One of the most ridiculous claims recently related to Menne et al 2010 and my surfacestations project was a claim made by DeSmogBlog (and Huffington Post who carried the story also) is that the “Urban Heat Island Myth is Dead“.
To clarify for these folks: Elvis is dead, UHI is not.
For disbelievers, let’s look at a few cases showing UHI to be alive and well.
CASE 1: I’ve measured it myself, in the city of Reno for example:
The UHI signature of Reno, NV – Click for larger image
Read the story of how I created this graph here The procedure and raw data is there if you want to check my work.
I chose Reno for two reasons. It was close to me, and it is the centerpiece of a NOAA training manual on how to site weather stations to avoid UHI effects.
CASE 2: NOAA shows their own measurements that mesh well with mine:
To back that up, the NOAA National Weather Service includes the UHI factor in one of it’s training course ( NOAA Professional Competency Unit 6 ) using Reno, NV.
In the PCU6 they were also kind enough to provide a photo essay of their own as well as a graph. You can click the aerial photo to get a Google Earth interactive view of the area. The ASOS USHCN station is right between the runways.
This is NOAA’s graph showing the changes to the official climate record when they made station moves:
Source for 24a and 24b: NOAA Internal Training manual, 2004-2007
Oops, moving the station south caused a cooling. Fixed now, all better.
What is striking about this is that here we have NOAA documenting the effects of an “urban heat bubble” something that DeSmog Blog says ” is dead”, plus we have NOAA documenting a USHCN site with known issues, held up as a bad example for training the operational folks, being used in a case study for the new USHCN2 system.
So if NOAA trains for UHI placement, I’m comfortable in saying that DesmogBlog claims of UHI being “dead” are pure rubbish. But let’s not stop there.
CASE 3: From an embattled scientist.
A paper in JGR that slipped in 2007 without much notice (but known now thanks to Warwick Hughes) is one from Phil Jones, the “former” director of the Hadley Climate Center in the UK. The paper is titled: Urbanization effects in large-scale temperature records, with an emphasis on China
In it, Jones identifies an urban warming signal in China of 0.1 degrees C per decade. Or, if you prefer, 1 degree C per century. Not negligible by any means. Here is the abstract:
Global surface temperature trends, based on land and marine data, show warming of about 0.8°C over the last 100 years. This rate of warming is sometimes questioned because of the existence of well-known Urban Heat Islands (UHIs). We show examples of the UHIs at London and Vienna, where city center sites are warmer than surrounding rural locations. Both of these UHIs however do not contribute to warming trends over the 20th century because the influences of the cities on surface temperatures have not changed over this time. In the main part of the paper, for China, we compare a new homogenized station data set with gridded temperature products and attempt to assess possible urban influences using sea surface temperature (SST) data sets for the area east of the Chinese mainland. We show that all the land-based data sets for China agree exceptionally well and that their residual warming compared to the SST series since 1951 is relatively small compared to the large-scale warming. Urban-related warming over China is shown to be about 0.1°C decade−1 over the period 1951–2004, with true climatic warming accounting for 0.81°C over this period.
Even though Jones tries to minimize the UHI effect elsewhere, saying the UHI trends don’t contribute to warming in London and Vienna, what is notable about the paper is that Jones has been minimizing the UHI issues for years and now does an about face on China.
Jones may have tried to hide CRU data, but he’s right about China.
CASE 4: From “The Dog ate My Data” who writes:
The Australian Bureau of Meteorology (BOM) blames Melbourne’s equal warmest overnight temperature of 30.6 degrees, on January 12 on the heat island effect. The previous time the city was that hot overnight was February 1, 1902.
The Age newspaper cites a meteorologist at the bureau, Harvey Stern,
Melbourne recorded its equal warmest overnight temperature, 30.6 degrees, on January 12. The previous time the city was that hot overnight was February 1, 1902.
A meteorologist at the bureau, Harvey Stern, said that Melbourne suffered from a heat island effect, in which a city is warmer than the surrounding countryside.
This was the case especially at night, because of heat stored in bricks and concrete and trapped between close-packed buildings.
I am stunned if that is correct firstly because BOM isn’t blaming Global Warming and secondly that the urban heat island effect directly receives the blame. With faults in the 2007 IPCC’s AR4 now pouring out I guess it is not suprising that attributions of weather events are now, shall we say, possibly becoming more circumspect.
CASE 5: Heatzilla stomps Tokyo
From the website “science of doom” who writes:
New Research from Japan
Detection of urban warming in recent temperature trends in Japan by Fumiaki Fujibe was published in the International Journal of Climatology (2009). It is a very interesting paper which I’ll comment on in this post.
The abstract reads:
The contribution of urban effects on recent temperature trends in Japan was analysed using data at 561 stations for 27 years (March 1979–February 2006). Stations were categorized according to the population density of surrounding few kilometres. There is a warming trend of 0.3–0.4 °C/decade even for stations with low population density (<100 people per square kilometre), indicating that the recent temperature increase is largely contributed by background climatic change. On the other hand, anomalous warming trend is detected for stations with larger population density. Even for only weakly populated sites with population density of 100–300/km2, there is an anomalous trend of 0.03–0.05 °C/decade. This fact suggests that urban warming is detectable not only at large cities but also at slightly urbanized sites in Japan. Copyright, 2008 Royal Meteorological Society.
Why the last 27 years?
The author first compares the temperature over 100 years as measured in Tokyo in the central business district with that in Hachijo Island, 300km south.
Tokyo – 3.1°C rise over 100 years (1906-2006)
Hachijo Island – 0.6°C over the same period
This certainly indicates a problem, but to do a thorough study over the last 100 years is impossible because most temperature stations with a long history are in urban areas.
However, at the end of the 1970’s, the Automated Meteorological Data Acquisition System (AMeDAS) was deployed around Japan providing hourly temperature data at 800 stations. The temperature data from these are the basis for the paper. The 27 years coincides with the large temperature rise (see above) of around 0.3-0.4°C globally.
And the IPCC (2007) summarized the northern hemisphere land-based temperature measurements from 1979- 2005 as 0.3°C per decade.
How was Urbanization measured?
The degree of urbanization around each site was calculated from grid data of population and land use, because city populations often used as an index of urban size (Oke, 1973; Karl et al., 1988; Fujibe, 1995) might not be representative of the thermal environment of a site located outside the central area of a city.
What were the Results?
Mean temperature anomaly vs population density, Japan
The x-axis, D3, is a measure of population density. T’mean is the change in the mean temperature per decade.
Tmean is the average of all of the hourly temperature measurements, it is not the average of Tmax and Tmin.
Notice the large scatter – this shows why having a large sample is necessary. However, in spite of that, there is a clear trend which demonstrates the UHI effect.
There is large scatter among stations, indicating the dominance of local factors’ characteristic to each station. Nevertheless, there is a positive correlation of 0.455 (Tmean = 0.071 logD3 + 0.262 °C), which is significant at the 1% level, between logD3 and Tmean.
Here’s the data summarized with T’mean as well as the T’max and T’min values. Note that D3 is population per km2 around the point of temperature measurement, and remember that the temperature values are changes per decade:
The effect of UHI demonstrated in various population densities
Note that, as observed by many researchers in other regions, especially Roger Pielke Sr, the Tmin values are the most problematic – demonstrating the largest UHI effect. Average temperatures for land-based stations globally are currently calculated from the average of Tmax and Tmin, and in many areas globally it is the Tmin which has shown the largest anomalies. But back to our topic under discussion..
And for those confused about how the Tmean can be lower than the Tmin value in each population category, it is because we are measuring anomalies from decade to decade.
And the graphs showing the temperature anomalies by category (population density):
Dependence of Tmean, Tmax and Tmin on population density for different regions in Japan
Quantifying the UHI value
Now the author carries out an interesting step:
As an index of net urban trend, the departure of T from its average for surrounding non-urban stations was used on the assumption that regional warming was locally uniform.
That is, he calculates the temperature deviation in each station in category 3-6 with the locally relevant category 1 and 2 (rural) stations. (There were not enough category 1 stations to do it with just category 1). The calculation takes into account how far away the “rural” stations are, so that more weight is given to closer stations.
Estimate of actual UHI by referencing the closest rural stations – again categorized by population density
And the relevant table:
Temperature delta from nearby rural areas vs population density
Conclusion
Here’s what the author has to say:
On the one hand, it indicates the presence of warming trend over 0.3 °C/decade in Japan, even at non-urban stations. This fact confirms that recent rapid warming at Japanese cities is largely attributable to background temperature rise on the large scale, rather than the development of urban heat islands.
..However, the analysis has also revealed the presence of significant urban anomaly. The anomalous trend for the category 6, with population density over 3000 km−2 or urban surface coverage over 50%, is about 0.1 °C/decade..
..This value may be small in comparison to the background warming trend in the last few decades, but they can have substantial magnitude when compared with the centennial global trend, which is estimated to be 0.74°C/century for 1906–2005 (IPCC, 2007). It therefore requires careful analysis to avoid urban influences in evaluating long-term temperature changes.
So, in this very thorough study, in Japan at least, the temperature rise that has been measured over the last few decades is a solid result. The temperature increase from 1979 – 2006 has been around 0.3°C/decade
However, in the larger cities the actual measurement will be overstated by 25%.
And in a time of lower temperature rise, the UHI may be swamping the real signal.
The degree of urbanization around each site was calculated from grid data of population and land use, because city populations often used as an index of urban size (Oke, 1973; Karl et al., 1988; Fujibe, 1995) might not be representative of the thermal environment of a site located outside the central area of a city.
Case 6: California Counties by population show a distinct UHI signature.
My friend Jim Goodridge, former California State Climatologist identified the statewide UHI signature issues way back in 1996. This graph had a profound effect on me, becuase it was the one that really made an impact on me, switching my views to being skeptical. Yes, I used to be a warmer, but that’s another story.
Goodridge, J.D. (1996) Comments on “Regional Simulations of Greenhouse Warming including Natural Variability” . Bull, Amer. Meteorological Society 77:1588-1599.
Goodrich (1996) showed the importance of urbanization to temperatures in his study of California counties in 1996. He found for counties with a million or more population the warming from 1910 to 1995 was 4F, for counties with 100,000 to 1 million it was 1F and for counties with less than 100,000 there was no change (0.1F).
He’s been quietly toiling away in his retirement on his computer for the last 15 years or so making all sort of data comparisons. One plot which he shared with me in 2003 is a 104 year plot map of California showing station trends after painstakingly hand entering data into an Excel spreadsheet and plotting slopes of the data to produce trend dots.
He used every good continuous piece of data he could get his hands on, no adjusted data like the climate modelers use, only raw from Cooperative Observing Stations, CDF stations, Weather Service Office’s and Municipal stations.
The results are quite interesting. Here it is:
I’ll have more interesting revelations from Jim Goodridge soon.
Case 7: NASA JPL’s climatologist says UHI is an issue
This press release from NASA Jet Propulsion Lab says that most of the increase in temperature has to do with ubanization:
[NASA’s JPL Bill] Patzert says global warming due to increasing greenhouse gases is responsible for some of the overall heating observed in Los Angeles and the rest of California. Most of the increase in heat days and length of heat waves, however, is due to a phenomenon called the “urban heat island effect.”
Heat island-induced heat waves are a growing concern for urban and suburban dwellers worldwide. According to the U.S. Environmental Protection Agency, studies around the world have shown that this effect makes urban areas from 2 to 10 degrees Fahrenheit (1 to 6 degrees Celsius) warmer than their surrounding rural areas.
Patzert says this effect is steadily warming Southern California, though more modestly than some larger urban areas around the world. “Dramatic urbanization has resulted in an extreme makeover for Southern California, with more homes, lawns, shopping centers, traffic, freeways and agriculture, all absorbing and retaining solar radiation, making our megalopolis warmer,” Patzert said.
CASE 8: You can see it from space. NASA (not the GISS division) measures it. Here’s a report they presented at the last AGU meeting in December 2009. Gee, that curve below looks like Reno, NV, doesn’t it?
The urban heat island effect can raise temperatures within cities as much as 5 C higher than the surrounding countryside. New data suggests that the effect is more or less pronounced depending on the type of landscape — forest or desert — the city replaced. Credit: NASA
NASA researchers studying urban landscapes have found that the intensity of the “heat island” created by a city depends on the ecosystem it replaced and on the regional climate. Urban areas developed in arid and semi-arid regions show far less heating compared with the surrounding countryside than cities built amid forested and temperate climates.
“The placement and structure of cities — and what was there before — really does matter,” said Marc Imhoff, biologist and remote sensing specialist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The amount of the heat differential between the city and the surrounding environment depends on how much of the ground is covered by trees and vegetation. Understanding urban heating will be important for building new cities and retrofitting existing ones.”
Goddard researchers including Imhoff, Lahouari Bounoua, Ping Zhang, and Robert Wolfe presented their findings on Dec. 16 in San Francisco at the Fall Meeting of the American Geophysical Union.
Satellite imagery of suburban (top) and urban Atlanta shows the differences in daytime heating, as caused by the urban heat island effect. Credit: NASA Goddard’s Scientific Visualization Studio
Yep, UHI is alive and well. Anybody with an automobile dashboard thermometer who drives a commute from country to city can easily measure UHI, and you don’t have to be a climate scientist to prove it to yourself.
UPDATE: For a primer on how UHI is not dealt with by NOAA and CRU, have a look at this Climate Audit post:
Realclimate and Disinformation on UHI
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Re
Morgan T (07:24:56) :
OT, but interesting and rather funny news from Sweden. In Stockholm the temperature has not been above freezing point at any time during the whole month of January and this has not happened since 1829 (Yes 1829) and SMHI (That is NOAA in Sweden) describs this event as a “sensation”.
But it is only Weather though.
Sarcasm off.
The effect of the UHI on Trends is also going to be totally dependant on the rate of change of Building and Population Expansion over the years.
Now that really would be hard to factor in when using a Rural Site that gets gobbled up by expansion to become an Urban one.
Hey Arianna: UHI is real. Even the folks at CRU know it:
From: “Jenkins, Geoff”
To: “Phil Jones”
Subject: London UHI
Date: Wed, 24 Sep 2008 15:37:34 +0100
Cc: “Wilby, Robert”
Hi Phil
Thanks for the comments on the Briefing report. You say “There is no evidence with London
of any change in the amount of the UHI over the last 40 years. The UHI is clear, but it’s
not getting any worse” and sent a paper to show this. By coincidence I also got recently a
paper from Rob which says “London’s UHI has indeed become more intense since the 1960s esp
during spring and summer”. Its not something I need to sort out for UKCIP08, but I thought
you both might like to be aware of each others findings. I didn’t keep a copy of Rob’s PDF
after I printed it off but I am sure you can swap papers. I don’t need to be copied in to
any discussion.
Cheers
Geoff
Harry (07:35:58) :
If the warming that occurred in the 1930’s and 1940’s is statistically no different then the 1980’s and 1990’s then there is no reason to be alarmed.
++++
Y’know, I’ve never believed that conclusion to be true, even if the predicate is granted. I’ve always felt that one of the great tragedies of this whole AGW furball was the proponents insisting on the “unprecedented” bit and all that went with that, and the (regrettably necessary, but better to have been avoided in the first place) skeptics righteous resistance of the diddling of the historic record.
But all of that doesn’t really matter, in the end, to my way of thinking. That the warming *could* be natural doesn’t mean it *is* natural. That the warming *could* be from C02 doesn’t mean it *is* from C02. Arguments over the historic record can’t really prove that one way or the other, and have been a whole a tremendous lot of wasted time better spent on trying to figure out the real basic questions on feedback sensitivities, energy budgets, and basic processes.
I hold the warmists responsible for this, as they chose that “unprecedented” battleground, and once chosen the rest was inevitable.
The desmogblog article was poorly worded, but let’s not lose sight of the big picture.
UHI isn’t dead; it never was. There are of course individual stations where you can see a UHI; oftentimes the UHI causes a fairly constant offset so it doesn’t matter to the trend; sometimes (Reno) the trend is affected as well.
But why highlight Reno, without discussing what adjustments are made at Reno? Reno was in fact highlighted in Menne et al (2009), BAMS 90: 993-1007. See Figure 8. Have a look.
The desmogblog aside, the real point is whether UHI effects are causing some significant impact in national or global means, after adjustments are made. This has been quantitatively analysed many different ways (comparisons of rural vs urban, rural vs overall, windy vs calm nights, etc), and the answer appears to be no. Highlighting the raw data from individual stations with a spurious warming trend (which matters) or stations with a fairly constant warm offset (which doesn’t matter) doesn’t affect that finding; you have to go a step further to see what difference it makes.
Dr.T G Watkins(Wales) (07:37:32) :
“Surely,the siting of the surface station is as important as population densities. A thermometer next to an a-c unit etc will read high even if it outside the only house for 50 miles, and no UHI correction ( assuming they are even made) will be performed. The siting survey needs to done for every station in the world for any accuracy to be achieved!”
Your sentiment is echoed on this website frequently. Would you have less, more, or the same amount of confidence in a thermometer mounted on a moving automobile?
Joel Shore (19:45:26) :
Anthony,
“If you read beyond the headline of the Desmogblog, you would see that “Urban Heat Island Myth is Dead“ was shorthand for the point that the urban heat island effects are not having a significant impact on the global temperature data sets that we are using to look at global warming.”
Joel,
How could menne’s study which is focused on US stations, and recall that the US is a pitifully small portion of the globe, say anything of note about the situation of UHI in the ROW. Let’s recall that when NASA got the US temps wrong, that people rightly pointed out that the US was a small portion of the globe. WRT Menne’s study Since I know it works from the wrong data set I would not even read it so I can’t see how someone can even claim a myth is busted, when the myth busting paper used the wrong data.
jknapp (21:26:52) :
“If a city has had a stable population, land use extent, and energy use over the years then the fact that it is warmer than rural shouldn’t effect the RATE of increase in temperature.”
I would like to see a study done comparing global warming to economies, housing development, urban sprawl, etc.
I’m certain most, if not all, of global warming can be attributed to that.
Roger (05:59:22) :
I wondered why night storage heaters had become obsolete and this explains it!
Heating blocks of concrete with cheap electricity overnight and releasing that stored heat during the day was a figment of my imagination and the warmth I felt was illusory.
Likewise, in the 60’s and 70’s when the “back to nature” people were actually trying it, various somewhat effective historical heating arrangements were described where heat was captured in the awake time by brick and stone, which would then decrease the in-house temp. drop overnight. However, having failed and with their further seperation from reality, now the people who obsess on and on about “sustainability” only want the Gov’t to wave a magic wand to make it “all better” – whatever “all better” means. These are very troubled people, imo, and are easily recruited by cynical or deluded “leaders”. But instead, each of them need to figure out and look at what is bothering them to begin with, if possible but often not, I’m afraid.
Phil M (08:49:27) said:
You are being dishonest again. No one proposes using thermometers mounted on cars for determining the average temperature of the world. However, you can get a clear indication of the extent of the UHI effect using them when driving through a city.
Joel Shore
I was just lamenting yesterday that I hadn’t seen you or Scott Mandia posting for a long time. Nice to see you back again. However your post wasn’t one of your best-there is no doubt that IPCC and Real Climate- amongst many others- try to downplay the problem.
Why not try and redeem yourself by answering my question( TonyB (00:22:53) concerning temperature profiles 🙂
Tonyb
The car thermometer certianly shows UHI!
During the recent, nay ongoing!, cold spell here in the UK, when I leave home to drive into the nearest town, some 15 miles away and another 40,000 people, then the thermometer rises by between 1-2 Centigrade. This is usually a trip done in the evening/night, so no rising sun to warm things up and the engine’s up to temperature within a few miles, so no confounding heat sources.
The comments that London & Vienna stopped “heating” in 1900 are dubious.
Wouldn,t the passing of clean air legislation and the reduction of smog that produced have any effect on ground temperatures?
Btw, Anthony/Evan–
Will you guys in your paper be proposing any way to improve the classification system currently in use to be more useful in grouping sites? From what Evan has been hinting at, obviously the “1s” at airports are flawed from what one would expect from a “1”. . .and thus classification improvements would seem to be in order to better group expected accuracy of results.
How about use this site information for UHI research?
http://testbed.fmi.fi/About_Testbed.en.html
Stan (03:20:22) :
“…As most of us AGW sceptics don’t deny that the world has warmed up over the last 150 years or so (and are mostly glad it did!) and yet most of the AGW proponents spend half their time trying to deny the existence of proven, established climate records (such as the MWP, LIA and UHI) it makes me wonder who should be labelled “deniers”.”
Stan, I learned the hard way that liars, thieves and conman always accuse the person telling the truth of the charges they are guilty of. If you find someone in your group is stealing, he is generally the one who is very quick to point the finger at someone else. I have seen this happen in several cases over my rather long life time. It is one of the reasons I doubted AGW.
Richard Wakefield (06:13:18) :
“painstakingly hand entering data into an Excel spreadsheet ”
The best is to enter or import that data into Access.
AHHhh but was the data on a computer or was it hard copy? Young folks keep forgeting much of the older original raw data is on paper not on computers.
As an avid bicyclist, one issue that immediately caught my eye in the photograph of the bicycle mounted thermometer is its location. It should be placed in front of the bicyclist, not directly behind him. It is well known that there is a vortex of heat and evaporating sweat being drawn off the bicyclist’s body as the bicycle moves forward. That they would place a sensitive thermometer inside that vortex area suggests that the study designers were more concerned with aesthetics than controlling for confounding variables.
Well there’s one aspect of these UHIs that is seldom mentioned. Those tar and concrete structures, that absorb solar radiation readily and rise to hotter temperatures; are also better radiators of LWIR thermal radiation which is a cooling effect.
I have often observed that a hot tar parking lot quickly cools within just a few minutes after sunset.
So personally, I don’t see that UHIs are a problem. They heat rapidly to higher temperatures, and then radiate faster to return LWIR to outer space, and then they cool rapidly after sunset.
The problem in my view, is that the modellers do not account for UHIs the way Gaia does. Gaia properly integrates all the gosintas and the gosoutas, for UHIs and swimming pools, and lawns and shrubbery, and comes up with a correct temperature to set for the average.
But the modellers seem to think it is ok to use that UHI measured temperature to represent the temperature of some totally different place that may be 1200 km away from the UHI.
Yes I know they do that for “anomalies”, but if the sampling strategy is inadequate for mapping absolute temperatures; then the baseline mean that anomalies are referred to is prone to errors
The tropical dry deserts are the ultimate in heat islands; and they also are the most efficient radiators, responsible for the strongest cooling during the noonday high temperatures.
On a related issue; can anybody point to any data relating to the difference between surface temperatures with high wispy clouds (which some insist are a warming influence), and the same location with the exact same water vapor profile; but lacking only those high wispy clouds.
In other words; how does one separate the surface warming due to atmospheric water vapor (a well known GHG) and the warming due to just the cloud, that still lets in a lot of sunlight, but somehow blocks a lot of outgoing LWIR.
There must be screeds of peer reviewed data on that subject, since all the text books claim that high clouds heat the surface, and the higher the clouds, the more they heat the surface. How to you take out the water vapor effect from the cloud effect ?
Was the locating of a temp sensor between two airport runways done deliberately to catch the extra heat from airliners taking off with full jet exhaust blowing horizontally while accelerating along the runway before heading upward? Or was it designed to respond also to the big volume of hot gases emanating right at ground level from the jets when the thrust reversers are blowing full-blast along the runway upon landing? Will we now see an effect of global cooling if the recession causes a reduction in takeoffs and landings?
REPLY: it was designed to measure the conditions on the runway, not climate. Even NOAA’s own meteorologists admit to this. See this video:
“ASOS…placed for aviation purposes…not necessarily for climate purposes.”
[youtube=http://www.youtube.com/watch?v=tl5Hsw-62A8]
geo (08:37:30) :
“…. Arguments over the historic record can’t really prove that one way or the other, and have been a whole a tremendous lot of wasted time better spent on trying to figure out the real basic questions on feedback sensitivities, energy budgets, and basic processes.
I hold the warmists responsible for this, as they chose that “unprecedented” battleground, and once chosen the rest was inevitable.”
The “unprecedented” warming was very necessary to stampede the unthinking human herd into agreeing to be fleeced by the World Bank. The leaked draft agreement called the “Danish Text” that had “Developing countries react furiously” shows this was the ultimate goal. http://www.guardian.co.uk/environment/2009/dec/08/copenhagen-climate-summit-disarray-danish-text
AGW never had anything to do with real science. It was a Con Game from start to finish and only now are the real facts surrounding that Con coming to light.
“AHHhh but was the data on a computer or was it hard copy? Young folks keep forgeting much of the older original raw data is on paper not on computers.”
That’s what OCR is for. And I’m not young, just 20 years of programming experience.
From George E. Smith 10:22:43:
The tropical dry deserts are the ultimate in heat islands; and they also are the most efficient radiators, responsible for the strongest cooling during the noonday high temperatures.
<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>
The imbalance between heat radiation in and out is apparent when walking on the hot sand at noon, especially if barefoot. Of course, re-radiation out to space at night restores any remaining imbalance.
But the analogy is still questionable because tropical dry deserts remain relatively fixed over a period of several decades, whereas the growth nature of UHIs, that keep spreading outwards over a period of decades, is quite different.
It is the growth factor of UHIs spreading out into the suburbs that can create the appearance of a rising global temperature over time. I believe this is why satellite temperature measurements, being unaffected by UHIs, show virtually no global warming over 40 years, whereas ground-based measuremants apparently do.
While population of our large cities is fairly constant, population rise in the surrounding suburbs has been rapid. I have wondered if increases in regional population over time could serve as a proxy for the UHI effect over time. More people means more houses with roofs, furnaces and electric power consumption/dissipation, more driveways, more roads, more schools, more shopping centers, bigger airports, etc., etc.
Bob
Jim Goodridge’s diagram showing long-term temperature trends in California is a powerful piece of evidence.
I look forward to his future revelations.
“Assessment of Urban versus Rural in Situ Surface Temperatures in the Contiguous United States: No Difference Found” (2003 – Journal of Climate)
Thomas C. Peterson, NCDC
In Part 1(c), Previous Research into UHI, he dismisses dozens of studies showing significant UHI effects because… their data was not first homogenized or adjusted.
Peer reviewed by Hansen and Jones?
Whoa… the Reno temperature graph bears a striking resemblance to the state of Virginia. Surely they are teleconnected?!