atmospheric CO2
pgleick | May 10, 2013The planet has passed a disturbing landmark, a marker on a continuing highway to climate disruption. On May 9th, the NOAA and the Mauna Loa observatory reported that atmospheric CO2 levels touched 400 parts per million. Before humans started burning fossil fuels, they were around 280 parts per million.
Mauna Loa measurements of carbon dioxide. From http://keelingcurve.ucsd.edu/
The last time atmospheric CO2 was at 400 parts per million was during the ancient Pliocene Era, three to five million years ago, and humans didn’t exist.
Global average temperatures were 3 to 4 degrees C warmer…