Aerosol radiative effects with MACv2

Kinne, Stefan

doi:https://doi.org/10.5194/acp-19-10919-2019

Articles | Volume 19, issue 16

https://doi.org/10.5194/acp-19-10919-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

BACCHUS – Impact of Biogenic versus Anthropogenic emissions...

https://doi.org/10.5194/acp-19-10919-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 16

Research article

|

29 Aug 2019

Research article |

| 29 Aug 2019

Aerosol radiative effects with MACv2

Stefan Kinne

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Final revised paper (published on 29 Aug 2019)
Preprint (discussion started on 03 Jan 2019)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Referee report for “Aerosol radiative effects with MACv2”', Anonymous Referee #2, 15 Mar 2019
RC2: 'Review', Anonymous Referee #1, 26 Mar 2019
AC1: 'author comments to the reviewers', Stefan Kinne, 19 Apr 2019
AC2: 'revised paper', Stefan Kinne, 19 Apr 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Stefan Kinne on behalf of the Authors (21 Apr 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 May 2019) by Athanasios Nenes

RR by Stephen E. Schwartz (05 Jun 2019)

RR by Anonymous Referee #2 (06 Jun 2019)

Suggestions for revision or reasons for rejection

The author has adopted most of the suggested changes, and satisfactorily justified not adopting the others, apart from one of the original major comments regarding omitting cloud adjustments in their work:
“In particular, the paper aims to provide an estimate of the aerosol forcing, but ignoring cloud adjustments seems a significant omission and requires much stronger justification, particularly when discussing potential uncertainties. For example, on P2L9‐10 the author states that feedbacks (adjustments) can be considered secondary, though the provided citation makes no such assertion – they just assume it for their purposes.”

Author response: "Here off‐line radiative transfer simulations a used. Thus, no feedbacks or (earth system) adjustments to the forcing can be considered. Fortunately, there is a recent RFMIP exercise where in long‐term simulations (with fixed SST) compare results of the (direct and first indirect) forcing from dual calls with the effective radiative forcing, which allowed atmospheric adjustments to the forcing in global models. The forcing differences are found to be relatively small on the order of 10% (Fiedler et al., 2019)."

While I appreciate these cannot easily be accounted for in the off-line framework used by the author, this omission requires justification in the introduction and an acknowledgment in the discussion on uncertainties. In particular, neither Fiedler et al. 2017 or 2019 show that cloud adjustments to the aerosol indirect effect are small. They choose to ignore cloud adjustments to simplify their framework, see in particular Section 2.2.2 of Fiedler et al. 2017. Whilst a similar argument could be made here, it should be done explicitly.

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ED: Publish subject to minor revisions (review by editor) (17 Jun 2019) by Athanasios Nenes

AR by Stefan Kinne on behalf of the Authors (19 Jun 2019) Author's response Manuscript

ED: Publish subject to technical corrections (27 Jun 2019) by Athanasios Nenes

AR by Stefan Kinne on behalf of the Authors (28 Jun 2019) Author's response Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Stefan Kinne on behalf of the Authors (09 Aug 2019) Author's adjustment Manuscript

EA: Adjustments approved (16 Aug 2019) by Athanasios Nenes

Short summary

Global distributions of aerosol radiative effects are calculated using aerosol properties of the MACv2 climatology and a satellite-retrieval-based relationship for the first indirect effect. Present-day climate cooling by anthropogenic aerosol is likely within a −0.7 to −1.6 W m⁻² range – with a best estimate at −1.0 W m⁻². Only about 1/3 of this TOA cooling is contributed by direct effects, which are more variable (even in sign) and stronger near pollution source regions than indirect effects.