by Tom V. Segalstad (1998)
A number of lifetimes and timescales are being used in both scientific and policy context to describe the behavior of heat-absorbing gases in the atmosphere. These concepts are very important for the discussion on whether anthropogenic CO2 will be accumulated in the atmosphere and exert an additional global “Greenhouse Effect” warming. If each CO2 molecule in the atmosphere has a short lifetime, it means that the CO2 molecules will be removed fast from the atmosphere to be absorbed in another reservoir.
The atmospheric residence time (i.e. lifetime; turnover time) of CO2 has been quantified based on measurements of natural radiocarbon (carbon-14) levels in the atmosphere and the ocean surface; the changes in those levels caused by anthropogenic effects, like “bomb carbon-14” added to the atmosphere by nuclear explosions; and the “Suess Effect” caused by the addition of old carbon-14-free CO2 from combustion of fossil fuels; and the application of gas exchange theory to rates determined for the inert radioactive gas radon-222. The results from these measurements are in Table 2, … in addition to the solubility data, and the carbon-13/carbon-12 mass-balance calculation. The last two recent methods give a lifetime of 5.4 years based on completely different methods.