Dear Philip,
I am happy to accept your revised manuscript for publication following some minor corrections. Numbers 7) and 18) are important. The rest are technical and will help with clarity.
Best,
Graham

1) “Knowledge of the global abundance
of aerosols suitable to act as cloud condensation nuclei
is fundamental to determine the strength of the anthropogenic
perturbation causing the radiative effect of aerosol–
cloud interactions”

I would remove “aerosols suitable to act as” from this sentence to avoid repetition with preceding sentence.

2) Equation 1 and throughout paper, I would suggest replacing \alpha with \AA (in TeX).
Then use \alpha to denote aerosol extinction (common practice) to avoid confusing unfamiliar acronyms like AEC.

3) Pg. 2, column 1: Of possible interest is a ground based CCN retrieval that uses clouds as targets (Feingold et al., 1998, J. Atmos. Ocean. Tech., 15, 1189–1196).

4) Change “. This study highlighted” to “The study highlighted” (reserve “This” for the current study).

5) “Limited-scale in-situ observations (Kapustin
et al., 2006) showed that the relationship of AI to
aerosol number and CCN is also strongly affected by relative humidity” (change position of “also”

6) “so self-consistent in this context
refers to the fact that the calculation*s* of the aerosol radiative
properties (based on Mie theory) and CCN (based on Köhler
theory) are fully consistent” (calculations… are… or calculation… is…)

7) This one is important: “Nonetheless, it should be noted that the
ability of models to mimic the spatial (in particular vertical)
and temporal (co-)variability of aerosol and humidity fields
introduces quantitative uncertainty (Haywood et al., 1997).”
(The existing “some uncertainty” really doesn’t say it accurately enough, or consider prior attempts at quantification like that of Jim Haywood et al., GRL 1997 that showed very large impact.)

8) “first consistent *model-based* global analysis”.

9) “In this study we are employing” —> In this study we employ

10)”in dependence on” —> based on

11) I assume that simulated measurements are done every 6 hours regardless of whether the sun is shining or not. It is likely that co-variability between aerosol and humidity will have a diurnal cycle. Might be interesting to explore this in a model that has a better representation of the diurnal cycle of the boundary layer.

12) “*also* activating smaller particles “ (move also)

13) “and (better) to AI”

14) Move “(y = 0.0027x 0.640 for CCN0.4%, r2 = 0.88)” to the end of the sentence, followed by the reference.

15) “*when* varying the averaging periods”

16) “Note that correlations between surface layer CCN and
AIAEC also deteriorate” (move ‘also’)

17) (e.g., McComiskey and Feingold) — add “e.g.”

18) In the conclusions: As in 7),
“introduces unknown quantitative uncertainty.” is an important change to be made.