|Dear Mr. Krikken and coauthors|
Thank you very much for your interesting paper “Attribution of the role of climate change in the forest fires in Sweden 2018”. I think that your paper can be accepted after doing some minor changes.
Please, modify the abstract. It provides contradictory information. In the first paragraph you say “we find a negative trend of the FWI for Southern Sweden over the 1979 to 2017 time period” but the second paragraph ends with “We however do not find a clear change of prolonged dry periods in summer months that could explain the increased fire weather risk.”. Perhaps this second conclusion refers to climate projections but, in this case, you should clarify it.
Figure 1 and so on. It is “burned area” not “area burned”. Please, modify.
Figure 1. What do you mean with “climatology over 2008-2017”? Do you refer to average annual value of burned area? What do you mean with “its individual years” Please, clarify the meaning of both terms in the main text.
Figure 4. You only work in the paper with two Sweden regions, then you cannot say “Map of Sweden with the three regions used in this study”. On the other hand, what is the criteria of this regionalization? Are they climate regions? Please, modify the text as convenient.
Line 49. You say: “found a strong influence between the recent increase in forest fires in California and the positive trend in vapor pressure deficit caused by anthropogenic climate change.” However, the temperature increase implies an increase of saturate vapor pressure and evaporation. Consequently, there is an increase of evapotranspiration and you can write “and the positive trend in evapotranspiration caused….”
Line 59. Please, add a short explanation to justify the reason of this difference between Southern Sweden and Northern Sweden. Afterwards, in line 145 you say “Since Southern Sweden has a different fire climate than Northern Sweden” but for the reader that does not know Sweden, a short explanation is needed.
Line 91. Delete the second bracket in “(GISTEMP, (Hansen et al., 2010)”.
Line 119. Delete the second bracket in “(CESM1, (Kay et al., 2014)”.
Line 121. Replace RCP85 by RCP8.5
Line 132. You say: “For the W@H simulations the GMST increase between the ‘natural forcing’ simulations and the ‘actual forcing’ simulations is 0.65ºC, which is very close to the observed warming.” But the last AR5 IPCC report showed that the warning was 0.85ºC and nowadays it is near 1ºC. The best will be to clarify in this sentence the period to which you refer when you say “observed warning”.
Line 142. In this case references are written without comma “(Ho et al. 2011; Ehret et al. 2012)”, but in the major part of the paper you add a comma after the dot. Please, review all the references cited in the text in order to homogenize them and adding the comma if necessary.
Lines 272-279. Please, delete or modify completely this paragraph. The non-linear model behavior observed or modeled is consequence of the non-linearity of atmospheric process and cannot be only related to the non-linearity of radiative processes. There exists a lot of discussion about this fact related with the dimming phase, mainly if you refer to the decade of 50’s when the anthropogenic climate change effect was still minor. There are a lot of factors related with forest fires production and non-linearity because they are also related with the potential combustible fuel. Vegetation has its own growth biorhythms that can depend of precipitation or temperature in other seasons of the year, and the climate change impact can be different for the different seasons of the year. I recommend you reading the papers from Turco et al., 2014 and Turco et al., 2018. The first one provides information about the different factors that can act in the forest fire risk and burned area. The second one can help you in the discussion about future scenarios
Turco, M., M.C. Llasat, J. von Hardenberg, A. Provenzale, 2014. Climate change impacts on wildfires in a Mediterranean environment. Climatic Change 125:369–380. DOI 10.1007/s10584-014-1183-3
Turco, M., J. J.Rosa-Cánovas, J. Bedia, S. Jerez, J. P. Montávez, M. C. Llasat and A. Provenzale, 2018. Exacerbated fires in Mediterranean Europe due to anthropogenic warming projected with nonstationary climate-fire models. NATURE COMMUNICATIONS | (2018) 9:3821 | DOI: 10.1038/s41467-018-06358-z | www.nature.com/naturecommunications
You obtain strong differences using the different models. Then it would be necessary to add a comparison of the FWI outputs from the models with forest fire observed data (burned area or number of forest fires) for the longest available period. I would recommend you in order to improve the paper and having a major impact, to add a figure with this information and discuss it in the results or discussion sections.