. CO₂ absorbs infrared radiation emitted by the Earth.
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Yes. CO₂ absorbs infrared radiation emitted by the Earth.
This happens because the CO₂ molecule can vibrate, and during these vibrations its electrical structure changes in a way that allows it to absorb specific wavelengths of infrared radiation.
The strongest absorption occurs around 15 micrometers (µm), which corresponds to thermal radiation emitted by the Earth's surface.
This phenomenon is known in physics as Infrared absorption.
What happens after CO₂ absorbs radiation?
After absorbing energy, two things can occur:
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Collisions with other air molecules (mainly nitrogen N₂ and oxygen O₂).
During these collisions the absorbed energy can be converted into heat. -
The CO₂ molecule can also re-emit infrared radiation.
This process is known as Radiative emission.
The re-emitted radiation is released in all directions:
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upward (toward space)
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downward (back toward Earth's surface)
Why does this create the greenhouse effect?
This mechanism produces what is called the Greenhouse effect.
In simplified steps:
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The Sun heats the Earth.
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The Earth emits energy as infrared radiation.
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CO₂ and other greenhouse gases absorb part of this radiation.
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They then re-emit it in all directions, including back toward the surface.
Because of this, some of the energy that would escape to space is redirected back toward the Earth–atmosphere system, increasing the overall heat retained.
Is the statement “CO₂ does not absorb radiation, it only passes it on” correct?
It is incomplete.
A more accurate description is:
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CO₂ first absorbs infrared radiation.
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Then it releases the energy again by:
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emitting infrared radiation
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transferring energy to other air molecules through collisions.
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Without the absorption step, the process would not work.
✅ In short
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CO₂ absorbs infrared radiation.
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It then re-emits the energy or transfers it to other molecules.
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This process contributes to the greenhouse effect.
If you want, I can also explain a very interesting point in atmospheric physics: why even a small concentration of CO₂ (about 0.04% of the atmosphere) can still significantly affect the Earth's radiative balance.