NHESS Paper by Patrick Oschweski et al.

The paper by Olschewski et al. investigates the temporal changes of two types of compound effects (false spring events and heat-drought concurrence during summer) for the Mediterranean region comparing occurrences of the recent past (1970-1999) with a high-impact climate scenario for a time period hundred years later.  Their study adds to the current knowledge of compound effects - which has previously done mostly done for past and current climatic setting – the changes of behaviour of a potentially extreme future. The study concludes with an important point which is often overlooked in climate adaption approaches: that locally refined investigations and adaptation strategies are required, as it is not correct to aggregate ‘typical’ climate patterns across larger parts of countries, as often the variations, in this case the intenseness of compound events, can be spatially very heterogeneous.

In their study, they use data set from the EUR-CORDEX database and applied a multivariate bias correction method to improve spatial representation of future extremes. The analysis is very detailed regarding the definitions and thresholds being used for the two compound sets and spatially highly precise by presenting very detailed compound information on historical and projected changes.

The borders of the Greater Mediterranean Region are not clear. Does it depend on some climatic definition or simply latitude sub-sections? Northern France and Southern Germany would normally not be considered as part of the Mediterranean Region. I would also like to ask the authors to discuss in more details the applicability of the HDCE definition: the results in Figure 9b for the future frequency of HCDE appear extremely large, however, it is after all mostly influenced by prolonged durations of future heatwaves under drought conditions. You may want to discuss your results in the light of other HDCE definitions.

Overall, the paper is very well presented, both in terms of visual information, language and consistency of arguments. I recommend minor revision to include several smaller points listed below and summarised above.

Minor comments

• Second sentence in abstract: “it is highly dependent on the impact” seems to be semantically wrong, as the Medierraenan Basin cannot depend on impact. Please correct phrasing
• Line 116 to 122 appears very detailed, the last sentence of this paragraph appears out of place – I suggest to link the description of climate zone to an updated definition, what the GMR actually is (see comment above)
• Line 124: not clear, what three types of cliamte data are meant: climate model output data, ERA5 data and ?
• If ERA5 data are used to validate current runs of climate models, the weaknesses of ERA5 data (certain over- and underpredictions) should already be mentioned here, and not only in the discussion.
• 1 Data: you might want to mention that for your climate forcing analysis you actually need information from the ocean – it was first not clear why you cannnot use ERA5-Land data for evaluating agricultural developments.
• Line 146: this is an abrupt introduction of the 13 model runs – I would suggest to heavly shorten the section 124-136 and put all information on data in the 3.1 data section.
• The same with Section 3.2: does this section need such a long, but inprecise introduction, and then additional sub-sections for compound event definitions. I would suggest to heavly shorten Lines 167-177)
• Section 3.2.2: how do you define an end of a drought? In McKees work, a drought ends, once the SPI value becomes from below -1 values again positive, i.e. includes values in the range of -1 to 0 if SPI had previously be below -1. This information is missed out in many papers – if you adopt another definition, you might want to state it more clearly.
• Line 272: you might want to add here that there are my different definitions for heatwave events, and no clear definition available for heat compound events.
• Lines 500 and 502: it is not the correct place in the article to discuss what is and what is not the aim of the study; you may want to consider to reword the two sentences.
• You have chosen the most extreme climate projections – do you have any indications what the medium projections would say regarding the two compound events?
• Could you derive some hypthesis, what the combined effects of the increases of both compounds would have on agriculture or vegetation dynamics?

This study applied a MBCn to improve the model result by reducing the bias compared to Univariate. The results showed how the FSE and HDCEs trend changed under the high impact scenario. Overall, the paper is clear and well presented. However, there is still some minor issues need to be addressed.

1. Line 270, I recommend heatwave events abbreviation could be used as HWE or HE, not HW.
2. Since the manuscript has so many abbreviations, it is better to create table or separate page as appendix to list them together to be easier to follow. Also, please define each acronym at the very beginning.
3. The MBCn method section needs more details, since it is important for readers to understand how method is applied.