what percentage of atmosphere is co2
The Earthâs atmosphere is 78 percent nitrogen, 21 percent oxygen and 1 percent other gases, including about 0.04 percent carbon dioxide.And yes, Earthâs CO2 concentration stood at 400 parts per million in May 2015.Earthâs CO2 levels have been increasing in recent decades due to human activities and also natural factors, and some estimates say as little as 3 or 4 percent of carbon dioxide in the atmosphere is due to humans.nd yes, Earthâs CO2 concentration stood at 400 parts per million in May 2015. Earthâs CO2 levels have been increasing in recent decades due to human activities and also natural factors, and some estimates say as little as 3 or 4 percent of carbon dioxide in the atmosphere is due to humans.