Background atmospheric CO₂ mixing ratios from individual flask air samples for Shemya Island, Alaska, U.S. Only measurements satisfying the data selection criteria fro background measurements are plotted. Consecutive background measurements are joined by lines. Background measurements interrupted by non-background measurements are not joined by lines.

Monthly atmospheric CO2 mixing ratios for Shemya Island, Alaska, U.S., expressed in parts per million (ppm) and
reported in the Scripps Institution of Oceanography X93 manometric mole fraction scale.  Annual values were
calculated by CDIAC for years with complete records.  Missing values are denoted by -99.99.




Year      Jan 	     Feb      Mar	April	  May	   June	     July      Aug     Sept	  Oct 	   Nov       Dec     Ann




1985    -99.99     -99.99   -99.99     -99.99   -99.99    -99.99    -99.99   -99.99   340.37     345.73   348.55    350.27   -99.99
1986    350.91     351.46   353.25     354.56   353.72    348.73    339.90   338.13   344.12     350.72   353.06    352.72   349.27
1987    353.53     354.52   355.24     356.50   356.64    352.74    342.50   337.06   342.93     348.71   351.16    354.07   350.47
1988    355.86     356.26   357.22     358.47   358.29    354.60    346.59   341.57   344.95     351.35   354.39    357.03   353.05
1989    358.81     358.54   358.92     360.22   360.02    355.15    346.43   342.48   346.88     353.04   356.09    357.63   354.52
1990    359.85     360.74   360.39     360.66   359.16    353.49    346.10   342.23   347.20     353.39   357.13    360.15   355.04
1991    360.82     360.76   361.95     363.29   362.82    357.10    348.52   344.29   349.05     355.12   358.05    359.71   356.79
1992    361.20     361.64   362.15     362.93   362.11    357.57    349.93   346.13   349.09     354.83   358.38    360.10   357.17
1993    361.53     361.93   362.18     362.86   363.10    359.06    350.10   346.10   349.47     355.20   358.96    360.95   357.62