*******************************************************************
*** Atmospheric CO2 mixing ratios (ppmv) derived from in situ   ***
*** air samples collected at Cape Matatula, American Samoa      ***
***                                                             ***
*** Source: Kirk W. Thoning                                     ***
***         Pieter P. Tans                                      ***
***         National Oceanic and Atmospheric Administration     ***
***         Climate Monitoring and Diagnostics Laboratory       ***
***         Boulder, Colorado USA 80303                         ***
***                                                             ***
*** February 2000                                               ***
***                                                             ***
*******************************************************************
Year   Jan.   Feb.   March  April   May    June   July   Aug.  Sept.   Oct.   Nov.   Dec. Annual
1976  332.24 331.90 331.32 331.09 330.67 331.17 331.14 331.15 331.29 331.45 332.03 331.93 331.45
1977  331.82 331.95 332.05 332.09 332.60 332.67 332.23 333.03 332.82 333.16 -99.99 -99.99 -99.99
1978  -99.99 334.76 335.15 335.33 335.00 335.15 335.00 335.76 335.75 -99.99 -99.99 -99.99 -99.99
1979  -99.99 336.13 335.86 336.57 335.81 336.03 336.28 336.33 336.32 336.62 336.73 336.87 -99.99
1980  337.44 337.60 337.89 337.34 337.77 337.99 338.39 338.30 338.19 338.11 338.54 338.83 338.03
1981  339.04 339.25 338.98 339.51 338.72 339.27 338.99 339.09 339.11 338.90 339.42 339.83 339.18
1982  340.39 340.38 340.33 340.20 339.99 339.87 340.55 340.71 340.36 339.90 340.31 340.23 340.27
1983  340.41 340.61 340.82 340.67 341.20 341.70 341.94 342.05 342.05 342.18 342.53 342.75 341.58
1984  343.08 343.39 343.45 343.37 342.47 342.85 343.20 343.33 343.39 343.37 343.46 344.07 343.29
1985  344.05 344.50 344.56 344.41 344.74 344.41 344.77 344.69 344.41 344.39 344.76 345.23 344.58
1986  345.56 345.71 345.76 345.85 345.55 346.29 346.23 345.89 345.98 346.06 346.05 346.21 345.93
1987  346.58 346.94 346.80 346.44 347.89 347.83 348.24 347.76 347.93 348.06 348.23 348.79 347.62
1988  349.30 349.75 349.67 350.63 349.62 349.65 349.93 349.97 349.59 349.92 350.40 351.03 349.96
1989  351.38 351.70 351.47 351.48 351.75 350.82 351.13 351.23 351.12 351.23 351.61 351.59 351.38
1990  352.20 353.10 -99.99 -99.99 352.08 352.78 352.64 352.71 352.77 352.59 352.74 353.26 -99.99
1991  353.84 354.52 354.17 353.55 353.48 353.95 353.91 353.58 353.54 353.65 354.26 354.69 353.93
1992  354.20 354.56 354.78 354.58 354.63 354.87 355.35 355.31 354.96 355.05 354.78 355.25 354.86
1993  355.38 355.34 355.93 355.59 354.67 355.42 355.41 356.10 355.74 355.82 356.14 356.63 355.68
1994  357.00 357.37 357.10 357.35 356.76 357.02 357.60 357.32 357.33 357.63 358.16 358.59 357.44
1995  358.54 359.30 359.31 359.03 359.43 359.28 359.50 359.31 359.17 359.47 359.89 360.15 359.37
1996  361.10 361.37 361.20 360.13 360.80 360.94 360.60 360.76 360.62 360.74 361.17 361.58 360.92
1997  361.77 362.06 362.37 361.87 361.12 361.12 361.93 361.89 361.90 -99.99 362.98 363.24 -99.99
1998  363.72 363.25 363.44 363.04 -99.99 -99.99 364.83 364.89 364.98 365.14 365.72 366.15 -99.99
Atmospheric CO2 mixing ratios are expressed in parts per million by volume (ppmv) and reported
relative to the dry air WMO mole fraction scale. Monthly means are derived from hourly and daily 
means that represent baseline (background) conditions. Annual means are the arithmetic means of 
the monthly values calculated by CDIAC. Annual means are provided only for years with complete 
monthly records. Missing values are denoted by -99.99.