The Urban Heat Island (UHI) is mapped in major U.S. cities

UGA study ranks US cities based on the urban heat island effect on temperatures

This graphic shows the annual average urban heat island effect in 2010. CREDIT University of Georgia

This graphic shows the annual average urban heat island effect in 2010. CREDIT University of Georgia

From the UNIVERSITY OF GEORGIA

Highlights

  • Urban heat island (UHI) intensities were estimated for the fifty most populous cities in the USA using PRISM climate data.
  • The urban morphologies of the cities were quantified using spatial metrics and the NLCD 2006 land use/land cover dataset.
  • The statistical analyses suggested that highly contiguous dense and sprawling urban development both enhance the UHI effect.
  • City contiguity should be considered when devising strategies for UHI intensity mitigation.
  • More discontiguous city configurations, especially if achieved by introducing urban green spaces, will likely reduce UHIs.

Athens, Ga. – Inner cities as well as suburbs show distinctly warmer temperatures–known as the urban heat island effect–than rural areas as a result of land use and human activities, which can affect rainfall, air quality and public health.

A University of Georgia study using a new method for calculating urban heat island intensities clarifies the conflict on whether urban density or sprawl amplify these effects more. It also provides a ranking of the top urban heat island cities among the 50 largest metropolitan statistical areas.

The urban heat island effect describes how the spatial configuration of cities, the materials in them (such as asphalt), lack of vegetation and waste heat can modify temperature.

The study, published in the journal Computers, Environment and Urban Systems, identifies Salt Lake City, Miami and Louisville as the top three urban heat island cities in the U.S.

Urban morphology–the patterns of a city’s physical configuration and the process of its development–has long been associated with the formation of urban heat islands. By examining the UHI intensities of 50 cities with various urban morphologies, the researchers evaluated the degree to which city configuration influences the UHI effect.

“The overall goal of our study was to clarify which urban form–sprawl or more-dense development–is most appropriate for UHI mitigation,” said the study’s lead author Neil Debbage, doctoral student in the Franklin College of Arts and Sciences’ department of geography.

The study establishes a method for estimating UHI intensities using PRISM–Parameter-elevation Relationships on Independent Slopes Model–climate data, an analytical model that creates gridded estimates by incorporating climatic variables (temperature and precipitation), expert knowledge of climatic events (rain shadows, temperature inversions and coastal regimes) and digital elevation.

The use of spatially gridded temperature data, rather than urban versus rural point comparisons, represents a new method for calculating a city’s canopy heat island intensity. The results identify the spatial contiguity of developed areas as a significant factor influencing the magnitude of the heat island effect.

“Not just whether cities have high-density development, but how the built infrastructure is connected–and disconnected by green spaces–has a great impact on heat island intensity,” said study co-author Marshall Shepherd, the UGA Athletic Association Distinguished Professor of Geography and Atmospheric Sciences.

“We found that more contiguous sprawling and dense urban development both enhanced UHI intensities. In other words, it does not appear to be a simplistic either-or situation regarding sprawl or density,” Debbage said.

The researchers hope the results can help influence local governments and city planners in the formulation of effective codes and policies to mitigate the urban heat island effect.

“It’s crucial to work toward a better understanding of the complex processes at the intersection of urbanization, climate and human health,” Shepherd said. “Current and future cities will be modified or designed with weather and climate in mind, and research at UGA will play a key role.

###

The study on “The Urban Heat Island Effect and City Contiguity” is available at http://www.sciencedirect.com/science/article/pii/S0198971515300089.

Abstract

The spatial configuration of cities can affect how urban environments alter local energy balances. Previous studies have reached the paradoxical conclusions that both sprawling and high-density urban development can amplify urban heat island intensities, which has prevented consensus on how best to mitigate the urban heat island effect via urban planning. To investigate this apparent dichotomy, we estimated the urban heat island intensities of the 50 most populous cities in the United States using gridded minimum temperature datasets and quantified each city’s urban morphology with spatial metrics. The results indicated that the spatial contiguity of urban development, regardless of its density or degree of sprawl, was a critical factor that influenced the magnitude of the urban heat island effect. A ten percentage point increase in urban spatial contiguity was predicted to enhance the minimum temperature annual average urban heat island intensity by between 0.3 and 0.4 °C. Therefore, city contiguity should be considered when devising strategies for urban heat island mitigation, with more discontiguous development likely to ameliorate the urban heat island effect. Unraveling how urban morphology influences urban heat island intensity is paramount given the human health consequences associated with the continued growth of urban populations in the future.

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175 thoughts on “The Urban Heat Island (UHI) is mapped in major U.S. cities

      • Mods … what happened to the Comments section in the previous article … “Proof-positive that AGW is not science… “World court should rule on climate science to quash sceptics, says Philippe Sands…” ???

      • If land use changes in a way that reduces the local temperature then you have negative UHI. I’m surprised there is so much negative UHI in the eastern U.S. How does Boston and Las Vegas have similar UHI? Makes me skeptical of the results, as does the obscure “city” outlines. The “city” of Las Vegas is apparently bigger than West Virginia.

    • I wondered the same thing – I can only assume (without time to read the paper) that it is suggesting that certain urban environments act as some form of heat soak (or sink) for the atmospheric temperature thereby lowering it? Weird! Will have to read it later!

    • Good question, I was looking at the map and was scratching my head. They’ve got San Diego and Las Vegas as negative.

    • How you may ask? If GISS is trying to make an adjustment…. so clearly if UHI is negative, we have to add a number to the temperature readings to “correct” them , making the temperature hotter, confirming the models !
      ;-}
      It would be more funny if it weren’t so true.

    • That’s the first thing I thought. It appears as though they are calculating the difference between the urban area, and the surrounding area, which is partially from UHI effects, but can also be from other effects such as land/sea breezes, different elevations, etc.

    • A very heavily irrigated Urban Area with a high density of trees relative to its surroundings would be plausible.
      But it strains credibility that even the thickest of urban forests can counteract the high density of asphalt and concrete roads, parking lots, roof areas, glass boxed high-rises, and stupendous use of electrical and fossil fueled energy.
      I live in West University, Texas, and tree rich enclave of Houston (Inner loop, SW of downtown). When you fly into Hobby on a clear night, right side window seat, West U is a black lake within a sea of city lights. The comparison is striking.
      If cities are bright at night, then it is hard to believe they are anything but strong positive Heat Islands.

      • “If cities are bright at night, then it is hard to believe they are anything but strong positive Heat Islands.”
        This observation is worth a Nobel Prize in Climatology. We don’t need to do anything more than look at a nighttime photo of the earth or any part of it. The brighter the artificial light the greater the heat island effect It is direct and obvious.

      • “If cities are bright at night, then it is hard to believe they are anything but strong positive Heat Islands.”
        I think that night lighting is actually one way that urbanization is detected for anti-UHI adjustments.

    • I was wondering the same thing, about negative UHI. I live near one of the negative UHI cities but outside the metro area. This is the Raleigh-Durham, NC metro area. Looking at the map, I clearly recognize that each section is divided into counties. The best I can figure is that the UHI effect is averaged over entire counties and some of those counties in the metro area can have a lot of non-developed areas.
      RDU is divided into several counties: Wake (Raleigh), Durham, Orange (Chapel Hill), Franklin, and Johnston. Wake and Johnston counties are very large. East and southwest of Raleigh but still in Wake county, there is still plenty of farmland. Franklin county, which borders Wake and Durham counties to the northeast and east respectively, is very rural for almost off the county, a lot of farmland. Johnston county is mostly rural too, except along a highway 70 and I-95 corridor. Northern Durham and southern Orange county are also lacking in subdivisions.
      So, taking it all into account, if you average the UHI effect over all the counties in the metro area, it might actually result in a negative. If you consider only the places within a certain distance from the main cities in the metro area, I would bet there would be no negative UHI.

      • Clearly some GerryManndering going on to come up with a new algorithm. They didn’t like the UHI effect, so they have come up with a new, more expansive definition.

      • With LA and New York City being the most negative?

        Don’t know what LA’s story is but I’m not surprised to see NYC negative. New York City may be a dense metropolis but it is also geographically unique, a giant 95% gravity fed evaporation tank. Its supply system brings in 1.2 billion USG/day of cool water through large underground pipes. City pressure can supply the first six stories of buildings by gravity alone. Everything about New York is huge, including the ~36 million gpd lost to leaks.
        The intense greenhouse effect of water vapor and a never ending scream of trapped solar energy re-re-re-re-re-radiating between ground and troposphere has made NYC the hellish burning slag of molten metal it is today. Thank God for night time, when the beds solidify long enough to get a few hours’ rest.

      • For example, NYC has the Atlantic Ocean winds which sweep in definitely in winter which is tremendously cold because of it but also much of summer! I lived in Park Slope, Brooklyn, 40 years ago and was a member of the tree planting committee.
        It was very hot there back then but look at today: very, very heavily treed streets with tons of shade everywhere! We planted many thousands of trees. Go to Bed-Stuy and you see few to no trees and the streets get very hot.
        Go to Park Slope and Prospect Park and it is cool, with the ocean winds sweeping the place thanks to it being the highest point in Brooklyn and much of Long Island. There are many microclimates in NYC also like Coney Island where I lived for five years, too.

    • Take the -1.37, make it positive and add it to the other categories and would look about right. Based on experience here, looks like these numbers might have been adjusted like the rest of the temp data set to reflect a “no problem” on the globull warming meme.

    • I’m guessing they wanted negatives to roughly balance the positives. That would allow net UH to be discounteded as a cause of any rising world temperature. Every rise MUST be attributed to a GHG. And mostly to CO2.
      The entire study probably hinges on how “we………..quantified each city’s urban morphology with spatial metrics.”

    • UHI is negative in several circumstances. In some desert communities.
      (google negative UHI for the relevant papers )
      In areas where the urbanscape has vegetation and the rural land is Bare
      In areas where the city sucks water from the surrounding rural area ( Oke did a study on this )
      bare ground as a land class is actually warmer than urban land ( on average )
      https://stevemosher.wordpress.com/2012/10/11/pilot-study-small-town-land-surface-temperature/
      Basically it s a myth that UHI is always positive and always large.

      • Evaporation can counter a portion of the UHI, but then you have higher humidity, which especially in desert areas keeps the region hotter at night. Regardless, adding all that concrete, asphalt and massive heat sources will easily swamp the small affect of evaporation.
        Once again Mosher has myth and reality reversed.

      • Steve, thanx for the link to your site. If I read the chart correctly, only a tiny fraction of the cities studied showed a negative UHI effect, and only during winter days. Right? If so, the huge majority of cities studied (large and small in size) showed moderate to very large, positive UHI effect.

      • Mark
        “Evaporation can counter a portion of the UHI, but then you have higher humidity, which especially in desert areas keeps the region hotter at night. Regardless, adding all that concrete, asphalt and massive heat sources will easily swamp the small affect of evaporation.
        Once again Mosher has myth and reality reversed.”
        wrong.
        start by reading all the papers this guy wrote
        http://web.cecs.pdx.edu/~sailor/CV.pdf
        Start with this one
        http://link.springer.com/article/10.1007/s00704-008-0017-5
        And you will see that urban areas ( portland in this case ) very often have areas of negative UHI
        The point is when you hear the word “city” you think Concrete. Sorry, every city is not Hong Kong
        The variablity is huge. Google LCZ sailor and Oke work

      • “Steve, thanx for the link to your site. If I read the chart correctly, only a tiny fraction of the cities studied showed a negative UHI effect, and only during winter days. Right? If so, the huge majority of cities studied (large and small in size) showed moderate to very large, positive UHI effect.”
        No. Part of the problem is the monolithic view people have of “cities”
        when you actually look at temperature across a city ( Like SF) you will find a wide range of temps from
        negative UHI to postive UHI.
        you people dont actually look.

      • I lived in the big blue (negative) Metro Boston UHI effect area I can attest that Steve is correct. The only trees left in New England are growing out of the asphalt in the cities. Cars are constantly running into them. The rest of New England is a beautiful sand desert.
        Is a sarc tag needed ?

      • Steve Mosher, Funny, the UHI map from U of G shows San Francisco as a large positive UHI intensity. So, by your logic, the North Pacific High channeled cool air through the Golden Gate would be the cause for a non-existent negative UHI in San Francisco? The Zhang and Imhoff study referenced at your site (which I commented on, prior to your jerk-like snark) studied 45 NE US cities (you think they may have looked at Boston?), and found insignificant negative UHI, only in the 1-10 km2 size, and only during winter days. The U of G paper is likely bunk.
        “you people don’t actually look”. Wrong once again.

      • I agree, Steven Mosher, that UHI can be negative and that the UHI is complex. But nationwide, it’s obvious that UHI is net positive in a big way. The adjustments that have UHI as a net negative strike me as absurd. Like someone said…just look at a night IR satellite pic.
        It would not be too difficult to model the UHI vs geography on a city by city basis. Then roll back the geography and land use with time and calculate model temperature 10, 20, 50 years ago. Then you would have a scientific basis for temperature adjustments. This, of course, would make the past warmer, which is a “no-no” which is probably why it hasn’t been done.

    • Dang it, ISvalgaard beat me to that question….
      Also curious; “The results indicated that the spatial contiguity of urban development, regardless of its density or degree of sprawl, was a critical factor that influenced the magnitude of the urban heat island effect.”
      How can “spatial contiguity” not be geometrically related to urban development density?

    • In desert landscapes we have created more green spaces and planted non-native trees everywhere.
      However, with the California drought, they are encouraging the use of rock-scapes. Walking by these homes during the day, the heat coming off can be pretty intense.

  1. CO2 is 400 ppm everywhere you go. CO2 can’t cause temperature differentials. Constants can’t cause change. These climate “scientists” should be forced to explain how 400 ppm in the city can cause a temperature differential with the 400 ppm rural areas. How can a constant 400 ppm cause such temperature differentials. Also, those temperature records are made during the daytime. How does CO2 cause daytime temperature records when CO2 is transparent visible light, the light that warms the day.

      • Yes, I know what the urban heat island effect. It is leading to an inflated global temperature. In no way can the urban heat island effect be caused by CO2. It is caused by viable light heating up asphalt and concrete. You have warming, but it isn’t due to CO2.

      • A grand total of nobody has ever claimed that UHI is caused by CO2. CO2 may play a very small role in it, but it is not the primary cause. That has always been thought to be buildings, concrete and the heat created by energy use in cities.

  2. The only two forwarding addresses on the website are yours and Ed’s. Do you want me to add other Committee members? If so, I will need their addresses.
    Jasper

  3. I have news for you. The urban area in Utah looks nothing like it’s depicted on the map above. There is nothing 15 miles west of downtown Salt Lake City and the cities to the north and south along the Wasatch Front except desert and mountains. Why does the heat map extend west to the border of Nevada?

    • You bring up a good point. Look at the two orange spots off the coast of California. Those are the two largest Channel Islands and have not changed their urbanization in recent memory. It looks like the delineations were done along county lines because the islands are administratively part of Los Angeles County with demonstrable UHI. West of Salt Lake City is the Great Salt Lake (for readers not familiar with the area), but could the lake be administratively part of a county with UHI and mapped as such?

    • The map has a resolution at the county-level. Most of the large area extending west to the Nevada border is Tooele County; the smaller “peninsula” reaching east appears to be Salt Lake County and Summit County. I assume the data employed was aggregated by county, and that most of the UHI in Tooele was in the east part of the county, influenced by Salt Lake City.

      • It must be by county. Most of Tooele county west of the Great Salt Lake consists of miles and miles of barren salt flats. The only possible UHI would be along the very eastern edge of the county.

    • I was fascinated by that huge area west of the Colorado that is mostly desert but with a band of well irrigated farmland bordering the river. I really don’t know what to make of what the map is trying to represent here. The whole area is a micro climate mess as any Motorcyclist living there could tell you.
      I am pretty sure that the narrative of the press release does not correlate very well with the paper. I would not be surprised if some of the issues being pointed out are a byproduct of the methodology that is addressed in the paper.

  4. The (press release?) states that their model used …climatic variables (temperature and precipitation), expert knowledge of climatic events (rain shadows, temperature inversions and coastal regimes) and digital elevation.
    Can someone who is willing to scale the pay wall tell how they handled wind?

    • Wind (or “breezes”) is mentioned for Miami. A possible reason for the higher UHI there than elsewhere is given as “potentially attributable to the tall skyscrapers along the coastline creating a wall effect, which would impede sea breezes from ventilating the city”.
      There is also a more general comment: “Climatological factors, such as wind speed and aridity, are also known to influence UHI intensities, but insignificant relationships were exhibited for the annual averages, with p-values of 0.97 and 0.79, respectively. However, when the monthly UHI intensities in 2010 were compared to the corresponding monthly wind speed and aridity values for each city individually, several significant correlations were discovered.” I can’t find where those “correlations” are explored further.
      There’s a lovely comment about the general use of statistics which should be meditated on by all AGWists. It reads: “For the estimated parameters to be unbiased, all relevant independent variables must be included in the model. Determining if all pertinent variables are incorporated is difficult, due to the infinite number of potential independent variables, and typically relies heavily on theoretical justification. Generally, a certain degree of specification bias is unavoidable in regression analysis since all relevant independent variables often cannot be included due to data limitations.”
      Finally, the paper found an average 0.37degC effect of UHI on minimum temperatures in 2010. While it doesn’t take this information further (its aim is to influence city planning), surely there must now be an assessment of thermometer siting to ensure that this figure has not (ahem) inadvertently been added to the record over the past 50 years or so? It would be a shame if the 50% of the rise that wasn’t due to data tampering turns out to be due to ignoring UHI 🙂

  5. The study establishes a method for estimating UHI intensities using PRISM–Parameter-elevation Relationships on Independent Slopes Model–climate data, an analytical model that creates gridded estimates by incorporating climatic variables (temperature and precipitation), expert knowledge of climatic events (rain shadows, temperature inversions and coastal regimes) and digital elevation.

    They didn’t actually measure the UHI. They used a computer model. Actually going out and measuring UHI is too simple; it clearly isn’t sufficient for qualify for a PhD.
    Perhaps data from surfacestations.org could be used to calculate a more reasonable figure for UHI for at least some sites.

      • Yep.
        “UHI intensities were estimated …”
        Why not just go and measure them?
        Of course, silly me, that would just prove something, and you can’t just prove something, you have to leave room for more frau….. , er …. scientific investigation.

    • So what is your methodology for measuring UHI? Do you have some magical UHI meter?
      Whether you like it or not, any UHI effect metric would be a derived quantity. They all need a fantasy value to use as a reference, i.e. the temperature that would have existed if the area was not urbanized. Deriving this fantasy value will always involve a model.

      • “Fantasy value?” How about a comparison to rural stations? Oh, wait…
        “…The use of spatially gridded temperature data, rather than urban versus rural point comparisons, represents a new method for calculating a city’s canopy heat island intensity…”

      • Michael Jankowski says:
        September 18, 2015 at 5:17 pm
        “…The use of spatially gridded temperature data, rather than urban versus rural point comparisons, represents a new method for calculating a city’s canopy heat island intensity…”

        It totally makes sense. If you have a dense enough grid you can produce a set of isotherms and nail the UHI. You could do a pretty credible job with about 1000 sensors …
        I’ve seen at least one science fair project where the student produced a temperature profile by driving from one side of town to the other, taking temperatures all the way.

        DesertYote says:
        September 18, 2015 at 4:20 pm
        … Whether you like it or not, any UHI effect metric would be a derived quantity. They all need a fantasy value to use as a reference, i.e. the temperature that would have existed if the area was not urbanized. Deriving this fantasy value will always involve a model.

        A profile or a set of isotherms will demonstrate UHI quite nicely. No need for any unattainable references, no need for models.
        The reason they use models is that they are much cheaper than doing physical measurements. Unfortunately they suffer from huge bogosity.

      • Michael Jankowski, you totally missed my point and that is, no matter what method is used, it is still based on a model. That is because the reference values do not actually exist in the real world but only in a fantasy world were the areas in question have not been urbanized. Therefor they must be deduced via a model. This is not a bad thing. It just is.
        One thing to note is that most cities are in low areas such as valley floors.

      • commieBob, looking at isotherms is NOT measuring the UHI effect. At best, it can be used to conclude that there is some UHI effect. That is all. It of itself does not produce a number representing the quantity of the UHI effect. Measuring presupposes a metric and a reference point. That reference point does not exist and thus must be deduced. If you use your beloved isotherm analysis, you still depends on a model to deduce a reference point. Maybe you do not understand what a model is?

      • DesertYote says:
        September 18, 2015 at 11:34 pm
        … your beloved isotherm … Maybe you do not understand what a model is?

        You’re straying into ad hominem territory. Be careful, everyone will think you’re a troll whether you have a serious point or not.

  6. Im guessing that big blue area from Nevada into California is due to Las Vegas. Lots of people leaving the doors open in the casinos and free AC is wafting across the desert.

  7. Wow! This is incredible. Their map shows Las Vegas and Denver metropolitan areas significantly cooling temperatures. I have spent time over the last two decades in both cities. The UHI effect is remarkably obvious in Las Vegas. It is also obvious in Denver.
    Perhaps the author’s should follow the Idsos’ method and have simultaneous temperature & CO2 measurements made in the cities and in the surrounding less urbanized areas.
    “Their final conclusion, therefore, is that the warming induced by the urban CO2 dome of Phoenix is possibly two orders of magnitude smaller than that produced by other sources of the city’s urban heat island (lower soil moisture levels and enhanced absorption of solar energy by urban surface materials, for example). Hence, although the presence of man and his alteration of the local environment are indeed responsible for high urban air temperatures (which can sometimes rise as much as 10°C above those of surrounding rural areas) and high urban near-surface atmospheric CO2 concentrations (which can sometimes top 600 ppm), the high urban near-surface air temperatures are not the result of a local CO2-enhanced greenhouse effect.” http://www.co2science.org/subject/u/summaries/phxurbanco2dome.php

  8. As with Climate, their models bear no relation to real life UHI as measured by thousands of people and shown on weather forecasts every day.

  9. I have to be deeply skeptical of most, but not all, of the blue areas. Land use change can, no doubt, cause regional cooling. Take a desert, irrigate it, plant it with trees or farms, repeat for fifty years and you can cool the land relative to the desert it was before — perhaps. I say perhaps because desert is actually very dry, and water is a major greenhouse gas, so even though daytime temperatures are very high, nighttime temperatures are often very low, so that the land could easily be cooler than land (or tropical ocean) at exactly the same latitude where it is humid night and day.
    However, one of those blue patches is right on top of where I live, and I have to say that I doubt it. There is a pronounced, readily observable UHI effect in the triangle area of NC. It is clearly visible in a glance at the temperature variations reported on personal weather stations on e.g. Weather Underground’s pages. One can see anywhere from 1 to 2 C warmer temperatures throughout Durham than are observed in the countryside a short distance outside of the city. One can also see it very clearly in the temperatures reported by the local airports (often used as the “official” sources for local temperatures. When I arrived in Durham 42 years ago, RDU airport had a single terminal and serviced a handful of (mostly propeller-driven) aircraft a day. It was in the middle of countryside that stretched over twenty miles between Raleigh and Durham (with Chapel Hill at that time still literally being a tiny college town with 90% of its population being the transient student population of UNC-CH). Today, there is very little actual “countryside” between the cities. RDU is flanked by I-40 (all 8 to 10 lanes of it), I-540 (8 more lanes) and US-70 (only 4 to 6 lanes), all of them jammed during rush hour, with major shopping centers flanking it on two sides. Morrisville was a tiny stoplight sized town back then, now it is a major suburban bedroom community with wall to wall shopping. Cary was a “blink and you’ve missed it” community back then (a population of around 8000 in 1970) — SAS hadn’t even moved in yet as its founder was still in school down the road a bit — and now it has a population of around 140,000. They have literally cut down entire forests and turned them into suburban housing, multiacre shopping centers, golf courses, and of course roadways everywhere.
    I recently drove out of Durham down NC 55 towards Cary and was shocked to see that I drove out of Durham and into Cary with no boundary at all in between. When my sister lived in Cary only fifteen or so years ago, we had to drive through twenty minutes of countryside to reach the edge of Cary.
    There is — in my considered opinion — no way in hell that the UHI effect in the triangle area is negative. The only thing that could “fool” a stupidly done study into thinking that is that they have also built two huge impoundments — Falls Lake and Jordan Lake — that collectively cover 40 square miles of the area. Temperatures measured out on the water are, no doubt, moderated by the fact that woodland has been replaced by water and of course the water never gets as hot as the surrounding air even in midsummer. However, that is equally obviously silly when considering UHI. It is a completely independent effect from UHI, and does not in any way either significantly alter the temperatures in the surrounding woodlands, let alone the temperature even a very few miles away from the lakes, nor does it have anything whatsoever to do with the generally growing gap between urban center and the surrounding mixed-use forest and farmland and with the sprawling expansion of that urban center.
    rgb

    • Duke… it is a model, Apparently they combine temperature and precipitation, who know how, to estimate UHI.

  10. FWIW, after 20 years of land surveying, and a love of the outdoors.
    I’ve learned that mosquitos love low lying swampy areas in the morning, youth is indeed wasted upon the youth, and leafy suburban neighborhoods are much cooler than the new subdivisions being built on farmland that offer no hope of any shade.

      • Yep, it does often seem that a lot of “vegetables” live in (and are elected to national office from) the most over-crowded metropolitan areas.
        But this graphic map from our friends at U of GA seems extremely crude. There are a lot of microclimates bundled into these MSAs. I can just about see in my mind’s eye, my grand-father’s 500+ acres, other farms, and several parks of several hundred wooded acres each, in the midst of one of them, lumped together with the HQ towers and manufacturing plants of a dozen or more sizable corporations.

    • I still take this chart with a grain of salt due to the basic nature of the calculation (which is an estimate of what the temperature should be, a dangerous prospect at the best of time), but it’s conclusions make sense, clustered around population centers and snaking around highways (heck, you can see I-30 clear as day from Atlanta almost all the way to El Paso). Compared to the initial chart at the top of the page, which just disagrees with basic sense.
      I can’t tell you what the mass of the moon is off the top of my head, but I can tell you that anything answer you give less than a trillion tons is certainly wrong without calculator or reference materials.

  11. “Not just whether cities have high-density development, but how the built infrastructure is connected–and disconnected by green spaces–has a great impact on heat island intensity,” said study co-author Marshall Shepherd.

    They need to define “connected”.
    Green spaces imply that there is no UHI at an airport.
    But it seems unlikely that London Heathrow would beat London Greenwich for the record hottest thermometer reading if that was that was the case.
    Woolly terms lead to fluffy thinking.

  12. UHI is obviously of interest to people living in cities, but is surely of no interest to climatology, as all US cities will have nearby rural stations that can be used instead for making the necessary doom laden statements about warming.
    I would quantify UHI by comparing city temperatures to those from the nearby rurals.

      • On Drudge this afternoon, there is yet another article about climate scientists demanding that sceptics be prosecuted.

      • MarkW, that will never happen. Warmists are frightened to debate their topic. They’re hardly likely to turn up in court to argue it in front of a judge.
        What we need are the Green Police, able to issue on the spot fines:

      • Billy, that was how the pre-Obama justice system worked. In the new improved justice system, the prosecutor skips the judicial phase and goes directly from indictment to the sentencing phase.
        Much more efficient.

    • What, you mean like where the blob representing Salt Lake City includes mostly the Bonneville Salt Flats?!? One can only imagine what underlying data were used. At least it’s not as bad as one paper I saw that showed the entire West Desert (Flats and surrounding area) as high tree-planting potential (because it didn’t currently have any trees – no kidding!). Not great scrutiny of the results in either case. Sheesh!

  13. Just read the Abstract and you would be welcome to conclude that these guys can not know anything of importance since they have to communicate it in the most spatially displaced diarrheic dumbfounding drivel ever invented! Beyond that…yeah Parks are nice in an urban environment and make it more livable for human beings whether it has any impact on the “heat island” effect or not.

  14. The climate modelling is divorced from reality yet again. I was an avid cyclist and motorcyclist for many years and the UHI ( before I knew what that was) effect was obviousand palpable for many Cities. I always knew when I was approaching a City ( especially on a cool evening) by the increasing air temperature – even before the fields gave way to urban buildings. It is hard to believe that the UHI is any less than 2 or 3 degrees Celsius for any sizeable City. I suggest that we send these Phd students out with bicycles and thermometers to get a grasp of reality…

    • Worldwide, UHI is reported as 2-3 degree C HIGHER in EVERY city in every daily weather forecast. New York (and many other cities) report +5 to +8 degrees F higher.
      This paper is nonsense.
      The Atlanta region is a dense forest – there are no roads where you can see the horizon for the pine trees and hills sprouting up in every unplowed, unmowed square meter of ground. But its “color” shows less than 1 degree HUI for the counties as far as 50 miles to the AL border. And across that border, these “digital modelers” have the central part of the state of Alabama (an even smaller urban area bisected by only two major highways) as one integrated mass of “urbanity” …

  15. Can you imagine the UHI in ancient Rome with all those folks crammed into the colosseum and cooking fires going all over town? The smell and air quality would probably bring anyone to appreciate the the relatively clean air in modern cities.

    • Uhi in ancient Rome is well documented. It was a city that had a million inhabitants and eventually stretched for some ffty miles
      The richer inhabitants escaped to the hills in summer and there was a well established network of ice sellers and umbrella sellers. Beech trees disappeared as temperatures rose.
      After the great fire Nero was entreated to rebuild thE city in tall blocks with narrow streets in order to provide shade.
      Our bbc weather forecasters daily refer to British cities being up to 4 or 5 degrees warmer than the countrside. I have never ever heard them say that any city will be cooler than its surroundings.
      Tonyb

  16. Note well the absurd color scale used in the map.
    The light blue encompasses the values Negative 0.43 to POSITIVE 0.16 deg C.
    The white (the same as the “unmeasured areas” is from Positive 0.17 to 0.51.
    For shame!

  17. I am not going to spend $42 to get the report.
    It sounds like yet another computer game, and computer games are not real science.
    The primary problem with the climate change cult is they try to predict the future, and the secondary problem is they do so with computer games that have no predictive ability.
    However, based only on my internal BS detector while reading this post, I believe after reading this “study” I would have determined it to be as valuable as a steaming pile of farm animal digestive waste products.
    Just like all climate computer games.
    To add some value to this post:
    I noticed the “Urban Heat Island” effect as a child on my bicycle:
    I grew up in a small village with a population of less than 1,000 people, and a small downtown with
    about a dozen stores.
    In the summer friends and I always noticed it was hotter “downtown” surrounded by cement, bricks, asphalt, parked cars, etc.
    We’d bicycle “downtown” on hot days to buy ice cream, and often started eating it while standing in front of the store on the hot asphalt or cement.
    Soon someone would say it was too hot to stand there, so lets get back on our bicycles, and finish the ice cream while riding our bikes out of “downtown”.
    So we noticed the UHI effect during the day in a tiny village (even though I believe it affects the nighttime temperature even more than the daytime temperature (as the cement, bricks, asphalt, etc. give up the heat they absorbed during the day).
    If there was an easy to notice UHI effect in a tiny village of fewer than 1,000 people, it would seem that a large percentage of surface weather stations would be affected by UHI effect — not just “urban” stations
    What percentage of weather stations are properly sited, surrounded by grass and trees, in an area never changed by economic growth?
    Probably not many, based on work Mr Watts has led in the past at www. surfacestations.org — real climate science, not the usual scary climate model BS predictions of gloom and doom.
    Probably none of this UHI effect really matters — NOAA is going to “adjust” the surface data until it eventually matches the confuser models anyway (heh, heh).

  18. I see someone else has just found the paper online and posted a dropbox link. I got it through ResearchGate. Here’s an explanation for the negative effects:
    In contrast to the intense UHIs of Salt Lake City,Miami and Louisville,
    the negative values in Fig. 4 indicate that a city was actually cooler than
    its natural surroundings. Riverside and Las Vegas exhibited the strongest
    urban cool islands (UCIs) of −1.37 and −0.76 °C, respectively.
    This “oasis effect” is largely due to the increased presence of moisture
    and heightened potential for evaporative cooling within the cities
    relative to the surrounding desert landscapes (Brazel, Selover, Vose, &
    Heisler, 2000). The Riverside UCI was a particularly extreme case that
    was partially influenced by the seasonality of aridity (Fig. 5), as the summertime
    UCI peak occurred during a phase of extremely arid conditions
    according to the De Martonne index.
    The regions are SMSA’s, not counties, I think (from a quick overview).

  19. Seeing Boston as negative tells me this “study” is laughable. You can FEEL the difference in the summer, it’s many degrees warmer in Boston than in suburbs only 15 miles away in any direction, especially in the early evening. The only time there is not much difference is in the spring time when there’s a strong sea breeze. But NEGATIVE??? No way.
    Just looking at Blue Hills versus Boston data from 1940 -2015 using “Climate at a Glance” shows Boston ~3 degrees warmer on average despite being right on the water.

    • Not to defend the study, but are the “suburbs only 15 miles away” part of the SMSA? I haven’t dug into the nuts and bolts of the study (don’t intend to, either), but SMSA’s are pretty broad (as are the colored blotches on the map) and probably average out a lot of variation in local climate, though I’m sure there is some effort to control for this. Whether valid or not I couldn’t say. But any criticism that is easy to make has a strong likelihood of having been considered somehow.

      • Those “counties” surrounding every major city in the plot are each 40 – 60 miles across.
        And, even in the densest plots (Pittsburgh, NJ, Atlanta, San Francisco, etc) there are many miles of greenery and low density (non-urban) “City and suburb” spanning much more than that 15 mile distance they used.

      • But any criticism that is easy to make has a strong likelihood of having been considered somehow.
        ____
        let’s try:
        there’s literally tons of papers showing UHI when one simply combines ev’rydays records of weather stations,
        distinguished city/rural.
        Why do a paywalled studie, running a never proofed computer model, noone asks neither pays for –
        could it be that
        there is ‘a strong likelihood of having been considered somehow’
        that operating time on climate modelling super computers has drastically fallen in price lastly and and hosts beg for use.
        ____
        Just asking – Hans

      • servus mod, servus WordPress,
        thx for coping with my dinglish.
        On my small millenium gadget aka cell phone emerges a hyperventilating
        ‘that operating time on climate modelling super computers has drastically fallen in price lastly and and hosts beg for use.’
        Not rare on this blog.
        and and – sure Your’e working on it.
        Regards – Hans
        [??? .mod]

  20. And yet UHI adjustments make the “data” hotter rather than cooler. No wonder these algorithms were kept secret for so long.

  21. According to the authors, in Vegas in December (and most of the rest of the year except for the spring) it is 1°C cooler in town than it is in the desert outside town.
    Anyone believe that?

    • Preposterous.
      When I was in Vegas in July of last year, it was 113 F on the Strip at nine at night. The desert had to be cooler.

      • Yes, the desert cools rapidly at night. I grew up in the Arizona deserts. The city of Tucson was always much hotter at night in summer than at our ranch.

      • All the swamp coolers have increased the average humidity noticeably in the city, which dramatically slows down the rate of cooling at night.

  22. They have invented or discovered something that nobody has ever suspected. A negative UHI effect. I wonder if they know how badly their new discovery conflicts with all known physics.
    On a more positive note:
    An organic chemist told me (many times) “Any theory which contradicts prior observation is Dead On Arrival”.
    We do not need to worry about it, we do not need to refute it, we do not need to argue about it, we do not need to disprove it. If an idea contradicts established observations, it is wrong.
    As we said in Chemistry, “Not faulty, Not flawed, Just Plain Wrong”. So much for Political Correctness.
    Any notion that the UHI of Boston is negative is DOA.
    We have been treated to many stupid/preposterous/fund grubbing papers recently at WUWT, leading up to the Paris COP, no doubt. This one just leaves me speechless.
    Boston UHI is negative, speechless. DOA.

  23. It is sad that students are no longer taught to check if their answer makes sense. These “researchers” clearly did not. It used to be, if you did a long, complicated mathematical calculation, the first thing you were taught to do in checking the answer was to look at it and see if it made general sense. Looking at the negative UHI for the Boston area would fail that check. Anyone living in the area knows that outside of the city itself it is cooler near the coast in the summer and fall by large amounts, and only marginally warmer in the winters. That’s why you travel to the coast in the summer. Boston itself is definitelyy warmer/hotter in the city than surrounding. But of course they could have based their Boston measurements on a location at the airport which is essentially IN Boston harbor. It would be a nice trick – use the downtown thermometers for global surface temperature, but then do this study using boston harbor with the cooling seabreeze for measuring UHI. I don’t know if that is what they did, but clearly the blue fails the test of whether the answer makes any sense. Next step after failing the sanity check should have been to go find their mistakes instead of publishing whatever their calculations spit out because they liked the answer.

  24. The Channel Islands National Park has an UHI. Okay. Tells anyone what they need to know about quality control.

  25. “…The study establishes a method for estimating UHI intensities using PRISM–Parameter-elevation Relationships on Independent Slopes Model–climate data, an analytical model that creates gridded estimates by incorporating climatic variables (temperature and precipitation), expert knowledge of climatic events (rain shadows, temperature inversions and coastal regimes) and digital elevation…”
    Well there you go…a model which includes “expert knowledge of climatic events.” How is that programmed in? lol.

  26. A max UHI intensity of 1.49°C? That doesn’t pass the sniff test. Oh, it’s even the annual average, so the calculated UHI intensities for summer months are blended with the probably lower figures for other seasons. However, NASA is on record for finding that “Summer land surface temperature of cities in the Northeast were an average of 7 °C to 9 °C (13°F to 16 °F) warmer than surrounding rural areas over a three year period.”
    http://wattsupwiththat.com/2010/12/14/image-the-urban-heat-islands-in-the-northeast/
    Anthony measured a 10F° (5.5C°) difference in Reno at night in late October.
    http://wattsupwiththat.com/2008/10/29/uhi-is-real-in-reno-at-least/

    • Incidentally, the press release of that NASA study says “Cities in desert regions, such as Las Vegas, in contrast, often have weak heat islands or are actually cooler than the surrounding rural area.” So there’s something to the negative UHI notion.

      • Katherine

        Incidentally, the press release of that NASA study says “Cities in desert regions, such as Las Vegas, in contrast, often have weak heat islands or are actually cooler than the surrounding rural area.” So there’s something to the negative UHI notion.

        No. They “claim” there is something to the negative UHI graphs that they worked to get published (prior to Paris). But UNLESS they are using a “daily average” that tries to combine those very cold non-UHI nights AROUND the desert cities with the very evident 3-5 degree C EVERYDAY temperature effects that actually are present in every city in the world – but in areas that vary with every county plotted in the map, their paper is falsified by Nature. (er, nature.)

      • Maybe it’s all the swimming pools at the hotels and the irrigation of the landscaping where normally there would only be desert? Plus the all high-rises probably cast long shadows. I suspect there’d be a lot more of those high-rise hotels in Las Vegas than Phoenix. But that’s speculation…assuming NASA’s claim is true.

      • Extensive evaporation might, and I repeat, MIGHT, be enough to counteract the effect of all that asphalt during the day, but at night, the resulting humidity will hold in the heat generated during the day.

      • Phoenix and surrounding areas still use flood and sprinkler irrigation which far outweigh the swimming pools (besides some areas of Phoenix have many swimming pools. The point, is it is easy to make hypotheses why Las Vegas has a negative UHI effect. But these hypotheses are easily to prove false when using observations and data as Idso and his colleagues did in Phoenix. Please go to the source linked above and see the value of observations and data.

  27. I know San Diego has some UHI mitigation programs, but negative? About a decade ago, it as among the highest.
    Atlanta was of the first UHIs to be studied I think. It as blamed for changing rain patterns…and this was back in the 60s or 70s. But it shows a mild with all that sprawl and concrete jungle since?

  28. Deserts cool rapidly at night. Very rapidly. Unless it is a box canyon with few trees, these radiate heat for a long time.
    Cities never cool quickly at night! Never! I know of no desert with miles of black asphalt, for example, not even in Death Valley and I grew up in the Southwest deserts and lived far from the cities much of the time including at Kitt Peak.
    In the evening, desert temperature changes cause a wind to rise up [which] cools things even faster but in the cities, buildings block this wind, another reason it is hotter in cities there. And I assure everyone, having also lived in Death Valley once, at night it gets downright COLD. Even in summer except the salt flats and even these are cold by dawn.

    • Humidity also plays a significant role in urban/rural/desert rates of cooling during the evening. A number of studies have found cities are relatively more humid in the evening, even though they may be less humid during the day. This is attributed to more dewfall outside urban areas, which brings urban aerosols into the picture.
      The wind you describe could be due to elevation differences. I haven’t experienced similar winds in the flat Australian deserts.

  29. Winter in the Chicago area, the ground freezes solid.
    Shovels don’t work against the frozen ground, so you pull out the pick and swing it as hard as you can (it helps to keep you warm ), and chip away at the frozen ground.
    It gets cold enough that even the laziest workers want to swing the pick.
    No mosquitoes though 🙂

  30. The problem is they used PRISM data.
    there isnt a person on the site ( except me I guess) who has any idea what prism data is and what its limitations are.
    jeez guys… go look at the details before spouting off.

    • Mr. Mosher, I see you passed up the chance to display your unequaled brilliance by explaining in a few words what the PRISM data is.
      But you certainly jumped at the chance to claim to be brighter, more dilligent, more thorough than anyone else, while at the same time providing ample evidence you haven’t even read all the comments here, from those whom you would so foolishly disparage.

    • Mosher does not read many comments. He does not need to, as he knows that of all WUWT readers, only he knows enough to understand climate related issues. 😉
      Prior mentions of PRISM (a model) in comments before Mosher’s at 9:02 pm :
      commieBob September 18, 2015 at 11:57 am
      Michael Jankowski September 18, 2015 at 5:26 pm
      He perhaps may not read the article summary, either, otherwise he’d have noticed PRISM was mentioned twice.

    • I do. I believe PRISM was developed about 20 years ago by that well known climate denier and debunked fired Oregon State Climatologist George Taylor.
      I haven’t Googled to check on that… but that’s my memory.
      The PRISM techniques do an excellent job of mapping climate data in physiographically complex areas. Taylor has always done excellent work and I found him to be a truly nice guy. Of course that was before the era of climate hatred.

  31. Several points.
    Urban aerosols can affect clouds, precipitation and hence temperatures up 200 km downwind. Hence any analysis needs to take account of wind direction.
    Urban albedo affects daytime and nighttime temperatures differently. Where an urban area has a higher albedo (generally the case), more sunlight is reflected upward and with less heat absorbed at the surface and re-radiated at night, nights are cooler. However, albedo changes to ground surfaces, vertical surfaces and roofs will have different effects on temperatures measured a few feet above the ground.
    All they seem to have found is that evapotranspiration of vegetated areas decreases temperatures, but paradoxically the increased humidity retains more heat near the surface due to the water vapour greenhouse effect, and it feels hotter to people, because as humidity increases, sweating becomes less effective at cooling us. Therefore their conclusions about mitigating UHI are wrong at a practical level. They need to take humidity into consideration.
    The study tells us little about the interesting question, which is how much UHI has changed over time? (and hence the effect the changes have had on the surface temperature record). 3 effects, probably account for most of the changes over time; vegetation and irrigation changes, albedo changes and aerosol changes. Just one example, where I live in Perth, about 50% of houses now have high albedo steel roofs, whereas 50 years ago none would have. A rough calculation gives me 2% of total solar insolation, which would have previously been absorbed at the surface is now reflected upward.

    • Keep in mind that all this UHI debate is largely unnecessary if we rely on satellite temperature data which is consistent, comprehensive, and calibrated.
      Surface thermometer data has so many localization and citing and consistency problems that the errors are almost as big as the signal and the adjustments are as big as the signals.

  32. Philip. Have you ever walked in a city at night or used the concept of impervious areas? Have you felt the temperature of asphalt?
    I cannot find by experience or data anything to support what you say: “Urban albedo affects daytime and nighttime temperatures differently. Where an urban area has a higher albedo (generally the case), more sunlight is reflected upward and with less heat absorbed at the surface and re-radiated at night, nights are cooler.”

  33. The fact that there are negatives values greater than half a degree indicates the results have a built in understatement of about a degree. A very large number of lawns kept looking green in areas of drought can result in about a half degree cooling but even this is optimistic.

  34. “Athens, Ga. – Inner cities as well as suburbs show distinctly warmer temperatures–known as the urban heat island effect–than rural areas as a result of land use and human activities, which can affect rainfall, air quality and public health.”
    The press release begins by describing UHI the way it is understood by all. Then they completely contradict themselves by reporting negative UHI. PRISM or no PRISM, this is sense-free. The green space in a city cannot make the city cooler than the countryside, as most of a city is not green space.
    What sort of scam is this?

    • “The green space in a city cannot make the city cooler than the countryside, as most of a city is not green space.”
      It can if the countryside is a desert like in Vegas. But overall, the net cooling added to the temp adjustments for UHI are crazy.

  35. The important fact is whether or not a land weather station has been affected by a CHANGE in the environment near it by economic growth, paint changes on the box, equipment changes inside the box, movement to a different location (possibly more than once), no longer in use, missing readings “infilled” by smarmy bureaucrats, and the repeated “adjustments”, “re-adjustments” and “re-re-re-adjustments”.
    I would suggest the “adjustments” are more important than the other factors — they show the obvious fact that smarmy data collectors have predicted the future climate, and have been repeatedly “adjusting” the data to make their (wild guess) predictions appear to be more accurate.
    In addition, over 70% of the planet is water, and I believe the ever-changing methodologies for measuring the surface temperature above the water is haphazard, non-global, far from accurate, and worthy of being the subject of a twenty-minute Three Stooges short.

  36. I have lived and predicted the weather day in, day out in Chicago, New York and San Diego and predicted the weather nationally for sixty years so my close up and prolonged encounter with the UHI is very real, more real than some computer model that seems to attempt to apply the same analysis to dramatically different geographic locations. In the flat plains where the dynamic weather pattern of fronts and pressure centers is powerfully in control, the UHI is very dramatic. Chicago, Omaha, Kansas City, Dallas, St Louis, etc have clear and well defined UHIs. In coastal locations where the the dynamic pattern has been altered by the Ocean waters and various mountain ranges that somewhat alter the wind flow, the UHI is still present but its pattern is dramatically altered by these geographic influences. New York, Boston and Philadelphia are examples of this sort of situation. On the west coast, there is very little dynamic weather, the Ocean and blocking of the Mountain ranges totally overwhelms the UHI. Seattle, San Francisco, Los Angles and San Diego are examples of this pattern.
    In the classic UHI the cities island of heat is carried 100 miles or more downstream by the prevailing wind and the heating also increases downwind precipitation measurably. And up wind of the city, both the cooling and drier conditions are very clear. It is the most obvious and dramatic and easily measurable impact of mankind on his climate. But the effect is not serious and has only tiny impact on the overall and continuing climate of Earth.

  37. I’ve read the all the comments up to this time and have not seen my understanding of the purpose of the paper expressed. The paper does not appear to be about understanding the UHI and how it affects regional, continental, and global temperatures. It appears to me to have a different purpose.
    Here to me, is the money quote:
    “ ‘We found that more contiguous sprawling and dense urban development both enhanced UHI intensities. In other words, it does not appear to be a simplistic either-or situation regarding sprawl or density,’ Debbage said.
    The researchers hope the results can help influence local governments and city planners in the formulation of effective codes and policies to mitigate the urban heat island effect.”
    Note that the purpose of the study is not to understand the magnitude of UHI temperatures so as to correct regional and planetary “average temperatures.” The purpose is influence “…codes and policies to mitigate the urban heat island effect” So they want to mitigate the UHI temperature effect. People often say they want to move away from warmer central city to the cooler countryside. Thus creating “urban sprawl” This study purports to show that there is no difference in UHI temperature between the urban core and the suburbs.
    Academics hate “urban sprawl.” They want everyone to live in densely packed urban areas. No doubt the study was started in hopes of showing the densely packed urban areas had lower UHI effects than urban sprawl. Since that didn’t happen, they can at least say “ See packing people densely in the Urban Core doesn’t produce any higher UHI temperature effect than urban sprawl, so that is not a reason to oppose cramming people together in the urban core.
    So the paper is not about temperature, it’s about city planning.

    • So it looks like ‘science to order’ then?
      Academics hate urban sprawl; they need some ‘scientific’ evidence that it’s the same in the suburbs as in town so as to discourage suburban development. Hey presto, paper delivered.

  38. Old Engineer: I agree that the U of Georgia paper is ostensibly about city planning and the breathtaking finding that “contiguity” is the real problem in dissipating UHI effects. Therefore, let us eschew contiguity… but, by the way our paper ALSO clearly shows that the overall UHI effect, though real, is hardly a problem since many cities are actually cooler than their surrounding land masses – therefore a “negative UHI” (or UCI)
    The John Christy / William Norris paper discussed here at WUWT several years ago left an impression on me, and though its premise was met with some skepticism, I agreed with it. See:
    IRRIGATION-INDUCED WARMING IN CENTRAL CALIFORNIA? John R. Christy and William B. Norris. University of Alabama in Huntsville, Huntsville (original paper)
    https://ams.confex.com/ams/pdfpapers/68739.pdf (original paper); and
    http://wattsupwiththat.com/2010/09/12/christy-on-irrigation-and-regional-temperature-effects/
    (WUWT commentary and discussion)
    The idea of Christy’s paper is that irrigated areas retain the day’s heat and expel it very slowly at night as the slow evaporation over crops and fields occurs. The heat is held close to ground level in a layer of high humidity, and if you take readings from within this blanket of warm humid air, the resulting temperature records appear to give lower highs during the day and higher minimum temps at night.
    All the old cans of worms need to be reopened for this paper to examine when, where and how these researchers took their readings, what data they selected to analyze, and how they chose to analyze it. Depending upon these several points, they could easily prove cooler urban areas relative to… something else. How they define that “something else” seems a little fishy.
    The researchers claim that “Denver” is such an example of “negative UHI”. The rough square in the middle of Colorado is blue because Denver is actually “cooler” than its surroundings. The square they’ve chosen is about 90 x 130 miles, or 11,700 square miles. The Denver metro area is, in fact, only about 155 square miles, so they’ve incorporated a huge chunk in the NE quadrant of the state for some reason, to contrast to the urban center. Why? My sense is that they gather data from within that giant section from which they can generate a rural temperature record. Key, here, is that much of this territory is agricultural and heavily irrigated. Zoom in on the quadrant in Google maps and you can see the wheels of contiguous green (from circular sprayers) dotting the landscape along the I-76 corridor all the way out the n-e corner of the state. This is heavily irrigated crop land – quite likely to yield the kinds of temps that they want for their purposes.
    Again, if they took their temps at the right time, using the right areas in this sampling, they’d have no problem setting up a false comparison between urban and rural temps.
    My 2 cents.

  39. Put thermometers on city buses and generate the data. Or deploy a network of stationary thermometers – automatic recording ones. You know that modeling has gone beyond the bounds of sensibleness when you don’t measure directly what is so easily possible. They have ridiculous huge polygons with legends that show ridiculous T ranges with bin limits in ridiculous decimal pointed numbers. A computer creation by idiots. Oh, I guess there was probably what some might call intelligent human intervention when the numbers came out to 10 decimal places in the raw.

  40. Now let’s look at what “good planning” enforces on investors and businesses for required numbers of asphalt parking places for each and every building permit. I don’t think Europeans visiting American cities realize what “good planning” has done over time to alter the landscape and the temperatures.

  41. I was just looking over the UHI ma above. I’m not sure about other “urban” areas they but the Denver area includes thousands of square miles that are not “urban” by any definition. The area includes all of Arapahoe and Adams counties which extend 50+ miles to the east of the “urban” area. It also includes all of Clear Creek, Gilpin and Park counties which are entirely mountainous with the largest city/town at a population of about 1,700 at an elevation of 7,500 feet. A full 2,000 fee higher than Denver official elevation. Fairplay, which is in Park county, is 50 miles from the “urban” area and almost 65 miles from the center of Denver, is at 9,900 feet elevation.
    Park county has a population of about 16,000 in 2,200 square miles. I don’t see how anybody could include these in the “urban” area of Denver.

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