"Carbon dioxide in the atmosphere was measured at just above 400 parts per million on Thursday, the highest daily average ever recorded at the flagship Mauna Loa station.
Preindustrial levels of carbon dioxide, as measured in ice bubbles, tended to oscillate between 180 and 280 p.p.m."
Full NYT story:
http://www.nytimes.com/2013/05/11/science/earth/carbon-dioxide-level-passes-long-feared-milestone.html
