According to Wikipedia he was a factor of 10 out, but around 100 times higher (4%) is still a very significant increase, no?
"Concentrations of CO2 in the atmosphere were as high as 4,000 parts per million by mass (ppm) during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years."
