NOTICE (March 2018): This website provides access to the CDIAC archive data temporarily. It will be gradually transitioned into data packages in the new ESS-DIVE archive. This site will continue to operate in parallel during and after the transition, and will be retired at a future date. If you have any questions regarding the data or the 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.