Why atmospheric MASS, not radiation? Part 2

Be sure to read Part 1 first, now …



DEFINING THE rGHE THROUGH THE ERL.

How is the rGHE defined in the most basic way? If you have a planet with a massive atmosphere, the strength of its “greenhouse effect” is defined as the difference between its apparent planetary temperature in space and the physical mean global temperature of its actual, solid surface. The planet’s apparent temperature in space is derived simply from its average radiant flux to space, not from any real measured temperature. It is assumed that the planet is in relative radiative equilibrium with its sun, so is – over a certain cycle – radiating out the same total amount of energy as it absorbs.

If we apply this definition to Venus, we find that the strength of its rGHE is [737-232=] 505 K. Earth’s is [288-255=] 33 K.

The averaged planetary flux to space is conceptually seen as originating from a hypothetical blackbody “surface” or ‘radiating level’ somewhere inside the planetary system, tied specifically to a calculated emission temperature. This level can be viewed as the ‘average depth of upward radiation’ or the ‘apparent emitting surface’ of the planet as seen from space. Normally it is termed the ERL (‘effective radiating level’) or EEH (‘effective emission height’).

The idea behind the ERL is pretty straightforward, but does it accord with reality? The apparent planetary temperature of Venus in space is 231-232K, based on its average radiant flux, 163 W/m2. Likewise, Earth’s apparent planetary temperature in space is 255K, from its mean flux of 239 W/m2. In both of these cases, the planetary output is assumed to match its input (from the Sun), so one ‘simple’ method one could use to derive the apparent temperature of a planet is by taking the TSI (“solar constant”) at the planet’s (or moon’s) particular distance from the Sun, and multiply it with 1 – α, its estimated global (Bond) albedo, a number that’s always <1, finally dividing by 4 to cover the whole spherical surface. Determining the average global albedo is clearly the main challenge when going by this method. The most common value provided for Venus is 0.75, for Earth 0.296.

But does the resulting value really say anything about the actual planetary temperature? If the planet absorbs a mean radiant flux (net SW) below its ToA, then how this flux affects the overall system temperature very much depends on the system’s total bulk heat capacity. If it is large, the flux will have little effect, if it’s small, the flux will have a bigger effect.

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Why atmospheric MASS, not radiation? Part 1

And so finally we have reached the stage where we will explain why the atmospheric insulating effect is inherently a ‘massive’ one and not a ‘radiative’ one. The answer is quite intriguing, maybe even a bit surprising to some, the solution rather subtle in many respects. I have settled for two posts, but could probably have written several, considering the bewildering amount of different aspects in some way or other pertaining to this whole issue.

I hope you can bear with me on what might seem like a rather repetitive style of writing in this first post. I have only done so in a humble attempt to punch through the basic idea presented, which might at first come off as a novel or unfamiliar one to most people.

The second post is more lengthy, gradually winding its way towards the final resolution. When reading it, always bear this first one in mind.

I will most likely at some point publish a (strongly) condensed version of these posts. However, their content and interconnected nature might take time to digest.

OK. Let’s begin …



TO NECESSITATE > TO ENABLE > TO CAUSE


In his ‘Physics Today’ feature article of January 2011, “Infrared radiation and planetary temperature”, Raymond T. Pierrehumbert stated the following about the proposed rGHE surface warming mechanism:

An atmospheric greenhouse gas enables a planet to radiate at a temperature lower than the ground’s, if there is cold air aloft. It therefore causes the surface temperature in balance with a given amount of absorbed solar radiation to be higher than would be the case if the atmosphere were transparent to IR. Adding more greenhouse gas to the atmosphere makes higher, more tenuous, formerly transparent portions of the atmosphere opaque to IR and thus increases the difference between the ground temperature and the radiating temperature. The result, once the system comes into equilibrium, is surface warming.”

This is a most interesting quote, one that reveals a central misconception lying at the heart of the rGHE and AGW hypotheses. In order to get his message across, Pierrehumbert employs two quite specific terms – “enable” and “cause” – as if they were almost interchangeable. They are not. Read the two highlighted sentences once more. “An atmospheric ‘GHG’ enables a planet to radiate at a temperature lower than the ground’s, if there is cold air aloft. It therefore causes the surface temperature to be higher than would be the case if the atmosphere were transparent to IR.”

How did he get from “enables” to “therefore causes”?

He seems to forget that there’s crucially a third term that needs to be included before this chain is complete and one is able to see the whole picture, and that term is “necessitate”.

Something necessitates an effect, but cannot cause the effect before it is enabled to do so.

I will explain … Continue reading

‘To heat a planetary surface’ for dummies; Part 5b

If there were no atmosphere on top of our solar-heated terrestrial surface, then Earth’s mean global surface temperature would likely be about 80 degrees lower than what it actually is (209 rather than 289K). And this would be in spite of the fact that in this case the solar heat input to the global surface would be almost 80% larger on average (296 rather than 165 W/m2).

Much of this cooling of the mean would simply come as a result of greatly amplified temperature swings between day and night and between the seasons. The larger the planetary surface temperature amplitudes in space and time, the lower the mean global planetary surface temperature needs to be to maintain dynamic radiative equilibrium with the Sun. This is why the Moon is so cold.

So we need to get this straight: The Earth’s surface would be a much colder place without an atmosphere on top of it. Even with much more solar heat absorbed. There is no escaping this. The lunar surface is about 90K colder than ours, on average.


SO WHAT DOES OUR ATMOSPHERE DO?

The short answer: It insulates the solar-heated surface.

Well, so how does it do this?

Mainly in four ways, three of which concern suppressing the effectiveness of convective cooling of the surface at a certain temperature.

Why is this important? Why convective cooling?

Consider a hypothetical single-room house. Continue reading

‘To heat a planetary surface’ for dummies; Part 5a

In 1938, English steam technologist Guy Stewart Callendar wrote what proved to be a seminal – one might even venture to call it the foundational – paper of the entire modern AGW pipe dream movement, with its rather determined effort at postulating what we today call the “Radiative (Atmospheric) Greenhouse Effect” (rGHE), or as some people would prefer it: the “Callendar Effect”.

In his paper – “The Artificial Production of Carbon Dioxide and Its Influence on Temperature” – Callendar argued that the increase in global atmospheric CO2  concentration due to our industrial endeavours would (and did) warm the world because of the alleged augmenting influence of this IR-active molecule on the so-called “sky radiation” (what we today call “(atmospheric) downwelling longwave radiation” (DLR, DWLWIR), more commonly known simply as “back radiation”):

“Few of those familiar with the natural heat exchanges of the atmosphere, which go into the making of our climates and weather, would be prepared to admit that the activities of man could have any influence upon phenomena of so vast a scale.

In the following paper I hope to show that such influence is not only possible, but is actually occurring at the present time.”

Notice here how Callendar was well aware that with his hypothesis, he was challenging a generally accepted scientific paradigm of his time, one which held that our climate and weather are natural phenomena with purely natural drivers, which can not in any meaningful way be influenced (globally, at least) by human activity.

Callendar claimed that it can. And that it does. He even went so far as to claim he could show it …

Well, then; by all means bring it on! To quote Carl Sagan:

“Extraordinary claims require extraordinary evidence.”

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I don’t get ‘the gravito-thermal effect’

Lately there’s been a bit of back-and-forth discussion going on on the so-called ‘Gravito-Thermal Effect’ (GTE) at a few notable climate blogs, like The Hockey Schtick, Tallbloke’s Talkshop, Clive Best and even Judith Curry’s Climate Etc. (in fact, this is where the lengthiest discussion thread on the subject is to be found).

To me the whole thing appears to arise from a fundamental misunderstanding of the adiabatic process (see the end of the post).

Something called the ‘Loschmidt Effect’, after a proposal in the 1870s by the Austrian scientist Josef Loschmidt, seems to lie at the heart of the GTE argument. Tallbloke brought it out from relative obscurity in a post in early 2012. A quote from a textbook describes the proposed effect as follows: Continue reading

How the IPCC turn calculated numbers into heat

‘Climate ScienceTM’ (represented and promoted by the IPCC) has so corrupted ordinary people’s way of thinking, that in order to demonstrate why there is no ‘atmospheric radiative greenhouse effect’ (rGHE), you have to start all the way from scratch. You have to step completely outside the framework of their concocted ‘mental model’ within which they shape their arguments.

‘Climate ScienceTM’ is afflicted with a dual case of monomania, two major fixations that they cannot and will not drop under any circumstances.

The first one is a complete linear trend line mania. They are unable to look at a data time series and not mentally project one onto it. The data – and especially the variation in it – basically doesn’t matter. Only the straight trend line plastered across it, from the one end to the other, does.

The second one, of direct relevance to this post, is their peculiar obsession with radiative flux intensities and their perceived direct correlation with the surface temperature of objects, expressed by the purely radiative Stefan-Boltzmann relationship. They clearly misinterpret and hence stretch the applicability of this law in the real world far beyond its actual justified range of operation, but absolutely refuse to recognise it. They worship (and use) it as sanctified truth.

Basically, they see the world in terms of radiation first and last. Everything in their world is in the end determined and controlled by thermal radiation. When it comes down to it, according to the warmists, you can simply scrape away everything else and just look at instantaneous radiative emission fluxes and directly know surface temperatures. As if we all lived in Max Planck’s conceptually pure radiative universe.

‘Climate ScienceTM’ thinks (or promotes the idea) that the temperature of any object – even real-world objects on Earth – is determined strictly by its radiative energy output (its emission flux), likewise that this final temperature is known and fixed even from the onset of heating, simply by the instantaneous intensity of its radiative energy input (the absorbed flux) minus convective loss (!).

In other words, if you only know the total (added) intensity of the instantaneous radiative energy flux input to the surface of an object and you are at the same time able to determine its energy loss through convection per unit of time, you will be able to tell its final temperature, no actual thermo-measurement required. Or, turn it around, if you know the temperature of an object, you instantly know the intensity of its radiative energy output, regardless of any simultaneous convective loss of energy.

(Well, you also need to know its surface emissivity/absorptivity, but according to ‘Climate ScienceTM’ most relevant real-world materials (like soil, rock, water, vegetation) possess emissivities close to unity anyway, and so can be approximated as (convecting) black bodies …!) Continue reading

On Heat, the Laws of Thermodynamics and the Atmospheric Warming Effect

On average, Earth’s solar-heated global surface is warmer than the Moon’s by as much as 90 degrees Celsius! This is in spite of the fact that the mean solar flux – evened out globally and across the diurnal cycle – absorbed by the latter is almost 80% more intense than the one absorbed by the former.

The Earth’s global surface, absorbing on average 165 W/m2 from the Sun, has a mean temperature of ~288K (+15°C).

The Moon’s global surface, absorbing on average 295 W/m2 from the Sun, has a mean temperature of >200K (-75°C).

A pure solar radiative equilibrium for each of the two bodies (according to the Stefan-Boltzmann equation: Q = σT4, assuming emissivity (ε) = 1) would provide them with maximum steady-state mean global temps of 232K (-41°C) and 269K (-4°C) respectively.

As you can well gather from this, the Earth’s surface is 56 degrees warmer than its ideal solar radiative equilibrium temperature, while the lunar surface is at least 70 degrees colder than its ideal solar radiative equilibrium temperature. That’s a spread of no less than 126 degrees! On average …

Still, these two celestial bodies are at exactly the same distance from the Sun: 1AU.

So what could possibly account for this astounding difference between such close neighbours?

Very simple: The Earth has an atmosphere. The Moon doesn’t. Continue reading