LA Times: The ratio of carbon dioxide in Earth's atmosphere is flirting with 400 parts per million, a level last seen about 2.5 million to 5 million years ago, according to the Scripps Institution of Oceanography at UC San Diego.
The Institution this week launched a daily Keeling curve update, showing the saw-toothed upward diagonal of rising carbon dioxide levels since the late 1950s.
Isolated measurements have peaked at above 400 parts per million in the Arctic, but scientists are more alarmed at steady...