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*** Atmospheric CO2 concentrations from Bering Island (ppmv)	***
***							        ***
*** September 1994						***
***						        	***
***  Source: A.M. Brounshtein					***
***         A.A. Shashkov					***
***         N.N. Paramonova					***
***         V.I. Privalov					***
***         Y.A. Starodubtsev					***
***         Main Geophysical Observatory			***
***         Karbyshev Str. 7					***
***         194018 St. Petersburg, Russia			***
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Year  Jan.   Feb.    Mar.   Apr.   May   Jun.   Jul.   Aug.   Sep.   Oct.   Nov.   Dec.  Annual
1986 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 337.5  336.9  345.4  349.4  351.8  354.9  -99.99
1987 353.2  353.7  355.1  357.0  359.0  354.1  343.0  336.2  340.1  -99.99 -99.99 -99.99 -99.99
1988 358.7  357.9  357.6  356.9  358.4  -99.99 345.1  343.5  -99.99 355.6  357.3  359.3  -99.99
1989 357.9  360.3  359.0  360.8  361.1  356.4  345.9  344.8  349.5  355.6  356.8  -99.99 -99.99
1990 -99.99 363.2  361.0  362.2  361.3  354.2  347.9  342.0  -99.99 356.2  359.3  360.6  -99.99
1991 360.3  361.1  362.4  363.7  363.4  357.5  350.3  346.3  348.9  357.8  361.6  359.4  357.7
1992 -99.99 363.3  364.0  364.1  365.1  352.2  349.9  345.5  351.5  357.4  361.3  359.8  -99.99
1993 368.1  363.7  367.2  364.7  358.3  359.2  357.3  -99.99 -99.99 362.0  361.6  363.7  -99.99

Atmospheric CO2 concentrations are expressed in parts per million by volume (ppmv). Monthly
averages are calculated from available individual flask measurements for a given month. Annual
averages are based on monthly means. All flask measurements have been adjusted for concentration
drift during storage time. The data scale presented here is based on initial manometric calibration
experiments during 1990-93 against a set of CO2-in-air standards provided by the Atmospheric
Environment Service (AES) of Canada. This scale is closely related to the SIO X87 mole fraction
scale through AES standards.
Note: None of the reference gases used by the Main Geophysical Observatory (MGO) has a CO2
concentration >355 ppmv. As a result, a linear extrapolation procedure has been applied to calculate
concentration values for air samples with concentrations >355 ppmv up to mid-1992. Since August 1992, 
one of the AES calibration gases has been used along with the MGO reference gases to avoid extrapolation.
The investigators estimate that the extrapolation error for measurements before 1992 does not exceed
0.15 ppmv.