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Comments 111151 to 111200:

  1. It's not us
    I covered the stratosphere and other upper atmospheric layer cooling in the Advanced rebuttal, James.
  2. Urban Heat Islands: serious problem or holiday destination for skeptics?
    For many reasons, generally well-covered in the previous thread, I am skeptical about Berényi Péter's claim (that UHI explains 0.4-0.6°C of the observed 20th century warming). The evidence for it seems to be scant to nonexistent. But, for the sake of argument, let's grant it. Land, of course, occupies only 29% of the Earth's surface, so a UHI effect of 0.4 to 0.6 C/century on land would represent 0.12 to 0.17 C/century globally. For comparison, the current (satellite-era) trend is +1.6 C/century. So BP's (inflated, IMHO) estimates would still mean that UHI explains 10% or less of the observed trend. But it's worse than that. Over much of the 29% that is land, the population density is effectively zero -- think Antarctica, Greenland, the Sahara, the Gobi, vast expanses of Siberian peatlands, etc. Just by eyeballing maps of world population density, I'd guess that around half the land surface of the Earth is effectively uninhabited. That would suggest that, based on BP's own figures, UHI explains between 2-5% of the post-1970 warming trend globally.
  3. Climate's changed before
    Thanks for the post Peter. To say the least, Scotese chart shows the lack of correlation between low CO2 troughs and glaciation periods and CO2 crests inter-glaciation periods. It is meant to represent averages through different periods. The chart you found in Royer's 2009 paaper is actually from 2004. Its referenced right on the paper. So its not too long after Scotese. She doesn't show CO2 and Solar variation separately on the graph, just combined as radiative forcing. Also, on a side note, please see this response to Royer's temperature sensitivity assumptions. Detailed Response to Royer et al.’s letter “CO2 as a primary driver of Phanerozoic Climate” Here is a more detailed (than Scotese) temperature reconstruction from Veizer, and CO2 reconstruction from Antarctic ice cores, Pagani and geocarb. Solar variation is left out to show CO2-temperature correlation only. I hope to post raw data for everyone when I find some time. And I'll try to respond to the other comments later tonight.
  4. Sea level rise: the broader picture
    JohnD @49 - "Can you elaborate as to the reasons why 0.3mm per year must be added to the Australian records and how this adjustment was arrived at as it appears very relevant to the discussion." The 1.2mm per year rate of rise from 1920 to 2000 around the Australian coastline, did not include the 0.3mm per year adjustment which is the GIA. This is detailed in Kurt Lambeck's 2002 paper here: Sea Level Change From Mid Holocene to Recent Time: An Australian Example with Global Implications The GIA explains why there is abundant geological evidence of the sea level around Australia being up to 3 meters higher than present, some 6000 - 7000 years ago, despite the sea level rising in that time.
  5. Hockey stick is broken
    TOP - where is the ad hominem in DC's article? Ie the attempt to discredit the argument by an attack on the persons of M&W, rather than on the argument that they present? DC helpfully makes it possible to check M&W version of history is correct or not, but the teeth of article deals with the technical argument.
  6. How we know an ice age isn't just around the corner
    Anne-Marie: A small tip: When importing text from another editor into the Skeptical Science editor, links usually get reset to point at just the main Skeptical Science landing point. Check links you import via the preview before posting (I found I had to import them one at a time to create a post with links that worked as I had intended). Maybe the other contributors, who post much more frequently than I, can offer more sage advice. The Yooper
    Response: Actually, Anne-Marie did it all correctly - it was when I tried to move her rebuttal into the blog post that things went awry. All my fault! :-(
  7. How we know an ice age isn't just around the corner
    A small nit: The title should either start with "How do ..." or omit the question mark. Also, following on to Tom_the_Bomb's comment, all the links point to the SkepticalScience homepage.
    Response: Egad, a whole swag of grammatical and HTML errors. All fixed, thanks to the first 3 commenters for pointing these out.
  8. Urban Heat Islands: serious problem or holiday destination for skeptics?
    Beautiful piece of work by The Yooper.
  9. How we know an ice age isn't just around the corner
    You omitted 'years' at the end of the first sentence. Good explanation.
  10. Urban Heat Islands: serious problem or holiday destination for skeptics?
    Daniel - Thank you for a lovely commentary here. Fortunately, I had already started on my beer (a homebrew vanilla oak barrel stout) before reading it :)
  11. Sea level rise: the broader picture
    JohnD I don't expect you to overturn the results of several thousand publications by researchers armed with extensive training and experience specific to their field in a comment thread at a climate blog. The probability of such a revelation would be low even if you were trained in this topic but worse, you're not keeping in mind your own limitations. On another thread here at Skeptical Science it became apparent that you did not understand the difference between latent and sensible heat and thus were able to synthesize a hypothesis about atmospheric heat transport entirely divorced from reality. Oblivious to this perfectly innocent gap in your awareness, you were quite comfortable and confident using the fallacious product of your oversight to challenge the work of people who after all are far more knowledgeable than you or I. Concerning this topic, you're apparently still not aware of material thrust in front you showing how multiple data sources have been drawn together to narrow the confidence interval of global sea level measurements. Instead you are continuing to talk about scientists as though they're naively leaning on their favorite instrumentation without bothering to exploit available cross-checks wherever possible. Look, this is not a fair fight. It's not even a fight at all, it can't be because you don't have any weapons, not even the equivalent of bare fists. You're one person with a necessarily and perfectly ordinary and ok highly limited perspective, versus a small army of people entirely preoccupied with levels of arcana of which the both of us are quite ignorant. Unless you can articulate your disbelief of what's reported to us in a highly elaborated form, richly detailed and entirely circumspect, you're not making an argument, you're simply disagreeing. To drive understanding forward you need to take into account everything that's been published on the crux of your disbelief, comprehensively. The kind of argument you need to make is what you can look at in the form of scientific publications.
  12. How we know an ice age isn't just around the corner
    "(Petit 2000)" links straight back to the SkepticalScience homepage. Other than that, good explanation.
  13. Urban Heat Islands: serious problem or holiday destination for skeptics?
    I approached this thread with nervous trepidation, fearing at last that the true cause of global warming was to be finally unmasked. That those stalwart souls, laboring long into the night, would finally reach the pinnacle of their aims & finally discredit AGW... ...and to see them come SO close...and fail, yet again! Oh, my anguish, my anguish! Guess that means that yet another hope of avoiding what seems to be our fate is gone. I didn't think it would end this way. Oh, well. Time for a beer. Hey, something shiny... The Yooper
  14. Hockey stick is broken
    TOP if M&W choose to include a narrative of the political history of paleoclimate studies in what is advertised as a technical critique and improvement of statistics employed in proxy temperature reconstructions, it's not an ad hominem attack when readers are arrested by this unusual feature and begin to speculate on why the extra material is included. The authors themselves after all have chosen to include this distraction; presumably they wished to call attention to their paper in this way. They've succeeded. To wit, this example paragraph, which you apparently did not notice when reading the paper: Quotations like the above and graphs like those in Figures 1, 2, and 3 are featured prominently not only in official documents like the IPCC report but also in widely viewed television programs (BBC, September 14, 2008), in film (Gore, 2006), and in museum expositions (Rothstein, October 17, 2008), alarming both the populace and policy makers. Al Gore? Alarming? Really? Can you spot the statistics in that? I can't, but I do read what many would term as "dog whistle" political words. Now do you notice how the choice to include political fluff makes it more difficult to discuss their work? Why do I have to ask, because I made M&W mention Al Gore, or because M&W chose to write about Al Gore instead of statistics?
  15. Sea level rise: the broader picture
    Johnd; Looking at your 2007 IPCC quote it is already outdated. Sea level rise is now 3.3-3.5 mm/yr. If you want to be knowledgable in anything you need to know what experts think. Not reading what experts think to keep an open mind means you cannot have an informed discussion. The rest of us have to continually correct the mistakes you make because you have not done your homework. Think about whether or not you want to be informed and up to date.
  16. It's Urban Heat Island effect
    This page starts with the statement that "A paper by Ross McKitrick ... and Patrick Michaels ... concludes that half of the global warming trend from 1980 to 2002 is caused by Urban Heat Island." (McKitrick & Michaels). It then provides evidence for the contrary view. An obvious question is not addressed as far as I can see: are the arguments presented by McKitrick & Michaels wrong, and, if so, why?
  17. Urban Heat Islands: serious problem or holiday destination for skeptics?
    Berényi - I read through much of the thread you linked to, but I didn't see any published papers. Can you repost links to anything published on this logarithmic UHI effect? The only reference I saw was to something blogged by Spencer, and given his track record (!) I want something published and reviewed before I take this UHI issue seriously.
  18. Hockey stick is broken
    Regarding McShane and Wyner: Is being reviewed. We will wait with baited breath. I guess I missed the "political freight" when I read it today. DC seemed to be going for the ad hominem argument in that regard. I would have preferred that DC skip over the jibes at political incorrectness and spent that time delving into the paper itself. There was a lot going on in those 45 pages. McShane and Wyner take their own shot at the climatological world for being statistically challenged as well. Data is data after all and that is the world of statisticians. One of the conclusions: ...we conclude unequivocally that the evidence for a ”long-handled” hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data. In other words, there might have been other sharp run-ups in temperature, but the proxies show them. The hockey stick handle may be crooked, but the proxies can't show it one way or the other. Note that McShane and Wyner don't necessarily think the historical record is all wrong, but rather that the anomaly signal that the global warming crowd is using is not necessarily detectable the data.
  19. Urban Heat Islands: serious problem or holiday destination for skeptics?
    BP, I just went back and read a bunch of your posts that you linked above and I hope that you do not waste our time again as you did on the linked thread. As I said above, your stuff used to have some ideas that you could defend. This does not rise to your old standards. Please cite peer reviewed material or at least something that can be pretended to be accurate, not a blog post on WUWT.
  20. Sea level rise: the broader picture
    JohnD - nature doesnt have opinions. It is surely a central tenet of science that people will reach the same conclusion from the same data - because there is only one reality. You are saying that you agree that your opinions are illogical but having illogical opinions is fine because it is the debate that matters not whether we are in fact doing future generations a hell of a lot of damage?
  21. The surprising result when you compare bad weather stations to good stations
    It's not bad/good data. It's good/better data. Problem solved ...
  22. Sea level rise: the broader picture
    doug_bostrom at 06:47 AM, one of the obvious outcomes if everybody only references the same sources is that everybody will draw the same conclusions as generally most studies put together a compelling case that appears logical not only to the authors, but to the readers also. This is especially so for those whose mindset has been preconditioned by prior acceptance of the author's credibility, and so are likely to be readily accept what has been written rather than to look for flaws in the reasoning. Where would that leave the debate? A feel good round of good old boys exchanging pleasantries? The process of logic which drives the reasoning of most people is such that it makes it difficult, (impossible?), to accommodate anything outside the step by step process which logic itself is. Thus those concepts that track outside the logical path, lateral to it, are left to the those who can connect seemingly unconnected concepts which ultimately become logic themselves after they have connected all the dots, which must be a great relief for that majority of people who are unable to do it themselves. Just as in history, it has been left to a few to explore for new land for those who don't want to risk leaving the comfort of close existence, but once new settlement has been established the masses are more than happy to populate it to the extent that are quite willing to pile on and live on top of one another, feeding off the sense of community that ironically had only come about by those who sought to extend the lateral boundaries the masses so willingly imposed upon themselves, and then continue to do so again. I really don't like confining myself in such a way, either in the regions I have explored, or the concepts that others present. I pay little attention to an authors name, instead look for value in the alternative concepts being developed, without which a sense of balance cannot be developed. I compare this to peoples taste in music. Many people have their favourite artists and religiously buy all their works irrespective of how the quality waxes and wanes, all the time ignoring others who have yet to establish themselves. Thus it becomes that the early works of that artist becomes valuable items as those who woke up late try to obtain them from those who saw the potential first up. However there are also those whose reputation was built on that first big hit that resonated with the masses, but then proceeded to produce duds whilst the faithful continued to believe that the talent was real. That sort of reminds me of this quote, "For example, the IPCC (2001) wrote “no significant acceleration in the rate of sea level rise during the 20th century has been detected”. In 2007 they said that “global average sea level rose at an average rate of 1.8 [1.3-2.3] mm per year over 1961 to 2003. The rate was faster over 1993-2003: about 3.1 [2.4-3.8] mm per year. Whether the faster rate for 1993 to 2003 reflects decadal variability or an increase in the longer-term trend is unclear”. end of quote.
  23. Urban Heat Islands: serious problem or holiday destination for skeptics?
    "Are the lower troposphere and sea-surface temperature trends also affected by UHI? It seems improbable given the lack of pavement in the middle of the Pacific, not to mention at the 600 km altitude of Aqua/AMSU." What about space junk? And the international space station? (no, I'm not being serious, but neither is BP ...)
  24. Berényi Péter at 08:28 AM on 1 September 2010
    Urban Heat Islands: serious problem or holiday destination for skeptics?
    There was already a long intermittent discussion of UHI here. Follow the thread.
  25. It's microsite influences
    For what it's worth, Watts put his three different boxes closer to each other than I would have, and put the newer paint spec one in the middle. That puts the one he expects to find higher temperatures in between two, too-close, bodies that both reflect SW and radiate LW. I can't predict what difference that made, but for someone really concerned about siting of instruments, he introduces his own siting problems.
  26. The surprising result when you compare bad weather stations to good stations
    Omnologos @13 - "The warming signal is so significant it shows up in both good and bad sites" is not an answer" And yet the warming shows up in both good and bad/poor sites, how do you explain that?. You might consider that some deep dark mystery, however......... Oh, and you do realize that if the data from the bad/poor sites is discarded (which seems to be the skeptic solution to everything they find inconvenient) then the US record will be adjusted upwards?. Given that science seems to take a back seat to your world view, is that really what you want?.
  27. It's microsite influences
    psilax, Re. #2, a good question. I looked up the Menne article and the Watts 2009 article to which it is a response. Watts suggests two driving causes for the upward bias of temperatures: The change in paint spec in 1979 and the introduction of the new type of thermometers in the 1980s. I suspect that Menne, et al, restricted their period of reporting to that which Watts was concerned about.
  28. Klaus Flemløse at 07:09 AM on 1 September 2010
    Urban Heat Islands: serious problem or holiday destination for skeptics?
    Please note form IPPC TAR: "These results confirm the conclusions of Jones et al. (1990) and Easterling et al. (1997) that urban effects on 20th century globally and hemispherically averaged land air temperature time-series do not exceed about 0.05°C over the period 1900 to 1990 (assumed here to represent one standard error in the assessed non-urban trends). However, greater urbanisation influences in future cannot be discounted." http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/052.htm To me it looks like we can't exclude UHI effect in the future. This is an important point.
  29. Sea level rise: the broader picture
    JohnD, you really ought to read the paper I've referred to twice above. I won't bother supplying the link again, look for "closing the sea level budget."
  30. Sea level rise: the broader picture
    Dappledwater at 22:34 PM, there are a couple of points in the quote you posted that are interesting. Firstly the reference to eustatic sea-level, which is a notional world-wide average and what is generally referred to by the IPCC and others. This is different to the local relative sea-level (LRSL), which correspond to changes in actual sea-levels at real and particular coastal locations. Can you elaborate as to the reasons why 0.3mm per year must be added to the Australian records and how this adjustment was arrived at as it appears very relevant to the discussion. The other point is the comment about the affect ENSO events have on sea level rise. This effect has to be taken into account with such events following much longer decadel cycles such as the PDO and other similar ocean based cycles that operate in all the oceans. However I am not sure whether the comment about the trend to more frequent, persistent and intense ENSO events since the mid-1970s is entirely correct. That period was almost evenly divided in the number of declared ENSO events with the first half seeing the SOI generally more positive and generally more negative in the second half. If that was the "trend" he was referring to then as a negative SOI is associated with El-Nino that would tend to indicate that if global warming also brings more frequent El-Nino events then that should result in a continually reduced trend if what you posted is correct.
  31. Sea level rise: the broader picture
    HR, The scientists who generated the data say 3.3 is more than 1.8. Are you more qualified to interpret the data? Ned pointed out before that 3.3 is a global value and the data for the south pacific is greater than the global average. Since the rise is different at different locations, we would not expect all the points to be the same. On the other hand, we expect the Global data to stay the same. You have to keep all the data in context. A global 1.8 changing to 3.3 is acceleration. 5.4 in one island in the south pacific does compare well to 3.3 globally. Pay attention to what you are comparing.
  32. Urban Heat Islands: serious problem or holiday destination for skeptics?
    BP Cite your source. here Dr. Hanson gives data that shows the UHI effect is small. Your claim of .2-.3 per doubling is in need of data. Dr. Hanson shows that ignoring the UHI effect does not alter the data analysis. Your claims recently have not been at the level you used to have. Maybe you need to review your assessments of the data.
  33. The surprising result when you compare bad weather stations to good stations
    Yes, Phila, one might say it's more waste heat. Heat, but no more light.
  34. The surprising result when you compare bad weather stations to good stations
    #37 I strongly suspect we have all made our points, sometimes more than once, and could continue for weeks. I strongly suspect that of the people who made their points here, exactly one of them was consistently wrong.
  35. Urban Heat Islands: serious problem or holiday destination for skeptics?
    As I recall, having looked at some of the "logarithmic population vs. temperature change" articles on WUWT, it was shown that all of the regions showed a similar temperature change. If the temperature trend was caused by UHI/population growth, it's necessary to show that in areas without population growth the trend is not present. I have seen no data to support this. As it stands the data indicates that (a) temperature trends have gone up, and (b) the world population has gone up. There is as yet no demonstration I'm aware of that temperatures have not gone up where the population has not gone up, which would be a minimal criteria for a cause-effect relationship. Correlation is not causation, as demonstrated here. Add to this the fact that the satellite temperature records have independently shown the same temperature trends, as Ned points out, and evidence for a UHI/population influence on temperature trends is awfully weak. Temperature trends appear to be independent of any UHI effects.
  36. Urban Heat Islands: serious problem or holiday destination for skeptics?
    BP writes: It is about 0.2-0.3°C per doubling of local population density for a very wide range of initial population densities [...] global population has doubled twice since the beginning of the last century (therefore about 0.4-0.6°C of the global trend is due to UHI) I'm curious how this unique and unsourced analysis takes into account the 70% of the planet covered by ocean. Are the lower troposphere and sea-surface temperature trends also affected by UHI? It seems improbable given the lack of pavement in the middle of the Pacific, not to mention at the 600 km altitude of Aqua/AMSU.
  37. Urban Heat Islands: serious problem or holiday destination for skeptics?
    #3, BP, do you have any actual research to cite, or do you just make this stuff up?
  38. Urban Heat Islands: serious problem or holiday destination for skeptics?
    "But as UHI is proportional to the logarithm of local population density, it is no wonder its effect on trend is not smaller for low population density areas. In fact it is expected to be a bit stronger there, because much smaller absolute numbers are needed to increase population density twofold." I fail to see how rural stations are affected by this. For the UHI to be noticeable, the immediate surroundings of a station have to be affected. Many rural stations are in areas where there has been little development, and I have yet to read a convincing argument that modest rural development (such as what we have seen in the last 50 years) could have an impact that would skew the temperature records. Do you have credible studies that support your various affirmations?
  39. The surprising result when you compare bad weather stations to good stations
    I must remember to wait for 24 hours after reading omnologos' posts before getting my blood pressure measured. Anti-science rantings such as his put my blood pressure up by way too many points.
  40. Hockey stick is broken
    McShane and Wyner's paper was tossed into the ring of public contention prior to being graced with the full benefit of review. Presumably this was voluntary on the authors' part, or let's hope so. DeepClimate has a lengthy post delving into various features of M&W, and as well there's a robust discussion in the comments there for folks who'd like to get caught up one way or another. DC is not the only outfit to notice the strangely situated political freight loaded onto the M&W train of thought.
  41. Hockey stick is broken
    Deep Climate has done a detailed analysis of the McShane and Wyner paper.
  42. Sea level rise: the broader picture
    38.Ned If +5.4 mm/year or +4.9 mm/year compare well with +3.3 mm/year then how different is 1.8mm/year (overall 20thC) from 3.3mm/year (past twenty years)? We seem to be arguing this second difference is significant but it doesn't look so different from a couple of numbers you say "compare very well".
  43. Temp record is unreliable
    The answer might be no. A STATISTICAL ANALYSIS OF MULTIPLE TEMPERATURE PROXIES: ARE RECONSTRUCTIONS OF SURFACE TEMPERATURES OVER THE LAST 1000 YEARS RELIABLE? McShane and Wyner. Submitted to the Annals of Applied Statistics One of the conclusions:

    ...we conclude unequivocally that the evidence for a ”long-handled” hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data.

    In other words, there might have been other sharp run-ups in temperature, but the proxies can't show them. The hockey stick handle may be crooked, but the proxies can't show it one way or the other.
    Moderator Response: Not the same topic. Try this thread for a better place to discuss McShane and Wyner:
    Is the hockey stick broken?
  44. Urban Heat Islands: serious problem or holiday destination for skeptics?
    but... but... I was sure if you dropped urban stations there would be an obvious decline in global temperatures! (just kidding)
  45. The surprising result when you compare bad weather stations to good stations
    Just to clarify: we are talking about USHCN criteria, not mines. Seemingly I have started off something 'round here. Since I find it less than kind to hijack somebody else's blog with a salvo of comments, apologies to all but I'll suspend things here, and perhaps post a note or two later today, plus something in my own blog. I strongly suspect we have all made our points, sometimes more than once, and could continue for weeks. That's part of the good/bad nature of the 'net. Thank you all, and to John Cook and the other authors, for the intellectual challenge.
  46. Sea level rise: the broader picture
    22.Dappledwater It's not just the Wenzel paper that shows no acceleration. It looks like the 18 satellite data doesn't show one. So you're saying the acceleration occured around 1950 and since then things have been moving at a steady rate? That's what I see from the figures you show. But the most prominant temperature rises and land ice melt have occured post 1970 and post 2000. It doesn't seem to fit. I don't think land/sea temp is as relevant as OHC. Try this old, white, male deniers presentation of the NODC data on OHC. Shouldn't we be seeing acceleration in teh 18 year satellite data?
    Moderator Response: The topic of ocean heat content is better explored on an appropriate thread. A robust discussion may be found here:

    Robust warming of the global upper ocean
  47. The surprising result when you compare bad weather stations to good stations
    Hi again omnilogos "My example is about going to see 100 doctors, _all_ making mistakes in measuring your blood pressure." Right, your example is about absolute accuracy. In this case, the right example would be going to see these 100 doctors every day for 30 years, and the doctors all make consistent errors in measuring your blood pressure. At the end maybe you would not know your absolute blood pressure, but you would certainly be able to tell how it had gone up or down over the years. You would know a lot about the trend. You CAN get useful trend information from imperfect data, and that is the point of the Menne paper.
  48. The surprising result when you compare bad weather stations to good stations
    omnologos, all your doctors' blood pressure readings of you are "wrong" by your criteria! You will never be able to find a doctor meeting your criteria, because there is no such doctor! If you research the definition of "blood pressure," you will discover that the concept is useless without an operationalization. Then you will be dismayed to discover that there are in fact a bunch of operational definitions, involving the patient sitting, lying, standing; the instrument being on the wrist or arm or other body part or even inserted in a blood vessel; the instrument being a microphone or a health care provider's ears in a stethoscope or a direct pressure sensor; and even the strength of the sound that marks the trigger for the measurement has multiple values. Have you ever noticed that none of your doctors has ever been consistent in demanding your posture be precisely "correct" for precisely one of the many requisite durations before measuring your blood pressure, let alone insisting that you be at the doctor's office at precisely the same time of day?
  49. Klaus Flemløse at 02:14 AM on 1 September 2010
    Urban Heat Islands: serious problem or holiday destination for skeptics?
    As I recall, IPPC states: In the past warming from UHI is insignifikant. In the future it may be signifikant. Please consider to included this in writing about UHI.
  50. Berényi Péter at 02:14 AM on 1 September 2010
    Urban Heat Islands: serious problem or holiday destination for skeptics?
    #1 RSVP at 00:10 AM on 1 September, 2010 "...results in a slightly warmer envelope of air over urbanised areas when compared to surrounding rural areas.." Why not express this in degrees centrigrade? It is about 0.2-0.3°C per doubling of local population density for a very wide range of initial population densities. This rule also works for sites considered "rural", although the exact value of the coefficient should depend on level of economic development as well. This is the reason behind similar trends in urban vs. rural sites. That is, even if scientists have been very careful to ensure that UHI is not influencing the temperature trends, they could only make sure the influence was about the same over all kinds of sites. Population density distribution is always fractal-like and population on average grows by the same percentage everywhere. The net result is "urbanization", when ever higher proportion of the population lives in really densely populated areas. But as UHI is proportional to the logarithm of local population density, it is no wonder its effect on trend is not smaller for low population density areas. In fact it is expected to be a bit stronger there, because much smaller absolute numbers are needed to increase population density twofold. The only correct check for the actual magnitude of the temporal UHI effect is to calculate temperature trends for sites where local population density has decreased for an extended period and compare them to the rest. Of course it is not easy to find such regions, because global population has doubled twice since the beginning of the last century (therefore about 0.4-0.6°C of the global trend is due to UHI). However, the quest is not impossible. For example several regions of the US experienced multi-decadal population decrease (southern West Virginia, Northern Maine, many regions of the mid-west). There are also excellent census data in the US, so it is pretty easy to locate such regions. Basically one should choose all the counties where population has decreased for the last thirty years, with a decreasing population in all the neighboring counties as well and which have climatic data for the entire period (something like Beckley city, Raleigh County, West Virginia). That's the job to be done for scientists, provided of course there are some who really want to be careful.

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