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Home » 2013 State of the Climate: Carbon dioxide tops 400 ppm

2013 State of the Climate: Carbon dioxide tops 400 ppm

The annual average concentration of carbon dioxide (CO2) in the atmosphere stood at 395.3 parts per million (ppm) in 2013—a 27 percent increase compared to conditions before the Industrial Revolution. On May 9, 2013, the daily average concentration of CO2 surpassed 400 ppm for the first time at the Mauna Loa Observatory in Hawaii.

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