The greenhouse effect is real. If there were no greenhouse gases in the atmosphere, earth would be a cold place. Compare Mars versus Venus – Mars has minimal greenhouse gas molecules in its’ atmosphere due to low atmospheric pressure, and is cold. By contrast, Venus has a lot of greenhouse gas molecules in its’ atmosphere, and is very hot. Temperature increases as greenhouse gas concentration increases. These are undisputed facts.
outgoing radiation = incoming radiation – changes in oceanic heat content
The image below from AER Research explains the radiative balance.
http://www.aer.com/scienceResearch/rc/rc.html
About 30% of the incoming shortwave radiation (SW) is reflected by clouds and from the earth’s surface. 20% is absorbed by clouds and re-emitted back into space as longwave (LW) radiation. The other 50% reaches the earth’s surface and warms us. All of that 50% eventually makes it back out into space as LW radiation, through intermediate processes of convection, conduction or radiation. As greenhouse gas concentration increases, the total number of collisions with GHG molecules increases. This makes it more difficult for LW radiation to escape. In order to maintain equilibrium, the temperature has to increase. Higher temperatures mean higher energies, which in turn increase the frequency of emission events. Thus the incoming/outgoing balance is maintained.
Click for larger image
http://www.aer.com/scienceResearch/rc/m-proj/lbl_clrt_mls.html
The important greenhouse gases are: H2O, CO2, O3, N2O, CO and CH4. The reason why the desert can get very cold at night is because of a lack of water vapor. The same is true for Antarctica. The extreme cold in Antarctica is due to high albedo and a lack of water vapor and clouds in the atmosphere, which results in almost all of the incoming radiation returning immediately to space.
An earth with no CO2 would be very cold. The first few tens of PPM produce a strong warming effect, and increases after that are incremental. It is widely agreed that a doubling of CO2 will increase atmospheric temperatures by about 1.2C, before feedbacks. So the debate is not about the greenhouse effect, it is about the feedbacks.
Suppose that the amount of reflected SW from clouds increases from 20% to 21%? That would cause a significant cooling effect. Thus the ability of GCM models to model future temperatures is largely dependent on the ability to model future clouds. Cloud modeling is acknowledged to be currently one of the weakest links in the GCMs. Given the sensitivity to clouds, it is perhaps surprising that some high profile climate scientists are willing to claim that 6C+ temperature rises are established science.
So the bottom line is that the greenhouse effect is real. Increasing CO2 will increase temperatures. If you want to make a knowledgeable argument, learn about the feedbacks. That is where the disagreement lies.
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Hi Steven,
I also really appreciate your effort and honesty in the process. I simply hope now that the scientific basis we’re sure of will not be endlessly disputed – continuously re-inventing the wheel is such a stupid loss of time, energy and money.
So I suppose the “big” questions you are disputing is whether the warming we are observing is due to the increase of CO2 or not, and if yes whether it is caused by human activities, am I right?
David Corcoran (23:08:26) :
The argument [is] whether Catastrophic Anthropogenic Global Warming (CAGW) will engender a runaway greenhouse effect that will turn our planet into a mirror of Venus in no time at all, geologically speaking.
This is incorrect. The argument is about feedbacks, but not runaway feedback. There will clearly be no runaway feedback since CO2 has been much higher in the past, and runaway feedback that would “turn our planet into a mirror of Venus” did not occur.
Scott,
That should be “relative humidity is a measure of actual H2O(gas) content compared to the maximum of H2O(gas) that can be “contained” at the temperature. The “contained” makes the atmosphere sound like a sponge, which it is not. That’s bad science, as shown in these pages:
http://fraser.cc/ follow prompts teaching, sci., met.,
and: http://www.ems.psu.edu/~fraser/Bad/BadGreenhouse.html
[snip- this comment is pointless and off color]
It is frequently argued that AGW is ‘just 200 year old physics’, and this helpfully makes clear why this is not true and is in fact willfully misleading.
It is simple physics that CO2 absorbs heat, and that a gas with more CO2 warms up more than the same one with less CO2. However, what happens next is a different, independent, and more complicated question, and is about feedbacks. The atmosphere is a system, not a gas. So it is perfectly possible that the figure of 1.2C for a doubling of CO2 could be right, but that the net effect of that doubling could be zero, 1.2C or much greater. It depends how the rest of the system reacts over time to the initial rise.
It is a bit like the argument that a given car will travel 40 miles on a gallon of gas is simple physics, and comes from the energy content of the gas, which is not subject to dispute. It is true that the energy content is not subject to dispute, but how far it takes a car of this particular design may be physics, but it is not simple physics, and is not primarily determined by the energy content of the gas. The key question about the climate is whether clouds are negative or positive feedbacks. Do clouds and rain and other atmospheric phenomena amplify smallish warmings from whatever cause, or do they lessen them?
This is connected to the argument about the MWP and RWP. If we can point to previous warmings followed by coolings which were not caused by CO2, it must be more plausible that there is something which can produce cooling in response to warming. So it must be plausible there is some form of negative feedback in the climate system.
The hard thing for AGW to explain, given the hypothesis it is obliged to make about climate sensitivity and feedback, is why cooling followed the MWP and RWP. This on the face of it is inexplicable if they are right about climate sensitivity and the direction of feedback.
I have a problem with the suggestion that a slightly warmer air could warm the oceans on a timescale that need cause any concern.
A warmer air increases the temperature differential between air and space and so could well accelerate energy loss to space before any significant effect on the oceans could occur.
I also see difficulties with the proposed ocean skin effect which has been put forward by AGW supporters to overcome the ocean warming problem but which has not yet been proved to be effective in the real world.
The saturation issue and the density issue should be treated seperately in relation to a single GHG.
It is quite true that a level of approximate saturation can be reached for any single GHG but for a planetary atmosphere as a whole the total density arising from all it’s constituents is the paramount factor.
In the case of CO2 on Earth such saturation is reached well before any increase in the quantity of CO2 could have a significant effect on total density because the proportion of CO2 is so small.
I’m sorry Steve but as TMTisFree has shown the GH effect IS still poorly understood. There are a finite number of radiant particles involved in the GH effect on this planet, simply adding more GH gasses into the atmosphere does not neccessarily equate to higher temperatures. That is what the temperature record is telling us.
As Dr. Hansen has correctly argued, increases in atmospheric temperature cause the ocean to warm up.
Is that what Dr Hansen has argued? His main point seems to be that ‘missing heat’, i.e. heat not yet evident in the atmosphere is atually accumulating in the oceans. I’d like to see the argument behind this since thermal emission from the atmosphere can only penetrate a few micron into the ocean ‘skin’.
And what happened to the LW backradiation to the surface?
http://www.telegraph.co.uk/earth/environment/climatechange/4808122/Scientists-find-bigger-than-expected-polar-ice-melt.html
What next?
With “saturated”, I have always understood that all of the energy at a given wavelength that is emitted is absorbed.
The Earth is a microwave oven and CO2 is food in it. If the effect is saturated, it means all the energy provided by the microwave (i.e. Earth emissions at the right wave length) will be absorbed by the food (CO2). When we have little food, the food will get very hot. However, as it is little food (low concentration of CO2 in the atmosphere), its total heat content or the total heat content inside the microwave will not be very big. When we have a lot of food (high concentration of CO2 in the atmosphere), it won’t get very hot but, as the concentration is greater, it will have a similar effect in the overall atmospheric temperature (heat content inside the microwave). Similar? I would rather say “exactly the same”.
If a higher concentration of molecules capable of absorbing the energy had any effect in an already saturated effect, we all would put huge plates full of food in the microwave. But this is not true. We know that if we put twice as much food, we need twice as much energy to make it reach the same temperature.
Learn about feedbacks indeed. 30% of the ocean is covered by strato-cumulus cloud, albedo about 60, while the open ocean is albedo effectively zero. How anthropic changes alter that thin cloud layer will have massive changes on the average albedo of the Earth, more than enough to change the temps.
If you look at Tinsdale’s graphs of maritime air temps you will observe an abrupt rise in temperature from 1939 to about 1943 (this effect is smeared out in the Hadley SST graphs as they’ve added a ‘correction’ which looks dubious to me) and I have postulated that the oil-spills from the Battle for the Atlantic reduced CCN numbers, lowered reflectivity during day and emmisivity by night, hence warming the upper levels of the sea. The Kriegesmarine effect is about oil, but you get the same result from surfactant. We cover the entire ocean surface every two weeks with a thin layer of pollution — you can even see it when an ice-floe melts, an oily smoothness all around the ice. That’s probably caused by phytoplankton, but I’d not be too surprised if it turns out to be caused by stuff entrained in the ice from the atmosphere over a few years.
Nozieres is researching bacterial surfactant effects on clouds. VOCALs is looking at strato-cu off the coast of Chile. I hope they’re checking the cloud particles for oil and surfactant pollution. If they find it them you read it here first: if not, please forget I said anything!
The science of feedbacks is extremely poor — this is where I draw the line when I hear the chant ‘the science is settled’. Until cloud feedbacks are intensively researched, all the hooha is just hand-waving.
JF
The figure shown is for summer at mid lattitudes. But it’s the winters that have become warmer between 1970 and 2000, not the summers. So I’d like to see the same diagram for winter conditions to see what the difference is.
Thanks for the post, it is certainly an issue that needs clearing up. I am wandering what literature the explanation of the greenhouse effect is based on. Is this essentially still based on the work of Arrhenius that was never validated? (Arrhenius, 1896).
I think your explanation can be best explained using hydraulics. co2 acts like rocks piled across a river, the temperature grade acts like the hydraulic grade. As the water slows to flow through the rock, water heads up behind due to the restriction, however adding more rocks past a certain point wouldnt increase the heading up of flow once it had reached equilibrium, only the first section of rock would really determine the depth (equivelent to trapped heat at the surface) and no flow would be sent backwards due to the net energy flow being downhill. Would this be a fair explanation?
I have read several papers that claim a chamber filled with co2 becomes no warmer in the sun than one with normal air, the same applies for tests using glass and polished rock saltcrystals . Doesnt the hypothesis then fail testing?
What are your thoughts on the following papers i.e. that convection is the main factor in the GE or that atmospheric mass determines the GE? http://www.ingentaconnect.com/content/mscp/ene/2003/00000014/F0020002/art00011 or http://www.springerlink.com/content/t341350850360302/?p=eaccc84960854cb0baba8d1d3860ac53&pi=2 (also see their response to the rebuttal) also http://xxx.lanl.gov/abs/0707.1161 claims to falsify the GE.
I think the practical testing issue needs to be resolved as does the contradiction of the second law of thermo dynamics beforfe I take the GE as rock solid theory.
@John F. Hultquist
Thanks for interesting links
If the effect is saturated, it means that no single 600/cm photon escapes the Earth. Then what happens to them?
A photon emitted by the Earth surface is quickly trapped by a CO2 molecule. The molecule increases its energy, or vibratory state. The most likely next thing is that the molecule emits back another photon of the same wavelength and reduces its energy, as a good absorber is a good emitter. If this happens, the new photon will be trapped by another CO2 molecule, as none can escape the earth at that wavelength: the effect is saturated. So nothing really happens: a molecule reduced its energy but another one increased it. However, the CO2 molecule can also reduce its energy by collisions with other molecules of a different kind, “passing” to them the vibratory state. Those molecules will in the end emit photons to release energy, but will do it at different wavelengths which are not saturated, and the energy escapes. In a stable situation, the ammount of energy emitted by the Earth Surface at 600/cm will be the same energy that CO2 molecules pass to other molecules by means of collisions and utterly escape the Earth at a different wavelength. In the tame it takes for the conversion to happen, CO2 molecules have an increased energy and this raises the overall atmospheric temperature.
What happens if we suddenly increase the concentration of CO2 molecules in the atmosphere? We have the same number of 600/cm photons at the origin, the Earth Surface. What happens is that each CO2 molecule traps less photons. There will be more molecules trapping energy, but each of them will trap less energy. There are more CO2 molecules but each of them has less energy than they used to, so the atmospheric temperature shouldn’t change yet. What we need to know is how this affects the speed at which heat or energy is transferred to molecules of a different kind so that the energy can be finally radiated to space. If each CO2 molecule traps less energy, they vibrate less and transfer less energy through collisions with other molecules. But at the same time, we have more molecules doing the same thing. What is more important? In which way do we transfer more energy through collisions? Is it with a few molecules colliding a lot or with a lot of molecules colliding less? For me, that is not clear at all. How is the process of finally transforming the wavelenght of the 600/cm photon faster, with a lot of CO2 or with little CO2? Do we have more 600/cm photons trapped in the atmosphere at a given time with a lot of not very energetic CO2 or with little but very energetic CO2?
“Steven Goddard (23:39:50) :
Molon,
What you are not considering is that LW is absorbed and emitted many times on it’s tortuous path out of the atmosphere. The more GHG, the more times it is absorbed.
Your argument is analagous to saying that one stop light has the same effect on your commute time as does 100 stop lights.”
This is all the SAME heat, it doesn’t matter how many times it is absorbed and re-emitted. If absorption heats, then emission cools.
You cannot have your perpetual motion machine!
And, IMHO, the analogy stinks! (As most analogies do; stick to explanation.)
AM
If we are heat balancing the Earth we need to know the rate of transfer of the heat from the magma through the crust. It would be a brave man who estimates the total nuclear fission power of the earth’s core and braver still to claim that it may be considered as being released uniformly over the globe.
I have a problem with the first graph- it implies a ‘budget’. If watt/in equals watt/out, then hotter days equal colder nights. Then, the mean temp would not change but remain a constant? I understand the chemistry because it’s so easy and provable (never met a theoretical chemist), but I’m still having trouble with the physics. This is just one of the reasons that I am still a ‘fence sitter’ on this subject. I will admit to being slightly skeptical, but that is just a personal trait. There are just so many different opinions from well respected scientists on both sides, and it isn’t nice or fair to beat up on them. Anthony- great site! Sending you a donation immediately. Enjoy your day…
Steve,
this is the first articel und WUWT that is disappointing for me. It is not a correct description of the situation.
Most important fact: Until now, there is NO physical correct description or definition of the greenhouse effect.
“outgoing radiation = incoming radiation – changes in oceanic heat content”
Wrong, you forget the latent heat of the water dampening out from the land (land ist mostly not total dry).
You forget the heat loss by convection (wind is blowing along the earth surface and is heated up).
The latter is important! Wind is heated up at the surface of the earth, is warmed by this, is rising, and is emitting (by GHG!) heat to the space and so is cooling. With this mechanism we have cooling by Greenhouse-Gases!
“If there were no greenhouse gases in the atmosphere, earth would be a cold place”
“The other 50% reaches the earth’s surface and warms us”
OK, if we have no greenhouse gases (no water, no CO2), almost 100% of the radiation reaches the surface (no clouds! amost no absorption!)), so it will be colder on the planet??
Why is the day temperature on the moon ca. 160 °C ? No Greenhouse gases!
Another mechanism: Water vapor is rising, it condenses, and the heat is emitted (to a large extent) to space! When the water is evaporating at the sea or landsurface, heat is taken away from the surface. Result of the process: The surface is cooled by the GHG water!
Please read the work of Prof. Gerhard Gerlich! It is essential for the understanding of the situation. Why you don’t ask him for a guest article? His E-Mail: g.gerlich@tu-bs.de
lgl (02:08:56) :
And what happened to the LW backradiation to the surface?
It simply warms slightly the surface. It is not sure if it is possible to experimentally discriminate this ‘indirect’ heat. But it is possible (and complicated) to calculate the probability of occurrence of this LW re-radiation and thus estimate the small theoretical heat added to the surface. Anyway, because atmosphere is transparent for this LW re-radiation, this slight warm is already accounted for when measuring temperature.
Bye,
TMTisFree
Thus the ability of GCM models to model future temperatures is largely dependent on the ability to model future clouds. Cloud modeling is acknowledged to be currently one of the weakest links in the GCMs. Given the sensitivity to clouds, it is perhaps surprising that some high profile climate scientists are willing to claim that 6C+ temperature rises are established science.
As a skeptic and a Meteorologist, several of my friends, co-workers and I don’t deny that the greenhouse effect does not exist. We all acknowledge that the greenhouse is important. CO2 is need for plant grow and respiration. My argument is that the computer models are taken as fact. I have used computer models to make weather forecast for years. I know from experience that the models are not reality and that they frequently wrong. They are tools used to help make an educated guess as to what the weather will do the next few days. Now, I know that weather is not climate, but the principle behind the models still stands with the climate models. They use the same equations as the forecast models. Climate scientists, who claim the 6C increase temperature from the model as fact, should consider getting more forecast experience.
Dr. Hanson argument that heating the atmosphere will heat the ocean is wrong. You have to ask yourself, how you boil water. You don’t blow hot air over the surface; you heat the water from below. The atmosphere can’t be totally responsible for the increase in SST; it might increase the temperature in the first few inches of the surface, but not the entire water column. The oceans are heated by incoming solar radiation and from underwater volcanoes.
Our climate and weather are very complex systems that have several different mechanisms working together and against each other to balance the incoming and outgoing heat. Changing a very small amount of trace gas is not going to produce a very large temperature increase. You have to consider solar constant, ocean currents and SST, atmospheric circulation and the distribution of the gases throughout the atmosphere. I do agree that an increase in CO2 will increase temperature, but not to the extent that some models and other scientist suggest.
“If you want to make a knowledgeable argument, learn about the feedbacks. That is where the disagreement lies.”
I think the disagreement lies in how well are computer models at predicting that a warmer future is bad. CO2 levels have been above 1000 PPM for the vast majority of the billion+ year history of life on Earth.
Thanks,
Tomcat
The number of “facts” stated in this “primer” which are, in fact, assertions without basis are mind boggling. One of the most glaring is the assertion that James Hansen’s “correct” statement that the atmosphere heats the ocean is in direct contravention of statements by the late Robert Stevenson, former director of the Scripps Institute and a Climate scientist of over 50 years experience who says categorically, there is no way the atmosphere can heat the ocean!
Another one is the assertion that Antarctica is cold because of a lack of water vapor. In fact the opposite is true. There is a lack of water vapor because it is cold. If there was enough water vapor in the antarctic atmosphere it would form clouds which would block what little sunlight manages to reach it and make it colder.
I find the whole article suspect in its approach.