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Discussion > Urban Heat Island Effect - Is It Real?

What is wrong with having had something "just occur to me"? Especially in the case where what I independently deduced is 1. not obvious, and 2. opposed by commonly available evidence (both Phoenix and Las Vegas officially are UHIs, opposite to what I would have predicted).

I am a geologist with a specialization in interpreting carbonate and evaporite rocks. My interest in climate came when I began to consider presenting a new undergraduate module on all aspects of fossil fuels. I quickly discovered that there was evidence and argument against the consensus which students were not being exposed to. One very small element was that UHI effects were probably not being fully accounted for. Until recently I saw no need to learn any more about the subject. It was therefore somewhat of a revelation to me to deduce something (the opposite of UHI) from basic principles.

You attack me once again for being an academic. There are plenty out there who you, with more justification, could admonish, but I am a poor target. I worked in "the real world", whatever that is, for a goverment agency doing research for industry and for industry itself, and since turning to teaching have used my experience of industry there.

What was the point of your post? What does it add to the discussion here? Your near obsession with attacking me is becoming boring. Please desist.

Sep 20, 2016 at 7:19 AM | Unregistered CommenterACK

Don't worry about it, it also just occurred to me that oasis should be cooler than the surrounding desert. But when you search the internet you just get a load of results for cruise ships and beat combos. but the the thought process was that the Nile Valley is a very long oasis and that must have a reverse UHI, an OCI (Oasis Cool Island) if you like, as will any river passing through desert. So do cities like Cairo have similar temperatures to the desert outside the river irrigated elongated oasis? I'll have to research further but my feeling is probably not quite as high.

Then I had a thought about the Okavango Delta which irrelevant on this thread.

Sep 20, 2016 at 7:52 AM | Unregistered CommenterSandyS

SandyS. My experience of Cairo is that, with the exception of small areas (Embassy area, Riverside walks), there is very little greenery. There are gardens in courtyards (so unseen) but I doubt they have more than a very immediate effect. The city commonly has a pall of smog, indicating inversion conditions - a common feature of areas with UHI.

I have tried ignoring PCar but it doesn't work, he just ups the stakes, over and over. I think his intention is to drive me from BH.

Sep 20, 2016 at 8:22 AM | Unregistered CommenterACK


I've appreciated your contribution to this thread (and elsewhere). Please don't be driven from BH.

Sep 20, 2016 at 9:24 AM | Unregistered CommenterMark Hodgson

Mark Hodgson. Thank you for your encouraging words. I have no intention of being driven from BH, but I must find a way of responding without counterpunching. Quite rightly others here grow tired of our bickering.

Sep 20, 2016 at 10:10 AM | Unregistered CommenterACK

Good to hear that you'll continue posting here.

Sep 20, 2016 at 10:46 AM | Unregistered CommenterSandyS

My experience of modern Cairo is that it is a really good example of not very much. The Pyramids represent the biggest and most durable man made objects, that have withstood thousands of years, with almost no maintenance let alone structural repair. Since then, the Egyptians have never really looked back, to understand what they got so right.

Saladin developed the Walled Citadel in the 12th Century, but could only make it habitable and defendable by building a deep well. This had to be supplemented with water wheels to provide water for the people and their animals.

Until the building of the Aswan Dam, Cairo never had sufficient water to waste any on elaborate fountains etc, and these days, the wealthy residents have airconditioning, and probably are not there in the hottest months.

Sep 20, 2016 at 12:10 PM | Unregistered Commentergolf charlie

golfCharlie. I was thinking about the Citadel when I mentioned the pollution of Cairo. Visiting this location I was struck by the fact that the Citadel had a welcome breeze and exists above the pollution level. Looking up the Citadel on Wikipedia I found a picture - On the Way between Old and New Cairo, Citadel Mosque of Mohammed Ali, and Tombs of the Mamelukes, by Louis Comfort Tiffany, c. 1872 - which shows the pollution is nothing new.

Sep 20, 2016 at 1:39 PM | Unregistered CommenterACK

ACK, that painting dated 1872 is from a few years after the Suez Canal was opened which turned Port Said into a major coal refuelling depot. A railway line between Cairo and Port Said had actually been in existence for 10(?) years before the canal was opened, presumably to link Cairo with a Mediterranean Port as the route to Alexandria was complicated by bridging the Nile Delta. The smoke haze depicted in the painting is possibly from coal, rather than firewood.

The Ancient Eqyptians tried/suceeded/failed (?) to construct a canal from the Nile at Cairo to the Red Sea. This was of great interest to Napolean, and reopening was possibly part of his larger plans for world domination. Nelson stuffed up his return travel plans at the Battle of the Nile, aka Aboukir Bay in 1798, and French Air Traffic Controllers and dockworkers have been exacting revenge ever since.

For UHI purpose, the difference in air temperature between the Pyramids to the West, the Airport to the East, The Citadel in the centre on higher ground, and somewhere else central to Cairo would be interesting, recorded 24/7 365 days pa. There really is very little vegetation!

Sep 20, 2016 at 3:41 PM | Unregistered Commentergolf charlie

ACK - please stop encouraging Pcar by responding to him as if he were capable of engaging in normal debate. It is horrible for people like me who visit BH for its ongoing discussions. I cannot fathom why you respond to Pcar's stupidities and his nonsense. Other commenters have pointed out that it makes BH website something to avoid.

Pcar's constant railing against 'academics' is the obvious sign of his acute sensitivity /chip-on-shoulder reaction resulting from his lack of education. You, as an educated man, do not have his excuse when the two of you oblige us to waste brain-seconds reading the infantile stupidities that the two of you post.

Sep 20, 2016 at 6:30 PM | Registered CommenterMartin A

Martin A. I appreciate your post, it will give me further incentive to ignore PCar in future. In my defence I usually treat people as they treat me. I did not take PCar to be uneducated at all. I, all to late, recognized his antipathy to academia, and thus to me, and his inability to be proven wrong. You might also recognize that I have tried in the past to ignore him.

I find your argument that "because I should know better", I should be able to withstand his jibes and insults alone. I have repeatedly been termed a troll, and not one person at BH has risen to my defense. Where was your condemnatary post to PCar?

I shall attempt to do better.

Mark. My apologies for cluttering up your excellent thread.

Sep 20, 2016 at 6:59 PM | Unregistered CommenterACK


No need to apologise. My intention when putting up the thread was to rise to Phil Clarke's (perfectly correct) suggestion that I shouldn't just say Petersen's 2003 work didn't prove the UHI effect wasn't real, but should put myself to the trouble of reading it, analysing it, and then sharing my thoughts on it. I hoped that others might be encouraged to contribute their thoughts on the subject, and am gratified by the extent to which you and others have done so.

In fairness to Petersen, I think his paper was well-written and well-researched. In some ways, it arrives at the conclusions that the rest of us seem to have reached - that there is a UHI effect, but it's complicated, and will vary from urban area to urban area, depending on the nature both of the urban area and of the surrounding countryside. I also don't argue with his conclusion that its effect will be less in terms of temperature readings if thermometers are placed in parks etc. That strikes me as nothing more than common sense.

Its main limitations, for me, are the limited nature of his statistics (3 years' worth, and only in the contiguous USA), some questionable methodology, and the sweeping use to which his work has been put by the world of climate alarmism. The final flaw is this additional conclusion, which really should have rang alarm bells when he wrote it:

"Additionally, as a community, we need to update our understanding of urban heat islands, to realize that this phenomenon is more complex than widely believed by those not immersed in the field. We should not view all oddly warmer stations as indications of UHI. Some urban stations are indeed warmer than nearby rural stations but almost the same number are colder."

That final sentence demonstrates when dogma and adjustments override common sense and the facts.It enables people like Phil to say stuff like this (on the zombie thread, some weeks ago):

"Well, I pointed you to the BEST study some might say the last word on UHI, and there's Petersen et al. Delta-UHI is simply not a reason to mistrust the surface record, globally the UHI trend is miniscule (No UHI in the oceans or deserts, only about 1% of the surface is urban.) Also constant comparisons are being done identify and adjust for non-climatic influences and all the evidence is that this homogenisation works well."

I'm glad I responded to the challenge. My work is not scientific, and I didn't have time to probe too deeply, but I hope I've done enough to demonstrate the weakness in that sort of thinking and argument. Thanks everyone for your input.

Sep 20, 2016 at 7:50 PM | Unregistered CommenterMark Hodgson

Mark Hodgson, it has always been important for Climate Scientists seeking to prove rising global temperatures, to find evidence of rising temperatures. Pretending UHI does not have an impact has been part of climate science.

As a country bumpkin, the idea that summers are getting hotter and drier, is not something I have any belief in at all. However, the idea that winters are not as cold as 40 years ago, is one that I can relate to, and farmers and gardeners tend to agree about. It is cold that kills, and no one is complaining. I hope it stays this way, but I am more worried about it getting colder, than warmer.

If it had not been for those expressing scepticism about climate sciences wilder claims, it is not clear to me that climate science would ever have addressed UHI. I remain unconvinced by their dismissive attitudes, and the UK Met Office's continued publication of new records for Heathrow proves it.

Sep 20, 2016 at 11:29 PM | Unregistered Commentergolf charlie

Lots of suppositions but...I drive quite often from a location 20 miles outside London into Central London and back. There is always a difference of 2-3 degrees on my car thermometer - ok, not a precise and well-calibrated instrument. Central London is always warmer than where I live and the ampunt of variation is fairly stable. I suggest that there is no difference in trend between the 2 locations. Trend is what is measured by using anomalies..

Of course, if my location became comparably developed as central London over the next 5 years, then ,my location will have a higher trend - UHI. However, over the long term, that is smoothed out.

In any case, we are not measuring a global temperature as a real quantity. It is an index of temperatures - such as the FTSE or the various price indices.

I cannot see the circumstances in which localised changes in urbanisation would leave a lasting impact on the global temperature indices.

Sep 21, 2016 at 1:22 AM | Unregistered Commenterdiogenes

Diogenes. I suspect it's not so simple. The UHI effect increases in city centres over time as well. There is a correlation between city size and UHI. In London, for instance, I would expect the UHI to have increased because of many factors, including the building of closely packed high rise buildings causing a canyon effect, and the paving over of countless front gardens for parking vehicles.

The other factor is that, if UHI contaminated increases in temperature have been used, then the temperature rise over the past century has been overestimated. When this over inflated temperature rise is attributed entirely to our CO2 emissions we get all sorts of climate nonsense forthcoming. I suspect it is this factor that has caused climate science to vigorously oppose the idea of UHI, suggest it is unimportant, or (as a last resort) claim that adjustments remove its influence.

Sep 21, 2016 at 7:19 AM | Unregistered CommenterACK

ACK Sep 21, 2016 at 7:19 AM
It is a complex thing and I suspect under researched. I haven't read the paper in question but Mark Hodgson says it is well written and well researched but is limited to mainland USA. Given a few minutes we could come up with several reasons why US cities are different from other areas around the world. For example I was amazed at the Skyway system in Minneapolis on my first visit, I was told that there are over 10km of Skyways interlinking buildings for all year round climate controlled pedestrian building to building access. I've no idea what effect this has no UHI but it certainly makes Minneapolis different from Manchester, as do the Mississippi and Minnesota rivers.

As weather stations are/were placed where it was easy for people to make daily records amy long record must be affected by urban encroachment to a greater or lesser degree. Until recent decades measurement of temperatures at sea would be limited to things like lighthouses, lightships and other permanent constructions mostly less than 100 miles off shore. So for measuring the global temperature we're stuck with a limited record which isn't that good or consistent.

So I go back to the BBC/ITV/Sky weather forecasts UHI value for anticyclonic weather of a few/several degrees for UHI in the UK.

Is the satellite record the only really global true record of "Global temperatures"? I'm not even sure that they are particularly reliable, how much calibration is done new to old? I'm not even sure if there is any parallel running (something that bothers me about land based measurements)..The whole thing is a mess not just UHI.

Sep 21, 2016 at 8:15 AM | Unregistered CommenterSandyS

Climate Scientists never accidently make mistakes that are not in their favour.

UHI will always produce numbers that are higher. Any adjustments are about reducing the over readings, not increasing the under readings. Over time, the margin of over read will slowly increase too.

Any paper that claims to deal with over readings will be based on past data, and will not reflect the increased degree of over read on the day the paper is published.

Sep 21, 2016 at 10:21 AM | Unregistered Commentergolf charlie


You make a fair point, though I'm not sure I entirely agree with this:

"I cannot see the circumstances in which localised changes in urbanisation would leave a lasting impact on the global temperature indices."

It all depends. If once-rural sites are increasingly urbanised (or if lightly-urbanised sites become heavily-urbanised), then the UHI effect will make a difference to the temperature trends reported/recorded there. In turn, it depends on what proportion of such sites are included in the total which gives the overall figure derived (as you say, FTSE-like) from the total of the readings used to measure global temperature. If such sites are a significant proportion of the whole, then the UHI effect will be having a significant impact on the stated trends.

Whilst I continue to think the UHI effect has been wrongly dismissed or minimised, your point does lead into another one where I've mused on discussion threads here in the past - how on earth do we measure the temperature of the planet in any meaningful way, especially when 2/3 of it is covered by sea? Of the remaining 1/3, there is probably an imbalance by number of readings in favour of the contiguous USA plus western Europe (especially the UK). As I've said a few times, by and large I accept that the people charged with maintaining the thermometers and making the readings are honestly doing their best to make appropriate adjustments and homogenisations etc. I just don't think, taken in the round, the stated figures are credible, for all of the above reasons.

Sep 21, 2016 at 10:24 AM | Unregistered CommenterMark Hodgson

Mark Hodgson. Trying to produce a single representative temperature for the whole globe is a wishful fantasy. It is done for propaganda purposes, so that the media, the Greenies and politicians can have an easily understood handle with which they can sell their news merchandise, advocate global political and economic solutions, or justify their actions to control and interfere more in people's lives. It has no reality.

If we really wanted to understand what has happened in our past and perhaps anticipate our near future, then we would have done things differently. Climate change in interglacials appears to affect different areas differently - look today at the very different responses of the Arctic and Antarctic. Surely, rather than trying to gauge the Earth's overall temperature, we should have devoted our time and effort more to assessing areas and regions where we are more certain of getting reliable average values. Areas such as the USA and southern Canada, Europe, Australia and New Zealand and employing our efforts to obtain more reliable data from areas like China, the Arctic, Brazil, South Africa. With this sort of data we could observe if these areas are changing in concert or differently. We would have data we could use. Now we have corrupted and massaged data that no one can really be sure about.

I'm not sure I agree about the sparcity of oceanic measurements. Certainly we have data from sea routes and are now infilling major gaps in our coverage with a variety of drifting automatic sensor packages, as well as satellite data.

Sep 21, 2016 at 11:39 AM | Unregistered CommenterACK

Sep 21, 2016 at 11:39 AM | ACK
As I see it ocean measurements have several problems, especially as you get further from land. None of the measurements will have been done to the same standard, they will be days and in the early 20th century weeks apart. Even today ships travel well known sea routes leaving huge areas untraveled. At one time many routes had a seasonal element, wool and tea for instance. The Union Castle had several ships which were laid up when their cargo was out of season, South African fruit I think. These records cannot really be used for scientific research, apart perhaps from the last few decades and 30-40 years is too short a timescale.

Sep 21, 2016 at 3:26 PM | Unregistered CommenterSandyS

SandyS, if people wanted to measure sea temperature for "scientific" purposes, they through a bucket into the water. From the first days of steam ships, recording engine temperature was a critical indicator of something having changed with the engine. The incoming temperature of the water to keep everything cool was therefore important.

It would not have been long before fishermen realised that temperature of the sea water varied, and certain temperatures were better for fishing. Subtle variations even a few miles apart would indicate different currents from different direction. The skippers of some fishing boats would place great importance on accurate recording of sea temperatures.

For ships simply looking to get from Point A to Point B, variations in sea water temperature were only relevent to the Chief Engineer, on that ship on that trip. Differences between ships on the same route were not particularly relevent to anybody else, so the depth of the water intakes, and whether the hull shape was causing surface or deeper water to be churned up and into the intakes was of no real concern.

Sep 21, 2016 at 4:28 PM | Unregistered Commentergolf charlie

golf charlie
Does that mean you agree that any ocean records of temperature are useless for scientific climate research purposes?

Regards natural variations being noticed by people whose livelihoods, and survival prospects depended on them I have a memory that the PDO (possibly some other natural fluctuation?) was discovered by research for salmon cannery owners who wanted to know why the catch was lower in some years.

Sep 22, 2016 at 8:11 AM | Unregistered CommenterSandyS

And El Nino by anchovy fishermen off the Peruvian coasts.

Sep 22, 2016 at 8:30 AM | Unregistered CommenterACK

SandyS & ACK

El Nino/El Nina as a description does come from the fishermen of the West Coast of South America. When it "went warm" there were no fish.

Alexander von Humboldt (Prussian) was the first European scientist to get stuck into South America, around 1800 when most of Europe was getting stuck up on Napolean. The Humboldt current goes up the same West coast of South America bringing cold nutrient rich water up from the Antarctic, making the Galapogos Islands so rich in fauna, and ensuring that underwater documentaries have to be filmed by people wearing wetsuits, as the water is cold!

I presume there is an aquatic bridge or underpass to prevent the Humboldt and Nino/Nina crashing.

SandyS, Climate Science has got into yet another mess over whether sea water samples and temperatures etc were taken in leather buckets etc. Data taken from sea water engine inlets on ships are just as fraught. Obviously this gives scope for "adjustments", and Climate Scientists always find what they want, after adjusting the raw data.

Sep 22, 2016 at 3:04 PM | Unregistered Commentergolf charlie

golfCharlie. I believe the first use of the term El Nino was for a coastal southerly flowing current that replaced the northward flowing Humbolt current around Christmas times, so no need for a bypass.

Also I believe the nutrient rich waters that normally occur off the Peruvian coast come from upwelling of deep Pacific waters (rather than from Antarctica) caused by the strong offshore directed winds. These stop blowing during El Nino events so no nutrient-rich waters and no abundant anchovies and mass starvation of seabirds.

I visited some of the guano islands in Peru in an open boat and can attest to the extremely cold conditions, necessitating warm clothing. The coldness comes from the coldness of the upwelling deep Pacific waters.

Sep 22, 2016 at 3:30 PM | Unregistered CommenterACK