I have revised the data publication entitled “Long-term phenological data set of multi-taxonomic groups, agrarian activities and abiotic parameters from Latvia, northern Europe” for journal Earth System Science Data.

The manuscript describes a phenological dataset from 1970 to 2018 in Latvia. I have evaluated the quality of the manuscript, the quality of the data, the quality of the presentation and the consistency of the data. I suggest accepting the manuscript.

1. About the manuscript:

The manuscript is well written. All the parts in the correct extension and organized.

Abstract is well structured, well written and all components (introduction to problem, objectives, method, results, conclusions) are clearly described. The data are properly presented.

Introduction is well written, concise, purpose of the manuscript is clear and concisely presented the data.

The methods are well described. Although the method follows a standard methodology, already described by many authors.

The data are well described in results and the limitations stated.

2. About the quality of the data:

The data presented here have extreme value. It covers 46977 observations following a standardised methodology. All of them are georeferenced and, when possible, BBCH code translated.

The quality of the database allows to find significant conclusions and to use the data in many fields of knowledge. The next figure shows the advance in flowering dates of Birch from the database, the top 1 airborne allergen in many countries:

3. About the consistency of the data:

There has been applied an appropriate QC procedure, ensuring the quality of the data.

The manuscript describes properly the data and their limitations.

4. About the presentation quality:

The presentation of the data is correct.

5. Global conclusion:

I recommend the publication of the manuscript which provides a clear and useful description of the valuable database.

Dear Authors,

I have reviewed the manuscript and data set,

The Manuscript provides access to a valuable data set, which was previous only available in analog and local format. The authors have invested in the digitization and the quality assurance of the data set. As a non native speaker I consider the manuscript well written and the description of the data is well structured. 

The manuscript includes a well described Quality Assurance procedures and includes a consideration of errors on the technical part of digitization and observation quality. Well appreciated is the approximation of shortcoming to the structure of the datasets, some of which are arising from the initial source of Citizen Science Observations and historical origin of the data. The indications that data come from a time without smart phones including a GPS positioning or even without a GPS system at all becomes important to the upcoming generations. The authors included all these considerations in their manuscript additonal with examples of different purposes the data set could be applied to.

The dataset is easy applicable and the visualization of the indivdual observations is straight forward. The timeseries of some observations clearly show the global trend of climat change by decreasing "day of year" for some of the observed phenomena.

The reference section need to be better structured, for the further processing of the manuscript. The separation of the individual references could be better formated