Question

Approximately 80% of infrared (IR) radiation emitted by Earth is trapped by greenhouse gases, causing the warming of Earth\'s atmosphere known as the greenhouse effect. Even though nitrogen (N2) and oxygen (O2) make up the majority of the atmosphere (~99%), they do not contribute to the greenhouse effect. However, carbon dioxide (CO2) is a major contributor. Why does CO2 contribute to the greenhouse effect, while N2 and O2 do not?

CO2 absorbs ultraviolet radiation escaping from the Earth\'s surface, creating a thermal barrier.

CO2 is capable of absorbing infrared radiation while N2 and O2 are not.

CO2 contributes to the greenhouse effect by absorbing the majority of ultraviolet radiation in the troposphere, trapping heat close to Earth\'s surface.

All infrared radiation is absorbed in the lower atmosphere (troposphere) and does not reach the upper atmosphere (stratosphere) where N2 and O2 exist.

Answer 1

Correct option: B. CO2 is capable of absorbing infrared radiation while N2 and O2 are not.

CO₂ absorbs infrared radiation being emitted by Earth’s surface. As a result, it increases its vibrational energy and gradually lose as IR radiation (heat). The overall effect is that CO₂ traps the IR radiation being lost by the Earth’s surface; and causes warming the Earth’s atmosphere while CO₂ molecules gradually emit IR radiation (for hours) at much longer wavelengths in form of heat.

N₂ and O₂ do not absorb IR in the range that is being emitted by Earth’s surface. Thus, they don’t act as greenhouse gases.    

Heat is only produced when EMR is emitted in form of IR.