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Unforced variations: Aug 2014

Filed under: — group @ 5 August 2014

This month’s open thread. Keeping track of the Arctic sea ice minimum is interesting but there should be plenty of other climate science topics to discuss (if people can get past the hype about the Ebola outbreak or imaginary claims about anomalous thrusting). As with last month, pleas no discussion of mitigation strategies – it unfortunately does not bring out the best in the commentariat.

222 Responses to “Unforced variations: Aug 2014”

  1. 201
    Chuck Hughes says:

    This series is in two parts. Bill Moyers interviews Dr. David Suzuki about the perils of Climate Change and the war on Climate Scientists. None of this sounds good to me.

    Part I:

    https://www.youtube.com/watch?v=rA-fNEhOUgw

    Part II:

    https://www.youtube.com/watch?v=mnSicq6Y1lY

    Part two is where Suzuki explains the general consensus amongst Climate Scientists and that most have said it is too late to do much. I know that we’re hoping for “the least worst outcome” and the sooner we act the better. I get that. I don’t like this notion that Climate Scientists are being muzzled. That makes my blood boil.

    David Suzuki hosted “The Nature of Things” for over 30 years and he’s taken on a variety of industries and stopped several corporations from destroying our natural resources but as he states, it’s a losing battle. I would like to hear an unvarnished opinion or two outlining the reality we’re currently faced with. I’m pretty sure I already have a good grasp of the situation but still….

    I would gladly volunteer my time and services if I knew what to do. Consequences be damned. If what David Suzuki is saying is correct I don’t see that speaking out makes much difference. I’d much rather go down fighting than throw up my hands. I welcome any straight forward opinions or corrections as to my take on what Dr. Suzuki is saying. Maybe some of you with experience can help me put this into context. Thanks.

  2. 202
    MARodger says:

    Hank Roberts @198.
    Your link to that blog comment is here.
    The commenter at that link you quote is using the words “cooling trend” but this is as ambiguous as Ruddiman et al. using the words “early anthropogenic warming.”

    The work being discussed (Liu et al 2014) shows models and proxies in disagreement over the holocene. If the speculated summer bias as proposed proves correct, the proxy record with its “cooling trend” would need to be shifted downwards compared with the instrument record. That would make Shakun’s holocene hockey stick even more dramatic than it is at present. And the ice albedo feedback is well known not to work so well in the models. So its a brave man who puts all his faith in a model’s ability to show a deglaciation accurately.
    Given that, I think it’s safe to say that the “cooling trend” isn’t in itself in any way “kind of up for debate.”

    And Ruddiman’s theories are of course contorversial. This is not helped by (for instance in the paper linked @198) talking of “early anthropogenic warming.” Surely this is actually ‘anthropogenic non-cooling’ whose size results from (I would assume) large ice-albedo feedbacks not occurring due to a small early anthropogenic boosting of GHG levels. It is safe to call them small (although massive per capita if they are anthropogenic) as the additional “40 ppm for CO2 and at least 250 ppb for methane” argued as the drivers of pre-industrial anthorpgenic positive forcings do not come anywhere close to the post-industrial increases.

  3. 203
    Radge Havers says:

    Chuck,

    Speaking as somebody on the Internet, I can tell you it’s quite a pickle. Our society apparently has a whole lot of inertia built into it. In other words you’re looking at initiating timely punctuated equilibrium. Put that way, in terms of planetary evolution (including geologic time, the average thickness of the human head and whatnot) you have an indication of the scale and difficulty of the problem in my estimation. It’s doubtful that there’s any real clarity to be found. Anywhere. It’s damn near an Existentialist issue. So we do our best.

    If you want something unvarnished, try this: there is no happy ending. None.

    Maybe a life well lived if you’re fortunate.

    —-
    RECAPTCHA: eccentric tskabot

  4. 204
    Killian says:

    Chuck Hughes said I would gladly volunteer my time and services if I knew what to do. Consequences be damned.

    As far as what to do, contact me. I’m happy to post e-mail here, if needed. I would post on it, but mitigation, which is what “what to do” means, is still banned on these fora, so far as I know.

  5. 205
    Meow says:

    @192: Congratulations, you have (not) discovered the force that prevents the atmosphere from collapsing into a molecularly-thin layer on the surface.

    For the details, let’s start with Trenberth et al’s canonical energy balance diagram [1], and assume that the atmosphere is in thermal equilibrium.

    That diagram shows the atmosphere receiving 356 W/m^2 from the surface via radiation, 17 W/m^2 via thermals, and 80 W/m^2 via latent heat. At the same time, the atmosphere receives 78 W/m^2 from absorption of incoming solar radiation. That totals 531 W/m^2. Since the atmosphere is in thermal equilibrium, it must somehow lose all that heat. It does so by emitting 333 W/m^2 to the surface and 199 W/m^2 to space, which totals 532 W/m^2. Accounting for rounding, the atmosphere is thus in energy balance.

    But what about radiation pressure? Isn’t there a net upward pressure? Yes indeed. It’s the pressure resulting from the emission difference of 356 W/m^2 (absorption from surface: pressure upward) – 78 W/m^2 (absorption from sun: pressure downward) – 199 W/m^2 (emission to space: pressure downward) + 333 W/m^2 (emission to surface: pressure upward) = 412 W/m^2.

    What is that pressure? Let’s start by converting the emission difference (412 W/m^2) into energy over the span of a second, thus obtaining 412 J/m^2. Now let’s assume that all of it is emitted and absorbed at CO2’s and H2O’s peak-ish emission wavelength of 14.5 um. Now a photon of that wavelength has a frequency f of 2.07*10^13 Hz, and thus an energy of hf of 1.37*10^-20 J (per Planck-Einstein). So each square meter of greenhouse gas (that is, the whole column of gas whose base has an area of 1 m^2) is subject to the net upward radiation pressure exerted by 3*10^22 photons/s.

    So again, what is the radiation pressure? Each photon has a momentum of h/λ, which is 4.6*10^-29 kg-m/s/photon, so the net momentum of all those photons is 1.4*10^-6 kg-m/s. Because those photons are emitted and absorbed over a second, the resulting net upward force is 1.4*10^-6 kg-m/s^2, and the pressure thus 1.4*10^-6 kg/m-s^2.

    But remember that the atmosphere is in thermal equilibrium, so that pressure is exerted against not just the greenhouse gases, but (via collisions between GHGs and everything else) against the whole column of atmosphere whose base has an area of 1 m^2.

    Not that it matters much, because the downward force due to gravity on that column of air is F=ma = ~10,000 kg * 9.8 m/s^2 = 98,000 kg-m/s^2.

    So, radiation pressure is not the force that prevents the atmosphere from collapsing, as it balances only 1 part in 7*10^10 of the force due to gravity.

    See “solar sail” for more on this sort of thing,

    [1] http://www.cgd.ucar.edu/ccr/aboutus/staff/kiehl/EarthsGlobalEnergyBudget.pdf

  6. 206
    Chuck Hughes says:

    The only thing happening in my state is they’re building larger freeways. No sign of solar or electric taking over any time soon. More gas wells going up every day. Plenty of earthquakes. We’re losing our hardwoods to infestation and fungus along with the bat population. Not to mention non stop logging of century old Oak and Hickory. Oh, and frequent and dramatic flooding events alternated with periods of severe drought and excessive heat. In 2012 it hit 114 degrees in Little Rock. We lost a lot of hardwoods due to shock that year. I assume it was the heat. The trees just turned brown and never lost their leaves.

    Killian, if you’re on social media (fb) send me a friend request. I’m using my real name until forced to enroll in a witness protection program.lol

  7. 207
    Hank Roberts says:

    MARodger, I’m not defending the Liu paper; do you think Liu et al. disagree with the pattern described for previous glacial cycles, with a rapid warming then a long slow cooling? — is there something (other than human activity) about this cycle and Holocene conditions?

  8. 208
    wili says:

    Chuck Hughes at #201–Thanks for the links. Well put. Me, too.

  9. 209
  10. 210
    Lynn Vincentnathan says:

    Does this idea carry any weight? (I found it on a blog):

    “…currents go through a regular cycle of 30 yrs absorbing and then 30 yrs releasing heat. The impact of this theory is to cut C02 temperature sensitivity in half, since it comes in a spurt lag model averaged over 50+ years.

    Cutting CO2 sensitivity in half destroys the value of all the models used by the IPCC.”

  11. 211
    Chris Colose says:

    Lynn- //”Does this idea carry any weight? (I found it on a blog):”//

    No, and I’ve taken the liberty of commenting on said blog…

  12. 212
    MARodger says:

    Hank Roberts @207.
    Your not signing up as a defender of Liu et al (2014) but I’d reckon they could do with a strong defence. To me, it didn’t read like a well founded paper so I don’t think it necessarily established anything at all.
    Symptoms of problems include its insistence that there is a mismatch between proxies and models w.r.t. global temperatures. They say “Numerous previous reconstructions have shown cooling trends in the Holocene, but most of these studies attribute the cooling trend to regional and/or seasonal climate changes,” but then skate over the word “most” as though it read ‘all’ which in my book is an error.
    And soon they describe the substance of their work. “This inconsistency between the reconstructed cooling and the inferred warming forced by GHGs and ice sheet poses the so-called Holocene temperature conundrum and will be the subject of this study.” Given the title of Liu et al 2014, is it not likely that this “conundrum” is their own invention? That should be made plain.
    And given that Liu et al (2014) is so much an analysis of Marcott et al (2013) (Oops. @202 I named the graph after Shakun.), Liu et al. does contain some worrying omissions. There is silence on Marcott et al’s comments made about seasonal bias. Not a squeak over their contradicting Marcott et al. on the findings from models.
    And that’s just for starters. Those with better grounding in this area may put me right (and this may be required given Liu has co-authored with the full set of Marcott et al. in the past), but the way I see Liu et al (2014), it has serious problems.

    As for their model capturing the spikey nature of previous interglacials (although beyond 420ky, some of the spikiness appears much reduced), I don’t think interglacials are entirely alike. For instance, the Eemian had a bigger orbital forcings than the Holocene. But the temperatures plotted in Liu et al. Figure 2 do seem to show a lazy response compared with the data in AR5 Fig 5.3.

  13. 213
    Unsettled Scientist says:

    Hey Guys,

    It has been a long time since I’ve had a chance to keep up with the current events in climate. One thing I would like to get an update on is the arctic sea ice melting. My links are currently stuck in limbo from Opera’s link, so digging through and trying to recover all those and migrate them to Chrome.

    Would y’all mind linking me to the site that monitors this again? I remember a couple summer’s ago we saw extreme melting. And I was curious if we were seeing this again, or if we are back to “normal” decline. I got some free time coming way right now, so I’m trying to get back up to speed on one of my favorite sciences in which I am not a professional.

    Thanks again to the contributors to this site, both those that run it and those who make positive contributions in the comments. I just read the April guest post on WGIII and it was fantastic.

    Note: forgot the captcha so I hope this doesn’t double post, sorry, it’s been that long!

  14. 214
    James McDonald says:

    Chris (#195) and Meow (#205) —

    Thank you. Your responses were exactly what I was looking for.

    I knew the effect had to be very small, but I didn’t have an intuitive grasp for the order of magnitude.
    (I was uncertain to about an order of magnitude regarding the order of magnitude of the effect. :)
    That intuition is now much refined.

    If I read your posts correctly, the blackbody calulator predicts an upward force of about 2 * 10^-6 Pa from the surface, while meow’s more detailed analysis gives a value of 1.4 * 10^-6 Pa as seen by the atmosphere.

    Would it be correct to assume that the difference (0.6 * 10^-6 Pa) is carried away by photons escaping to space? (Or am I reading too much into the precise values provided?)

    Also, thanks for the connection to pair-instability supernova — I’d seen the term in passing but hadn’t given it much thought until your post. Two insights for the price of one question!

    Thanks again…

  15. 215
    James McDonald says:

    Kevin (#197) and sidd (#199) —

    Thanks for your responses, but I think Chris and Meow really nailed it.

    You both reacted dubiously to my assumption that the CO2 molecules would absorb more IR photons from below, so I should clarify:

    I was NOT assuming that the CO2 molecules have any sense of direction — in fact, I assumed that the probability of any single IR photon being absorbed was independent of its direction of approach.

    But the earth is radiating more IR photons out to space than are arriving from space to earth, so at every level there is a net excess of upward IR photons available to interact with the atmosphere. At all altitudes the IR spectrum appears brighter from below, just as the visible/UV spectrum appears brighter from above.

    (Regarding the “end of the story” about downward IR photons, I simply assumed that some signficant fraction of them would be absorbed to produce thermal excitations, as opposed to reflecting back up or being used for photosynthesis, etc., thus heating the earth and raising its temperature, which of course would then increase earth’s emitted blackbody radiation (Stephan/Boltzman fourth power law) until a new equilibrium was reached.)

  16. 216
    Chris Dudley says:

    James (#214),

    300 K was a round number so there is no significance in the different results. The online calculator assumes complete opacity which for Thomson scattering shading into combined Compton-inverse Compton scattering is a fair assumption. The Earth’s atmosphere is pretty transparent is some spectral windows so you’d correct for that in a more precise calculation.

  17. 217
    Chuck Hughes says:

    Just an observation… this thread has become much more science oriented and a lot shorter. Only 216 posts to date. :)

  18. 218
    Hank Roberts says:

    > Earth is radiating more IR photons out to space than are arriving from space to earth
    You can look that up: “mean free path” — but IR is not the radiation imbalance that affects us.
    Solar infrared is a small part of the total incoming energy that warms the planet.
    The Sun is brighter in the infrared than the Earth is, yet the upper atmosphere loses heat to space.

    > about downward IR photons, I simply assumed
    You can look that up. IR photons aren’t reflected, and aren’t used for photosynthesis.

    Logic didn’t work to figure this stuff out. Logic was tried for a very long time. As it turned out, serious computer calculation was required to understand the effects you’re trying to work out. Seriously, see Spencer Weart’s History: first link under “Science Links” in the right sidebar on every page.

  19. 219

    #213, Unsettled Scientist–

    The link you are looking for is this:

    http://neven1.typepad.com/blog/

    As to this year’s melt, it has again been a tad on the slow side, with the burning question at the moment being, will 2014 come in just above or just below 2013’s mark? The usual suspects are indulging in a bit of triumphalism over this, replete with references to Al Gore conflating conditional projection with absolute prediction.

    Yesterday’s extent, per IJIS, was5,218,262 km2, up a tad from the 30th, and leading on commenter to call minimum, almost certainly prematurely. (Last year’s minimum in IJIS data occurred on September 12, a fairly typical date OTTOMH, and clocked in at 4809288 km2.)

  20. 220
    Meow says:

    @214: I think the primary cause of the different results is the different assumptions about the temperature of the emitting surface. Chris explicitly chose 300K, whereas I implicitly chose the temperature of a differentially-thin layer of atmosphere where half of the photons are absorbed/emitted above and half below. That layer (whose height of ~2 km is often called the “effective emission altitude” or “average height of emission”; see http://scienceofdoom.com/2013/01/08/visualizing-atmospheric-radiation-part-three-average-height-of-emission/ ) has a temperature of ~275K. If you plug that into the radiation-pressure calculator, you get 1.44*10^-6 pa.

    BTW, http://www.scienceofdoom.com is a fantastic resource on atmospheric physics.

  21. 221
    sidd says:

    Rye (2014) doi:10.1038/ngeo2230

    “Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge”

    “We estimate that an excess freshwater input of 430 ± 230 Gt yr−1 is required to explain the observed sea-level rise.”

    This, of course, is far in excess of mass waste from Antarctic grounded ice, but after adding in the contribution from thinning of floating ice shelves, agrees to within error bars. The paper underscores the fact that, in Antarctica, that floating ice shelves are losing mass much faster than grounded ice.

    There seems to be a comparable thermosteric contribution at depth.

    “Remarkably, the modelled anomalous SSH signal is comprised of comparable halosteric and thermosteric contributions, with the former being focussed in the upper ocean and the latter at depth. Thus, the model suggests that the directly forced halosteric sea-level rise around antarctica is amplified by a positive thermosteric feedback.”

    In this regard, they refer to one of my favorites,

    Purkey, S. G. & Johnson, G. C. Antarctic bottom water warming and freshening: Contributions to sea level rise, ocean freshwater budgets, and global heat gain. J. Clim. 26, 6105–6122 (2013)
    doi: 10.1175/JCLI-D-12-00834.1

    “Similarly, Southern Ocean deep and bottom waters have warmed significantly in the period of our study, inducing a thermosteric sea-level rise of ∼1 mm yr−1 (ref. 23) that is comparable to the signal discussed here.”

    There are caveats:

    “Although the spatial footprint of the deep thermosteric change extends well beyond the Antarctic subpolar seas23 , in poor agreement with our observed signal and model results, …”

    The ocean model is NEMO, with dynamic ice and reanalysis based (CLIVAR) atmospheric forcing. Nice paper.

    sidd

  22. 222
    Unsettled Scientist says:

    #219 kevin mckinney –

    Yes, that is exactly what I was trying to find, thank you very much! I was never really a fan of Al Gore’s movie, especially because the 2000 election makes an appearance. Seriously, what a distraction from the subject matter. But I always tell people to ignore names, forget the politicians, and don’t pick your favorite scientist and only listen to them. It’s one thing to have someone that inspires you. I know that I, along with many physicists, have something of scientist crush on Feynman, but I certainly don’t look to him for all my knowledge/perspective of the material.