NOAA Mauna Loa CO2 Data


NOAA release date for monthly CO2 data:

September 7, 2015 

Atmospheric CO2
Mauna Loa Observatory (Scripps / NOAA / ESRL)
Monthly Mean CO2 Concentrations (ppm)
Since March 1958


The monthly MLO data set is reposted by in 2 formats:

 NOAA CO2 Data for the Mauna Loa Observatory     PDF Version 

Source Data

Mauna Loa Monthly Mean CO2

Source data published by the National Oceanic and Atmospheric Administration (NOAA)

Mauna Loa Annual Mean CO2

Source data published by the National Oceanic and Atmospheric Administration (NOAA)


Data Notes

  • At, data for March 1958 - April 1974 was obtained by Charles David Keeling of the Scripps Institution of Oceanography (Scripps).  Data for CO2 since May 1974 was obtained by the National Oceanic and Atmospheric Administration (NOAA).   The Scripps Institution of Oceanography also maintains a CO2 monitoring program at the Mauna Loa Observatory.  Click here to access the Scripps data for the Mauna Loa Observatory.   
  • Monthly mean CO2 concentrations are determined from daily averages for the number of CO2 molecules in every one million molecules of dried air (water vapor removed).  Annual mean CO2 concentrations are the arithmetic mean of the monthly averages for the year.  Atmospheric CO2 concentrations are expressed as parts per million (ppm).


  • NOAA data published within the past year is preliminary and subject to change by NOAA due to its recalibration of the reference gas mixture used or other quality control procedures.  In some cases, data from earlier years may be changed for the same reasons.  Usually, these changes are minor. See the NOAA change log and notes that was started in August 2008 to keep a public record of the adjustments and reasons for the adjustments.   


  • All data in this table is republished from the most current data available from NOAA.  Data is republished independently by Pro Oxygen at to make it easier for people to see the latest atmospheric CO2 data and trend information.  A delay of 4 to 24  hours typically occurs between the release of monthly data by NOAA and the publication of updates at   The accuracy of republished data can be checked by reviewing the source data.   In the event that a publication error is detected, please send details to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .   



More Data



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