1. General comments

This well-written and informative editorial summarises the main findings from the recently published Baltic Earth Assessment Reports (BEARs) and the most important knowledge gaps identified in them. It also nicely puts the BEARs in context, explaining their position in the history of Earth system research and climate change assessments for the Baltic Sea basin, as well as their connection to the stakeholder-oriented fact sheet that the Baltic Earth Expert Network on Climate Change has recently produced.

Overall, this is work well done. I only have a few minor comments on its substance and a few more suggestions for improving the wording and presentation.  

2. Comments on substance and presentation

1. What does "today successfully completed" refer to? Do you mean that all the work of the working groups has been completed or that scenario simulations have been completed?
2. has been warming. "is warming" implicitly predicts that the observed faster warming can be extrapolated to the future, which may or may not be true.
3. L103-104. This sentence could be interpreted to mean that this is the third BEAR assessment. Suggested reformulation, beginning from L102: The two BACC books adopted a format inspired by the IPCC assessment reports. The present special issue in Earth System Dynamics is the third assessment. It takes a new format of Baltic Earth Assessment Reports (BEARs), encompassing 10 peer-reviewed scientific journal articles.
4. I only found 30 years (but not 25) from Lehmann et al. (2022).
5. L147-148. As an advance over the previous assessments?
6. would still result (doubling of pCO₂ is something that international climate policy very much strives to avoid).
7. L181-183. I think this sentence simplifies a bit too much. Even without GIA, the mean sea level rise in the Baltic Sea would differ from the global mean, due to (e.g.) the gravitational effect of the melting of Greenland ice. Furthermore, the changes in extremes might differ from those in the mean sea level, although (as noted on L185-186) there is no consensus that there would be a large difference.
8. L186, If the ensemble size (rather than model weaknesses) is indeed the limiting factor, then there is no reason to expect that statistically significant changes would occur in the real world, where only one realization of climate change will be observed. Therefore, I would replace "probably because available climate model ensembles are too small" by something like "suggesting that these changes will likely be small compared with natural variability".
9. "Antarctic" should be "Greenland". Due to the gravitational effects, melting of Greenland will increase sea level much less in the Baltic Sea than in the global mean.
10. I guess this increase mainly affects the southern parts, and less if at all the north, where the absolute sea level rise and the GIA largely compensate each other. "increase in these coastal areas" would implicitly convey this.
11. Perhaps "recent brightening"? While brightening (i.e., increased solar radiation) has been observed in the last few decades, it was preceded by a general dimming between the Second World War and the 1980s, presumably due to increased aerosols.
12. L244-245. Adding surface waves to coupled atmosphere-ocean system models?
13. has not been considered?
14. L266-269. The lack of increasing solar radiation in summer is also most likely affected by the lack of time-varying aerosols in many of the RCMs. By contrast, the projected decrease in anthropogenic aerosol emissions in the GCM simulations leads to a future increase in solar irradiation (Boé et al. 2020, Climate Dynamics, https://link.springer.com/article/10.1007/s00382-020-05153-1). If the projected decreases in aerosol emissions are realized, the GCM simulations should probably be judged more plausible regarding the changes in solar irradiation and perhaps also summer temperature.
15. cannot exhaustively take into account?

3. Technical comments

1. Delete "more than". 19 is the exact number according to Table 1.
2. biogeochemical
3. mean surface salinity?
4. Figure 2. The y axis label should be "Temperature anomaly" rather than "Temperature".
5. 2022a. Furthermore, the order of this and the previous reference (Meier et al., 2022b) should be switched.

This paper is an editorial overview of 10 papers published representing the The Baltic Earth Assessment Reports.  Consequently, its content and quality rests on those ten detailed assessments focusing on the Baltic Earth Grand Challenges and working group topics that summarize current knowledge about past, present and future climate changes of the Baltic Sea region.  This reviewer also conducted peer reviews of two of those 10 papera and found them very comprehensive and insightfully synthetic.  This editorial overview accurately and effectively summarizes the main point of each of the ten papers and presents a discussion of the key knowledge gaps that cut across them. I think it is a very effective capstone for the collection of papers.  This Baltic Earth Assessment Report builds on previous regional assessments for the Baltic Sea region in a way that fills an important gap by integrating regional knowledge and scale with the global assessments conducted by the IPCC.  In that regard it is unique among  large coastal and ocean regions, which would do well to emulate this example.  

I found only a few minor points in the text that the authors may wish to consider in finalizing the paper, indicated below by line numbers:  

32 I am surprised that Germany is not included in this list.  Although only a small part of Germany lies in the catchment, this is about the same area as Denmark and Germany is the only littoral state not included.

36 “Anthroposphere” is not a term yet in very widespread usage, but is mentioned several times in this summary.  It would helpful to provide a more expansive definition here when it is first mentioned, something like “that part of the environment that is made or modified by humans for use in human activities.”

82 “Rural” generally refers to countryside, typically including agriculture, would it be better to state this as “subarctic wilderness in the north”?

157–158 Awkwardly stated: “the increase of anoxic bottoms have still increased  . . .” Do you mean the area of anoxic bottoms?

186 It is not exactly clear what is meant by “available climate model ensembles are too small”? Too few, sparse, limited?

197–198 Should not the acceleration of sea level rise in the Baltic be somewhat more that the global mean because of its greater sensitivity to gravitational contributions from ice loss in Antarctica?

General comments:

By wrapping up and summarising a series of Baltic Earth Assessment Reports (BEARs) already published in ESD, this article definitely corresponds to the scope of journal. While the article is in a way “a review of reviews”, its novelty is mostly expressed in the Discussion part proposing and justifying further research directions to be addressed by Baltic Earth. Although the presented conclusions are fully supported by the material presented, it would be advisable to supplement the concluding part with a brief outlook on expected future continuation/update of the series. Throughout the paper authors emphasize the review character of the reports it summarises, emphasizing impressive amount of reviewed scientific literature. Content of this paper is clearly reflected in tis title. The list of references is fully adequate both in terms of number and quality.

In several occasions it is felt that there is a space for improving language (e.g. word order in sentences), therefore prior final publishing it is advisable to carry out a repeated language check.

Specific comments:

L27: consider completing the Abstract with mentioning contribution of BEARs to producing HELCOM’s CCFS – this is very important input to practice.

L31-32: consider relocating this sentence to section 1.2.

L44: consider replacing “carbon and biogeochemical cycles” by “biogeochemical cycles including carbon”. Kulinski et al. , 2022 encompasses both nutrients and carbon.

L181-183: sentence is unclear

L208-212: consider rephrasing. Listing all phenomena, human activities, pressures etc. “factors” might be seen a confusing. Note that “land cover” is mostly natural while “land use” completely human-induced.

L215-217: Clarify the sentence starting with “After climate change...”

L301-302: seem repetition of L205-219

L333-343: consider shortening. Excessive list of all new data sources draws attention away from the main point: necessity to model small scale processes

L370-371: consider clarifying the point. E.g. Development of integrated Earth system models accounting for anthropogenic changes...

L381-383: Clarify sentence

L403: competing the Concluding remarks by some future outlook on BEARs would be strongly advisable

Figure 3: Picture is difficult to comprehend. Some links seem missing. Consider revisiting.

Table 3. Categorising economic sectors into “natural”, “industrial” and “services” and attributing specific “factors” to these “sectors” (e.g. ecosystem services) seems confusing. Any chance use more traditional approach of categorising pressures?  e.g. https://www.eionet.europa.eu/etcs/etc-icm/products/etc-icm-reports/etc-icm-report-4-2019-multiple-pressures-and-their-combined-effects-in-europes-seas        

Technical corrections:

L19: end: consider replacing “between” by “among”

L43: delete “Phase II” in brackets

L59: consider placing BACC before BEARs i.e. in chronological order.

L65: consider deleting repeated “anthroposphere”

L67-69: consider reformulating this sentence to clarify that BOTH BACC books and Bears are based on scientific literature.

L71-72: consider leaving out “in their synthesis effort”

L103: replace “assessment of a new format” by “assessment in a new format”  

L117-118: consider replacing “from the Bear material” by “based on the BEAR material”

L119: move http address of CCFS to footnote

L129-130: consider improving language: ...we highlight and ... propose...

L132-133: Seems a repetition of L69-71

L147: consider relacing “In contrast” by “In supplement”

L226: consider replacing “brightening” by “reducing cloud cover”

L231: “river input of dissolved...”

L232: consider replacing “proceeds” by “succeeds” or continues

L328-329: consider modifying word order

L453: consider finding better phrase for “corresponding arguments”

L377: consider streamlining phrase “...in many cases several causes are responsible...”

L395-396: consider simplifying the last sentence of this para