Friday, 12 June 2020

Next chapter - the desert's day/night energy budget

The Consensus has no explanation as to why the 'Greenhouse Effect' is actually negative during the day - the surface is a lot cooler than it would be without any atmosphere (or 'greenhouse gases') whatsoever; but at night, the 'Greenhouse Effect' is larger than what they say it is (average 33 C at the Earth's sea level) even though there's no radiation coming in from the Sun.

It's impossible to disprove their basic logic by comparing predictions with outcomes because they keep bolting bits on (like the pre-Copernican model of the Solar System), with the end result that there isn't any coherent logic to disprove (believe me, I have tried working backwards from the IPCC's Global Energy Budget and couldn't reconcile it between day and night).
So that's today's chapter of my never-to-be-published book. Instead of trying to make sense of The Consensus, let's see if we can explain it using common sense and basic physics/maths and see where that gets us (like Copernicus starting again from scratch, rather than tweaking things by adding yet another concentric circle).

1. The sensible assumption is that the atmosphere acts like a blanket, it is warmed up by day (while shielding what is beneath it from the extreme highs) and gives off/loses that stored warmth by night. (An Economy 7 heater does the opposite). And that would be correct, but we shouldn't take analogies too far, so let's do the numbers. See caveats/footnote*.

2. We set up our spreadsheet again and type in the variables to predict hard surface temperatures for the Moon and a desert at the Equator on Earth, just to make sure we have used the right equations and get sensible answers. The Moon can get a bit hotter than 108 C, but its day is much longer, so that looks about right.

3. But deserts do not all warm to 73 C - that's the clue bat! The typical/average day time temperature is 32 C (the highs can be higher), this works backwards to 500 W/m2 being received/emitted. At night the deserts cool to just above freezing (the lows can be lower), which works backwards to 328 W/m2. Those 328 W/m2 aren't coming from the Sun (it's night time), they are coming from/being emitted to the boundary layer. That gives us a typical diurnal temperature variation of 30 C and total average W/m2 received/emitted of 828 W/m2 over 24 hours. (To use two fancy new phrases I learned recently).

4. When the sun is directly overhead a dry desert at the Equator, total 1,380 W/m2 is coming in (Joules per second per m2), of which 40% is reflected (albedo = 0.4), leaving 828 W/m2 to be absorbed/stored as warmth. The hard surface absorbs 60% (500 W/m2) and the boundary layer absorbs 40% (328 W/m2), so it all reconciles very nicely (after some trial and error).

5. As you can see, we do not need to add or subtract any 'back radiation' from 'greenhouse gases' - and why go looking for something if there is no evidence for it? We do not need to distinguish between conduction, convection and radiation or worry about whether or not air can absorb/emit infra red. And it's the dry desert, so we don't need to worry too much about the Latent Heat of Evaporation/Condensation either. We just need to apportion the total energy budget (828 W/m2) sensibly between hard surface and boundary layer; between day and night; between warming and cooling (etc etc, it's all a bit circular) to get sensible answers.

Here are the workings for you to reverse engineer and check. 32C and 2C are highlighted yellow to show they are my assumptions, the maths then follows as sure as night follows day...

* Caveats/footnote

As a separate topic, the Real Greenhouse Effect warms the surface overall - and cools the upper atmosphere. That has to do with the vertical energy distribution (aka 'lapse rate') and not the day-night difference, which is what we are considering here.

The Real Greenhouse Effect is only about 18 K, not the much vaunted 33 K, because if you assume no atmosphere (and no 'greenhouse gases'), there would be no clouds either, which would bring down Earth's overall albedo from 0.3 to 0.1 - two-thirds of the visible surface would be oceans with albedo 0.06 and one-third dry land with albedo 0.18, average 0.1. The lower albedo would mean an effective (and likely actual) temperature of 270 K (a bit higher then on the Moon because of lower albedo). Compare this with actual average temperature (with atmosphere and clouds etc) of 288 K = Real Greenhouse Effect 18 K.

The equilibrium vertical energy distribution takes time to establish and maybe it never is. "Weather" is just the atmosphere's way of trying to attain that equilibrium and its work never ceases. Here we are just looking at a 24-hour period in isolation; focusing on the difference between day and night temperatures rather than absolute temperatures; and making the simplistic assumption that the lower troposphere is warmed from the ground upwards and both cool in tandem, which is true on a short timescale.