Climate Change Milestone - 400ppm

For homo sapiens, the epochal news is that CO2 levels in the atmosphere have exceeded 400 parts per million for the first time in human existence, which continues a 200-year rise that is now accelerating. [Guardian]

Hourly readings above 400ppm have been recorded six times in the last week, and on occasion, at observatories in the high Arctic. The Mauna Loa station, sited at 3,400 m and far away from major pollution sources in the Pacific Ocean, has been monitoring levels for more than 50 years and is considered the gold standard.

"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. At this pace we'll hit 450 ppm within a few decades," said Ralph Keeling, a geologist with the Scripps Institution of Oceanography which operates the Hawaiian observatory.

Keeling Curve