by Roy W. Spencer, Ph. D.
This is an update to my previous posts [here and here on WUWT] describing a new technique for estimating the average amount of urban heat island (UHI) warming accompanying an increase in population density. The analysis is based upon 4x per day temperature observations in the NOAA International Surface Hourly (ISH) dataset, and on 1 km population density data for the year 2000.
I’m providing a couple of charts with new results, below. The first chart shows the global yearly average warming-vs-population density increase from each year from 2000 to 2009. They all show clear evidence of UHI warming, even for small population density increases at very low population density. A population density of only 100 persons per sq. km exhibits average warming of about 0.8 deg. C compared to a nearby unpopulated temperature monitoring location.
In this analysis, the number of independent temperature monitoring stations having at least 1 neighboring station with a lower population density within 150 km of it, increased from 2,183 in 2000, to 4,290 in 2009…an increase by a factor of 2 in ten years. The number of all resulting station pairs increased from 9,832 in 2000 to 30,761 in 2009, an increase of 3X.
The next chart shows how the results for the U.S. differ from non-US stations. In order to beat down the noise for the US-only results, I included all ten years (2000 thru 2009) in the analysis. The US results are obviously different from the non-US stations, with much less warming with an increase in population density, and even evidence of an actual slight cooling for the lowest population categories.
The cooling signal appeared in 5 of the 10 years, not all of them, a fact I am mentioning just in case someone asks whether it existed in all 10 years. I don’t know the reason for this, but I suspect that a little thought from Anthony Watts, Joe D’Aleo & others will help figure it out.
John Christy has agreed to co-author a paper on this new technique, since he has some experience publishing in this area of research (UHI & land use change effects on thermometer data) than me. We have not yet decided what journal to submit to.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
John W. (14:20:29) :
The preceding post wasn’t there when I submitted. So I’ll add that it seem Nick B. and I are having the same thought.
Welcome to the nut house!
I think there could be significant variables in play region to region, country to country, over time, etc. I spent probably too much time pontificating on power usage trends on Dr. Spencer’s previous posts, but there are probably hundreds of potential variables in play (avg. size of house, avg. pop per house, # cars on the road, per capita energy consumption rates, surface area trends of roads and road surface types, land use patterns, etc). Lots to think about.
Cheers!
IN the US most suburban development starts with tree less land, that was farm ground, then as people move in they landscape and add auto watered lawns, ornamental trees, perennial flower beds, privacy fences, and major shade trees, line the new roadside. The settling of the entire mid west started out treeless in the 1800’s, now the trees make most of the houses in suburbs of small towns hard to distinguish from the air.
It is a lot different than cutting prime old forests and bringing in herds of goats, sheep, lama, camels, yaks, water buffalo, etc. in third world countries, that denude the local forage until they have to move. Much can be said for factory farming and super markets with trucking system distribution in between.
HoiPolloi,
Dr. Spencer and I are looking at different things, so there is really no inconsistency per se. Dr. Spencer is looking at the difference in absolute temps between stations of differing pop density. I looked at trends in anomalies for stations with under 1 pop density, under 2 pop density, under 10 pop density, over 100 pop density, over 500 pop density, and over 1000 pop density.
Ron Broberg and I are planning to do something a bit more similar to Dr. Spencer’s work based on comparing the change in pop density at each station from 1990-2005 to the temp trend, though first we need to figure out how imprecise the geolocation is in the station metadata…
Hm!!! did that post before i meant it?
If the pop density goes from 10 to 100people/sqkm the UHI effect is 0.4C
Must know over what area is the pop density measured?
Current:
in hong kong 6,348.641/km^2
in US it is 32.073/km^2
in UK it is 246/km^2 average
Ireland:
http://homepage.tinet.ie/~cronews/geog/census/densanim.html
Armargh
1841 185/sqkm
1901 100/sqkm
2002 102/sqkm
So using the Armargh observatory data it should show a decreesing temperature
I’ll see if I can find a plot.
Be right back
If you plot the data with a linear x-axis, how flat are the lines from 10/km^2 to 800/km^2?
It looks like the there is a steep rise below this range and a steep rise above this range. Do you have any idea of what is happening? e.g. an area gets an airport above 800/km^2.
Don’t know if it matters but all of the plots have a similar shape and it would be interesting to know what causes that.
Harry Lu (15:39:03) :
“1841 185/sqkm
1901 100/sqkm
2002 102/sqkm
So using the Armargh observatory data it should show a decreesing temperature
I’ll see if I can find a plot.
Be right back”
I’d be interested in what you find, but be aware, Dr. Spencer only did the time sequence for recent years and the UHI effect may and (probably) have a different outcome. You’d have to use the same time sequence to have a proper comparison.
Tom G, as I understand UHI, it is not only direct surface changes that cause it. The construction of walls and other things reduce the cooling winds and breezes. The UHI effect on daily average temperatures mostly derives from the elevation of minimum temperatures at night.
Harry Lu (15:39:03) :
If the pop density goes from 10 to 100people/sqkm the UHI effect is 0.4C
Going from 10 to 100 is ~0.2C for most years. Some years it’s 0.6-0.4=0.2 and other years it’s 1.1-0.9=0.2C. You need to subtract the span to get the temperature influence, not the direct number.
Well, everyone else is commenting on the US difference, so I’ll toss in some thoughts.
Urbanization in the US includes sub-urbanization. Given that farmers regard trees as weeds that shade valuable crops, as farmland gets suburbanized, tree population increases.
US population spread is just that, spread. Subdivisions pop up in farmland, often miles from city limits and not close to other subdivisions. The gaps fill in over time, but the the density increase is gradual and happens over the range of densities.
In Europe or Asia, additional population gets shoe-horned in next to existing dense housing. You have a fairly sharp divide in density. The urban density stays the same, just covers more area, and the rural part just retreats.
Dr Spencer has some interesting data — But isn’t the UHI going to vary from place to place based on the geography, how the city is built, and what major industry the ‘area’ may be involved in. I suspect it would vary greatly, city to city and would not be very easy to quantify.
Wouldn’t the only real way to know for each ‘city’ to run an experiment like the famous Watts driving tour?
“”” Roy Spencer (12:21:40) :
James…my original results were based upon the year 2000 only, and (as I recall) global data…not US-only.
Also, I have changed to log-plots, since (as you mentioned) warming in the global average IS much stronger at low population densities. “””
Well not exactly logarithmic at the US low end Dr Roy; but certainly a much more infrormative format for you to use for this data.
Now I’d be whooping it up in the aisles, if I could just see a mean global surface temperature via logarithmic CO2 abundance over the last 600 million years curve that was even a faint shadow of yours. I’m not at all embarrassed to call your curves Logarithmic; or close enough so.
George
Some confounding factors:
Consider that population density is a proxy for heat production/absorbtion, which is highly dependent on what type of buildings you use and whether you have adequate heating or air conditioning. U.S. cities are in decline; the mayor of Detroit is proposing to bulldoze 1/4 of the city. Many have questioned stopping there (joke), but, the point is that the red-brick buildings of older hollowed-out cities will be mismatched to the population. Detroit should have a bigger heat-island effect per population density than Beijing.
Northern american cities & European cities love red brick and tinted glass as well as asphalt & pavers for sidewalks; perfect for absorbing heat. Other cultures might like more reflective materials. You might want to do a spider web plot, where you draw a line between all stations on your map & color code by anomaly (based on your UHI warming vs. Pop Density plot). Anamalous cities should color differently when paired with their surroundings. You may discover something about these cities that way.
The slight negative effect at low densities in the US could be what you might call a `golf course’ effect. In arid parts of the US lightly populated urban areas can be greener than rural because people plant gardens, lawns, trees, and water them.
Soooo. . . as I recall, there are some portions of the globe that appear to be heating faster than others in traditional analysis. Siberia, I think, is one? Do we know how those sites have been doing re population density per km, since this shows relatively small increases in PD give rather large UHI increase results?
o/t but while Spencer/Christy may run into trouble trying to get this important paper published in the scientific literature, this UNDP/UNEP/World Bank-backed ‘journo’ has no problems –
9 March: IPS: Violent Backlash Against Climate Scientists
By Stephen Leahy*
“I have hundreds” of threatening emails, Stephen Schneider, a climatologist at Stanford University in California, told Tierramerica.
He believes scientists will be killed over this. “I’m not going to let it worry me… but you know it’s going to happen,” said Schneider, one of the most respected climate scientists in the world. “They shoot abortion doctors here.”..
*This story was originally published by Latin American newspapers that are part of the Tierramerica network. Tierramerica is a specialised news service produced by IPS with the backing of the United Nations Development Programme, United Nations Environment Programme and the World Bank.
http://www.ipsnews.net/news.asp?idnews=50607
Stephen Leahy’s Summary
An independent environmental journalist for 15 years my writing has been published in dozens of publications around the world including New Scientist, The London Sunday Times, Maclean’s Magazine, Earth Island Journal, The Toronto Star, Wired News, Audubon, BBC Wildlife, and Canadian Geographic.
I am the international science and environment correspondent for the Rome-headquartered Inter Press Service News Agency (IPS), the world’s 6th largest global news agency.
My IPS articles are published in over 500 newspapers and magazines all over the world reaching an estimated 200 million readers in up to 20 languages. IPS news is also broadcast by over 1000 radio stations, potentially targeting over 150 million listeners.
I also write for IPS affiliate, Tierramerica, located in Mexico City and IPS bureaus in Johannesburg and New Delhi.
http://ca.linkedin.com/in/stephenleahy
Oct 2009: IPS: CLIMATE CHANGE: Four Degrees of Devastation
By Stephen Leahy
The prospect of a four-degree Celsius rise in global average temperatures in 50 years is alarming – but not alarmist, climate scientists now believe…
The climate negotiators heading to Copenhagen in December must accept the fact that the world’s carbon emissions must eventually stop – and stop completely…
http://www.ipsnews.net/news.asp?idnews=48791
Roy:
Until you can convince me that the stations themselves are not corrupt for micro-climate influences, your entire approach is as suspect as Jim Hansen’s luminosity approach. I simply don’t see the physics of a massive jump in UHI for population densities below 100 persons per sq. km. Unless you address how much energy has to be generated by the 100 persons to generate a heat capacity that releases in a manner that raises the mean temperature, you are just playing with the numbers. That, itself, is not a bad thing, I suppose. But you need to get confidence in station placement and construction and do the math on the physics before you have even the begining of a credible new UHI analytical approach.
David Schnare, Ph.D.
Center for Environmental Stewardship
Thomas Jefferson Institute for Public Policy
Many commenters here are confusing UHI with GW. UHI is thermometer error that produces false warming estimates for the entire region around an urban centre / thermometer location. GW is an estimate of the drift in average temperature* globally over time. Urban areas make up a very, very small proportion of the entire globe. The objective is not to cool cities but to get good T data for the larger study.
* “Global temperature” is, of course, a non-sensical notion because of the chaotic, transient, thermally partitioned nature of global heat. There simply is no place to stick a huge thermometer and get a true planetary reading. Al Gore hasn’t returned my phone calls.
George E. Smith (16:31:09) :
Almost everything in the climate exhibits a logarithmic nature.
Temperature itself is logarithmic with respect to the energy which drives it so we should expect to see it here as well.
Thanks Roy
The change to Log-Linear plot helps alot. Suggest exploring Non-OECD vs OECD to see if high vs low economic growth is significant. eg especially China, vs Russia, France or Germany.
(Note the comments of Chinese stations being moved out with urban population growth).
Looking at UHI vs time may show other interesting relationships. Could the 2x variation around 100 to 200 show some variation with el Nino or solar cycles?
Could the “negative” UHI in the US at low population densities be related to shifting stations to airports? – e.g. where there is low population density but higher UHI for “rural” stations.
BTW James Hansen is floating around Australia at the moment (no doubt a paid junket) spreading his nonsense:
http://www.theaustralian.com.au/news/opinion/only-a-carbon-tax-and-nuclear-power-can-save-us/story-e6frg6zo-1225839327862
I guess that buys you guys a temprary reprieve.
Dr. Spencer,
The difference between US and non-US result is striking, typically on the order of +1 deg C for non-US regions above 100/km2. Since ‘non-US’ covers a great deal of territory, it might be useful to add one other parameter to this analysis that differentiates based on: latitude. Re-analyzing your data taking this one variable into account might explain the significant different between US and non-US results, and (if it proves to be statistically significant) would provide a more powerful argument to apply your UHI correction on a global basis. Latitude seems likely to correlate with UHI because, the warmer the “background” (i.e. the lower the latitude) the less relative change that human activity (population, buildings, electrical gear) would have on the local temperature. In contrast, in colder climes (i.e. higher latitudes), human activity would be likely to have a more pronounced effect on the local temperature. Simple example: If 1000 people (body temps 98 F) stand together as a tight crowd, the temperature above that crowd will be minimally different if the ambient temperature were 80 F (low latitude) compared to if the ambient temperature were 30 F (high latitude).
Nice work!
Wow! It appears that “Energy Star” appliances and weatherization are having no effect in terms of decreasing the slope of the most recent curves. UHI effect can’t be all due to concrete and asphalt.
“Real Climate” claims that the urban temperature monitoring stations are biased “too cool”, since the urban temperatures are adjusted to account for UHI. Does anyone here besides me have difficulty with that claim?
David Schnare (16:39:52) : “Roy: Until you can convince me that the stations themselves are not corrupt for micro-climate influences, your entire approach is as suspect as Jim Hansen’s luminosity approach….”
So what? All approaches are suspect, aren’t they? Roy, I’d take that comment with a bag of salt. I don’t think anybody’s in a position to vet all the umpteen thousand stations as Dr. Schnare suggests. Your approach is almost certainly no worse than Dr. Hansen’s, and a perfectionist strategy at this point would just be silly.
By all means, pursue your statistical investigation along the various paths. I’m particularly intrigued by the large annual variation in the global curves. Why should that be so? And why should the US differ so markedly from the rest of the world? As mentioned by others, splitting the study into four time-of-observation groups should be done. A look at the effect of latitude might be productive, too. The apparent dip in the US data may be related to standard error. I think you’re digging in the right place.
Armargh pllot as promised.
http://img52.imageshack.us/img52/1456/armargh.png
according to wiki irish pop decrease by 50% from 1840 to 1890. Assuming pop was 185/sq then by 1890 it was 90/sq
This would give a drop of about 0.2degC
This would flatten the initial hump by a bit (1/8th)
So Armargh still shows a warming of about 1 deg C allowing for UHI.
It is intersting to think that rural depopulation could explain the higher temperatures in the early 20th Cent. Perhaps AGW is worse than we think!