******************************************************************* *** Atmospheric CO2 mixing ratios (ppmv) derived from in situ *** *** air samples collected at Mauna Loa, Hawaii *** *** *** *** 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 1974 -99.99 -99.99 -99.99 -99.99 333.15 332.07 330.99 329.17 327.39 327.25 328.26 329.51 -99.99 1975 330.69 331.41 331.84 333.26 333.92 333.39 331.81 329.90 328.56 328.45 329.29 -99.99 -99.99 1976 331.65 332.66 333.53 334.80 334.80 334.14 332.88 330.64 329.01 328.62 330.13 331.63 332.04 1977 332.74 333.23 334.91 336.01 336.82 336.13 334.75 332.53 331.27 331.21 332.36 333.47 333.79 1978 334.74 335.22 336.52 337.77 338.00 338.04 336.39 334.33 332.35 332.33 333.77 334.80 335.36 1979 336.20 336.65 337.79 338.95 339.03 339.22 337.58 335.51 333.83 334.05 335.26 336.70 336.73 1980 337.81 338.26 340.07 340.87 341.48 341.30 339.36 337.84 335.98 336.07 337.22 338.33 338.72 1981 339.35 340.47 341.73 342.47 343.02 342.46 340.78 338.61 337.04 337.13 338.49 339.85 340.12 1982 340.93 341.67 342.78 343.71 344.31 343.41 341.96 339.79 337.91 338.10 339.27 340.67 341.21 1983 341.43 342.68 343.46 345.10 345.75 345.36 343.91 342.07 339.99 340.12 341.33 342.94 342.85 1984 343.87 344.60 345.20 347.09 347.36 346.73 345.41 343.23 341.30 341.49 342.85 344.40 344.46 1985 345.08 345.89 347.46 348.00 348.75 348.19 346.58 344.61 343.02 342.92 344.23 345.57 345.86 1986 346.43 346.95 347.88 349.57 350.34 349.72 347.77 345.86 344.79 344.33 345.67 346.89 347.18 1987 348.19 348.55 349.51 351.13 351.84 351.51 349.82 347.69 346.38 346.49 347.75 349.03 348.99 1988 350.21 351.62 352.18 353.55 354.14 353.62 352.56 350.41 348.84 348.95 350.05 351.29 351.45 1989 352.72 353.10 353.65 355.41 355.71 355.15 353.79 351.35 349.84 350.11 351.26 352.63 352.89 1990 353.65 354.71 355.53 356.09 357.08 356.11 354.71 352.66 351.08 351.37 352.81 354.22 354.17 1991 354.85 355.67 357.04 358.41 358.99 358.00 356.00 353.79 352.20 352.22 353.70 354.98 355.49 1992 356.07 356.87 357.73 358.91 359.46 359.19 356.73 354.79 352.78 353.22 354.16 355.42 356.28 1993 356.77 357.16 358.27 359.16 360.08 359.41 357.36 355.32 353.89 354.03 355.27 356.69 356.95 1994 358.01 358.82 359.74 361.13 361.49 360.60 359.20 357.23 355.44 355.89 357.42 358.74 358.64 1995 359.74 360.59 361.59 363.05 363.56 363.08 361.57 358.91 357.94 357.78 359.21 360.45 360.62 1996 361.82 362.95 363.88 364.27 364.94 364.70 363.31 361.17 359.36 359.33 360.62 361.96 362.36 1997 362.83 363.87 364.24 366.02 366.47 365.31 364.07 362.01 360.03 360.49 362.19 364.11 363.47 1998 364.99 365.80 366.95 368.44 369.32 368.79 367.59 365.63 363.84 364.19 365.36 367.01 366.49 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 denoted by -99.99.