cafeamericainmag.com
There has been a lot of CW discussion on climate change. This is an article written by someone that used to strongly believe in anthropogenic global warming and then looked at all the evidence before arriving at a different conclusion. The articles goes through what they did.
I thought a top-level submission would be more interesting as climate change is such a hot button topic and it would be good to have a top-level spot to discuss it for now. I have informed the author of this submission; they said they will drop by and engage with the comments here!
Jump in the discussion.
No email address required.
Notes -
Your linked post mentions nothing about adiabatic lapse rate nor how it can explain Venus' temperature being much higher than would be predicted from blackbody equilibrium. Care to explain in detail what you mean?
The linked post is meant to show that using Venus to corroborate a model is foolish, as that same reasoning was used to predict it had the same temperature as Earth. It provides just as much support to any more modern theory, namely, none at all.
For an adiabatic lapse rate on Venus description see: https://youtube.com/watch?v=_4KG0-2ckac ,
After admonishing me for comparing model predicted temperatures of Venus to observation, you link me to a video where the adiabatic lapse model is compared to observations, asserts without independent evidence that this fully explains venus' surface temperatures, and what's more tries to generalize this to earth. This is unsound logic by your own argument.
In any case, I would appreciate it if you would explain your position to me in text, here, rather than sending me links. Or at least provide additional commentary along with the link. After watching that video I am no closer to understanding how adiabadic lapse rate results in surface temperatures in excess of blackbody nor why I should favor this over the greenhouse effect.
Sure. The grand canyon is a good starting point. The temperature at the bottom of the canyon is hotter than at the top. Why is that? It's not due to the greenhouse effect. It's due to earth's adiabatic lapse rate.
Essentially, gravity pulls air in the atmosphere downwards, doing work to compress it, which increases its pressure and temperature. The hotter air then starts expanding and rising (being displaced by the cooler air being brought down), which causes it to cool and decrease in pressure. This is an ongoing process. Notably, it has nothing to do with any radiative properties of the atmosphere (i.e. the greenhouse effect). It can be calculated from basic values of the mass of air and gravity: https://phys.libretexts.org/Bookshelves/Thermodynamics_and_Statistical_Mechanics/Heat_and_Thermodynamics_(Tatum)/08%3A_Heat_Capacity_and_the_Expansion_of_Gases/8.08%3A_Adiabatic_Lapse_Rate .
The lapse rate is essentially the same on Venus as on Earth, and as Venus's atmosphere is thicker than Earth, the lapse rate has a longer way to go, resulting in a higher temperature increase. It must be noted the pressure on Venus's surface is 90x that of Earth's.
The blackbody calculation presumes no atmosphere and thus no adiabatic lapse rate. The presence of an atmosphere and gravity introduces this mechanism by which work is done, heating the air as it compresses and gets close to the surface. It explains the tropospheric temperature gradient and, it must be re-iterated, has nothing to do with any radiative properties of the air. Any atmosphere, even one without any greenhouse gases whatsoever, would have this feature.
The question then is: as the adiabatic lapse rate explains the grand canyon temperature difference, why would it not also explain the temperature difference between the surface and the effective blackbody temperature? It must be noted the effective temperature of Earth (255K, -18C) is indicative of the average amount radiated by an entire column of surface plus atmosphere above. As we've established there must be a gradient due to the lapse rate, the average of this column must necessarily be somewhere in the middle. Below is hotter, above is cooler.
No, sorry, a rhetorical question is not an argument. For the second time, you are still doing the thing you accuse your opponents of: positing that some effect is explained fully by your own pet model without providing any independent evidence that it does so.
Are you or are you not trying to rule out that radiative heat transport is a significant factor in atmospheric temperature?
If you neglect radiative heat transport then atmosphere temperature can only ever be less than surface temperature, which is blackbody.
On the other hand, if you include radiative heat transport, then you must acknowledge that different gasses have different absorption/emission spectra and so their behavior cannot necessarily be compared on 1-1 ( or equal density) basis.
By saying so you are endorsing the point of the article, which is that this isn't sufficient evidence. I agree. I would certainly never advocate spending trillions of dollars on global projects on this basis without doing further research. Yet that's precisely what the climate alarmists want us to do with their "pet model"s.
And trillions is not an exaggeration! "Without creating the conditions for the massive engagement of the private sector, it will be impossible to move from the billions to trillions that are needed to achieve the SDGs.", said by the Secretary General of the UN in 2023: https://www.un.org/sg/en/content/sg/statement/2023-01-18/secretary-generals-remarks-the-world-economic-forum .
Until then, I can just point out that we have two mutually exclusive explanations, that can't both be right, and insufficient experimental evidence to say which is the correct one. Further on the GHE side of it we have a supposedly powerful physical effect with no experimental (and thus causal) proof that it exists (despite all other physical effects being able to be demonstrated experimentally, even gravity with the Cavendish experiment). And on the adiabatic lapse rate side of it we have rock-solid proof that this is how Earth's atmosphere actually does operate (it does have a lapse rate, the dry rate and moist rates essentially perfectly line up with the rates computed from first principles, etc) and thus it must necessarily also operate in Venus's atmosphere (as physics is universal and works the same everywhere).
Hmm... so obviously the only way the Earth as a system loses energy is to space via radiation. The "effective temperature" isn't actually a physically real temperature but rather the temperature corresponding to a hypothetical blackbody that would have the same emission as the average radiative emission of Earth to space. And obviously an entire column of surface plus air above it, is what will as a whole be radiating to space.
The question of whether the radiative heat transport warms the surface past the blackbody temperature is separate from the above considerations.
You're leaving out the entire rest of the atmosphere: conduction, convection, water, moisture, latent heat, phase changes, winds, adiabatic lapse rate, etc. etc.
The moon's effective blackbody temperature is the same as Earth's, -18C. Yet it gets to +120C during the day and -120C at night. It's both much hotter and much colder than Earth and than the effective blackbody temperature.
The entire atmosphere participates in the redistribution of this heat, to be cooler during the day and warmer at night. Not just the tiny percent that absorbs and emits infrared radiation.
By neglecting all that and leaving only one option, radiation, of course your thoughts will naturally be directed towards assuming and thus believing that it must account for everything. But you leave out all the rest.
Not to mention that by considering the effective blackbody temperature, you're considering an average and also neglecting the fact that there's day and night, that the Sun warms the planet more on its day side than night side, etc.
Their non-radiative effects can be. All that is needed for adiabatic lapse rate is to have mass, heat capacity, and gravity. CO2 accomplishes this as well as any other gas.
As to what effect the differing radiative properties have (which differing properties they do have), that is indeed what's under discussion here.
As far as I can see, you still have not given any explanation for how the lapse rate effect can result in temperatures far in excess of blackbody (day/night temps being irrelevant since we are interested in average temperatures)
Take a packet of gas that starts at the surface, rises to its maximum height, and then falls back to the surface. Initially it will be in equilibrium with the surface temperature. If the gas does not absorb or emit significant radiation, then it will have the same temperature at the end of the round trip as the start. There is still no mechanism by which the gas packet temperature would exceed the surface temperature nor by which surface temperature would exceed blackbody.
If a packet of gas does not exchange (absorb or emit) significant energy via radiation then the "whole column of air" will not transfer energy to space.
The day & night is relevant here. The sunlight has the potential to heat the ground to over 100ºC (212ºF). The reason it doesn't get that hot is because the ground conducts heat to the air, which then convects upwards. So the sunlight, during the day, has the power to heat the surface far above the blackbody average.
Then, you just need to compare temperatures at differing elevations to see that the adiabatic lapse rate has a real effect on the temperatures you find there. Compare bottom of grand canyon to top of grand canyon to high up on a mountain-top. The air pressure at all of these levels is, of course, higher than the air pressure would be without an atmosphere, which is zero.
So we know for a fact that gravity causing increased air pressure results in higher temperatures than those found at lower air pressures. This is observable, empirical, and irrefutable. I wrote some more detail about the lapse rate here: https://www.themotte.org/post/960/the-vacuity-of-climate-science/205320?context=8#context .
The atmosphere, thus-warmed during the day, then prevents the night-time temperatures from getting as cold as they do without an atmosphere (-100ºC on the moon), much like how a blanket works.
The net effect of the above is evidently that it is cooler during the day than without an atmosphere, warmer at night than without an atmosphere, and the 'average' temperature is overall higher than without.
This is a misunderstanding. Blackbody temperatures are often reported as global averages, which is why the moon daytime high is above the "blackbody temperature" -- because the average blackbody temperature includes the night side. You can do the Stefan boltzmann calculation for the day side of the moon. You will find that the daytime blackbody temperature is about 400k, which is very close to the measured daytime surface temperatures.
This is the part that you still have not shown. I would appreciate it if you would do just the thermodynamics 101 energy balance calculation to show the effect.
A packet of air on the surface on the day side will perhaps pick up energy from the surface. This warms the air, but also cools the surface. If this packet of energy is moved to the night side, it will deposit it's energy onto the surface; the surface will warm and the packet will cool. This tends to equalize temperatures between day and night sides but cannot provide a net increase in temperature (of sum of day and night side) due to conservation of energy. The global average temperature is still blackbody (day side being warmer than global average blackbody and the night side being colder).
No, the blanket analogy is invalid. If the gas is transparent to radiation, then it provides no barrier to radiative heat transport from the surface. In fact, the presence of a gas would reduce the insulating effects because it provides a conductive/convective path away from the surface (vacuum being the best insulator).
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link
More options
Context Copy link