Dave,

Gravity is not at all the same as an enclosure with fixed volume. It’s also a constant. When temperature changes, the height of the atmosphere at a given pressure changes, but the pressure at the surface doesn’t change (at least to a first approximation), as it would if the volume were fixed. If anything, the pressure would decrease slightly with increasing temperature because the force of gravity decreases slightly with altitude.

Physicists use the constant volume partial differential equations for thermodynamics because they’re simpler (more elegant). Chemists use the constant pressure equations because those apply to the way chemical reactions are usually run, open to the atmosphere.

]]>Sorry – I know this was long ago but the DeWitt reply is something that others seem to confuse. DeWitt states “Planetary atmosphere remember. There are no enclosures” This is both true and false. There is no physical enclosure, but there is gravity acting as a force creating a sort of flexible enclosure. So as far as I understand, you are correct Jerry – when you heat an atmosphere, V and P are variables that will respond to maintain PV=nRT. Proponents of the gas law explaining an atmosphere’s temperature all seem to misunderstand that this formula is about how these variables relate – not how the gas got its energy. But I struggle to articulate this.

]]>Mark and NK: If you go to the Modtran website, you will find that no plausible change in stratosphere ozone will have any effect on DLR.

NK, I didn’t understand much about this paper. In Figure 1 and 2, the changes in reflected SWR and LWR are -0.10 and -0.021W/m2/yr. (Negative values for heat lost by the climate system to space.) If these are SWR and LWR feedbacks to warming over the past four decades (roughly 0.02 K/yr), dividing gives SWR and LWR feedback parameters of -5 and -1 W/m2/K! That would make ECS about 0.5 K/doubling, so something may be wrong.

Looking at the amount of noise in the LWR channel, the slope could easily +/-50%, so this data is not inconsistent with the conventional view that LWR feedback is about -2 W/m2/K (-3.2 W/m2K from Planck feedback plus +1.1 W/m2/K from WV+LR plus weakly positive cloud LWR feedback). LWR has increased from about 237.5 in 1980 to 238.3 W/m2 in 2017 with a STD of about 2.5 W/m2.

If SWR feedback is positive the slope of the reflected SWR vs. time plot in Figure 1 would have to be negative, not positive. SWR feedback is conventionally believed to be about +0.5 to +1.0 W/m2/K. This is way off. However, the spike is reflected SWR is about right (3-4 W/m2) for Pinatubo in 1993 and smaller for El Chichon in 1982. Reflected SWR has grown from about 103 W/m2 in 1980 to 107 W/m2 in 2017 with the value in any 2 hour period varying by +/-5 W/m2.

One hint about the nature the problem is that the data taken every 2 hours was transformed to induce stationarity. This process must have removed the seasonal 8 W/m2 increase in LWR associated with summer in the NH. There are regular seasonal changes in reflected SWR due to the 7% increase in SWR arriving in NH winter in the due to the elliptical nature of the Earth’s orbit and snow cover in the NH winter.

The other thing worth remembering is MERRA is a re-analysis product – changing sources of observations proceeded through a climate model to produce a best fit to all of the data. There are questions about Paltridge’s paper about re-analysis data showing humidity in the upper troposphere falling with time. It would be nice if this data were “right”, but I’m not expecting it to be.

]]>Mark writes: You have just given the ātop of atmosphereā explanation again, with which I am familiar. Nullius repeated this above. I quite like that one. It took me a couple of weeks of mulling before I spotted the obvious flaws. So at least it[ās a bit of an intellectual challenge!”

A lot of words have been written above, so the “obvious flaws” you spotted aren’t clear to me. Could you please be kind enough to copy and paste the key passages above describing those flaws in a reply?

What is clear is that, if the rate of radiative cooling to space across the TOA slows and the rate of incoming SWR remains, then the law of conservation of energy demands that it warm somewhere below the TOA until incoming and outgoing radiation are again in balance.

Mark also wrote: PS, you donāt need to take a Schwarzschild Equation out of context and fudge the variable to prove that upper atmosphere emits less radiation than the surface. Itās a lot colder up there (because of the gravity induced lapse rate), so of course it emits less.

I didn’t take Schwarzschild’s Equation out of context – I am applying it to the real context, our atmosphere is it really is today. While Schwarzschild’s Equation is used to calculate radiative fluxes between grid cells in an AOGCM, it can not predict temperature anywhere that convection also transfers a significant amount of heat – in other word in the troposphere. Temperature is an INPUT used in the B(lambda,T) term to calculate how radiation changes in intensity. The other input is the density of GHG(s) – n. The OUTPUT from Schwarzschild’s Equation is a CHANGE in radiative flux, not any prediction about temperature – such as why it is colder in the upper atmosphere.

As you correctly note, it is colder in the upper troposphere. This is mostly, but not solely, because the atmosphere is unstable to buoyancy-driven vertical convection, where the local lapse rate exceeds a moist adiabatic [gravity-dependent] lapse rate. However, as in noted in my first comment, temperature is never the result of a single mechanism of heat flux – it is the net result of all mechanisms. The word “adiabatic” in “moist adiabatic lapse rate means with no gain or lost of heat (for example, by radiation), which isn’t the case in the troposphere. What we observe on the average is close to a moist adiabatic lapse rate because heat transfer by convection is often significantly faster than by radiation.

Furthermore, at wavelengths in the atmospheric window (ca 800-1000 cm-1), the coldness of the upper troposphere has no effect on outgoing radiation, which has the same intensity as it did leaving the surface.

]]>NK, good find. The extra DSR is probably because of ozone depletion.

]]>Well lets make the target object no bigger than that small area of the focus spot of radiation. Then the target object is hotter than the source, not necessary the sun. As SoD says, transfer from cold to hot is not outlawed . He calls outlawing that is “imaginary”. Therefore temperature higher at the target than the source from focused radiation is not outlawed. What do you think.

]]>Dinero,

Sorry, it doesn’t work that way. For example, you can’t achieve a higher temperature than the sun’s visible surface by simply focusing sunlight on an object. Period. The part you missed is that the object focused on radiates in all directions while only a small fraction of the area being radiated to has a higher temperature.

]]>It may be around 0,8 W/m2. And DSR (shortwave radiation) has increased much more, about 3,6 W/m2. As seen from figures in a paper : Analyzing changes in the complexity of climate in the last four decades using MERRA-2 radiation data. Alfonso Delgado-Bonal et al 2020.

All the change of DLR can be attributed to change of DSR and perhaps some surface warming, which is attributed to change of clouds. A conclusion that can be drawn is that change of CO2 has no effect on back-radiation, in the real world. Or can it be another explanation?

Frank, thanks for the time and trouble. You have just given the “top of atmosphere” explanation again, with which I am familiar. Nullius repeated this above.

I quite like that one. It took me a couple of weeks of mulling before I spotted the obvious flaws. So at least it[‘s a bit of an intellectual challenge!

PS, you don’t need to take a Schwarzschild Equation out of context and fudge the variable to prove that upper atmosphere emits less radiation than the surface. It’s a lot colder up there (because of the gravity induced lapse rate), so of course it emits less.

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