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Atmospheric CO2 from Flask Air Samples at Mauna Loa Observatory, Hawaii, U.S.A.

graphics Graphics   data Data


C.D. Keeling and T.P. Whorf
Carbon Dioxide Research Group,
Scripps Institution of Oceanography,
University of California, La Jolla, California 92093-0444, U.S.A.

Period of Record



Atmospheric CO2 samples were collected roughly twice per month until 1981, and at roughly weekly intervals thereafter. Samples are collected in 5-L evacuated glass flasks, and then returned to the Scripps Institution of Oceanography (SIO) where CO2 concentrations have been determined using an Applied Physics Corporation (APC) nondispersive infrared gas analyzer. Further information on measurements, calibration procedures and analysis is available in the references listed below.

Map showing location of Mauna Loa, Hawaii, U.S.A.
Mauna Loa, Hawaii, U.S.A.
Barren lava field of an active volcano
19°32' N, 155°35' W, 3397 m above MSL
Map of Hawaii


The average of unflagged data for the first complete year of measurements (1962) was 318.4 ppmv; 2001 values averaged 371.2 ppmv, for an upward trend of 1.35 ppmv/year. Graphics here show the first and last year of data, to display the change in mean over time and the annual amplitudes. Long term trend curves are better displayed using SIO's monthly averaged data.


CITE AS: Keeling, C.D. and T.P. Whorf. 2004. Atmospheric CO2 concentrations derived from flask air samples at sites in the SIO network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.