"Atmospheric CO2 Concentrations from Mauna Loa, Hawaii" Source: C. D. Keeling and T.P. Whorf Scripps Institution of Oceanography University of California concentrations in parts per million (ppm) Year Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Annual 1959 315.42 316.31 316.5 317.56 318.13 318 316.39 314.65 313.68 313.18 314.66 315.43 315.83 1960 316.27 316.81 317.42 318.87 319.87 319.43 318.01 315.74 314 313.68 314.84 316.03 316.75 1961 316.73 317.54 318.38 319.31 320.42 319.61 318.42 316.63 314.84 315.16 315.94 316.85 317.49 1962 317.78 318.4 319.53 320.42 320.85 320.45 319.45 317.25 316.11 315.27 316.53 317.53 318.3 1963 318.58 318.93 319.7 321.22 322.08 321.31 319.58 317.61 316.05 315.83 316.91 318.2 318.83 1964 319.41 322.05 321.73 320.27 318.53 316.54 316.72 317.53 318.55 319.04 Calculated with available data 1965 319.27 320.28 320.73 321.97 322 321.71 321.05 318.71 317.66 317.14 318.7 319.25 319.87 1966 320.46 321.43 322.23 323.54 323.91 323.59 322.24 320.2 318.48 317.94 319.63 320.87 321.21 1967 322.17 322.34 322.88 324.25 324.83 323.93 322.38 320.76 319.1 319.24 320.56 321.8 322.02 1968 322.4 322.99 323.73 324.86 325.4 325.2 323.98 321.95 320.18 320.09 321.16 322.74 322.89 1969 323.83 324.27 325.47 326.5 327.21 326.54 325.72 323.5 322.22 321.62 322.69 323.95 324.46 1970 324.89 325.82 326.77 327.97 327.9 327.5 326.18 324.53 322.93 322.9 323.85 324.96 325.52 1971 326.01 326.51 327.02 327.62 328.76 328.4 327.2 325.27 323.2 323.4 324.63 325.85 326.16 1972 326.6 327.47 327.58 329.56 329.9 328.92 327.88 326.16 324.68 325.04 326.34 327.39 327.29 1973 328.37 329.4 330.14 331.33 332.31 331.9 330.7 329.15 327.35 327.02 327.99 328.48 329.51 1974 329.18 330.55 331.32 332.48 332.92 332.08 331.01 329.23 327.27 327.21 328.29 329.41 330.08 1975 330.23 331.25 331.87 333.14 333.8 333.43 331.73 329.9 328.4 328.17 329.32 330.59 330.99 1976 331.58 332.39 333.33 334.41 334.71 334.17 332.89 330.77 329.14 328.78 330.14 331.52 331.98 1977 332.75 333.24 334.53 335.9 336.57 336.1 334.76 332.59 331.42 330.98 332.24 333.68 333.73 1978 334.8 335.22 336.47 337.59 337.84 337.72 336.37 334.51 332.6 332.38 333.75 334.78 335.34 1979 336.05 336.59 337.79 338.71 339.3 339.12 337.56 335.92 333.75 333.7 335.12 336.56 336.68 1980 337.84 338.19 339.91 340.6 341.29 341 339.39 337.43 335.72 335.84 336.93 338.04 338.52 1981 339.06 340.3 341.21 342.33 342.74 342.08 340.32 338.26 336.52 336.68 338.19 339.44 339.76 1982 340.57 341.44 342.53 343.39 343.96 343.18 341.88 339.65 337.81 337.69 339.09 340.32 340.96 1983 341.2 342.35 342.93 344.77 345.58 345.14 343.81 342.21 339.69 339.82 340.98 342.82 342.61 1984 343.52 344.33 345.11 346.89 347.25 346.62 345.22 343.11 340.9 341.18 342.8 344.04 344.25 1985 344.79 345.82 347.25 348.17 348.74 348.07 346.38 344.52 342.92 342.62 344.06 345.38 345.73 1986 346.11 346.78 347.68 349.37 350.03 349.37 347.76 345.73 344.68 343.99 345.48 346.72 346.97 1987 347.84 348.29 349.24 350.8 351.66 351.08 349.33 347.92 346.27 346.18 347.64 348.78 348.75 1988 350.25 351.54 352.05 353.41 354.04 353.63 352.22 350.27 348.55 348.72 349.91 351.18 351.31 1989 352.6 352.92 353.53 355.26 355.52 354.97 353.75 351.52 349.64 349.83 351.14 352.37 352.75 1990 353.5 354.55 355.23 356.04 357 356.07 354.67 352.76 350.82 351.04 352.7 354.07 354.04 1991 354.59 355.63 357.03 358.48 359.22 358.12 356.06 353.92 352.05 352.11 353.64 354.89 355.48 1992 355.88 356.63 357.72 359.07 359.58 359.17 356.94 354.92 352.94 353.23 354.09 355.33 356.29 1993 356.63 357.1 358.32 359.41 360.23 359.55 357.53 355.48 353.67 353.95 355.3 356.78 356.99 1994 358.34 358.89 359.95 361.25 361.67 360.94 359.55 357.49 355.84 356 357.59 359.05 358.88 1995 359.98 361.03 361.66 363.48 363.82 363.3 361.93 359.49 358.08 357.77 359.57 360.69 360.9