The big picture
The big picture

Earth's early atmosphere probably contained lots of carbon dioxide, water vapour and nitrogen, with little or no oxygen. Over geological time, carbon dioxide fell to a tiny fraction of the air, about 0.04% today.
The big picture
The big picture

Earth's early atmosphere probably contained lots of carbon dioxide, water vapour and nitrogen, with little or no oxygen. Over geological time, carbon dioxide fell to a tiny fraction of the air, about 0.04% today.