The 2012 average annual concentration of CO2 in the atmosphere (Mauna Loa Observatory) is 393.84 parts per million (ppm).   The 2011 average is 391.65 ppm.  

For the past decade (2003-2012) the average annual increase is 2.1 ppm per year.  The average for the prior decade (1993-2002) is 1.7 ppm per year.    Annual data for 2012 was first posted January 3, 2013, by the Scripps Institution of Oceanography in the United States. 

Since the 1958 start of precision CO2 measurements in the atmosphere, the annual mean concentration of CO2 has only increased from one year to the next.   The CO2 data below provide a simple view of the annual trend. 

Year        CO2 (ppm)           Notes

2012        393.84

2011        391.65

2010        389.92                   

2009       387.35                   Copenhagen Accord

2008       385.45                  

2007       383.61                

2006       381.83 

1997       363.76                   Kyoto Protocol

1992       356.37                   Earth Summit in Rio de Janeiro

1987       348.93                   The last year when the annual CO2 level was less than 350 ppm

1959       315.98                   The first year with a full year of instrument data 

Source Annual CO2 Data:  Scripps Institution of Oceanography: CO2 Program

More Information:

Annual and monthly data for atmospheric CO2  |  1958 - present  |  MLO / Scripps & NOAA

Accelerating rise of atmospheric CO2

Seasonal fluctuation in atmospheric CO2

Monthly data for atmospheric CO2