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Hockey sticks: Round 27

Filed under: — group @ 24 October 2005

Two more teams in the seemingly endless jousting over the ‘hockey-stick’ have just made their entry onto the field. In the first two (of four) comments on the original McIntyre and McKitrick (2005) (MM05) paper in GRL, von Storch and Zorita, and Huybers have presented two distinct critiques of the work of M&M.

The two comments focus on the ‘PC normalisation’ issue raised in MM05 which we discussed previously. Specifically, von Storch and Zorita show that in a GCM model emulation of the Mann, Bradley and Hughes (MBH) method, changing the PC normalisation technique makes no difference to the eventual reconstruction (i.e. it is not the normalisation that creates the ‘hockeystick’), consistent with earlier conclusions. Huybers comments that neither of the two suggested normalisations are actually optimal, and proposes a third method which looks like it gives results halfway between MBH and MM05. However, given the von Storch result, this too is unlikely to matter in the final reconstruction.

Huybers additionally makes an interesting point regarding the calculation of significance levels in MM05 and shows that a crucial step (the rescaling of variance of the proxies to match the variance in the instrumental calibration period) was missed out. Including it produces results identical to MBH.

For each comment comes a reply, and in the M&M responses, they introduce a number of further complications and focus on the quality of some of the proxies that were input data into the MBH methodology. We note as an aside that this is quite a different criticism than claiming that MBH’s methodology contains ‘coding errors’ (to quote one of the Ms). Indeed, the quality of paleo-climatic data and its relationship to climate variables has been discussed all along (see for instance MBH99).

Their further calculations will take time to assess, but of the original claims in MM05, the first (the PC normalisation issue) demonstrably makes no difference to the reconstruction, and the second (the calculation of the significance of the RE statistic) was just wrong. So for this round at least, it looks like ‘Hockey Team: 2, MM: 0′.

Look out for the next bout coming to a journal near you…


133 Responses to “Hockey sticks: Round 27”

  1. 1
    CharlieT says:

    “For each comment comes a reply”
    I cant see them!

    [Response: Sorry. Only versions I can find are subscription only at GRL: here and here. - gavin]

  2. 2
    greg meyerson says:

    hi:

    I am an english professor teaching a course on global warming using some of the most accessible material I can find. anyway, we are reading crichton’s book and the main paper I wish them to write on crichton is a response to the science claims in the book. I’ve found much useful on this site for just this purpose so I want to thank you.

    so that’s a comment and here’s a question: skimming thru essex and mckitrick, I recall that they claim that global temperature doesn’t exist. claims like this for ordinary people are so stunning as to cause temporary paralysis.

    I’d like your take on this sort of comment(assuming I’m correct about e and m). . surely, it involves the confusion of local and global you have mentioned many times. In fact, I think they verge on saying there is no climate, only weather; no global, only local and regional. playing amateur sociologist of knowledge, I think some of this denial of the global comes from their general philosophical commitment to free markets, assumptions which tend to view only the individual as real, making larger institutions or “systems” metaphysical (an illusory abstraction).

    but if they’re going to say something like this, I’m wondering if they are consistent. do they ever chime in to admit that there is warming but that it’s caused by natural variability? what DO they say about increasing greenhouse gases in the atmosphere? can they even cite richard lindzen as an ally since Lindzen believes in the “atmosphere,” and it seems plausible to me that e and m have no right to this concept. if there is no global temperature, there is no global atmosphere either–merely atmospheres (local).

    This skeptics debunking of “the global” as a “reification” (I think they actually use this term that used to be reserved to marxists) strikes me as similar to creationists denying “methodologicall naturalism.” It is a “debunking” of something so fundamental that it makes one’s jaw drop–as I noted above, using paralysis rather than drooling as a metaphor.

    anyway, I rarely see responses to this specific clam of the skeptics (which I’ve only actually seen in essex et al). is it because it’s so stupid? or because it’s a special case of the local/global mistake?

    [Response: I'm not sure the E&M claim makes any sense. Global sfc t obviously does exist. The only way to make sense of it is to interpret them as saying that sfc t is not conserved, unlike say heat content (which isn't conserved either, but changes in it represent energy flows in and out). The problem is that for most purposes (fluxes of heat into the oceans, and hence ocean warming and hence sea level rise; or biosphere responses) what you care about *is* the surface temperature. Why is why everyone pays attention to it. Plus its best-measured. If you're looking for more debunking skeptic nonsense, then you can also try this and this - William]

  3. 3
    Brooks Hurd says:

    CharlieT
    You may find what you are looking for here.

  4. 4
    nanny_govt_sucks says:

    I’d be interested to see your line-by-line critique of the M&M replies. Perhaps this will help put some of these long-contested issues to rest?

    [Response: Right now we are just observing - it is probably for the commenters to respond to the replies should they feel that is necessasy. There are still a number of papers going through the works so we will probably wait for the dust to settle... -gavin]

  5. 5
    Coby says:

    Re #2:
    Greg,

    Check here:
    http://www.realclimate.org/index.php?p=74
    http://www.realclimate.org/index.php?p=76

    and also here:
    http://www.boston.com/news/globe/ideas/articles/2005/02/06/checking_crichtons_footnotes/

    There is some discussion of Taken by Storm and temperature averages here that is quite illuminating:
    http://timlambert.org/2004/05/21

  6. 6
    Stephen Berg says:

    Re: “So for this round at least, it looks like ‘Hockey Team: 2, MM: 0′.”

    So, the head-to-head record is Hockey Team: 27, MM: 0, since this was Round 27? Way to sock it to ‘em!

  7. 7
    Steve Bloom says:

    Re #2: Make sure to cover Spencer & Christy’s satellite data come-down (covered in a recent post here) and the fresh paper marking the end of Lindzen’s “iris effect” (very new so still not analyzed in any public spot I’m aware of), abstract at http://www.sciencemag.org/cgi/content/abstract/1115602v1 .

  8. 8
    Sanderson says:

    Well strictly speaking this website is more environmentalist than scientific. It is highly evaluative and argues from many assumptions that have no scientific validity.

  9. 9
    Eli Rabett says:

    As near as I can make out Essex and McKitrick are going back to a basic principle of thermodynamics, that temperatures are intensive quantities that cannot be added (or averaged, it comes to the same thing). For example given a pot at 30 C and a bowl of water at 20C, you can’t average the temperatures to find what the final temperature will be when you pour the water into the pot. The ENERGY of different parts can always be added (or averaged), and the final temperature deduced (General Chemistry I, General Physics I).

    For homogeneous sytems (the atmosphere, for example) there is a simple linear relationship that relates the energy of any part of the system to the temperature, for example, by volume E = V C T where V is the volume of a packet, C the specific heat per unit volume and T the temperature. This means that for the homogeneous atmosphere, you CAN add the temperatures, divide by the total volume and get a meaningful average temperature. That average is simply related to the average energy of the system as long as the specific heat is constant with respect to the range of the temperature variation. This is the case for the atmosphere.

    If one were being pedantic, one would say that the average surface temperature is linearly proportional to the average energy content of the atmosphere at the surface and that changes in the average surface temperature proportionally track changes in the average energy content of the atmosphere at the surface. As far as I can see, E&M do not recognize this.

  10. 10
    Eli Rabett says:

    Dear Sanderson,

    Please be specific as to which assumptions made on this site have no scientific validity. We do not do drive bys.

  11. 11

    Re #7,

    Steve, there seems to be some discrepancy with the Chen ea. findings, whom used the same satellite data (HIRS) for the upper troposphere humidity (UTH). They found a drop of 0.2% of UTH near the equator and 0.15% in the subtropics over the period 1985-1994. In the same period, cloud cover reduced with -1.7% and -0.33% for the same regions and sea surface temperature increased with 0.083 C. This is reflected in radiation trends of 5 W/m2 IR radiation back to space and 2 W/m2 less reflection of sunlight for the period 1985-2000, which results in 3 W/m2 net loss to space. According to Chen ea., the difference is not due to changes in clear sky radiation (too small, which may point to small differences in water vapour column), but in cloud cover.

    A significant difference further is that the radiation balance (see Wielicki, fig. 2) shows very large changes for both the 1992 Pinatubo and the 1998 El Nino. The latter can be seen in the water vapour trend of Soden ea., but the Pinatubo cooling (0.5 C with a corresponding drop in water vapour) seems to be underestimated.

    Lindzen may be wrong by looking at too small scale (tropical storms), but the overall tropical radiation balance (30N-30S) seems to respond to a warmer climate by emitting more heat to space…

  12. 12
    Yelling in the Fog says:

    Re #4:

    Nanny, your request for a critque of the replies shows an interest in the topic. So perhaps you have moved beyond the stage where refered to RealClimate the the neo-con-wannabe climate history revisionism site?

    Regards,
    Y.

  13. 13
    greg meyerson says:

    thanks to both cody and eli for helpful comments.

    tim lambert says the following in response to e and m:

    “In their briefing, Essex and McKitrick claim that physics provides no basis for defining average temperature and:

    ‘In the absence of physical guidance, any rule for averaging temperature is as good as any other. The folks who do the averaging happen to use the arithmetic mean over the field with specific sets of weights, rather than, say, the geometric mean or any other. But this is mere convention.’

    Physics does, in fact, provide a basis for defining average temperature. Just connect the two systems that you want to average by a conductor. Heat will flow from the hotter system to the colder one until the temperatures are equalized. The final temperature is the average. That average will be a weighted arithmetic mean of the original temperatures. Which is why the folks doing the averaging use weighted arithmetic means rather than the geometric mean.”

    Eli: is this consistent with the answer you gave me? forgive my ignorance but as I tell my students, the secret to learning is to get over the fear of looking stupid. I have some questions about your pot and bowl example and so would like your email if you wouldn’t mind: but is this example a good analogy for the atmosphere? Is the relation between regional temperatures analogous to water temps in pots and bowls? (I realize the analogy was meant for another purpose)

    on the lambert website, while others raise the thermodynamic explanation of e and m’s claim, lambert himself focuses on e and m’s claim that statistical techniques for interpreting data can give you incompatible results, the same data interpreted as so much warming in one framework and so much cooling in the other.

    This appears to be a skeptical argument about the use of statistics.

    I assume this website is for the general public. are there prerequisites? how ignorant are we permitted to be (in my view, the answer should be “pretty damn ignorant” if you want the website to make sense to ordinary people). can people recommend a “global warming for dummies” type thing that can teach some of the rudimentary physics? much of the problem here is science illiteracy.

    gm (which could be greg meyerson or our proverbial grandmother)

    [Response: I don't think the E&M stuff is very interesting, but I seem to have written a post on it (well actually, on why no-one is interested in it :-), and since this is self-promotion day, its here - William]

  14. 14
    John Finn says:

    Gavin

    I’m not sure I’ve seen the H-S reconstruction properly, so can you or anyone provide a reference via a link for me.

    Thanks

    [Response:The original paper is available at http://www.meteo.psu.edu/~mann/shared/articles/mbh98.pdf -gavin]

  15. 15
    John Cross says:

    GM:

    I believe that what Tim was trying to show was that you could manipulate the statistics but that if handled properly they would show warming. For example, if I recall correctly, Tim found that one method that was used my M was to “pad” the data with zeros where no data existed. This would obviously introduce a false cooling into the data.

    John

  16. 16
    greg meyerson says:

    re 9 and homogenous systems.

    so then m and e’s mistake about global temp is that they treat the atmosphere as something other than a homogenous system? meaning that–in terms of your example–they treat homogenous systems as bowls and pots (filled with water)?

    is this right?

    thank you all–and I forgot to thank william too.

  17. 17
    edward lanwermeyer says:

    The hockey stick discussion, and its elegant exposition recently notwithstanding, I am at a loss why social scientists of a variety familiar to most universities have not addressed the implications of the climate record upon human (mostly European) bahaviour, since 1000.With some exceptions they seem innocent of the developments in reconstructing past climates. The final graph of Gavin et. al, taken from the newer paper of Moebius et. al. which they cite is the single most tantalizing physical record of the Northern Hemisphere I have ever stumbled on ..anybody out there with a social science orientation wish to address this ?

    writing from Columbus (edward lanwermeyer)

  18. 18
    Steve Bloom says:

    Re #16 (GM): Bowls and pots of differing and unknowable volumes, for that matter.

  19. 19
    Tom Fiddaman says:

    Re #1

    M&Ms extended replies are on their blog: look for Huybers (10/19) and von Storch (10/4).

  20. 20
    Steve Bloom says:

    Re #11 (FE): No one questions that hotter tropics will result in increased heat flow into space; the issue is how much. Ferdinand, I started having a look at the relevant papers, and noticed a couple of things: Soden was a co-author of the 2002 Wielicki paper you cite, in 2002 Soden was lead author of yet another paper in Science, this one focused on the effects of the Pinatubo eruption, Wielicki and Wong (also an author of the 2002 Wielicki paper) were in turn co-authors of a 2003 IEEE paper debunking the iris effect, and… how in the world can so many scientists, many of them frequent collaborators, screw up something this fundamental over such a long period of time and have most of it get through peer review in the same prestigious publication? I’m just speculating here, but assuming for the sake of argument that there is some contradiction between the 2002 Science papers and the new Soden Science paper, did it occur to you that maybe the science has advanced a bit in the 3-1/2 years between their publication dates? I think you need to do some more homework. (I find Google Scholar very useful for making sure I locate all the relevant papers.)

  21. 21
    Lynn Vincentnathan says:

    If it’s ice hockey, the game might get called off due to thaw.

  22. 22
    Eli Rabett says:

    Mostly for Greg Meyerson: Our different examples are exactly the same. However, the final temperature of the systems brought into contact are not “average” temperatures. Formally, this equilibrium is the temperature at which the entropy of the system + surroundings is a maximum :(. Intuitively, we know that this is the temperature at which both bodies (pot+water) are at the same temperature, and this temperature is rather simple to calculate by equating the heat flow from one body to the other under the constraint that they reach the same final temperature.

    OTOH, if the atmosphere is uniform, then you have a much simpler case where the energy of every unit volume is linearly proportional to the temperature in Kelvin, and this, like energy can then be added or averaged as you will.

    Which brings me to the next point. The errors McKitrick makes about averages are much worse than Tim Lambert describes. Because the atmosphere is homogeneous any average of absolute temperature is meaningful. However, since the linear average is meaningful, the one can make the average using any linear temperature scale with an arbitrary zero (you could use Celcius, Fahrinheit, Rankine, or what you will) since you can always write T(Rabett) = T(K) + To(Rabett) for every temperature.

    One cannot be so cavalier with other types of averages. For temperature scales where there are negative values in the data set, root mean square will not produce a meaningful result because negative and positive values of the same magnitude contribute the same positive amount to the average. If negative values are found in the data set the sign of the geometric average depends only on whether the number of negative values is even or odd. If there are zeros in the data set, the geometric average is ALWAYS zero and so on.

    If you want to use these other sorts of averages, you MUST use a zero that is lower than any element of the data set, e.g. absolute zero, so there are no negative or zero values of temperature in the data set. Lambert shows that in those cases the various averages, although not identical are close. McKitrick does not do this. He does not even recognize the problem. His examples are not even wrong.

  23. 23
    John Finn says:

    I thought I posted this question earlier.

    [moderator:Yes, you did. It was eliminated on the basis of our comment policy (see our discussion of "signal vs. noise"). Postings which seek to muddy the issues, rather than clarify them, are often eliminated, especially when the tone seems inappropriate. This comment was screened in to make a point. See below.]

    There are 4 NH temperature (actual measurements) records which go back at least 200 years, i.e. Eastern US, Sweden, Central England and Armagh Observatory.

    [moderator:This is just wrong. There are 9 that go back to 1777, 4 that go back to 1753. There are many reviews of the data by Jones, Bradley, and others. Please aquaint yourself with the facts before posting. Sometimes we will correct factual errors in comments, sometimes we will simply screen out the comments altogether if the net effect is to disinform our readers, as we don't have the time to correct every fallacy.]

    None of these records exhibit any behaviour remotely similar to the hockey stick shape.

    [moderator:This too is just wrong. In fact, the available instrumental temperature records, when formed into a hemispheric mean, closely match the reconstructions. See the review paper on "Climate Over Past Millennia" by Jones and Mann (2004) (figures 2 and 3). In fact, it is clear that the instrumental estimates run a bit warm relative to all of the proxy reconstructions (i.e., they suggest even less of a "little ice age" in the 18th and 19th centuries). This is likely due to problems with thermometer sun exposure, which is particularly pronounced during the summer at high latitudes, prior to the modern introduction of "Stevenson screens". There is much literature on this. You can start out with the review paper cited. ]

    Don’t you think this is strange?

    [moderator:What appears strange actually, is your willingness to post a comment without familiarizing yourself with the basic facts first. In the future, please make sure to familiarize yourself with facts before posting here. Thankyou.]

  24. 24
    Stephen Berg says:

    More evidence of climate warming:

    “MAJOR CORAL BLEACHING EVENT EXPANDS ACROSS CARIBBEAN, SEVERE IN PUERTO RICO AND U.S. VIRGIN ISLANDS

    NOAA’s New Coral Reef Watch Satellite Bleaching Alerts Aiding Managers”:

    http://www.noaanews.noaa.gov/stories2005/s2526.htm

  25. 25
    greg meyerson says:

    thanks eli:

    I need to know something about the difference between arithmetic and geometric mean. I’ll ask a math friend.

    but if you want to help me, I’m at meyerson@att.net

    I actually get the point about square roots–I think.

    Arithmetic mean: avg=1/n(x1+x2+…+xn). Geometric: avg=(x1*x2*…*xn)^(1/n); where “^” is to-the-power-of – William

  26. 26
    Lynn Vincentnathan says:

    Re #8, let me clarify the difference between scientists and environmentalists. I assure you the hosts of this site are definitely scientists, though I heard of a Chicago scientist buying a SunFrost frig (1/10 the electricity of other frigs), so some might also be environmentalists in their private lives.

    SCIENTISTS follow “THE SCIENTIFIC MODEL” of avoiding false positives (making a claim when it is false); that is, they do not make claims unless there is high confidence that they are right (usually 95% certainty), so as to protect their reputations; otherwise no one will believe them again (like the boy who called wolf).

    ENVIRONMENTALISTS, those concerned about reducing harm to people and the earth, follow “THE MEDICAL MODEL” of avoiding false negatives (acting as if there is no problem, when indeed there is); that is, they do not need high certainty of a problem to start addressing it. It’s unimaginable for a doctor to tell a patient that there is only 94% certainty that the lump is cancerous, so they won’t operate. Some environmentalists even follow the precautionary principle of disallowing actions, unless they are proven safe –like not emitting GHGs beyond needs and simple pleasures, unless we are 99% certain AGW is not happening (the higher level of certainty is due to the risks being so grave).

    I’m an environmentalist. I already figured AGW was happening back in 1990, 5 years before it reached 95% scientific certainty in 1995 (as did Pope John Paul II, who told us it is everyone’s responsibility to solve), and I started reducing my GHGs in cost-effective ways and am saving $$hundreds per year without lowering my living standard. Since evidence of GW has continued to pour in and become stronger & stronger (and since I’m saving heaps of money by abating it), I don’t think any contrarian or scientist can convince me to start emitting more GHGs, even if it becomes 100% certain AGW is not happening.

    The HOCKEY STICK was a done deal for me back in 1990, well before the first articles came out on it. Regular GW is no longer my greatest concern. I’m on to worrying about RUNAWAY GW, or the VENUS EFFECT, our human-induced warming causing nature to start emitting more & more GHGs (CO2, CH4) in positive feedback fashion, perhaps leading to near extinction of life on earth, as happened from GW during the end-Permian extinction, and the other 4 great extinctions. I’m convinced we’re already into or on the brink of the 6TH MASS EXTINCTION, though we may not reach scientific certainty until itâ??s a done deal. Itâ??s possible we may not be able to reverse this, even with big GHG cuts, but I have to keep doing my best with the hope it’s not too late – and would keep doing my best, even if scientists finally do tell me it’s too late (hoping they’re wrong). That’s what it means to be an environmentalist (or Christian, or Buddhist, etc).

  27. 27
    Tom Fiddaman says:

    Re 26

    #8 was hardly deserving of an answer, but I’d draw a different distinction. Science is about figuring out how things work, and the usual test of understanding and usefulness is prediction. Success at prediction is enhanced by maximizing the number of different hypotheses (models) you can generate and test against numerical data and other available information. 95% confidence levels and the like are used as a sieve to reject the bad models, but that doesn’t mean there’s a 95% chance of being right. The curse of course is that 5% of the time you’re wrong randomly, and those results are disproportionately interesting, and thus likelier to be published. However, time eventually resolves such problems by providing more data to test out-of-sample predictive capability. It would be great if there were some way to update the proxies and test temperature reconstructions; that would really lay to rest (or not) all the accusations of spurious correlation etc.

    Environmentalism, on the other hand, is more about values – do you care if polar bears go extinct? Do you prefer the mall or the forest? etc. Science and environmentalism may get intertwined if, for example, you prefer the mall but predict that environmental side effects might compromise the ability of industrial society to build more of them.

    I see no real problem if many scientists are also environmentalists. If they were systematically biasing their own results through wishful thinking or more sinister means, a lot more of GW theory would have been refuted in the last 15 years.

    As an aside, SunFrosts are perhaps 1/10 the energy of a lousy old fridge or perhaps a big commercial fridge, but the best ordinary top freezer consumer fridges are now very good; a SunFrost might use 2/3 the energy. It’s rather striking to me how many people will buy a $6000 SubZero or Northland of dubious efficiency without batting an eye, and how few will shell out less than half that for a SunFrost. Shows how far we are from actually confronting the issue.

  28. 28
    John S says:

    Lynn,

    Not wanting to rain on your doom and gloom. But, surely the fact that there is still life on earth despite previous huge changes in our atmospheric composition suggests that the Venus effect is a bad science fiction scenario rather than a serious possibility. Indeed, let’s just suppose that we wipe ourselves out with an event of similar magnitude to the end-Permian extinction. In your apocalyptic scenario that removes the cause of the atmospheric imbalance and the earth can go back to some more hospitable equilibrium – no? The fact that the earth has been capable of sustaining life for the past billion or so years suggests to me that you might be worrying a little too much.

  29. 29
    Dano says:

    But, surely the fact that there is still life on earth despite previous huge changes in our atmospheric composition suggests that the Venus effect is a bad science fiction scenario rather than a serious possibility.

    I’m not really taking sides here, but pointing out that for the underlying support of the “don’t worry” argumentation here to be effective, IMHO, the premise must be that the previous 5 extinctions were caused by sentient beings that knew and debated the consequences of their actions, thus everything turned out OK ’cause there’s still sentient beings around to choose their fate. My sniff test for this argument causes my head to jerk back and my nose to scrunch up.

    Anyway, the post topic was about Hockey Sticks and debating attribution, and the comments got around to noticing that debating consequences is more fruitful than attribution. I agree.

    Fer chrissake, getting bogged down in the attribution is a subset of the larger debate on action. Let us keep that in mind when we calculate our personal energy expenditures.

    Best,

    D

  30. 30
    garhane says:

    I would like to extend congratulations from a general reader who has followed this blog, and the evolution of climate science for a few years. The success of the Real Climate group in the brief life of the blog has been steady and swift. Now the blog has become authoritive, while it continues to offer an absolutely fascinating and truly educational read, delivered with style. One pictures the coach full of the members of the Pickwick Club careening down the road towards a noisy dinner with lots of good talk afterward. And now here is the Wall Street Journal giving prominence to two more supporting accounts in the historical review of climate summed up, figuratively,by the Hockey Stick. And is that the dean of the lot, von Storch, offering what looks like a substantial climb down from a rather rude comment only a year ago. And who do we see behind the parade carrying broom and dustpan. Can it be Don Quixote McKitrick and Sancho McIntyre. Clearly the burden of the work has not proven excessive, so I hope one can look forward to a lot more of the same education in science the general reader receives from the scholars who contribute to Real Climate. Even those who oppose you have enriched the blog, and it just does get any better than that.

  31. 31

    Re #20,

    Steve, if the laws of thermodynamics still hold, then a net extra loss of 3 W/m2 (top of atmosphere) should give more cooling (or less warming, dependent of the absolute values). In the same period, the direct increase of GHGs has given some 0.7 W/m2 more heat retention (at the surface). The difference may be a result of (observed) faster air circulation over the tropics. The more recent papers touch on related topics, but it is not clear to me (yet) where the differences are, as e.g the last paper substracts signals of different satellites, while the first uses only one signal. Need a few days more to find it out…

  32. 32

    re:#13

    Some intro-level global climate change articles which I will shamelessly recommend to you (from the NASA Earth Observatory, a site I contribute to).

    Global Warming
    primer on anthropgenic warming

    Will Runaway Water Warm the World?
    Arbiters of Energy
    discussions of the Iris effect and water-vapor feedbacks

    Under a Variable Sun
    solar forcing

    Tango in the Atmosphere: Ozone and Climate Change
    self-explanatory

  33. 33
    greg meyerson says:

    The arithmetic mean (or average) of a group of n numbers is just their sum divided by n. So the arithmetic mean of 6, 10, and 23 is 39/3 = 13.

    The geometric mean of a group of n numbers is the nth root of the product of those numbers. So the geometric mean of 5, 45, and 120 is the cube root of 5�45�120 or 30.

    hi william: I got the above answer to my question about arithmetic and geometric means–equivalent to yours, but you have to admit, the above is a lot simpler for “dummies” (aka most of the population). 39/3 = 13; sum of x1,x2,xn (1/n).

    best imo is using both types of examples.

    as I mentioned, I am an english professor (critical theory, am. lit and advanced comp) teaching at an hbcu (historically black college or univ); I am teaching a comp course where all our readings are on global warming. this course has to educate–and I purposely picked subject matter on which I am pretty much like they are, though with better research habits.

    most of them are afraid of science and know little math. I suspect the american population isn’t much different.

    this issue, like many others, is too important to be left to the experts and too important for the experts to be left out. so the experts have an enormous responsibility, especially given the declining state of science ed and ed in general in public schools. but also given the disciplinary division of labor.

    don’t you guys want at some point students from high schools and universities to be able to ask questions of the bloggers and get answers they really understand?

    at my university, we are trying to set up a program for first two years of college that is highly interdisciplinary and focused on integrating science education into curriculum as whole. writing courses are great for this and it would be good in such courses–those housed in humanities– to know enough to be able to do more than analyze the rhetorics of science in texts and films of pop culture (lone heroic scientist in day after tomorrow; lone heroic scientist in state of fear + naive liberal lawyers).

    I realize the whole issue of audience is very difficult to solve.

    thanks.

    and great job.

    gm

    [Response: Audience: fair point. I would say, that we are writing for people who won't be too scared by 1/n(x1+...+xn). That means that someone else will have to translate for people who prefer "the arithmetic mean (or average) of a group of n numbers is just their sum divided by n. So the arithmetic mean of 6, 10, and 23 is 39/3 = 13". I agree with you: there will indeed be people who prefer the latter. Maybe you will have to do the translation! - William]

  34. 34
    greg meyerson says:

    thank you robert!!

    g

  35. 35
    Eli Rabett says:

    For greg meyerson and others:

    If you want to know the meaning of some mathematical or scientific term, there are two good places to go on the net. The first is the wikipedia (http://wwww.wikipedia.com) the second is Eric Weisstein’s world of science (http://scienceworld.wolfram.com/).

  36. 36
    Brooks Hurd says:

    Re:23

    There are many reviews of the data by Jones, Bradley, and others. Please aquaint yourself with the facts before posting.

    Can you please direct me to Jone’s data so that I can aquaint myself with the facts?
    Thanks

    [Response: See the link provided to the Jones and Mann review paper. -mike.]

  37. 37
    Lynn Vincentnathan says:

    RE #28

    [moderator: some argumentative language has been removed. lets watch the ad hominem please. We don't want flame wars on this site!]

    And for the millions who will die as AGW gets worse, and perhaps the billions who may die IF runaway GW kicks in & leads to the 6th mass extinction. I think we must not let this happen. Failure is not an option.

    And it’s not just millions or billions I’m concerned about. Each single life is precious, and it’s not good to be in the business of killing people. That’s my main point.

    I do agree that Earth is not Venus – some scientists have already told me how much they hate the label “Venus effect,” but I find it informative, simply because it gives some idea about the runaway global warming that did happen 5 times on Earth (which later, obviously, stabilized back to livable conditions).

    RE #27,

    [moderator: some argumentative language has been removed.]

    You probably didn’t have the wonderful 10th grade education in ecology that I had, so I can’t blame you if you fail to understand that all life is connected (along with the inorganic world), and that killing off non-human species could have negative effects on humans – esp. capstone species, food crops, livestock…

    I also don’t like false dilemmas like “it’s either them animals or us people.” I prefer to have my cake & eat it too. Now get busy finding out how we can save the earth (incl. the polar bears) and still live somewhat high on the hog. I want solutions, not “it’s impossible” rhetoric.

    And thanks to the scientists for bringing the problem of AGW & the hockey stick to light, so we can be forewarned and do something about it.

  38. 38

    The global mean temperature is trivially easily defined, and is usually taken to be an arithmetic mean.

    You could make a case that the physically important quantity is not temperature, but its fourth power. However, although this would weigh tropical regions more than polar ones, I think it’s fair to say that the global mean surface value of T^4 is also increasing far beyond background variability.

    I can’t imagine why you would want a geometric mean, but to do that on a continuous field you would just get the antilogarithm of the average logarithm. Again it is surely increasing above background variability.

    If someone can come up with a definition of temperature that has some objective justification and under which definition it isn’t rapidly climbing, that would be interesting, but of course no one has done such a thing. The best you could do would be to say something like “average global temperature is mostly the average temperature over the North Atlantic”, which is hardly global, is it?

    So this “average temperature” complaint is just another red herring.

    The world is warming up, pretty much as was predicted in 1990 or so. We are more confident than ever that the globe will warm up more, and faster, for a few decades beyond the time when serious changes in anthropogenic net emissions start. After that the prediction problem gets harder, but the more we rock the boat, the bigger the risk into the far future.

  39. 39
    Lynn Vincentnathan says:

    Sorry for my hasty (worst deleted) response. I agree with nearly everything written in #27. I have too often heard people misconstrue environmentalism as mainly to do with saving the polar-bears, or baby seals, etc. A red flag went up. It’s usually the anti-abortionists, who then go on to say environmentalists don’t care about human life. Or the economically concerned, who fear environmental actions will harm economic sufficiency (jobs) or wealth — as if the environment were totally unnecessary to human life & well-being.

    There are, of course, many branches of environmentalism from conservative “not-in-my-backyard” to radical “people are a disease on the planet.” (Contrarians will sometimes pick the latter with which to smear all – so the label “environmentalist” has become pejorative nowadays.) Most environmentalists I know are between those extremes — concerned about people (their lives & well-being), as well as the non-human world. Most have some ecological understanding.

    AGW should be of concern to nearly all types of environmentalists, and to non-environmentalists concerned about life and health, economic sufficiency, wealth, national security, and maintenance of human freedoms. It just seems to me that many of those folks (contrarians) don’t really understand how the natural + sociocultural/psychological world works and that their best interests would be served by abating, rather than arguing the details of, AGW. Of course, we need bonafide science skeptics to keep science honest; it’s the contrarians, whose motives seem to be to thwart environmental actions (and environmental science), that concern me.

    Perhaps we need a lot more science to continue making the claim for AGW more and more robust, simply because many people aren’t taking AGW seriously (though I personally don’t need so much science to act, esp when those actions save money).

    I wonder what it will take to get people to understand that AGW is very likely happening, that the threats may be dangerous to very dangerous (& we’re most likely already seeing the harms), and there’s even a possibility of runaway GW, that could be much more serious. I wonder if any amount of science will convince the contrarians. This is a much tougher nut to crack that I had thought 15 years ago.

    BTW, I think the mall may not be bad environmentally speaking – most have public transport to them, or at least you can buy nearly everything you need there, without driving all over the place. It could be built using “green” architecture & alternative energy sources. And if you get lured into a mall (& do mainly window-shopping, like we do), then you won’t be driving around just for fun, but walking around – good for the health, too.

  40. 40
    Brooks Hurd says:

    Mike,

    Can you please direct me to Jone’s data so that I can aquaint myself with the facts?
    Thanks

    [Response: See the link provided to the Jones and Mann review paper. -mike.]

    Where can I find this link? I have lookede on the site, but I have not been able to find it.

    [Response:The link is provided in comment #23 of this post. -mike]

    Thanks,

  41. 41
    Eli Rabett says:

    Let me pick some nits with Michael Tobis’ proposal. An arithmetic average for temperatures defined over some region of the atmosphere, or any homogeneous system, is not an arbitrary choice. Remember that for a gas under atmospheric conditions, temperature and energy are linearly related**. Thus, if you want to talk about Total Energy in a volume of air = average energy x unit volume, you can use = Temperature x 5/2 RT x volume.

    Since you can trivially define the total energy in the atmosphere, or in some portion of it (say 1 meter from the surface), and the volume in that layer, you can find the total and average energies thus, you can sensibly define the average temperature.

    This is much simpler than what Michael proposes as an alternative, if for no other reason that the emissivity is balanced by the absorption, which is not proportional to T^4. Further, Michael’s proposal REQUIRES the use of absolute temperature, something that McKitrick DID NOT DO. My points were that a. If you use the Kelvin scale, there will not be much difference in the result averaged any which way and b. an arithmetic average has a simple justification based on thermodynamics.

    It ain’t rocket science folk, that is a two semester course.

    *less water vapor, but the contribution to the total energy of the atmosphere is small. Note that this is NOT the case for energy transport. Two different things.

  42. 42
    Donald E. Flood says:

    Hello,

    For the past ten years, I have been working in SPC (“Statistical Process Control”) for a major telecommunications company. (And, let me state the disclaimer that my “opinions” are my own and NOT those of my employer!) Beginning in the Year 2000, I have regularly created some time series X-Bar charts using the following datasets:

    http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts.txt
    ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/land_C.all

    A simple regression on both datasets yields a p-value < 0.0005 over time, indicating that global temperatures are increasing with respect to time. The same observation would also be true for CO2 concentrations in the atmosphere. Together, a basic Pearson correlation coefficient yields statistically significant results, indicating that CO2 emissions are having a real statistical association with the increase in global temperatures. Granted, this is the “correlation versus causation” issue, but, IMHO, the simplest explanation would be that increasing CO2 concentrations are causing the increase in global temperatures!

    Given the strong association between increasing CO2 concentrations and increasing global temperatures, how can any scientist embrace the “null hypothesis” and say that CO2 emissions are NOT correlated with the increase in global temperatures? Is not it generally accepted within scientific research that one cannot â??proveâ?? the null hypothesis? Or, am I “missing something” here??

    Sincerely,

    Don Flood

  43. 43
    Sanderson says:

    Real Climate is political commentary. I was pointing out that enviromentalism and science are not a priori connected. And that the Real Climate website is an enviromentalist website run by scientists. Otherwise there is no reason for it to exist.

    [Response:I disagree. We started this because there was (is) a desire out 'there' for scientists to explain what it is they think they know and why they think they know it. We are not an 'environmentalist' site and we do not advocate specific policies. We talk about the science, and any perception that you have that this is political is false. -gavin]

  44. 44
    Joseph O'Sullivan says:

    Is the hockey stick receiving more attention in scientific literature because of politically motivated people (M&M) questioning it? If there were no political implications of the science and M&M did not cast doubt, would the hockey stick discussion have stopped in the scientific literature and the discussion moved on to other questions?

    [Response: The scientific discussion continues, independent of M&M. Check for example [[Image:2000_Year_Temperature_Comparison]] and the refs therein – William]

    Re # 8 and the other comments related to #8 its again about the political implications of the science. The difference between environmentalists and scientists is that the environmental groups are the main political advocates for regulatory action. Environmentalists are using the information that scientists find to argue that the science shows that global warming laws should be passed.

    Environmentalists, particular in the US, have been the driving force in getting environmental regulations enacted. This political success has really ticked off political conservatives and their allies in affected industries. They have gone to great efforts to malign environmentalists. The usual tactic is to falsely equate environmentalists, environmentalism and their political positions with extremism. Claiming that environmentalism is like Christianity unfortunately feeds into this.

    The information scientists provided, when objectively examined, supported environmentalists call for action. Realizing this conservatives/industry started to malign the scientific community. A common tactic is to conflate environmentalists and scientists: environmentalism = extremism, and environmentalist = scientist ergo science = extremism.

    A good news story is here:
    http://www.luntzspeak.com/graphics/NewYorkTimes.NewsStory.pdf
    http://www.luntzspeak.com/graphics/LuntzResearch.Memo.pdf

  45. 45
    Jo Calder says:

    Re #44. Joseph: can you supply evidence for the proposition that M&M are politically motivated? Cheers, — Jo Calder

  46. 46
    Lynn Vincentnathan says:

    RE #44, I agree with nearly all you wrote. Except to point out that there are many types of environmentalists. Going beyond the conservative/extremist continuum (mentioned in #39), there is a Great Tradition/Little Tradition continuum. The national & international env orgs deal with national/international policy, laws, and cases against polluters. But the vast majority of environmentalists are the ordinary folks back home who recycle (there is a GHG component to that in the energy saved using recycled materials, esp aluminum), conserve energy, become efficient, use alt energy when available…

    Of course, many of these folks also send their annual dues into the national/international orgs – so they are acting both locally & globally. This is the important point: We wouldn’t need environmental laws & regs, if everyone would act right & do the environmentally prudent things. I still have hope that the bulk of people will wake up to env problems & start solving them in their daily lives. The more that happens, the less laws we need.

    But what made me an environmentalist? It was those Sunday school values I learned as a kid. So, religion is very much a part of environmentalism. I guess atheists into doing good & saving the earth have picked up some quasi-religious values along the way.

    Sure glad my mom taught me to be a nonconformist & not follow the sheep over the cliff – otherwise I’d be ashamed to be an environmentalist. But I’m proud of it. I only ask that contrarians not throw too much rotten food at me. Why not try composting it instead.

  47. 47
    Armand MacMurray says:

    Re #43:
    Gavin, you note that “We talk about the science, and any perception that you have that this is political is false.”
    Steve McIntyre has posted that he submitted to this thread what seems to be a completely scientific and non-political posting on this topic (see quoted post beginning “von Storch and Zorita…” at http://www.climateaudit.org/?p=419). It doesn’t seem to have been allowed through to the blog here yet. Is it still “in processing?”

    [Response: Well, what Gavin said seems true to me. As for the CA post... there seems a determined attempt to personalise this by some people which I think is regrettable. The comment policy on this site is written by us all - William]

  48. 48
    joshua corning says:

    comment i found at climate audit

    “von Storch and Zorita did not replicate the MBH98 methodology in key respects. In particular, their paper indicates that they did principal components on the correlation matrix of short-centered data, where as MBH98 did singular value decomposition (SVD) on the short-centered data matrix itself. The VZ procedure simply does not generate hockey stick shaped PC1s and cannot be used to test the impact of the MBH98 methodology.

    Secondly, VZ endowed their pseudoproxies with much stronger correlations to gridcell temperature than exist in the controversial North American tree ring network. They assumed a minimum correlation of 0.3, whereas the 15th century MBH98 tree ring network has an average correlation to gridcell temperature of ~0.08 (with relative strong average correlation to precipitation.)

    [Response: I read this. It made no sense to me. The 15th C temperature is *reconstructed* from, amongst other things, tree rings. The correlation to the true temperature is unknown - William]

    Thirdly the VZ minimum correlation assumption effectively excluded the study of the potential impact of proxies affected by nonclimatic trends (such as arguably, CO2 fertilization of bristlecones).

    The MBH98 PC methodology is actually not a “principal components” methodology as defined by Preisendorfer [1988], which requires the use of time-centered data and explicitly excludes de-centered data (page 26).

    [Response: So what? - William]

    VZ did not analyze the impact of the MBH98 method on MBH98 proxies and, since their replication of MBH98 methods was flawed, does not show that problems with MBH98 PC methodology did not matter.”

    [Response: I have also read a number of posts on climateaudit.org, and I think that a large fraction of what it has to say is mumbo-jumbo. Take for instance the statement that since they used an annual mean value, they should use discrete wavelet anaysis (post on Moberg's work). This doesn't make sense. Furthermore, it has a go at the iid-test, but without making any point - just insinuations. To my mind, one of the classic examples of how they twist the logic can be found in Are Temperature Trends affected by Economic Activity?. -rasmus]

  49. 49
    Armand MacMurray says:

    Re: #1
    Gavin, here are non-subscription-only links to the replies:
    http://www.climateaudit.org/pdf/mcintyre.vzreply.pdf
    http://www.climateaudit.org/pdf/mcintyre.huybersreply.pdf

  50. 50

    von Storch and Zorita did not replicate the MBH98 methodology in key respects. In particular, their paper indicates that they did principal components on the correlation matrix of short-centered data, whereas MBH98 did singular value decomposition (SVD) on the short-centered data matrix itself. There’s a big difference. The VZ procedure simply does not generate hockey stick shaped PC1s in the way that the MBH98 procedure does and cannot be used to test the impact of the MBH98 methodology.

    [Response:Are you sure that they did not estimate the eigenvectors/values, rather than applying an SVD to the correlation matrix? Usually, PCA involves either applying an SVD to a matrix of the data or an eigenvalue analysis to the co-variance/correlation matrix. To apply SVD to a correlation matrix sounds a bit odd to me - but then I must admit I haven't read the paper by VZ. I do, however, believe that von Storch is very competent when it comes to statistics and linear algebra, so if VZ did so (did they?), then there probably is a good reason for it... - rasmus]

    Secondly, VZ endowed their pseudoproxies with much stronger correlations to gridcell temperature than exist in the controversial North American tree ring network. They assumed a minimum correlation of 0.3, whereas sites in the 15th century MBH98 tree ring network has an average correlation to gridcell temperature of -0.08 (with relative strong average correlation to precipitation.)

    Thirdly the VZ minimum correlation assumption effectively excluded the study of the potential impact of proxies affected by nonclimatic trends (such as arguably, CO2 fertilization of bristlecones).

    The MBH98 PC methodology is actually not a “principal components” methodology as defined by Preisendorfer [1988], which requires the use of time-centered data and explicitly excludes de-centered data (page 26).

    VZ did not analyze the impact of the MBH98 method on MBH98 proxies and, since their replication of MBH98 methods was flawed, does not show that problems with MBH98 PC methodology did not matter.


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