Concentrations of CO2 in the atmosphere

Monitoring Division of NOAA/Earth System Research Laboratory has measured carbon dioxide and other greenhouse gases for several decades at a globally distributed network of air sampling sites [Conway, 1994]. A global average is constructed by first fitting a smoothed curve as a function of time to each site, and then the smoothed value for each site is plotted as a function of latitude for 48 equal time steps per year. A global average is calculated from the latitude plot at each time step [Masarie, 1995].
(Source: Earth System Research Laboratory (ESRL), part of National Oceanic and Atmospheric Administration (NOAA), http://www.esrl.noaa.gov/gmd/ccgg/trends/global.html#global)

Unit of Measurement: 

Parts per million (ppm)

Description to get data: 

Table is at the bottom.