Modifying emissions scenario projections to account for the effects of COVID-19: protocol for CovidMIP

Lamboll, Robin D.; Jones, Chris D.; Skeie, Ragnhild B.; Fiedler, Stephanie; Samset, Bjørn H.; Gillett, Nathan P.; Rogelj, Joeri; Forster, Piers M.

doi:https://doi.org/10.5194/gmd-14-3683-2021

Articles | Volume 14, issue 6

https://doi.org/10.5194/gmd-14-3683-2021

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

https://doi.org/10.5194/gmd-14-3683-2021

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

Articles | Volume 14, issue 6

Development and technical paper

|

22 Jun 2021

Development and technical paper |

| 22 Jun 2021

Modifying emissions scenario projections to account for the effects of COVID-19: protocol for CovidMIP

Robin D. Lamboll, Chris D. Jones, Ragnhild B. Skeie, Stephanie Fiedler, Bjørn H. Samset, Nathan P. Gillett, Joeri Rogelj, and Piers M. Forster

Download

Final revised paper (published on 22 Jun 2021)
Preprint (discussion started on 10 Dec 2020)

Interactive discussion

Status: closed

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

- Printer-friendly version

- Supplement

RC1: 'Review of Lamboll et al', Anonymous Referee #1, 06 Jan 2021
- SC1: 'Reply to RC1', Robin Lamboll, 16 Jan 2021
- AC2: 'Reply on RC1', Robin Lamboll, 19 Feb 2021
RC2: 'Review', Anonymous Referee #2, 15 Jan 2021
- AC1: 'Reply on RC2', Robin Lamboll, 19 Feb 2021

Peer-review completion

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

AR by Robin Lamboll on behalf of the Authors (13 Mar 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (23 Mar 2021) by Sophie Valcke

RR by Anonymous Referee #3 (02 Apr 2021)

Suggestions for revision or reasons for rejection

I was called in as a third reviewer in light of two diverging reviews, hence I will keep this review at a relatively high level, without commenting too much on the details. One reviewer is fairly critical of the work and its rationale, one reviewer asks for minor revisions. The authors have provided responses to the two reviewers and made relatively minor revisions to the manuscript.

In their manuscript Lamboll et al. have revised recent emissions and existing scenarios to account for the short-term and the long-term impacts of the Covid-19 pandemic. They propose that these revised scenarios serve as a basis for a Covid-MIP which is also described in the proposal.

I find the manuscript to be clumsy and a little difficult to read. The revised version has done little to improve this. The manuscript relies heavily on Forster et al. (2020) and I had to go back to this article to understand the content of this manuscript. This is not good practice, a manuscript ought to be readable as a stand-alone document.

While I do see some value in a rapid response tool to update emissions scenarios, I am rather sceptical as to what the authors are trying to achieve with Covid-MIP.

Strand 1: the climate perturbation induced by the reductions in emissions during and after the lockdowns (“two year blip”) is very likely to be undetectable given the amount of variability in the weather/climate system. Running ensemble will help to extract a small signal from the simulations but what for? The Covid-19 period is nevertheless of great interest in that it can be used to evaluate the atmospheric chemistry component of the climate models. However this would require nudged simulations and/or a clever comparison to observations so as to “control the weather”. While nudged simulations are mentioned in the manuscript, they are optional. In the end, I am concerned that the climate modelling groups participating to Covid-MIP will use a lot of computing time to find out fairly small changes in atmospheric composition and climate. What the authors expect to learn on the climate system needs to be much better demonstrated in the manuscript. This may require a prior quantification of the changes expected before embarking the community in a new MIP.

Strand 2: the proposed scenarios (fossil-fuelled recovery, moderate green stimulus, strong green stimulus) are very schematic. To my knowledge, the IAMs do not have a representation of the macroeconomics relevant to the prediction of the impacts of the recovery packages on emissions (typically one would need to resolve money transfers between the different stakeholders, who lends or gives money to whom and what for?). I tend to think IAMs are basically useless to predict the impact of the recovery packages on emissions. In this context the green stimulus scenarios put forward in the manuscript look like wishful thinking, and I do not see their usefulness beyond existing SSP scenarios. I would be happy to be contradicted but I have not seen a convincing argumentation in the manuscript. Furthermore if new scenarios are to be built, simple climate models are there to make new quick projections. Again, what will be learned by running complex Earth System Models for these three new schematic scenarios?

As I said above, I do see a value in adjusting scenarios in near-real-time given ongoing changes in current socio-economic conditions: GDP growth (or reduction) in the last few years, implementation (or lack of) of climate policies (e.g. carbon price in different world regions), etc. In a sense SSP scenarios used for CMIP6 are already outdated, especially the low ones. The transition between past and future emissions is also poorly represented in these scenarios, with some continuity in emissions but not in the rate of change of the emissions. Maybe the work of the authors can go some way into that direction. Note that there are several initiatives to monitor emissions in near-real-time, it would be interesting to know how the work by the authors compare with others.

In conclusion, the work presented by Lamboll et al is insufficiently motivated. It makes the whole manuscript a little unclear and it is hard to judge if the methodologies chosen to correct the emissions based on various proxies are sound or not for the objectives, given that the objectives themselves are poorly described / not convincing. I recommend rejection.

Note that this paper may be relevant to this study:
https://acp.copernicus.org/articles/21/3091/2021/

Hide

RR by Ben Sanderson (06 Apr 2021)

ED: Reconsider after major revisions (15 Apr 2021) by Sophie Valcke

Dear Author,

Thank you for your revised manuscript that has indeed answered the remarks of Referee #1. However, the third review I asked in light of the two diverging initial reviews is very negative and asks for rejection of your paper. I have read the third reviewer's comments carefully and I consider that overall they are more a criticism of the utility of a COVID MIP at all -including the associated computational cost for modelling centers- that a fundamental rejection of the content of your paper. Therefore, I decided not to reject your paper but to ask for some important revisions along the lines of the third reviewer's comments and I consider I can handle the evaluation of your next revisions myself.

In particular, please address the following major comments:

- put a great focus on the nudged experiments and/or on a clever comparison to observations so as to “control the weather” in your protocol in order to favour the short term detection of climate effects of emissions changes

- better describe the objectives of your paper so to motivate the methodologies chosen; better describe/quantify the expected impacts on the climate system so to better justify embarking the community in a new MIP

- address the comment that the manuscript is “clumsy” and “difficult to read” and that one should not have to go back to Forster et al. (2020) to understand the content of your manuscript

- provide an argumentation against the fact that IAMs are basically useless to predict the impact of the recovery packages on emissions, which would imply that the proposed scenario are not providing anything significant beyond existing SSP scenarios

- comment the issue that simple models could be used instead of ESMs to reduce the cost

- the poor representation of the transition between past and future rate of change of the emissions

Thank you very much, I am looking forward a revised version of your manuscript addressing these comments.
With best regards

Hide

AR by Robin Lamboll on behalf of the Authors (04 May 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (19 May 2021) by Sophie Valcke

Short summary

Lockdowns to avoid the spread of COVID-19 have created an unprecedented reduction in human emissions. We can estimate the changes in emissions at a country level, but to make predictions about how this will affect our climate, we need more precise information about where the emissions happen. Here we combine older estimates of where emissions normally occur with very recent estimates of sector activity levels to enable different groups to make simulations of the climatic effects of lockdown.