# Percentage Carbon Dioxide in Earth's Atmosphere

Not Reviewed
CO_2_"ATM" = 0.039 %
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MichaelBartmess.Percentage Carbon Dioxide in Earth's Atmosphere
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32aedaed-d497-11e3-b7aa-bc764e2038f2

This constant defines the typical volumetric percentage of Carbon Dioxide present in a sample of the Earth's atmosphere.  Dry air by volume contains the following major constituents:

• 78.09% nitrogen
• 20.95% oxygen
• 0.93% argon
• 0.039% carbon dioxide

The amount of water vapor contained in air is on average 1% but varies.  (Humidity is a pain; gotta love Colorado.)