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Global Greenhouse Gas Levels Reach Historic Milestone

Carbon emissions continue to increase to new record levels as atmospheric carbon dioxide levels breach the 400 parts per million mark for the first time, having increased by 27% since the late 50s. This is the highest concentration of CO2 the planet has experienced for at least 800 millennia!

When the history of humanity's struggle to combat climate change is written, few characters will play as prominent a role as Charles David Keeling. A geochemist, Keeling developed an accurate method of measuring CO2 in the atmosphere, and in 1958 began recording background levels of the gas at the Mauna Loa Observatory in Hawaii.

That was the start of the famous Keeling Curve, which has tracked the steady rise of atmospheric carbon dioxide. Those levels have soared from 315 parts per million when Keeling began, to a grim milestone reached last week, as atmospheric concentrations exceeded 400 parts per million.

Keeling's son, Ralph, is now the director of the California-based Scripps CO2 Program, which was founded by his father and which recently launched a Web site designed to let the public follow the unsettling rise in carbon dioxide emissions. In an interview with Yale Environment 360 senior editor Fen Montaigne, Ralph Keeling discusses his father's work, reflects on the meaning of CO2 levels climbing higher than they've been in at least 800,000 years, and expresses hope that crossing the 400 ppm mark may play a role in awakening the public to the dangers of runaway climate change. "Bringing about change requires people to be aware of what's going on," said Keeling