Unforced variations: Dec 2011

Open thread for December…

406 comments on this post.
  1. J Bowers:

    Hacked climate emails: police seize computers at West Yorkshire home

    No arrests, they’re just pulling their finger out at last, seizing Tallbloke’s laptops as he was one of the recipients of the emails. Jeff Id got a notice from the DoJ via WordPress, too.

  2. Snapple:

    This is so terrific!

  3. Radge Havers:

    Hank @ 296

    “increasingly successful mimicry of someone who knows the science”

    That’s a very good point and worth reiterating. Unfortunately it’s something that should probably be factored into responses to propagandists so that you’re not just training better liars. My take: if you’re going to engage with these sorts, consider that it becomes more about tough love, getting into there heads and presenting the facts of the matter so that they’re put in an uncomfortable and ineffective position–less about science education which is designed for constructive and open minds.

  4. Hank Roberts:

    “increasingly successful mimicry of someone who knows the science”

    Yah. My first exposure to that was in 1966, as a very young biology student, hearing a professional defend DDT in debate with a young passionate postdoc who was doing research on eggshell thickness. It was also my first real understanding of the terribly vulnerable underbelly of the traditional liberal education, which values charm and verbal skills more than science.

  5. Hank Roberts:

    Some references follow to go with this story

    Pau, S., Wolkovich, E. M., Cook, B. I., Davies, T. J., Kraft, N. J. B., Bolmgren, K., Betancourt, J. L. and Cleland, E. E. (2011), Predicting phenology by integrating ecology, evolution and climate science. Global Change Biology, 17: 3633–3643. doi: 10.1111/j.1365-2486.2011.02515.x


  6. Susan Anderson:

    On the recent development in the UK investigation into the CRU thefts, Steve McIntyre is AFAIK a bigger player in the distractionalist fake skeptic attack machine than Tallbloke, and appears to be another target of the investigation.

  7. Ron R.:

    Question: Would it be a an appropriate to assume that during the MMCO trees and shrubs grew faster and larger due to the increased amount of CO2 in the atmosphere (from volcanoes), the warming and tropicalizing of the climate and the subsequent necessarily longer growing season?

    I’ve tried to get some information about the various trees in the Ginkgo Petrified Forest (ginkgoes, walnuts, maples, elms, oaks etc.) size wise compared to todays average for those families but so far no luck. Anyone know if they were bigger? Any paleobotonists out there?

    Two, if this can be assumed can we also assume that modern trees and shrubs should similarly begin to increase in size for similar reasons?

    [Response: By MMCO I assume you refer to the Miocene. Faster, yes; larger, not necessarily. The same holds true today. Increased CO2 affects the rate of carbon assimilation, via an increase in biophysical efficiency (reduced photo-respiratory loss). Time to a defined size can certainly be affected by the drivers you mention, but maximum size is another matter, because other biological and physical limitations are involved, such as the ratio of photosynthetic to respiratory tissue (which changes with size), the basal metabolic rate, leaf architecture and display geometry, competition, and the efficiency of water conduction through the xylem (among others); these things determine the carbon balance of the tree and/or the limits to growth.–Jim]

  8. Peter Backes:

    About GD time:


    Wouldn’t it be great to find out the identities of the trolls behind the curtains?

  9. Hank Roberts:

    > trees … size wise compared to todays average

    Few places today have a full grown tree of almost any species.
    This place does: http://colebrooklandconservancy.org/trees.html

    [Response: Nice find. A couple of the best places to see large trees at a landscape scale, in a relatively intact ecosystem in the eastern U.S., are Great Smokey Mountain NP, the nearby Joyce Kilmer forest, and Porcupine Mountain State Park, Upper Peninsula, Michigan. There are a number of much smaller areas as well, but these are the big ones.–Jim]

  10. Ron R.:

    Thanks Jim.

    Ok, trees increase in height but not necessarily girth in response to increased CO2. Of course that extra height will need extra width to support it. But for physiological limitations, perhaps a set amount of stoma per leaf, you’re saying that there is a limit to how wide it can get in response to CO2.

    [Response: No, I was talking about all growth; primary (height) vs secondary (width) is a separate issue altogether, under different, often species-specific controls and constraints. But you are right that stomate density is an important determinant of physiological response to CO2 concentration]

    Perhaps the more general response is to increase the numbers in the community (as we see in rain forests today) rather than the size of individuals? Still in subtropical areas of less rain it would seem intuitively that individuals themselves would compensate by growing larger?

    [Response: That’s population dynamics–even further removed from direct CO2 effects. Way too confounded. And there is no separating total number from average size in plants–they are always negatively correlated, via competitive thinning]

    All the same, i’m wondering if anyone has done an actual comparison of trees and shrub size between periods of heightened and lowered atmospheric carbon?

    [Response: Some have looked at radial growth rate, using fossilized tree rings. But I don’t know that any have compared maximum size. That would be very difficult–you’d need entire intact specimens.]

    One other question, the temps were on average 3 degrees C warmer during the Middle Miocene Climate Optimum and I’ve read the ppm of atmospheric carbon between 460 and 580; is that correct?

    Hank, that webpage reminded me of an old photograph I saw somewhere once but can’t find now of a giant old oak tree absolutely dwarfing the horses (and wagon?) underneath it. I seem to remember John Muir in it too but maybe that’s wrong.

    [Response: There are pictures of him underneath massive valley oaks. Underneath various massive trees for that matter.]

  11. Chris Colose:

    Ron R,

    I don’t know much about tree physiology, but I can say that there is an empirical relationship between stomatal pore density on tree leaves and CO2 that is often used as a proxy for paleo-CO2 levels, but breaks down at higher concentrations (above 1000 ppm in most cases) and in this limit the stomatal proxy only provides a lower constraint on paleo-CO2. There are several other big CO2 proxies used before the ice core era, including Boron isotopes and alkenones .

    [Response: You basically have it Chris. But to clarify a little, the breakdown at higher values was observed mostly in experimental situations, and even there, mostly in a certain kind of experimental situation–open top chambers, not so much in greenhouses where things are better controlled. Conversely, some fossil-based evidence continues to show response up 2500 ppm and above (McElwain and Chaloner, 1995. Stomatal density and index of fossil plants track atmospheric carbon dioxide in the Palaeozoic., Ann. Bot. 76, 389-395.). The big difference between the two of course, is that the fossil-based stuff is under potential genetic selection and therefore more maleable, whereas the experimental stuff is not–it’s generally the same plants, tested over a short time period and high CO2 fluxes. Very different beasts.–Jim]

    As for your other question- Since the early Miocene (~23 mya – present) CO2 was typically at pre-industrial range to slightly higher than modern (e.g., less than 500 ppm in the Pliocene, see the Beerling and Royer commentary in Nat. Geoscience this year for a Cenozoic CO2 history).

    Most of the decline in CO2 from the big ‘greenhouse’ climates came before the Miocene between 50-25 mya, in line with the growth of the Antarctic ice sheet (see the most recent Pagani et al 2011 paper in Science). And yes, temperatures were several degrees warmer, and in the pliocene at least, sea levels 10-30 m higher, and several times this for the Late Cretaceous to Miocene.

  12. Philip Dooley:

    I am going to try to explain global warming to a 9th grade class of honors students early this Tuesday (20th). Upon reviewing the material, I am confused about exactly what altitudes the CO2 warming forcing originates. In response to the saturation argument, I have seen claims that the effect is in the stratosphere where there is no convection. David Archer implies that the effect is in the troposphere, with temp rises less than the lapse rate keeping the air stratified. Are storms and other convection currents rare enough to consider the troposphere stratified ? Can you tell me or send a link : Between what altitudes does 90% of the CO2 forcing effect occur ? Do you have a graphic for a multi layer model of the atmosphere ? How many layers did Gilbert Plass use ?

  13. Ron R.:

    Thanks for the reply Jim.

    [Response: Some have looked at radial growth rate, using fossilized tree rings. But I don’t know that any have compared maximum size. That would be very difficult–you’d need entire intact specimens.]

    It would seem that fossilized trees found in the Ginkgo Petrified Forest (Wanapum) would be a good place to begin. Middle Miocene, buried whole in ash courtesy of the huge Columbia River Volcanism.


    [Response: Excellent. That goes on my list of places to see. Not sure those are whole trees though. And see response to Chris above–Jim]

    Chris, thanks for your comments. Of course the Miocene and Pliocene climates were two entirely different animals. Warm and wet /cold and dry.

    This study has a nice chart if you can get to it.

    Another very similar one.

    Regarding the ppm (but will look for your cites – perhaps an update?).

  14. wush:

    Off the wall, Oh, Look! more dust.
    There is twice as much dust in the atmosphere as there was 100 years ago.
    “There is a strong possible loop where the climate becomes drier and windier causing more dust, and more dust affects radiation, so it feeds back on climate.”

    Increasing desertification, more erosion from agricultural soils, increasing areas of dusty hard surfaces, roads and buildings, urban dust islands, mining mountains, open cast mining, deforestation, slash and burn, dust and more dust.
    During past glaciations, the amount of dust in the atmosphere was higher than during interglacial periods, thus more heat was likely reflected from the Earth’s atmosphere back into space.
    How long before there is enough dust to do this?
    I see, so we warm things up, make dust, and create an ice age, great.

  15. Chris Colose:

    Philip Dooley (312)

    You have to be careful about over-interpreting the simple one or two layer models of the greenhouse effect. In reality, the “forcing” originates almost everywhere in the vertical, and certainly most of the effect of CO2 is in the troposphere. The upper troposphere is particularly important here for a number of reasons- one is that the temperature is much colder than the surface, which is the whole reason you can generate the big dips in the thermal emission spectrum that you see in David Archer’s book, particularly at 15 microns wavelength (or 667 cm^-1 wavenumber). This, in turn, implies that for any given temperature the outgoing emission to space is reduced with an increase in CO2.

    If you look closely at some of the images in Archer’s book, you may notice an inversion in the dip of the thermal infrared spectrum near the center of the CO2 band. This is because the stratosphere is warmer than the tropopause, and thus emission near the center of the CO2 band increases as CO2 is increased with temperature held fixed. The increased emission turns out to have a large effect in cooling the stratosphere, rather than having a large impact on the surface; at the surface the contribution is dominated by the decreased emission in the wings of the CO2 band (which are tropospheric).

    I am not sure what you are getting at in terms of the stability, which I don’t recall Archer getting into much (though I don’t have the text in front of me), but the key thing for the greenhouse effect is that temperatures are declininng with height at all. But in the tropics (especially over the ocean), the temperature profile tends to stay near a moist adiabat, implying little Convective Available Potential Energy (CAPE). In mid-latitudes, the thinking with convection is a bit different, and vertical ascent is typically diagnosed with forcing mechanisms (such as the QG omega equation or Q-vector convergence).

  16. Craig Nazor:


    About your UHI quote, you said:” There have been others who have reported that, hence the statement.”

    So how can we tell if you actually believe what you are saying, or if you are instead referring to research in which you don’t actually believe? And why would you do that? It’s fundamentally dishonest, and guaranties to disgust those with whom you are debating, as these comments demonstrate.

    Do you have any recent research to offer that claims that UHI effects are contributing 10% of the observed warming?

    Which leads me to another point: You appear to believe that world average temperature has not warmed in the past ten years. At the same time, human population has increased, urbanization has increased, and human use of energy (and the ubiquitous energy byproduct, extra heat) has increased. So what has happened to all that extra urban heat?

    To rephrase your statements: Increasing UHI effects are contributing up to 25% of the observed warming, but there has been no observed warming in the past 10 years.


    I don’t think that you actually believe that. But the only other explanations would be that 1) somehow you are mean-spirited enough to actually WANT to waste the time of all these intelligent people here (I don’t believe that, either), or that 2) someone has put you up to this.

    Which is it?

  17. Ron R:

    Jim @ #313: That goes on my list of places to see.

    Mine too. along with Fly Geyser (related geologically) and another wonder.


  18. Edward Greisch:

    Red herring: Diverting attention from the real subject.

    30 Ray Ladbury: Truth as a weapon: See “FOOL ME TWICE; Fighting the Assault on Science in America” by Shawn Lawrence Otto; Rodale Books. Says: “science is a political act.”

    Science has been loosing status to “New Age” “truth is relative” stuff. Science is too difficult for most people. “Religion Explained” by Pascal Boyer talks about how people try to do all of their thinking as if everything was a person. They have a big subconscious sub-processor for interactions with other people. They can’t do math or logic.

    So just the truth isn’t going to work. You also have to say that science works and why science works and everything else doesn’t and that the opposition is telling lies. The lies are a problem. Point out that they are reading this on a computer that depends on physics being true.

    41 Ray Ladbury: By the time truth wins, it could be too late. People have believed unbelievable things for thousands of years.

    49 Donald Oats: But the alternatives to truth feel better. And they don’t require hard thinking. Hard thinking hurts.

    51 Ray Ladbury: Who said anything about sane? Sanity hasn’t even been defined yet, as far as I know.

    62 David Horton: “intelligent person”. There is the problem. There aren’t many of them.

    rasmus: Your “perception of what science is all about.” Yes, that is exactly what Shawn Lawrence Otto is talking about. When you have people saying that “truth is relative and “my” truth is just as good as your truth,” science is in trouble. Otto says it has been too long since scientists, except for Carl Sagan, did any speaking out. wmar, Adrian O. and Dale R. McIntyre, PhD all sound perfectly reasonable on dotearth, but you know otherwise. WUWT gets higher scores from click counters than RealClimate does.

    I don’t agree that there are just a few devilish people to blame and that is all there is to it. [There are fossil fuel companies, but in a world of scientists, the fossil fuel companies wouldn’t stand a chance.] I think that the problem is the basic design of the human brain. The fossil fuel money is bad, but not the only problem.

    There are very few people who are able to become scientists because, until now, science wasn’t required for survival. Now, everybody has to be a scientist or we are in trouble at the species level.


  19. J Bowers:

    Re. 314 wush

    That’s interesting.

    * Asthma, Coral and African Dust
    * NASA: When the dust settles

    In addition to affecting marine ecosystem health, the researchers suspect that the dust may trigger respiratory health problems in humans. According to Shinn, levels of asthma on the islands of Barbados and Trinidad are among the highest in the world. “The incidence of asthma on Barbados and nearby Trinidad, as documented by the Caribbean Allergy and Respiratory Association (CARA), has increased 17-fold since 1973,” he said. “And that was the first year that Prospero’s graph showed a big spike in the dust record there.”

  20. Radge Havers:

    EG @ 318

    I think you may be zeroing in on something here.

    They have a big subconscious sub-processor for interactions with other people.

    From a very early age people will instinctively read intention into very simple shapes and movements.

    The lies are a problem.

    They are effective, especially if you don’t call them out quickly and in simple terms for what they are. It’s also a bad idea to let light weight, heavily slanted caricatures be passed off by portentous blowhards as the wisdom of the ages. They may seem trivial and transparent to you, but people get swept away by them.

  21. John E. Pearson:

    “Hydraulic fracturing techniques — despite causing a growing controversy — are creating a once-in-a-generation boom in oil and gas drilling in the United States, and the opportunity to build many more pipelines to carry new supplies to market.”


  22. Hank Roberts:

    Hydraulic fracking also works to the benefit of the bottled-water and private utility water companies. They will be happy to sell you professionally cleaned-up water, not that nasty polluted stuff from the aquifers that has the fracking residue and all those other toxic wastes in it.

    $$PROFIT$$ — they don’t count the costs.

  23. Ray Ladbury:

    Edward Greisch, If a member of a species has a deficiency in perception sufficiently severe that it cannot identify a threat, that member will not last long. Likewise, if the majority of a species has a similar deficiency, the species will either evolve or become extinct.

    Our species has a deficiency when it comes to adequately perceiving risk. We have developed corrective lenses as it were–science and quantitative risk assessment–but if people refuse to use them, then eventually we will reach a disastrous outcome. Even if we stumble through the crisis of climate change without realizing the worth of science and quantitative reasoning, some disaster will get us eventually.

  24. Ron R.:

    Chris Colose — 17 Dec 2011 @ 1:42 PM

    Thanks for that reference to Nature Geoscience. Here’s a free version (don’t tell them).


  25. Ron R.:

    The trigger?


    Re: Hank’s link,


    If the phenological response to increased CO2 and climate change includes increase in the growth of plants (in both community number and individual size)

    [Response: ??; thought we had gone over that–Jim]

    it would seem wise to allow and even encourage this Gaian-like reply (rather than resort to our usual short sighted policies – in this case slash and burn – thereby leaving only the high CO2 levels).

  26. Philip Dooley:

    Chris Colose (315)

    Thanks for the extra information. The model that I like is multiple layers of glass with a vacuum in between them on a greenhouse. Adding more CO2 adds more sheets of glass.

    My concern about stability is that any convection shorts out the insulating effect of the CO2. The troposphere has to be stratified most of the time for the CO2 to do much warming. If the CO2 effect is distributed thru the troposphere, then the added heat is also distributed, resulting in a uniform expansion of the troposphere and raising the tropopause.


  27. SecularAnimist:

    This is probably more appropriate for the Unforced Variations thread, but John E. Pearson at #55 and Kevin McKinney at #68 have noted yesterday’s New York Times article on warming arctic permafrost and methane releases, with Kevin mentioning that it is a good article though with some “simplifications” that “grated a bit”.

    I agree that it is mostly a good article, with intelligible straightforward reporting that is mostly based on the real science being done by real scientists in this field. But here’s what really “grated” with me — stuck right in the middle of the article:

    Citing permafrost temperatures for northern Alaska — which, though rising rapidly, remain well below freezing — an organization called the Center for the Study of Carbon Dioxide and Global Change claimed that permafrost is in “no more danger of being wiped out any time soon than it was in the days of our great-grandparents.”

    So who or what is this “Center for the Study of Carbon Dioxide and Global Change”? The organization is not identified, or described, nor is it referred to anywhere else in the article, nor is any reason given for citing its views.

    Well, folks, it turns out that the Center is a “think-tank” funded by ExxonMobil and run by two brothers, Keith and Craig Idso, who have worked for the fossil fuel lobbying organization the Western Fuels Association, producing denialist propaganda. The Center’s public position is that “there is no compelling reason to believe there will necessarily be any global warming as a result of the activities of man, especially those activities that result in CO2 emissions to the atmosphere” (emphasis added).

    One might have thought the time was past when major news organizations felt the need to “spike” their news reports on global warming issues with talking points from the fossil fuel industry’s paid propagandists — without, of course, identifying them as such — to “balance” the views of, well, actual scientists.

    One would have been sadly mistaken.


  28. Hank Roberts:

    > Ron R. … if the phenological response … includes …. growth …

    The physiological response to strychnine includes hyperalertness.

    In both instances: add for a while, for some, with other effects.

  29. Lynn Vincentnathan:

    I’m just catching up on my blogging, and came across on Catholic Answers Forum “Nobel Prize-Winning Physicist [IVAR GIAEVER] Resigns Over Global Warming.”

    I read in Wiki that he’s a physicist (in areas not remotely connected to climate science), so why should his voice, I’m wondering, and I told them that.

    Is there anything more that you all know about him?

  30. Ron R.:

    Hi Jim. I reread your answers @ 307 & 310. Sorry and thanks, I must have misunderstood. That seems counterintuitive. Will have to do more personal study.

  31. Ray Ladbury:

    Giaever is a condensed matter theorist. There is absolutely no reason why his background should give him any understanding of climate science. He has no climate publications, no publications in related fields, zip. It’s another case of a physicist gone emeritus, that is, they find they are too old to make further contribution in their area of expertise, so they decide to straighten out one of the sciences they perceive as “softer”.

  32. Imback:

    @326 Philip Dooley,
    I haven’t read the whole thread, so sorry if I repeat earlier points. Because expanding air cools, a neutrally stratified troposphere is actually colder with height. And the greenhouse effect warms when the troposphere is colder with height. Thus convection, which promotes neutral stratification, does not deter the greenhouse warming effect.

  33. Hank Roberts:

    > Center for the Study of Carbon Dioxide and Global Change …

    wikipedia: (also known as CO2Science)


    “… rather than its promise of ‘separating reality from rhetoric in the emotionally-charged debate that swirls around the subject of carbon dioxide and global change’, on the contrary CO2 Science twists the most recent science, ever so subtly, to suggest that there is no link between carbon dioxide levels and climate change.”

    So their reputation got so bad they changed their name?

  34. Dan H.:

    The answer to your last question is neither. I am simple trying to uncover the truth, as any good scientist would.
    With regards to your extra urban heat, several other parameters good lood to the reduction. These include, but are not limited to, the recent solar minimum, volcanic activity, and ENSO fluctuations. Many prominent climatologists have pointed to these causes as an explanation to the temperatures of the past decade. Additionally, James Hanson has blamed aerosols generated from coal burning in China. Urbanization is only one factor in temperature changes. Over short timeframes, such as a decade, fluctuations in one or more variables can combine to mask other effects.

  35. Rattus Norvegicus:

    Ray, you mean like this?


  36. Craig Nazor:


    So how can the UHI effect be contributing up to 25% of the warming if the planet has not warmed?

    By denying the strong scientific consensus about anthropogenic global climate change, as well as rejecting a proper statistical analysis of global temperature data, you are obscuring science, not uncovering it.

  37. MARodger:

    Dan H @334
    This truth you seek – does it always have to include your proposed long term warming trend of ~0.6 deg C? If this trend does have to be included, it is probabbly why you are having difficulties espressing your position to folk who consider such a trend as fictitious as that fabled archipelago, the Urban Heat Islands.

  38. Kevin McKinney:


    Well, FWIW, the CSCDGC (nee CO2Science) comment wasn’t one of the things that grated; it struck me as so spectacularly dumb that it actually made me laugh out loud. My feeling was that it was self-refuting–and self-discrediting for the CSCDGC.

    Should I have taken it more seriously than that? Sometimes the denialist hall of mirrors erodes my sense of perspective. . .

  39. Hank Roberts:

    “… all of the investment on solar water heater can be got back in 2~4 years. After 2~4 years, we can use hot water free.”

    A wide variety of innovatively designed solar hot water collectors is available.

    Here is a balcony systems for apartments:

  40. Maya:

    Did anyone mention this? How different a world it would be if everything were powered with the sun and wind instead of dead dinosaurs.

    “Researchers from the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have reported the first solar cell that produces a photocurrent that has an external quantum efficiency greater than 100 percent when photoexcited with photons from the high energy region of the solar spectrum.”

  41. Philip Dooley:

    Imback @332

    Yes, I understand the cooling as the air rises, but the air is still warmer or wetter than the air around it so it continues to rise and carry upward the heat that the CO2 effect is trying to trap. This effect is obvious during summer thunderstorms. Also , supersaturated air is also common. I guess that it boils down to : what percentage of the time is the troposphere quiet and stratified ?


  42. wush:

    Re, 319 J Bowers,
    Thanks for the interesting links.
    I’m probably putting two and two together and making five! But maybe… Increasing incidences of Asthma in Britain follow a similar pattern to the Caribbean. Highest Asthma Rate in the World, 1 Wales, 3 Scotland , 5 Ireland.
    I wonder if some of this dust is transported up to Europe from the Caribbean on the Gulf Stream winds!
    Dust mix does not match those currently used in climate models.


    The amount of dust actually injected into the atmosphere, though, may have been significantly underestimated
    the amount of coarse dust driven into the atmosphere by wind is at least double and may be eight times as much as previously thought.
    What is clear is that it is yet another example of how fiendishly complicated the atmosphere is, and what a broad set of approaches is required to understand it.

    Question;- Is it correct to say,
    If there is more air-born dust there will be more sites for water vapour to condense onto so more cloud formation, precipitation, cooling in summer (albedo) and warming in winter(cloud cover)taking place as a consequence?

  43. Ron R.:

    Doing a bit more research. I’d been thinking that with higher CO2 plants would perhaps have increased stoma density to incorporate more of that carbon into their woody structure but hadn’t realized that according to recent studies that with increasing atmospheric carbon stoma density actually decreases to decrease the loss of water, due (I suppose) to higher resulting temps. And as you indicate though there are other factors involved as well.


    I wonder though if, assuming all other things were equal as you say, it’s possible that in response to increased selective pressure from long term high amounts of CO2 in the atmosphere as existed during the Miocene (there must be some reaction) that after perhaps an initial negative response, such as today’s closing off of stoma, in time plants would have evolved a more positive adaptational (if nonpermanent) response that would allow them to use the extra carbon to their benefit. I mean, it seems to me that closing off stoma is non-optimal. Could plants have evolved some mechanism to accomodate (something not apparent in the fossil record) such as, for example, separate stoma for respiration and transpiration, thus allowing for the increased intake of carbon while simultaneously closing off water vapor pores?

    If I’m seem too obtuse please pardon.

    [Response: Not obtuse; great questions. Right–the stomatal/CO2 correlation is negative: higher CO2 = fewer stomata, to an asymptote (you have to retain some stomata). The plant is attempting to optimize the gain of carbon relative to the loss of water. This has been known for a while. Plants are nothing if not the world’s greatest optimizers. More later.–Jim]

  44. Imback:

    @341 Philip Dooley,
    Consider an idealized case where convection immediately and completely mixes the troposphere to always be neutrally stratified. If the air is dry, then the temperature would decrease with height by the dry adiabatic lapse rate of about 10 degrees C per kilometer. If the air is totally saturated, then the temperature would decrease with height by the saturated adiabatic lapse rate of approximately 5 degrees C per kilometer. (The actual troposphere’s lapse rate is generally in between.) My point is that in either case, the troposphere has a definite lapse rate of getting colder with height. Thus the greenhouse warming effect is not deterred by convection.

  45. MMM:

    Ron R: #343: I think what you are missing is the concept of “limiting nutrient”: to you, increased CO2 means more stomata so a plant can get more of it, but to a plant, more CO2 means that CO2 is less of a limiting nutrient, so it can spend less effort to get the same amount (or a bit more) CO2, and instead work on other limiting factors: Jim mentions loss of water as being one of those factors, another common one is nitrogen availability (and there is some research showing that as CO2 concentration increases, the ratio of carbon to nitrogen in the plant increases: the extent to which plants can do this is still an open question: the extent to which low-nitrogen-content leaves are less nutritious to grazers is another question).

    [Response: They’re coupled: a reduced transpiration stream will reduce nutrient uptake, altering the C:N and other nutrient ratios.–Jim]

    In a low CO2 environment, a plant would grow many more stomata, because it would be desperate for any CO2 that it could get. Sort of like in a low-oxygen environment, you breathe more often and more deeply, but in a high oxygen environment, you can get away with breathing shallowly and infrequently (why waste energy on breathing if you don’t have to?).

  46. Ron R.:

    MMM, I hadn’t thought of it that way. The idea that a plant only wants so much carbon as that’s all it needs. Thanks.

    Still, we know that the ‘only needs so much so that’s all it takes’ model is not always true in nature. During the same time period, the Miocene, animals grew to huge dimensions (megafauna) because of an abundance of primary productivity – more food available. So they seemed to have been trying to maximize their use of it to maximize themselves. I’m not sure frugality in the face of abundance is nature’s way.

    So the question is, could there have been megaflora as well?

    [Response: Ron you have some misconceptions. Plants don’t “only need so much” carbon (within the limits set by the light-dependent reactions of photosynthesis). If plants could get unlimited supplies of CO2 without any penalty, they would. But they can’t, because the gain of carbon necessarily requires the loss of water, which for the vast majority of land plants in turn has further effects like reduced ability of the plant to cool itself, reduced nutrient uptake, etc. It’s these kinds of tradeoffs and constraints and feedbacks that have to be well understood before any informed judgment on your original question about maximum tree size can be made. It’s a highly complex system–I only mentioned a couple of simple examples to illustrate that point. Also, animal size is not determined by primary productivity.–Jim]

  47. David B. Benson:

    wush @342 — Yes, if more aerosols then there are more condensation nuclei. However, that might possibly inhibit forming large enough droplets to have sensible clouds much less precipitation. The physics is more complex than I understand well.

  48. Richard Simons:

    Ron: Evaporative cooling seems to be an important function of stomata that might stop their numbers from reducing by much in plants from areas that get hot (and it need only be for an hour or two on critical days). A hint of this is given by members of the stonecrop family. They have separated the light-trapping part of photosynthesis from the CO2 fixing part, reducing water loss by closing their stomata during the day, only opening them at night. However, AFAIK, they are primarily found in cool, dry habitats, likely because they overheat in warmer places. As Jim says, the situation is complex and ‘more CO2 = more growth’ or ‘more CO2 = fewer stomata = better drought tolerance’ are both wildly simplified, if not almost completely untrue.

    [Response: This is Crassulacean Acid Metabolism (CAM), the third most common photosynthetic system (after C3 and C4). It is present in numerous families, but most notably the Cactaceae and Euphorbiaceae. It exists primarily in taxa that have lifeforms that experience very dry conditions, including e.g. epiphytes (plants not rooted in the ground) or those growing in areas of minimal soil depth, including rock faces, desert pavements etc. The stonecrops (Sedum spp.) are a genus within the Crassulaceae, the family the system was first discovered in. One correction: the relationship between stomate density and atm. CO2 is solid when considered across generations (or elevations), over a broad range of tree taxa (e.g. ginkgo, oaks, willows, spruces, dawn redwood, hemlock), although the sensitivity at higher CO2 levels varies. This is the basis of their use as paleo-CO2 estimators–Jim]

  49. Ron R.:

    Jim, I agree with your main statement in 346. I just thought that MMM’s idea, if I understood it right, was interesting.

    Another interesting thing to note though is that the Middle Miocene was also the start of the “Clarendonian Chronofauna” (According to SD. Webb), a period spanning of one of the greatest evolutionary bursts in both terrestrial and sea life. Could that have been caused by the increased food available which was in turn caused by high CO2? Was the Middle Miocene a true “land of the giants”? I’m not stating, just asking.

    It’s coincidental that the decline in CO2 with the buildup of the Antarctic ice sheet was followed by a large extinction event, that of the mid-Hemphillian. While temps probably played a large role, perhaps declining productivity did as well?

    About the PP question, actually I believe that it has been one of the explanations for body size for a awhile. True, that not everyone buys it as the main driver but I think enough do. Against it though might be the fact that there were megafauna in the Pleistocene as well, a time of vastly decreased CO2. Were they just genetic hangers on? I don’t know.

    [Response: There are highly productive systems where maximum animal body size is small (estuaries, many forests) and conversely there are far less productive systems where body size reaches toward the largest known (grasslands, savannas, tundra). There’s not a good relationship there–Jim


    Anyway I know that I have a lot to learn and appreciate your patience and that of the other posters here..

    [Response: Thanks for your interest in the topic!]

  50. wush:

    David B Benson @347-Thanks for your reply. I was taught a long time ago that we need dust to form clouds (some at least) and now it seems we are underestimating the quantity of dust in the atmosphere, by at least double and maybe considerably more. My understanding is that present climate models are geared to estimates of large particles but really they should be accounting for the actions of smaller ones too. These discrepancies highlight the limitations of our understanding of our changing climate IMO.
    We are told aerosols and their actions are one area of great uncertainty in climate change. It seems to me they may be far more influential than we think!