First, most of the carbon dioxide in the atmosphere has been removed and laid down as limestone sediments and fossil "fuels".
(most of the carbon dioxide in the atmosphere; has been removed; T:First) (most of the carbon dioxide in the atmosphere; laid down; as limestone sediments and fossil "fuels)
most of the carbon dioxide in the atmosphere most of the carbon dioxide in the atmosphere
has been removed laid down
T:First
as limestone sediments and fossil "fuels