AK: “You’re looking for built-up areas encroaching on the station, but isn’t the Urban Heat Island effect dependent on lots of buildings?”
No, you are confusing classifications with reality. Certainly it is true that the more built up an area is, the more UHI effect you would expect there. But all we are talking about with UHI is the effect on instruments that results from the addition of man made structures around the instrument. So, indeed, if you have an instrument on a farm and if you put a concrete parking lot next to it, the instrument is going to start yielding higher temperatures. And that is what we care about – not the fact that the name has “urban” in it. On the other hand, if you have a thermometer in the middle of a city and it’s already built up, you won’t see much change if you put up another building or parking lot a mile away. Of course total city build up will effect the temperature over time because the larger the warmed area is the harder for the heat to dissipate. But when you start to build in a rural area, immediately around the instrument, the effect can increase even faster than it can in an already built up urban area. And that rural area won’t change its classification status for a very long time and until the building gets really dense.
I’m only pulling this out of my backside, but I would guess that out of 39,000 thermometers in their study they would be lucky to have a thousand with no UHI effect. These things are almost never put in national wilderness areas. They are near roads, close to where someone is able to read them and maintain them. And such areas are naturally subject to population growth.
But really, do you need to know any more than that they came up with a conclusion of “none, or negative, UHI effect” to know that they are doing it wrong. Come on – a little common sense please.
