829997,691834414,691835916],"class_list":{"0":"post-383743","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","6":"hentry","7":"category-uncategorized","8":"tag-atmospheric-co2","9":"tag-carbon-cycle-models","10":"tag-carbon-dioxide-co","11":"tag-carbon-isotope","12":"tag-isotope-fingerprint","14":"fallback-thumbnail"},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/06\/0ChatGPT-Image-19.-Juni-2025-16_27_21.png?fit=1536%2C1024&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-1BPp","jetpack-related-posts":[{"id":310414,"url":"https:\/\/climatescience.press\/?p=310414","url_meta":{"origin":383743,"position":0},"title":"The Conclusion Humans Drive Atmospheric CO2 Increases Is Undermined By Carbon Isotope Data","author":"uwe.roland.gross","date":"19\/03\/2024","format":false,"excerpt":"\u201cFrom modern instrumental carbon isotopic data of the last 40 years, no signs of human (fossil fuel) CO2\u00a0emissions can be discerned.\u201d \u2013 Koutsoyiannis, 2024","rel":"","context":"In \"CO2\"","block_context":{"text":"CO2","link":"https:\/\/climatescience.press\/?tag=co2"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0OSC_Microbio_08_07_CCycle.jpg?fit=1200%2C844&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0OSC_Microbio_08_07_CCycle.jpg?fit=1200%2C844&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0OSC_Microbio_08_07_CCycle.jpg?fit=1200%2C844&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0OSC_Microbio_08_07_CCycle.jpg?fit=1200%2C844&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0OSC_Microbio_08_07_CCycle.jpg?fit=1200%2C844&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":311158,"url":"https:\/\/climatescience.press\/?p=311158","url_meta":{"origin":383743,"position":1},"title":"Humans Add Little to Rising CO2 March\u00a02024","author":"uwe.roland.gross","date":"21\/03\/2024","format":false,"excerpt":"Overall, the findings in this paper confirm the major role of the biosphere in the carbon cycle (and through this in climate) and a non-discernible signature of humans.","rel":"","context":"In \"carbon cycle\"","block_context":{"text":"carbon cycle","link":"https:\/\/climatescience.press\/?tag=carbon-cycle"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0-carbon-cycle.png?fit=1200%2C926&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0-carbon-cycle.png?fit=1200%2C926&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0-carbon-cycle.png?fit=1200%2C926&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0-carbon-cycle.png?fit=1200%2C926&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/0-carbon-cycle.png?fit=1200%2C926&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":374844,"url":"https:\/\/climatescience.press\/?p=374844","url_meta":{"origin":383743,"position":2},"title":"Whose CO\u2082 is it Anyway? Ocean Fizz or Smokestack Blame","author":"uwe.roland.gross","date":"12\/04\/2025","format":false,"excerpt":"Picture this: it\u2019s a hot day, and you grab a soda can that\u2019s been in the sun. You crack it open\u2014psssht\u2014and CO\u2082 fizzes out, tickling your nose, maybe spraying your shirt if you\u2019re slow. It\u2019s a tiny chaos, a burst you can\u2019t control. Now imagine that fizz across the ocean\u2019s\u2026","rel":"","context":"In \"carbon cycle\"","block_context":{"text":"carbon cycle","link":"https:\/\/climatescience.press\/?tag=carbon-cycle"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/04\/0bubbles-Myrmidon.jpg?fit=1200%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/04\/0bubbles-Myrmidon.jpg?fit=1200%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/04\/0bubbles-Myrmidon.jpg?fit=1200%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/04\/0bubbles-Myrmidon.jpg?fit=1200%2C800&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/04\/0bubbles-Myrmidon.jpg?fit=1200%2C800&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":363287,"url":"https:\/\/climatescience.press\/?p=363287","url_meta":{"origin":383743,"position":3},"title":"Central Japan Was 3\u00b0C (And Up To 7\u00b0C) Warmer Than Today Throughout the Early to Mid-Holocene","author":"uwe.roland.gross","date":"25\/01\/2025","format":false,"excerpt":"\u201cBased on the records of the\u00a0\u03b4\u00b9\u2078O\u00a0stalagmite, the [Holocene Thermal Maximum] occurred between 10.9 and 6.7 ka [Honshu, Japan], reaching its peak temperature (15.0\u00b0C) around 7.0 ka. 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