NOTICE (July 2017): CDIAC will cease operations on September 30, 2017. Data will continue to be available through this portal until that time. A new DOE data archive is now at Lawrence Berkeley National Laboratory and is named ESS-DIVE. Data stored at CDIAC is being transitioned to ESS-DIVE and will be available from ESS-DIVE by September 30, 2017. 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.