Review of egusphere-2022-954 ‘The 2018 west-central European drought projected in a warmer climate: how much drier can it get?’ by Aalbers et al.

General comments:

In their paper `The 2018 west-central European drought projected in a warmer climate: how much drier can it get?´, the authors investigate the impact of global warming on soil moisture drought severity for the year 2018 in west-central Europe. With this aim, pseudo-global warming (PGW) experiments with a regional model were performed, forced by three GCMs for three different global warming levels (+1.5K, +2K, +3K).  Their results show, that under global warming the 2018 drought episode experiences strongly enhanced summer temperatures, but a fairly modest soil moisture drying response compared to the change in climatology as evaporation is already strongly moisture-constrained during present-day condition. In more general, the authors show that the drought risk in west-central Europe is strongly enhanced under global warming.   

This work provides is a valuable contribution to our understanding of the consequences of global warming on extreme events (here drought) observed so far. The methods, techniques and the experimental setup applied in this study are sound and state of the art; the use of different GCMs (considering an ensemble mean for each GCM) to create the perturbations under global warming provides robust estimates of how global warming might modify the 2018 drought event. Beside some minor comments, this study is a very valuable contribution to NHESS.    

Minor Comments

L62: What does the abbreviation SPEI stand for?

L135ff: Usually, global warming levels (GWL) are defined based on the pre-Industrial reference period (1850-1900). In the IPCC AR6 report, the global warming between 1850-1900 and 2011-2020 is estimate with 1.09K, thus meaning roughly GWL1. Based on the Paris agreement, the long-term temperature goal is to keep the rise in mean global temperature to well below 2K (GWL2) above pre-industrial levels, and preferably limit the increase to 1.5K (GWL1.5). To avoid any confusion, between the IPCC based and your GWLs (based on the 1991-2020 period), a short note might be helpful.

L144ff: Can you comment briefly about the model quality of the 3 GCMs in comparison with observation? Is for example the temperature bias of the reference period you use (1991-2020) the same for all models? Or are the GCMs that already show enhanced global warming for this period in comparison with the observational record?

L258: Should read ‘over the British Isles’

L393: The 2011 spring drought is not indicated in Figure 6b. Could you add this year to the graphs?  

Figure1: E_p is missing in the list of variables in (a); the orange lines for the observations (obs) for 2018-2019 are hard to see; consider to use a more striking color.

Figure2: Consider moving the column with JFM as the first column; would better reflect the course of the year.

General Overview:

The authors investigate the impact of global warming on soil moisture drought severity in west-central Europe by employing pseudoglobal warming (PGW) experiments.

The manuscript is well written and the methodology is sound and the results are novel.  In my opinion, the manuscript can be accepted after minor revision mentioned below.

• The authors mention “future weather analogues” in the manuscript but actuallaly no analogue metdology is applied (e.g. Sánchez-Benítez et al., https://doi.org/10.1016/j.wace.2019.100238 ). I would suggest the authors to change the wording on “weather analogues” throughout the manuscript.
• Despite the methodology is sound, I had difficulty to follow section 2.2. Can the authors re-write section 2.2.
• Why the authors exclude 2018-2020 from the climatology?