| Summary: | The Carbon Dioxide Research Group, Scripps Institution of Oceanography, University of California, San Diego, has provided this data set, which includes long-term measurements of near-surface atmospheric CO2 concentrations at 10 locations spanning latitudes 82 degrees N to 90 degrees S. Most of the data are based on replicated (collected at the same time and place) flask samples taken at intervals of approximately one week to one month and subsequently subjected to infrared analysis. Periods of record begin in various years, ranging from 1957 (for the South Pole station) to 1985 (for Alert, Canada), and all flask data records except for Christmas Island and Baring Head, New Zealand extend through year 2001. Christmas Island data end with August, 2001 and Baring Head data end with October 2001. Weekly averages of continuous data from Mauna Loa Observatory, Hawaii, are available back to March 1958. Similar weekly averages are also available for La Jolla, California, from November 1972 to October 1975, and for the South Pole from June 1960 to October 1963. At the South Pole, however, this weekly averaged data is usually based on only one day of continuous sampling, and only about 2 averages per month are given. Flask data from all stations include replicate measurements and flagged questionable data; thus, they differ from the usual presentations of CO2 data (e.g., Keeling and Whorf, 2004) which are monthly averaged values fitted to curves as discussed by Keeling et al. (1989). Questionable data are flagged with asterisks; the user is accordingly advised to use caution in including them in analysis or in interpreting them without reference to the flag codes that provide the rationale for data rejections. The data are available in 13 ASCII files: 10 files give the flask measurements corresponding to each of the 10 locations; 2 additional files, one for La Jolla and another for the South Pole, each give about three years of averages, derived from continuous samples, to represent the corresponding weekly averages; another file gives weekly averages of the continuous record since 1958 at Mauna Loa, Hawaii. These long-term records of atmospheric CO2 concentration complement the continuous records made by SIO, and also complement the long term flask records of the Climate Monitoring and Diagnostics Laboratory of the National Oceanic and Atmospheric Administration. All these data are useful for characterizing seasonal and geographical variations in atmospheric CO2 over several years, and for assessing results of global carbon models. Flask data provide information about instantaneous departures from the hourly or multi-hourly averages derived from the continuous data, and at the same time serve as a quality check on those averages. Additionally, flask samples can be archived for future analyses as more refined measuring techniques become available. Temporal and geographical variations in the flask data are similar to those in the continuous data. Annual averages and amplitudes of the annual cycle of atmospheric CO2 concentration both decrease from high northern latitudes to high southern latitudes. Peak annual CO2 concentrations occur in spring, around May in mid latitudes of the Northern Hemisphere and September or October in mid latitudes in the Southern Hemisphere.
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