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
CO2 unprecedented rate of increase  (WMO 2017)
1 June 2020 Atmospheric CO2 highest in 23 million years 
Why are CO2 emissions highly cumulative
​ in the atmosphere?​
VIDEO Scripps animation record of atmospheric CO2,
​800,000 year ago to 2019

NOAA ESRL
Greenhouse gas concentrations
November 2021
​417 ppm mean.