<p>I'm trying to understand the atmospheric greenhouse effect. If CO2 absorbs lots of IR radiation emitted from the Earth's surface, does it not also shield the same wavelength radiation that is coming from the sun? Would this shielding not have a 'cooling' effect. Does CO2 block incoming IR from the sun?</p>

<p>What is the ratio of energy absorbed by atmospheric CO2 from IR coming from the Earth vs directly from the Sun?</p>

CC BY-SA 4.0
2019-07-02T11:07:50.240Z
The whole point is that the incoming (non IR) wavelengths coming in are reradiated as IR. I'm voting to close this as a duplicate because that other question (though different) has your [answer](https://earthscience.stackexchange.com/a/4602/595).
Jan Doggen
CC BY-SA 4.0
2019-07-02T12:21:07.667Z
the infrared radiation from the sun is shortwave infrared and is not stopped by the atmosphere,the earth emits infrared radiation in longwave radiation and a lot of this gets absorbed and radiated back to the suface of earth(the atmosphere behave like a hi pass filter in infrared)
trond hansen
CC BY-SA 4.0
2019-07-02T13:06:44.157Z
I find it unlikely that the sun provides no IR in the same wavelength as CO2 absorbs. I'm trying to understand the relative scale between Earth CO2 IR back radiation and Sun direct CO2 wavelength IR radiation.
Andy
CC BY-SA 4.0
2019-07-02T14:16:58.490Z
@Andy you can take a look here http://agron-www.agron.iastate.edu/courses/Agron541/classes/541/lesson09a/9a.3.html to see the composition of sunlight.
trond hansen
CC BY-SA 4.0
2019-07-02T14:37:56.043Z
this is the part reaching the ground,most of the UVA reaches the ground and some of the UVB reaches the ground but no UVC-UVX reaches the ground,and as you can see shortwave ir reaches the ground but little longwave ir are able to reach the ground.
trond hansen
CC BY-SA 4.0
2019-07-02T16:32:46.820Z
As others have noted, there is very little long-wave IR energy coming from the sun.  What little there is, however, does not cause a cooling effect.  It gets absorbed by the CO2 in the atmosphere just as outgoing radiation would be, and is thus a heating effect.  Once that energy is absorbed it reradiates both downward and upward.
Mark
<co2><greenhouse-gases>
What is the ratio of energy absorbed by atmospheric CO2 from IR coming from the Earth vs directly from the Sun
Andy
# What is the ratio of energy absorbed by atmospheric CO2 from IR coming from the Earth vs directly from the Sun

(Asked by: username_0 on 2019-07-02)

I'm trying to understand the atmospheric greenhouse effect. If CO2 absorbs lots of IR radiation emitted from the Earth's surface, does it not also shield the same wavelength radiation that is coming from the sun? Would this shielding not have a 'cooling' effect. Does CO2 block incoming IR from the sun?

What is the ratio of energy absorbed by atmospheric CO2 from IR coming from the Earth vs directly from the Sun?

**Tags:** co2, greenhouse-gases

> **Comments:**
> **username_1**: The whole point is that the incoming (non IR) wavelengths coming in are reradiated as IR. I'm voting to close this as a duplicate because that other question (though different) has your [answer](https://earthscience.stackexchange.com/a/4602/595).  
> **username_2**: the infrared radiation from the sun is shortwave infrared and is not stopped by the atmosphere,the earth emits infrared radiation in longwave radiation and a lot of this gets absorbed and radiated back to the suface of earth(the atmosphere behave like a hi pass filter in infrared)  
> **username_0**: I find it unlikely that the sun provides no IR in the same wavelength as CO2 absorbs. I'm trying to understand the relative scale between Earth CO2 IR back radiation and Sun direct CO2 wavelength IR radiation.  
> **username_2**: @username_0 you can take a look here http://agron-www.agron.iastate.edu/courses/Agron541/classes/541/lesson09a/9a.3.html to see the composition of sunlight.  
> **username_2**: this is the part reaching the ground,most of the UVA reaches the ground and some of the UVB reaches the ground but no UVC-UVX reaches the ground,and as you can see shortwave ir reaches the ground but little longwave ir are able to reach the ground.  
> **username_3**: As others have noted, there is very little long-wave IR energy coming from the sun.  What little there is, however, does not cause a cooling effect.  It gets absorbed by the CO2 in the atmosphere just as outgoing radiation would be, and is thus a heating effect.  Once that energy is absorbed it reradiates both downward and upward.  

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