Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
1958 | -999 | -999 | 315.71 | 317.45 | 317.50 | -999 | 315.86 | 314.93 | 313.19 | -999 | 313.34 | 314.67 | -999 |
1959 | 315.58 | 316.47 | 316.65 | 317.71 | 318.29 | 318.16 | 316.55 | 314.80 | 313.84 | 313.34 | 314.81 | 315.59 | 315.98 |
1960 | 316.43 | 316.97 | 317.58 | 319.03 | 320.03 | 319.59 | 318.18 | 315.91 | 314.16 | 313.83 | 315.00 | 316.19 | 316.91 |
1961 | 316.89 | 317.70 | 318.54 | 319.48 | 320.58 | 319.78 | 318.58 | 316.79 | 314.99 | 315.31 | 316.10 | 317.01 | 317.65 |
1962 | 317.94 | 318.56 | 319.69 | 320.58 | 321.01 | 320.61 | 319.61 | 317.40 | 316.26 | 315.42 | 316.69 | 317.69 | 318.45 |
1963 | 318.74 | 319.08 | 319.86 | 321.39 | 322.24 | 321.47 | 319.74 | 317.77 | 316.21 | 315.99 | 317.07 | 318.36 | 318.99 |
1964 | 319.57 | -999 | -999 | -999 | 322.23 | 321.89 | 320.44 | 318.70 | 316.70 | 316.87 | 317.68 | 318.71 | -999 |
1965 | 319.44 | 320.44 | 320.89 | 322.13 | 322.16 | 321.87 | 321.21 | 318.87 | 317.81 | 317.30 | 318.87 | 319.42 | 320.03 |
1966 | 320.62 | 321.59 | 322.39 | 323.70 | 324.07 | 323.75 | 322.40 | 320.37 | 318.64 | 318.10 | 319.79 | 321.03 | 321.37 |
1967 | 322.33 | 322.50 | 323.04 | 324.42 | 325.00 | 324.09 | 322.55 | 320.92 | 319.26 | 319.39 | 320.72 | 321.96 | 322.18 |
1968 | 322.57 | 323.15 | 323.89 | 325.02 | 325.57 | 325.36 | 324.14 | 322.11 | 320.33 | 320.25 | 321.32 | 322.90 | 323.05 |
1969 | 324.00 | 324.42 | 325.64 | 326.66 | 327.38 | 326.70 | 325.89 | 323.67 | 322.38 | 321.78 | 322.85 | 324.12 | 324.62 |
1970 | 325.06 | 325.98 | 326.93 | 328.13 | 328.07 | 327.66 | 326.35 | 324.69 | 323.10 | 323.07 | 324.01 | 325.13 | 325.68 |
1971 | 326.17 | 326.68 | 327.18 | 327.78 | 328.92 | 328.57 | 327.37 | 325.43 | 323.36 | 323.56 | 324.80 | 326.01 | 326.32 |
1972 | 326.77 | 327.63 | 327.75 | 329.72 | 330.07 | 329.09 | 328.05 | 326.32 | 324.84 | 325.20 | 326.50 | 327.55 | 327.46 |
1973 | 328.54 | 329.56 | 330.30 | 331.50 | 332.48 | 332.07 | 330.87 | 329.31 | 327.51 | 327.18 | 328.16 | 328.64 | 329.68 |
1974 | 329.35 | 330.71 | 331.48 | 332.65 | 333.09 | 332.25 | 331.18 | 329.40 | 327.44 | 327.37 | 328.46 | 329.58 | 330.25 |
1975 | 330.40 | 331.41 | 332.04 | 333.31 | 333.96 | 333.59 | 331.91 | 330.06 | 328.56 | 328.34 | 329.49 | 330.76 | 331.15 |
1976 | 331.74 | 332.56 | 333.50 | 334.58 | 334.87 | 334.34 | 333.05 | 330.94 | 329.30 | 328.94 | 330.31 | 331.68 | 332.15 |
1977 | 332.92 | 333.42 | 334.70 | 336.07 | 336.74 | 336.27 | 334.93 | 332.75 | 331.58 | 331.16 | 332.40 | 333.85 | 333.90 |
1978 | 334.97 | 335.39 | 336.64 | 337.76 | 338.01 | 337.89 | 336.54 | 334.68 | 332.76 | 332.54 | 333.92 | 334.95 | 335.50 |
1979 | 336.23 | 336.76 | 337.96 | 338.89 | 339.47 | 339.29 | 337.73 | 336.09 | 333.91 | 333.86 | 335.29 | 336.73 | 336.85 |
1980 | 338.01 | 338.36 | 340.08 | 340.77 | 341.46 | 341.17 | 339.56 | 337.60 | 335.88 | 336.01 | 337.10 | 338.21 | 338.69 |
1981 | 339.23 | 340.47 | 341.38 | 342.51 | 342.91 | 342.25 | 340.49 | 338.43 | 336.69 | 336.85 | 338.36 | 339.61 | 339.93 |
1982 | 340.75 | 341.61 | 342.70 | 343.56 | 344.13 | 343.35 | 342.06 | 339.82 | 337.97 | 337.86 | 339.26 | 340.49 | 341.13 |
1983 | 341.37 | 342.52 | 343.10 | 344.94 | 345.75 | 345.32 | 343.99 | 342.39 | 339.86 | 339.99 | 341.16 | 342.99 | 342.78 |
1984 | 343.70 | 344.51 | 345.28 | 347.08 | 347.43 | 346.79 | 345.40 | 343.28 | 341.07 | 341.35 | 342.98 | 344.22 | 344.42 |
1985 | 344.97 | 346.00 | 347.43 | 348.35 | 348.93 | 348.25 | 346.56 | 344.69 | 343.09 | 342.80 | 344.24 | 345.56 | 345.90 |
1986 | 346.29 | 346.96 | 347.86 | 349.55 | 350.21 | 349.54 | 347.94 | 345.91 | 344.86 | 344.17 | 345.66 | 346.90 | 347.15 |
1987 | 348.02 | 348.47 | 349.42 | 350.99 | 351.84 | 351.25 | 349.52 | 348.10 | 346.44 | 346.36 | 347.81 | 348.96 | 348.93 |
1988 | 350.43 | 351.72 | 352.22 | 353.59 | 354.22 | 353.79 | 352.39 | 350.44 | 348.72 | 348.88 | 350.07 | 351.34 | 351.48 |
1989 | 352.76 | 353.07 | 353.68 | 355.42 | 355.67 | 355.13 | 353.90 | 351.67 | 349.80 | 349.99 | 351.30 | 352.53 | 352.91 |
1990 | 353.66 | 354.70 | 355.39 | 356.20 | 357.16 | 356.22 | 354.82 | 352.91 | 350.96 | 351.18 | 352.83 | 354.21 | 354.19 |
1991 | 354.72 | 355.75 | 357.16 | 358.60 | 359.34 | 358.24 | 356.17 | 354.03 | 352.16 | 352.21 | 353.75 | 354.99 | 355.59 |
1992 | 355.98 | 356.72 | 357.81 | 359.15 | 359.66 | 359.25 | 357.03 | 355.00 | 353.01 | 353.31 | 354.16 | 355.40 | 356.37 |
1993 | 356.70 | 357.16 | 358.38 | 359.46 | 360.28 | 359.60 | 357.57 | 355.52 | 353.70 | 353.98 | 355.33 | 356.80 | 357.04 |
1994 | 358.36 | 358.91 | 359.97 | 361.26 | 361.68 | 360.95 | 359.55 | 357.49 | 355.84 | 355.99 | 357.58 | 359.04 | 358.88 |
1995 | 359.96 | 361.00 | 361.64 | 363.45 | 363.79 | 363.26 | 361.90 | 359.46 | 358.06 | 357.75 | 359.56 | 360.70 | 360.88 |
1996 | 362.05 | 363.25 | 364.03 | 364.72 | 365.41 | 364.97 | 363.65 | 361.49 | 359.46 | 359.60 | 360.76 | 362.33 | 362.64 |
1997 | 363.18 | 364.00 | 364.57 | 366.35 | 366.79 | 365.62 | 364.47 | 362.51 | 360.19 | 360.77 | 362.43 | 364.28 | 363.76 |
1998 | 365.32 | 366.15 | 367.31 | 368.61 | 369.29 | 368.87 | 367.64 | 365.77 | 363.90 | 364.23 | 365.46 | 366.97 | 366.63 |
1999 | 368.15 | 368.87 | 369.59 | 371.14 | 371.00 | 370.35 | 369.27 | 366.94 | 364.63 | 365.12 | 366.67 | 368.01 | 368.31 |
2000 | 369.14 | 369.46 | 370.52 | 371.66 | 371.82 | 371.70 | 370.12 | 368.12 | 366.62 | 366.73 | 368.29 | 369.53 | 369.48 |
2001 | 370.28 | 371.50 | 372.12 | 372.87 | 374.02 | 373.30 | 371.62 | 369.55 | 367.96 | 368.09 | 369.68 | 371.24 | 371.02 |
2002 | 372.43 | 373.09 | 373.52 | 374.86 | 375.55 | 375.41 | 374.02 | 371.49 | 370.71 | 370.25 | 372.08 | 373.78 | 373.10 |
2003 | 374.68 | 375.63 | 376.11 | 377.65 | 378.35 | 378.13 | 376.62 | 374.50 | 372.99 | 373.00 | 374.35 | 375.70 | 375.64 |
* missing data = -999
** Source:
Keeling, C.D. and Whorf, T.P. 1998. Atmospheric CO2 concentrations -- Mauna Loa Observatory, Hawaii, 1958-1997 (revised June 2004). NDP-001. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Monthly values are expressed in parts per million (ppm) and reported in the 2003A SIO manometric mole fraction scale. The monthly values have been adjusted to the 15th of each month.