Climate scientists blame the high temperatures on Venus on the greenhouse effect.
Given that Venus surface receives very little sunlight, and that nights there are months long with no drop in temperature, it is absurd to compare the Venusian climate to a greenhouse.
Venus has a similar lapse rate to Earth, despite a very different atmospheric composition. This shows that the lapse rate is due to the pressure gradient, not the atmospheric composition.
I like Miatello’s discussion. Venus has no water vapor.
What is pressure gradiant due to ?
The weight of the atmosphere above it.
and is that not a function of the atmospheric composition. ?
“What is the force per unit area that is always applied perpendicularly to a surface as determined by a planet’s gravitational force in combination with the total mass of a column of gas above a location?”
It’s more a function of quantity. Yes, the molecular weight of the Venusian atmosphere is higher than ours, but the amount of material is what matters here. Surface pressure on Venus is ~93 bar but its gravity is lower at ~8.9 m/s² or 90% of Earth’s so Venus just has a LOT more gas in its atmosphere. In a few billion years the solar wind will have stripped a lot of it away and that pressure will drop as will the temperature.
All of the planets in the solar system with thick atmospheres have a tropopause at 0.1 bar pressure (Mars is the exception because it does not get to 0.1 bar).
The atmospheric temperature at the tropopause/0.1 bar of all the other planets is the effective radiating temperature of that planet (solar radiation/4*(1-Albedo)/5.67E-8)^.25. Below that, the atmospheres warm up at relatively the same rate as the atmospheric pressure rises. The composition of the gases at the atmosphere does not seem make any difference.
It should be a physics principle since it appears to be universal. It is just the way gases emit and absorb energy. It is a basic physical property.
http://astrobites.org/2013/12/31/unifying-planetary-atmospheres/
http://www.nature.com/ngeo/journal/v7/n1/full/ngeo2020.html
I should have added that, above the tropopause, the composition of the gases does matter to the temperature profile but that is probably just a boundary condition. At more than 0.1 bar pressure, temperature is governed by a lapse rate. Below 0.1 bar pressure, specific absorption wavelengths matter more.
On these sort of threads in general…
Mainstream science is defined by tight specialization. In fact that’s pretty much the case in the mainstream of all fields. This leads to big blind spots. It’s the result of requiring degrees, licenses, peer approvals, and so on to be in these fields.
Of course none of these things stop people from teaching themselves. These people come from other fields. They see the glaring blind spots because they have a much broader knowledge.
To see Venus accurately requires someone to have interest in a variety of fields. The narrowly defined experts can’t get it right because they are ignorant of the other pieces. This is another problem with state intellectuals, they are commonly very narrow in their knowledge. And since this society requires titles of authority for everything, we can forget about having this rule by experts to ever work. The experts are just that, experts with a narrow focus who make interventions that just make for other problems because they are incapable of seeing the bigger picture, the larger system, the actual scope of the complexity involved.
Very well said. I’ve always believed that was the reason why so many fundamental discoveries were made during the Renaissance… an educated man was expected to understand science and music, engineering and poetry, mathematics and farming. I had about 12 college “majors” at 6 schools in my youth from music to engineering. I’d do double majors, ignore the filler courses and take all the specific core classes and then move on to another subject. I figured the more you knew about a wide variety of subjects, the easier any of them would be. It took forever to get my first degree, but I got a pretty good education out of it.
“Of course none of these things stop people from teaching themselves. These people come from other fields. They see the glaring blind spots because they have a much broader knowledge. ”
How true. And sometimes they cannot see a few hidden simplicities, not complexities, staring them in the face when it comes to other thick atmospheres present in out solar system showing that particular composition matters little.
Amen! The Venusian lapse rate and temperatures from the one bar altitude up closely mirrors that of Earth’s atmosphere. Why this key fact does not register with the Venusian “runaway greenhouse effect” crowd is a mystery. Greenhouse gases and grey body aerosols certainly have a role in the Venusian atmosphere by radiating heat to space but the torrid surface temperature if primarily a function of the atmospheric mass.
I understand how compression creates heat. Not sure I understand how steady state pressure causes heat.
The stratosphere of Venus has an anomalous (negative) temperature gradient. The other six bodies in our solar system have positive temperature gradients in their stratospheres.
What causes the anomalous gradient on Venus? You guessed it………..the high concentration of CO2:
http://www.nature.com/ngeo/journal/v7/n1/abs/ngeo2020.html
I am trying to reproduce Robinson & Catling’s work on the Venusian atmosphere using Finite Element Analysis. Already it is clear why radiative transfer processes in the troposphere guarantee a negative lapse rate equal to -g/Cp. Once the pressure reaches ~0.5 bar the atmospheric absorption is proportional to the pressure squared, rendering the lower atmosphere essentially opaque in most of the thermal Infra Red.
As a result, attempts to map Venusian geology based on the emissivity of surface rocks have proved difficult. (Direct thermal IR emission from the surface peaks at around 4 microns).
If my (multi-layer) FEA model performs decently it will be a simple matter to add cloud layers that are lacking in the R&C model.
IWhen you say “Already it is clear why radiative transfer processes in the troposphere guarantee a negative lapse rate equal to -g/Cp.”, can you explain how one may see this clarity? Is there a common quantifiable CO2 dependent explanation for the lapse rates of Earth and Venus?
From the abstract:
” However, it is not obvious why the tropopause occurs at the specific pressure near 0.1?bar. Here we use a simple, physically based model to demonstrate that, at atmospheric pressures lower than 0.1?bar, transparency to thermal radiation allows short-wave heating to dominate, creating a stratosphere. At higher pressures, atmospheres become opaque to thermal radiation, causing temperatures to increase with depth and convection to ensue. ”
If the opacity of CO2 is the reason, shouldn’t we expect its partial pressure to be the point of commonality? Why would an atmosphere with 90+% CO2 to share a common pressure with one having <0.05% CO2?
A ballon filled with a breathable atmosphere from Earth would float above Venus at an altitude where the pressure is 1 bar and the temperature is similar to Earth surface temp.
http://orbitalvector.com/Venus/Venus%20Airships/VENUS%20AIRSHIPS.html
Reblogged this on Centinel2012 and commented:
Its my understanding that Hansen’s climate change theories are based on his work that height Carbon Dioxide levels on Venus are the sole reason that Venus is so hot (not with standing that hot women are cool) and that he translated that into the situation here on earth. Its also my understanding that the upper atmosphere where this “heat” was supposed to appear isn’t getting hot; so that would seem to me to dis create the whole concept?