The CO2 molecule vibrates. As a matter of fact, it vibrates in three different ways. As it vibrates, it absorbs and emits the radiant heat (energy) of our sun as it reaches our earth, and it does so very well and very efficiently … That’s just what it does.
The CO2 molecule is composed of three atoms: one atom of carbon (C) and two atoms of oxygen (O). Hence CO2, carbon dioxide (“di” refers to “two”).
The carbon and oxygen atoms move around each other and interact with each other at different frequencies. Each different way of moving around constitutes a vibration mode.
In one vibration mode, with the oxygen and carbon atoms interacting at a certain frequency, the CO2 molecule attracts and absorbs the energy (radiant heat) of the sun. Just the way a magnet might attract a paper clip.
As the molecule absorbs the energy of the sun, it switches into another vibration mode, moving faster. In this faster vibration mode, with the carbon and oxygen atoms interacting at another frequency, the energy of the sun is emitted. Think of two magnets, repulsing each other.
This is a very good thing. Without the presence of these little CO2 factories doing their work day in and day out, absorbing and emitting the radiant heat (energy) of our sun, our planet would be a frozen ball of ice.
These little CO2 factories do their work well and efficiently. That’s just what they do. The more of them there are in the atmosphere, the more radiant heat is absorbed and emitted into the air all around all of us.
See:
“What is Infrared?” | Jim Lucas, Live Science, 26 March 2015
“Carbon Dioxide Absorbs and Re-emits Infrared Radiation” | UCAR Center for Science Education
“Molecules Vibrate” | UCAR Center for Science Education
“John Tyndall” | Wikipedia
“Introduction to Structure Determination; Infrared: Introduction” | Prof. Adam Bridgeman, School of Chemistry, The University of Sydney, 2017.