What a load of crap. During the Permian extinction about 250 MM years ago CO2 was at around 3000 ppm. At the Jurrassic/Cretaceaous extinction we were still at around 2000ppm – that’s the time when giant dinos stomped earth. CO2 levels during the last 500 Million years were almost always higher than now. Very low CO2 concentrations like now are very exceptional in the record.
Last July, the concentration of CO2 in the atmosphere was 408 ppm. In the last 400 million years, a CO2 concentration 300 ppm was considered high.