Guest post By Ben Herman and Roger A. Pielke Sr.
During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere. We would like to briefly explain the arguments that have been put forth and why they are incorrect. Two of the primary arguments that have been used are
- By virtue of the second law of Thermodynamics, heat cannot be transferred from a colder to a warmer body, and
- Since solar energy is the basic source of all energy on Earth, if we do not change the amount of solar energy absorbed, we cannot change the effective radiating temperature of the Earth.
Both of the above statements are certainly true, but as we will show, the so-called “greenhouse theory” does not violate either of these two statements. (we use quotation marks around the words “greenhouse theory” to indicate that while this terminology has been generally adopted to explain the predicted warming with the addition of absorbing gases into the atmosphere, the actual process is quite a bit different from how a greenhouse heats).
With regards to the violation of the second law, what actually happens when absorbing gases are added to the atmosphere is that the cooling is slowed down. Equilibrium with the incoming absorbed sunlight is maintained by the emission of infrared radiation to space. When absorbing gases are added to the atmosphere, more of emitted radiation from the ground is absorbed by the atmosphere. This results in increased downward radiation toward the surface, so that the rate of escape of IR radiation to space is decreased, i.e., the rate of infrared cooling is decreased. This results in warming of the lower atmosphere and thus the second law is not violated. Thus, the warming is a result of decreased cooling rates.
Going to the second statement above, it is true that in equilibrium, if the amount of solar energy absorbed is not changed, then the amount of IR energy escaping out of the top of the atmosphere also cannot change. Therefore the effective radiating temperature of the atmosphere cannot change. But, the effective radiating temperature of the atmosphere is different from the vertical profile of temperature in the atmosphere. The effective radiating temperature is that T that will give the proper value of upward IR radiation at the top of the atmosphere such that it equals the solar radiation absorbed by the Earth-atmosphere system.
In other words, it is the temperature such that 4 pi x Sigma T4 equals pi Re2 Fso, where Re is the Earth’s radius, and Fso is the solar constant. Now, when we add more CO2, the absorption per unit distance increases, and this warms the atmosphere. But the increased absorption also means that less radiation from lower, warmer levels of the atmosphere can escape to space. Thus, more of the escaping IR radiation originates from higher, cooler levels of the atmosphere. Thus, the same effective radiating temperature can exist, but the atmospheric column has warmed.
These arguments, of course, do not take into account feedbacks which will kick in as soon as a warming (or cooling) begins.
The bottom line here is that when you add IR absorbing gases to the atmosphere, you slow down the loss of energy from the ground and the ground must warm up. The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway. But the radiational forcing due to the addition of greenhouse gases must result in a warming contribution to the atmosphere. By itself, this will not result in a change of the effective radiation temperature of the atmosphere, but it will result in changes in the vertical profile of temperature.
The so-called “greenhouse effect” is real. The question is how much will this effect be, and this is not a simple question. There are also questions being raised as to the very sign of some of the larger feedbacks to add to the confusion. Our purpose here was to merely point out that the addition of absorbing gases into the atmosphere must result in warming, contrary to some research currently circulating that says to the contrary.
For those that might still question this conclusion, consider taking away the atmosphere from the Earth, but change nothing else, i.e., keep the solar albedo the same (the lack of clouds would of course change this), and calculate the equilibrium temperature of the Earth’s surface. If you’ve done your arithmetic correctly, you should have come up with something like 255 K. But with the atmosphere, it is about 288 K, 33 degrees warmer. This is the greenhouse effect of the atmosphere.
“Jim D says:
July 24, 2010 at 9:37 am
tallbloke, Stephen Wilde,
I see where we differ. You think that downward longwave flux has no influence at all on ocean temperature in the long term. I don’t agree at all with that view. By keeping the top of the ocean from cooling towards 255 K (as it would with just mean solar radiation), it maintains the thermal profile in the ocean, preventing convective mixing that would otherwise bring the colder water down and reduce the ocean heat content.”
If the energy from extra downward longwave flux is removed to latent heat of evaporation in the air via increased evaporation (possibly even a net cooling effect)
how could it affect maintenance of the thermal profile ?
I’ve been into this in exhaustive detail here:
http://climaterealists.com/index.php?id=4245
because I regard it as an important issue.
tallbloke,
Now we are splitting hairs. I never said the IR penetrates the ocean, but I think we agree it has an impact on the deeper layers through preventing convection that would happen without it. The longwave energy into the skin layer is very important to the overall budget of the deeper layer.
[reply] try using italics tags instead. RT-mod
RT,
Thanks for the suggestion.
John
You could be right that the atmosphere is 33 degrees warmer than that determined by the Stephen Boltzmann equations, which you than describe as the atmospheric greenhouse effect. You than seem to imply that the greenhouse gasses (on earth these are actually only trace gasses) are solely, or at least substantially, responsible for this.
On which assertion or facts you base this on is not clear.
Apollo 14 and 17 measurements on the moon, show an even higher 40 degrees warmer temperature, than these formulas suggest, without an atmosphere.
It is actually 60 degrees warmer on the night side and 20 degrees cooler on the day side, ie. the temperature is not really warmer, but is actually only dampened.
By only looking at the average temperature we actually came to the wrong conclusion.
Which is probably the same with earth 33 degree difference. This difference is determined by averaging the temperature of the earth (day, night, summer, winter),
by averaging the solar radiation at the surface, which itself is averaged out as a non rotating disc (instead of a sphere). This surface is than given the average albedo
of earth to determine the average black body radiation (based on the average solar radiation received at the surface), which then is converted to temperature and compared to the average temperature at the surface. No consideration is given to the fact that radiation budget on the day side is vastly different to that on the night side.
From the lunar results above we can see that this is actually highly non linear and averaging would give a completely wrong result.
The lunar temperatures suggest that the Stephen Boltzmann formulas do not give the correct results. They ignore the fact that in reality bodies have mass, which absorb some of the solar radiation and conduct them inwards, instead of emitting this radiation immediately, resulting in a lower day side temperature. One could thus say they store the energy and emit this again, once there is no solar radiation on the night side. This is gives than the higher night temperatures.
The capacity of a material to store some heat, depends on its specific heat.
Materials on the land surface and the water in the ocean play a similar role on earth. They together with processes in the atmosphere (including absorbtion and emitting
capacities of greenhouse gasses) play a dampening effect on the real temperature, which can potentially be achieved by earth. However the specific heat (the energy needed to raise the temperature by a unit amount) of water is far higher then that of dry air (mostly oxygen and nitrogen – pure C02 is even lower), resulting in a far higher heat capacity of the oceans than the atmosphere. (The land surface is also very much higher, here the capacity varies with the type of soil and vegetation coverage – also the heat capacity of moist air is slightly higher then dry air, this however is difficult to measure, since the capacity of air to hold the moist depends on the
temperature)
Because of the higher heat capacity, the flow of heat energy will always be dominated by the flow from the oceans and land surface to the atmosphere and not the otherway round.
Now which part of the earth is more likely be able to change the surface temperature? A change in the insulation of the atmosphere due to slight overall changes in the
composition of the atmosphere (CO2 is usually sighted, since humans have been responsible in some of its increase) thereby retaining some extra radiation or a change in say the processes which determine ocean temperature? The capacity of greenhouse gasses to contribute to the overall warming of earth is probably vastly overstated.
Extra greenhouse increases may actually only delay the time the radiation takes to be emitted to space. What we actually really only know about greenhouse gasses
is, that they intercept some radiation (depending on the frequency and the type of gas) and emit it in any direction, i.e. they disperse it, instead of concentrating it,
which might be a more likely scenario to cause more warming.
There is also another concept which is usually also mentioned in conncetion with the greenhouse effect: downwelling radiation (or back radiation – not adressed in this article, but in some comments). They do exits otherwise they would not have been measured.
There are however two assumption related to this, which I want to address:
1. The assertion that because they exist the greenhouse effect is real: Here we have the assumption that only greenhouse gasses can emit this radiation, since they are the
once who absorb them in the first place and the rest of the atmosphere is actually transparent.
This is actually wrong, since every molecule solid, liquid or gaseous emits radiation, as long as it is heated above the absolute zero temperature (-273 degrees celsius).
The type and intensity of the emitted radition depends on the actual temperature. The heat gets into the atmosphere through other processes than radiation, like
conduction, convection and evaporation.
2. The claim that the downwelling radiation actually warms the surface, from which it was emitted from, in the first place.
This would violate the First Law of Thermodynamics, which basically says that you cannot raise the temperature of a system, without applying extra energy (some work)
to that system. If for example a black body surface receives 1 unit of solar radiation it will need to emit 1 unit of infrared radiation. If however some of that emitted
radiation (say 0.1) is intercepted (by say a greenhouse gas) and emitted back to the surface, than if the claim above is true, the surface will be made warmer by that 0.1
unit, which the surface also needs to emit. Thus it is emitting 1.1 units from the 1 unit of solar radiation, which is clearly wrong.
Many claims about the greenhouse hypothesis have become fact by repetition. They never really have been proven and some are the result of misleading observations. For the greenhouse hypothesis to become a theory it needs many more solid observation, which can be proven not to be the result of other processes.
The lunar measurements alone contradict this hypothesis at least in earth environment. As long as these measurements cannot be explained, in the context of this hypothesis, it cannot stand if we really want to follow the scientific method.
899 says:
July 24, 2010 at 12:30 am
You’re either a comedian paid to post inanity, or you’re just plain inane.
If the Sun radiates to the Earth, and the Earth begins to heat, the heat energy will re-radiate from the Earth and into space.
And back towards the sun.
This is so because space is cooler than either the Sun or the Earth.
If the only two objects in the universe were the Sun and the Earth, and space didn’t exist, then please DO TELL how the cooler Earth is going to transfer heat back to a very much hotter Sun.
By radiation of course which does not require a temperature gradient.
You’ll get back on that, won’t you?
Done, I suggest you read up on radiation heat transfer, your knowledge is sadly lacking.
Phil. says:
July 23, 2010 at 8:35 pm
REPLY: I have fixed it for you. – Anthony
Thanks, that’s what comes from posting in a noisy Starbucks instead of home. 😉
Stephen Wilde says:
July 24, 2010 at 9:37 am
Jim G said:
“GHG’s trap enough of that sunshine to maintain the earth at an nice range where surface life can thrive.”
Just a thought, Jim. How much is ‘trapped’ by those pesky GHGs and how much is ‘trapped’ by our oceans.
________
The oceans act as a heat sink, not as a trap in the sense of GHG’s. GHG’s quickly absorb and retransmit LW radiation, altering the direction of some of that back towards the ground, out into space, or toward other GHG molecules in the atmosphere, where it is once more absorbed and retransmitted. The oceans can store heat over long periods at multiple depths, releasing it through multiple daily and natural oscillating cycles, from simple daily evaporation, to hurricanes, ENSO, etc.
Peter says:
Sorry if I was unclear. What I was saying is that the 4 W/m^2 does not refer to the surface radiation budget. Indeed I think that you are correct that the actual increase of radiation at the surface is larger. I am not sure what it is. People talk about the surface radiation budget a lot less because it is a lot less useful to think about. It is easier to think in terms of the radiative budget at the top of the atmosphere and then the constraints on the temperature structure of the atmosphere in order to derive the surface warming.
Jim D says:
July 24, 2010 at 10:03 am
Now we are splitting hairs. I never said the IR penetrates the ocean,
Hang on a minute. Upthread you said:
Jim D says:
July 24, 2010 at 8:42 am (Edit)
As far as the ocean is concerned it absorbs 92% of the solar flux and 99% of the longwave (back radiation) flux. It doesn’t care if it is solar or longwave (IR) – a Watt per square meter is a Watt per square meter. You can’t choose one input and ignore the other.
So, yes you did say that longwave penetrates the ocean and a longwave co2 emitted watt is as effective t transferring heat to the ocean as a shortwave solar watt. And you were incorrect about that, as you now agree.
OK, so now to the rest of your post:
but I think we agree it has an impact on the deeper layers through preventing convection that would happen without it. The longwave energy into the skin layer is very important to the overall budget of the deeper layer.
This is armwaving. What longwave energy into the ‘skin layer’? Where are the experimental results to back up your claims?
Show me the data.
John Whitman,
I would stand by what I said. When they refer to things slowing down, they are talking about reducing rates. The equilibrium is an equilibrium of rates of heating and cooling. Slowing down the loss of energy is slowing down the cooling rate. I said CO2 reduces surface cooling rates, as they did. I could go into the whole faucet, sink, plug-hole, water level, analogy here, but I won’t, and I’ll just point to it as a good one for understanding rates and equilibria.
Stephen Wilde,
Yes the heating rate is not entirely constant, and there are lots other factors, but for the purposes of this thread, we are looking at the effect of CO2 and keeping other things constant. Certainly willing to debate other issues on relevant threads.
R. Gates says:
July 24, 2010 at 10:12 am (Edit)
The oceans act as a heat sink, not as a trap in the sense of GHG’s.
Correct, but it’s solar energy the ocean traps, not longwave from the atmosphere, as I’m discussing with Jim D. Take a read and report back.
‘So, yes you did say that longwave penetrates the ocean and a longwave co2 emitted watt is as effective t transferring heat to the ocean as a shortwave solar watt. And you were incorrect about that, as you now agree.’
That could then be offset by the cooling effect the ensuing evaporation ?
I think this is an interesting point actually – everone talks about the warming of back radiation to the earths surface, but what about the effect it may have as it hits the oceans (71 % of the planets surface) and causes evaporation – that may have a net cooling effect. Has this ever been studied ?
George E. Smith says:
July 24, 2010 at 8:02 am
Reed, You are welcome to live in a well mixed mixture of distilled water and ice.
The rest of us don’t; so your observation has no relation to the greenhouse effect on earth; that stops us from being at 255K.
So believe whatever you want. I’m too busy trying to help people who want to learn to bother with straw man arguments.
Fair enough. We don’t live in a mixture of distilled water and ice. We also don’t live on a ping-pong ball either empty of filled with lead. (see your post : July 23, 2010 at 10:58 am). And for what it’s worth, you changed the “rules of ping-pong ball conduction” in mid-argument. Before you filled the ball with lead, you assumed the energy from the sun would very quickly be distributed over the surface of the ping-pong ball so that the “empty” ping-pong ball would quickly be isothermal (a single temperature). I believe you said:
“I will also make the body to have infinite thermal conductivity; well very high anyway; and it is a thin shell like a ping pong ball so that it is of very low mass and heat capacity.”
Then when you filled the ball with lead, you argued that the side of the ball removed from the sun had to be heated via thermal conduction through the lead. I believe you said:
“Now the radiation impinging on our heavy ball is still totally absorbed; but now the ball is not infinitely thermally conductive, so the rate at which heat travels through the ball to the unradiated isde slows down as most of the heat has to propagate through the lead core, which isn’t such a great conductor.”
In your discussion of the ping-pong ball and the sun, you made a point that from the thermal perspective as viewed from the sun, the fact that the ball is full of lead has no thermal effect. In that vein, if the ping-pong ball shell possessed “infinite thermal conductivity” before the lead was added, it does after the lead is added. As such, the heat being absorbed by the ping-pong ball shell will rapidly be distributed over the ping-pong ball’s surface and the lead will be heated by all surfaces of the ping-pong ball not just from the side facing the sun.
I guess the point of this post is to note that most of us are trying to understand a very complex subject. We come with various backgrounds, prejudices, and amounts of knowledge. When I mentioned a mixture of distilled water and ice, I wasn’t trying to present a strawman that refuted what you had to say. For the most part I agree with your conclusions. I used the example of water and ice to represent the fact that not all solar energy when absorbed by the Earth immediately becomes heat. Some of it is converted into phase state changes, as well as other forms such as chemical (photosynthesis), potential (water being raised to higher elevations), etc. My example of distilled water and ice may have been a poor choice, but I don’t believe it is irrelevant to a discussion of the greenhouse effect–after all the world has a whole lot of ice (albeit not distilled water).
If I offended you by my previous comment (and I guess this one), I apologize. I, too, am trying to understand.
tallbloke,
So the skin layer where the longwave is absorbed is not part of your definition of the ocean, but it is part of mine. Again hair-splitting.
Data? Do a mental experiment. Imagine what would happen to the ocean if the IR flux into it stopped, given that the solar flux alone can only maintain 255 K. Something approximating that effect happens on clear nights. What goes on in the ocean then? There must be data for that. I suspect it cools at the top and convects down, but you must be saying the skin layer remains detached somehow.
Rob says:
July 24, 2010 at 10:35 am (Edit)
‘So, yes you did say that longwave penetrates the ocean and a longwave co2 emitted watt is as effective t transferring heat to the ocean as a shortwave solar watt. And you were incorrect about that, as you now agree.’
That could then be offset by the cooling effect the ensuing evaporation ?
Maybe. This is where we get into the realm of things Roger Pielke Sr lists on his ‘stuff we don’t know about’ section.
stevengoddard says:
July 24, 2010 at 8:28 am
Posted this on the wrong thread earlier:
—————–
I need to clarify a point. It is true that the adiabatic temperature gradient dominates the temperature profile – but this would not occur without the greenhouse effect.
If greenhouse gases did not exist, the atmosphere would remain nearly uniformly cold and would not convect. Without convection, the adiabatic lapse rate would be zero.
I will refute this experimentally. Over deserts, the Sahara for example, there are very few ppm of greenhouse gases. The temperature is around 0C at night and over 50C during the day, not uniformly cold. In addition of course there are winds, hot air rises, cold air comes down.
N2 and O2 without green house gases would settle to a different temperature but convection would surely exist if we are talking of an earth type planet.
“R. Gates says:
July 24, 2010 at 10:12 am (Edit)
The oceans act as a heat sink, not as a trap in the sense of GHG’s.”
And the proportionate scales are ?
If the oceans act as a sink they also act as an output.
Where does the effect of the air fit in as a comparison ?
Where does the effect of CO2 as a minor portion of the total greenhouse effect fit in as a comparison ?
Where does the effect of anthropogenic CO2 as a minor part of natural CO2 (no one suggests that ALL the recent rise is anthropogenic) fit in as a comparison.
I submit total insignificance and any such effect as there may be is negated by an unmeasurable change in the speed of the hydrological cycle as per the findings of Professor Miscolczi
Sorry about the use of italics in my immediately preceding post. I can’t seem to use html properly. The last three paragraphs should NOT be in italics.
Sorted. RT-mod
p.s.
http://en.wikipedia.org/wiki/Lapse_rate
Tallbloke writes:
“Yes, but Earth got cooler by radiating into the atmosphere in the first place. That the point 899 is trying to make I think. So the fact that moastly water vapour and a little bit of co2 send half back again before finally failing to catch the ball and letting it out into space is neither here nor there, except indsofar as the number of times they do catch it and bounce it back to Earth slows down the cooling rate.”
You are calculating net radiation absorption for the object. I have no quarrel with that calculation. However, you then apply your reasoning to a individual emission of radiation and, in doing so, you deny it causality. Consider an analogy. In my fireplace are five logs of uniform size and all are blazing brightly. One log rolls out of the fireplace. I scoop it and put it back in. Net change to the fire in the fireplace is zero. There is your calculation. But then you apply it to the individual log that had rolled out and you say that it does not add energy to the fire – but that is clearly false, right? The log that I scooped back into the fireplace is a cause and has effects. You are denying causality to the emissions of radiation coming from CO2 molecules.
Everyone reading this forum owes you a great debt of gratitude for your first-rate contributions. Thanks so very much.
Jim D asked:
“Do a mental experiment. Imagine what would happen to the ocean if the IR flux into it stopped, given that the solar flux alone can only maintain 255 K. Something approximating that effect happens on clear nights. What goes on in the ocean then? There must be data for that. I suspect it cools at the top and convects down, but you must be saying the skin layer remains detached somehow.”
If the downward IR flux were to cease then the oceans would cool more slowly due to reduced rate of evaporation.
And your point is ?
It is some time since I published my article suggesting that logically more downward IR flux should increase ocean cooling and not decrease it. It has not yet been rebutted.
Jim D says:
July 24, 2010 at 10:24 am
John Whitman,
I would stand by what I said. When they refer to things slowing down, they are talking about reducing rates. The equilibrium is an equilibrium of rates of heating and cooling. Slowing down the loss of energy is slowing down the cooling rate. I said CO2 reduces surface cooling rates, as they did. I could go into the whole faucet, sink, plug-hole, water level, analogy here, but I won’t, and I’ll just point to it as a good one for understanding rates and equilibria.
—————————–
Jim D,
I appreciate you spending time to comment. Of all aspects of life time is the most precious.
I respect Pielke Sr. I think he and Ben Herman are right. It is getting at more understanding of the time aspect of what they say that is the purpose of my thought. Again my thought is =>”It appears to me that therefore, it is the rate of change of the rate of change of T (temp of earth system) that is caused by the rate of change of CO2 concentration (earth atmosphere)”.
?Or do I have that backwards?
John
Jim D says:
July 24, 2010 at 10:40 am
tallbloke,
So the skin layer where the longwave is absorbed is not part of your definition of the ocean, but it is part of mine. Again hair-splitting.
Liquid water is in the ocean, water molecules busy evaporating are leaving the ocean for the air. What is and where is this “skin layer” of which you speak? How thick is it? What differentiates it from the rest of the ocean? Why are you flip flopping between agreeing longwave radiation doesn’t penetrate the ocean, and still trying to say it does?
Data? Do a mental experiment. Imagine what would happen to the ocean if the IR flux into it stopped, given that the solar flux alone can only maintain 255 K. Something approximating that effect happens on clear nights. What goes on in the ocean then? There must be data for that. I suspect it cools at the top and convects down, but you must be saying the skin layer remains detached somehow.
My bold.
There is no IR flux into the ocean, because it can’t penetrate beyond it’s own wavelength. You are still trying to say it does, but saying so don’t make it so.
The rnext bit is red herring. We’ve previously agreed the greenhouse effect works by slowing down the rate of cooling, so why are you now trying to say the greenhouse effect doesn’t operate if downwelling longwave doesn’t penetrate the ocean, which it can’t?
The ocean surface will cool at night as it gives up heat-energy by conduction to cooler night air, by evaporation caused by longwave radiation being stopped at its surface, by radiation as it emits longwave into the air, and by convection as cool air sinks from the top of the troposphere and wafts across the surface to replace the warm rising air carrying the evaporated water aloft.
When Roger Pielke Sr has sorted out his list of unknowns and we’ve got the data to untangle that lot, we can talk again. 🙂
tallbloke says:
July 24, 2010 at 10:24 am
R. Gates says:
July 24, 2010 at 10:12 am (Edit)
The oceans act as a heat sink, not as a trap in the sense of GHG’s.
Correct, but it’s solar energy the ocean traps, not longwave from the atmosphere, as I’m discussing with Jim D. Take a read and report back.
_______
This concept, often repeated here on WUWT, that LW back radiation from GHG’s in the atmosphere cannot possibly effect the ocean heat flux is too simplistic. It is absolutely true that LW radiation cannot penetrate beyond the skin layer of the ocean, however, the skin layer is absolutely critical in determining heat flux rising from deeper sunlight heated layers. LW heating of the skin layer of the ocean reduces the size of the temperature gradient through the skin layer and reduces the flux. Thus, if the absorption of the LW emission from atmospheric GH gases reduces the gradient through the narrow suface layer, the heat flux from the deeper layers will be reduced, leaving more of the heat introduced in the top 300 meters or so to remain there to increase water temperatures.
I know several experiements in the field have been carried out to prove this is exactly the case, and I’ll look for those links…