Earth  ID: 4962

Atmospheric Carbon Dioxide Concentrations

Using the complete record of Mauna Loa CO2 monthly mean data, the timeplot featured on this page displays the ongoing Keeling’s research and observations: the monthly average of atmospheric CO2 concentration values, which show the seasonal cycle of CO2 (jagged/wavy red line) and the seasonally-adjusted mean values (adjusted/straight red line). The jagged/wavy red line visualizes natural oscillations caused by plant growth cycles, while the adjusted/straight red line demonstrates the steady increase over time that is caused by human activities, such as the burning of fossil fuels.

To illustrate the significance of the steady increase of atmospheric CO2 since 1958 and to provide a visual understanding of the monthly average CO2 values as they are measured in parts per million (ppm):
  • Monthly CO2 values are plotted on the range of [0-500] ppm over the period of March 1958 to December 2021 (present).
  • The pre-industrial CO22 average of 278 ppm is marked as an orange block.
  • As time passes the monthly adjusted percent increase is calculated relative to the pre-industrial CO2 value of 278ppm and is shown next to a red arrow.
As the timeline unfolds, we can see an increase growing from 13% in March 1958 to more than 50% in December 2021.

In addition to highlighting the steady increase of CO2 in the Earth’s atmosphere, this timeplot underpins the historical contributions of the Keeling Curve to climate science, as it was designated a National Historic Chemical Landmark by the American Chemical Society in 2015. Continuous and precise observations across agencies and institutions are critical to help scientists and the public understand the linkages between increases in CO2 and human-caused climate change.

The rest of this webpage offers a version of the timeplot with dark background, the Keeling Curve, as of December 2021 and data sources.

Data Sources:

  • Trends in Atmospheric Carbon Dioxide by NOAA. The visualization featured on this page utilizes the complete record from the Mauna Loa CO2 monthly mean data for the period March 1958-December 2021 (accessed: January 7, 2022). Within the data record the continuous monthly average values are represented in the visualization as the jagged/wavy line that shows the seasonal cycle of CO2 and the monthly de-seasonalized mean values are represented in the visualization as the adjusted line.

    Citation: Dr. Pieter Tans, NOAA/GML ( and Dr. Ralph Keeling, Scripps Institution of Oceanography (

    Citation: Keeling, Ralph F; Keeling, Charles D. (2017). Atmospheric Monthly In Situ CO2 Data - Mauna Loa Observatory, Hawaii (Archive 2021-09-07). In Scripps CO2 Program Data. UC San Diego Library Digital Collections.

Used Elsewhere In


Visualization Credits

Helen-Nicole Kostis (USRA): Lead Visualizer
Mark SubbaRao (NASA/GSFC): Lead Producer
Andrew J Christensen (SSAI): Visualizer
Laurence Schuler (ADNET): Technical Support
Ian Jones (ADNET): Technical Support
Eric Sokolowsky (GST): Technical Support
Please give credit for this item to:
NASA's Scientific Visualization Studio

Science Paper:
Keeling C.D. et al. (2005) Atmospheric CO2 and 13CO2 Exchange with the Terrestrial Biosphere and Oceans from 1978 to 2000: Observations and Carbon Cycle Implications. In: Baldwin I. et al. (eds) A History of Atmospheric CO2 and Its Effects on Plants, Animals, and Ecosystems. Ecological Studies (Analysis and Synthesis), vol 177. Springer, New York, NY.

C. D. Keeling, S. C. Piper, R. B. Bacastow, M. Wahlen, T. P. Whorf, M. Heimann, and H. A. Meijer, Exchanges of atmospheric CO2 and 13CO2 with the terrestrial biosphere and oceans from 1978 to 2000. I. Global aspects, SIO Reference Series, No. 01-06, Scripps Institution of Oceanography, San Diego, 88 pages, 2001.

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Data Used:
Mauna Loa CO2 monthly mean data also referred to as: Trends in Atmospheric Carbon Dioxide
Observed Data - NOAA and Scripps
Dr. Pieter Tans, NOAA/GML ( and Dr. Ralph Keeling, Scripps Institution of Oceanography (
Note: While we identify the data sets used in these visualizations, we do not store any further details nor the data sets themselves on our site.

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GCMD keywords can be found on the Internet with the following citation: Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version