Post #47728 by Dope1 on the US Policy board

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…is never “settled”, in reality. There’s always something to learn.

In this case, all the climate models are relying on some assumptions that aren’t inclusive of everything:

https://wattsupwiththat.com/2025/06/16/settled-sci...

The recent Nature study titled “Old carbon routed from land to the atmosphere by global river systems” is not only a rigorous piece of scientific work—it’s also a spectacular indictment of the so-called “settled science” of climate change. This 2025 paper is a flaming arrow into the heart of carbon cycle certainty, unearthing yet another inconvenient truth: over half of the CO2 emitted from rivers comes from carbon sources that are hundreds to thousands of years old—not from recent fossil fuel emissions or current biological activity.

Woof.

The paper in question:
https://www.nature.com/articles/s41586-025-09023-w
Rivers and streams are an important pathway in the global carbon cycle, releasing carbon dioxide (CO2) and methane (CH4) from their water surfaces to the atmosphere1,2. Until now, CO2 and CH4 emitted from rivers were thought to be predominantly derived from recent (sub-decadal) biomass production and, thus, part of ecosystem respiration3,4,5,6. Here we combine new and published measurements to create a global database of the radiocarbon content of river dissolved inorganic carbon (DIC), CO2 and CH4. Isotopic mass balance of our database suggests that 59 ± 17% of global river CO2 emissions are derived from old carbon (millennial or older), the release of which is linked to river catchment lithology and biome. This previously unrecognized release of old, pre-industrial-aged carbon to the atmosphere from long-term soil, sediment and geologic carbon stores through lateral hydrological routing equates to 1.2 ± 0.3 Pg C year−1, similar in magnitude to terrestrial net ecosystem exchange. A consequence of this flux is a greater than expected net loss of carbon from aged organic matter stores on land. This requires a reassessment of the fate of anthropogenic carbon in terrestrial systems and in global carbon cycle budgets and models.

Bolding mine.

From WUWT:
Translation: We were missing a carbon leak as big as the net carbon uptake of all land-based ecosystems. That’s like losing a financial ledger entry equivalent to your annual revenue and still claiming your books balance.

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And here’s the rub:

The authors admit they don’t know whether the increase in old carbon emissions is from natural variability or anthropogenic disturbance. In their own words:

“Whether or not anthropogenic perturbation has increased the leak of old carbon…remains a notable knowledge gap”.

Yet we’re told with absolute certainty that the Earth will warm by 1.5°C unless we ban gas stoves, eat bugs, and shut down reliable energy. This study exposes just how deeply uncertain and unresolved the feedbacks in the carbon cycle remain.

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