Gee where have we seen something like this before? Dads/Moms and Grandparents: if you’d like your children/grandchildren to be able to do something on UHI for the spring science fair, here’s an easy to do idea. – Anthony
From Science @ NASA.gov – Satellites Pinpoint Drivers of Urban Heat Islands in the Northeast
Cities such as New York, Philadelphia, and Boston are prominent centers of political power. Less known: Their size, background ecology, and development patterns also combine to make them unusually warm, according to NASA scientists who presented new research recently at an American Geophysical Union (AGU) meeting in San Francisco, Calif.
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, the new research shows. The complex phenomenon that drives up temperatures is called the urban heat island effect.
Heat islands are not a newly-discovered phenomenon. Indeed, using simple mercury thermometers, weather watchers have noticed for some two centuries that cities tend to be warmer than surrounding rural areas.
Likewise, researchers have long noticed that the magnitude of heat islands can vary significantly between cities. However, accurate comparisons have long eluded scientists because ground-based air temperature sensors tend to be unevenly distributed and prone to local bias. The lack of quantifiable definitions for urban versus non-urban areas has also hindered comparisons.
Satellite technology, which offers a more uniform view of heat islands, is in the process of changing this. The group of researchers from NASA’s Goddard Space Flight Center in Greenbelt, Md., presented results based on a new method for comparing heat islands at the AGU meeting.
Providence, R.I.
| Visible Light | Surface Heat | Developed Land | Vegetation Cover |
|---|---|---|---|
| › Larger image | › Larger image | › Larger image | › Larger image |
Buffalo, N.Y. 
| Visible Light | Surface Heat | Developed Land | Vegetation Cover |
|---|---|---|---|
| › Larger image | › Larger image | › Larger image | › Larger image |
Satellite-produced maps of Providence and Buffalo highlight the role that differences in development patterns and vegetation cover can have on the magnitude of a city’s urban heat island. Though the two cities have the same approximate size, Providence has a significantly stronger heat island. Credit: NASA/Earth Observatory
“This, at least to our knowledge, is the first time that anybody has systematically compared the heat islands of a large number of cities at continental and global scales,” said Ping Zhang, a scientist at Goddard and the lead author of the research.
Land surface temperatures in cities, particularly densely-developed cities, tend to be elevated in comparison to surrounding areas — a phenomenon called an urban heat island. Credit: NASA
Heat islands can be deadly. This graph shows how the number of deaths spiked in Paris during a sweltering heat wave in 2003. Credit: University of Hawaii at Manoa/Benedicte Dousset
Air conditioning systems release waste heat into the atmosphere such that their widespread use can inadvertently elevate city air temperatures. This graph shows the result of a model that calculated the likely magnitude of the effect during the 2003 heat wave in Paris. Credit: Météo France/Cécile de Munck
Surface temperatures vary more than air temperatures during the day, but they both are fairly similar at night. Credit: EPA
› Larger image Development produces heat islands by replacing vegetation, particularly forests, with pavement and other urban infrastructure. This limits plant transpiration, an evaporative process that helps cool plant leaves and also cools air temperatures, explained Robert Wolfe of Goddard, one of the scientists who developed the method.
Dark city infrastructure, such as black roofs, also makes urban areas more apt to absorb and retain heat. Heat generated by motor vehicles, factories, and homes also contributes to the development of urban heat islands.
A New View
The new method for comparing cities, which the team of scientists has honed for about two years, involves the use of maps of impervious surface area produced by a United States Geological Survey-operated Landsat satellite, and land surface temperature data from the Moderate-resolution Imaging Spectroradiometer (MODIS), an instrument aboard NASA’s Aqua and Terra satellites.
Impervious surfaces are surfaces that don’t absorb water easily, such as roads, roofs, parking lots, and sidewalks. Land surface temperatures tend to be higher and more variable than air temperatures, but the two generally vary in sync with each other.
By analyzing data from thousands of settlements around the world, the Goddard team has pinpointed key characteristics of cities that drive the development of heat islands. The largest cities, their analysis shows, usually have the strongest heat islands. Cities located in forested regions, such as the northeastern United States, also have stronger heat islands than cities situated in grassy or desert environments.
Most recently, the Goddard group has shown that a city’s development patterns — whether a city is sprawling or compact — can also affect the strength of its heat island.
By comparing 42 cities in the Northeast, they found that densely-developed cities with compact urban cores are more apt to produce strong urban heat islands than more sprawling, less intensely-developed cities.
The compact city of Providence, R.I., for example, has surface temperatures that are about 12.2 °C (21.9 °F) warmer than the surrounding countryside, while similarly-sized but spread-out Buffalo, N.Y., produces a heat island of only about 7.2 °C (12.9 °F), according to satellite data. Since the background ecosystems and sizes of both cities are about the same, Zhang’s analysis suggests development patterns are the critical difference.
She found that land cover maps show that about 83 percent of Providence is very or moderately densely-developed. Buffalo, in contrast, has dense development patterns across just 46 percent of the city. Providence also has dense forested areas ringing the city, while Buffalo has a higher percentage of farmland. “This exacerbates the effect around Providence because forests tend to cool areas more than crops do,” explained Wolfe.
Cities in desert regions, such as Las Vegas, in contrast, often have weak heat islands or are actually cooler than the surrounding rural area. Providence, R.I.; Washington, D.C.; Philadelphia, Pa.; Baltimore, Md.; Boston, Ma.; and Pittsburgh, Pa.; had some of the strongest heat islands of the 42 northeastern cities analyzed.
“The urban heat island is a relative measure comparing the temperature of the urban core to the surrounding area,” said Marc Imhoff, the leader of the Goddard research group. “As a result, the condition of the rural land around the city matters a great deal.”
Heat Island Impacts
Ratcheting up temperatures can have significant — and deadly — consequences for cities. Heat islands not only cause air conditioner and electricity usage to surge, but they also increase the mortality of elderly people and those with pre-existing respiratory and cardiovascular illness.
The U.S. Environmental Protection Agency estimates that, between 1979 and 2003, heat exposure has caused more than the number of mortalities resulting from hurricanes, lightning, tornadoes, floods, and earthquakes combined.
“It is the lack of cooling at nighttime, rather than high daytime temperatures, that poses a health risk,” said Benedicte Dousset, a scientist from the University of Hawaii who also presented data about heat islands at the AGU meeting.
Dousset recently analyzed surface temperature images of Paris and showed the spatial distribution of heat-related deaths during a sweltering heat wave in 2003. Some 4,800 premature deaths occurred in Paris during the event, and excess mortality across Europe is thought to be about 70,000.
The risk of death was highest at night in areas where land surface temperatures were highest, she found. Buildings and other infrastructure absorb sensible heat during the day and reradiate it throughout the night, but the cooling effect of evaporation is absent in cities. The lack of relief, particularly among the elderly population, can be deadly, she explained.
Ramped up air conditioning usage may have even exacerbated the problem, other data presented at the meeting suggests. Cecile de Munck, of the French Centre for Meteorological Research of Meteo-France, conducted a series of modeling experiments that show excess heat expelled onto the streets because of increased air conditioner usage during heat waves can elevate outside street temperatures significantly.
“The finding raises the question: what can we do to design our cities in ways that will blunt the worst effects of heat islands?” said de Munck, who notes also that her research shows that some types of air conditioning exacerbate heat islands more than others.
Making sure cities have trees and parks interspersed throughout the compact urban cores can also help defend against heat islands. And studies shows that painting the surfaces of roads and buildings white instead of black and creating “green” roofs that include vegetation can soften urban heat islands.
“There’s no one solution, and it’s going to be different for every city,” said Dousset. “Heat islands are complex phenomena.”
Related Links:
Beating the Heat in the World’s Big Cities
http://earthobservatory.nasa.gov/Features/GreenRoof/
EPA Heat Island Resources
Ecosystem, Vegetation Affect Intensity of Urban Heat Island Effect
www.nasa.gov/mission_pages/terra/news/heat-islands.html
Urban Heat Island: Baltimore
http://earthobservatory.nasa.gov/IOTD/view.php?id=36227
Scientific Visualization Studio: Related Materials
http://svs.gsfc.nasa.gov/vis/a010000/a010600/a010699/index.html
Briefing Materials: Slideshows
Lead Author Ping Zhang; Goddard Space Flight Center
Benedicte Dousset, University of Hawaii
Cecile de Munck; French Centre for Meteorological Research of Meteo-France
› Download pdf Adam Voiland
NASA’s Earth Science News Team
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Wow.. 2 items below you called for a sick bag and to boykott the AGU, now they are good again for news. How inconsequent is that? Either you shun them or you don’t.
London also generates its own microclimate, known as the Urban Heath Island (UHI), which can result in the centre of London being up to 10°C warmer than the rural areas around London.
It would be interesting to see the central London temp data from 1860 to present.
http://www.london.gov.uk/lccp/ourclimate/overheating.jsp
From the air vent,
Real Climate Extract;
The Urban Heat Island Effect has been examined quite thoroughly and simply found to have a negligible effect on temperature trends. Real Climate has a detailed discussion of this here. What’s more, NASA GISS takes explicit steps in their analysis to remove any such spurious signal by normalizing urban station data trends to the surrounding rural stations. It is a real phenomenon, but it is one climate scientists are well aware of and have taken any required steps to remove its influence from the raw data.
Normalizing urban station data trends to the surrounding rural stations.
If they can do that they must have enough rural stations to construct the data set in the first place without using the currupt urban data.
Am I missing something.
Not only do Pro AGW “scientist” underestimate urban heat island by an order of magnitude, in many cases these “adjustments” are used to actually cool the historical record and make the present appear warmer. No one really notices or complains when temps are lowered a degree for say December 1910. And all of a sudden AGW appears out of thin air, except it is not actual warming, it is an artifact of MANNipulation.
It would be funny in a sad scary kind of way if these rent seeking “scientist” searching for the heat demanded by global warming actually missed the start of a potentially harmful cooling trend.
They did it already, when they changed “Global Warming” to ” Climate change/climate disruption”….but, this time, they will have to change of “climate scientists”, and, perhaps, they will choose from the skeptics’ ranks….. 🙂
A couple of points.
1. The peak bias you see of 7C to 9C is by no means a daily occurance.
2. There are cooling biases as well. You can see this in any heatmap of a city. Oke
called these “cool parks”
3. The bias is modulated by winds ( over 7m/s) and by clouds and rain.
4. There is a similar project going on in EU looking at 10 cities at very fine resolutions:
See here
http://www.urbanheatisland.info/
with data down to 30 cm accuracy!
http://www.urbanheatisland.info/index.php?option=com_content&view=article&id=5&Itemid=14
Makes sure you read all the newsletters.
In it you will find more imagery and a description of the following studies
“In one study (Van Weverberg et al., 2008), which resulted from a collaboration between VITO and the
Catholic University of Leuven, the effect of urbanisation on temperature observed at the Uccle
meteorological station was simulated using an advanced meteorological model coupled to a scheme of the
urban surface energy balance. In order to reproduce surface characteristics of the pre-industrial situation in
the model, in particular the degree of urbanisation, use was made of ancient but very detailed maps
established at the end of the 18th century by cartographer Joseph de Ferraris.
Simulations were then conducted (1) for the present-day situation, and (2) for the pre-industrial situation, the latter with a much smaller urban area of Brussels than today’s. The main conclusion was that urbanisation around the Uccle meteorological station near Brussels had a significant effect on the observed warming trend, amounting to about half the observed value of 1.4 K warming that has occurred since the start of the measurements in 1833. A similar result was obtained recently, by Hamdi et al. (2009), who conducted another modelling exercise on
Brussels, focusing on the period 1960-1999. They found that, during this period, 0.62 K of the observed warming could be attributed to urbanisation and the urban heat island phenomenon. ”
if you live in Brussels you can access this:
http://geowebgis.irisnet.be/BXLHEAT/mapviewer.jsf?langue=NL
That gives you an indication of the “heat island” down to 30 meters. You should note
that there are hot spots and cool spots. It all depends where the temperature sensor is placed.
The bottomline is this. Metadata is now being collected to assess the UHI question in a more rigorous way. People should avoid:
1. focusing on peak measures.
2. Thinking the urban enviroment is uniformly hotter. As Oke has shown and these images confirm, there are substantial cool islands as well. Also, Oke has shown that the magintude of UHI depends on the surrounding rural enviroment.
3. Expecting all the warming we have seen to magically disappear.
i know you (watts up with that) have been talking about UHI for along time. It seems so obvious. I dont understand why it has taken so long for the dark side to think about this. Im glad to have had this website educate me on this matter many months ago!! thanks!!
But Hansen’s GISS “claims” that he needs only a 0.01 “correction” for the total UHI impact on ALL thermometers worldwide.
Yet the cities average 5.0 to 7.0 degrees C higher.
The Ping Zhang and Marc Imhoff AGU presentation effectively refutes Phil Jones’ and teams’ claims that UHI is so minimal that it can be ignored. Would someone who is conversant with Jones’ paper(s) on this subject please post the citations for one or two of the most widely cited papers on this subject. I would like to use this information to challenge a couple of “reporters” who write on this subject.
btw, the leak of the CRU emails has, IMO, had a large and growing result. McShane/Wyner, O’Donnell, et al, the widespread derision with which the various “investigations” were greeted, Judith Curry’s road that lead to her Climate Etc. and various other dialogues of her’s with we “denialists” that resulted in the RC crowd accusing her of apostasy, a Congressional hearing with the likes of Lindzen being invited are a few examples that come to mind. More on this in Tips and Notes.
a 4 year old kid could have told them that I wonder how many $…………………0000 it cost to come up with this statment
Mondo says “”Sorry to be pedantic..”
Your point about Delta UHI is only partly valid. If the total number of measuring stations has been skewed towards urban areas (as I believe is the case) then actual UHI is significant. And even if this were not the case, UHI as a human contribution to global warming becomes more significant than human CO2 emissions. Take a look at the graph of global human population growth. After about 1950 it takes off like a rocket.
pinches nose to impersonate tanoy…
AGW has left the building
Jeff L says:
December 14, 2010 at 11:32 am
“ground-based air temperature sensors tend to be unevenly distributed and prone to local bias”
And why then do we trust the historic surface temperature record ????
——————————
Also, why then would it be ok to extrapolate over large distances if they are indeed ‘prone to local bias’.
Lots of impervious surface area at airports where many weather stations are located, although not so many people. If the metric changes from night lights to impervious area, the UHI adjustments at airports will be large.
Why is this such a freaking surprise? Ten years ago I was at an ASHRAE conference where the EPA representative was talking about green roofs to reduce the UHI effect – apparently it’s only a heat island when it’s convenient for their specific philosophy. Or maybe an EPA heat island isn’t the same as a IPCC heat island. Aaaargh!
robuk – absolutely. Especially since double glassing hasn’t arrived yet with force in the UK. If you are in London’s outskirts it is so different to the center. Normally, snow only lasts for a morning, so you have hurry to take advantage. In 2006, I took a day off only to go to Regent’s Park early to take some snow shots because I knew it would be gone by noon and so it was… this year was better, but typically, snow doesn’t last in London. (I take snow pics every year there is any, since it is a privilege to get to see some…)
It would seem to me that the calculations to set the temperature anomalies, thus proving we are warming to hell are anomalous. Kinda sorta fudged unintentionally on purpose. NASA would appear to have some scientists that are prepared to buck the system, one can hope that they are not pilloried in any way.
Taking into account the large number of badly sited thermometers, The death of many thermometers and the UHI misrepresentation, mass sackings and a new start to the temperature record is needed.
My best guess would be that a real temperate record would show cooling from the high points in our interglacial, unsurprising as we are nearing it’s end.
If you zoom in on Providence, the biggest hot spot looks suspiciously like an airport, Providence Airport I think.
The “no expansion of city limits” speculation is absurd. Streets have been paved with asphalt concrete over time, converted from much less UHI effect materials, as have been parking lots, converted from PCC or other much less UHI effect materials. Each vehicle running emits at least 100,000 new BTUs of heat per hour, and roof coverings have changed from much less UHI effect coverings.
Once raw land has been developed, single family home used property has been converted to apartments and high buildings, with hugely greater amounts of heat released. The higher the building, if heated or air conditioned, the more heat released.
Asphalt concrete is maintained by slurry seal coatings or renewed AC surfacing, restoring streets, roads and highways to their highest UHI effect on a regular basis. Electricity usage and other fuel usage has increased greatly, emitting much more heat over time. AC units use power and emit lots of heat, as do any other electrical appliances.
There is no “answer” to this UHI effect, other than reducing population density substantially, and converting back to “raw”, agricultural land, covered with greenery, and living in primitive conditions, and that’s not going to happen any time soon. Humans have to live somewhere, and now release huge amounts of heat by doing so, compared to yesteryears.
BTW, a nation’s economy is directly proportional to the amount of energy consumed by that nation, as is the standard of living of the population. Think about it.
Can someone explain the oft stated claim by warmists that the satellite temperatures are similar to the surface temperatures in recent history, so valiating the surface data?
I think that the surface temps in an Urban area should be included in the UHI. We experience the heat of those surfaces. The radiation from the rock face on a building works just like the IR from the Sun, you feel the heat. If measuring temperatures is about what we, as humans experience, then we need to take the whole world into account, not just the ambient air temperature. Whether asphalt pavement, or concrete, or reflective glass walls, man has changed his environment.
I disagree with almost everyone that has posted.
It does not matter if a city has grow or not. Does not matter how many people, cars, etc either. Airports do not matter either. None of that matters……..
All that matters is that there is no way of knowing, and no way of correcting to 1/10th and 1/100th of a degree.
Here are two examples of just two of the many cities, Providence, R.I. (21.9 °F) warmer, Buffalo, N.Y., about 7.2 °C (12.9 °F).
The point is, no one can tell if any city’s UHI changed.
And yet, with the thousands of cities, somehow they have been able to come up with some formula that is correct. Not just correct, but correct to 1/10th and 1/100th of a degree.
…….yeah right
“It does not matter if a city has grown or not”
There are too many cities, too many changes that can effect UHI…………..
Well,
Looking at their slides they they are looking at the same stuff I have recently put into the metadata for GHCN V3.
1. ISA impervious surface area from Landsat. Problem. ISA is not a measurement. ISA is an estimate based on a regression model that uses Nightlights and Population count.
However, the population counts that go into ISA are Landscan data and Landscan data is proprietary, Still ISA appears to be a good predictor of whether a site is rural or urban.
2. They used surrounding rural landscape ( vegatation) this is good as well since Oke notes that the urban heat island is effected by the surounding rural area. Here they focused on land use, Oke suggests water use matters as well.
When Time permits I’ll use their metadata to construct a list of Rural stations around the world. ( its actually already done )
Jeff (of Colorado) says:
December 14, 2010 at 12:09 pm
True, but would be hard pressed to find a major city (except Venice) that has stayed the same size over the last 100 years. Since cities have grown over the last 100 years, then their UHI has grown and that must be subtracted from recorded temperatures to get accurate changes.
They compare urban with it`s rural neighbour to extract the UHI signal out of the urban temp when they could use rural in the first place, someone please explain why this is acceptable.
Just to remind you,
http://climategate.tv/2009/12/11/picking-out-the-uhi-in-climatic-temperature-records-%E2%80%93-so-easy-a-6th-grader-can-do-it/
So science will have its day in the sun, no matter how many psuedo-scientists try to keep data in the dark. The question is, how many more bricks of the AGW edifice have to be kicked away before the whole rotten construction comes tumbling down?