Invited Response to Andrews

Abstract

justed assessment of fossil fuel-derived CO 2 in the atmosphere (Skrable et al. 2022). We believe that our letter to which Andrews refers and the supporting document available through the link therein provide detailed and adequate information to support our position. We provide some additional reinforcing information here in an attempt to clarify our position and respond to Andrews' criticism with reference to items 3 and 4, which he specifies in the beginning of his letter.Andrews' claim is that the disappearance of fossil-derived CO 2 in the atmosphere is associated with the process of isotope exchange caused by molecular exchange between the atmosphere and CO 2 reservoirs, such that 14 CO 2 concentrations in the atmosphere are increased when fossil-derived CO 2 exchanges with non-fossil CO 2 . An important point to bear in mind is that our assessments are of annual average concentrations of fossil and non-fossil derived CO 2 in the atmosphere. They incorporate any consequences of isotope exchange that have occurred. Our use of the term "non-fossil CO 2 " means that such CO 2 does not contain the anthropogenic fossil component and is basically the same as what existed in the atmosphere prior to the industrial revolution. As we have described earlier, changes from initial values in 1750 of the fossil and non-fossil components are independent of each other.Annual changes are much less affected by mixing/ isotope exchange processes than are longer term assessments. If we look at annual emissions of CO 2 into the atmosphere and evaluate annual increases in our calculated atmospheric CO 2 fossil-derived concentrations, we find fossil changes are much less than what would be predicted from the annual emissions. The values we are using are those from Table 2 of our supporting document (http://links. lww.com/HP/A230). The first column in Table 1 contains the years for the chosen interval. Changes expressed in columns are from the end of the first year to the end of the second year. The second column contains our results for the See https://sos.noaa.gov/catalog/datasets/ocean-atmosphere-co2exchange/#:~:text=When%20carbon%20dioxide%20CO2,certain% 20areas%20of%20the%20ocean. Accessed