NOTICE (September 2017): Data previously stored at the CDIAC archive are being transitioned to the new, ESS-DIVE archive. This website provides access to the CDIAC data during the transition. If you have any questions regarding the new archive or the data transition, please contact

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Mauna Loa atmospheric CO2 record


data Data


C. D. Keeling and T. P. Whorf


Since 1958, air samples have been continuously collected at Mauna Loa Observatory and analyzed by infrared spectroscopy for CO2 concentrations. Data are averaged to give monthly and annual atmospheric CO2 concentrations.

These data represent the longest continuous record of atmospheric CO2 concentrations in the world. This precise data record covers a single site (Mauna Loa Observatory, Hawaii). It is a reliable indicator of the regional trend in the concentration of atmospheric CO2 in the middle layers of the troposphere and is critical to CO2-related research.