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Unforced Variations: Oct 2019

Filed under: — group @ 1 October 2019

This month’s open thread. Please try to stick to climate science topics.

151 Responses to “Unforced Variations: Oct 2019”

  1. 51

    RT 44: Is the Pillsbury Dough Mann moderating these comments? Is he in the State Penn or Penn State?

    BPL: Does your Mommy know you’re using her computer?

  2. 52
    zebra says:

    John Pollack,

    “philosophy”
    “because they aren’t exactly the same”
    “I’m interested in finding out how much and how fast”

    Well, in my universe, science is informed by philosophy… there’s that whole “Philosophy of Science” thing, right? But anyway, here, my questions seem perfectly relevant in the real world of science:

    -How precise a determination of “how much and how fast” are you looking for?
    -How exactly or inexactly does something have to match for you to characterize it as “not different”?

    There’s a famous philosophy of science term you might have heard… handwave. So far, that seems to be all you’re doing.

    You reference climate models that predict droughts. OK, what more do you want, in the way of “how much and how fast”? Can you explain what you think the 1930’s events tell us about those predictions, that hasn’t been incorporated into the models?

    Giving concrete answers would seem the obvious first steps if you sincerely want to advance the discussion.

  3. 53
    Alastair B. McDonald says:

    @39 Zebra wrote
    “… You agree that if we start with no radiation from the surface, we have only spontaneous radiation from CO2 molecules, which would be equally “up” and “down”. (For simplicity, ignoring all the other directions.)

    Now, we increase the surface radiation in increments. What is the formula by which we calculate “the ratio” of stimulated to spontaneous emissions?”

    I don’t really agree that there is no radiation from the surface. However, the formula you are asking for is the given by the Einstein relation:

    A21 = (2hv^3/c^2)B21

    where A21 is the coefficient of spontaneous emission, B21 is the coefficient of stimulated emission, (and B12 is the coefficient of absorption – Einstein spoke German, not English!), h is Planck’s constant, v is the frequency and c is the speed of light. The point is that spontaneous emission increases with the cube of the frequency.

    @42 MA Rogers cites a blogger Greypilgrim to argue that spontaneous emissions are greater than stimulated emissions at low frequencies, but he is contradicted by the mentor DrClaude.

    I will just add that laser emissions are stimulated emissions and it is generally believed that you need a laser to produce them, but that is not true. The CO2 laser is widely used because the CO2 frequencies are low enough to produce stimulated emissions.

  4. 54
    Rex Tasha says:

    51 Bartholomew Paul Leveson
    Hello Barty,

    Great comment, well thought out, I like to adjust my discourse to the level of the site. Looks like I miscalculated as the level is not strictly juvenile but contains a lot pseudo-scientific ego-boosting and you are one of the better ego-boosters.

    The talk of an 80-year cycle is interesting (I am ego-boosting here) please refer to Tony Heller to see how really hot it was in the 1930s. Looking forward to a witty reply.

    PS: My mommy gave me the computer for keeps.

  5. 55
    Rex Tasha says:

    I fail to see how the discussion of an 80-year cycle advances the cause. Everyone knows from the hockey stick that temperature has remained flat from 800 years ago until the current AGW. As the tipping point approaches this sort of rank speculation is borderline illegal.

  6. 56
    Al Bundy says:

    ABM: when a photon of the correct frequency collides with an excited molecule a second photon is emitted in the same direction as the first. In other words, both travel upwards.

    CCH: Photons are emitted randomly due to the increased energy state. Photons don’t know the direction the photon came from that increased the energy.

    AB: The direction of the “exciting” photon isn’t covered in ABM’s scenario. He’s talking about whacking an already-excited molecule.

    MAR: “there’s always much more spontaneous than stimulated emission.” As a result the photons emitted by GHG are predominantly any-which-way.

    AB: So CCH is talking about the practical and ABM is getting out his microscope so as to study minutia instead?
    _____________

    #38 John Pollack: the pattern is likely to repeat eventually

    zebra: Why? The climate system is very different now.

    AB: I read John’s “pattern” as a set of the similar (such as “Indian monsoon”) as opposed to “this exact pattern”. Did I read you right, John?

  7. 57
    Alastair B. McDonald says:

    @41 Ray Ladbury wrote

    “Alastair,
    We’ve been through this before. You don’t have the foggiest idea what you are talking about. If the only source of surface warming were TSI, then the night time temperature of the planet would be a whole helluvalot colder than any temperature ever recorded on Earth.

    Backradiation can be measured at the surface. Your argument is not with me, but with reality.”

    Ray,

    When I last raised this I got similar unscientific comments such as yours here. I was just hoping there that there might be someone here now who would discuss the science seriously.

    What temperature is a whole helluvalot colder in Kelvin? What about the temperatures recorded in Siberia or Antarctica? They are a lot colder than the temperature in your back yard, which does not fall to that level overnight because the surface is kept warm by the soil beneath, which is ultimately heated by the effect of geothermal heat.

    You are the one who should not confuse the theories used to produce computer models with reality.

  8. 58
    Al Bundy says:

    RT 44: Is the Pillsbury Dough Mann moderating these comments? Is he in the State Penn or Penn State?

    BPL: Does your Mommy know you’re using her computer?

    AB: OMG!!! It’s Mike Worth-a-Pence

  9. 59
    O. says:

    Two Interviews (german language):

    Klimaforscherin Fredi Otto über Extremwetterereignisse – Jung & Naiv: Folge 437

    Dr. Friederike Otto: Untersucht Auswirkungen des Klimawandels

    Interestingly, in the second interview, F. Otto mentions, that their models are calculated on a farm of private PCs. They use the BOINC-infrastructure.
    Sofar I have only seen BOINC-projects, which seemed not very interesting to me. This one does make sense to me.

    This is the page of the BOINC-climate-project:
    climateprediction.net

  10. 60
    Alastair B. McDonald says:

    Re #43

    Barton,

    Cloudless nights are not colder because more radiation is being lost from the surface. Since the surface is colder less radiation is being emitted. Cloudless nights are colder because there are no clouds to reemit blackbody radiation back to the Earth.

    Re #48
    CC Holley,
    You wrote:
    “Neither Saussure nor Fourier had any concept of a greenhouse gas.”
    No, but they did understand that the air is heated by the “greenhouse” effect.

    “Saussure made a device which was essentially a miniature greenhouse. He showed that it trapped solar heat from the sun; however, he had no explanation for why it did so.”

    In fact, he did. He conducted an experiment with a box with no sides which showed him that, since that did not warm the air, the reason the air got warmer in his box was because it trapped the air. This idea was also proposed by Proffesor R. W. Wood in 1909. See: http://www.wmconnolley.org.uk/sci/wood_rw.1909.html

    You then copied from an unattributed source a translation from Saussure Chapter 35, paragraph 933: “Physicists are not unanimous as to the nature of sunlight. Some regard it as the same element as fire, but in the state of its greatest purity. Others envisage it as an entity with a nature completely different from fire, and which, incapable of itself heating, has only the power to give an igneous fluid the movement which produces heat.” and commented that “Saussure lived at a time when scientists were just starting to study the nature of heat. He had no clue as to the difference between infrared and short wave radiation.”
    That is untrue! In fact, if your excerpt had been continued you would have found that Saussure reports an experiment which he conducted with M. Pictet that showed obscure heat (IR radiation) could be transmitted between concave mirrors. His hot box was not a model of the Earth’s atmosphere. He used it as a helio-thermometer to show that solar radiation at the top of a mountain was only slightly greater than that on the plains below, i.e. solar radiation is only slightly absorbed by air. It is the obscure heat from the surface of the Earth which warms the air where we live.

    You can read it all, in his own words, here.

    If your source is “Let It Shine: The 6,000-Year Story of Solar Energy” by John Perlin I have to warn you it contains several misconceptions.

  11. 61
    Alastair B. McDonald says:

    Re Brian Dodge @49
    You wrote:
    “There is the small matter of relaxation time between when the molecule absorbs a photon and becomes excited, and the time it emits a photon. How does the molecule remember which way the photon was going when it was absorbed?”

    It doesn’t. That results in a spontaneous emission, or if that does not happen before a second photon arrives, a stimulated emission occurs (with no relaxation time I guess). The greenhouse molecules can also become excited as the result of a collision with another molecule.

  12. 62
    nigelj says:

    Alastair B. McDonald @60

    “Cloudless nights are not colder because more radiation is being lost from the surface. Since the surface is colder less radiation is being emitted. Cloudless nights are colder because there are no clouds to reemit blackbody radiation back to the Earth.”

    This is patently ridiculous. I do not have a science degree but I know enough and have enough sense to see the holes in this reasoning. During the day the sun warms the ground along with some energy from greenhouse gases, yes? At night the ground is not “cold” it glows with invisible infra red energy. Basic physics says hot things give up their energy. This energy heats the air, and if there are no clouds, more escapes to space so the clear nights are colder than cloudy nights. Stop wasting time debating the basics.

  13. 63
    MA Rodger says:

    Alastair B. McDonald @53,
    You set out the equation:-

    A21 = (2hv^3/c^2)B21

    where A21 is the coefficient of spontaneous emission, B21 is the coefficient of stimulated emission. We should perhaps fill in the rest of it which I make as h = Planck’s constant = 6.6e-34 Js, v = frequency = [for 15 microns] 2.0e+13 Hz, c = speed of light = 3.0e+8 m/s.

    This equation is a little different thn the one presented on this Wikithing page of Einstein’s Coefficients which gives A21/B21 = F(v) = 8πhv^3/c^2. And I would add that I am entirely unfamiliar with the derivation of these equations.
    (I can only repeat that these equations apply to a gas in equilibrium, thus the total emissions (spontaneous & stimulated) will equal the absorption.)
    So I know not whether this equation is being mis-applied to the GHG actions in our atmosphere. A further consideration is deriving the correct form of the equation from the alternatives. (We are not alone in finding this untrivial. This webpage discusses the same and finds three entirely different versions, this even though it uses one of our references!!)

    Yet this does not prevent us calculating the ratio A21/B21. (Here I assume either that our two derivations are correct or that the large difference presented by the webpage discussion cited above is of no significance – they increase the 8 x 10^9 below to either 3 x 10^18 or 1 x 10^45 yet the answer for our purpose is the same – they are all exceedingy big numbers.) If my trusty abacus has not lost any more beads, I make A21/B21 (as per that @53, the different equation from Wikithing will not make a great difference) = 1.2e-10. Thus for every spontaneously emitted photon there will be about eight billion stimuated photons, presumably the consequence of that initial spontaneous emission.

    Now the pathlength of a 15 micron photon in the lower atmosphere is of the order of 1m. The atmosphere is roughly 10,000m deep. A photon emitted from the surface would be absorbed (B12) within 1m but, in doing so, it will be responsible for 8 x 10^9 stimulated photons. Now this may suggest that this resulting stimulation would propagate through successive re-stimulations up and out of the top of the atmosphere. Yet there is no evidence for this.
    And as well as the surface, there is also the any-which-way spontaneous emissions from the CO2 in the atmosphere which will also be generating 8 x 10^9 stimulated emissions. So would the 8 x 10^9 stimulated photons propagate for a distance of several kms with the atmosphere? If they do, the atmosphere’s downward spontaneous emissions would be contributing to a very healthy back-radiation.
    There are measurements of these IR fluxes in the atmosphere. Do they support this massive stimulated propagation? Or do we have a misunderstanding of the equations being derived from the phyics? Or, heaven forfend, have we stumbled across a problem with the physical theory?

  14. 64
    zebra says:

    #53 Alastair B McDonald,

    Ok, I see the problem. You seem to be confusing the coefficients with the actual rates of emissions.

    Using classical terms for simplicity:

    1. The ratio of spontaneous/stimulated emissions (SP/ST) is dependent on the number of atoms in the excited state and the number of photons incident on them. More photons, more ST.

    2. The number of atoms in the excited state is determined by both incident radiation and excitation by collisions, and the decay rate.

    But the ratio A21/B21 is simply a constant for all those calculations.

    If you still think it is relevant, perhaps you could show the math that leads to your conclusion?

  15. 65
    zebra says:

    #56 Al Bundy,

    AB, the 1930’s was an extreme phenomenon that occurred once, and the monsoon happens every year, so no, it isn’t the same.

    In the near term, we expect phenomena like the monsoon to undergo extreme excursions as we move away from the original equilibrium state… but it is still identifiable as “the monsoon”.

    Are you going to predict (absent a model) that in 80 years, if we keep producing CO2 at the current rate, there will still be a recognizable ‘monsoon’?

    When he says

    The pattern is likely to repeat eventually, since there were even worse megadroughts in the pre-industrial period. When it does, the extra 100+ ppm of CO2 will result in even more intense heat and drought,

    it implies that we are not in fact changing the climate.

  16. 66

    RT 54: please refer to Tony Heller

    BPL: The day I need that crackpot to tell me anything I’ll just check into a mental hospital, thank you very much.

  17. 67
    Mal Adapted says:

    “Rex Tasha”: LMGTFY.

  18. 68
    mike says:

    CO2 levels dropping back in the 2.5 ppm increase range at this moment.
    Last Week

    Sep. 29 – Oct. 5, 2019 407.96 ppm 2.47 ppm over this week 2019
    Sep. 29 – Oct. 5, 2018 405.49 ppm 24.11 ppm over this week in 2009
    Sep. 29 – Oct. 5, 2009 383.85 ppm

    Waiting on Sept monthly numbers, not posted yet at co2.earth

    What does it mean? More CO2, more heat for the thousands of years that these new emissions will remain in the atmosphere (unless we actually deploy a technology that will remove CO2 from oceans or atmosphere).

    Warm regards,

    Mike

  19. 69
    Mr. Know It All says:

    53 – ABM
    “A21 = (2hv^3/c^2)B21

    where A21 is the coefficient of spontaneous emission, B21 is the coefficient of stimulated emission, (and B12 is the coefficient of absorption – Einstein spoke German, not English!),…”

    Your equation does not have a “B12” term.

    60 – ABM
    “Cloudless nights are not colder because more radiation is being lost from the surface. Since the surface is colder less radiation is being emitted. Cloudless nights are colder because there are no clouds to reemit blackbody radiation back to the Earth.”

    That is not my understanding of how radiation heat transfer works. On a clear night, the surface can “see” (radiate to) the cold, black sky at what, -250F (wild guess)? Because the rate of heat transfer is proportional to the 4th power of the temperature difference, the rate of heat transfer is higher than on a cloudy night. On a cloudy night, the surface can only “see” the clouds which aren’t very cold compared to the black void of space, resulting in a lower rate of heat transfer.

    61 – ABM
    Here’s a 5 minute video explaining how CO2 emits photons:
    https://www.youtube.com/watch?v=-EJOO3xAjTk

  20. 70
    Steven Emmerson says:

    ABM@53 wrote:

    The point is that spontaneous emission increases with the cube of the frequency.

    .(LMGTFY) This is true but irrelevant as a far more comprehensive analysis finds that

    Under conditions as found in the troposphere with collision rates between molecules of several 109 s−1, any induced transition rate due to the thermal background radiation is orders of magnitude smaller [emphasis mine], and even up to the stratosphere and mesosphere, most of the transitions are caused by collisions, so that above all they determine the population of the states and in any case ensure a fast adjustment of a local thermodynamic equilibrium in the gas.

    (in this context, “induced” is a synonym for “stimulated”), and

    An asymmetry in the up- and downwelling eigen radiation (only from atmosphere) will be found with a stronger contribution in downward direction, which is caused by the lapse rate as well as the density profile over the atmosphere with higher temperature and pressure at lower atmospheric layers and therefore a higher net downward radiation.

  21. 71
    Hank Roberts says:

    DSCOVR Satellite Could be Revived With Software Fix in 2020 |
    | from the there’s-life-in-the-old-satellite-yet dept. |
    | posted by janrinok on Sunday October 06, @16:29 (Science) |
    | https://soylentnews.org/article.pl?sid=19/10/06/0710232 |
    +————————————————————————-+

    [0]takyon writes:

    [1]Software fix planned to restore DSCOVR

    A space weather and Earth observation satellite that has been offline for more than three months could be restored to normal operations with new software, but that fix is not expected to be completed until early next year.

    In a Sept. 30 statement, the National Oceanic and Atmospheric Administration said that it has been working with NASA and an unnamed company on a “software fix” to restore the Deep Space Climate Observatory, or DSCOVR, [2]which went into a “safehold” June 27.

    Those efforts, the agency said, are making progress, but it doesn’t expect DSCOVR to resume operations soon. “Engineers report that intermediate test results of the software fix have been positive and they expect it to be incorporated during the first quarter of calendar year 2020,” NOAA said in its statement.

    [3]Deep Space Climate Observatory.

  22. 72
    John Pollack says:

    Al Bundy @56 Yes, you read me right. The pattern I was referring to is something similar but not identical to something that happened at a previous time. For example, a multi-year North American mid-continental drought. We had one in the 1930s, and a weaker one in the 1950s. There were also fairly intense droughts in 1988 and 2012 that didn’t become multi-year. The records established in the 1930s were really extreme. If we ran the same general pattern with another 110ppm of CO2 in the atmosphere, it could get hot and dry beyond the imagination of people who haven’t looked at the old records.

  23. 73
    John Pollack says:

    Zebra @65 I most certainly am saying that we are changing the climate. However, I do not see any evidence that we are changing it in such a way as to eliminate the development of meridional standing waves that tend to repeat their position over time. In the past, these have set up at a variety of longitudes, and for a variety of time periods. We are still seeing this occur. Mid-continental North American droughts still develop, such as in 2012. Do you seriously believe that we have seen the last of the mid-continental droughts (as opposed to droughts in the West or Southeast), due to climate change?

  24. 74
    sidd says:

    That factor of 8*pi*H*nu^3/c^2 is simply the energy density in the window nu to nu + d(nu)

    The expression is commonly seen in terms of the fifth power of inverse wavelength but two powers of lambda get eaten in the conversion from d(lambda) to d(nu). Alas, for my sins, i am quite familiar with the derivation.

    Mr. MacDonald would benefit from working through the radiation calculations in our host Prof. Pierrehumbert’s excellent book on atmospheres. But I doubt it. He has been flogging the same arguments for many years now on this and other fora.

    sidd

  25. 75
    sidd says:

    I should correct my previous comment:

    the energy density is 8*pi*nu^2/c^3 in the window from nu to nu + d(nu)

    but it gets multiplied by the energy of a photon of frequency nu

    E(nu) = h*nu

    giving you that extra factor of nu and an h

    sidd

  26. 76
    sidd says:

    I should correct and extend my previous comment:

    the number of radiation modes per unit volume is 8*pi*nu^2/c^3 in the frequency window from nu to nu + d(nu)

    to get an energy per unit volume in that frequency interval from nu to nu+ d(nu) multiply by the energy of a photon of frequency nu

    E(nu) = h*nu

    giving you that extra factor of nu and an h

    (This is a “real” energy if every mode were occupied by exactly one photon. But photons are bose einstein, so one must multiply by the BE factor 1/(exp((h*nu)/(k*T)) – 1) to get the actual energy per unit volume per unit frequency in blackbody radiation )

    So the ratio of the A and B coefficients is just the energy density per unit volume per unit frequency interval at frequency nu assuming that each allowable mode were occupied by one photon.

    got to be careful here A and B do _not_ have the same units. so the ratio is not dimensionless

    sidd

  27. 77
    Alastair B. McDonald says:

    Re Nigel @62 Who wrote:

    “This is patently ridiculous. I do not have a science degree but I know enough and have enough sense to see the holes in this reasoning. During the day the sun warms the ground along with some energy from greenhouse gases, yes? At night the ground is not “cold” it glows with invisible infra red energy. Basic physics says hot things give up their energy. This energy heats the air, and if there are no clouds, more escapes to space so the clear nights are colder than cloudy nights. Stop wasting time debating the basics.”

    Thank you Nigel. That is good advice. I will “stop wasting time debating the basics” with people who do not understand science.

  28. 78
    Alastair B. McDonald says:

    Ee #69 where Mr. Know It All says:

    53 – ABM
    “A21 = (2hv^3/c^2)B21

    where A21 is the coefficient of spontaneous emission, B21 is the coefficient of stimulated emission, (and B12 is the coefficient of absorption – Einstein spoke German, not English!),…”

    Your equation does not have a “B12” term.

    ABM Yes, because that is the coefficient of absorption.

    60 – ABM
    “Cloudless nights are not colder because more radiation is being lost from the surface. Since the surface is colder less radiation is being emitted. Cloudless nights are colder because there are no clouds to reemit blackbody radiation back to the Earth.”

    That is not my understanding of how radiation heat transfer works. On a clear night, the surface can “see” (radiate to) the cold, black sky at what, -250F (wild guess)? Because the rate of heat transfer is proportional to the 4th power of the temperature difference, the rate of heat transfer is higher than on a cloudy night. On a cloudy night, the surface can only “see” the clouds which aren’t very cold compared to the black void of space, resulting in a lower rate of heat transfer.

    ABM Sorry, but I have promised Nigel to stop wasting my time debating the basic.

    61 – ABM
    Here’s a 5 minute video explaining how CO2 emits photons:
    https://www.youtube.com/watch?v=-EJOO3xAjTk

    It is wrong. It does not mention that if an excited CO2 molecule is hit by a photon it will emit two photons, called stimulated emission. The CO2 in the atmosphere is excited by collisions with other air molecules (as well as by photons), with the result that most CO2 emissions near the Earth’s surface are stimulated emissions.

  29. 79
    Alastair B. McDonald says:

    Re #70 where Steven Emmerson says:

    ABM@53 wrote:

    The point is that spontaneous emission increases with the cube of the frequency.

    SE @70 (LMGTFY) This is true but irrelevant as a far more comprehensive analysis finds that

    Under conditions as found in the troposphere with collision rates between molecules of several 10^9 s−1, any induced transition rate due to the thermal background radiation is orders of magnitude smaller [emphasis mine], and even up to the stratosphere and mesosphere, most of the transitions are caused by collisions, so that above all they determine the population of the states and in any case ensure a fast adjustment of a local thermodynamic equilibrium in the gas.

    ABM All that’s Googled is not Gold [A. B. McDonald, 2019]). Your quote is by Hermann Harde who has already been exposed for junk science. See Hard Times.
    But what he is saying is that molecules are mainly excited by collisions rather than by the absorption of stimulated emissions. He does not seem to regard the absorption of spontaneous emissions as significant.

    SE @70 (in this context, “induced” is a synonym for “stimulated”), and

    An asymmetry in the up- and downwelling eigen radiation (only from atmosphere) will be found with a stronger contribution in downward direction, which is caused by the lapse rate as well as the density profile over the atmosphere with higher temperature and pressure at lower atmospheric layers and therefore a higher net downward radiation.

    ABM I think he has got that wrong. 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.

  30. 80
    Alastair B. McDonald says:

    Re Zebra @64 who wrote: “If you still think it is relevant, perhaps you could show the math that leads to your conclusion?”

    Rather than do the maths which is complicated, I will just give you a quote from Atkins Physical Chemistry Eighth Edition page 435:

    The growth of the importance of spontaneous emission with increasing frequency is a very important conclusion, as we shall see when we consider the operation of lasers (Section 14.5). The equality of the coefficients of stimulated emission and absorption implies that, if two states happen to have equal populations, then the rate of stimulated emission is equal to the rate of stimulated absorption, and there is then no net absorption.

    Spontaneous emission 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 emission and absorption. Then the net rate of absorption is given by Wnet = NBρ − N′B′ρ = (N − N′)Bρ (13.12)and is proportional to the population difference of the two states involved in the transition.

    Water vapour and carbon dioxide are both excited into rotational and vibrational states. Electronic excitation is not relevant at terrestrial radiation frequencies.

  31. 81
    mike says:

    September monthly CO2 numbers from CO2.earth:

    September CO2

    Sep. 2019: 408.55 ppm
    Sep. 2018: 405.59 ppm

    looks like 2.96 ppm increase. Monthlies are noisy generally, but I don’t think there is much ENSO type wobble in the comparison of 2018 and 2019, so I think the increase is probably pretty close to the background rate at this time. Pretty close imo would be plus or minus 0.2 ppm

    More CO2 equals more heat. I think that equation is generally settled science.

    Cheers

    Mike

  32. 82
    nigelj says:

    zebra @65 posts some stuff:

    “The pattern is likely to repeat eventually, since there were even worse megadroughts in the pre-industrial period. When it does, the extra 100+ ppm of CO2 will result in even more intense heat and drought,”

    “it implies that we are not in fact changing the climate.”

    I do not see how climate change would be inconsistent with a continuing cycle of mega droughts (which climate change would probably further amplify). My understanding as a layperson is climate change is defined as an increase in global temperatures that is of more than 30 years duration (so its not just a short term cycle). If that’s the case, its hard to see intuitively why a temperature increase of 1 or 2 degree c will stop existing natural cycles like megadroughts. It’s not clear what causes mega droughts, but droughts in places like N America can have multiple causes including hot el nino years. There is no evidence el ninos are decreasing in any way, and the opposite seems more likely in a warming climate.

    Droughts are related to convective processes that are not obviously going to be decreasing, and droughts sometimes relate to blocking highs with some evidence these may actually increase in frequency. I stand to be corrected. Droughts also relate to human activity but that is a separate issue. Climate is changing and theres no evidence this means established mega drought cycles would change significantly in their fundamental nature, and plenty of evidence they would get more intense.

  33. 83
    Keith Woollard says:

    OK, genuine scientific question… if there is a positive feedback from increasing CO2, then why isn’t there one for increasing H2O?

    [Response: But there is. -gavin]

  34. 84
    Chuck says:

    Rex Tasha says:
    6 Oct 2019 at 1:34 PM

    Wow! Another idiot troll. Somebody opened the flood gates. I guess that’s what happens when the “president” attacks the scientific community and declares Climate Change a “Chinese hoax”.

  35. 85
    Al Bundy says:

    Alistair B. McDonald: Cloudless nights are not colder because more radiation is being lost from the surface. Since the surface is colder less radiation is being emitted. Cloudless nights are colder because there are no clouds to reemit blackbody radiation back to the Earth.

    nigelj: At night the ground is not “cold” it glows with invisible infra red energy. Basic physics says hot things give up their energy. This energy heats the air, and if there are no clouds, more escapes to space so the clear nights are colder than cloudy nights. Stop wasting time debating the basics.

    AB: “colder” does not equal “cold”. Please quote accurately. ABM is right. Ignoring that weather systems move, if it is 70F at 6PM on a clear day then the Earth’s surface will be colder at midnight than it would be if it were cloudy.

    And the rest of your comment is just parroting Alistair while missing that you agree with him – the clouds and other extra H2O during cloudy conditions absorb more of the Earth’s surface’s radiation (and those clouds and GHGs heat the air)

    KIA, the temperature of the clouds or the sky has nothing to do with how much the Earth radiates. You’re looking at net, which obscures everything we’re talking about. Note that if you stand next to a fire you will warm said fire (assuming environmental temperature is below your body temperature). And your link only discusses one type of emission instead of two.

    And here is a situation where the scientists should weigh in. With a rational comment system that would happen.
    ________

    zebra: Are you going to predict (absent a model) that in 80 years, if we keep producing CO2 at the current rate, there will still be a recognizable ‘monsoon’?

    AB: No. And you’re getting hung up on an irrelevant factoid. The return rate and predictability of a weather pattern (monsoons fail) is way beyond the scope of my point. Perhaps “a 500 year storm per current conditions (as opposed to what used to be normal)” works better for you.

    zebra: When he says

    The pattern is likely to repeat eventually, since there were even worse megadroughts in the pre-industrial period. When it does, the extra 100+ ppm of CO2 will result in even more intense heat and drought,

    it implies that we are not in fact changing the climate.

    AB: I took his comment much softer than you did, using context and flavor to interpret his point as “something will spike sometime”, especially since he used a reference to a long-gone climate regime to nail down his point. You interpreted the post to mean a specific spike. Both stances “work”, which is why I asked the source himself.

  36. 86
    Brian Dodge says:

    In followup to my comment 3 Oct 2019 at 6:56 PM, I was asked a question on Facebook in a discussion about the “enormous Antarctic Glacier on the verge of collapse” news reports, and my reply is below – any comments?
    Anonymous – Height of the ice shelf over these underwater cavities determines structural collapse, doesn’t it?
    Brian Dodge Yes. initially, the Ice sheet is supported structurally by bedrock, As the cavity grows(below sea level, the isostatic pressure from the intruding water gradually replaces the mechanical support from grounding.As the top of the cavity grows towards sea level, the pressure drops towards zero, so all the ice mass above sea levelhas to be supported by mechanical stress distributed through the ice sheet, either compressive stress, like an arch, or bending stress, like in a beam. How much each contributes depends on the aspect ratio and shape of the ice roof over the cavity. The ratio of the mass of the roof above sea level to the mass below sea level determines how much stress has to be carried by mechanical stress in the ice. if there is ~nine times the mass below sea level as there is above, then water pressure supports the mass. Since the dynamic sea level varies tidally, with waves, and with winds “piling” up” water against the coast, there is a zone where the ice is sometimes resting on bedrock, and sometimes floating. and in fact the grounding line moves back and forth several kilometers with the tides, something not yet built into the models. Where the bed is retrograde, the grounding line moves forth and back; this change in sign means the melting forces are now fighting a downhill battle. The tidal flow, the pumping action, probably increases the melt, but the devil is in the details. The ice sheet might be plastic enough that is just slumps into the cavity as is melts from below, or it might sustain stresses until it collapses spectacularly.
    https://climatesight.files.wordpress.com/…/retrograde…
    “For simple scalings, the comparison to the coupled framework shows that a quadratic as opposed to linear dependency on thermal forcing is required.” and that’s with a prograde bed
    https://www.researchgate.net/…/Initial-ice-sheet-in…
    https://www.youtube.com/watch?v=hC3VTgIPoGU
    https://www.youtube.com/watch?v=9lkh7TEsX2E [note the sound change about 38 seconds in]

  37. 87
    Alastair B. McDonald says:

    Re #63

    MA Rodgers,

    Thank you for your comments. It is nice to have someone who does not treat me like an idiot.

    As regards your post, I do not want to get into this too deeply. Quantum mechanics is very complicated, and I have another project which is more urgent. But I will make a few points about your post.

    There are actually two equations called the Einstein relations. They are roughly:
    A21 = (2hv^3/c^2)B21
    and
    g1A12 = g2B21
    As you point out at equilibrium absorption = emission but this is not true in the boundary layer in the lowest part of the atmosphere where the temperature rises during the day and falls during the night. Above the boundary layer, i.e. upper troposphere etc, the atmosphere is in a state of local thermodynamic equilibrium (LTE).

    Your path length for a photon is, I suspect, between air molecules but for stimulated emission, it is the distance between excited CO2 molecules. Moreover, as you rise in the atmosphere the density decreases so this distance will expand even further.

    Molecules can also be excited by collisions with other molecules, so the spontaneous emissions will depend on the temperature of the air.

    Hope this helps,

    Cheers, Alastair.

  38. 88
    Kevin Donald McKinney says:

    #69–

    ABM: Cloudless nights are colder because there are no clouds to reemit blackbody radiation back to the Earth.

    KIA: On a clear night, the surface can “see” (radiate to) the cold, black sky at what, -250F (wild guess)? Because the rate of heat transfer is proportional to the 4th power of the temperature difference, the rate of heat transfer is higher than on a cloudy night.

    These statements are functionally equivalent, as I understand it. What the surface “sees” is incoming radiation, either from interstellar space at ~3 K or from cloud (at whatever altitude.)

    I’ve mentioned it before, but the first systematic observations that I’m aware of go back to the early years of the 19th century, and the researches into dew by William Charles Wells, originally of Charleston, SC:

    https://hubpages.com/education/Global-Warming-Science-In-The-Age-Of-Washington-And-Jefferson-William-Charles-Wells

  39. 89
    Killian says:

    How ironic the first direct quote from anyone I can remember that echos my comments over the years re risk comes from JP Morgan.

    Sad, really.

    But all of that analysis may be deficient, they indicated.

    “The economics of climate change is really in the tails of the probability distribution, and in the risk of disastrous outcomes,” they wrote.

    https://www.yahoo.com/finance/news/jpmorgan-economists-warn-black-swan-014559065.html

  40. 90
    Geoff Beacon says:

    I’ve seen this twitter thread with Yue Dong and Gavin Foster in it, presenting results from the CMIP5 models and CMIP6 models.

    @TheFosterLab

    It shows the more recent CMIP6 models running hotter than the CMIP5 models. Can anything straightforward be said about this?

    I was wondering about feedbacks missing in the earlier models but I suspect that’s too simplistic.

    Help!

  41. 91
    Al Bundy says:

    Barry,
    It’s obvious that the parties are (deliberately?) Missing each other’s points. But ABM seems to be saying that for CO2 stimulated emissions dominate, so it takes a CO2 resonating “hit” on a CO2 molecule to get said CO2 molecule to emit, and since that emission will be in exactly the direction as the hitter, CO2 can either direct energy towards space OR have its energy contributed to atmospheric temperature via collisions, in which case OTHER molecules provide back radiation.

    Others have said that spontaneous emissions dominate.

    I just wish the people involved would stop stuffing cotton and wax in their ears while shouting, “I can’t hear you”

  42. 92
    Ray Ladbury says:

    Keith Woolard@83: “OK, genuine scientific question… if there is a positive feedback from increasing CO2, then why isn’t there one for increasing H2O?”

    There is! And it’s in the models. However, H2O content is determined (largely) by the temperature, so it, and the resulting feedback are best handled as a feedback to the independent variable–increasing CO2.

  43. 93
    zebra says:

    #80 Alastair B McDonald,

    You thanked MAR for not treating you like an idiot. I’m not treating you like an idiot, but I am treating you as someone who is not communicating very well, and trying to help get your position (right or wrong) articulated more clearly.

    So far, I understand that you believe, (contrary to empirical evidence as far as I know), that downward radiation at the wavelengths associated with CO2 is not greater than that escaping to space.

    What I asked was for you to explain the relevance of the equation you gave. You haven’t done that. We’re talking about a specific wavelength, so bringing up higher frequencies isn’t particularly useful. Your citation simply confirms what I said, which is that the populations of states and the incident radiation determine the net effect.

    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.

  44. 94
    zebra says:

    #73 John Pollack, also Al Bundy,

    JP, in case you missed my earlier response at #52:

    You reference climate models that predict droughts. OK, what more do you want, in the way of “how much and how fast”? Can you explain what you think the 1930’s events tell us about those predictions, that hasn’t been incorporated into the models?

    Giving concrete answers would seem the obvious first steps if you sincerely want to advance the discussion.

    AB, we have models. The people who write the models probably know way more about the 1930’s conditions than anyone here. And, they…you know…write the freakin’ models.

    What JP is dodging is the same question as with the hurricane/parallel Earth scenario. What kind of precision are we talking about?

    “Big droughts will probably occur”.

    Yeah, duh, so what? “Big”? “Drought”? Meaningless.

    I thought we were all trying to do the warrants thing, eh?

  45. 95
    Mr. Know It All says:

    91 – Al Bundy

    I am not shouting at anyone. In comment 69, I did give my understanding of why clear nights are colder. I may have gotten it wrong. This phenomenon is one of the basics of AGW. If people HERE don’t understand it, why would the man on the street believe them?

    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, the thermal radiation physics, etc that occurs between the surface of the earth and outer space, including in every layer of the atmosphere. I’ve been asking for that info since day 1, and have yet to see it clearly spelled out. Perhaps it is too complicated for a non-physicist to understand? I don’t know. Is there a physicist reading this who can help us to understand the basis of AGW? Not a child’s diagram showing earth’s energy balance. I’m talking the math, physics, and chemistry for each layer from the surface to deep space.

  46. 96
    Russell says:

    “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 ”

    Stop playing the village ignoramus and read a bloody textbook.

    The one by RC contributor Ray Pierrehumbert has been available online for longer than you’ve been complaining . Who knows, you might even inspire Al and Bill to follow suit.

  47. 97
    Ray Ladbury says:

    Mr. KIA, The fact that you haven’t found it doesn’t mean it hasn’t been done. It has…repeatedly. Every global climate model is an example of such a complete explanation. I am not sure what it is that you are missing.

    1) Do you understand the incoming energy coming from the Sun? If not, what is confusing you?
    2) Do you understand how the sunlight heats the planet’s surface–both ocean and land? If not, where are you getting lost?
    3)Do you understand that a material, heated to a particular temperature, radiates with a spectrum that approximates a black body at the same temperature? (Note: there are subtleties here. There are no true black bodies, and there is no black body radiation that doesn’t obey the quantum mechanical rules for emission and absorption of the material. And so on.) Make sure you understand this.
    4)Do you understand that the temperature of Earth means that it is radiating predominantly in the infrared?
    5) Do you understand the cooling of the atmosphere up to the stratosphere with altitude and the fact that each higher layer radiates with a lower temperature black body spectrum than the one below it?
    6) Do you understand the absorption of outgoing IR radiation by greenhouse gasses and how this stops that radiation from leaving Earth?
    7) Do you understand the processes by which a CO2 molecule relaxes after having been excited by an IR photon? There are subtleties here. The excited vibrational state of CO2 is relatively long-lived (~microseconds), so there is a reasonable probability that it will relax by means of a collision with another non-greenhouse gas molecule before it relaxes by emitting an IR photon. In this manner, CO2 equilibrates with the other gasses in the atmosphere.
    8) Do you understand that the layer of gas where the IR photon was absorbed is cooler than the surface–so it will emit less IR radiation than did the surface?

    If you can get this far, you will probably understand the basic physics. There is more–for instance how back-radiation heats the ocean. But the above summarizes the basics unless I am forgetting something important (and I am confident my colleagues will correct me if I have).

  48. 98
    nigelj says:

    Al Bundy @85, while it pains me to say this, like extracting one of my own teeth with pliers, with no anaesthetic other than a lot of alcohol, I may have misinterpreted AMs comment on the greenhouse effect at night:(

  49. 99
    Brian Dodge says:

    “Your path length for a photon is, I suspect, between air molecules but for stimulated emission, it is the distance between excited CO2 molecules.”
    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 an be absorbed versus the probability that it will hit an excited CO2 molecule and cause stimulated emission? Did Herr J. Koch measure the temperature required in a column of air so that it produced 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 an cause stimulate emission? What’s the probability that an excited CO2 molecules will collide with another molecule, and convert that store energy to heat?

  50. 100
    nigelj says:

    Mr KIA @95, the details of the greenhouse effect and how it works in our atmosphere are really complex. Have a look at a climate model and there are dozens of differential equations etcetera and advanced physics. I can see what they are trying to do and how the energy balance equations work generally, but most of it is beyond me because I havent studied it at that level.

    This stuff can’t be simplified very much. I’ve said it before you either have to trust the experts, or do a physics degree or read a few textbooks. Of course a lay person can get quite a reasonable undertstanding of the basics, but wont fully undertand all the details and maths no matter how smart they are. Theres no substitute for studying the subject. No criticism of yourself intended.

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