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Albatross at 02:58 AM on 23 February 2014'It's been hot before': faulty logic skews the climate debate
The hubris of ideologues like Abbott when it comes to science is just scary-- this is someone tasked with running a whole continent, yet feels he can make critical decisions based on only his opinions. If I were an Australian I'd be pretty scared for the future.
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tlitb1 at 02:54 AM on 23 February 2014MP Graham Stringer and CNN Crossfire are wrong about the 97% consensus on human-caused global warming
@DB
Redundant comment so remove if you want but I'm happy with the fix of my comment and thanks for fixing it.
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Albatross at 02:53 AM on 23 February 2014'It's been hot before': faulty logic skews the climate debate
Great post John, high time someone challanged Abbott's nonsensical and unsubstantiated claims. Now will the rest of the media do the same? Sadly, probably not.
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Timothy Chase at 02:47 AM on 23 February 2014A Hack By Any Other Name — Part 1
I too, am looking forward to part 2, of course. Reminds me of how Real Climate was hacked at one point. That was back at the beginning of Climategate.
Appropriately named, that. A break-in was used to illegally obtain documents intended to be used for the purpose of systematic smear campaigns. But the similarity breaks down soon after that.
In this case, the crooks got away. Then the smear campaign actually worked for a while, with the press working often as unwitting accomplices, putting the victims of the attack on trial rather than trying to uncover those who were behind the criminal act.
With the break-in at Real Climate, the perpetrators uploaded a zip of the files they thought they could best spin for their campaign to the Real Climate server. They were planning on making a post that would include a link to the file.
But at the time Gavin Schmidt was in the system. He noticed that someone had broken in, then soon realized they were still there. At that point he shut down the server. He said something about it a while back, I believe in an interview.
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Ger at 02:24 AM on 23 February 2014A Hack By Any Other Name — Part 1
Private forums on a vpn?
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Dikran Marsupial at 02:11 AM on 23 February 2014Solar Cycle Length proves its the sun
jsmith regarding Lassen (1995) you probably ought to also read Thejil and Lassen (2000) (yes, that Lassen), which reports that the correlation broke down when further data became available.
Solar forcing of the Northern hemisphere land air temperature: New data
P Thejll, ,K Lassen
Abstract
It has previously been demonstrated that the mean land air temperature of the Northern hemisphere could adequately be associated with a long-term variation of solar activity as given by the length of the approximately 11-year solar cycle. Adding new temperature data for the 1990s and expected values for the next sunspot extrema we test whether the solar cycle length model is still adequate. We find that the residuals are now inconsistent with the pure solar model. We conclude that since around 1990 the type of Solar forcing that is described by the solar cycle length model no longer dominates the long-term variation of the Northern hemisphere land air temperature.
Journal of Atmospheric and Solar-Terrestrial Physics, Volume 62, Issue 13, September 2000, Pages 1207–1213
doi:10.1016/S1364-6826(00)00104-8
[emphasis mine]
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philr at 01:44 AM on 23 February 2014A Hack By Any Other Name — Part 1
Passwords should always be stored as salted hashes:
https://crackstation.net/hashing-security.htm
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Bob Lacatena at 01:22 AM on 23 February 2014Solar Cycle Length proves its the sun
I would also point out that the author of Reichel 2001 is... an economist.
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chriskoz at 23:29 PM on 22 February 2014How we know the greenhouse effect isn't saturated
I want to lift your spirits guys by saying that someone like me, has been reading your explanations and learned, as opposed to mgardner, a lot from your posts. Thank you! Especially to HK for very informative pictures and reference to Science of Doom, to Bob Loblaw for reference to Manabe 1964, and to Tom Curtis for overall summary. Sorry to those I did not manage to mention this time...
Like mgardner, I can boast that I have the necessary backgroound to grasp this science, but my attitude, unlike mgardner's, respect the science first (and all people who made it possible for me to learn it, starting from Manabe-san in the topic at hand), then try to assimilate it, finally comment/ask questions only at the end when new knowledge is too difficult or incompatible with my previous knowledge. mgardner's priorities are backwards to my priorities.
Tom@79, your explanation what radiation models do can be summarised as: double integration of IR energy function along altitude and frequency. If the function was as simple as Beer-Lambert law (also applicable to pressure vs altitude) and each frequency were absorbed independently, we'd have an easy analytical solution. But because the world is not that simple (natural broadening due to Heisenberg principle, Doppler broadening due to fast moving - 500m/s - air molecules, finally pressure, or collisional, broadening due to collisions between CO2 and other air molecules) the function becomes too complex, and frequencies inter-dependent to resolve it analytically. Therefore, it is resolved numerically as you described. The "effective altitude of radiation" as a is such model is an abstract term, defined by the amount of energy caried out to space within a particular band of IR and the lapse rate. That's a nice, valid definition and makes perfect intuitive sense to me [1]... Further, if you integrate total IR, energy you can define the "mean altitude of radiation" as total amount of IR energy within the lapse rate. And again, it makes perfect intuitive sense.
With such definition, the argument in the subject article (that GHE never saturates) can be understood even better. If you add CO2, the mean altitude of radiation will always rise no matter how much CO2 you had in the first place (even on Venus). That's because:
- the initial mean altitude of radiation cannot be infinite (some energy must be escaping the planet, otherwise the planet would heat up infinitely which is absurd)
- the aditional CO2 must be pushing the initial mean altitude higher, because all of the physical phenomenons involved (gas mixing, Beer-Lambert law, Doppler broadening, pressure broadening) collectively increase the IR absorption at the previous mean altitude of radiation.
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[1] Well, except the case of a band around 667cm-1, which is emitted from stratosphere: it could have been emitted from troposphere at the same temperature (linear T lapse rate does not hold in stratosphere) so there is an ambiguity in this case.
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cgs at 22:40 PM on 22 February 2014Unprecedented trade wind strength is shifting global warming to the oceans, but for how much longer?
I have a couple of questions concerning the model projections:
1. Can anyone tell me the relationship between what the authors call the AR4+AR5 model projections and the model projections shown in figure 1.4 of the latest IPCC report?2. Also, does anyone know why the authors begin their model projections in 2000 and not 1990 as in the figure I referenced in #1.
Thanks for any information!
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tlitb1 at 20:49 PM on 22 February 2014MP Graham Stringer and CNN Crossfire are wrong about the 97% consensus on human-caused global warming
Hence for example, one of Roy Spencer's five papers captured by our literature search was put in [category 5], because it proposes negative feedbacks will minimise future global warming.
This concept of "capturing" a specific paper in a category and naming its authors does not seem to be an intrinsic part of the Cook et al paper's methodology or purpose, so I wondered if the authors of the Cook et al paper could answer a question for me?If the Cook et al authors think a paper can be captured in a category like this by the initial abstract rating process, would a later different author(s) self-rating "release" the paper from this category?
For example, with this category 5 captured paper of Spencer's (which had 3 other authors), had Spencer and one other author replied with a rating of 3, and the two other authors with the abstract rating of 5, this would mean the overall rating would be 4 wouldn't it?
Moderator Response:[DB] Fixed text per request.
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Solar Cycle Length proves its the sun
jsmith - Lassen & Friis-Christensen have been repeatedly debunked, and in fact the paper you refer to is a later work by the same authors that the opening post was discussing, namely the errors made by those authors. Reichel 2001 has but 12 citations in 13 years, including three using Granger causality analysis demonstrating that natural variation including the sun is not the dominant factor in the last half century of climate change.
The statement made in the opening post, that "Solar cycle length as a proxy for solar activity tells us the sun has had very little contribution to global warming since 1975.", still holds true under examination.
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jsmith at 14:04 PM on 22 February 2014Solar Cycle Length proves its the sun
Strictly speaking, the "What the Science Says" box at the top of this page is inaccurate: there are other papers which claim to have found a correlation between solar cycle length and temperature, such as Lassen 1995 and Reichel 2001.
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Sceptical Wombat at 11:06 AM on 22 February 2014Dodgy Diagrams #1 - Misrepresenting IPCC Residence Time Estimates
I have a slightly different analogy. Firstly I half full the bath with cold water (I prefer my thought experiments to be as sustainable as possible), and set the cold water tap so that the level stays constant - so far the same as your analogy. Then I turn on the hot water tap just a little bit. Now the level in the bath will start rising. The amount of hot water in the bath at any time will be very small ("CO2 from fossil fuels only accounts for 0.x% of atmospheric CO2") but only an idiot would claim that the act of turning on the hot water tap was not the cause of the rising level. When the bath is nearly full you turn off the hot water tap. The level in the bath will go down, because of the extra pressure, but much more slowly than it rose and it will only asymtotically approach its original level.
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Sceptical Wombat at 10:54 AM on 22 February 2014A Hack By Any Other Name — Part 1
One thing I think you should stop doing is holding passwords in plain text. A better way is to use a one way encryption algorithm and to only store the encrypted password. That way you never know my password and so no one else can get it from you. If I forget my password you issue a new one and require me to change it.
Moderator Response:[BL] Passwords are not and have never been stored in the database as clear text. They are and always have been encrypted, and they are never decrypted. Rather, the password sent by the user is encrypted, and that encrypted password is compared to the encrypted password stored for the user. If they match, then the password supplied by the user is valid.
[BL] Correction, I just looked at the code, and passwords are decrypted in the "Forgot your password" function -- but that doesn't represent much of a security hole, because it can't be used to breach the system, and it can only be used to steal passwords if you already have the password and so can change a user's e-mail, or otherwise have access to that person's e-mail.
Either way, that particular flaw doesn't represent a pressing issue, at least compared to the effort it would take to correct.
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Rob Honeycutt at 10:28 AM on 22 February 2014How we know the greenhouse effect isn't saturated
This could be a case of "I don't (can't, won't) understand until I get the result that I'm looking for."
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Tom Curtis at 10:19 AM on 22 February 2014How we know the greenhouse effect isn't saturated
One addition to my post @81, mgardner has been quite critical of people above for not answering the questions he purportedly asked. He has acted, in other words, as though they had an obligation an answer him. Well, they do not. They do not, firstly because they are volunteers; secondly, because he is ungrateful; and thirdly because the question he wants to focus on is uninteresting. There are far more scientifically informative questions that could be asked - like for example, "how does modtran work". When provided with answers to those informative questions (ie, informative answers to his questions as posed), mgardner has been at his most ungrateful.
He will now, no doubt, complain that his ingratitude has lead to his questions being ignored. He is welcome to those complaints to. He is just not welcome to anymore of my time.
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Tom Curtis at 10:11 AM on 22 February 2014How we know the greenhouse effect isn't saturated
mgardner @80, you are welcome to your opinion, and to waste your time pursuing it. You are not welcome to waste my time on trivial technicalities. Look it up and work it out for yourself. Then when you have, if you still think it interesting, come and let us know the answer, and why it is interesting. In the meantime, your repeated questioning on a trivial point is just spam. Don't be surprised, therefore, if we put you in our personal spam folders (ie, ignore what you have to say, and ask questions about) in future.
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Rob Honeycutt at 09:29 AM on 22 February 2014A Hack By Any Other Name — Part 1
Looking forward to part two!
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mgardner at 09:28 AM on 22 February 2014How we know the greenhouse effect isn't saturated
Tom Curtis@78
"But the further details for which you seek serve no purpose either scientifically, or in terms of general education."
You are welcome to your opinion, Tom.
With respect to general education, I have always assumed that I was protected by the concept of academic freedom in making those kinds of decisions for myself. I do have some experience in this area, and, unless you plan to fly in for the next holiday, you are not the one who is going to be drawing little pictures for my brother-in-law, right?
With respect to scientific purpose, some of the most fruitful physicists of our time have "gone back to the classroom"-the physics 101 classroom-- because it served to clarify their conceptualizations. At the least, for an interested student, wouldn't these 'purposeless' inquiries give some insight into the thinking of those who developed MODTRAN, to which we refer so often?
And then there's the final question-- what's the harm? If HK wants to exercise his chops, is there some policy that prohibits it? I was accused of being 'critical' but several people seem to want to criticize my curiosity. I have always been delighted (and amazed) when students thought for themselves and asked questions.
If this gets me moderated out, so be it. You seem to be much more welcoming and tolerant of 'skeptics' who take up lots of space to little effect.
Moderator Response:[JH] Please lose the condescending attitude.
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How we know the greenhouse effect isn't saturated
Tom Curtis - Agreed. I believe I stated one of those points before regarding the range of altitudes emitting, "...the sum of that emission adding up to the oft-noted temperature equivalent profiles seen in satellite observations of those band". This makes emission from a single layer at that observed temperature an incorrect way of thinking about the physics, as it is a mean altitude, not a single one.
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Tom Curtis at 08:27 AM on 22 February 2014How we know the greenhouse effect isn't saturated
mgardner @77, your question serves no apparent purpose.
You have asked a series of questions on this topic, and have had a perfectly acceptable response to those questions since at least Dikran Marsupial's responce @37, where his final paragraph stated:
"IIRC the lower atmosphere isn't completely opaque to IR, so it probably isn't best to think too strongly about it in that way, instead there is a band in the atmosphere from which the bulk of IR is radiated. Some may come direct from the surface, but not much as it is absorbed in the trophosphere, most will be emitted from the air higher up in the atmosphere, which is cold. The more CO2 you add, the higher in the atmosphere it needs to be radiated from in order not to be absorbed before it escapes. I suspect there is a probability distribution that shows the density of the height in the atmosphere from which IR photons escape; the mean increases with increasing CO2."
Nothing since then has done any more than flesh out details of this basic picture, and perhaps illustrate it better. One key point here is that talking in terms of layers as hard boundaries defined for x,y, such that below x, at wavelength y, no photons emitted escape to space makes no sense. That is DM's first point in the paragraph above. And yet you return to the assumption that such defined boundaries make sense, that in scientific use they are anything more than an approximate, but sometimes useful convention.
In radiation models, the atmosphere is divided into thin layers. For each layer, l, and for each wave number (or some other conveniently small division of frequency) emissions are calculated. The absorption of the total upward radiation for the layer below, l-1, is calculated. The model then passes to the next upward, l+1, layer the total upward radiation from l, ie, the sum of upward emissions plus (1-absorption) of the total upward radiation from the preceding layer. The same is done for downward radiation in the opposite direction. No attempt it made to track the exact point of origin of radiation in the total upward radiation from each level because it is superfluous information. Such models calculate the actual upward or downward radiation at any level with stunning accuracy.
If asked where the radiation that escapes to space comes from, they modellers indicated that it comes from the "effective altitude of radiation", which is defined as "that altitude that has the same temperature as the brightness temperature of the radiation to space at a given wave number" (or other conveniently small division of frequency). Thus talk of the layer from which radiation comes is just a shorthand way of mentioning the temperature weighted mean altitude from which the radiation comes. Nothing more.
In more popular parlance, we can say (and this is literally true) that increased CO2 increases the mean altitude from which the IR radiation escapes to space, and that if that mean altitude is cooler, then the IR radiation escaping to space will be reduced. But the further details for which you seek serve no purpose either scientifically, or in terms of general education.
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mgardner at 07:06 AM on 22 February 2014How we know the greenhouse effect isn't saturated
HK@76
Thank you. Like your other posts, this is very thorough and well written.
My interest is in the area (nominally 5 km) where we say that 'most of the energy is radiated to space'. And, because my goal is to explain or 'draw a picture' (literally or verbally) at the simplest level, I wish to discuss only one wavelength resulting in somewhere between big x and little x.
So, let's say we define at about 5 km two layers of 100 m thickness (as in that graph @55 we both like). We call the top one A and just below it B. (I use top and bottom "plane" to indicate the boundaries not to confuse with "the" surface of Earth). Also, I will simply use zero rather than negligible for quantities. And, CO2 is the only GHG for this discussion.
A has zero CO2, and B has some. (I say that A is transparent, and B is translucent.) C, which begins at the bottom plane of B and goes down x, is 'opaque' since nothing originating below its bottom plane reaches B.
How do we characterize the radiation flux and the temperature for these layers, first as described, and then after we add CO2 in the equivalent amounts to each?
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How we know the greenhouse effect isn't saturated
mgardner @64 & 73:
You want some examples of how long a path of air must be to reduce the amount of IR radiation passing from one end to the other to a “negligible” level?If a “negligible” fraction of surviving radiation is defined as 1% (my arbitrary choice), it should be possible to calculate some path lengths of air needed to achieve this, assuming that my layman understanding of the Beer-Lambert law is reasonably correct. First a hypothetical example to show the principle:
Suppose that 25% of the radiation at a particular wavelength is absorbed by 1 metre of air. The next metre will absorb 25% of the remaining radiation and the same fraction will be absorbed by each successive metre after that (75% surviving through each metre).
The surviving fraction through 5 metres is 0.755 = 0.237, for 10 metres the fraction is 0.7510 = 0.056 and so on. In this case it takes 16 metres of air to reduce the surviving radiation to a negligible level, since 0.7516 = 0.01 = 1%.
And now some real data:
This graph from this article by Science of Doom shows the fraction of radiation entering one end of a 1 metre path of air at sea level that is transmitted (survives) to the other side. The CO2 concentration is 380 ppm, and the radiation originating within the air itself is ignored. The y-axis goes from 0 (no radiation transmitted) to 1 (all radiation transmitted), and the x-axis covers the wavelength interval from 15.15 micron (left) to 14.88 micron (right), i.e. around the very strongest absorption band of CO2. (10,000 / wavenumber = wavelength in microns)
As you see, 99% of the radiation is transmitted at 662 cm-1, while only 2% is transmitted at 667.5 cm-1, so the radiation at 667.5 cm-1 is already reduced to an almost negligible level by only one metre of air at sea level!
A calculation like the one above shows that it takes 458 metres of air to reduce the radiation at 662 cm-1 to a negligible level (0.99458 = 0.01) while it only takes 1.18 metres (0.021.18 = 0.01) to achieve the same for radiation at 667.5 cm-1. (See the last paragraph in Tom’s comment @67)If we ignore the complexities caused by pressure broadening and so on (I’ll leave that to the experts!), these path lengths are roughly inverse proportional to the atmospheric pressure. If the pressure drops to 0.2 bar (at about 12 km) the number of CO2 molecules per m3 is only 1/5 of that at sea level, so you need a 5 times longer path to get the same absorption as at sea level. That should translate to 2.3 km for radiation at 662 cm-1 but still only 5.9 metres for radiation at 667.5 cm-1. In the middle of the stratosphere (30 km / 0.01 bar) the same path lengths are about 46 km (!) and 118 metre, respectively.
(this approach only works for well-mixed gases like CO2, not for water vapour that is strongly concentrated in the lower troposphere)So, mgardner, the “x” you have been asking for can be anything from a metre to tens of kilometres, depending on wavelength, altitude and other factors, including how you define the term “negligible”.
Did this help?
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One Planet Only Forever at 02:40 AM on 22 February 2014'It's been hot before': faulty logic skews the climate debate
ubrew12,
I postulate that:
"Abbott has only made a statement that sounds like what people who desire to get away with benefiting from the unsustainable and damaging burning of fossil fuels will readily accept. He has claimed what that type of person wishes to hear and prefers to believe. And he does it without any substantial evidence to support his claim, because the evidence actually substantially contradicts such a claim."
It appears that Abbott is one of the many powerful and wicked people who are trying to take advantage of that potential popularity to benefit from unsustainable and damaging attitudes and actions any way they can get away with.
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michael sweet at 02:24 AM on 22 February 2014How we know the greenhouse effect isn't saturated
mgardner,
The people you are posting with are volunteers who have gone to a lot of effort to find graphs and explainations that will answer your questions. They are searching the background data for information outside of their specialties. You have thanked their efforts with criticism. Has it occured to you that the problem may be that your questions have been poorly phrased from the beginning? You appear to have specific needs for your answer that it is difficult for others to understand. Perhaps you need to do your own homework, instead of criticizing others for doing a poor job of it. You could be building your knowledge by searching for the answer yourself.
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Dikran Marsupial at 22:37 PM on 21 February 2014How we know the greenhouse effect isn't saturated
mgardner, as you continue to be ill-mannered and dismissive towards attempts to address your ill-posed questions, even after my appology in post 63, consider my participation in this discussion over.
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mgardner at 21:15 PM on 21 February 2014How we know the greenhouse effect isn't saturated
HK@70
"What if the diagram in @55 had showed radiation from a narrower wavelength interval, say 14.5-15.5 microns in stead of 13-17? I’m sure the radiation within each CO2 concentration would originate from a much narrower altitude interval and look more like a “layer” in the atmosphere (more like what mgardner has claimed). "
HK, please look at the graph @55. Look at the label of the vertical axis.
Now, read carefully what I said @64.
What have I so far claimed about radiation originating in a 'layer' other than what the graph says? Again, my original problem was the original 'layers' language of the explanation-- about 'radiating layers moving up to where it is colder'.
I've now quoted myself so often I guess there is not much point-- I think it is the hammer and nail problem. Whatever question I ask, the answer is going to be the one that everyone has learned to repeat.
Moderator Response:[JH] Ypou are now skating on the thin ice of escessive repetition which is prohibited by the SkS Comments Policy. Please cease and desist.
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michael sweet at 21:09 PM on 21 February 20142014 SkS Weekly News Roundup #7
Many here follow the Arctic Sea Ice. For those who don't, this sea ice map from Feb 20 shows astonishing melting near the North Pole. The North Pole is not imaged since the satalites do not fly directly over it, but it is clear that there are open areas of ocean at the North Pole in the middle of winter! It will be interesting to see what the NSIDC has to say about this in their monthly comment around March 7. Of course the total sea ice extent is near record lows. Another interestng melt season ahead.
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ubrew12 at 20:13 PM on 21 February 2014'It's been hot before': faulty logic skews the climate debate
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Doug Hutcheson at 19:21 PM on 21 February 20142014 SkS Weekly Digest #7
My apologies - I have just seen the repost of The Conversation article here and that is where I should have commented.
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Doug Hutcheson at 18:47 PM on 21 February 20142014 SkS Weekly Digest #7
John, thanks for going in to bat for reason and logic at The Conversation today. The comments were instructive, but cut off all too soon for my liking. Still, it gave the deniers a chance to enjoy a feeding frenzy, so it was also amusing, in a black kind of way.
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meher engineer at 17:25 PM on 21 February 2014Snows of the Nile: The search for vanishing equatorial glaciers
i have just seen the preview. It dii lok interesting, particularly since I have never heard of these African mountains I tried to rent the video from Vimeo but failed.
meher engineer
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One Planet Only Forever at 13:51 PM on 21 February 2014'It's been hot before': faulty logic skews the climate debate
I postulate that:
"Faulty logic is not skewing the climate debate. The desire to benefit from burning fossil fuels is causing many people to readily accept absolute nonsense that sounds like what they wish to hear and prefer to believe. And many powerful and wicked people are trying to take advantage of that potential popularity any way they can get away with."
And to poke at another twisted piece of the pervasive and persistent irrational thought processes of that group:
"I will only change my mind about that when it is conclusively proven with absolute certainty to my satisfaction that what I prefer to believe is not to be believed."
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PhilMorris at 10:02 AM on 21 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
I suppose as a website devoted to the valuable activity of debunking denialist attitudes towards AWG you provide a valuable service, and as such, quoting 'consensus' information that supports AWG makes sense. But I suspect for a growing number of people AGW is all too real with 100% certainty, and for many people it is happening all too fast. Over the last few years there has been a continual stream of research papers that make the IPCC projections clearly conservative insofar as the pace at which climate change is occurring. In the last couple of weeks alone there were two research papers that continue the bad news.
"Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus" by England et. al, Nature Climate Change adequately explains that the so-called surface temperature ‘hiatus’ has been caused by abnormally strong Pacific Trade winds, which have driven heat into the deep Pacific, and that when those abnormal trade winds abate, we're in for a continued and rapid surface temperature rise.
The second is “Observational determination of albedo decrease caused by vanishing Arctic sea ice” by Pistone et. al.,
PNAS, showing that the loss of ice albedo over the last 30 years is equivalent to an additional 25% of global CO2 forcing. I’m betting that isn’t part of any of the climate models, meaning those climate models vastly underestimate the rate at which climate change is happening. Hm, prehaps that's why we may expect a summer ice free Arctic before 2020, some 30 years ahead of the latest IPCC 'projections' (Maslowski et. al, Ann. Rev. Earth Planet. Sci, 2012)I follow the literature rigorously and perhaps I’m simply blind to certain things but I have yet to see a single ‘good news’, peer reviewed research paper that has stood the test of time, and suggests that things are not as bad as they appear to be.
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How we know the greenhouse effect isn't saturated
Agree with your comment about the non-saturation, Tom!
Unlike the MODTRAN graph, the annotations in the diagram were not added by me. They can be found in the original diagram in the article from 2007. -
Tom Curtis at 09:06 AM on 21 February 2014How we know the greenhouse effect isn't saturated
KR @69, thanks for the advise. Oddly, I read "HK", and intended to type "HK", but apparently my fingers didn't get the message.
HK @70, first, apologies for the misattribution. Second, yes I believe we are saying the same thing.
I like the new diagram from RC. It is particularly interesting to pay attention to the logarithmic scale of the absorption factor, which should drive home the very large differences in the width of the emission profile for small changes in wavelength.
One slight point about the diagram, however. It includes the two relatively highly absorbing bands at 13.9 (720 cm-1) and 16.2 microns (620 cm-1)in the region saturated at 1xCO2. From the modtran graph, they are still clearly in the wings, and become deeper (less emissions to space) with higher CO2. The statement that the region is saturated is, therefore, clearly a simplification and should not in fact be understood as saying that there is no further strengthening of the greenhouse effect across that entire band with increased concentration.
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How we know the greenhouse effect isn't saturated
Tom Curtis @67: Your point seems to agree with what I’ve tried to explain below, which was written before I read your last post:
Agree with Dikran that your diagram is very interesting! I’ve included it in my growing collection of climate graphics.
All of you: Regarding the discussion about of “opaque” layers, have you taken into account that the absorption of IR by CO2 is extremely dependent on the radiation’s wavelength, even within a relatively narrow wavelength interval like 13-17 microns in the diagram? I think that explains why the radiating layers of CO2seem to be so diffuse, i.e. spanning over so large altitude ranges.
Take a look at this diagram from the previously mentioned RealClimate article about the saturation argument. (It also demonstrates another important aspect of this, namely the widening of the absorption band.)
As you see, there is a more than 1000-fold increase of the absorption factor from 13 to 15 microns, and at least a 100-fold reduction from 15 to 17 microns. When that is taken into account, my interpretation of the diagram in @55 is the following:
The radiation from the lower troposphere (in the 1000 ppm case) comes from the periphery of the absorption band, say 13-13.5 and 16.5-17 microns. It’s weak despite coming from fairly warm CO2 because the radiation is partly blocked by CO2 higher up.
The radiation from the middle troposphere comes from wavelengths closer to the centre of the absorption band; say 13.5-14.5 and 15.5-16.5 microns. It’s stronger despite coming from colder CO2 because much less of the radiation is blocked by CO2 higher up. The radiation from the lower troposphere on these wavelengths is completely blocked because CO2 absorbs more strongly here.
The radiation from the upper troposphere and lower stratosphere comes from the central part of the absorption band (14.5-15.5 microns), with the radiation closest to 15 microns originating in the upper part of the stratosphere (even above Felix Baumgartner!). This radiation weakens partly because the CO2 here is very cold, and partly because the wavelength interval where CO2 is able to absorb and radiate gets narrower as the altitude increases (you get less radiation from a 1 micron wide interval than a 4 micron wide). And of course, it’s impossible for any photons in the 14.5-15.5 micron interval to escape to space from the lower and middle troposphere because CO2 absorbs so strongly in this part of the spectrum.
The same goes for the curves for lower CO2 concentrations, but the altitude with peak radiation (about 8 km for 1000 ppm) will be lower while the radiation itself is higher in the warmer parts of the atmosphere.
What if the diagram in @55 had showed radiation from a narrower wavelength interval, say 14.5-15.5 microns in stead of 13-17? I’m sure the radiation within each CO2 concentration would originate from a much narrower altitude interval and look more like a “layer” in the atmosphere (more like what mgardner has claimed).
Does all this make sense, or have I missed something crucial here?
Moderator Response:[JH] Unnecessary white space eliminated.
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Phil at 08:44 AM on 21 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
william @5
On the contrary side, there have been numerous cases where the only scientist that was correct was an individual against all the other scientiests.
I wonder whether this is really true. It would be good to have examples, but to pre-empt the usually case quoted, here in Thomas Kuhn from "The Copernican Revolution" (Chapter 6)
Therefore, when in 1616, and more explicitly in 1633, the Church prohibited teaching or believing that the sun was at the centre of the universe and that the earth moved around it, the Church was reversing a position that had been implicit in Catholic practise for centuries. The reversal shocked a number of devout Catholics, because it committed the Church to opposing a physical doctrine for which new evidence was being discovered almost daily ...
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How we know the greenhouse effect isn't saturated
Tom Curtis - Credit for that excellent MODTRAN graph goes to HK, not to me. The handle are unfortunately easily cross-read.
At least this isn't as bad as when there were three different 'Hank's actively commenting...
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Dikran Marsupial at 08:15 AM on 21 February 2014How we know the greenhouse effect isn't saturated
Cheers Tom, that is very interesting, it makes the shapes of scaddenp's plot a little less surprising (but still interesting), and hopefully helps answer mgardners question.
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Tom Curtis at 07:58 AM on 21 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
Prufocks @7, you have touched on a point which is a slight weakness of the paper. One of the strengths of Oreskes' original study is that she identified papers that did not include direct assessment of anthropogenic contribution to global warming, and did not include them in those that affirm global warming. This did not prevent her study being attacked by "skeptics" with the argument from irrelevent denominator (ie, the claim that she overstated support for the concensus because x papers did not support the concensus because they never directly address the issue). In formulating the categories for Cook et al, Cook et al did not include a category for those papers that explicitly address attribution. Consequently "attribution papers" tend to get sorted into "impacts", "methods", and occassionally "mitigation". The problem is that we cannot, from the paper, directly address the propotion of attribution papers support consensus.
Having said that, Dana has said on a couple of times that 100% of recent attribution papers support >50% anthropogenic contribution to recent warming. I suspect his definition of an attribution paper in that comment may be a bit tighter than one that would have been used in the survey; but cannot be sure without conducting a mini survey of my own.
It should be noted that the "obvious" problem with extending the analysis beyond attribution papers to those that merely accept AGW and go on from there is not a problem at all. Scientists do not simply accept claims. If they adopt AGW as a working hypothesis, it is because they have read a significant number of relevant papers, or at least review papers, and been convinced by the evidence. I am sure there are exceptions, but not enough to distort the result. That means that a general survey like Cook et al will pick up on whether or not controversy about a theory is general, or restricted to a small group unconvinced - and clearly the later is the case.
It should be noted that the criticism of the concensus paper is coming from people who, in general, accept the OISM petition as evidence that there is no concensus, ie, they accept that the signing of an internet petition by bachelors or vetinary science, is evidence that there is no concensus of climate science; but they do not accept that detailed discussion of the consequences of anthropogenic warming by climate scientists is evidence, if those climate scientists assume global warming in that study rather than prove it from first principles.
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Prufrocks at 07:31 AM on 21 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
This will undoubtable mark me as a troll of some type (I'm only vaguely familiar with the myriad sub-types)... but I'm not, I'm a lay-person trying to keep up. I'm pretty strongly (~95%) on board with AGW and find no denialist or fake-skeptic credible. I'm somewhat confident to rebut many of their debunked claims and make the case for AGW. Though not diligent enough, my main sources are SS, RC, Tamino, Crock.
But, I'm finally spending some time with "Quantifying the consensus on anthropogenic global warming in the scientific literature" (John Cook et al 2013 Environ. Res. Lett. 8 024024 doi:10.1088/1748-9326/8/2/024024). I've downloaded the datafile.txt and randomly searching citations and going to the original articles online and, where possible, full article not just abstract.
I'm somewhat surprised to see how many of those who "endorse" AGW without quantifying it (groups 2 & 3) seem mostly to be "accepting" it as a premise for their paper rather than forming a conclusion of AGW based on their paper. Which I'm guessing is perfectly fine, appropriate & expected and the little suprise may only reflect my own naïveté. Ever since Oreskes' study – which I accept as being very strong and persuasive – and based on my own observations of the lit, without thinking I had just assumed that 'active climate researchers actively peer-review publishing,' and not rejecting AGW, were most often supporting their conclusion with more or less new data or new analysis (I recognize this does frequently apply).
Am I mischaracterizing? Am I wrong in wondering or wrong in even remarking on it? I have to believe the denialists are squawking about it.
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Tom Curtis at 06:57 AM on 21 February 2014How we know the greenhouse effect isn't saturated
Dikran Marsupial @65, it is important to interpret scaddenp's graph in the light of KR's excellent annotated MODTRAN graph:
For context, Scaddenp's graph is for transmission of 13-17 micron radiation. That is radiation with a Wavenumber of 590-770 cm-1. As such it includes the full width of the notch shown in the graph above, not just the central values. A graph showing just 15 micron radiation (=666.7 cm-1) would show a much narrower effective emission profile for each concentration, and indeed, would show an altitude such that below that altitude, emitted IR radiation is nearly completely absorbed. In contrast, a graph of just 13 or 17 micron radiation would more closely resemble something like the 100 ppmv profile (I also do not have the chops to calculate it, and would need to do so to be sure).
Looking carefully at Scaddenp's graph, you will show that all curves have a right skew, so their mean value of emission is higher than their modal value. That makes things slightly awkward in that we need to guesstimate (if we cannot calculate) that mean value in relating it to the atmospheric profile shown by KR. However, in general the curve of a particular wave number in the 590-770 band will have an effective emission profile with a mean altitude of emission equivalent to the 1000 x (300- brightness temperature)/6.5. As such, even the emission profile of CO2 with a wave number equivalent to the bottom of the trough is not shown on Scaddenp's graph.
Quoting mgardner, he wrote:
"For some altitude h (e.g. 5 km), and for some wavelength (lambda), I think there is an altitude h-x such that the number of such (lambda) photons emitted from a plane at that level (h-k) which reach h is negligible."
(My emphasis)
As I have noted, at 15 microns (666.7 cm-1), that is correct. Indeed, at 15 microns absorption is so strong that I have seen a 15 micron spike in atmospheric spectra recorded in an aircraft from the amount of warmed, cabin air between the window and the instrument (much less than a meter). It is probably also true for the plateau in emissions on either side of 15 micron spike (which has a mean altitude of emission in the tropopause). However, it is not a usefull formulation for CO2 emission in general, because of necessity it will neglect the wings were the important action is occuring with respect to increases in CO2 concentration. On the other hand, in simplified models and discussions, climate scientists treat all emissions as coming from the mean altitude of emission - a simplification that is surprisingly accurate (I am told).
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Rob Honeycutt at 05:44 AM on 21 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
William... Definitely, consensus is not how science progresses. But consensus is how we can evaluate relative risk for things we can never have perfect knowledge of.
What surveys like this give us is a method by which to make value judgements required in order for action to take place.
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william5331 at 05:23 AM on 21 February 2014Vision Prize: scientists are worried the IPCC is underestimating sea level rise
I'm still uncomfortable with surveys of scientists to see how many believe in one thing or another. On the contrary side, there have been numerous cases where the only scientist that was correct was an individual against all the other scientiests. I'm not suggesting that that is the case here. The evidence for climate change and it's likely effects are pretty overwhelming and, I think, grossly underestimated but consenses is not part of science.
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How we know the greenhouse effect isn't saturated
mgardner - I'm afraid you're mischaracterizing my posts (and perhaps mixing them with others, as I have not referenced Beers law). I've found your requests for 'opaque' layers quite difficult to decipher, in part as (a) there has been no definition of 'negligible' stated, (b) path length increases as a continuum with decreasing GHG concentration/pressure, and (c) you've kept asking about 'opaque layers' while stating that you think layers are not a proper way to think about the matter - the combination of those factors making it impossible to suggest any dividing lines. Or, quite frankly, for me to follow what you have been asking for. I have not intended to be rude - just trying to answer the questions as I understood them.
The discussion appears to be progressing now that there is sufficient understanding of terms and of your queries - I will leave you to that.
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Dikran Marsupial at 04:03 AM on 21 February 2014How we know the greenhouse effect isn't saturated
mgardner wrote "For some altitude h (e.g. 5 km), and for some wavelength (lambda), I think there is an altitude h-x such that the number of such (lambda) photons emitted from a plane at that level (h-k) which reach h is negligible."
My reading of scaddenp's graph suggests that for 400ppmv, the maximum power of photons in this band is emitted from about 4km in altitude (about 0.44 watts m^-2), but there is about 0.24 watts m^-2 of photons in this band that reach space directly from the surface, which is far from negligible. Thus there is no truely opaque layer (in this sense) from which the radiation of IR photons from the surface is negligible, at least for current atmospheric CO2 concentrations. Or to put it another way, whatever the values of h and x are, they are too large to fit within the Earths actual atmosphere.
I suspect you really need to use something like MODTRAN to get a definitive answer to this question, however the realclimate article I mentioned earlier in the thread provides this diagram:
Apparently at 300ppm, the CO2 in a column of the Earths atmosphere is equivalent to a 2.5m tube of pure CO2 (at sea level pressure and 20C). The graph shows the proportion of light transmitted through the tube as a function of length. In this case the transmission is still falling appreciably from tube lengths corresponding to 1xCO2 to 4XCO2, which suggests that there isn't a truely opaque layer within the tube in this thought experiment either. Note that this is not really realistic (as the article points out because not all of the atmosphere is at 20C or sea level pressure).
I'd say it was a mixture of (1) and (3), I don't (currently) have the chops to perform the calculations, but hopefully I can help in getting into the ball-park and help to better formulate the problem (you do have the required security clearance though ;o).
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mgardner at 03:24 AM on 21 February 2014How we know the greenhouse effect isn't saturated
DM@63
That pesky "real world" is intruding on our fun little universe here, so I will try to briefly give you something to think about while I take a little time to attend to it. I don't think we're quite communicating yet...
Here's what I mean when talking about an opaque layer. And please remember, I am setting up a simplified, idealized case to further my understanding-- I'm gathering up elements from which I can synthesize an accurate model that works for me, not anyone else. Once I do that, you are free to tell me that I am wrong or that yours is better.
Scaddenp's graph refers to emissions "from a hundred meter layer".
I treat that as a plane.
In my earlier reply to KR, I said something like:
"For some altitude h (e.g. 5 km), and for some wavelength (lambda), I think there is an altitude h-x such that the number of such (lambda) photons emitted from a plane at that level (h-k) which reach h is negligible."
and
"I don't know what x is, or how many subsequent such layers descending from h-x there may be."
To my mind, there are three legitimate ways to answer that:
1) "You're wrong, there's only one (or no such) layer and it goes to the surface. Here's the calculation using this wavelength and Beer's law." (KR's response, sans the calculation, which to me is obviously wrong.)
2) "You are correct, I come up with (n) such layers, and the thicknesses vary thusly as we descend."
3) "Sorry, I don't have the chops to provide you with the numbers you are looking for." or maybe "Sorry, you don't have the required security clearance?"
This can also be applied to the question of how the amount of radiant energy embodied in those photons is attenuated, as measured by radiant energy arriving at h.
Hope that's clearer. I will be back and try to discuss the more general case.
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DSL at 02:50 AM on 21 February 20142014 SkS Weekly News Roundup #7
Not engaging in the conversation directly; just tossing in a few recent and relevant references to supplement Tom's points:
Zhou et. al 2013 - "An Analysis of the Short-Term Cloud Feedback Using MODIS Data."
Evan & Norris 2012 - "On global changes in effective cloud height."
Keep in mind that ENSO plays a significant role in triopical cloud top height and that the measurements discussed in Evan & Norris cover slightly more than the last decade, a decidedly La Nina-ish period. Nevertheless, after accounting for a systematic error in sampling, a positive trend in CHT is found for the period.
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