The National Oceanic and Atmospheric Administration's Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) has measured CO2 in air samples collected weekly from a global network of sites since the late 1970s and from two stations since the late 1960s. Determinations of atmospheric CO2 mixing ratios in the air samples collected in glass flasks are accomplished by nondispersive infrared gas analysis. All CMDL flask samples are measured relative to standards traceable to the World Meteorological Organization Central CO2 Laboratory operated by C. D. Keeling at the Scripps Institution of Oceanography. These measurements constitute the most geographically extensive, carefully calibrated, internally consistent atmospheric CO2 data set available and are essential for studies aimed at better understanding the global carbon cycle budget.
This data report documents monthly atmospheric CO2 mixing ratios and CO2 measurements obtained by analyzing individual flask air samples from the NOAA/CMDL global cooperative flask sampling network. Records of measurements at 40 land-based sites and of shipboard measurements covering 14 latitude bands in the Pacific Ocean and South China Sea are provided. These include the earliest NOAA/CMDL flask CO2 records, which date back to 1967, and records for all operating sites through 1993. Approximately 60,000 individual flask CO2 measurements are provided, including those not considered indicative of regional background tropospheric conditions. Each measurement is flagged according to the degree the CO2 determination satisfies the NOAA/CMDL data selection criteria.
Analysis of the NOAA/CMDL flask CO2 database shows a long-term increase in atmospheric CO2 mixing ratios since the late 1960s. Growth rates for individual sites and the global growth rate vary over time. The database shows a hemispheric gradient that varies over time from 2-5 parts per million (ppm). Detailed analyses have been published by the authors and these reprints are provided as an appendix of this data report.
This report and all the data it describes are available from the Carbon Dioxide Information Analysis Center (CDIAC) without charge. The NOAA/CMDL flask CO2 database comprises 163 data files totaling 8.5 megabytes in size. The data are provided on a variety of media, including 9-track magnetic tape, IBM- or Macintosh-formatted floppy diskettes, 8-mm tape, and 0.25-inch tape cartridges. This database may also be obtained by accessing CDIAC's anonymous file transfer protocol (FTP) area or the NOAA/CMDL anonymous FTP area on the Internet. This database may be subsetted or reformatted for users upon request. This report describes how the samples are collected and analyzed and how the data are processed, defines limitations and restrictions of the data, describes the contents and format of the data files, provides tabular listings of the monthly CO2 records, and contains two reprints that offer greater detail on methodologies and analysis results.
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