Wildfire air pollution hazard during the 21st century

Knorr, Wolfgang; Dentener, Frank; Lamarque, Jean-François; Jiang, Leiwen; Arneth, Almut

doi:https://doi.org/10.5194/acp-17-9223-2017

Articles | Volume 17, issue 14

https://doi.org/10.5194/acp-17-9223-2017

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

https://doi.org/10.5194/acp-17-9223-2017

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

Articles | Volume 17, issue 14

Research article

|

31 Jul 2017

Research article |

| 31 Jul 2017

Wildfire air pollution hazard during the 21st century

Wolfgang Knorr, Frank Dentener, Jean-François Lamarque, Leiwen Jiang, and Almut Arneth

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Final revised paper (published on 31 Jul 2017)
Supplement to the final revised paper
Preprint (discussion started on 06 Jul 2016)

Interactive discussion

Status: closed

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

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- Supplement

AC1: 'References to "Fig. 10"', Wolfgang Knorr, 24 Aug 2016
RC1: 'review', Anonymous Referee #1, 02 Sep 2016
RC2: 'review of Knorr et al.', Anonymous Referee #2, 19 Sep 2016

Peer-review completion

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

AR by Wolfgang Knorr on behalf of the Authors (07 Dec 2016) Author's response

ED: Referee Nomination & Report Request started (09 Jan 2017) by Dominick Spracklen

RR by Anonymous Referee #3 (13 Mar 2017)

Suggestions for revision or reasons for rejection

This manuscript presents a study on the effects of humans and climate on fire activity and consequences for air pollution across the 21 century. The Authors use LPJ-GUESS with SIMFIRE to produce a set of future fire emissions (based on GFED4s for present-day) and the chemical transport model CAM-Chem to study air quality impacts. The effect of climate and human intervention on future fire activity and air pollution is an important topic and results from this work are of relevant interest for the readers of the ACP. This manuscript is a revised version of a previously submitted manuscript. However, despite the substantial work done by the Authors to address the reviewers’ comments, I find the manuscript still very confusing and poorly organized and cannot be published as it is.

The PM2.5 concentrations simulated with CAM-Chem using the SIMFIRE fire emissions are key in the revised manuscript. However, this additional analysis does not blend within the manuscript and is missing important information. For example, CAM-Chem does not provide directly PM2.5 as an output, what species did the Authors consider to calculate PM2.5? The Authors do not discuss how well CAM-Chem represents PM2.5 (without seasalt and dust). My understanding is that Tilmes et al (2016) does not evaluate PM2.5, rather individual PM2.5 species. The simulations planned with CAM-Chem are not clear until the reader gets to the results. I understand that there were some computing time constrains. However, air quality simulations are typically performed for at least 10 years to consider any interannual climate variability. Also, the Authors could have run a simulation without fires in 2090 to determine the delta PM2.5 from fires.

The manuscript seems to be written in patches and gives the impression that the unnecessary figures from the previous version were moved to supplementary materials. For example, the paper shows first results from wildfires, peat and deforestation fires with the SSP2, SSP3 and SSP5 and RCP4.5 and RCP8.5 scenarios for 2000-2100 (Supplementary Materials). Then, it shows wildfire PM2.5 emissions against population for SSP3/RCP45&CLE and SSP5/RCP85&MFR for 2010, 2030, 2050 and 2090. Why aren’t deforestation and peat fire emissions included in the analysis here? Finally, it presents PM2.5 concentrations from CAM-Chem for 2010 and 2090 for SSP3/RCP45-CLE, SSP3/RCP45-CLE and SSP5/RCP85-MFR. Again here, only wildfire emissions are considered. Can the Authors identify the key points they want to show and remove the rest?

One important result is the % of people that will be exposed to PM2.5 levels above the WHO air quality standard (10 ug/m3) as a result of fire pollution. The Authors show these results in Figure 5 and Table 2. I may be missing something in the analysis, but in Fig. 5 I do not see any population range with PM2.5 levels above 10 ug/m3, except for Asia. Also, over Sub-Sahara Africa and Middle East PM2.5 concentrations are typically dominated by dust and this emission source is not considered. Over these regions, a small influence of fire pollution may make population be exposed to PM2.5 levels > 10 ug/m3.

Some additional notes:

PM2.5 is PM$_{2.5}$.

Spracklen et al. (2009) and Yue et al. (2013) were the first studies to examine PM2.5 impacts from future wildfires. These results should be referenced. Val Martin et al. (2015) also showed future PM2.5 changes as a result of fires with CAM-Chem.

Line 200. The Authors should cite Lamarque et al. (2012), instead of (2010).

Line 240-241 Why were the simulations done at 1 deg and the analysis at 1/2 deg? It does not make sense to me to increase resolution if the bulk fire emissions are at 1 deg.

Line 324. I don’t see how SIMFIRE differs from GFED4s in Figures S5 and S6.

Figure 3. I find a bit odd that changes in annual PM2.5 emissions wrt population in Sub-Sahara Africa and South&Southeast Asia are very similar or even identical. These two regions are different in terms of fire regimes, anthropogenic emissions and population, correct?

References:
Lamarque, J.-F., Emmons, L. K., Hess, P. G., Kinnison, D. E.,
Tilmes, S., Vitt, F., Heald, C. L., Holland, E. A., Lauritzen, P. H.,
Neu, J., Orlando, J. J., Rasch, P. J., and Tyndall, G. K.: CAMChem:
description and evaluation of interactive atmospheric
chemistry in the Community Earth System Model, Geosci.
Model Dev., 5, 369–411, doi:10.5194/gmd-5-369-2012, 2012.

Spracklen, D. V., Mickley, L. J., Logan., J. A., Hudman, R. C.,
Yevich, R., Flannigan, M. D., and Westerling, A. L.: Impacts of
climate change from 2000 to 2050 on wildfire activity and carbonaceous
aerosol concentrations in the western United States, J.
Geophys. Res., 114, D2030, doi:10.1029/2008JD010966, 2009.

Val Martin, M.; Heald, C.L.; Ford, B.;
Prenni, A.J.; Wiedinmyer, C. 2013. A
decadal satellite analysis of the origins
and impacts of smoke in Colorado.
Atmospheric Chemistry and Physics. 13:
7429–7439. doi:10.5194/acp-13-74292013.

Yue, X., Mickley, L. J., Logan, J. A., and Kaplan, J. O.: Ensemble
projections of wildfire activity and carbonaceous
aerosol concentrations over the western United States
in the mid-21st century, Atmos. Environ., 77, 767–780,
doi:10.1016/j.atmosenv.2013.06.003, 2013

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RR by Anonymous Referee #2 (14 Apr 2017)

ED: Reconsider after minor revisions (Editor review) (25 Apr 2017) by Dominick Spracklen

AR by Wolfgang Knorr on behalf of the Authors (26 May 2017) Author's response Manuscript

ED: Publish as is (14 Jun 2017) by Dominick Spracklen

AR by Wolfgang Knorr on behalf of the Authors (15 Jun 2017)

Short summary

Wildfires cause considerable air pollution, and climate change is usually expected to increase both wildfire activity and air pollution from those fires. This study takes a closer look at the problem by examining the role of demographic changes in addition to climate change. It finds that demographics will be the main driver of changes in wildfire activity in many parts of the developing world. Air pollution from wildfires will remain significant, with major implications for air quality policy.