The Earth's atmosphere is 78 percent nitrogen, 21 percent oxygen and 1 percent other gases, including about 0.04 percent carbon dioxide. And yes, Earth's CO2 concentration stood at 400 parts per million in May 2015.
How much carbon dioxide is in the air?
Oxygen and carbon dioxide. The Earth's early atmosphere is believed to have been mainly carbon dioxide with little or no oxygen gas. The Earth's atmosphere today contains around 21 percent oxygen and about 0.04 percent carbon dioxide.
What is the current concentration of carbon dioxide in the atmosphere?
The global concentration of carbon dioxide in the atmosphere – the primary driver of recent climate change – has reached 400 parts per million (ppm) for the first time in recorded history, according to data from the Mauna Loa Observatory in Hawaii.