The concentration of carbon dioxide in the atmosphere on Dec. 15 was 399.26 parts per million (ppm). The level for Dec. 14 was 398.09.
One year ago = 396.30.
1958 = 318
800,000 years ago = 260
In April, May, and June of 2014 the level exceeded 400 ppm, highest in almost one million years.
Readings are taken daily at the Mauna Loa Observatory in Hawaii for the Scripps Institution of Oceanography. Go to https://scripps.ucsd.edu/programs/keelingcurve/
