Warming is due to the Urban Heat Island Effect

This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.


The apparent rise of global average temperatures is actually an illusion due to the urbanization of land around weather stations, the Urban Heat Island effect.


Urban Heat Island Effect has been examined quite thoroughly and simply found to have a negligible effect on temperature trends. Real Climate has a detailed discussion of this here. What’s more, NASA GISS takes explicit steps in their analysis to remove any such spurious signal by normalizing urban station data trends to the surrounding rural stations.  It is a real phenomenon, but it is one climate scientists are well  aware of and have taken any required steps to remove its influence from the raw data.

But heavy duty data analysis and statistical processing aside, a little common sense and a couple of pertinent images should put this idea to bed.  Here is an image, taken from Astronomy Picture of the Day (a wonderful site, by the way), of the surface of the earth.  It is a composite of hundreds of satellite images all taken at night.  (The large version is well worth the download time!)

Aside from being very beautiful, it is a perfect indicator of urbanization on earth. As you can see, the greatest urbanization is over the continental United States, Europe, India, Japan, Eastern China and generally coastal South America.

This next image was taken from NASA GISS. It is a global surface temperature anomaly map which shows warming (and infrequently, cooling) by region.

 Look at North America, look at Europe, at Asia, Australia, Africa and the Poles and compare them to the urbanization in the image from APOD. There is quite simply no way to discern any correlation whatsoever between urbanization and warming.  If the UHI effect were the cause of warming in the globally averaged record, we would see it in this map.

The claim that Global Warming is an artefact of Urban Heat Island Effect is simply an artefact of the Urban Myth Effect.

Addendum: Wikipedia has a very good article on this subject. Among all the interesting details it mentions a few papers that directly discuss efforts to identify and quantify UHI influences on the global temperature trend including this one which would be a good one to cite:

A 2003 paper (“Assessment of urban versus rural in situ surface temperatures in the contiguous United States: No difference found”; J climate; Peterson; 2003) indicates that the effects of the urban heat island may have been overstated, finding that “Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures.” This was done by using satellite-based night-light detection of urban areas, and more thorough homogenisation of the time series (with corrections, for example, for the tendency of surrounding rural stations to be slightly higher, and thus cooler, than urban areas). As the paper says, if its conclusion is accepted, then it is necessary to “unravel the mystery of how a global temperature time series created partly from urban in situ stations could show no contamination from urban warming.” The main conclusion is that micro- and local-scale impacts dominate the meso-scale impact of the urban heat island: many sections of towns may be warmer than rural sites, but meteorological observations are likely to be made in park “cool islands.”

If necessary, be sure to refer to all the other ways we know that the global warming trend is not an artefact of anything, it is real.

This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic.

“Warming Due to Urban Heat Island Effect” was first published here, where you can still find the original comment thread. This updated version is also posted on the Grist website, where additional comments can be found, though the author, Coby Beck, does not monitor or respond there.

123 thoughts on “Warming is due to the Urban Heat Island Effect

  1. crakar

    You seem to be confusing science with politics. If you want to debate the science, that’s fine, but the fact that governments procrastinate or attend junkets has nothing to do with the issue at all. Government’s are well known for telling lies (WMD), pork-barrelling, spending taxpayers money on themselves etc etc. But that does not and cannot change the science.

    I accept AGW as an undenialable fact. Does that mean I believe Al Gore? No, of course not. I know he exaggerates and tells half-truths; he is a politician after all. Does that mean I believe an ETS is the ony way or even the best way to deal with the issue. Of course not, but then again, it is not my field of expertise – I am not an economist. Do I accept the claims regarding current sea level rises in places like Kiribati? No, definitively not. I have been there and I know what the true situation is.

    Finally, you ask why governments around the world procrastinate. The answer is really simple. Its because of people like you. You vote, and governments answer to their constituents. It doesn’t matter if those constituents are morons, or only vote with their hip-pockets, or vote because they like the way someone looks; governments have to do what these people want or they get kicked out and replaced by someone else. And as long as there are people out there who complain about the cost of addressing climate change and how it will raise the price of electricity or petrol etc, there will be idiot politicians like Tony Abbott who pander to these views. Unfortunately, it affects all of us, and we will all have to suffer the consequences of inaction.


  2. Mandas,

    People like me are making the government procrastinate? How is this possible? Does Krudd read Coby’s blog?

    Krudd has the IPCC, the consensus and hollywood stars in his corner and yet i and poeple of my ilk have stopped him from acting. Surely you jest.

    I do believe Krudd went to the last election promising action on climate change and he got voted in, where i come from that is called a mandate and yet here we are slowly absorbing the calamity of the insulation scheme and still waiting for Krudd to explain his ETS.


  3. Why does he need to explain it? He has a mandate – or so you say. Accordingly, those pesky MPs in the opposition and minor parties should just get out of the way and let the government do what they were elected and have a mandate to do. And since the Coalition also had an ETS as their policy at the last election, and since they made a deal with the government to pass the legislation only a few weeks ago, why does the creationist in charge of the Liberal Party prevent it from happening? It isn’t the government who is stopping the ETS from passing, remember?

    You are being extremely disengenous as usual crakar. I don’t think that even you are foolish enough to think that governments and oppositions are not swayed by public opinion. How about you state your real opinion on the subject, rather than just being the abominal no man on everything.

    If everyone in the country supported an ETS, it would be passed in an instant. The reason it hasn’t been is because we have a fundy for an opposition leader, and idiot MPs spend their days talking to morons who whinge that the price of electricity will go up if we put a price on carbon, and who know nothing about science but think they know better than people who study the climate for a living. You know that. I know that. Everyone knows that.


  4. Am I the only person who thinks the insulation scheme was a terrific thing? The whingers have crippled a scheme that really benefitted the environment. According to the ABS there are about 10,000 house fires per year in Australia, and electrocution is dwarfed next to heart disease, stroke, and even car accidents, as a cause of death. If people see fit to jump up and down and demand resignations on that basis, no transport or health minister would last a month in office. Fix it and move on is the appropriate response.


  5. mandas #99, I think my comment concerning the energy budget should be fairly clear.

    There is increased absorption of IR in the 10 micron window, as it’s called, but since we don’t look in longer wavelength regions with satellites (15+ micron), it’s hard to say whether or not the energy emitted at those longer wavelengths is making up for it or not. Because 10 micron light that is absorbed by CO2 gets redistributed to the internal degrees of freedom of the molecule before it’s re-emitted back out to space, we should not expect to see energy absorbed at 10 microns to be re-emitted at the same wavelength. It will be emitted at a longer wavelength, or lower energy. Some of that energy is also re-emitted back at the surface of the earth for the whole process to begin again.

    As I said before, some of the energy also gets transferred to other molecules, mostly diatomic nitrogen and oxygen molecules, and those also emit light that travels to space. Because nitrogen and oxygen lack permanent molecular dipoles, however, this energy is transferred via rotational relaxation pathways versus vibrational relaxation pathways in CO2 and water. The rotational spectra of these molecules is in the Gigahertz or microwave region of the EM spectrum and I think most of it is picked up by NASA’s microwave sounder unit, though I don’t know if anyone has tried to model how much of that spectra is due to energy transferred from excited CO2 collisions.

    So one has to look at all of these different pathways to get a view of how efficiently energy reaches back to space after a CO2 absorption event. It’s not good enough to simply point out that the light in the 10 micron window has lower intensity than in the past. It’s like taking a questionable bucket, plugging one hole and claiming that the bucket must now be filling up. You need to check for other holes before such a claim can be made.

    Crakar #100,

    pressure makes a difference. The higher the density of the atmosphere, the more inertia it will have and the longer it will take to respond to changes. This may be why it is easier to reproduce observational data with general circulation models. The atmosphere may always be closer to a steady-state then the one here on earth. That and the fact that there are no oceans.

    But I really think the fact that the Coriolis force on Venus is so small plays a more important factor since it drives a great deal of the atmospheric dynamics we see on earth. The largest components of both the vorticity and divergence equations predicting how winds behave as vectors include the Coriolis parameter, proving it’s importance in earth’s climate system for atmospheric dynamics.

    As far as logarithms go, yes even if one has a situation where the optical density of a sample is 1000 (the transmission through the sample is 10^-1000, or 1 in 10^1000 photons is NOT absorbed), the sample is still not ‘saturated’. Saturation does not refer explicitly to optical density, although I have even seen climate texts use such language. Saturation in it’s explicit definition refers to creating a situation where a group of absorbers cannot absorb light of a specific wavelength any longer. The only way to create such a situation is to optically pump the absorbers very hard (with lots of energy) so that the vast majority of them lie in quantum states that are no longer resonant with the incoming light. In quantum optics, such situations are called electromagnetically induced transparency. I think Uncertain Principles has a couple posts on it if anyone is interested in it.

    So there will be diminishing returns on CO2 ability to provide heat to the lower parts of the atmosphere via IR absorption, but because I can’t seem to find a good number for the molar extinction coefficient of CO2 at relevant wavelengths, it’s hard for me to say whether we find ourselves in such a situation currently.


  6. maxwell

    “…You need to check for other holes before such a claim can be made….”

    Actually, no I don’t. AGW is a theory which is well supported by the basic tenets of science (ie greenhouse theory and the absorbtion of long wave radiation by CO2), and it is supported by observations (ie temperature increases and by an observed reduction in the energy loss from the system). In other words, it has both plausibility, scientific principles, and observation on its side. So it passes all the tests to be considered a valid theory.

    However, like all theories, it must have ‘falsibility criteria’ which state that – if such is shown to be true or such and such can be shown to be not true or not occurring, then the theory would have considered to have failed or require modification. I have listed some of those ‘falsibility criteria’ in previous posts; however, as most of them fall under the category of basic science tenets, it is unlikely that any of them could be shown to be false.

    The only real tests which could disprove the AGW theory (in my mind) are that the observed reduction in energy loss from the system is balanced by a reduction in incoming energy, or that the extra energy is either being used for purposes other than warming or is lost by some mysterious means.

    The first point – reduction in incoming energy – is not supported by observation. Indeed, one of the ‘catchcries’ of the denialist movement is “it’s the sun stupid!!”. In other words, some denialists claim that temperature increases are the result of increased solar activity. If there has been an increase in solar activity then we are in real trouble, because not only would that mean there was less energy escaping, it would also mean there was more energy going into the system. And that would be a recipe for disaster.

    The second and third point are somewhat related. However, the most important point to make about both of them is that there are absolutely no observations to support them. You are fond of suggesting a number of potential hypotheses, but if you want to falsify the theory, you are going to have to do more than that – you will need to produce the evidence. Unfortunately, since all observations support a warming of the climate, your hypotheses are inconsistent with both the theory and the observations. IF the excess energy etc was being lost into space or was being converted into other forms, then what is causing the observed warming?

    Me – I’m going to fall back onto the age old principle of Ockham’s Razor. I have a theory that is plausible, underpinned by basic principles, and supported by observation. I have listed falsibility criteria, none of which have been demonstrated. You need to provide some form of evidence or otherwise to demonstrate why you think I am wrong – not just a bunch of hypotheses with no evidence to support them.


  7. mandas,

    Taylor and Bitterman did an extensive study of the many relaxation pathways that CO2 takes after excitation to the state accessible in the 10 micron window (Review of Modern Physics Vol. 41 Num. 1). There are 4 different relaxation pathways, 1 radiative and 3 radiative-collisional, that lead to the emission of a photon that has less energy than the initially absorbed 10 micron photon. Two of them are in the region of the IR that are currently not measured by satellites. They are very important in understanding the dynamics of the CO2 laser.

    So there is the experimental evidence. How does a position that denies the existence of this and a mountain of other evidence on the subject of vibrational relaxation equate applying Occam’s Razor? It seems rather ridiculous to claim that because no one has attempted to measure these wavelengths in the context of climate science means that they play no important role. It’s like a creationist claiming because there are no ‘missing links’ that evolution must be wrong. Well done.


  8. Crakar: read your response. Too much material there to attack at once.


    Any chance to make this subtopic a thread:

    “What would it take to convince me/you?”


  9. Mandas re 103,

    I think the main reason why KRudd has gone quiet on “the greatest moral issue of our time” is because Copenhagen failed.

    Secondly he was first to blink and lost all credibility, as he threatened a double dissolution if his ETS/CPRS was shot down a second time. Well it got shot down and then he said we will try again after Xmas meanwhile COP15 was a flop and now the ETS has been pushed back to May i believe. Now apart from Abott you need to recognise the greens role in all this and how they have finally shown the oz people their true colors, they are a protest party not an environmental one, its about time they came clean.

    But never fear KRudd has promised a double dissolution om his private health insurance bill.

    Now with this talk about CO2 you do realise that this is only part of the AGW theory dont you? This part is fairly well understood and what you and Maxwell are doing is discussing the finer points. We all accept an increase in any GHG will increase the temp somewhat (in theory anyway) but in the real world the increase in temp can induce feed backs so your next step is to explain the +ve feed back from WV and maybe methane.

    Of course only empirical evidence will be accepted.


  10. Maxwell

    Firstly, thank you for the information about the Taylor and Bitterman paper from 1969 re the “Survey of Vibrational Relaxation Data for Processes Important in the CO2-N2 Laser System”. Unfortunately, I couldn’t access the full paper so am unable to comment. However, I did read Taylor’s 1973 paper on “Energy Transfer Process in the Stratosphere”, which is probably a lot more relevant anyway. If you couple the reading of this with Joly and Robin (1998) on “Vibrational relaxation of CO2 in a CO2-N2 mixture. Part 1: Survey of available data” you can get a pretty clear picture of the whole process, including information post the original paper in 1969. And I have to ask you, what makes you think that no-one has either thought about this or has included it in their calculations? Perhaps you should read Kuo_Nan Liou’s book on the subject: “ An Introduction to Atmospheric Radiation”. It’s quite definitive.

    Now, on to your post, in particular, this statement:

    “….It seems rather ridiculous to claim that because no one has attempted to measure these wavelengths in the context of climate science means that they play no important role. It’s like a creationist claiming because there are no ‘missing links’ that evolution must be wrong. Well done….”

    I have to hand it to you there. I think you have beaten out crakar to the most disingenuous statement ever posted here. I have made no such claim about the importance or otherwise of CO2 relaxation in the atmosphere. You are the one making the claim that the relaxation of CO2 emitting radiation at wavelengths greater than 15 microns can explain why the theory of AGW climate change is flawed, but you can’t prove it because no-one has conducted the necessary measurements. And you call me a creationist?


  11. crakar

    At least we can agree about the Government and the ETS- in general anyway. I don’t necessarily think that the PM is not pushing the issue because of Copenhagen, rather it has just dropped of the political radar and isn’t a major issue with a lot of people. He is a politician, and will chase things that he considers to be vote winners. Of course, one of the reasons the ETS and climate change are not considered as important by voters as they used to be is that the drought has broken in a big way. Most people can’t differentiate weather from climate, so while there is a drought people are concerned about climate change, but as soon as it rains people think it isn’t anything to worry about anymore.

    Ad to the question on feedback etc, I won’t hog the thread and will leave that for later.


  12. You know Mandas there might be a reason why people think the way you say they do, remember i mentioned Tim Flannery before?


    Here is alarmist Tim at his best, in 2007 he ran around in ever decreasing circles babbling incoherently, something to do with Brisbane needing a desal plant now the dams are 90% full.

    It all comes back to credibility same as KRudd if COP15 had of been a success we would have our ETS by now Abott would of had no choice but to vote for. Of course the greens would of voted against in protest.

    By the way where do you work? Near the RAAF base in Elizabeth?


  13. No – I work in the city. I used to work at the RAAF Base – but that was when I was in the RAAF in my former life.

    I also used to live in Toowoomba a few years ago, so I am well aware of what was being said about the need to do something about the water supply in SEQ. The current situation is just a temporary reprieve though. There are too many people there – and getting more all the time – for the limited water supply available.


  14. Mandas,

    “but that was when I was in the RAAF in my former life” you see we have something in common. :-))

    To all,

    I read a story in the paper yesterday which said it was the coldest winter in 30 years in the UK and the coldest since 1962 in Scotland and Ireland


    Ironically below that story we had another about Phil Jones, who was asked by some English polly about why he never gave out his data (FOI etc) Jones gave his reasons and then went on to say that he never gave the data to the peer reviewers either. He was then asked why, Jones replied “because they never asked”.

    So much for the peer review process.


  15. mandas,

    ‘You are the one making the claim that the relaxation of CO2 emitting radiation at wavelengths greater than 15 microns can explain why the theory of AGW climate change is flawed…’

    No, I’m not. I’m explaining how YOUR thinking about this aspect of climate change is flawed.

    You were going through ways of presenting the problem that you thought proved your thinking about this problem. It basically boiled down to conservation of energy concerns. I merely pointed out you weren’t conserving all the energy. You challenged such a claim and I proved you wrong.

    That’s what happened.

    I’m sure other people have thought about these problems. I was just pointing out to YOU that you need to think about them to get a coherent picture of what is happening.

    Furthermore, there is no need to ‘prove’ to you that these processes are happening in the atmosphere. They happen naturally in any gaseous mixture of CO2, O2, N2 and water vapor. That’s the point of the 1969 paper and since then the CO2 laser has become a standard in industrial lasers based on such 40 year old treatments, I have no reason to doubt the paper’s validity.

    In the paper you cite from 1998, in fact, the authors go out of their way to mention that one of the reviews of data contains information from this 1969 paper from Taylor and Bitterman. I guess its importance stood the test of time.

    If anything, this 1998 paper proves that even given all of the coherent spectroscopic techniques that we have developed over the course of the last forty years (since 1969), we still have not been able to paint as complete a picture of CO2 relaxation dynamics as would be necessary to understand how ALL the energy in the atmosphere escapes back to space. In the conclusion section, the authors (Joly and Robin) state,

    ‘Even though a considerable work has been undertaken in the field of the vibrational relaxation of the CO2 over the last thirty years, the authors of the different compilations do not agree with each others and there exists a lack of some important data (for the Fermi resonance for example).’

    Since your argument depends on our having a coherent picture of energy gets back to space (how else can one invoke conservation of energy?), this statement seems to fly in the face of your conclusions. If there are important processes that result in unknown relaxation pathways, then it’s very hard to assess whether current or past measurements of a particular range of wavelengths are ‘good enough’ to claim radiative balance has been broken significantly or changed in some significant way.

    ‘Perhaps you should read Kuo_Nan Liou’s book on the subject: “ An Introduction to Atmospheric Radiation”. It’s quite definitive.”

    Why don’t you sum it up for me in the context of these relaxation pathways and our current knowledge of them? Because if it doesn’t discuss them, then it’s far from definitive on this particular issue.

    As I pointed out before, why is it more reasonable to assume that physical processes that normally happen in everyday circumstances in mixtures of relevant gases should not happen in the atmosphere? It’s most definitely not an application of Occum’s Razor.


  16. Roy Spencer is grasping at straws with that post. Maybe Tamino will post a statistical beat-down on it. Spencer’s history – he’s (lead, I think) on the UAH satellite temps. For a while, UAH showed no warming, which made Spencer the darling of the deniers. Spencer ignored a lot of pointed questions about how his processing worked (satellite temps have to be corrected for orbital drift and a lot of other effects) until finally somebody else did a definitive analysis showing his mistakes (including a sign error on an important correction term). Now the UAH data shows a clear 0.13C/decade trend. RSS (the other satellite record) shows 0.15 and the two surface records (GISS and Hadcrut) show about 0.17. (That’s all from memory, so if I’m off by 0.01, it’s not an agenda.) Anyway, he’s still trying anything to play down the trend, suggest it’s natural instead of anthropogenic, etc. If I understand his new UHI theory, it’s turned around – that small population increases in sparsely populated areas cause more temp gain than actual urban areas experience from a proportionate population increase. So instead of urban heat islands, he’s talking about exurb/rural heat donuts. But the point of UHI is that the areas are small and should be discounted. But this new definition of the places showing “spurious” warming must be half the country. That’s not spurious! It’s just silly.


  17. I think Christy is the lead guy on the UAH sat reconstructions. I know it was Christy who personally responded to the first exposures of errors a decade or so ago, it was he who was at the big round-up with the RSS and other people put together to help settle things early in the Bush administration.

    Also, after the last round of corrections to the UAH stuff (last month) Spencer published Christy’s explanation as to what was done, and why. If Spencer were the lead guy I’d expect him to publish his own explanation.


  18. We have all heard about the Berkely Earth Surface Temperature (BEST) study, which is being conducted by Dr Richard Muller and is (was?) being supported by Anthony Watts to hopefully support his hypothesis about climate change all being the result of poor station siting and the UHI.

    And we all know that Watts tried to disown the report that Muller provided to Congress with his initial findings that there were no significant errors in the instrumental record – certainly not in the way that Watts had hoped.

    Well, the results are now in, and guess what? Watts and his denialism have been blown out of the water by the evidence. Newspaper article here:


    BEST information here:


    I wonder what Anthony’s response will be? I’m betting he won’t accept the evidence, but will continue with his ideological spin and denialism – because that’s all he has. He certainly has no integrity.


  19. Thanks for the post.

    Here’s you’re answer, Mandas:

    The Berkeley Earth Surface Temperature project puts PR before peer reviewa

    Posted on October 20, 2011 by Anthony Watts

    Readers may recall this post last week where I complained about being put in a uncomfortable quandary by an author of a new paper. Despite that, I chose to honor the confidentiality request of the author Dr. Richard Muller, even though I knew that behind the scenes, they were planning a media blitz to MSM outlets. In the past few days I have been contacted by James Astill of the Economist, Ian Sample of the Guardian, and Leslie Kaufman of the New York Times. They have all contacted me regarding the release of papers from BEST today.

    There’s only one problem: Not one of the BEST papers have completed peer review.

    And so on. I suppose we are to surmise from this that AW insists on the “gold standard” of peer review in whether we should accept scientific claims about climate change.


  20. skip

    Yes, the guy’s hypocrisy is absolutely breathtaking. This is the same person who has spent much of the last few years complaining about how the peer review process is broke, and publishing – on his website – article after article on climate change, none of which were subject to peer review. Now he is complaining that the BEST papers are not peer reviewed (yet!). The mind boggles with just how much of an arrogant arsehole he is.

    And of course there was Watts statement that he would accept the results of the project, even if they went against him. Yet he has spent the past few months since Muller testified before Congress attempting to distance himself from the study and trying to overturn the results that clearly show – with unequivocal evidence – that he is wrong. Even worse, two of the study authors are Muller and Judith Curry, people who Watts thought were on his side.

    There is no doubt that Watts can’t even spell integrity – let alone demonstrate that he is capable of displaying any.


  21. He is now claiming that no-one ever doubted that global warming is taking place, merely questioning the ‘A’ part and the magnitude of the warming. Meanwhile, in the comments (as far as it is possible to tease out meaning from them) his supporters seem about equally divided between those who agree with him and those who insist that warming is not taking place. Neither group seems to be aware of the existence of the other.


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