A simple argument is put forth against the idea that the radiative properties of an atmosphere somehow serve as the CAUSE of elevated steady-state planetary surface temps. Continue reading
UPDATE, June 19, 2017: The new ‘CERES EBAF Ed4 Sfc’ dataset arrived in May. The updated version proves even more detrimental to the idea of an “enhanced GHE” than the older one. The average sfc radiant heat loss (net LW, OLR) in the Congo is now reduced from 51 to 34 W/m2, while the same flux in the Sahara-Sahel has increased from 103 to 107 W/m2. At the same time, the solar heat inputs (net SW, ASR) in both regions are now more or less equal: 173.6 W/m2. Which means that the tropospheric column above the Congo surface appears to restrict its radiant heat loss to less than a third (rather than ‘just’ half) of its equivalent flux in the Sahara-Sahel region. So with the same heat INPUT from the Sun, but with a radiant heat loss more than three times larger (!) per unit time than in the Congo, the Sahara-Sahel surface is STILL several degrees WARMER on average than in the Congo!
OK, so commenter “Norman” asked me at Roy Spencer’s blog to clarify my position on whether a “more IR active atmosphere” would necessarily produce a higher average annual surface temperature at the bottom of that atmosphere. His inquiry in full:
Then you would also agree that increasing GHG in the atmopshere (the quantity makes a difference since it decreases the heat out) will lead to the end result of a warmer surface?
Good. That is what the basic point is all about.
Does the amount of GHG in the atmosphere change the equilibrium temperature of the Earth’s surface?
In your other writings you have states some GHG is necessary but the quantity does not matter. what is your current understanding?
More GHG warmer surface?
Less GHG cooler surface?
Or No change once a certain amount is present?
If in both cases the solar flux to surface remains the same.
So what do we mean by a “more IR active atmosphere”? Well, a proponent of the AGW idea (that of the anthropogenically “enhanced GHE”), like Norman here, would simply say: more “GHGs”. But what does this actually entail? It would lead to an atmospheric column that is more opaque (that is, less transparent) to outgoing surface IR. The idea is that the so-called “GHGs”, the IR active gases (and clouds, mind you), would absorb it more strongly, sort of “capture it” on its way out, and reradiate it in ALL directions, not just the upward one, thus diminishing the net flux of IR moving away from the surface and in the direction of space. And what is this net flux of outgoing IR from the surface? It’s the surface radiant HEAT loss, its Qout(LW).
So Norman’s central claim is this one: “(…) increasing GHG in the atmopshere (the quantity makes a difference since it decreases the heat out) will lead to the end result of a warmer surface (…)”
Well, will it? What does empirically based data from the real Earth system have to say about it?
We return to Africa. Continue reading
Specifically how is the AGW mechanism for global surface warming supposed to work? How is the global “ocean heat content (OHC)” supposed to be increasing under a strengthening “radiative greenhouse effect (rGHE)”?
By reducing the surface’s ability to cool via thermal radiation (IR).
Here’s the basic idea:
Assuming the mean solar input [Qin] stays the same and assuming changes in evaporative-convective losses [Qout ev] only ever come in the form of responses to preceding “greenhouse”-induced warming, that is, these losses stay constant until such warming occurs, then the only mechanism for warming (of surface and/or ocean bulk) is a reduction in surface radiative losses [Qout rad], i.e. in the ‘radiant heat loss’ or – same thing – the ‘net LWIR flux’ coming off the surface:
Balance: ΔQin = ΔQout ev + ΔQout rad → 0 = 0 + 0
Imbalance: ΔQin = ΔQout ev + ΔQout rad → 0 = 0 + (-1) = -1
When less heat goes out than what comes in, warming ensues. It’s that simple …
This is the theory.
Now, do we see this AGW warming mechanism at work in the Earth system today? Can we observe it empirically? Can we follow in the available data the ongoing strengthening of the rGHE resulting from our continued fossil fuel emissions?
In fact, we observe the exact opposite of what the theory above says should happen! Continue reading
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.
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
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.”
Update (March 24th) at the end of this post – a kind of a response from Feldman.
There was much ado recently about a new paper published in ‘Nature’ (“Observational determination of surface radiative forcing by CO2 from 2000 to 2010″ by Feldman et al.) claiming to have observed a strengthening in CO2-specific “surface radiative forcing” at two sites in North America going from 2000 to the end of 2010 (a period of 11 years) of about 0.2 W/m2 per decade, and through this observation further claiming how they have shown empirically (allegedly for the first time outside the laboratory) how the rise in atmospheric CO2 concentration directly and positively affects the surface energy balance, by adding more and more energy to it as “back radiation” (“downwelling longwave (infrared) radiation” (DWLWIR)), thus – by implication – leading to surface warming.
In other words, Feldman et al. claim to have obtained direct empirical evidence – from the field – of a strengthening of the “greenhouse effect”, a result, it would seem, lending considerable support to the hypothesis that our industrial emissions of CO2 and other similar gaseous substances to the atmosphere has enhanced, and is indeed enhancing still, the Earth’s atmospheric rGHE, thus causing a warming global surface – the AGW proposition.
From the abstract:
“(…) we present observationally based evidence of clear-sky CO2 surface radiative forcing that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2.”
“These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels (…) are affecting the surface energy balance.”
So the question is: Do these results really “confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions”?
Of course they don’t. As usual, the warmists refuse to look at the whole picture, insisting rather on staying inside the tightly confined space of their own little bubble model world. Continue reading