UHI is real, in Reno at least

A couple of days ago there was a guest post from Russ Steele citing a California study “Feeling the Heat” on global warming that just didn’t seem to add up.  One of the stations cited as having climate change related warming was Reno, NV. So, I decided to do a field experiment to test this. The results show clearly that UHI exists in Reno.

Here is what Russ wrote a couple fo days ago:

Feeling the Heat was published by Environment California a non-profit group a few weeks ago, claiming 2007 was the tenth warmest year on record and that the mountain west was experiencing above-average temperatures.  Full report here: Download feeling_the_heat_ca.pdf One of the examples given for the high western temperatures was Reno Nevada with a average temperature of 55.3 degrees in 2007, four degrees higher than the 30 years average temperatures from 1971 to 2000.

…Up front in the EC report the author dispatches UHI as having any influence on the climate change, citing studies by Easterling, PD Jones and Parker…

Well I decided to test this myself tonight, since I’m driving through Reno on my return home, I arranged an overnight stay. With me is my NIST calibrated data logger, NIST Calibrated temperature probe, a vehicle mounted Gill IR shield, my laptop computer, and my trusty vehicle. See my previous post “Road Kit

I chose Virginia Street as the transect route, since it remains relatively straight, level, and crosses all of Reno, including the built up southern suburbs and downtown. It is the original “main street” for Reno.

Here is the result of my South to North transect driving Virgina Street overlaid on a Google Earth image oriented to match the timeline of the transect:

Click for larger image

The weather tonight was perfect. Light winds, clear skies.

Here is the data from the Reno airport ASOS, which also happens to be a USHCN climate station:

Time Temp   Dew   RH  Wind  Wind     Vis  WX Sea Level Altimeter  Station

Point        Dir Speed              Pressure   Setting Pressure

(PDT)  (f)    (f) (%)       (mph) (miles)          (mb)  (inches) (inches)

1:55 am   44    25   47  CALM         10.00 CLR    1023.0     30.30   25.788

12:55 am   48    24   39  CALM         10.00 CLR    1023.4     30.31   25.797

11:55 pm   51    23   33   WSW     3   10.00 CLR    1023.7     30.31   25.797

10:55 pm   54    23   30     S     6   10.00 CLR    1024.1     30.32   25.805

For those interested, I have the raw source data from my datalogger in CSV form for the South to North Reno transect here. (PDF)

Note the placement of the airport, which has it’s ASOS weather station used in many climate studies essentially in the north end middle of the airport. The Reno UHI bubble does extend into this area.

Reno_asos_wide_view_2

Click for a larger image

I also did a reverse transect, driving the same route in reverse immediately. Plus a route near the airport. I’ll have more tomorrow, its 2AM and I’m tired.

UPDATE:

Jeff Id inquired in comments “how is it mounted to the car/” Here is the answer:

uhi-sensormount.jpg

The temperature sensor (inside the Gill IR shield) mounted on the vehicle using an improvised window mount.

Also, the time of night that I made the transect (11:15PM to 11:39PM) allowed me to maintain a nearly constant speed during the transect due to the lack of traffic. Plus Virginia street has  stoplights set for all green unless there is cross traffic. I was fortunate to have to stop only once during the entire drive, and that was in the downtown area. I kept an eye on the temperature reading during the stop, and no change was recorded.

I’ll have a complete post in the next day, still catching up from my trip.

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Neil Crafter

Excellent stuff Anthony.
Up to 10 degrees F difference, quite amazing. And what does GISS most generously allow in their adjustments for UHI? less than 1 degree I believe.
Why oh why can’t there be a full blown study on UHI to put the facts out there clearly about the impact of UHI ? – wait, I think I know the answer!
Look forward to seeing your follow ups.
Neil

steven mosher
TerryS

Even the BBC weather forecasters (and by extension the Met Office and Hadley Centre) accept large UHI effects. At least one of the BBC overnight forecasts earlier this year predicted a 4C temperature difference between rural areas and towns and cities in the UK. Rural areas where predicted to be -4C and town and cities 0C.
I wonder if they will sacrifice accuracy for AGW correctness and narrow that gap in their predictions this winter.

Mike Bryant

This is tremendous. This stuff cannot be refuted.
Thanks,
Mike

Dan Lee

This brings up something I’ve been thinking about over the past week or two regarding GISS, which seems to be the ‘official’ dataset referred to by the media (and thence the rest of the world, since the media is supposed to be the public’s eyes and ears for what’s going on in the world while we’re living our daily lives).
The oceans have lost a huge amount of heat content in the el ninos of the past 10-15 years, which have sometimes come one right after another. The 2007 one may have wrung out the last of was accumulated since the 80’s, since temperatures dropped like a rock when then one was done.
IF Svensmark is right, the oceans will be slow to replenish that heat given the cosmic ray situation that NASA was on about a couple of weeks ago. The oceans might spend the next ?? number of years shaded by a lot more nice fluffy clouds than they’re used to.
Those clouds will also change the earth’s albedo, and not only will the oceans be slow to warm back up, everything else will be slower to gather heat as well.
IF there is anything to the what the solar guys are saying (sorry Leif, speculating here), and Solar Cycle 24 turns out to be a dud, if they’re right then that will contribute further to the general cooling.
A hockey stick may be a bad way to describe temperatures over the past 1000 years, but its not a bad representation of human population growth. That will demand land-use changes in the form of more agriculture land use, and in many parts of the world, that means fewer forests and urban areas.
This will also contribute to changes in earth’s albedo, not to mention how much extra wood will get burned for heating if things stay cool for an extended period.
People tend to migrate toward cities and suburbs, which will expand accordingly, and more and more of those nice rural temperature stations will become absorbed by expanding urban areas.
Which will have a direct impact on the GISS temperature set because thanks to its proponents’ continual “dispatching” of UHI as a factor, and its owner’s propensity for adjusting it in a way that matches his models, global temperatures might be dropping off a cliff for several years before the media, our window on the world, even notice that anything is happening.
They did a real good job noticing problems with the Reno’s UHI, right? Ha.
So thanks Anthony, for keeping UHI front and center for us. Without your work I don’t think anyone would know just how serious and widespread that issue is.

MattN

I see something similar every day I drive across Charlotte, NC. I start my commute in rural Kings Mountain, drive throught Charlotte, and wind up in rural Midlands, NC. I see, every day, at least a 5-6F increase in temperature as I drive through.

Dan Lee

Oops, above I meant “…fewer forests and MORE urban areas…”

Allen63

Could not make things much clearer than that — regarding the potential of the UHI effect to disturb a multi-decade temperature record.

Chris Wright

If you watched the recent BBC ‘Climate Wars’ series you will recall that the presented did an excellent demonstration of UHI at Las Vegas. He simply measured the temperature, drove into the city and measured the temperature again. It was several degrees higher.
The really odd thing is that he did not refute this in any way. But what he failed to mention is that the IPCC gives a ludicrously low value for the UHI effect. If the UHI is far larger, as seems almost certain, then a very simple logical conclusion flows from that: the global temperature trend over the last few decades has been exaggerated. Last year Michaels and McKitrick demonstrated a very significant UHI effect. They concluded that if UHI were properly taken into account then the real warming over recent decades is only a half of the normally stated amount.
The presenter is a scientist and seemed a reasonable person. But it never seemed to occur to him that his own demonstration of UHI refuted his own arguments.
As I understand it, the main argument against strong UHI involves windy and windless days. It seems a bizarre argument, bearing in mind that all you have to do is grab a thermometer and measure the UHI yourself, as Anthony has done.
Chris

A couple comments, tongue in cheek:
1) You took measurements with a weather station mounted over a paved road? That’s as bad as a USHCN station in a parking lot, maybe worse!
2) “I also did a reverse transect, driving the same route in reverse immediately.” Next time, consider turning the car around. However, your actions would be considered normal in Boston on one-way streets, at least it is among taxi drivers.
A little more seriously, I don’t have hard data, but I’ve noticed that between my usual parking place at work (shaded in the afternoon, at the bottom of a short hill going up to self-storage place) and the Turnpike heading north, I’ll see a 2-3 F rise. Some of it may be from sun, the temperature sensor is in the exterior rearview mirror, but I think most is from the hillside and car being in the shade at work.
At the hour you were driving, the solar effects would be quite different.

Joe Zeise

What about altitude affecting the start and finish readings?

Steven Goddard

One month ago, the UK Met Office made this statement –
25 September 2008 The Met Office forecast for the coming winter suggests it is, once again, likely to be milder than average. It is also likely that the coming winter will be drier than last year.
http://www.metoffice.gov.uk/corporate/pressoffice/2008/pr20080925.html
How are they doing so far?
29th October 2008 Arctic blast turns large swathe of the UK white as London sees first October snowfall in 74 YEARS
http://www.dailymail.co.uk/news/article-1081135/Arctic-blast-turns-large-swathe-UK-white-London-sees-October-snowfall-74-YEARS.html

ASOS data, reformatted, minus date and max/min temps:

Time Temp Dew RH Wind Wind Vis WX Sea Level Altimeter Station
Point Dir Speed Pressure Setting Pressure
(PDT) (f) (f) (%) (mph) (miles) (mb) (inches) (inches)
1:55 am 44 25 47 CALM 10.00 CLR 1023.0 30.30 25.788
12:55 am 48 24 39 CALM 10.00 CLR 1023.4 30.31 25.797
11:55 pm 51 23 33 WSW 3 10.00 CLR 1023.7 30.31 25.797
10:55 pm 54 23 30 S 6 10.00 CLR 1024.1 30.32 25.805

ASOS data, reformatted, minus date and max/min temps, this time with spaces changed to  :

    Time Temp   Dew   RH  Wind  Wind     Vis  WX Sea Level Altimeter  Station
              Point        Dir Speed              Pressure   Setting Pressure
   (PDT)  (f)    (f) (%)       (mph) (miles)          (mb)  (inches) (inches)
 1:55 am   44    25   47  CALM         10.00 CLR    1023.0     30.30   25.788
12:55 am   48    24   39  CALM         10.00 CLR    1023.4     30.31   25.797
11:55 pm   51    23   33   WSW     3   10.00 CLR    1023.7     30.31   25.797
10:55 pm   54    23   30     S     6   10.00 CLR    1024.1     30.32   25.805

If that doesn’t work, I give up….

Alan the Brit

So, common then somebody, just when is Solar Cycle 24 going to start in earnest?
Dr Hathaway & the Solar Prediction Panels & others seem to be having little more than wild stabs at it. First it was Autumn 06 definitely & wild & furious to boot peaking in 2010-2011, Spring 07 for sure, probably Autumn 07, looks like Spring 08 now, well, Autumn 08 has come & we’re heading into the “gone” phase as winter overtakes us, speculation about Spring 09 has been dabbled with even less confidence than previous “Guessing Games”. With all that brain power & computer power I would have thought someone would hit the nail on the head.
And are the Arctic temperatures +5°C higher up there or are they lower?
Have clever & powerful people embarrassingly succumbed to being little more than Medieval prophets, adjusting dates when their “end of the world is nigh” prediction fails, rushing back to the crystal ball for anther check, perhaps it was a speck of dust on the other side of the glass that threw them out, then making another prediction to compensate!
Guess what, yet another UK University study has claimed with great accuracy that Solar variations have little or no impact on climate! I wonder which Sun they’re looking at. Hmmmm! and the band played “Believe it if you like!”, as my late father used to say.

Bill Illis

The UHI is estimated to be just +0.05C on average across all temperature monitoring stations. I guess they are assuming that there are enough rural stations with no UHI to offset the urban stations which are impacted by UHI.
But let’s just do some basic math with that assumption. The Reno UHI looks to be 5F to 6F or 3C, which is pretty typical for a large city (Reno might be a little small to get into the large city category but Anthony’s measurements show the same impact none-the-less.)
If Urban stations have an average +3.0C UHI and the average UHI across all stations is only +0.05C, then the number of rural stations must be 98.3% of the total number of stations and the urban stations must be only 1.7% of all stations.
Change the UHI to just 1.5C for large cities and we still end up with 3.3% of stations are urban and 96.7% are rural.
Obviously, the math doesn’t work here because the number of urban stations is a large fraction, approaching half, of the total and the UHI average should be closer to 1.0C.

JimB

Anthony,
Thanks for providing first hand, the chance to see science in action…it’s fascinating to witness things like this unfold.
Jim

joshv

A simple question that perhaps Anthony can answer based on his meteorological experience.
Why don’t we calculate average surface temperature using the techniques meteorologists use to produce those nice temperature gradient maps (isobars? I am not sure of the exact term)?
Use the known temperature points to interpolate a temperature field for all lat/lons, and then sample that field at regular grid points. This corrects for UHI quite naturally, as the vast majority of grid points in a regular sampling grid would be rural. Sure, UHI would influence the overall average, but urbans areas would probably represent just a few percentage of the sample points. Lacking a good way to remove UHI from the temperature signal (other than ignoring urban areas altogether), this would seem to be the best way to handle it.

MattN

“I see something similar every day I drive across Charlotte, NC. I start my commute in rural Kings Mountain, drive throught Charlotte, and wind up in rural Midlands, NC. I see, every day, at least a 5-6F increase in temperature as I drive through.”
This mornings drive:
6:45 33F at the house
7:20 38F at the intersection of I85 and I77 in Charlotte (LOTS of concrete/asphalt)
7:50 29F in the parking lot at work.
I see this EVERY day. My commute covers 60 miles accros 3 counties. Those that refuse to acknowledge UHI effect are the true deniers.

ared

Come on, guys. No one denies UHI is real. The question is: does urbanisation affect trends over large periods of time for a significant number of stations. In the case of the Reno airport, which probably started very rural in the thirties and is now in a very large area of concrete and asphalt, this is very likely. And there are sure to be many other stations like it, leading to the IPCC underestimating the effect on the trend.
But just driving through the city proves absolutely nothing about whether the Reno time series is compromised by urbanisation or not. It just proves that the Reno station is not measuring the temperature that would’ve been had the city not been there. But to say something meaningful from a climate perspective, you need to compare the Reno trend to the trend of a nearby station outside of the UHI-bubble. Or you’d need data from the same trip half a century ago, that would be informative as well.
REPLY: Ared do your research before spouting off. Parker and Petersen claim UHI is insignificant, clearly it is not. EC says Reno UHI is insignificant, clearly it is not. The National Weather Service uses Reno’s UHI in their own training manual, so clearly it impacts the sensor.
http://wattsupwiththat.com/2008/01/10/how-not-to-measure-temperature-part-46-renos-ushcn-station/
It shows up as a hot spot in USHCN contours done by Steve McIntyre.
http://www.climateaudit.org/?p=1748
Clearly UHI exists in Reno. I’m not interested in a long debate on this, as I’m on the road. – Anthony

Jim Goodridge

Anthony, Helmut Landsberg would have been proud of you for illistratiog the urban climate so well.

JimB

“But just driving through the city proves absolutely nothing about whether the Reno time series is compromised by urbanisation or not.”
Okay…non-scientist here again, so humor me.
From my perspective, if you show me a graph that shows, in general, that things have increased over all, and I say “But what about this thing called UHI?”, and you say “We’ve accounted for that with a formula, and that effect is Xdeg, which we’ve used to adjust all the values.”, and someone goes and actually MEASURES it, and it turns out to be Z, not X, then it calls the whole graph into question, at least for me.
“Into question” being the operative term…
Jim

Ed Scott

Near-record cold, and mountain snow
Snow is accumulating this afternoon in the North Carolina mountains, and the rest of the Carolinas is shivering in the first cold outbreak of the season.
http://www.charlotteobserver.com/local/story/283717.html

Mike Bryant

Right Ared,
It means nothing whatsoever. I was wondering how long it would take for someone to say that.
I wonder if the name A Red means anything.
Mike B.

jmrSudbury

A couple of thoughts. What was the day like in Reno? Was it clear and sunny with only a light wind? What about a cloudy day followed by a clear evening? Or a clear day followed by a cloudy evening? Or a foggy day or a high wind day? It is interesting to see that the UHI exists, but how often does it exist and to what magnitude? — John M Reynolds

Patrick Henry

I ride my bicycle everywhere, day and night. On calm, clear nights there is often a 10-15 degree difference between a bike trail through a 20 meter wide greenbelt, and the surrounding neighborhoods with asphalt and brick.

Jeff Alberts

The UHI is estimated to be just +0.05C on average across all temperature monitoring stations. I guess they are assuming that there are enough rural stations with no UHI to offset the urban stations which are impacted by UHI.

Which is, of course, ridiculous. Using one site to adjust another has no relevance in reality.

jcl
Lucy

Great visual. Not knowing how your equipment was set up, it did raise a question. Did you maintain a constant speed throughout the trip? For example, if you were driving slower in one area could heat from your car have raised the temperature?
REPLY: Relevant question. The Gill IR shield prevents a lot of this, I tried very hard to maintain 35-40 mph through the transsect, and that partly why I chose this time of night…all the stoplights go green on Virginia street at this late hour. The one time I did hit a red light due to cross traffic, I watched the sensor reading carefully while stopped, no change. – Anthony

onscrn

Let me suggest that you make your first reference to UHI in each post be “Urban Heat Island (UHI),” so that people like me, who aren’t familiar with the term don’t have to do a search and scroll to find it. Good work in checking these things out.

Stu Miller

re Steven Mosher
I interpret the graph you linked as showing that the UHI effect for Reno has indeed been adequately accounted for by NOAA’s homogenization process?????

SteveSadlov

That’s fascinating. When driving roughly that same route in mid winter, after there has been snow, I notice the snow cover is the inverse of this transect, more or less. This cannot be attributed solely to elevation, as the elevation change along the transect is not that great.

ared

Jim, Mike, global warming is about the planet being warmer now than it was a certain time ago. Suppose Reno already had reached its current size & shape 50 years ago. Would the UHI effect have been the same as it is today? Probably very close. So would the UHI have affected the long-term trend? Hardly.
Now, what Anthony has done, is prove that Reno has a UHI, beyond a shadow of a doubt. The IPCC does not deny that, look at page 237 for AR4:
“Urban heat island effects are real but local, and have not biased the large-scale trends.”
So in order to prove the IPCC wrong, you have to prove that UHI’s have affected trends, not just that they are real, because the IPCC already agrees to this. In order to prove that the UHI has affected the trend, you need to either compare the current UHI-bubble to the bubble 50 years ago, or you have to proof that the trend in Reno is different from the trend in a nearby station outside the UHI-bubble. Otherwise you are arguing over something that everybody already agrees upon.

Frank Mosher

Having ridden a motorcycle for most of the last 40 years, i can attest to UHI firsthand. Colder in rural areas, and significantly colder in low lying rural areas.

Alan the Brit (05:45:20) :
So, common then somebody, just when is Solar Cycle 24 going to start in earnest?
Dr Hathaway & the Solar Prediction Panels & others seem to be having little more than wild stabs at it.

Made in March 2007:
http://www.leif.org/research/When%20is%20Minimum.pdf
SC24 so far:
http://www.leif.org/research/Region%20Days%20per%20Month.png

Fred

Not related to this post, I just wanted to call your attention to the following:
U of OK decertifies professor over Global Warming skepticism
A popular professor of environmental geology seems to be under attack by the University of Oklahoma because of his skepticism over global warming this month.
In October Dr. David Deming, a teacher for the U of OK for over a decade, was informed that his “general education” certification was being revoked for his class. This will result in many students passing over his class when they choose their classes in the future.

tarpon

Too bad the wizards of smart at the climate center couldn’t do this and produce scientific data instead of gibberish that supports the hoax.
I notice that instead of measuring the UHI affect, the climate center try to estimate it. As others state, the actual measurements don’t support the estimate, nor does the math.
Sort of like the effeect of the sun is so small as to not be a factor. Wanna bet.

ALAN D. MCINTIRE

There are two different points at issue here:
1. UHI effects on temperature readings
2. The increase in the UHI effect over the last century.
Presumable UHI affected temperature readings a century ago also. If rural temperature readings increased 0.65 degrees over the last century, say from 14 to 14.65 C, and if urban readings increased 0.7 degrees over the last century, say from 16 to 16.7 C, then the 0.05 C adjustment would be correct. What would be needed to verify the adjustment one way or the other would be to get comparison tables of rural readings and urban readings for various regions extending over the century.
I suspect the increase in urban temperatures over rural temperatures over the last century has been a lot more that 0.05 C, but current readings of urban temperatures doesn’t settle the argument one way or the other.

Ed MacAulay

Ric Werme (05:07:28) :
the temperature sensor is in the exterior rearview mirror, but I think most is from the hillside and car being in the shade at work.
Minor point but we had a discussion with a mechanic a few weeks ago. All or almost all cars have the sensor up just behind the grill so we see a rapid temp change as we drive thru different areas. The mirror is just the digital readout area, or in the Ford Fushion the readout is down by the a/c controls.

@ared (07:47:32) :
1) Anthony started http://www.surfacestation.org to determine if the data from the surface stations is even reliable. It is increasing looking like it is not and the bias is on the warming side do to poor siting.
2) UHI is not limited to big cities, as is supposed by many. Example: Cooperstown NY and Maryland NY are practically next to each other but Cooperstown shows a marked warming trend in the past 100 years, but Maryland shows a cooling trend for the same period. Both are considered rural stations. You can access the U.S. Historical Climatology Network (USHCN) Data Set and graph stations for yourself at http://www.co2science.org/data/ushcn/ushcn.php. However… I strongly suggest you bear in mind point #1 and visit http://www.surfacestation.org to check if the site has been surveyed and if a trend bias due to siting/operation was identified.
3) We all agree that the IPCC acknowledges that UHI is a factor that needs to be backed out, but the disagreement is if the amount of adjustment by the IPCC reflects the true UHI/Siting Bias.

Bruce

Ared, the trend (which is cooling as of today) is significantly less than the UHI of 3-4C,
So in fact, my guess is that earth has not warmed in 30 years or more.
And satellite records show that. Ground based temps are totally contaminated.

Ron McCarley

This comment doesn’t relate to this UHI article, but I find it interesting that the Wikipedia article on global cooling shows the W. Antarctica Peninsula warming dramatically during the 1965-75 period, during a period of global cooling. It makes one wonder what was driving such warming. Could it be that something else is operating there, maybe volcanic activity or something else?

ared

Dee, I know all this. I’m just making the point that knowing the size of one UHI at one moment in time does not prove the IPCC wrong. You need to know how UHI develop over time and what effect many of them have on long-term global trends to say something usefull about whether 0,05 per century is wrong or not.

Rob

UHI London,
London experiences a phenomenon called the Urban Heat Island effect (UHI), which means the centre of London may be up to nine degrees warmer at night than the surrounding countryside.
http://www.london.gov.uk/mayor/environment/climate-change/london.jsp
UHI Hong kong,
After analyzing the data, PolyU researchers found that there was an average temperature difference of 7° to 8°C between urban and rural areas in a winter night, and the maximum difference could be as high as 12°C.
http://www.polyu.edu.hk/cpa/polyu/hotnews/details_e.php?year=all&news_id=1435
UHI at Beijing and Wuhan stations
Implications of temporal change in urban heat island intensity observed at Beijing and Wuhan stations
“In summary, temporal trends of annual and seasonal mean SAT for time periods of 1961~2000 and 1981~2000 at Beijing and Wuhan stations and their nearby rural stations are all significantly positive, and the annual and seasonal urban warming for the two periods for Beijing and Wuhan stations is also positive and significant. The annual urban warming at the city stations can account for about 65~80% of the overall warming in 1961~2000, and about 40~61% of the overall warming in 1981~2000.
http://www.agu.org/pubs/crossref/2007/2006GL027927.shtml
If 50% of the weather stations are urban, given these examples being the norm for that 50% the UHI effect must surely wipe out the majority of the reported warming, 0.05%, pull the other one.

stan

Ared,
The biggest issue is credibility. The IPCC is supposed to be so expert on the subject of golbal warming that we must incur trillions in costs and consign the world’s poor to a future bereft of any chance of improvement (re: death, disease, starvation, etc) on the basis of their expertise.
The IPCC says that UHI effect is very small. The IPCC is wrong. This should jeopardize their credibility. Note also, the IPCC relies on a famous study for their view that the effect is small. When asked for access to the data used in the study, the author said that the dog ate his homework. Yet, the IPCC continues to rely on the eaten homework instead of the many, many observations of the UHI. One would hope that such reliance reflects on the IPCC’s lack of credibility.
If they can’t get the basics right, they ain’t experts. At least, not nearly expert enough to damn billions of people to lives of unnecessary misery, disease and death.

Leon Brozyna

I wonder how many desk bound NCDC/GISS types ever engage in such field work as you regularly undertake.
One has to wonder how many of the stations in the USHCN are impacted by the UHI besides the obvious siting problems you’ve exposed at the surfacestations project.
And yet, despite all these problems, it seems the data provided by satellite is still being treated almost as a novelty. Turf battles can be so petty…

Rob

ALAN D. MCINTIRE (08:05:25) :
says, Presumable UHI affected temperature readings a century ago also.
Take a look Alan,
http://www.john-daly.com/stations/stations.htm

ared

stan, the IPCC doesn’t say that the UHI effect is small. It says that after correcting for the effect, the impact on global trends is small.
And Anthony, I’m disappointed at your reply as it is obvious I’m not attacking your work, merely the unwarranted conclusions drawn from it by others, whom I specifically name in all but my first reply.
REPLY: Be disappointed all you like, it worries me not, but your version of “obvious” may not be the perception of others, nor can you expect them to glean that perception unless you clearly spell it out as to whom you are disagreeing with. The simple fact is that you haven’t done your homework on the UHI history of Reno, of which there is quite a bit. I’d kindly suggest that you read up on it. – Anthony

Steve Keohane

ared, look at the datat collected thus far at surfacestations.org. Closing in on half the stations in the US reveals a minimum of 5 deg. F bias. The remaining stations will have to have a strong negative bias to offset this, and that isn’t physically possible. This is the source of GISS temperatures, Hansen’s record of warming.

stan

Ared,
As noted on this site recently, GISS says that the UHI in Manhattan is less now than it was 100 years ago. Does anyone really believe that? Manhattan?! (and not the one in Kansas)
As the various articles showing temperature histories of certain towns which have been cited here in the recent past show, there simply is no way that the UHI can be as small as the IPCC maintains. On the one hand, the Greens have screamed about the horrors of urban sprawl (all that concrete and asphalt!). But the IPCC tells us that it is minimal. BS.
The temperature records are garbage. The “adjustments” to temp data, the infilled data, the changes to past data, the poor siting that no one ever bothered to check, the “dog ate my homework” studies, the SWAGS, the secrets, the refusal to share data — it’s a massive, sloppy mess. As Steve Mc has pointed out, this garbage would get a stock promoter sued for fraud. No one could possibly get a new drug approved with science this sloppy. No one would even bother to try.
But we’re going to alter the course of world history on the basis of this crap!?!?