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Discussion > GHG Theory step by step

Aug 7, 2017 at 1:52 PM | Supertroll. Thank you! The closest I have been to an active (ish) volcano, was at anchor in the waters off Stromboli

Yellowstone geysers are a good analogy, because they are well known! I know Yellowstone is monitored in case she blows again etc, and the surface of the land varies with bulges etc, but do the geysers blow as regular now as they used to? Or in other words is the heat output from Yellowstone a variable, or a constant, over decades? Centuries?

How many Yellowstone Calderas are now known to be bubbling away beneath the sea, that were not known about in the 1980s?

The layout of tectonic plates was revealed by the US listening for nuclear tests etc, but satellite technology cannot penetrate the ocean depths with heat sensing imagery (to the best of my knowledge) Do we know, or is it educated guesswork, the actual extent of Black Smokers, or other sea bed heat emitters?

It all comes back to https://en.m.wikipedia.org/wiki/There_are_known_knowns

Rumsfeld stated:

"Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones."

Rumsfeld could have been talking Climate Science.

Aug 7, 2017 at 5:24 PM | Unregistered Commentergolf charlie

In the entirely unlikely eventuality that the heat from any kind of volcanic source (the heat, not the dust/sulphur/whatever) was of a magnitude able significantly to change the climate that would be far scarier than the effects of a little CO2.

Aug 7, 2017 at 6:48 PM | Unregistered Commenterrhoda

Aug 7, 2017 at 6:48 PM | rhoda

Thank you! I meant to elaborate about the cooling effect of dusty emissions.

Volcanic activity only causes heat, when Climate Scientists say so. Another known unknown, that nobody really seems to know about, unless it produces the answer they want.

Aug 7, 2017 at 6:55 PM | Unregistered Commentergolf charlie

golf charlie asked, some time back, if we could get on with the next step when CO2 does its warming in the atmosphere.

ssat covered this to a large extent back at page 1. The argument goes that CO2 absorbs outgoing IR radiation which, after an unspecified delay, re-emits in a random direction. Increasing amounts of CO2 increase this opacity to outgoing IR, with the result that the effective top of the atmosphere moves to a higher altitude before the IR radiates to space. The loss to space must maintain energy balance with solar insolation, so the effective black body temperature is now at a higher altitude. The lapse rate then suggests that the surface is now at a higher temperature than previously, hence global warming.

I don't know if I have explained that very well. Perhaps EM will correct me. The truth is that I am fairly uncomfortable with the explanation. Let us get the story right first before I, and maybe others, start picking holes in it.

Aug 7, 2017 at 7:02 PM | Unregistered CommenterSchrodinger's Cat

I think Mr Hart has hit upon a key to the problem: climate “science” appears quite happy with the internal variability that can thrust up the extremes of an el Niño or a la Niña, yet anything which churns up less than that has to be the fault of… well, CO2 – or, more specifically, human-produced CO2. (Presumably, natural CO2 is a more benign gas, and is also another one of the mysterious constants that climate “science” depend upon – after all, if these things are not constant, then these “scientists” might be mistaken about the eee-vils of (man-made) CO2.)

I do wonder what the excuses will be when the cooling can no longer be denied.

Aug 7, 2017 at 8:58 PM | Registered CommenterRadical Rodent

Schrodinger's cat

That's about right, though you forgot DWLR. You need a mechanism to recycle some of the energy radiated from the surface back to the surface. Without that you cannot explain how the surface can radiate more energy to the atmosphere than radiates from the atmosphere to space.

I suggest we forget about global warming and changing CO2. Let us work out how the greenhouse effect works at a constant CO2 first.

Lots of interacting variables to play with.

There are feedback loops between latitude, insolation, surface temperature, atmospheric pressure, tropopause height, tropopause temperature, and DLWIR to be considered. The greenhouse effect you actually get depends on the equilibrium values to which all these variables settle.

This is not a static system, but a dynamic equilibrium. Change one variable and all the others adjust.

Where do you want to start? Perhaps some non-controversial physics; the interaction between latitude, insolation and effective radiating altitude, the tropopause height. That is about 12km in the tropics and 9km at high latitudes. Understand why and you understand quite a lot which is useful when it gets complicated.

Aug 7, 2017 at 9:45 PM | Unregistered CommenterEntropic man

Incoming 342 less 30% for albedo, outgoing around 240. What's the problem?

Aug 7, 2017 at 10:37 PM | Unregistered Commenterrhoda

Rhoda

You gave figures for the tropopause, the radiating height. At that height you would expect incoming and outgoing radiation to be equal, and they are.

The problem is that a typical square metre of surface radiates considerably more power than the tropopause and that energy has to go somewhere. The surface radiates 390W/m^2 while the tropopause only radiates 240W/m^2. That leaves 390-240 = 150W/m^2 which has been absorbed by the atmosphere between them and must be accounted for.It does not stay in the atmosphere, which would then become much warmer than the surface.

If a square metre of surface radiates 390W/m^2, them to maintain a constant temperature it must receive 390W/m^2.

240W/m^2 reaches that surface from space. The other 150W/m^2 is energy which was absorbed by the atmosphere and then reradiated back to the surface. 240 + 150 = 390. The books balance.

I have simplified. The actual energy budget is more complex, but this illustrates the principle.

Schrodinger's cat

You mention one mechanism for the greenhouse effect. In fact there are two, both dependant on the way that CO2 and water absorb and reradiates IR photons.

1) insulation

Any insulator works by slowing the rate of heat transfer. An IR photon radiated by the surface is absorbed by a CO2 molecule and quickly reradiated in a random direction. It is then absorbed by another CO2 molecule and reradiated. After multiple collisions the photon has followed a random walk. This is much longer than the straight upward path. Between that and the time spent absorbed it takes much longer to reach space than it would without greenhouse gases.

2) Recycling

A photon is radiated from the surface. It is repeatedly absorbed and reradiated. The photon has two possible escape paths. It can escape upwards to space or hit the surface and be reabsorbed. 50% of photons are reabsorbed, returning their energy to the surface and keeping the surface warmer than it would be without greenhouse gases.

Aug 8, 2017 at 12:19 AM | Unregistered CommenterEntropic man

EM, one of my old hobby horses was to ask whether anybody ever modelled one square metre of actual surface and then measured a matching square metre for a time. I don't believe that has happened, and I believe it might produce a surprise.

Now, can I cook anything with DWLIR?

What does the profile of LW radiation by altitude look like? By night? By latitude?

Don't the waves/particles of radiation travel at the speed of light, and therefore no matter what their path from surface to space they are gone in microseconds, and therefore don't heat anything? They are not 'trapped', they are free to go, and they do.

Aug 8, 2017 at 7:57 AM | Unregistered Commenterrhoda

Aug 7, 2017 at 9:45 PM | Unregistered Commenter Entropic man That's about right, though you forgot DWLR. You need a mechanism to recycle some of the energy radiated from the surface back to the surface. Without that you cannot explain how the surface can radiate more energy to the atmosphere than radiates from the atmosphere to space.

My post, Jul 17, 2017 at 6:03 PM was an attempt to knock that old canard on the head. The temperature of the near surface atmosphere is equal to the surface temperature at thermal equilibrium. The two balance out. BUT there is also 123W (NASA figure) leaving the surface which combines with the 40W (NASA) leaving directly via the atmospheric window to = 163W, the 240W(NASA) – 77W(NASA) reflected. There is an average 123W net moving up through the atmosphere, (like batons in a huge relay race, if you will) constantly.

Because there is a lapse rate (leaving why for another day), there is no thermal equilibrium between successive layers yet this imbalance exists even with an energy balance at top of atmosphere. It is apparent that the temperatures at all altitudes are those that become necessary to drive 123W outward through increasingly thinning greenhouse gases until they become thin enough for the 123W to escape. The average temperature to escape is 255degK. The average temperature to drive the escape is 288degK. The difference, 33degK, does not come from DWLR but from the sun's 163W reaching the surface.

DWLR is not an energy source. It is indicative of the energy in the atmosphere at any altitude and varies with it. The energy in the atmosphere supports its volume by thermalisation. Thermalisation is temperature. Greenhouse effect is an atmospheric temperature effect, not an energy effect (40W passes through it unmolested).

It follows that as the surface and the near surface exchange zero energy, all greenhouse effect energy appears only in the atmosphere and only at thermalisation. The flux at the surface is several times greater than the escape flux but it is maintained by 123W solar radiation.

If you want to know about increase in greenhouse effect, examine the atmospheric profile. Any additional energy is there, supporting its new volume: look at balloon data, not computer models.

If climate science then wishes to claim (and they do) that there is energy accumulating elsewhere, then they will have to show a mechanism for that.

Aug 8, 2017 at 9:30 AM | Unregistered Commenterssat

Rhoda

The earliest 1D climate models did as you described. They considered vertical energy flow in a narrow column of atmosphere from surface to space without considering horizontal effects.That was all a 1970s tech computer could handle. The results still match reality.


You asked about cooking with DWLR before. As I said before, it is too diffuse. Nor can you boil an egg by putting it on your kitchen windowsill in the Sun. That does not mean that sunlight does not exist.


Longwave radiation is produced at all altitudes. In the troposphere it is rapidly absorbed. Above the tropopause upward radiation mostly escapes to space. Most of the OLR is produced in a band around 12km above the surface in the tropics.

That altitude decreases with surface temperature because air decreases in volume with decreasing temperature. At night and at higher latitudes the radiating altitude is lower. Thus at high latitudes the radiating altitude is around 9km.

As a rule of thumb, a change in surface temperature of 1C would produce a change in radiating altitude of 60 metres.

Without GHGs photons would escape in nanoseconds. The delay to microseconds is enough to maintain the reservoir of retained energy and increase the temperature.

Aug 8, 2017 at 9:46 AM | Unregistered CommenterEntropic man

Edit, Para 5;

maintained by 163W solar radiation

Aug 8, 2017 at 9:49 AM | Unregistered Commenterssat

Looks like an interesting debate brewing. ssat - If you have the time, I would welcome more explanation. Can you give any links that would help me?

Aug 8, 2017 at 1:24 PM | Unregistered CommenterSchrodinger's Cat

Aug 8, 2017 at 9:46 AM Entropic man As a rule of thumb, a change in surface temperature of 1C would produce a change in radiating altitude of 60 metres.
Without GHGs photons would escape in nanoseconds. The delay to microseconds is enough to maintain the reservoir of retained energy and increase the temperature.

Two explanations for GE in one post!

Actually, a change of radiating altitude would be the cause of an increase of surface temperature according to the current, popular theory. If you want to discard that and go for delay in escaping energy then you would need to say why a) you deny the consensus and b) why you support an alternative:) But let's stick with the consensus;

Adding greenhouse gases raises the altitude of the 255degK average escape temperature. Sliding down the lapse rate you will arrive at 288degK current average temperature. The question: is that now at some altitude itself with (say) 299degK being the new surface temperature?

The answer is that it depends on the lapse rate in the *new condition: if it has tended to the drier then possibly no; the wetter then yes. But wetter brings more cloud and as Prof Lindzen says, we don't know enough about clouds.

* To further confuse, the popular theory also states that an increase in altitude of the escaping radiation results in a lower temperature and therefore energy out is less: more energy (dare I say trapped) means higher temperature. They probably mean this to apply while Co2 is increasing. I would have thought that the day=warming, night=cooling observation would have disavowed them of that.

Aug 8, 2017 at 4:08 PM | Unregistered Commenterssat

Given that molecular collisions take place much more frequently than exchanges of photons between CO2 molecules and water vapour is plentiful compared to CO2 and of course all this kinetic energy aids convection, what about all this trapped heat being radiated to space by CO2?

What about the CO2 absorption bands being saturated?

Aug 8, 2017 at 7:10 PM | Unregistered CommenterSchrodinger's Cat

Sorry, should have been radiated to space by water vapour.

Aug 8, 2017 at 7:12 PM | Unregistered CommenterSchrodinger's Cat

"If a square metre of surface radiates 390W/m^2, them to maintain a constant temperature it must receive 390W/m^2."

That square metre is under no obligation to maintain its temperature. Any given metre in the real world will be getting warmer or colder most of the time. It will not be receiving 390 either, most of the time. It will in any case not be radiating alone. Convection probably assisted by evaporation will be dominant.

If it pushes up the tropopause, so what? The heat is coming from the surface and the amount is not affected by CO2. Nor does any downward lapse rate pushback occur. That is unphysical.

That 150 w/m2, which mysteriously disappears between the surface and the TOA, makes no sense at all at least if we expect to find it only as radiation.

The whole construction just looks magical. And it is not being measured, it's an over-simplified illustration for the gullible.

Anybody got a one-frame picture of the Earth radiating all that 240 watts at once. All I could find was a collage of 1km2 observations collected on multiple passes.

Aug 8, 2017 at 9:26 PM | Unregistered Commenterrhoda

…it's an over-simplified illustration for the gullible.
Oooh… I like that. For a person married to a house, you are pretty smart.

Aug 8, 2017 at 10:43 PM | Registered CommenterRadical Rodent

Ssat

Oops, that should have been " a change in surface temperature of 1C would produce a change in radiating altitude of 120 metres." (Remember, lapse rate is generally quoted as 9K/km so a 1C surface temperature change produces a 1/9km change in tropopause height)

In my post to Rhoda I was trying to keep it simple enough to make my point about energy recycling clear.. Mentioning that the the 239W average OLR consists of 169W radiating from the tropopause, 30W from clouds and 40W radiating directly from the surface through the atmospheric window would have obscured my point.

The lapse rate relationship you described is the relationship between tropopause height and surface temperature. It is not the mechanism, but the relationship which emerges from the mechanism.

The linked mechanisms I described show how energy moves through the troposphere and how it accumulates as photons, as vibrational energy in CO2 and kinetisc energy in other gas molecules, and in the ocean and surface as specific heat. When the energy flows and stored energy in different parts of the system reach equilibrium the surface temperature and tropopause height emerge from that equilibrium.

A step change in CO2 content raises the radiating altitude. That initially upsets the equilibrium by reducing the radiating temperature and reducing the OLR. More energy is retained within the system and the surface temperature rises.

Because of the lapse rate temperatures then rise at all altitudes throughout the troposphere. Eventually the temperature at the radiating altitude increases to a value at which the OLR is sufficient to balance the incoming radiation and temperatures stabilise once more.

This relationship is visible in the Holocene record. Milankovich warming increased temperatures and triggered CO2 release from storage. That caused a further increase in temperature and more CO2 release. Eventually after 10,000 years and an increase of 80ppm CO2 the system reached equilibrium 5C warmer.

Today the relationship is harder to see because we are in a period of rising CO2 i and the system is permanently out of equilibrium.

Rhoda is right in one sense. Temperature is easily measured but is a proxy for energy levels in different parts of the system. To understand how the system operates, you would do better following the energy rather than the temperatures.

Scrodinger's cat

Research band spreading.

In the current atmosphere CO2 absorbtion is saturated at its 15micrometre spot wavelength, but absorbs unsaturated across a band four micrometres wide in the IR spectrum from 13 to 17micrometres.

Increase the amount of CO2 and the width of the saturated band increases. So does the width of the unsaturated band.

At some point we might have a saturated band between 13 and 17 micrometres within an unsaturated band from 11 to 19 micrometres.

Bottom line? If you regard saturation as a limiting CO2 concentration beyond which further warming stops, you are mistaken. As the centre of the band saturates IR absorbtion increases at the edges. You can get all the way to Venus conditions (95%CO2, 90 bar) without reaching a saturation limit.

Aug 8, 2017 at 10:53 PM | Unregistered CommenterEntropic man

Rhoda

That 150 w/m2, which mysteriously disappears between the surface and the TOA, makes no sense at all at least if we expect to find it only as radiation.

Have you not been reading what I say?

Most of that 150W ends up as vibrational energy, or kinetic energy carried by the molecules which make up the surface and atmosphere. You might care to research the concept of specific heat.

Aug 8, 2017 at 11:01 PM | Unregistered CommenterEntropic man

EM, "The earliest 1D climate models did as you described. They considered vertical energy flow in a narrow column of atmosphere from surface to space without considering horizontal effects.That was all a 1970s tech computer could handle."

The SGCM we used as students at Reading was a full 3D GCM based on the Hoskins and Simmons model from 1975.

http://www.met.reading.ac.uk/~mike/dyn_models/igcm/

linking to the 1975 abstract at

http://onlinelibrary.wiley.com/doi/10.1002/qj.49710142918/abstract

The current GCMs are still basically this model with lots of extra parameterisations bolted on and run at higher resolution.

On the original topic in trying to understand what the greenhouse effect is it seems it always comes down to following the lapse rate down from the tropopause and the theory is that extra CO2 raises the level of this radiating layer thus raising the surface temperature when following the same lapse rate down

This always seemed one of those vaguely possible but exceptionally flimsy theories. By biggest problem is that Convection and the Water Cycle are dominant and always just skirted around in the explanations.

Aug 8, 2017 at 11:43 PM | Unregistered CommenterRob Burton

Actually EM the Met Office say there first model was in 1965 and similar models to the link from 1975 were developed through the 70's

http://www.metoffice.gov.uk/research/modelling-systems/history-of-numerical-weather-prediction

Aug 9, 2017 at 12:05 AM | Unregistered CommenterRob Burton

Rob Burton

Agreed. All the discussion focuses on the surface temperature, lapse rate tropopause height relationship and not on the underlying physical mechanism.

I mentioned the energy transfer mechanisms involved in my August 8th, 1219am post but everybody has gone straight back to talking about radiative heights and lapse rates.

If you have an alternative mechanism which would produce the observed temperature profile I would like to see your numbers.

Aug 9, 2017 at 12:21 AM | Unregistered CommenterEntropic man

Aug 9, 2017 at 12:21 AM | Unregistered CommenterEntropic man

I didn't understand any of the numbers you posted. I don't really pay much attention to numbers like that anyway as there is always a massive assumption made to get to them anyway. I am very much a 'show me the data' person which can then be discussed on what it means.

In relation to actual data, currently staying on the Mississippi and it is staggering to see the role of real climate change on the history of this river in the last 10000 years or so since the last glacial maximum.

Aug 9, 2017 at 4:34 AM | Unregistered CommenterRob Burton

Rob Burton

"I am very much a 'show me the data' person"

"I didn't understand any of the numbers you posted."

"I don't really pay much attention to numbers like that anyway"

Do you see the contradiction here?

I think that your attitude is why few scientists bother to engage on sites like this.

Aug 9, 2017 at 8:44 AM | Unregistered CommenterEntropic man