Four hundred parts per million

Image: The Keeling Curve

economist.com - May 11th, 2013

Charles D. Keeling, mostly known as Dave, was a soft-spoken, somewhat courtly man who changed the way people and governments see the world. A slightly aimless chemistry graduate with an interest in projects that took him out into the wild, in 1956 he started to build instruments that could measure the proportion of carbon dioxide in the atmosphere, a scientific topic which, back then, was barely even a backwater. In 1958, looking for a place where the level of carbon dioxide would not be too severely influenced by local plants or industry, he installed some instruments high up on Mauna Loa, a Hawaiian volcano.

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