Under-Reported “Old” Carbon is Not the Source of Increases in Atmospheric CO2

Introduction

A recent paper published in the Journal Nature by Dean et al. provides an interesting and compelling argument that a significant source of atmospheric CO₂ has been underestimated by carbon budget models. The study, Old carbon routed from land to the atmosphere by global river systems looks at the origin of the CO₂ released by river water into the atmosphere and concludes that the amount of ancient (millennia old) CO₂ is higher than has been used in the current carbon cycle models.

This “leakage” of ancient carbon, found in soil, sediments, and geological stores, is reported to be comparable in magnitude to the net exchange of carbon between land and the atmosphere. The findings also suggest that plants and shallow soil layers may be removing more CO₂ than previously thought, but this is offset by the release of old carbon from rivers.

A recent interpretation of this paper and its use of carbon isotopes called into question the well-established connection between human CO₂ emissions and the 50% increase in atmospheric CO₂. Here, we re-establish the validity and linkage of ¹³C/¹²C isotopic ratio to human emissions of CO₂ from the burning of fossil fuels.

Read the full report as a PDF here.

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