State of Our Climate Atmospheric CO2 Concentration
NOAA 10 Mar 2016 'Carbon dioxide levels are increasing faster than they have in hundreds of thousands of years. It’s explosive compared to natural processes'. Today’s human-made CO2 increase is 200 times faster, a dramatic rate compared to natural processes, Pieter Tans, leader of NOAA’s Global Greenhouse Gas Reference Network
Preindustrial concentration (WMO) CO2 278 ppm
At over 400 ppm atmospheric CO2 is the highest in 15-20 million years 2009 A. Tripati Coupling of CO2 ... of the Last 20 Million Years 2013 Yi Ge Zhang A 40-million-year history of atmospheric CO2