July 15, 2015

Scientists estimated global average carbon dioxide concentration at 397.2 parts per million (ppm) in 2014, as the global growth rate of carbon dioxide continues to accelerate. 

July 13, 2014

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.