Atmospheric CO2 concentrations at Mauna Loa
| Year | Jan. | Feb. | March | April | May | June | July | Aug. | Sept. | Oct. | Nov. | Dec. | Annual |
| 1958 | -99.99 | -99.99 | 315.71 | 317.45 | 317.5 | -99.99 | 315.86 | 314.93 | 313.19 | -99.99 | 313.34 | 314.67 | -99.99 |
| 1959 | 315.58 | 316.47 | 316.65 | 317.71 | 318.29 | 318.16 | 316.55 | 314.8 | 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 | 316.19 | 316.91 |
| 1961 | 316.89 | 317.7 | 318.54 | 319.48 | 320.58 | 319.78 | 318.58 | 316.79 | 314.99 | 315.31 | 316.1 | 317.01 | 317.65 |
| 1962 | 317.94 | 318.56 | 319.69 | 320.58 | 321.01 | 320.61 | 319.61 | 317.4 | 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 | -99.99 | -99.99 | -99.99 | 322.23 | 321.89 | 320.44 | 318.7 | 316.7 | 316.87 | 317.68 | 318.71 | -99.99 |
| 1965 | 319.44 | 320.44 | 320.89 | 322.13 | 322.16 | 321.87 | 321.21 | 318.87 | 317.81 | 317.3 | 318.87 | 319.42 | 320.03 |
| 1966 | 320.62 | 321.59 | 322.39 | 323.7 | 324.07 | 323.75 | 322.4 | 320.37 | 318.64 | 318.1 | 319.79 | 321.03 | 321.37 |
| 1967 | 322.33 | 322.5 | 323.04 | 324.42 | 325 | 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 | 322.9 | 323.05 |
| 1969 | 324 | 324.42 | 325.64 | 326.66 | 327.38 | 326.7 | 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 | 323.1 | 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 | 324.8 | 326.01 | 326.32 |
| 1972 | 326.77 | 327.63 | 327.75 | 329.72 | 330.07 | 329.09 | 328.05 | 326.32 | 324.84 | 325.2 | 326.5 | 327.55 | 327.46 |
| 1973 | 328.54 | 329.56 | 330.3 | 331.5 | 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 | 329.4 | 327.44 | 327.37 | 328.46 | 329.58 | 330.25 |
| 1975 | 330.4 | 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 | 333.5 | 334.58 | 334.87 | 334.34 | 333.05 | 330.94 | 329.3 | 328.94 | 330.31 | 331.68 | 332.15 |
| 1977 | 332.92 | 333.42 | 334.7 | 336.07 | 336.74 | 336.27 | 334.93 | 332.75 | 331.58 | 331.16 | 332.4 | 333.85 | 333.9 |
| 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 | 335.5 |
| 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 | 337.6 | 335.88 | 336.01 | 337.1 | 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 | 342.7 | 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 | 343.1 | 344.94 | 345.75 | 345.32 | 343.99 | 342.39 | 339.86 | 339.99 | 341.16 | 342.99 | 342.78 |
| 1984 | 343.7 | 344.51 | 345.28 | 347.08 | 347.43 | 346.79 | 345.4 | 343.28 | 341.07 | 341.35 | 342.98 | 344.22 | 344.42 |
| 1985 | 344.97 | 346 | 347.43 | 348.35 | 348.93 | 348.25 | 346.56 | 344.69 | 343.09 | 342.8 | 344.24 | 345.56 | 345.9 |
| 1986 | 346.29 | 346.96 | 347.86 | 349.55 | 350.21 | 349.54 | 347.94 | 345.91 | 344.86 | 344.17 | 345.66 | 346.9 | 347.15 |
| 1987 | 348.02 | 348.47 | 349.42 | 350.99 | 351.84 | 351.25 | 349.52 | 348.1 | 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 | 353.9 | 351.67 | 349.8 | 349.99 | 351.3 | 352.53 | 352.91 |
| 1990 | 353.66 | 354.7 | 355.39 | 356.2 | 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 | 358.6 | 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 | 353.01 | 353.31 | 354.16 | 355.4 | 356.37 |
| 1993 | 356.7 | 357.16 | 358.38 | 359.46 | 360.28 | 359.6 | 357.57 | 355.52 | 353.7 | 353.98 | 355.33 | 356.8 | 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 | 361.64 | 363.45 | 363.79 | 363.26 | 361.9 | 359.46 | 358.06 | 357.75 | 359.56 | 360.7 | 360.88 |
| 1996 | 362.05 | 363.25 | 364.03 | 364.72 | 365.41 | 364.97 | 363.65 | 361.49 | 359.46 | 359.6 | 360.76 | 362.33 | 362.64 |
| 1997 | 363.18 | 364 | 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 | 369.3 | 368.87 | 367.64 | 365.77 | 363.9 | 364.23 | 365.46 | 366.97 | 366.63 |
| 1999 | 368.15 | 368.86 | 369.58 | 371.12 | 370.97 | 370.33 | 369.25 | 366.91 | 364.6 | 365.09 | 366.63 | 367.96 | 368.29 |
| 2000 | 369.08 | 369.4 | 370.45 | 371.59 | 371.75 | 371.62 | 370.04 | 368.04 | 366.54 | 366.63 | 368.2 | 369.43 | 369.4 |
| 2001 | 370.17 | 371.39 | 372 | 372.75 | 373.88 | 373.17 | 371.48 | 369.42 | 367.83 | 367.96 | 369.55 | 371.1 | 370.89 |
| 2002 | 372.29 | 372.94 | 373.38 | 374.71 | 375.4 | 375.26 | 373.87 | 371.35 | 370.57 | 370.1 | 371.93 | 373.63 | 372.95 |
(Carbon Dioxide
Information Analysis Center (CDIAC))