Dear authors

Thank you very much for answering the comments of the two reviewers. I appreciate your effort to address all comments, to perform new simulations, and provide relevant clarifications. I invite you to submit an accordingly revised version of your manuscript.

Both reviewers requested major revisions and both indicated their willingness to review your revised manuscript. I will therefore send them again your MS for a hopefully final check.

I recommend to attach to your reply a manuscript version with changes highlighted (track-change) to ease the review process.

Thank you for submitting your work to Biogeosciences. With kind regards, Fortunat Joos

Dear authors

Your MS has been assessed again by one of the original reviewer. I am pleased to accept your manuscript for publication in BG subject to minor revision (review by editor).

As you will see from the referee report, the referee asks for an additional figure:
"An additional figure, or two figures actually, that would be interesting are maps of the total changes between the highest resolution CO2 forcing and the global annual CO2 forcing (magCO2), GPP and NBP (instead of incremental changes and differences between the steps). I think the regional bias may be more interesting than the 0.1 Pg C difference, because many things can be changed in a model to get a change of 0.1 Pg C NBP, and known regional biases due to a simplification in the CO2 forcing are therefore interesting. Maybe as % of GPP and NBP? I.e. a clear figure of the estimated maximum regional impact of the common simplified CO2 forcing."

I believe that this is a valuable suggestion that likely improves the value and impact of your manuscript. I therefore suggest that you follow the advise by the reviewer and that you add this additional information to your manuscript.

Looking forward to receive your updated manuscript.

Thank you for submitting your work to Biogeosciences.

With best wishes, Fortunat Joos

Dear authors

thank you for the addition of the supplementary figure. I am happy to accept your study for publication.

Thank you for submitting your work to Biogeosciences.

With kind regards, Fortunat Joos