Levels of CO₂ concentrations are presented at the World Level. Data are reported as a dry air mole fraction defined as the number of molecules of carbon dioxide divided by the number of all molecules in air, including CO₂ itself, after water vapor has been removed. The mole fraction is expressed as parts per million (ppm).Source: Dr. Pieter Tans, National Oceanic and Atmospheric Administration (NOAA). Global Monitoring Laboratory, Trends in Atmospheric Carbon Dioxide Data (https://gml.noaa.gov/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography, Carbon Dioxide Measurements (https://scrippsco2.ucsd.edu/). Accessed on 2023-03-28.Category:  Climate Change DataData series: Monthly Atmospheric Carbon Dioxide ConcentrationsMonthly Atmospheric Carbon Dioxide Concentrations, Year on Year Percentage ChangeMetadata:Data is available since 1958 and are acquired from the National Oceanic and Atmospheric Association Global Monitoring Laboratory.  The monthly CO₂ concentrations measured at Mauna Loa Observatory, Hawaii, are used to represent world estimates. The carbon dioxide data on Mauna Loa constitute the longest record of direct measurements of CO2 in the atmosphere.Methodology:The details of measurement of CO₂ concentrations at the Mauna Loa Observatory are available at the following link: https://gml.noaa.gov/ccgg/about/co2_measurements.htmlThe year-on-year changes in the CO₂ concentrations are calculated by the IMF.Disclaimer:The Mauna Loa data are being obtained at an altitude of 3400 m in the northern subtropics, and may not be the same as the globally averaged CO₂ concentration at the surface.Users are encouraged to examine the documentation, metadata, and sources associated with the data. User feedback on the fit-for-use of this product and whether the various dimensions of the product are appropriate is welcome.