Urban heat island effects are real but local, and have not biased the large-scale trends. A number of recent studies indicate that effects of urbanisation and land use change on the land-based temperature record are negligible (0.006ºC per decade) as far as hemispheric- and continental-scale averages are concerned,

I believe that there are NO weather stations in the deserts, deserts cover 14% of the planets land mass, there were NO weather stations in the oceans that is until recently, other than the odd sailor throwing a bucket over the side of a ship, Oceans cover 70% of the planet, his means only 16% of the planet has been covered by weather stations since the early 1900`s and most of these were and still are in the western hemisphere. The US covers 2% of that 16%, that`s quite large, Brazil I believe has less than a dozen, that`s not many for its size.

Every study that has looked at individual city stations and their immediate rural stations sees an urban bias of up to 2 degrees C, its only the likes of Jones and Peters that discount this as trivial.

What appears clear to me is that from around 1900 to 1998 there has been a rise in temperatures seen by the ground stations, this rise in temps has been caused I believe by the steady conversion of the predominantly rural stations (cool stations) around 1900 to predominantly URBAN (warm stations)in 1998. I believe this accounts for at least 0.4 of the rise seen over that time and that rise is NOT associated with CO2.

I also believe that the UHI effect even though it is real will no longer effect global temps as already said the vast majority of these stations are now URBAN,(they are all in high temperature areas and measure only the immediate surrounds of where the station is situated) the few rural stations left will have NO impact on the overall trend.
Agw has occurred but was caused NOT by CO2 but by the misinterpretation of the ground station data by misguided individuals such as Hanson,Jones and Mann. The only impact UHI can now have on global temps is through India and China who are still in the process of urbanisation. Do the same team that fiddle the ground data fiddle the satellite date, hasn`t the satellite data been aligned with the dodgy ground temps.

Example: Is massive UHI warming in China distorting Jones et al gridded T data ?
http://www.warwickhughes.com/blog/?p=45

The Jones et al 1990 Letter to Nature: a rebuttal of some key points.
http://www.warwickhughes.com/papers/90lettnat.htm

Urban warming effects in China by Ren:

Abstract:
Temporal change in urbanization-induced warming at two national basic meteorological stations of China and its contribution to the overall warming are analyzed. Annual and seasonal mean surface air temperature for time periods of 1961~2000 and 1981~2000 at the two stations of “Beijing and Wuhan Cities and their nearby rural stations all significantly increase. Annual and seasonal urbanization-induced warming for the two periods at Beijing and Wuhan stations is also generally significant, with the annual urban warming accounting for about 65~80% of the overall warming in 1961~2000 and about 40~61% of the overall warming in 1981~2000. This result along with the previous researches indicates a need to pay more attention to the urbanization-induced bias probably existing in the current surface air temperature records of the national basic stations”.

http://climatesci.org/2007/03/16/two-papers-on-the-urban-heat-island-effect-on-temperatures/

try this link.
http://www.climateaudit.org/?p=1859

Steve McIntyre of climateaudit has done this see link below.

http://aycu26.webshots.com/image/48825/2003305333281076257_rs.jpg

Both plots level out at or around 1998.

Most of the sites are now Urban and have been for the last 10 years or so therefore the ground temps for those last 10 years and all future years should not have a warming UHI bias.

We may see over the coming years little or no temperature increase if the UHI effect was real.

Seems like this kid and his dad are doing more real science than Hansen does. Playstation Climate Modeling is one thing, but going out and getting your hands dirty is where it all starts. No data points, no models.

“Troll,” incidentally, got its name from “trolling,” which is, loosely described, net fishing. Trolls are people who say inciteful things to start meaningless arguments and derail the main argument of a thread – the inciteful behavior being the net, with which they’re attempting to catch the thread, or the participants within it, whichever you prefer. My behavior is closer, in fact, to “flaming.” That is, attacking another forum member. You’re the troll, because you derail arguments with petty and meaningless linguistic debates. I’m the flamer, because I attack you afterwards. (This post, incidentally, might qualify as trolling – calling you an idiot certainly doesn’t.)

I find it bizarre that the author of the blog never ever responds to any comments left, but seems to have accrued a bunch of yapping supporters who have appointed themselves as interpreters and clarifiers of what he is trying to say. Rather than let idiots like adirian assume they know what he meant, maybe it would be really useful if he could explain what he thought the IPCC said, and how exactly his measurement of the very well known urban heat island effect caused by Phoenix ‘contributes a small bit to science’.

Let’s take your points in one by one.

First, who here is denying that warming has taken place? There’s considerable debate about how much, and when, but nobody is claiming that climate is static.

Second, nobody, in spite of your fervent wishes, has claimed that the IPCC doesn’t know about UHI. We’ve been over this, and you seem to have a reading comprehension problem.

Third – hey, you’re grouping. Wildly and erratically. Which shouldn’t be surprising, since you’ve shown you aren’t that good at statistics. So let’s de-group, shall we?

You have the people who accept warming is taking place – everyone here, basically – who… deny human involvement? No, nobody has done that. They’ve debated the DEGREE of human involvement. I/e, if climate changes have happened in the past, and we don’t have the information on what caused them or to what extent any of the variables had – to what extent can we determine precisely how much of the current warming trends are attributable to human influence?

Then you have – a completely different group – those who say warming will be good. Actually, I don’t see them, what I see here are people who say that the economic damage resulting from interference will be worse than the heating which would otherwise take place.

And speaking of evidence that would shift people from their views – what, exactly, would shift you from yours? Say, conclusive proof that the temperature records for the past century are heavily biased? What about proof that the historic link between CO2 and temperature doesn’t have causality link that was assumed when the models you defend were developed? Or historic proof that high CO2 levels are not sufficient even to sustain high temperatures, much less produce them?

All this evidence exists. So what’s the magic piece of evidence that would make you realize – hey, there is good reason to be SKEPTICAL. To regard the claims as UNPROVEN. Nobody here denies AGW – the position is, as hard as this is for you to understand, THAT IT IS UNPROVEN. That IS the true argument taking place here, and until you wrap your head around at the very least the difference between skepticism and denial, you’ll just serve as amusement to the rest of us.

It’s easy to divorce political and scientific, incidentally – it’s just this easy: Cocaine hurts people. That’s the science question, and, unlike climate, it is pretty well proven. The political question is whether or not to ban it. And, you see, it’s a completely different question. The political and scientific questions here are also different, and it is your presumption that they are the same, not ours.

Yes, you’re right about the true argument. The problem is that while it’s obvious that rapid warming is very bad (eg 35,000 death in Europe’s heatwave of 2003, increasing strength of hurricanes, disruption of water supply due to glaciers disappearing, etc etc etc), there are people who deny that any warming is taking place, who try to suggest that the IPCC doesn’t even know about urban heat islands and so can’t be trusted, who if they accept that any warming is taking place, deny humankind’s involvement, and who even say that actually warming will be good for us all. And on the evidence of this blog and most people posting here, there is not a single piece of evidence that will shake people from these views, which they have adopted for political reasons, not scientific.

“I also know of no plausible explanation of the current rapid warming that doesn’t involve the warming effect of 100ppm extra CO2 since 1850.”

May I offer

1. Changes in solar irradiance
2. Changes in cosmic ray flux, which affect water droplet formation and cloud nucleation
3. Periodic or even chaotic shifts in ocean circulation patterns
4. Changes in land use patterns as forests are changed to grass and cropland, and in some cases back again
5. Natural methane emmissions from carbonate ices

Let’s also not lose sight of the fact that the true argument is not over whether the average temperature of the Earth will rise two degrees or 2.5 degrees. The argument is over what the costs of changing the trend are, and whether or not they exceed the benefits to be gained.

For example, If the cost of the food I eat goes up a dollar a day, I may notice it in some vague way, but it will not affect my life to any great
extent. However, to a large portion of the Earth’s human population, that dollar a day would mean the difference between sufficiency and hunger.