Atmospheric CO{sub 2} concentrations -- Mauna Loa Observatory, Hawaii 1958--1986

Since 1958, CO{sub 2} concentrations at Mauna Loa Observatory have been obtained using a nondispersive, dual detector, infrared gas analyzer. Air samples are obtained from air intakes at the top of four 7m towers and one 27m tower. Those involved in the monitoring project have attempted to improving sampling techniques, reduce possible contamination sources, and adjust data to represent uncontaminated, true conditions throughout the twenty-eight year sampling period. The gas analyzer is calibrated by standardized CO{sub 2}-in-nitrogen reference gases twice daily. Flask samples are taken twice a month for comparison to the data recorded using the infrared gas analyzer. Data are scrutinized daily for possible contamination and archived on magnetic tape for further scrutiny and adjustment. Daily, monthly, and annual averages are computed for the Mauna Loa data after deletion of contaminated samples and readjustment of the data. These averages have shown a steady rise in annual average concentration from 316 parts per million by volume (ppmv) in 1959 to 346 ppmv in 1986