Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

O'Connor, Fiona M.; Abraham, N. Luke; Dalvi, Mohit; Folberth, Gerd A.; Griffiths, Paul T.; Hardacre, Catherine; Johnson, Ben T.; Kahana, Ron; Keeble, James; Kim, Byeonghyeon; Morgenstern, Olaf; Mulcahy, Jane P.; Richardson, Mark; Robertson, Eddy; Seo, Jeongbyn; Shim, Sungbo; Teixeira, João C.; Turnock, Steven T.; Williams, Jonny; Wiltshire, Andrew J.; Woodward, Stephanie; Zeng, Guang

doi:https://doi.org/10.5194/acp-21-1211-2021

Articles | Volume 21, issue 2

https://doi.org/10.5194/acp-21-1211-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

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https://doi.org/10.5194/acp-21-1211-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 2

Research article

|

29 Jan 2021

Research article |

| 29 Jan 2021

Assessment of pre-industrial to present-day anthropogenic climate forcing in UKESM1

Fiona M. O'Connor, N. Luke Abraham, Mohit Dalvi, Gerd A. Folberth, Paul T. Griffiths, Catherine Hardacre, Ben T. Johnson, Ron Kahana, James Keeble, Byeonghyeon Kim, Olaf Morgenstern, Jane P. Mulcahy, Mark Richardson, Eddy Robertson, Jeongbyn Seo, Sungbo Shim, João C. Teixeira, Steven T. Turnock, Jonny Williams, Andrew J. Wiltshire, Stephanie Woodward, and Guang Zeng

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Final revised paper (published on 29 Jan 2021)
Supplement to the final revised paper
Preprint (discussion started on 03 Feb 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of O'Connor et al. Climate Forcing in UKESM1', Anonymous Referee #1, 27 Feb 2020
RC2: 'Review', Anonymous Referee #3, 15 Apr 2020
AC1: 'Author response to reviewer comments on acp-2019-1152', Fiona O'Connor, 31 Jul 2020

Peer-review completion

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

AR by Fiona O'Connor on behalf of the Authors (11 Aug 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (23 Aug 2020) by Michael Schulz

RR by Anonymous Referee #3 (05 Sep 2020)

Suggestions for revision or reasons for rejection

I have one principle comment :
The fact that the differences shown in global maps which are not statistically significant have been removed from the plots ("masked out in white"). I do not think this is a good approach.

Then I have a list of small comments and suggestions (on language, typos, different ERF values in text and tables, ...) :
Eqs (4), (6) and (7) : formulas which consist out of several lines, only need a "," or "." after the last line. So Eqs. (4), (6) and (7) do not need a "," at the end of the line.
"Year" : "Year" is often written in capital letters - I do not think that is necessary
line 18-19 : the combination "by ..., it ..." : I would possibly skip both "by" and "it"
Table 1 : the expression "4x1850" is a bit strange (but maybe ok to keep it)
line 210-211 : possibly add "and" before "surface seawater"
line 241 : "LBC, Finally" : "," -> "."
line 278 : maybe add "the" before "National Institute of Meteorological Science"
line 318 : (ERFcs' ) : white space can be removed
line 320 : modelled-derived -> model-derived
line 324 : considered -> taken into account
Table 3 : LWcs', SWcs', NETcs' : I suggest to write also the subscript straight (as, e.g., on line 399)
Table 3 : on the line with GHG : I would write CO2, N2O, and CH4 with lowered indices
Table 3 : on the line with O3 precursors : I would write O3 with lowered indices
line 361 : "signal.Further" : white space needed between "signal." and "Further"
Figure 3, caption : the references to panels like "a)" and "b)" appear here after the description. In most other figures they appear before the description.
line 397 : Etminan et al., (2016) : "," can be removed
line 409 : "cf." : I would not used "cf." here
line 411 : 0.14+/-0.02, whereas 0.16 in Table 3
line 421 : 0.25+/-0.03, whereas +/- 0.04 in Table 3
line 424 : "of0.09" : white space needed between "of" and "0.09"
line 425 : ( 0.25 : whte space between "(" and "0.25"
line 425 : 0.25 +/- 0.03, whereas +/- 0.04 in Table 3
line 473 : 0.74 +/- 0.03, whereas +/- 0.02 in Table 3
line 476 : 0.12 +/- 0.03, whereas +/- 0.02 in Table 3
line 481 : "and are due to indirect effects" -> "and is due to indirect effects"
line 509 : aren't the SW CRE and LW CRE values interchanged compared to Table 3?
line 516 : "CH4," : the "," is also written as a subscript
line 562 : -0.46 +/- 0.01 : the value in the figure looks more negative than just -0.46 (might be also related to the resolution of the figure)
line 601 : "And (iii) Internal" : "Internal" should not start with a capital letter
line 606-621 : the numbers in this paragraph do not have uncertainty estimates : -0.70 (line 612), -0.15 (line 615), 0.05 (line 619) and -0.99 (line 620)
line 636 : 0.21 +/- 0.04 : "+/- 0.04" is written in red
line 688 : "toODSs" : white space needed between "to" and "ODSs"
Figure 10, caption : piClim-NOX -> piClim-NOx
line 710 : "take account of" : I would think that "take into account" or "account for" sounds better
line 794 : 0.33 +/- 0.03 whereas 0.04 in Table 3
line 803 : Thornhill et al. (2020) also shows ... : I would write "show" (plural)
line 840-843 : after the "... three ... are discussed: ...", one would except that all 3 experiments follow in the second part of the sentence. Here only one experiment follows, and the next seperate sentence treats the two other experiments.
line 875 : twice "-1.0" -> twice "-1.00" (to be in agreement with the precision of the uncertainty estimate)
line 882 : "Figure 13" -> "Fig. 13"
line 888 : "lland" -> "land"
line 909 : "andaerosol-free" : white space between "and" and "aerosol-free"
line 914 : reference "Noblet-Ducoudre et al. (2012)" is not found in reference list
line 915 : "increased from about 1850-1970 in North America and from 1900-1980 in ..." : I suggest to write : "increased from about 1850 to 1970 in North America and from 1900 to 1980 in ..." or "increased over the period 1850-1970 in North America and over the period 1900-1980 in ..."
line 908-927 : the numbers in these paragraphs have no uncertainty estimate : -0.28 (line 918), -0.08 (line 918), and -0.20 (line 927).
line 1027 : what's -> what is
line 1044 : "with a fully coupled ESM" : if "fully-coupled" refers to coupling with the ocean, then this sentence is maybe a bit strange : the quantification of the ERf has happened with the atmosphere-only configuration of the model

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RR by Anonymous Referee #1 (27 Sep 2020)

Suggestions for revision or reasons for rejection

This is an excellent revision and I thank the authors for such a positive response to the review comments.

I am very happy to recommend acceptance of the paper. It can be accepted as is, but I have a few rather minor comments/suggestions that the authors may wish to attend to.

There is a further matter that I think requires an Editor decision. The handling of the unpublished Morgenstern paper is much better in the new version, especially in acknowledging that UKESM may be an outlier. Nevertheless, unlike (I think) all the other unpublished papers in the new version, it is not available in Discussion form, or available on a preprint service (e.g. as is the Pincus paper). I wonder if it should be insisted that it be made available in this form, if acceptance remains an issue or is likely to be significantly delayed.

Comments

37: “it is outside the range of previous estimates, and”. Maybe indicate which way it is outside the range? More negative or less negative?

41: RA – since this abbreviation is used only once in the abstract, I suggest not using it all.

200: Figure caption. “HC” in header – It seems that HC is being used before being defined. As it is not in any way a standard acronym (I still think “hydrocarbon” (or "Hadley Centre!")) I suggest spelling this out in the caption.

419: N2O forcing. With apologies, I might have spotted this in the first version. There is a further possibility to explain the higher ERF/RF here, that goes beyond the RF and ERF. The Etminan expressions crudely account for the changing concentrations of methane (and CO2) as overlapping gases in their parameter M-bar (and C-bar). Now in experiment piClim-N2O, the background concentrations of CH4 and CO2 are unchanging, and hence it would be more appropriate to compare the UKESM forcing against the Etminan forcing with M-bar and C-bar concentrations specified at their 1850 levels. My guesstimate is this would only increase the N2O forcing by 5-10%, so closing the gap a bit, and the authors may, in any case, already have accounted for this. The same applies for the other forcings (CO2 and CH4) calculated from the expressions in Etminan, but the effects of these changing overlaps must be much smaller

463: “having a stronger global O3 decline” – given my comment above about the (non) availability of the Morgenstern paper, I suggest that this statement could be made more quantitative – how much stronger is the decline? And similarly, is that decline significantly stronger than what are (compared to many constituents) quite good observations of that decline?

898: typo “lland”

900: “stronger than observed” – perhaps some quantitative hint would be useful here?

909: typo “andaerosol”

1063: assuming that this is the UK body, then “National Environmental Research Council” is doubly wrong. It is “Natural” and “Environment” (it is correct later in the Acknowledgements,

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ED: Publish subject to minor revisions (review by editor) (07 Oct 2020) by Michael Schulz

AR by Fiona O'Connor on behalf of the Authors (16 Oct 2020) Author's response Manuscript

ED: Publish as is (22 Nov 2020) by Michael Schulz

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Short summary

This paper calculates how changes in emissions and/or concentrations of different atmospheric constituents since the pre-industrial era have altered the Earth's energy budget at the present day using a metric called effective radiative forcing. The impact of land use change is also assessed. We find that individual contributions do not add linearly, and different Earth system interactions can affect the magnitude of the calculated effective radiative forcing.