Carbon dioxide in atmosphere reaches landmark level

At 400 parts per million, greenhouse gas concentration is now higher than it has been for millions of years

May 10, 2013 at 5:43 pm - More than 2 years ago

On May 9, the atmosphere above Hawaii’s Mauna Loa volcano reached a milestone: For the first time since record keeping began there in 1958, the daily mean carbon dioxide concentration reached 400 parts per million.