There is some merit to the understanding of Greenhouse Gases. A greenhouse works, right?
The frequency of light is different in the two scenarios you describe. White light, composed of many high frequencies, from the Sun can penetrate atmospheric CO2, though much of the lower frequency infrared cannot. When it strikes the Earth, it warms it and the Earth emits a lot of infrared. This can, now, not easily escape the CO2 in the atmosphere. The result is greater warmth.
Of course, these dimwits are lying about the magnitude of this effect and the necessity of atmospheric CO2 to life, I believe. Like COVID they use a juvenile understanding of a subject and the endless energy of their jaws to see if they can get others to work for them.
Thanks for the info about frequency. That makes sense.
There is ten times more of water vapors in the atmosphere than carbon dioxide and its ability to trap solar heat reflected from the Earth surface (heat capacity) is several times higher than the one of said carbon dioxide. Which means the effect of carbon dioxide of trapping solar energy is minuscule comparing to the same effect coming from the water vapors. Now, try to regulate the content of water vapors in the atmosphere having all world oceans surrounding the continents where humans live. These people (of Greta Thunberg variety) are just uneducated morons, and their hockey sticks are symbols of their idiocy.