Atmospheric CO₂

Measurements of atmospheric CO₂ concentration in our program began in 1957 at La Jolla, California and at the South Pole, and in 1958 at Mauna Loa Observatory. These measurements were gradually extended during the 1960's and 1970's to comprise sampling at an array of stations from the Arctic to Antarctica.

Solid circles denote locations of stations for flasks collected for CO₂ and CO₂ isotope measurements. Open circles denote locations of flasks collected for the parallel program Scripps O₂ in atmospheric O₂ measurements.

The primary (in situ) record from Mauna Loa is based on measurements made with an analyzer at the site. At all other stations, the records are based on flask samples returned to our La Jolla laboratory for analysis. Flasks have also been redundantly collected at Mauna Loa. Isotopic measurements on flask samples of the ¹³C/¹²C and ¹⁸O/¹⁶O ratios of CO₂, which we began in 1978, have gradually been expanded to include all stations where we measure the CO₂ concentration.

Mauna Loa Record

The increasing amount of CO₂ in the atmosphere from the burning of fossil fuels has become a serious environmental concern. Central to this concern is the question whether a rise in CO₂ constitutes a peril to humans by raising world temperatures, as many scientists now claim. That a rise in CO₂ is occurring is unquestionable, however. Mauna Loa Observatory (MLO) data are providing dramatic evidence of that: they show amounts more than 35% over amounts recorded before the Industrial Revolution, and a rise of 6% in the last 19 years alone.

The first unmistakable evidence of atmospheric CO₂ increase was furnished by continuous measurements made at MLO and by measurements of flask samples collected periodically at the South Pole. These data, obtained in connection with the International Geophysical Year (IGY), were precise enough to indicate a rise in concentration in 1959 when compared with the results of the previous year (Keeling, 1960). Further measurements have shown a persistent year-to-year increase.

Over the many decades that the Scripps CO₂ program has been in existence, additional programs have joined the effort in making related measurements. The largest and most comprehensive of these is the NOAA-GMD program, which initiated measurements at Mauna Loa and other sites in the 1970s (www.esrl.noaa.gov/gmd/ccgg/trends). Since then, two independent records of CO₂ changes have been maintained in parallel at Mauna Loa. The following figure overlays the two records.