Age: The world's carbon dioxide levels are on the cusp of reaching 400 parts per million in the atmosphere for the first time in 3 million years.
The daily CO2 level, measured at the Mauna Loa Observatory in Hawaii, stood at 399.72 parts per million last Thursday, and a few hourly readings had already risen above 400 parts per million.
''I wish it weren't true, but it looks like the world is going to blow through the 400 ppm level without losing a beat,'' said Ralph Keeling, a geochemist at the...