1. In lines 79-80, it is the committee’s understanding that the U.S. Climate Reference Network been shelved or at least stalled.
2. Most countries do not know about the GCOS Monitoring Principles, mentioned in lines 87-88.
3. Many of the recommendations in lines 150-160 may be difficult to achieve based on cost considerations. The GCOS aim is to get the data first, then work on metadata. Getting pictures of sites will only be useful if they are taken at regular intervals.
4. In lines 198-199, there is a GCOS working group of the Ocean Observing Panel for Climate (OOPC) and the Atmospheric Observing Panel for Climate (AOPC) looking at Sea Surface Temperature biases.
5. In line 287, locating the reference sonde stations for comparison with satellite overpasses requires observations at different times at each station. Thus, the CCSP authors may want to reconsider this recommendation.
6. Better use of statistics is needed in lines 366-369.
7. In lines 402-407, there are at least two comments on Kalnay and Cai (2003) and there should also be a reference to Simmons et al. (2004). Several criticisms of the Kalnay and Cai approach have been identified.
8. The recommendations for “tightly constraining” the dataset for reanalyses in line 425 is not possible or wise owing to continual changes in all observations, including sondes.