Question

Why are oxygen and nitrogen not called greenhouse gases?

Answer 1

• The ability to absorb and re-emit infrared energy is what makes CO₂ an effective heat-trapping greenhouse gas. Not all gas molecules are able to absorb IR radiations.
• Nitrogen and Oxygen, which makes up more than 90% of the earth’s atmosphere, do not absorb infrared radiations.
• Oxygen and Nitrogen aren’t greenhouse gases and neither are any diatomic molecules (gas molecules composed of two atoms).
• The absorption of infrared by gases occurs in molecules with a “dipole moment” these are molecules which can vibrate in a way that allows them to absorb infrared, but diatomic molecules don’t have a dipole moment and are consequently transparent to infrared.