10,000 year ice temperature chart (Greenland)

[blizzard1024]

Go to imgur.com and you should be able to drag-and-drop your image into the upload box. Failing that, goto more repy options and "attach files" is available in the lower right (see below)

[skierinvermont]

Doesn't answer his question.

 

This does:

 

http://www.realclimate.org/index.php?p=142

 

The figures come from Schmidt 2010. 

 

The current greenhouse effect is 33C total. Earth's surface is 33C warmer than it would be without any greenhouse gases. Since the spectral absorption of the various gases overlap, removing any one of them causes the other to compensate. Thus it is impossible to say how much of the greenhouse effect is due to one gas because they all act in concert. One way to measure it is to say how much of the greenhouse effect is removed by removing one gas (this is the minimum % due to this gas). The other way is to say what % of the greenhouse effect remains when one gas is the only gas remaining (this number is the maximum % attributable to this gas). 

 

Removing CO2 removes 36% of the GHE. Removing CO2 removes 9% of the GHE. Removing O3 and other trace gases would remove maybe 5% of the greenhouse effect. 

 

If H2O were the only GHG remaining, 66% of the greenhouse effect would remain. If Co2 were the only gas left 26% of the GHE would remain. 

[FloridaJohn]

 

 "It only absorbs IR radiation in the 15 micron spectral band. It can only have influence at around -50C which is in the upper troposphere, especially

the tropics." 

 

This is BASIC radiative transfer. Look it up on google or in a textbook. 

 

 

Thanks for the help. If it is so basic, I would assume it would be trivial for you to come up with a reference. If it is difficult for you to come up with a reference, then I imagine it would be even more difficult for me, since you apparently know a great deal more about this than me.

 

My question relates more to your statement that CO2 can "only have an influence at around -50C which is in the upper troposphere." From my limited knowledge of this topic, my understanding is that CO2 absorbs and then re-emits the radiation back towards the earth. In other words, preventing it from escaping out ot space. I have not found any reference that says any warming from CO2 can only take place in the troposphere, or that any warming would remain there and not return to the lower atmosphere.

 

Perhaps you can enlighten me on where I am in error. I would prefer an actual explanation with references, not another directive to "look it up myself."

[blizzard1024]

Thanks for the help. If it is so basic, I would assume it would be trivial for you to come up with a reference. If it is difficult for you to come up with a reference, then I imagine it would be even more difficult for me, since you apparently know a great deal more about this than me.

 

My question relates more to your statement that CO2 can "only have an influence at around -50C which is in the upper troposphere." From my limited knowledge of this topic, my understanding is that CO2 absorbs and then re-emits the radiation back towards the earth. In other words, preventing it from escaping out ot space. I have not found any reference that says any warming from CO2 can only take place in the troposphere, or that any warming would remain there and not return to the lower atmosphere.

 

Perhaps you can enlighten me on where I am in error. I would prefer an actual explanation with references, not another directive to "look it up myself."

 

CO2's primary Infrared absorption band is centered around the 15 micron wavelength. Using Wein's Displacement Law which correlates peak blackbody emission at a specific

wavelength to temperatures, the 15 micron absorption band of CO2 corresponds to -50C or about  223K.  Hence CO2 does not have any direct influence on terrestrial temperatures near the Earth's surface except maybe the extreme cold winter air masses like those in Siberia and in Antarctica. But the upper troposphere has temperatures in this range so that is where CO2 increases are expected to have the most influence. Of course warming the upper troposphere without increasing thermal emission to space from more GHGs would in turn warm the lower and middle troposphere. Thus a doubling of CO2, using radiative transfer modeling, comes up with an external positive TOA forcing of about 3.7 W/m2. If you use the Stephan-Boltzmann law, this equates to about 1.2C assuming no feedbacks. It is the feedbacks and hence climate sensitivity where there is so much debate. If the feedbacks are negative, then there would be less than 1.2C warming, if they are positive we see more warming...some studies suggest much more. So, in a nutshell, all reasonable atmospheric scientists believe that some warming occurs with increasing CO2. The question is how much? that is where all the attacks occurs on this forum. If you counter or question the higher climate sensitivities you are labeled a "denier" or worse.  Scientists should always question results especially from computer models. If we have real world observations like from satellites that conclusively show strong positive feedbacks being observed NOW then many more skeptical scientists would not be so skeptical. the atmosphere is way too complicated to believe we have it all figured out.... 

[Vandy]

CO2's primary Infrared absorption band is centered around the 15 micron wavelength. Using Wein's Displacement Law which correlates peak blackbody emission at a specific

wavelength to temperatures, the 15 micron absorption band of CO2 corresponds to -50C or about  223K.  Hence CO2 does not have any direct influence on terrestrial temperatures near the Earth's surface except maybe the extreme cold winter air masses like those in Siberia and in Antarctica.

 

That's not a correct use of Wein's Displacement Law. As you state yourself, the Law describes peak emission wavelength for a certain temperature. But we are talking about absorption by CO2, not emission. I think you may be trying to use Kirchoff's Law here, equating the peak absorption wavelength to the peak emission wavelength. But that's only valid for matter in thermal equilibrium, which isn't the case here. Even worse, the law applies to black-bodies, which absorb all incident radiation regardless of wavelength/frequency. But as the graphs you posted above clearly show, CO2 selectively absorbs at certain wavelengths (unlike Earth and the Sun, which are approximately black-bodies). So we cannot apply Wein's Law to describe its wavelength of peak emission.

[blizzard1024]

That's not a correct use of Wein's Displacement Law. As you state yourself, the Law describes peak emission wavelength for a certain temperature. But we are talking about absorption by CO2, not emission. I think you may be trying to use Kirchoff's Law here, equating the peak absorption wavelength to the peak emission wavelength. But that's only valid for matter in thermal equilibrium, which isn't the case here. Even worse, the law applies to black-bodies, which absorb all incident radiation regardless of wavelength/frequency. But as the graphs you posted above clearly show, CO2 selectively absorbs at certain wavelengths (unlike Earth and the Sun, which are approximately black-bodies). So we cannot apply Wein's Law to describe its wavelength of peak emission.

 

Absorption equals emission via Kirchoff's Law in this case. And the emission that occurs would be equivalent to blackbody emission near -50C. What happens is that with increasing CO2 there is more emission that takes place at -50C which is at a lower temperature. Since there is more emission at a lower temperature there is less emission from the Stefan-Boltzmann law and the whole system has to warm up to achieve equilibrium. That is where the external TOA forcing of 3.7 W/m2 comes from for a doubling of CO2.

[blizzard1024]

Absorption equals emission via Kirchoff's Law in this case. And the emission that occurs would be equivalent to blackbody emission near -50C. What happens is that with increasing CO2 there is more emission that takes place at -50C which is at a lower temperature. Since there is more emission at a lower temperature there is less emission from the Stefan-Boltzmann law and the whole system has to warm up to achieve equilibrium. That is where the external TOA forcing of 3.7 W/m2 comes from for a doubling of CO2.

If you look at this emission spectra, you see that CO2 absorption band is close to a blackbody radiating at around 220-225K or so which is around -50C.  This chart uses wavenumber but 650-700 wavenumber is about 15 microns wavelength. 

[skierinvermont]

Your use of Weins law is obviously incorrect. You're saying that there is no light at 15 microns for CO2 to absorb unless the temperature is -50C. This is obviously false. The surface of the earth emits at all different wavelengths. That's why trees are green. Dirt is brown. The ocean is blue. The desert is yellow. 

[The_Global_Warmer]

For the laymen on this(me)

 

How are tens of thousands scientists wrong and blizzard right?

[blizzard1024]

Your use of Weins law is obviously incorrect. You're saying that there is no light at 15 microns for CO2 to absorb unless the temperature is -50C. This is obviously false. The surface of the earth emits at all different wavelengths. That's why trees are green. Dirt is brown. The ocean is blue. The desert is yellow. 

 

Not it is not. This is a correct use of this law.  You are correct in that all objects emit radiation in all wavelengths. However, the peak radiance at a given wavelength is very very strongly a function of the temperature of the emitting substance. Trees are green because they reflect and scatter visible light and we perceive a green color. They are not emitting in the visible spectrum hardly at all...in fact the emission in that part of the spectrum is negligible at Earth temperatures. Wien's Displacement law is a way of estimating the temperature that correlates to a wavelength of maximum emission in the electromagnetic spectrum. So air molecules that are -50C emit strongest at around 15 microns. That is why the earth radiates primarily in the IR part of the spectrum and the sun radiates in the visible and UV parts. But it is a curve and there is not one single temperature to one single wavelength dependance.  By increasing CO2 in the atmosphere, it increases the absorption of radiation in the 15 micron band which has it maximum emission at -50C. What this does is increase the emission of air at -50C over what it used to be. By the Stefan-Boltzmann law, there is less emission since -50C is colder. Less emission means that the whole system warms up to achieve equilibrium. Hence, a doubling of CO2  =  +3.7 w/m2 of external TOA forcing. Radiative transfer is not my specialty (I only took undergrad and grad courses in it 20+ years ago!!) so if someone has more to offer here please do.

[blizzard1024]

For the laymen on this(me)

 

How are tens of thousands scientists wrong and blizzard right?

What? Read what I posted.... tens of thousands of scientists would agree with this. That is the so-called "settled" part of the science. Doubling CO2 = +3.7 w/m2 TOA external forcing as I state above. What's the issue with this?

[Vandy]

Wien's Displacement law is a way of estimating the temperature that correlates to a wavelength of maximum emission in the electromagnetic spectrum. So air molecules that are -50C emit strongest at around 15 microns. That is why the earth radiates primarily in the IR part of the spectrum and the sun radiates in the visible and UV parts. But it is a curve and there is not one single temperature to one single wavelength dependance.  By increasing CO2 in the atmosphere, it increases the absorption of radiation in the 15 micron band which has it maximum emission at -50C.

 

Again, you are making an elementary mistake here. Wien's Law only applies to black-bodies. CO2 gas is not a black body. Rather, CO2 has an emission spectrum based on its molecular properties and broadening effects typical of gasses. Therefore you can't use Wien's Law to relate the radiative emission of CO2 gas to its temperature.

[The_Global_Warmer]

What? Read what I posted.... tens of thousands of scientists would agree with this. That is the so-called "settled" part of the science. Doubling CO2 = +3.7 w/m2 TOA external forcing as I state above. What's the issue with this?

 

But you think the effects of this are negligible vs what everyone else thinks.

[chubbs]

Blizzard is omitting a few qualitative points. CO2 is realtively effective in absorbing outgoing radiation in the upper atmosphere because it is well mixed unlike water vapor which is concentrated near the surface. Due to GHG relatively little outgoing radiation escapes from the surface most comes from the atmosphere at lower temperature than the surface. Increasing absorption in the upper atmosphere warms the surface since the surface must radiate more to maintain the same outgoing radiation to space. 

[blizzard1024]

Again, you are making an elementary mistake here. Wien's Law only applies to black-bodies. CO2 gas is not a black body. Rather, CO2 has an emission spectrum based on its molecular properties and broadening effects typical of gasses. Therefore you can't use Wien's Law to relate the radiative emission of CO2 gas to its temperature.

 

Ok. Forget about Wien's law. The Earth's surface radiates close to a blackbody and CO2's main absorption band is at 15 microns. We can agree on that. If you look at an emission spectra above the Earth you will see the 15 micron absorption band from CO2 which correlates to around 225K or so (near -50C). Thus it is absorbing and emitting radiation at -50C. By increasing CO2 you get more emission at -50C. Since you have more emission at a lower temperature than before with added CO2, you get less total emitted energy via Stefan Boltzmann law (sigmaT4). Thus the whole earth system warms up due to this imbalance. This is calculated to be 3.7 w/m2 for a doubling of pre-industrial CO2 levels. Using S-F law, this equals around 1.2C assuming no feedbacks. This will only be negligible if feedbacks are only small positive or negative. This is where all the debate is. The feedbacks. 

[blizzard1024]

Blizzard is omitting a few qualitative points. CO2 is realtively effective in absorbing outgoing radiation in the upper atmosphere because it is well mixed unlike water vapor which is concentrated near the surface. Due to GHG relatively little outgoing radiation escapes from the surface most comes from the atmosphere at lower temperature than the surface. Increasing absorption in the upper atmosphere warms the surface since the surface must radiate more to maintain the same outgoing radiation to space. 

thanks