Professional Paper 1386–A
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Figure 4. Graph of the “Keeling Curve,” the instrumental record of the measurement of the concentration of carbon dioxide (CO2) in the Earth’s atmosphere at the Mauna Loa Observatory, Hawaii from 1958 (313 ppm) to 2009 (390 ppm). From figure at National Oceanic and Atmospheric Administration (NOAA) Web site: [http://www.esh.noaa.gov/gmd/ccgg/trends/co2_data_mlo.html].