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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Comments 126351 to 126400:

  1. Was there a Medieval Warm Period?
    I see what you're saying. I'll take a closer look at Mann's paper next weekend as well as his sources.
  2. Was there a Medieval Warm Period?
    The data is obviously not there otherwise McI would have taken it and reproduced the experiment. No doubt giving his own slant on the results. In fact if the data was free and easily available I wouldn't be surprised if multiple skilled individuals (from both sides of the debate) attempted the same thing. If I had the skill I'd do it tomorrow. The data isn't there in a useable form. I think there is sufficient evidence within the leaked emails to see that is a fact. After all if it's out there why would Jones be threatening to delete stuff so McI can't get his hands on it. Judith Curry's comments on this, while I'd be critical of some points, have at least been an attempt to shed light on the matter.
  3. Was there a Medieval Warm Period?
    This stuff is fascinating. In the last few days I've been looking at studies that Co2science.org lists that address the MWP. Now, I checked out this website and I understand they are not impartial, so please don't waste time explaining that. The thing is, I looked at several of the actual studies at the source (I have academic access) for different areas of the SH dealing with the MWP and to be honest, from a layman's point of view they look just as plausible as Mann's study. How would you address the seeming difference between Mann's results showing the MWP to be limited geographically and the results from other researchers which show a MWP in the SH?
    Response: Mann's study does show regions in the Southern Hemisphere that showed warmth comparable to the latter 20th Century. Eg - the north of South America, mid-Africa, parts of Australia. I would suggest digging through the studies cited at co2science.org, see which regions they focus on and compare those regions to Mann's study. And please report back on what you find.
  4. Was there a Medieval Warm Period?
    We are going to now start to play fair.
    Accusing researchers of scientific fraud based on UNUSED RESULTS found in a program they've toyed around with, when none of that shows up in the published research which is how results are communicated, isn't "playing fair". It's participating in McCarthyism.
  5. Was there a Medieval Warm Period?
    Neither of us are tree ring experts. But I do know that this stuff is EXTREMELY complicated statistical and mathematical data and corrections have to be made for various reasons. Are you trying to tell me that when you write software, everyone can figure out the steps A & B that may have gotten you to G? Are you telling me that it would be quite easy to find steps C to F.
    I would never claim that software engineering is easy, nor understanding other people's code. I don't mind, that's one reason my hourly rate is so high. No one has ever said that science is easy, either. Why this expectation that "anyone can figure out the steps"? I understand the tree ring stuff in quite a lot of detail because I've invested time into doing a fair amount of reading, but I don't know enough to write my own RCS code to create my own chronologies, and I see no reason to learn. But experts in the field can, without doubt (actually I think McI did, but I have no idea if he's done it correctly).
  6. Was there a Medieval Warm Period?
    nofreewind, Gavin already explained at RealClimate that you (and others) are wrong about that code.
  7. Was there a Medieval Warm Period?
    I'm not a climatologist or a computer scientist. But at least I know how to search the internet a little bit! RSVP @17 -- you made two highly uneducated and unscientific assertions: one about expectations and the other about kool-aid. Here is the oldest reference I can find to show how wrong you are (I'm quoting a Cecelia Bitz post at Real Climate): 'Manabe and Stouffer (1980) first popularized the phrase “polar amplification” to describe the amplified rate of surface warming at the poles compared to the rest of the globe in their climate model’s response to increasing GHG levels. Their early climate model had a simple ocean component that only represented the mixed layer of the water. Their model had roughly symmetric poleward amplification in the two hemispheres, except over the Antarctic continent, where they argued the ice is too thick and cold to melt back (see Fig 1). Both poles warmed more at the surface than the midlatitudes or equatorial regions.' I wonder if you'll see this confirmation of the model expectations and start to think that the experts actually know something (and knew it a long time ago). It seems popular, in some circles, to say: Notice that they say "climate change" now instead of "global warming"? What happens in minds when people are told that the IPCC (guess what CC stands for!) was formed in 1988. And what happens in those minds when they find out regional differences in warming were expected before then? When the expectations are met or exceeded by the observations, do they acknowledge that the science made good/useful predictions or do they run off to claim "Kool-Aid" about something else?
  8. Was there a Medieval Warm Period?
    I apologize for possibly misleading someone who knows even less than me. Because obviously there is plenty of tree ring data on the CRU servers, and much of it is related to Mann. Here is comment regarding Mann data. http://www.americanthinker.com/2009/11/crus_source_code_climategate_r.html scroll halfway down. I think you will find that this tree ring data, proxies etc. is EXTREMELY complicated to reproduce, even for an expert, I am sure even for a like-minded colleague. Dhogaza - since 11/20/09 the game has completely changed. We are going to now start to play fair. Truth is the child of time...... --------------------------------------- Climate Audit, can be found throughout the source code. So much so that perhaps the most ubiquitous programmer's comment (REM) I ran across warns that the particular module "Uses 'corrected' MXD - but shouldn't usually plot past 1960 because these will be artificially adjusted to look closer to the real temperatures." What exactly is meant by "corrected” MXD," you ask? Outstanding question -- and the answer appears amorphous from program to program. Indeed, while some employ one or two of the aforementioned "corrections," others throw everything but the kitchen sink at the raw data prior to output. For instance, in the subfolder "osborn-tree6\mann\oldprog," there’s a program (Calibrate_mxd.pro) that calibrates the MXD data against available local instrumental summer (growing season) temperatures between 1911-1990, then merges that data into a new file. That file is then digested and further modified by another program (Pl_calibmxd1.pro), which creates calibration statistics for the MXD against the stored temperature and "estimates" (infills) figures where such temperature readings were not available. The file created by that program is modified once again by Pl_Decline.pro, which "corrects it" – as described by the author -- by "identifying" and "artificially" removing "the decline." But oddly enough, the series doesn’t begin its "decline adjustment" in 1960 -- the supposed year of the enigmatic "divergence." In fact, all data between 1930 and 1994 are subject to "correction." And such games are by no means unique to the folder attributed to Michael Mann. A Clear and Present Rearranger In two other programs, briffa_Sep98_d.pro and briffa_Sep98_e.pro, the "correction" is bolder by far. The programmer (Keith Briffa?) entitled the "adjustment" routine “Apply a VERY ARTIFICAL correction for decline!!” And he or she wasn't kidding. Now IDL is not a native language of mine, but its syntax is similar enough to others I'm familiar with, so please bear with me while I get a tad techie on you. Here's the "fudge factor" (notice the brash SOB actually called it that in his REM statement): yrloc=[1400,findgen(19)*5.+1904] valadj=[0.,0.,0.,0.,0.,-0.1,-0.25,-0.3,0.,-0.1,0.3,0.8,1.2,1.7,2.5,2.6,2.6,2.6,2.6,2.6]*0.75 ; fudge factor These two lines of code establish a twenty-element array (yrloc) comprising the year 1400 (base year, but not sure why needed here) and nineteen years between 1904 and 1994 in half-decade increments. Then the corresponding "fudge factor" (from the valadj matrix) is applied to each interval. As you can see, not only are temperatures biased to the upside later in the century (though certainly prior to 1960), but a few mid-century intervals are being biased slightly lower. That, coupled with the post-1930 restatement we encountered earlier, would imply that in addition to an embarrassing false decline experienced with their MXD after 1960 (or earlier), CRU's "divergence problem" also includes a minor false incline after 1930.
  9. Was there a Medieval Warm Period?
    >As a software engineer with nearly 40 years experience in my field, this complaint makes me laugh. Neither of us are tree ring experts. But I do know that this stuff is EXTREMELY complicated statistical and mathematical data and corrections have to be made for various reasons. Are you trying to tell me that when you write software, everyone can figure out the steps A & B that may have gotten you to G? Are you telling me that it would be quite easy to find steps C to F. With all due respect to Mann, there are various tricks used to correct data for variables, do you think all of various data tricks and methodology were completely explained in a few data files on a server? Do you think the Congressman ordered the Wegman report and the release of data, after the NAS report, because all of this very complex data, with necessary corrections was widely available? That doesn't make "common sense" to this layperson. Didn't you read any of the emails lately which openly discussed not releasing data? The emails may not matter to the science or the reality of climate, but it certainly sheds light on the entire process of how this work is done.
  10. The physical realities of global warming
    I hate to have to keep repeating this, but it is ridiculously simple to assert that population is the only factor that matters. Environmental degradation = population x units of consumption per capita x degradation per unit of consumption. Pretend that you could reduce population by 35% in 10 years and keep everything else the same. That's actually less effective than keeping population level and reducing each of the other two factors by 20%. What is more plausible? India has a population of about a billion, and this billion people imports very little per capita. The ecological footprint (see wikipedia) of the United States is much greater than that of India. Look here: http://tinyurl.com/yjo54rc (from the wikipedia article). See how flat the line is beyond 4 hectares per capita? That means with current technology and infrastructure, much of the developed world could scale back greatly without giving up hardly anything. Development of better policies and technology and, yes, inclusion of reasonable incentives wrt reproduction will have to get us the rest of the way to a sustainable future. Population isn't the only factor that matters.
  11. Was there a Medieval Warm Period?
    NFW: I don't understand. I know Mann works at Penn State, news article yesterday. I didn't know that his data is kept at CRU or NASA GISS, aren't they keepers of temperatures, no tree-ring data?
    Yes, I thought you were talking about McI's whining about 2% of the data used by CRU not some of the tree ring used in Mann's reconstructions.
    The Hockey Stick was pre-2001, yet here I read in the Wegman Report dated 2006 http://www.climateaudit.org/pdf/others/07142006_Wegman_Report.pdf pages 48-49 "4. In response to the letter from Chairman Barton and Chairman Whitfield, Dr. Mann did release several websites with extensive materials, including data and code.
    "releasing several websites" means "here's the URL to the website ..."
    The material is not organized or documented in such a way that makes it practical for an outsider to replicate the MBH98/99 results. For example, the directory and file structure Dr. Mann used are embedded in the code. It would take extensive restructuring of the code to make it compatible with a local machine.
    Oh, gosh, such an insurmountable obstacle, you might have to partition a disk and recreate Mann's directory structure on it, the horror! The unscientificness of it! As a software engineer with nearly 40 years experience in my field, this complaint makes me laugh. It might take a day or so to replicate the environment or to change the directory and file structure embedded in the code. Big deal. If this counts for quality criticism among denialists (and I know it does), then they're just being pathetic. Note the goalpost move, though: 1. The code is secret, we can't run it! 2. The code is public, but it's got hardwired directories in it! We can't run it! Pffft. Scientists aren't in the job of providing software *products* they're in the job of writing code useful for their own research. A ROTFLMAO moment for this highly-qualified software engineer.
  12. Was there a Medieval Warm Period?
    NFW>McIntyre piece http://www.climateaudit.org/pdf/ohio.pdf is his describing how hard he tried to get the actual raw data and couldn't. dhogaza REPLY >The 2% of the data that CRU is not, legally, able to hand out freely. The other 98%, of course, which is all that NASA GISS uses, has been available on the internet for years now. NFW: I don't understand. I know Mann works at Penn State, news article yesterday. I didn't know that his data is kept at CRU or NASA GISS, aren't they keepers of temperatures, no tree-ring data? The Hockey Stick was pre-2001, yet here I read in the Wegman Report dated 2006 http://www.climateaudit.org/pdf/others/07142006_Wegman_Report.pdf pages 48-49 "4. In response to the letter from Chairman Barton and Chairman Whitfield, Dr. Mann did release several websites with extensive materials, including data and code. The material is not organized or documented in such a way that makes it practical for an outsider to replicate the MBH98/99 results. For example, the directory and file structure Dr. Mann used are embedded in the code. It would take extensive restructuring of the code to make it compatible with a local machine. Moreover, the cryptic nature of some of the MBH98/99 narratives means that outsiders would have to make guesses at the precise nature of the procedures being used." So this was the 3rd investigation of Mann. The 1st was the NAS report, then the Congressional hearing, which spawned The Wegman Report. So Wegman says in response to the Congressman Mann released the data. Why did he have to release it if it was at CRU or NASA? Also, they basically state they can't reproduce it because it is such a complicated thing to do. Well, we will have a fourth official inquiry into this matter, maybe the science is not settled, Penn State administration thinks something is not settled. The NAS found his work "plausible", that is pretty much the entire summation of their findings. I am no grammar expert, but isn't plausible a step below possible? Would you use the word plausible to define something that you have a high level of confidence in?
  13. Was there a Medieval Warm Period?
    There is a beautiful graphic of the MWP here. Looks like your german cousin!!
  14. How do we know CO2 is causing warming?
    guinganbresil, in Harris 2001 there's a discussion on the 800-1000 cm-1 range. A short excerpt: "The observed 1 K or so enhancement of the 800-1,000 cm-1 difference signal would be consistent with this, and could also arise from a change in the mean cirrus microphysical properties. We cannot separate these two effects, but we do conclude that the observed window difference spectra strongly indicate an effect involving residual small ice crystal effects, incompletely cleared from the data."
  15. Was there a Medieval Warm Period?
    nofreewind, your graph also stops in 1950 so you can't make any connection between post 1950 warming and solar activity. This was a distortion used by other well known deniers.
  16. Was there a Medieval Warm Period?
    nofreewind, it's hard to comment on a graph without the figure caption or an explanation. It appears to be a reconstruction of solar activity based on 14C cosmogenic production, not sunspot numbers. Anyway, it's related more to solar physics than to climate; in particular, to the possible link between gravitational influence of the planets and the sun activity.
  17. Was there a Medieval Warm Period?
    nofreewind: Supposedly, sunspots were observed as far back as 28 B.C.
  18. How do we know CO2 is causing warming?
    The figure 1C "Change in spectrum from 1970 to 1997 due to trace gases" from the Harries 2001 paper gives the impression that the measured outgoing long wave spectrum has shown an overall drop over the measured range. The figure 1B from Harries 2001 shows the measured difference between the 1970 IRIS and 1997 IMG spectra and it shows a notable increase in the OLR over the range ~800-1000 cm^-1. This increase is also seen in the spectra shown in Griggs 2004 and Chen 2007. Is the decrease in OLR in ~650-750 cm^-1 band greater than the increase in the band 750-1000 cm^-1? It seems to me that for the radiative imbalance to result in overall cooling that the total OLR integrated over the whole band should be decreasing with increasing CO2.
  19. Was there a Medieval Warm Period?
    I know that the suns influence on climate is in dispute, even the skeptics don't seem to be agree on the sun
    The really great thing about denialist "theories" is that they're so self-contradictory yet many denialists hold them all to be true at once. So you can have Watts screaming "there's no warming, it's just UHI" in the morning, and "it's the sun!" during lunch.
  20. Was there a Medieval Warm Period?
    What I like best about McIntyre piece http://www.climateaudit.org/pdf/ohio.pdf is his describing how hard he tried to get the actual raw data and couldn't.
    The 2% of the data that CRU is not, legally, able to hand out freely. The other 98%, of course, which is all that NASA GISS uses, has been available on the internet for years now. Same with Briffa ... Briffa said, "go ask the Russians, it's their data", McIntyre got it from the Russians in 2004, and continued to scream "Briffa won't give me the data", and later, when called on it, "oh, I didn't know it was the same data ..." Sheesh. McIntyre reminds me of a two year old with a migraine.
  21. Was there a Medieval Warm Period?
    I know that the suns influence on climate is in dispute, even the skeptics don't seem to be agree on the sun. But could someone tell me if the Warmers accept this solar activity graphs as true. Even if the affect on climate is just a coincidence, because I remember reading that Warmers saying that there is not enough energy in the suns "changes" to add energy to our system. http://www.landscheidt.info/images/newc141.jpg I find these Fagan books fascinating for many reasons, I just ordered a few more. The Little Ice Age book is so interesting because Fagan goes to great lengths to give all the historical references about the long periods w/o sunspots in the LIA. And what makes these books even better is he is a AGW believer, so we know when he talks history/archeology he is not attacking nything. But I am curious about that graph, were people really measuring sunspots in the MWP? Apprently the telescope wasn't even invented until the 1600's.
    Response: I've reproduced the JPEG image you linked to. I can't confirm the veracity of the graph as it doesn't cite sources but qualitatively it looks right.



    This graph doesn't come from sunspots - as you say, the reliable sunspot data doesn't go earlier than 1600. But solar activity also has an effect on carbon isotopes so this data would be taken from carbon captured in tree wood.

    Note that this graph ends in the early 20th Century. The rise in solar activity in the early 20th Century coincides with early 20th Century warming. If the graph was extended to present times, you would find that solar activity flattened in the 1950s and has shown no long term trend since then (if anything, a slight cooling trend in recent decades). Since the 1970s, sun and climate have gone in different directions.
  22. It's cosmic rays
    I am sure the global warming denialists are going to climb onto the bandwagon that cosmic rays are found to influence tree ring growth - http://news.bbc.co.uk/earth/hi/earth_news/newsid_8311000/8311373.stm - and then try to tie that to proof that cosmic rays are responsible for climate change. What really amuses me about climate change denialists is the fact that they postulate all of these other reasons for climate change, like cosmic rays, water in the atmosphere, and so on, and then state that there is no climate change, or at least that it is not anthropogenic. What a great cop out so that life can continue as normal. And so it goes........
  23. Was there a Medieval Warm Period?
    Ian, I have time to read this site, and I don't consider this site as "nonsense", in fact this seems like quite a scientific place compared to most of what I read. What I like best about McIntyre piece http://www.climateaudit.org/pdf/ohio.pdf is his describing how hard he tried to get the actual raw data and couldn't. Then he asked for advice to reproduce the data with new samples and was told it was terribly technical to do. After a Starbucks coffee he found the same crooked, erratically growing Bristlecone that were used to take the initial samples. No I don't know much about tree rings, but as layperson I am surprised that the scientists use crooked, erratically growing trees as a proxy for anything whatsoever. But I would appreciate someone pointing me to the nonsense in the paper, I am sure RealClimate has it figured out somewhere. Excuse me, but I don't have formal climate science training and obviously regular common sense fails when analyzing many of these issues. I am willing to learn, but need more than "trust me, I did these complex mathematical calculations/error massaging which you could never understand".
  24. Was there a Medieval Warm Period?
    dhogaza, yes I inadvertently referred to the divergence that Briffa discussed in the illegally released e-mails with THE divergence problem which predated Briffa's paper. However, nofreewind was (I think, it is hard to follow most denier's thinking) discussing the Briffa divergence. nofreewind, I do not have the time to waste reading what will no doubt turn out to be non-scientific nonsense by SM.
  25. Was there a Medieval Warm Period?
    "How comes Wikipedia doesn't even mention the word divergence in their Hockey Stick controversy article? Is this divergence something that was somewhat hidden before ClimateGate, or is this something that has been discussed as part of the ClimateAudit work?" The divergence problem (along with various other uncertainties) was discussed well before Steve McIntyre began his crusade against climate science. See John's post "What do the hacked CRU emails tell us?" and note the following article. Not sure about the Wikipedia article, but my take is that it covers mostly the political controversy instigated by M&M. It would be nice to update the Wikipedia article to include the fact that relevant issues such as the divergence problem were already documented in the peer-reviewed literature (some people seem to think McIntyre discovered this). Consider also that the original "hockey stick" graph contained a large uncertainty range, something consistent with a more pronounced MWP and LIA. See also the latest Mann et al. reconstruction. http://www.ncdc.noaa.gov/paleo/pubs/mann2008/mann2008.html thingadonta, "All that the final map, relative to the above discussion, shows, is show that the older proxies in the MWP are not picking up warmer temperatures the way modern instrumental methods do. " Well if one has already concluded that the MWP was warmer than today (based on?), that conclusion might make sense (keep in mind that reconstructions without tree rings reveals a similar pattern). I think there are many who badly want to believe that. Although it has no impact on greenhouse gas physics (although some might argue a more variable climate is a more sensitive one), if skeptics can show the MWP is equal or warmer than today, they think it will help convince folks that modern warming is entirely natural.
  26. Was there a Medieval Warm Period?
    >Nofreewind, you don't really understand much about tree rings, do you? you are right! but i have a good head for finding out the truth and 8 yrs of science degrees. >In fact the divergence problem is only associated with a very small number of trees from one particular place. These are the rings reported by Briffa. You mean there was no divergence in the MBH reconstruction? It is incorrect that much of the Mann 2001 IPCC graph was primarily from a few bristlecone's in Colorado? What is "nonsesne" in this paper? http://www.climateaudit.org/pdf/ohio.pdf Seriously, have all climate scientists taken the time to look at the archeological history. (FAGAN, FAGAN, FAGAN - and he is one of yours!)I think if you did you would agree that the warming from 1976 to 1998 was completely unremarkable, at least the rate of change, even the CET series will tell you that. I agree that that 1998 might have been the warmest year for at least 500 years. And the past decade might be the warmest for 500 years or so. If there is even such a things as "global temperature". How comes Wikipedia doesn't even mention the word divergence in their Hockey Stick controversy article? Is this divergence something that was somewhat hidden before ClimateGate, or is this something that has been discussed as part of the ClimateAudit work? If they can't calibrate their instruments with good recent hopefully 100% accurate temperature data, (???), how do they know there weren't period of hundreds of years in length 200 or so years ago where there was "divergence".
    Response: The divergence problem was discussed in the peer review literature as early as 1995, suggesting a change in the sensitivity of tree growth to temperature in recent decades  (Jacoby 1995). There have been a number of papers since then examining the problem. For more info, see the page on the tree-ring divergence problem.

    And for the record, if you're talking about global temperature, 1998 is not the hottest year on record. 2005 is.
  27. Was there a Medieval Warm Period?
    The variation in spatial data and distribution (ie maps above) would not 'average out' in a large dataset, as they are not 'random uncertainties'; they are in-built weaknesses inherant whenever one uses proxies
    You only need a sample size with sufficient spatial distribution to build a map of a particular resolution. So what you have to do here is to prove that the 1,000 proxies Mann has studied don't support the resolution he's claiming in his analysis. Yes, the spatial resolution is not as good as you go further back and have less spatial data. I note that the proxy reconstruction map uses big boxes- relatively poor resolution - while modern temperature maps such as the decadal map John's posted has much higher resolution.
    This quite predictably, and expectedly, actually enhances and highlights, rather than 'averages out', the outliers etc of an older dataset, when compared to a modern standard.
    I see no basis for this claim whatsoever.
    The MWP data is therefore misinterpreted, and which is also the skeptical contention of the hockeystick of Mann et al 1998-that the proxies are not picking up the full range of warmth of the MWP.
    Nor this - not that it matters. A warmer MWP than science actually supports doesn't impact the reality that a warmer tomorrow's going to require extremely expensive mitigation efforts.
  28. Skeptical Science housekeeping: Comments Policy
    My intention was not to define skepticism. I wanted to define what a dogmatic view was in contrast to skepticism, and did so by pointed out a method that skeptics uses. This method is more or less equal with the quotation you give above in the first part. Then in the second part when you write, "The antithesis of genuine skepticism is to decide your beliefs, then use cognitive dissonance to do away with any evidence that contradicts your beliefs.” Makes me even more puzzled, as this is only a reformulation of my definition of a dogmatic viewpoint. Basically your long replay can be condensed into “I agree”. However after all these words you still avoided to address the point I made, namely that this site fails it mission. So, it is utterly unclear to me what you actually are trying to tell me in you replay as you seams to only repeat what I already have said.
  29. Skeptical Science housekeeping: Comments Policy
    While I often disagree with you I applaud your even handed approach to comments and consider such housekeeping fair. There has been far too much mud slinging in this debate across all the sites I read - I wish they would all adopt such policies.
  30. Was there a Medieval Warm Period?
    re13: "Actually, you'd expect random uncertainty in the data set to average out, given a sufficient sample, and a 1000 proxies is a large sample ..." The variation in spatial data and distribution (ie maps above) would not 'average out' in a large dataset, as they are not 'random uncertainties'; they are in-built weaknesses inherant whenever one uses proxies, which will tend to increase with age in comparison with a standard dataset (eg 1961-1990). (Much the same reason human history becomes more unreliable the further back in time you go-these 'unreliables' dont 'average out', they just get worse). This quite predictably, and expectedly, actually enhances and highlights, rather than 'averages out', the outliers etc of an older dataset, when compared to a modern standard. This is what 'standards' are supposed to do, highlight discrepancies in a non-standard dataset, which ironically, is just what the paper of Mann et al 2009 does. The MWP data is therefore misinterpreted, and which is also the skeptical contention of the hockeystick of Mann et al 1998-that the proxies are not picking up the full range of warmth of the MWP. This new Mann et al paper largely shows this again to be the case. The final graph is also a bit misleading, relative to the above discussion. If the proxies do not pick up past warmer periods well, and moreover will always show a greater number of (spatial) outliers and in-built variations and uncertainties, it will be a rather misleading and false comparison if they are then placed against any other warm instrumentally-based data. All that the final map, relative to the above discussion, shows, is show that the older proxies in the MWP are not picking up warmer temperatures the way modern instrumental methods do.
  31. The physical realities of global warming
    pdt Its not about CO2. Its about global warming. And the solution is to control population growth. We are in a bind like an animal trapped in quicksand. The more you try to move the deeper you sink. There is no technological solution, because no matter what you do, you will always be generating more heat. The only solution is to control population into the future with the realization that the Earth can house only so many people. End of story.
  32. Was there a Medieval Warm Period?
    Referring to the last graph. It seems odd that temperature anomalies are seen to affect the northern polar regions more accutely, whereas this region is plunged in darkness almost half the year. This does not seem to play into the idea that CO2 is the main cause of global warming. If this were the case, you would expect a distribution with the largest anomalies in the equatorial regions happening first. What the map seems to indicate is direct convective warming of the polar regions from a warmer atmosphere, and if man made, likely due to latent exothermal pollution sources. I am aware that this is not a popular idea, as I've been told that this energy doesnt amount to a hill of beans, but on the other hand, I am also suppose to believe in a environment that is precariuosly sensitive. It is sensitive, but not that sensitive, etc. At any rate, I understand, once you have sipped the Kool-Aid, its too late. There is no going back.
  33. Was there a Medieval Warm Period?
    nofreewind You said "So the tree ring data fits the MWP when we didn't even have thermometers, but it doesn't fit the era when we had literally thousands of surface based temperature stations throughout the world." I totally agree! --------------------------------- John, In previous articles, in looking for proof for global warming, local Antartic cooling is played down as not counting, whereas in this article, local conditions are interpreted as just a shifting of the Earths energy distribution.
    Response: The way to approach Antarctic cooling is the same as the approach to the Medieval Warming Period. Rather than focus on a specific region while neglecting the broader picture, look at the global pattern. Figure 3 above demonstrates that while there has been cooling in some Antarctic regions, the full global picture is that of warming. The planet has a net energy imbalance and is accumulating heat. This is in contrast to the global temperature pattern during the Medieval Warming Period which only suffered a mild energy imbalance and consequently showed a mild net warming.
  34. Was there a Medieval Warm Period?
    Surely that list of caveats also applies to the data that 'fits' the model.
    Why? Liebig's Law of the Minimum is well-established, has nothing to do with climate science or paleo reconstructions of tree-ring temperature proxies, and is based on sound understanding of plant physiology important to science-based agriculture. Essentially you're saying "I don't like what I'm hearing, so I don't accept it".
  35. Was there a Medieval Warm Period?
    How does 300years of La Nina conditions work?
  36. Was there a Medieval Warm Period?
    Because you are comparing high quality recent observations with past reconstructions, you would expect the past reconstructions to show more regional variation simply as a result of much lower quality data
    Actually, you'd expect random uncertainty in the data set to average out, given a sufficient sample, and a 1000 proxies is a large sample ...
  37. Was there a Medieval Warm Period?
    #7 Shawnhet you can get the map of the proxy positions from the supplementary data. See link in #12
  38. Was there a Medieval Warm Period?
    With regard the the Mann paper. John it would be useful for you to show the map of proxy locations (i.e. the rest of fig2 from Mann) for those that can't access the paper. Although I think everybody can access the supporting data freely here. To describe the spatial data for the MWP as sparse I think is generous. There are 6 proxy data sets for the whole area east of the horn of Africa. I would be interested how you get the large blue (cold) area in central eurasia when there are no proxy records for that area. Although its difficult to overlap the temp and proxy maps it appears that the only proxy points around central eurasia conicide with the couple of hotspots in that region. Also there are no proxy data over any ocean regions, most of africa, anywhere in S.America away from the west coast, the whole of malaysia/indonesia/philipines/australia(except tasmania)/pacific Islands, the middle east,Western Europe..... Do you get the point!! I really struggle to see he can allocate a colour to most of the globe during the MWP. I'd love to see the reviewers comments.
  39. East Antarctica is now losing ice
    Seems like this article is very alarming that Antarctica is losing ice at an accelerating rate. And during summer!
  40. Was there a Medieval Warm Period?
    #3 dhogaza Surely that list of caveats also applies to the data that 'fits' the model. I've noticed a trend were data that fits the theory is often simply presented and described while data that goes against the theory is often followed by a list of possible explanations to invalidate it. That's assuming the researchers have the grace to present it in the first place.
  41. CO2 is not the only driver of climate
    Gord, I must say I admire the patience with which you, Gord, have explained some physical basics that for some reasons are called laws. The reasons should by now be clear to even the most stubborn ones. I thank you for the lessons.
  42. The physical realities of global warming
    RSVP, "Population is the ONLY point when no realistic energy alternatives are on the table" then yes, you're right. Before the fossils era (carbon included) energy came mostly from burning trees; in the then developed world forests were cut down. If "no realistic energy alternatives [came to] the table" we could not be where we are now. Definitely. For sure. Absolutely. In other words, if you do not allow for energy alternatives there's no solution. But not just for global warming, it would be impossible any development of the human race.
  43. The physical realities of global warming
    RSVP, Fine, then how much CO2 is generated for things absolutely necessary to sustain human life? For example, in the United States, ~60% of the primary energy sources we consume are ejected as heat. The only reason this is true is because of the incredibly low price we pay for these primary energy sources.
  44. Was there a Medieval Warm Period?
    Can anyone who has read the paper please let me know how they can possibly get sufficient proxy data to cover the entire globe? I am particularily curious how they would work out the anomalies for the oceans. Is there some sort of algorithm at work here? Cheers, :)
  45. Was there a Medieval Warm Period?
    The consensus in Norway seems to be that in the period 500-1500, the temperature in Scandinavia was 0.5-1 oC higher than the 1961-90 mean, which by no means seems to be reflected in fig 1. You may download a pdf (in Norwegian) from http://nou-klimatilpassing.no This is a official report, documenting climate changes and discussing possible changes towards 2100.
  46. Was there a Medieval Warm Period?
    Good post. For comparison, here's the anomaly map for the last couple of decades, same base period. Different color scale, but we can get the idea. It seems a bit unusual for both MWP and LIA to show a warm anomaly in the North Atlantic, until it's noted that the map is an offset from the 1961-1990 average, which showed generally cooler temperatures in that region during that period. Here is the 1961-1990 period in comparison to the 1900-2008 average. It would be interesting to see the MWP and LIA in context of the last century average (a more apples to apples comparison in terms of timeframes being compared), and also in comparison with the last 20 years. What's notable is that the anomaly map from the study isn't a comparison with the recent decade or two but with the 1961-1990 average.
    Response: You know, when I was writing this post, I did think it would be useful to compare current temperature patterns to the MWP pattern. But in my defence, it was approaching midnight when I wrote this post and I had just spent 5 hours that afternoon playing cricket in incredibly hot and humid Queensland conditions. But enough excuses! I've added the temperature pattern of the last decade. Thanks for the comment.
  47. What does past climate change tell us?
    Riccardo, "luckly the CO2 we release with respiration does not come from fossile carbon ;) " You with drawing attention from the real point I made. The point was to show that the claim that it demands "hard work" to release 29 giggatonnes of CO2 in the atmosphere is at best a misleading, and at worst a false, claim.
  48. Was there a Medieval Warm Period?
    Having said all of the above, let me make clear that I'm just a layman with too much time on my hands, interpreting stuff I've read that's written by the experts. I may have, in fact likely have, gotten some of it wrong, so YMMV.
  49. Was there a Medieval Warm Period?
    Actually, Ian, the divergence problem refers to tree ring chronologies, mostly at high latitudes, that show *less* growth than expected in relation to increased temps in the 1960s. I think the paper you cite (Salzer et al) shoot down those who claim that recent *accelerated* growth in bristlecone pines at high elevations (but not latitudes) might be due to CO2 fertilization or something else other than a response to temps. It solidifies the bristlecone pine proxy so scathingly dismissed by skeptics (they also saw no significant difference between stripbark trees and those that don't show that growth pattern). However ... to nofreewind ... Ian's point still holds partially in that not all high latitude tree ring chronologies suffer from the divergence problem (in particular Briffa's Yamal reconstructions, which is probably why McIntyre is so focused on trying to demolish that particular reconstruction with such vehemence). There are three possible likely sources of the divergence problem: 1. anthropogenic changes (air pollution, for instance) 2. precip or snowmelt timing changes (causing drought/water stress rather than temp to be the limiting growth factor after temps warm to a certain point) 3. global dimming (which from my reading is thought to be a stretch, i.e. not likely) If #1 is true, then the current divergence has no relevance for reconstructions in the deep past. If #2 is true, it's only a problem where temps were warm enough in the past to trigger enough change in precip and/or snow melt timing changes to cause that to become the limiting growth factor. This could lead to an underestimation of the MWP from what I can see, but wouldn't be a factor at other times during the reconstructions. But there are other proxies, including (but not only) tree ring proxies not showing the divergence problem, that show a cooler-than-today MWP for many regions (and at least one northern siberian tree ring chronology showing a warmer regional MWP) that well, you end up with what Mann '09 here says ... some regional warming greater than today, some regional cooling, over all no global warming comparable to today. Oh, there are actually two more potential gotchas in the divergence problem: 4. Use of RCS rather than certain other smoothing techniques causes it to go away to some extent in many of the chronologies, i.e. there are end point problems with some smoothing techniques that contribute to an artificial "tailing off". 5. The thermometers are typically at lower elevations and some distance away from the various tree sites used by researchers, so there are microclimate differences that would lead one to expect that the temp and proxy results would differ. AFAIK, pretty much all of the above are being actively looked into by researchers, judging from a relatively recent review paper I've read (2007).
  50. Skeptical Science housekeeping: Comments Policy
    @OP I all friendly manner I like to give some criticism to this post and the site in general. To be skeptical is not to prove everyone else wrong with "conclusions" from "data", it is to ask oneself the question "What if *I* am wrong?" and try to interpret data in a new set of ideas – which is knows as formulating a theory about data. Refuting everyone else is not to be skeptic, but is the definition on believing in a dogma. In this respect I think this site fails a mission of being skeptical. Its focus seams to be to prove any skeptic argument wrong as the "science is settled" and thus no alternative theories can be correct.
    Response: Thanks for your comments. Personally, I like the Oxford Dictionary definition of skeptic:
    ‘A seeker after truth; an inquirer who has not yet arrived at definite conclusions’
    Eg - a true skeptic doesn't let their preconceived notions influence how they interpret data and science. My observation is that by this definition, global warming skepticism is anything but skeptical. The antithesis of genuine skepticism is to decide your beliefs, then use cognitive dissonance to do away with any evidence that contradicts your beliefs.

    The common pattern with global warming skeptic arguments is that they focus on a narrow piece of the puzzle while ignoring the broader picture. This is textbook cognitive dissonance. The antidote to this approach is simple - present the broader picture. The goal of this website is simple - attempt to present the broader picture by explaining what the peer reviewed science says.

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