characteristics—errors in existing radiation corrections and how they affect the trends. Table 2.1 should include specific instruments and pixel size for satellite measurements. Humidity and wind measurements should be excluded from the table, although the authors may want to discuss how these measurements can be useful proxy diagnostics if measured carefully with climate-quality monitoring.

4. In lines 88-89, near-surface air temperatures over land are measured about 1.5-2 m above the ground level at official weather stations, rather than 1.5 m.

5. A reference is needed for this statement.

6. The caption for Figure 2.2 should state that the pressure levels at the y-axis are radiosonde “mandatory reporting levels”.

7. In lines 217-226, the reference for Global Positioning System-Radio Occultation (GPS-RO) is Kursinski et al. (1997). The comparison between GPS-RO and radiosonde data has shown that the GPS-RO soundings are of sufficiently high accuracy to differentiate performance among the various radiosonde types (Kuo et al., 2005). Also, the report should discuss the findings of Schroder et al (2003) on MSU versus GPS. In particular, Schroder et al. (2003) found that UAH T4 retrievals in the Arctic lower stratosphere in winter were biased relative to temperatures derived from GPS Radio Occultation measurements.

8. The statement “the method of calibrating a radiosonde before launch may introduce time-varying biases” in lines 543-544 needs clarification.

9. The references at the end of this review include several additional papers that should be considered for inclusion in Chapter 2 of the Temperature Trends report.