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MA Rodger at 01:25 AM on 12 April 2017Science of Climate Change online class starting next week on Coursera
Curiousd @19.
While we have now both sourced Pierrehumbert, are now looking at the same writing, and while you do say “I think we should get this straight before talking about the other issues“, do note my apprehension expressed @18 concerning the use of the 1976 US Std Atmosphere as a global average.In producing a better global average than the single values fo single the 1976 US Std Atmosphere, the UoC model does provide regional/seasonal alternatives for analysis. I have endeavoured to gain a global average by weighting these regional/seasonal UoC alternatives. Using the surface temperature outputs from the UoC model, the weighting that provided a parity of global average temperature is 50% tropics and 12½% for the 4 remaining latitude/seasons. This is not an unreasonable outcome. It would fit with global coverage 70ºS to 70ºN. (The Chen et al analysis coverage is 80ºS to 80ºN.)
The calculated TOA IR flux from the UoC model when weighted in this manner yield a global average global of 265.9Wm^-2, a significant increase on the 1976 US Std Atm output. If the 1½% to 2% is added to this sum (representing the additional IR in the 0-1800cm^-1 band used by Chen et al but excluded by the UoC model (your 'Correction Number One'), we arrive at a TOA IR flux range of 270-271Wm^-2. These values are now very close to the measured global value used by Chen et al (273.7Wm^-2) and their calculated values (271.7, 274.2, 277.0Wm^-2) . That the UoC calculator comes so close is pretty impressive for a webpage-calculator. -
curiousd at 23:47 PM on 11 April 2017Science of Climate Change online class starting next week on Coursera
Hi M A Rodger,
Look at http://cips.berkeley.edu/events/rocky-planets-class09/ClimateVol1.pdf
Unfortunately the thorough discussion of the various angles one might use under different circumstances on page 191 in my text does not appear to be in this. However, page 190 does have the statement after equation 4.69 "For strong lines the equivalent width is...." Note that within the radical is the symbol L sub S for the "strong path". Note that in equation 4.67 the set of terms q(p)/ g cos theta appear together. The q(p) is not a constant as it is for CO2 up to 100 km, but if I multiply by 1.7 the factor 1.7 being constant comes outside the integral. This complication does not come about for the CO2 case since q is constant and comes outside the integral.
I am assuming that SpectralCalc correctly takes care of the integral of q(p)dp between pressures.
BTW..One of the limitations of both MILA and Spectral Calc is that both have no ability for the user to resolve altitude steps less than 1 km. Of course, both MILA and SpectralCalc have a length resolution much less than this in the underlying program. For MILA I think I recall from the button for the underlying program that the length resolution is one centimeter. MILA is free, SpectralCalc is amazingly reasonable and Modtran6, which I have also purchased is expensive! But with Modtran six, one has a resolution in length at least down to a meter, a wavenumber range way more than I would ever need, and it deals with scattering. But although I am quite familiar with SpectralCalc I can now only do rudementary things with Modtran6, just because I have not studied the program very much. It is breaking in a new GUI interface, other wise I never would have purchased this package.
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jgnfld at 23:30 PM on 11 April 2017Sea ice falls to record lows in both the Arctic and Antarctic
My bad.
Extrapolation is _always_ suspect, true. but at least interpolation in this case can likely be attributed to observable temp/weather changes.
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curiousd at 22:47 PM on 11 April 2017Science of Climate Change online class starting next week on Coursera
Hi M A Rodger,
The reference is my well worn copy of "Principles of Planetary Science" ,Raymond T. Pierrehumbert, Cambridge University Press, third 2014 printing, ISBN 978 - 0 - 521 - 86556 - 2 Hardback. Some time ago in a completely different context I was given an URL for a free online copy by someone on SS. Maybe Tom Curtis??? Even then there is a strange thing...almost all of the ONLINE version is the same as the book, but some of the book material has been left out. Maybe I can dig up the URL to the on line version someplace on my computers, but no guarantees.
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MA Rodger at 20:20 PM on 11 April 2017Science of Climate Change online class starting next week on Coursera
curiousd @19.
It seems we discuss a work by Pierrehumbert. It would be good to be sure we are discussing the same work so a proper reference would be good. The work you reference should be listed here although likely it will be this work you offer up for discussion. (By the way, my initial thought @14 had been solely to provide the links, not to comment on them.)
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curiousd at 11:26 AM on 11 April 2017Science of Climate Change online class starting next week on Coursera
As I said, increasing the water vapor concentration by 1.7 is only because it has precisely the same effect on the radiation emitted as using a 54 degree angled path, even though I am using a vertical path. This is because 1 / cos 54 degrees is 1.7/cos zero degrees. The angle 54 degrees is by some measures, close to the optimum angle to do this.
Here is another way of looking at it. Consider the equation for a "path" such as in equation 4.67 in Pierrehumbert for the strong line limit in the Curtis-Godsen Approximation. There is a factor in the equation for the "path" LS which is q(p)/cos theta. The q(p) refers to the specific mass as a function of pressure. The equivalent width of a Lorenzian line is given by W = 2 x sqrroot (S(Tnought)*gamma (p0))* times LS where LS is the "strong path" (Pierrehumbert top of page 230.) Gamma (p0) is the line width at surface atmospheric pressure. S(Tnought) is the Line Strength analagous to a mass absorption coefficient at the surface of the Earth, where in this approximation one neglects the temperature dependance of the Line Strength. This is all part of an old way to estimate transmittance values without cranking out a line by line result. q(p) is a specific mass which may vary with height ; therefore pressure. Thus, it is a constant for CO2 up to order 100 km; however, water vapor is concentrated near the Earth surface. But no matter; a vertical path (cos zero = 1) ; using 1.7 times q(P)) is mathematically exactly the same as q(P) in the numerator and cos 54 degrees in the denominator. Now that we have SpectralCalc to hand us transmittance values on a platter, it is much easier and quicker to merely multiply the q(P) by 1.7 instead of actually changing to an angled path.
The chief technical person for "SpectralCalc" has told me that the same issue comes up in their radiance programs as in old ways of computing transmittance. Using a 54 degree angled path whilst multiplying the quantity with units of (watts / square meter steradian wave number) by pi is a" quick and dirty approximate way" of converting to diffuse upward flux by averaging over all angles.
The SpectralCalc expert has told me that the SpectralCalc way is to use a "fourth order quadrature" but what I do is a "quick and dirty way to proceed."
Bottom line..what MILA does is to angle integrate all angles and do it correctly. I do not know how to do this, so I use the old recipe for converting intensity to OLR by multiplying by p1 and effectively using a 54 degree straight line path.
(This is sometimes called the "diffusivity approximation" see Science of Doom under greenhouse effect, part 6 the equations , or page 171 in Grant Petty's text book for a drawing of the method. Also see in Liou, p. 127. Liou states that "in general a four point Gaussian quadrature will give accurate results for integration over the zenith angle"..but "for many atmospheric applications it suffices to use (shows equation involving the diffusivity factor.) See Pierrehumbert on page 191 who describes the method at length and even compares the various angles one might use.
Note that 400 ppm x 1.7 is 680 ppm. In my post 9 above you will note that for CO2 if I use a factor of 1.7 to multiply the 400 ppm present day CO2 concentration but do not integrate over angles then I get good agreement with MILA for 400 ppm where they do integrate over angles.
I think we should get this straight before talking about the other issues.
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chriskoz at 11:15 AM on 11 April 2017Heartland: What's your story?
For those who haven't read it or forgotten, it's worth to refresh one's mind by looking at CC Cluedo post to appreciate the extent of consilience in the science of climate change/AGW attribution. Especially the evidence matrix at the bottom.
Any comparison to the contrarian "arguments" by Heartland simply does not exist: any Heartland talk is just silly noise.
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John Hartz at 09:35 AM on 11 April 2017Heartland: What's your story?
Consilience is a very good word. Unfortunately, it is also "science-speak" and therefore it isn't a particularly good word to use in communicating climate science to the average person.
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chriskoz at 08:55 AM on 11 April 20172017 SkS Weekly Climate Change & Global Warming Digest #14
ThanksTom for that video. Michelle is a very prolific talker, as for a scientist :)
The most remarkable is her admission in the last minute of the video: those deniers who invited her to talk on camera dsid first "probe" her what she would say on the subject of the show and then, when herr point did not suit their opinion, they simply did ask a different question on air: simply did not allow her to talk...
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Tadaaa at 08:17 AM on 11 April 2017Heartland: What's your story?
@ bigchip
to reinforce JH's point i even know, without looking it is an article by Micheal Shermer
conversly i can guess with a high degree of acuracy a denier link to science, just from the URL
it is usually the Zwally antartic study, or the recent "greening" study
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nigelj at 08:10 AM on 11 April 2017Heartland: What's your story?
Consilience is a good word. Everything points at fossil fuels causing a greenhouse effect, from many lines of evidence and different fields of enquiry. If it walks like a duck, and quacks like a duck, it probably is a duck.
Natural causes for the recent warming period have been exhaustively investigated, and ruled out. Every possible idea has been suggested, and evaluated (and this is a good thing). It seems very improbable that we have missed some natural cause.
We are 95% sure we are causing climate change, yet many don't take the problem seriously. This doesn't make sense, because with anything else 95% proof would be sufficient. If some local government authority said they are 95% sure the local river is polluted by bacteria from cows, I think most people would accept this as compelling enough, especially when the evidence is explained.
Of course theres a particularly ruthless campaign to spread doubt about the climate science.
Our other main problem is politicians captive to fossil fuel, business, and ideologically motivated lobby groups. You have to get this out of politics somehow, and tax payer funded election campaigns is one option. At the very least, make activities of lobby groups, funding sources, and donations to election campaigns very public and transparent, so the public can see what influence is operating.
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bjchip at 07:28 AM on 11 April 2017Heartland: What's your story?
Oy! A forceful placement of climate change - Interesting form that slip takes though, taking a chance.
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bjchip at 07:25 AM on 11 April 2017Heartland: What's your story?
Thanks Sarah and I am pretty sure most people here know it. The mainstream media needs to hear it. I expect that more than half the talking heads will be forced to look it up.
:-(
A forceful placement of climate chance as a "Theory" well substantiated and co-equal to other established and accepted theories (eg. Evolution) can cancel much of the noise being injected by the denialsphere.
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Sarah at 07:09 AM on 11 April 2017Heartland: What's your story?
Consilience is indeed an excellent term for the agreement among multiple streams of evidence for climate change.
We should use that word more often; it's a feature notably lacking in alt-theories of climate.
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MA Rodger at 04:51 AM on 11 April 2017Science of Climate Change online class starting next week on Coursera
curiousd @15,
I should confess that my comment @14 was quite a bit more than I had initially intended to say, and I can see I have erred in places (but only in places).Concerning your "Correction Number One", the value presented by the UoC calculator as 'Upward IR Heat Flux' is calculated over the range 100cm-1 to 1500cm-1 and I think we can say with confidence that such a restricted spectrum will be ignoring 3.6% of 255K blackbody radiation spectrum. Of course, the TOA spectrum is only a very very approximate blackbody spectrum. I did a very quick scaling of this graph which plots TOA flux from 0cm-1 to 2000cm-1 and suggests there is somewhat less than 3.6% unaccounted, perhaps only a further 2% in the 0cm-1 to 2000cm-1 range leaving potentially 0.5% of unaccounted blackbody radiation above 2000cm-1.
It seems I was in error interpreting what your "Correction Number Two" was about. On reflection, your second correction appears to be suggesting that MODTRAN does not correct for the horizontal component of radiative transfer. This I cannot believe. And I fail to grasp the logic of your correction - increasing water vapour by a factor of 1.7 (=1/cos54º, the angle being the average for the integral). If such a correction were to be made, surely it would also require a similar adjustment to all other GHGs.
Chen et al (2013) does indeed concern clear-sky data (specifically 2004 data) and thus is comparable with 'No Clouds or Rain.' Note that Chen et al compares observations with reanalyses which use MODTRAN5 to calculate the TOA spectra flux. The comparisons of flux over the spectrum 0 – 1800 cm-1 are scattered either side of the observation with roughly 1% accuracy. This result suggests that MODTRAN in an apples-v-apples analysis does not need correction. The use of the 0 – 1800 cm-1 spectrum also reduces the blackbody IR beyond the range 100cm-1 to 1500cm-1 to 2.8% and scaling that graph of TOA IR it reduces to 1.4%.
Concerning the use of 1976 US Std Atmosphere. This is a global average for the full annual cycle and with non-liner calculations such an average cannot be as acccurate as the Chen et al analysis. If the impact of using a spectrum 100cm-1 to 1500cm-1 is roughly 2%, a little under half of the descrepancy you set out @10, it may be worth considering if a less crude averaging method can be shown to reduce that remaining 3%.There may still be other explanations. It is not impossible to believe that the UoC calculator contains simplifications (as yet undiscovered by us) even though it produces some very convincing-looking outputs.
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John Hartz at 04:35 AM on 11 April 2017Heartland: What's your story?
To get a basic understanding of what climate models are, check out this recently posted article...
Yes, we can do ‘sound’ climate science even though it’s projecting the future by Kevin Trenberth & Reto Knutti, Conversation US, Apr 5, 2017
Note: Trenberth & Knutti recommend using the word projection (rather than predicition) to describe the output of climate models.
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DaveMartsolf at 03:40 AM on 11 April 2017We're heading into an ice age
Deep thank yous to Yail Bloor, Tom Curtis, and scaddenp. Together you have cleared up all my questions regarding the interrelated processes that are bringing out an unfortunate future to our planet. I totally understand now why current and near future increased levels of CO2 will be around for centuries. And, scaddenp's link to Howard Lee's article describing an outcome of rapid CO2 increase that I did not think possible. I can understand why these facts have not been made into a movie, although they should be. I want to thank all of you for opening my eyes and for filling in all the blanks in my understanding. May our future generations find a way to survive The Once and Future Planet.
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bjchip at 03:21 AM on 11 April 2017Heartland: What's your story?
The word that nobody seems to know is
"consilience"
...and it is what makes the climate change theory an established theory, much like evolution, not a hypothesis.
https://www.scientificamerican.com/article/why-climate-skeptics-are-wrong/
Moderator Response:[JH] Rest assurred that the SkS author team and most of our regular readers know the meaning of the word consilience.
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John Hartz at 03:05 AM on 11 April 2017Heartland: What's your story?
Suggested supplemental reading:
Climate Change Skeptic Group Seeks to Influence 200,000 Teachers by Katie Worth, Frontline, Mar 28, 2017
Climate Change-Deniers ‘Spam’ Thousands Of Teachers With Anti-Global Warming Packages by Nick Visser, Huffington Post US, Mar 30, 2017
How climate skeptics are trying to influence 200,000 science teachers by Charlie Wood, Christian Science Monitor, Mar 30, 2017
Déjà vu all over again: Heartland Institute Peddling Misinformation to Teachers about Climate Change by Brenda Ekwurzel, Union of Concerned Scientists, Apr 7, 2017
Educators Decry Conservative Group's Climate 'Propaganda' Sent to Schoolteachers by Phil McKenna, InsideClimate News, Apr 10, 2017
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Tom Curtis at 20:10 PM on 10 April 20172017 SkS Weekly Climate Change & Global Warming Digest #14
Moderator Response:[JH] Thanks for the excellent suggestion. I will insert the video into next week's Digest.
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curiousd at 19:47 PM on 10 April 2017Science of Climate Change online class starting next week on Coursera
Hi Glenn,
But not before what I havedone is thoroughly vetted, as the editors of BAMS suggest. The only way to thoroughly vet this is to continue to post my arguments and have experts at S.S. try to shoot them down. I suspect that the place where the largest effect ofthe correction is would be in estimating the relative contribution of CO2 relative to water vapor on the earth's temperature, since the tails between 2 wn and 100 wn, and 1500 to 2200 wn have extremely strong water vapor absorption but negligible CO2 absorption. I am building up to this.
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Jim Hunt at 17:13 PM on 10 April 2017Sea ice falls to record lows in both the Arctic and Antarctic
jgnfld @7 - Was your remark addressed to me? If so, that's not what I'm arguing.
I was merely pointing out that CBD seemed to have misread a PIOMAS graph, and the suggestion that "the yearly max volume now is roughly equivalent to where the yearly min volume was in 1980" is not correct:
The physical validity of those exponential extrapolations is of course open to question!
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John Mason at 14:59 PM on 10 April 2017Past and Future CO2
The Foster et al paper is now available at:
http://www.nature.com/articles/ncomms14845 -
Glenn Tamblyn at 14:22 PM on 10 April 2017Science of Climate Change online class starting next week on Coursera
curiousd
The person to contact regarding this would be Professor David Archer at UoC. The Modtran calculator site is part of a set of tools he uses in running on-line courses about climate science.
d-archer@uchicago.edu -
Paul D at 05:51 AM on 10 April 2017The Myth of 'Clean Coal'
Should have said in my comment at (3) that the Southampton CHP plant uses gas not coal. It provides heat to local domestic customers and refrigeration and heat to a large retail complex, the electricity is sold to the docks.
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Paul D at 05:37 AM on 10 April 2017The Myth of 'Clean Coal'
Ironically some of the best research into the inefficiencies of producing energy from coal has been produced by US government researchers.
They spotted the obvious in that no powerplant can extract all the energy from a piece of coal and that is even before taking into account the losses created from the energy that can be extracted.
Humanity has wasted a lot of potential that was ever in coal even before you take into account it's horrendous polluting qualities.
One obvious flaw is the poor thermal energy efficiency of power stations. Most power stations would be better off as CHP plants with the main product being heat and refigeration from the 60% wasted energy. That leaves 40% for electricity production - a secondary product (or it should be).
That of course requires a near socialist attitude towards energy production as the heat and cooling products MUST be used by local residents and businesses without much competition!
This is done at one location in the UK (Southampton) and many Scandanavian locations.
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bjchip at 05:35 AM on 10 April 2017Inconceivable! The latest theatrical House 'Science' committee hearing
Adding to that excellent link ( 10: John Hartz ) would be this
http://www.vox.com/science-and-health/2017/1/27/14395978/donald-trump-lamar-smith
The T-rump taking an obvious place in the Lysenko comparison, and more obvious now than ever.
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Mike Blair at 04:19 AM on 10 April 2017Sea ice falls to record lows in both the Arctic and Antarctic
The article title "Sea ice falls to record lows in both the Arctic and Antarctic" has been misinterpreted by some deniers in UK. They probably have not read the article, but they take 'record' to be a verb, not an adjective, and so are claiming that the sea ice levels haven't fallen as low as predicted. I suppose it's the law of unintended consequences, and the article itself couldn't be plainer in its explanation, but please, take a little more care!
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curiousd at 23:47 PM on 9 April 2017Science of Climate Change online class starting next week on Coursera
I thank M.A. Rodger for his critique; it is exactly what I want.
(1) I can think of no other way to "disseminate the corrections to the Modtran online community directly " than to post such corrections as I have developed on "Skeptical Science" and "Science of Doom".
(2) The corrections I have made use SpectralCalc, a relatively inexpensive and wonderful tool for learning or teaching about atmospheric science. It would go well with Modtran. I can go further and take my violation of the plane - parallel approximation into account.
(3) I am not sure what you mean about the 1.7 factor being the correction I make. The1.7 factor is to expand the underlying wavelength range in the most correct way; to make the most "correct correction" . I cannot (or have not yet taught myself how to do it) actually integrate the intensity over many different angles. Modtran Chicago does this; that is better than my method, which is to use the "diffisivity approximation" approach and multiply by pi whilst at the same time effectively switching from a vertical path to one at 54 degrees. My table in post nine shows that by using a vertical path corresponding to 693 ppm - which has the identical effect as a straight line path at 54 degrees and 400 ppm - I can nearly duplicate the Modtran result for "CO2 only" where the Modtran result is for 400 ppm but they integrate outgoing intensity over all directions. I then carry over the 1.7 so that my "correction is more correct" for the water vapor bands. My correction is to expand the band width to 2 wn through 2200 wn from the original 100 wn to 1500 wn.
With respect to the comparison to Chen, et al: Since I use the U.S. Standard Atmosphere, which is supposed to be a type of world wide average, why is it so unexpected that my result isclose to that of Chen, et al ?
(You get something pretty close to the correct CO2 only climate sensitivity if you use MILA in U.S. standard atmosphere and the 0.98 emissivity; despite the fact that the present best value is by Myhre, who I believe found it improved the result to average over many locations? M.A. Rodgers, is the previous italacized sentence correct ?)
Also, regarding your criticism: Thus your 260.2w/sqm is calculated from MODTRAN applies only to "1976 U.S. Standard Atmosphere" and "No Cloud or Rain".
The idea of a "Clear Sky" OLR measurement is to obtain the OLR with no clouds or rain. Otherwise it would not be a clear sky experiment.
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MA Rodger at 19:54 PM on 9 April 2017Science of Climate Change online class starting next week on Coursera
curiousd @6-10,
The first question to ask you is - Have your "corrections" been "disseminated directly within the Modtran user community online" ? As you report @6, it is the advice of the BAMS editors that you should do this. It would also be my advice.
The two "corrections" you describe here (if I understand correctly) concern firstly the impact of IR beyond the range 6.67-100μm which you calculate as being significant yet outside the calculations made by the MODTRAN model, and secondly the lack of spherical adjustment for height in that model.
Regarding the first of these, using the on-line calculator at SpectralCalc.com, the value of blackbody radiation beyond 6.67-100μm amounts to 3.6% at 255K. I would assume the creators of MODTRAN were not unaware of that situation when they determined the wavelength limit of the model.
Regarding the second correction, the spherical effect on IR flux over 70km of atmosphere would be about 2%. While this may or may not be of significance to the MODTRAN model, the adjustment you make to the MODTRAN inputs to simulate this effect is surely incorrect. Your adjustment is "multiplying the standard ropospheric water vopor concentration" by 1.7. Concerning your use of Chen et al (2013) to provide a check on your correction, you should note that the value in Chen el al Table 3 is a "near-earth global annual mean" and so not actually comparable with any setting available on the MODTRAN interface. Those settings only provides for certain 'Locality' and weather, settings which greatly impacts the "Upward IR heat flux" . Thus your 260.2w/sqm is calculated from MODTRAN applies only to "1976 U.S. Standard Atmosphere" and "No Cloud or Rain".
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curiousd at 19:00 PM on 9 April 2017Science of Climate Change online class starting next week on Coursera
Glenn, I don't think I am criticizing the Modtran site at all. It is an excellent teaching tool and my point is that an instructor could use these corrections along with Modtran to better illustrate certain important results. For instance, I suspect most students would never look at the underlying program button, and therefore simply stating someplace on the web site or in classroom hand outs that an emissivity of 0.98 is assumed and there is a cut off issue would improve things.
As a case in point, I myself went down the following dead end regarding the emissivity issue. If one simply takes the MILA OLR looking down from the surface and compares to what is expected from the Stefan Boltzmann law you appear to have an emissivity of 0.92 because of the cut offs at 100 wn and 1500 wn. But at time I was using MILA for my purpose I had no clue about the cut offs and assmed the program must assume an emissivity of 0.92.
If someone is using the MILA program to test whether he/she is correctly using Scwarzchild's equation to obtain, say, the co2 no feedback climate sensitivity---where else can you obtain the OLR versus altitude, even in any textbook?---that person will run into contradictions with such a low assumed emissivity. (This is the subject of my next post here.)
All this would be improved just by warning the user of the wavelength cutoffs and that the assumed emissivity is 0.98 not 0.92 on the output website the user uses. The way I discovered this, after months of work, was to digitize the output of MILA and integrate the case of co2 only at 400 ppm and then test my use of the trapezoid rule for integration. I happened to have used an underlying Planck distibution that went from 5wn to 2000 wn. My answer for the integration was significantly too large. So I changed the range of the integration to 100 wn to 1500 wn and got close to the MILA output.
Then I knew.
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Glenn Tamblyn at 18:11 PM on 9 April 2017Science of Climate Change online class starting next week on Coursera
curiousd
Here is a link, from the UoC site, to a technical summary of MODTran from the company who wrote the code - Spectral Sciences Inc. Note the distribution list to the Air Force. Note on the first page of the introduction, the range of wavenumbers is from 0 to 17,900 cm-1. This upper limit is defined by the range of the data in the HiTran database, not a limit in the code per se.
http://climatemodels.uchicago.edu/modtran/berk.1987.modtran_desc.pdf -
Glenn Tamblyn at 18:00 PM on 9 April 2017Science of Climate Change online class starting next week on Coursera
curiousd
Just a point of clarification. MODTran is a commercially available medium resolution Radiative Transfer Code. It is developed by the US military, primarily through the Air Faorce laboratory system, although they outsource the actual coding. In contrast the Uni of Chicago is hosting a copy of MODTran and supplying configuration parameters to it for their web interface and then showing results from their run.
So the criticisms you are making are more likely related to the configuration setup by UoC not anything built into the software itself which is a more general purpose tool. The emissivity of 0.98 for example would be their setup parameter, and is actually a reasonable average of the actual emissivities of materials on the Earths surface which tend to range between 0.96 to 0.995. Similarly the wavenumber range will be a choice by UoC, rather than built in. -
curiousd at 11:31 AM on 9 April 2017Science of Climate Change online class starting next week on Coursera
Correction number two
Clear sky OLR measurements from satellites are of considerable interest since the properties of the atmosphere are being studied without the complications of cloud cover. For the "Modtran Infrared Light in the Atmosphere" (MILA) leave all default settings of greenhouse gases in place but choose the U.S. Standard atmosphere with no clouds. The uncorrected clear sky output flux observed by the virtual observer at 70 km is 260.2 W/m2 .
It should be kept in mind in what follows that unlike CO2, which maintains a constant concentration up to ~ 100 km, the water vapor content is concentrated close to the Earth's surface. (This may be seen by clicking the "temperature" button underneath the plot of altitude versus temperature in MILF, and compare CO2 andwater vapor on the drop down menu.)
Using the same SpectralCalc atmospheric path radiance application described in the previous two posts, I set the water vapor scale of the water vapor path to 1.7 instead of the default 1.0. This corresponds to the diffusivity approximation with an effctive angle to verticalof 54 degrees as described in the previous two posts. The radiant emission is calculated for the bands between 2 wn to 100 wn and 1500 wn to 2200 wn, again as described above. These outputs are associated with water vapor since the atmosphere for these wavelength ranges is essentially transparent to CO2 but the water vapor is a strong absorber. For a .98 emissivity, the corrected OLR is 266.7 W/m2 . If the Modtran output is - in addition to adding the pieces between 2 and 100; 1500 to 2200 wn, adjusted to correspond to an emissivity of one for the Earth's surface, the clear sky OLR becomes 272.1 W/m2 . This is compared to the value of the clear sky OLR obtained by Chen, Huang, Loeb, and Wei using the AIRS spectrometer of 273.74 W/m2
Chen, et al "Comparisons of Clear - Sky Outgoing Far IR Flux Inferred from Satellite Observations....." Table Three, Journal of Clima,Vol 30, No 9, May 2017.
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curiousd at 10:13 AM on 9 April 2017Science of Climate Change online class starting next week on Coursera
Altitude in km, OLR in W / M2
Altitude S.Calc 683 ppm Modtran 400 ppm
0 360.2 360.2
1 357.5 357.6
2 353.1 352.9
3 348.5 348.5
4 344.5 344.4
5 340.2 341.0
6 336.4 337.5
7 333.1 334.4
------------------— skipping several entries
18 320.8 324.6
Only major isotopologue of CO2 used in Spec Calc results. Again, 0.98 Earth surface emissivity. Constrained to 100 wn to 1500 wn. For CO2 the windows between 2 wn and 100 wn, and 1500 wn and 2200 wn are transparent. But this is not true for water vapor.
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curiousd at 09:57 AM on 9 April 2017Science of Climate Change online class starting next week on Coursera
In order to proceed further with my corrections to Modtran Infrared Light in the Atmosphere (MILA) I need to include some background material. Here are results for OLR of CO2, only greenhouse gas, U.S.standardatmosphere Modtran. I use SpectralCalc atmospheric paths radiance calculator, looking down. A virtual source is on the Earth's Surface, operating between the 500 wn and 850 wn of the CO2 bending mode. Temp 288.2 K, emissivity 0.98 to match Modtran. In addition to the 500 - 850 wn window the transparent (for CO2, although not water vapor, this will come up later) bands between 100 to 500 and 850 to 1500 wn are included, again to match MILA conditions. The "diffusivity approximation" as described, for instance on the Science of Doom website in part 6 of "The Equations" under the Greenhouse Effect, is used with an effective 54 degrees angle to the vertical to go from upward intensity to OLR with units of w/meter squared. It is not a good match to SpectralCalc to actually use angled paths, for one thing the angled paths in SpectralCalc are "real" paths which are strongly refracted. The "diffusitivity" approximation needs idealized straight line paths. In expressions for the optical thickness the factor q/cos theta always appears, where q is a concentration of the GHG, which in the case of CO2 can be considered constant up to 100 km. Say theta was chosen to be 60 degrees. Since cos 60 degrees is (1/2) the factor q/cos 60 = 2q/cos0.
Therefore one just needs to keep a vertical path and multiply the concentration by 2. In my case I use an effective angle to vertical of 54 degrees and multiply the q by 1.7. Modtran actually integrates over the output angles from 0 to 180 degrees. I calculate for a vertical path with q = 683 ppm for CO2 to compare with Modtran for 400 ppm. Below are the results in the next post.
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Evan at 09:12 AM on 9 April 2017Elevator Pitches - Chapter 02 - Radiative Gases
Anything that increases the translational, rotational, or vibrational energy of a molecule will increase its temperature. Energy added to one storage mode (e.g., vibration) is redistribted to the other storage modes until they are all in equilibrium. This happens within a time scale so small that for most considerations it is instantaneous.
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John Hartz at 04:31 AM on 9 April 2017Clouds provide negative feedback
Speaking of clouds and manmade climate change, here’s a handy reference document recently published by the WMO…
Humanity has a primordial fascination with clouds. The meteorological and hydrological communities have come to understand through decades of observation and research that cloud processes – from the microphysics of initial nucleation to superstorms viewed from satellites – provide vital information for weather prediction, and for precipitation in particular. Looking at clouds from a climate perspective introduces new and difficult questions that challenge our overall assumptions about how our moist, cloudy atmosphere actually works.
Clouds are one of the main modulators of heating in the atmosphere, controlling many other aspects of the climate system. Thus, “Clouds, Circulation and Climate Sensitivity” is one of the World Climate Research Programmes (WCRP) seven Grand Challenges. These Grand Challenges represent areas of emphasis in scientific research, modelling, analysis and observations for WCRP and its affiliate projects in the coming decade.
Understanding Clouds to Anticipate Future Climate by Sandrine Bony, Bjorn Stevens & David Carlson, Bulletin nº Vol 66 (1) – 2017
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jgnfld at 01:30 AM on 9 April 2017Sea ice falls to record lows in both the Arctic and Antarctic
Volume always keeps increasing for a while after the extent peak. Yet volume has never been so low at this point in the cycle. Why do you argue that increasing volume in April means there is nothing to worry about re. overall volume?
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macquigg at 01:10 AM on 9 April 2017It's not bad
Eclectic @ #372: It is viewed from the point of view of the human race...
Yes, that is the easy part. Rising sea levels are clearly bad. Worse heatwaves, droughts and floods are clearly bad. The hard part is knowing whether the effects will be good or bad, and if bad, what is the cost of adaptation compared to giving up fossil fuels.
We have to look at the effects one-by-one:
1) Sea level rise. Clearly bad, but we have a few decades to adapt. Do not rebuild in the flood zones of New Orleans. Do some careful planning on the costs of relocating Miami, lower Manhattan, etc.
2) Average temperature rise. We have a few decades for a migration to cooler areas.
3) Shifting climate patterns. This seems like the biggest worry, because it can happen rapidly, and rapid change can be costly.
I think we make a mistake by assuming all shifts will be in a bad direction. I live in the Southeast part of Arizona, and the hot summers here have been getting milder on the eastern edge of the Sonoran Desert. Over a larger area (California and Arizona) the drought is getting worse. A few more years, and the Tucson area could be cut off from its life supply, water from the Colorado River. That would be an economic disaster, and it could happen in just a few years. The resulting collapse in the real estate market could happen instantly.
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scaddenp at 12:36 PM on 8 April 2017We're heading into an ice age
"should be a caveat that those Pliocene-Pleistocene Series precursors to our current situation had to have had both non-anthropormorphic entrances to and exits from their warm periods."
I am not quite sure I follow you, especially with regard to entrance/exit of warm periods. In very broad terms, CO2 has been falling right through the Cenozoic, with exception of PETM. In transition from Pliocene to Pleistocene, CO2 (and surface irradiation) had fallen to level where Milankovich cycles could drive an ice-age cycle. Prior to then, climate was too warm (and CO2 too high). Noone is disputing that orbital forcings drive the Pleistocene ice ages, though turning variations in albedo at 65N into a global event involves several feedbacks of which CO2/CH4 feedbacks are very important. These are hardly analogues of current situation. The pace of change for a start is orders of magnitude faster. If we keep warming, we will also get carbon cycle feedback enhancing the warming but not for 100s of years.
Perhaps time to look at "Climate has changed before" article as well? Or have I completely misunderstood you?
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nigelj at 12:01 PM on 8 April 2017Inconceivable! The latest theatrical House 'Science' committee hearing
Chriskoz @18, the hearings on climate change involving Mann reminds me of a "kangaroo court" that is one of your Australian expressions, for a jacked up court with bad rules, and stacked to ensure a certain result!
Trump sure likes to use his right to free speech. He forget's that with free speech (and I'm a big supporter) comes responsibilities for accuracy, fairness, honesty. He obviously couldn't care less, or is so dumb he just doesn't get it. For democracy to work optimally, it requires people understand both rights and responsibilities.
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chriskoz at 10:38 AM on 8 April 2017Inconceivable! The latest theatrical House 'Science' committee hearing
Tom Curtis@17,
Indeed, your "multitude of sins" is happening in US (also to the lesser extent in other democracies such as Westminster system) and the sinners are largely immune. I'm not talking about people in power abusing their parliamentary priviledges but about ordinary people. Example: the libel lawsuit by Michael Mann against National Review is going on for many years and not proceeding. NR are citing First Amendment in their defence, so far successfuly. It's no brainer to most people who understand the case that it's a classic example of obstructing the truth with an intention to defame by NR, and the judgement in favour of Mann should be swift, yet under the strong protection of First Amendment, NR are still avoiding the penalty.
Your definition of freedom "implies that the choices in electing are free", and access to free and objective education, which, if I understand your point, means self-correcting process similar to scientific discourse be applied to all other discourses of life, esp. political discourse. We are clearly seing that it does not happen in the real world, and US in particular. The funders of First Amendment conceived it to protect defendants in cases like Mann vs. NR. But nothing was invented to protect people against fake news we are experiencing today. Funders thought if people are given unlimitted free rights to discuss whatever they like (but no obligation to stand behind their words and no penalties for failing to do so), the objective truth would emerge from the discussion. Obviously, it did not work and culminated in total erosion of GOP from reality. Yet, amazingly, they're still functioning (togethr eith their President!) and call themselves democraticaly elected representatives, according to Constritution.
They're still spreading blatant lies to the public. The very setup of the hearing we're looking at, is a blatant lie: 1 mainstream scientist (Mann) vs. 3 "sceptics", while the real setup according to the available evidence should be 30:1. And they get away with this lie because of their parliamentary priviledge and First Amendment. And uneducated people continue having a wrong picture that there is still a signifficant uncertainly on th etopic of AGW. I haven't watched the hearing (no time) so one thing I don't understand while Mann did not raise this false balance lie to the microphone. That would be his "biggest moment" if he did. Yet from what I know he complacently answered the same questions as he did 15-odd years ago, as if he accepted the false setting of that discussion. Likely the procedural restrictions did not allow him to say anything but stick strictly to the questions. Well, he could have broken that procedure in the name of the 'freedom' in your sense, yet he chose not to. He was likely so compromised by the procedures, that I suspect even First Amendment would not protect him. We might even talk about a suppression of truth in this case.
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Tom Curtis at 10:00 AM on 8 April 2017We're heading into an ice age
Dave Martsolf @379, carbon cycle models have shown that a significant portion of the excess CO2 in the atmosphere will be retained for many thousands of years. This has been illustrated, along with the relevent processes for drawing down CO2, by David Archer:
The important thing here, however, is not so much the retained fraction as the rate at which CO2 is drawn down, which approximately matches the rate at which temperatures approach equilibrium with a constant CO2 concentration. The approximate match of the rates means that with zero emissions, temperatures remain approximately constant:
That means that if we were to eliminate all CO2 (and other greenhouse) emissions over night, we could expect an equilibrium temperature of 1 C above the preindustrial. If we allow cumulative emissions 1000 GtC before ceasing all emissions, we could expect an equilibrium temperature of 2 C. On current policy settings, the stable temperature will be at least 3 C, if achieved at all (it only requires 5-10% of current emissions to result in a constant, or even slightly rising concentration, and no policy pursued by any government currently pursues zero emissions).
Those estimates hide a host of details. For instance, while GMST will be approximately constant with zero emissions, ocean temperatures will continue to rise for a short period, while land temperatures fall slightly. Sea level will continue to rise, both because of the rising ocean temperatures and because the ice sheets will melt back in the face of the constant elevated temperatures.
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Jim Hunt at 07:41 AM on 8 April 2017Sea ice falls to record lows in both the Arctic and Antarctic
Chris @2 - Although Arctic sea ice extent has passed it's maximum for this year, volume is still increasing. The situation is bad, but not as bad as you're suggesting!
The September average volume in 1980 was just over 16 thousand km³.
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Yail Bloor at 05:01 AM on 8 April 2017We're heading into an ice age
DaveMartsolf, concerning CO2 residence time, warming potential can last centuries.
It is true that an individual molecule of CO2 has a short residence time in the atmosphere. However, in most cases when a molecule of CO2 leaves the atmosphere it is simply swapping places with one in the ocean. Thus, the warming potential of CO2 has very little to do with the residence time of CO2.
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DaveMartsolf at 04:54 AM on 8 April 2017We're heading into an ice age
As a second comment I was intrigued by scaddenp's first link in the discussion above, a link to John Mason's 2013 post regarding past geologic records of 400ppm CO2 found in Russia's Lake E, referred to as a super-interglacial, and ending with the query, is this what we are headed for? Likely, the answer is yes, but as I mentioned above there should be a caveat that those Pliocene-Pleistocene Series precursors to our current situation had to have had both non-anthropormorphic entrances to and exits from their warm periods. If the earlier entrance to the 400ppm plus CO2 atmosphere happened as relatively quickly as ours has, then that past cycle might mimic ours. Does anyone reading this know if the record shows that the CO2 level changed that rapidly, perhaps as the result of some extraterrestrial fireball such as created Lake E and may have burned up all flora on the planet within several years or less? My apologies for being so uninformed in these things. But, I am so curious.
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curiousd at 02:45 AM on 8 April 2017Science of Climate Change online class starting next week on Coursera
Correction number one:
Consider the following settings for "Modtran Infrared Light in the Atmosphere" (MILA)
1. All greenhouse gas concentrations set to zero.
2. 1976 U.S. Standard Atmosphere.
3. Looking down from 70 km
4. Temperature offset at minus 33.2 K, giving a grount temperature of 255 K.
The out going long wavelength radiation (OLR) is then given by MILA as 225.075 W/meter squared.
From the "Black Body Calculator" of SpectralCalc, at 255 K, emissivity 0.98, in the 2 wn to 100 wn range the band radiance (SpectralCalc terminology) is 0.554602 W/meter squared steradian. Multiply by the pi available steradians of a Lambertian surface to obtain a flux of :
(a) 2 wn to 100 wn outgoing flux of 1.742 W/meter squared.
By a similar procedure for 1500 wn to 2200 wn one obtains
(b) 1500 wn to 2200 wn flux of 6.3437 W/meter squared
Then for the 0.98 emisivity case the corrected MILR output is 225.075 plus 1.742 plus 6.3437 = corrected flux of watts/meter squared of 233 watts/meter squared. This is what one obtains by using an expanded wave number range from 2 wn to 2200 wn, assuming emissivity of 0.98.
If instead of an emissivity of 0.98 one uses an emissivity of unity then by a similar procedure one obtains a corrected output flux of 1.777 w/meter squared plus 231.144 watts/ meter squared plus 6.473 watts /meter squared equals 239 watts/meter squared. Note that here the output of MILA between 100 wn and 1500 wn is changed from 225.065 watts / meter squared to 231.144 watts per meter squared to correspond to emissivity of one instead of the MILF emissivity of 0.98.
The context of these results is the following: A number of treatments of elementary environmental science, such as written, for instance by Archer or by Wolfson, show that an Earth with no greenhouse effect, but assuming a best estimate of cloud albedo, is in thermal equilibrium with incoming solar radiation if the average Earth surface temperature is quite close to 255 K. This temperature corresponds to an OLR of 239.7 watts/meter squared for thermal IR emissivity of one, by using the Stefan-Boltzmann law. The best value from sophisticated satellite analysis for the top of the atmosphere by Trenberth, Fasullo, and Kiehl, BAMS 90, 2009, 311 - 323 is 239 watts/meter squared. These authors assume an emissivity in the thermal IR for the Earth's surface of 1.0.
I will wait to see if others accessing Skeptical Science and reading this post believe my analysis is correct or not, before posting my next correction which is for the value of the cloud free earth OLR.
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curiousd at 01:22 AM on 8 April 2017Science of Climate Change online class starting next week on Coursera
The underlying Planck distribution for the free website "Modtran Infrared Light in the Atmosphere" is displayed in the user output for a range between 100 wn and 1500 wn. I have accidentally found out that this wavenumber range is not just a graphical convenience. The underlying program does have this somewhat limited wavenumber range.
If one investigates the output of the "Show Raw Model Output" button, two features become evident:
1. The underlying computer program does really have a range limited to 100 wn - 1500 wn.
2. The underlying computer program assumes an earth surface emissivity of 0.98.
I have developed corrections to "Modtran Infrared Light in the Atmosphere" for several fundamental cases. The corrections could be made to a class by verbal instructions and do not require any re-writing of the program.
I submitted an authorship proposal to the "Bulletin of the American Meteorological Society" (BAMS). The suggestion of the Board of Editors of BAMS is the following:
"Your corrections to Modtran sound promising for a wide audience. However, the editors feel that BAMS is not the appropriate venue for vetting and distributing this information. For proper exposure and discussion, they would be more productively disseminated directly within the Modtran user community online." In the spirit of the suggestion of the BAMS editors I post below the first of my corrections.
Moderator Response:[JH] Embedded url into free website "Modtran Infrared Light in the Atmosphere".
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DaveMartsolf at 23:36 PM on 7 April 2017We're heading into an ice age
Yes, I was joking on that point and understood on the 1000s of years time required to melt all the ice.
But, don't all these forecasts assume some type of elevated CO2 presence for years to come? I understand that even the most hopeful time scale for full conversion from fossil fuels to renewables with or without the nuclear option is still estimated to be many years away, but I do believe this will happen, and sooner than many people predict today. As that happens, and as we figure in the relatively rapid natural sequestration of our currently elevated atmospheric CO2 levels (half life in the order of only 20-30 years), I still wonder what the models will show when ocean temperatures have been elevated through all the current (and perhaps for another 50-100 years into the future) CO2 emissions to rather suddenly find their warmed surfaces evaporating into crystal clear skies that can quickly radiate all that heat (but not the moisture) into space. It will be a unique set of conditions not often seen on the planet.
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