English: "Surface average atmospheric CO2 concentration (ppm). Since 1980, monthly data are from NOAA/ESRL (Dlugokencky and Tans, 2022) and are based on an average of direct atmospheric CO2 measurements from multiple stations in the marine boundary layer (Masarie and Tans, 1995). The 1958–1979 monthly data are from the Scripps Institution of Oceanography, based on an average of direct atmospheric CO2 measurements from the Mauna Loa and South Pole stations (Keeling et al., 1976). To account for the difference of mean CO2 and seasonality between the NOAA/ESRL and the Scripps station networks used here, the Scripps surface average (from two stations) was de-seasonalized and adjusted to match the NOAA/ESRL surface average (from multiple stations) by adding the mean difference of 0.667 ppm, calculated here from overlapping data during 1980–2012."