I am still a bit puzzled because the sun's ir must cause warming but I think I can see how it all fits together now. The first trick, which I had already spotted, was to realise that the earth and sun spectra peak in very different places. The second trick is to realise that 1367 W/m2 go in and come out so the area under the curves at the top of the atmosphere must be the same. That defines the relative amplitudes of the spectra and the temperatures give the shift.
So, yes, I understand that it is constant so shouldn't be a concern but so is visible and that is always the start of the explanation. I suppose it happens because of the emphasis on the CO2 link. But again, from Darwinist's picture (I had already seen it but my eyes are open wider now) the sun still affects the H2O.
I don't know that ignored is the right term. The infrared radiation from the Sun is a different part of the IR spectrum than the infrared radiation from Earth. The Sun's infra-red radiation is near infra-red and is part of the short wave radiation we receive from the Sun.
It is often included in calculations using highly-detailed radiative transfer models. It gets absorbed by CO2 just like infrared from Earth does, so it causes a bit of 'top down' heating of Earth's atmosphere.
Adding more CO2 would in principle boost this 'top down' heating, and it would also increase the amount of heat radiated upwards by CO2. Kind of like the greenhouse effect, but in reverse.
Because of how the Sun sends us relatively little infrared light on average, CO2 causes us to warm up on average because it does a better job of preventing heat escaping from Earth than it does light from the Sun getting in.
Using a blackbody spectral calculator, you can see this:
http://www.spectralcalc.com/blackbody_ca...
Compare the amount between 13-14 micron wavelength with the total across 0-50 microns. Use 288 K for Earth's temperature, and 6000 K for the Sun's.
About 5-6% of Earth's emission is in this band, where CO2 absorption is important. This compares with about 0.005-0.006% of the Sun's spectrum. The heat from the Sun is actually a little less than that emitted by Earth's surface (because the greenhouse effect recycles lots of with the atmosphere), so the absorption of sunlight by CO2 at this wavelength is tiny compared with the traditional greenhouse effect.
The IR from the sun is primarily shortwave, there is very little energy in the longwave IR range that is relevant to greenhouse gases. That part of the solar spectrum that is in the longwave range will warm the atmosphere a little, but the primary source of heating is from the Earth's surface.
You could use Planck's Law and calculate what fraction of the solar radiation is in that range if you like, or you could use the radiance calculator at http://astrogeology.usgs.gov/tools/therm... to make your own plots for the Earth and Sun. If you do, I think you'll find the intensity of solar radiation at greenhouse gas wavelengths is down by several orders of magnitude from its shortwave peak.
EDIT for Jim Z's answer: I don't know what he is talking about, if he read the answers from MTRstudent I'm sure he didn't understand them.
EDIT for your additional details: nobody is making any "assumptions" about how much of the sun's output is visible. We are saying that the emission is peaked in the visible spectrum, but there is substantial energy in the UV and near infrared. There is substantially less energy when you get to the infrared where the greenhouse gase atmospheric absorption bands are. If you use MTRstudent's calculator compare the band radiance between 0-2 micron and 2-100 micron. The spectral radiance from 0-2 is about 16 times greater than that between 2-100.
It forms part of TSI so it would be wrong to say it was ignored. But is there any reason it should be considered separately? As others have said, the amount of solar IR at the wavelengths associated with greenhouse gasses is tiny, and in any case, virtually constant.
If a picture paints a thousand words, then this one paints just about everything we need to know.
http://www.barrettbellamyclimate.com/use...
Edit: re your update; it can be seen from the link above that most of it is transmitted through the atmosphere and would warm the surface in the same way as visible light. There is some absorption by water vapour, but most of the water vapour absorption is from surface radiation rather than solar.
Perhaps someone could correct me if I am wrong, but I'm pretty sure that the distinction between visible and shortwave infrared is an artificial one, presumably based only on the limits of our vision.
It's not. The difference between solar and planetary emissions are longwave vs shortwave not infrared vs ultraviolet. That is energy that travels with a wavelength above 4 micrometers. The Earth emits energy at wavelengths longer than this. There is some overlap but it is a very small portion of the total.
https://www.e-education.psu.edu/natureof...
You seem to be forgetting that greenhouse gases only absorb radiation at specific frequencies (within the longwave spectrum or those frequencies emitted by the Earth).
http://www.chem.arizona.edu/chemt/C21/si...
You'll have to switch between wavenumber and wavelength for the above site.
Those areas where greenhouse gases absorb within the Earth's blackbody emissions curve are what cause the greenhouse effect. There are, of course, other areas where certain greenhouse gases can absorb. For instance, the absorption band associated with CO2 and the greenhouse effect is centered at about 15 micrometers. There also exist two other absorption bands for CO2 as well that are mainly outside of the Earths blackbody emission curve. Different absorption bands are associated with different modes of excitation of the molecule.
It mainly warms the atmosphere, it does warm land surfaces but not as much as the shorter band waves, it's effect over water is negligible, as it can only penetrate a few molecules deep, although it probably stimulates evaporation.
http://commons.wikimedia.org/wiki/File:S... <== solar spectrum.
The largest component is in the visible light range of 400nm to 700 nm (nanometer wave length)
Infrared is over 1000 nm, where solar output drops off dramatically.
I don't know that ignored is the right term. The infrared radiation from the Sun is a different part of the IR spectrum than the infrared radiation from Earth. The Sun's infra-red radiation is near infra-red and is part of the short wave radiation we receive from the Sun.
https://ca.images.search.yahoo.com/image...
And near infra red anything shorter than 3μm.
Because you can't tax it! Simple s that!
About half of the energy radiated by the sun is in the infra red region. Why is this always ignored when people describe the greenhouse effect?
What happens to it? Presumably, it hits the greenhouse gases and causes some warming?
It is not ignored by climate scientists.
Because it can't be taxed.
Jeff, I noticed that it is MTR and Peggy that seem to be forgetting it is absorbed only in certain frequencies and it doesn't matter if if is going down or up.
https://www.google.com/search?q=co2+abso...
http://scottishsceptic.co.uk/2011/03/17/...
My link didn't work quite right for one of the charts. It grabbed the wrong one but the one I wanted is to the right.
It is simple Peg. All IR isn't absorbed. Only a portion of the spectrum is absorbed as you should know.
Here is a link for you not that I think you will understand it.
http://www.climate4you.com/GlobalTempera...
it is not ignored
