This dataset contains high-precision long-term atmospheric measurements of greenhouse gases (CO, CO2, N2O and CH4 ) using Off-Axis Integrated-Cavity Output Spectroscopy (OA-ICOS). The measurements were taken at Kjølnes Atmospheric Observatory (KJN).

The Kjølnes Atmospheric Observatory (70°51'07.9\"N 29°13'56.3\"E) has been operational since August 2013. Two OA-ICOS devices, connected in series and sharing a suite of calibration and reference gases, have been employed to make continuous measurements of atmospheric CO2, CH4, N2O and CO concentrations. The data are calibrated by performing a linear regression upon the weekly measurements of three calibration (tied to the latest NOAA calibration scales) cylinders. The quality control procedure incorporates regular measurements of a dedicated reference cylinder (Target Tank), carefully calibrated at Max-Planck Institute for Biogeochemistry (Germany).