A joint global carbon inversion system using both CO2 and 13CO2 atmospheric concentration data

Chen, Jing M.; Mo, Gang; Deng, Feng

doi:https://doi.org/10.5194/gmd-10-1131-2017

Articles | Volume 10, issue 3

https://doi.org/10.5194/gmd-10-1131-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/gmd-10-1131-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 10, issue 3

Development and technical paper

|

16 Mar 2017

Development and technical paper |

| 16 Mar 2017

A joint global carbon inversion system using both CO₂ and ¹³CO₂ atmospheric concentration data

Jing M. Chen, Gang Mo, and Feng Deng

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Final revised paper (published on 16 Mar 2017)
Preprint (discussion started on 17 May 2016)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'general review', Peter Rayner, 30 Jul 2016
- AC1: 'Reply to both reviewers', Jing Chen, 17 Oct 2016
- AC2: 'Answer to Peter Rayner's questions', Jing Chen, 17 Oct 2016
RC2: ''A Joint Global Carbon Inversion System Using Both CO2 and ^{13}CO2 Atmospheric Concentration Data' by Chen et al.,', Anonymous Referee #2, 19 Sep 2016
- AC3: 'Answer to reviewer 2', Jing Chen, 17 Oct 2016

Peer-review completion

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

AR by Jing Chen on behalf of the Authors (25 Nov 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Dec 2016) by Tomomichi Kato

RR by Anonymous Referee #2 (20 Dec 2016)

RR by Peter Rayner (29 Jan 2017)

Suggestions for revision or reasons for rejection

I believe the authors have done a satisfactory job of addressing the reviewers' comments and that the paper should now be published.

I agree that the question of using the dilution effect in the Jacobian for C13 observations remains a matter of debate. Since this forum is archived and accessible it seems a good place to continue the debate so I will respond to the authors' response:

First I will say that we debated long and hard about using this term in the Rayner et al. (1999) study. I am still cautious rather than confident about our conclusion. The choice depends on what is included in the target variables and the prior estimates. For Rayner et al. (1999) we only included long-term means and trends in the isoflux. Thus there was no scope for the isoflux to respond to short-term variations. This is not physically correct; if a net flux changes the disequilibrium of the atmosphere then the isoflux will respond. We needed some way to include this effect and the best way we could think of (given the target variables at our disposal) was to modulate the C13 response to a net flux.

The case for this paper is different but, I think, not completely different. Short-term variations in the isoflux for the prior are captured by the process models, provided that these models are forced with actual C13 atmospheric records. This effect is accounted for by the modification of the observations used in the inversion. However as soon as one varies a flux from the prior this response is no longer correct since the calculated isoflux pertains only to the prior estimate. Thus I still believe the dilution should be applied to variations from the prior fluxes. I'm also quite prepared to be wrong and don't think this question should hold up this paper further.
I believe the authors have done a satisfactory job of addressing the reviewers' comments and that the paper should now be published.

I agree that the question of using the dilution effect in the Jacobian for C13 observations remains a matter of debate. Since this forum is archived and accessible it seems a good place to continue the debate so I will respond to the authors' response:

First I will say that we debated long and hard about using this term in the Rayner et al. (1999) study. I am still cautious rather than confident about our conclusion. The choice depends on what is included in the target variables and the prior estimates. For Rayner et al. (1999) we only included long-term means and trends in the isoflux. Thus there was no scope for the isoflux to respond to short-term variations. This is not physically correct; if a net flux changes the disequilibrium of the atmosphere then the isoflux will respond. We needed some way to include this effect and the best way we could think of (given the target variables at our disposal) was to modulate the C13 response to a net flux.

The case for this paper is different but, I think, not completely different. Short-term variations in the isoflux for the prior are captured by the process models, provided that these models are forced with actual C13 atmospheric records. This effect is accounted for by the modification of the observations used in the inversion. However as soon as one varies a flux from the prior this response is no longer correct since the calculated isoflux pertains only to the prior estimate. Thus I still believe the dilution should be applied to variations from the prior fluxes. I'm also quite prepared to be wrong and don't think this question should hold up this paper further.

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ED: Publish subject to minor revisions (Editor review) (06 Feb 2017) by Tomomichi Kato

AR by Jing Chen on behalf of the Authors (15 Feb 2017) Author's response Manuscript

ED: Publish as is (17 Feb 2017) by Tomomichi Kato

AR by Jing Chen on behalf of the Authors (26 Feb 2017) Manuscript

Short summary

A joint inversion system is developed for estimating the carbon fluxes in 39 land and 11 ocean regions of the globe using both atmospheric CO₂ and ¹³CO₂ stable isotope data. In particular, a biospheric model is developed to model both CO₂ and ¹³CO₂ fluxes over land to constrain the inversion. Relative to CO₂-only inversion, the joint inversion system improved the partition between land and ocean carbon fluxes and possibly the distribution of the fluxes among land regions as well.