Timeline for Why is radiative forcing from $\rm CO_2$ logarithimic and not a decreasing exponential?
Current License: CC BY-SA 4.0
12 events
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| Feb 9, 2023 at 7:41 | history | edited | J.G. | CC BY-SA 4.0 |
Added missing $-$ signs in exponents
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| Oct 17, 2019 at 12:39 | comment | added | Alan Rominger | ok, sure, it's still model data but uses the full spectrum instead of the baby model here. I don't have an accurate idea of how different actual measurements would be, but I didn't expect any major departure. | |
| Oct 15, 2019 at 16:40 | comment | added | Livid | "And people have, of course, pointed out that the real behavior doesn't exactly follow this model. Here is some real data. I found it to look surprisingly logarithmic. Source" Which curve do you think is real data? It looks like all model output to me: agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/98GL01908 | |
| Aug 12, 2019 at 13:05 | comment | added | Alan Rominger | I meant for Ψ(lambda) to be a function - the function in the graph. When I said "specific to the thermal distribution", I'm trying to wave away other influences. The function is specific to the atmospheric conditions (exactly how much I don't know), including temperature, and this is a very abstract discussion. | |
| Aug 12, 2019 at 9:11 | comment | added | Diger | Unfortunately the link doesn't work anymore. What do you mean by "but I really mean the cross section specific to the thermal distribution of the CO2 molecules"? Isn't the optical thickness $\tau=C \sigma \, L$ with some length $L$? I'm not why your crosssection $\Psi$ is the coefficient of to concentrations? What "cross-section" do you mean? Obviously not cm$^2$. | |
| Aug 23, 2011 at 23:06 | vote | accept | Alan Rominger | ||
| Aug 23, 2011 at 16:09 | comment | added | Omega Centauri | Full computer simulation is what I meant, by using a radiation transport code (on a model of the atmosphere). The lineshape arguments like most back of the envelope arguments, are useful for building intuition, not so much for final results. | |
| Aug 23, 2011 at 11:54 | comment | added | Alan Rominger | @Omega I've read the "first order" claim before, and I imagine it comes from the Taylor series. As in, you could add the 2nd and 3rd order terms. But I feel like that doesn't address the other assumptions either. I feel like the full solution would be to just discretize the cross section as a function of wavelength and apply attenuation. Then again, I wonder why blackbody radiation from the atmosphere itself isn't considered and I feel like a full computer model would be needed for that. But I'm just rambling at this point. | |
| Aug 23, 2011 at 11:49 | history | edited | Alan Rominger | CC BY-SA 3.0 |
add comparision
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| Aug 22, 2011 at 22:09 | comment | added | Omega Centauri | I believe that covers the basic physics, its the line shapes that lead at first order to a log dependence of forcing. Of course the planetary scientists and climatologists, run more sophisticated radiation transport models, and have curves for forcing versus concentration (which does depend upon other atmospheric components as well). These curves can be fit to forcing versus log of concentration, and are roughly linear in the earth climate relevant zone. I believe the forcing is known to roughly 10%. | |
| Aug 22, 2011 at 20:37 | history | edited | Alan Rominger | CC BY-SA 3.0 |
small note
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| Aug 22, 2011 at 20:29 | history | answered | Alan Rominger | CC BY-SA 3.0 |