31 May 2012: C02 Milestone Reached
As Levels Hit 400 PPM Across Arctic

For the first time in at least 800,000 years, atmospheric concentrations of carbon dioxide have crossed the threshold of 400 parts per million (ppm), with stations across the Arctic recording these record levels, the Associated Press reports. Global concentrations have hit 395 ppm, but in recent months levels of carbon dioxide in the atmosphere surpassed 400 ppm in the Arctic because of the lack of CO2-absorbing vegetation in the Far North in winter and spring. Pre-industrial levels of CO2 were about 280 ppm, and numerous scientists said that hitting the 400 ppm threshold was a worrisome sign that industrial society continues to emit planet-warming greenhouse gases at an alarming rate. Jim Butler, global monitoring director at the National Oceanic and Atmospheric Administration’s Earth System Research Lab in Colorado, called the new high a “troubling milestone.” Carnegie Institution ecologist Chris Field, a leader of the Intergovernmental Panel on Climate Change, said, “It is an indication that we’re in a different world.” Levels exceeding 400 ppm have been recorded this spring in Alaska, Greenland, Norway, and Iceland.