At Baring Head, weekly air samples are collected in 5-L evacuated glass flasks exposed in triplicate. Flasks are returned to the SIO for CO2 determinations, which are made using an Applied Physics Corporation nondispersive infrared gas analyzer. In May 1983, the CO2-in-N2 calibration gases were replaced with CO2-in-air calibration gases, which are currently used (Keeling et al. 2002). ... Data are in terms of the Scripps "03A" calibration scale.
On the basis of flask samples collected at Baring Head and analyzed by SIO, the annual average of the fitted concentrations of CO2 rose from 334.04 ppmv in 1978 to 380.43 ppmv in 2007. This represents an average annual growth rate of over 1.6 ppmv per year in the fitted values at Baring Head.
Credit: Keeling, R.F., S.C.Piper, A.F. Bollenbacher and J.S. Walker. 2008. Atmospheric CO2 records from sites in the SIO air sampling network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.