Climatologies of aerosols for the ECHAM-HAM model are presented, motivated by the need for more interpretability. This is important and useful work and complements other efforts to simplify the aerosol microphysics such as HAMlite and MACv2-SP. An interesting analysis of the potential challenges of the simpler climatology approaches for CCN in humid conditions near cloud base is presented. The more complex aerosol climatology roughly maintains aerosol forcing and climate sensitivity as in the default model (at least, as it is calculated by the authors) while the simpler CCN/IN climatology does not maintain forcing: it’s useful to see that some simplification can be achieved with minimal loss of ‘equifinality’ while more simplification, while still useful in some situations, does degrade key performance metrics. The paper is well written.

Minor comment

In Figure 5 it would be helpful to show observations from CERES level 3 data, or from (for example) the Grosvenor et al CDNC dataset, to put the differences between the models in context of the difference between models and observations. Or simply state the typical scale of model-observation discrepancies (likely > 25% in many regions for CDNC at least, I imagine) to give this context, and also provide context to the discussion around line 455.

Editorial comments

The text in Figure 2 is too small.

Would be useful to include a sentence explaining why sections 2.1-2.4 are important to the paper – just a statement that these parameterizations are the ones that relate aerosols to clouds and/or differ between the simulations presented would suffice.

Fig 5 caption needs to define ‘mxpT’ and ‘cold’

L429 believes->beliefs

The discussion of the relative merits of different possible simplification approaches is more appropriate in the introduction than in the summary; I suggest the authors move lines 431-442 to the introduction.