The National Oceanic and Atmospheric Administration's (NOAA) Climate Monitoring and Diagnostics Laboratory (CMDL) has measured CO₂ in flask air samples from a global network of sites since the late 1970s and from Niwot Ridge, Colorado, since the late 1960s. The size of this network has grown over time and presently consists of 38 fixed sampling sites. The measurements from these sites are complemented by shipboard measurements made in the Pacific Ocean and South China Sea (Fig. 1 and Table 1). Determinations of CO₂ mixing ratios are made by nondispersive infrared gas analysis. These measurements constitute the most geographically extensive, carefully calibrated, internally consistent atmospheric CO₂ data set available (Conway et al. 1994a).

Results from analysis of CO₂ measurements from the NOAA/CMDL cooperative flask sampling network have been presented in Komhyr et al. (1985a), Tans et al. (1989a,b; 1990), Thoning et al. (1989), and Conway et al. (1988, 1993, 1994a). Atmospheric CO₂ mixing ratios from individual flasks have been documented by the Carbon Dioxide Information Analysis Center (CDIAC) in Gammon et al. (1984) and Conway and Tans (1990). Monthly atmospheric CO₂ mixing ratios have been documented in Conway et al. (1990, 1991, 1994b). This data document provides atmospheric CO₂ mixing ratio records from individual flasks for all past and present sampling locations and monthly CO₂ mixing ratio records for all sites for which sufficient data exists to calculate representative monthly averages. The earliest NOAA/CMDL flask CO₂ measurements date back to 1967, and virtually all sites have records through the end of 1993.

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