Dear Jianyang Xia,

Many thanks for your response to reviewer comments. I have contacted one of the original reviewers, and concur with them that you have addressed the main points raised by both referees. However, there are a few remaining issues I would like you to address.

1) Please justify your use of the entirely new 3-pool model, when there are a range of existing Community Land Models available?

2) In your response to reviewer 2, please provide more detail on the new approach. What would drive soil C input? Would the model be calibrated against data from all sites?

3) It is difficult to follow how transit time from the same Q10-based first-order kinetics model would be so insensitive to temperature (see Fig R1 in the supplement to their replies to my comments).

I'd like to ask you to address these remaining points in your revision of the manuscript.

Best wishes,
Jens-Arne Subke

Dear Dr Xia,

As i explained in my e-mail a few days ago, the manuscript you are currently revising will be considered as requiring major revisions, and I look forward to receiving a fully revised version, also noting my comments on additional points in my previous message.

Best wishes,
Jens-Arne Subke

Dear Dr Xia,

I have reviewed your response to referee comments, including the more recent request for further clarifications. I think that the way in which you have revised the manuscript now take account of all points raised.

There are a number of remaining issues with clarity in the text which I detail below I would like to ask you to implement these in the text and re-submit the manuscript before final acceptance, i trust that these can be done reasonably quickly, assuming that you agree with my comments.

I look forward to receiving your (hopefully) final verions.

Best wishes,
Jens-Arne Subke

Page. 2, Line. 2: Please capitalise first letter of all words in Earth System Models.
P. 2, L. 3: “mean age” of C atoms is not correct. Please change to “mean residence time”.
P. 2, L. 7: Please change: “(median of 4 years, with interquartile range of 1 to 25 years)”.
P. 2, L 11-14: Make 2 sentences, with full stop after “temperature” (end of line 12).
P. 2, L. 13: Comma needed after “biomes”.
P. 2, L. 17: Please change to: “… soil C dynamics in regions limited by temperature or moisture”.
P. 3, L. 3: As above, please use capitals for each of the words “Earth System Models”.
P. 3, L. 9-10: Please rephrase to: “It is difficult to reduce or even diagnose this uncertainty, as many processes…”
P. 3, L. 19/20: Please rephrase: “…,and the construction of a benchmarking database of available observation is urgently needed (Koven et al., 2017).
P. 3, L. 24: Rephrase: “…commonly defined as “turnover time”, calculated by dividing SOC stock by C fluxes such as …”.
P. 4, L. 5: “mean residence times” rather than “mean ages”.
P. 4, L. 20-22: This sentence is not clear. I suggest making it into 2 sentences: “ τsoil was calculated under the homogenous one-pool assumption at steady state for all studies. Data from observations and CMIP5 ensemble were then used to calculate the τsoil based on both one-pool and three-pool models.
P. 5, L. 4/5: Use active voice; “We constructed a database…”.
P. 10, L. 14: Text in brackets: “(median of 60 years, with interquartile range of 8 to 29 years)”. For subsequent results, simply state “(X with Y to Z years)”.
P. 11, L. 11: adjust spaces: “0.5° x 0.5°” (i.e. spaces either side of x, but not before degree sign).
P. 11, L. 14: delete “was” at end of line
P. 12, L. 5: “show”, not “shown”. Delete “both” at end of line.
P. 12, L. 18: delete “the” before “equation (12)”. Change “showed” to “show” at end of the line.
P. 12, L. 19: delete “the” before CLM4.5”. Change “Fig. 6” to “Fig. 5”.
P. 12, L. 24: Rephrase: “Higher NPP values simulated by ESMs…”
P. 13, L.4-6: However, other processes such as the microbial dynamics, SOC stabilization and nutrient cycles could affect τsoil, but are so far not fully considered by CMIP5 models (Luo et al., 2016).
P. 13, L. 23: Is it fair to say that the model data base “is” a useful tool (rather than “could be”?
P. 13, L. 24: Delete “Thus”.

Dear Dr Xia,

Many thanks for making the changes I requested on your manuscript. There is one small remaining issue on clarity, where i think i didn't make my request clear to you. Could i ask you to make the following changes throughout the manuscript, please? After that, I am quite sure that I can accept the manuscript at last!

P. 4, l. 7: Apologies if this was not clear. For the first time when you state median in interquartile range, please make this clear. So in this line, please state “(Median = 4 years; interquartile range = 1 to 25 years)”. Following that, please use “31; 5 to 84 years”, etc. within the abstract. In the results section, please repeat the full text in brackets, i.e. on page 10, line 15, please state “(Median = 60 years; interquartile range = 8 to 29 years)”. From then, simplify to “16; 3 to 156 years”, etc.

Best wishes,
Jens-Arne Subke

Dear Dr Xia,

Many thanks for making the final changes, oi am now happy for this manscript to be published.

Best wishes,
Jens-Arne Subke