Guest post by John Kehr from: The Inconvenient skeptic
There are many times when I am putting together articles that I need to compare the results of my research to the models of the theory of Anthropogenic Global Warming (AGW). In this manner I can contrast the results and predictions directly. This way I understand how the different views relate to each other.
Recently I was trying to find the total amount of energy (forcing) that the warmists claim CO2 is responsible for in the atmosphere. The reason I wanted this is because I have recently completed my full analysis of absorption and I wanted to compare my results to the warmist views. While this article is not about my results, it will focus on some interesting results that I found using their models. Because I was searching for the warmist views about energy I was using information from their sites (and citations of course). While that might seem strange, they generally have lots of good information there.
The starting point is the basic equation they use to determine the forcing caused by a change in CO2 concentration.
CO2 Forcing Equation
This equation provides the amount of energy in W/m2 that a difference in two CO2 concentrations should cause.
While looking for the total forcing of CO2 in the atmosphere, I found an interesting article on the Skeptical Science (SkS) site that had an answer to my question (citation). They state that the radiative flux caused by CO2 is 32 W/m2. I will use the information from that article several times. When I compare the energy calculated by the forcing equation using CO2 levels of 1 ppm and 390 ppm I get a result of 31.9 W/m2. So far things are looking consistent for the theory of AGW. Here is a chart of the forcing from 1 ppm to over 1000 ppm.
Proposed Model of CO2 Forcing
The next step is to determine how much warming this energy causes. For this I use the next important equation that the AGW model uses. That is the climate sensitivity.
Climate Sensitivity: Warming caused by Forcing
Again I found lots of discussion and references at the SkS website (Hansen et al. 2006) where they provide their views about climate sensitivity. This equation is straightforward and simple to decipher. They generally calculate it by looking at a period of time with a temperature change and then estimate the change in forcing. For example if increasing CO2 caused a forcing of 2 W/m2 and the observed temperature change was 5 °C, then the climate sensitivity would simply be 2.5 °C /(W/m2).
One thing to be aware of is that the sensitivity is usually not shown directly. Most warmist publications display the results in terms of temperature change that will happen as a result of forcing. For example the most commonly used quantity for climate sensitivity is 3.0 °C for a doubling of CO2. To determine the climate sensitivity they are using it is simply:
λ = (3°C / 3.7 W/m2 ) = 0.81 °C/(W/m2)
I am going to use the direct climate sensitivity instead of the temperature effect that a forcing will cause. This will make my numbers look a little different, but here is the conversion.
Proposed Range of Climate Sensitivity
When comparing climate sensitivity it is very important to know exactly which form is being used. I will be using the actual climate sensitivity instead of the CO2 doubling form. The best way to check is to look at the units being used.
The most common estimate is the 0.81 °C/(W/m2). That is what corresponds to the 3 °C temperature increase for a doubling of CO2. The full range is what I have shown in the table. Some estimates do go a little higher or lower, but the 0.43-1.13 °C/(W/m2) is the most widely accepted range.
SkS puts the climate sensitivity at the 0.81-0.92 °C/(W/m2). I am going to use the 0.81 °C/(W/m2) as the default value for the warmists as it is the most commonly used value.
So far all of this seems perfectly reasonable and hopefully acceptable. This is also where the wheels start to come off.
I decided to look at another method to determine the climate sensitivity. I am troubled by the method normally used because it is very hard to know the exact forcing and cause of the temperature change. So I decided to use what should be a less controversial method, but somehow I doubt it works out that way.
I decided to use the total Greenhouse Effect (as the ΔT) and then the energies involved. The total Greenhouse Effect is perhaps the least controversial aspect of the Global Warming debate. I will use the normally accepted value of the Greenhouse Effect as 30 °C.
Now by using the climate sensitivity value it is possible to compare what portions of the Greenhouse Effect (GHE) are caused by different components. Since the accepted forcing value for CO2 is accepted as 32 W/m2 it is now possible to determine the total impact that CO2 has on the total GHE.
ΔT = (0.81°C/(W/m2)) * 32 (W/m2) = 25.9 °C
While that might not immediately seem unreasonable. The entire stated effect of the GHE is 30 °C. So according to the accepted climate sensitivity and CO2 forcing equations, CO2 accounts for 86% of the total GHE.
So all other factors in the Earth’s climate account for 14% of the GHE and CO2 by itself accounts for the other 86%. This can also be compared to the number of CO2 doublings that take place from 1 ppm to 390 ppm. That is roughly 8.6 CO2 doublings (1,2,4,8,16,32,64,128,256,390 ppm). Using 8.6 doublings from 1 ppm gives 25.8 °C. So their model is coherent, but saying that CO2 causes 86% of the GHE is extremely incorrect.
This means that the methods being used for determining temperature change based on forcing and climate sensitivity are flawed. Any result that puts CO2 at 86% of the GHE is wrong. Earlier I showed that the forcing model and the accepted total forcing have a good match. That would indicate that the problem is with (at least partially) the estimated climate sensitivity.
So I worked backwards. Assuming that the total temperature change caused by the GHE is 30 °C and then the total energy inputs are the total forcing. The total GHE is not very controversial. Very few people will argue that the Earth is not warmer as a result of the atmosphere. Without the atmosphere the Earth would be around -15 °C and with the atmosphere it is currently about 15 °C. That 30 °C difference is caused by the insulative effect caused by the atmosphere.
That leaves forcing as the problem in determining the correct climate sensitivity. The same article that stated CO2 as 32 W/m2 also stated that water vapor causes a forcing of 75 W/m2. If I assume that water vapor and CO2 are the ONLY factors I get a total forcing of 107 W/m2. This would indicate:
λ(30%) = (30°C /107W/m2) = 0.28 °C/(W/m2)
Already using very poor assumptions the climate sensitivity is already much lower (by almost 3x) than the accepted value. This still puts CO2 at 30% of the total GHE, so even this estimate for climate sensitivity is still too high.
The normally discussed range of CO2 effect on the GHE is 9-26%. Assuming that the 32 W/m2 remains accurate for the forcing magnitude of CO2 results in climate sensitivities of:
λ (9%) = (30°C / 356 W/m2 ) = 0.08 °C / (W/m2 )
λ (26%) = (30°C / 123 W/m2 ) = 0.24 °C / (W/m2 )
At 9% of the GHE the climate sensitivity must be 10x lower than what is currently accepted. There is one more possible scenario that I want to cover.
If I look at the Radiation Budget (Kiehl, Trenberth 1997) I get a total forcing from the surface to the atmosphere of 452 W/m2. That would include the energy from evaporation, convection and radiative transfer and subtracting out the open window of 40 W/m2. If I use the 32 W/m2 for CO2 with that total energy then CO2 accounts for 7% of the total GHE. Then the climate sensitivity is:
λ (total energy) = (30°C / 452 W/m2 ) = 0.066 °C / (W/m2 )
That is what the real lower limit of the climate sensitivity is. The flaw in the estimates for climate sensitivity is the assumption that all temperature change is caused by the greenhouse gas forcing. If the climate was as sensitive as the much higher estimates currently in use are, the Earth would be a very unstable place as small changes in energy would cause large changes in temperature.
Using the total GHE determined climate sensitivities, here are the CO2 doubling effects on the climate.
GHE Determined Climate Sensitivities
What this shows is that trying to determine the climate sensitivity from a change in measured temperature and then assuming it was caused by a particular forcing is incompatible from the determination of climate sensitivity from the actual GHE. In choosing between methods it is the GHE that is a known quantity. Since the measurements have been done to determine the individual parts of the GHE, that seems to be a much more reliable method than “assuming” that a particular forcing caused a certain change in temperature.
The IPCC and the general AGW method of determining climate sensitivity is about an order of magnitude different than the method of using the total GHE and then calculating the components. This is a significant scientific disparity.
The difference the climate sensitivity makes to the temperature projections based on increasing CO2 concentrations are significant. Assuming the same CO2 forcing while using the different climate sensitivity values results in the following effects of CO2 on the global temperatures.
Red: The AGW accepted climate sensitivity of 0.81 (3C for doubling) Green: Climate sensitivity of 0.28 (1C for doubling) Blue: Climate sensitivity of 0.066 (0.24C for doubling)
The total GHE of 30 °C is incompatible with the currently accepted IPCC values of climate sensitivity and CO2 forcing. In order for the GHE to be compatible, the total effect of the greenhouse would have to be closer to 100 °C which would result in a global temperature of ~85 °C. This strong overstatement of the climate sensitivity substantially weakens the idea that CO2 could cause measurable change in the Earth’s climate, much less the type of danger that is often being stated.
This does not mean that CO2 is not a significant portion of the Earth’s greenhouse, but it does limit the role that it plays in the total GHE. The climate sensitivity is what prevents the sum of the parts from being greater than the whole and the sum of the parts cannot be greater than the total observed GHE. If the current estimates of CO2 forcing and climate sensitivity do not fit within the parameters of the total GHE effect, those estimates must be incorrect.
Dave Springer says:
1. Rising temps caused by CO2 allow the atmosphere to hold more water vapour. This is a greenhouse gas with more than double the effect of CO2. It is a feedback rather than a forcing, but it still results in rising temps beyond what CO2 alone is responsible for.”
That’s utter nonsense and we wouldn’t be alive to talk about it if were true. Water doesn’t care what makes it warmer so more water vapor would spawn more water vapor in your thesis and we’d have a runaway greenhouse. Since the earth has never experienced a runaway greenhouse the positive feedback you describe simply and demonstrably does not exist.
This is basic physics. I’m not going to sit here debating with utter fools who are willfully ignorant of basic physics. The ‘runaway greenhouse’ effect? Hahahahaha. That’s the oldest one in the AGW denial book. Why don’t you go do some reading about the real science behind climatology instead of sitting here in this ignorant echo chamber? Oh wait, I know. It’s because your masters tell you that the real science is ‘propaganda’.
For you people, black can be white and white can be black. Anything will do as an argument so long as it ‘proves’ that nothing mankind can do could possibly have an effect on nature. And you actually sit there and try to patiently explain to me your little pet theory that has been debunked so many times that we’re sick of it.
I should never have come here in the first place, and rest assured, I never will again. The amount of stoopid on display is absolutely mind-boggling.
[I’m going to leave your words in place exactly they were written. Perhaps against my judgment as a mod – since they violate several posting guidelines – but they are, shall we say , “instructive” about attitudes and prejudices and flat-earth constructs. Robt]
“Anything in the atmosphere which is capable by any mechanism of absorbing some part of the OUTGOING RADIANT ENERGY from the EARTH; must necessarily reduce the total amount of OUTGOING RADIANT ENERGY the earth LOSES over time; and that must result in a HIGHER mean global Temperature.”
Sure, that isn’t how I’d describe it but still the end result is a higher equilibrium temperature somewhere but not necessarily near ground or sea level. On a water world you can’t ignore evaporation and convection. When water evaporates it cools the surface where it evaporated. Pretty much everyone knows that, right?
The Sahara desert has a mean temperature of 86F while tropical rain forests have mean temperatures of 81F.
You’d think with all that vapor in the rain forest it wouldn’t be cooler than a desert. Yet it is and still yet the CO2 content in the well mixed atmosphere is the same in both places.
But wait it gets worse for the case that more water vapor, a strong greenhouse gas, automatically makes it hotter.
The albedo of desert sand is 40% whereas that of a rainforest is 10%. The surface of the desert is absorbing 30% less energy from the sun than the rainforest yet the mean desert temperature is higher.
So here’s a perfect moment to ask: What’s Up With That?
The surface albedo of the desert is
Steve Metzler says:
October 27, 2010 at 6:39 am
Ad hominen is all you have in response to me? So soon? I really must’ve hit a nerve there. Sorry about that. The truth hurts, don’t it?
Tom Folkerts;
So, in fact, water DOES block the energy differently in different directions.>>
It most certainly does not. You are conflating two issues. Water vapour blocks a given frequency or wavelength exactly the same regardless of direction. Determining how much of a given wavelength is travelling in a given direction is another matter, and yes the mix of “downward” wavelengths is different than the mix of “upward” wavelengths. May seem like a subtle difference but it isn’t.
Alex Heyworth says: October 26, 2010 at 12:06 am
One point that really bugs me about virtually every paper, post and comment I have ever seen on climate sensitivity and/or the earth’s energy budget is that everyone assumes that these issues can be satisfactorily explored on the basis of a static model. It is assumed that day and night, variations in TOA insolation due to the earth’s elliptical orbit, seasonal changes due to the inclination of the earth’s axis , and variations in the energy budget due to geographical location ,can all be averaged out without any impact on the analysis. Nowhere have I ever seen any proof that this assumption is valid, or even a reasonable approximation.
It isn’t valid, as shown by Kramm et al:
http://hockeyschtick.blogspot.com/2010/10/another-paper-on-fallacy-of-greenhouse.html
@Steve Metzler
So now that I’ve either taught you or reminded you that deserts at tropical latitudes have a mean surface temperature 5F degrees warmer than tropical rain forests despite the fact that the surface of the rain forest is much darker than desert sand and absorbs 30% more energy from the sun let’s move on to the tropical ocean surface temperature. Oceans are almost black so they absorb nearly 100% of any insolation reaching the surface or 40% more than desert and 10% energy than a rain forest. Plus the humidity is consistently high so there’s lots of water vapor to work as a greenhouse gas.
That should REALLY get the mean surface temperature cranked up, right?
Wrong. The mean surface temperature of the tropical ocean is 68F and nearly constant year round.
So how come when we look at all these places where the incoming energy at the top of the atmosphere is the same and the concentration of CO2 is the same the cooler surfaces are always the ones where there is more water vapor?
I granted at the beginning that increased CO2 will raise land surface temperatures but the effect is primarily where there is a dearth of liquid and gaseous water. So you’ll see what little effect it has primarily in the northern hemisphere because there’s more land in the NH and more in higher northern latitudes than lower latitudes because that cool refreshing water cycle is less active the farther north you go due to falling temperatures.
Instead of ad hominem as your sole response try explaining these observations according to natural law as you understand it. You can include the ad hominem if it makes you feel better just don’t skip the science.
Did you not conveniently miss the negative feedback of the clouds (er, water vapor) that is busily reflecting additonal solar energy from the earth – before it ever
(1) penetrates the atmosphere,
(2) hits the earth/water/plants/concrete;
(3) heats up the earth/water/plants/concrete – at different rates and by different amounts and in different ways
(4) gets re-radiated from the earth/water/plants/concrete – at different rates and by different amounts and in different ways and at different wavelengths
(5) sees that re-radiated energy penetrate the (same/more/different water-vapor-barriered) atmosphere back up into the troposphere to
(6) supposedly see the radiation energy get re-absorbed by the CO2
(7) before it can re-radiate again either up or down
(8) to be either re-reflected by the greater/same/lesser amount of water vapor/clouds/CO2 that is present?
So – The whole CAGW argument centers on the (false) assumption that “nothing else changes in the atmosphere from the-year-before-nasty-humans-added-CO2-soot-aerosols” to “the next 50/100/1000 years if humans keep adding the same amoiunts )or more!) nasty stuff into the atmosphere.”
But clouds? No – They are assumed the same. Past temperature changes of equal magnitudes to today’s changes? Ignored. Records changes and erased. Historical and written records changed to make the climate models simplistic assumptions come out right.
But the models fail at the 5 year point. The 10 point. The 15 year point. They cannot even make the last 30 years come out right except by artificially introducing aerosols – with no measured worldwide data to account for the modeled finagle factor needed.
But on this “model” we place a 1.3 trillion dollar tax debt.
Dave:
That should REALLY get the mean surface temperature cranked up, right?
Wrong. The mean surface temperature of the tropical ocean is 68F and nearly constant year round.
So how come when we look at all these places where the incoming energy at the top of the atmosphere is the same and the concentration of CO2 is the same the cooler surfaces are always the ones where there is more water vapor?
It is ironic (and a telling proof of your question!) that the hottest/driest/least worthy and most worthless place on the earth – the Gobi Desert and Sahara Deserts are also the places with the highest CO2 levels, and least water vapor, least plant life, and least arable soil?
Dave Springer says: October 27, 2010 at 5:59 am
You can’t heat water with infrared radiation. Infrared radiation is completely absorbed by the first layer of water molecules at the surface. You can increase the evaporation rate of water with infrared light but you can’t heat it.
Interesting — I had never thought about that. And after thinking about it, I’ll even go so far as to say IR almost always COOLS the oceans. (But that is only a part of the story!)
Since the air cools off as you go higher in elevation, the oceans would be warmer (on average) than the air above them. Hence the top layer would generally be COOLING due to more IR heading out from the warm water than heading in from the cool air. This would make the very top layer COOLER than the layers below — very rarely warmer. (And sources I saw suggest this layer is on the order of 10^-5 m –> very thin, but not “one molecule thick.)
The IR is slowly COOLING the oceans. But then there is the visible light. It can as does penetrate several meters into the oceans. It is heating this layer several meters thick, which (when combined with the IR) could indeed warm the oceans.
More food for thought.
http://oceanworld.tamu.edu/resources/oceanography-book/oceansandclimate.htm
There’s your feedback effect from water vapor. It cools the average surface temperature of the planet by an incredible 100 degrees F according to George Philander who holds a PhD in Atmospheric and Ocean Sciences from Harvard and is a full professor of same at Princeton. Philander was the director and/or chairman of Geoscience and Atmospheric and Oceanic Science at Princeton from 1990-2006.
@Steve Metzler
So to sum up the effect of CO2 on the earth’s surface temperature it:
1) initially raises the average temperature from below freezing to above freezing
2) at that point it activates the water cycle
3) the water cycle takes over from greenhouse gases and puts a cap on global average temperature via strong negative feedback to increasing temperatures
The only thing we have to fear is a tipping point where the average temperature of the planet falls below freezing pretty much ending the water cycle and raising the albedo of the planet from near 10% to over 80% which is equivalent to the sun becoming 70% dimmer.
And you, evidently, want to get us closer to that tipping point instead of farther away from it. Incredible. Just f’ing incredible.
racookpe1978 says:
October 27, 2010 at 11:23 am
Yes, indeed I did and it was purposeful. My pedagogic style is to leave some deductions up to the student as a means of helping me judge how well he understands the underlying principles and ability to carry them out to the proper conclusions. The tropical rain forest, at an altitude of a kilometer or more above the canopy has an average albedo higher than that of desert sand due to all the clouds. The canopy itself (the actual surface where we and most other terrestrial life lives and breathes) still has an albedo around 10% so my statement is still true but it wasn’t the whole truth. I left the rest of the truth as an exercise for the reader. You picked up on it pretty quick. Let’s hope Steverino does too.
Tim Folkerts says:
October 27, 2010 at 11:38 am
I understand IR hitting a water surface creates convection in the top millimeter. Presumably that’s because the topmost layer of molecules is being removed by evaporation which cools the next layer of molecules down and then they sink a little bit and are replaced by slightly warmer molecules from below which are then carried off by evaporation and so on. I’m not sure if there’s any consensus on whether the effect is net cooling or warming of the water. The sign of the temperature change is probably dependent on relative humidity and winds. I looked and wasn’t able to find anything that stated that more than 20% of the downwelling IR energy could be absorbed in any circumstance. So it’s probably technically possible to heat water with infrared if you can keep the air above it perfectly still and saturated with water vapor. In the real world that is very rare and would require some sort of temperature inversion near the surface to prevent convection from carrying the water vapor upward just like the tropopause under most circumstances stops convection from proceeding into the stratosphere.
Tim Folkerts says:
October 27, 2010 at 4:54 am
“…The incoming light from the sun has much of its energy in the form of visible light, which passes quite easily thru the vapor and down to the earth – maybe 20% of the energy is blocked. But the outgoing radiation is almost entirely IR. I don’t have the specific numbers handy, but water vapor certainly blocks over half of the outgoing radiation…”
I trust you are aware that 54% of the sun’s radiation is in the infra-red (IR) region?
This means that over half the incoming radiation must also be blocked by water vapour. It is also interesting to note that the atmosphere is densest at ground/ocean level and has the highest humidity here. Therefore, most of the outgoing IR is absorbed by the first yards of atmosphere above the surface. In addition, over 90% of absorbed photons are not re-emitted, rather due to collisions with other molecules they are converted into kinetic energy. The heat is then dissipated in the upper atmosphere and eventually out to space.
Until climate scientists stop using computer models, and start to try and understand real world macro-physics, no insight about how our climate operates will be forthcoming. It’s a travesty that so much money has been spent to deliver so little!
Just to make my position crystal clear…
There’s not a doubt in my mind that more CO2 over arid land surfaces (arid due to either geography or high latitude) raises the average temperature by the no-feedback amount of around 1.1C per doubling beginning at a baseline of 200+ ppm. In more humid conditions and over water not so much if at all. Overall, it will increase the average temperature over the entire planet but the distribution of the temperature increase is not homogenous. It tends to warm up the frozen places first where it helps to bring the temperature above freezing and thus activate the water cycle which then puts a cap on further heating and it tends to leave the warm humid places unchanged.
To verify this we can look back into the geologic column where we find that when the earth is warmer overall by just 6-8 degrees and CO2 concentration is upwards of 2000ppm it’s pretty much a green planet from pole to pole. Call me strange if you want but I tend to prefer green plants to barren rock and ice. The only reason a person wouldn’t want more CO2 in the atmosphere is either because they’re in love with rocks and ice (I call them “ice huggers”) and/or they don’t understand how the greenhouse effect works to set surface temperatures in conjunction with the water cycle on a world with an inclined axis and 70% covered by a global ocean an average of 4000 meters deep.
Fear the cold. Embrace the warm. Fossil fuels – burn baby burn. Use it before you lose it. I doubt we can prevent the near term end of the Holocene interglacial with the puny amount of CO2 we can pump into the air by burning fossil fuels but one thing is for damn sure – we’ll hasten the end by pumping less of it into the atmosphere.
“”””” Tenuc says:
October 27, 2010 at 1:12 pm
Tim Folkerts says:
October 27, 2010 at 4:54 am
“…The incoming light from the sun has much of its energy in the form of visible light, which passes quite easily thru the vapor and down to the earth – maybe 20% of the energy is blocked. But the outgoing radiation is almost entirely IR. I don’t have the specific numbers handy, but water vapor certainly blocks over half of the outgoing radiation…”
I trust you are aware that 54% of the sun’s radiation is in the infra-red (IR) region? “””
Well actually not really. A text book plot of the actual solar spectrum places the peak spectral irradiance at about 480 nm which puts the visible IR boundary of 800 nm at 1.67 times the peak wavelength. Standard Black Body radiation curves, suggest that only 40% of the total is at longer wavelengths than that. But a detailed table of actual TSI spectrum values says that 56.023% of the total is at SHORTER than 800; which means only 44% is in the IR.
That is not an inconsequential difference from 54%.
These numbers are from 20th century research; so I dare say that a 2010 review would change some of the numbers a bit; but climatists are busy trying to determine the correct R^2 value to use for their statistical research results; so they are not really interested in real physical data gathering.
It is interesting to contemplate the enormity of the supercomputer computations that Lacis et all had to go through to show that CO2 is the big control knob.
He said that the GHG (and presumably non GHG feedback gases like H2O) have absorption spectra containing “thousands” of absorption lines; each of which has to be individually calculated.
So for some arbitrary location somewhere in the atmosphere, and at some earth location at some epoch of time; you have to determine from the model what the local Temperature and Density are; and the species living there, then for each of the thousands of spectral lines you have to determine the Doppler and pressure line broadening for those circumstances; and integrate the total energy that will be absorbed from whatever EM radiation flux is passing through that sample; and you do that for each of the thousnds of lines; and then you compute the local temperature change that will result from that temperature change, and the resulting atmospheric thermal radiation that occurs, and then you have to move on to the next atmospheric layer; both up and down to compute the changes in the temperature, and pressure, and then recalculate all the line broadenings and new absorption spectrum appropriate for those conditions; and then after you are finished with the analysis for that location from the surface to outer space, you then have to go to the next spatial location and repeat the whole process, until you have a properly Nyquist sampled set of spatial data ; and then you have to repeat the whole process for the neaxt time epoch to see how it all changed ; and perhaps keep doing that until you have properly Nyquist sampled perhaps a whole year of sun orbiting changes; and meanwhile you have to deduce what phase changes will take place for non-GHG feedback mechanisms like H2O vapor and clouds; and then when finally you have figured out what the mean global surface Tempertaure is for all of this data set; you have to go and do it all over again but now with twice as much CO2, so you can compute how much the Temperature changes for the CO2 doubling; to arrive at a final value for Climate Sensitivity.
I knew there was a reason, that I didn’t go into the climatism field; it just seems like too much hard work; and I can see why you have to revamp your results from time to time; when people say you aren’t doing it properly.
But since I spent so much of my hard earned dollars in taxes to buy a supercomputer for Drs Lacis, and Schmidt it is good that they have done this pioneering work for us; so that we don’t have to.
But I still have a lot of confidence in my stick on a sandy beach; and I keep coming to the same conclusion:-
HEY !! IT’S THE WATER !!
I noted somewhere above that near surface temperature inversions potentially stop convection enough to allow downwelling IR energy from CO2 to not quickly rise back up from a wet surface in the form of latent heat of vaporization. I said those should be rare very near to the surface.
Turns out they’re not that rare. Fog is the result of near-surface temperature inversion. Most of us have seen it before and a few of us see it more than they’d like but it’s still can’t be called common in most places at most times. Fog is cooler than the air above it which stops it from rising and brings the vaporization rate below it to essentially zero.
Inversions farther up from the surface, if they persist, end up spawning violent weather when they’re eventually penetrated as all the pent up convective energy is released around the point of penetration (thunderstorms and hurricanes). There was a recent graphic on WUWT showing the track of colder water in the Atlantic underneath the path of the larger hurricanes so I think it’s safe to say that these events end up cooling the surface too before they’re over.
George E. Smith says:
October 27, 2010 at 3:06 pm
re; 44% of insolation in the IR range
Keep in mind that’s almost all in the near IR spectrum where CO2 is transparent to it. CO2 is not a significant absorber of solar spectrum energy. Water vapor is opaque in the near IR however. Hardly any radiation from the sun is in the far IR where CO2 becomes opaque. The earth’s surface on the other hand radiates almost exclusively in the far IR with a couple of CO2’s sweet spots right near the peak power frequency. But it shares one of those sweet spots with water vapor so in the presence of water vapor CO2’s effectiveness is diminished to some extent.
davidmhoffer replies to: “So, in fact, water DOES block the energy differently in different directions.”
It most certainly does not. You are conflating two issues. Water vapour blocks a given frequency or wavelength exactly the same regardless of direction.
I agree 100% that a given wavelength is blocked the same in either direction.
the mix of “downward” wavelengths is different than the mix of “upward” wavelengths. May seem like a subtle difference but it isn’t.
And that is exactly my point. See, for example, this earlier post for a handy diagram of the spectra of incoming radiation from the sun and outgoing radiation from the surface. http://wattsupwiththat.com/2010/05/06/hyperventilating-on-venus/
Incoming radiant energy is ~25% absorbed; outgoing radiant energy is 85% absorbed. Most of this is due to water. How can you disagree with “water DOES block the energy differently in different directions.”
George E. Smith says: October 27, 2010 at 3:06 pm
A text book plot of the actual solar spectrum places the peak spectral irradiance at about 480 nm which puts the visible IR boundary of 800 nm at 1.67 times the peak wavelength.
Except text books also put the visible/Ir boundary at 700 nm — perhaps as far as 750 nm, but I have never seen a source that puts it quite as far as 800 nm.
Obviously this fuzzy boundary for IR means that the numbers will also be a bit fuzzy. (Of course, what we call it will not change how much is absorbed by H2O or CO2.)
I’m a bit confused by your comments, Dave.
I understand IR hitting a water surface creates convection in the top millimeter. Presumably that’s because the topmost layer of molecules is being removed by evaporation …
I was actually making a point which I believe is the opposite of your conclusion. I say IR creates convection by COOLING the surface, not warming it!
You considered the IR hitting the surface, but I never see you consider the IR LEAVING the water. The IR leaving must almost certainly be more than the IR arriving, since the ocean surface is almost certainly warmer than the average temp of the atmosphere above it that radiates down. The warmer water must then be radiating more IR up than the atmosphere is radiating down. So since net IR energy is leaving the water, the water must be cooling at the surface due to IR.
The COOL water at the surface causes convection. (Warm water at the surface would cause very little convection, since the warm water would want to stay at the surface.)
I looked and wasn’t able to find anything that stated that more than 20% of the downwelling IR energy could be absorbed in any circumstance.
You explicitly claimed that “Infrared radiation is completely absorbed by the first layer of water molecules at the surface.” Unless I am missing something, your statement assumes (and I agree) that water is very close to a perfect black body for IR and hence absorbs 100% of the downwelling IR. (Although I still think that you need at least several thousand molecular layers to absorb the IR – not jsut a single layer.)
Other issues you mention like wind and humidity certainly play additional roles in surface temperature, but the IR itself is cooling the surface!
Tim Folkerts says:
October 27, 2010 at 8:19 pm
George E. Smith says: October 27, 2010 at 3:06 pm
“Obviously this fuzzy boundary for IR means that the numbers will also be a bit fuzzy. (Of course, what we call it will not change how much is absorbed by H2O or CO2.)”
The fuzzy boundary is because the boundary is an arbitrary point set by the frequency response range of the human eyeball. Some animals see farther into the near infrared than others. Rattlesnakes can see into the far infrared. Birds and bees can see into the ultraviolet. EMR is EMR. Wavelength primarily changes the way the wave propagates through matter. For instance a microwave will go through the ionosphere but radio waves can be reflected by it. Visible and infrared light won’t penetrate a sheet of paper but the paper is almost transparent for microwaves and radio waves and semi-transparent to x-rays. There’s no particular point where nature lays down a border saying “red stops here and becomes infrared”.
“You explicitly claimed that “Infrared radiation is completely absorbed by the first layer of water molecules at the surface.” Unless I am missing something, your statement assumes (and I agree) that water is very close to a perfect black body for IR and hence absorbs 100% of the downwelling IR.”
Yes but that doesn’t mean it does or does not raise the sensible temperature. Water and water vapor can co-exist at exactly the same temperature yet the vapor can carry a tremendously larger amount of absorbed energy as latent heat that will become sensible heat again when it condenses. Latent heat isn’t radiative. It’s transported mechanically.
George E. Smith says:
October 27, 2010 at 3:06 pm
“A text book plot of the actual solar spectrum places the peak spectral irradiance at about 480 nm which puts the visible IR boundary of 800 nm at 1.67 times the peak wavelength. Standard Black Body radiation curves, suggest that only 40% of the total is at longer wavelengths than that. But a detailed table of actual TSI spectrum values says that 56.023% of the total is at SHORTER than 800; which means only 44% is in the IR.
That is not an inconsequential difference from 54%.”
The 54% came from “Power From The Sun” -2001 – William B. Stine and Michael Geyer
Hi George, it looks like we could be falling foul of the definition of where the IR range begins. They peg IR as starting at 0.7 micrometers, while your text puts the boundary at 0.8 micrometers – enough to account for the discrepancy perhaps?
“””” Tenuc says:
October 28, 2010 at 7:30 am
George E. Smith says:
October 27, 2010 at 3:06 pm
“A text book plot of the actual solar spectrum places the peak spectral irradiance at about 480 nm which puts the visible IR boundary of 800 nm at 1.67 times the peak wavelength. Standard Black Body radiation curves, suggest that only 40% of the total is at longer wavelengths than that. But a detailed table of actual TSI spectrum values says that 56.023% of the total is at SHORTER than 800; which means only 44% is in the IR.
That is not an inconsequential difference from 54%.”
The 54% came from “Power From The Sun” -2001 – William B. Stine and Michael Geyer
Hi George, it looks like we could be falling foul of the definition of where the IR range begins. They peg IR as starting at 0.7 micrometers, while your text puts the boundary at 0.8 micrometers – enough to account for the discrepancy perhaps? “””
Hi Tenuc,
Well I am sure you are correct about the source of the discrepancy. It’s also not a point worth spending a lot of words on. I’m quite happy to use your number of 700 rather than 800.
Lots of references to the entire EM spectrum, simply say that “light” (visible) is the single octave from 400 to 800 nm. I know I used those numbers in an Application Note on Photometry of LEDs in a 1972ish industry paper; and I recall making the statement that more information is communicated to humans in that single visible Octave than from the entire remaining 24 or 25 or so octaves of the generally observable EM spectrum. Just a brash statement for effect to say we see a hell of a lot with our eyes.
But to get a bit more critical, I would go to “The Science of Color.” published by the Committee on Colorimetry of the Optical Society of America (to which I belong; society; not committee). They give an early 1924 CIE plot of the Photopic Eye Response (not low light Scotopic), which they plot from 380 to 700 nm. They also show a 1931 Chromaticity diagram (color triangle) that terminates at 700 nm.
But that 700 nm Red is qute visible to at least young eyes; in fact it is very visible; and a table of standard Tri-stimulus values of the Spectrum (perimter of the chromaticity diagram) (monochromatic), which gives 1.0002 at 555nm for the peak ybar value drops to 0.0041 at 700 nm (and about the same at 420 nm). The red drops to 0.0001 ybar at 760 nm; and at my age I can’t see that; and they terminate the table at 780 with a nominal zero value.
It so happens that the Standard wavelength we use for VCSEL laser diodes as used in Optical Laser mice is 780 nm; and none of us can see those. We use that wavelength because Silicon CMOS sensors are more efficent for 700-780 nm wavelenghts than for the 900 nm of real IR lasers.
So pedantically 400nm is clearly visible, and 800 is clearly not visible and not much useful red is contained in the 700-780 range. So I’m not unhappy with a 700 nm cutoff, and your numbers so long as we cite that cutoff so we know where we get the numbers from. The boundary line is not too germane to the argument as to how solar spectrum energy is treated; only the numbers shift a little.
George