Climate change alert: Global carbon dioxide tops 400 ppm for first time

The first time an atmospheric carbon dioxide concentration of above 400 parts per million was measured was in the Arctic in 2012. That same threshold was reached at the National Oceanic and Atmospheric Administration’s Mauna Loa Observatory in Hawaii in 2013. And now, NOAA reports the monthly global average concentration of the greenhouse gas has surpassed 400 parts per million for the first time. This isn’t good. In fact, the last time it happened was up to 5 million years ago.  Read more at http://www.washingtonpost.com