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Solar spectral stumper

Filed under: — gavin @ 7 October 2010

It’s again time for one of those puzzling results that if they turn out to be true, would have some very important implications and upset a lot of relatively established science. The big issue of course is the “if”. The case in question relates to some results published this week in Nature by Joanna Haigh and colleagues. They took some ‘hot off the presses’ satellite data from the SORCE mission (which has been in operation since 2003) and ran it through a relatively complex chemistry/radiation model. These data are measurements of how the solar output varies as a function of wavelength from an instrument called “SIM” (the Spectral Irradiance Monitor).

It has been known for some time that over a solar cycle, different wavelengths vary with different amplitudes. For instance, Lean (2000) showed that the UV component varied by about 10 times as much as the total solar irradiance (TSI) did over a cycle. This information (and subsequent analyses) have lent a lot of support to the idea that solar variability changes have an important amplification via changes in stratospheric ozone (Shindell et al (2001), for instance). So it is not a novel finding that the SIM results in the UV don’t look exactly like the TSI. What is a surprise is that for the visible wavelengths, SIM seems to suggest that the irradiance changes are opposite in sign to the changes in the TSI. To be clear, while the TSI has decreased since 2003 (as part of the descent into the current solar minimum), SIM seems to indicate that the UV decreases are much larger than expected, while irradiance in visible bands has actually increased! This is counter to any current understanding of what controls irradiance on solar cycle timescales.

What are the implications of such a phenomena? Well, since the UV portion of the solar input is mostly absorbed in stratosphere, it is the visible and near-IR portions of the irradiance change that directly influence the lower atmosphere. Bigger changes in the UV also imply bigger changes in stratospheric ozone and temperature, and this influences the tropospheric radiative forcing too. Indeed, according to Haigh’s calculations, the combination of the two effects means that the net radiative forcing at the tropopause is opposite in sign to the TSI change. So during a solar minimum you would expect a warmer surface!

Much of the longer term variance in solar output has been hypothesised to follow what happens over the solar cycle and so if verified, this result would imply that all current attributions to solar variability of temperature changes in the lower atmosphere and surface ocean would be of the wrong sign. Mechanisms elucidated in multiple models from multiple groups would no longer have any validity. It would be shocking stuff indeed.

Conceivably, there might be another missing element (such as a cosmic-ray/cloud connection) that would counteract this physics and restore the expected sign of the change, but no-one has succeeded in finding any mechanism that would quantitatively give anything close the size of effect that would now be required (see our previous posts on the subject).

So is this result likely to be true? In my opinion, no. The reason why has nothing to do with problems related to the consequences, but rather from considerations of what the SIM data are actually showing. This figure gives a flavour of the issues:

(courtesy Judith Lean). Estimates of irradiance in three bands are given in each panel, along with the raw measurements from various satellite instruments over the last 30 years. The SIM data are the purple dots in the third panel. While it does seem clear that the overall trend from 2003 to 2009 is an increase, closer inspection suggests that this anti-phase behaviour only lasts for the first few years, and that subsequently the trends are much closer to expectation. It is conceivable, for instance, that there was some undetected or unexpected instrument drift in the first few years. The proof of the pudding will come in the next couple of years. If the SIM data show a decrease while the TSI increases towards the solar maximum, then the Haigh et al results will be more plausible. If instead, the SIM data increase, that would imply there is an unidentified problem with the instrument.

In the meantime, this is one of those pesky uncertainties we scientists love so much…

254 Responses to “Solar spectral stumper”

  1. 201
    Harol-radd Pierce Jr says:

    Average Person says on 17 October 2010 at 5:12 PM

    It is not necessary for trace greenhouse gases to sustain the water vapor. The heat content of the ocean (quite large) is more than adequate to sustain the water vapor.

    The wind is the force that transports most all water vapor from surface water into air. Declining air pressure also speeds up the transport of water vapor into air.

    Evaporation of water in still air is slow process. Set out pan of water in the kitchen and measure how long it takes to evaporate. Then refill the pan and the use a small fan to blow air across the surface of the water.
    The time for evaporation will be greatly reduced.

  2. 202
    David B. Benson says:

    Average Person @197 — Without CO2, temperature would plumet well below the freezing point of water. There goes the water vapor.

  3. 203
    Ray Ladbury says:

    Average Person, we have something in common. Neither of us has any idea what you are talking about!

    You say, “the preponderance of evidence is sounding more like ‘I work at NASA so I’m right.'”

    I’m sorry, too many big words? How about “the vast majority of the evidence”. Or how about just “the evidence”. The greenhouse effect raises Earth’s temperature by about 33 Kelvins. CO2 is responsible for about 7 of those degrees. We know this. We’ve known it for about a century. Yes water vapor is important. However, without CO2, we’d be living (or rather not living) on a ball of ice.

  4. 204
    Thomas says:

    Average person @197. The quantity of heat in the ocean (except as far as it affects sea surface temperatures is not the issue). The issue with regards to the atmospheric concentration of water vapour is that it is a balance between two processes, the avaporation of water, and condensation -either as dew/frost or as precipitation. So while the non-condesable GHGes may only directly raise the average temperature by a litte bit, that small temperature rise alters the rates of both these processes in favor of more atmospheric water vapor. That is why we consider it to be a feedback, because it amplifies the effect of the noncondesable gases. Trying to argue in the rhetorical sense, that since water vapor does most of the heavy lifting warming wise, the others don’t matter is wrong scientifically. Unfortuantely there is no escape from having to make mathematical models, and then use mathematics to tell us the effects of various things. trying to avoid math, and modeling in favour of rhetorical argumentation is a horribly error prone process. Thats why math is pretty much the language of science.

  5. 205
    Hank Roberts says:

    Folks, you can just point Av to
    and maybe we can get back to the topic.

    I wanted to thank John Baez above for pointing out that this (the topic) is about a recent report of a suggestion of a possibility, not a confirmed observation.

  6. 206
    VeryTallGuy says:


    “I was wondering if anyone could provide me with the definition of a denier.”

    Someone who is in denial. Wikipedia has it spot on:
    “Denial is a defense mechanism postulated by Sigmund Freud, in which a person is faced with a fact that is too uncomfortable to accept and rejects it instead, insisting that it is not true despite what may be overwhelming evidence.”

    Describes the reaction to climate change perfectly.

  7. 207

    #197 Average Person

    I’m in agreement with Ray Ladbury (#203). The post doesn’t make sense.

    Average person. ON the following page, there is a short one minute video explaining a little bit about the greenhouse effect.

    Fee & Dividend: Our best chanceLearn the IssueSign the Petition
    A Climate Minute: Natural CycleGreenhouse EffectClimate Science HistoryArctic Ice Melt

  8. 208
    Harol-radd Pierce Jr says:

    David B. Benson says on 17 October 2010 at 7:00 PM:

    “Average Person @197 — Without CO2, temperature would plumet well below the freezing point of water. There goes the water vapor”

    That is absolute nonsense and just flat out wrong. In the tropics there is about 12 of light and 12 hours of darkness and at the equinoxes the sun is directly overhead. There is no way the tropics are going to freeze up.

    [Response: The Lacis et al experiments (like similar results in Voigt and Marotzke (2009)), show that without CO2, water vapour decreases precipitously, and the global mean temperature goes well below freezing. Unfortunately, your determination that this is nonsense is not much of a rebuttal. How about some actual evidence? – gavin]

    As the earth orbits the sun, one hemisphere heats ups for about six months while the other hemisphere cools down. At about the 50 deg latitude there are about 16 hrs of daylight in summer.

    At 0 deg C there is 4.85 g or 269 millimoles of water vapor for 100% humidity but only 0.76 g or 17.4 millimoles of CO2 per cu meter. The OH2 to CO2 ratio is 15 to 1. To first approximation and all other things being equal, OH2 molecules absorb 94% of the IR light (i.e., the out-going long wavelenght IR).

    At 30 deg C there is 30.4 g or 1,690 millimoles of water vapor for 100% humidity but only 0.61 g or 13.8 millimoles of CO2 per cu meter. There is less CO2 because air is about 20% less than dry air at STP. In this case, OH2 molecules would absorb about 99.2% of the IR light.

    At -10 deg C there is 2.4 g or 133 millimoles of water vapor per cu meter for 100% humidity.

    In a desert at 20 deg C and about 4% rel humidity there are equal amounts of OH2 and CO2 molecules.

    Although humidity is quite variable through out atmosphere, water vapor will absorb most of the IR light most of the time.

  9. 209

    CM, #164–Thanks for clarifying. I knew there was a drop–albeit one considerably exaggerrated in some respects–but find it hard to tell (looking at GHCN tables) what “counts” at which point. Is it really just as simple as who issued a report in which year, or is there a requirement for number of years reporting at a given point? Or is that in Vose & Peterson somewhere?

    Also, presumably some of this data could be “brought in” still, as many of the stations are reporting to Environment Canada, but for some reason are not having the data forwarded to GHCN–yes? (You can view reports for them on Environment Canada’s website–mostly hourly temps are available.)

  10. 210


    Are there any satellites (with sufficient resolution in light intensity) which have been trained consistently on astronomical objects with a reasonably high albedo (Jupiter or other planets, or asteroids) which could be used as a proxy for the intensity of solar light in the visible spectrum? That is, could the SORCE result (increase in visible light during a TSI low) be confirmed by comparing minor changes in intensity in images gathered for astronomical/planetary study purposes? If so, might it be possible to confirm or refute the SORCE results by using planetary images, and then to study those images for periods prior to SORCE becoming operational?

    Or is there too much variability in planetary/asteroid albedo for that level of granularity? Or is there no such satellite to begin with (either appropriately sensitive to intensity, or with consistently measurable images in the desired time frames)?

  11. 211
    Harol-radd Pierce Jr says:

    ATTN: Gavin

    What “experiments”? The results from climate model runs are just computational speculation and conjecture and do not count as valid experimental results.

    What metric do you use for CO2 in climate model calculations? If it is ppmv, then your models and results are absolutely worthless. The metric that should be used is either mass per unit volume or millimoles per unit volume.

    After analysis, the concentration for CO2 in a sample of local air is reported for purified dry air (PDA) which does not occur in the earth’s atmosphere and is comprised of nitrogen, oxygen, the inert gases, which are the fixed gases, and CO2, The composition of PDA (i.e., the relative amounts of the fixed gases) is fairly uniform through out the atmosphere and is idependent of location, elevation, pressure, temperature, and humidity except for minor local variations in particular with respect to CO2. This is the origin of the term “well-mixed atmospheric gases.”

    For PDA at STP (i.e., 273.15 K and 1 atm. pressure), there are presently about 390 ml, 17.4 millimoles, 766 mg, or 0.000766 kg of CO2 in 1 cubic meter. The density of PDA at STP is 1.29 kg per cubic meter.

    In real air there is no unifrom distributon of the masses of the consituents including water vapor and clouds in the atmosphere in space and time as is shown by daily weather maps of the various regions of the earth. High pressure cells have more mass of the gases than do low pressure cells, and thus there is no uniform distribution of CO2 in the atmosphere. Air containing water vapor is less dense than dry air and has less mass of fixed gases and CO2

    Clouds are liquid water in the air, and the tiny droplets of water will contain the atmospheric gases, the amount of which will depend on local temperature and pressure. Since clouds move about they can transport CO2 in the liquid phase from location to location. Depending on local conditions, they can release into local air some on the gases or evaporate and release all the gases and water vapor. The clouds can also release rain drops which will carry the atmospheric gases to the earth’s surface.

    The positive water feed back hypothesis is wishful thinking, i.e., speculation. The wind is the most important mechanism that transports water from the oceans,lakes, ponds, etc onto and into the land. Air pressure also influnces humidity. High pressure cell have dry hot or cold air whereas low pressure cells usually bring rain, snow, or ice pellets.

    BTW, what is the geomerty of the atmosphere and the earth used in climate models calculations?

    [Response: So let me get this straight, you think that your back of the envelope hand waving trumps a calculation made using a climate model? On the basis of what? If you can find a similar calculation (that takes account of the atmopsheric and ocean heat transports, the change in latent and sensible heat, the shifts in the radiative effect as the concentrations of various components decrease etc. and that gives a dramatically different answer, then we can compare. But simply to assert that the answer is unpalatable to you is no argument at all. And for your information, positive water vapour feedback is not ‘wishful thinking’ (I would much prefer that it was smaller than it is), but rather an experimentally and observationally determined fact. Read Dessler, Sherwood, Del Genio or Soden etc. etc.

    You ask a couple of questions that make it clear that you are not very familiar with climate models (which is no problem), but perhaps you should investigate the answers before so forthrightly and unequivocally condemning them. FYI, climate models use spherical geometry and calculate radiative transfer using the appropriate concentration units. – gavin]

  12. 212
    Chris Colose says:

    Harol-Radd Pierce Jr.

    Read this article on the relative roles of the various greenhouse gases in the atmosphere. Also this PhysOrg article has a good writeup on the Schmidt et al 2010 JGR paper.

    The clear take-home point is that while water vapor is the “most important” greenhouse gas in terms of amount of infrared absorption (which is closer to half of the absorbed IR than the 94% number you quoted), it is ultimately the trace molecules (CO2 primarily, which do not condense from an Earthlike atmosphere) that controls the supporting framework for the terrestrial greenhouse, and what governs its ability to change in time.

    Finally, other feedbacks mean that the Earth’s climate would change enormously if you removed all of the CO2 from the atmosphere. First the water vapor feedback becomes relatively unimportant in the limit of the cold temperatures being considered, but what’s more, the albedo of the planet heightens considerably. In this GISS model, the global mean temperature drops on the order of 35 K by removing just CO2 from the atmosphere (much more than the no-feedback 7 K number quoted by Ray Ladbury). This means the greenhouse effect can account indirectly for even more than 33 K of warming and without it the planet is undoubtedly in a deep snowball. And CO2 provides the skeletal structure for this effect.

  13. 213
    Rod B says:

    VeryTallGuy, just for the record it does not describe the reaction to climate change perfectly.

  14. 214

    212 (Rod B),

    Just for the record, your reaction to denial applying to climate change is one of the symptoms of denial.

  15. 215
    Hank Roberts says:

    Here, Rod, Tall Guy:
    Now can we please talk about the topic instead of the hobbyhorse?

  16. 216
    Rod B says:

    Harol-radd Pierce Jr (208), relative and absolute humidity charts assume a ubiquitous source of water to provide the vapor. I’m not sure what the source would be at -10C (let alone -34C). I think sublimation produces magnitudes less vapor than evaporation, though I don’t have the numbers and might be a bit off in scope. Where would your 2.4 g/cu.m. at -10C come from?

  17. 217
    Hank Roberts says:

    This guy copypastes under multiple names, if anyone’s trying to keep track of his seltzer-cloud theory, e.g.

    Aug 27, 2010 … Since clouds move about they can transport CO2 in the liquid phase from location to location. Depending on local conditions, they can ……/our-jgr-paper-on-feedbacks-is-published/
    Sep 24, 2010 … Since clouds move about, they can transport CO2 in the liquid phase from location to location. Depending on local conditions, they can ……/engelbeen-on-why-he-thinks-the-co2-increase-is-man-made-part-4/

  18. 218
    Fred Moolten says:

    To Gavin and others – a question regarding CO2-mediated forcing in the absence of feedbacks. Specifically, how do models estimate the effect of a CO2 doubling to yield an estimated 1.2 C change, such as the one cited in the recent paper by Lacis et al?

    In the 1981 Hansen et al Science paper (with Andy Lacis as a coauthor), the Earth’s effective emission temperature (255 K) is related to the surface temperature via a flux-weighted mean radiating altitude and a constant lapse rate. The constancy of the lapse rate requires that any calculated change at a specified altitude will be matched by the same change at the surface. Using the Stefan-Boltzmann equation, the calculated change for the generally accepted forcing of 3.7 W/m^2 (it was 3.8 in the Hansen paper) yields a temperature change of 1 C rather than the 1.2 C of the models.

    In the Hansen et al paper, the above relationship was described as an approximation rather than an identity, and it seems clear that the models have used a different approach to the calculation of the no-feedback temperature change – one that may not rely on a single averaged “emission altitude” together with a fixed lapse rate applied to that altitude. My question is “in what way do the models depart from that simplified formulation?” Lapse rates are not identical in all parts of the globe, and I suppose an averaging in the 2x CO2 scenario could change the weighting so that the average lapse rate changes, but from my reading of how the results are calculated, that does not seem to be the explanation.

    Are forcings for different spectral bands computed differently and then combined into a weighted average, each representing a different radiating altitude? What other variables contribute to the difference between the 1 deg C and the 1.2 deg C estimates for the 2x CO2 scenario? If lapse rate constancy is assumed, a 1.2 C difference at the surface implies a 1.2 C difference at every given altitude above that still follows the same lapse rate.

    [Response: The no-feedback temperature change in a global model will of course be weighted by area and time and is not as simple as assuming S-B at the emission level. It will be different in the tropics and the poles and the weighting will vary as well. – gavin]

  19. 219
    John E. Pearson says:

    212 Chris remarked to the Radd dude that: “it is ultimately the trace molecules (CO2 primarily, which do not condense from an Earthlike atmosphere) ”

    The Radd dude lives in an alternate reality in which CO2 is transported in the liquid phase at atmospheric pressure.

    “Since clouds move about they can transport CO2 in the liquid phase from location to location. “

  20. 220
    Patrick 027 says:

    Re 211 Harol-radd Pierce Jr –

    1. a molecule of one substance and a molecule of another substance cannot be expected to be equal

    2. in sufficiently warm humid conditions, water vapor would absorb nearly 100 % of LW radiation from the surface, but still leave plenty of room for other greenhouse gases (and/or higher level clouds) to contribute to the greenhouse effect. How? Because the optical thickness of the water vapor is concentrated near the surface (more so than well-mixed gases), where it is at a similar temperature to the surface. The near-surface water vapor and low-level clouds can only reduce the OLR to a flux corresponding to such temperatures (in some conditions they can actually increase the OLR – nocturnal or other inversions). A significant amount of the opacity of well-mixed gases, and higher-level water vapor and clouds, sits ‘on top’ of the lower atmosphere, is found where temperatures are generally much colder, and thus can reduce the OLR more.

    3. Yes, gases dissolve in water. The actual mass of water in clouds is quite small, and the amount of gas that can be carried in such form is very small (though I don’t know the exact numbers offhand- perhaps you could provide them? Note that the volume of condensede water is a very small fraction of the volume of air in a cloud.). There is a cummulative effect over many thousands of years whereby CO2 is removed from the atmosphere (tending to respond to climate so as to balance slow geologic emission – organic sequestration), though this isn’t simply because CO2 dissolves in rain – it is because that rain, with the slight acidity from that CO2 and sometimes some other things, can chemically weather exposed rock surfaces, washing ions such as Ca++ into the ocean, … (bunch of other stuff) … etc. (I don’t know the ratio of CO2 dissolved in rain to the CO2 actually sequestered from the atmosphere by the chemical weathering by that rain – suspect it’s quite a bit larger than 1 – but anyway, the point is that the processes that add and remove CO2 from the air (particularly photosynthesis and respiration/decomposition/combustion) can’t, except in some environments particularly near the surface (under a forest canopy, for example) generally keep up with the mixing of the air by atmospheric circulation to make much difference to the bulk of the atmosphere, so much as to be important to radiation (some variation is detectable and interesting but that doesn’t make it all-important).

    4. Aside from water vapor and clouds, and temperature variations, the greenhouse effect would be reduced in low-pressure systems and increased in high pressure systems; however, lapse rates and cloud and water vapor also vary. The variability of surface pressure on a horizontal surface is generally quite small relative to the total; of course the variability due to topography is important, hence higher elevations would (for the same albedo) tend to be cooler even without mixing, and can, like places with dry air and clear skies, have larger diurnal temperature ranges. Radiation can significantly alter temperature near the surface over land over short time periods, but otherwise the effects of radiation on global climate are more important via cummulative effects over longer time periods.

    5. Water vapor is transported by atmospheric flow. It is removed by condensation and added by evaporation. Temperature affects those last two in a direct way.

  21. 221
    Dan H. says:

    The idea that clouds can transport CO2 in the liquid phase appears to be believed by one person. Sorry Mr. Pierce, but even Roy Spencer rejected that idea. The idea that gases such as CO2 are not evenly distributed in the atmosphere, similar to water vapor, is also not readily accepted (apart from source releases, the gases mix in relatively short time frames, otherwise we would be blanket on the surface with the heavier gases and suffocate).
    Removing all the CO2 from the atmosphere, besides being impossible, would yield calculated results which have no meaning (similar to dividing by zero). The interactions cannot simply be removed for calculation purposes. Hence, certain assumptions are made regarding temperatures, OLR, lapse rates, etc. These values are not perfect, and uncertainties in these calculations become multiplied when feedbacks are included.

  22. 222
    VeryTallGuy says:

    Hank Roberts

    That editorial – “With one exception, none of the Republicans running for the Senate… accept the scientific consensus that humans are largely responsible for global warming.”

    Scary stuff.

    Back on topic, what I don’t understand is why this paper is seen as so significant vs global warming. If anything, it seems to me as a total amateur that even if confirmed, if anything it further reduces the already relatively small effect of the solar cycle and makes it even less likely to be the sun wot did it. Have I misunderstood something ?

  23. 223
    Hank Roberts says:

    Harold (under various names) Pierce has been the’s wrong repeatedly by experts, including Roy Spencer at the above link. He won’t get it. It’s a hobbyhorse.

  24. 224
    Rod B says:

    Bob (Sphaerica) (214), Oh! Go on! The alcoholic often denies he has an alcohol problem. The non-alcoholic often denies he has an alcohol problem. And this shows what, exactly?

    A nit: I was responding to VeryTallGuy’s specific definition of denial, not necessarily to a more broad definition.

  25. 225
    David B. Benson says:

    Harol-radd Pierce Jr initiated quite an interesting exchange, with Gavin and Chris Colose providing useful links.

    In this series of comments, I first want to mention that CUP will soon publish Ray Pierrehumbert’s \Principles of Plantetary CLimates\. For this small matter and for many others, perhaps larger issues, I encourage you to pre-order (or request a nearby lending library to pre-order [I have]) a copy or several to lend out yourselves.

    The second thing is that at least once in the remore past, Terra did freeze over, or nearly completely so (the geologists argue this small point):
    and then this leads make to Professor Pierrehumbert’s book, but I won’t give away the answer.

  26. 226
    David B. Benson says:

    Here is Joe Romm’s take on the Lacis et al. and Schmidt et al. papers:
    It contains helpful graphics along with extensive quotations from GISS press releases and also direct quotations from the two lead authers.

    The only surprise for me was the narrow band of above freezing temperatures directly along the equator. Standard pen&paper approximations don’t find that effect. Perhaps it goes away after a millenium or two?

  27. 227
    Septic Matthew says:

    203, Ray Ladbury: The greenhouse effect raises Earth’s temperature by about 33 Kelvins. CO2 is responsible for about 7 of those degrees. We know this. We’ve known it for about a century. Yes water vapor is important. However, without CO2, we’d be living (or rather not living) on a ball of ice.

    What would be the distribution of temperature without CO2? Would there be no seasons (temporal distribution generally)? Would the equatorial regions be as frozen as the Andes (geographic distribution generally)?

  28. 228
    SecularAnimist says:

    VeryTallGuy quoted Wikipedia: “Denial is a defense mechanism postulated by Sigmund Freud …”

    Few of Freud’s patients were paid to lie by ExxonMobil and Koch Industries.

  29. 229
    stevenc says:

    Nice, you don’t allow me to respond to comments directed at me but you allow comments that are directed at me. That is low and doing so shows your level of integrity. I disagreed with you before but respected you. Feel free to scratch the last part of that now.

  30. 230
    David B. Benson says:

    Septic Matthew — Follow the link in my 226.

  31. 231
    Septic Matthew says:

    229, David B. Benson

    Thanks. Looks like our messages crossed in the aethersphere. Like you, I have Raymond Pierrehumbert’s book bookmarked, and I plan to buy it when it is published.

  32. 232
    Thomas says:

    Horold and others:
    You can actually measure return IR radiation pretty easily. I have one of those infrared thermoters, mine cost $100, but you can find some models at half to a quarter of that cost. They have a cone of sensitivity of a few degrees (narrow field of view costs more). So you can point them up at the sky and measure the effective temperature of the sky. If you do it you will discover some things, dry clear skies are cooler than dry (humid skies). Clouds warm things significantly. You can use Stephan-Boltzman to estimate downgoing (and upgoing) IR fluxes, etc.

  33. 233
    Hank Roberts says:

    Figure 2: … Quicktime movie (10.3 MB) of a Varanger simulation which combines reduced solar luminosity, 40 ppm CO2, and reduced ocean heat transport. The simulation runs 60 model years from initial, non-snowball conditions until an equilibrium result is obtained.

  34. 234

    HP, that less water evaporates in colder air is an observed fact, AND one theoretically explained by statistical mechanics and physical chemistry, AND one mathematically described by the Clausius-Clapeyron relation. If the Earth gets cold enough, water vapor drops precipitously and the tropics freeze along with everything else. There is good geological evidence that it has already happened at least three times (the Huronian, Vendian, and Sturtian glaciations). Google “Snowball Earth.”

  35. 235
    CM says:

    [off-topic] Re: GHCN station numbers / Canada / Detroit News story,

    correction to my #164: With duplicate time series removed, I get 496 Canadian stations in 1989, rather than 623, and a somewhat less sharp drop, since the other numbers I gave are not affected.

    Kevin McKinney #209,

    – Uh, for each year, I’m just counting the number of lines in the v2.mean dataset with Canadian station data for that year, and (after slapping forehead) eliminating duplicates (where there’s more than one line with the same station and same year). Was that clear? For the whole v2.mean dataset, I find I can very closely replicate the Peterson & Vose 1997 [PV97] graph, so I just may have chanced on the same method. (Don’t speak Fortran, so haven’t used the tools provided with GHCN.)

    – The GHCN v2 dataset already includes stations with at least 10 years of data, PV97 say.

    – It is my understanding that only a limited subset of stations are being updated automatically in real time (see PV97, “Updates”), and the retro-active filling-in of more station records takes place irregularly, as and if someone takes the trouble. But a GHCN v3 is now in beta, and it looks like that’s where the action is these days (see Zeke Hausfather’s sneak peak, including yet another look at how little the global mean temp record is affected by these ups and downs).

  36. 236

    #235–CM, thanks for letting those of us who are interesting profit from your time & effort. It probably seems pretty basic to you, but it’s helpful to me & probably some others as well.

    I’m going to rush off and have a look at the “sneak peek” now. . . .

  37. 237

    “. . .those of us who are interested. . .”

    Well, hopefully not boring, too, but that’s not what I meant to type.

  38. 238
    CM says:

    Kevin, I do count you among the interesting! And thanks a lot, but I’m an amateur, learning as I go, so take my stuff with a pinch of salt. When something looks like it can be done in 20 lines of Perl, I just get this urge to try. Oh, and I meant “peek”, not “peak”.

  39. 239
    Septic Matthew says:

    233, Hank Roberts, thank you

  40. 240
    Jacob Mack says:

    Even with the well established posiitve feedbacks there are great limits to how mcuh the globe can warm based again on simple physics.

  41. 241
    Hank Roberts says:

    > great limits
    The PETM involved biology as well as simple physics. Is that the warmest ever?

  42. 242

    JM 240: Even with the well established posiitve feedbacks there are great limits to how mcuh the globe can warm based again on simple physics.

    BPL: It only has to warm a few degrees to wipe out human civilization.

  43. 243

    Thought I’d post this here to, though off topic, on target.

    October Leading Edge report features Cuccinelli’s ‘Witch Hunt regarding his attempt to undermine publicly funded science by attacking Michael Mann

    Well, this won’t be my last word on this subject. That probably goes for many others as well.

    Relevant comments and criticisms always welcome

  44. 244

    240 (Jacob Mack),

    You are so right! Just using common sense (and, of course, fizzix), I’d computorionally guesstimate that the maximum, worst case swing for the earth’s surface temperature is at most 3%, maybe 4%! That’s a small number, right?

    Let’s see, earth’s surface, 281K, times 4% divided by 100 = 11.24˚C maximum warming, which is hair more than 20˚ F.

    You are so right! There’s nothing to worry about!

  45. 245

    JM, the world only has to warm a few degrees for human civilization to collapse.

  46. 246

    Apologies to all. In my haste, I apparently mis-spelled “computortionally”.

    [These are just the sort of errors that come back to haunt the well-meaning researcher, scientist or just plain smarter-than-everyone-else-because-I-said-so-and-anyway-who-the-heck-are-you-to-question-me sort of person.]

  47. 247
    Didactylos says:

    Jacon Mack said: “there are great limits to how mcuh the globe can warm”

    What, then, is the upper limit?

    We can’t use temperatures from millions of years ago, because the sun is hotter now. How can we place an upper limit?

    If we suppose that we release all the stored carbon (from fossil fuels, ice, tundra, clathrates, etc) so that the atmosphere returns to a state not seen for many millions of years – and add in the effects of a hotter sun – I can’t see any hypothetical “upper limit” being particularly beneficial for humanity.

    Can you?

  48. 248
    John E. Pearson says:

    240: Jacob Mack said: “there are great limits to how mcuh the globe can warm based again on simple physics.”

    Nonsense. Let’s hear your simple physics that limits warming to less than, say, 20C.

  49. 249
    Thomas says:

    “there are great limits to how mcuh the globe can warm based again on simple physics.”
    Well, there is always thermodynamics. That says we can’t get the planet any hotterthan the surface of the sun. Although that’s hardly a useful constraint on our models.

  50. 250
    Paul van Egmond says:

    Also, the fact that no fossil remains of humans were discovered from the eocene period. Clearly that is proof that humans couldn’t live in such a warm climate ;-)