The Diagonal Comparisons that underpin 'Climate Science'

The very cornerstones of Climate Science are two Diagonal Comparisons.

[To give examples:

FAIR COMPARISON: women's current wages in the UK -vs- men's current wages for similar work. This means something. If there is a difference, it needs explaining and maybe action needs to be take to level up.

DIAGONAL COMPARISON: nominal women office workers' wages in 1982, not adjusted for inflation -vs- Premier League footballer wages in 2022. That would be a Diagonal Comparison and of no relevance to anything.

You have to measure and calculate things as accurately as you can and then compare like-with-like i.e. changing only one variable, or as few as possible.]

Unfortunately for me, you have to be well versed in the Climate Science belief system (which I am) to know what I am talking about. And most of the well versed are of course Believers who just believe it all; the Sceptics mainly quibble about the finer details and don't look at the very foundations of the belief system. I can but do my best...
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Here goes. From RealClimate.org ("Climate Science from Climate Scientists...").

Diagonal Comparison #1

33 ºC is the difference between the mean surface air temperature of the planet and the blackbody radiating temperature (i.e. the temperature a blackbody would need to radiate at to be in equilibrium with the incoming solar radiation given an albedo of about 0.3) ["effective temperature"]. So far so good.

They define the true meaning of "effective temperature" in parentheses and correctly calculate Earth's effective temperature at 255K. What they do not mention is that this a hypothetical value only! It is only a very rough indicator of the actual temperature of "the surface" (cloud cover and that part of the sea and land that is cloud-free)*. You have to make several adjustments to work out the likely actual temperature.

They pretend however that 255K is a reliable indicator. They then compare 255K with the measured temperature of one part of "the surface" (at sea level) which is 288K. Hey presto, 33 degrees of Greenhouse Effect!

The 255K calculation, while correct in an abstract sense, is wildly inappropriate as a basis for comparison. Unless you are prepared to make on one or more of the assumptions that:
- clouds, sea and land have 100% emissivity. This is the biggest one, the overall weighted average is more like 80% emissivity, which would get adjusted effective temp. up to about 270K (reducing the 33 degrees by half). That's why they refer obliquely to 'blackbody' (which means 100% emissivity) instead of saying "assuming 100% emissivity", which would have people asking "Why assume anything? Why not use actual emissivity if it's relevant?", and/or
- clouds are at sea level, and/or
- clouds, sea and land are all the same temperature, and/or
- clouds, sea and land are all a uniform pale blue colour with albedo 0.3, and/or
- clouds don't exist (even though their existence reduces albedo and hence reduces effective temp), and/or
- there is no lapse rate, and/or
- without 'greenhouse gases' there would be no lapse rate, and/or
- without 'greenhouse gases' there would be less cloud cover and/or cloud altitude would be lower.
None of those assumptions is in any way correct, they are all reality-denying nonsense.

The obvious flaw with the 255K vs 288K comparison is that it not comparing like-with-like. Effective temperature is based on "what does the planet look like from space?". What you see from space is two-thirds clouds with patches of cloud-free sea or land. So when you calculate effective temperature, you are estimating the weighted average temperature of "what you can see from space", which is clouds and cloud-free sea and land.

The bulk of sea and land which are beneath clouds most of the time are irrelevant here, they could be pitch-black in colour with zero albedo - that wouldn't affect albedo as seen from space so doesn't affect our spaceman's calculation of effective temperature. Similarly, our spaceman can't tell through his telescope whether the white patches are clouds (low emissivity; unknown altitude) or snow fields (high emissivity) so he knows that his calculation of a planet's effective temperature is only a rough guide to its actual temperature.

The sea surface and land are of course warmer than clouds, because clouds are higher up. So what the Climate Scientists are really saying is "a warm thing is warmer than the average of the warm thing and some cold things, especially if you calculate the average using the wrong method." which is meaningless and irrelevant.

In the table at the end of this post, I refer to the effective temperature calculated the wrong way as B, line 28. Measured sea level temperature is A, line 288.
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This is NOT how you work out 'effective temperature' (if you want to get a meaningful answer). What you do is: take emissivity and topography/altitude into account of all the constituent parts (and ignore sea and land that is below clouds - there is separate more or less closed cycle for this) of "the surface"* and work out what temperature all the constituent parts of "the surface" would have to be to emit as much LW radiation to space as they, in total, absorb from the Sun.

This calculation is a bit tricky, but it's easy enough working backwards from actual temperatures and emissivity of the constituent parts of "the surface"* to see if you get the 'right' amount of outgoing LW. This is the the scientific way. You find that clouds, sea and land are at the required temperature/altitude emit, overall and on average, the right amount of LW (E, line 35 - this is the same as absorbed incoming solar radiation, C, line 22).

So there is no discrepancy between actual temperatures and effective temperature, if you calculate effective temperature correctly and make a fair comparison, like-with-like. There is no 33 degree difference to explain away; it's not even 8 degrees, it is +/- nothing. Sea/land surface has to be warmer than expected to emit more LW than first expected to compensate for the fact that clouds are as warm as expected (257K, line 5 vs 255K, line 28) BUT have low emissivity and so emit less LW than first expected. The overs and unders cancel out. So when our spaceman lands and finds that the sea level surface of the planet is warmer or colder than he calculated from afar, he is not too surprised.

Diagonal Comparison #2

While that is one way to assess the strength of the basic greenhouse effect, another one is measure the amount of long wave radiation from the surface that is absorbed in the atmosphere (by greenhouse gases incl. water vapour, clouds, aerosols, etc.). That is currently about 150 W/m2 and would be zero with no greenhouse effect at all.

They are comparing upwelling LW from sea and land, assuming 100% emissivity (D, line 33 = 390 W/m2) with C, line 22, 240 W/m2. There is, unsurprisingly, a 150 W/m2 difference. They say "Look! GHG's are trapping or blocking 40% of outgoing LW. This is what is heating the planet.". To be fair to this lot, they do mention clouds, which are actually responsible for all the absorbing they try to blame on 'Greenhouse Gases'.

Two-thirds of that hypothetical 390 W/m2 LW emitted at sea level (D, line 33 - they should be using 367 W/m2 at line 34, but hey) hits the underside of clouds and is either absorbed by the clouds or reflected back down. What gets to space is the weighted average of what clouds emit upwards and what the cloud-free sea or land emits (E, line 35), which is exactly the same as incoming solar (C, line 22)*.

So again, this is like saying "a warm thing emits more LW than the average LW emitted by the warm thing and some cold things, especially if you overstate the LW emitted by the warm thing and ignore the existence of the cold things" i.e. meaningless and irrelevant.
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* I put an asterisk after "the surface" as this is a very important concept. Imagine a freshly made sponge cake, still warm from the oven that has just had some icing applied (I think you are supposed to let the sponge cool down first, but I'm in a hurry... to find an analogy). The main sponge part = sea or land. Two-thirds of the cake's surface is covered in icing = the clouds. "The surface" of the Earth cake is two-thirds icing and one-third exposed sponge. Whatever heat exchange there is between the sponge and icing is irrelevant as far as the outside world (space) is concerned. For the cake to cool down, all that matters is the LW which is emitted by the exposed (non-iced) sponge and the icing. Including the LW radiation hypothetically emitted by the covered part of the sponge is insane and insanely stupid.

On Venus, the high temperature of the sponge (hard surface) is irrelevant as it is all covered with a thick layer of icing (clouds). The temperature of the upper parts of the clouds is pretty much the same as the calculated effective temperature. There is a separate set of rultes to reconcile temperatures as between hard surface and clouds and there is no 'Greenhouse effect', let alone a 'runaway Greenhouse Effect' on Venus. On Mars, there is barely any icing (a few low altitude dust clouds) so although there is more CO2 per m2 on Mars than there is water vapour and CO2 added together on Earth, there is little or no Greenhouse Effect on Mars.
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Here is my list of assumptions and summary workings in case anybody want to check. This is all the coherent bits of actual information and proper phsyics that I have pieced together from blogs and articles by 'Climate Scientists'. They can't deny that they have said all this, although they do when it suits them.

Click to enlarge/read more clearly.