the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The effect of forest cover changes on the regional climate conditions in Europe during the period 1986–2015
Marcus Breil
Vanessa Schneider
Joaquim Pinto
Abstract. Afforestation affects the earth’s climate system by changing the biogeochemical and biogeophysical characteristics of the land surface. While the regional effects of afforestation are well understood in the tropics and the high-latitudes, its climate impact on the mid-latitudes is still subject of scientific discussions. The general impact of afforestation on the regional climate conditions in Europe during the last decades is investigated in this study. For this purpose, regional climate simulations are performed with different forest cover fractions over Europe. In a first simulation, afforestation in Europe is considered, while this is not the case for a second simulation. We focus on the years 1986–2015, a period in which the forest cover in Europe increased comparatively strong, accompanied by a strong general warming over the continent.
Results show that afforestation has both local and non-local effects on the regional climate system in Europe. Due to an increased transport of turbulent heat (latent + sensible) into the atmosphere, afforestation leads to a significant reduction of the mean local surface temperatures in summer. In northern Europe, mean local surface temperatures were reduced about -0.3 K with afforestation, in central Europe about -0.5 K and in southern Europe about -0.8 K. During heat periods, this local cooling effect can reach to -1.9 K. In winter, afforestation results in a slight local warming both in northern and southern Europe, because of the albedo effect of forests. However, this effect is rather small and the mean temperature changes are not significant. In downwind direction, locally increased evapotranspiration rates with afforestation increase the general cloud cover, which results in a slight non-local warming in winter in several regions of Europe, particularly during cold spells. Thus, afforestation had a discernible impact on the climate change signal in Europe during the period 1986–2015, which may have mitigated the general warming trend in Europe, especially on the local scale in summer.
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Marcus Breil et al.
Status: final response (author comments only)
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RC1: 'Comment on bg-2023-94', Anonymous Referee #1, 05 Jul 2023
The paper uses CCLM in order to investigate what effects afforestation in the year 1986 to 2015 had on the climate in Europe. I think the paper has a clear idea and research agenda and properly executes on it. From my point of view an improvement is needed in the validation. The paper discusses effects on temperature and precipitation but only looks at the model performance with respect to temperature. I think a discussion similar to temperature but looking at precipitation is needed.
Even though the authors look at averages and extremes of the two variables, the validation only looks at averages. I think one can live with that but, again, a look at precipitation (averages) is needed.
Could you indicate or mention in Figures 3 and 4 which values were significant?
Maybe 2 stylistic notes:
The authors repeat the mechanisms that lead to the efects very often. I think it is good to repeat things but maybe not so often.
[Disclaimer: not a native speaker] The English word "whereby" means "by, through", it doesn't match the German "wobei".
Other minor notes on English: 294 "visible" -> "can be seen" / 320 "stronger pronounced" -> "pronounced more strongly" (occurs several times) / 414 is "buoyancy" the correct word here (not saying it's wrong and not entirely sure what you wanna say, but I only know it from liquids, do you mean something like convection?) / 474 "certain" -> "some" / 474 "reached as high" -> "reached values up to"
Citation: https://doi.org/10.5194/bg-2023-94-RC1 -
RC2: 'Comment on bg-2023-94', Anonymous Referee #2, 13 Sep 2023
Breil et al present a quantification study of afforestation impacts on regional climate in Europe in the late 20th and early 21st century. This topic is of interest due to afforestation effects masking increasing temperatures from climate change during this period. The novelty of the work lies in explicitly quantifying this impact.
While the core concept and method of the manuscript are sound, the current presentation reads more like a textbook chapter on climate than a current research article. This is due to a high level of repetitiveness throughout the text as well as weakly developed greater context, mostly in the discussion and conclusion sections. The authors also present results from Wilcoxon Rank Sum Testing without including this technique or research goal in their methods.
Possible additional context:
There are a variety of topics that come to mind to give the paper greater context and interest.
Given the results, what might the impact of additional afforestation in Europe be? In other regions? How might the results be different if different vegetation types were modelled (ie., evergreen broadleaved trees)? How did the strength of temperature effects vary with size of afforested region?
Introduction
L42, Replace biogeophysical with physical, as that is what is meant
L42-45 are nearly identical with L73-75.
Methods
Local vs Non-local, defining all non-afforesting grid cells as non-local seems like a generous definition for the regions (as opposed to say, just the surrounding grid cells within a particular afforesting patch). Please justify this choice.
Results
L363-375, The text here can be reduced and figures moved to supplementary materials.
Discussion
L400 – 411, Be more specific about the effect seen in other studies (ie., list their values in a comparable way to your work). How did these other studies deal with local vs non-local effects?
Conclusion
The climate masking point should be expanded and moved into the main body of the discussion. Conclusion should be saved for reiterating your main messages from the discussion, not introducing new synthesis of the results.
Citation: https://doi.org/10.5194/bg-2023-94-RC2
Marcus Breil et al.
Marcus Breil et al.
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