Scripps Institution of Oceanography, La Jolla, CA

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Lessons for long-term earth observations

Charles David Keeling directed a program to measure the concentrations of CO2 in the atmosphere that continued without interruption from the late 1950's through the present. This program, operated out of Scripps Institution of Oceanography, is responsible for the Mauna Loa record, which is almost certainly the best-known icon illustrating the impact of humanity on the planet as a whole. Lessons can be learned about making long-term measurements based on the experiences of this program.

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The idea of making measurements at Mauna Loa arose while Charles David Keeling was a post-doc at Cal Tech. In the course of working on a project involving carbon in river water - a project that incidentally required making measurements of CO2 in air - Charles David Keeling made a key discovery. What he discovered was that when he sampled the air remote from forests, cities, and other obvious sources or sinks for CO2, he always got almost the same value of 310 ppm. Previous measurements of CO2 in the atmosphere did not show such constancy, but these measurements had been made by wet chemical methods that were considerably less accurate than the dry manometric method he was employing. This postdoctoral experience taught him two key lessons that were to guide his entire career: (1) that the earth system might behave with surprising regularity, and (2) the necessity of making highly accurate measurements to reveal that regularity.