Time dependences of atmospheric Carbon dioxide fluxes

TL;DR

This paper estimates the atmospheric CO2 retention time using a simple model, revealing a maximum of less than 23 years for CO2 transfer to sinks and highlighting rapid terrestrial oscillations.

Contribution

It introduces a mass conservation analysis combining observed CO2 deficits and fossil fuel growth to estimate CO2 transfer times and flux dynamics.

Findings

Maximum CO2 transfer time constant is less than 23 years.

Rapid oscillations in CO2 levels have a time constant of about one month.

CO2 stabilization is predicted within 25 years if emissions cease.

Abstract

Understanding the lifetime of CO2 in the atmosphere is critical for predictions regarding future climate changes. A simple mass conservation analysis presented here generates tight estimations for the atmosphere's retention time constant. The analysis uses a leaky integrator model that combines the observed deficit (only less than 40% of CO2 produced from combustion of fossil fuels is actually retained in the atmosphere, while more than 60% is continuously shed) with the exponential growth of fossil fuel burning. It reveals a maximum characteristic time of less than 23 year for the transfer of atmospheric CO2 to a segregation sink. This time constant is further constrained by the rapid disappearance of 14C after the ban of atmospheric atomic bomb tests, which provides a lower limit of 18 years for this transfer. The study also generates evaluations of other CO2 fluxes, exchange time constants and volumes exchanged. Analysis of large harmonic oscillations of atmospheric CO2 concentration, often neglected in the literature, indicate a strong. fast, time varying flux in and out of the atmosphere, with an exchange time constant of little more than one month. The correlation of oscillation amplitude with landmass distribution indicates that this oscillation may have a predominantly terrestrial origin. It is predicted that if the increase of anthropogenic CO2 production is halted, the CO2 concentration will stabilize within a quarter century.