RKS

Thanks for the additional links. Very helpful.

NiV;

There is a famous quote from H. L. Mencken "For every complex problem there is an answer that is clear, simple, and wrong."

Occam's razor shifts the burden of proof to the more complex explanation. As the simpler explanation has been discussed here, the more complex radiative greenhouse effect (with its failures in prediction of tropospheric hot-spot etc) is the current underdog imho.

I have a problem with those saying there is no back radiation.

If that is so, why does an upward pointing IR sensor pick up radiation and why does it show a peak at 15 micrometres (wavenumbers 600), the main IR emission wavelength for CO2?

EM

I do not recall at anytime reading a statement that claimed back radiation did not exist: was that a deliberate wind-up?

When back radiation does rear its head (groan) it is usually by persons who do not want to leave the apparent comfort of the current radiative explanation of GE. They appear on both sides of the AGW argument *strangely. As Martin A has pointed out with Pierrehumbert's nutshell (thanks), it is not necessary to invoke the term to explain GE. However, to accept the radiative model of GE it is necessary to believe back radiation can do work. I've even had people tell me that any explanation of GE which is not purely radiative is in fact an explanation of another phenomena altogether!

*The radiative model is so pervasive that I liken it to Stockholm Syndrome when I see persons who claim to be sceptics of it clinging to its precepts.

Now of course, radiation is necessary for without it the whole atmosphere would collapse to the surface But that is all it does - support the atmosphere. So, while you are out and about pointing your IR sensor upward, have you ever stopped to think what it is you are doing? (Hint, point it sideways, measure side radiation and work out what that is doing.)

Do GCM's get Venus correct when the correct details are plugged into the current models for the Earth. Venus is a much, much simpler planet to model and definitely has 'greenhouse gases' in abundance.

Martin A, ssat

I've been rereading your discussion. Most of what you say I agree with. The back radiation comment wasn't aimed at you and I'll happily ask BH to wipe it I'd annoys you.

One point though. The greenhouse effect does not warm, in the sense of increasing heat input into the system. That would violate the conservation of energy law.

What it does is to reduce the rate of cooling, producing an equilibrium temperature less cold than would occur without GHGs.

By extension, increasing GHG concentration exacerbates the reduction in cooling. Whether you regard this as occurring because of increased downwelling radiation or because of increased TOA altitude the effect is to create an increased imbalance of incoming over outgoing radiation.

This imbalance leads to an increase in system temperature until the outgoing radiation increases to balance the incoming radiation and a new equilibrium is achieved.

If you want to decouple GHG concentration from warming you will need to explain why this does not happen under your rules.

Martin A

I think you will find that the tropopauae and the effective TOA are equivalent, occuring at the atmosphere's minimum temperature altitude.

My impression was that lapse rate was a function of gravity, air composition and the gas laws, and that the lapse rate itself is independant of surface temperature, (though it may change as increasing surface temperature increases atmospheric water content).Temperature at any altitude is therefore a dependant variable of surface temperature.

You can predict temperature at altitude from lapse rate and surface temperature; you can also use temperature at altitude and lapse rate to predict surface temperature.

With increasing surface temperature atmospheric volume increases, but the lapse rate stays the same. This pushes the tropopause to a higher altitude and lower pressure, hence the lower temperature. Once above the tropopauae the stratosphere warms with increasing altitude as usual, but from a colder tropopause.

Pierrehumbert's quote seems to assume that lapse rate determines surface temperature. I think he has cause and effect confused. Surface temperature determines temperature at altitude, with lapse rate the mechanism by which their relationship is determined.

"the more complex radiative greenhouse effect (with its failures in prediction of tropospheric hot-spot etc) is the current underdog imho."

The tropospheric hotspot is a predicted result of the increased humidity from water vapour feedback changing the lapse rate, reducing the slope, which causes altitudes above the average altitude of emission to space to warm more, while altitudes below it warm less. It's got nothing to do with the radiative GHE explanation. The issue is, (as many sceptics have been saying for a long time,) the feedbacks. The models project massive water vapour feedback magnifying the 1 C sensitivity to something like 3.5 C. The failure to find the hotspot is a failure of the modelled feedbacks, not a failure of the basic GHE physics.

"you'll get *reduction* of surface temperature because the lapse rate has changed sign over part of the range of heights. Will you not?"

Yes, assuming the profile stays the same shape.

The inversion of lapse rate in the stratosphere is because of the presence of ozone there, which absorbs UV warming the air. The ozone builds up there because the inversion prevents convection, reducing mixing with the lower atmosphere, and the air is therefore extremely dry. The location of the tropopause depends on a balance of different influences and varies with latitude and other factors. I'm not sure if the profile would stay the same shape in such altered circumstances.

But apart from that, yes, you understand correctly.

"My impression was that lapse rate was a function of gravity, air composition and the gas laws, and that the lapse rate itself is independant of surface temperature, (though it may change as increasing surface temperature increases atmospheric water content).Temperature at any altitude is therefore a dependant variable of surface temperature."

The adiabatic lapse rate is indeed a function of gravity and the gas laws, but it only sets the gradient, it says nothing at all about the intercept. The intercept adjusts to ensure the Earth radiates to outer space the same amount of energy it absorbs. Any hot body radiating in a vacuum warms or cools until the radiating surface radiates the appropriate amount of energy. Therefore, it's the temperature of the effective radiating surface that is set, and temperatures above and below that are then dependent on it: defined in relation to it by the lapse rate.

Dung - after 8 pages and just about a month's worth of comments nobody seems to have addressed your original question - Is there an upper boundary to the GHE.?

There is a paper by a Hungarian Climate scientist which suggests that there is such a boundary and that the Greenhouse effect is "saturated" on earth as there is an enormous reservoir of greenhouse gas in the form of water vapour available due to the earth's being covered about 70% by water. Rising levels of CO2 in the atmosphere appear to reduce the water vapour content in the atmosphere while the near surface temperature remains relatively stable.

The paper citation is :-

Miscolczi Ferenc, Idojaras 2007, 111, No1.
The Greenhouse effect in semi transparent planetary atmospheres.

A summary and explanation of Miscolczi's hypothesis ( including the mathematics and comparisons between the GHE of earth and Mars) can be found at:-

www.nige.files@worldpress.com/the saturated greenhouse effect of ferenc miskolcz1

A simpler explanation by Miklos Zugoni is available on the Science and Public Policy Institution website.

A second line of supporting evidence that there is an upper temperature boundary can be found by consideration of the temperature and atmospheric CO2 concentration over geological ( Phanerozoic) Time. These estimates are derived from the O18/O16 ratios of cacarbonate rich sequences in deep sea sediments ( back to the Cretaceous) and of cap carbonates from earlier periods, and the stomata densities of fossil plants. Such a comparison shows, with two exceptions) that even at extremely high CO2 concentrations of several THOUSAND ppm the average atmospheric temperature seems to have been capped out at around 22 deg C.

The two exceptions were geologically brief excursions to as high as 26/29 deg C in the Permo/Trias and the Paleocene Eocene Thermal Maximum which briefly reached similar temperatures for about 85,000 years. The same results show that there were two excursions to LOW temperatures in Ice ages in the Ordovician and a very cool period in the Jurassic when CO2 levels were very high ( several thousand ppm).

Otherwise low CO2 concentrations correlate with low global temperatures as in the Permo-Carbonifierous and our own Pliestocene-Holocene glacial periods where CO2 concentrations of a few hundred ppm are found when temperatures fluctuate between 8deg C in glacial epochs and 15 deg C in Inter glacial periods such as the one we enjoy at present.

It seems that when average temperatures are low the temperature is quite unstable and minor variations in solar out put and the interplanetary magnetic field as well as orbital and rotational variations such as Milancovic Cycles can perturb the climate and swing it from the glacial to interglacial states.

In such cold epochs when CO2 is at very low levels of a few hundred ppm there is a rapid response of atmospheric CO2 concentration to variations in ocean temperature as discussed extensively by other commentors.

NiV:

1 Therefore, it's the temperature of the effective radiating surface that is set, and temperatures above and below that are then dependent on it: defined in relation to it by the lapse rate.

That is my understanding and a point I have been trying (poorly) to make. If I could add to that, perhaps you would care to agree or disagree?

The height of that effective radiating temperature is supported by the energy below it.

My interest in this topic is not a technical interest but as a consequence of being affected by it through its calls for action. You mention feedbacks and quite rightly as that is where the alarm is generated. But the feedbacks are riding on the back of the stated 1 C for a doubling of CO2. However, I don't calculate that additional CO2 raising the height of the effective radiating temperature sufficiently to match this (in fact, its trivial) and therefore the feedback projections are incorrect. I did ask earlier in the thread if anyone knew of where this 1 C comes from? It may inform me of where I am going wrong.

EM: This imbalance leads to an increase in system temperature until the outgoing radiation increases to balance the incoming radiation and a new equilibrium is achieved.

Or as I believe, more likely, the (tiny) diurnal CO2 increases have a near immediate effect on increasing the height of the effective radiating surface which raises bottom of atmosphere temperature without any affect on the balance between incoming and outgoing radiation. Why would a newly-minted molecule of CO2 affect the speed of changes in the height of the effective radiating surface: the range certainly, but the speed?

"There is a paper by a Hungarian Climate scientist which suggests..."

The Miscolczi paper was examined over at the ClimateAudit forum when it first came out. It took about a day for somebody to spot that Miscolczi has mis-applied the Virial theorem, and everything derived after that point was wrong. (He claimed the atmosphere was gravitationally bound and therefore the simplified inverse-square form of it applied. But the Earth's atmosphere is bounded from below by the solid surface.) I didn't bother spending any more time on it, but some people have gone into further detail...

"The height of that effective radiating temperature is supported by the energy below it."

What does that mean? How does the energy there "support" it?

The height of the level emitting to space is the surface that would be 'visible' from space if you could see with infra-red eyes. That's got nothing to do with the energy in the air below it. That's purely to do with how opaque the atmosphere is.

"My interest in this topic is not a technical interest but as a consequence of being affected by it through its calls for action."

Indeed. That's why a lot of people care about what would otherwise be a pretty obscure bit of physics. But it leads to problems when people on *both* sides selectively accept-without-question/ignore technical details depending on what it implies politically. It's perfectly human and understandable, and people mostly do it without even realising what they're doing (we are all blind to our own cognitive blind spots), but science doesn't work like that. The technical arguments matter.

That's where the other side went wrong, and what got them into trouble. They tried to simplify the technical uncertainties to present a clear and convincing message to the general public. But the technically-aware segment of the public saw what they were doing, and they lost credibility. It's not enough to get the right answer - all the calculation and argument to get there has to be right (and seen to be right) too. If you stand up as a climate sceptic and confidently present a theory which someone else can show to be wrong, you damage the credibility of climate scepticism. And if what you're concerned about is being affected by the calls for action, as opposed to pushing one's own pet theory, why would you want to risk that?

"I did ask earlier in the thread if anyone knew of where this 1 C comes from?"

As I understand it, it comes from applying HITRAN to determine the atmospheric absorption/emission profile at evenly spaced locations around the globe, adjusting the temperature profile at each point iteratively until the energy balances, and taking an average. It's not something that can be done on the back of an envelope.

But I haven't seen all the details set out explicitly and would be interested myself.

"As I stated earlier, the Venus example shows factual evidence that the level of CO2 in the atmosphere has no effect on temperature."

I assume you mean:

"The fact that the MEASURED temperature of the strata of Venusian atmosphere which is at Earth lower tropospheric pressure, ie 1 bar, is at exactly the correct temperature for it's distance from the Sun. ie the Earth's atmosphere would be at the same temperature [as this section of Venus' atmosphere] at the same distance from the Sun as Venus."

The solar constants for Venus and Earth are 2639 W/m^2 and 1368 W/m^2, which gives a ratio of 1.73 in power and hence a ratio of the fourth root of 1.73 = 1.14 in temperature. Since the albedo on Venus is 0.78 rather than Earth's 0.3, Venus reflects most of the incoming sunlight, far more than Earth, and using instead only the absorbed energy ought to be cooler than Earth. (The effective radiative temperature T_eff is 255 K for Earth and 225 K for Venus.)

The temperatures at the 1 bar level are 288 K for Earth and about 350 K for Venus, as far as I know. Venus is thus about 22% hotter than Earth at the 1 bar level, when it ought to be cooler. And even if you ignore the albedo, is still about 20 K too warm.

Not that I'd expect such simplistic comparisons to give you an accurate estimate of the temperature there. Venus is a very different set-up to Earth.

Null is in verba

Venus is indeed very different.

Take a look at its energy budget .

Surface radiation is 16600w/m^2 and almost all of it is back radiated.

"Surface radiation is 16600w/m^2 and almost all of it is back radiated."

True, but irrelevant.

Any opaque material contains internal radiation between its constituent atoms. The water of Earth's oceans emit around 400 W/m^2 both up and down from every 20-micron-thick horizontal layer throughout the bulk, meaning that every cubic metre of water is constantly emitting about 40 MW of "back radiation" internally. And it has absolutely no effect on its temperature. It all cancels out.

NiV: Thanks for the answer about the 1 C. As for a pet theory to push, I don't have one although I do have some 'pet questions' and I have pushed.

".....all the calculation and argument to get there has to be right (and seen to be right) too."

So, perhaps the questions should be: who is doing this; why is it taking so long; is there some sort of log-jam in the way and how can the process be speeded up?

RKS

The 'Shattered Greenhouse' page that you introduced to BH looked very interesting at first blush. I've read through it again and it appears that he has applied no albedo in his foundation calculations for the remainder of his deliberations. I think that there is at least one other problem, not that it matters after the first.

RKS

How do you justify talk of a pause when the warmest year in the record is 2010, followed by 2005. Depending on your preferred dataset 1998 is third or fourth?

Figures at the bottom of this page .