Numerous records now show how we humans are altering the planet, with potentially global consequences for climate. But the first and now iconic examples of documenting global climate change were the precise measurements of the concentration of carbon dioxide in the atmosphere made at the mountain station on Mauna Loa, Hawaii, by Charles David Keeling. If the world today realizes that it has a problem and needs to curb emissions of greenhouse gases, it in large part owes this knowledge to Keeling s painstaking efforts. Keeling was born in Pennsylvania in 1928, and studied chemistry and isotope geochemistry in Chicago. After completing his PhD, in 1953 he moved to the California Institute of Technology, and became interested in the problem of measuring levels of CO_2 in the atmosphere. Before that time, the prospect that levels of atmospheric CO_2 could be altered on a global scale because of the burning of coal, gas and oil was largely theoretical. At the end of the nineteenth century, Svante Arrhenius and Arvid Hogbom had suggested that temperature might be affected by greenhouse gases. But the possibility of increasing atmospheric CO_2 was of no concern because the ocean was believed to absorb most of any increase.
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