homo sapiens
pgleick | December 4, 2013Just to provide a little perspective, here are the latest data and a graph on atmospheric carbon dioxide, with information going back 800,000 years. Present day is on the far right ("You are here"). The data come from the atmospheric monitoring program of the Scripps Institution of Oceanography, La Jolla, California and can be found here.
I've also noted the approximate period when homo sapiens first appeared -- thought to be around 150,000 to 200,000 years ago. During all human existence, pre-industrial levels of CO2 never exceeded around 275 parts per million (ppm). They touched 400 ppm…