Climate – crossing a line

From the New York Times, a record high measurement of carbon dioxide in the atmosphere.

Carbon dioxide in the atmosphere was measured at just above 400 p.p.m. for the 24 hour period ending at 8 p.m. E.D.T. on Thursday, the highest daily average ever recorded.

Prehistoric levels of carbon dioxide, as measured in ice bubbles, tended to oscillate between 180 and 280 p.p.m.