This month’s open thread. Please try to stick to climate science topics.
Reader Interactions
195 Responses to "Unforced Variations: Oct 2019"
John Pollacksays
Zebra #94 Yes, I did miss your #52 comment, so thanks for repeating.
We seem to be missing each other’s meaning, so I’ll try to lay mine out for you. I’m not sure that it will fit your idea of a “warrant thing.”
I am in agreement with the science on AGW, but science is not a static thing. As knowledge is gained, understandings and emphasis change. I was a forecaster for 30+ years, and I’ve seen a lot of weather systems come and go. Occasionally, they wreck people’s lives in the process, and I care about that. As the knowledge and models both advanced, my forecasts got better.
I care that with ongoing climate change, things are liable to get a lot worse, both for humans and the rest of the planet. My job was basically as a communicator/translator of complex weather patterns and models, and rendering a prediction that was meaningful to ordinary people. I am now attempting to understand the climate research as best I can in order to effectively communicate what that means to ordinary people.
I’m living in the central U.S., a region with large variability in weather, both from day to day and year to year. I see the same basic weather patterns repeated. Climate change has not eliminated these patterns, so far, and I see no reason to believe that it will in the next 50-100 years, at a minimum. What I’m expecting is a change in the frequency and intensity of the basic patterns as greenhouse gas forcing influences the co-existing variability.
I am also leaving room to notice new patterns if and when they appear. I have only seen a few, so far. My reference point to what is a “new pattern” is the history of regional weather and climate. So, the 1930’s were an extreme point for which we have a good instrumental record. The Dust Bowl is the most famous event, but there were many other anomalies of the type that occur when there is are a lot of strong blocking patterns and meridional flows.
There has been a lot of research in the past few years suggesting that these blocking/meridional flow patterns are getting more extreme as the result of climate change. However, most of the empirical studies I’ve seen only go back 30-40 years, and therefore exclude the 1930s, which was an extreme period prior to polar ice loss, polar amplification, and another 110 ppm of CO2. I’m hoping that future research will give us some better idea of how much of the current extreme blocking is due to climate change, and how much to natural variability as an old pattern has perked up again.
Meanwhile, I find myself between two extremes of attribution. There are plenty of people around here who believe that all of the variability we see is natural, and humans aren’t causing climate change. On the other hand, there are people who are attributing every extreme they see to climate change. I honestly believe that the truth lies somewhere in between, and I can be guided by what has happened in the past (e.g. the 1930s) vs. what hasn’t happened at least during the instrumental record. Thus, I share the concern about the extreme mid-continental wetness we’ve been seeing with increasing frequency in the past decade. But I also know that a blocking pattern at a different longitude can set up an extreme drought.
My thinking is in terms of probabilities and trends rather than of parallel universes or great and strictly defined precision. It would be nice to know if we need to be prepared for a megadrought, worse flooding, or both, in the next 20 years. There are some big reservoirs on the upper Missouri River. Should we try to empty them to avoid a dam break, keep them full in case there’s a drought, or change the levels we’re aiming for to even out the probabilities better? Those are the kind of specifics that I’m interested in.
David B. Bensonsays
Mr KIA @95 — For an intermediate level textbook see “Fundamentals of Planetary Climate” by Ray Pierrehumbert. Don’t expect to see it duplicated here.
TPainesays
My thanks to MA Rodger for post #246 in last months “Unforced Variations”. My Wi Fi has been out so I haven’t been able to reply. Also my mistake in not stating he was using the Maue’s Accumulated Cyclone Energy (ACE) Index. The information you provided is very helpful.
KIA: I’ve been asking for that info since day 1, and have yet to see it clearly spelled out.
BPL: And you’ve been given that information over and over again, pointed to more detailed explanations elsewhere on the web, and no matter how much we explain it to you, you will complain that no one is explaining it to you. If you really want a good explanation, CRACK A FREAKING BOOK. I’d recommend starting with John Houghton’s “The Physics of Atmospheres.” Work the problems.
The majority of the public obviously isn’t going to do that, so simplified explanations which capture most of the physics is obviously the way to go.
It is correct that the path length of a photon between its CO2 (spontaneous or stimulated) emission and it creating a stimulated emission will be measured between excited CO2 mollecules. And we should add that the path length of a photon between its CO2 emission and CO2 absorption will be from an excited CO2 molecule to an unexcited CO2 molecule.
And, yes, the level of spontaneous emissions are dependent on temperature so the higher in the atmosphere, the less such emissions there will be, this of course, the mechanism that lies behind CO2 climate forcing.
And, yes, the higher in the atmosphere, the lower the air density so there will be less CO2 molecules to emit/absorb photons. And as it also results in the photon path length increasing, density itself has no impact on the density of photons flying about – with lower density, the fewer the emissions/absorptions but the further the photons fly.
But that all said, we get down to the ratio of A21/B21. The equations (whatever equilibrium version is correct) all yield B21 as being massively bigger than A21.
But I feel I have been misrepresenting A21/B21 as the proportion of simultaneous/stimulated emissions. This, of course, would be:-
A21/(B21p[v])
and when I have a few uninterrupted minutes, I will have a go at calculating that ratio properly.
H2O content is determined (largely) by the temperature
Yes indeed. The Clausius-Clapeyron relation is the answer to the denialist “water vapor is the most important greenhouse gas!” The control of atmospheric water vapor by temperature was worked out by the mid-19th century, well in time to guide Arrhenius’s 1896 model of CO2-forced global warming. I’m guessing KW didn’t know that.
Steven Emmersonsays
Alastair B. McDonald@79 wrote:
Your quote is by Hermann Harde who has already been exposed for junk science.
This rebuttal is invalid for several reasons: 1) it is an ad-hominem attack; 2) the paper in question is about the carbon cycle and not about radiative transfer by atmospheric CO2; and 3) most importantly, it doesn’t address the issue: that the overwhelming majority of atmospheric CO2 emissions is due to collisions rather than stimulation.
He also wrote:
The intensity of eigen (stimulated and spontaneous) radiation will increase as altitude decreases. Thus the radiation emitted from lower levels will be greater and net radiation will travel upwards.
For this assertion to be credible, he needs to provide a reference to peer-reviewed scientific literature affirming his assertions that 1) the overwhelming majority of atmospheric CO2 emissions are due to stimulation; and 2) the overwhelming majority of subsequent energy transfer is upward.
“I think it is time for a complete explanation by a climate scientist of how it actually works. Not from a meteorologist, Al Gore, or Bill Nye, but from someone who understands the particle physics“
Yup need someone from CERN, LOL. This is one for the ages.
Alastair B. McDonaldsays
Zebra @93 wrote:
“Now you say “CO2 is excited into rotational and vibrational states”. Again, what’s the relevance of that? Are you saying that a CO2 molecule in such an excited state would not undergo spontaneous emission, assuming no other interactions?
That doesn’t require difficult math at all… just yes or no.”
New special report from IPCC lists array of increasing risks facing oceans and ice in a warming world. (My notes: It talks about accelerated ice loss in Greenland and Antarctica making the IPCC worst case scenarious more likely, also covers rising confidence that category 4 and 5 hurricanes are increasing in number, and concerns about carbon from melting permafrost)
zebrasays
#101 John Pollack,
I appreciate your effort to explain yourself; unfortunately, the substance is still too vague to allow for a serious discussion. You say:
There has been a lot of research in the past few years suggesting that these blocking/meridional flow patterns are getting more extreme as the result of climate change. However, most of the empirical studies I’ve seen only go back 30-40 years
You gave two references earlier. One was a meteorological comparison of two two-month time periods, (in 1987 and 1994) and the other a millenial-scale modeling exercise (on drought) that used 1901-2005 for instrumentally-verified input.
I really don’t understand what you are trying to say about “including the 1930’s”… as I pointed out earlier, and you continue to ignore, the models…the one you yourself referenced… do exactly that. So what’s the problem??
If you are a meteorologist, then surely you understand the difference between weather and climate. But here, the only interpretation I can arrive at is that you are conflating the two.
“I think it is time for a complete explanation by a climate scientist of how it actually works. Not from a meteorologist, Al Gore, or Bill Nye, but from someone who understands the particle physics“
Yup need someone from CERN, LOL. This is one for the ages.
Mr. IAT has, again, frankly disclosed his scientific meta-illiteracy. Let’s see if he’ll settle for a complete explanation by one Delbert G. Van Ornum of Plasmadyne Corporation, appearing in the Journal of Meteorology in 1961. I found it in 90 seconds on Google Scholar, searching for “quantum infrared backscatter cloud” without quotes. Another 10 seconds turned up observational confirmation by G.T. Cherrix and B.A. Sparkman in a NASA internal report, in 1967. I could only reach the abstract of another promising hit from 1967, by Carrier et al. in Applied Optics, titled “The Backscattering and Extinction of Visible and Infrared Radiation by Selected Major Cloud Models”. Republicans were much more ‘liberal’ then, to be sure.
Of course, there’s always the seminal paper by physicist Gilbert Plass, in the Quarterly Review of the Royal Meteorological Society in 1956. It’s included in The Warming Papers, edited by RC contributors David Archer and Ray-Pierre Humbert. An image of the book’s cover appears in rotation on the right-hand side of this very page. Jeez, it’s only a click away!
IOW, long since asked and answered. Once again: science is a way of trying not to fool yourself, that only works if you’re trying. Mr. IAT, sadly, has made it abundantly clear he prefers to fool himself. If he didn’t, he’d lose his explicit warrant for commenting here, namely to bring his fantasy culture war to his imaginary enemies. I grudgingly grant his talent for provocation!
zebrasays
#109 Alastair B. McDonald,
“no”
If that is the case, what I have now said twice (and MAR perhaps has read, and so corrected himself,) what is relevant is the distribution of states and the incidence of radiation.
So far, you haven’t given any quantitative or qualitative analysis of those conditions to justify your argument.
It seems obvious that if we have a system in equilibrium, in which spontaneous emissions occur from CO2, and we increase the number of CO2 molecules, then we are surely increasing the probability of spontaneous emissions in the relevant wavelengths.
So, can you explain your reasoning to the contrary?
Mr. Know It Allsays
102 and 104 – David B.Benson and BPL:
Thank you both for the book recommendations. Good references for all of us.
;)
108 – Paul P.
“Yup need someone from CERN, LOL. This is one for the ages.”
Addressing the issue of the ratio of spontaneous to stimulated photon emissions in the atmosphere, the Wikithing page gives for the equilibrium condition:-
A[21]n[2] + B[21]n[2]p(v) = B[21]n[1]p(v)
and
A[21]/B[21] = F(v)
with A[21], B[21] and B[12] respectively the coeffts for Spontaneous emission, Stimulated emission and Absorption.
I calculated this F(v) quantity up-thread @63 to be a very small number. There was some doubt as to the form of the equation for F(v) but we were talking 1.2e-10 or smaller.
Yet this A[21]/B[21] ratio is the ratio of the coefficients, not the ratio of emissions which would be
Spontaneous/Stimulated = A[21]n[2] / B[21]n[2]p(v)
where
p(v)[v,t] = F(v) x 1/(e^(hv/kT)-1)
therefore
Sp/St = A[21]/B[21] x 1/p(v) = F(v)/F(v) x e^(hv/kT) – 1
where h = Planck’s constant = 6.6e-34 Js, v = frequency = [for 15 microns] 2.0e+13 Hz, K = Boltzmann’s constant = 1.4e-23 j/K and T = temperature ≈270 K.
So the ratio Spontaneous emissions/Stimulated emissions = 32.
It thus appears that stimulated emissions are not the dominant emissions and if so the photon emissions will be spontaneous or stimulated by a spontaneously emited photon and thus entirely any-which-way. The directionality of emission from the surface will be disappeared within a single path-length which is, what, about a metre? (This assuming I have’t dropped a bead from my abacus along the way.) And I am a lot happier now than I was @63 as the implications of this ratio Sp/St now appears to fit the physical situation.
Ray Ladburysays
MA Rodger,
Just look at the physics–for spontaneous emission to play a significant role, an IR photon of the proper wavelength must pass near an already excited CO2 molecule. Spontaneous emission in MASER or LASER is significant only because both the flux of photons AND the population of excited atoms/molecules is large.
Also, realize that there is another competitor for the relaxation–collision between an excited CO2 molecule and ANY gas atom/molecule can cause the excited CO2 molecule to transfer its extra energy to the other atom/molecule. This process is not negligible. Alastair really doesn’t know what he’s talking about.
Icebreaker is struggling to find stable ice to establish research station in the Arctic. I think this might be what Peter Wadhams saw coming. Wadhams is going to be much closer to the target with his projection on timing of ice in the Arctic than the folks who rejected his projection and imagined decades of stable ice in the Arctic for decades to come. Blue ocean event. Here we come. I think that’s a feedback loop driver, isn’t it?
Should be fine. After we perfect direct air capture we can build the global icemaker to fix the albedo problem with disappearance of sea ice.
CO2? How are we doing? Peachy!
October 6 – 12, 2019 408.39 ppm
October 6 – 12, 2018 405.50 ppm 2.89 ppm over last year
October 6 – 12, 2009 384.06 ppm 24.33 ppm over same week in 2009
(co2.earth)
Nothing skyrockety, just steady increase and increase rate has been accelerating. More CO2, more heat.
GISTEMP has posted for September with an anomaly of +0.90ºC, the second lowest GISTEMP anomaly of 2019-so-far. (They span from +1.17ºC to +0.86ºC.)
It is the second warmest September on the GISTEMP record, just behind of 2016 (+0.91ºC) and ahead of 2014 & 2015 (both +0.84ºC), 2018 (+0.81ºC), 2017 (+0.79ºC) and 2013 (+0.77ºC).
It is the 27th highest anomaly on the all-month GISTEMP record. The spike in the TLT (UAH & RSS were recording 8th & 6th warmest all-month anomaly on record) isn’t seen in the surface measurements, perhaps a repeat of the TLT spike that occurred in Autumn 2017 after (similar to this year) surface measurements had been high earlier in the year. (Poor Roy Spencer was so disturbed by UAH’s TLT spike that he has set out an explanation on his blog.)
Now with three-quarters of the year complete, 2019 sits quite firmly in 2nd place for the year-to-date. To drop to 3rd place by end-of-year behind 2017 would require Oct-Dec to average less than +0.83ºC while 1st place looks beyond reach as it would require Oct-Dec to average higher than a sweltering +1.19ºC.
The table is ordered by Jan-Sept averages.
“What percentage of the CO2 molecules are excited? Given that, what’s the probability that a photon of the appropriate wavelength will hit an unexcited CO2 molecule and be absorbed versus the probability that it will hit an excited CO2 molecule and cause stimulated emission? ”
The CO2 molecules are mostly excited (and relaxed) by collisions. The per cent which is excited at any temperature is given by the Boltzmann distribution:
nj/ni = (gj/gi).e^-(Ej -Ei)/kT, (4.19)
where nj, Ej, and gj denote the volume density, energy, and statistical weight of the jth excited state, respectively.[Thomas & Stamnes, 1999, p. 101].
”
I believe a figure of ~7% is the excitation level for the 15um band of CO2 at STP, which would be the probability of a photon producing stimulated emission. (For laser action, a probability of greater than 50% is needed.)
You asked:
“Did Herr J. Koch measure the temperature required in a column of air so that it produced an equilibrium of IR out versus IR in, i.e. where the probability that an incoming photon will be absorbed is equal to the probability that it will hit an excited molecule and cause stimulate emission? ”
No, AIUI, the energy absorbed by the gas was lost through the walls of the apparatus. But I have translated Dr Koch’s paper here.
You also asked:
“What’s the probability that an excited CO2 molecule will collide with another molecule, and convert that store energy to heat?”
That is covered by the Boltzmann distribution.
Mr. Know-It-All,
You can’t back your way out of that embarrassment, as particle physics is about the fundamental nature of matter, which is distinct from condensed matter physics. Welcome to the club of Judith Curry, who tried to associate droplet nucleation with Bose-Einstein statistics. In communicating science, you really need to have a grasp of the fundamental physics, otherwise you end up looking foolish.
“It thus appears that stimulated emissions are not the dominant emissions and if so the photon emissions will be spontaneous or stimulated by a spontaneously emitted photon and thus entirely any-which-way. The directionality of emission from the surface will be disappeared within a single path-length which is, what, about a metre? (This assuming I haven’t dropped a bead from my abacus along the way.) And I am a lot happier now than I was @63 as the implications of this ratio Sp/St now appears to fit the physical situation.”
The main cause of excitation of CO2 molecules in the troposphere is by collisions, not by irradiation i.e stimulated absorption. An excited molecule has a half-life, which when it expires causes a spontaneous emission. If the molecule is relaxed by a collision before the half-life expires, obviously it will not emit. The half-life decreases as frequency increases, but at the low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.
“If that is the case, what I have now said twice (and MAR perhaps has read, and so corrected himself,) what is relevant is the distribution of states and the incidence of radiation.”
The distribution of states is determined by collisions, not by radiation as everyone seems to think. See my reply to MA Rodger above.
zebra, you also wrote:
“It seems obvious that if we have a system in equilibrium, in which spontaneous emissions occur from CO2, and we increase the number of CO2 molecules, then we are surely increasing the probability of spontaneous emissions in the relevant wavelengths.
So, can you explain your reasoning to the contrary?”
no again. I am not arguing “to the contrary”!
But the boundary layer of the troposphere is not in equilibrium. Its temperature is continually changing.
I have not discussed an increase in CO2. However, if you do increase CO2, then you will increase the number of excited molecules. So spontaneous emissions will increase, but so will the stimulated emissions.
However, if you increase the CO2 so much that the pressure increases, then the time between collisions will decrease and fewer spontaneous emissions will occur.
I should have explained earlier that the population of excited states is set by collisions, but I had forgotten. Sorry.
siddsays
Consider an excited CO2 molecule at 2 m height the atmosphere. It is sitting in a bath of other molecules and radiation at STP
Three things can happen to it, listed in order of increasing probability
a) stimulated emission
b) spontaneous emission
c) collisonal relaxation
The probability of c) is much larger than that of b), and that of b) is much larger than that of a)
Now consider an unexcited molecule. It can get to the excited state by the reverse of a), b) or c)
At equilibrium, detailed balance requires that exactly as money CO2 molecules wind up in the excited state as exit. Further, Detailed balance requires that exactly as many get there thru the reverse of a) as leave thru a) and similarly for b) and c)
As far as directionality of stimulated emission goes, the excited CO2 molecule is sitting in a bath of _omnidirectional_ radiation since the layer above it radiates as well as the layer below, to within radiative imbalance. So the photons from stimulated emission emerge in all directions, again to within the radiative imbalance between the layer above and below.
If it is claimed that the situation is out of equilibrium, then one must explain why a layer does not heat to incandescence or cool to the freezing point of the gas.
Alastair B. McDonald @122,
You say:-
☻ “The main cause of excitation of CO2 molecules in the troposphere is by collisions, not by irradiation i.e stimulated absorption.”
I agree.
☻ “An excited molecule has a half-life, which when it expires causes a spontaneous emission. If the molecule is relaxed by a collision before the half-life expires, obviously it will not emit. The half-life decreases as frequency increases, …”
I agree and would add that I recall the half-life is of the order of a tenth of a second while the rate of collision is measured in microseconds. So very very few excited CO2 mollecules result in a spontaneous photon emissions. Almost all end with a collision with another air mollecule, very likely the same mechanism from which the excitation arose.
☻ “…but at the “low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.”
This assertion seems to be based solely on the idea that an excited CO2 mollecule has such a small chance of spontaneous emission that the chance of stimulated emission is therefore much higher. I don’t see that the one follows the other. As well as potentially enabling stimulated emission from an excited CO2 mollecule, a 15-micron photon will be absorbed by a non-excited CO2 mollecule. The proportion of excited/non-excited CO2 is the decider here. I’m sure if this were calculated it would show that non-excited CO2 dominates, not excited CO2 mollecules. Thus a photon is far more likely to be absorbed than to stimulate emission.
MA Rodger,
Just look at the physics–for spontaneous emission to play a significant role, an IR photon of the proper wavelength must pass near an already excited CO2 molecule. Spontaneous emission in MASER or LASER is significant only because both the flux of photons AND the population of excited atoms/molecules is large.
Also, realize that there is another competitor for the relaxation–collision between an excited CO2 molecule and ANY gas atom/molecule can cause the excited CO2 molecule to transfer its extra energy to the other atom/molecule. This process is not negligible. Alastair really doesn’t know what he’s talking about.
MA Rodger,
Ray Ladbury is confusing laser action with emissions from greenhouse gases. Laser action is pure stimulated emission. Greenhouse gases emit a mixture of stimulated and spontaneous emissions, the ratio being a function of wavelength. Greenhouse gases, operating in the far infrared, emit more by stimulated emissions than by spontaneous emissions.
15 Oct 2019 at 4:27 AM
Alastair B. McDonald further to my comment @105,
…
Yet this A[21]/B[21] ratio is the ratio of the coefficients, not the ratio of emissions which would be
Spontaneous/Stimulated = A[21]n[2] / B[21]n[2]p(v)
where
p(v)[v,t] = F(v) x 1/(e^(hv/kT)-1)
As I understand it, the ratio of the emissions is [A21]n[2]/[B21]/[n2] = F(v), not p(v). [n2] which is the level of molecules excited by collisions and absorption applies to both stimulated and spontaneous emissions and cancels. A molecule will emit if and only if it is excited.
There is a problem you raised earlier – what is F(v)?
You are using 2hv^3/c^2
Wikipedia states 8hv^3/c^2
Thomas and Stamnes give it as 2hv^3/c^2
Goody and Yung give it as 8hv^2/c^3
and Atkins gives it as 8hv^3/c^3
The difference may be caused by v (nu?) being in units of Hz^-1 or cm^-1 but that on;y gives us two alternatives. interchangeing 8 and 2 will not affect the ratio by much but the use of c^3 or c^2 will!
therefore
Sp/St = A[21]/B[21] x 1/p(v) = F(v)/F(v) x e^(hv/kT) – 1
where h = Planck’s constant = 6.6e-34 Js, v = frequency = [for 15 microns] 2.0e+13 Hz, K = Boltzmann’s constant = 1.4e-23 j/K and T = temperature ≈270 K.
So the ratio Spontaneous emissions/Stimulated emissions = 32.
It thus appears that stimulated emissions are not the dominant emissions and if so the photon emissions will be spontaneous or stimulated by a spontaneously emitted photon and thus entirely any-which-way. The directionality of emission from the surface will be disappeared within a single path-length which is, what, about a metre?
It is more than a metre. The blackbody photon has to travel until it reaches an excited molecule to then produce a stimulated emission. But you are making a valid point that once we are far from the surface stimulated emissions will be produced by spontaneous multidirectional photons.
In fact, my original idea that there would be less radiation downwards is flawed:-(
(This assuming I have’t dropped a bead from my abacus along the way.) And I am a lot happier now than I was @63 as the implications of this ratio Sp/St now appears to fit the physical situation.
Ray Ladburysays
Alastair:”The half-life decreases as frequency increases, but at the low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.”
NO!!! MA Rodgers has shown that spontaneous emission is >30x more likely than stimulated emission, and that analysis did not take into account the competing process of collisional relaxation, which further reduces the population of excited molecules and therefor candidates for stimulated emission. It is as if you are simply refusing to read the many, many refutations of your delusion!
And NOAA has posted for September with an anomaly of +0.95ºC, a little up on August (GISTEMP was down a little). The anomalies for 2019-so-far span from +1.10ºC to +0.87ºC.
It is =1st warmest September on the NOAA record, equalling 2015 (+0.95ºC) and just ahead of 2016 (+0.94ºC), followed by 2017 (+0.86ºC), 2018 (+0.83ºC), 2014 (+0.79ºC) and 2012 (+0.74ºC).
It is the 13th highest anomaly on the all-month NOAA record (27th highest in GISTEMP).
Now with three-quarters of the year complete, 2019 sits in 2nd place for the NOAA year-to-date. To drop to 3rd place by end-of-year behind 2017 would require Oct-Dec to average less than +0.90ºC (a drop more likely to happen in NOAA than in GISTEMP) while 1st place again looks beyond reach as it would require Oct-Dec to average higher than a sweltering +1.15ºC.
The table is ordered by Jan-Sept averages.
15 Oct 2019 at 4:27 AM
Alastair B. McDonald further to my comment @105,
…
Yet this A[21]/B[21] ratio is the ratio of the coefficients, not the ratio of emissions which would be
Spontaneous/Stimulated = A[21]n[2] / B[21]n[2]p(v)
where
p(v)[v,t] = F(v) x 1/(e^(hv/kT)-1)
As I understand it, the ratio of the emissions is [A21]n[2]/[B21]/[n2] = F(v), not p(v). [n2] which is the level of molecules excited by collisions and absorption applies to both stimulated and spontaneous emissions and cancels. A molecule will emit if and only if it is excited.
There is a problem you raised earlier – what is F(v)?
You are using 2hv^3/c^2
Wikipedia states 8hv^3/c^2
Thomas and Stamnes give it as 2hv^3/c^2
Goody and Yung give it as 8hv^2/c^3
and Atkins gives it as 8hv^3/c^3
The difference may be caused by v (nu?) being in units of Hz^-1 or cm^-1 but that on;y gives us two alternatives. interchangeing 8 and 2 will not affect the ratio by much but the use of c^3 or c^2 will!
therefore
Sp/St = A[21]/B[21] x 1/p(v) = F(v)/F(v) x e^(hv/kT) – 1
where h = Planck’s constant = 6.6e-34 Js, v = frequency = [for 15 microns] 2.0e+13 Hz, K = Boltzmann’s constant = 1.4e-23 j/K and T = temperature ≈270 K.
So the ratio Spontaneous emissions/Stimulated emissions = 32.
It thus appears that stimulated emissions are not the dominant emissions and if so the photon emissions will be spontaneous or stimulated by a spontaneously emitted photon and thus entirely any-which-way. The directionality of emission from the surface will be disappeared within a single path-length which is, what, about a metre?
It is more than a metre on average that the blackbody photon has to travel until it reaches an excited molecule to then produce a stimulated emission. But you are making a valid point that once we are far from the surface stimulated emissions will be produced by spontaneous multidirectional photons.
In fact, my original idea that there would be less radiation downwards is flawed:-(
zebrasays
127 Alastair B. McDonald,
Thank you. I am delighted, and encouraged… [not because your idea was flawed ;-)], but that you demonstrated for readers how actual scientific reasoning and discussion is supposed to work.
I think we are all familiar with getting attached to an idea and needing outside input to fully develop it, one way or the other.
Now if only we could get the Denialist idiots to sincerely engage, and admit an error when the evidence is presented… yeah, sure…
Your quote is by Hermann Harde who has already been exposed for junk science.
This rebuttal is invalid for several reasons: 1) it is an ad-hominem attack; 2) the paper in question is about the carbon cycle and not about radiative transfer by atmospheric CO2; and 3) most importantly, it doesn’t address the issue: that the overwhelming majority of atmospheric CO2 emissions is due to collisions rather than stimulation.
Sorry, I got carried away trying to show Harde is a climate change denier. I need not have bothered since he has signed the “There is no climate emergency” petition at number 7 in Scientists from Germany.
As far as his science goes, it is not true that “that the overwhelming majority of atmospheric CO2 emissions are due to collisions rather than stimulation.” Collisions do not cause emissions, they excite molecules. Molecules can also be excited by (stimulated} absorption. Emissions only happen from excited molecules and can be stimulated or spontaneous. It seems that Harde believes that spontaneous emissions are only produced by molecules excited by collisions.
Stephen, you also wrote:
He [Alastair] also wrote:
The intensity of eigen (stimulated and spontaneous) radiation will increase as altitude decreases. Thus the radiation emitted from lower levels will be greater and net radiation will travel upwards.
For this assertion to be credible, he [Alastair] needs to provide a reference to peer-reviewed scientific literature affirming his assertions that 1) the overwhelming majority of atmospheric CO2 emissions are due to stimulation; and 2) the overwhelming majority of subsequent energy transfer is upward.
On page 549 of Atkins, P. W. (1997) Physical Chemistry (5th), 5th (with corrections)., Oxford University Press it is stated “Spontaneous emissions can be largely ignored at the relatively low frequencies of rotational and vibrational transitions, and the intensities of these transitions can be discussed in terms of stimulated emissions and absorptions.” Atkins Physical Chemistry is now in its 11th edition and is widely used in universities in both the UK and the USA. I hope you find this a convincing reference to show that the majority of CO2 emissions are due to stimulation.
With regards to your second point, if the radiation at lower altitudes is stronger than that at higher altitudes, then there will obviously be a net flow of radiation from the stronger to weaker regions.
siddsays
Re: what is F(nu)
F(nu) is an unfortunate construct. The equations are perfectly clear: The rate of stimulated emission is proportional to B21*n2*rho(nu) and the rate of spontaneous emission is A21*n2
what is rho(nu) ? it is just the density of states for photons times the Bose-Einstein function for energy distribution h*nu/(exp(-h*nu/kB*T)-1)
What is the density of states: it is the number of allowed states (number of states per unit frequency per unit volume) or 8*pi*nu^2/c^3 (remember, 2 polarizations and all that, and there’s a factor of 4*pi from the volume term)
So you do the multiplication and you find that F(nu) results from the abstraction of the h*nu from the numerator of the BE distribution leaving the denominator behind. so you get an h and an extra nu in F
for an explanation of the confusion in various expressions with various assorted coefficients and different powers of pi, c, nu, h etc. see end of section 3 on page 4 of
Alastair B. McDonald @122, “…but at the “low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.”
This assertion seems to be based solely on the idea that an excited CO2 mollecule has such a small chance of spontaneous emission that the chance of stimulated emission is therefore much higher. I don’t see that the one follows the other. As well as potentially enabling stimulated emission from an excited CO2 mollecule, a 15-micron photon will be absorbed by a non-excited CO2 mollecule. The proportion of excited/non-excited CO2 is the decider here. I’m sure if this were calculated it would show that non-excited CO2 dominates, not excited CO2 mollecules. Thus a photon is far more likely to be absorbed than to stimulate emission.
MA Rodgers,
What I am saying is that 3 things can happen to an excited molecule. It can be 1) relaxed by a collision, 2) it can be stimulated into an emission, or 3)it can spontaneously emit. What I and Profesor Atkins are saying is that option 2 is much more likely than option 3.
I think you wrote that option 3 is in the order of 1 second, so that is plenty of time for option 2 to occur.
Consider an excited CO2 molecule at 2 m height the atmosphere. It is sitting in a bath of other molecules and radiation at STP
Three things can happen to it, listed in order of increasing probability
a) stimulated emission
b) spontaneous emission
c) collisional relaxation
The probability of c) is much larger than that of b), and that of b) is much larger than that of a)
The probability of c) will decrease as altitude increases but that is irrelevant since it will not change b) or a). Note that a) is A21, and b) is B21. Therefore the ratio is given by av^3, where a is a constant and v is the frequency. See Eqn. (8) in the translation of Einstein’s original paper. Thanks to Steven Emmerson who linked to Herman Harde’s paper which references this translation along with other goodies.
sidd continues:
Now consider an unexcited molecule. It can get to the excited state by the reverse of a), b) or c)
At equilibrium, detailed balance requires that exactly as money CO2 molecules wind up in the excited state as exit. Further, Detailed balance requires that exactly as many get there thru the reverse of a) as leave thru a) and similarly for b) and c)
It is not true that a) and b) are reversible. What occurs is d) absorption. Thus for detailed balance a) + b) = d). See Einstein’s paper.
As far as directionality of stimulated emission goes, the excited CO2 molecule is sitting in a bath of _omnidirectional_ radiation since the layer above it radiates as well as the layer below, to within radiative imbalance. So the photons from stimulated emission emerge in all directions, again to within the radiative imbalance between the layer above and below.
True.
If it is claimed that the situation is out of equilibrium, then one must explain why a layer does not heat to incandescence or cool to the freezing point of the gas.
Sorry sidd, but each day the boundary layer does heat, and each night it cools.
Ray Ladburysays
Alastair, Good fricking gods, you are dense! NO, a laser is NOT pure stimulated emission. Spontaneous and stimulated emission compete just as in every other process. It is just that in a laser, you have an inverted population and a high photon flux, making stimulated emission more likely. No such conditions exist in the atmosphere, so stimulated emission is not very likely.
Disagree? OK, then explain why the downwelling photons in the CO2 band (or the upwelling photons from TOA) are not correlated.
Steven Emmersonsays
Alastair B. MacDonald (ABM)@132 wrote
As far as his science goes, it is not true that “that the overwhelming majority of atmospheric CO2 emissions are due to collisions rather than stimulation.” Collisions do not cause emissions, they excite molecules.
The paper under discussion described how collisions cause an excited CO2 molecule to emit a photon and how these emissions far outweigh spontaneous or stimulated ones. Apparently, he misunderstood this point.
ABM also wrote
Atkins Physical Chemistry is now in its 11th edition and is widely used in universities in both the UK and the USA. I hope you find this a convincing reference to show that the majority of CO2 emissions are due to stimulation.
For this to be taken as evidence that stimulated emission is the primary mechanism by which CO2 emits a photon in the atmosphere (where CO2 is a very minor component), he must provide a reference to peer-reviewed scientific literature detailing atmospheric CO2 emissions.
siddsays
i need to be more detailed on detailed balance …
consider two photon states differing by 1 in occupation number. Call them states M,N with M+1=N
M is 0 or greater
Look at the transition N to M (absorption.) Clearly this is proportional to the initial number of photons N
Now look at the transition M to N (emission.) This must also be proportional to N=M+1
The part proportional to M (occupation number in the initial state) is the stimulated emission. The constant bit is spontaneous emission which exists even when M is 0.
M = 0 is an interesting case …
sidd
siddsays
In my previous comment i left out a lot that matters, probably the most important being the occupation numbers of the atoms in ground and excited states, which are governed by boltzmann statistics. We must put in boltzmann statistics also to get a closer picture. This is done in the wikipedia article on einstein coefficients.
sidd
siddsays
Re: boundary layer cools and heats diurnally
Cool. So integrate over a day and work with the averages
More relevant, the ratio between flux of spontaneously emitted radiation to stimulated radiation is A21/(B21*rho(nu)) and is equal to the denominator in the Bose function exp(h*nu/(kB*T)) – 1
if you plot as a function of T is about 25 to 45 in the range 250-300K
At earthly temperatures, spontaneous emission is much more likely at 15 micrometer line of interest. And there is no directionality up or down to the spontaneous emission to within the sub 1% radiative imbalance.
Alastair B. McDonald @134,
Concerning Options (1), (2) & (3):-
These are indeed the three outcomes for an excited CO2 molecule which will have been excited by Case (A) a collision with aonther air milecule or Case (B) absorbing a passing photon. The overwhelming majority of excited CO2 molecules will end with Option (1) as these collisions occur in microseconds, just as the overwhelming majority of excitations result from Case (A) – collisions.
It is then true that Option (3) does take on average perhaps ten-thousand-times longer and thus, for that average relaxation time, a CO2 would somehow have to survive (or dodge) some 10,000 collisions. But there are many CO2 molecules excited by these large number of collisions and on average a portion of them will relax far more rapidly enacting Option (3) and thus Option (3) will remain significant.
As for Option (2), such events do require Option (3) to provide the photons to stimulate these Option (2) emissions. The ratio of Option (2) and Option (3) will thus depend on the proportion of CO2 molecules that are in an excited state. That proportion is:-
n[2]/(n[1]+n[2])
these values n[1] & n[2] having been used up-thread @116 within the equation
A[21]n[2] + B[21]n[2]p(v) = B[12]n[1]p(v).
And you will recall that using that equation @116, I calculated that Option (3) would be 32-times more likely then Option (2).
So yes, there is “plenty of time for Option (2) to occur” but what we are missing is enough passing photons as most will encounter an unexcited CO2 molecule resulting in Case (B) before they have the chance to encounter an excited molecule and trigger Option (2).
Alastair, Good fricking gods, you are dense! NO, a laser is NOT pure stimulated emission. Spontaneous and stimulated emission compete just as in every other process. It is just that in a laser, you have an inverted population and a high photon flux, making stimulated emission more likely. No such conditions exist in the atmosphere, so stimulated emission is not very likely.
Disagree? OK, then explain why the downwelling photons in the CO2 band (or the upwelling photons from TOA) are not correlated.
The Wikipedia entry above continues: “A laser differs from other sources of light in that it emits light coherently.” I assume you meant coherently when you wrote correlated. If tou are unfamiliar with the term coherent, look it up in Wikipedia.
The reason that stimulated emissions in the atmophere are not coherent is because they are not colliminated as they are in a laser. See this Wikipedia entry.
I had hoped that that I might learn something from your posts, but it seems that our roles are reversed. You called me dense, what does that make you?
Brian Dodgesays
Alastair B. McDonald et al.
Why is there more radiation coming from the sky in the 14-16 micron band(presumably from atmospheric CO2)than coming up from the atmosphere + ground at 20km?
Alastair,
If a photon is emitted via stimulated emission, it will have identical properties and direction to the stimulating photon. No such correlation exists that I have seen.
zebrasays
Alastair B McDonald (and those responding),
ABM, at #127, you said:
“In fact, my original idea that there would be less radiation downwards is flawed:-(”
And I applauded you for admitting an error.
I also said that this was a good example of the kind of discussion that should occur… all these people did the math for you and clarified the physics involved.
But now, I am back to what I said originally: I have no clue what you (ABM) are still arguing about, whether because you are actually confused, or just communicating very poorly.
Maybe you could make a simple declarative sentence to say what you are trying to say? The point being that this helps focus your own thinking, and then, again, right or wrong, MAR, sidd, et al, can respond coherently.
Chucksays
Mike:Icebreaker is struggling to find stable ice to establish research station in the Arctic. I think this might be what Peter Wadhams saw coming.
I’ve always felt that Wadhams had a good chance of being correct about an ice free Arctic by 2020. Even if he’s off by a couple of years I would still say he was correct.
Keith Woollardsays
So Mal and Ray, if H2O has a self driven positive feedback, and it has the greatest greenhouse affect, what negative feedback counters this pre-man?
mikesays
Large loss of CO2 in winter observed across the northern permafrost region
“Recent warming in the Arctic, which has been amplified during the winter1,2,3, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)4. However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates5,6. Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662 TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (−1,032 TgC per year).”
Keith Woollard @147,
Following you question up-thread @82, you respond to Ray Ladbury @92 (who descibes the changes of atmospheric H2O and any resulting temperature variation being determined by temperature and thus not independent of the factors that initiate those primary changes in temperature) and Mal Adapted @106 (who explains that the relationship between atmospheric H2O levels and temperature was understood back in the 19th century).
In your response you decribe this H2O feedback effect as “self-driven” and ask “What negative feedback counters this pre-man?” It appears plain to me that you fail to grasp the impact of the H2O feedback within the climate.
Imagine CO2 levels double. The direct result is an increase in global temperature of +1ºC. This increase results in extra H2O in the atmosphere, raising global temperature by a further +0.66ºC, a temperature increase which itself results in extra H2O in the atmosphere, raising global temperature by a further +0.44ºC and so on – a further +0.30ºC, +0.20ºC, +0.13ºC, +0.09ºC ans so on. These increases will reach a limit, adding +2.0ºC to the original +1ºC CO2 increase.
But now imagine the CO2 levels revert to the original level. All that additional atmospheric H2O is then rained away back to the original H2O level and the original global temperature is thus restored.
The sole functioning of H2O is to amplify any forced warming/cooling. This amplification has (to a greater or lesser extent) operated pre-AGW, pre-man, pre-whatever, all the way back to the formation of the Earth’s atmosphere.
This is a simplistic but robust description with no need to invoke ‘counteracting negative feedbacks’.
Zebra #94 Yes, I did miss your #52 comment, so thanks for repeating.
We seem to be missing each other’s meaning, so I’ll try to lay mine out for you. I’m not sure that it will fit your idea of a “warrant thing.”
I am in agreement with the science on AGW, but science is not a static thing. As knowledge is gained, understandings and emphasis change. I was a forecaster for 30+ years, and I’ve seen a lot of weather systems come and go. Occasionally, they wreck people’s lives in the process, and I care about that. As the knowledge and models both advanced, my forecasts got better.
I care that with ongoing climate change, things are liable to get a lot worse, both for humans and the rest of the planet. My job was basically as a communicator/translator of complex weather patterns and models, and rendering a prediction that was meaningful to ordinary people. I am now attempting to understand the climate research as best I can in order to effectively communicate what that means to ordinary people.
I’m living in the central U.S., a region with large variability in weather, both from day to day and year to year. I see the same basic weather patterns repeated. Climate change has not eliminated these patterns, so far, and I see no reason to believe that it will in the next 50-100 years, at a minimum. What I’m expecting is a change in the frequency and intensity of the basic patterns as greenhouse gas forcing influences the co-existing variability.
I am also leaving room to notice new patterns if and when they appear. I have only seen a few, so far. My reference point to what is a “new pattern” is the history of regional weather and climate. So, the 1930’s were an extreme point for which we have a good instrumental record. The Dust Bowl is the most famous event, but there were many other anomalies of the type that occur when there is are a lot of strong blocking patterns and meridional flows.
There has been a lot of research in the past few years suggesting that these blocking/meridional flow patterns are getting more extreme as the result of climate change. However, most of the empirical studies I’ve seen only go back 30-40 years, and therefore exclude the 1930s, which was an extreme period prior to polar ice loss, polar amplification, and another 110 ppm of CO2. I’m hoping that future research will give us some better idea of how much of the current extreme blocking is due to climate change, and how much to natural variability as an old pattern has perked up again.
Meanwhile, I find myself between two extremes of attribution. There are plenty of people around here who believe that all of the variability we see is natural, and humans aren’t causing climate change. On the other hand, there are people who are attributing every extreme they see to climate change. I honestly believe that the truth lies somewhere in between, and I can be guided by what has happened in the past (e.g. the 1930s) vs. what hasn’t happened at least during the instrumental record. Thus, I share the concern about the extreme mid-continental wetness we’ve been seeing with increasing frequency in the past decade. But I also know that a blocking pattern at a different longitude can set up an extreme drought.
My thinking is in terms of probabilities and trends rather than of parallel universes or great and strictly defined precision. It would be nice to know if we need to be prepared for a megadrought, worse flooding, or both, in the next 20 years. There are some big reservoirs on the upper Missouri River. Should we try to empty them to avoid a dam break, keep them full in case there’s a drought, or change the levels we’re aiming for to even out the probabilities better? Those are the kind of specifics that I’m interested in.
Mr KIA @95 — For an intermediate level textbook see “Fundamentals of Planetary Climate” by Ray Pierrehumbert. Don’t expect to see it duplicated here.
My thanks to MA Rodger for post #246 in last months “Unforced Variations”. My Wi Fi has been out so I haven’t been able to reply. Also my mistake in not stating he was using the Maue’s Accumulated Cyclone Energy (ACE) Index. The information you provided is very helpful.
KIA: I’ve been asking for that info since day 1, and have yet to see it clearly spelled out.
BPL: And you’ve been given that information over and over again, pointed to more detailed explanations elsewhere on the web, and no matter how much we explain it to you, you will complain that no one is explaining it to you. If you really want a good explanation, CRACK A FREAKING BOOK. I’d recommend starting with John Houghton’s “The Physics of Atmospheres.” Work the problems.
The majority of the public obviously isn’t going to do that, so simplified explanations which capture most of the physics is obviously the way to go.
Alastair B. McDonald @87,
It is correct that the path length of a photon between its CO2 (spontaneous or stimulated) emission and it creating a stimulated emission will be measured between excited CO2 mollecules. And we should add that the path length of a photon between its CO2 emission and CO2 absorption will be from an excited CO2 molecule to an unexcited CO2 molecule.
And, yes, the level of spontaneous emissions are dependent on temperature so the higher in the atmosphere, the less such emissions there will be, this of course, the mechanism that lies behind CO2 climate forcing.
And, yes, the higher in the atmosphere, the lower the air density so there will be less CO2 molecules to emit/absorb photons. And as it also results in the photon path length increasing, density itself has no impact on the density of photons flying about – with lower density, the fewer the emissions/absorptions but the further the photons fly.
But that all said, we get down to the ratio of A21/B21. The equations (whatever equilibrium version is correct) all yield B21 as being massively bigger than A21.
But I feel I have been misrepresenting A21/B21 as the proportion of simultaneous/stimulated emissions. This, of course, would be:-
and when I have a few uninterrupted minutes, I will have a go at calculating that ratio properly.
Ray Ladbury:
Yes indeed. The Clausius-Clapeyron relation is the answer to the denialist “water vapor is the most important greenhouse gas!” The control of atmospheric water vapor by temperature was worked out by the mid-19th century, well in time to guide Arrhenius’s 1896 model of CO2-forced global warming. I’m guessing KW didn’t know that.
Alastair B. McDonald@79 wrote:
This rebuttal is invalid for several reasons: 1) it is an ad-hominem attack; 2) the paper in question is about the carbon cycle and not about radiative transfer by atmospheric CO2; and 3) most importantly, it doesn’t address the issue: that the overwhelming majority of atmospheric CO2 emissions is due to collisions rather than stimulation.
He also wrote:
For this assertion to be credible, he needs to provide a reference to peer-reviewed scientific literature affirming his assertions that 1) the overwhelming majority of atmospheric CO2 emissions are due to stimulation; and 2) the overwhelming majority of subsequent energy transfer is upward.
Mr. KNOW IT ALL said:
Yup need someone from CERN, LOL. This is one for the ages.
Zebra @93 wrote:
No.
https://www.yaleclimateconnections.org/2019/10/brief-overview-of-new-ipcc-report-on-oceans-and-ice-risks/
New special report from IPCC lists array of increasing risks facing oceans and ice in a warming world. (My notes: It talks about accelerated ice loss in Greenland and Antarctica making the IPCC worst case scenarious more likely, also covers rising confidence that category 4 and 5 hurricanes are increasing in number, and concerns about carbon from melting permafrost)
#101 John Pollack,
I appreciate your effort to explain yourself; unfortunately, the substance is still too vague to allow for a serious discussion. You say:
You gave two references earlier. One was a meteorological comparison of two two-month time periods, (in 1987 and 1994) and the other a millenial-scale modeling exercise (on drought) that used 1901-2005 for instrumentally-verified input.
I really don’t understand what you are trying to say about “including the 1930’s”… as I pointed out earlier, and you continue to ignore, the models…the one you yourself referenced… do exactly that. So what’s the problem??
If you are a meteorologist, then surely you understand the difference between weather and climate. But here, the only interpretation I can arrive at is that you are conflating the two.
Rex Tasha says:
6 Oct 2019 at 1:07 PM
Bore Hole Troll
Paul Pukite (@whut):
Mr. IAT has, again, frankly disclosed his scientific meta-illiteracy. Let’s see if he’ll settle for a complete explanation by one Delbert G. Van Ornum of Plasmadyne Corporation, appearing in the Journal of Meteorology in 1961. I found it in 90 seconds on Google Scholar, searching for “quantum infrared backscatter cloud” without quotes. Another 10 seconds turned up observational confirmation by G.T. Cherrix and B.A. Sparkman in a NASA internal report, in 1967. I could only reach the abstract of another promising hit from 1967, by Carrier et al. in Applied Optics, titled “The Backscattering and Extinction of Visible and Infrared Radiation by Selected Major Cloud Models”. Republicans were much more ‘liberal’ then, to be sure.
Of course, there’s always the seminal paper by physicist Gilbert Plass, in the Quarterly Review of the Royal Meteorological Society in 1956. It’s included in The Warming Papers, edited by RC contributors David Archer and Ray-Pierre Humbert. An image of the book’s cover appears in rotation on the right-hand side of this very page. Jeez, it’s only a click away!
IOW, long since asked and answered. Once again: science is a way of trying not to fool yourself, that only works if you’re trying. Mr. IAT, sadly, has made it abundantly clear he prefers to fool himself. If he didn’t, he’d lose his explicit warrant for commenting here, namely to bring his fantasy culture war to his imaginary enemies. I grudgingly grant his talent for provocation!
#109 Alastair B. McDonald,
“no”
If that is the case, what I have now said twice (and MAR perhaps has read, and so corrected himself,) what is relevant is the distribution of states and the incidence of radiation.
So far, you haven’t given any quantitative or qualitative analysis of those conditions to justify your argument.
It seems obvious that if we have a system in equilibrium, in which spontaneous emissions occur from CO2, and we increase the number of CO2 molecules, then we are surely increasing the probability of spontaneous emissions in the relevant wavelengths.
So, can you explain your reasoning to the contrary?
102 and 104 – David B.Benson and BPL:
Thank you both for the book recommendations. Good references for all of us.
;)
108 – Paul P.
“Yup need someone from CERN, LOL. This is one for the ages.”
Ask and ye shall receive. They’re on it like stink on poop:
https://home.cern/news/press-release/cern/cerns-cloud-experiment-shines-new-light-climate-change
113 – Mal Adapted
“…. I grudgingly grant his talent for provocation!”
Thank you for the compliment.
:)
Alastair B. McDonald further to my comment @105,
Addressing the issue of the ratio of spontaneous to stimulated photon emissions in the atmosphere, the Wikithing page gives for the equilibrium condition:-
with A[21], B[21] and B[12] respectively the coeffts for Spontaneous emission, Stimulated emission and Absorption.
I calculated this F(v) quantity up-thread @63 to be a very small number. There was some doubt as to the form of the equation for F(v) but we were talking 1.2e-10 or smaller.
Yet this A[21]/B[21] ratio is the ratio of the coefficients, not the ratio of emissions which would be
where h = Planck’s constant = 6.6e-34 Js, v = frequency = [for 15 microns] 2.0e+13 Hz, K = Boltzmann’s constant = 1.4e-23 j/K and T = temperature ≈270 K.
So the ratio Spontaneous emissions/Stimulated emissions = 32.
It thus appears that stimulated emissions are not the dominant emissions and if so the photon emissions will be spontaneous or stimulated by a spontaneously emited photon and thus entirely any-which-way. The directionality of emission from the surface will be disappeared within a single path-length which is, what, about a metre? (This assuming I have’t dropped a bead from my abacus along the way.) And I am a lot happier now than I was @63 as the implications of this ratio Sp/St now appears to fit the physical situation.
MA Rodger,
Just look at the physics–for spontaneous emission to play a significant role, an IR photon of the proper wavelength must pass near an already excited CO2 molecule. Spontaneous emission in MASER or LASER is significant only because both the flux of photons AND the population of excited atoms/molecules is large.
Also, realize that there is another competitor for the relaxation–collision between an excited CO2 molecule and ANY gas atom/molecule can cause the excited CO2 molecule to transfer its extra energy to the other atom/molecule. This process is not negligible. Alastair really doesn’t know what he’s talking about.
https://www.bbc.com/future/article/20191014-climate-change-arctic-expedition-finds-itself-on-thin-ice?ocid=global_future_rss&ocid=global_bbccom_email_15102019_future
Icebreaker is struggling to find stable ice to establish research station in the Arctic. I think this might be what Peter Wadhams saw coming. Wadhams is going to be much closer to the target with his projection on timing of ice in the Arctic than the folks who rejected his projection and imagined decades of stable ice in the Arctic for decades to come. Blue ocean event. Here we come. I think that’s a feedback loop driver, isn’t it?
Should be fine. After we perfect direct air capture we can build the global icemaker to fix the albedo problem with disappearance of sea ice.
CO2? How are we doing? Peachy!
October 6 – 12, 2019 408.39 ppm
October 6 – 12, 2018 405.50 ppm 2.89 ppm over last year
October 6 – 12, 2009 384.06 ppm 24.33 ppm over same week in 2009
(co2.earth)
Nothing skyrockety, just steady increase and increase rate has been accelerating. More CO2, more heat.
Warm regards
Mike
GISTEMP has posted for September with an anomaly of +0.90ºC, the second lowest GISTEMP anomaly of 2019-so-far. (They span from +1.17ºC to +0.86ºC.)
It is the second warmest September on the GISTEMP record, just behind of 2016 (+0.91ºC) and ahead of 2014 & 2015 (both +0.84ºC), 2018 (+0.81ºC), 2017 (+0.79ºC) and 2013 (+0.77ºC).
It is the 27th highest anomaly on the all-month GISTEMP record. The spike in the TLT (UAH & RSS were recording 8th & 6th warmest all-month anomaly on record) isn’t seen in the surface measurements, perhaps a repeat of the TLT spike that occurred in Autumn 2017 after (similar to this year) surface measurements had been high earlier in the year. (Poor Roy Spencer was so disturbed by UAH’s TLT spike that he has set out an explanation on his blog.)
Now with three-quarters of the year complete, 2019 sits quite firmly in 2nd place for the year-to-date. To drop to 3rd place by end-of-year behind 2017 would require Oct-Dec to average less than +0.83ºC while 1st place looks beyond reach as it would require Oct-Dec to average higher than a sweltering +1.19ºC.
The table is ordered by Jan-Sept averages.
…….. Jan-Sept Ave … Annual Ave ..Annual ranking
2016 .. +1.06ºC … … … +1.01ºC … … … 1st
2019 .. +0.95ºC
2017 .. +0.93ºC … … … +0.92ºC … … … 2nd
2015 .. +0.83ºC … … … +0.90ºC … … … 3rd
2018 .. +0.83ºC … … … +0.85ºC … … … 4th
2010 .. +0.75ºC … … … +0.72ºC … … … 6th
2014 .. +0.74ºC … … … +0.74ºC … … … 5th
2007 .. +0.70ºC … … … +0.66ºC … … … 9th
2005 .. +0.67ºC … … … +0.68ºC … … … 7th
2013 .. +0.66ºC … … … +0.68ºC … … … 8th
2002 .. +0.66ºC … … … +0.62ºC … … … 13th
Re 99 where Brian Dodge says:
“What percentage of the CO2 molecules are excited? Given that, what’s the probability that a photon of the appropriate wavelength will hit an unexcited CO2 molecule and be absorbed versus the probability that it will hit an excited CO2 molecule and cause stimulated emission? ”
The CO2 molecules are mostly excited (and relaxed) by collisions. The per cent which is excited at any temperature is given by the Boltzmann distribution:
”
I believe a figure of ~7% is the excitation level for the 15um band of CO2 at STP, which would be the probability of a photon producing stimulated emission. (For laser action, a probability of greater than 50% is needed.)
You asked:
“Did Herr J. Koch measure the temperature required in a column of air so that it produced an equilibrium of IR out versus IR in, i.e. where the probability that an incoming photon will be absorbed is equal to the probability that it will hit an excited molecule and cause stimulate emission? ”
No, AIUI, the energy absorbed by the gas was lost through the walls of the apparatus. But I have translated Dr Koch’s paper here.
You also asked:
“What’s the probability that an excited CO2 molecule will collide with another molecule, and convert that store energy to heat?”
That is covered by the Boltzmann distribution.
Mr. Know-It-All,
You can’t back your way out of that embarrassment, as particle physics is about the fundamental nature of matter, which is distinct from condensed matter physics. Welcome to the club of Judith Curry, who tried to associate droplet nucleation with Bose-Einstein statistics. In communicating science, you really need to have a grasp of the fundamental physics, otherwise you end up looking foolish.
Re 116 where MA Rodger says:
“It thus appears that stimulated emissions are not the dominant emissions and if so the photon emissions will be spontaneous or stimulated by a spontaneously emitted photon and thus entirely any-which-way. The directionality of emission from the surface will be disappeared within a single path-length which is, what, about a metre? (This assuming I haven’t dropped a bead from my abacus along the way.) And I am a lot happier now than I was @63 as the implications of this ratio Sp/St now appears to fit the physical situation.”
The main cause of excitation of CO2 molecules in the troposphere is by collisions, not by irradiation i.e stimulated absorption. An excited molecule has a half-life, which when it expires causes a spontaneous emission. If the molecule is relaxed by a collision before the half-life expires, obviously it will not emit. The half-life decreases as frequency increases, but at the low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.
Re 114 where zebra says:
“If that is the case, what I have now said twice (and MAR perhaps has read, and so corrected himself,) what is relevant is the distribution of states and the incidence of radiation.”
The distribution of states is determined by collisions, not by radiation as everyone seems to think. See my reply to MA Rodger above.
zebra, you also wrote:
“It seems obvious that if we have a system in equilibrium, in which spontaneous emissions occur from CO2, and we increase the number of CO2 molecules, then we are surely increasing the probability of spontaneous emissions in the relevant wavelengths.
So, can you explain your reasoning to the contrary?”
no again. I am not arguing “to the contrary”!
But the boundary layer of the troposphere is not in equilibrium. Its temperature is continually changing.
I have not discussed an increase in CO2. However, if you do increase CO2, then you will increase the number of excited molecules. So spontaneous emissions will increase, but so will the stimulated emissions.
However, if you increase the CO2 so much that the pressure increases, then the time between collisions will decrease and fewer spontaneous emissions will occur.
I should have explained earlier that the population of excited states is set by collisions, but I had forgotten. Sorry.
Consider an excited CO2 molecule at 2 m height the atmosphere. It is sitting in a bath of other molecules and radiation at STP
Three things can happen to it, listed in order of increasing probability
a) stimulated emission
b) spontaneous emission
c) collisonal relaxation
The probability of c) is much larger than that of b), and that of b) is much larger than that of a)
Now consider an unexcited molecule. It can get to the excited state by the reverse of a), b) or c)
At equilibrium, detailed balance requires that exactly as money CO2 molecules wind up in the excited state as exit. Further, Detailed balance requires that exactly as many get there thru the reverse of a) as leave thru a) and similarly for b) and c)
As far as directionality of stimulated emission goes, the excited CO2 molecule is sitting in a bath of _omnidirectional_ radiation since the layer above it radiates as well as the layer below, to within radiative imbalance. So the photons from stimulated emission emerge in all directions, again to within the radiative imbalance between the layer above and below.
If it is claimed that the situation is out of equilibrium, then one must explain why a layer does not heat to incandescence or cool to the freezing point of the gas.
sidd
Alastair B. McDonald @122,
You say:-
☻ “The main cause of excitation of CO2 molecules in the troposphere is by collisions, not by irradiation i.e stimulated absorption.”
I agree.
☻ “An excited molecule has a half-life, which when it expires causes a spontaneous emission. If the molecule is relaxed by a collision before the half-life expires, obviously it will not emit. The half-life decreases as frequency increases, …”
I agree and would add that I recall the half-life is of the order of a tenth of a second while the rate of collision is measured in microseconds. So very very few excited CO2 mollecules result in a spontaneous photon emissions. Almost all end with a collision with another air mollecule, very likely the same mechanism from which the excitation arose.
☻ “…but at the “low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.”
This assertion seems to be based solely on the idea that an excited CO2 mollecule has such a small chance of spontaneous emission that the chance of stimulated emission is therefore much higher. I don’t see that the one follows the other. As well as potentially enabling stimulated emission from an excited CO2 mollecule, a 15-micron photon will be absorbed by a non-excited CO2 mollecule. The proportion of excited/non-excited CO2 is the decider here. I’m sure if this were calculated it would show that non-excited CO2 dominates, not excited CO2 mollecules. Thus a photon is far more likely to be absorbed than to stimulate emission.
Re 117 where Ray Ladbury says:
MA Rodger,
Ray Ladbury is confusing laser action with emissions from greenhouse gases. Laser action is pure stimulated emission. Greenhouse gases emit a mixture of stimulated and spontaneous emissions, the ratio being a function of wavelength. Greenhouse gases, operating in the far infrared, emit more by stimulated emissions than by spontaneous emissions.
Re 116 where MA Rodger says:
15 Oct 2019 at 4:27 AM
Alastair B. McDonald further to my comment @105,
…
Yet this A[21]/B[21] ratio is the ratio of the coefficients, not the ratio of emissions which would be
Spontaneous/Stimulated = A[21]n[2] / B[21]n[2]p(v)
where
p(v)[v,t] = F(v) x 1/(e^(hv/kT)-1)
As I understand it, the ratio of the emissions is [A21]n[2]/[B21]/[n2] = F(v), not p(v). [n2] which is the level of molecules excited by collisions and absorption applies to both stimulated and spontaneous emissions and cancels. A molecule will emit if and only if it is excited.
There is a problem you raised earlier – what is F(v)?
You are using 2hv^3/c^2
Wikipedia states 8hv^3/c^2
Thomas and Stamnes give it as 2hv^3/c^2
Goody and Yung give it as 8hv^2/c^3
and Atkins gives it as 8hv^3/c^3
The difference may be caused by v (nu?) being in units of Hz^-1 or cm^-1 but that on;y gives us two alternatives. interchangeing 8 and 2 will not affect the ratio by much but the use of c^3 or c^2 will!
It is more than a metre. The blackbody photon has to travel until it reaches an excited molecule to then produce a stimulated emission. But you are making a valid point that once we are far from the surface stimulated emissions will be produced by spontaneous multidirectional photons.
In fact, my original idea that there would be less radiation downwards is flawed:-(
(This assuming I have’t dropped a bead from my abacus along the way.) And I am a lot happier now than I was @63 as the implications of this ratio Sp/St now appears to fit the physical situation.
Alastair:”The half-life decreases as frequency increases, but at the low” frequency of the CO2 15um band, emissions from excited molecules are mainly by stimulated emissions. In other words, excited molecules are relaxed by photons more often than by “timing out”.”
NO!!! MA Rodgers has shown that spontaneous emission is >30x more likely than stimulated emission, and that analysis did not take into account the competing process of collisional relaxation, which further reduces the population of excited molecules and therefor candidates for stimulated emission. It is as if you are simply refusing to read the many, many refutations of your delusion!
And NOAA has posted for September with an anomaly of +0.95ºC, a little up on August (GISTEMP was down a little). The anomalies for 2019-so-far span from +1.10ºC to +0.87ºC.
It is =1st warmest September on the NOAA record, equalling 2015 (+0.95ºC) and just ahead of 2016 (+0.94ºC), followed by 2017 (+0.86ºC), 2018 (+0.83ºC), 2014 (+0.79ºC) and 2012 (+0.74ºC).
It is the 13th highest anomaly on the all-month NOAA record (27th highest in GISTEMP).
Now with three-quarters of the year complete, 2019 sits in 2nd place for the NOAA year-to-date. To drop to 3rd place by end-of-year behind 2017 would require Oct-Dec to average less than +0.90ºC (a drop more likely to happen in NOAA than in GISTEMP) while 1st place again looks beyond reach as it would require Oct-Dec to average higher than a sweltering +1.15ºC.
The table is ordered by Jan-Sept averages.
…….. Jan-Sept Ave … Annual Ave ..Annual ranking
2016 .. +1.06ºC … … … +0.99ºC … … … 1st
2019 .. +0.95ºC
2017 .. +0.94ºC … … … +0.91ºC … … … 3rd
2015 .. +0.88ºC … … … +0.93ºC … … … 2nd
2018 .. +0.81ºC … … … +0.83ºC … … … 4th
2010 .. +0.76ºC … … … +0.73ºC … … … 6th
2014 .. +0.74ºC … … … +0.74ºC … … … 5th
1998 .. +0.70ºC … … … +0.65ºC … … … 9th
2005 .. +0.66ºC … … … +0.67ºC … … … 8th
2013 .. +0.66ºC … … … +0.68ºC … … … 7th
2007 .. +0.65ºC … … … +0.62ºC … … … 15th
Re 116 where MA Rodger says:
15 Oct 2019 at 4:27 AM
Alastair B. McDonald further to my comment @105,
…
Yet this A[21]/B[21] ratio is the ratio of the coefficients, not the ratio of emissions which would be
Spontaneous/Stimulated = A[21]n[2] / B[21]n[2]p(v)
where
p(v)[v,t] = F(v) x 1/(e^(hv/kT)-1)
As I understand it, the ratio of the emissions is [A21]n[2]/[B21]/[n2] = F(v), not p(v). [n2] which is the level of molecules excited by collisions and absorption applies to both stimulated and spontaneous emissions and cancels. A molecule will emit if and only if it is excited.
There is a problem you raised earlier – what is F(v)?
You are using 2hv^3/c^2
Wikipedia states 8hv^3/c^2
Thomas and Stamnes give it as 2hv^3/c^2
Goody and Yung give it as 8hv^2/c^3
and Atkins gives it as 8hv^3/c^3
The difference may be caused by v (nu?) being in units of Hz^-1 or cm^-1 but that on;y gives us two alternatives. interchangeing 8 and 2 will not affect the ratio by much but the use of c^3 or c^2 will!
It is more than a metre on average that the blackbody photon has to travel until it reaches an excited molecule to then produce a stimulated emission. But you are making a valid point that once we are far from the surface stimulated emissions will be produced by spontaneous multidirectional photons.
In fact, my original idea that there would be less radiation downwards is flawed:-(
127 Alastair B. McDonald,
Thank you. I am delighted, and encouraged… [not because your idea was flawed ;-)], but that you demonstrated for readers how actual scientific reasoning and discussion is supposed to work.
I think we are all familiar with getting attached to an idea and needing outside input to fully develop it, one way or the other.
Now if only we could get the Denialist idiots to sincerely engage, and admit an error when the evidence is presented… yeah, sure…
Re 107 where Steven Emmerson says:
Sorry, I got carried away trying to show Harde is a climate change denier. I need not have bothered since he has signed the “There is no climate emergency” petition at number 7 in Scientists from Germany.
As far as his science goes, it is not true that “that the overwhelming majority of atmospheric CO2 emissions are due to collisions rather than stimulation.” Collisions do not cause emissions, they excite molecules. Molecules can also be excited by (stimulated} absorption. Emissions only happen from excited molecules and can be stimulated or spontaneous. It seems that Harde believes that spontaneous emissions are only produced by molecules excited by collisions.
Stephen, you also wrote:
On page 549 of Atkins, P. W. (1997) Physical Chemistry (5th), 5th (with corrections)., Oxford University Press it is stated “Spontaneous emissions can be largely ignored at the relatively low frequencies of rotational and vibrational transitions, and the intensities of these transitions can be discussed in terms of stimulated emissions and absorptions.” Atkins Physical Chemistry is now in its 11th edition and is widely used in universities in both the UK and the USA. I hope you find this a convincing reference to show that the majority of CO2 emissions are due to stimulation.
With regards to your second point, if the radiation at lower altitudes is stronger than that at higher altitudes, then there will obviously be a net flow of radiation from the stronger to weaker regions.
Re: what is F(nu)
F(nu) is an unfortunate construct. The equations are perfectly clear: The rate of stimulated emission is proportional to B21*n2*rho(nu) and the rate of spontaneous emission is A21*n2
what is rho(nu) ? it is just the density of states for photons times the Bose-Einstein function for energy distribution h*nu/(exp(-h*nu/kB*T)-1)
What is the density of states: it is the number of allowed states (number of states per unit frequency per unit volume) or 8*pi*nu^2/c^3 (remember, 2 polarizations and all that, and there’s a factor of 4*pi from the volume term)
So you do the multiplication and you find that F(nu) results from the abstraction of the h*nu from the numerator of the BE distribution leaving the denominator behind. so you get an h and an extra nu in F
For a clear explanation see :
http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/phodens.html
http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html#c3
for an explanation of the confusion in various expressions with various assorted coefficients and different powers of pi, c, nu, h etc. see end of section 3 on page 4 of
https://arxiv.org/abs/physics/0202029
sidd
MA Rodger, at 125 you wrote:
MA Rodgers,
What I am saying is that 3 things can happen to an excited molecule. It can be 1) relaxed by a collision, 2) it can be stimulated into an emission, or 3)it can spontaneously emit. What I and Profesor Atkins are saying is that option 2 is much more likely than option 3.
I think you wrote that option 3 is in the order of 1 second, so that is plenty of time for option 2 to occur.
Re 124 where sidd says:
The probability of c) will decrease as altitude increases but that is irrelevant since it will not change b) or a). Note that a) is A21, and b) is B21. Therefore the ratio is given by av^3, where a is a constant and v is the frequency. See Eqn. (8) in the translation of Einstein’s original paper. Thanks to Steven Emmerson who linked to Herman Harde’s paper which references this translation along with other goodies.
sidd continues:
It is not true that a) and b) are reversible. What occurs is d) absorption. Thus for detailed balance a) + b) = d). See Einstein’s paper.
True.
Sorry sidd, but each day the boundary layer does heat, and each night it cools.
Alastair, Good fricking gods, you are dense! NO, a laser is NOT pure stimulated emission. Spontaneous and stimulated emission compete just as in every other process. It is just that in a laser, you have an inverted population and a high photon flux, making stimulated emission more likely. No such conditions exist in the atmosphere, so stimulated emission is not very likely.
Disagree? OK, then explain why the downwelling photons in the CO2 band (or the upwelling photons from TOA) are not correlated.
Alastair B. MacDonald (ABM)@132 wrote
The paper under discussion described how collisions cause an excited CO2 molecule to emit a photon and how these emissions far outweigh spontaneous or stimulated ones. Apparently, he misunderstood this point.
ABM also wrote
For this to be taken as evidence that stimulated emission is the primary mechanism by which CO2 emits a photon in the atmosphere (where CO2 is a very minor component), he must provide a reference to peer-reviewed scientific literature detailing atmospheric CO2 emissions.
i need to be more detailed on detailed balance …
consider two photon states differing by 1 in occupation number. Call them states M,N with M+1=N
M is 0 or greater
Look at the transition N to M (absorption.) Clearly this is proportional to the initial number of photons N
Now look at the transition M to N (emission.) This must also be proportional to N=M+1
The part proportional to M (occupation number in the initial state) is the stimulated emission. The constant bit is spontaneous emission which exists even when M is 0.
M = 0 is an interesting case …
sidd
In my previous comment i left out a lot that matters, probably the most important being the occupation numbers of the atoms in ground and excited states, which are governed by boltzmann statistics. We must put in boltzmann statistics also to get a closer picture. This is done in the wikipedia article on einstein coefficients.
sidd
Re: boundary layer cools and heats diurnally
Cool. So integrate over a day and work with the averages
More relevant, the ratio between flux of spontaneously emitted radiation to stimulated radiation is A21/(B21*rho(nu)) and is equal to the denominator in the Bose function exp(h*nu/(kB*T)) – 1
Recall A21/B21 = 8*pi*h*nu^3/c^2 = F(nu) and rho(nu) = F(nu)/(exp(h*nu/(kB*T) – 1 )
if you plot as a function of T is about 25 to 45 in the range 250-300K
At earthly temperatures, spontaneous emission is much more likely at 15 micrometer line of interest. And there is no directionality up or down to the spontaneous emission to within the sub 1% radiative imbalance.
sidd
Alastair B. McDonald @134,
Concerning Options (1), (2) & (3):-
These are indeed the three outcomes for an excited CO2 molecule which will have been excited by Case (A) a collision with aonther air milecule or Case (B) absorbing a passing photon. The overwhelming majority of excited CO2 molecules will end with Option (1) as these collisions occur in microseconds, just as the overwhelming majority of excitations result from Case (A) – collisions.
It is then true that Option (3) does take on average perhaps ten-thousand-times longer and thus, for that average relaxation time, a CO2 would somehow have to survive (or dodge) some 10,000 collisions. But there are many CO2 molecules excited by these large number of collisions and on average a portion of them will relax far more rapidly enacting Option (3) and thus Option (3) will remain significant.
As for Option (2), such events do require Option (3) to provide the photons to stimulate these Option (2) emissions. The ratio of Option (2) and Option (3) will thus depend on the proportion of CO2 molecules that are in an excited state. That proportion is:-
And you will recall that using that equation @116, I calculated that Option (3) would be 32-times more likely then Option (2).
So yes, there is “plenty of time for Option (2) to occur” but what we are missing is enough passing photons as most will encounter an unexcited CO2 molecule resulting in Case (B) before they have the chance to encounter an excited molecule and trigger Option (2).
Re 136 where Ray Ladbury says:
Ray, you might be interested in this excerpt from Wikipedia: “A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term “laser” originated as an acronym for “light amplification by stimulated emission of radiation”.
You also wrote
The Wikipedia entry above continues: “A laser differs from other sources of light in that it emits light coherently.” I assume you meant coherently when you wrote correlated. If tou are unfamiliar with the term coherent, look it up in Wikipedia.
The reason that stimulated emissions in the atmophere are not coherent is because they are not colliminated as they are in a laser. See this Wikipedia entry.
I had hoped that that I might learn something from your posts, but it seems that our roles are reversed. You called me dense, what does that make you?
Alastair B. McDonald et al.
Why is there more radiation coming from the sky in the 14-16 micron band(presumably from atmospheric CO2)than coming up from the atmosphere + ground at 20km?
https://scienceofdoom.files.wordpress.com/2011/04/petty-2-upward-and-downward-radiation-p223.png
https://www.pnas.org/content/111/46/16297
Would seem to me that spontaneous, or stimulated by spontaneous, downwelling radiation is larger.
https://www.pnas.org/content/111/46/16297
Alastair,
If a photon is emitted via stimulated emission, it will have identical properties and direction to the stimulating photon. No such correlation exists that I have seen.
Alastair B McDonald (and those responding),
ABM, at #127, you said:
“In fact, my original idea that there would be less radiation downwards is flawed:-(”
And I applauded you for admitting an error.
I also said that this was a good example of the kind of discussion that should occur… all these people did the math for you and clarified the physics involved.
But now, I am back to what I said originally: I have no clue what you (ABM) are still arguing about, whether because you are actually confused, or just communicating very poorly.
Maybe you could make a simple declarative sentence to say what you are trying to say? The point being that this helps focus your own thinking, and then, again, right or wrong, MAR, sidd, et al, can respond coherently.
Mike:Icebreaker is struggling to find stable ice to establish research station in the Arctic. I think this might be what Peter Wadhams saw coming.
I’ve always felt that Wadhams had a good chance of being correct about an ice free Arctic by 2020. Even if he’s off by a couple of years I would still say he was correct.
So Mal and Ray, if H2O has a self driven positive feedback, and it has the greatest greenhouse affect, what negative feedback counters this pre-man?
Large loss of CO2 in winter observed across the northern permafrost region
“Recent warming in the Arctic, which has been amplified during the winter1,2,3, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)4. However, the amount of CO2 released in winter is not known and has not been well represented by ecosystem models or empirically based estimates5,6. Here we synthesize regional in situ observations of CO2 flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662 TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (−1,032 TgC per year).”
https://www.nature.com/articles/s41558-019-0592-8
It’s happening now. I wish the facts were otherwise. This is going to have consequences for my kids and grandkids.
Bummer.
Mike
The largest negative feedback is outgoing LWR–as it always has been.
Keith Woollard @147,
Following you question up-thread @82, you respond to Ray Ladbury @92 (who descibes the changes of atmospheric H2O and any resulting temperature variation being determined by temperature and thus not independent of the factors that initiate those primary changes in temperature) and Mal Adapted @106 (who explains that the relationship between atmospheric H2O levels and temperature was understood back in the 19th century).
In your response you decribe this H2O feedback effect as “self-driven” and ask “What negative feedback counters this pre-man?” It appears plain to me that you fail to grasp the impact of the H2O feedback within the climate.
Imagine CO2 levels double. The direct result is an increase in global temperature of +1ºC. This increase results in extra H2O in the atmosphere, raising global temperature by a further +0.66ºC, a temperature increase which itself results in extra H2O in the atmosphere, raising global temperature by a further +0.44ºC and so on – a further +0.30ºC, +0.20ºC, +0.13ºC, +0.09ºC ans so on. These increases will reach a limit, adding +2.0ºC to the original +1ºC CO2 increase.
But now imagine the CO2 levels revert to the original level. All that additional atmospheric H2O is then rained away back to the original H2O level and the original global temperature is thus restored.
The sole functioning of H2O is to amplify any forced warming/cooling. This amplification has (to a greater or lesser extent) operated pre-AGW, pre-man, pre-whatever, all the way back to the formation of the Earth’s atmosphere.
This is a simplistic but robust description with no need to invoke ‘counteracting negative feedbacks’.