Obvious science: NASA finds vegetation essential for limiting city warming effects

From the “department of limiting UHI” and NASA/GODDARD SPACE FLIGHT CENTER

The temperature difference between urban areas and surrounding vegetated land due to the presence of impervious surfaces across the continental United States. Credits: NASA's Earth Observatory

The temperature difference between urban areas and surrounding vegetated land due to the presence of impervious surfaces across the continental United States. Credits: NASA’s Earth Observatory

 

Cities are well known hot spots – literally. The urban heat island effect has long been observed to raise the temperature of big cities by 1 to 3°C (1.8 to 5.4°F), a rise that is due to the presence of asphalt, concrete, buildings, and other so-called impervious surfaces disrupting the natural cooling effect provided by vegetation. According to a new NASA study that makes the first assessment of urbanization impacts for the entire continental United States, the presence of vegetation is an essential factor in limiting urban heating.

Impervious surfaces’ biggest effect is causing a difference in surface temperature between an urban area and surrounding vegetation. The researchers, who used multiple satellites’ observations of urban areas and their surroundings combined into a model, found that averaged over the continental United States, areas covered in part by impervious surfaces, be they downtowns, suburbs, or interstate roads, had a summer temperature 1.9°C higher than surrounding rural areas. In winter, the temperature difference was 1.5 °C higher in urban areas.

“This has nothing to do with greenhouse gas emissions. It’s in addition to the greenhouse gas effect. This is the land use component only,” said Lahouari Bounoua, research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study.

The study, published this month in Environmental Research Letters, also quantifies how plants within existing urban areas, along roads, in parks and in wooded neighborhoods, for example, regulate the urban heat effect.

“Everybody thinks, ‘urban heat island, things heat up.’ But it’s not as simple as that. The amount and type of vegetation plays a big role in how much the urbanization changes the temperature,” said research scientist and co-author Kurtis Thome of Goddard.

The urban heat island effect occurs primarily during the day when urban impervious surfaces absorb more solar radiation than the surrounding vegetated areas, resulting in a few degrees temperature difference. The urban area has also lost the trees and vegetation that naturally cool the air. As a by-product of photosynthesis, leaves release water back into to the atmosphere in a process called evapotranspiration, which cools the local surface temperature the same way that sweat evaporating off a person’s skin cools them off. Trees with broad leaves, like those found in many deciduous forests on the East coast, have more pores to exchange water than trees with needles, and so have more of a cooling effect.

Impervious surface and vegetation data from NASA/U.S. Geologic Survey’s Landsat 7 Enhanced Thematic Mapper Plus (EMT+) sensor and NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra and Aqua satellites were combined with NASA’s Simple Biosphere model to recreate the interaction between vegetation, urbanization and the atmosphere at five-kilometer resolution and at half-hour time steps across the continental United States for the year 2001. The temperatures associated with urban heat islands range within a couple degrees, even within a city, with temperatures peaking in the central, often tree-free downtown and tapering out over tree-rich neighborhoods often found in the suburbs.

The northeast I-95 corridor, Baltimore-Washington, Atlanta and the I-85 corridor in the southeast, and the major cities and roads of the Midwest and West Coast show the highest urban temperatures relative to their surrounding rural areas. Smaller cities have less pronounced increases in temperature compared to the surrounding areas. In cities like Phoenix built in the desert, the urban area actually has a cooling effect because of irrigated lawns and trees that wouldn’t be there without the city.

“Anywhere in the U.S. small cities generate less heat than mega-cities,” said Bounoua. The reason is the effect vegetation has on keeping a lid on rising temperatures.

Bounoua and his colleagues used the model environment to simulate what the temperature would be for a city if all the impervious surfaces were replaced with vegetation. Then slowly they began reintroducing the urban impervious surfaces one percentage point at a time, to see how the temperature rose as vegetation decreased and impervious surfaces expanded.

What they found was unexpected. When the impervious surfaces were at one percent the corresponding rise in temperature was about 1.3°C. That temperature difference then held steady at about 1.3°C as impervious surfaces increased to 35 percent. As soon as the urban impervious surfaces surpassed 35 percent of the city’s land area, then temperature began increasing as the area of urban surfaces increased, reaching 1.6°C warmer by 65 percent urbanization.

At the human level, a rise of 1°C can raise energy demands for air conditioning in the summer from 5 to 20 percent in the United States, according the Environmental Protection Agency. So even though 0.3°C may seem like a small difference, it still may have impact on energy use, said Bounoua, especially when urban heat island effects are exacerbated by global temperature rises due to climate change.

Understanding the tradeoffs between urban surfaces and vegetation may help city planners in the future mitigate some of the heating effects, said Thome.

“Urbanization is a good thing,” said Bounoua. “It brings a lot of people together in a small area. Share the road, share the work, share the building. But we could probably do it a little bit better.”

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137 thoughts on “Obvious science: NASA finds vegetation essential for limiting city warming effects

    • so where is the GISS adjustment of 3.C DOWNWARDS for temperatures stations in those areas marked red on the above chart? since cities are growing, this adjustment DOWNWARD should be getting larger and larger the closer we get to the PRESENT.
      Instead, GISS has adjusted temperatures UPWARDS to correct for UHI, and is adjusting temperatures downward in the PAST. The exact opposite of what the chart above shows.
      Leave it to NASA/GISS. Government work at its finest. They were supposed to study space, so they launched a mission to planet earth. They were supposed to correct for UHI. Instead they reversed the sign and made UHI worse.

      • Exactly! They have essentially provided a map of the data proving what others have said for a long time.
        As I began looking at the map UHI appeared to match exactly with urban centers. As you look closer, however, there appear to be large areas with relatively low population densities that are shaded red, i.e. the area east of Dallas to the Arkansas border, the Missouri/Illinois border north of St Louis, Pennsylvania/Ohio border between Pitt and Cleveland, etc. These are likely the exact areas where the nearby urban temperatures are being used for rural areas and have affected them the most.
        Furthermore, this shows quite nicely the artificially high temperatures within many cities themselves created from using the chosen temperature stations at airports. This is especially true in the west where the cities actually have far more vegetation and tree cover than would be there naturally. Denver is a perfect example. Look at the satellite imagery of Denver, the city is far greener than the dry steppes to the east that much of the city is actually built on. The airport is also located east of the city on the hot and dry steppes and you can guess where the temperature station is.

      • So here’s a question related to UHI, for the PhD Physics mathematicians out there.
        Down here in Silicon Valley, you know that you are in the City of Sunnyvale, because the road is under construction. Any road; any time.
        But specifically, last week, the CoS decided to re-blacktop our whoe neighborhood, so all the hundreds of cars that people park on the streets in our housing development, all had to be moved to remote locations for two days, and the streets were closed from dawn to dusk. Too bad if you needed to get in or out of your house during the day; you would b driving on raw tar.
        So we moved out cars to a nearby ultimate fighting center, where they hve a big parking lot (used to be a supermarket).
        So I walked back home to watch how they were going to pull off this UHI construction project.
        One of the road workers was very helpful in explaining to me, exactly what they were doing.
        So after prefilling some of the more prominent asphalt crevasses, by hand; more or less, they went along the street, and spread a (surprisingly uniform) layer of crushed rock (stones). But this was not just any old crushed rock. The pebbles were remarkably uniform in size, and the worker explained that they were the 3/8 inch layer.
        Nex step was to baste the whole road surface with a film of tar, not quite deep enough to submerge the 3/8 inch stones. my guess is that peak to peak size variation on these stones, was about 15 % of the 3/8 mean size.
        Then while the tar was still hot, they added a second layer of crushed rock, this time using 1/4 inch mean pebble size. Both sizes of stones consisted of pseudo cubical stones, so there were plenty of sharp corners. Nothing was remotely spherical.
        Then a second thin film of tar, and a final layer of sand were added. The result was that almost all of the surface area of the stones etc, were now painted with tar, but projected up through the tar leaving a very rough but well leveled surface.
        If I had to bet, I would guess that the actual total exposed fractal surface area was perhaps five times the global geometrical area for an optically smooth surface.
        so now here is the question.
        An optically smooth surface of one square meter, would intercept one square meter worth of incident solar energy (with a cosine obliquity factor) and absorb most of it if tar black, and warm up to some surface Temperature, depending on the surface reflectance (albedo) and the thermal conductivity and specific heat of the materials.
        Such a surface would approximate a black body radiator at whatever steady state Temperature it reached during the day; so it would emit LWIR radiation in a constant radiance Lambertian angular distribution pattern.
        Such a pattern follows the Lambert cosine law: I(theta) = I(0) cosine(theta).
        For such as source, the total emitted radiant emittance is given by E = pi. I(0).
        If you could see t visibly it ould be equally bright in any direction.
        But what about my new hi tech silicon valley road surface ??
        Well it intercepts exactly the same amount of solar energy, and would tend to have the same optical reflectance coefficient.
        But now it has a somewhat fractal surface area perhaps five times as large with surfaces much larger than the wavelength oriented at a great range of angles.
        If this surface reached the same Temperature as an optically smooth one, then every element of that surface, must be a Lambertian radiator, at exactly the same rate as for a smooth surface, but with five times the area.
        Well each of those mini Lambertian sources, is pointed at its own angle, and they get in each other’s way, and as a consequence, the overall radiant emittance pattern is likely to be close to isotropic, rather than Lambertian. Well at least over a quite large fraction of the 2 pi steradians .
        As a result for the same surface temperature, this patterned surface, must have a higher Total emittance than an optically smooth surface; and consequently, at a given solar insolation value, this surface must run somewhat cooler than a smooth surface.
        Well we’ve had “unprecedented” high temperatures since they put this in, but I must say, I do not feel a noticeable thermal blast of heat from our new street.
        At some point, they will come back with a broom, and sweep up any sand, and 1/4 or 3/8 inch rocks that aren’t glued down and it will be good for the next 50 years; well they’ll find some reason to dig it up again, because it is still in Sunnyvale.
        g

    • “As a by-product of photosynthesis,”
      Which actually REQUIRES CO2..
      The obvious logical solution is that we need MORE CO2 to cool the cities. 🙂

        • According to the latest modelling the bad CO2 is that breathed out by skeptics and the good CO2 is that exhaled by warmists. They only want to stop the bad CO2.

    • But he ‘s a skeptic. So he most be wrong. Who would want to listen to a real climate scientist ? Everyone with a garden knows about the cooling effect of a tree.

  1. “This has nothing to do with greenhouse gas emissions. It’s in addition to the greenhouse gas effect. This is the land use component only,” said Lahouari Bounoua, research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study.
    ____
    and so they used
    NASA’s Simple Biosphere model to recreate the interaction between vegetation, urbanization and the atmosphere.
    ____
    to not interfere with real world observations.
    ____
    and ‘greenhouse gas emissions’
    is an additional phrase to get rid off.
    Last Greens Standing.
    What happened to sustainability. Hans

    • Well… ALW (anthropogenic local warming) and AGW (*anthropomorphic global warming) tend to be lumped together by global warmers.
      AGW is mostly caused by GHG. ALW mostly isn’t.
      ALW is about the same magnitude as AGW but won’t be affected by GHG control measures.
      Doing something about ALW isn’t a bad idea and will reduce the “apparent” AGW forcing.
      *note – anthropogenic is the correct term.

      • And where is land based stations of record based with its own 1-5 degree error for many of those stations. I see almost all the warming and cause of higher lows in this study that could prove UHI is really the cause of what is misnamed AGW. One could say it is UHI not CO2 stupid.

      • But if UHI raises temperature about 2 degrees then the world’s real temperature is about 2degrees less than modelled. I’m almost embarrassed to write that it’s so obvious, how do the war mists remove this challenging point?

      • Well, I tend to believe there is:
        1 W/m2 CGAGW
        1 W/m2 AGW
        1 W/m2 ALW
        1 W/m2 Natural Forcings
        That explains the observed warming.
        That says the ALW effect (UHI + other people driven changes) is responsible for 1/4°C just like all the other effects when averaged over the whole planet or about 1°C (since non-ice sheet land is 26% of the planet) averaged over the land area.
        Russia has non-UHI UHI in northern areas since they got fuel allotments based on temperature and the northern areas under communism overstated how cold it was.

      • fuel allotments based on temperature
        ========================
        government grants to study warming are based on finding warming. the grants would dry up pretty quick if they found cooling. so who in their right mind would report cooling if they found it?
        those people would quickly lose their funding. without funding they have no means to report the cooling. so they are not going to report any cooling they find. they will sweep it under the rug and stick their hands out for more grants, reporting only the warming.

      • PA you can believe anything you want but first ask where those land based temps are taken and through Anthony’s excellent work we know they are off by up to 5 degrees. Use RSS or UAH data sets and do the math if you actually did it at all and your numbers all go out in the cold.

      • Jon Alldritt August 26, 2015 at 7:08 pm
        PA you can believe anything you want but first ask where those land based temps are taken and through Anthony’s excellent work we know they are off by up to 5 degrees. Use RSS or UAH data sets and do the math if you actually did it at all and your numbers all go out in the cold.

        http://www.scielo.org.mx/img/revistas/atm/v20n3/a4f5.jpg
        If you look at asphalt vs soil vs grass/tree studies it is pretty obvious the 50+ W/m2 outgoing IR from hard manmade surfaces with low albedo and no latent heat loss is means much higher temperatures in urban areas. 2 meters above the surface the air is up to 10°C warmer. But it only amounts to about 1 W/m2 in the US averaged over the whole country or about 1/4°C.
        A February study measured downwelling IR and 22 PPM = 0.2 W/m2 translates to about 1.05 W/m2 since 1900.
        Climate4you tracks CGAGW and it is around 0.23°C since 2008 and may be 0.3°C or more higher since 2000. But the 0.23°C is certain and moving (generally increasing).
        The solar forcing since 1900 is around 1 W/m2 Insert your favorite estimate here.
        There is some mismeasurement and gamesmanship. But the fact they don’t separate ALW (UHI and so forth) from AGW (GHG and so forth) means they really don’t have to play with the numbers much except to achieve the “warmest EVAH” years, and make the models not look completely ridiculous..

    • The results sound fishy to me, jump in UHIE at 1% impervious area and then constant until 35%??
      Something seems very wrong here.

      • It looks to me like the “1%” was dispersed across the entire area, instead of how it would be done in the real world, e.g. a house/houses in a single location with a roadway.
        In what I think the model’s case would be, where 1% of every square meter was turned to asphalt, I could see an immediate temperature swing by a large amount and then hardly a budge for a fractional increase of asphalt within every square meter.

      • Jon, I think the late Michael Crichton mentioned that in his book ‘State of Fear’, published in 2004.

  2. “Everybody thinks, ‘urban heat island, things heat up.’ But it’s not as simple as that
    B.S. it is as simple as that, sure it’s a complex mess to disentangle the amount of heat, and given the poor statistical controls that could exist in any model it’s really tough, but it’s as simple as that. Cut down trees and create roads, then build houses and things heat up.

    • Well it can get a bit more complicated. You can push aside the sagebrush, pave roads, build business and residences, line the streets with trees and lawns and you’ve change the heat which direction?

      • Phoenix roads are not all lined with trees and lawns. You can fry an egg on asphalt in the summer, but it won’t work if you put one in the desert sand. I doubt that urban areas ever go cooler than the surrounding area, even if geographical location and altitude were equal.

        • somebody else made note of the fact that by surface area there really isn’t much “urban island” compared to all else. Which is, of course, the whole point of not allowing that effect to bias the surface temperature data to start with.

      • As I remember Phoenix, even in the winter, live trees and especially grass require regular watering, otherwise they’re toast.
        Many residents just go with the flow and plant desert plants that live with the watering provided by nature, javelin, jackrabbits, coyote, drunks and sometimes even rain.
        Instead of grass their lawns are gravel, stones, rocks and sometime Astroturf; though the sun beaches Astroturf badly.
        Those famed golf courses use substantial amounts of water to keep their grass and landscaping alive.
        All of that extra water raises the Phoenix humidity above local desert areas. Water evaporates and cools the area, but the extra humidity adds to local warming plus makes the warmth less of a desert heat; though Phoenix is still a desert heat (dry).
        Heat out to local outcrops and even the small mountain and one can find areas as hot as Phoenix; mostly in washes, gullies and irregular rocky areas.
        What goes a long way towards making these particular areas hot are:
        A) desert varnish – a dark red to black mineral coating (generally iron and manganese oxides and silica); much like asphalt and dark brick.
        B) interrupted air movement, much like urban environments.
        Sitting down on a desert varnish rock can definitely burn a person. Turn the rock over first.
        Add in all of a city’s heat generating sources; A/C, buses, cars, restaurants, etc… makes the city more uncomfortable than the surrounding desert if not hotter.
        In National Lampoon’s Vacation movie, cousin Eddie (Randy Quaid) heads outside to start the barbecued chicken and proceeds to flop chicken down onto rocks lining the driveway.
        Well, that method of cooking chicken doesn’t really work, but it sure feels like it. The chicken will dry out amazing fast. Though every fly downwind arrives very quickly; buzzards, vultures and condors take much longer. Crows, jays and ravens are more likely though coyotes will often arrive to chase them off.
        I should point out that Eddie’s abode was outside of Las Vegas and substantially North of Phoenix and definitely cooler.

      • surface area there really isn’t much “urban island” compared to all else
        ====================
        nonsense. thermometers are not located randomly. they are not restricted to rural areas only.
        thermometers are predominately located near areas of blacktop and urbanization. 150 years ago, humans used 4% of the land area for cities and agriculture combined. today we use 4% for cities alone, and 40% for combined cities and agriculture.
        4% total 150 years ago. 40% total today. the thermometers are not limited to a random sample of the 60% remaining. far from it. a large part of what they are measuring is the change of climate resulting from 4% to 40% total land use over 150 years.

    • My house in SW Florida near the Gulf coast faces west. It is stucco over block and takes a beating all afternoon from the Sun. Late in the afternoon and early evening you can stand a few feet away and feel the heat coming from the building. Years ago I got to thinking that this heat is going straight up through the soffit into my attic and out the ridge vents in the roof. Since the air coming off the house and into the vents is warmer than the air that normally should be going into the vents, the house is probably not cooling as well as it should. I planted bushes and tall plants to shield this part of the house from the Sun and it made a marked difference. A very “green” way to keep my house cooler. But we have known about this for a long, long time.

      • Amen. My well treed yard is a delightfully cool refuge on a hot sunny afternoon.
        BTW: Mark Steyn’s “A Disgrace to the Profession” continues to do well. “Amazon Best Sellers Rank: #300 in Books (See Top 100 in Books) “

    • “Anywhere in the U.S. small cities generate less heat than mega-cities,” said Bounoua. The reason is the effect vegetation has on keeping a lid on rising temperatures.
      B.S. The reason is that mega-cities have more impervious surfaces. Period.
      You can get any result you want from a computer model. In the end, it’s only the real world that counts.

      • Well given that the presence of vegetation indicates surfaces that are NOT impervious I don’t personally see any contradiction. Vegetation certainly CAN make life more tolerable, not only does it provide shade but the evaporation of water from foliage also produces a cooling effect. This has been widely studied by city planners and was well know in the ancient world. Both the Greeks and Romans laid out parks in their cities to provide cool public spaces. The moors in Spain perfected this as can still be seen in the Alhambra

    • https://scienceofdoom.files.wordpress.com/2010/04/surface-energy-budgets-p42-color-robinson-499px.png
      Asphalt is worse than a desert (low albedo). Easily 50+ W/m2 worse average LW IR worst than a vegetative surface. If you take the 3% urban area in the US and assume 50 W/m2 more IR (about 13.5°C warmer) that is about 1.6 W/m2 more ALW on average in the US than grass/vegetation.
      The Virginia highway department says asphalt roads get 33°C above ambient so these are real numbers.
      Yeah, it pretty much appears that simple.

  3. I can understand Kansas City and Minneapolis-St. Paul metro areas showing dark red on the map, but why would the Yakama Indian Reservation (SW of Yakima, WA) be a solid color? Very remote area of Washington.

    • Ginna,
      You mention the Yakama Res but, in fact, the red shading that begins about there extends northward almost to the border with Canada. Interestingly, I live about 60 miles north of Union Gap, the geographic feature, just about where the boundary is.
      This entire stretch of “UHI” appears to coincide with shrub-steppe environments and much rock of several types, including Columbia River Basalts. There is a nice photo on this Washington Trails Association page:
      http://www.wta.org/go-hiking/seasonal-hikes/spring-destinations/hiking-coulee-country-big-skies-early-spring

    • From Nasa’s and Noaa’s map imagery, I think they got a deal on red paint and ordered it by the tanker load.

    • If this was a true UHI map? California should be “blood red” compared to Washington State. I have been down to those areas and the only thing that I can think of that could be red through there as far as UHI is concerned might be Spokane and a way smaller foot print for Yakima which is a fruit growing ( way COOLER) region. This map is in error. (oh on retrospect did they include on that area hydro dams generation stations and nuclear facilities?

      • I believe that the map is ‘modeled’ and what is portrayed is model UHI, not actual.
        Which brings up several points.
        NOAA and other temperature keepers (abusers) have been informing us public that UHI temperature effects are allegedly negligible.
        All of a sudden, someone in NASA recognizes UHI potential and then models UHI?
        It’s that simple?
        What in blazes took them so long?
        I wonder how the parameters used for determining UHI were derived?
        Now that the warmists suddenly admit that UHI can be substantial; any chance they might use some of those $trillions for real science?

    • There are a lot of apple, soft fruit, hops, and grape farms all along the desert east of the Cascades. It is remote, but apples don’t care. Water is cheap and plentiful, the weather abiding, and the CO2 level is improving crop yields, but more can’t hurt. This is same desert north of I-90 is where the fires are burning. There’s almost no bare land here and even after the fires have come through all is regenerated in the next spring/summer cycle. Else we wouldn’t be having these damn fires. Visit the Okanogan and the Columbia Basin on the web. It’s an amazing place like no other. It is a place made by fire, ice and megafloods. It is here, too, that you find Canada’s only desert.
      Plants are a major contributor to Willis Eschenbach’s emergent phenomena hypothesis. A little rain goes a long way toward creating new or larger plants that absorb CO2 and solar energy and convert it to matter and finally life-giving coal. Plants also create shadows that prevent soil from converting broad spectrum light to LWIR that struggles so hard to return to space. Green can be seen from space. That’s a good thing.

      • I just remembered where I learned this business about plants. I lived in Hawaii in the 1950’s and would spend as much time barefoot (even to school) and at the beach as possible. One quickly learns to avoid walking on beach sand (and parking lots) because it is unbearably hot – but any stretch of sand that has even a thin growth of crabgrass on it is quite pleasant. It is the same with dirt roads that crisscrossed much of Hawaii. You walk in the center where the grass grows, not in the tire tracks that are bare soil – too hot. You also step on a lot of thorns in the grass, but every kid in Hawaii quickly develops a thorn-avoidance walk to minimize that.

    • I suspect that the map is partially the result of a computerized automatic image classification system that may “see” ag land as “urban” sometimes. Misclassification can happen when the classification is not supervised and corrected (“trained”) for special conditions. The primary predictors for temperature they are using are “impervious” surfaces, i.e. roads. Since the computer is handicapped in real-world experience, you might sometimes see things like grids classified as “urban,” and assumptions made about the cover. It isn’t so much how well the bear dances though, the surprise is that it is dancing at all.

  4. What fraction of the USA land area can be categorized as aggregated urban heat island. 1% or less?

    • Depending on the classification system it can be as high as 4-5% of the land has been modified for human uses “other than agriculture.” The USDA Inventory of Land Use has Urban pegged at 2.8%.

      • Interesting.
        So reserved parkland in cites (the green patches on urban maps) are Urban Heat Island UHI are included. I can see asphalt and concrete and steel being categorized, but trees and grass and parks? I see a job here for some tedious person, Willis? to scan a cloudless map of the USA and count green pixels and black pixels and blue/gray pixels.
        Still 2.8% seems high. THX.

    • What fraction of USA stations with urban heat island does the NCDC “choose” to use as the standard stations in the temperature record? Answer, well, it changes every month based on what they want to show but it is the majority.
      What fraction of world stations used by the NCDC suffer from urban heat island trend alteration? Answer. Well, it depends on what they want to show. Which is more and greater warming every month so the urban heat island affected stations grows every month.

      • True. Physically, the urban area is a small proportion of the whole, but they have a high proportion of the thermometers and are extrapolated to areas without few or no thermometers, so their impact on global temperature is out of proportion to their area. For global temperature, it’s now best to use the satellite measures.

    • I-90 is a heat island that runs coast to coast. All the interstates are long, narrow heat islands. Every road or parking lot is a heat island. Roof tops, too. Line a highway with trees the way the Romans did and the problem goes away. I don’t think it is possible to calculate to any useful level of certainty what you ask for. Buildings confound the problem by throwing long shadows, for example, so square footage is a nonsense starting point.

      • Yeah, but then fools would drive their vehicles off the road and into trees. Someone would complain about that.

    • Why?
      For large areas, UHI susceptible influence is 100%. Check the Northeast population centers for their influence.
      Plus, the official temperature stations in those urban areas are not located in parks.

  5. So with the great dying of the thermometers, didn’t the majority of the surviving stations lean more to urban siting?
    Maybe they should have looked a little deeper.

    • Maybe you are seeing Spokane, WA. The map is very poor.
      However, in southeast ID there are several NW-to-SE trending red lines. These are mountain ridges. On Google Earth: Go to Diamond Peak, ID – then back off a bit to see the mountain ranges there.

      • I know what is there and it looks like they picked out the valleys for some spurious reason. Certainly not much in the way of urban there.

      • If there are agricultural grids in the areas, the classification grid probably classified the grid as “impervious.” In California areas bordering major Interstates with extensive agricultural grids are categorized as “urban.” Pure humbug. It also show strips of intense UHI along US 395 south of Lake Tahoe between Boundary Peak and Crestview(?) – again totally bogus. One possibility there might be if they used a thermal image, since that area is an active geothermal area. Of course that area is mostly desert so possibly “grey” pixels were classified wrongly, then you would expect Nevada to be really bright too, but – hmmm, there aren’t that many roads in Nevada possibly there was a weighting factor in the classification algorithm. You know, this time the problem may not be the model so much as the “data.”

  6. “Anywhere in the U.S. small cities generate less heat than mega-cities,” said Bounoua. The reason is the effect vegetation has on keeping a lid on rising temperatures.”
    Gee, wouldn’t the reason be that the smaller cities simply aren’t as large as the “mega-cities”?

    • Well, the trees in a dense city might not get as much direct sunlight, may not get as much water to their roots, and may, or may not, appreciated the warmer temps.

  7. I think the red areas are a little too spread out. All of RI? Almost all of NJ?. All of eastern MA? Long Island has some pretty remote rural areas – especially the eastern half. I know some pretty remote areas in NJ and eastern MA…
    Probably most of the global warming thermometers are located in the red areas though…

    • How abut the Delmarva Peninsula south of Salisbury. Ever been there? Outside of Wallops Island (the launch facility) it is RURAL. The map is way off locally and perhaps regionally.

  8. Anthony, the idea may seem obvious, but even they didn’t get it right:
    ”….leaves release water back into to the atmosphere in a process called evapotranspiration, which cools the local surface temperature the same way that sweat evaporating off a person’s skin cools..”
    1) They totally neglected the energy absorption in photosynthesis (and some reflection) of the tree which is why it is cooler in the shade of a tree than in the sun.
    2) Also, the UHI isn’t all caused by impervious surfaces absorbing insolation from the sun. Surely, this centralized massive consumption of energy, air conditioning exhausting building heat out to the outside. Even a few million people each give off something like 200 BTU/hr, say 5000 BTU/day, enough to heat 4000cubic meters of air by 1C. (Can this be correct here? I’m a little foggy from a poor sleep, [1200 J/m^3 of air to raise it 1C and 1BTU=1,005J would raise a room 5m^2 by 1C). If so, not so insignificant.

    • Yet no one has said a word in months about the magnetic north pole shifting more than 100 miles towards the east near Siberia. Would this not have an effect on weather patterns all over the world?

      • vukcevic regularly posts showing correlation between climate and magnetic poles. the solar wind for example is free to enter the earth’s atmosphere at the poles, where it can interact with the atmosphere. it seems likely and reasonable that this interaction might affect climate in ways not well understood. for example, the magnetic field could affect electrons differently than protons, leading to charge differentials and ionization.

    • Well there are plenty of cities with little or no air conditioning that show the UHI effect. Even small cities like Cambridge UK can be a couple of degrees higher temperature than the surrounding villages and apart from a couple of shopping centres there is not much AC in use. My office overlooks a pedestrianized shopping street. On a hot day you can really feel the heat radiating off the pavement, A block away the small park area is noticeably cooler.

    • I’d say not insignificant.. Standard HVAC engineering practice uses a figure, depending on activity, of around 400 Btuh per person, 245 sensible/155 latent

    • Average Monthly Consumption (kWh) of US residences (2013) is a bit over 900 kWhr per month.
      http://www.eia.gov/electricity/sales_revenue_price/xls/table5_a.xls
      900 kWHr/month * 1000 WHr/ kWHr = 900,000 WHr / 730 Hr/Hr/month = 1233 W avg
      A 3,000 SF house * 0.093 m^2/SF = 279 m^2
      1233 W / 279 M^2 = 4.42 W/m^2
      Compare to => 3.7 W/m2, as calculated change in forcing from a doubling of CO2.
      And does your house use more or less energy per SF of space than an office building or store or factory?
      data from NASA/U.S. Geologic Survey’s Landsat 7 Enhanced Thematic Mapper Plus (EMT+) sensor and NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra and Aqua satellites were combined with NASA’s Simple Biosphere model to recreate the interaction between vegetation, urbanization and the atmosphere at five-kilometer resolution and at half-hour time steps across the continental United States for the year 2001.
      Again data proving UHI has been available since 2001 and not reported?

  9. But, but, but I thought that urban heat was negligible, especially after thermometer adjustments and removals (especially in the cooler areas)……

    • Just what I was thinking! For years we’ve been told that UHI doesn’t exist, or is even opposite to what we might think, and all of a sudden NASA of all people tell us UHI has always existed! All we need now is for them to work out where their thermometers are and to put 2 and 2 together… another 30 years perhaps?

  10. I wonder as to what weight all the US surface temperature stations have in creating the “global temperature” as compared to the handful of surface temperature stations that exist in Antarctica? Sorry for this non sequitur, but does anyone know? (This question was inspired by the fact that the UHI effect is non-existent in Antarctica.)

    • It’s actually not non-existent. McMurdo base, for instance, has a realized UHI from the development that’s gone on there.

      • Thanks, but my question still stands. I read that there are only 8 temperature recording stations in Antarctica as opposed to perhaps thousands in the United States. Given that the surface area of Antarctica is far greater than that of the United States, are adjustments made to the “global temperature” based upon surface measured. IOW, do the 8 Antarctic temperature recording stations have the same weight for global temperature measurement as perhaps the thousands of US temperature recording stations?

      • do the 8 Antarctic temperature recording stations have the same weight for global temperature measurement as perhaps the thousands of US temperature recording stations
        ===============
        since the Antarctic is larger than the US, less than 8 temperature stations should be adequate to measure the temperature of the USA. so why do they use more?

  11. They could mandate using cement for roads instead of asphalt and painting roofs white and buildings mostly white – that would reflect light away rather than absorbing it to generate heat.

    • Bad idea in part. Most roads are asphalt because asphalt is an inexpensive material for bulk batching and makes for a good surface. Mainly though, it’s easy to repair. Concrete (not cement) is another story.

      • but asphalt is a fossil fuel product and thus not sustainable. and since concrete is made using fossil fuels and releases additional CO2, it is not sustainable. rocks are sustainable, but not suitable for road building, as you cannot glue them together without cement or some fossil fuel based adhesive.
        what we need are wooden roads, glued together with horse glue, because metal fasteners are also not sustainable. you can always grow more trees and horses. and our cars should be made of wood so they are also sustainable.

        • Except horses exhale CO2 so we’d need a different glue perhaps a paste made from flour and water? Flour to be hand-ground from organic wheat of course.

  12. “The study, published this month in Environmental Research Letters, also quantifies how plants within existing urban areas, along roads, in parks and in wooded neighborhoods, for example, regulate the urban heat effect.”
    It also likely quantifies the effect on the so called global warming of the UHI corrupting the non UHI ‘signal’. Maybe the ‘climate scientists’ are just getting round to realising the magnitude of the data corruption problem and some are now running interference by distraction, turning merde into manure so to speak.

  13. Elsewhere on the planet, vast uninhabited areas without temperature stations are awarded the temperature designations of the two Urban Heat Islands (averaged, of course) at either end of their expanse.
    I think that NASA and its reputation have been hijacked!!!
    The “Space” in the NA”S”A acronym used to refer to where you might find the Moon, Planets, and Stars, not zones between Earthbound temperature sensors.

  14. Is there a way to determine what percentage of temperature sensors are located in the red zone and how much those temperature reading are adjusted for UHI, if any?

  15. Look at all the frickin’ liberals on the coasts and around big cities like Chicago heating’ the whole damn place up so much. C’mon liberals, do your part in limiting glowbull warming!

  16. There is something else in play here. A lot of “urban” areas and even small towns have street lightning, this can also throw growing seasons for trees etc out of wack. By artificially lengthening the growing season for tree growth around street lamps ( and this could even kill them by being unprepared for winter) you can add even more variables to the mix. It may be a small point but seeing that every one’s knickers are in a knot about a few parts ppm’s of C02 I thought I’d throw this in.

  17. Perhaps not as obvious as it should be; here in South Africa, I live in a city called Johannesburg; Our mean temperature is lower, and the humidity higher, than the surrounding area called the Highveld. Perhaps not coincidentally, we were also at one stage the largest man-made forest in the world. This is largely made up of so-called invasive species, which were regularly tended and supplied with water by the inhabitants. These are also the plants that this article identifies as having the most cooling effect, as the most efficient “pumps” of water. We are now removing these plants in the name of water thrift, and replacing them with indigenous species, which are not efficient water “pumps”. I wonder what the local climate will be like in another 100 year’s time… I might not have to live that long to see a demonstration, though. A local wine farm won a “green” award for removing invasive species from it’s land, and proudly announced that after the last bluegum was removed, a stream started flowing that had not done so for a long time. The stream water did not miraculously just appear there, so it was most likely that it was being pumped into the atmosphere as water vapour by the “invasive” trees. I’m sure that this is bound to affect the local microclimate, to which wine grapes are supposed to be particularly sensitive. I will be following the news on this particular vineyard with great interest for the foreseeable future.

  18. Well, this is not a surprise, but yet one of the most useful studies by nasa. I am only a bit wondering why the author claims that this is an “addition” to the co2 warming. if I don’t mistake, it’s a source of warming which is already recorded by temperature stations in cities. therefore for those looking for the real impact of co2, uhi should be substracted from the raw temperature.
    The alarming thing is that, in growing cities (over the course of decades), most of the warming measured is the consequence of a growing uhi. Yet the temperature record has been adjusted so that rural warming trends match city warming trends, whereas only about 3% of the planet is urbanised. It’s a scientifical non-sense.

    • Watch the “drift” of climate science papers as the presidential election approaches. If a republican president becomes more likely with the Congress remaining in “red” hands there will be more papers with an element of reality in them even from US government agencies. This could be a positioning paper as NASA have been under attack in the Senate for their spending on climate as opposed to rockets.

  19. Around half the heat lost from the surface comes from evaporation from plants. It therefore also follows that plants are essential in reducing the amount of rain that finds its way into rivers.
    Most “global warming” was never anything to do with CO2, but was instead a reduction in the level of plants in and around places where there were temperature sensors. Even a really basic knowledge of the atmospheric cooling tells us this is true, yet for political reasons certain academics and government organisations have been carrying out a campaign of hate against any who dared to suggest anything other than CO2.

  20. London (UK) UHI case:
    http://cimss.ssec.wisc.edu/climatechange/globalCC/lesson7/images/UHI_London.gif
    credit wisc.edu
    Narrative:
    “The intensity of the heating varies across a city, with the highest temperatures found near the city core. For instance, under clear skies and light winds, temperatures in central London (see figure ‘above’) during the spring reached a minimum of 11° C (52° F), whereas in the suburbs they dropped to 5° C (41° F), a difference of 6° C (11° F).”
    Beneficial aspect of the London’s UHI, considering large population and many old poorly insulated homes, is considerable saving on the winter heating bills. My energy consumption (kW, gas CH , both buildings of early 1960’s similar construction) fell by about 30% in the winter months, by moving some years ago from isotherm “6C” to the edge “11C” area.

    • vukcevic August 26, 2015 at 1:09 am That fits well with the weather forecasts, they always talk about at least 5 or 6 degrees colder in the county side compared to the Cities in the UK.
      1 to 3 degrees is nowhere near enough and Berkely’s estimate is totally laughable.

    • The difference must be higher outside suburb / or in rural areas. How NASA found out the claim, I would like to know the science and also how vegetation can limit the heat absorbed by the concrete or black top roads. Main cause of CC is urbanization. Millions of Square KMS of land surface is covered by concretes and black topped roads transforming the soil surface into dry land that is worse than desert. Deserts can hold water and let ground water recharge but urban areas only drain water to sea and stops evaporation which is vital for rain cycle.

  21. So, What they found was that if you have less solid, manmade material and more natural material you get less UHI. OMG; who’d a thunk it.

  22. DA I could have told them that 40 years ago. Also ,”Obvious science”, they will fine higher humidity in city with large amount of vegetation. We live on a swamp cooler planet.

  23. Now that they’ve gotten that 1.3°C to 1.6°C range nailed down, it’s a good bet those figures will be used to adjust rural temps upward so that they’re comparable to urban temps. It would be probably be too much to expect of NASA’s Goddard Space Flight Center to deduct the figure from urban temps to remove the UHI component. After all, if they did that, they might get cooling.

  24. Useless, taxpayer-funded model-driven garbage. NASA has become a joke, in large part thanks to Coal-Trains-of-Death climate clown Hansen.

  25. Urbanization is generally a bad thing. It promotes economic disparity, which must be subsidized, and social strife, which must be suppressed. And, apparently, global warming. Every heat island counts.

  26. It’s really not that simple and more trees won’t fix it. Thermal mass/specific heat of building materials concentrated in urban areas not only absorb more, they are also cool much slower than rural areas. Add to that heat released from building systems and automobiles, which is also absorbed by those same building materials. UHI effect on the climate is not going away. Even if populations completely dispersed the structures will still maintain a measure of heat island.

  27. Well, well UHI strikes again, I wish someone would make up their minds. Twenty years ago an EPA presenter emphasized UHI and what we needed to do to mitigate it. Then five years ago articles were published indicating than UHI had no impact on warming statistics (they used a city with temperature records back to the 17th century to “prove” that UHI was not an issue).. Anxiously awaiting the next reversal.

  28. Only way to keep land surface cool is by keeping moist all over as soil used to be before urbanization. The difference must be higher outside suburb / or in rural areas. How NASA found out the claim, I would like to know the science and also how vegetation can limit the heat absorbed by the concrete or black top roads. Main cause of CC is urbanization. Millions of Square KMS of land surface is covered by concretes and black topped roads transforming the soil surface into dry land that is worse than desert. Deserts can hold water and let ground water recharge but urban areas only drain water to sea and stops evaporation which is vital for rain cycle.

  29. I’ M Right in the middle of one of their red spots sitting among several lakes with 100’s of acres of state forest in my back yard. The forest here is so thick satellite TV isn’t available and radio is spotty yet they show me in an UHI. FRAUD

  30. …And CO2 is good for vegetation. Problem solved even before it started as they have been preaching how CO2 levels continue to rise.

  31. Very odd that Western Illinois, AKA “Forgottonia,” shows so much dark red. I never realized those little towns like Bushnell, Colchester, La Harpe, and Oquawka were such powerful urban heat islands…or something.

  32. Can anyone overlay this map with the distribution of contributing weather stations?
    I would bet a rather substantial amount that the great majority of weather stations (according to this map) should have between a 1 and 3 C UHI-linked warming that should be SUBTRACTED from the station data when trying to estimate the CO2 linked part of global warming. But I never grapped any of the maps that show the distribution of stations. I just remember them being denser in the urban areas and sparse in precisely the places where the urbanization is sparse. I wouldn’t be surprised if a lot of them live inside even the sparser network of red dots on the west-central part of the continent.
    rgb

      • Sort of. My browser has issue with it. Then there is the resolution issue on the map above, too. Offhand they look like they have some overlap, but I’m not sure I can manage to screen scrape the two and construct a transparent overlay, at least not until I have a lot more time.
        Sad, really — this would be an interesting way of checking GISS’s UHI correction that is quite independent of what they are using now.
        rgb

        • I have KML files for all of the NCDC stations, but they are quite dense once read into google maps.
          If you can figure out how to get the nasa data into google maps (or something that reads the KML file) I’ll gladly forward it, it might already be in sourceforge, but I generate them automatically. Put I haven’t segregated them by year, let alone which ones nasa used to create any particular temperature/UHI data set.
          http://sourceforge.net/projects/gsod-rpts/files/Reports YearlyContinental_Ver_2.1.zip

        • rgbatduke

          Sad, really — this would be an interesting way of checking GISS’s UHI correction that is quite independent of what they are using now.

          I understand Hansen’s NASA/GISS urban heat island “correction” uses each month’s “latest” NASA light survey index of all of the US (clouds and all?) to re-correct every year’s data of every temperature value based on the nighttime light value. Theory being, higher night time light values mean more electric use mean more “urbanization” mean more UHI to “correct for” – regardless of what the actual surface temperatures were then, are now, or will be in the future. Further, the “night index correction” means no single month’s value can be directly against ANY previous recorded value, since the whole temperature set is recalibrated every computer run based on an ever-changing “value” not related to the previous month, year, decade, or 30 year interval.
          Thus, if flares from a gas field or a “highlight” or halo effect were present, then the temperature records themselves are changed based on the assumed amount of night light measured. So, a pristine surface temperature station is changed arbitrarily, while a downtown record (Central Park or the Detroit airport or the Philadelphia Airports or – to pick obvious examples) are compared against ever-darker urban settings.

  33. Where to place a Stevenson Screen?
    Lest us assume that there are 10,000 Stevenson Screens located on continental USA. Where would you place them if you had the chance to place them all?
    1) Place them in a pattern where they would be equidistant from any others, (Triangular elements?) and cover the whole USA?
    2) Ensure that 3% of them are located with UHI locations? Any on inland water bodies?
    None next to restaurant stove exhausts, or emergency diesel exhaust pipes, etc.

  34. In cities like Phoenix built in the desert, the urban area actually has a cooling effect because of irrigated lawns and trees that wouldn’t be there without the city.

    As regards Phoenix, that is a figment of someone’s imagination.
    Most new developments around Phoenix don’t have grass lawns, and they have few trees. They have crushed rock “lawns” with drought-resistant plants and drip irrigation.
    One notable exception in the Phoenix area is Arizona State University at Tempe. There’s plenty of irrigated foliage there, and it’s just south of Tempe Town Lake, a small replica of the now-dry Salt River that once had a ferry boat on it. Tempe Lake was created in 1999. North of the lake is the well-watered 125-acre Phoenix Zoo. Tempe ASU station temperatures began a decline in 2001.
    Here’s a comparison of Jun-Jul-Aug mean minimum temperature trends at Phoenix Sky Harbor Airport and Casa Grande—a farming community 41 miles SSE of the airport that grew into a Phoenix suburb in the 2000s:
    https://verdeviews.files.wordpress.com/2015/08/phoenix-casagrande-avg-lows2.gif?w=584
    Do you see any “cooling effect” at either location?

  35. Wait… concrete and asphalt heat up when exposed to the sun and create different temps in a city than in a place with no concrete and asphalt?
    Well, I guess I can finally apply for my own study on the topic “Water – Is it wet?”

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