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arXiv · 2609.38063

Variations of atmospheric 12CO2 and 13CO2 from the year 1000 to 2024

W. A. van Wijngaarden·W. Happer
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Abstract

A simple model gives good agreement between observed emissions of CO2 into the atmosphere from the combustion of fossil fuels and observed increases of the atmospheric concentrations C of CO2 and decreases of the isotope delta value delta13C. If fossil fuel emissions were to cease the model predicts that: (1) the difference between the CO2 concentration C and the preindustrial value, Co = 280 ppm, would decay exponentially with time constant of 60 y; (2) the difference between the concentration-delta-value product C x delta13C and the preindustrial value Co x delta13Co = (280 ppm) x (-6.5%%), would decay exponentially with a time constant of 8 y. The decay times are different because of isotopic exchange, largely driven by photosynthesis and respiration on the land.

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W. A. van Wijngaarden, W. Happer. 2026-09-29. Variations of atmospheric 12CO2 and 13CO2 from the year 1000 to 2024. https://arxiv.org/abs/2609.38063

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