Question

Gases that comprise >99% of your atmosphere are not greenhouse gases, but CO2 is considered to be a greenhouse gas. Why?

Answer 1

The earth’s atmosphere is composed of a variety of gases–in fact, 99% of the Earth’s atmosphere consists of two gases: nitrogen ( N2), which makes up 78%, and oxygen (O2) whichaccounts for 21%. The other 1% is a mix of argon, neon, ozone, carbon dioxide, water vapor, methane and other trace gases .

The energy from the sun travels to the earth in the form of electromagnetic waves and warms it up. The earth in turn cools itself off by radiating long wavelengths of thermal radiation back to space. Certain gases in the atmosphere absorb these outgoing electromagnetic waves. This is very important; with no such greenhouse gases, the planet would be a giant ice ball with an average temperature of -18 ̊ Celsius, or 0 ̊ Fahrenheit. Life as we know it would not exist! The greenhouse gases are able to absorb the thermal radiation and send some of the energy back down to earth. But why are some gases able to do this and others not? It turns out that a molecule that has the capability of vibrating in different ways can absorb different wavelengths. It then can emit heat back to warm the earth.

In CO2 moleuclae , carbon atom is in the middle with a slight positive charge and there is an oxygen atom on each side with a slight negative charge. (O=C=O). Due to this structural arrangment it can vibrate in different direction and ultimatly absorb different wavelengths which finally emits to the earth.