Here's an interesting paper on longwave (infrared) radiation in the Earth's atmosphere:
Does Surface Temperature Respond to or Determine Downwelling Longwave Radiation? L. R. Vargas Zeppetello, A. Donohoe, D. S. Battisti, 19 February 2019.
It's open access.
Here's the abstract:
Downward longwave radiation (DLR) is often assumed to be an independent forcing on the surface energy budget in analyses of Arctic warming and land-atmosphere interaction. We use radiative kernels to show that the DLR response to forcing is largely determined by surface temperature perturbations. We develop a method by which vertically integrated versions of the radiative kernels are combined with surface temperature and specific humidity to estimate the surface DLR response to greenhouse forcing. Through a decomposition of the DLR response, we estimate that changes in surface temperature produce at least 63% of the clear-sky DLR response in greenhouse forcing, while the changes associated with clouds account for only 11% of the full-sky DLR response. Our results suggest that surface DLR is tightly coupled to surface temperature; therefore, it cannot be considered an independent component of the surface energy budget.
What this means, I think, is that you can't calculate forcings just from greenhouse gas concentrations with something do simple like this for temperature change.
I know I've done this in the past.
Anyway I just discovered this paper so I haven't read it yet. I'm looking forward to it. I don't know how or if this affects climate models. I'm guessing not, since they deal with radiation physics (etc.) from first principles.
4 comments:
Perhaps you should think of the relationship between DLR and surface temperature as an equilibrium. All else being equal the amount of DLR depends on the amount of emitted surface radiation. Change one and the other responds.
Both surface temperature and DLR are also responsive to other forcings.
If increased water vapour increases high cloud, DLR increases and surface temperature follows.
If decreased pollution decreases albedo surface temperature increases and DLR follows because the surface emits more radiation.
Increased CO2 increases DLR which increases the radiation reaching the surface and hence surface temperature.
Thus forcing which affect DLR then influence surface temperature. Forcing which directly influence surface temperature will then influence DLR.
The author of that paper has a really nice article about some who misread the point of his paper. He writes, " A strong feedback between surface temperature and downwelling longwave radiation does not mean that carbon dioxide emissions have no impact on the longwave component of the planetary energy budget. In fact, just the opposite is true: The strong feedback means that greenhouse emissions can have a substantial effect on longwave radiation."
https://eos.org/opinions/dont-at-me-what-happened-when-climate-skeptics-misused-my-work
Thanks a lot for the link, Scott.
Thanks EM.
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