The authors have nicely revised the manuscript according to the suggestions by the reviewers. As editor, however, I request three small further modifications; after that the manuscript can be accepted for ESD:

1) Reviewer #1 suggested to replace ppm by ppmv throughout the text and the authors did this - however, this is not correct. ppm as used in the carbon cycle community denotes "mole fraction" in dry air (actually mumol CO2/mol dry air). This is not equivalent to ppmv because CO2 is a non-ideal gas. Indeed WMO-GAW specifically recommends to use ppm units. We also adhered to this practice in chapter 2 and chapter 6 in IPCC AR5; and also the cited SIO CO2 website consistently uses ppm.

2) In the greenhouse effect description the authors state that in the absence of the greenhouse effect, the Earth's temperature would be -19C. This is only true if the albedo of the Earth would remain the same, i.e. assuming the same cloud cover. E.g. just removing the atmosphere would not lower the temperature to -19C. The sentence could be made more precise by stating this in order to avoid misunderstandings.

3) The authors refuse to take on the suggestion by referee #2 to also mention the 13C method (revised manuscript: page 20, line 974, original manuscript: page 1631, line 23) in identifying the relative roles of land vs ocean variability and trends. If the O2/N2 method is mentioned here, clearly also the 13C method merits be mentioned.

This manuscript can now be published. I just suggest that in the newly introduced pp on the 13C method that the last two sentences are dropped - they confuse the reader. Anybody interested might better consult the cited literature.