Global warming is not caused by CO2

[Andre]

Are you saying that average global temperature is not increasing?

I merely showed the results of the computations of the Hadley weather office and the RSS satellite observation for global temperatures:

which would make it a bit difficult to maintain that the global temperatures continued to rise in the last decade, despite the continuous rise of the CO2. Moreover the trend change corresponds to the trend change of the Albedo of Pallé et al 2006. But they missed that, since they omitted testing their results to global temperature series, which leads to that very curious but wrong assumption that albedo and temperature rose together.

Furthermore, in addition to the explanation of Vanesch:

2. greenhouse gasses are the main cause for the atmosphere to be warmer than grey body temperature.

Chilingar et al 2008 deal with the role of convection and latent heat mentioned by Vanesch and substantiate why these are the main vectors for heating the atmosphere to be warmer than grey body temperature. It's the OP subject in this thread

Apart from that from that 33 degrees difference, the more that must be attributed to convection/latent heat, the less is available for pure greenhouse effect, which would also mean lesser effects of changes in greenhouse gas concentrations.

3. increases concentration of greenhouse gasses increase the temperature of the atmosphere significantly,

Appears to be very obvious, the increase of radiative gasses would interact more with IR radiation in the absorption and emission of energy, which would lead to more energy in transit in the atmosphere molecules, ie higher atmospheric temperatures and more energy redirected to the Earth surface. But that's not what Miskolsky 2007 finds (thread here) who argues, based on observations, that the optical depth for IR radiation does not change notably with changes in greenhouse gas concentration.

So, having feasible conflicting hypotheses, it seems appropriate to revert to all available observations to see which notion is supported and which is not.

So, where is the evidence for global warming being caused by human activity / increase of greenhouse gas concentration?

 

[Andrew Mason]

Furthermore, in addition to the explanation of Vanesch:


Chilingar et al 2008 deal with the role of convection and latent heat mentioned by Vanesch and substantiate why these are the main vectors for heating the atmosphere to be warmer than grey body temperature. It's the OP subject in this thread
Apart from that from that 33 degrees difference, the more that must be attributed to convection/latent heat, the less is available for pure greenhouse effect, which would also mean lesser effects of changes in greenhouse gas concentrations.

Given Chillingar's earlier work I have serious doubts about the reliability of his conclusions. In any event, all you have shown is that there is another theory that is inconsistent with the hypothesis (that increased CO2 concentrations in the atmosphere will lead to global warming). You need facts.
Chillingar's model may be too simple. One cannot divorce the atmosphere from the earth. One has to take into account and the physical and biological effects that these increases of atmospheric CO2 may have on the further release of greenhouse gases.

Appears to be very obvious, the increase of radiative gasses would interact more with IR radiation in the absorption and emission of energy, which would lead to more energy in transit in the atmosphere molecules, ie higher atmospheric temperatures and more energy redirected to the Earth surface. But that's not what Miskolsky 2007 finds (thread here) who argues, based on observations, that the optical depth for IR radiation does not change notably with changes in greenhouse gas concentration.

So, having feasible conflicting hypotheses, it seems appropriate to revert to all available observations to see which notion is supported and which is not.

So, where is the evidence for global warming being caused by human activity / increase of greenhouse gas concentration?

Again, this is merely another theory which conflicts with the hypothesis. You need facts. Moreover, it is a theory that has not yet been subected to rigourous testing or peer review.

AM

 

[Andrew Mason]

Indeed. What you write is the difference between what I like to call suggestive evidence (sure there is !) and conclusive proof, and what annoys me is that the first is presented as the second. There's a big difference between both on the scientific side. In the second case, it becomes almost ridiculous to contest the statement, while in the first case, a critical analysis is due, and by flipping too fast from the first to the second, one could make a big mistake and "lock it in".

I would agree with you that the anthropogenic global warming model has not been proven scientifically. The "consensus" of climate scientists does not mean it is proven. It may be generally correct but in need of refinement. Or it may be completely wrong and some other theory that has not yet been developed may provide the correct explanation. All I am saying is that to disprove it one needs proven facts that are inconsistent with the theory. If it is not disproven AND there is no plausible, rational alternative explanation that is consistent with all known facts, then it is the only explanation that scientists and governments can support.

So far, I do not see any other explanation that is consistent with the known facts.

For example:

1. the increase in CO2 is not caused by volcanos. Volcanos contribute only a few hundred megatonnes of CO2 a year - less than one percent of total global CO2 emissions. See this article.

2. The warming trend is not consistent with the solar cycles. See also:
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000099000004048501000001&idtype=cvips&gifs=yes.

I would say that the biggest problem facing "CO2 is the sole drive for AGW and this will lead to dramatic increases in temperature" as a definitive statement is that there is no ab initio model, purely based upon physically known facts (with no fitting parameters) that numerically predicts correctly all the main quantities involved.

I don't think the IPCC is saying that CO2 is the sole driving force for AGW. Scientists are merely saying that human emissions of CO2 contribute to global warming. There may be other significant factors and it may be even more complex that it appears.

But even if there were other significant factors and even if CO2 should turn out not to be the main cause of GW, the fact is that 30 GT of CO2 is being dumped into the atmosphere each year. How long do we continue mindlessly and wastefully burning fossil fuels and unnecessarily adding new CO2 to the biosphere? For example, we know that a lot of this is taken up by the oceans. How long can this go on before the acidification of the oceans becomes a problem?

AM

 

[Andre]

Given Chillingar's earlier work I have serious doubts about the reliability of his conclusions.

This is an ad homimen. I have shown in that thread that a similar study came to the same conclusion and all are peer reviewed including this one. Hence one should look at the work directly, instead of shooting the messengers and find flaws in the logic or find compelling evidence against it.

You need facts.

Exactly, where is the evidence that changes in greenhouse gasses have been a decisive factor in changes in global temperature in the geologic past?

In favor of Chilingar et al is this thread which essentially shows that no activity could be attributed to the variation of CO2.

 

[Andrew Mason]

This is an ad homimen. I have shown in that thread that a similar study came to the same conclusion and all are peer reviewed including this one. Hence one should look at the work directly, instead of shooting the messengers and find flaws in the logic or find compelling evidence against it.

It is not up to me to find flaws in the logic or compelling evidence against it. It is up to scientists who work in that field to do it. Until his theory is vetted and tested by scientific peers, one is left with the scientist's reputation. It is not a matter of attacking the person. You are asking us to accept Chillingar's word that he has done a correct analysis based on correct experimental work. His reputation is not one that inspires confidence in me that I can put any weight in his conclusions before his work is fully vetted and tested.

AM

 

[Andrew Mason]

Exactly, where is the evidence that changes in greenhouse gasses have been a decisive factor in changes in global temperature in the geologic past?

That is not really the issue. A scientific theory is not proven by the abundance of evidence in favour of it. Such evidence just tests it. A theory is "proven" by the lack of evidence establishing facts that contradict it and the existence of evidence proving facts which conflict with all alternative theories.

The observations of the precession of mercury and the bending of light by the sun did not prove the Theory of General Relativity. Since 1915 scientists have not established any fact that conflicts with the Theory of General Relativity. That doesn't mean it is correct. But since no one has come up with another plausible theory that explains all the observed phenomena, it is the one we go with. AGW is kind of like that.

AM

 

[Andre]

Again, the mere existence of alternate hypotheses warrants a closer look of the evidence supporting or falsifying any hypothesis. The basic idea of Chilingar et al is indeed extremely basic. I learned that principle of convection some 40 years ago (wow really, am I that old?), when applying for a glider flying permit.

Estimates of quantifying that effect, is sophisticated modelling for highly skilled profesionals, granted, but testing the effect of large CO2 changes in the Pleistocene past, can be done more easily and again, the results of that do support a significant role for CO2 to regulate temperatures.

But feel free to demonstrate where changes in CO2 were likely to have caused changes in temperatures, that warrants the idea of the strong warming effects.

Let's make this very easy. Check this:

http://arxiv.org/ftp/arxiv/papers/0804/0804.1126.pdf

Due to other activities it may be some days to react to that.

 

[Andrew Mason]

Chilingar et al 2008 deal with the role of convection and latent heat mentioned by Vanesch and substantiate why these are the main vectors for heating the atmosphere to be warmer than grey body temperature. It's the OP subject in this thread

Not having access to this article, can someone explain the mechanism by which convection and latent heat are supposed to cause cooling?

The latent heat must be the latent heat of water because CO2 does not change state in the atmosphere on on the Earth's surface. While evaporation of water does have a cooling effect on the Earth's surface, water vapour in the atmosphere is a GHG that traps heat. In any event, for net cooling, you have to have an INCREASE in the amount of water vapour in the air. This will only occur if the vapour pressure increases, which requires an INCREASE in temperature. So the argument seems to be there will be a cooling effect only if the temperature increases.

I am not sure how convection causes net cooling either. Convection is the result of an air mass that is not in thermal equilibrium. The heat flow within the air mass does work (on parts of itself). So, by the first law of thermodynamics, the internal energy (temperature) of the moving air will not increase as much as it would if the air remained stationary. But it will still increase because but the overall flow of heat into the air must still be positive in order for convection to occur (2nd law of thermodynamics). (And this also results in a more volatile air mass, which is hardly a benefit).

AM

 

[Andre]

Not having access to this article,

PM me an email address.

The latent heat must be the latent heat of water because CO2 does not change state in the atmosphere on on the Earth's surface.

2500 J/g water is not something neglglible.

water vapour in the atmosphere is a GHG that traps heat.

Why would that be? water has excellent radiative properties in a big frequency range throughout the IR and would increase the radiative activity (absorption/emission) in ALL directions. But the clouds are emitting closer to the top of the atmosphere, increasing the chance that an emitted energy parcel escapes into space rather than returns to the Earth surface. Moreover, the amount of water vapor at higher levels is declining fast, providing less obstruction to emitted IR photons. So the higher the effective radiation altitude, the bigger that chance of emitted energy leaving the atmosphere rather than returning to the Earth surface.

can someone explain the mechanism by which convection and latent heat are supposed to cause cooling?

Convection removes warmer air from the surface, to be replaced by cooler air from above (disregarding adiabatic expansion/compression effects). The ascending water vapor, having taken up the evaporation energy (2500 J/g) is relatively 'cold' and because of that, it does not emit a lot of photons (Stefan Boltzman). As the convecting air gets higher, condensation is taking place, releasing the latent heat, which can now emit IR photons from a higher altitude, increasing that chance of escape into space.

So if you'd increase the GHG in the atmosphere, the greenhouse effect at the surface layers increase, heating it faster, increasing the instability and causing more convection, which means more latent heat goimg up, producing more clouds, with two effects: more radiation into space and increasing the albedo which decreases insolation.

 

[vivesdn]

If this evaluation of water vapour effect is accurate, a high albedo surface as forests would be a cooling system: it provides energy and water (trees are continuously evaporating water) to convection.

Among several theories to explain Little Ice Age, one states that Black Death was the cause of a human population decrease, and this decrease was the cause of a significative amount of fields reclaimed by forests. So the effect would be through cloud formation more that CO2 reduction.

Not a proof of anything, but just some hypotheses that match together and with facts...

 

[Andrew Mason]

PM me an email address.

Done

Why would that be? water has excellent radiative properties in a big frequency range throughout the IR and would increase the radiative activity (absorption/emission) in ALL directions.

Well, its really not a matter of dispute that water vapor is a greenhouse gas, which mean that it traps heat. The fact that the water molecule radiates energy has little to do with it. If matter is in thermodynamic equilibrium, it will radiate as much as it absorbs. The Earth has to radiate as much energy as it absorbs. The composition of the atmosphere does not change this fact. It just affects the temperature at which equilibrium occurs. The question is: what is the surface temperature at Earth's thermodynamic equilibrium?

But the clouds are emitting closer to the top of the atmosphere, increasing the chance that an emitted energy parcel escapes into space rather than returns to the Earth surface. Moreover, the amount of water vapor at higher levels is declining fast, providing less obstruction to emitted IR photons. So the higher the effective radiation altitude, the bigger that chance of emitted energy leaving the atmosphere rather than returning to the Earth surface.

This may have some logical appeal. But it is more complicated than that.The clouds are in thermodynamic equilibrium with the surrounding air. So the water molecules in clouds or at all levels in the atmosphere must be absorbing as much energy as they are radiating.

In order to have a cool surface, the surface has to radiate energy into space directly without being absorbed by the atmosphere. If it is absorbed by the atmosphere it will necessarily be radiated from the atmosphere at the same rate. This means the temperature of the atmosphere (and therefore the surface) will increase. That is the essence of the greenhouse effect.

AM

 

[vanesch]

This may have some logical appeal. But it is more complicated than that.The clouds are in thermodynamic equilibrium with the surrounding air. So the water molecules in clouds or at all levels in the atmosphere must be absorbing as much energy as they are radiating.

If the atmosphere were in thermodynamic equilibrium, there would be no convection.
As you say yourself, it is pretty complicated, but I'm pretty sure that convection leads to cooling, as heat is transported from a hotter place to a colder place, where it can radiate away easier than if it were confined to its hotter place.

In order to have a cool surface, the surface has to radiate energy into space directly without being absorbed by the atmosphere. If it is absorbed by the atmosphere it will necessarily be radiated from the atmosphere at the same rate. This means the temperature of the atmosphere (and therefore the surface) will increase. That is the essence of the greenhouse effect.

Yes, that's true, as long as things are static. But if you consider the cycle: hot surface heats (through radiation or even through conduction) lower air layer, by convection this layer moves up to high altitudes, and there it cools through radiation, before coming down again as cold air, you get a net heat transport which is not considered by radiation only.
Now, there are 2 things which promote convection: 1) temperature gradient 2) evaporation (water vapor is lighter than air)
(ok, there's also specific density, and some argue that the increase of heavy CO2 in the atmosphere promotes convection - I'm not clear about that).

So it seems at first sight that convection is going to act as a negative feedback (a regulatory mechanism) on radiative forcing, no ?

 

[Andre]

There can never be a equilibrium because of the daily cycle. Mind that the solar flux varies between 0 and 1367 * Cos (inclination) Wm2. At night the atmosphere cools a few degrees due to outradiation allowing for convection during the day again.

Even in theoretical equilibrium (Earth hypothetical in tidal lock with the sun) the IR radiative cooling of the upper atmospere would keep the convection going.

 

[Andrew Mason]

If the atmosphere were in thermodynamic equilibrium, there would be no convection.
As you say yourself, it is pretty complicated, but I'm pretty sure that convection leads to cooling, as heat is transported from a hotter place to a colder place, where it can radiate away easier than if it were confined to its hotter place.

There is no doubt that for a given amount of heat flow into an air mass the temperature will be greater if the air remains static than if convection occurs. But this is just basic thermodynamics. The air does not cool by radiation. The rising warmer air will cool much more quickly due to conduction of heat to the cooler surrounding air than to radiation. The atmosphere will radiate exactly the amount of radiation that it absorbs - it cannot cool by radiation. Besides, the radiation from the atmosphere is in all directions. Just as much radiation is directed from the atmosphere toward the earth. It is this radiation from the atmosphere back toward the Earth that increases the surface temperature.

Without any radiation being absorbed by the atmosphere, the surface temperature of the Earth would be 255K (-18 C), based on a .3 albedo factor (ie. Earth emissivity .7). This is just simple blackbody physics - Stefan Boltzmann law. We know that the Earth surface is warmer than this - about 279 K. So the "theory" that the presence of infrared absorbing atmosphere increases the surface temperature has a pretty solid factual foundation. We are living proof of that.

Yes, that's true, as long as things are static. But if you consider the cycle: hot surface heats (through radiation or even through conduction) lower air layer, by convection this layer moves up to high altitudes, and there it cools through radiation, before coming down again as cold air, you get a net heat transport which is not considered by radiation only.
Now, there are 2 things which promote convection: 1) temperature gradient 2) evaporation (water vapor is lighter than air)
(ok, there's also specific density, and some argue that the increase of heavy CO2 in the atmosphere promotes convection - I'm not clear about that).

So it seems at first sight that convection is going to act as a negative feedback (a regulatory mechanism) on radiative forcing, no ?

The only way convection can increase is if the atmosphere's temperature increases. While is true that for a given heat flow into an air mass the static air mass will have a higher temperature than the convecting air mass (because work must be done on the air mass to get it moving) the temperature still increases.

AM

 

[Andre]

There is no doubt that for a given amount of heat flow into an air mass the temperature will be greater if the air remains static than if convection occurs. But this is just basic thermodynamics. The air does not cool by radiation. The rising warmer air will cool much more quickly due to conduction of heat to the cooler surrounding air than to radiation.

Better check out the textbooks on this. Cooling during convection is adiabatic and is caused by expansion

The atmosphere will radiate exactly the amount of radiation that it absorbs -

Plus the amount of energy that went into the evaporation after it is released again during condensation.

 

[vanesch]

There is no doubt that for a given amount of heat flow into an air mass the temperature will be greater if the air remains static than if convection occurs. But this is just basic thermodynamics. The air does not cool by radiation. The rising warmer air will cool much more quickly due to conduction of heat to the cooler surrounding air than to radiation. The atmosphere will radiate exactly the amount of radiation that it absorbs - it cannot cool by radiation. Besides, the radiation from the atmosphere is in all directions. Just as much radiation is directed from the atmosphere toward the earth. It is this radiation from the atmosphere back toward the Earth that increases the surface temperature.

Without any radiation being absorbed by the atmosphere, the surface temperature of the Earth would be 255K (-18 C), based on a .3 albedo factor (ie. Earth emissivity .7). This is just simple blackbody physics - Stefan Boltzmann law. We know that the Earth surface is warmer than this - about 279 K. So the "theory" that the presence of infrared absorbing atmosphere increases the surface temperature has a pretty solid factual foundation. We are living proof of that.
The only way convection can increase is if the atmosphere's temperature increases. While is true that for a given heat flow into an air mass the static air mass will have a higher temperature than the convecting air mass (because work must be done on the air mass to get it moving) the temperature still increases.

I'm not contesting the greenhouse effect of course. (btw, I'm not even contesting AGW ; I'm contesting the scientific certainty of AGW at the level promoted by the IPCC, because IMO there are difficulties in this explanation - difficulties which might be overcome, but which will need more scrunity than actually displayed by their authors).

However, concerning convection, I must disagree. Of course, the amount of heat radiated by the atmosphere is equal to what it absorbs, but what counts, is how much of this is UP and how much of this is DOWN. In fact, what counts, is the "thermal resistance" of the atmosphere, that is, what is the temperature gradient necessary to bring a certain heat flux from the surface to the outer space. Of course, this "resistance" is composed not only of conduction, but also of radiation (the usual transport mechanism) but also of convection, and is as such a non-linear resistance.
It should be obvious that if hot air can move higher up, without having to transport its heat via radiation into the overlying layers, but flow directly to a higher place, that the effect of this on the overall resistance is to lower it. It is an extra transport mechanism of heat outward.

 

[Andrew Mason]

Cooling during convection is adiabatic and is caused by expansion.

The only way adiabatic expansion of air can reduce the temperature of the air is if it does work. (if it expands but does no work, ie. a free expansion - the temperature does not change). If it does work on surrounding air by adiabatically compressing it, the temperature of the surrounding compressed air will increase. This is because, by the first law, if dQ = 0 (adiabatic), dT = W/nCv where W is the work done on the gas (ie. if work is done by the gas, W<0 and dT is negative; if work is done on the gas, dT is positive).

Chillingar's paper appears to ignore the simple fact that by absorbing infrared radiation emitted by the Earth's surface, the atmosphere reradiates some of that energy back to the earth. It doesn't just radiate outward (ie into space or the stratosphere). If the atmosphere does not absorb any (very little) of the inward radiation from the sun but absorbs and reradiates back to the Earth much of the outward IR radiation from the surface, the radiation energy flux incident upon the Earth's surface is greater than it would be with a non-IR absorbing atmosphere. Since the inward energy flux has to equal the outward energy flux if there is thermal equilibrium, the presence of IR absorbing gases in the atmosphere has to increase the energy flow away from the surface - meaning it has to increase surface temperature. The only question is how much of this energy flow is carried away by radiation and how much by other energy transfer mechanisms. Chillingar et al suggests that more than ALL of the additional energy is carried away by convection. I don't understand how that can be and I have no faith in his ability to analyse it correctly, so I will await confirmation of his "theory" by real data and by the reviews of his scientific peers.

AM

 

[vanesch]

The only way adiabatic expansion of air can reduce the temperature of the air is if it does work. (if it expands but does no work, ie. a free expansion - the temperature does not change). If it does work on surrounding air by adiabatically compressing it, the temperature of the surrounding compressed air will increase. This is because, by the first law, if dQ = 0 (adiabatic), dT = W/nCv where W is the work done on the gas (ie. if work is done by the gas, W<0 and dT is negative; if work is done on the gas, dT is positive).

The adiabatic cooling comes about because the pressure is lower at higher altitude, and as such it does work (yes, "free" expansion does work).

Chillingar's paper appears to ignore the simple fact that by absorbing infrared radiation emitted by the Earth's surface, the atmosphere reradiates some of that energy back to the earth. It doesn't just radiate outward (ie into space or the stratosphere). If the atmosphere does not absorb any (very little) of the inward radiation from the sun but absorbs and reradiates back to the Earth much of the outward IR radiation from the surface, the radiation energy flux incident upon the Earth's surface is greater than it would be with a non-IR absorbing atmosphere. Since the inward energy flux has to equal the outward energy flux if there is thermal equilibrium, the presence of IR absorbing gases in the atmosphere has to increase the energy flow away from the surface - meaning it has to increase surface temperature.

I didn't read that paper. And your explanation is of course correct. But what actually happens is that you can consider a gas column as different layers, and each layer radiates upward and downward, and absorbs from the layers on top and below it. And as such, you can consider that the net effect is radiation that has to "work its way outward" from the ground to the upper layers, into the "outward radiation" part. Now, depending on how easy it is to get absorbed and re-emitted and so on, the higher must be the temperature gradient between "outer space" (essentially 0) and the emitting Earth surface (essentially the absolute temperature of the Earth surface) for a given energy flux, which has to equal of course the total incoming solar flux (minus albedo). As such, an absorbing and re-emitting set of layers acts as a kind of " distributed thermal resistance", each layer adding a bit of resistance to the whole path of the thermal flux from ground level to outer space.

This resistance is nothing else but the "greenhouse effect". However, they are not linear resistors like in Fick's law in heat conduction.

Now, if you can have a "transport mechanism" which takes heat from a lower layer, and put it *directly* into a higher layer, then you will improve the overall heat flux, simply because you've shunted a set of layers (resistors). This will then lower the overall effective heat resistance of the entire atmosphere. That's what convection does, and that's also (apart from changing albedo) what evaporation and condensation in higher layers does. So this diminishes the thermal resistance, and hence the overall greenhouse effect.

The only question is how much of this energy flow is carried away by radiation and how much by other energy transfer mechanisms. Chillingar et al suggests that more than ALL of the additional energy is carried away by convection. I don't understand how that can be and I have no faith in his ability to analyse it correctly, so I will await confirmation of his "theory" by real data and by the reviews of his scientific peers.

As I said, I didn't read the paper, and I would also be surprised to see that it carries away *everything*, but for sure, it must carry away *something*.

And that's BTW the main difficulty I have with the current claims of certainty of AGW: there seems to be a discrepancy between the "purely physical numbers" for CO2 doubling (between 0.8K and 1.5K for a static atmosphere), and the IPCC "best fit" of 3K (between 1.5K and 6K) without any "first principles", but just a fit to the data *assuming* that the only drive is the CO2 radiative forcing ; in other words, the famous positive feedbacks which are not modeled, but which are *postulated*. That doesn't mean that they are not there, but I would have liked to see somewhat more "hard physics" in there before being certain about the claim.

 

[Andrew Mason]

The adiabatic cooling comes about because the pressure is lower at higher altitude, and as such it does work (yes, "free" expansion does work).

If an expanding gas does work then it is not a free expansion. If it does work it cools but the gas that it does work on warms. There can be no net cooling. It is prohibited by the second law of thermodynamics.

All convection does is lower the temperature gradient by mixing the air. It does not alter the average temperature of the air. We are talking about convection in the troposphere which extends up to about 60,000 feet (11 miles or 17 km) and an existing thermal gradient of 6.5 Kelvin/ km. Chilingar is suggesting that additional CO2 will increase the average temperature of the atmosphere but cause more convection so that smaller thermal gradient results in an actual decrease of temperature at the surface.

Chilingar has problems explaining how his model fits Venus. Does the 95% CO2 atmosphere of Venus cool the surface of Venus? Venus has a very high albedo factor of .75 (compared to Earth's .3). Although its solar irradiation is about double Earth's (2614 watts/m^2 versus 1367 for earth), the albedo results in a lower blackbody temperature (231 K or - 42 C versus 255K for earth). But, in fact the surface temperature of Venus is much higher (750 K!). At an altitude of 100 km the temperature goes down to 180K. This means it has an average temperature gradient of 5.7 degrees K per km. compared to Earth's 6.5. But this slightly lower gradient certainly does not result in a lower surface temperature.

Chilingar explains Venus by suggesting that chemical reaction in the upper troposphere on Venus - suggesting that this is creating a continuous heat source that heats the surface from something less than its blackbody temperature to 750 K! He just throws this out as if it was a proven fact! This appears to be news to NASA.

AM

 

[vanesch]

If an expanding gas does work then it is not a free expansion. If it does work it cools but the gas that it does work on warms. There can be no net cooling. It is prohibited by the second law of thermodynamics.

Think of the individual parts as locked up in balloons. One balloon goes up, containing hot, wet air, and another one, containing dry, cool air, goes down. The air in the rising balloon will expand, and cool adiabatically, and the balloon going down will be compressed and will adiabatically heat. If both movements compensate, all the other air will not be compressed or expanded, will at most be horizontally displaced, and will not undergo any effect.

All convection does is lower the temperature gradient by mixing the air. It does not alter the average temperature of the air. We are talking about convection in the troposphere which extends up to about 60,000 feet (11 miles or 17 km) and an existing thermal gradient of 6.5 Kelvin/ km. Chilingar is suggesting that additional CO2 will increase the average temperature of the atmosphere but cause more convection so that smaller thermal gradient results in an actual decrease of temperature at the surface.

I don't think that there will be an actual *cooling* but as I said, I haven't studied that paper. I'm just talking in general about convection. If convection MIXES air, then there is no convection! It would then be diffusion. Convection is the flow within flux tubes of air in the vertical direction, driven by a density gradient (itself induced by composition - water vapor - or temperature). Of course, there will be *some* mixing due to microturbulence, and there will be *some* conduction. But I take it that you can consider convection essentially as a loopy flow with "air bubbles" going up, and other "air bubbles" going down as if they were adiabatically insulated, like in balloons.

So IMO, convection cannot do anything else but *reduce* the greenhouse effect as compared to a static atmosphere. If Chilingar claims that it *overcompensates* and actually leads to a cooling, then I should study his argument, but it is not my point. My point is simply that convection IS a more efficient way to cool the surface than *just* radiation transport through a static grey atmosphere, and as such, when taken into account, will lead to some diminishing of the greenhouse effect as compared with a non-moving atmosphere.

Chilingar has problems explaining how his model fits Venus. Does the 95% CO2 atmosphere of Venus cool the surface of Venus? Venus has a very high albedo factor of .75 (compared to Earth's .3). Although its solar irradiation is about double Earth's (2614 watts/m^2 versus 1367 for earth), the albedo results in a lower blackbody temperature (231 K or - 42 C versus 255K for earth). But, in fact the surface temperature of Venus is much higher (750 K!). At an altitude of 100 km the temperature goes down to 180K. This means it has an average temperature gradient of 5.7 degrees K per km. compared to Earth's 6.5. But this slightly lower gradient certainly does not result in a lower surface temperature.

Chilingar explains Venus by suggesting that chemical reaction in the lower troposphere on Venus are creating a continuous heat source that heats the surface from something less than its blackbody temperature to 750 K! He just throws this out as if it was a proven fact!
This appears to be news to NASA.

As I said, I'm not arguing Chilingar's paper, and if that claim is there, it would be very dubious indeed.

Just a single remark concerning Venus, which just occurs to me right now, and not with much thought behind it: it is funny that the vertical gradient on venus and Earth are similar, given the totally different situations. That could mean that there is a kind of maximum gradient in the atmosphere above which strong feedback mechanisms such as convection lock up the maximum gradient. As such, there is a maximum greenhouse effect for a given atmospheric thickness (pressure).

 

[Andre]

Mind that there is likely no convection in the lower atmosphere of Venus

http://cat.inist.fr/?aModele=afficheN&cpsidt=14488583

No air conditioner there

 

[Andrew Mason]

If convection MIXES air, then there is no convection! It would then be diffusion. Convection is the flow within flux tubes of air in the vertical direction, driven by a density gradient (itself induced by composition - water vapor - or temperature). Of course, there will be *some* mixing due to microturbulence, and there will be *some* conduction. But I take it that you can consider convection essentially as a loopy flow with "air bubbles" going up, and other "air bubbles" going down as if they were adiabatically insulated, like in balloons.

That isn't exactly the way convection works, though. The air isn't contained in little packets or in confined channels. Convection necessarily increases mixing. Watch a smoke stack. A chimney operates entirely by convection. But look what happens to the hot smoke/vapour escapes the chimney. It mixes, rapidly, into the surrounding air. This is just the inevitable effect of random thermal molecular motion. Convection on earth, of course, results in winds. That is the result of the differences in heating of the air because of the difference in intensities of solar energy incident upon the surface at different latitudes/locations and the different heat transfer mechanisms over land/sea/forests/deserts etc.

So IMO, convection cannot do anything else but *reduce* the greenhouse effect as compared to a static atmosphere. If Chilingar claims that it *overcompensates* and actually leads to a cooling, then I should study his argument, but it is not my point. My point is simply that convection IS a more efficient way to cool the surface than *just* radiation transport through a static grey atmosphere, and as such, when taken into account, will lead to some diminishing of the greenhouse effect as compared with a non-moving atmosphere.

And my point is that convection can't lower the average temperature of the atmosphere. It simply redistributes the heat. Convection is not air conditioning.

AM

 

[Andre]

That isn't exactly the way convection works, though. The air isn't contained in little packets or in confined channels. Convection necessarily increases mixing. Watch a smoke stack. A chimney operates entirely by convection. But look what happens to the hot smoke/vapour escapes the chimney. It mixes, rapidly, into the surrounding air. This is just the inevitable effect of random thermal molecular motion. Convection on earth, of course, results in winds. That is the result of the differences in heating of the air because of the difference in intensities of solar energy incident upon the surface at different latitudes/locations and the different heat transfer mechanisms over land/sea/forests/deserts etc.

Don't look at chimneys, look at cumulus type clouds, that's visual convection in action. The sharp defined boundaries proof that mixing is not a predominant factor at first. At higher altitudes the high winds cause mixing and you can see the anvil dissipate but that is after the convective phase.

http://www.geos.ed.ac.uk/abs/Weathercam/Clouds.html
http://svs.gsfc.nasa.gov/vis/a000000/a003300/a003393/index.html

 

[vanesch]

That isn't exactly the way convection works, though. The air isn't contained in little packets or in confined channels. Convection necessarily increases mixing. Watch a smoke stack. A chimney operates entirely by convection. But look what happens to the hot smoke/vapour escapes the chimney. It mixes, rapidly, into the surrounding air.

Yes, and at that point, convection stops, and becomes diffusion. That is because a stack is a small jet of air into a big static mass, and the hydrodynamics is such that this quickly becomes turbulent, microturbulent, and hence mixes, at which point there is no net hydrodynamics anymore.

But for big airmasses that's not true: ask any deltaglider or glider plane pilot. You really have massive upflows and downflows with just marginal mixing and diffusion at the border.

This is just the inevitable effect of random thermal molecular motion. Convection on earth, of course, results in winds. That is the result of the differences in heating of the air because of the difference in intensities of solar energy incident upon the surface at different latitudes/locations and the different heat transfer mechanisms over land/sea/forests/deserts etc.

You give a counter example yourself: wind. Wind is the horizontal equivalent of convection. Now, on northern moderate lattitudes, you have typically that if the wind blows from the south, it becomes warmer, and when the wind blows from the north, it gets colder. As such, wind (horizontal "convection") is very effective and capable of transporting heat over larger distances than normal diffusion (conduction in this case) would be able to do.

And my point is that convection can't lower the average temperature of the atmosphere. It simply redistributes the heat. Convection is not air conditioning.

That would be correct in an isolated atmosphere. But the atmosphere acts as a thermal resistor between the ground (heat source) and outer space (heat sink). As such, the main effect of the atmosphere is heat transport, and "redistributing heat" is everything we are concerned with here.

Think of it this way: consider a piece of carbon paper, through which we force a current (injection on the left, drain on the right). That represents the heat flow which the Earth surface needs to evacuate. The voltage difference needed to do so will depend upon the resistance of the sheet and represents the temperature. Now, convection acts as a kind of "short circuit", in the way a piece of copper placed on the sheet would. The piece of copper is not a current source. It doesn't alter the total charge of the sheet. It just shunts a part of the resistance. As such, the overall effective resistance of the sheet lowers, and for the same current, a smaller potential difference is needed.

 

[Andre]

Wind is the horizontal equivalent of convection.

That's called advection

Mind also that vertical convection in unstable atmospheric conditions is not the only form of convection. It also happens when cold and warm air masses collide, forming http://www.answers.com/warm%20front . Due to the density difference the warmer air mass is forced over the colder air mass, also transporting energy to higher levels for easier out radiation of IR.

the idea of cold front (upper) and warm fronts (lower) :

http://rst.gsfc.nasa.gov/Sect14/3_warmcoldfronts.jpg

But the strongest convection and hardest rain is associted with occluding fronts:

http://www.mrsciguy.com/sciimages/cyclone03.gif

where the wedged formed warm air section is squeezed up when the trailing cold front overruns the leading warm front.



Disclaimer: Meteorology just happens to be basics for flying, especially in the weather dominated west Europe. That's how one gets to know these things. But one may wonder if and to what extend these vertical energy transport effects are understood and simluated correctly in the climate models.

 

[Bystander]

(Snip)The atmosphere will radiate exactly the amount of radiation that it absorbs - it cannot cool by radiation. Besides, the radiation from the atmosphere is in all directions. Just as much radiation is directed from the atmosphere toward the earth. It is this radiation from the atmosphere back toward the Earth that increases the surface temperature.(snip)

This isn't just for AM --- everybody please go back and review Kirchoff's Law.

Regarding convective heat transfer from the surface to the tropopause, there is the adiabatic cooling of rising air masses, and the adiabatic warming of falling air masses to consider, plus whatever radiative heat transfers occur between sun and various air masses, between Earth surface and air masses, between CMB and air masses, and among air masses; i.e., it ain't obvious, the measurements ain't been done, and they aren't likely to be accomplished to a "definitive" level of certainty anytime soon.

 

[Andrew Mason]

This isn't just for AM --- everybody please go back and review Kirchoff's Law.

I am not sure what you are suggesting. It is not simply a matter of looking at the Earth from space as blackbody radiation problem. That analysis will give you the blackbody temperature of the Earth as viewed from space but it will not give you the temperature on the surface. The surface temperature will depend on how much energy is reaching the surface from space (the sun) and how much energy is reaching the surface from the matter above the surface ie. the atmosphere. That is a function of the temperature of the atmosphere and also how reflective and transparent that atmosphere is to IR radiation emitted from the Earth's surface.

A car sitting in the sun gets warm because a lot of short wavelength radiation (solar temperature 6000K) enters causing the car to emit long wavelength radiation (car temperature about 300K). The glass is transparent to short wavelength radiation but reflects and also absorbs/reradiates long wavelength IR radiation back into the car. So the radiation into the car is more than just the solar radiation.

Now, convection will cause air will move around in the car. But this doesn't really cool the inside of the car much. You won't get cool.

AM

 

[vanesch]

Now, convection will cause air will move around in the car. But this doesn't really cool the inside of the car much. You won't get cool.

It is highly artificial as example of course, but consider that the car only gets hot through solar radiation through the window and that the roof of the car is in the shadow. In that case, convection DOES cool the car a little bit, as more heat is transported to the roof of the car, so that more heat is conducted out and radiated away by the metallic roof, than if there were no convection and only the seats got very hot, and had to radiate away their heat to the roof.

In other words, facilitating the heat transport from the source (here, the seats of the car, that convert solar light into heat) to the dump (the roof) removes heat somewhat quicker.

 

[Andre]

http://www.gi.alaska.edu/ScienceForum/ASF8/817.html is how a greenhouse really works:

...Whether bare or covered by a greenhouse, the ground absorbs radiation from the sun and heats up. The increase in temperature is conducted to the air next to the earth; that air then warms and expands, thus becoming less dense than the air higher up. The lighter air rises, allowing cooler and denser air to take its place at the surface and absorb more heat from the warmed ground. Thus the radiation absorbed by the ground goes into heating a deepening layer of air. Above open ground on a sunny day in summer, the heated layer of air may easily be a mile or more deep, and since the warming is spread over such a large mass (a deep layer of air plus a very thin layer of soil and vegetation), the temperature rise is diluted by the sheer amount of stuff that must be heated. (Think of how slowly the temperature rises in a large kettle full of water which is set on a hot stove for five minutes.)

In a greenhouse, this mixing is confined to the layer of air trapped under the roof, so there is a much smaller mass to be heated. Essentially, the large kettle full of water has been replaced by one with half an inch of water on its bottom, and as a result the water will warm up much faster. This also explains why ventilation is so important in keeping a greenhouse from overheating. (A closed car in the sun heats up due to the same mechanism.)...

 

[billiards]

It is well understood that the "greenhouse effect" is a misnoma. An actual greenhouse works by physically preventing air from convecting heat outside of its glass housing. The "greenhouse" effect in the atmosphere is completely different, it works by gas particles absorbing energy in specific bands of the the electro-magnetic spectrum and re-emitting this energy, some of which goes back towards the earth.

Convection is the most efficient form of heat transfer, of course it accounts for a great deal of the Earth's dissipated energy. So much so that I don't think that small changes in CO2 will drive a significant increase in this dissipative mechanism. In fact, I don't really see why it would necessarily act as a convection enhancer in the first place, perhaps it even has the reverse effect? Given that CO2 covers bands of the electro-magnetic spectrum not covered by water vapour or methane, I reckon it's probably more important as a greenhouse gas, because if it weren't there the energy would be free to escape.

As for the discussion surrounding the scientific method, I think we have to look at this science less as a pure mathematical science, such as the type of science that Feynman was doing, and more as a kind of "geophysical hazards" type science. This is mixed with political, financial and of course sociological considerations which detract from the pure science - I don't mean that in an "excuses for poor science" kind of way - it's just how this science is. For example, take the study of volcanology, if the scientist who studies the volcano thinks it's going to erupt, she does her best to check the science but she cannot be 100% certain that it will go; it's still her job to let people know she thinks it's going to go, perhaps she will give them a degree of certainty and allow the authorities to handle the PR. Of course I'm not saying that Feynman was wrong, he was most certainly right in my opinion, and it is a shame that climate science (and Earth sciences in general) isn't closer to the rigourous science conducted by the likes of Feynman, but the complexity of the macroscopic scale forbids it. Incidentally, I'm not so sure that the anthropogenic CO2 emissions = global warming hypothesis is presented as being "proven", I seem to remember a "90% certain" from the IPCC.

To quote a famous glaciology paper, Mann 1978, when the fear of global warming first started to emerge:

Schneider sums up the dilemma facing mankind: despite the crudities and inadequacies of present techniques for modelling the climatic effects of increasing atmospheric CO2 content and the resultant doubts about the magnitude of the warming that would actually occur, we cannot afford to let the atmosphere carry out the experiment before taking action because if the results confirm the prognosis, and we should know one way or another by the end of the century, it will be too late to remedy the situation on account of the long residence time of CO2 in the atmosphere (Keeling and Bacastow estimate that, if all accessible fules were burnt, restoration of pre-industrial levels of CO2 would take at least 10,000 yr).

S

 

[Andrew Mason]

http://www.gi.alaska.edu/ScienceForum/ASF8/817.html is how a greenhouse really works:

A greenhouse can use many different techniques for regulating and/or storing heat. These do not illustrate the greenhouse principle. The principle is simple: let shortwave radiant energy in and trap the longwave radiation on its way out.

There is a popular misconception that the greenhouse effect is misnamed, suggesting that the trapping of heat by CO2 in the atmosphere is fundamentally different than the use of glass in a greenhouse. The principle is the same, although the mechanism is different. In a greenhouse the glass reflects the IR radiation back into the greenhouse ie. the IR radiation is not absorbed and reradiated by the glass. With CO2 the IR radiation emitted by the surface of the Earth is absorbed by the CO2, so the temperature of the CO2 increases. The CO2 then emits IR radiation - half of it back toward the earth.

AM

 

[Bystander]

http://www.wmconnolley.org.uk/sci/wood_rw.1909.html

from post #29 this thread, R. McL.

 

[vanesch]

It is well understood that the "greenhouse effect" is a misnoma. An actual greenhouse works by physically preventing air from convecting heat outside of its glass housing. The "greenhouse" effect in the atmosphere is completely different, it works by gas particles absorbing energy in specific bands of the the electro-magnetic spectrum and re-emitting this energy, some of which goes back towards the earth.

Convection is the most efficient form of heat transfer, of course it accounts for a great deal of the Earth's dissipated energy. So much so that I don't think that small changes in CO2 will drive a significant increase in this dissipative mechanism. In fact, I don't really see why it would necessarily act as a convection enhancer in the first place, perhaps it even has the reverse effect? Given that CO2 covers bands of the electro-magnetic spectrum not covered by water vapour or methane, I reckon it's probably more important as a greenhouse gas, because if it weren't there the energy would be free to escape.

As for the discussion surrounding the scientific method, I think we have to look at this science less as a pure mathematical science, such as the type of science that Feynman was doing, and more as a kind of "geophysical hazards" type science. This is mixed with political, financial and of course sociological considerations which detract from the pure science - I don't mean that in an "excuses for poor science" kind of way - it's just how this science is. For example, take the study of volcanology, if the scientist who studies the volcano thinks it's going to erupt, she does her best to check the science but she cannot be 100% certain that it will go; it's still her job to let people know she thinks it's going to go, perhaps she will give them a degree of certainty and allow the authorities to handle the PR. Of course I'm not saying that Feynman was wrong, he was most certainly right in my opinion, and it is a shame that climate science (and Earth sciences in general) isn't closer to the rigourous science conducted by the likes of Feynman, but the complexity of the macroscopic scale forbids it. Incidentally, I'm not so sure that the anthropogenic CO2 emissions = global warming hypothesis is presented as being "proven", I seem to remember a "90% certain" from the IPCC.

To quote a famous glaciology paper, Mann 1978, when the fear of global warming first started to emerge:

Schneider sums up the dilemma facing mankind: despite the crudities and inadequacies of present techniques for modelling the climatic effects of increasing atmospheric CO2 content and the resultant doubts about the magnitude of the warming that would actually occur, we cannot afford to let the atmosphere carry out the experiment before taking action because if the results confirm the prognosis, and we should know one way or another by the end of the century, it will be too late to remedy the situation on account of the long residence time of CO2 in the atmosphere (Keeling and Bacastow estimate that, if all accessible fules were burnt, restoration of pre-industrial levels of CO2 would take at least 10,000 yr).

S

I fully agree with what you write, and I always pointed out that AGW is 1) a genuine possibility, that, given the data, is certainly plausible and 2) that given the potential damage (although that can also be disputed, but ok...) of AGW, even if there were only a 30% chance of it actually happening in dramatic proportions, we should try to mitigate it. So, given the current state of affairs, I think that there is no discussion that we should at least plan how to get our CO2 emissions down, just in case. But that's the social and political part.

However, science is science and it is not because the means to gather proof are harder, that truth is easier to find and hence that one has to be less rigorous. And what disturbs me profoundly in the *scientific* discussion of AGW, is that open but sceptic inquiry is now frowned upon - while it should be the prevailing attitude. When you look at the IPCC and all the supportive bodies around it, it seems that if you even dare to question certain hypotheses of the AGW theory, you are stamped as a heretic, a climate sceptic, etc... with the underlying insinuation that you are or a crackpot, or that you have some or other vested interest in denying AGW, or that you have yourself leading by your emotions and are in a psychological state of denial.

We have had, according to their saying, official members of the IPCC here on this board requesting that discussions be closed simply because they were putting in doubt aspects of the AGW hypothesis, and that this should be treated as crackpot stuff, as if it were creationism or something of the kind. I find this, given the current state of knowledge, a very very worrisome attitude on the scientific level. It is the thing I try to point out (and I might come over as an AGW denier because of that, which I'm not).

Again, there's enough stuff on the table to say that it is not completely crazy to think of AGW, and given its potential dangers in its most extreme forms, that by itself is sufficient to warrant careful policies. Even a 10% chance of AGW (which means that there is 90% chance that AGW is not true) should make us err on the side of caution. Nobody would accept, say, a 10% chance that we would ignite the atmosphere in the coming century or 10% chance of some other global disaster. So the very absence of total proof that there is no AGW is sufficient to warrant careful policies.

But that has *nothing* to do with the question whether it makes sense or not to investigate in the difficulties that the AGW theory still faces. The very fact that taking on this position now makes you a heretic, or a non-scientist, or a spokesman of this or that presumed lobby, is, to me, as a scientist, profoundly shocking.

Also the 90% certainty displayed by the IPCC is itself just a statistical estimate of a distribution of responses to radiative forcings which is based upon certain hypotheses which are then given 100% a priori certainty. I think it is a very optimistic estimate of the actual state of knowledge.

 

[Andre]

We have had, according to their saying, official members of the IPCC here on this board requesting that discussions be closed simply because they were putting in doubt aspects of the AGW hypothesis, and that this should be treated as crackpot stuff, as if it were creationism or something of the kind.

I should not react to the less apparent due diligence of that IPCC groupthink but this is insane. If you can't win the discussion, remove the opponent. Why wasn't this alleged IPCC member invited to refute the rebuttals and demonstrate the robustness of the climate change notion?

Problem is that all evidence has evaporated; the ice cores; the hockeystick and the actual records.

In the beginning there were the ice cores showing a remarkable correlation between "temperature" and carbon dioxide. Given the greenhouse effect hypothesis this appeared to be a rather convincing substantiation, which certainly warranted climate caution.

But later research showed a substantial lag of CO2, following temperatures and the alternate guess of explaining it away as positive feedback, has never been substantiated. Instead, the characteristic behavior of positive feedback is missing. It actually shows that CO2 did nothing observable, essentially falsifying the estimated greenhouse effect of CO2.

Then came the hockey stick, Mann et al ironing out the wrinkles of the Medieval Warming Period and the Little Ice age in the last millennium; showing an overwhelming convincing nobrainer correlation between temperatures and CO2 both rising dramatically in the last millenium.

But then it was demonstrated that the hockey stick was mainly based on an incorrect algoritm, causing all Monte Carlo simulations to produce hockeysticks. Later reconstructions of the last millennium do show the Medieval Warm Period and the Little Ice Age again, demonstrating the predominance of natural variability independent of CO2. Mind that he discussion, whether or not the Medieval Warm Period was warmer than today, is irrelevant and plays no role in asserting the “warming power” of CO2.

An then the actual records; indeed the temperatures and CO2 were rising simultaneously in the last quarter of the last century, again suggesting causality. However the warming trend diminished around the beginning of this century, while the CO2 continued to rise, again demonstrating that natural variability outperforms CO2.

Notice also that melting glaciers, a warmer Arctic and rising sea levels, merely proof changing conditions, but not what caused those changes. Furthermore, notice also that climate model runs, based on the unproven hypothesis merely constitute circular reasoning. That’s no evidence either.

So what is the evidence left that supports substantial warming due to rising levels of CO2? I can’t think of any. Instead we have competing hypotheses (Chilingar et al 2008, Miscolczi 2007) explaining why the basic idea’s of the greenhouse hypothesis may be incorrect.

But it doesn’t matter since we have to curb emissions anyway to transit to sustainable energy, right? Wrong. It matters because science is turned into ideology or dogma here to enforce policy. That will backfire hard eventually when proven incorrect in the future. Perhaps we should let the governments be run by engineers, who can’t afford basing their designs on unproven dogmas.

 

[wolram]

The worrying thing to me is, that scientists can not derive an experiment to prove or dis prove AGW, the laboratory is Earth and is tangible, or is it that this problem IS so testable?