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2. On average, what percentage of the Earth's atmosphere by volume consists of carbon dioxide?

Carbon dioxide exists at an average concentration of about 390 parts per million in the Earth's atmosphere, according to monthly reports by National Oceanic and Atmospheric Administration. Prior to the Industrial Revolution, it existed in concentrations of 278 ppm.

Carbon dioxide exists at an average concentration of about 390 parts per million in the Earth's atmosphere, according to monthly reports by National Oceanic and Atmospheric Administration. Prior to the Industrial Revolution, it existed in concentrations of 278 ppm.

Carbon dioxide exists at an average concentration of about 390 parts per million in the Earth's atmosphere, according to monthly reports by National Oceanic and Atmospheric Administration. Prior to the Industrial Revolution, it existed in concentrations of 278 ppm.

Carbon dioxide exists at an average concentration of about 390 parts per million in the Earth's atmosphere, according to monthly reports by National Oceanic and Atmospheric Administration. Prior to the Industrial Revolution, it existed in concentrations of 278 ppm.

NASA/Reuters/File
(Read caption)

About 4 percent

 

About 0.4 percent

 

About 0.04 percent

 

About 0.004 percent

 
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