1. The Pacific decadal oscillation which is also one of the main climate mode that can affect

ENSO and indeed on the ozone concentrations. The authors didn’t explain why other

climate modes are not considered and

why only three (Dipole mode Index, Southern

Annual Mode and North Atlantic Oscillation) climate modes.

2. Try to elaborate mainly the common schemes in the Atmospheric Chemistry Modules

that are in the models (other than the three models BCC_CSM2_MR, IPSL_CM6A_LR

and MPI_ESM1_2_LR) as the behavior of these models in connection to the response of

ENSO on ozone variation is similar.3. The Text S1 which explains about the method that has been adopted should be mentioned

under the method section 2.2 rather than in the supplement. It helps the reader to have a

quick through of the methodology adopted in the study.

4. Why did you consider only 1000 hPa, 850 hPa, 500 hPa and 300 hPa ? Are these pressure

levels enough to represent the respective atmospheric region of the atmosphere (like

middle troposphere, upper troposphere). As ENSO is responsible for changes in winds

and circulation patterns. It is also expected to have impact on the transport of ozone from

the lower troposphere to upper troposphere and lower stratosphere. It would be

interesting if you can check if the features are same in the upper levels (above 300 hPa

just below the tropopause)

Line Nos.:42:43: Did you check if the findings obtained using CMIP6 and CMIP5 ? If so where

did you find the changes that resulted in the current result?

Line Nos.: 51: The list of the models mentioned in Table S1 should be shifted to the main

manuscript instead of supplement.

Line Nos. 53:55: The authors are suggested to explain little more on the findings of the cited

papers rather than just citing the paper.

The Figures can be of more clarity (mainly the stippling in figures are not at all visible (for

example Figure 1 (a)) are not visible clearly, The titles in the Figure 3 should be made little big)

This study investigated the effect of ENSO on tropospheric ozone over the period 1850-2014, focusing on the 300, 500, 850 and 1000 hPa. The authors also used the probability for the absence of Granger causality from ENSO to ozone concentrations. The topic is interesting. However, before it can be considered for publication, some aspects need more explanation.

1. My major concern is that can the current CMIP6 model simulations including the ozone chemistry and it related physical and chemical processes. For example, the first BCC model does not have atmospheric chemistry model (Table S1), how can it predict ozone? The No.3-6 are all CESM2 model. Do these model configurations predict tropospheric ozone with fully atmospheric chemistry? The MAM4 is the name of aerosol module not the atmospheric chemistry. Also, are the simulated ozone in these models evaluated? Some models cannot well reproduce the global distribution of ozone and some cannot characterize the response of ozone to ENSO signal shown in observations.
2. The conclusions about the effect of ENSO on seasonal ozone in the troposphere can be added to the abstract.
3. Line35-40: It is suggested to provide the details of the uncertainties regarding the causal effects of ENSO on global tropospheric ozone. Although the authors provided some references, the information from these references should be strengthened.
4. The effect of ENSO on ozone in the lower troposphere is more significant than that in the upper and middle troposphere. Please elaborate the reason. Moreover, the models’ agreement is weak in reproducing ozone in the lower troposphere and the standard deviation is high in the tropics. In this context, is the conclusion that ENSO affects the lower troposphere in the tropics convincing?
5. Line 116 “The significant impacts of ENSO on ozone … might be associated with the transport of ozone from east Asia”. If so, the effect of ENSO on ozone over east Asia should be found. But it doesn't. Can you add some explanation about it?