Currently, there is too little carbon dioxide in the atmosphere. It is at about 400 ppm and during the Cambrian Period, which was the geological period in which more species of plants and animals were created in the entire history of the planet, levels of carbon dioxide were at 4,500 ppm. The world needs to burn more coal, oil and natural gas to increase levels of CO2 because history shows that the more CO2 there is in the atmosphere, the better it is for plants, animals and humans.