LiveScience: The proportion of carbon dioxide in the atmosphere is set to break 400 parts per million this month, levels not seen in 3 million years, according to one of the best climate records available.
The Keeling Curve, a daily record of atmospheric carbon dioxide, has been running continuously since March 1958, when a carbon dioxide monitor was installed at Mauna Loa volcano in Hawaii. On its first day, the observatory measured a carbon dioxide concentration of 313 parts per million (ppm). That number...