Mapping Projected Variations of Temperature and Precipitation Due to Climate Change in Venezuela
, Pedro GarcÃa 3, Franklin Paredes-Trejo 4 and AnÃbal Rosales 1Round 1
Reviewer 1 Report
The manuscript entitled “Mapping projected variations of temperature and precipitation due to climate change in Venezuela” focused on exploring the spatial patterns of changes in climate variables among different regions from1980s to mid-21st century in Venezuela. The topic of study is important for us to understand the specific spatial changes of precipitation and temperature in Venezuela under global warming in the future, as well as provides some references for the formulation of land use and agricultural adaptation measures in different regions in a warming future to some extent.
The overall structure of the study is relatively complete. However, there are two main concerns after I reviewed this manuscript.
First, the authors select two sets of data (1970-2000;2041-2060) comes from WorldClim 2.1 to compare the changes of climate variables. However, historical data comes from meteorological station interpolation, while future data comes from MPI-ESM1.2-LR model prediction. It should be pointed out in the paper whether these two parts of data have been verified in the original data set before use. If not, I think verification should be carried out before comparison to ensure the comparability of the two sets of data.
Second, it seems to be only a phenomenon description of the study. On the basis of exploring the change of climate variables, more specific agricultural adaptation measures and land use policy suggestions for different regions should be propound. It would make the whole study more meaningful. In view of the extensive influence of the Hydrology journal, I would not recommend that the manuscript be accepted before the authors deal with these issues I mentioned.
Abstract: This part of writing is concise, but maybe the sentence “However, these changes… regions” could be deleted. The fact that any natural environment attribute variables is spatially continuous is not the main conclusion of this study.
Introduction: This part is generally fine, but the brief description of the research method requires more precise expression. Furthermore, the study significance, logic, and readability can be further improved.
Specifically:
Line84-86: The main research methods should be briefly described here, rather than the geospatial representation approaches mentioned in the paper.
Materials and Methods: The description is also clear, but I would suggest that human activities such as agricultural production should be included in the description of the area. In addition, the abbreviation of the Coupled Model Intercomparison Project Phase 6 is CMIP6. (The same in many parts on the paper)
Results and Discussion: Two things should be noted. First, there are some overdiscussion.
For example:
Line360-362: “Our results …droughts” The results show only change in temperature and weak change in precipitation, but don’t directly show changes in the hydrological cycle. Drought includes meteorological drought, hydrological drought, agricultural drought, etc. The evaluation of meteorological drought also needs to consider the change of evapotranspiration. In addition, the combined effect on crops and vegetation is uncertain because of the weak changes in rainfall in the region and the significant increase in atmospheric carbon dioxide concentrations expected in future warming. So this conclusion should be drawn with caution.
Second, a specific development proposal should be propounded according to the background conditions of different regions and climate changes.
Figure and table: Data presentation needs to be further improved.
Specifically:
Figure 3-6: Only need to plot the data within the study area. In other words, the data part of the image needs to be clipped.
Figure 3,4,6: Perhaps the rate of change is a better indicator of the relative degree of change than the absolute amount of change.
Figure 4: The four graphs may be displayed using the same standard hierarchical legend.
Figure 5: The title of the figure should be modification. The figure is a direct presentation of data, not a data overlay.
Figure 5,6: These two images can be combined into one diagram, or just Figure 6 can be shown.
Table 1: As the author mentions in line 173 of the paper, I think the standard deviation should be added when showing the average temperature of the two periods. (The same in table 3)
Table 4: Please check this table for accuracy. Maybe the shaded area should be symmetrical from top left to bottom right of the chart.
Overall, this study is meaningful. However, considering that this study is just a description of some phenomena (at least in my current opinion), I might suggest that the authors overhaul the manuscript before can be accepted by Hydrology, due to the significant influence and wide readership of this journal.
Author Response
REVIEWER 1
Main concerns:
Reviewer: First, “…it should be pointed out in the paper whether these two parts of data have been verified in the original data set before use. If not, I think verification should be carried out before comparison to ensure the comparability of the two sets of data.”
Response: WorldClim 2.1 provides these data in spatially compatible GeoTiff files. We were concerned on the validity of these data to represent Venezuelan climatic conditions. Hence, we based our selection on prior validations of such data (lines 112-118 and 134-139 of the document). In addition to this
Reviewer: Second, “…On the basis of exploring the change of climate variables, more specific agricultural adaptation measures and land use policy suggestions for different regions should be propound.“
Response: In response to this suggestion, we include some brief considerations in lines 312-317 and 325-327 of the new version of the document. We are currently working on a research project to propose adaptation measures and land use policies for some agricultural regions of Venezuela. However, we do not have substantial results yet.
Reviewer: Abstract: This part of writing is concise, but maybe the sentence “However, these changes… regions” could be deleted. The fact that any natural environment attribute variables is spatially continuous is not the main conclusion of this study.
Response: We agree with this observation. The following sentence has been deleted: “However, these changes are continuous and gradual throughout the territory and do not conform to clear boundaries between physiographic regions”
Reviewer: Introduction: This part is generally fine, but the brief description of the research method requires more precise expression. Furthermore, the study significance, logic, and readability can be further improved.
Specifically:
Line84-86: The main research methods should be briefly described here, rather than the geospatial representation approaches mentioned in the paper.
Response: we acknowledge this fault in the first version of the paper and, consequently, rewrote the Introduction. In the new version, lines 67-74 briefly describe the methods applied.
Reviewer: Materials and Methods: The description is also clear, but I would suggest that human activities such as agricultural production should be included in the description of the area.
Response: Lines 78-83 have been added to the description of the area to include this kind of information.
Reviewer: In addition, the abbreviation of the Coupled Model Intercomparison Project Phase 6 is CMIP6. (The same in many parts on the paper).
Response: the abbreviation of the Coupled Model Intercomparison Project Phase 6 was changed to CMIP6 each time it appears in the document.
Reviewer: Results and Discussion: Two things should be noted. First, there are some overdiscussion.
For example:
Line360-362: “Our results …droughts” The results show only change in temperature and weak change in precipitation, but don’t directly show changes in the hydrological cycle. Drought includes meteorological drought, hydrological drought, agricultural drought, etc. The evaluation of meteorological drought also needs to consider the change of evapotranspiration. In addition, the combined effect on crops and vegetation is uncertain because of the weak changes in rainfall in the region and the significant increase in atmospheric carbon dioxide concentrations expected in future warming. So this conclusion should be drawn with caution.
Response: We removed this inference from the document.
Reviewer: Second, a specific development proposal should be propounded according to the background conditions of different regions and climate changes.
Response: Please see lines 312-317 and 325-327 of the new version of the document.
Reviewer: Figure and table: Data presentation needs to be further improved.
Specifically:
Figure 3-6: Only need to plot the data within the study area. In other words, the data part of the image needs to be clipped.
Figure 3,4,6: Perhaps the rate of change is a better indicator of the relative degree of change than the absolute amount of change.
Figure 4: The four graphs may be displayed using the same standard hierarchical legend.
Figure 5: The title of the figure should be modification. The figure is a direct presentation of data, not a data overlay.
Figure 5,6: These two images can be combined into one diagram, or just Figure 6 can be shown.
Table 1: As the author mentions in line 173 of the paper, I think the standard deviation should be added when showing the average temperature of the two periods. (The same in table 3)
Table 4: Please check this table for accuracy. Maybe the shaded area should be symmetrical from top left to bottom right of the chart.
Response: All tables and figures were changed according to these observations.
Reviewer 2 Report
Please see the attach file
Comments for author File: 
Comments.pdf
Author Response
Reviewer 2
Reviewer: 2.2 Climatic data: This part should be rewritten with more detailed methodology description
Response: As requested, we rewrote this part with a more detailed description of the climate data we used as input (lines 106-149 in the new version of the document). We use historical climate data from 1970-2000 because that is the available dataset in WorldClim 2. In addition, most of the work previously done on this subject in Venezuela has compared the years 2000 and 2050. On the other hand, we selected the period 2040-2060 for the future climate because our work attempts to draw attention to the need to implement geographically specific adaptation measures to climate change in a short time.
Reviewer: 2.3. Regionalization
A regionalization of the country made by another author is used here, and it is not planned to make a new one based on the results obtained from the expected changes in temperature and precipitation. This negates the place of this part in a separate point. Its location is in 2.1 Study area.
Response: We decided to keep this section changing its redaction to the form it is presented in lines 151-156 in the document.
2.4. Data analysis
Reviewer: Rows 154-156 : “A random sample of 2100 pixels (150 per region) was drawn for statistical comparison of projected variations in temperature and precipitation between physiographic regions, with 95% probability.” –
Was only one sample assessed or was the assessment repeated at least several times for each area? There is no way that the result will be the same for every sample, especially considering the varied orography and the large variation of rainfall in individual sub-regions.
Response: based on this observation, we decided to apply a technique called zonal statistics that allowed us to calculate statistics of the data using all the pixels in every physiographic unit. However, we still used a single random sample of 150 pixels per region to determine whether differences between physiographic units were statistically significant at 95% probability. If the statistical test indicates that there are significant differences between two physiographic regions with this probability level, it implies that, if we repeat the sampling process 100 times, 95 of the times we will find that the result will be different between those regions.
Reviewer: Rows 161-165: Why is the principal component analysis was applied to random samples of 50 pixels per region and not as above to samples of 150 pixels per regions?
It is not clear why it was chosen to analyze 5 parameters for temperature (mean annual; daily minimum and maximum; annual minimum and maximum temperatures) and only one for precipitation (annual precipitation sums).
Response: we excluded the section on principal component analysis because of its limited contribution to the paper.
- Results
Reviewer: 3.1. Temperature
Row 168 – From where it follows that the average temperature in Venezuela will increase by 1°C?
Rows 172-174 (Table1) – the standard deviation of mean annual temperature for 2 periods is not presented in Table 1. In the last column, only the difference of the two values is presented. How the values for each of the periods were obtained?
Response: Table 1 includes now the average of all the physiographic regions and the standard deviation in °C. By repeating the calculations, it was verified that the model projects an average increase of 1.8 °C for the entire country instead of 1°C.
Reviewer: In Table 1, the change in average annual temperature by region ranges from 0.1 to 2.4 °C, while Figure 3 presents changes from -0.99 to 3.93 °C, i.e. there is a possible decrease in temperatures for some areas, which is not described at all.
Response: The legend in Figure 3 was modified to eliminate the value -99 °C. That value appeared in the legend but did not appear on the map.
Reviewer: The legend of all Figures (3-6) should change on a continuous scale. It is not a good idea to use the same palette for both period magnitude distribution and anomaly mapping. They have to be different because that's how they confuse readers. On Figures 3-4 only the temperatures differences between two periods were presented so it’s possible to use the same color scale for this. But for precipitation a different color scheme would be more appropriate.
With the wide range of variation in the annual amount of precipitation in Venezuela - from 300 to 4000 mm - it is not applicable to draw conclusions based on absolute differences from current and future values. That being said, all regions are approximately in the area of a decrease in precipitation of about 10-15%, which does not support the thesis of a clear indication of drought due to climate change. Differences between 2 periods for precipitation must be presented in %, otherwise they are not comparable. Only then can conclusions be drawn about expected climate changes and their impact on different physiographic regions in Venezuela.
Figure 6 - To represent precipitation anomalies, the color scheme must necessarily be different from the those for the two periods.
Response: We modify every figure and table in the Results considering the reviewer's observations. In addition, we removed the inference on droughts from the result discussion.
Reviewer 3 Report
- Failure to explain accuracy and validation indicators regarding the use of research methods based on models and data.
- Lack of accurate data comparison based on climate change prediction models.
- Failure to accurately explain the accuracy and validation of the application of statistical tests based on the nature of the data and the research model
- Showing and explaining in detail the cartographic features of some Figs.
Author Response
Failure to explain accuracy and validation indicators regarding the use of research methods based on models and data.
Lack of accurate data comparison based on climate change prediction models.
Failure to accurately explain the accuracy and validation of the application of statistical tests based on the nature of the data and the research model
Showing and explaining in detail the cartographic features of some Figs.
Response: The new version of the document responds each of these observations.
Round 2
Reviewer 2 Report
The topic of climate change and adaptation to it is extremely important for all countries of the world. Therefore, it is extremely important that the assessments for future changes are very carefully made and the conclusions well reasoned.
Comments for author File: 
Comments.docx
Author Response
Mapping projected variations of temperature and precipitation due to climate change in Venezuela
Jesús A. Viloria, Barlin O. Olivare, Pedro García, Franklin Paredes-Trejo and Aníbal Rosales
Second review:
Reviewer 2
Reviewer: “…there is no significant improvement in the description of the research method and the method of calculation.”
Response: We replaced systematically “beginning of the 21st century” for “1970-2000” and “middle of the 21st century” for “2041-2060” throughout the text.
Reviewer: “…everywhere it is claimed that the comparison is between the climate at the beginning of the 21st century and that in the middle… These statements should be corrected throughout the text.”
Response: We replaced systematically “beginning of the 21st century” for “1970-2000” and “middle of the 21st century” for “2041-2060” throughout the text.
Reviewer: “There is a huge difference in the estimated average temperatures in the two versions of the article, while the precipitation values are the same. How were these significantly higher temperatures obtained? …”
Response: You are right, difference in the estimated average temperatures between the two versions of the article is huge. We were also concerned by this difference and carefully reviewed all our analyses since such a bias was too large to result from poor sampling. Besides, for the second version of the article, we used all the data instead of a sample. Finally, we discovered that we used an erroneous data set to compute the data on temperature change for the second version.
We repeated the analysis using the appropriate data set and corrected the results of Table 1. These results are similar to those of the first version of the article. It is opportune to draw your attention to the column "Number of pixels" in Table 1. The number of values corresponding to each physiographic region indicates that by applying zonal statistics, we use the entire data population instead of a sample for this calculation (see Materials and Methods, lines 213 to 216).
Reviewer: “… if new calculations were made for temperature, why was this not also done for precipitation?...
Response: Table 3 presents the new calculations performed for precipitation. Again, the values in the "Number of pixels" column reveal that our calculations were based on the entire population of data rather than a sample.
Reviewer: “… it is precisely in the conclusions that there are the fewest corrections compared to the previous version.”
Response: The conclusions of the article remained unchanged due to a lack of time. In addition, none of the reviewers made specific comments on this section. In this new version (the third) of the article, we have introduced changes in the conclusions.
Reviewer: “In new version again there is no significant improvement in the description of the research method and the method of calculation.”
Response: We introduced new changes in the Materials an Methods section.
Reviewer 3 Report
· It seems necessary to control the writing of the text.
· It is necessary to edit some figures based on cartographic features.
· A detailed explanation should be provided for the use of the Nemenyi test in the article, although this test shows the basis for comparing groups, and the nature of its use in the article is necessary.
· The lack of a proper explanation of the spatial variability of variables is one of the points that should be expressed more precisely.
· In drawing spatial variability, different spatial models should be explained more precisely in expressing the results.
Author Response
Reviewer 3
Reviewer: “It is necessary to edit some figures based on cartographic features”
Response: We replaced the geographic grid with a scale bar and a north arrow in figures 2, 3, 4, 5, and 6. We also divided the former figures 5a and 5b into figures 5 and 6 to increase legibility.
Reviewer: “A detailed explanation should be provided for the use of the Nemenyi test in the article, although this test shows the basis for comparing groups … the nature of its use in the article is necessary.”
Response: We have added the text between lines 224-235 to briefly explain the Nemenyi test.
Reviewer: “The lack of a proper explanation of the spatial variability of variables is one of the points that should be expressed more precisely…”
Response: We included text lines 482-498 in the new version of the article to describe the spatial variability of the projected changes in annual temperature and precipitation. However, we did not attempt to explain this variability because of the uncertainty of the input data.
Round 3
Reviewer 2 Report
In this form, the article can now be published.
However, I think that with such small differences in the change in average temperatures (up to 9%) and precipitation (0-12%), the discussions and conclusions made about the impact of climate change are a bit exaggerated and more suitable for a journalistic publication, and not for a reasoned scientific publication. More in-depth regional studies are needed to see if it is climate change at all or something else.
Author Response
The authors are grateful for the reviewer's comments and observations. In this regard, a paragraph was added in the conclusion about the need to carry out more in-depth regional scientific studies to determine if it is climate change or something else:
Line 1223:
Overall, Venezuela is particularly vulnerable to changes in temperature and precipitation patterns associated with climate change. However, it is essential to ensure that the factors responsible for environmental changes in different regions are accurately identified to implement the appropriate interventions. Therefore, it is crucial to conduct more in-depth regional scientific studies to determine whether climate change is the sole cause of environmental changes or if other factors are contributing. Conducting detailed studies can provide valuable insights into the specific causes of environmental changes, enabling policymakers and stakeholders to implement targeted interventions that address the root causes of the problem. Ultimately, regional scientific studies are essential for developing comprehensive strategies to combat climate change and ensure the sustainable use of natural resources.
