the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Mar 2026
ESD Ideas: Quantifying global and regional contributions to climate change projection uncertainty
Abstract. Hawkins and Sutton (2009) developed a framework to partition total uncertainty in future climate projections into three components: internal variability, model uncertainty and scenario uncertainty. Here, we propose an extension of this framework that separates the contributions of global and regional processes. This enables a more physically based interpretation and improved understanding of the origins of projection uncertainty.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Earth System Dynamics.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-517', Anonymous Referee #1, 04 May 2026
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RC2: 'Comment on egusphere-2026-517', Anonymous Referee #2, 08 Jun 2026
This study extends the work of Hawkins and Sutton (2009) by partitioning the model and scenario uncertainty into regional and global components. This is useful and interesting research which is worth publishing. Overall, the text, analysis, and presentation is of high quality.
The only major comment I have on this work is that more discussion/ analysis of the MGW method is needed here to understand the uncertainty in this/ potential issues. Ideally, the authors could explore/ discuss alternative methods to understand the differences in global projections. However, this would be a significant additional demand and delay publication, so if this is not possible the authors should certainly discuss the limitations of the MGW method. In particular, if different models reach a given temperature level at different times, we would expect different regional patterns due to the differing inertia of the atmosphere, oceans, etc. Therefore a good chunk of the “regional uncertainty” could be due to this inertia effect rather than true differences in regional uncertainty between the models. This should be discussed and ideally the fraction of explained uncertainty in the analysis due to this should be analysed.
In Figure 1, panel f, the split between scenario and model and regional and global is somewhat unclear due to the overlap of the hatching, perhaps the scenario hatching could be changed to a different colour or design to make the transition clearer.
The paper mentions the different contributions to uncertain with different variables and regions, it would be really interesting to see this, perhaps as an additional panel in Figure 1 or in supplementary material which could be references.
Citation: https://doi.org/10.5194/egusphere-2026-517-RC2
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Review of Bintanja et al.
This ideas paper extends the Hawkins & Sutton (2009) uncertainty framework to separate the model response and scenario components into regional and global parts, using a specific case study example of Northern Europe. The analysis is interesting and should be published. Hopefully the authors are considering a more detailed paper highlighting different regions where the separations may behave very differently, and for other variables such as precipitation?
I have some comments which the authors may like to consider:
1) Methodological description - personally I found the description of the methodology slightly confusing and disjointed. In particular lines 38-45 could perhaps be moved later in the discussion rather than breaking the description of what is calculated and shown? Lines 33-37 could be expanded with the further details from later paragraphs about how the uncertainty separation is actually done?
2) Figure 1: (a) The region name could be given in the figure somewhere; (b) Is 'reduced regional projections' the best term for the MGW projections?; (c) Could the authors include the total variance for global processes? I think this would help with the explanation of the new separation; (d) Should the black hatched area be broken into blue and green hatching instead to indicate global model and global scenario components?; (e) Could the regional labels in the final panel say 'regional model' and 'regional scenario' for clarity?
3) line 60 - the authors say 'This global model uncertainty exceeds its regional counterpart at all timescales'. However, looking at the Figure this seems to be true only after ~2035ish and not before?