Useful and important work that certainaly needs to be documented.

Development of datasets where best and most recent regional information can be used and integrated into global products is obviously needed. While initially there might be some trade offs between overall global consistency and level of detail included allowing for, for example, improved spatial features, there is a long term advantage that will lead to identifying and resolving issues or quickly improving quality for the global product. At the same time, such work can feedback to local/regional developers to address some of the issues identified so that further versions will be seamlessly integrated in global work to keep it up to date. Some of the aspects how this work can serve and stimulate the process of continues improvement of both regional and global products could be reflected in the paper and conclusions.

In general, this is a very 'dry' technical text which could benefit from some simplification to highlight key elements of work and challenges when compiling the inventory while leaving some of the detailed descriptions to SI. I have been struggling a little to find key information about the data flow or process in the main text while liked very much the very well written concise information about the inventories in the SI; probably the first time where I enjoyed reading, or going through, SI more than the main paper ;-). 

More specific comments:

Line 36-37: I am a bit confused reading the sentence starting with 'Most regional inventories...'. Not sure what are the authors saying; isn't it that typically the local/regional inventories will have more information that global products and so will improve over those? Here it reads as they are compared against the global LPS database that is a benchmark?

Line 67-74: Could authors provide a more explicit information as to what and why information may be lost due to these requirements? The following sentences  provide examples but why is it that a more detailed regional information (if available) cannot be included in globally consistent inventories? 

Table 2: In the third row thee is '-' for the column of CO2. What does it mean? i'd expect reference to ff, bf... 

Line 150: Could authors add a word of rationally why biofuels are included and agr and wildfires are not?

Table 3: Category 4C refers to 'waste incineration' and so i assume since this is under energy sector refers to incineration with energy recovery. Do you cover also emissions (and where) from open burning of municipal or industrial waste?

Table 3 on page 8: Is this really a continuation of Table 3? It seems to have a different structure.

Table 4: See question above on open waste burning, i.e, municipal or industrial waste. Is this covered or not in the 'waste incineration category'...I assume not but then do these inventories account for that?

Section 2.2.3. The Table 3/4 are not easy to plow through and while they contain some detailed information, I was wondering if there is a way to develop and overview table or a map that can show which (global or regional) inventory is used for a given region/sector indicating where gap-fills are done and with which inventory. Stay at a general level to give an overview rather than a lot of details. The detailed tables can be included in the SI and the won space could be possibly used to explain what challenges are still remaining, even after gap-filling so that the national/regional em inventory developers could potentially address them. Current text and information in the tables makes it, in my view, very difficult to get an overview.

Line 175: I realize that maybe the difference will be small but in principle, one probably can allocate the information to respective countries by splitting emissions by area within the pixel belonging to each specific country?

Table 6: Suggest reducing use of 'swd' ene, Res, tro+trn+.... can these be spelled out like in other columns? These three letter codes are also not explained anywhere in the paper; i know several can be easily guessed..but not all

Line 347: The sentence starting with 'Small differences..." Looking at the Fig 3, they seem larger than in totals?

Line 390: China is typically not classified as part of 'South East Asia' but either as part of 'East Asia' or 'North East Asia'

Lie 460 to 477: Some of these statements and discussion is referring to great details and I wonder if this can be simplified highlighting typical (occasionally occurring) features of misplaced, lost information and refer to some specific examples which can be moved to SI.

Conclusions: I am missing here clear statements why this inventory shall be used and is an advancement compared to other work. Further, bring in key identified gaps/problems and suggest either solutions or how further work could resolve them. 

This study contributes to global high-resolution CO2 emission inventories by integrating data from several regional inventories. The undertaken workload is substantial, and the resulting dataset is valuable. However, there is room for improvement in the text to clearly articulate the limitations of previous studies and the advancements introduced by CoCO2-MOSAIC. Additionally, some errors need attention, such as unifying the terms COCO2 and CoCO2.

Here are some detailed questions and suggestions:

REAS (Regional Emission Inventory in Asia): I think it includes East, Southeast, and South Asia, not exclusively Southeast Asia. Please check.

L33: "CoCO2-MOSAIC1.0 has the highest CO2ff and CO2bf emissions globally…" Would it be better to provide specific numerical values or explanations for clarity?

L36-L37: "Most regional inventories…" is confusing, as pointed out by Reviewer 1. Besides, large emitters are not limited to power plants. Could you provide more clear information about the point-source emission in each database you use?

L85: "Compared to global inventories, CoCO2-MOSAIC 1.0 includes all available regional information, without the limitation of providing spatially and methodologically consistent emissions." You may clarify further on the limitations related to "spatially and methodologically consistent emissions."

Figure 1: If “x” means "No", why GEAA-AEI is used for Gap-filling?

3.3.1: You may define "super-emitters" and explain the choice of flux > (7.9e-6 kg/m2/s) as indicated in Table 9.

L470: Despite the explanation of REAS 3.2.1's coarse resolution, the missing of three big power plants in China (Figure 6) is noteworthy. I see that your focus on power plants in another submission (Guevara, 2023), do you have an explanation for this discrepancy?

L555: As the regional inventories are available only for 2015, I worry about the continuity of emissions from 2015 to 2018. Have you conducted any analyses addressing this potential discontinuity?