Tweeting as CO2 passes 400 ppm

On May 9, 2013, the daily average from the Mauna Loa observatory exceeded 400 parts per million for the first time since measurements began in 1958, and most likely, for the first time in human history. Scientists and press officers at the Scripps Institution of Oceanography who oversee the measurements decided to mark this milestone with a Twitter campaign that raised awareness far and wide. Learn more at EARTH Magazine.

The Mauna Loa record of atmospheric CO2 since 1958. http://keelingcurve.ucsd.edu/
The Mauna Loa record of atmospheric CO2 since 1958. http://keelingcurve.ucsd.edu/